Coal desulfurization by aqueous chlorination

A method of desulfurizing coal is described in which chlorine gas is bubbled through an aqueous slurry of coal at low temperature below 130 degrees C., and at ambient pressure. Chlorinolysis converts both inorganic and organic sulfur components of coal into water soluble compounds which enter the aqueous suspending media. The media is separated after chlorinolysis and the coal dechlorinated at a temperature of from 300 degrees C. to 500 degrees C. to form a non-caking, low-sulfur coal product.

Technical Field 
The present invention relates to desulfurization of coal and carbonaceous 
substances and, more particularly, to a low temperature process for 
removing sulfur from coal. 
Background Art 
The U.S. reserve of coal is about 3 trillion tons. Although the most 
abundant (80%) fossil fuel in America is coal, the U.S. consumption 
pattern is quite a reversal of form in terms of utilization, with coal 
representing only 17%, oil and gas about 78%. 
The demand for all fossil fuels combined is expected to double by the year 
2000, even with increasing the use of nuclear power. While the domestic 
supply of crude oil and natural gas is not likely to keep pace with the 
energy demand, coal can play an important role in filling such a gap and 
thus reduce the requirements for imported supplies of oil and gas. 
Coal, the fossilized plant life of prehistoric times, contains various 
amounts of sulfur due to the nature of its origin. Under most existing 
commercial technology, the generation of electricity from coal poses 
environmental problems because of sulfur oxides and particulate emissions. 
Since most of the coals in this country, particularly the Eastern and 
Midwestern coals, have high sulfur content (&gt;2%) there is a need for an 
economical process of converting high sulfur (2%) coals to clean fuel 
(&lt;1.2 lbs of SO.sub.2 emission per million Btu by EPA standard) in order 
to utilize coal as a source of energy without causing serious air 
pollution. So the need for converting massive coal reserves to 
clean-burning solid fuel, liquid fuel and pipeline quality gas is 
self-evident. If the vast coal reserve is converted to clean fuel, it can 
supply most of the energy needs of the United States for the next three 
centuries. 
At the present time, about one-half of the electric power in the United 
States is generated from natural gas and petroleum; most of the other half 
is from coal. If the coal is converted to clean fuel for electric 
utilities, petroleum and natural gas would be released for other essential 
uses, especially as a starting material for the synthetic rubber and 
plastics industry. 
Sulfur in coal occurs in two types, generally in approximately equal 
amounts of inorganic sulfur primarily as pyrites with minor amounts of 
sulfates and of organic sulfur in the forms of thiophene, sulfide, 
disulfide and mercaptan chemically bound in the organic structure of coal. 
The sulfur oxides in the combustion gases of coal can be removed by stack 
gas scrubbing methods but those are expensive processes and produce large 
amounts of sludge. Hydrodesulfurization processes which remove sulfur from 
the fuel before combustion are effective. They are used extensively in 
petroleum desulfurization and many coal conversion processes under 
development. However, they are also expensive due to the cost of hydrogen 
and severe operating conditions required. 
Physical separation methods can only remove the inorganic sulfur. Other 
desulfurization schemes under investigation such as TRW Meyers' process 
and Battelle Hydrothermal Coal Process are either primarily for inorganic 
sulfur removal or are operated at high temperature and pressure resulting 
in high process cost and in the physical disintegration of the coal. 
A promising new process utilizing chlorine for removing organic and 
inorganic sulfur is described in U.S. Pat. No. 4,081,250. The three-stage 
process includes an initial room temperature chlorine treatment of coal 
slurry suspended in solvent/water media. After chlorinolysis a batch 
hydrolysis and solvent recovery is carried out. Finally, dechlorination at 
300 degrees C. to 450 degrees C. yields a desulfurized coal product. This 
process requires use of a chlorine resistant solvent such as methyl 
chloroform which is recovered by steam distillation. Operating experience 
has shown that sizable losses of solvent inherently occur for various 
reasons which may include physical absorption of solvent on solid and/or 
tarry residues and also chemical hydrolysis of methyl chloroform. 
Furthermore, methyl chloroform is a precursor to human carcinogens and may 
be damaging to the ozone layer. Methyl chloroform may be unstable and 
hydrolyze under the conditions practiced in this process. The process 
produces contaminated waste water which must be treated before discharge. 
It was previously believed that methyl chloroform or other organic solvent 
was necessary to dissolve coal components and to carry the organic sulfur 
compounds into solution for reaction with chlorine in the solvent phase. 
DISCLOSURE OF THE INVENTION 
It has now been discovered that organic solvent is not necessary to the 
desulfurization of coal by chlorine and that all that is required is a 
minimum amount of liquid medium to carry chlorine which penetrates the 
coal particle and reacts with the sulfur compounds. An aqueous, 
solvent-free carrier is equally effective, if not, superior medium for the 
chlorinolysis desulfurization reaction. 
The aqueous chlorinolysis process does not require a separate hydrolysis 
step thus eliminating the capital cost of a separate vessel, process-water 
cost and clean-up of the waste leaching water. Furthermore, distillation 
is not required to recover the solvent again resulting in a considerable 
savings in capital equipment and energy. Large quantities of coal can be 
readily handled and treated in a single reactor vessel and multipurpose 
filter-dechlorinator. The use of costly solvent potentially hazardous to 
operating personnel and to the environment is eliminated. The process can 
be operated at ambient conditions and the agitation of an aqueous coal 
slurry in a pipelines may be suitable for practice of the chlorinolysis 
step of the process. 
Chlorinolysis produces improved feedstock for combustion and gasification 
operations as the final treated coal is rendered completely non-caking and 
non-swelling. The organic sulfur removal is a significant advantage of 
this process. Being chemically bound to the organic structure of coal this 
sulfur is most difficult to remove without incurring high process cost. 
The desulfurization process of this invention can be used as a 
pretreatment step before combustion or gasification. The processing scheme 
is simple and is compatible with current coal processing technologies. 
Furthermore, no feeding or filtration problems are expected. Since this 
coal desulfurization process is at atmospheric pressure and mostly at low 
temperature the process cost is expected to be much lower than other 
desulfurization schemes. 
These and other features and attendant advantages of the invention will 
become readily apparent as the invention becomes better understood by 
reference to the following detailed description when considered in 
conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
As shown in FIG. 1, pulverized coal is mixed with water in mixing apparatus 
10 to form an aqueous coal slurry 12 containing from 15 to 60% by weight 
of coal preferably about 20 to 40% by weight. The fine size coal and 
aqueous suspending media provide efficient access for chlorine to the coal 
particles in chlorinator 14. Chlorine is added continuously through line 
16. The chlorine is provided in a stoichiometric ratio of 3.5 to 4.0 moles 
of chlorine per mole of total sulfur. The particular amount added to the 
coal slurry depends on the size of the coal, duration of chlorination, 
chlorine injection rate, temperature and amount of sulfur in the coal. 
Typically, from 10% to 50% by weight of chlorine is added to high sulfur 
coal containing it least 2% total sulfur. The chlorinated coal is 
delivered through line 18 through separation means 20 which can be a 
filter or centrifuge or like device. The separated coal can be washed with 
water in the device 20. The washed coal is then delivered to 
dechlorination unit 22 through line 24 and is heated to a temperature of 
from 300 degrees C. to 450 degrees C. to yield a treated, low-sulfur coal. 
Chlorinonlysis is conducted at a low temperature generally below 130 
degrees C. preferably from ambient, e.g. 20 degrees C. to 100 degrees C. 
The chlorinolysis step can be operated at ambient atmospheric pressure or 
at elevated pressure of from 1 to 5 atmospheres. The coal slurry should be 
agitated during chlorinolysis. Chlorine dispersion into the coal slurry is 
significantly improved by use of good agitation. During chlorinolysis the 
pyritic and organic sulfur in the coal is converted to sulphate sulfur 
which dissolves in the aqueous media. Effective desulfurization is 
achieved at a chlorine flow rate of from 1.0 to 50 SCF per hour, per 
kilogram of coal usually about 3 to 25 SCF per hour per kilogram of coal 
in about 0.1 to 3 hours. The coal slurry may remain in the reactor or in a 
holding tank following chlorination to complete hydrolysis and leaching of 
the soluble sulfate reaction products into the aqueous media. The 
hydrolyzed coal is then dechlorinated to a chlorine content below 1.0%, 
preferably at 0.1% by heating the coal with inert gas to a temperature 
above 300 degrees C. The hydrogen chloride evolved during chlorination and 
dechlorination can be recovered as a valuable byproduct or it can be 
converted to chlorine gas for recycle by a commercial process such as the 
KEL-CHLOR process developed by M. W. Kellogg Company. 
The desulfurization process is capable of desulfurizing diverse types of 
organic material in addition to coal such as petroleum, oil shale, 
industrial waste, particularly black liquor residue from sulfate or 
sulfite pumping. The coals suitable for desulfurization treatment in 
accordance with this invention can be bituminous, sub-bituminous or 
lignite containing at least 0.2% sulfur. Pulverization aids the 
chlorinolysis reaction rate. Typically, the coal will be pulverized and 
classified to 40 to 325 mesh, usually from 100 to 200 mesh. 
A more detailed process is illustrated in FIG. 2. Water and powdered coal 
are added through lines 40, 42 respectively to slurry tank 44 containing 
mixing element 45. Chlorinolysis reactor 46 contains a chlorine diffuser 
such as a sparger ring or fritted diffuser element 48, an internal steam 
coil 50 having an outlet exhausting into the reactor, an agitator 47 and a 
slurry inlet 52 and a slurry outlet 54. The slurry is transferred through 
line 56 to inlet 52. Steam generator 58 is operated to deliver steam to 
the coil 50 to maintain reaction temperature, suitably at 65 degrees 
C..+-.5 degrees and the valve 60 on chlorine supply cylinder 62 is 
activated to deliver the required amount of chlorine to the slurry in 
reactor 46. 
After chlorinolysis has proceeded to completion, the slurry is transported 
through line 54 by means of pump 74 when valve 71 is open to continuous 
separation and wash station such as a porous loop belt or screen 76 driven 
by rollers 78. The coal can be washed by means of spray heads 80 mounted 
over the screen 76. The dewatering of the slurry can be assisted by 
vacuum, not shown. The washed slurry is then fed to a continuous 
dechlorinator 82 containing cylinder 84 which is rotated by drive means 86 
and is externally heated by electrical heating coil 90 to a uniform 
temperature form 350 degrees C. to 450 degrees C. for 10 to 60 minutes. 
The heated cylinder 90 is mounted in a sleeve of insulation 84 such as 
refractory material. The cylinder is purged to remove HCl by means of a 
flow of inert gas 92 such as nitrogen. The purge gas is removed through 
line 94 to a scrubber 96 containing a HCl absorbent such as caustic. 
Examples of practice follow: 
EXAMPLE 1 
A sample of Illinois No. 6 Knox coal coded as Raw Coal PSOC 190 was 
analyzed by ASTM-approved methods. Moisture content was 16 wt.%. Total 
sulfur was 2.49%; pyr. S. was 0.16; organic sulfur was 1.53% and sulf. S 
was 0.80%. 
Then 11.6 grams of PSOC-190 coal was ground to -100 to +200 mesh, admixed 
with 350 cc of water, chlorinated at 0.2 SCFH of chlorine for 60 minutes 
in a stirred reactor equipped with a reflux condenser, dry ice cold trap 
and sodium hydroxide scrubber. The chlorination temperature was 60 degrees 
C. with a miximum temperature rise during the first ten minutes of 
reaction of 5 degrees C. The treated coal, after chlorination, was 
filtered and dried under vacuum up to 95 degrees C. for two hours. No 
hydrolysis or dechlorination was attempted. Analysis of the product showed 
the following: 
______________________________________ 
Total sulfur removal 47% 
(Organic + pyritic) S removal 
29% 
______________________________________ 
EXAMPLE 2 
When chlorinolysis was repeated under the conditions of Example 1 with 
methyl chloroform as the suspending medium, the total sulfur removal was 
only 17% and (Organic+pyritic) S removal was 27%. It is to noted that the 
presence of 16% moisture in the feed coal would provide some water content 
during chlorinolysis. 
EXAMPLE 3 
When chlorinolysis was repeated under the conditions of Example 1 an equal 
mixture of water and chloroform as the suspending medium the total sulfur 
removal was only 12% and the (Organic+pyritic) S removal was 26%. 
Thus, in these small batch experiments an organic solvent-free, aqueous 
medium provides significantly improved desulfurization. 
A further set of comparison runs were conducted as follows. 
100 grams of coal sample ground to -100 to 200 mesh, 200 grams of solvent, 
30 grams of water, chlorinated at 0.5 SCFH of Cl.sub.2 for 45 minutes in a 
stirred 500 ml. flask equipped with a reflux condenser, dry ice cold trap 
and gas holder over water. Methyl chloroform was distilled from the sample 
after chlorination was ended and water had been added. Sample was washed 
to remove water soluble sulfate compounds, dried and then dechlorinated at 
400 degrees C. for 30 minutes. Only a 2 to 4 gram sample was dechlorinated 
at a time. Chlorination was conducted at a water bath temperature of 65 
degrees C. With the exothermic heat of reaction, the reaction temperature 
was probably somewhat higher but was confined to 74 degrees C. maximum, 
i.e., B.P. of methyl chloroform. The data is presented in the following 
table. 
TABLE 1 
__________________________________________________________________________ 
Raw Coal 
Treated Coal 
Sulfur Removal 
(%) (%) (%) 
__________________________________________________________________________ 
Example 4 
Coal PSOC 190 [Illinois # 6] 
Total S 
3.05 1.43 53 
Control Run Pyr. S 1.05 0.05 95 
Methyl chloroform solvent 
Org. S 1.90 1.38 27.4 
H.sub.2 O/Coal-0.3 Sulfate S 
0.10 0 -- 
Example 5 
Coal PSOC 190 [Illinois #6] 
Total S 
3.05 1.59 48 
Methyl chloroform solvent 
Pyr. S 1.05 0.07 93.5 
H.sub.2 O/Coal - 0 Org. S 1.90 1.52 20.0 
Time: 45 minutes Sulfate S 
0.10 0 -- 
Example 6 
Coal PSOC 219 [Kentucky # 4 Bitum] 
Control Run 
Methyl chloroform solvent 
Total S 
2.56 0.91 65 
H.sub.2 O/Coal = 0.3 Pyr. S 1.4 0.15 89.5 
Time: 45 minutes Org. S 1.08 0.76 29.6 
Sulfate S 
0.08 0 -- 
Example 7 
Coal PSOC 219 [Kent. # 4 Bitum.] 
Total S 
2.56 0.90 65 
Water as solvent Pyr. S 1.4 0.23 83.5 
Methyl chloroform = 0 
Org. S 1.08 0.67 38.0 
H.sub.2 O/Coal = 2 Sulfate S 
0.08 0 -- 
Time: 45 Minutes 
__________________________________________________________________________ 
As can be observed from Table 1, the run (Example 7) utilizing water as the 
suspending and leaching medium provided the highest organic sulfur removal 
and equal total sulfur removal to the control run using anhydrous methyl 
chloroform (Example 5), or methyl chloroform-water mixtures (Example 4 and 
6). 
Further experiments were conducted in a bench scale, acid brick lines 
reactor providing chlorination of 2 kilogram batches of coal at a water to 
coal ratio of 2/1 at temperatures of 50 to 150 degrees C. and pressures of 
0 to 100 psig using gaseous chlorine injected into the coal slurry. The 
coal-water slurry is dewatered and washed in a vacuum filter and then 
dechlorinated by an electrically heated Lindberg furnace equipped with a 
5-inch diameter by 5 feet long rotary tube with a 2 kilogram coal 
capacity. 
The reactor was leak tested under nitrogen pressure, purged with nitrogen 
and charged with two kilograms of coal (100 to +200 mesh, weight corrected 
for coal moisture) and four kilograms of solvent (either methylchloroform 
or water). In most runs, the reactor off-gas valve to the reflux condenser 
was closed with injected chlorine confined to the coal slurry and ullage 
space in the reactor. Agitation was set in the first few runs at 275 RPM 
based on Chemineer design standards. With the majority of runs agitation 
was set at 565 RPM, the maximum agitator speed. Direct steam injection 
provided reactor preheat to the desired operating temperature in 20 to 30 
minutes. Chlorine flow was then initiated to the reactor and adjusted to 
the prescribed flow rate. For operation at elevated pressures, a high 
initial flow rate of chlorine was set to establish the desired pressure 
and then reduced to the desired flow rate and/or flow rate compatible with 
maintaining the pressure level. Cooling water flow was adjusted to control 
the reactor temperature at prescribed levels. Coal slurry samples were 
obtained at 15, 30, 45 and in some cases 90 minutes. Samples were 
approximately 100 grams obtained close to the wall and near the reactor 
bottom. Stirring was sufficiently intense to insure a representative coal 
slurry sample. 
Chlorine injection was initially through a 1/4-inch stainless steel tube 
located to the side and near the reactor bottom, beneath the turbine 
impeller. With high chlorine flow rates (&gt;20 SCFH) and poor chlorine 
diffuser injection, there was a rapid reactor pressurization, i.e., 20-30 
psig in &lt;5 minutes. A reduced chlorine flow rate (10 SCFH) and good 
chlorine diffuser injection provided relatively little reactor 
pressurization (i.e., &lt;5 psig) in 30 to 45 minutes until the coal slurry 
was apparently saturated with chlorine. At that point, rapid reactor 
pressurization occurred unless chlorine flow was stopped or sharply 
reduced. In some runs, chlorine flow rates had to be substantially reduced 
form initial values at the start of the reaction in order to avoid over 
pressurization with a closed reactor system. In some cases a continuous 
vent of off-gases, i.e. chlorine, was maintained to allow continued 
chlorine injection into the coal slurry. With fritted glass diffusers, 
problems were experienced with plugging by coal tar after 20 to 30 minutes 
of reaction time. This problem was also encountered when a teflon diffuser 
tube was used with hole sizes less than 1/32-inch. Chlorine dispersion 
into the coal slurry was also found to be improved by increasing agitator 
speed form the initial setting of 275 RPM to 565 RPM. 
After chlorination, reactor pressure is reduced by venting reactor gases 
through the reflux condenser, gas holder and to the caustic scrubber. With 
methylchloroform in the reactor, four kilograms of water are added and 
direct steam injection is used to heat the reactor and flash distill the 
methylchloroform to the condenser and solvent recovery tank. Steam is 
added until the temperature rise goes from 74 degrees C. to approximately 
100 degrees C., indicating that methylchloroform removal is complete. 
Hydrolysis is considered to be essentially complete during the 
chlorination reaction since water is present from the steam condensate in 
reactor preheat and coal moisture. Flash distillation of methylchloroform 
normally takes 45 to 60 minutes. After solvent recovery, the coal-water 
slurry is cooled, removed through the bottom drain into a hooding tank and 
transferred to the batch vacumn filtration unit. 
With water as the solvent, the flash distillation step is circumvented. To 
provide comparable reactor operating conditions between methylchloroform 
and water runs, some water solvent runs were made with the coal slurry 
held in the reactor for one hour at temperatures of 65 to 100 degrees C. 
after the chlorination. Thus, if additional reaction or leaching of the 
coal was possible during the additional holdup time, this would be 
indicated by comparing analytical results of the processed bulk samples 
and samples withdrawn prior to the holdup period. 
The coal-water slurry is added to the batch vacuum filtration unit. An 
exhaust blower provides 20 to 30 inches of water column vacuum. A water 
spray manually applied provides a displacement water wash of the filter 
cake with water/coal addition at 2/1. 
Coal samples were removed form the vacuum filter and dried in a vacuum oven 
overnight at 100 degrees C. A majority of sulfur analyses were performed 
on the dried but undechlorinated coal samples. Some sulfur form analyses 
were performed in duplicate on dechlorinated and undechlorinated samples. 
Analytical results were found to be comparable. Since the dechlorinator 
was not available until late in the program, a majority of chlorinated, 
washed, dried coals were stored for up to 3 months in closed glass 
containers before dechlorination. 
Dechlorination of the coal was obtained in a Lindberg furnace equipped with 
a rotary 5-inch diameter by 5-foot long tube. The furnace and tube were 
preheated to the operating temperature of 400 degrees C., flushed with 
nitrogen and charged with 2 kilograms of coal. Approximately 30 minutes 
were required to heat the coal charge to 400 degrees C. while maintaining 
a nitrogen purge of 30 SCFH. The coal is then held at 400 degrees C. for 
an additional 30 to 60 minutes. Tube rotation was maintained at 4 RPM. 
After dechlorination, furnace heat was shut down while maintaining the 
nitrogen purge. After 30 to 60 minutes of cooling, the coal was removed 
and stored in a closed glass container. 
The major portion of coal analyses including sulfur forms (pyritic, sulfate 
and total sulfur), ultimate analyses, proximate analyses and trace element 
analyses of both raw and treated coal samples were conducted according to 
the ESCHKA method for total sulfur analysis and ASTM approved procedures 
for pyritic and sulfate sulfur with organic sulfur determined by 
difference. A majority of coal samples were analyzed before 
dechlorination. A Leco acid-base analyzer was used to provide immediate 
total sulfur analyses after completion of each test run. Because of 
potential chlorine interference, 2-4 gram samples of the treated coal were 
first dechlorinated in a laboratory unit before Leco sulfur analyses. 
Water filtrate solutions form the chlorinator and vacuum filter were 
analyzed for sulfates, chlorides, iron and trace elements. 
The 5 coals selected for the bench-scale batch reactor tests are listed in 
Table 2 with attendant analyses for organic, pyritic and total sulfur. 
They are bituminous coals obtained from Ohio, Illinois and Kentucky. Five 
tons each of PSOC 276 and PSOC 282 were obtained directly form the mine 
site. Coal samples of PSOC 219 and 026 were obtained form the Penn State 
Coal Bank during the laboratory scale test program. Island Creek Coal was 
obtained form DOE. PSOC 282 represents a washed coal with an original 
unwashed sulfur content of 2.2 weight percent, versus 1.62 weight percent 
ottal sulfur for the washed coal. Preliminary coal desulfurization data 
are reported for only four of the coals with the Island Coal results 
pending rom the analytical laboratory. 
A total of 44 test runs were conducted with 15 runs on coal PSOC 276, 19 
runs on coal PSOC 282, 2 runs on PSOC 219, 3 runs on PSOC 026 and 5 runs 
on Island Creek Coal (Western Kentucky, Union County #9 Seam). Only a 
portion of the analytical data are available for presentation at this 
time. 
TABLE 2 
__________________________________________________________________________ 
ERDA Ash 
PSOC Content 
Sulfur Content, Wt. % 
Number 
Seam, County and State 
Rank (Wt. %) 
Organic 
Pyritic 
Total 
__________________________________________________________________________ 
276 OHIO, No. 8, Harrison OHIO 
HVA, Bit. 
11.2 1.19 2.67 3.89 
282 Ill. No. 6, Orient No. 6 
Bit. 6.7 0.74 0.78 1.62 
Mine, Washed* 
219 Kentucky No. 4, Hopkins, 
HVA, Bit. 
8.1 0.77 0.74 2.14 
Ky. 
026 Ill. No. 6, Saline, Ill. 
HVC, Bit. 
10.8 1.62 4.20 3.47 
Island 
Western Kentucky, Union 
Bit. 12.6 1.53 1.97 3.54 
Creek 
County No. 9 Seam 
__________________________________________________________________________ 
*Unwashed Coal Had 2.2 wt. % Total sulfur, 22 wt. % ash. 
A smmary of operating conditions for the chlorinolysis reaction and 
attendant coal desulfurization data for organic, pyritic and total sulfur 
is presented, Table 3. Desulfurization data are presented for reaction 
times of 15, 30, 45 and 90 minutes with methylchloroform and water as 
solvents. Operating conditions ranged from: 63 to 130 degrees C., 0-60 
psig, chlorine feed rates of 5 to 24 SCFH. Methylchloroform runs were 
generally confined to 65 degrees C. and water runs were at 65 to 130 
degrees C. 
The bench scale batch reactor was operated under the following conditions: 
Coal, 2 kilograms, -100 to +200 mesh; solvent to coal, 2/1; preheat steam 
condensate added to reactor, 300-500 grams at 65 degrees C., 2500 grams at 
130 degrees C., additional water in solvent runs zero except for 160 grams 
in run 7 and moisture in coal; agitator speed runs (1-6) at 275 rpm, runs 
(7-44) at 530 rpm: Chlorine injection, runs (1-7) 1/4 inch tubing, runs 
(8-19) fritted glass diffuser, runs (20-44) 1/4.times.1/2 inch diameter 
Teflon tubing drilled with 1/4 to 1/8-inch holes, nominal size 1/8-inch. 
The data on coal desulfurization by low temperature chlorinolysis follows 
in Table 3. 
3 TABLE 3 
Operating Conditions Time (Minutes)/Residual Sulfur (Wt. %) Run Temp 
Pressure Chlorine Feed 15 30 45 90 and Date (.degree.C.) (psig) 
(SCFH) (kg) ORG PYR TOT. ORG PYR TOT. ORG PYR TOT. ORG PYR TOT. ORG PYR 
TOT. 
Coal PSOC 276 With Methyl Chloroform as Solvent 7-5/24/79 63 1-3 19 
1.32 1.19 2.67 3.89 1.35 1.03 2.38 1.24 0.62 1.92 1.20 0.50 1.71 
0-6/5/79 65 9-13 10 0.68 1.29 1.51 2.80 1.41 0.99 2.40 1.31 0.64 1.95 
1-5/4/79 65 1-27 15 1.05 1.31 1.19 2.50 1.28 0.65 1.92 1.32 1.37 1.69 
2-5/8/79 65 12-29 15 1.00 1.29 0.78 2.07 -- -- -- -- -- -- 3-5/10/79 
65 1-50 15 1.00 1.29 1.10 2.39 1.27 0.58 1.85 1.22 0.48 1.70 Average 
65 1.31 1.12 2.43 1.30 0.71 2.02 1.26 0.50 1.76 Removal (%) 65 
-10.1 58.0 37.5 -9.2 73.4 48.1 -5.9 81.3 54.7 Coal PSOC 276 With Water 
as Solvent 4-5/15/79 65 1-42 11 0.75 1.19 2.67 3.89 1.16 1.79 2.95 1.40 
1.21 2.62 1.30 1.19 2.49 8-5/30/79 65 1-5 11 0.78 1.24 1.53 2.78 
1.32 0.98 2.31 1.36 0.66 2.02 9-6/1/79 65 2-5 11 0.78 1.33 1.80 3.13 
1.29 1.58 2.88 1.35 1.08 2.43 11-6/7/79 77-89 4-38 16 0.36 1.21 2.04 
3.26 -- -- -- -- -- -- -- -- -- 12-6/8/79 90 1-10 13 0.88 1.30 2.01 
3.32 1.37 1.51 2.88 1.49 0.98 2.48 5-5/18/79 99 1-38 6 0.39 1.17 
2.00 3.17 1.34 1.24 3.08 1.34 1.50 2.84 6-5/21/79 102 1-48 22 1.47 
1.21 1.53 2.74 1.27 1.10 2.37 1.22 0.92 2.14 16-6/18/79 123 26-35 9 0.79 
1.37 1.31 2.68 1.38 1.21 2.59 1.26 1.07 2.32 1.40 0.97 2.37** 
13-6/12/79 125 32-47 6 0.37 1.21 1.47 2.68 1.31 1.28 2.58 1.39 1.24 
2.63 14-6/13/79 128 23-45 15 0.99 1.33 1.48 2.81 1.29 1.05 2.33 1.26 
1.12 2.38 Average 1.25 1.70 2.95 1.33 1.29 2.63 1.33 1.08 2.41 
Removal (%) -5.0 36.3 24.2 -11.8 51.7 32.4 -11.8 59.5 38.0 Coal 
PSOC 282 With Methyl Chloroform as Solvent 27-7/20/79 62 4-20 16 1.05 
0.74 0.78 0.78 0.70 0.61 1.37 0.63 0.57 1.26 0.56 0.62 1.28 0.55 0.66 
1.21 17-6/29/79 65 0-11 5 0.36 0.53 0.54 1.10 0.38 0.48 0.95 0.53 
0.47 1.05 21-7/10/79 65 6-40 20 1.32 0.64 0.45 1.17 0.48 0.46 0.99 
0.32 0.55 0.94 0.13 0.69 1.00 23-7/13/79 65 0-45 22 1.51 0.59 0.48 
1.17 0.36 0.54 1.02 0.17 0.71 0.99 25-7/18/79 63 0-7 8 0.52 -- -- -- -- 
-- -- -- -- -- -- -- -- 19-6/25/79 85 2-18 16 1.10 0.71 0.51 1.22 
0.54 0.45 1.05 0.41 0.52 0.99 Average 0.63 0.52 1.21 0.48 0.50 
1.05 0.40 0.57 1.05 0.34 0.67 1.10 Removal (%) 14.9 33.3 25.3 
35.1 35.9 35.2 45.9 27.0 35.2 54.0 14.1 32.1 Coal PSOC 282 With Water as 
Solvent 15-6/15/79 70 1-4 13 0.87 0.74 0.78 1.62 0.71 0.61 1.32 0.74 
0.41 1.15 0.73 0.35 1.07 18-6/22/79 88 2-7 12 0.80 0.76 0.54 1.29 
0.71 0.42 1.14 0.71 0.40 1.11 22-7/12/79 90 0-39 12 1.66 0.75 0.50 
1.26 0.73 0.42 1.16 0.71 0.40 1.11 0.55 0.37 0.91 24-7/17/79 130 20-53 
10 0.65 0.79 0.54 1.33 0.74 0.45 1.18 0.80 0.44 1.24 0.67 0.40 1.06 
Average 0.75 0.55 1.30 0.73 0.42 1.16 0.74 0.40 1.13 0.61 0.38 
0.98 Removal (%) -1.3 29.5 19.7 1.3 46.1 28.4 0.0 48.7 30.2 17.6 
51.2 39.5 Coal PSOC 219 With Methyl Chloroform as Solvent 28-7/23/79 65 
3-40 10 1.40 0.77 0.74 2.14 0.54 0.49 1.16 0.53 0.42 1.10 0.32 0.58 0.97 0 
.06 0.73 0.96 Removal (%) 29.9 33.8 45.8 31.2 43.2 48.6 58.4 21.6 
54.7 92.2 1.4 55.1 Coal PSOC 219 With Water as Solvent 29-7/25/79 65 
6-37 21 1.43 0.77 0.74 2.14 0.83 0.39 1.34 0.86 0.32 1.28 0.80 0.20 
1.09 0.86 0.14 1.00 Removal (%) -7.8 47.3 37.4 -11.7 56.7 40.2 
-3.9 72.8 49.1 -11.7 81.1 53.3 Coal PSOC 026 With Methyl Chloroform as 
Solvent 31-7/29/79 90 40 20 1.38 1.74 1.10 3.53 1.46 0.48 2.11 1.34 0.37 1 
.85 1.31 0.49 1.78 0.88 0.69 1.74 Removal (%) 9.9 60.0 39.2 17.3 
69.2 46.7 19.1 59.2 48.7 45.7 42.5 49.8 Coal PSOC 026 With Water as 
Solvent 30-7/16/79 65 30 19 1.26 1.59 0.65 2.34 1.69 0.37 2.06 1.69 
0.20 1.89 1.54 0.13 1.31 32-7/30/79 90 35 24 1.62 1.50 1.31 3.41 1.81 
0.62 2.42 1.72 0.32 2.04 1.69 0.23 1.92 Average 1.62 1.20 3.47 1.70 
0.63 2.38 1.70 0.34 2.05 1.69 0.21 1.90 Removal (%) -4.7 47.5 
31.4 -4.7 71.7 40.9 -4.3 82.5 45.2 4.9 89.2 47.8 
*O-Organic, PPyritic, TTotal 
**60minutes reaction time 
Inspection of the data in Table 3 indicates no apparent correlation of coal 
desulfurization for any of the coals with respect to temperature, pressure 
and chlorine flow rates. A substantial reduction of chlorine flow into the 
coal slurry did reduce coal desulfurization in Run 5 when equipment 
failure, i.e., corrosion of the chlorine injection tube provided injection 
of chlorine only into the top surface layer of coal slurry and ullage 
space of the reactor. However, changes in gaseous chlorine injection from 
a 1/4 inch tube opening located beneath the agitator impeller to a 
standard fritted glass diffuser element and finally to a Teflon tube 
drilled with 1/74 to 1/8-inch holes did not appear to affect the extent of 
desulfurization but did substantially alter the chlorine addition to the 
coal slurry solution. Use of chlorine injectors providing large gaseous 
chlorine bubbles into the coal slurry created a rapid reactor 
pressurization by chlorine whereas use of improved gas diffusers, smaller 
injection holes, provided very little reactor pressurization until an 
apparent coal slurry saturation with chlorine at 30 to 45 minutes. A 
substantial variance in temperature, pressure and chlorine flow rates 
existed between runs so that a substantial effect of these variables on 
coal desulfurization would have been evident if it existed. Reactor times 
of 15 and 30 minutes were sufficiently short so that kinetic effects could 
be observed in this operating range. A reaction time of 45 minutes 
provided a leveling off and/or peaking of coal desulfurization. 
Sulfur forms are listed in Table 3 for individual runs. Since temperature, 
pressure and chlorine flow had no apparent correlation with 
desulfurization data, all of the runs with a given coal and given solvent 
(methylchloroform or water) were averaged (Table 2) and average residual 
sulfur forms plotted with respect to reaction time. Average sulfur 
reductions in addition to average sulfur residuals were also calculated 
for organic, pyritic and total sulfur for each of the coals and solvents 
and plotted. 
A summary table of average sulfur removals for organic, pyritic and total 
sulfur is included, Table 4 for a reaction time of 45 minutes. Sulfur 
removals are indicated both as weight percent sulfur removal and as a 
percent removal of original sulfur. 
The bench scale batch reactor was operated under the following conditions: 
45 minute reaction time, 2 kg Coal -100 to +200 mesh, methyl chloroform 
runs at 65 degrees C., water runs at 65-130 degrees C., pressure at 0-60 
psig; chlorine feedrate at 5 to 24 SCFH; agitator speed 275-530 rpm, live 
steam preheat condensate to coal, 10-20 percent at 65 degree C., 125 
percent at 130 degrees C. (Ref. Table 3). The data follows. 
TABLE 4 
______________________________________ 
Organic Pyritic Total 
Sulfur Sulfur Sulfur 
Removal Removal Removal 
(Wt. (Wt. (Wt. 
Coal Solvent %) (%) %) (%) %) (%) 
______________________________________ 
PSOC-276 
MC* -0.07 -6 2.17 81 2.13 55 
PSOC-276 
H.sub.2 O 
-0.14 -12 1.59 60 1.48 38 
PSOC-282 
MC 0.33 46 0.21 27 0.57 35 
PSOC-282 
H.sub.2 O 
0 0.0 0.38 49 0.49 30 
PSOC-219 
MC 0.45 58 0.16 22 1.17 55 
PSOC-219 
H.sub.2 O 
-0.03 -4 0.54 73 1.05 49 
PSOC-026 
MC 0.43 19 0.61 59 1.69 49 
PSOC-026* 
H.sub.2 O 
0.19 -4 0.99 82 1.58 45 
______________________________________ 
*Methyl chloroform 
The data indicates that: 
(1) No organic sulfur removal for coal PSOC 276 with an apparent (but not 
significant) increase in organic sulfur. 
(2) Remaining coals PSOC 282,219 and 026 showed organic sulfur removal of 
19 to 58 plus percent with methylchloroform and no apparent decrease in 
organic sulfur with water as a solvent. (Apparent contradictory laboratory 
scale data exists showing better organic sulfur removal with water as a 
solvent with coals PSOC 190 and PSOC 219 than with methylcloroform.) 
(3) Apparent increases in organic sulfur are not considered significant 
since analytical accuracy is probably less than measured organic sulfur 
increases. 
(4) Total sulfur removal is greater with methylchloroform as a solvent for 
coal PSOC 276 relative to water (55% vs. 38%). Remaining coals show slight 
but not significantly greater decreases of total sulfur with 
methylchloroform versus water. Coals PSOC 219 and 026 show approximately 
50% total sulfur removal and PSOC 282 shows approximately 30 to 35% total 
sulfur reduction. 
(5) Pyritic sulfur removals for coals PSOC 282, and 026 were greater with 
water, 49 to 82% versus 22 to 59% for methylchloroform aided pyritic 
sulfur removal relative to water. 
(6) Although some apparent reductions in organic and pyriticsulfur values 
are indicated by extending the reaction time from 45 to 90 minutes, the 
apparent increased reductions in one sulfur form are apparently nullified 
by an apparent increase in the alternate sulfur form (organic vs. pyritic) 
such that the total sulfur reduction appears to be a maximum at 45 
minutes. Since only partial analytical data are available, conclusions are 
preliminary subject to obtaining remaining data from the batch reactor 
chlorination. 
After the treated coal slurry is flash distilled, washed and vacuum 
filtered, thermal dechlorination is obtained in a rotary tube, capacity 2 
kilograms of coal, using a Lindberg electric furnace. Dechlorination was 
carried out with the electric furnace and tube preheated to 400 degrees C. 
Coal was then added, with 30 minutes required to heat to 400 degrees C. 
and an additional 30 to 60 minutes used for thermal dechlorination at 400 
degrees C. with a nitrogen purge at 30 SCFH and 0.5 psig. Coal was cooled 
for approximately 30 to 60 minutes in the rotary tube before removal. 
Dechlorination data are presented for coal PSOC 276, Table 5. Treated 
dried coal before dechlorination showed 4-8 weight percent chlorine. After 
dechlorination the chlorine content was 0.5 to 0.88 weight percent. 
Laboratory scale data in Phase 1 glassware showed somewhat better 
dechlorination results. A final reduction scale data in glassware showed 
somewhat better dechlorination results. A final reduction of residual 
chlorine values to that present in the original coal or 0.1 weight percent 
is desired. 
The batch-scale batch reactor was operated under the following conditions. 
2 Kilograms chlorinated coal PSOC, 30 minutes coal preheat from 25 degrees 
C. to 400 degrees C., 30 minutes at 400 degrees C.; nitrogen purge, 
pressure=0.5 psig) 
The data follows. 
______________________________________ 
Before After 
Dechlorination 
Dechlorination 
Run Cl (Wt. %) Cl (Wt. %) 
______________________________________ 
7 - 5/24/79 6.94 0.75 
8 - 5/30/79 4.09 0.60 
10 - 6/5/79 5.83 0.88 
12 - 6/8/79 8.01 0.98 
Raw Coal PSOC 276 
0.17 -- 
______________________________________ 
The bench scale batch reactor studies with 2 kilograms of coal/batch 
provided a broader range of pressure and temperature operating conditions 
than that originally explored in the laboratory scale studies. The 
introduction of water in lieu of methylchloroform as a solvent shows 
considerable promise for total sulfur removal, although organic sulfur 
removal by water as a solvent has only been demonstrated in lab scale work 
to any significant extent. Increase in operating temperature and pressure 
does not appear to improve coal desulfurization. 
Engineering cost analysis indicates an overall process cost of $13 to $19 
per ton for PSOC 219 coal containing 2.56 weight percent of total sulfur 
for the solvent process and at least $4 per ton less for the water 
process. The chlorinated coal may be solvent extracted to yield a 
feedstock suitable for liquifaction or gasification instead of being 
thermally dechlorinated. The process of this invention provides a high 
degree of sulfur removal under mild conditions (65 degrees C., 1 atm) 
using low cost reagents (water, Cl.sub.2). Most of the chlorine consumed 
can be recovered as HCl which can be converted to chlorine. The final 
product is an improved feedstock for combustion, liquefaction or 
gasification since it is non-caking and non-swelling. 
It is to be realized that only preferred and exemplary embodiments of the 
invention have been illustrated and that numerous substitutions, 
alterations and modifications are all permissible without departing form 
the spirit and scope of the invention as defined in the following claims.