(LURGI)

Is GYPSUnl
Deco~position Co~ercia11y

Ready No-w?

by

Pet e r L ij d t k e
Lurgi GmbH, Frankfurt, Germany

A 1. a n N. S i 1 b e r b erg
Lurgi Corporation, River Edge/New Jersey, USA

for
AICHE Clearwater Convention
1988
 (LURGI)
- 1 -

Introduction

Lurgi, who has been involved in gypsum decomposition for

the past three or four decades has from time to time been
required to take a step back from our activities and access
where the industry is going? (or not going?).

That is to say that just because Lurgi has extensive

experience in:

Gypsum decomposition
Pyrite roasting
Sulphur recovery
H2S04-production
Sintering
Calcining
Cement production
CFB's
Kilns
Traveling grates

does not mean that the economics of a technically feasible

plant or concept based upon these operations is attractive.

In fact, that is what we are here to discuss today.

Is Gypsum Decomposition Commercially Ready Now?

Based upon Lurgi's in depth knowledge and experience in the

above mentioned fields and unit operations Lurgi seriously
doubts the viability of incorporating gypsum decomposition
into the fertilizer industry now.
 (LURGI)
- 2 -

1 Aim of Phosphogypsum Decomposition

As we all know phosphogypsum is the ultimate destination of

most of the sulfur consumed in the production of phosphoric
acid. Approximately 120 million tons of phosphogypsum are
produced annually through out the world. Of this some 30
million tons per year are produced in Florida, alone.

Power plant flue gas desulfurization units also generate

considerable quantities of calcium sulfate and calcium
sulfide. These are already the subject of serious environ-
mental concerns in some countries.

Obviously, recycling of the sulfur content of the gypsum

o would offer many advantages:

a) Some countries like Tunesia, Morocco and South Africa

have phosphate deposits but need to import the sulfur
required to produce sulfuric acid. They must use hard
currency to pay for the sulfur they import.

b) Reprocessing the phosphogypsum eliminates dumping prob-

lems. In Central Europe (where new gypsum piles are
infeasible) it is virtually impossible to obtain a con-
struction permit for a new phosphoric acid plant if the
resulting gypsum is discharged into rivers or the sea.
Additionally restrictions on existing phosphoric acid
plants are becoming more and more stringent, involving
considerable cost.

A process using phosphogypsum as a raw material and

thus reducing the existing gypsum piles would be most
welcome as it would also eliminate the liquid effluents
and gaseous emissions from such disposal areas.
 (LURGI)
- 3 -

(
c) Thermal decomposition of gypsum is an endothermic
reaction. If a low-cost fuel could be successfully used
to recover the value of the sulfur from the gypsum we
would have an attracti7e concept. Decomposition may be
worth considering utilizing coal tailings, high sulfur
coals, petroleum coke or sulfur-laden waste gases whose
disposal are costly, thus providing a double benefit.

d) The decomposition of gypsum should be examined not only

from the point of view of recovering the sulfur, (in
the form of sulfuric acid), but also the generation of
useful byproducts such as quick lime, cement or road
aggregate, all of which are of a certain commercial
value. Ammoniumsulfate produced from gypsum and ammonia
has been commercialised already some 60 years ago
(Merseburger Process).

e) In past years, the phosphate fertilizer industry has

not enjoyed great profits. It was widely believed that
only the sulfur suppliers benefited from the crisis of
the fertilizer industry. Prices of nearly $ 200 per ton
of sulfur supplied, which had to be paid, seemed to
prove this. Gypsum decomposition might make the ferti-
lizer industry independent of sulfur suppliers.

These advantages are so obvious (Figure 1) that one wonders

why such decomposition plants have not been built every-
where. Are there no suitable processes ? Is no capital
available for such plants ? Has the industry been
sleeping ?

Unfortunately, the answers to these questions are very com-

plex.
 (LURGI)
- 4 -

Nothing will be presented in this paper about the direct

use of phosphogypsum (1). It is well-known by all of us
that natural 9ypsum can be replaced by phosphogypsum, that
phosphogypsum can be used as: Fertilizer, a soil condi-
tioner, a settin9 retardant for cement, for conversion to
ammonium sulfate, a filler for paper, paint and plastics,
and in the building industry. Althou9h these applications
have been successfully demonstrated in many places around
the world, they consume only about 10 - 15 , of the world
phosphogypsum production. The exception to this is Japan,
where practically all the phospho9ypsum produced is put to
other uses. In fact phosphogypsum is even imported from
other countries (such as Korea) because natural 9ypsum is
scarce.
 (LURGI)
- 5 -

2 Decomposition Processes

2.1 Muller - Kuhne Process

The Muller-Kuhne process coproduces sulfuric acid and

Portland cement by thermal decomposition of gypsum in a
rotary kiln. A semi-commercial plant commenced operation in
1916. Since then an additional 25 units have been built
throughout the world (Table 1). The most recent unit was
built in China in 1987. Presently the plants in East
Germany and hopefully the one in China are in operation.

The basic reactions of the Muller-Kuhne process are still

the same as 70 years ago (2):

Part of the calcium sulfate is reduced with carbon to yield

calcium sulfide

CaS04 + 2 C -------> 4 CaS + 2 C02

The carbon required for the reduction is added in the form

of coke.

In the hotter zone, the calcium sulfide reacts with addi-

tional calcium sulfate

CaS + 3 Ca S04 -----> 4 CaO + 4 S02

Experts believe that the reduction to calcium sulfide is

not a solids reaction, but has CO as an intermediary
product. The presence of cement clinker additives (Si02,
A1203 and Fe203) decreases the temperature of this reaction
to about 900C.
 (LURGI)
- 6 -

Finally, the calcium oxide reacts with the oxides (5i02,

A1203, Fe203) exothermally in the sintering zone to produce
cement clinker.

The necessary sintering temperature is approximately 1350 -

1400C. The rotary kiln offgas consists of 502, C02' 02' N2
and H20. It is purified in a gas treatment plant and pro-
cessed to sulfuric acid in a contact plant according to the
overall reaction

The clinker quality depends heavily upon accurate ratios

between the carbon and calcium sulfate quantities. In
actual operation, a carbon surplus of approximately 20 % is
provided, since a part of the carbon is burned and cannot
be used for reduction.

Over years of operation the process was further refined and

advanced. Noteable improvements were made in the areas of
feed preparation, process control, and energy efficiency.

Initially, only natural gypsum was used as a raw material.

Phosphogypsum was first introduced in the thirties. The
engineers learned how to handle it over the following
several years.
 (LURGI)
- 7 -

A plant consists of the following unit operations

(Figure 2):

1. Drying and calcining of "phospho gypsum

2. Grinding of additives
3. Preparation of kiln feed meal
4. Decomposition of gypsum and clinkering
5. Production of sulfuric acid

The phosphogypsum is dried and calcined in order to expel

surface moisture and some of the crystal water. Fuel costs
can be reduced by using hemihydrate phosphogypsum produced
for instance by the Norsk Hydro Hemihydrate Phosphoric Acid
Process. The additives (0.2 t clay, 0.1 t sand, 0.1 t coke
per tonne of clinker) are dried, ground and mixed in appro-
priate proportions.

The feed material is preheated counter-currently to the

offgas from the rotary kiln before it is fed to that kiln,
(which is slightly inclined). The. inclination and rotation
of the kiln moves the material thru the kiln and into the
clinker cooler.

The rotary kiln is fired with pulverized coal, fuel oil or

natural gas. As mentioned before, decomposition of the
calcium sulfate and clinkering takes place in the kiln. The
clinker is cooled with air and, after the addition of
gypsum, the material is ground to cement. This cement is
delivered to the cement silos for interim storage prior to
shipment.

The hot gases leaving the heat exchanger upstream of the

kiln are dedusted, demisted, dried, and finally processed
to sulfuric acid.
 (LURGI)
'- 8 -

2.2 Lurgi Circulating Fluid Bed Process (CFB)

Thermal decomposition of gypsum is an endothermic process.

The more successfully the process parameters can be con-
trolled and the heat losses minimized, the more economic
the process will be.

The circulating fluid bed provides the mechanism to meet

these requirements (Figure 3).

The sequence of reactions is similar to that of the

Muller-Kuhne process. The fluid bed furnace is provided
with a reducing section promoting the decomposition of the
calcium sulfate. In the upstream oxidising section the
reaction is completed.

This has the advantage of being able to closely control the

system temperatures (within a range of 900 - 11000C), as
required by raw material variations. The same is true for
the oxygen content of the gas in order to prevent an
inverse reaction. The decomposition products are S02-laden
gas and CaO. A clinker mix is produced when the appropriate
additives such as Al203, Si02, Fe203 are fed to the CFB
chamber together with the gypsum (4). Clinkering cannot be
achieved in the same unit because it requires higher
temperatures. A conventional rotary kiln is therefore used
to clinker the material in a counter-current flow to the
heat source at the discharge end.
 (LURGI)
- 9 -

This circulating fluid bed system has some very specific

advantages

exact control of all process parameters (like tempera-

tures, gas composition)
minimum heat losses
no premixing of raw materials required
no rotating equipment, except air blowers

If the desired products are CaO and sulfuric acid, the

plant will consist of the following unit operations
(Figures 4):

1. Drying and calcining of phosphogypsum

2. Decomposition of gypsum
3. Production of sulfuric acid

If clinker and/or cement and sulfuric acid are the desired

products, the plant will consist of the following unit
operations (Figure 5):

1. Drying and calcining of phosphogypsum

2. Grinding of additives
3. Preparation of kiln feed meal
4. Decomposition of gypsum
s. Clinkering
6. Production of sulfuric acid
 (LURGI)
- 10 -

2.3 OMC/FIPR Process

The basic goal of the development work pursued jointly by

Davy McKee Corporation (OMC) and the Florida Institute of
Phosphate Research (FIPR) is to apply the commercially
proven circular grate sintering machine to the decomposi-
tion of phosphogypsum to produce 502 gas (which can be
processed to sulfuric acid), and aggregate material for
road construction. (3)

Carbonaceous materials such as petroleum coke, lignite or

coal are used as reductants and, pyrite as a fuel. The
phosphogypsum together with a binder are mixed, pelletized,
and charged to the sinter machine. Ignition burners are
( used to fire the raw material mix and initiate the combined
decomposing and sintering process. A suitable gas flow
arrangement at the sinter machine (similar to that deve-
loped for iron ore sintering) ensures that the gases pro-
duced in the decomposition and sintering process contain a
maximum of 502.

At the end of the cycle, the sintered material is crushed,

cooled and screened, then part of it is recycled to the
sinter machine as a bottom layer, the so-called hearth
layer.
 (LURGI)
- 11 -

According to publications, the use of pyrite has signifi-

cantly improved the quality of the sintered material.
Unfortunatley it has also brought another sulfur bearing
material to the process. This means that eventually more
sulfuric acid is produced than consumed. Thus putting the
phosphoric acid and phosphogypsum production out of
balance. The last flow sheets for the DMC/FIPR process of
which we are aware are based upon using the phosphogypsum
and pyrite as they are delivered with their natural mois-
ture content. The coal, on the other hand, is gasified
separately and the residual char used as a reductant at the
sinter machine while some part of the fuel gas is used to
operate the ignition burners.

The process as a whole is reportedly rendered more cost-

effective by gasifying additional coal and burning the
gaseous components to generate steam and/or electricity.
The LP steam is used to concentrate the phosphoric acid.
Some of the sulfur which may be introduced with the coal is
eliminated separately - again for reasons of
cost-effectiveness. But the flow sheet becomes very
complex, due to the dependence of the unit operations.

Hence, the DMC/FIPR process comprises the following unit

operations (Figure 6):

1. Preparation of raw materials

2. Pelletizing
3. Coal preparation
4. Coal gasification
5. Fuel gas processing
6. Gas turbine system
7. Power generation
8. Circular grate
9. Aggregate processing
10. Sulfuric acid production
 (LURGI)
- 12 -

(
3 Comparison of Capital and Operating Cost

3.1 Assumptions

a) Capital Costs

T.I.C. for new process plants within battery

limits, including cost for commissioning;

infrastructure in existence;

cost for land, taxes, dues not included;

location Unites States, 1987;

no prov~s1on has been made for unit operation to

clean phosphogypsum from impurities, like P20S, F
or others;

cogeneration facilities are included if electric

power is produced and exported:

cost data are based on Lurgi in-house estimates and

for the DMC/FIPR process from Davy communication,
dated March, 21, 1988:

provisions for capital expenditures during

construction period have not been included:

depreciation 10 years

interest rate 10 %, 10 years

calculated TIC x g,l x 0.575

H2S04 production per annum
 (LURGI)
- 13 -

b) Operating Cost

Comparison is based on a feed of 1.000.000 mt

phosphogypsum per year (analysis as per Table 2);

Coal analysis as per Table 3;

The sulfur content of the coal is converted to

sulfuric acid in these examples. This is the reason
for slightly different sulfuric acid capacities for
the processes.
 (LURGI)
- 14 -

3.2 Capital Cost

3.2.1 Muller-Kuhne Process

MM$

1. Drying of phosphogypsum 50
3 lines (3030 tpd) / . jC c
y;lovLD 3f; S-t-- / Ivf2~
2. Preparation of kiln feed meal
(3400 tpd) 6

3. Decomposition and clinkering 104

3 lines

4. Sulfuric acid production 40

1 line (1500 tpd)

TIC MM/$ 200

 (LURGI)
- 15 -

3.2.2 Lurgi CFB Process (CaO)

MM$

1. Drying and calcining 16

(3030 tpd)

2. Decomposition 30

3. Sulfuric acid production 37,5

(1500 tpd)

T!C MM/$ 83,5

 (LURGI)
- 16 -

3.2.3 Lurgi CFB Process (Clinker)

MM$

1. Drying and calcining

of phosphogypsum (3030 tpd dry) 16

2. Preparation of kiln feed meal

(4080 tpd) 2,5

3. Decomposition and clinkering 40

4. Sulfuric acid production 38,7

(1500 tpd)

TIC -MM/$ 96,2

 (LURGI)
- 17 -

3.2.4 OMC/FIPR Process

MM$

1. Preparation of raw materials

(receiving, storage, reclain)
gypsum, pyrite,binder
(4100 tpd dry) ) 11

2. Preparation of coal (570 tpd)

3. Coal Processing
37,5
4. Gas turbine system, power
generation )

5. Circular grate
26,5
6. Aggregate processing (1940 tpd) }

7. Sulfuric acid production (2300 tpd) 53

TIC MM/$ 128

 (LURGI)
- 18 -

3.3 Production Cost per Ton of Sulfuric Acid

3.3.1 Muller-Kuhne Process

Capacity: 478 500 tpy sulfuric acid

On-stream factor 330 dla
TIC 200 million $

Cost item Unit consumption Unit cost Cost per

tit H2S04 $ t of H2S04

Raw materials
Phosphogypsum 2,1 1,0 2,1
Coal 0,1 35,0 3,5
Clay 0,07 10,0 0,7
Sand 0,07 10,0 0,7

Utilities
Fuel oil 0,25 120,0 30,0
Cooling water, m3 70,0 0,005 0,35
Electric power, kWh 250,0 0,05 12,5

Products (Credit)
Clinker (1, 0) (33,0) (33,0>

Labour
Production 15 per shift x 4,5 x 20.000 $ 2,82
Overhead 100 % of production labour 2,82

Cagital related cost

Maintenance material 4 % of TIC 16,72
insurance and taxes

Depreciation and interest 65,83

 (LURGI)
- 19 -

3.3.2 Lurgi-CFB Process

Capacity: 495 000 tpy sulfuric acid

On-stream factor 330 d/a
TIC 83,5 million $

Cost item Unit consumption Unit cost Cost per

tit H2SO4 $ t of H2SO4

BaH mate[j.al:a
Phosphogypsum 2,0 1,0 2,0
Coal 0,1 35,0 3,5

tltj,lj.tj,e:a
Cooling water, m3 70,0 0,005 0,35
Electric power, kWh 110,0 0,05 5,5
Coal 0,2 35,0 7,0

f[Qal.ls::t:a
CaO 0,45 -,- -,-
LabQl.Ir
Production 7 per shift x 4,5 x 20.000 $ 1,27
Overhead 100 % of production labour 1,27

Cagj,ta 1 [elated cQ:at

Maintenance material 4 % of TIC 6,75
insurance and taxes

Depreciation and interest 26,57

$ 54,21
 (LURGI)
- 20 -

3.3.3 Lurgi-CFB Process (Clinker)

Capacity: 511 500 tpy sulfuric acid

On-stream factor 330 dla
TIC 97 million $

Cost item Unit consumption Unit cost Cost per

tit H2S04 $ t of H2S04

Raw materials
Phosphogypsum 2,0 1,0 2,0
Coal 0,1 35,0 3,5
Fly ash 0,2 7,0 1,4

Utilities
Coal 0,3 35,0 10,5
Cooling water, m3 70,0 0,005 0,35
Electric power, kWh 130,0 0,05 6,5

Products (Credit)
Clinker ( 0,9) (33,0) (29,7)

Labour
Production 9 per shift x 4,5 x 20.000 $ 1,58
Overhead 100 % of production labour 1,58

Cagital related cost

Maintenance material 4 % of TIC 7,58
insurance and taxes

Depreciation and interest 29,86

$ 35,15
 (LURGI)
- 21 -

3.3.4 DMC/FIPR Process

Capacity: 759 000 tpy sulfuric acid

On-stream factor 330 dla
TIC 128 million $

Cost item Unit consumption Unit cost Cost per

tit H2S04 $ t of H2S04

Raw materials
Phosphogypsum 1,33 1,0 1,33
Coal to char 0,11 35,0 3,85
Pyrites (90 % FeS2) 0,36 28,0 10,08
Binder 0,1 10,0 1,0

Utilities
Coal to energy 0,14 35,0 4,9
Cooling water, m3 42,0 0,005 0,21
Pond water 83,0 0,003 0,25
Boiler feed water 1,13 0,1 0,11

Products (Credits)
Aggregate 0,85 5,0 (4,25)
Steam 0,52 10,0 ( 5,2)
Electric power, kWh 140,0 0,05 ( 7 , a)

Labour
Production 16 per shift x 4,5 x 20.000 $ 1,89
Overhead 100 % of production labour 1,89

Capital related cost

Maintenance material 4 % of TIC 6,74
insurance and taxes

Depreciation and interest 26,56

 (LURGI)
- 22 -

3.4 Results

Assuming a price of sulfuric acid of 30 - 40 US $ per ton

for all processes the cost of raw materials, utilities,
maintenance, and labour absorb the selling price.

1. Miiller-Kiihne 105,04 $
2. Lurgi CFB (CaO) 54,21 $
3. Lurgi CFB (Clinker) 35,15 $
4. DMC/FIPR 42,36 $

Credits for byproducts like clinker, aggregate, quick lime

will improve the picture but the financial charges (inte-
rest, depreciation) again neutralize the result.

All cases do not provide a return on investment at present

conditions.
 (LURGI)
- 23 -

4 Technical , Economic Assessment

Apart from the economics of phosphoqypsum decomposition,

which can to a certain extent be described and evaluated by
looking at the operating costs, there are a number of other
aspects which are all mutually interrelated and therefore
cannot be assessed separately:

a) Technical reliability of the processes

b) Product quality
c) Market potential
d) Environmental aspects

( a) Technical Reliability

1. Muller-Kuhne-Process

As previously mentioned, a number of industrial-scale

plants based on the Muller-Kuhne process are still
operating. The largest single-train unit of this type
was designed for a phosphogypsum throughput of approxi-
mately 175 000 tpy. Future development must aim at
larger capacity in order to reduce the capital invest-
ment per ton. However in a large rotary kiln it is
difficult to accuratly control the temperature, gas
concentration and rate of deposits.
 (LURGI)
- 24 -

2. Circulating Fluid Bed (CFB)

--------------------------
CFB reactors are commercially used for a variety of raw
materials throughout the world. Lurgi ran pilot tests
at their Frankfurt laboratories to verify that such
units are suitable for phosphogypsum decomposition. The
pilot test runs were on a continuous basis. The resu~t
ing 502 gas was converted to sulfuric acid in a Pera-
cidox wash unit. No industrial-scale phosphogypsum
decomposition plant based on a circulating fluid bed
process has been commissioned to date.

3. OMC/FIPR Process

The circular grate sintering machine has for many years

proven its merits as a unit operation in the iron
industry. Lab scale, batch tests were made to study its
applicability to phosphogypsum decomposition. An order
has been placed for a continuous pilot plant.

Commercial coal gasification plants are already operat-

ing. However, the design of such plants has to allow
for the various specific properties of the coals used.
A continuous pilot plant for combined decomposition/
gasification can certainly be constructed, but we are
not aware of any current plans to do so.
 (LURGI)
- 2S -

b) Product Quality

The main decomposition product, at least for the pur-

poses of this paper, is sulfuric acid. The market
offers technologies by which highly concentrated and
sufficiently pure sulfuric acid can be produced under
the given conditions. An appropriate gas treatment unit
can be designed to remove such impurities like dust,
fluorine, and P20S from the gases. This gas treatment
plant - for all three processes alike - constitutes a
major critical section of the complex.

A second product can be clinker and/or cement. For

obvious reasons, quality requirements are stringent.
The cement quality depends on the process arrangement,
(which will not be discussed in detail here), but even
more on the raw material quality. The maximum P20S
content and the fluorine content of the phosphogypsum
are limited. Amounts of less than 1.0 % P20S, or better
even 0.6 % P20S, can be reached by two~stage phosphoric
acid processes such as the Norsk Hydro Hemidihydrate
process. However, the specified fluorine contents of
less than 0.4 % F in the phosphogypsum requires parti-
cular purification processes or specific raw phosphate
mixes.

A third product, i.e. aggregate for road construction,

also needs to meet stringent quality requirements:
Mechanical strength, chemical stability, degradation
resistance are important characteristics. We understand
the first samples tested in the lab produced
satisfactory results. Whether the radioactivity of the
has any adverse effect in this application has to be
checked with authorities.
 (LURGI)
- 26 -

A fourth possible product - quick lime - contains al~

the impurities from the phosphogypsum. Moreover, the
quick lime is essentially dead burnt and is very fine.
We have not yet made any detailed investigations as to
its marketability.

c) Market Potential

Sulfuric acid will certainly be welcome in those geo-

graphic areas where phosphogypsum is available and
which are dependent upon elemental sulfur. If sulfuric
acid produced by gypsum decomposition is economic and
the price is independent of the fluctuations of world
market prices of sulfur, the fertilizer industry would
be pleased. However, the energy situation of most exis-
ting plants would have to be studied in detail since
steam from sulfur burning would no longer be availabe
for phosphoric acid concentration. Modern phosphoric
a~id processes can, however, produce highly concen-

trated phosphoric acid directly from the filter and can

virtually operate without steam. A modification of
existing plants to use these processes is neither
complicated technically nor costly.

The Muller-Kuhne process produces a ton of clinker/

cement along with each ton of sulfuric acid. Clearly,
cement transportation costs from the producer to the
consumer are an important factor. Cement market equili-
brium, for instance in Florida, may be notably
disturbed by one or two new cement plants.
(
 (LURGI)
- 27 -

Such a plant however would, be most welcome in Algeria

where cement production is insufficient. Although in
this case too, the location is important in view of
transportation costs.

Obviously present cement producers are not enthused at

the prospect of every fertilizer complex becoming
cement producer. Therefor we should endeavor to include
cement manufacturers as part of the team that develops
a gypsum decomposition plant. Or, at least look to them
as a good market for the quick lime (which is a good
feed material to the cement kiln).

The market potential for aggregate material may be

assumed to be even more dependent upon local condi-
tions. Florida is an ideal market, because there are
virtually no local materials which could be used as
road aggregate. In Algeria, on the other hand, artifi-
cial aggregate has virtually no market.

d) Environmental Aspects

It was only a few years ago in the USSR that a gypsum

decomposition project (based upon the Muller-Kuhne pro-
cess) was not realized because it did not ensure that
the fluorine content in the effluents would be within
statutory limits. Throughout the world, regulations are
becoming more prohibitive.
 (LURGI)
- 28 -

Phosphogypsum impurities such as heavy metals (Table

4 + 5) and fluorine, which cannot be tolerated in the
products, must be eliminated. This means that a
disposal area is required and that one is left with an
additional problem.

Some countries are seriously considering placing statu-

tory limits on levels of radioactivity, whether it
comes from natural or from artificial sources.

As it is inevitable that when one uses such complex raw

materials as phosphogypsum and low-cost carbon fuels,
particular attention will have to be given to the
potential environmental impact.
 (LURGI)
- 29 -

Conclusions

As you are probably aware Lurgi as a company is uniquely

qualified (by way of our worldwide experience in providing
plants and units wnich cover all aspects of each of the
presented technologies and in fact all of the processes
currently and historically applied to gypsum decomposition
and/or processing) to answer the question presented by this
paper:

Is gypsum decomposition commercially ready now?

We know that pnosphogypsum decomposition is possible by a

commercial process - the Muller-Kuhne process. The fact
that this process has not dominated the field throughout
the world is essentially because of economic factors. The
technical problems inherent in this process have been
mastered.

The other processes nave not yet been demonstrated at

commercial scale. There may well still be a few technical
problems ahead. However, economic obstacles may be even
greater. Unless very favorable conditions prevail, these
processes are currently unsuitable to provide an acceptable
R.O.I. based upon Western standards. This may be different
in the future if there is a decisive change in the general
situation. There will certainly be special cases where
phosphogypsum decomposition may be viable.

All we ask is when you think of gypsum decomposition,

think of Lurgi!
 (LURGI)

Figure 1

Phosphogypsum Destiny

Phosphate Rock Sulfuric Acid

~
Phosphoric
Acid Process

- Phosphoric Acid

Phosphogypsum

Fuel

Treatment Decomposition

Sulfuric
Acid
Enviromental Building Material Clinker
Problems Soil Conditioner Lime
Ammonium Aggregate
Sulphate
rtJ -I:;;:
fvx (, tt1rs
-f/1~
 (LURGI)
Figure 2

Muller - Kuhne Process

Phosphogypsum Additives, Coal

Drying and Calcining Grinding

Decomposition and Clinkering

Clinker Cooling Sulfuric Acid Plant

Clinker Sulfuric Acid

 Figure 3
Highly concentrated
502 off-gases

TertiQry air

'\.

Gypsum and cemen .t

specific additives

Fuel and
redu c ti on agen t
Material discharge

'---___--a..-_ _ Ftuidi sati on air

CLURGI) (FB for Gypsum

 (LURGI)
Figure 4

Lurgi Circulating Fluid Bed

Process (Li me)

Phosphogypsum, Fuel

Drying and Calcining

Decomposition

Sulfuric Acid Plant

Lime Sulfuric Acid

 (LURGI)
Figure 5

Lurgi Circulating Fluid Bed

Process (Clinker)

Phosphogypsum Additives, Coal

Drying and Calcining Preparation

Decomposition

Clinkering Sulfuric Acid Plant

Clinker Sulfuric Acid

 (LURGI)
Figure 6

DMC / FIPR Process

Phosphogypsum Pyrites Coal

Feed Material
Coal Processing
Preparation

Fuel Gas
Cleaning

r Sulfur
Fuel G-a-s--"";
~----~----~~ ~----------~~
Steam and Power
Decomposition
Generation

Sulfuric Acid
Aggregate
Plant

Aggregate Sulfuric Add Steam Power

Table 1

Muller-Kuhne Process
Reference List

Location Year No. No. of Capacity Remarks

of kilns S.A.-Plants H2S04 tpd

Leverkusen, Germany 1918 1 40 Pilot Plant

Wolfen, Germany 1936 1 2 2 x 50

1938 1 2 2 x 50
1954 2 4 4 x 50

Billingham, U.K. 1931 1 1 130

1935 1 1 200
1955 1 1 280
f'I
Miramas, France 1938 1 10 Pilot Plant c:
Widnes, U.K. 1955
1966
1
1
1
1
210
210 ...0"
Whitehaven 1955 2 2 2 x 180
1962 1 1 240
1966 2 2 300

Linz, Austria 1954 1 1 150 (230)

Coswig, Germany 1960 2 2 2 x 250

1962 2 2 2 x 250

Wizow, Poland 1955 2 2 520

Palabora, South Africa 1972 1 1 350

China 1987 1 1
 (LURGI)

(
Tab~e 2

Typical Phosphogypsum Analysis

(% by weight, dry basis)

CaO 30,0 - 32,0 % (30) **

S03 42,0 - 44,0 % (42,4) **
P205 0,65 %
F 1,0 %
A1203 0,2 %
Si02 2,0 %
( Fe203 0,1 %
K20 0,02 %
MgO 0,1 %
H2 0 * 19,0 %
free moisture 12,0 %

* water of crystallization
** for calculation of capacities

(
 (LURGI)

(
Table 3

Typical Coal Analysis

Low-grade bituminous coal

(% by weight, dry basis)

C 57,5 %
H 4,0 %
0 7,5 %
N 1,1 %
H2 O 5,0
"
c. S
Ash
8,0
16,9
"
"
 (LURGI)

Table 4

Heavy Metals in Phosphogypsum (1)

from Maritime and Magmatic Phosphates

(typical average in ppm)

Maritime Magmatic

C. Zn 15 1

Cu 6 4

Pb 4 6

As 5 3

Ni 9 < 1

Hg 0,1

Cd 8 < 1
 (LURGJ)

(
Table 5

Cadmium in" Phosphate Rock (5)

(typical average in ppm)

Algeria 23

Israel 26

Jordan 1

C Marocco 17

Nauru 90

Senegal 84

Togo 54

Tunesia 56

Florida 8

(
 (LURGI)

(
References:

K. Weterings: The utilisation of phosphogypsum

Proceedings No. 208, The Fertilizer
Society 1,982

H. W. Gosch: Production of Sulfuric Acid and Portland

Cement from Phosphogypsum - Technical and
Economical Aspects -
Seminar: Raw materials in South Africa
March 1 - 3, 1983

(3) T. J. Kendron,
G. M. Lloyd: Phosphogypsum to Sulfuric Acid with
Cogeneration - a Competitive Edge
Second Int. Symposium on Phosphogypsum
December 1986

( 4) K. Knosel,
R. Lutz: New Technology for the Processing of
Phosphogypsum to H2S04 and Cement clinker
Seminar on Phosphogypsum Utilization
Istanbul, Turkey 1987

(5) H. V. Plessen,
G. Schimmel: Verminderung des Cadmium Gehaltes von
Rohphosphaten und Mineraldungern
Chem. Ing. Techn 59, Nr. 10, S 772 - 778

(6) M. Tacke,
A. N. Silberberg: Is Gypsum the Alternative?
AICHE Lakeland, Florida 1986