US2127542A - Electrical carbonization of coal - Google Patents

Description

A 8 R. B. STITZER V 2,127,542-

EJ 'JECTRICAL CARBONIZATION OF COAL Filed Aug. 14, 1935 2 Sheets-Sheet 1 Ed/ph a SflfZer 4 INVEN TOR BY v ATTORNEY 2 Sheets-Sheet 2 FIG; 3

R. B. STITZERI ELECTRICAL CARBONIZATION 0F COAL Filed Aug. 14, 1935 Aug. 23, 1938.

FIG. 4

INVENTQR ATTQRNEY I! 14 1/4 via 1 1 144 ap, 5. Sfifze/ Patented Aug. 23, 1938 UNITED STATES ELECTRICAL CARBONIZATION 0F COAL Ralph B. Stltzer, Shefiield, Ala Application August 14, 1935, Serial No. 36,165

10 Claims.

(Granted under theact oi. March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) This application is made under the act of March 3, 1883 as amended April 30, 1928, and the invention herein described may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to the process of electrical carbonization of solid carbonizable materials, particularly the'carbonization of bituminous coal to form a coke suitable for domestic and industrial uses. 7

One of the objects of this invention is to provide a continuous method and an efficient means for the carb'onization of solid carbonizable materials in which electrical current is used as a 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. Still another object of this invention is to provide a means for the withdrawal of the volatile carbonizatlon products, which is a particularly serious problem when highly coking coals are carbonized. Other objects of the invention include the provision of a method for the I 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 electrical resistor and continue the passage of current through the coke formed around the resistor until the entire charge is carbonized, followed by the removal ofthe coke, thereby presenting a discontinuous operation, These and 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 the heating elements during the time in which they are plastic and the car-' bonized residue prevents rapid heat transfer from the element to the coal mass; third, the plasticizing of a charge of coking coals seals the space between the particles of chargeand makes the withdrawal of the volatile carbonization products plication Ser. No. 52,853, filed December 4, 1935,

now U. S. Pat. No. 2,093,493 issued September 21, 1937, I have described and claimed a process for making fuel gas from carbonlzable material and more specifically a process for making a fuel'gas, consisting of a mixture of coal gas and water gas, from coals I have found 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 'the charge to keep the uncarbonized charge in the inner zone substantially free" from volatile condensable carbonization products, by withdrawing the inert gas with the volatile carbonization products upwardly through the outer zone of the carbonized 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 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.

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

Fig. l is a diagrammatic, vertical, sectional view of one form ofapparatus for the embodiment of my process, A

Fig. 2 is a vertical, sectional view of the electrical carbonlzation retort,

plan view of the section a-n in a plan view of the sectionC-Cin of the section D-D in into the inner zone in the top of retort-l, which is surrounded by partition 1. The charge of coal surrounded by the 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 l, and represented by electrodes- 8. The coal in the charge between the electrodes 3, is carbonized largely from the heat produced by the passage of an: electrical current through the care ibon portion of the charge surrounding the coal Fig. 3 ice plan view of the section A-A in.

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 temperature 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 the retort. 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 sufli'cient 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 upwardly through the coke in the outer zone at the top of the retort and are withdrawn at the top of this outer zone. This mixture of gas from the retort, together with entrained solid and liquid particles, passes through the air condenser 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 gas from the retort is condensed by indirect cooling with water and separated from the gas. The gas from the retort from which substantially all the condensable volatile matter has been removed passes into the inlet of the blower Ill, which serves to maintain 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 7, into the top of the inner zone of the retort.

vIn 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 1), 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 that occupied on passing the bottom of partition 2. The coke a, serves as a resistor when it comes in contactwith the electrodes 3. and the heat produced by the passage of the electrical current thru'the coke a, carbonizes the coal b, of the charge adjacent to it. The coal so carbonized in turn serves" as a resistor and the carbonization proceeds. Since, however, the

.operation is a continuous one, the amount of uncarbonized coal b, left in the charge as it passes through the zone between the electrodes 3, is continually diminished 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 through the inlet 6, passes upwardly and cools the hot carbonaceous product in which the coke a, from the charge and the coke resulting" from the carbonization of coal b, is practically indistinguishable. The inert gas so heated serves to assist 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 down-. wardly and keeps the uncarbonized coal 1), 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 gas from the retort.

In Fig. 3, which is a plan 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 the charge I), in the inner zone by partition 2.

In Fig. 4, which is a plan 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 of the charge 27.

In Fig. 5, which is av plan view of a section of the retort I, through the electrodes, 0 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, which has not yet become carbonized.

In Fig. 6, which is a plan view of a section of the retort I, between the elevation of the bottom of the electrodes and the bottom of the retort, a represents the coke portion of the charge and the carbonized portion of the charge, the two being practically indistinguishable at this point.

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 the intermediate and finished products involved.

The term solid carbonizable material shall mean and include solid carbonizable material, which has not been subjected to a carbonization process, and which may be heated to a sufliciently high superatmospheric temperature to remove the volatile products which it contains with the formation of a solid carbonized residue useful as a domestic or industrial fuel or otherwise in the arts. Examples of solid carbonaceous material include anthracite coal, non-coking and coking bituminous coals, and materials of recent vegetable origin, such as woods and nut shells. The term "carbonized material shall mean and includeany solid carbonaceous product resulting 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 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 the carbonization of bituminous coal and it is preferred to use a hardwood charcoal derived from the same type of hardwood that preferably is such that it will pass through a l"- mesh and be retained on a 0.25" mesh. Screenings which otherwise have little value for metallurgical purposes may be used for this purpose. Should these screenings contain a considerable excess 01 very fine material, such as below a 0.25" mesh, a small proportion of this material could be incorporated with the carbonizable, portionof the charge when this portion of the charge is acoking coal. The size of thesolid 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 and 90 to 70% by weight, respectively.

The vertical retort shown in the respective- The partition in the top of the retort which forms the' outer and inner zones in which the carbonized and carbonizable materials, respectively, are charged may be 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 oirthe cross section of the zone above and be-r tween 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. a

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 eleccarbonaceous residue through which it passes countercurrently, to a temperature below the ignition point of the carbonaceous residue in air: This rate has been found to be approximately 5 to 15 cubic feet of retort gas per pound ofcarbonizable material charged in carbonizing 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 bottom of the retort may be derived from any source, so long as it is not substantially reactive at any stage of the carbonization process, or so long as it does notcontain any substantial 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 gas produced by this process, and steam. It is ordinarily preferred to use steam as the inert gas without or with admixture of any of the above mentioned gases. used during low temperature carbonization of a carbonizable material, as well as during a high temperature carbonization of a carbonizable ma; terial, in which the temperature of the carbonaceous material reaches 1 700 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 these same 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. 7

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 rate has beenfound to be approximately one to three cubic feet of inert gas per pound of carbonizable. material in carbonizing 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 topoi 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 materials as natural gas, producer gas, water gas, and fuel gas produced by this process. It is ordinarily preferred to use fuel gas produced by this process.

The gas from the retort 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 at or near the top of the outer zone in the top of the retort and is cooledstepwise to remove tarry matterand other condensable ma-' terials by such means as one or a plurality of aircooled condensers and one or a plurality of watercooled indirect condensers. The gas so treated may be used nowas a source of the supply of the inert gas used in the process or this gas may be scrubbed to remove valuable'by-products, such as ammonia and other nitrogenous compounds. and otherwise prepare the retort gas for use as a fuel gas, such as by the removal of hydrogen sulfide and other sulfur compounds. In either case only a portion of the treated gas from the retort is required to supplythe inert gas used in the process. The pressure of the gas leaving the retort is maintained at substantially atmospheric pressure by means of a blower inthe condensing and scrubbing system, preferably between the two. At least a portion of the gas discharged from the blower is maintained at a sufficient pressure to be supplied to the bottom and the top Steam alone may be of the retort without additional compression. Otherwise, the scrubbing system maybe maintained under a pressure at least equal to that required to deliver the inert gas to the retort at the proper pressure.

The retort shell is built with standard masonry 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 a gas-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 disclosed than has been possible heretofore. Coking coal is charged 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 is possible to 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:

1; Process of carbonizing coking coal which comprises, charging coke continuously into an outer zone in the top of a vent retort of square cross section, surrounding and gas-imperviously separated from an inner zone, with both zones open at the bottom and extending downwardly until they are adjacent to but above a heating zone in a substantially horizontal section of the retort; charging the coal continuously into the inner zone in the top of the retort; passing an electrical current, supplied to the'sides of the heating zone through the charge in the heating zone, the characteristics of the current being regulated so that the heat produced on passing through the charge in the heating zone is sufficient to cause the coal to be substantially carbonized when it has passed through the heating zone; passing a portion of the coal gas subsequently produced into the retort, near the bottom, countercurrent to the direction of flow of the charge to cool the coke below the heating zone and to heat the coal and coke above the heating zone; passin g'a small proportion of the coal gas subsequently produced into the. top of the inner zone; withdrawing the retort gas, comprising the small proportion of coal gas admitted into the top of the inner zone, the volatilized products of carbonizatiomand the coal gas admitted near the bottom of the retort, from the top of the outer zone at the top of the retort; separating the condensable materials from the retort gas so withdrawn to yield a coal gas; and

withdrawing-the cooled coke continuously from the bottom of the retort.

2. Process of carbonizing solid carbonizable material which comprises, charging carbonized carbonizable material continuously into an outer zone in the top of a vent retort of square cross section, surrounding and gas-imperviously separated from an inner zone, with both zones open at the bottom and extending downwardly until they are adjacent to but above a heating zone in a substantially horizontal section of the retort; charging the solid carbonizable material continuously into the inner zone in the top of the retort; passing an electrical current, supplied to the sides of the heating zone through the charge in the heating zone, the characteristics of the current being regulated so that the heat produced on passing through the charge in the heating zone is suflicient to cause the solid carbonizable material to be substantially carbonized when it has passed through the heating zone; passing a portion of the fuel gas subsequently produced into the retort, near the bottom, countercurrent to the direction of flow of the charge to cool the carbonized material below the heating zone and to heat the solid carbonizable material and carbonized carbonizable material above the heating zone; passing a small proportion of the fuel gas subsequently produced into the top of the inner zone; withdrawing the retort gas, comprising the small proportion of fuel gas admitted into the top of the inner zone, the volatilized products of carbonization and the fuel gas admitted near the bottom of the retort, from the top of the outer zone at the top of the retort; separating the condensable materials from the retort gas so withdrawn to yield a fuel gas; and withdrawing the cooled carbonized product continuously from the bottom of the retort.

3. Process of making coke from coking coal which comprises, forming a column of the coal surrounded by a column of coke above a heating zone in a substantially horizontal section of a vertical retort with the inner zone above the heating zone containing the coal and the outer zone above the heating zone containing the coke, gasimperviously separated from each other from the top of the retort to a location adjacent to the heating zone; passing an electrical current, supplied to the sides of the heating zone, through the charge in the heating zone, the characteristics of the current being regulated so that the heat produced on passing through the charge in the heating zone is suilicient to cause the coal to be substantially carbonized when it has passed through the heating zone but insuilicient to heat the coke in the heating zone to the temperature ,of conversion of any substantial proportion of the steam subsequently admitted in contact with the coke into water gas; passing steam into the retort, near the bottom, countercurrent to the direction eie flow of the charge to cool the coke below the heating zone and to heat the coal and coke above the heating zone; passing a small amount of inert gas into the top of the inner zone; and withdrawing the retort gas, comprising the inert gas admitted into the top of the inner zone, the volatilized products of the carbonization and the steam admitted near the bottom of the retort, from the top of the outer zone at the top of the retort.

4. Process of making a carbonized material from a carbonizable material which comprises, forming a column of the carbonized carbonizable material surrounded by a column of carbonized material above a heating zone in a substantially horizontal section of a vertical retort with the inner zone above the heating zone containing the carbonizable material and the outer zone above the heating zone containing the carbonized ma"- terial, gas-imperviously separated from each other from the top of the retort to a location ad- N jacent to the heating zone; passing an electrical current, supplied to the sides of the heating zone, through the charge in the heating zone, the characteristics'of the current being regulated so that the heat produced on passing through the charge in the heating zone is suiiicient to cause the carbonizable material to bensubstantially carbonized when it has passed through the heating zone but insufiicient to heat the carbonized material in the heating zone to the temperature of conversion of any substantial proportion of the steam subsequently admitted in contact with the coke into water gas; passing steam into the retort, near the bottom, countercurrent to the direction of flow oi the charge to cool the carbonized material below the heating zone and to heat the solid carbonizable material and the carbonized carbonizable material above the heating zone; passing a small amount of inert gas into the top'of the inner zone; and withdrawing the'retort gas, comprising the inert gas admitted into the top of the inner zone, the volatilized products of the carbonization and the steam admitted near the bottom of the retort, from thetop of the outer zone at the top of the retort.

5. Process of making coke from coking coal which comprises, passing an electrical current,

supplied to the sides of the heating zone in a sub-' stantijaily' horizontal section or a retort, through heating zone, with the characteristics of the current being so regulated that the heat produced on passing through the charge in the heating zone is sufficient to cause the coal to be substantially; carbonized when it has passed'through the heating zone; passing an inert gas through the heating zone countercurrent to the direction of flow oi the charge oi said zone; passing a small amount 0! an inert gas downwardly through only the coal portion of the charge above the heating zone to a location adjacent to the heating zone; and withdrawing the retort gas, comprising the inert gas admitted into the top of the inner zone. the volatilized products of the carbonization and the inert gas passed through the heating zone, from the top or the outer zone at the top of the retort.

6. Process oi making carbonized material from produced on passing through the charge in the heating zone is sufllcient to cause the carbonizable material to be substantially carbonized when it has passed through the heating zone; passing an inert gas through the heating zone countercurrent to the direction of flow of the charge of said zone; passing a small amount of an inert gas downwardly through only the coal portion of the 1 charge above the heating zone to a location ad- ,iacent to the heating zone; and withdrawing the aromas retort gas, comprising the inert gas admitted into the top oi the inner zone, the volatilized products of the carbonization and the inert gas passed through the heating zone, from the top of the outer zone at the top of the retort.

'1. Processor carbonizing coking coal which comprises, heating a section of a column of charge, which comprises coking coal surrounded by an envelope oi coke, to a superatmospheric temperature suflicient to carbonize the coal by passing an electrical current between electrodes located in contact with and on opposite sides of the section of the charge, and by passing a cur- ,rent of inert gas upwardly thru the section of the charge; passing inert gas downwardly thru a column-oi coal above the section of the charge to keep the .uncarbonized coal substantially free from condensable carbonization products; and withdrawing the inert gas and the volatile carbonization products thru the coke surrounding the coal above the section oithe charge, the coke being separated from the coal by a gas-impervionspartition.'

8. Process of --carbonizing solid carbonizable material which comprises heating a section of a column of charge, which comprises solid carbonizable material surrounded by an envelope of carbonized carbonizable material, to a superatmospheric temperature sumcient to carbonize the solid carbonizable material by passing an electrical current between electrodes located in contact with and on opposite sides of the section of the charge, and by passing a current of inert gas upwardly thru the section oi the chargeypassing inert gas downwardly thru a column of solid carbonizable material above the section of the charge to keep the uncarbonized solid carbonizable material substantially free from condensable carbonization products; and withdrawing the in-. ert gas and the volatile carbonization products.

thru the carbonized carbonizable material surthe section of the charge, the carbonized carbonizable material being separated from. the solid carbonizable material by a gas-impervious partition.

9, Steps in the process of carbonizing coking coal which comprises passing a current of inert gas downwardly thru a column oi the coal portion of the charge, which is surrounded by a coke portion of the charge, the two portions being separated by a gas-impervious partition as the charge approaches the zone of carbonization between electrodeato keepthe uncarbonized coal substantially free from condensable carbonization products; and withdrawing the inert gas and the volatile carbonization products upwardly thru the coke portion of the charge.

10. Steps in the process oi carbonizing solid carbonizable material which comprises passing a current of inert gas downwardly thru a column 01' the solid carbonizable material portion of the charge, which is surrounded by a carbonized carbonizable material portion of the charge, the two portions being separated by a gas-impervious partition as the charge approaches the zone of carbonization between electrodes, to keep the uncarbonized solid carbonizable material substantially free from condensable carbonization products; and withdrawing the inert gas and the volatile carbonization products upwardly thru the carbonized carbonizable material portion of the charge.

, RALPH B. STITZER.

CERTIFICATE OF CORRECTIOIL' Patent No. 2,127, 51,2. August 2 19 RALPH B. STITZER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line 52, for the word."carbonizable" read carbonaceous; and line 59, for "carbonaceous" read carbonizable; and that the said Letters Patent should be read with this correction therein tlnt the same may conform to -'the record of the case in the Patent Office.

Signed and sealed this 11th day of. October, A. D. 1958 Henry Yen Aradale (Seal) Acting Commissioner of Patents.

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