US2094027A - Apparatus for electrical carbonization of coal - Google Patents

Description

Sept 28, 593?. R. a, STITZER 2,094,027

APPARATUS FOR ELECTRICAL CARBONIZATION 0F COAL Original Filed Aug. 14, 1935 2 Sheets-Sheet l COAL RETORT :LEci'Rom: SCRUBBER 3 AIR CONDENSER I couoznssn 4m? FUEL GAS q i TRANSFORMER gown NSATE c c mosnsxrs i com: 51 AM FIG. I

5040/7 B. Sfifzer INV/ENTOR YMEM ATTORNEY Patented Sept. 28, 1937 UNITED STATES PATENT OFFICE APPARATUS FOR ELECTRICAL CARBONIZA- TION F COAL Ralph B. Stitzer, Sheifield, Ala.

Original application August 14, 1935, Serial No.

Divided and this application December 4,1935, Serial No. 52,852

2 Claims.

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) terials, particularly the carbonization'of bituf.

minous coal to form a coke suitable for domestic and industrial uses.

This application is a division of my original application, Ser. No. 36,165, filed August 14, 1935.

One of the objects of this invention is to pro- 5 vide a continuous and efiicient apparatus for the carbonization of solidcarbonizable materials in which electrical current is used as the source of the heat required for the operation. Another object of this invention is to eliminate the difliculties encountered in the carbonization of those coals which become plastic prior to carbonization.

' Other objects of this invention include the provision for a means of withdrawal of the volatile carbonization products, which is a particularly se-v rious problem when highly coking coals are carbonized.

It has been proposed that solid carbonizable materials be heated by a flexible electrical heating element located in the central portion of a column or coal with the lower end of the element connected with a mechanical device for reducing the coke residue into fragments sufliciently reduced to facilitate removal from the retort. It

has been proposed also to heat a charge centrally with an'electrlcal resistor and continue-the passage of current through the coke formed around the resistor until the entire charge is carbonized,

followed by the removal of the coke, thereby presenting a discontinuous operation. These and 40 other processes, of which the above examples are,

illustrative, have certain disadvantages, each of which may include one or more of the following: First, the process is discontinuous; second, coking coals adhere to theheating elements during the 45. time in which they are plastic and the carbonized I residue prevents rapid heat transfer from the element to the coal mass; third, the plasticizing 55 I have discovered a continuous process for the electrical carbonization ,of solid carbonizable material, by electrically heating a column of solid carbonizable material surrounded by an envelope of carbonized material; by passing a supply of inert gas downwardly through the inner zone of 5 .the charge to keep the uncarbonized charge in the inner zone substantiallyfree from volatile condensable carbonization products, by withdrawing the inert gas with the volatile carbonization products upwardly through the outer zone of the carboni'zed portion of the charge which is separated from the inner zone by a gas'impervious partition .in the upper portion of the retort; by separating tar and other condensable materials from the. j gases so withdrawn to form a fuel gas which may be used as a source of the inert gas admitted "to the top of the column of the coal charge and. by passing a portion of the fuel gas or other inert gas upwardly from the bottom of the retort to cool the coke below the zone of electrical heating and to heat the ,coal and coke above that zone. 5

In the accompanying drawings, which form a part of the specification, and wherein reference symbols refer to like parts whenever they occur,

Fig. 1 is a diagrammatic, vertical, sectional view of one form of apparatus for the embodi: ment of my process;

Fig. 2 is a vertical, sectionalview of the elec trical carbonization retort,

Fig. 3 is a horizontal sectional view taken at the sectional line A--A in Fig. 2,

Fig. 4 is a horizontal sectional View taken at the sectional line B--B in Fig. 2,

Fig. 5 is a horizontal sectional view taken at the sectional line' (3-0 in Fig. 2, and

Fig. 6 is a horizontal sectional view taken at the sectional line D -D in Fig. 2. 1

In Fig. 1, coke is charged into the outer zone in the top of the vertical carbonization retort l, 40 which is between the inner wall of the retort and the gas impervious partition 2. Coal is charged into the inner zone in the top of retort I, which is surrounded by partition 2. The charge of coal surrounded bythe' envelope of coke moves downwardly through the retort between a pair of electrodes or a plurality of electrodes, located 'in and flush with the opposite faces of the wall of, the retort I, and represented 'by electrodes 3. The

coal in the charge between theelectrodes 3, is carbonized largelyfrom the heatproduced by the. passage of an, electrical current through the carbon portion of the chargesurrounding the coal portion of the charge, which serves as a resistor between electrodes 3', the current to the electrodes being supplied from the electrical service lines 4, through the transformer 5. The hot coke which has passed downwardly past electrodes 3,

is cooled to a temperture below its ignition point in air by the upward passage of an inert gas, comprised of steam and some fuel gas, admitted near the bottom of the retort at a plurality of points represented by inlet 6. The cooled coke is withdrawn from the bottom of theretort by the coke withdrawal means, l3. The inert gas admitted at inlet 6, is heated by contact with the hot coke below the zone of the electrodes 3, and with additional heat obtained in the zone between the electrodes passes upwardly to heat the charge in the zone immediately above the electrodes. A further amount of an,- inert gas, comprised of fuel gas, is admitted through inlet 1, into the top of the inner zone in the top of the retort, into which the coal is charged and is passed downwardly in a suificient volume to keep the uncarbonized coal in the inner zone substantially free from condensable carbonization products. The gaseous mixture consisting of the inert gas admitted at the bottom of the retort, the inert gas admitted at the top of the inner zone of the retort, and the volatile carbonization products, pass up wardly through the coke in the outer zone at the top of the retort and'are withdrawn at the top of this outer zone. This gas from the retort, together with entrained solid and liquid particles, passes through the aircondenser 8, where the major portion of the tarry matter is removed, and through the condenser 9, in which the major portion of the remaining volatile condensable material in the retort gas is condensed by indirect cooling with water and separated from the gas. The gas from theretort from which'substantially all the condensable volatile matter has been removed passes into the inlet of the blower I 0,

which serves tomaintain a substantially atmospheric pressure in the top of the outer zone of the retort I, and the gas delivered by blower I0 is treated in scrubbers II and I2 to remove valuable by-products, such as ammonia and other nitrogen compounds, and otherwise prepare the gas from the retort for use as a fuel gas, such as by the removal of hydrogen sulfide and other sulfur compounds. A portion of this fuel gas is used as the supply for the inert gas admitted near the bottom of the retort I, through inlet 6, and into inlet 1, into the top of the inner zone of the retort.

In Fig. 2, the coke a, charged into the outer zone in the top of retort I, between the inner wall of the retort and partition 2, passes downwardly and surrounds the charge of coal b, which is fed into the top of the inner zone surrounded by partition 2. The coke a, and the coal 1), continue to pass downwardly into the zone between the electrodes 3, in substantially the same relative position which they occupied on passing the bot-.

tom of partition 2. The coke a. serves as a res1stor when it comes in contact with the eleccarbonizes the coal 2), of the charge adjacent to it.

The coal so carbonized in turn serves as a reas it passes through the zone between the electrodes 3, is continually .until the coal 1), has been carbonized in its entirety at the time, or shortly after it passes the elevation of the bottom of the electrodes 3. The inert gas admitted point.

I table origin, suchas woods and nut shells. trodes 3, and the heat produced by the passage of the electrical current through the coke 0,

through the inlet 6, passes upwardly and cools the hot carbonized product in which the coke a, from the charge and the coke resulting from the carbonization of coal 1), is practically indistinguishable. The inert gas so heated serves to as- 5 sist in the heating of the charge between the electrodes 3, and to preheat the charge in the zone above the elevation of the top of the electrodes.3. The inert gas admitted through the inlet I, in the top of the inner zone of the retort, passes downwardly and keeps the uncarbonized coal b,in the inner zone substantially free from condensable carbonization products. The volatile carbonization products and the inert gas admitted at the bottom of the retort, together with that admitted at the top of the inner zone of the retort, pass upwardly through the coke a, into the outer zone in the top of the retort and are withdrawn from the top of this zone as the retort gas.

In Fig. 3, which is a horizontal sectional view of a section near the top of retort I, the coke portion of the charge a, in the outer zone is shown separated from the coal portion of thecharge b, in the inner zone by partition 2.

In Fig. 4, which is a horizontal sectional View of a section of retort I, below the elevation of the bottom of the partition and above the elevation of the top of the electrodes, the coke portion of the charge a, is shown enveloping the coal portion 30 of the charge b.

In Fig. 5, which is a horizontal sectional iew of a section of the retort I, through the electrodes, a represents the coke portion of the charge and the carbonized portion of the charge, the two being practically indistinguishable at this point,

surrounding the coal portion of charge b, whic the retort, a represents the coke portion of the charge and the carbonized portion of the charge, the two being practically indistinguishable at this It is evident that there are numerous factors which will influence conditions for the most satisfactory operation of my invention, the actual. limits of which cannot be established except by a detailed. study of each set of raw materials and 50 the intermediate and finished products involved. The term solid carbonizable material shall mean and include solid carbonaceous material, which has not been subjected to a carbonization process, and which may be heated to a sufficiently high superatmospheric temperature to remove the volatile products which it contains with the formation of a solid carbonized residue useful as a y domestic or industrial fuel or otherwise in the arts. Examples of solid carbonaceous material 60 include anthracite coal, non-coking and coking bituminous coals, and materials of recent vege- The term carbonized material shall mean and int cludeany solid carbonaceous product resulting '65 from the carbonization of a solid carbonizable material. Examples of carbonized material include low and high volatile cokes and charcoal. In the operation of my process and apparatus it is preferred to use the carbonized portion of the charge derived from substantially the same source as the uncarbonized portion of the charge, ,1. e., it is preferred to use a coke from bituminous coal in connection with thecarbonization of bituminous coal and his preferred to use a" hardwood f5 charcoal derived from the same type of hardwood that is being carbonized, in. order that the respective resulting products may be of uniform character.

The size of the carbonized portion of the charge preferably is such that it will pass through a 1" mesh and be retained on a 0.25" mesh. Screenings which otherwise havev little value for metallurgical purposes may. be used for this purpose. Should these screeiiings contain a considerable excess of very fine material, such as below a 0.25" mesh, a small proportion of this material could be incorporated with the carbonizable portion of the charge when this portion of the charge is a coking coal. The size of the solid carbonizable material preferably is such that this portion of the charge will pass through a 2.5" mesh screen.

The ratio by weight of the carbonized material to the carbonizable material may vary within considerable limits, depending upon the materials being processed. Using coke from bituminous coal and a coking coal of the sizes given above, the proportions may be varied from 10 to 30% and 90 to 70% by weight, respectively.

The vertical retort shown in the respective drawings has a square cross section but this cross section may be rectangular, hexagonal, octagonal,

' elliptical, round, or any other symmetrical cross section, so long as the electrodes may be so placed in the opposite faces and flush with the inner faces of the .retort wall and operated in such a manner as to obtain complete carbonization of the carbonizable material which passes throughthe zonebetween the electrodes.

'The partition in the topof the retort which forms the outer and inner zones in which the carbonized and carbonizable materials, respectively, are charged maybe concentric to the inner wall of a retort of uniform cross section from top to bottom or the cross section of the upper section of the retort and the partition within may be circular regardless of the nature of the cross section of the zone above and between the electrodes. The partition forming the outer and inner zones extends from the top of the retort to an elevation located above the elevation of the top of the electrodes, preferably to an elevation located above the top of the electrodes equal to the distance between the electrodes, but may vary within a reasonable range, depending upon the nature of the carbonizable material charged and the volume of inert, gas per unit weight of charge, passed downwardly through the charge in the.inner zone.

The electrodes may be a pair,-or a plurality of electrodes, located in and flush with opposite faces of the retort. The power supplied to the electrodes may be single phase or three phase alternating current or direct current obtained from a standard-power circuit. ingcurrent is used, the transformer required is preferably a variable transformer in order to permit flexibility in operation, due to such im- ,portant factors as a change in the quality of r the charge and the charging rate. I

The inert gas is admitted to the retort through a plurality of inlets near or through the bottom of the retort at a suflicient rate to cool the\ hot carbonized residue through which it passes countercurrently, to a temperature below the ignition point of th'e carbonaceous residue in air. This rate has been found to. be approximately to 13 cubic feet of retort gas per pound of carbonizable material charged in carbon'izing a, coking coal at the rate of 400 to, 1000 pounds When 'alternatstantial proportion of material which is reactive at any stage in the carbonization process,

and may include such materials as natural gas, producer gas, water gas, fuel gasproduced by this process, and steam. It is ordinarily preferred to use steam as the inert gas without or I with admixture of any of the. above mentioned gases. Steam alone may be used duringlow temperature carbonization of a carbonizable material, as well as during a high temperature carbonization of a carbonizable material, in which the temperature of the carbonaceous material reaches 1700 to 1900 F., particularly when it is necessary to produce a gas of high calorific value. Under such conditions of high temperature carbonization, there is some dissociation of the water vapor but the operation of this process is so controlled as to prevent any substantial dissociation under the conditions for high temperature carbonization .used. Under thesesame conditions, the hydrocarbons in inert gas containing the same are decomposed and result in the production of 'a gas of lower calorific value than that obtained using steam alone.

The inert gas is admitted into the top of the inner zone of the retort through one, or a plurality of inlets, at such a rate as to' keep the uncarbonized material in the inner zone substantially free from condensable products. This ratev has been found to be approximately one to three cubic feet of inert gas per pound of carbonizable material in carbonizlng a coking coal at the rate of .400 to 1000 pounds per square foot of retort cross section between the electrodes per hour. The inert gas admitted into the top of the inner zone of the retort may be derived from any source, so long as it is not substantially reactive at any stage of its contact with the carbonizable portion or carbonized portion of the charge, or so long as it does not contain any substantial proportion of material which is reactive at any stage of its contact with the portions of the charge and may include such ma 1 this process.

The retortgas, which consists of the volatile carbonization products and the inert gas admitted both at the bottom and at the top of the retort, is withdrawn from a plurality of the outlets ator'near the top of the outer zone in-the top of the retort and is cooled stepwise to reinove tarry matter andother condensablematerials by such means as one or a plurality of air-cooled condensers and one or a plurality of ,watercooled indirect condensers. The gas so treated maybe used now as a source ofthe supply of the inert gas used in the processor this gas may be scrubbed to remove valuable Icy-products,

such as ammonia and richer nitrogenous compounds, and otherwise prepare the gas from the retort for use as a fuel gas, such as by the removal of hydrogen sulfide and other sulfur compounds. In either caseonly a portion of theard brick construction with a refractory lining.

The electrodes, preferably made of carbon block, are located in opposite faces and flush with the inner faces of the retort in a mid-section of the retort. Substantially gas-tight-charging mechanisms, fitted into agas-tight metal retort top, supply the carbonized material and the carbonizing material from their respective hoppers into the inner and outer zones, respectively, in the top of the retort.

I have found it possible to charge carbonizable material at a much'higher rate by using my process and apparatus as herein described than has been possible heretofore. Coking coal ischarged and carbonized at a rate of more than 400 pounds per square foot of retort cross section between the electrodes per hour, as compared with a rate of less than 100 pounds per square foot of retort' section per hour, using another process and apparatus. I have found also that it ispossibleto accomplish the carbonization using my process and apparatus herein described by the use of a considerably smaller quantity of electrical energy.

For instance, in the ,carbonization of a coking coal at the rate of- 450 pounds per square foot of retort cross section between the electrodes per hour, 310 kw. hr. per ton of coal charged were required as compared to the other process and apparatus referred to above at the rate of 88 pounds of coking coal per square foot of retort cross section per hour, 350 kw. hr. per ton of coal were required.

It will be seen, therefore, that this invention actually may be carried out by the modification of certain details without departing from its spirit or scope.

I claim: i. In an apparatus for the electrical carbonizatlon of coal in a vertical retort bypassing a column of charge, which comprises coking coal surrounded by an envelope of coke, between electrodes located in contact with and on opposite sides of the charge, the combination of a vertical retort; a gas impervious partition extending from the top of the retort to an elevation above the elevation of the top of the electrodes located in v .the face ofopposite walls of the retort from one half to the full distance between the electrodes, to form an inner zone and an outerzonein the top of the retort; a means for admitting inert gas into the top of the inner zone, into which coal is charged, to keep the uncarbonized coal substantially free from volatile carbonization products;' a means for admitting inert gas to a zone in the retort below the elevation of the bottom of the electrodes and a means for withdrawing a gaseous mixture, which-comprises the inert gas admitted into the top of the inner zone, inert gas admitted to the zone below the electrodes and V the volatile carbonization products, from the top of the outer zone, into which coke is charged.

2. In anapparatus for the electrical carbonization of solid carbonaceous material in a vertical retort by passing a column of charge, which comprises solid carbonaceous material surrounded by an envelope of carbonized carbonaceous material, between electrodes located in contact with and on opposite sides of the charge, the combination of a vertical retort; a gas impervious partition extending from tlie top of the retort to of the retort from one half to the full distance an elevation above the elevation of the top of the electrodes located in the face of opposite walls *between the electrodes, to form an inner zone-

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