US2158816A - Coke making process - Google Patents

Description

May 16, 1939.

M. D. CURRAN COKE MAKING PROCESS Filed April 2, 1937 /Vaar/'ce D. C uffa f? drrcf Patented May 16, 1939 2,158,816

`A UNITED STATES PATENT OFFICE come MAKING Pnoonss Maurice D. Curran, Glendale, Mo., assignor to Tar & Petroleum Process Company, Chicago, Ill., a, corporation of Illinois Application April 2, 1937, Serial No. 134,552

10 Claims. (Cl. 20E- 9) The present invention relates to improvements ing zone is due to the fact that the heat is not in coke making processes. carried inward to the mass of coal by the passage The present application is in part a continuof hot vapors or gases.

ation of application Serial No. 91,325, led July According to the method of coking in which 18, 1936, by the present applicant. Subject matthe bed of coal or its equivalent is shallow in ter analogous in some respects to the subject comparison to its width and in which the/heat matter of this application is described and claimed is applied below the bed of coal or the like, Va-

in applicants co-pending application Serial No. pors of distillation, water vapors and fixed gases 117,032- from the coal adjacent to the bottom of said bed More particularly thepresentinventionrelatesto are liberated at the beginning of the coking pe- 10A improved processes for controlling the characriod, a substantial portion 0f these vapors und teristics of the coke resulting from the treatment gases passing upward through the coal and imof coal or other hydrocarbon containing material. parting their heat to the cooler coal mass. This The invention has particular applicability to results, first, in the Vaporization of waterin the methods of manufacturing coke in which the layer coal and then in vaporization of volatile matters l5 of coal or equivalent material is shallow relative and Subsequent partial COIidenSation of the va to the width thereof. Stated more particularly, pors, provided the temperature in the upper porthe present invention relates to methods of mantion of the charge iS SllCiently low, followed by ufacturing coke employing coke ovens 0f the redistillation and elimination from the coal mass a0 Knowles type, an example of which is illustrated as the coking process proceeds. The passage of 20 and described in the patent to Knowles and vapors and gases through the coal mass results McIntyre No. 1,635,280, patented July 12, 1927. in a transfer of heat by means of convection to According to the type of oven referred to, coal the coal mass and an increased thickness of the or equivalent material is disposed on a horizontal coking zone which may attain a thickness of two -i'loor heated by nues extending beneath said floor, inches or more in the case of coals having a high 25 l the coking iioor forming a part of the coking coking index. The result of this ladditional chamber, the oven having means for charging thickness in the coking zone is a trapping of vacoal, means for withdrawing vapors and gases, Dors or gases within the coking zone and the means for sealing the ends of the chamber, and forming of bubbles by said vapors and gases. l means permitting the pushing of the. resulting 'I'he resistance of the thickened coking zone leads 30 coke out of the coking chamber, to an unusually porous structure in the coke The coking process as carried out in the which in turn increases the reactivity of the coke Knowles type of oven diiers materially-from the t0 Oxygen. and, other things being equal, i11- coking process as carried on in ordinary by-` creases combustibllityl product ovens in which the vertical height of An object of the present inventionis to provide 35 the coal charge is great relative to the width an inexpensive DIOCGSS formaking 810W volatile thereof. In the ovens just referred to the vapors C031 Suitable fOr blending With a high Volatile Coal of distillation, together with the water vapor refor the manllfffctule 0f COke.

sulting from the drying of the coal, proceed up- A further obJect is to provide a process of mak-y 40 ward and Outward through the massof cke 1ying the low volatile coal above referred to from 40 ing adjacent to the coking walls, Except at the the same kind of coal with which it is to be mixed top of the coking charge, practically no vapors later in the manufacture 0f Cokey or gases pass through the coal mass in the middle A further Object iS 130 provide the 10W Volatile of the oven, since the resistance of the latter to coal referred to ai the seme time that the mixl fluid flow is greater than the resistance through ture 1S being coked Without requiring additional 46 the coke and upward along the side walls. The apparatus 01' additinal Processes. consequence is that the heat necessary for cok- A further object is to provlde all imDrOVed ing is supplied to the coal by conduction rather method fOr 1310111161118 a COmmeICially desirable than by convection, and the coking zone is very coke without the necessity for using high-priced 5o narrow, not over a fraction of an inch in thicklow volatile coal.v In the manufacture ofeoke, 5g ness. By coking zone is meant the narrow and difficulties are' encountered if high volatile coal progressively moving body of liquid coal which is treated according to known coking processes, results from the application oi heat and which among which difficulties may be mentioned the contains the hydrocarbons subsequently given Iact that the coke ngers are small and are not off, leaving the coke. This condition o1 the cokmarketable for many purposes. 55

A further object of the present invention is to provide an improved process whereby the percentage of cell structure of the coke may be controlled whereby to produce desired characteristics. It has been discovered that the thickness as well as the viscosity of the material in the coking zone varies rather closely in accordance with the coking qualities of the coal. Coal having a high coking power will present in the Knowles type of oven during the coking process a thicker and more viscous material in the coking zone than will a coal of low coking power. It is a further object, therefore, of the present invention to provide a process of coking by which the coking power of the charge may be modified to change the viscosity and thickness of the material in the coking zone and to produce any desired variation, within limits, with respect to the total volume of cells and the size of said cells in the resulting coke.

Further objects will appear as the description proceeds.

Figure 1 of the drawing is a more or less diagrammatic representation of the action within a Knowles type of oven operated according to the present invention; and

Figure 2 is a diagrammatic view illustrating a cycle of operation according to the present invention.

In said diagram the horizontal oven floor is indicated by the numeral I and the roof thereof is indicated by the numeral 2. Side walls are indicated by the numerals 3-3. The oven is shallow relative to its Width and length. The horizontal floor I is heated by means of gases passing through flues 4 4 below said floor. Coal or equivalent material is disposed upon said floor l. Means (not shown) will be provided for charging coal into the oven chamber, other means, such as the uptake 4a, will be provided for withdrawing gases and vapors, and means will also be provided for sealing the ends of the chamber. The oven will be so constructed that a charge of material, after having been treated, may be pushed out of the coking chamber. Figure 1 of the drawing represents conditions when a particular heat treatment has been completed and the charge is ready to be pushed out of the coking chamber. Under these conditions the charge within the coking chamber will be in three rather distinct layers, indicated by the numerals 5, 6 and l.

The lowermost layer 5 according to the present invention will be coke, the various fingers of which are indicated by the numerals 5a--5a. Above the layer 5 of coke is a layer of plastic material 6, which layer is always at approximately the softening temperature of the coal being treated. This plastic layer 6 will in service be a tarry mass in which the coal has become liquefied. Above the layer 6 is alayer 1 of coal in unfused condition. The coal in layer 1 has a temperature always below the softening temperature of the coal. In service a certain amount of hot gases from the coke zone 5 will pass laterally to the walls and upwardly into the chamber above the layer 1. Under these conditions the topmost portion of the layer 1 maybe in swollen condition, but in service the coal in the layer 1, even at the topmost portion thereof, will not be fused. An explanation of this phenomenon which occurs to applicant is that the gases passing upwardly from the plastic layer 6 become cooled in passing through the layer l and prevent the fusing of even the uppermost portion ofv said layer 1. Moreover, the hot gases passing upwardly along the side walls will tend to pass oi through the uptake 4a, whereby said layer l will be protected against temperatures above the fusing temperature of the coal in said layer l.

The heat treatment according to the present invention is carried on from the bottom of the charge toward the top, where the upper part of the charge, that is--in the layer l, is considerably devolatilized but is not changed in its physioal form. The only change in the layer 'l is the driving out of moisture and part of the volatile matter, that is-those volatiles which come oile at temperatures below the softening temperature of the coal. According to the present invention there is no fusing of the upper part of the charge, inasmuch as the temperatures at that region are below the fusing temperature of the coal. As indicated above, the temperature conditions in the upper part of the charge should be maintained at a value below the softening temperature thereof, to the end that the physical form of the coal in the upper part of the charge is not materially changed. When the material in the lower part of the charge, that is-in the layer 5,

'has been coked and While the material in the upper portion of the charge, that is-in the layer l, is in its partially devolatilized unfused condition, the charge is removed from the oven.

The manner in which the material may be treated will depend largely upon the individual practical conditions confronting the operator. If preferred, the charge, after being cooled, may be screened to remove the largely devolatilized pieces of soft coke resulting from the breaking up of the layer 6 and to remove the partially devolatilized coal. According to the step referred to, these pieces of coke and partially devolatilized coal are preferably crushed, although crushing is not essential. According to a process at present preferred, the pieces of coke. and partially devolatilized coal are crushed to a size which will pass through a ten mesh screen. This material, preferably in crushed condition, is intimately mixed with the coal in the next batch to be treated. It will be understood that the intimacy of the mixture may be promoted by grinding the coal to relatively small size. By varying the proportions of the soft coke and partially devolatilized coal with respect to the coal to be treated; it is possible to produce coke of the physical characteristics usually desired.

Figure 2 indicates diagrammatically the cycle of operation. After the treatment in the Knowles type of oven as above described, the charge is pushed out of the oven and the partially devolatilized coal and soft coke are separated from the commercial or hard coke. 'Ihe partially devolatilized coal and soft coke are then mixed with fresh coal for the next batch.

In practice in the manufacture of coke, the run-of-oven product is usually crushed and sized as required by market conditions. The smaller pieces, for example that which passes through a 1/2 to 1% inch screen, is commonly called braize. This braize has no particular function according to the present invention, but for practical purposes may be included along with the soft, mildly coherent coke and the partially devolatilized coal. The broken pieces of hard coke, which form only a smallpercentage of the braize, have little or no binding power, but the soft, mildly -coherent coke and the partially devolatilized coal have a surface ailinity for tar vapors and melting bitumen, and the mixture with raw coal produces a more thoroughly melted and cemented coke than can be obtained from a mixture of high temperature braize and coal.

If preferred, the charge which has been removed from the oven may be treated as follows:

The upper layer 1 of said partially devolatiiized coal is separated from the fused, more or less coherent layer 6, which layer is composed of soft coke. The soft coke comprising said layer 6 may be utilizedy along with the'hard coke resulting from the layer 5. With some types of coal the layer- 6 of soft, mildly coherent coke will screen olf with the partially devolatiiized coal in layer 1. With other types of coal, this layer 6 will screen off with the coke in layer 5. The pieces of partially devolatilized coal resulting from the layer 'I are in condition to be mixed with a succeeding batch to produce coke of the desired characteristics. Expressed in other language, the partially devolatilized coal which haslbeen produced from high volatile coal now presents many of the desirable characteristics of mined .low volatile coal. tilized coal are preferably crushed, although crushing is not essential. This partially devolatilized coal, preferably in crushed condition, is

intimately mixed with fresh coal in the next batch to be treated. It will be understood that the intimacy of the mixture may be promoted by grinding thev coal to relatively small size. By varying the proportions of the partially devolatiiized coal with respect to the raw coal in a batch, it is possible to produce coke of the physical characteristics usually desired. The partially devolatiiized coal has a surface affinity for tar vapors and melting bitumen, and the mixture with raw coal produces a more thoroughly melted and cemented coke than can be obtained from a mixture of high temperature braize and coal, or than can be obtained from high volatile coal itself.

According to the present invention the partially devolatiiized coal of the rdesired quality is produced in one operation at the same time and in the same process at which the high temperature coke is made. The addition of, for example, a two-inch extra height of coal on top of the normal charge of coal improves the heat econonw of the process, because these two inches of material, when heated to the lower temperature as contemplated by the present invention, radiate less heat from the charge, and by the insulating effect thereof assist the coke below to reach the high temperature desired. It may be stated at this point that no difficulties arise from the presence of the low temperature partially devolatii-l ized coal on top of the high temperature coke, but, on the contrary, the addition of the extra height of coal on top of the normal charge will exert a pressure upon the lower coal and thus help to reduce its porosity, and thus make it suitable for certain metallurgical processes.

According to the present invention the special partially devolatiiized coal referred to may be added to the raw coal in relatively large percentages, giving in the case of certain coals a very high grade, high temperature coke.

`The partially devolatiiized coal contemplated in the present invention has a different function than braize would have, in that the material contemplated herein unites homogeneously with the raw coal in the same manner as a low volatile coal, which costs moremoney in many localities. With braize the uniting of said braize is not with the raw coal but with the coke. The result of this last mentioned union is a poorer The pieces of partially devolabond than is the case with the uniting of the two coals. It may be noted that in order to produce a desirable coke which will stand handling without undue breakage it is necessary to use in the manufacture of said coke a low volatile coal to the extent of to 25 per cent of the mixture. The present invention makes it possible to utilize a high volatile coal, and, by treating as described, to obtain a sufficiently low volatile coal to accomplish the purpose.

It is intended to cover all modifications of the present invention that fall within the scope of the lappended claims.

What is claimed is- 1. The cyclic process of producing coke which consists in providing a bed 'of high volatile, cokable coal shallow relative to its width and length, applying heat thereto below said bed to coke the lower portion of said bed, stopping the coking process at a point which will produce a predetermined amount of partially devolatiiized coal and mildly coherent soft coke at `the top of the charge, which partially devolatiiized coal has the moisture driven therefrom and those v01-Vv atiles removed which come off below the softeningvtemperature of said high volatile, cokable coal, separating this devolatiiized coal and soft coke from the hard coke produced below it, mixing said devolatiiized coal and soft coke with a.

succeeding charge of coal, and repeating the coking process referred to.v

2. The method ofA preparing coke which consists in intimately mixing with high volatile, cokable coal a predetermined portion of partially devolatiiized coal and mildly coherent soft coke, heating from below a shallow bed of said mixture to coke the lower portion of said bed and stopping the heating process at a point which will produce a predetermined amount of partially devolatiiized coal and mildly coherent soft coke on top of said bed, which partially devolatiiized coal has the moisture driven therefrom and those volatiles removed which come oil` below the softening temperature of said high volatile, cokable coal and separating out the desired constituents resulting from said operation.

3. The process of producing coke of desired physical characteristics with respect to size and total volume of pores which consists in mixing soft coke and largely devolatilized coal with a charge of high volatile, cokable coal, heating from below a shallow bed of said mixture to coke the lower portion of said bed, and stopping the heating process at a point which will produce a predetermined amount of partially devolatilized coal and mildly coherent soft coke on top, of said bed, which partially devolatilized coal has the moisture driven therefrom and those volatiles removed which come off below the softening temperature of said high volatile, cokable coal.

4. The cyclic process of producing coke of desired physicalcharacteristics with respect to size and total volume of pores which consists in mixing soft coke and largely devolatilized coal with a charge v of high volatile, cokable coal, heating from below a shallow bed of said mixture to coke the lower portion of said bed, stopping the heating process at a point which will produce a predetermined amount of partially devolatilized coal and mildly coherent soft coke on top of said bed, which partially devolatilized coal has the moisture driven therefrom and those volatiles removed which come oir below the softening temperature of said high volatile, cokable coal, removing said devolatilized coal and soft coke from said charge, and mixing said devolatilized coal and soft coke with coal for a succeeding coking charge.

5. The cyclic process of producing coke which consists in providing a bed of high volatile, cokable coal shallow relative to its width, applying heat thereto below said bed to coke the lower portion of said bed, stopping the coking process at a point below that which will fuse the top portion of said bed but which will drive off the moisture from and cause a partial devolatilization of the coal in the upper portion of said bed, removing the resulting devolatilized coal, mixing said devolatilized coal with a succeeding charge oi' high volatile, combustible coal, and repeating the coking process referred to.

6. The method of producing a partially devolatilized coal suitable for coking purposes which 'consists in providing a bed of coal shallow relative to its width, applying heat thereto below said bed,. stopping said heating process at a point at which the lower portion of said bed is coked and at which the moisture and part of the volatiles are driven off from the upper portion of said bed but below a point which will cause fusion of the coal in the upper portion of said bed, and separating the partially devolatilized coal from the remainder of the charge.

7. The process of producing coke of desired physical characteristics with respect to size and total volume of pores which consists in mixing largely devolatilized coal in unfused condition with a charge of high, volatile, cokable coal and heating from below a shallow bed of said mixture, limiting the time of said heating step so that only the lower portion of said bed is coked and the upper portion of said bed has its moisture removed and is in partially devolatilized but unfused condition.

8. The cyclic process of producing coke of desired physical characteristics with respe'ct to size and total volume oi. pores which consists in' mixing largely devolatilized coal in unfused condition with a charge of high volatile, cokable coal, heating from below a shallow bed of said mixture to coke the lower portion of said bed, stopping the heating process at a point which will produce a predetermined amount of partially devolatilized coal in unfused condition, which coal has its moisture and part of its volatiles driven therefrom, removing said devolatilized coal from said charge, and mixing said devolatilized coal with raw coal for a succeeding coking charge.

9. The method of producing a physically strong coke in a cyclic operation which consists in coking a mixture of high volatile, cokable coal and partially devolatilized material such as produced in a later step of the operation, heating this mixture in a flat layer from below, carrying said heating operation to a point where a hard, physically strong coke and a layer of partially devolatilized coal are produced which partially devolatilized c oal has the moisture driven therefrom and those volatiles removed which come off below the softening temperature of said high volatile, cokable coal, separating the coke from the partially devolatilized coal, and returning the partially devolatilized material to the rst'step of the operation.

10. 'I'he method of producing a physically strong coke which consists in coking a mixture of high volatile, cokable coal and relatively low volatile coal, heating this mixture in a i'lat layer from below, carrying said heating operation to a point where a hard, physically strong coke and a layer of partially devolatilized coal are produced, which partially devolatilized coal has the moisture driven therefrom and those volatiles removed which come off below the softening temperature of said high volatile, cokable coal.

MAURICE D. CURRAN.

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