US2664390A - Carbonization of coal - Google Patents

Description

Dec. 29, 1953 E. F. PEVERE ET AL CARBONIZATION OF COAL Filed NOV. 19, 1948 Patented Dec. 29, 1953 2,664,390 CARBON IZATION F COAL Ernest F. Pevere, Beacon ham, and Howard V.

, George B. Arnold, Glen- Hess, Beacon, N. Y., as-

signors to The Texas N. Y., a corporation of Delaware Application November 19, 1948, Serial No. 61,013

3 Claims.

This invention relates to a process for the production of nely divided particles of ook from coal. The process of this invention may be applied to coals of various types, especially bituminous coals and lignite. The process is particularly applicable to the treatment of bituminous coals.

In the conventional processes for the production of coke from coal, the coal is heated, sometimes in the presence of a hot gas, to drive oli volatilizable constituents from the coal. Carbonization or coking of the coal is generally carried out in a fixed bed in a coke oven. More recently, processes have been developed for carbonization of coal in particle form by passing hot gasses upwardly through a, bed of coal particles under conditions of iiow such that the particles are partly suspended in and agitated by the gas stream, eiiecting iluidization of the entire bed of particles. For successful operation of the uid bed carbonization process, it is necessaryto use coal of a rather narrow range of small particle sizes. This generally involves extensive grinding of the coal and sizing it prior to carbonization.

In the process of the present invention, fine grinding and carefulvsizing of the coal are not necessary, almost any size lump or particle being suitable for the process. In accordance with this process, coal is liqueed by heating in the presence of a liquid hydrocarbon and atomized. The resulting particles of atomized coal are dispersed in a gas stream and subjected to distillation at an elevated temperature While in a dispersed condition.

An object of this invention is to provide an improved process. for the distillation of coal. Another object is to provide an improved process for the production of nely divided particles of coke from coal. Still another object is to provide a process for the conversion of coal particles of random sizes to uniform small particles of coke. A further object is to provide a process for the production of high quality carbon from coal. Other objects and advantages will be apparent to those skilled in the art from the following detailed description of the invention.

Most coals may be rendered plastic by heating in an inert atmosphere. The plastic point and degree of uidity obtainable on heating varies somewhat with dilierentv coals. Coals which contain large amounts of anthraxylon and transluscent attritus exhibit greater uidity than those which contain large amounts of opaque attritus and fusain. Generally, coal becomes plastic at Company, New York,

a temperature within the range of from about 550 to about 700 F. When coal is heated in the presence of a mineral oil, the coal and oil become miscible and may be mixed to form a substantially homogeneous viscous liquid. Some hydrocarbon oils, especially hydroaromatics, such as tetralin, decalin, and oil fractions obtained from coal, act as solvents and aid in the liquefaction of the coal.

At temperatures above about 700 F., there is a condensation of free radicals or unsaturated compounds (generated by thermal decomposition of coal substance) into materials more stable than the original coal substance. At temperatures above about 825 F., the rate of precipitation of insoluble polymer may exceed the rate of liquefaction. The coal should be kept at a temperature as low as possible during liquefaction and subsequent handling in the liquid state to prevent excessive precipitation of the solid polymer. The optimum temperature for liquefaction is dependent upon the type and source of the coal, and the period of time the coal must be kept in liquid state, and is best determined by trial for any given coal.

When the coal is llqueiied with the oil with mechanical mixing, a substantially homogeneous liquid mixture may be obtained. Finely divided solid particles may be present in the mixture, either as a result of incomplete solution, precipior both. This mixture may be atomized without further treatment other than removal of oversize solid particles. On the other hand, when the particles of coal are extracted with oil without agitation, about per cent by weight of the coal is taken into solution in the oil leaving a porous friable solid residue. The liquefied coal, or extract, obtained by extraction is susbtantially free from ash and may be used in the present process for the production of high purity carbon. The undissolved portion of the coal is particularly suitable for reaction with steam or with a mixture of steam and oxygen for the production of a mixture of carbon monoxide and hydrogen.

In accordance with preferred practice of this invention, coal is liqueiied by admixing it with a liquid hydrocarbon at a temperature within the range of about 550 to 850 F. The resulting liquid is atomized into a carbonization zone operated at a temperature within the range of from about 900 to about 1500 F. Near atmospheric pressures are advantageously used. Fixed gases derived from the coal are used as dispersing medium for atomization and suspension of the coal.

-`expenditure of power.

The coal may be liquefied at a temperature within the range of 550 to 700 F. and the resulting liquid heated to a temperature within the range of from about 800 to about l000 F. prior to atomization. The pressure maintained on the liquerleld coal feed stream prior to atomization is preferably sufficient to prevent any substantial amount of vaporization. Heat for carbonization may be supplied by heating the liqueiied feed stream, the inert gas stream, the carbonization reactor, or by a combination of these methods. The inert gas stream is preferably preheated to a temperature on the order of 160Go l.; it may be heated to a considerably higher temperature;

In a preferred embodiment .ofthis invention,

the liquid mixture of coal 'ande-il is atomized and the droplets dispersed in a heated stream of inert gases having a velocity suicie'nt toA suspend the particles. The suspended particles are maintained at a temperature of from about SGO to about l300 F. during carbonization. y Thel quantity of oil combined with the coal to form a liquid feed stream which may be atomized with conventionaleduipment may varyconsiderably depending upon the type of `coal and oil used in vthe preparation step. Generally, a quantity of oil equivalent to about 50 per cent by weight based on the weight of the coal is sufficient although larger amounts are often advantageous from the standpoint of viscosityreduction.

The particle size of the coal fed tothe process is not of particular importance. The smaller particles are more quickly lidueed. paru ticles Should be o such size that substantially complete liquefaction takes piace in a reasonable period of time. Generally, it is desirable to use particles ranging from about' 1/2 inch in aver age diameter to powder.

In the present process, it is not necessary to resort to fine grinding or pulverization of the coal prior to preparation oflthe feed. lt is ccntemplated that'in most applications of the process, the coal will be reduced onlyV to a particle size such that the largest particles are. dissolved or disintegrated prior to. dischargeo the liquid from `the liqueiaction equipment. CoalY may be 'crushed mechanically to a particle size of 1/2 to 1/4" in average diameter with a relatively small The process lends itself totreatment of waste or low market valueslack coal produced in mining and handling operations.

The Vato'mized. coal may be carboniaed under conditions otemp'erature satisfactory for conventional carbonization of coal. In general, the temperatures used for distillation of coal range from about 900 to about 2000" F. or higher. The lower temperatures Within this range are preferred, as the yield of valuable products from the coal is favored by lov.7 temperature distillation. In the 'conventional processes it is dinicult to carbonize coal'at temperatures on the or der of 900 to 1G00 F.

Carbonization may be carried out efficiently at the lower temperatures by the process of this in vention. In atomized form the coal particles are more readily distilled than in conventional particle form. The oil also aids in the distillation of the coal. Anoil fraction obtained from the process and having a boiling range of from about 400 to about .500 F., for example, is readily vaporized at the coal distillation temperature. Such volatile oils used for plasticizing or iduefying the coal in the present process aid in the distillation of the coal and recovery of desirable volatilizable constituents therefrom by reducing the effective partial pressure of the volatilizable constituents. Distillation is also favored by the passage of gases through the distillation zone. The coke particles may be maintained in the carbonization zone as a fluid bed. The particle size of the product may be controlled by regulation of the droplet size produced on atomization,

lulverized coke entrained in the gas stream may be separated therefrom by means'of a suitable separator, for example, a cyclone separator. The hydrocarbon liquid and condensible volatilizable constituents from the coal are recovered from the eiiluent gas stream. A part of the gas resulting fromy the carbonization may be recycled to the carbonization zone as inert gas for atomization andY suspension of the coal. This gas may also be used as fuel, e. g., to supply heat to the distillation process. The carbonized product is in the form of small spherical particles which are eminently suitable for gasification in a fluid bed and are very reactive as fuel.

rlhe invention willl be more readily understood from the following detailed description and the accompanying drawing. Y

rlhe figure is a diagrammatic elevational view illustrating a preferred mode of carrying out the process of the present invention. y

W ith reference to the drawing, coal is supplied to a hopper 5 through a conduit t. From the hopper, the coal may be fed through conduit 1 into liquefactioh vessel 8 or through conduit 9 into liquefaction vessel Il). Any number of such vessels may be employed. While coal and oil are charged to one of the vessels to prepare a liquefied coal feed stream for carbonization, another is discharged to the carbonization step. When a vessel has been filled with coal from the hopper, inert gas may be admitted from line i2 to the vessel toV purge it of air and' other gases. Valve i3 associated with vessel 8, and Valve it, associated with vessel Il), are provided for this purpose. lThe purged gases may be vented from the vessels 8 and li)L through valves l5 and I6V respectively;

Preheated oil from line I8 may be'admitted to vessel 8 through valve i9 and to vessel I'O'through valve 2b. When a vessel is chargedl with coal and hot oil, the valves are closed and the coal at least partially liquefied due to the combined erect of heating the coal and the solvent or plasticizing action of the oil.

Mechanical Vmixers 2i and 22 are providedto disintegrate anddisperse any undissolvedresidue or precipitated solid-material from the coal. A substantially homogeneous liquid mixture of coal substance and oil is thus obtained.A

Generally, sufficient heat for the liquefaction may be'supplied bypreheating the oil' stream Additional heat may be supplied directlyY to the liqueiaction vessels by' suitable means'not illustrated in the drawing. The oil maybe' supplied to the vessel at least partially in vapor'formunder a pressure sufcient to cause condensation in the liquefaction vessel and'thereby Vfurnishing additional heat for heating'the coal.

The resulting liquid coalfeed'is discharged from the vessel 8 through valve 23and'ff'r'o'm vessel l0 through valve 24' toa charge pump''.

Inert gas from line i maybe admitted to the vessel during the period of discharge ofthe liquefied coal therefrom. The inert gas may be supplied under sui'cient pressure to maintainthe desired pressure within the vessel to prevent substantial flashing of volatile hydrocarbons and aid in discharging theli'queed coal therefrom.

From the charge pump 25, theliquefled coal 'feed stream is passed through a heating coil 32 wherein it is heated to a temperature within the range required for carbonization. The liquefied `coal feed is charged through line 33 into an atomizer 34 associated with carbonization zone 35. Alternatively, part or all of the coal feed stream-may be fed without preheating directly from the charge pump to the atomizer 34 through line 36 as controlled by valve 31.

The atomizer 34 may be of conventional type and is constructed of materials which are resistant to erosion. A suitable atomizer may be one of the spray type wherein the liquid is forced under pressure through an orifice of small diameter. The atomized particles are dispersed in a stream of hot inert gases supplied to the carbonization zone through line 40.

The carbonized particles of coal, or coke, are entrained in the hot gas stream and discharged Athrough line 4| into a cyclone separator 42. The coke is separated from the hot gas stream and discharged from the cyclone separator through line 43. The hot gas stream, which contains vapors of the oil used in the preparation of the feed stream and volatilized constituents from the fresh coal feed, is discharged from the cyclone separator through line 44, cooled in a cooler 45, and passed to a separation system 41.

In the separation system, a gaseous fraction comprising methane and other gases resulting from distillation of the `coal is separated from the normally liquid products of distillation comprising, for example, light oil, middle oil and tar fractions. A portion of the gases from the separation zone is recycled through line 49 and pump 50 to a heating coil 5| wherein the gases are heated and introduced into the carbonization zone through line 40. Part or all of the remaining portion of the gases may be discharged from the system through line 52 for use as fuel or other purposes. A light oil fraction is withdrawn from the separation zone through line 53, a middle oil fraction, through line 54, and a tar fraction through line 55.

The light oil fraction, the middle oil fraction, or a mixture of the two may be recycled to the liquefaction zone through line 51. The remaining middle oil may be subjected to hydrogenation in Vapor phase inaccordance with general conventional practice for production of motor fuels. Other oils may be supplied, if desired, to the oil stream in line 51 through line 58. The oil stream is pased to a pump 59 which forces the oil at the desired pressure through a heating zone 60 wherein it is preheated to the desired temperature prior to admission to the liquefaction zone via line I8.

Heat may be supplied to the carbonization zone by direct heating of the Walls of the vessel or retort in which the carbonization is carried out. For this purpose, a furnace 62 may be provided surrounding the carbonization vessel. Fuel may be supplied to the furnace from line 63 from any suitable source and fuel gases discharged therefrom through duct 64. A portion of the gaseous fraction resulting from the distillation of the coal may be supplied to the furnace 62 by line 65 as fuel.

It will be understood by those skilled in the art that various alternatives in the way of equipment and methods of handling the various streams and utilizing the heat contents thereof to maximum advantage may be resorted to. In the interest of simplicity, various conventional 6 pieces of apparatus such as control valves, heat exchangers and thelike have been omitted from the drawings and description of the process.

In a typical operation of a process of the type illustrated in the drawing, Pittsburgh bed coal containing about 2 per cent water, 31 per cent volatile matter, 58 per cent ash, as received, is subjected to carbonization. The coal is charged to a `lique faction vessel in the form of lumps ranging from about 1/2 to about 1A" in average diameter. This coal is mixed with a middle oil fraction obtained from the distillationof coal. Approximately equal parts by weight of coal and oil are charged to the liquefaction vessel. The oil has a boiling range of from about 450 to about 550 F., and is preheated to a temperature of about 825 F. prior to admixture with the coal. A pressure ofabout 300 pounds per square inch gauge is maintained on the liquefaction vessel to insure liquid phase conditions. The coal and oil are subjected to mechanical agitation to insure dispersion of carbonaceous residue. About 65 per cent by weight of the coal is taken into solution by the oil and the remaining 35 per cent dispersed in the form of minute particles. The resulting liquid coal stream, at a temperature of 600 F., is atomized with an inert gas comprising largely methane. The atomized particles are suspended in the inert gas at a temperature of about 1000 F. The gases and dispersed coal particles are passed through an elongated tubular retort which is externally heated where they are further heated to a temperature of about 1200 F. Coke particles resulting from distillation and carbonization of the coal are separated from the entrained gas stream as a granular product of relatively uniform particle size.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for the carbonization of a fusible coal containing volatilizable constituents with the production of dry solid powdered coke and recovery of said volatilizable constituents which comprises contacting said coal in particle form with a normally liquid hydrocarbon solvent for coal substance, agitating said coal particles with said solvent at a temperature above the temperature at which said coal is rendered plastic and ,Within the range of from about 550 to about 700 F. whereby said coal becomes miscible with said oil solvent and a substantially homogeneous liquid mixture containing all of the original components of said coal is obtained, atomizing said liquid mixture into a stream of a substantially inert gas thereby suspending said atomized liquid therein, passing the suspension upwardly through an externally heated carbonization zone maintained 'at a temperature of from about 900 to about 1,300 F., maintaining said atomized liquid in suspension in said carbonization zone for a period of time sufficient to effect substantially complete volatilization of said hydrocarbon solvent and volatilizable constituents of said coal and form dry solid particles of coke suspended in vaporous product of volatilization, and subsequently separating said solid particles of coke from volatilized products.

2. A process for the carbonization of a fusible coal containing volatilizable constituents with per cent fixed carbon vand 9 the production of dry solid powdered coke and reco-very of said volatilizable constituents which comprises contacting said coal in particle form with a normally liquid hydrocarbon solvent for coal substance and agitating said coal particles and said solvent at a temperature above the teniperature at Which said coal is rendered plastic and within the range of from about 550 to '700 F., whereby said coal is rendered miscible With said oil and substantially homogeneous liquid mixture containing all of the original components of said coal is obtained, heating said liquid mixture to a temperature Within the range of from about 900 to about 1,300 F'. at a pressure sucient to prevent substantial vaporization of said liquid, atomizing said liquid mixture into a stream of substantiallyr inert gas, passing said suspension upwardly through an externally heated carbonization zone, maintaining said suspension at a temperature within the range of from' about 960 to 1,300o F. and at a substantially atmospheric pressure in said carbonzation zone for a period of time sufficient to effect volatilization of sub stantiall-y all of the Volatilizable constituents of said mixture and produce dry solid particles of coke suspended in vaporous products of volatilization, and subsequently separating said solid particles 0I" coke from the volatilized products of carbonization.

3. A process for the oarb'onzation of a fusible coal containing' volatilizable constituents with the production of dr-y solid powdered coke and recovery of said volatilizable constituents which comprises contacting said coal in particlel form with a normally liquid hydrocarbon solvent for coal substance, agitating said coal particles with said solvent at a temperature abovev the temperature at which said coal is rendered plastic and within the range of from about 55() to about 700 E. whereby said coal becomes miscible With said oil solvent and a substantially homogeneous 8 liquid mixture containing all of the original components of said coal is obtained, atomizing said liquid mixture into a stream of a substantially inert gas thereby suspending said atomized liquid therein, passing said suspension upwardly through an externally heated carbonization zone, maintaining said suspension at a temperature Within the range of from about 900 to about 1,300 F. Within said carbonization zone for a period of time sufcient to effect substantially complete volatilization of said oil and volatilizable constituents of said coal and form dry solid particles of coke suspended in vaporous products of volatilization comprising normally gaseous hydrocarbons and normally liquid hydrocarbons including solvent for said coal substance, subsequently separating said solid particles of coke from the volatilized products, separating normally gaseous hydrocarbons from said volatilized products, supplying said normally gaseous hydrocarbons to said atomization step as said inert gas, separating a normally liquid hydrocarbon fraction containingsolvent for said coal substance from said volatilized products, and passing said liquid hydrocarbon traction into contact with said coal as said hydrocarbon solvent.

ERNEST F. PEVERE. GEORGE B. ARNOLD. HOWARD V. HESS.

References Cited in the le of this patent UNITED STATES PATENTS Number Name y Date 1,687,763 Hampton Oct. 16, 1928 1,868,737 Eglof July 26, 1932 1,904,586 Winkler et al Apr. 18, 1933 1,925,005 Rose et al Aug. 29, 1933 1,979,838 McCloskey Nov. 6, 1934 2,105,515 either Jan. 18, 193s 2,309,540 Rollman et al. Jan. 26, 1943

Claims (1)

1. A PROCESS FOR THE CARBONIZATION OF A FUSIBLE COAL CONTAINING VOLATILIZABLE CONSTITUENTS WITH THE PRODUCTION OF DRY SOLID POWDERED COKE AND RECOVERY OF SAID VOLATILIZABLE CONSTITUENTS WHICH COMPRISES CONTACTING SAID COAL IN PARTICLE FORM WITH A NORMALLY LIQUID HYDROCARBON SOLVENT FOR COAL SUBSTANCE, AGITATING SAID COAL PARTICLES WITH SAID SOLVENT AT A TEMPERATURE ABOVE THE TEMPERATURE AT WHICH SAID COAL IS RENDERED PLASTIC AND WITHIN THE RANGE OF FROM ABOUT 550 TO ABOUT 700* F WHEREBY AND SAID COAL BECOMES MISCIBLE WITH SAID OIL SOLVENT AND A SUBSTANTIALLY HOMOGENEOUS LIQUID MIXTURE CONTAINING ALL OF THE ORIGINAL COMPONENTS OF SAID COAL IS OBTAINED, ATOMIZING SAID LIQUID MIXTURE INTO A STREAM OF A SUBSTANTIALLY

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