US 2717868 A
Description (OCR text may contain errors)
Sept. 13,1955 GQRIN ET AL DESULFURIZATION OF LOW TEMPERATURE CARBONIZATION CHAR 3 Sheets-Shem?- 1 Filed April 16, 1954 6 ATMOSPHERES PARTIAL PRESSURE OF HYDROGEN I ATMOSPHERE PARTIAL PRESSURE OF HYDROGEN (MINUTES) HYDROGENATION TIME FIG.
EVERETT GORIN- AND CLYDE W. ZIELKE IN V EN TORS ATTORNEY Sept. 13,, 1955 GQRIN ET AL 2,717,868
DESULFURIZATION OF LOW TEMPERATURE CARBONIZATION CHAR Filed April 16, 1954 5 Sheets-$heet 2 NON METALLURGICAL METALLURGICAL ///////9}AL7 COAL LOW TEMPERATURE GAIRBONIZATION AND SES CHAR y COKE OVEN DESULFURIZATION m E A 20 BLENDING 1 BLENDED CHAR 46 AND COAL COMPRESSION HIGH BTU GAS 4o 26 a9 HYDROGEN SULFIDE REMOVAL A 38 LOW SULFUR A 34? METALLURGICAL COKE TAR RECOVERY 36 EVERETT GORIN AND CLYDE w. zuaLK INVENTORS TAR KL 6 W FIG. 2
ATTORNEY Sept. 13, 1955 GORlN ET AL 2,717,868
DESULFURIZATION OF LOW TEMPERATURE CARBONIZATION CHAR Filed April 16, 1954 5 Sheets-Sheet 3 K :0: X 3 .I
FLuuilzzo m DESULFURIZATION (D u. D r- (0 Q 2 E m 2 GAS COOLING HEATING HEATING ll] 9 a s ..l 8 a 1 z 0 m 55 E O 2 n: O E O I 2 2 J EVERETT GORIN AND 1 m cum: w. ZIELKE m g g INVENTORS ATTORNEY be drasti a y reduced United States Patent Office 2,7l7,868 Patented Sept. 13, 1&5
2,717,868 D U RI O LOW EMPER TURE CARBONIZATI'ON Everett Gorin and Clyde W. Zielke, Pittsburgh, Pa., as-
signors to Pittsburgh Consolidation Coal Company, Pittsburgh, Pa., a corporation of Pennsylvania Application April 16, 1954, Serial No. 423,613 11 Claims. (Cl. 202-31) presence of hydrogen and methane.
Low temperature carbonization char is the solid residue which remains following the distillation of coal under low temperature carbonization conditions. In general, low temperature carbonization of coal is carried out in the temperature range of about 800 to 1400 F. The char product is a low density, friable, solid material constituting more than v6O per cent of the total products of the process. This invention is also applicable to the cokes produced under low temperature conditions from materials other than coal, for example, pitch cokes, petroleum cokes, and solid residue from low temperature carbonization of ilignites and the like.
Where high sulfur coals are utilized in a low temperature carbonization process the resulting char has a corresponding high sulfur content. Frequently the sulfur content of such chars will exceed two per cent by weight. In order to utilize these chars as a premium product, it is desirable that the sulfur content be reduced without substantial reduction of the carbon content. If the sulfur content of these chars could be reduced, the value of the chars as chemical raw materials or as blending materials in the production of metallurgical coke would be greatly increased.
We have discovered a method whereby the sulfur contamination of low temperature carbonization chars without an accompanying substantial loss of carbon content. AccorldingQtp our method the'high sulfur content char is treated ,at elevated temperatures (1100 to 1700" F.), under a total pressure exceeding about atmospheres, with a gas containing hydrogen, methane, and substantially no hydrogen sulfide. Substantial quantities of methane in they treating gas are required to suppress the carbon consumption, e. g. in excesslof 5 volume per cent. :On'the other hand only a small concentration .of hydrogen sulfide, .e. g. of the order .of 2 volume .per cent, will suppress -.the desired desulfurization.
Although some .desulfurization occurs one atmosphere, .the contacting :time required to effect appreciable sulfur removal is so great 'as .to be commericially vunfeasible. We have Jfound that the-rate of sulfur removal increases markedly with increasing partial pressures of hydrogen. With hydrogen partial pressures in exce s of bou th e tmosph res igni an s fur at a pressure .of
moval can ;be carried iout in contacting times which :are
The treating gases employed in .our idesulfurizatiop system y be obtaine ea in isal y. Q ename s puls oven gases from metallurgical ovens are ideally suited for the purpose. Alternatively, the treating gases may be produced intrinsically by a thermal devolatilization of the char itself. Such a system requires recovery of the spent treating gases from the desulfurization stage, removal therefrom of hydrogen sulfide, and recirculation of the hydrogen sulfide-free gases through the desulfurization stage.
For a clearer understanding .of the present invention, its objects and advantages, reference should be had to the following description and accompanying drawings in which:
Figure l is a graphical illustration demonstrating the sensitivity of char desulfurization rates to hydrogen partial pressure;
Figure 2 is a schematic flow diagram of one embodiment of the present invention; and
Figure 3 is a schematic flow diagram of another embodiment of the present invention.
To illustrate the efiect which the hydrogen partial pressure of the treating gases has upon the sulfur removal, ,a series of tests was conducted with a typical high sulfur char (sulfur content 1.92 Weight per cent). In one test the char was treated at 1600" F. with gases having one atmosphere of hydrogen partial pressure. In another test the same char was treated at 1600 F. with gases having six atmospheres of hydrogen partial pressure. In Figure l, the weight percentage of sulfur removal is plotted against the contact time between char and treating gases for both investigations. With the particular char tested a treatment time of 25 minutes at 6 atmospheres hydrogen partial pressure was effective in removing more than 50 per cent of the sulfur contained in the original char. More than 4 hours contact time would be required to remove 50% of the sulfur from char using treating gases containing only one atmosphere hydrogen partial pressure. Hence, to achieve commercially feasible contact times the hydrogen partial pressure ,of the contacting gases should be substantially in excess of one atmosphere, preferably in excess of three atmospheres.
Where these tests were conducted with hydrogen alone .as a treating gas, significant quantities of carbon from the char were consumed. While the rate of carbon consumption under hydrogen treatment at one atmosphere pressure is negligible, the carbon depletion occurs at a rapid rate under the elevated pressures which we have found necessary to obtain commercially feasible rates of desulfurizat ion. -We have discovered however that the carbon depletion which accompanies desulfurization can be minimized by including methane in the treating gases. Accordingly it is possible to remove sulfur from high sulfur char :at a rapid rate without reducing the carbon content of the char if the treatment is carried out under elevated pressures with gases containing methane.
To illustrate the inhibiting effect of methane on the carbon consumption during char desulfurization, a series of tests was conducted with typical low temperature char having a sulfur content of 1.92 weight per cent. The char was treated under desulfurizing conditions at a temperature of 1600" F. with three treating gases which differed in their methane/hydrogen ratio. The contact time in each test was minutes. The partial pressure of hydrogen in each test was 6 atmospheres. The results are set fo rth in Table I.
Table I..Desulfurizati0n of char with gases having difierent methane/ hydrogen ratios Carbon Sulfur Inlet Gas Run Composition gfi li jf %???59 HlHz cent cent From Table I it is seen that increasing the methane .content of the treating gases for char desulfurization permits the treatment to be carried out to the same level of sulfur removal without incurring large carbon losses. With pure hydrogen as a treating gas, 5.50 weight per cent of the carbon is consumed during the treatment, with an accompanying loss of hydrogen from the system. However when the treating gases have a methane/hydrogen ratio of 0.15, the same degree of desulfurization is effected with a negligible loss of carbon and hence a negligible loss of hydrogen. Table I bears out our discovery that the presence of methane does not alter the desulfurization rate, but merely inhibits the rate of carbon depletion.
When treating char with hydrogen sulfide-free gases, the rate of desulfurization is determined by the hydrogen partial pressure and the temperature. The included methane of the treating gases has no effect on the desulfurization process.
We have found that the volume ratio of hydrogen to methane in the treating gases entering a desulfurization stage should exceed about 2.0. Moreover, the volume ratio of hydrogen to methane in the treating gases entering a desulfurizing stage should not excee about 15.
One outlet for low temperature carbonization char is as a blending material in the preparation of metallurgical coke. Generally the specifications imposed by the metallurgical industry for product coke limit the sulfur content to less than one per cent. Since 50 to 70 per cent of the sulfur in the coke oven charge remains in the product coke, coke oven operators usual- 1y specify that coals to be used in blending possess less than 2% of sulfur. However, the reserves of accessible low sulfur coals for blending are being exhausted so that higher sulfur content blending materials must be used in coke ovens without exceeding the maximum sulfur content specifications for the product coke.
The present invention can be employed to utilize high sulfur coals in an integrated coke oven installation. According to our new method, the high sulfur coals are subjected to an initial low temperature carbonization treatment which produces valuable tars and gases in addition to the solid residue, char. The char from the low temperature carbonization stage is desulfurized by treatment with coke oven gases. The resulting desulfurized char thereupon can be blended with high volatile metallurgical grade coking coal or even with other high sulfur coal and charged to the coke ovens.
Figure 2 is a schematic flow diagram of a metallurgical coke installation which sulfurization system to permit the use of high sulfur coals in the preparation of metallurgical grade coke. In the drawing, a non-metallurgical coal 10, containing two to four per cent by weight of sulfur is subjected to a low temperature carbonization treatment 12. Preferably the carbonization treatment is conducted under fluidized conditions to produce a finely divided char product. However carbonization systems other than those employing the fluidized technique may be employed. Carbonization vapors comprising valuable tar and gases are recovered as a product at 14. The carbonization is carried out at a temperature of 800 to 1400 F. for a sufficiently long period of time to assure the desired evolution of volatile material from the char at the selected operating temperature. volatile content of 10 to 20 per cent by weight is desirable in the char. The char is recovered and passed to a desulfurization stage 13'; as indicated by the line 16.
The desulfurization stage 18, which will be more fully described hereinafter, effects a reduction of char sulfur content to permit its use in subsequent coke oven blending operations. The low sulfur char, following residence of 10 to 100 minutes in the desulfurization stage, is recovered at 20 containing less sulfur than the char at 16, and is blended with metallurgical coals 22 employs our new (16- U in a blending stage 24. Generally up to about four parts of metallurgical coal 22 will be blended with each part of desulfurized char from line 20. If the desulfurlzatron in stage 18 is carried out exhaustively, a higher level of sulfur can be tolerated in the metallurgical coals 22. Preferably the metallurgical coals 22 have a low sulfur content, however.
The resulting blend is passed as indicated at 26 to conventional high temperature coke ovens 28 where the usual high temperature coking occurs to produce a low sulfur metallurgical coke indicated at 30. Coke oven vapors are recovered from the coke oven through line 32 and freed of tars in conventional tar recovery equipment 34. Tar is separately recovered at 36. Tar free coke oven gases are recovered at 38, substantially freed of hydrogen sulfide in conventional equipment 39, passed through a conduit 40, compressed in a compressng unit 41, and sent through line 42 to the desulfurizatron stage 18 for treating high sulfur char. We have found that coke oven gases under pressure are suitable for reducing the sulfur content of high sulfur char and concurrently producing high B. t. u. content gases contaming a small quantity of hydrogen sulfide. The sulfur 1n the solid char is removed through reaction with the hydrogen in the coke oven gases, the high B. t. u. gas results from partial thermal devolatilization of the char and from reaction between the hydrogen of the gases and the carbon of the char. With coke oven gas 1n the desulfurizing stage we prefer to employ a temperature within the range of 1100 to 1400" F. and a pressure within the range of 5 to 15 atmospheres.
Following treatment of the char in the desulfurizing stage, the spent coke oven gases have an increased B. t. u. content. In addition the gases contain a small quantity (less than 2 per cent by volume) of hydrogen sulfide resulting from the desulfurization reaction. These gases, recovered through conduit 44, are under the elevated pressure maintained in the desulfurizing stage and are preferably recycled into the fresh coke oven gas stream 38 for hydrogen sulfide removal, recompression and further use as treating gases. A portion of the recycle gas stream can be withdrawn as a high B. t. u. product gas through conduit 46.
An analysis of a typical coke oven gas is presented at page 43 of Gaseous Fuels by Louis Shnidman, published by the American Gas Association in 1948:
ANALYSIS OF COKE OVEN GAS Component: Volume per cent Hydrogen sulfide 0.7 Carbon dioxide 1.7 Nitrogen 0.9 Hydrogen 56.7 Carbon monoxide 5.7 Methane 29.6
It is seen that the principal constituents of coke oven gases are hydrogen, methane and carbon monoxide, with hydrogen as the preponderating component. The partial pressures of the hydrogen and methane are controlling in our desulfurization process. The carbon monoxide of coke oven gases has no detectable inhibiting effect on the desulfurization.
The following illustration indicates the importance of employing elevated pressures when treating high sulfur chars with coke oven gases for desulfurization.
(a) Where low temperature carbonization char is treated for 100 minutes at 1100 F. using coke oven under a total pressure of 1.75 atmospheres, there is substantially no carbon consumption, but the sulfur content of the char is reduced by only about 8 per cent.
(b) Where low temperature carbonization char is treated for 100 minutes at 1100 F. using coke oven gas under a total pressure of 10.5 atmospheres, 5.1 percent of the carbon is consumed, but 55 per cent of the sulfur is removed from the char.
Table II sets forth the composition of the char before and after treatment with coke oven gases under 110:5 atmospheres total pressure.
Table II.--Cmposition of char before and after treatment with cake oven gases at 10.5 atmospheres pressure The application of our invention to an integrated metallurigical coke plant illustrates one way in which our new process can be utilized with extrinsic treating gases. Our invention also can be utilized with intrinsic gases which are generated from the char itself as :will be illusstrated in connection with the flow sheet of Figure 3. In the intrinsic treating system fluidizable low temperature char is concurrently heated and partially devola-tilized prior to its entry into a fluidized desulfurization reaction zone. While undergoing the partial devolatilization the char gives ofi a gas containing hydrogen and methane which is suitable for use as the desulfurizing treatment gas. The fluidized desulfurization reaction vessel has suf- -ficient solids capacity to provide the required :contact time for achieving the desired degree of desulfurization of the char. In the embodiment illustrated in Figure 3 a char devolatilization stage of the pebble heater type is illustrated. The devolatilization stage comprises a gas cooling (pebble heating) vessel 102 disposed above a central pebble heating vessel 104. Extrinsic heat is applied to the pebbles in the central heating zone 104 to supply the heat requirements for devolatilization. The bottom vessel 106 of the pebble heater is a char heating and devolatilization vessel. Here the heated pebbles surrender their heat to the char. Cooled pebbles are recycled from the vessel 106 through a solids lifting device 108 to the vessel 102.
Low temperature carbonization char produced in a fluidized technique process or crushed to a fiuidizable size consist is stored in a surge vessel 110. This char should be capabale of passing through an 8 mesh Tyler screen (preferably through a 14 mesh Tyler screen) to satisfy the operability requirements of the pebble heater devolatilization stage. Preferably the char in the vessel 110 is maintained at an elevated temperature, forexam ple 900 F. Where our new process is integrated with a low temperature carbonization process, the hot product char from the carbonization process could be used directly. Hot fluidizable char from the vessel 110 is withdrawn continuously through a conduit 112 whence it is picked up and suspended in a stream of flowing recycle gases from conduit 114. The gases in conduit 114 contain hydrogen, methane and substantially no hydrogen sulfide. These gases are under sufficient pressure to satisfy the requirements of char desulfurization.
The suspended solids stream for hot char in recycled gases is introduced through conduit 116 into the bottom of the devolatilization vessel 106. The recycle gases and suspended char pass upwardly through the interstices of the downwardly moving pebbles in the vessel 106 and are recovered as a suspended stream from the top of vessel 106 through a conduit 118. In passing through the devolatilization stage 106 the char is heated to a temperature in the range 1300 to 1700 F. This thermal treatment serves to drive additional volatile material from the char in the form of gases containing hydrogen and methane. The quantity of gas generated in the devolatilization stage depends upon the dilference in temperature of the vessel 106 and the temperature at which the char was formed by low temperature carbonization. 'Where the char has been formed at a temperature of about 900 F. a devolatiliz ation temperature of about 1100 F. should be sufiicient for the chat to supply autogenously the treating gas requirements for desulfurization. The pebbles which circulate downwardly in a moving bed through :vessels 1.02, 104, 106 and upwardly in the solids lift 108 are for example from 7 to inch in diameter. The cool pebbles entering the vessel 102 ,at its top are heated .by countercurrent exchange with a hot stream of gas passing upwardly through the vessel 102. Partially heated pebbles descend into the central heating vessel 104. Fuel gases can be burned in the vessel 10.4 to supply .the necessary heat to the pebbles. The highly heated pebbles descend to the volatilizalion vessel 1.06 where they are contacted concurrently with the char undergoing .devolatilization. The superficial linear velocity of the particles through the pebble bed (not through the interstices .ofthe pebbles) is about 4 meters per second.
A typical .c-har from a fluidized low temperature car- ,bonization process carried out at 950 F. contains about 12 to 14 .Per cent volatile material .by Weight and about 1.9 percent sulfur by weight. The Tyler screen analysis cumulative) of this char is as follows:
- Weight per Screen size: cent retained On 35 V 24.4
On ,1-00.. V 96.1
On 150 p 99.1
Through 1 50 100.0
Upon thermal .devolatilization .of this char at 1600 F,.,
gases are produced having the following moisture free composition "by volume:
Per cent Hydrogen 70 to 82 Methane 12 to 17 a b n M n fi-a-s-a- --.---r----- 5 t0 The net gas production at 1600 F. is about 2.1 standard cubic feet per pound of dry char.
Thus it is seen that the devolatilization gases can contain 7;0 to ;82 p.er cent vof hydrogen and sufficient'methane to exhibit a Liz/(3H4 ratio of 4 to 7, which is ideal for desul furizati on under ;conditions which minimize carbon consumption.
Deuolat'ilized char together with recycle gases and'the gases generated during the devolatilization reaction passes through conduit 11 8-to the :fluidized desulfurization vessel 120 which has sufficientsolids hold-up capacity to provide .the contact time required to carryout the desired desul- 'furization. Preferably the contact time of the char is from 1010 minutes. The vessel is maintainedat -a temperature of about 1300 to 1'700" F. The lineal velocity of the gases passing upwardly through the vessel 2120 (0.2 to 2.0 feet persecond) -is selected to maintainthe desiredcondition:of fiuidization. A total ;pressure.of;about 5 to 15 atmospheres (preferably 5 to 10 atmospheres) is maintained in the vessel 120. 'In order that the gases and entrained char willnotpass upwardly from vessel 106 into -.vessel 104, it is essential thatthe pressure drop-of the path through the vessel 104 exceed that .ofthe .alternate desired path of the entrained char, through conduit 118, vessel 120 and conduit 126. Hot gases and entrained low sulfur eharleave ;the vessel 1'20 through a conduit 126 for heat exchange with coal pebbles in the gas cooling .vessel 102. The cooledgases of the ,desulfurization reaction together with entrained low sulfur char are recovered from the vessel 102 through .aconduit 128. Suspended low sulfur char is removed from thegas stream in a cyclone sepa- 7 rater 130, and are recovered as product through conduit 132. The solids-free gases pass through a conduit 134 to a hydrogen sulfide removal stage 136 where the gases are substantially freed of their hydrogen sulfide content.
Thereupon the gases pass through conduit 139 to a compression unit 140 which increases their pressure to the desired operating level. To avoid build-up of gases in the system, the net gas product is withdrawn through conduit 142. This gas comprises hydrogen, methane and carbon monoxide.
In the system described in Figure 3, the char used as feed should have sufiicient residual volatile material to supply via devolatilization the treating gases required for the desulfurization reaction. Moreover the devolatilization stage should be carried out at a temperature in excess of that at which the char feed material was prepared. The desulfurization stage itself must be carried out at elevated pressures and at temperatures in the range of 1300 to 1700" F. The gas recycled to the system must be essentially free of hydrogen sulfide and must contain hydrogen and methane.
Insofar as possible, steam should be excluded from the entire system since steam will react with carbon within the contemplated temperature range to effect a Watergas reaction which consumes carbon and produces significant quantities of carbon monoxide which may exert a slight inhibiting effect on desulfurization in concentrations exceeding about 20 per cent.
We have in addition established that small char briquettes, i. e., less than 1 inch cubes, can be successfully freed of sulfur under the temperature, pressure and treating gas compositions herein set forth provided the process apparatus is modified to accommodate non-fiuidizable solids. Vessels which will accommodate downwardly moving beds of larger particulate solids can be substituted for the fluidized treatment vessels shown in Figures 2 and 3 where char briquettes are being processed.
And now, according to the provisions of the patent statutes, we have explained the principle, preferred construction, and mode of operation of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.
1. The method of treating low temperature carbonization char having a high sulfur content which comprises contacting said char with a gas containing hydrogen and methane and substantially no hydrogen sulfide under a pressure in the range of 5 to 15 atmospheres and at a temperature in the range of 1100 to 1700 F. for a period in the range of to 100 minutes and recovering the treated char having a low sulfur content.
2. The method of removing sulfur from low temperature carbonization char which comprises establishing a bed of said char, passing into said bed a gas containing hydrogen, methane and substantially no hydrogen sulfide, maintaining said bed under a pressure of 5 to atmospheres and a temperature of 1100 to 1700 F., and recovering char having a low sulfur content from said bed after it has been in said bed for a period of 10 to 100 minutes.
3. The method of removing sulfur from low temperature carbonization char which comprises establishing a bed of said char, passing through said bed in intimate contact with said char a gas containing hydrogen and methane and no hydrogen sulfide, whose volume ratio of hydrogen and methane is at least 2.0, maintaining said bed under a pressure of 5 to 15 atmospheres and a temperature of 1100 to 1700 F., and recovering low sulfur char from said bed after it has been in said bed for a period of 10 to 100 minutes.
4. The method of removing sulfur from low temperature carbonization char which comprises establishing a bed of said char, passing through said bed in intimate contact with said char a gas containing hydrogen and methane and substantially no hydrogen sulfide, whose volume ratio of hydrogen to methane is less than 15, maintaining said bed under a pressure of 5 to 15 atmospheres and a temperature of 1100 to 1700 F., and recovering low sulfur char from said bed after it has been in said bed for a period of 10 to minutes.
5. The method of removing sulfur from low temperature carbonization char which comprises establishing a bed of said char, passing through said bed in intimate contact with said char a coke oven product gas containing hydrogen and methane which has been substantially freed of hydrogen sulfide, maintaining said bed under a pressure of 5 to 15 atmospheres and a temperature of 1100 to 1700 F, and recovering low sulfur char from said bed after it has been in said bed for a period of 10 to 100 minutes.
6. The method of removing sulfur from low temperature carbonization char which comprises producing a devolatilization gas by heating said char to a temperature in the range of 1300 to 1700 F. in the presence of a gas containing hydrogen and methane under a pressure of 5 to 15 atmospheres, establishing a bed of thus heated 9 char, passing through said bed in intimate contact with said char the said devolatilization gas, maintaining said bed under a pressure of 5 to 15 atmospheres and a temperature of 1300 to 1700 F., recovering gases from said bed, removing substantially all hydrogen sulfide from said recovered gases, returning recovered gases substantially free of hydrogen sulfide to said bed for further char treatment, and recovering low sulfur char from said bed after it has been in said bed for 10 to 100 minutes.
7. The method of preparing metallurgical coke from high sulfur, non-metallurgical coal which comprises carbonizing said non-metallurgical coal under low temperature carbonization conditions, recovering the resulting high sulfur char, establishing a bed of said char in a desulfurizing stage at 1100 to 1400 F. under a pressure of 5 to 15 atmospheres, passing coke oven product gases substantially free of hydrogen sulfide through said bed in intimate contact with said char, recovering low sulfur char from said desulfurizing stage after it has been in said stage for a period of 10 to 100 minutes, blending said low sulfur char with metallurgical coal and coking the resulting blend in coke ovens, recovering a low sulfur metallurgical coke from said coke ovens, recovering the coke oven product gases, removing substantially all hydrogen sulfide from said coke oven gases, and passing hydrogen sulfide-free coke oven gases through said desulfurizing stage.
8. The method of preparing metallurgical coke from high sulfur, non-metallurgical coal which comprises carbonizing said non-metallurgical coal under low temperature carbonization conditions, recovering the resulting high sulfur char, establishing a bed of said high sulfur char in a desulfurizing stage at 1100 to 1400 F. under a pressure of 5 to 15 atmospheres, recovering a low sulfur char from said desulfurizing stage after it had been in said stage for a period of 10 to 100 minutes, blending said low sulfur char with metallurgical coal and coking the resulting blend in coke ovens, recovering low sulfur metallurgical coke from said coke ovens, recovering coke oven product gases, removing substantially all hydrogen sulfide from said coke oven product gases and increasing their pressure to 5 to 15 atmospheres, passing pressurized, substantially hydrogen sulfide-free coke oven product gases through said bed of char in said desulfurizing stage in intimate contact with said char, recovering at least a portion of the gases from said desulfurizing stage, removing substantially all the hydrogen sulfide from said recovered gases, restoring the pressure of said recovered hydrogen sulfide-free gases to a value in the range of 5 to 15 atmospheres, and passing said pressurized, recovered, hydrogen sulfide-free gases through said desulfuriz-' ing stage in intimate contact with said char.
9. The method of removing sulfur from low temperature carbonization char having a high sulfur content which comprises heating said char to a temperature of 1300 to 1700 F. to effect partial devolatilization of said char, establishing a bed of said char at a temperature of 1300 to 1700 F. and a pressure of to 15 atmospheres in which said char is retained for a period of to 100 minutes, passing through said bed in intimate contact with said char the gases evolved from said char during its partial devolatilization, and recovering low sulfur char from said bed.
10. The method of removing sulfur from low temperature char having a high sulfur content which comprises heating said char to a temperature of 1300 to 1700 F. to effect partial devolatilization of said char, establishing a bed of said char at a temperature of 1300 to 1700 F.
' and a pressure of 5 to atmospheres in which said char is retained for a period of 10 to 100 minutes, passing, through said bed in intimate contact with said char the gases evolved during its partial devolatilization, recovering low sulfur char from said bed, recovering at least a portion of the gases passing through said bed, removing substantially all hydrogen sulfide from the recovered gases and increasing their pressure to a value of 5 to 15 atmospheres, and recycling said recovered gases to said bed.
11. The method of treating low temperature carbonization char having a high sulfur content which comprises entraining said char in a stream of gases containing hydrogen, methane and substantially no hydrogen sulfide, heating said gases and entrained char to a temperature of 1300 to 1700 F. by passing said stream through a pebble heater whereby said char is partially devolatilized, passing said stream into a fluidized desulfurization zone maintained at 1300 to 1700 F. and under a pressure of 5 to 15 atmospheres where said char is retained for a period of 10 to minutes, recovering low sulfur char from said desulfurizing zone, recovering at least a portion of the gases from said desulfurizing zone, removing substantially all hydrogen sulfide from said gases, and increasing the pressure of said gases and recirculating said gases substantially free of hydrogen sulfide as a stream through the preceding steps.
References Cited in the file of this patent UNITED STATES PATENTS 1,789,380 Edwards et al. Jan. 20, 1931 2,201,050 Oberle May 14, 1940 2,342,862 Hemminger Feb. 29, 1944 2,600,078 Schutte et a1 June 10, 1952 2,693,999 Reed Nov. 9, 1954 FOREIGN PATENTS 690,791 Great Britain Apr. 29, 1953