US3455789A - Process for continuous carbonization of coal - Google Patents

Description

PROCESS FOR CONTINUOUS CARBONIZATION OF COAL Filed 00t- 21, 1965 July 15, 1969 w. s. LANDERS 5 Sheets-Sheet 1 o v $5200 m foucouom J NQ .6 M 8 3208 moo 7 6; 338m .amcwucoo U2 0 INVENTOR W/LL/AM .5. LANDERS BY I 29.3mm 22233 $5200 F HU 305 2205 3801.2]. .ll||' mm PROCESS FOR commuous CARBONIZATION 0F can Filed Oct. 21, 1965 W. S. LANDERS July 15, 1969 3 Sheets-Sheet 3 WILL/AM s. LANDERS BY: .511,

M G. Ail/z,

United States Patent Othce 3,455,789 Patented July 15, 1969 3,455,789 PROCESS FOR CONTINUOUS CARBONIZATION OF COAL William S. Landers, Denver, Colo., assignor to the United States of America as represented by the Secretary of the Interior Filed Oct. 21, 1965, Ser. No. 500,439 Int. Cl. C10b 47/24, 49/10 US. Cl. 201-31 6 Claims ABSTRACT OF THE DISCLOSURE Caking coals are carbonized without agglomeration of the resultant coke by entraining particles of the coal in a gas-to-coal ratio of at least sci/pound, preferably 7-20 sci/pound; and passing the entrained particles through a carbonizer tube wherein the particles are retained for about 10 to 60 minutes. During the start-up operation, only char is fed to the carbonizer until a steadystate condition is obtained after which coal is fed thereto.

The invention herein described and claimed may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of royalties thereon or therefor.

This invention relates to the carbonization of coal and provides a continuous process for treating coal particles in a high-temperature stream to remove volatile components from the coal and obtain a char product, In particular, the process relates to a start-up method and operating process wherein agglomerating coals are carbonized by introducing the coal particles into a vertical reactor having an oxidizing gas, whereby the coal is entrained in the gas stream. Other aspects of the invention include the use of specific gas-to-coal ratios to prevent the agglomeration of caking coals during the carbonizing treatment.

In the past char has had its meaning restricted to that of a solid residue from the carbonization of a non-caking coal such as anthracite, sub-bitmuinous coal, and lignite. However, when used in the present invention, it is intended that it refer to a flowable, non-adhering substance in contra-distinction to the usual coke product. Coke is a porous, coherent mass resulting from the destructive distillation of a caking coal, such as high-volatile or low-volatile bituminous coal, It is a carbonaceous residue having carbon as its principal constituent and residual volatile components. It has been discovered that residual carbon particles may be made from caking-type coals that are fiowable chars, rather than agglomerated cokes. This is achieved by the continuous carbonization of caking-coal particles in an entrained bed of oxidizing gas using a gas-to-coal ratio greater than 5 s.c.f./pound. The product char is a highly-desirable carbonization residue which may be used as a non-smoking domestic fuel, as a replacement for coal as a boiler fuel in generating electrical power or for mixture with coal, or even as a metallurigical material where the char is especially low in residual volatiles.

Accordingly, it is an object of this invention to provide a process for carbonizing coal particles in an entrained bed of gas in a vertical reaction vessel by feeding a cakingtype coal to the reactor under such conditions as to separate the volatile components from residual carbon particles while entraining the particles in a vertically-flowing stream of oxidizing gas. In particular, it is an object of this invention to present a novel process for carbonization of bituminous coal whereby agglomeration of the coal particles is prevented by operating under conditions of temperature, gas-to-coal ratio, linear velocity, and particle size to produce a char product entrained in a flowing stream of gas.

These and other objects and advantages of the present invention will appear more fully from the following description made in connection with the accompanying drawing wherein like reference characters refer to the same or similar parts throughout the various views and in which:

FIG. 1 is a schematic fiow diagram of the process and apparatus used in this invention;

FIG. 2 is a vertical cross-sectional view of a reactor used in the process, and

FIG. 3 is a vertical cross-sectional view of another embodiment of the reactor.

Referring to the drawing, FIG. 1 shows the apparatus used in the new process, including the necessary equipment for separating the product stream into its various constituents. A vertical reactor 10 is shown wherein coal to be carbonized is fed into the reactor bottom through a coal-charging system comprising a main coal bin 12 in which the coal particles are stored. An auxiliary storage bin 14 holds a quantity of char used in the start-up procedure to obtain on-stream conditions for the reactor 10. Coal or char may be fed through charging lines 16 and 18 to a rotary variable-speed feeder 20 into conduit 22 where it is entrained in a stream of carrier gas from line 23 and is transferred to the bottom of reactor 10. Hot air is introduced to the reactor 10 by a system having a pump or blower 24, discharging into conduit 25, and diverted into a combustion stream 26 and an air stream 27. A gas-solids stream 28 leaves the reactor 10 at the top and enters the primary separator 30, where heavy char particles are removed from the stream. Additional solids are separated from the gas stream by three cyclones 32. Not shown in the drawing and optional in the post-treatment method is an impinger, following the cyclone separators 32. The impinger is a vessel containing several lengths of chain, suspended vertically; these provide a large surface area, which trap some of the solids suspended in the gas stream.

The product stream equipment from the primary separator to the impinger is jacketed to permit the use of hot gases around the equipment, which prevents the volatile components of the stream from condensing with the char product. Portions of this hot gas may be taken from the reactor jacket in the embodiment of FIG. 2. Normally the solids separating apparatus is maintained at a temperature near the carbonization temperature in reactor 10.

After removing the solids from the product stream, a series of operations are conducted for liquifying the remaining volatile constituents in the stream, such as heavy and light tars, oils and water. The higher-boiling portions of the condensibles are liquified in an air-cooled condenser 34, in the form of a downcomer tube having a tar receiver located at the bottom of the vertical condenser. The lower-boiling tars are removed by a water-cooled vertical condenser 36 and a wet, electrostatic precipitator 38. Water and some light oil are removed from the gas stream by a secondary water-cooled condenser 40, which is a vertical cylindrical tube. Remaining light oil is condensed in an oil scrubber 42, which is a packed column in which No. 20 SAE motor oil is circulated by a pump 43. Process gas is withdrawn from the system by pump or blower 44. The gas may be sampled at this point and diverted to a storage tank or flared. A portion of the process gas may be used as a transport gas for the coal entering reactor 10, and may be mixed with air in line 23, 26, 27, etc. Also, the gas may be utilized as a fuel to heat the jackets surrounding the solids separating equipment 30 and 32. At the end of a run, a quantity of char may remain in the reactor 10. This char can be removed from the reactor bottom through char drain line 46 and stored in column char receiver 48.

There are two principal embodiments of the invention. The first embodiment, as shown in FIG. 2, utilizes heat outside the reactor column to maintain the reaction temperature. The second, as shown in FIG. 3, generates all necessary heat for the carbonization by oxidation of coal particles in the reactor column.

In FIG. 2 a mixture of coal particles and transport gas, which may be an inert fluid or an oxidizing gas, such as air, or mixtures of these, is introduced into the reactor 10. The reactor comprises a circular column 50 which has a diameter of 8 inches in one example of the invention. The column has an overall length of 16 feet that i insulated by a suitable high-temperature material, such as refractory 52. The lower portion of the column is constructed of Nicalloy up to a flame impingement area 54, which is clad with A3 inch 309 alloy for a flame guard. Above the impingement zone 309 alloy is used for the column material to about 6 /2 feet from the column top, and thereafter the column material is 347 alloy. Conical portions 55 and 56 fabricated from 321 alloy are used at the entrance and exit ends of the column. Column 50 is heated externally by combustion of a fuel gas in a combustion chamber 58, and the combination gases are forced by blower 24 to impinge upon the column 50 and pass along the outside of the column in a heating space 60, which is about 1 /2 inches around the circular column. Thereafter the hot gases, having a temperature up to about 1900 F., pass out of the top portions of reactor via conduit 62, and may be utilized for heating separators 30 and 32. The heating space 60 is formed by disposing insulation 52 around column 50, and strengthening the reactor with a metal shell 64. Various column lengths have been used, and no particular length is critical for the process. Use of longer columns permits the gas flow rates to be higher.

The embodiment of the invention shown in FIG. 3 uses no external heating of the reactor column. The carbonizing column has an internal diameter of 10 inches and a length of 26 feet. The interior or the reactor is a cast, abrasion-resistant refractory 70, backed up by insulation 52 comprising insulating brick and cast insulation. The reactor is enclosed in a 48-inch cylindrical steel shell 64. A spring-loaded seal 72 is provided between the combustion chamber 58 and reactor column 70, which seal may be closed after the reactor 10 is sufficiently heated to create conditions for a self-sustaining process by oxidation of coal particles using transport gas.

There are several aspects of the present invention which are notable. First, a process has been discovered wherein caking coals may be carbonized continuously in a vertical reactor column to produce char without agglomeration of coke material in the reactor. In the past it has been necessary to pre-oxidize caking coals, or to add char to caking coal to prevent agglomeration, or to mix the coal with inert material. In the instant method by the use of a particular air-to-gas ratio in the column, raw crushed caking coal, such as bituminous coal, may be directly carbonized to form a product char that is fluid and easily handled. The amount of residual volatile material in' the char is determined mainly by the carbonization temperature. At high temperatures a char having low residual volatiles is obtained. For instance, in a carbonization process at 1600 F. a char is obtained having suflicientlylow residual volatile components to be suitable for metallurgical use.

An important expedient has been discovered for use with bituminous caking coals in the initial stages of reactor start-up. This comprises a pre-heating step to bring the reactor up to carbonization temperature, or higher, and feeding char to the reactor under substantially the same conditions used for caking coal until a relatively steady-state condition is obtained, and then terminating the char flow while introducing bituminous coal particles. The change-over procedure from char to coal operation may be gradual or instantaneous. This method prevents agglomeration of caking coal in the reactor column, thus allowing a continuous process without frequent maintenance shut-downs. The novel start-up procedure is not necessary for non-caking coals, such as lignite, su b-bituminous, or anthracite. These latter coalsmay be introduced into the reactor immediately after preheating without fouling the equipment.

The continuous operation of the reactor column for a feed stream of caking-type coal particles is achieved only under certain conditions of flow. The gas flowing in the column is referred to as transport gas and should be distinguished from the carrier gas used to transfer the coal or char particles from their storage bins to the reactor. While the carrier gas combines with other gas in the reactor in some embodiments of the invention, it may form the whole of the transport gas in other embodiments. For instance in the operation of the system shown in FIG. 2, the carrier gas from line 22 is introduced directly into the reactor column without dilution with other gases. In the operation of the reactor shown in FIG. 3, the carrier gas may be only that amount necessary to feed the coal to the column base, where the transport gas in the column is supplemented by combustion gases through valve or seal 72. The important features of the process are the ratio of air in the transport gas to caking-type coal and the velocity of the transport gas through the column. An air to coal ratio of at least 5 standard cubic feet per pound of coal is the minimum amount permitted under continuous operating conditions.

The standard cubic foot of gas (s.c.f.) is that measured at 30" Hg and 60 F. A ratio of 7 to 14 s.c.f./pound and higher is preferred, and use of ratios as high as 20 s.c.f./ pound are used where a high-temperature carbonization at about 1600" F. is desired. This latter ratio appears to be about the upper limit used in any practical operation; however, higher ratios may be used in some circumstances. The superficial flow rate of transport gas in the reactor column should be at least 2.5 feet per second in order to prevent the formation of a fluidized bed of bituminous coal particles, which would tend to form a coherent mass and plug the column. A preferred flow rate of about 5 to 8 feet per second is used in the process. Proper design of the reactor diameter and length will provide a suflicient linear flow rate of the vertically-flowing transport gas. Operating pressure for the process does not appear to be critical, and 5 p.s.i.g. has been found to be satisfactory.

Particle size of the coal feed is a factor in determining the various conditions of carbonization, such as temperature, residence time, gas flow rate, etc. As a practical matter the maximum coal particle diameter should be about inch. Particle distribution should be the natural amounts produced by crushing the coal. In the examples given the feed coal was that which passed through a inch or inch screen in a hammer mill in which the raw coal was crushed.

The average residence time in the carbonization reactor column depends on the desired devolatilization rate and several factors must be considered. For the successful production of a high-quality char, an average residence time of to 60 minutes is satisfactory.

Pre-heated air may be used as the carrier gas or transport gas in the system. Tests using a inch pipe for line 22 having a length of about 50 feet and pre-heat temperatures up to 850 F., resulted in an increased capacity for carbonizing coal in the reactor. An air-to-coal ratio of 5.2 sci/pound was obtainable, and no appreciable preoxidation of the feed was observed, although residence time in the conduit 22 was short.

In the processes used in operating the reactors shown in FIG. 2 and FIG. 3, some char, tar, and coal carbonization gas products are consumed during the process, the relative amounts of each being a function of particle size, reactor geometry, gas-to-coal ratio, temperature, and other variables. For some applications, particularly for those in which both the char and tar have value beyond their ordinary value as fuels, it is desirable to reduce the internal consumption of the products. This may be accomplished by controlling the amount of oxygen contacting the products in the reactor. In the embodiment of FIG. 2, the only gas in contact with the coal is that supplied through line 22. By using a low air-to-coal ratio this may be achieved, or process gas may be introduced into the transport gas to reduce the oxygen content. In the embodiment of FIG. 3 a similar approach may be taken, or operation of the auxiliary furnace during the processing of coal will supply a desired amount of hot non-oxidizing gases through moveable seal 72 from combustion chamber 58.

EXAMPLE 1 High-volatile B bituminous caking-type coal from the Liddell seam, New South Wales, Australia was crushed by a hammer mill through a %fi'inch, round-hole screen, mixed and stored in raw coal bins. The carbonization was carried out in the 8-inch reactor shown in FIG. 2.

Data from five runs are given in Tables 1a to 1c. Various conditions of reactor temperature, feed rates, and air-to-coal ratio are given.

In run No. 1, carbonization conditions of 1,000 Pl, coal feed rate of 200 lbs./hr., and air carrier gas feed rate of 1,490 s.c.f./hr. were selected to give a product char having a volatile content of to 17 percent, dry basis. An entrained bed was developed by using char feed for one hour, after which raw coal was charged under conditions of continuous carbonization.

Run No. 2 was essentially the same as No. 1, except that sufficient external heat was supplied from jacket space 60 to maintain a temperature of 1300 F. Char was fed during start-up for about 35 minutes.

Run No. 3 was identical to No. 1 except that the carbonization temperature was 1,150 P. During the first hour after termination of the start-up coal was fed at 75 lbs/hr. and air at 1,440 s.c.f./hr. Thereafter the rates from No. 1 were used.

In run No. 4 the conditions of No. 1 were maintained and the reactor length was changed from 13.5 to 16 feet. Due to the geometry changes slightly higher temperatures were observed in the lower portions of the reactor column.

Run No. 5 utilized similar conditions to No. 1 with an air feed rate of 1,620 s.c.f./hr., and a carbonization temperature of 960 F.

Table la summarizes the results of analyses for coal and char composition and particle size using standard U.S. sieves. Table 2b sets forth the operating conditions for the five runs; and Table 10 gives product yields for 35 char, volatile products, and gases in the product streams.

TABLE 1a.CHEMICAL AND PHYSICAL PROPERTIES OF GOALS USED AND CHARS FROM CARBONIZA'IION TESTS ON AUSTRALIAN COAL carbonization run and temperature No. No. 2 No. 3 N0. 4 No. 5 1,000 F 1,300 F. 1,150 F. 1,000 F. 960 F Raw Char Raw Char Raw Char Raw Char Raw Char Proximate analysis as received:

Moisture.-. 6. 1 0. 0 5. 5 0. 0 5. 8 0. 0 6. 1 0. 0 5. 9 0. 0 Volatile rna 35. 8 15.3 36. 0 8. 7 35. 9 12. 2 35.8 15. 4 35. 9 15. 8 Fixed carbon 45. 6 64. 9 45. 9 68. 5 45. 8 66. 2 45. 6 63. 4 45. 7 64. 7 Ash 12. 5 19.8 12. 6 22. 8 12. 5 21. 6 12. 5 21. 2 12. 5 19. 5

Total do 100. 0 100.0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100, 0

Ultimate analysis, as received:

Hydrogen percent. 5. 5 2. 7 5. 4 1. 9 5. 4 2. 3 5. 5 2. 5 5. 5 2. 7 Carbon. d 66. 0 68. 9 67. 3 70. 4 67. 2 69. 3 66. 9 68. 2 67. 1 68. 3 Nitrogen 1. 6 1. 9 1. 6 1. 8 1. 6 1. 0 1. 6 2. 0 1. 6 2.1 Oxygem. 13. 0 6. 1 12. 6 2. 6 12. 8 4. 4 13. 0 5.6 12. 8 6. 8 Sulful .d .5 .6 .5 .5 .5 .5 .5 .5 .5 .6 Ash do. 12. 5 19. 8 12. 6 22. 8 12. 5 21. 6 12.5 21. 2 12. 5 19. 5

Total .do. 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0

Size consist, cumulative retained on No. 4 screen "percent" 0. 0 0. 0 0. 0 0. 0 0. 0 0. O 0. 0 0. 0 0. 0 0. 0 No.8screen do .2 .5 .4 .5 .2 .1 .2 .5 .3 .5 No. 16 screen do.- 3. 4 13.3 3. 0 5. 0 3. 7 2. 3 3. 9 8. 1 3. 5 10. 2 No. 30 sereen do 18.0 33. 3 18. 9 9. 4 18. 2 8. 3 18. 6 20. 0 18.0 28. 9 No. screen do 44.4 50. 8 45. 6 19.4 46. 2 19. 0 44. 8 32. 6 45. 6 47. 3 N0. screen do 69. 7 63. 2 71. 3 38. 2 71. 4 38. 1 69. 5 47. 4 71. 1 60. 7 No. 200 screen... .do 85. 7 74. 7 86.8 59. 9 86.1 59. 0 85.3 63. 5 86. 7 72. 0 Pan .do 100. 0 100. 100. 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 Average size inch 0. 0153 0. 0218 0. 0162 0- 0103 0. 0158 0.0087 0. 0156 0. 0148 0 0156 0. 019 2 TABLE 1b.PILOT PLANT CARBONIZATION OF AUSTRALIAN COAL: OPERATING CONDITIONS Average Goal teed carbonization temperature, F. Char coal rate, as- Air-to-coal retention Carbonization diameter, carbonized, Air rate, ratio m.a.t., Top of Middle of Base of time, run N 0. inch lb./hr. s.c.i./hr. s.c.fJhr. reactor 2 reactor reactor hour 1 Weight of reactor bed, pounds 1 Char retention time= Solids flow rate, pounds per hour 2 Top-ot-reactor temperatures were used for all data analysis.

No. 4 No. 5 1,000 F. 960 F.

As car- As carbonized M.a.f. bonized Mai.

Carbonization run and temperature No. 1 No.2 No.3 1,000 1,300 F. 1,150 F.

As car- As car As carbonized Mal. bonized Mat. bonized Mat.

TABLE 1c.YIELDS OF PRODUCTS FROM AUSTRALIAN COAL CARBONIZED IN AN 8-IN-CH, ENTRAINED-BED REACTOR Char ..pereent Air for transport std. cubic feet per pound" Carbonization yields, based on coal and air rates:

706809 7 9 L L 3 n 27 .Ll L 3. 5

612597 &&L. s n

T0tal .do..

Moisture in coal, as earbonized. d

Garbonization yields, per ton, based on coal rate:

Char. pounds. Tar

inous caking coal (East Temperature in a test run at a Proximate analysis, as received, percent:

EXAMPLE 2 The reactor shown in FIG. 3 was operated in the carid bitum Allen, Las Animas County, Colorado) bonization of a highly flu coal feed rate of 320 lbs/hr. and a carbonizing temperature of 1230 F. The reactor column had a 10-inch inside 0569 Ohio 5 Moisture. diameter and an eifective length of about 25 feet. The raw coal feed was untreated except for crushing. The reightly above the desired preselected ggg g gg d'percen 1 temperature by means of hot gases from combustion chamber 58 using natural gas as a fuel. The hot gases Heating value, B. .u./ Size consist, cumulative retained on, percent:

tered into line 22 from char bin 14. .T he

char, which is non-agglomerating, filled the reactor as 21 Average size, inch Packing density, lb./cu. f

actor 'was heated s1 flow from the combustion chamber 58 through seal 72 40 into the base of reactor column 70 and then are vented from the system. When the reactor was sufiiciently preheated, seal 72 was closed and a metered flow of ambient air was introduced through line 23, and char from a previous run was me low-density turbulent bed of particles, and began to fiow out of the top of the reactor through line 28 to the primary separator 30. Steady-state conditions or process a Lengt Temperature F.

Moisture in coal as carbonized. Ash in coal as earbonize Bas1s- Air for transport s.c.f./lb

l, and may vary considerably with reac- 5 line 16 to permit the mixing of coal and char. After a few minutes (3 to 5 minutes for this example) equilibrium were established within about 60 minutes, and variables such as temperature, pressure, transport gas flow rates, etc., obtained those values for the desired carbonization reaction conditions. The start-up time using char solids is not critica tor design.

Continuous operation using raw coal feed is begun by opening the char feed line 18 is closed and coal alone is fed to the reactor. Final adjustments in the air and coal feed rates shm MOT

are made to obtain the exact carbonization temperature desired. Results of the process are summarized in Tables 2a to 2e.

Table 2a gives the chemical and physical properties of the raw coal feed and of the char, includ sis and bulk density data rimary tar, and Table composition analysis, 512

Product yields are given in Table 2b, and solids collection data, plus a summary of yields are in Table 20. Table 2d gives the properties 0 TABLE 20.-YIELDS AND DUST SEPARATION DATA FROM ENTRAINED CARBONIZATION RUN ON EAST ALLEN COAL Overall operation:

Total coal carbonized pounds 1517.0 Start-up char do 271.0 Total solids collected do 1203.5 Solids in tar plus light oil percent 8.37 Ash in tar plus light oil do .62 Total solids collection:

Primary separator percent 84.44 First cyclone do 11.38 Second cyclone do 1.63 Third cyclone do .15

Total all collectors -do 97.60

Total solids in tar do 2.40 Efiiciency of all collectors after first cyclone percent 42.6

Dust loading, at T&P 1 leaving reactor, gr./ cu. ft.:

Entering primary separator perccnt 117.5 Leaving primary separator do 18.3 Leavingfirst cyclone do 4.91 Leaving second cyclone "do..- 2.99 Leaving third cyclone and entering tar train do. 2.81

Balance period, yields based on hourly coal and air rate, as carbonized:

Char percent 34.4 Tar dn 4.1 Light oil do 1.2 Gas do 51.1 Water do. 7.6 Unaccounted for do 1.6

Total do 100.0

Carbonizing rate lb./hr 320.0 Air rate s.c.f./hr 3690 Vapors leaving reactor cu. ft./ min. (at T&P) 219.7 Vapors leaving reactor s.c.f./min 86.2

1 Temperature and pressure.

TABLE 2d.-PROPERTIES F DRY PRIMARY TAR OF EAST ALLEN COAL Carbonizing temperature, F 1, 230 Specific gravity of dry tar, (20/20 O.) 1. 255 Moisture in tar, percent 0. 2 Benzene insoluble matter, dry, percent- 13.82 Quinoline insoluble matter, dry, percent 7. 86 Ash content, dry tar, percent 0. 69 Distillation pressure, mm. Hg abs. 620 Primary distillation yields, weight-percent:

Distillate 9. 4 Pitch 88. 3 Loss 2. 3 Temperature of decomposition, G 331 Specific gravity oi distillate (20l20" O.) 1. 070 Yield of distillate, volume-percent 11. 0

270386 0. 270380 Cl. Residue 11. 3 Loss- 1. 0

Composition 0! distillate, volume-percent:

Tar acids 40. 1 Tar bases 5. 2 Neutral oil 54. 7 Composition of neutral oil, volume-percent Olefins 37. 9 55. 0 7. 1 Pitch residue:

Softening point, cube-in-air, C 195 Specific gravity (25l25" C.) l. 286

1 At point 01 maximum average recorded temperature in reactor. 1 Temperature of decomposition oi distillate.

TABLE 2e.-OHEMICAL COMPOSITION OF GASES FROM PILOT PLANT OARBONIZATION OF EAST ALLEN 1 After passing through light oil (activated carbon) absorber.

The use of a pneumatic carrier line for conveying feed coal and char to the reactor is not a critical or essential feature of the present invention. Coal or char may also be fed to the base of the reactor column by other means, such as a screw conveyor. Neither is the method disclosed for pre-heating the reactor to carboni zation temperature an essential element. Such expedients as electrical heating or fossil fuels such as coal, oil or natural gas may be utilized for pre-heating the equipment.

The invention has been illustrated by specific examples, but there is no intent to limit the invention to the specific details so disclosed in the description and drawing, except insofar as set out in the following claims.

What is claimed is: 1. A method for carbonizing bituminous coal to produce char and reaction products comprising the bituminous coal being sized to form a feed having a size passing through a inch screen;

feeding bituminous coal particles into a carbonization reactor maintained at a temperature suflicient to volatilize tar, oil, and gas from the coal;

entraining the particles in a stream of gas flowing vertically through the reactor; the gas-to-coal ratio being at least 7 to 20 sci/pound; the residence time of particles in the reactor being about 10 to 60 minutes; and

separating char and volatile components in the product stream and wherein reactor start up to preheat the reactor to operating temperatures prior to the carbonization process comprises feeding only char to the reactor to obtain relatively steady state carbonization temperatures, then terminating the char flow while introducing bituminous particles when operating temperatures are obtained, whereby agglomeration of the bituminous coal in the reactor column is avoided.

2. The method of claim 1 wherein the reactor is maintained at a temperature in the range of about 820 to 1600 F., and the gas-to-coal ratio is in the range of 7 to 20 s.c.f./ pound.

3. The method of claim 2 wherein the gas stream has a superficial velocity of about 5 to 8 feet per second, and the maximum particle size is 4 inch.

4. The method of claim 1 wherein said bituminous coal is a caking-type coal.

5. The method of claim 1 wherein said stream of gas contains oxygen, and in which thermal energy for maintaining reactor temperature is obtained from oxidation of carbonaceous material in said reactor.

6. The method of claim 5 wherein substantially all of the thermal energy required for maintaining reactor temperature is supplied by oxidation of carbonaceous mammal by References Cited UNITED STATES PATENTS 2,955,988 10/1960 Sabastian 201-31 XR 2,998,354 8/1961 Brown et a1 20l3l XR NORMAN YUDKOFF, Primary Examiner D. EDWARDS, Assistant Examiner U.S. Cl. X.R. 20l-42

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