US1856252A - Process of carbonizing coal - Google Patents

Description

May 3 11932. 0. H. HERTEL PROCESS OF CARBONIZING COAL Filed Dec. 4, 192,5

Patented May 3, 1932 U'll'llt) HERTEL, OF CHICAGO, ILLINOIfi PROCESS F CARBONIZING GOAL Application filed December 4, 1925. Serial No. 73,171.

This invention relates to the production of a fuel or" novel and desirable characteristics through the carbonization of bituminous coal and the like.

Coke produced by carbonizing coal at high temperatures is very porous, and because of the great extent of surface it burns rap-idly and produces an intense heat. This is also true of coke produced in an experimental way by the various methods heretofore proposed of carbonizing coal at relatively low temperatures.

In the production of high-temperature coke and in the production of coke by previous methods of so-called low-temperature carbonization, a larger percentage of the volatile constituents of the coal has been driven off than is desirable in domestic fuel.

The low density of the product and the relatively small percentage of volatile material remaining therein have been due partly to the use of temperatures in excess of that at which exothermic reactions will be useful in the coal, and partly to the fact that while the as material was plastic it was free to expand as gas was being evolved therefrom. I have discovered that it only sufficient heat be applied to the coal to initiate exothermic reaction within the coal, and if the material be maintained under pressure while plastic, the product will be substantially without pores and hence relatively dense, will contain a relatively large percentage of volatile material, will burn with moderate intensity, and 38 will not produce clinkers.

When a typical variety of bituminous coal is placed in a retort and the retort subjected to sufiicient heat to raise the temperature of the contents to about 390 (3., exothermic re- 40 action occurs in the coal, the temperature rising slightly and then subsiding as the reaction is completed, gas and vapors being meanwhile liberated. The char resulting from this reaction is deep black in color and has a vitreous luster. If the char thus produced be raised to a temperature of about 475 C.,additional exothermic reaction occurs with the evolution of gas and vapors, the color of the char changing to a gray black and having, when struck, a metallic ring of higher pitch than that of the char first produced.

Certain methods heretofore used in carbonizing coal at relatively low temperatures have resulted in the production of an excessive percentage of breeze. In order to dis pose of the breeze and to improve the strength of the coke, the breeze has been mixed with raw coal in varying proportions. As will readily be understood, the passing of a large percentage of the product through the retort a second timev increases the expense of treatment to a substantial extent.

In view of the fact that the term lowtemperature coke is very indefinite as 'to the character of the material carbonized, the temperature employed, and the density, structure, hardness, color, luster and volatile content of the product, I shall hereinafter use the more general term char.

The object of the present invention is th production of a fuel which shall be sufficiently hard and strong so as not to be subject to excessive degradation in handling, which shall be sufficiently dense so that it may be shipped economically and so that it shall not burn with excessive intensity, which shall contain a relatively large percentage of volatile matter, and which shall not form clinkers.

The invention also aims to provide a method of carbonizing coal whereby the product shall be uniform in quality and whereby the production of an excessive percentage of breeze shall be avoided.

While some of the desirable results just mentioned may perhaps be attained in some form of continuous process, I believe that the greatest degree of efiicienc-y can be obtained in a batch process which will allow the material .to be at rest while it is setting, and which will permit of maintaining pressure upon the material while it is plastic and while undergoing the change from plasticity to rigidity.

I have therefore selected for illustration two forms of apparatus wherein the material may be treated in batches, as distinguished from apparatus through which the material moves continuously as a'stream.

In the accompanying drawings, Figure 1 is a vertical sectional view of one form of apparatus by means of which my improved process may be practiced.

Fig. 2 is a transverse sectional view of a rotor comprised in said apparatus.

Fig. 3 is a longitudinal sectional diagrammatic view of another form of apparatus which may be used in producing said fuel.

For a detailed descri tion of the apparatus shown in Fig. 1, re erence may be made to my application Serial No. 699,402, filed March 15, 1924. It will be sufficient here to say that 10 denotes a vertical elongated retort which is relatively narrow in one direction, say, about thirty inches in width. The

' retort has a slight taper inwardl toward the top to facilitate the discharge 0 char downward. Any preferred form of furnace, as,

for example, the furnace 12, may be used to apply heat to the exterior of the retort. At the lower end of the retort are discharge chutes 26 which are closed in any preferred manner, as by means of trap doors 27. 28 denotes a bottom for the retort, said bottom being arranged to be lowered fromthe normal position shown in dotted lines to. that shown in full lines when the contents of the retort are to be discharged.

A feed hopper 3O communicates with the upper end of the retort and is provided with a trap door 31. An upwardly tapering weight 32 is movable up and down within the retort, the weight being shown in charging position in full lines in Fig. 1. The granular or powdered coal being charged into the retort is compelled to pass down through a relatively narrow space between the weight and the retort wall in the form of a thin stream or layer, which in falling exposes the grains and small lumps of coal to the heat of the retort, thus causing a rapid and uniform heating of the coal before the same is deposited at rest, which substantially reduces the time consumed in carbonizing the charge. When the retort is fully charged the weight 32 is lowered onto or pressed against the material by any preferred means, as, for example, the hydraulic cylinder 35, the piston 36 of which is connected to said weight by means of a piston rod 33, cross head 33 and rods 34. By this means the weight can be raised or lowered as well as adjusted to resist yieldingly the pressure of the swelling charge, to place pressure upon the mass while plastic, and to discharge the char at the end of the operation.

The gases and vapors evolved from the charge are withdrawn through a pipe 40 communicating with the upper end of the retort.

Within the retort is rotatably mounted a tubular member 44. A thirty-inch retort would have a rotor of approximately twelve inches in diameter. While the rotor may be cylindrical and mounted to rotate upon its central axis, the rotor is preferably of such cross-sectional form as to exert pressure upon the contents of the retort as the rotor" turns. Herein the rotor is shown as consistin of a cylindrical tube having a longitudinally extending plate or sole 44" secured thereto. The rotor 44 may be rotated in any preferred manner, as, for example, by means of bevel gearmg 45.

Means is provided for internally heating the rotor 44. While such means may be of any preferred character, there is herein shown a candle 46 like that fully described in my application Serial No. 28,614, filed May 7, 1925. The candle is supplied with gas by means of pipes 47 provided with valves 48.

In use, the retort 10 is filled with powdered or granular coal and the weight 32 operated topress against the charge. Heat being apphed to the outside of the retort 10 and to the interior of the rotor 44, the charge is rapidly heated, the entire mass being substantially uniformly raised in temperature by reason of the application of heat both externally and internally, and through the action of the rotor. The latter serves to distribute heat to the charge, since the coal will follow the eccentric portion of the rotor,

thus causing agitation of the coal. Friction treatment increases the surface exposed tothe heat of the retort and the rotor, and thus assists to reduce the time of operation. As the rotor turns the coal moves to fill the constantly shifting gas passage until the stage where the coal becomes plastic is reached.

When the mass begins to set there is less and less tendency to close in around the rotor and thus the delivery of heat to the mass from the rotor is in a measure self-regulating, the amount of heat supplied to the mass from the rotor being automatically reduced as the need for the application of heat diminishes.

As the mass becomes plastic, it tends to flow into the shifting gas passage and thus close the latter, but the rotation of the rotor is sufficiently rapid to maintain a passage for the gas. Moreover, in its rotation the rotor exerts lateral pressure on the charge, which assists to impart a desirable density and hardness to the char. Pressure is also exerted upon the contents of the retort by means of the weight 32, whereby the char is rendered relatively dense and hard.

In Fig. 3 is illustrated diagrammatically a form of apparatus comprising a cylindrical retort which is closed at one end by means of a removable cap 51. The opposite end of the retort is closed by a piston 52, by means of which pressure may be placed upon the contents of the retort by operating the screw 53. The latter engages an internally threaded portion 54 carried by a yoke 55 which is pivoted or otherwise suitably secured to the retort so that the piston, When withdrawn, may be swung aside to permit of charging the retort. In the piston 52 are openings 56 for the escape of gases and vapors. The retort 50 having been filled with granular or pulverized coal and pressure having been placed upon the charge by means of the screw 53, the retort may be inserted into any suitable form of furnace. The screw 53 may be operated from time to time to maintain pressure upon the charge. When the mass fuses the piston 52 may be advanced to maintain the mass under pressure, this pressure being maintained until the material has set. The retort may then be withdrawn from the furnace, the cap 51 removed and the char expelled by means of the piston 52 and the screw 53.

In accordance with my process, the heat to which the coal is subjected is just sufficient to fuse the coal and initiate exothermic reactions therein. (In the case of the coals with which I have experimented, the coal is heated to about 390 C.) I thereby reduce the cost of the product by economizing fuel and by shortening the time of treatment. The product also is improved, in that it retains a relatively large percentage (approximately 14%) of volatile matter." By keeping the material under pressure, pores are largely eliminated, the char being relatively dense, hard and strong, the apparent specific gravity of the char being about 1.0. Inasmuch as the material is at rest while it is setting, the char is stronger and harder than char produced by processes which involve movement of the material while it is setting; and there is a very small, practically negligible, percentage of breeze. The entire charge is substantially uniform in character, each lump being substantially like all the other lumps, and each lump being homogeneous or uniform in character throughout. The product is black in color and has a vitreous luster.

By reason of its density and high volatile content, the char produced by the process herein described is particularly well adapted for domestic use. The high volatile content conduces to ease in igniting the fuel, while its density prevents excess vely rapid combustion and insures against fusion of the fuel and the production of clinkers.

While the improved fuel herein described is especially adapted for domestic use, it may also be used in place of ordinary coke in gas-making plants.

I claim as my invention:

1. A process of carbonizing coal that will go through an exothermic reaction accompanied with plasticity upon being heated to a predetermined temperature which consists in heating a definite batch of coal just sufliciently to initiate such exothermic reaction. in the batch, and maintaining the batch under mechanical pressure while the batch is plastic and while setting, Vapors to escape, the material belng at rest while setting.

2. A process of carbonizing coal that will become plastic when heated to about 400 C. which consists in heating a definite batch of coal just to about 400 C. and maintaining the batch under mechanical pressure until it has set, while allowing gas and vapors to escape freely.

3. A process of carbonizing coal that will become fused when heated to a predetermined temperature which consists in arrangin a batch of coal in the form of a relatively thin layer, applying heat to opposite sides of the layer just sufficiently to raise the temperature of the coal to the fusing point, and applying mechanical pressure to the fused material until it has set, while allowing gas and vapors to escape freely.

4. A process of carbonizing coal that will go through an exothermic reaction accompanied with plasticity upon being heated to a predetermined temperature which consists in. heating a definite batch of coal just sufliwhile allowing gas and j ciently to initiate exothermic reaction in the andallowing the batch to be at rest while settin 5. A process of carbonizing coal that will become plastic when heated to a predetermined temperature range, which consists of confining a batch of the coal in a vertical column having a central longitudinal passage therethrough, heating the batch externally and also internally from within said passage just up to said temperature range, agitating said batch while in granular form, and applying mechanical pressure to the top of said batch and to said batch from within said passage while the batch is plastic and while setting, and allowing gases and vapors to escape freely.

In testimony whereof, I have hereunto aflixed my signature.

or'ro H. HERTEL.

Images