Fuel 113 (2013) 287–299

Contents lists available at SciVerse ScienceDirect

Fuel
journal homepage: www.elsevier.com/locate/fuel

Review article

Coke oven gas: Availability, properties, purification, and utilization

in China
Rauf Razzaq, Chunshan Li ⇑, Suojiang Zhang
Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences,
Beijing 100190, PR China

a r t i c l e i n f o a b s t r a c t

Article history: The global demand for energy is constantly on the rise because of population explosion, rapid urbaniza-
Received 22 August 2012 tion, and industrial growth. Existing energy resources are struggling to cope with the current energy
Received in revised form 20 May 2013 requirements. Aside from exploring renewable energy alternatives, available energy resources must be
Accepted 22 May 2013
utilized to their maximum potential. Coke oven gas (COG) is highly rated as a valuable by-product of coal
Available online 14 June 2013
carbonization to produce coke in the steel industry. Typically, a single ton of coke generates approxi-
mately 360 m3 COG. China annually produces 70 billion N m3 COG; however, only 20% of the gas pro-
Keywords:
duced is utilized as fuel. Disposing COG without an effective recovery and efficient utilization is a
Coke oven gas (COG)
COG reforming
serious waste of an energy resource and results in environmental pollution. COG is regarded as a poten-
Methanol synthesis tial feedstock for hydrogen separation, methane enrichment, and syn-gas and methanol production. It
Methanation can also be effectively utilized to produce electricity and liquefied natural gas. The availability, properties,
purification, and utilization of COG are reviewed in the current study. COG utilization routes are summa-
rized in detail, with focus on some major industrial projects in China and other countries that are based
on COG utilization technology.
Ó 2013 Elsevier Ltd. All rights reserved.

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
2. COG properties and purification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
2.1. COG properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
2.2. COG purification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
2.2.1. NH3 removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
2.2.2. COG desulfurization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
3. COG utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
3.1. COG combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
3.1.1. Direct COG combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
3.1.2. COG combustion for electricity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
3.2. Direct reduction iron (DRI) production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
3.3. Feedstock for hydrogen separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
3.4. Hydrogen and syn-gas production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
3.4.1. Partial oxidation (PO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
3.4.2. Dry (CO2) and steam reforming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
3.5. Methanol synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
3.6. COG tar utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

Abbreviations: COG, coke oven gas; GDP, gross domestic product; BF, blast furnace; Syn-gas, synthesis gas; CV, calorific value; BFG, blast furnace gas; BTX, benzene,
toluene and xylene; HCs, hydrocarbons; CHP, combined heat and power; SOx, sulfur oxide; DRI, direct reduction iron; EAF, electric arc furnace; PSA, pressure swing
adsorption; WGSR, water–gas shift reaction; PO, partial oxidation; FTS, fischer tropsch synthesis; CPO, catalytic partial oxidation; S/C, steam/carbon; RWGSR, reverse water–
gas shift reaction; COx, CO and CO2; GHGs, green house gases; GHG, green house gas; SNG, synthetic natural gas; CNGCL, China Natural Gas Corporation Limited; LNG,
liquefied natural gas; CCPP, combined cycle power plant.
⇑ Corresponding author. Tel./fax: +86 10 82544800.
E-mail address: csli@home.ipe.ac.cn (C. Li).

0016-2361/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.fuel.2013.05.070
288 R. Razzaq et al. / Fuel 113 (2013) 287–299

3.7. COG methanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

4. Overview of COG utilization technology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
5. COG investment and economy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
5.1. World scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
5.2. China’s perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
6. Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298

1. Introduction 60% of the total global coke production. The annual COG produc-
tion in China for 2007 was estimated at around 70 billion N m3.
The threat of the world’s energy supply by depletion of fossil However, only 20% of the produced COG is utilized as fuel; most
fuel reserves, along with rapid industrialization and urban growth, of the gas is directly discharged into the atmosphere, with serious
has not only encouraged the search for alternative energy sources, environmental consequences and considerable energy waste.
but it has also pushed for an effective and efficient utilization of Developing new technologies to recover and utilize COG from the
available ones. Fossil fuels have predominantly been the major en- steel industry is therefore urgently needed [11,12]. In China, the
ergy source for industrial, transportation, and domestic use over coking enterprises located near coal mines only recover 24% of
the centuries. Approximately 90% of the global energy require- the COG by-product, losing a high percentage of potential energy
ments are covered by these sources alone [1]. Global primary en- as well as generating 25 Mt of carbon dioxide (CO2) [8]. Moreover,
ergy usage rose by approximately 2.4% in 2007 and is likely to converting COG into more energy-valued products can signifi-
increase further in the future, with developing Asian countries con- cantly enhance the energy efficiency of the steel industry in China.
tinuously improving their standard of living. The energy demand in COG has been highly investigated as an important source of
China rose by 7.7%, followed by 6.8% and 1.6% in India and US hydrogen (H2), with Japan making some early developments in
respectively [2]. For the past decade or so, China has enjoyed the establishing a sustainable H2 production technology from COG
most drastic economic growth, with a 10% increase in the gross [12]. Purwanto and Akiyama [13] proposed a simple method of
domestic product (GDP). This growth allowed China to recover H2 production from COG. Onozaki et al. [14] performed the partial
quickly from the 2007–2008 financial crisis. With such economic oxidation and steam reforming of tar from hot COG to produce H2
and population boom, the energy consumption in China is also at low cost and high efficiency without using any catalyst. H2
on the rise and, more importantly, strongly affects the global en- enrichment in COG can also be achieved through catalytic methane
ergy balance [3]. CH4 reforming via catalytic partial oxidation [15]. The use of mem-
The energy structure of China has traditionally been dominated brane technology can also lead to synthesis gas (syn-gas) produc-
by coal. Although other fuel options have also entered the energy tion through the partial oxidation of COG [12]. The syn-gas
setup in the past few decades, coal still plays a leading role in Chi- (CO + H2) produced from COG via various routes, such as partial
na’s energy scenario. Model forecasts predicted an annual increase oxidation, steam reforming, or dry reforming, can be utilized to
in coal demand by almost 2% for 2010 [4]. With a coal reserve of an produce important organic products, such as methanol [16]. Cata-
estimated 5570 billion tons, the third largest in the world, China is lytic co-methanation of CO and CO2 in COG can also be used for
regarded as the world’s largest coal producer and consumer [5]. CH4 enrichment. The choice and nature of a catalyst can signifi-
For the past few decades, steel has become an icon of modern cantly affect both the activity and selectivity in CH4 production.
urbanization and industrial development, with coal serving as The use of both transition and noble active metal supported cata-
the backbone of the iron and steel industries. According to the lysts with different oxide supports have been previously reported
World Coal Association, approximately 70% of the total global steel for CO and CO2 hydrogenation to produce CH4 [17–21].
production relies on coal [6]. The steel industry has played an In the current review, we discuss the availability of COG with
important role in the economy of China because of its rich coal re- respect to the steel industry and coke gas production, focusing
serves, with a rapid growth overtaking that of Japan to become the on China’s perspective. The purification and utilization of COG is
largest steel producer in the world. Despite such achievements, largely discussed, and current utilization routes and future techno-
the energy efficiency of China’s steel industry is the lowest among logical research and developments in the said field are considered.
the major steel-producing countries around the globe. However, COG utilization facilities in China are highlighted, with key
research and development are continuously improving the energy
efficiency to achieve a sustainable development [7]. In 2004, the
average net energy usage for the coking process in China was
Table 1
4.3 GJ/t, whereas the international average was 3.8 GJ/t [8]. Mass and energy flow of a typical coke-making plant
Coke oven gas (COG), sometimes simply called ‘‘coke gas,’’ is a [10].
by-product of the coke-making process, where volatile coal matter
Energy input (42.7 GJ/t coke)
is generated as COG, leaving carbon intensive coke behind. Coke is Coal 91.44%
a very strong macro-porous carbonaceous material produced by Electric power 0.37%
the carbonization of a specific coal grade or of different coal blends Fuel gas (firing gas) 7.61%
at temperatures P1400 K. Approximately 90% of coke produced Steam 0.58%

from blends of coking coals is used to maintain the iron production

process in a blast furnace (BF) [9]. Typically, 1.25–1.65 tonnes of Energy output (42.7 GJ/t coke)
Coke 69.63%
coal produces a single tonne of coke, while generating approxi- COG 17.92%
mately 300–360 m3 of COG (6–8 GJ/t coke) [8]. Table 1 shows the Tar 2.77%
energy balance for a typical coke-making plant along with different BTX 0.98%
raw materials and product distribution [10]. In China, the annual Sulfur 0.05%
Energy loss 8.65%
coke output in 2007 was about 335 million tons, or approximately
 R. Razzaq et al. / Fuel 113 (2013) 287–299 289

investment groups and companies at the forefront of a constantly Table 3

developing technology. Finally, some concluding remarks are also Heating value of some typical gaseous fuels [25,26].

presented. Fuel type Heating value

(MJ/m3) (MJ/kg)
2. COG properties and purification Natural gas 40.6 56.6
Coke oven gas 19.9 41.6
2.1. COG properties Water gas 18.9 21.9
Blast furnace gas 3.9 2.7
Producer gas 5.8 5.2
Before the advent of natural gas, COG was used to meet the
domestic energy demand for industrial cities such as Sheffield
generation. Compared with the coking facilities around the globe,
and Birmingham in England. However, COG was soon replaced
coke plants in Germany have acquired the highest technically pos-
by CH4. COG is essentially a mixture of combustible gases such
sible standards today. However, engineers and researchers are con-
as CO, H2, and CH4, and non-combustible ones, including CO2 and
tinuously working to increase the overall plant efficiency and
N2 [22]. During the coking process, the composition of the released
environmental standards [10].
gas may vary depending on the nature of the utilized coal (Table 2).
The basic COG treatment process in the steel industry has not
Although COG is regarded as a non-standard gaseous fuel, it still
significantly changed in several years. Typically, hot, raw COG from
has a reasonable energy content and calorific value (CV), which de-
coke oven batteries undergoes the following processes prior to NH3
pend on the nature of coal and the type of carbonization used. With
and acid gas removal [30,31]:
a high H2 content, COG has a CV of 19.9 MJ/m3, which is five times
higher than that of blast furnace gas (BFG) (3.9 MJ/m3) [8]. Table 3
1. Hot COG is pre-cooled from a large volume of coal tar mixture
provides the heating values of natural gas and other synthetic gas-
via direct contact with a weak aqueous ammoniacal solution
eous fuels for comparison.
directly sprayed into the collection system. The hot gases are
As previously mentioned, the type of carbonization process sig-
cooled to a temperature between 70 and 100 °C using pri-
nificantly affects the production of COG and its properties. A low-
mary coolers. During this process, approximately 30% of the
temperature carbonization process performed at 700 °C produces
initial amount of NH3 and most of the tar components are
a semi-coke, resulting in lower COG and ammonia yields and high
removed. After utilization, the discharged liquid, also known
tar. COG released under this process has a high CV with low H2
as the ‘‘flushing liquor,’’ is recycled for further use.
content. High-temperature carbonization produces a high COG
2. The gas is further cooled to a temperature ranging from
yield with less tar and high NH3. Moreover, the CV of the generated
28 °C to 30 °C using either direct or indirect secondary cool-
COG is lower, with a high H2 content [27].
ers. In direct coolers, COG is cooled via direct contact with a
counter-current stream of the same ammoniacal solution.
2.2. COG purification
The hot spent solution escaping from the unit is cooled
using water-cooled coils and again recycled for further
The optimization of the industrial COG purification process has
use. For indirect coolers, shell-and-tube heat exchangers
become highly significant in achieving an efficient, economical,
are deployed, with cooling water running inside the tubes
and eco-friendly purification. The potential for improvement is
and hot COG flowing outside.
huge, especially in the adsorption and desorption units of a COG
3. Finally, the cooled COG is passed through an electrostatic
purification plant [28]. COG is a complex mixture of various com-
precipitator to remove very fine tar droplets. Some facilities
ponents; aside from those listed in Table 2, COG also contains other
are also equipped with an on-site tar distillation unit.
minor constituents, such as NH3, hydrogen cyanide, ammonium
4. Naphthalene is recovered in a separator unit, followed by
chloride, tar components (tar acid gases such as phenolic acid,
the removal of light oil. COG is fractionated to recover ben-
and tar base gases such as pyridine), and carbon disulfide. Of these,
zene, toluene, and xylene (BTX).
H2, CH4, CO, and paraffinic and unsaturated gases are useful in the
final clean gas composition, whereas small amounts of CO2, N2, and
During the coke-handling, quenching, and screening processes,
O2 are retained in the final gas. The by-product plant should re-
‘‘coke breeze’’ is produced, which can be used either on-site in the
move as much of the remaining constituents as possible, both prac-
sinter plant or sold as a usable by-product.
tically and economically [29]. Traditionally, a coking plant is
A COG cooling system with a closed water circulation cycle pre-
connected to a network of integrated steel- and ironworks. A BFG
vents the escape of pollutants into the atmosphere, which results
with low CV is used to heat the coke ovens, and CV is increased
from using a cooling tower. The system has low installation costs
by the addition of COG. In most energy-efficient facilities, excess
and increased efficiency through the use of highly efficient, self-
COG is utilized in small energy-intensive processes within the
cleaning helical heat exchangers, rather than conventional ones.
plant, such as ignition furnace heating, rolling mills, and power
Moreover, because COG has no direct contact with the cooling
water, recycled water can be directly utilized [32].
Table 2
A conventional process for the COG treatment plant is shown in
Composition (vol%) of COG produced during the
coke-making process in the steel industry [23,24].
Fig. 1. Water and tar contents are transferred into a crude tar recov-
ery unit, and COG is then cooled at around 27 °C. NH3 and hydrogen
COG constituents vol%
sulfide (H2S) are scrubbed in a scrubbing unit, and benzole is re-
H2 55–60 moved and recovered for further utilization. The water used in
CH4 23–27 the scrubbing unit is recycled before being re-pumped into the
CO 5–8
CO2 1–2
scrubber. Finally, NH3 is cracked using a catalyst at high tempera-
N2 3–6 ture and atmospheric pressure into N2 and H2 (2NH3 M N2 + 3H2)
C2H4 1–1.5 while H2S is obtained as elemental sulfur through ‘‘Claus process’’.
C2H6 0.5–0.8 A biological effluent treatment unit continuously recovers and
C3H6 60.07
decomposes different hydrocarbons (HCs) and nitrogenous com-
H2S 63.2E5
pounds [10].
290 R. Razzaq et al. / Fuel 113 (2013) 287–299

Fig. 1. Schematic diagram of a typical COG treatment process [10].

2.2.1. NH3 removal value of 60.5 g/m3. Therefore, the use of NH3 to remove H2S from
Conventionally, NH3 in COG is removed while in contact with COG has gained considerable attention. The process includes the
the gas containing a solution of sulfuric acid to form ammonium capture of H2S using liquid NH3, followed by treatment with acid
sulfate, which is then recovered, crystallized, and dried before it gas under the ‘‘Claus process’’ (Fig. 1) to obtain elemental sulfur
is sold as fertilizer. More advanced modern processes of NH3 re- which can be sold as a commercial product. China has installed five
moval from COG include the water wash process [33]. After COG such units based on this sulfur removal technology from COG. Cer-
is cooled to 27 °C in the secondary cooler, the gas is introduced tain advantages associated with this process include zero toxic
into the NH3 removal unit equipped with a stripping section. The emissions and the generation of a useful by-product (sulfur) [34].
gas then enters the adsorption section of the vessel, while a portion During COG desulfurization, one-third of the H2S content is first
of adsorbed solution is cooled and recycled. Water from the free consumed under partial oxidation according to the following
NH3 stripper is introduced at the top of the absorber. Water from reaction:
the stripping section is continuously cooled and recycled, while ex-
3H2 S þ 3=2O2 ! 2H2 S þ SO2 þ H2 OðgÞ ð1Þ
cess water is treated in the fixed NH3 stripper before discharge.
Lime or caustic soda is used to react with non-volatile acids to re- After the oxidation reaction, H2S undergoes a Claus reaction, as
lease the fixed NH3, allowing it to be steam-stripped from the solu- follows:
tion. Vapors escaping from both stripping units are passed through
a partial condenser to recover and dispose NH3 and other acid 2H2 S þ SO2 ! 2H2 OðgÞ þ 3=nSn ð2Þ
gases. A typical water wash NH3 removal process reduces COG-
The reaction is performed between 230 and 250 °C over an Al2O3
NH3 content from 200–500 g/100 scf to 2–7 g/100 scf [30].
catalyst.
One disadvantage of the above process is that the high NH3 con-
2.2.2. COG desulfurization tent in acid gas can trigger a secondary route of oxygen consump-
The removal of hydrogen sulfide from COG using NH3 liquor is tion to produce water, N2, and NOx, resulting in low elemental
well-established in the coke-making industry and regarded as a sulfur content. Another major drawback includes the poisoning
sufficiently developed separation process. According to European of the catalyst by H2S. To overcome this problem, a high-tempera-
standards, H2S in COG must be removed to the acceptable residual ture (>1100 °C) catalytic oxidation of H2S is required. The joint
 R. Razzaq et al. / Fuel 113 (2013) 287–299 291

removal of NH3 and H2S from COG using the Ama-sulf technology thermal heat loss via reinforced sealing and the thermal insulation
was thus introduced. This approach involves the partial oxidation of coke oven batteries [40]. Raw COG can be burned on-site for use
of H2S and the simultaneous decomposition of NH3 over a Ni cata- in BFs and in coke batteries in the coking process. Otherwise, the
lyst at 1100 °C to 1200 °C [34,35]. gas can be used to generate steam for power and electricity.
Another challenge to this process is the imperfect H2S separa-
tion from aqueous ammoniacal solution, in which approximately 3.1.1. Direct COG combustion
2% H2S remaining in the stripping solution causes environmental After the subsequent removal of heavy HCs, COG with a heating
problems due to SOx emissions [36]. Park et al. [36] studied the value of approximately 18.6 MJ/m3, can be effectively combusted
selective removal of H2S from COG in the presence of water vapor in small combustion units such as process heaters and boilers.
and NH3 over V2O5/SiO2 and Fe2O3/SiO2 catalysts. The catalysts COG combustion results in the generation of very low levels of haz-
showed high selectivity toward H2S removal, with low SO2 forma- ardous air pollutants, similar to those generated by the natural gas
tion. The results showed a complete conversion of H2S to a mixture combusting unit. COG shares similar combustion properties with
of elemental sulfur and ammonium salt. natural gas (e.g., flame temperature), indicating that both gases
would result in the efficient destruction of combustible organic
3. COG utilization compounds under optimal combustion conditions [41,42].
In China, some indigenous coke ovens are heated via the direct
For both commercial and environmental reasons, particular combustion of COG in a coal carbonization chamber. In the case of
importance is given to the utilization of coke-making by-products, machinery ovens, COG is combusted inside a coal carbonization
including COG. COG contains approximately 30 wt% tar as heavy chamber, and the coke oven is heated via heat transfer between
HCs and 70 wt% in the form of light gases, including bulk H2 and the chamber walls. Some of the coking coal may be burned during
CH4. Conversion of the entire COG (including tar) into lighter fuel the coke-making process because of direct COG combustion in the
constituents can in term of figures meet approximately 4.1% of oven [43].
the global demand for electric power generation [37]. To date, dif-
ferent on-site and off-site COG utilization routes have been pro- 3.1.2. COG combustion for electricity
posed, including energy generation and syn-gas, H2, methanol, In the steel industry, different surplus combustible gases can
and CH4 production (Fig. 2). COG at the high temperature of serve as potential feed stocks to generate heat and electricity for
800 °C has continuously attracted increasing attention as one of combined heat and power plants (CHP). A BFG with a low heating
the most promising sources of H2. Through catalytic reforming value can be mixed with COG to generate sufficient energy for
and water–gas shift reaction (WGSR), the amount of H2 produced power production [44]. The first COG-based CHP system in China
from COG will be several times higher than that of the original has been in operation since 2006 at Shandong Jinneng Coal Gasifi-
H2 in the feed COG [38]. Over the years, hot COG has been cooled cation Co., Ltd. (Jinneng, China). The system consumes 9700 m3/h
and cleaned to obtain a number of important chemicals, including COG at a power generating capacity of approximately 1.60 kW h/
toluene, benzene, and other HCs; this process results in valuable m3, with 3.09 kg simultaneous steam production [45]. Fig. 3 shows
thermal and chemical energy loss. Therefore, the concept of hot a simplified process in a COG-based CHP plant.
COG utilization should be highly considered to address both eco-
nomic and environmental issues [39]. 3.2. Direct reduction iron (DRI) production

3.1. COG combustion Conventional BF iron making is popular throughout the world
because of the readily available coke and continuous improve-
As one of the key discharge products from a coke-making plant, ments in BF technology. BF processes account for almost 90% of
hot COG at a high temperature (800 °C) carries 20–30% valuable the global total iron production. Although the process is regarded
thermal energy. The first step toward COG utilization should al- as highly efficient, it also has some key disadvantages, including
ways be the use of such thermal energy and the reduction of the availability of high metallurgical-grade coke and iron ore as

Fig. 2. Potential routes to COG utilization [10].

292 R. Razzaq et al. / Fuel 113 (2013) 287–299

Fig. 3. Simplified process in a COG-based CHP plant [45].

Fig. 4. A schematic diagram of an integrated COG-based DRI plant in the steel industry [44].

potential feed stocks, high running costs, and the generation of process fuel with hot DRI, before the process fuel is admitted into
gaseous pollutants such as CO2 and sulfur oxide (SOx). The direct the reformer. Alternatively, purified COG can be converted into a
reduction process can serve as a complementary alternative to iron reformed gas under steam reforming, and the resulting gas can
making in the steel industry. The process is regarded as environ- produce DRI (Fig. 4). A mixture of recycled gas from the direct
ment friendly, with less dependence on high-grade metallurgical reduction plant and COG is heated in a reducing gas heater and
coke. During this process, the reduction of iron oxides is conducted introduced as the reducing gas to the reduction zone of the DRI
in a solid state below the fusion temperature of pure Fe. The oxy- reactor. The process is conducted at a counter flow, with an intro-
gen is extracted from the iron ores (Fe2O3/Fe3O4) leaving behind duction of O2 and hot tar gas inducing partial oxidation to produce
gangue constituents (un-valuable minerals) in the sponge iron, DRI. CH4 from COG is converted to H2 and CO at the bottom of the
which must be separated in the electric arc furnace (EAF). Different reduction zone. Gas leaving the DRI reactor is cleaned via CO2 re-
reducing gases are used for this purpose, including CO, CH4, and moval to produce tail gas. The resulting DRI may be used in the
H2; other carbon-bearing materials may also be utilized [46–48]. BF, in the converter, or in the EAF [10,53].
An increase in the use of DRI processes has recently been observed
due to less investment costs as compared to a BF technology 3.3. Feedstock for hydrogen separation
[49,50]. Although DRI produces less amount of CO2 as compared
to BF technology, the amounts off-gas emissions are fairly high Efficient, high-performance, and low-cost technologies for H2
calling for a subsequent gas-recycling during the process [51]. production are urgently needed to boost H2 consumption, which
CH4 is mainly utilized as a reducing gas for DRI production and is is regarded as a future clean energy source. At present, H2 can be
popular among countries with rich natural gas reserves. China re- produced from an extensive range of source materials, including
lies on coke-making and BF processes because of its vast coal re- fossil fuels, alcohol, biomass, and some industrial chemical by-
serves. Natural-gas-based DRI production technology includes products [54,55]. COG containing 50–60% H2 is a high-potential
Midrex and Hyl processes, and the Finmet process, which uses a source of H2, especially in countries with high coke production
fluidized bed [46]. and utilization [56]. Joseck et al. [57] estimated the net amount
COG from an existing coking facility can be used as an alterna- of H2 that can be produced annually from COG is approximately
tive reducing agent to natural gas in the DRI process for steel pro- 370,000 t/yr. The production is based on the following ratios: coke:
duction [44]. Ahrendt and Beggs [52] patented a method coal (0.7 t/t), COG: coke (506 m3/t), and H2:COG (0.043 kg/m3). At
establishing the use of high sulfur-containing COG for the direct present, some on-site coke plants in the steel industry use pressure
reduction of iron oxides. The process is based on an in-situ desul- swing adsorption (PSA) technology to obtain H2 from COG. The
furization of the reducing gas (COG) via the reaction of sulfur in the process is carried out in a cyclic adsorption-desorption operation
 R. Razzaq et al. / Fuel 113 (2013) 287–299 293

Fig. 5. Schematic diagram of H2 separation from COG using the PSA system [57].

using different adsorbant materials such as alumina oxides or zeo- the energy and cost input associated with H2 production [71]. To
lites [24]. Fig. 5 illustrates a typical PSA unit for H2 separation from develop a commercial process for H2 production from COG using
COG. Other important H2 separation techniques include cryogenic a membrane reactor, high-temperature modules with gas-tight
distillation and membrane separation. PSA and cryogenic distilla- seals operating at 850 °C should be fabricated. The large membrane
tion are the two commercially available processes for H2 purifica- area requirement brings additional problems, including sealing
tion but they are considered to be highly energy intensive. and the high pressure drop. Therefore, tubular membranes have
Membrane separation technique provides an attractive alternative been developed to minimize such engineering obstacles, including
to obtain high purity hydrogen using dense metallic membranes. high-temperature seals [72]. Zhang et al. [72] used a high-temper-
The process consumes less energy and provides a possibility of a ature membrane reactor system to assess the oxygen permeation
more continuous operation [58]. Although large scale industrial flux and the conversion of CH4 in COG. The closed-one-ended
application of H2 separation through membrane technology still membrane tube on the stainless steel support was sealed using a
needs to be addressed and more economical and environmentally silver-based reactive-air-brazing alloy with 8 mol% CuO. COG, with
friendly ways to recover H2 from COG would be required in the fu- a typical commercial composition of 57.09% H2, 28.18% CH4, 7.06%
ture [59]. CO, 3.16% CO2, and 4.51% N2, was fed into the membrane reactor
that has its annulus region packed with a commercial Ni-based cat-
3.4. Hydrogen and syn-gas production alyst. Air was blown into a smaller tube inside the membrane tube.
The membrane reactor was operated at 875 °C. CH4 conversion, H2
H2 rich syn-gas is an important raw material in many industrial and CO selectivity, and oxygen permeation fluxes were deter-
processes for the synthesis of different organic chemicals and fuels mined. A CH4 conversion of approximately 95% was achieved,
[60–64]. At present, bulk of syn-gas production comes from steam along with H2 and CO selectivity of approximately 91% and 99%,
reforming of natural gas and oil through a catalytic reaction [65]. respectively.
COG reforming provides an attractive alternative to a less energy Yang et al. [12] also reported the partial oxidation of CH4 in COG
intensive and clean syn-gas production [12,44,66–68]. to syn-gas using a Ba1.0Co0.7Fe0.2Nb0.1O3d membrane in a mem-
brane reactor. The reaction was performed using NiO/MgO as the
3.4.1. Partial oxidation (PO) catalyst. The reforming process was successfully performed at
PO (oxy-reforming) has been highly investigated as a potential 875 °C with 95% CH4 conversion, 80% H2 selectivity, and 106% CO
route to H2 and syn-gas production due to its mild-exothermic nat- selectivity. Cheng et al. [39] achieved H2 enrichment from stimu-
ure making the process more economical and less energy-intensive lated hot COG using a combined medium of a membrane reactor
compared with stream reforming [69]. CH4 oxy-reforming for H2 equipped with a Ru–Ni/Mg(Al)O catalyst. The technique, utilizing
enrichment in COG is attracting considerable attention from both the partial oxidation of HCs under atmospheric pressure, resulted
the academia and the industry. Moreover, the process can also pro- in twice the amount of net H2 present in the feed gas. The aiding
duce syn-gas (H2/CO ratio 2) considered suitable for methanol catalyst used in the process exhibited high catalytic activity and in-
and fischer tropsch synthesis (FTS). Although non-catalytic PO to creased the carbon resistance. Corbo et al. [69] studied H2 produc-
produce syn-gas is a well established process, the use of catalyst tion through the catalytic partial oxidation (CPO) of CH4 and
can significantly reduce the operating conditions i.e. temperature, propane using Ni/Al2O3 and Pt/CeO2 catalysts; both reactions re-
pressure and make process more economical. However, additional sulted in high H2 yields.
problems associated with catalyst deactivation through carbon
deposition and metal sintering should be addressed [70]. Another 3.4.2. Dry (CO2) and steam reforming
problem is the high cost associated with pure oxygen supply. To CH4 reforming of COG for H2 and syn-gas production can also be
address this problem, a new reformer with mixed ionic and elec- achieved through dry and steam reforming reactions [73,74]. Both
tronic conducting oxygen-permeable ceramics is being investi- the reactions are considered to be energy intensive due to their
gated and developed. Most recently, ceramic membrane endothermic nature. Dry reforming produces syn-gas with low
technology has proven quite effective in air separation and natural H2/CO ratio which is more suitable for the production of higher
gas conversion. This technology provides a combination of oxygen HCs. The process contributes towards fixation of two important
separation from air and partial oxidation of CH4 in a single unit. GHGs i.e. CO2 and CH4. However, catalytic deactivation through
The application of this combined technology significantly reduces carbon deposition is a major problem for such a reaction [70,75].
294 R. Razzaq et al. / Fuel 113 (2013) 287–299

Coal char proved to be an active catalyst for CH4 reforming, with surpass 32 million tons each year, with high growth rates nearly
low carbon formation and high selectivity. Zhang et al. [73] re- matching the GDP. COG with high H2 contents is considered ideal
cently investigated the CO2 reforming of CH4 in COG over coal char for a sustainable methanol production. In China, the COG-based
(acting as a catalyst) under the following reactions: methanol production capacity of Shanxi reached 2.06 million tons
in 2006 [80].
CH4 ! C þ 2H2 ð3Þ
Syn-gas produced from COG partial oxidation, dry reforming,
and/or steam reforming is considered highly useful in methanol
CH4 þ CO2 ! 2CO þ 2H2 ð4Þ
synthesis. Although steam reforming of COG has been more inten-
The reaction operates at 700 °C to 1200 °C, and nearly 100% CO2 sively studied compared to dry reforming, the latter has some
conversion was attained at approximately 1065 °C. Fidalgo et al. advantages over the former, including energy savings resulting
[76] studied dry CH4 reforming in a microwave-assisted reactor from CO2 utilization/recycling, as shown in Fig. 6. Moreover, COG
over an activated carbon catalyst. Such heating mechanism proved dry reforming produces syn-gas with a H2:CO ratio of approxi-
superior in CO2 methane reforming compared with conventional mately 2, which is considered ideal for methanol synthesis [16].
methods. Results showed that 100% CH4 and CO2 conversion can During syn-gas production, H2 in the feed COG can cause two
be achieved for a long period at an optimum temperature range major problems: (a) a shift in the reaction equilibrium to the reac-
of 700–800 °C. Certain thermodynamic factors play an important tants, resulting in low CH4 and CO2 conversion to syn-gas; and (b)
role in the COG CH4 conversion to syn-gas via steam, including the induction of the undesired RWGSR. Both effects result in a de-
the H2O:CH4 ratio, the conversion temperature, and the reaction crease in H2 content in the final syn-gas, which in turn results in a
time. Experimental results have shown that a H2O:CH4 ratio be- low H2:CO ratio, which is unsuitable for methanol synthesis. How-
tween 1.1 and 1.3 and a temperature range of 1223–1273 K were ever, results suggested that RWGSR has a more significant effect on
optimum for maximum CH4 conversion. A CH4 conversion of the process compared with the shift in the reaction equilibrium. To
P95% can be achieved over a H2O:CH4 ratio of 1.2 and at a temper- limit H2 consumption under RWGSR, the reaction should be con-
ature of 1223 K [77]. ducted at higher temperatures (P1000 °C) [16]. Maruoka and
Catalytic steam reforming of CH4 is currently the most studied Akiyama [81] proposed a new method for thermal energy recovery
and applied process for H2 enrichment and syn-gas production. from hot flue gases generated by the steel-making convertor. The
The reaction does not need any gas purification system as in case process includes the use of both latent and endothermic heat from
of PO and CO2 reforming. It is also suitable for high pressure appli- the reaction. The stored heat after recovery is supplied to COG to
cations and provides easy separation of products. Moreover, steam induce steam reforming of CH4 and obtain syn-gas, which is then
reforming can produce syn-gas with high H2/CO ratio, which is utilized for methanol synthesis. Results indicated the process to
suitable for the synthesis of different chemicals in many industrial be quite promising for large scale methanol production.
processes [70,74,78]. COG steam reforming process occurs through
the following main reactions [74]: 3.6. COG tar utilization
CH4 þ H2 O $ CO þ 3H2 ð5Þ
Hot COG released at a very high temperature (750–850 °C) from
coking facilities contains 100 g/m3 tar (benzene, toluene, naph-
CH4 þ CO2 $ 2CO þ 2H2 ð6Þ
thalene, and sulfide). Tar separation from hot COG not only results
in valuable heat loss, but also has serious environmental conse-
CO þ H2 O $ CO2 þ H2 ð7Þ
quences, with the additional challenge of recovering tar from the
The product selectivity and final composition may be influenced by stripping liquid. Hot COG tar can be converted into small, lighter
some side reactions including dry reforming (6) and WGSR and re- HCs via catalytic hydro-cracking or reforming reactions using the
verse water–gas shift reaction (RWGSR) (7). During steam reform- sensible heat and chemical energy of hot COG [82,83]. Ni-based
ing, carbon deposition can be successfully addressed by injecting catalysts have been largely investigated for the hydro-cracking of
more steam than required stoichiometrically to carry out the complex higher HCs because of their low cost and high activity.
reforming reaction (H2O/CH4 > 1) [24]. Yang et al. [74] studied However, such catalysts are also prone to sulfur poisoning, carbon
steam reforming of COG using NiO/MgO catalyst. A high CH4 con- deposition, and sintering, especially when operated at high reac-
version (97%) under low steam/carbon (S/C) ratio was achieved tion temperatures, which result in serious catalyst deactivation.
at 875 °C with less carbon deposition and enhanced thermal stabil- A key advantage of using hot COG is its 10–15% water content,
ity. It was revealed that CH4 and CO2 conversions strongly depend which drives the steam reforming reaction to counter coke forma-
upon S/C molar ratio and reaction temperature. Cheng et al. [79] re- tion during COG tar hydro-cracking [82]. Fei et al. [83] used Ni/Ce–
ported H2 enrichment through catalytic reforming of hot COG using ZrO2/Al2O3 catalysts with varying Ni-loading and Ce–Zr contents to
Ni/Mg(Al)O catalysts. The process can successfully utilize the sensi- study the hydro-cracking of a model tar (toluene, naphthalene)
ble heat that may otherwise be wasted resulting in considerable en- from a hot COG. The reaction was conducted at 800 °C under atmo-
ergy loss. Results showed that the amount of H2 in the resultant spheric pressure. The catalyst exhibited high activity, long-term
mixture increased 4-fold in comparison to the starting mixture with stability, and some sulfur tolerance. The tar constituents were all
S/C molar ratio of 1.7. converted into lighter gaseous fuels even at a low steam-to-car-
bon-mole ratio (steam: C = 0.44). Coke formation was negligible
3.5. Methanol synthesis over a 7 h operating period, and the catalyst showed excellent per-
formance in the direct removal of tar compounds in hot COG and
Methanol is an important chemical feedstock that can be used converting them into useful light HCs. Ni/MgO/Al2O3 catalysts
to produce different chemicals, including formaldehyde, methyl [82] also exhibited excellent activity, stability, and carbon resis-
tertiary butyl ether, and acetic acid. Methanol is also used as a tance for the catalytic hydro-cracking of tar in hot COG. The results
key solvent in many industrial processes, as fuel cells in automo- showed complete conversions of tar compounds into light fuel
biles, and for power generation. The production capacity of meth- gases, whereas the presence of H2S in the feed gas actually inhib-
anol in China was expected to reach 25 million tons by the end of ited carbon deposition, resulting in an enhanced catalytic activity
2010, with nearly 80% of the production relying on coal-based and long-term stability. Bimetallic catalysts have also been inves-
technologies. The global demand for methanol is also expected to tigated for the catalytic reforming of tar compounds from hot
 R. Razzaq et al. / Fuel 113 (2013) 287–299 295

Fig. 6. Dry CO2 reforming of COG for methanol synthesis [16].

COG. Catalysts promoted the complete conversion of toluene in hot the catalyst both for the reactivity and selectivity. The methanation
COG tar into light CH4, CO, and CO2 gas molecules between 600 and of CO2 is more rapid and more selective compared with that of CO
750 °C at atmospheric pressure. Therefore, a high H2 content and a over Ni, Fe, Rh, and Ru catalysts [90]. Ni is the most studied and
low reaction temperature promote CH4 formation [84,85]. considered the most suitable catalyst for methanation of carbon
oxides because of its high selectivity for CH4 and its relatively
3.7. COG methanation low price [91–94]. Different support materials have been used for
the dispersion of Ni and other active metals, including SiO2, Al2O3,
The catalytic co-methanation of CO and CO2 (COx) in COG for TiO2, ZrO2, CeO2, and zeolite [95–99]. The activity and selectivity of
CH4 enrichment can be regarded as a simple and highly efficient the supported metal catalysts are strongly affected by the amount
way of producing gas with high heating value and extensive indus- of metal loading, the size of the dispersed metal particles, the inter-
trial and commercial use. COG methanation can occur without the actions between the support and the active species, and the com-
addition of other reagents while CH4 can be separated as a valuable position of the support material [100]. Since methanation is an
and clean fuel. The reaction has been extensively used in the re- exothermic reaction, the reaction heat results in severe metal sin-
moval of carbon oxides from gas mixtures in NH3 plants, as well tering and poor catalytic stability. Therefore, it is imperative to de-
as in H2 purification in refineries and ethylene plants [86]. Sabatier velop highly active low temperature methanation catalysts to
and Senderens [87] first studied the methanation reaction at the ensure long-term thermal stability and also minimize operating
beginning of the 20th century. They found that Ni and other metals costs for large scale industrial applications. Table 4 lists the differ-
(Ru, Rh, Pt, Fe, and Co) catalyze the reaction of CO with H2 to pro- ent catalytic systems used for COx methanation reaction.
duce CH4 and water [88]. Many reactions take place during CO and Catalytic CO and CO2 methanation have been mostly performed
CO2 hydrogenation, and CH4 is formed as a result of the competi- using a fixed-bed catalytic reactor. However, the use of an efficient
tion between such reactions. CO reacts with H2, provided that reactor designed using electrochemical techniques can prove
the stoichiometric ratio of the reactants (H2/CO) is at least 3:1, highly cost-effective and environmentally friendly by providing
according to Eq. (R-1). However, for a feed gas with a low H2/CO maximum yield with minimal waste production [106]. Bebelis
ratio, CO may be hydrogenated via the reaction in Eq. (R-2). CO2 et al. [107] studied the electrochemical CO2 methanation reaction
methanation is carried out under a higher H2/CO2 ratio (Eq. (R- over a Rh/YSZ catalyst and concluded that high CH4 production
3)). Undesired WGS reaction occurs in accordance with Eq. (R-4) rates can be achieved as a result of an increase in the Rh catalyst
which may significantly affect CH4 selectivity. Another reaction potential (electrophobic property) while operating at a tempera-
(Eq. (R-5)) may also occur in case of low H2/CO ratio, resulting in ture range of 346–477 °C. An extensive experimental study on
carbon formation and catalyst deactivation [88,89]. the methanation reaction using a fluidized bed reactor operated
at 320 °C has also been conducted very recently. For all the exper-
CO þ 3H2 $ CH4 þ H2 OðgÞ DH0289K ¼ 206:2 kJ=mol ðR-1Þ iments, a commercially synthesized Ni/Al2O3 catalyst with a large
surface area was used. The reactor achieved 100% CO conversion
2CO þ 2H2 $ CH4 þ CO2 DH0289K ¼ 247:3 kJ=mol ðR-2Þ to CH4. The experimental results revealed that the methanation
activity inside a fluidized reactor is significantly affected both ther-
CO2 þ 4H2 $ CH4 þ 2H2 OðgÞ DH0289K ¼ 164:9 kJ=mol ðR-3Þ modynamically and by the reaction boundary conditions. More-
over, an additional benefit of a zero-carbon deposition was also
CO þ H2 O $ CO2 þ H2 DH0289K ¼ 41:2 kJ=mol ðR-4Þ achieved, providing the catalyst with high durability and enhanced
lifetime [88].
2CO $ C þ CO2 DH0289K ¼ 172:54 kJ=mol ðR-5Þ
The methanation reaction for CO and CO2 is usually performed 4. Overview of COG utilization technology
between 150 and 400 °C in a catalytic reactor. The choice and prep-
aration of the catalyst is the most crucial stage in CH4 synthesis COG processing and utilization will not only boost the energy
using COG. Numerous studies have revealed the importance of efficiency of the steel industry but also prevent the emission of
296 R. Razzaq et al. / Fuel 113 (2013) 287–299

Table 4
Comparison between the different catalysts used for COx methanation reported in literature.

Catalyst Preparation method %XCO %XCO2 Highlights Ref.

Ni–Co/CeO2–ZrO2 Co-precipitation 100 95 – Feed gas with similar composition to COG [101]
– High COx conversion
– CH4 selectivity of 99%
Ni/ZrO2 Wet-impregnation 100 100 – Low temperature COx methanation [91]
– Promising system for H2 purification
Co3O4 Precipitation 100 _ – CO methanation in COG [102]
– Catalyst active at very low temperature (177 °C)
Ni/Zr–Sm Oxidation reduction 100 30 – Complete CO conversion at 200 °C [21]
treatment
– High conversion attained using a second reactor in series
– Long-term stability
Ru/carbon Wet-impregnation 100 50 – Complete CO conversion at 340 °C for solo CO methanation – Poor methanation activity for [103]
nanofibers CO/CO2 mixtures
– Undesired RWGSR can be inhibited by injecting 30% water (steam)
Ru/Al2O3 Impregnation 100 20 – Complete selective CO methanation at 220 °C [104]
– Operating at high gas-hourly-space-velocity
– Very low H2 consumption
Rh/Al2O3 Impregnation 99.9 30 – Higher CO conversion [86]
– CO2 suppression caused by addition of 30% water content
– 99% CH4 selectivity
Ru/TiO2 Wet-impregnation 100 _ – Complete and selective CO methanation at 230 °C [105]
– Long-term catalyst stability

Table 5
Technological evaluation of different COG utilization routes.

COG utilization Technology Advantages Disadvantages

COG combustion – Direct combustion – Easy on-site implementation – Problems of COG surplus
– Steam and electricity – Low operating cost – Need to remove heavy HCs
generation
– Simple in operation – Combustion inefficiencies
DRI production – COG as reducing gas – Easy to industrialize – COG purification and reforming requirements
– Low investment costs – Potential SOx emissions
– Lower energy consumption – Greater amounts of off-gas emissions
– Enhanced steel quality – Resource issues
– Less CO2 emissions – Early stages of development
Hydrogen separation – PSA – Developed both industrially and commercially – Adsorbant recycling issues
– Highly energy intensive
– Requires purification of heavy and light HCs
– Membrane separation – High purity H2 – Less developed industrially
– Consumes less energy – Separation required for heavy HCs
– Low capital and operating costs
– Simple and Continuous operation
– Cryogenic distillation – Commercially available process – High operating costs
– High H2 purity – Needs further development
Hydrogen and syn-gas – Partial oxidation – Low Operating costs – Problems associated with pure oxygen supply
production
– Less energy intensive – Carbon deposition and metal sintering in case of a
catalytic system
– High energy efficiency
– Ideal syn-gas ratio for fine chemical synthesis
– Dry reforming – High product selectivity – Energy intensive process
– Potential utilization of GHGs (CO2, CH4) – Low H2/CO ratio
– Low H2/CO ratio suitable for higher HC synthesis – High carbon deposition
– Steam reforming – H2 enrichment – Energy intensive process
– Low carbon deposition – High H2/CO ratio needs adjustment for methanol
and/or FTS
– Suitable for high pressure applications
– Ease of product separation
Methanol synthesis – Partial oxidation – CO2 utilization/recycling – Issues relating H2/CO ratio adjustment
– Dry reforming – Ideal H2/CO ratio for methanol synthesis in case of – Technology under development
dry reforming
– Steam reforming – Industrially viable process
COG tar utilization – Hydro-cracking – Hot COG utilization – Carbon deposition and catalyst deactivation
– Tar reforming – Eliminates tar separation process – Technology under development
– Recovery of valuable energy (sensible heat and
chemical energy)
COG methanation – Methane enrichment – Simple in operation – Carbon deposition
– High COx conversion – Metal sintering
– High CH4 selectivity – Technology under development
 R. Razzaq et al. / Fuel 113 (2013) 287–299 297

harmful green house gases (GHGs) including CO2 and CH4. COG Another running project by Camco-Eurofo in Shanxi Province cap-
with high H2 contents carries huge industrial and commercial va- tures waste COG for power generation in a combined cycle power
lue considering the future hydrogen economy. At present many plant (CCPP). The unit is expected to generate 864,667 MW h of
steel enterprises are trying to minimize their COG surplus while electricity per year, with an annual 849,576 ton CO2 emission
utilizing the gas in different on-site process during steel making. reduction [114].
Although extensive research and development has been carried The COG-based methanol production project, one of the largest
out to utilize COG surplus, substantial amount of COG is still being of its kind, began production in 2009 in Changzhi City, China. It is a
wasted resulting in poor production efficiencies and GHG emis- multi-investor project run by the Tianji Coal Chemical Industry
sions. Table 5 provides a summary of different COG utilization pro- Group Co., Ltd. and the Shanxi Lu’an Environmental Energy Devel-
cesses with some key advantages and disadvantages. opment Co., Ltd. The project is designed to recover 400 million m3
of raw COG to be converted into 300,000 tons of refined methanol,
11,000 tons of crude benzene, and 10,000 tons of ammonium sul-
5. COG investment and economy
fate each year. Both investors poured 1.36 billion CNY into the pro-
ject, with expectations of further technological advancements in
COG with high energy content not only serves as an important
the COG utilization field [115]. Recently, another methanol produc-
heat and power source for a coking facility, but is also an important
tion plant of the Wuhai Shenhua Energy Company in the Xilaifeng
feedstock from which a number of valuable chemicals and byprod-
Industrial Zone has been placed in the production line. This COG-
ucts can be recovered.
to-methanol production unit is based on a new energy-efficient
and cost-effective patent technology developed by Sichuan Tianyi
5.1. World scenario Science and Technology. The plant is expected to reduce coal-based
methanol production costs by 1100–1200 yuan/ton and gas-based
In the past, US iron and steel industry relied heavily on by-prod- methanol by 800–1000 yuan/ton, thereby enabling China to com-
ucts such as COG for its electricity production. However, with the pete with the Middle East, which enjoys the lowest cost in natural
increase in natural gas supply and reliance on electric arc furnaces, gas-based methanol production in the world [116].
the on-site COG utilization for self-generated electricity has de- For a typical COG plant, the determination of product costs,
clined significantly [108]. Almost 40% of the COG produced in the including purified COG, tar, benzene, and sulfate, helps in deter-
US is now being utilized as a fuel in BF to replace part of the natural mining the overall efficiency of the process. Cost analysis of COG
gas. US Steel Corp. has reported an annual savings of over 6 million in coke plants is conducted on the basis of planned profit levels
dollars with a payback period of less than a year while utilizing for commercial purified COG minus the cost associated with the re-
COG as BF fuel. The company with a state-of-the art COG process- moval of NH3, aromatic HCs (tar), and H2S from raw gas. On such
ing and cleaning facility at Clairton coke plant, processes the COG basis, the raw material (coking coal) should also be considered to
until its content is approximately 50–60% H2. Moreover, the sulfur achieve an improved cost distribution between raw materials
content of the COG is significantly reduced during the cleaning and products. Hence, the total net cost of individual products
processing, allowing it to be used efficiently in the BF [109]. should be distributed with respect to the relative volumes in which
COG with a low calorific value can be burnt in specially adapted they are produced [117].
turbines with up to 33% efficiency. Mitsubishi Heavy Industries has
successfully developed such turbines which are installed in many
steel plants around the world such as Kawasaki Chiba Works (Ja- 6. Concluding remarks
pan) and Corus Ijmuiden (Netherland) [110]. In Brazil, the Com-
panhia Siderurgica Tubaro (CST) power project based on the The fast economic growth rate of China is pushing its energy
Rankine regenerative cycle, utilizes off-gasses such as COG and sector to the limit, with some serious environmental conse-
BFG with a total capacity of about 200 MW [22]. A Swedish based quences. As the largest producer and consumer of coke, China re-
SSAB Strip Products which is an integrated steel plant is consider- lies heavily on its vast coal reserves to meet its energy demand.
ing COG reforming for methanol production. The company esti- The coal chemical industry in China is expected to become an
mates that approximately 400 GW h of COG would be available important player in ensuring a sustainable development for a
per year for methanol production, yielding approximately green future.
300 GW h of methanol [111]. In Ukraine, The Alchevsk Coke Plant COG is an important and valuable by-product produced during
power generating project with waste heat recovery is successfully the coke-making process in the iron and steel industries. China
installed to displace the use of natural gas and grid electricity. The annually produces large amounts of COG, but most of the gas is
system consists of a highly efficient boiler firing COG and BFG cou- not recovered and used to its potential. COG contains valuable
pled with a 9 MW turbine generator with a net annual power gen- combustible constituents, such as CH4 and H2, with a reasonable
erating capacity of 54 GW h [112]. heating value. The first step toward COG utilization is its recovery
and purification from a coke battery. Hot COG can be used in a BF
5.2. China’s perspective as make-up gas or in heating furnaces within a coking facility. Raw
COG is sent to a treatment plant for NH3, H2S, and tar (BTX) re-
Given its high COG throughput, China proves an ideal place for moval. Different by-products obtained during COG purification
research and investment in sustainable COG utilization technolo- can be marketed and individually sold.
gies. Haldor Topsoe, a Danish-based company, has signed contracts COG after purification is considered suitable for H2, syn-gas, and
to build two of the world’s largest COG plants in China to replace methanol production. The large amount of H2 in COG can be effi-
natural gas (SNG) plants. The project is under contract with China ciently separated using the PSA technology. Installing a PSA unit
Natural Gas Corporation Limited (CNGCL), operating under the Pet- to recover H2 from COG for onsite use or separate sale is highly rec-
ro-China Group. The plant in Wuhai is set to convert waste COG ommended in the steel industry. The high H2 content of COG also
into clean and valuable liquefied natural gas (LNG). The production makes COG an ideal feedstock for syn-gas and methanol produc-
facility has a capacity of 650 million N m3 of LNG/yr and is ex- tion. The installation of such COG utilization units within a coking
pected to be in operation by 2012. The facility will be a model facility can promote the self-sufficiency and environmental friend-
for sustainable development for the energy sector in China [113]. liness of the steel industry.
298 R. Razzaq et al. / Fuel 113 (2013) 287–299

Enrichment of the CH4 content in COG can also be achieved [20] Kustov AL, Frey AM, Larsen KE, Johannessen T, Nørskov JK, Christensen CH. CO
methanation over supported bimetallic Ni–Fe catalysts: from computational
through catalytic co-methanation of CO and CO2. Research is
studies towards catalyst optimization. Appl Catal A – Gen 2007;320:98–104.
needed in developing a highly active and stable methanation cata- [21] Habazaki H, Yamasaki M, Zhang B-P, Kawashima A, Kohno S, Takai T, et al. Co-
lyst that could promote the complete COx conversion at a low tem- methanation of carbon monoxide and carbon dioxide on supported nickel
perature and, at the same time, maintain high CH4 selectivity. and cobalt catalysts prepared from amorphous alloys. Appl Catal A – Gen
1998;172:131–40.
Although large-scale, cost-effective commercial COG methanation [22] Modesto M, Nebra SA. Exergoeconomic analysis of the power generation
may not be viable, a small pilot scale can be successfully applied system using blast furnace and coke oven gas in a Brazilian steel mill. Appl
within a coking facility, depending on the COG availability and Therm Eng 2009;29:2127–36.
[23] Liao H, Li B, Zhang B. Pyrolysis of coal with hydrogen-rich gases. 2.
CH4 demand. Desulfurization and denitrogenation in coal pyrolysis under coke-oven gas
For the past few years, research and development in COG utili- and synthesis gas. Fuel 1998;77:1643–6.
zation technology have made it a highly commercial and profitable [24] Bermúdez JM, Arenillas A, Luque R, Menéndez JA. An overview of novel
technologies to valorise coke oven gas surplus. Fuel Process Technol
industry in China, attracting both local and international investors. 2013;110:150–9.
Aside from some installed COG recovery and utilization facilities, a [25] Basu P, Cen K, Jestin L. Boilers and burners: design and theory. Springer; 2000.
number of projects are in the pipeline to effectively harness COG [26] Ray HS, Sing BP, Bhattacharjee S, Misra VN. Energy in minerals and
metallurgical industries. New Delhi: Allied Publishers; 2005.
for power, LNG, and methanol production on a large commercial [27] Gupta CK. Chemical metallurgy: principles and practice. John Wiley & Sons;
scale. 2006.
[28] Faber R, Li P, Wozny G. Sequential parameter estimation for large-scale
systems with multiple data sets. 2. Application to an industrial coke-oven-gas
Acknowledgement purification process. Ind Eng Chem Res 2004;43:4350–62.
[29] Wright K. Coke oven gas treatment; tar, liquor, ammonia; 2011.
[30] Kohl AL, Nielsen RB. Gas purification. Texas: Gulf Professional Publishing;
The authors gratefully acknowledge financial support from the 1997.
National Natural Science Foundation of China (No. 21006113 and [31] Cheremisinoff NP. Handbook of air pollution prevention and control.
51104140), the National High Technology Research and Develop- Butterworth-Heinemann; 2002.
[32] Kazak LA, Syrova LF, Moralina NF, Li VM, Romanov VN. Final cooling of coke
ment Program of China (No. 2011AA050606). oven gas. Coke Chem 2010;53:405–9.
[33] Riegel ER, Kent JA. Riegel’s handbook of industrial chemistry. Springer; 2003.
[34] Platonov OI. Desulfurization of coke-oven gas. Coke Chem 2007;50:226–31.
References [35] Nazarov VG, Zubitskii BD. Promising technologies for processing coke-oven
gas at Russian enterprises. Coke Chem 2008;51:62–7.
[1] Abdullah AZ, Razali N, Mootabadi H, Salamatinia B. Critical technical areas for [36] Park DW, Chun SW, Jang JY, Kim HS, Woo HC, Chung JS. Selective removal of
future improvement in biodiesel technologies. Environ Res Lett 2007;2:1–6. H2S from coke oven gas. Catal Today 1998;44:73–9.
[2] Lior N. Energy resources and use: the present (2008) situation and possible [37] Li L, Morishita K, Takarada T. Light fuel gas production from nascent coal
sustainable paths to the future. Energy 2010;35:2631–8. volatiles using a natural limonite ore. Fuel 2007;86:1570–6.
[3] Ito T, Chen Y, Ito S, Yamaguchi K. Prospect of the upper limit of the energy [38] Cheng H, Lu X, Hu D, Zhang Y, Ding W, Zhao H. Hydrogen production by
demand in China from regional aspects. Energy 2010;35:5320–7. catalytic partial oxidation of coke oven gas in BaCo0.7Fe0.2Nb0.1O3Ld
[4] Cattaneo C, Manera M, Scarpa E. Industrial coal demand in China: a provincial membranes with surface modification. Int J Hydrogen Energy
analysis. Resour Energy Econ 2011;33:12–35. 2011;36:528–38.
[5] Yue B, Wang X, Ai X, Yang J, Li L, Lu X, et al. Catalytic reforming of model tar [39] Cheng H, Lu X, Liu X, Zhang Y, Ding⁄ W. Partial oxidation of simulated hot
compounds from hot coke oven gas with low steam/carbon ratio over Ni/ coke oven gas to syngas over Ru–Ni/Mg(Al)O catalyst in a ceramic membrane
MgO–Al2O3 catalysts. Fuel Process Technol 2010;91:1098–104. reactor. J Nat Gas Chem 2009;18:467–73.
[6] Coal statistics; 2010. <http://www.worldcoal.org/resources/coal-statistics/> [40] Bisio G, Rubatto G. Energy saving and some environment improvements in
[accessed 02.08.11]. coke-oven plants. Energy 2000;25:247–65.
[7] Guo ZC, Fu ZX. Current situation of energy consumption and measures taken [41] Institute AIaS. Saving one barrell of oil per ton (SOBOT). A new roadmap for
for energy saving in the iron and steel industry in China. Energy transformation of steelmaking process; 2005.
2010;35:4356–60. [42] Institute Acacc. Regulation of sources firing coke oven gas under the
[8] International Energy Agency. Tracking industrial energy efficiency and CO2 industrial combustion coordinated rulemaking (ICCR); 1998.
emissions: In support of the G8 plan of action. France: Energy Indicators; [43] Polenske KR. The technology energy environment health (TEEH) chain in
2007. China: a case study of cokemaking. Springer; 2006.
[9] Dıez MA, Alvarez R, Barriocanal C. Coal for metallurgical coke production: [44] Johansson MT, Soderstrom M. Options for the Swedish steel industry – energy
predictions of coke quality and future requirements for coke making. Int J efficiency measures and fuel conversion. Energy 2011;36:191–8.
Coal Geol 2002;50:389–412. [45] Coke oven gas; 2011. <http://mysolar.cat.com/cda/layout?m=299939&x=7>
[10] Diemer P, Killich HJ, Knop K, Lüngen HB, Reinke M, Schmöle P. Potentials for [accessed 17.12.11].
utilization of coke oven gas in integrated iron and steel works. In: 2nd [46] Xu C, Da-qiang C. A brief overview of low CO2 emission technologies for iron
International meeting on ironmaking/1st international symposium on iron and steel making. J Iron Steel Res Int 2010;17:01–7.
ore, September 12–15, 2004. Vitoria, Espirito Santo, Brazil; 2004. [47] Chukwuleke OP, Cai J-j, Chukwujekwu S, Xiao S. Shift from coke to coal using
[11] Yue B, Wang X, Ai X, Yang J, Li L, Lu X, et al. Catalytic reforming of model tar direct reduction method and challenges. J Iron Steel Res Int 2009;16:1–5.
compounds from hot coke oven gas with low steam/carbon ratio over Ni/ [48] Kuramochi T, Ramírez A, Turkenburg W, Faaij A. Comparative assessment of
MgO–Al2O3 catalysts. Fuel Process Technol 2010;91:1098–104. CO2 capture technologies for carbon-intensive industrial processes. Prog
[12] Yang Z, Ding W, Zhang Y, Lu X, Zhang Y, Shen P. Catalytic partial oxidation of Energy Combust Sci 2012;38:87–112.
coke oven gas to syngas in an oxygen permeation membrane reactor [49] Price L, Sinton J, Worrell E, Phylipsen D, Xiulian H, Ji L. Energy use and carbon
combined with NiO/MgO catalyst. Int J Hydrogen Energy 2010;35:6239–47. dioxide emissions from steel production in China. Energy 2002;27:429–46.
[13] Purwanto H, Akiyama T. Hydrogen enrichment technology development [50] Johansson MT, Söderström M. Options for the Swedish steel industry – energy
using a by-product gas in the steel making processes. Curr Adv Mater efficiency measures and fuel conversion. Energy 2011;36:191–8.
Processes 2005;18(1):272. [51] Hu C-q, Chen L-y, Zhang C-x, Qi Y-h, Yin R-y. Emission mitigation of CO2 in
[14] Onozaki M, Watanabe K, Hashimoto T, Saegusa H, Katayama Y. Hydrogen steel industry: current status and future scenarios. J Iron Steel Res Int
production by the partial oxidation and steam reforming of tar from hot coke 2006;13:38–52.
oven gas. Fuel 2006;85:143–9. [52] Ahrendt WA, Beggs D. Apparatus for direct reduction of iron using high sulfur
[15] Zhang Y, Li Q, Shen P, Liu Y, Yang Z, Ding W, et al. Hydrogen enrichment of gas. US patent 4270739; 1981.
coke oven gas by reforming of methane in a ceramic membrane reactor. Int J [53] Chatterjee A. Sponge iron production by direct reduction of iron oxide. PHI
Hydrogen Energy 2008;33:3311–9. Learning Pvt. Ltd.; 2010.
[16] Bermúdez JM, Fidalgo B, Arenillas A, Menéndez JA. Dry reforming of coke [54] Weinert JX, Shaojun L, Ogden JM, Jianxin M. Hydrogen refueling station costs
oven gases over activated carbon to produce syngas for methanol synthesis. in Shanghai. Int J Hydrogen Energy 2007;32:4089–100.
Fuel 2010;89:2897–902. [55] Chun YN, Song HW, Kim SC, Lim MS. Hydrogen rich gas production from
[17] Park J-N, McFarland EW. A highly dispersed Pd–Mg/SiO2 catalyst active for biogas reforming using plasmatron. Energy Fuels 2008;22:123–7.
methanation of CO2. J Catal 2009;266:92–7. [56] Onozaki M, Watanabe K, Hashimoto T, Saegusa H, Katayama Y. Hydrogen
[18] Jacquemin M, Beuls A, Ruiz P. Catalytic production of methane from CO2 and production by the partial oxidation and steam reforming of tar from hot coke
H2 at low temperature: insight on the reaction mechanism. Catal Today oven gas. Fuel Process Technol 2006;85:143–9.
2010;157:462–6. [57] Joseck F, Wang M, Wu Y. Potential energy and greenhouse gas emission
[19] Sharma S, Hu Z, Zhang P, McFarland EW, Metiu H. CO2 methanation on Ru- effects of hydrogen production from coke oven gas in U.S. steel mills. Int J
doped ceria. J Catal 2011;278:297–309. Hydrogen Energy 2008;33:1445–54.
 R. Razzaq et al. / Fuel 113 (2013) 287–299 299

[58] Adhikari S, Fernando S. Hydrogen membrane separation techniques. Ind Eng investigation of hydrodynamics, mass transfer effects and carbon
Chem Res 2006;45:875–81. deposition. Chem Eng Sci 2011;66:924–34.
[59] Shen J, Wang Z-z, Yang H-w, Yao R-s. A new technology for producing [89] Sehested J, Dahl S, Jacobsen J, Nielsen JRR. Methanation of CO over nickel:
hydrogen and adjustable ratio syngas from coke oven gas. Energy Fuels mechanism and kinetics at high H2/CO ratios. J Phys Chem B
2007;21:3588–92. 2005;109:2432–8.
[60] Edwards JH, Maitra AM. The chemistry of methane reforming with carbon [90] Fujita S, Terunuma H, Nakamura M, Takezawa N. Mechanisms of methanation
dioxide and its current and potential applications. Fuel Process Technol of CO and CO2 over Ni. Ind Eng Chem Res 1991;30:1146–51.
1995;42:269–89. [91] Da Silva DCD, Letichevsky S, Borges LEP, Appel LG. The Ni/ZrO2 catalyst and
[61] Wang X, Li M, Wang M, Wang H, Li S, Wang S, et al. Thermodynamic analysis the methanation of CO and CO2. Int J Hydrogen Energy 2012;37:8923–8.
of glycerol dry reforming for hydrogen and synthesis gas production. Fuel [92] Zhao A, Ying W, Zhang H, Ma H, Fang D. Ni–Al2O3 catalysts prepared by
2009;88:2148–53. solution combustion method for syngas methanation. Catal Commun
[62] Xu B-Q, Sun K-Q, Zhu Q-M, Sachtler WMH. Unusual selectivity of oxygenate 2012;17:34–8.
synthesis: formation of acetic acid from syngas over unpromoted Rh in NaY [93] Jwa E, Lee SB, Lee HW, Mok YS. Plasma-assisted catalytic methanation of CO
zeolite. Catal Today 2000;63:453–60. and CO2 over Ni–zeolite catalysts. Fuel Process Technol 2013;108:89–93.
[63] Liu Y, Murata K, Inaba M, Takahara I, Okabe K. Synthesis of ethanol from [94] Gao J, Jia C, Li J, Gu F, Xu G, Zhong Z, et al. Nickel catalysts supported on
syngas over Rh/Ce1xZrxO2 catalysts. Catal Today 2011;164:308–14. barium hexaaluminate for enhanced CO methanation. Ind Eng Chem Res
[64] Gutiérrez Ortiz FJ, Serrera A, Galera S, Ollero P. Methanol synthesis from 2012;51:10345–53.
syngas obtained by supercritical water reforming of glycerol. Fuel [95] Park J-N, Mc Farland EW. A highly dispersed Pd–Mg/SiO2 catalyst active for
2013;105:739–51. methanation of CO2. J Catal 2009;266:92–7.
[65] Ramos L, Zeppieri S. Feasibility study for mega plant construction of synthesis [96] Galletti C, Specchia S, Saracco G, Specchia V. CO-selective methanation over
gas to produce ammonia and methanol. Fuel 2013;110:141–152. Ru–cAl2O3 catalysts in H2-rich gas for PEM FC applications. Chem Eng Sci
[66] Guo J, Hou Z, Gao J, Zheng X. Production of syngas via partial oxidation and 2010;65:590–6.
CO2 reforming of coke oven gas over a Ni catalyst. Energy Fuels [97] Takenaka S, Shimizu T, Otsuka K. Complete removal of carbon monoxide in
2008;22:1444–8. hydrogen-rich gas stream through methanation over supported metal
[67] Bermúdez JM, Fidalgo B, Arenillas A, Menéndez JA. CO2 reforming of coke catalysts. Int J Hydrogen Energy 2004;29:1065–73.
oven gas over a Ni/cAl2O3 catalyst to produce syngas for methanol synthesis. [98] Tada S, Shimizu T, Kameyama H, Haneda T, Kikuchi R. Ni/CeO2 catalysts with
Fuel 2012;94:197–203. high CO2 methanation activity and high CH4 selectivity at low temperatures.
[68] Li YB, Xiao R, Jin BS. Thermodynamic equilibrium calculations for the Int J Hydrogen Energy 2012;37:5527–31.
reforming of coke oven gas with gasification gas. Chem Eng Technol [99] Eckle S, Augustin M, Anfang H-G, Behm RJ. Influence of the catalyst loading on
2007;30:91–8. the activity and the CO selectivity of supported Ru catalysts in the selective
[69] Corbo P, Migliardini F. Hydrogen production by catalytic partial oxidation of methanation of CO in CO2 containing feed gases. Catal Today
methane and propane on Ni and Pt catalysts. Int J Hydrogen Energy 2012;181:40–51.
2007;32:55–66. [100] Czekaj I, Loviat F, Raimondi F, Wambach J, Biollaz S, Wokaun A.
[70] Andrew PE, York, Tiancun Xiao, Green MLH. Brief overview of the partial Characterization of surface processes at the Ni-based catalyst during the
oxidation of methane to synthesis gas. Top Catal 2003;22:345–58. methanation of biomass-derived synthesis gas: X-ray photoelectron
[71] Zhang Y, Liu J, Liu Y, Ding W, Lu X. Perovskite type oxygen permeable spectroscopy (XPS). Appl Catal A – Gen 2007;329:68–78.
membrane BaCo0.7Fe0.2Nb0.1O3d for partial oxidation of methane in coke [101] Razzaq R, Zhu H, Jiang L, Muhammad U, Li C, Zhang S. Catalytic methanation
oven gas to hydrogen. Rare Metals 2010;29:231–7. of CO and CO2 in coke oven gas over Ni–Co/ZrO2–CeO2. Ind Eng Chem Res
[72] Zhang Y, Cheng H, Liu J, Ding W. Performance of a tubular oxygen-permeable 2013;52:2247–56.
membrane reactor for partial oxidation of CH4 in coke oven gas to syngas. J [102] Zhu H, Razzaq R, Jiang L, Li C. Low-temperature methanation of CO in coke
Nat Gas Chem 2010;19:280–3. oven gas using single nanosized Co3O4 catalysts. Catal Commun
[73] Zhang G, Dong Y, Feng M, Zhang Y, Zhaoa W, Cao H. CO2 reforming of CH4 in 2012;23:43–7.
coke oven gas to syngas over coal char catalyst. Chem Eng J [103] Jiménez V, Sánchez P, Panagiotopoulou P, Valverde JL, Romero A.
2010;156:519–23. Methanation of CO, CO2 and selective methanation of CO, in mixtures of CO
[74] Yang Z, Zhang Y, Wang X, Zhang Y, Lu X, Ding W. Steam reforming of coke and CO2, over ruthenium carbon nanofibers catalysts. Appl Catal A – Gen
oven gas for hydrogen production over a NiO/MgO solid solution catalyst. 2010;390:35–44.
Energy Fuels 2009;24:785–8. [104] Dagle RA, Wang Y, Xia G-G, Strohm JJ, Holladay J, Palo DR. Selective CO
[75] Wang S, Lu GQ, Millar GJ. Carbon dioxide reforming of methane to produce methanation catalysts for fuel processing applications. Appl Catal A – Gen
synthesis gas over metal-supported catalysts: state of the art. Energy Fuels 2007;326:213–8.
1996;10:896–904. [105] Panagiotopoulou P, Kondarides DI, Verykios XE. Selective methanation of CO
[76] Fidalgo B, Domınguez A, Pis JJ, Menendez JA. Microwave-assisted dry over supported Ru catalysts. Appl Catal B – Environ 2009;88:470–8.
reforming of methane. Int J Hydrogen Energy 2008;33:4337–44. [106] Wang W, Wang S, Ma X, Gong J. Recent advances in catalytic hydrogenation
[77] Zhang J, Zhang X, Chen Z, Li L. Thermodynamic and kinetic model of of carbon dioxide. Chem Soc Rev 2011;40:3703–27.
reforming coke-oven gas with steam. Energy 2010;35:3103–8. [107] Bebelis S, Karasali H, Vayenas CG. Electrochemical promotion of
[78] Rakass S, Oudghiri-Hassani H, Rowntree P, Abatzoglou N. Steam reforming of CO2 hydrogenation over Rh/YSZ electrodes. J Appl Electrochem 2008;38:
methane over unsupported nickel catalysts. J Power Sources 1127–33.
2006;158:485–96. [108] Ruth M, Amato A. Vintage structure dynamics and climate change policies:
[79] Cheng H, Yue B, Wang X, Lu X, Ding W. Hydrogen production from simulated the case of US iron and steel. Energy Policy 2002;30:541–52.
hot coke oven gas by catalytic reforming over Ni/Mg(Al)O catalysts. J Nat Gas [109] Richlen S. Using coke oven gas in a blast furnace saves over 6$ million
Chem 2009;18:225–31. annually at a steel mill. In: OoITEEaR energy. U.S. Department of Energy,
[80] Xie K, Li W, Zhao W. Coal chemical industry and its sustainable development Washington; 2000.
in China. Energy 2010;35:4349–55. [110] Worrell E, Neelis M, Price L. Energy efficiency and carbon dioxide emissions
[81] Maruoka N, Akiyama T. Exergy recovery from steelmaking off-gas by latent reduction opportunities in the US iron and steel sector. Ernest Orlando
heat storage for methanol production. Energy 2006;31:1632–42. Lawrence Berkeley National Laboratory, LBNL-41724; 1999.
[82] Yang J, Wang X, Li L, Shen K, Lu X, Ding W. Catalytic conversion of tar from hot [111] Johansson MT, Söderström M. Options for the Swedish steel industry –
coke oven gas using 1-methylnaphthalene as a tar model compound. Appl energy efficiency measures and fuel conversion. Energy 2011;36:191–8.
Catal B – Environ 2010;96:232–7. [112] Nordic Environment Finance Corporation (NEFCO). Baltic Sea Region testing
[83] Fei Y, Baohua Y, Xueguang W, Shuhua G, Xionggang L, Weizhong D. ground facility project profile: Alchevsk Coke Plant Waste Heat Recovery
Hydrocracking of tar components from hot coke oven gas over a Ni/Ce– Project, Ukraine; 2012. <http://www.nefco.org/cff>.
ZrO2/c-Al2O3 catalyst at atmospheric pressure. Chin J Catal 2009;30:690–6. [113] Haldor Topsoe awarded the world’s largest coke oven gas to SNG plants in
[84] Cheng HW, Lu XG, Hu DH, Ding WZ. Catalytic reforming of model tar China; 2011. <http://www.topsoe.com/news/News/2011/070411.aspx>
compounds from hot coke oven gas for light fuel gases production over [accessed 17.08.11].
bimetallic catalysts. Adv Mater Res 2010;152–153:860–3. [114] Improving China’s industrial efficiency through technology transfer; 2011.
[85] Cheng HW, Lu XG, Ding WZ, Zhong QD. Catalytic reforming of model tar <http://www.eccm.uk.com/en/casestudyeurofo.html> [accessed 17.08.11].
compounds from hot coke oven gas over Pd promoted Ni/Mg(Al)O catalysts. [115] New coke-oven gas to methanol production line runs in Shanxi; 2009. <http://
Adv Mater Res 2011;197–198:711–4. chemguide.asia/news/2009/05/26/coke-oven.html> [accessed 17.08.11].
[86] Panagiotopoulou P, Kondarides DI, Verykios XE. Selective methanation of CO [116] World’s single largest coke-oven gas-based methanol unit goes into
over supported noble metal catalysts: effects of the nature of the metallic operation; 2010. <http://www.chemchina.com/wps/wcm/connect/
phase on catalytic performance. Appl Catal A – Gen 2008;344:45–54. libchemchina/siteenglish/areanewsandvideos/areanews_en/899adc8044fed
[87] Sabatier P, Senderens JB. New methane synthesis. C R Acad Sci Paris 79ebb80bb5174f66c04> [accessed 17.08.11].
1902;134:514–6. [117] Vashchilin SV, Osipovich TV, Ermolenko TA, Kotlyarov EI, Kornilova VA,
[88] Kopyscinski J, Schildhauer TJ, Biollaz SMA. Methanation in a fluidized bed Chefranova LS. Improved cost calculations of coke-oven gas at coke plants.
reactor with high initial CO partial pressure: Part I – experimental Coke Chem 2009;52:186–8.