09 Comb&ion (burners, combustion systems)

01101781 Computational evaluation of low NO, operating Hz in HZ/air flames. In the present paper we mobilize and extend some
conditions in arch-fired boilers relevant research which, among other things, proves this particular
Fueyo, N. et al. J. Eng. Gas Turbines Power, 1999, 121, (4), 735-740. viewpoint to be untrustworthy, replacing it with more robust and
In the present paper, a computational model is used to simulate the readily used criteria tailored to high molecular weight (SC > 1) species.
aerodynamic, thermal, and chemical conditions inside an arch-fired As an immediate corollary of the results presented/discussed here,
coal boiler. The model is based on the Eulerian-Eulerian concept, in many previous ‘L-S-free’ theoretical studies of (large of small) ‘Lewis
which Eulerian conservation equations are solved both for the gas and number effects in combustion’ must be re-examined and extended since
the particulate phases. A NO, formation and destruction sub-model is ‘extreme’ nonunity Lewis number effects and significant L-S transport
used to calculate the local concentration of NO. The model is used to effects will frequently ‘go together.’ Often, lack of direct experimental
simulate a range of operating conditions in an actual, 350 MW, arch- information about the relevant thermal d#fuusion ,factor wr, or even
fired boiler, with the aim of reducing, using primary measures, the complexity of the underlying kinetic theory expressions for aT, are used
emissions of NO,. The model results shed some light on the relevant to ‘justify’ neglecting L-S species transport. To overcome this we
NO.-formation mechanisms under the several operating conditions. suggest and exploit two remarkably simple but rational approximate
Furthermore, they correlate well quantitatively with the available field methods to estimate aT for ‘heavy’ species via the already familiar
measurements at the plant, and reproduce satisfactorily the tendencies Schmidt number VA/DB~, in the ideal gas, high temperature limit. We
observed under the different operating modes. also provide, as a corollary, simple but rational correlations/estimates
for anticipating the simultaneous consequences of Fick and Ludwig-
Soret diffusional transport, including appreciable modifications of the
01101782 State-of-art technology of SCR system for coal
recovery factor for mainstream chemical energy in surface-catalysed
fired boiler
combustion. Using instructive examples for non-premixed and surface-
Nakatani, H.K. et al. FACT (Am. Sot. Mech. Eng.), 1999, 23, 493-496.
catalysed combustion, we demonstrate the importance of L-S transport
More than 18 years have passed since the first SCR system for the coal
for heavy fuel vapour species (even the normal paraffins C,,H2,, + z
fired plant in the world provided by Mitsubishi was put into commercial
smaller than eicosane (n = 20), as well as for flame intermediates
operation. During the above period, SCR catalyst has been developed
(including soot precursors, such as polycyclic aromatic hydrocarbons
to overcome any difficulties which we experienced, especially because
(PAHs) up to coronene (C24H12). We conclude that it is not only bona
the flue gas contains the large amount of dust compared with gas and
fide soot particles that are appreciably influenced by ‘thermophoresis’
oil fired unit. For example, dust plugging, SO2 oxidation rate, pressure
in such laminar diffusion flames - even for coronene we estimate that
loss and erosion have been the main items to be solved. This paper
the dimensionless ‘thermophoretic diffusivity’: a~D~~/v,, is already
reviews with no references the background of the above items and test
about 0.47, not far from the particle-limit value of 0.5385. Put another
result which was conducted before the application to the actual unit to
way, in combustion applications the L-S effect, while known to be
confirm the initial performance and the durability against them. In
important for diffusion flames involving H(g) and Hz(g), does not
addition to the above, the efforts to reduce the catalyst volume for coal
‘disappear’ for heavier vapours, only to ‘suddenly’ reappear for bona
fired unit by means of the application of smaller pitch catalyst is also
fide nanoparticles (e.g. ‘soot’)!
presented together with the inspection result of smaller pitch catalyst
after the operation.
01101786 A comprehensive biomass combustion model
Jones, J.M. et al. Renewable Energy, 1999, 19, (l-2), 229-234.
01101783 Techno-economic analysis of NO, reduction
A combustion model for wheat straw is discussed and compared to that
technologies in p.f. boilers
of a bituminous coal, Pittsburgh No. 8. The input data into the
McCahey, S. et al. Fuel, 1999, 78, (14), 1771-1778.
combustion model for both cases were generated using the FG-DVC
The impact of NO, reduction technologies upon a supercritical coal
(functional group-depolymerization, vaporization, crosslinking) coal
fired p.f. (pulverized fuel) power station has been investigated using
devolatilization model, which had been validated in part experimental.
the ECLIPSE process simulator. Technical, environmental, and
The combustion behaviour of the two fuels are investigated using a
economic assessments were performed, based upon a model of the
laminar flow computational fluid dynamics model of a drop-tube
Amer 9 Power Station at Geertruidenberg, the Netherlands. Selective
furnace. The results indicate that, because of the low calorific nature of
catalytic reduction (s.c.r.) achieves the largest reduction in NO,
the straw volatiles, the combustion takes place at a lower temperature,
emissions, to below 50 mg/N m3, but at an additional electricity cost
but with rapid ignition and rapid devolatilization. The straw char is
of 0.21 pence (P)/kWh over the base case. The additional cost for coal-
highly microporous with relatively high ash and oxygen contents;
over-coal reburning is 0.03 p/kWh, reducing NO, emissions to below
consequently, the burnout is quicker than the analogous coal char
200 mg/N m3. Only high unburnt carbon losses or high-priced reburn
burnout.
coal justify the use of a coal micronizer. Natural gas-over-coal
reburning requires an unrealizable natural gas price of f0.98iGJ to
compete with coal-over-coal reburning. Gas prices between f1.76/GJ 01101787 A multi-fluid model for simulating turbulent gas-
and f1.93/GJ are required for it to compete with s.c.r. particle flow and pulverized coal combustion
Guo, Y.C. Chan, C.K. Fuel, 2000, 79, (12), 1467-1476.
Based on the pure two-fluid model for turbulent reacting gas-particle
01101784 Wa and results of optimization of the operation
flows with combusting pulverized coal particles, a new comprehensive
of an OP-430 g oiler in the Potnan Karolin Power Plant for
model for pulverized coal combustion was developed by incorporating
reduction of NO, emission
a modified k-&p model, a general model of pulverized coal
Korzuch, S. et a/. Energetyka, 1999, 53, (7), 337-341. (In Polish)
devolatilization and a general model of char combustion. Both gas-
The plant operates two pulverized coal-fired boilers OP-430, 2K and
phase and particle-phase conservation equations are described using
3K. The boilers are of a tight wall type, each producing 430 t/h steam of
Eulerian coordinates, and these equations are discretized and inte-
540°C and 13.5 MPa. The primary method deN0, was applied in the
grated in the computational cell. As the first stage of numerical
boilers, and the modernization was completed in 1997 for the boiler modelling of pulverized coal combustion in the cyclone furnace, three-
2K, and, after additional changes, in 1998 for the boiler 3K. During dimensional simulation of turbulent gas combustion and gas-particular
restarting of the boilers optimization of their operation was conducted,
flows has been made. The predicted results show that there is a near
including mills, burners and nozzles, and air quantity and its
wall recirculating zone at the bottom of the cyclone furnace, and the
distribution. recirculating zone enhances ignition and flame stabilization. The
predicted tangential velocity distribution of both the gas phase and
the particle phase similar to those of the Rankine vortex.

01/01788 Co-firing of coal and straw

09 COMBUSTION Overgaard, P. et al. Biomass. Proc. Biomass Cotzf. Am., 4th, 1999, 2,
1299-1305. Edited by Overend R.P., Chornet E.
In 1995 Danish utility company MIDTKRAFT converted the 150 MW,
pulverized coal-fired Studstrup power station unit 1 into co-firing of
coal and straw for technological demonstration purposes. The
Burners, combustion systems conversion consisted of establishing a straw per-processing plant with
a capacity of 20 tonne/h, corresponding to 20% of the total energy
input at full load, and modifying the burner system. After plant
commissioning in January 1996, a two-year demonstration programme
01101785 ‘Heavy’ Species Ludwig-Soret Transport Effects was initiated. The objective of the programme was to evaluate the
in Air-Breathing Combustion influence of co-firing upon boiler plant performance, combustion
Rosner, D.E. et al. Combustion and Flame, 2000, 123, (4), 547-560. chemical, heat surface deposits and corrosion, residue quality and
In the combustion community there seems to be a persistent view that emissions. This paper describes the plant conversion and results from
Ludwig-Soret (L-S) (thermally driven, non-Fickian) species diffusion the demonstration period. One result from the programme is that the
will only be important for (011.molecular weight species, such as H and fly ash is not usable in the cement and concrete industry due to a high

216 Fuel and Energy Abstracts May 2001

 09 Combustion (burners, combustion systems)

concentration of potassium and chlorine. Laboratory-scale straw mostly on volatile or fixed carbon content. Development of pore
leaching tests have shown that the contaminating products can be structure, ash effects and reactivity of a char play an important role in
easily removed. ELSAM has therefore initiated further R&D activities, combustion, release of nitrogen oxide (NO + NzO), SOz and heavy
where a pilot extension plant will be erected in connection with the metal emissions. In this review contributions and relative importance of
straw per-processing plant. The paper describe the objectives of this heterogeneous catalysed and non-catalysed reactions of gases and
programme. radicals in devolatilization, volatile and char combustion is analysed.
Further, influence of combustion conditions on measured reaction
01101789 Coal pyrolysis as a means to recover valuable rates, burning particle temperatures and emissions has been assessed,
chemicals from coal based on experimental measurements.
Miura, K. Inr. J. Sot. Mater. Eng. Resour., 1999, I, (2), 222-229.
In a review with 9 references on the authors own work, several pyrolysis 01101794 Comi;onents, formulations, solutions, evaluation,
methods are presented and the method of solvent swelling of coal with and application of comprehensive combustion models
coal is discussed. It is possible to increase the coal conversion, the Eaton, A.M. et al. Prog. Energy Cornbust. Sci., 1999, 25, (4), 387436.
liquid yield, and the benzene, toluene, and xylene yield significantly by A review, with 246 references. Development and application of
the control of the primary and secondary gas phase reactions. The key comprehensive, multidimensional, computational combustion models
concept of this method was the matching of the radical donation rate are increasing at a significant pace across the world. While once
and the formation rate of the coal fragments. A second method was a 2- confined to specialized research computer codes, these combustion
stage conversion of the coal starting with an oxidation step to degrade models are becoming more readily accessible as features in commer-
the coal macromolecular networks, and to solubilize the oxidized coal cially available computational fluid dynamics (CFD) computer codes.
into conventionally used solvents, followed by the pyrolysis of the Simulations made with such computer codes offer great potential for
solubilized coal. By this method an Australian brown coal was use in analysing, designing, retrofitting, and optimizing the perform-
converted for 81% into volatile products under mild conditions. ance of fossil-fuel combustion and conversion systems. The purpose of
this paper is to provide an overview of comprehensive combustion
01/01790 Cofiring biomass with coal utilizing water-cooled modelling technology as applied to fossil-fuel combustion processes,
vibratlng grate technology This overview is divided into three main parts. First, a brief review of
Giaier, T.A. Eleniewski, M.A. Biomass, Proc. Biomass Conf. Am., 4th, the state-of-the-art of the various components or submodels that are
1999, 2, 1343-1348. Edited by Overend R.P., Chornet E. required in a comprehensive combustion model is presented. These
Co-firing biomass with coal has been used successfully for many years submodels embody mathematical and numerical representations of the
in conventional combustion grates by the pulp and paper industry for fundamental principles that characterize the physicochemical phenom-
systems generating up to 70 MW. Water-cooled vibrating grates allow ena of interest. The submodel review is limited to those required for
biomass co-firing to be used by larger utility size systems. This paper characterizing non-premixed, gaseous and pulverized coal gasification
discusses both new boiler installations and retrofit applications. and combustion processes. A summary of the submodels that are
available in representative computer codes is also presented. Second,
the kinds of data required to evaluate and validate the predictions of
01101791 Combustion kinetics of char from pyrolysis of
comprehensive combustion codes are considered. To be viewed with
coal with coke-oven gas. Distribution to combustion
confidence, code simulations must have been rigorously evaluated and
apparent activation energy of char
Liao, H. et al. Ranliao Huaxue Xuehao, 1999, 21, (3), 245-250. (In validated by comparison with appropriate experimental data, prefer-
Chinese) ably from a variety of combustor geometries at various geometric
scales. Three sets of validation data are discussed in detail. Two sets
Combustion kinetics of chars from pyrolysis of Xianfeng lignite with
COG was studied in detail. The combustion kinetics model of char was are from the highly instrumented, pilot-scale combustor called the
controlled profile reactor (CPR) (one natural gas-fired and one coal-
set by the following equation -dX/dt = 6K(l - X)“66e2/podu. A new
fired), and the other set is for a full-scale, corner-fired 85 MW. utility
method was suggested to describe the distribution of apparent
boiler. Third, representative applications of comprehensive combustion
activation energy during the combustion of char. It was found that
models are summarized, and three sets of model simulations are
the apparent activation energy shows the similar but reverse shape with
compared with experimental data. The model simulations for the three
combustion rate plot during the combustion of char and spreads over
47-95 kJ/mol. The lowest apparent activation energy was found in the test cases were made using two commonly used, CFD-based computer
combustion conversion (f) -4O(wt.%,daf). In the combustion of the codes with comprehensive combustion model features, PCGC-3 and
same char, there is a definite correlation between combustion rate and FLUENT 4.4. In addition to the standard version of FLUENT,
apparent activation energy, i.e. high burning rate is related to low predictions were also made with a version of FLUENT incorporating
apparent activation energy. Thus, apparent activation energy can be advanced submodels for coal reactions and NO pollutant formation.
used to describe the combustion reactivities of char.
01101795 Concept for the production of pure carbon black
01101792 Combustion of high calorific value waste through the combustion of natural gas without CO* and the
material: Organic atmospheric pollution production of electric power
Mastral, A.M. et al. Environ. Sci. Tech&., 1999, 33, (23) 41554158. Ellingsen, 0. PCT Int. Appl. WO 99 61,530 (Cl. CO9C1/48), 2 Dee
Waste tyre combustion in an atomic fluidized-bed reactor (7 cm i.d., 76 1999, NO Appl. 199812,374, 26 May 1998. 10.
cm height) has been performed in a laboratory plant with the aim of A process for the combustion of hydrocarbons, such as natural gas, oil
studying the polycyclic aromatic hydrocarbon (PAH) emissions as a or the like, for producing energy, the combustion taking place in
function of combustion temperature. The main aim has been to insufficient air so as to reduce the COz emissions and at the same time
compare these organic emissions with the ones obtained when coal is produce pure carbon in the form of filter cakes containing oil for later
burned at the same combustion conditions. PAH emissions have been use, e.g. in existing coal-fired power stations, thereby reducing the
analysed in solids collected in two cyclones at the exit of the reactor sulphur emissions therefrom, and/or the use of the carbon in the
and in a trap system formed by a condenser, a filter (20 pm), and an metallurgical industry.
adsorbent. After PAH extension with DMF by sonication, fluorescence
spectroscopy in the synchronous mode (FS) has been used as an 01101798 Desulphurization and denitrogenation in
analytic technique to quantify the PAHs emitted. Higher PAH copyrolysis of coal with hydrogen-rich gases
emissions are generated when this waste material is burnt at the same Liao, H. et al. Ranliuo Huaxue Xuehao, 1999, 27, (3), 268-272. (In
conditions used for coal atomic fluidized-bed combustion. Chinese)
The desulphurization and denitrogenation were systematically investi-
01101793 Combustion processes -solid and liquid charring gated by analysing the chars and tars from copyrolysis of Yanzhou
fuels. Structural changes, heterogeneous reactions and high-sulphur bituminous coal with coke-oven gas (COG), synthesis gas
emissions (SG) and hydrogen. The results indicated that at the condition of 3
Svoboda, K. et al. Acta Mont., Ser. B, 1999, 9, 55-79. MPa, up to 650” with a heating rate of lO”/min, the desulphurization of
In combustion of solid and some liquid, charring fuels, homogeneous coal pyrolysis with COG, SG and hydrogen were almost equal (about
and heterogeneous reactions describing phenomena in fuel/char 80% wt%, ad), the order of denitrogenation were: hydrogen (41%) >
particle and in adjacent surroundings are generally needed for SG(35%) > COG(30%). The distributions of sulphur in char, oil and
complete and realistic modelling of burning. Rank of coal (solid or gas was very similar under the three reactive gases, and i.e. about 20%
liquid fuel), heating rate, size of particles and reaction conditions in char, 10% in tar and 70% (difference) in gas, respectively.
(temperature, gas concentrations, pressure) effect behaviour, structural Compared with hydropyrolysis at the same hydrogen partial pressure,
changes and reactivity of coal (fuel) particles during drying, devolati- the desulphurization of coal pyrolysis with coke-oven gas increased
lization, gas phase oxidation of volatiles and char combustion. At about 4.5%, however, the denitrogenation decreased about 3.5%.
relatively lower temperatures of combustion (~1000°C) the catalytic There is an important desulphurization advantage for hydropyrolysis
effects of ash, CaO and other solids on combustion rate of volatiles and using COG and SG instead of pure hydrogen. Compared with the
transformation of N-precursors to nitrogen oxides are usually copyrolysis of coal with COG, Yanzhou coal pyrolysis under SG can
significant. The rate of burning or gasification of a solid fuel depends reach the same desulphurization and higher denitrogenation.

Fuel and Energy Abstracts May 2091 217

 09 Combustion (burners, combustion systems)

Oil01797 Dynamic features of closed combustion systems of the functional groups in coal except some aromatic C-C bonds have
Oppenheim, A.K. Kuhl, A.L. Progress in Energy and Combustion vanished during the pyrolysis, and some nitrogen-containing functional
Science, 2000, 26, (+6), 533-564. groups such as -CN groups are simultaneously introduced into the
A rational approach to dynamic features of closed combustion systems chars.
is of direct relevance to the interpretation of exothermic processes in
enclosures, such as the cylinders of piston engines, as objects of
control. For this purpose they have to be expressed in terms of non- 01/01802 Slag- and lime-based composition for
linear dynamics. The paper presents a method developed in this respect desulfuriration in coal combustion
on the basis of the principles of thermostatics and kinetics, supported Liang, W. ef al. Faming Zhuanli Shenqing Gongkai Shuomingshu CN
by heat transfer. The dynamic stage of combustion, manifested by 1,155,575 (Cl. ClOLlO/O4), 30 Jul 1997, Appl. 96,109,822, 18 Sep 1996.
monotonic pressure augmentation, is then carved out of the whole by 5. (In Chinese)
separating it from the initial stage of ignition and the final stage of The desulphurization agent for coal combustion is prepared by
decay. Formulated thereupon is an inverse problem: the determination grinding and mixing slag 30-40, lime 30-40, FezOs l-3, BaClz 2-3,
of the dynamic properties of the exothermic process, in terms of the Ca(NOs)z 3-5, MgClz 2-3, LizCOs 1-2, Ba(NOs)z 2-4, NaNOs 5-8,
history of fuel consumption, from a measured pressure profile. NaOH 2-4, CaCOs 2-4, KMn04, 0.2-0.3 and NaCl 5-8 wt.%, then
Particularly instrumental in this respect are: (1) the life fincrion heating the mixture to 200” for 10 h under stirring. The optimal
expressing these variables in analytic form, and (2) the correlation, composition of the desulphurization agent is slag 35, lime 34, FezOs 2,
deduced from heat transfer studies, permitting the energy lost by heat BaClz 2, Ca(NOs)z 4, MgClz 2, LizCOs 1, Ba(NOs)z 2, NaN03 6,
transfer to the walls to be evaluated from pressure records. The NaOH 3.8, CaCOs 3, KzMn04 0.2 and NaCl 5 wt.%.
implementation of the method is illustrated by a diagnosis of the
effectiveness with which the exothermic process of combustion is
executed in piston engines. 01101803 SO1 emission behavior of a small PFBC test
equipment
Saito, I. cl al. Nippon Enerugi Gakkaishi, 1999, 78, (I 1). 921-928. (In
01101798 Prediction of the behaviour of biomass ash in Japanese)
fluldized bed combustors and gasifiers This paper reports the results of investigation on sulphur dioxide
Arvelakis, S. Ed al. J. Therm. Anal. Calorim., 1999, 56, (3), 1271-1278. reaction in a pressurized fluidized bed. In case of fluidized bed
Two types of agricultural residues (wheat straw and olive residue) in combustion, sulphur retention depends upon excess air ratio and
untreated and pretreated (fractionation, leaching) form were tested as fluidized bed height (gas residence time) respectively. Study of SOz
concerns their ash melting behaviour during fluidized bed combustion injection into various points conducted that sulphur dioxide was
and gasification by thermal analysis techniques. The techniques applied removed rapidly and completely in the fluidized bed and splash zone.
included DSC, simultaneous DSC/TG, and TG-MS for the determi- Bed material, which consisted in Ca compounds and coal ash,
nation of low-temperature ash melts and losses caused by the performed high sulphurization ability against the high COz partial
volatilization of alkali material. In combination with ash elemental pressure. Therefore, these results suggested that it had high sulphur-
analyses on the materials, the applied techniques proved to offer ization performance zone and its mechanism was not able to explain
valuable information for prediction of the ash behaviour in fluidized only direct sulphation of CaC03. The coal character dependence of
bed reactors sulphur retention was explained the influence of coal combustion style
in the fluidized bed and inorganic sulphur content in the coal.
01101799 Pyrolysis of an agricultural by-product: a According to combustion style observation study, when coal particles
characterization study burn separately and rapidly in the fluidized bed, SOz emission of these
Cukierman, A.L. er a!. Biomass. Proc. Biomass Cot$. Am., 4/h, 1999, 2, coals was high. Addition to that inorganic sulphur in the coal tend to
1201-1207. Edited by Overend R.P. Chornet E. burn over fluidized bed zone. On the other band, when coal particle is
Evolution of chemical and textural features characterizing shells of cohesive, its primary particle burned slowly in the bed and SOz
peanut (Arachis hypogaea) species subjected to three different emission of this kind of coal was low.
pyrolysis temperatures is analysed by several techniques. Surface areas
of the raw material and pyrolysed samples are evaluated from physico-
adsorption measurements employing Ns at 77 K and COz at 298 K. 01101804 Supersonic combustion of kerosene/Hz-mixtures
Results point to significant feature changes, which are, in general, in a model scramjet combustor
strongly affected by pyrolysis conditions, and in particular by pyrolysis Gruenig, C. Mayinger, F. Comhusr. Sci. Technol., 1999, 146, (I-6). I-
temperature. Furthermore, kinetic measurements of peanut shells 22.
pyrolysis are performed by non-isothermal thermogravimetric analysis, Liquid hydrocarbon supersonic combustion has been experimentally
from ambient temperature up to 1123 K. A kinetic model reported in investigated. Kerosene was burnt in a steady, vitiated Mach 2.15-air
the literature, which takes into account the significant chemical and flow of a model scramjet combustor. The fuel is injected into the
physical changes occurring within the residue in the course of the supersonic air stream by means of pylons. The effervescent atomization
pyrolysis process, as evidenced from the results of chemical and method has been employed such that the liquid fuel is injected as a
textural characterization, was applied. This model properly describes spray. By means of the Mie scattering technique the fuel jet structure
actual kinetic data over the wide range of temperatures used. was visualized and the evaporation rate estimated. The mechanisms of
ignition and combustion of the kerosene/Hz-mixture were studied and
compared with the case of hydrogen combustion. Combustor ignition
01101800 Pyrolysis of biomass by rotating cone flash limits have been detected. Fuel-specific combustion phenomena are
pyrolysis device discussed. It was found that for the kerosene combustion a gas dynamic
Xu, B. et al. Huanjing Gongcheng, 1999, 17, (5), 71-74. (In Chinese) feedback mechanism strongly affects the supersonic combustion
A rotating cone flash pyrolysis device for pyrolysis of biomass was
process.
introduced. The heating rate of the device was 1000” se’, gas retention
time 0.3 s, and solid retention time 0.5 s. The main pyrolysis
equipment, technology parameters, and the characteristics of the 01101805 The predictions of coal/char combustion rate
pyrolysis product were described. Biomass is a renewable energy using an artificial neural network approach
resource, and biomass pyrolysis is a thermal chemical process which Zhu, Q. et al. Fuel, 1999, 78, (14). 1755-1762.
can produce liquid, gas, and solid fuels in complete absence of 0s or In this study, the use of an artificial neural network for predicting the
with a limited Oz supply. The yield of bio-oil reached 60%. reactivity of coal/char combustion was investigated. A database
containing the combustion rate reactivity of 55 chars derived from 26
01101801 Pyrolysis of low rank coals in nitrogen plasma coals covering a wide range of rank and geographic origin was
Qiu, J. et al. Huagong Xuehao (Chin. Ed), 1999, 50, (5), 586-591. (In established to train and test the neural networks. The heat treatment
Chinese) temperature of the chars ranged from 1000 to 1500°C and the
The flash pyrolysis of three low rank coals in a nitrogen plasma jet at combustion rate reactivity of the chars were measured using thermo-
atmospheric pressure has been studied. The coal undergoes very fast gravimetric analysis in a temperature range of 420-600°C. Three
reactions with highly reactive plasma species, which produces a large correlation parameter sets were compared, which contained a coal rank
amount of gas and char. The main components of the gas products are parameter (either vitrinite reflectance or fixed carbon content), a
hydrogen, methane, carbon monoxide, acetylene and cyanoacetylene. parameter representing the extent of pyrolysis, combustion tempera-
The concentration of cyanoacetylene in the gas is related to that of ture, and char surface area. The results showed that when sufficient
acetylene. Acetylene acts as the precursor of cyanoacetylene. The amount of training data are available, a amount neural network model
acetylene yield depends on the coal type and the experimental can be developed to predict the combustion rates of coal chars with
conditions, and increases as the. volatile matter content of coal good accuracy and robustness. Fixed carbon content appeared to
increases and as the coal feeding rate is reduced. A maximum correlate better than random vitrinite reflectance R. with combustion
acetylene yield of 22.31% by weight on a carbon basis is obtained rates of coal chars. Total surface areas of the chars correlated to the
from Zhalainuoer lignite when the coal particle size is less than 74 Frn combustion rates and when these values were used as one of the inputs
and the coal feed rate is 5.1 g.min -I. The FTIR spectra reveal that all to the neural network, better predictions were achieved.

218 Fuel and Energy Abstracts May 2001

 70 Engines (power generation and propulsion, electrical vehicles)

01101909 The redictions of coaflchar combustion rate In this work, a new Semi-Closed Gas Turbine Cycle (SCGT)
using an artific Pal neural network approach configuration is presented, named Semi-Closed Gas Turbine/Regen-
Zhu, Q. et al. Fuel, 1999, 78, (14) 1755-1762. erative Combined Cycle (SCGT/RCC). The SCGT/RCC is an hybrid
In this study, the use of an artificial neural network for predicting the combination of the SCGT/CC and SCGTIRE cycle concepts, including
reactivity of coal/char combustion was investigated. A database both partial regeneration of the gas turbine and coupling to a
containing the combustion rate reactivity of 55 chars derived from 26 bottoming steam cycle by a small-size Heat Recovery Steam Generator
coals covering a wide range of rank and geographic origin was (HRSG). An energy and exergy analysis is carried out for several
established to train and test the neural networks. The heat treatment configurations and operating conditions. A preliminary analysis of the
temperature of the chars ranged from 1000 to 1500°C and the RHE size, COr absorption potential and related effects on the cycle
combustion rate reactivity of the chars were measured using thermo- performance is presented, at several operating conditions and
gravimetric analysis in a temperature range of 420600°C. Three investigating three possible plant operation modes. The performance
correlation parameter sets were compared, which contained a coal rank of the SCGT/RCC is very interesting at optimized operating conditions
parameter (either vitrinite reflectance or fixed carbon content), a (specific power exceeding 550 kI/kg of compressor inlet flow rate,
parameter representing the extent of pyrolysis, combustion tempera- efficiencies close to 50% including a 80% COz removal). This plant is a
ture, and char surface area. The results showed that when sufficient promising solution that combines the positive features of semi-closed
amount of training data are available, a neural network model can be gas turbines, allowing a drastic reduction of size and capital costs for
developed to predict the combustion rates of coal chars with good both HRSG and RHE and maintaining high values of performance.
accuracy and robustness. Fixed carbon content appeared to correlate
better than ran om vitrinite reflectance Rs with combustion rates of
01/01910 Effect of interior guide tubes in cross-flow turbine
coal chars. To1 al surface areas of the chars correlated to the runner on turbine performance
combustion rates and when these values were used as one of the Olgun, H. Inr. J. Energy Res., 2000, 24, (1 I), 953-964.
inputs to the neural network, better predictions were achieved.
The cross-flow turbine has attracted much attention as a source of
hydropower generation for small and micro-systems, especially for low
011019iJ7 The role of two-stage combustion in the head establishments. Such turbines have a distinct advantage of lower
development of oscillations during fluidized bed initial and operating costs over other small scale turbines, but their
combustion of gases efficiency is lower than others. Efficiency predictions of these turbines
Zukowski, W. Fuel, 2000, 79, (14), 1757-1765. are generally based on the assumption that the entire flow crosses from
Unstable combustion of methane-air mixtures in a bubbling fluidized the first stage to the second stage of the turbine runner. In this study,
bed of catalytic material has been observed and analysed. With the interior guide tubes were designed and used inside the runner of a
reactor continuously supplied with the substrates, oscillations of state cross-flow turbine to collect and guide the crossing flow towards the
variables, especially the bed temperature and the degree of conversion second stage of the runner. The interior guide tubes were designed on
of methane can take place. It was found that the process either the basis of observed flow patterns inside the runner. Experimentally,
oscillates, with different oscillation ,periods, or the system attains a three different types of tubes were tested. The laboratory tests were
steady state. These dynamic phenomena are represented in terms of conducted to calculate the turbine efficiency with different gate
time and phase plots. A physical model ash been proposed, treating the openings of nozzle and different positions of interior guide tubes.
whole system as a cascade of two chemical reactors, in which Results of this work with and without interior tubes have been
conversion of the substrates into the products can take place. The presented in this paper. When the experiments were done with and
bubbling, fluidized bed, containing most of the solids is the first, without interior guide tubes, it has been found that turbine efficiency
catalytic reactor. The freeboard, with few solid particles, constitutes the with the interior guide tube decreased about 5%.
second reactor, with homogenous combustion dominant. Mass trans-
port from the first to the second reactor and the heat transport from 01/01811 Emissions performance of oxygenate-in-diesel
the second to the first reactor, make up a feedback system. This can blends and Fischer-Tropsch diesel in a compression
lead to the oscillations observed. Using this simple model, a ignition engine
mathematical description of the whole system has been developed. Cheng, AS. Dibble, R.W. Sot. Automat. Eng.. [Spec. Publ.] SP, 1999,
On the basis of the quantities measured, some of the model parameters SP-1482, 237-246.
were estimated and comparison between numerical calculation and Engine fuel tests were conducted with two oxygenates blended with
experimental results have been carried out. This confirmed that the conventional diesel and a synthetic Fischer-Tropsch (F-T) diesel to
assumptions about the physical structure of the reacting system were determine their emissions reduction potential. The oxygenated
basically correct. additives evaluated were dimethoxy methane (DMM) (also known as
methyl) and di-ethyl ether (DEE). Blends of 5, 10, 20 and 30% by
volume were investigated. The test engine was a 1993 Cummins B5.9
01101809 Upper igniting coal briquets diesel, and data was collected for steady state operation at nine engine
Wang, L. Faming Zhuanli Shenqing Gongkai Shuomingshu CN speed-load conditions. Experimental results show that all of the test
1,162,627 (Cl. ClOL5/06), 22 Ott 1997, Appl. 96,104,670, 18 Apr fuels reduce PM when data is averaged across the nine engine
1996. 7. (In Chinese) operating modes. The largest reductions in PM were observed with a
The upper-igniting coal briquettes consist of Iighting briquets and bl%nd>f 30% DMM in diesel, which yielded a 35% reduction compared
common briquets, prepared by pulverizing, blending, extruding, and to the baseline diesel fuel. Lower DMM blend levels also resulted in
drying, and the ratio of them being 1:9; the lighting briquets are placed PM reductions but to a lesser extent. On a modal averaged basis, F-T
over the common ones when burnmg. The lighting briquets are diesel reduced hM emissions by 29%. and DEE in concentrations of 10
composed of bituminous coal or lignite 39-49, KNOs and Ba(NO,)z to 30% reduced PM emissions by between 13 and 24%. On a modal
35-37, sawdust charcoal 15-25, and organic binder l-2 wt.%; the averaged basis, NO, emissions for F-T diesel and the DMM and DEE
common briquets composed of bituminous coal or lignite 72-76, loess blends were reduced by between 1 and 10%. Corresponding increases
24-28, white ash 2-4, organic binder 1-2 wt.%. The bituminous coal or in fuel consumption (beyond that necessary to compensate for the
lignite can be Number l-5 lignite from Indonesia, and the optimal ratio differences in energy densities) were also observed. Modal averaged
of KNOs and Ba(NO& is 1:7-8. The degree of grinding briquettes is emissions of total hydrocarbons and carbon monoxide were in most
<2 mm, and the organic binder is starch. cases higher for the test fuels, but their overall levels remained low.
Investigation of individual modal data revealed large differences in the
effect of the DMM and DEE blends on PM emissions. In general,
measured PM levels were drastically (as much as 76%) lower for the
higher engine power test models. For the lower power modes, however,

10 ENGINES PM emissions were often unchanged or even increased.

01101812 Engine arrangement for combustion of gases

loaded with impurities
Heuwieser, B. Laubenstein, S. Ger. Offen. DE 19,918,946 (Cl. ClOKl/
Power generation and propulsion, 32) 16 Dee 1999, DE Appl. 19,819,089, 29 Apr 1998. 4. (In German)
An impurity-containing fuel gas (especially biogas) is passed through
electrical vehicles (I) a heat exchanger functioning as a dryer-dehumidifier where the
relative humidity of the gas is decreased by increasing temperature and
(2) an adsorber filled with activated coal, AlzOs, and zeolite to remove
impurities before feeding into a gas engine which drives an electrical
01/01999 A new semi-closed gas turbine cycle with CO* generator. After combustion, exhaust gases are passed through a heat
separation exchanger and a conventional catalytic converter to a chimney and
Fiaschi, D. Manfrida, G. Energy Convers. Manage., 1999, 40, (IS-l@, released to the atmosphere. Heating of the feed gas in the heat
1669-1678. exchanger is done by (1) using cooling water from the gas engine, (2)

Fuel and Energy Abstracts May 2001 219