US2026923A - Method of operating retorts to produce coke, gas, and oil - Google Patents

Description

Jan. 7, 1936.

A. W. WARNER METHOD OF OPERATING RETORTS TO PRODUCE COKE, GAS AND OIL Original Filed Oct. 27, 1951 l-leaflrg Zone Cool/n5 Zon Gaseous proalcxis of comusic'on d .Phsfa'c cone 1565 yases s 3 n /0 I] 457 dlZd/OI 6km flieam arwl aaes fiffeaml sji iun Go K 2 emu lNVENTOR BY mg &

ATTORNEYS Patented Jan. 7,

PATENT OFFICE METHOD OF OPERATING RETORTS TO PRODUCE "COKE, GAS, AND 01L Arthur Woodward Warner, Media, Pat, assignor to Isbell Porter Company, Newark, N. J a corporation of New York ded and this application February 2, 1933, Serial No. 654,891

3 Claims. (01. 292-15) This invention relates broadly to operating methods for coking retorts for the purpose of producing high grade coke, low temperature oils and fuel gas from coking coals. I

One of the important objects of this invention involves methods for producing and'controlling the plastic gas resistant barrier which forms in coking retorts-at the point of transition of the coal into coke.

A further object of this invention is the provision of methods for use in treatment of coking fuels in which an accurate control of the reaction is obtained for the continuous production of uniform coke, gas and oil.

Another object of this invention involves a method of maintaining a plastic barrier which forms when coal is coked so that the gases formed within the barrier may readily escape to the outside thereof.

A still further object of this invention is to form and control the size and position of the plastic barrier and maintain it vented in order to secure uniform products and uniform operation conditions.

Another object of this invention involves the control of the plastic barrier or film so as to keep the vapors formed on each side thereof separated until they are beyond the heating zone.

An additional object of this invention involves the formation of the plastic barrier in a column -of coking fuel, the venting thereof, and the removal of the gases formed or introduced within the barrier from near the top of the column so that the fuel is preheated before it reaches the coking zone. a

- A still further object of this invention involves the control of the plastic barrier by control of the throughput of both coal and'heating gases for the purpose of producing a high grade coke of relatively high volatile content while main-.

taining the production of gaseous products at a minimum. I

These and many other objects as will appear from the following disclosure are secured by means of this invention.

This invention resides substantially in the steps and series of steps as will be apparent from th following description:

This application is a division of my co pending application, Serial No. 571,332, filed, October 27, 1931.

Referring to the drawing the single featureis a vertical cross sectional view through the apparatus of this invention illustrated diagram; matically. a

The apparatus and method of this invention.

relate to and involve the heat treatment of solid carbonaceous fuels, such asjcoal, lignite, oil, shale and the like, and particularly coking coals for the purpose of producing therefrom high grade coke of uniform size, low temperature oils and gaseous fuels. The invention may be applied to continuous'internally heated retorts, regardless of the source of heat, whether generated within the charge or externally. In coking retorts of this type it has been found that at the-surface of transition of the coal into coke a plastic barrier or film forms which is more or less gas impervious. This film is composed of melted coal which is produced at a temperature of around 750 degrees F. The film or barrier is in a plastic state and normally has a thickness of approximately one-quarter of an inch. This barrier of melted coal exists between the uncoked coal and the formed coke.

It has been found that the formation of this film is the cause. of the difficulties normally encountered in the production of coke at either high or low temperatures in continuous internally heated retorts. Because the film is gas impervious, the gaseous products formed within it are not easily removed and as a result a back pressure is built up within the retort. Furthermore, the formation of this film has been found to be the cause of, thelack of uniformity in the operation of such retorts and the products produced thereby.-

' The prime object of this invention is to employ this very barrier or film for the purpose of producing uniform operation and uniform products.

In-both externally and internally heated continuous retorts the plastic barrier occurs in the form of an inverted cone with the apex pointing downwardly. By means of this invention the position of the cone is reversed and its apex is vented to permit the escape of the gaseous products formed within it. Venting of the plastic cone is effected by feeding a central core of coke into the retort in such a manner as to maintain the top of the cone open so that the gaseous products formed within it may pass freely through thegas pervious cokgcore.

In ordina'rflntemally heated continuous vertical retorts, especially when using fine sized coking coal, this plastic hollow, unvented cone tends to shift about in the retort varying both its size and pfiition under different operating conditions so that itis impossible to produce uniform products and uniform operating conditions. 23y means of this invention the position ofthe plastic cone is relatively, fixed and its size is controlled to aid in producing uniform products and operating conditions.

The retort which may be constructed in ac-- suitable discharge apparatus such as is shown in s the drawing comprising a caslng- 2 within which are mounted rotatable discharge gates 3. The. top of the retort is provided with a cover 4 which is shown as provided with a depending skirt 4 and upwardly extending feed hoppers 4 provided with covers I". It is likewise apparent that the form of'feeding mechanism employed may be of any of the well known types. The general characteristic of the feeding mechanism is merely that it shall be able to feed the coal continuously into the retortwithout substantially opening the retort to the atmosphere. There are many known types of continuous feed hoppers for such retorts. Extending centrally through the cover 4 is a tube 6 of any suitable cross section and provided with a cove 1. This tube is ver-, tically slidable through e cover. The top of the retort is provided with gas take-off connections 5 of which only one is shown.

Extending around the retort near the base of the heating zone, is a tuyere provided with\; a series of discharge connections 9 opening'directly into the retort. Just below the tuyre 8 is a second tuvere "likewise provided with space discharge connections ll opening into the retort. At It is a connection into the retort provided with a nozzle by means of which steam, or any suitable neutral gas, may be discharged into the retort.

As indicated in the drawing the retort may be divided into three zones. The lower zone is termed the "cooling zone" in which the coke and other residue is gradually cooled. In the next zone, called the heating zone, the fuel is heated either by the introduction of sensible heat through the tuyeres or by direct combustion to a temperature to liberate the gaseous productsthereof. The last zone is called the "pre-heating zone" and represents the volume where the fresh incoming fuel is heated by the gases ascending from the heating zone. In the pre-heating zone, for weakly coking coals, the higher boiling point volatiles may be made to condense on the relatively cold incoming fresh fuel. The heaviest condensation products flow back toward the heating zone where they are cracked down into simpler forms and revolatilized, thereby augmenting the deficient coke forming constituents of the coal.

The method of this invention and the apparatus disclosed operates continuously. In other words, fuel is continuously fed into the top and travels continuously downwardly through the retort and out at the bottom. As already stated, there are many known forms of feeding and discharging mechanism for eifecting such a continuous operation.

In the operation of this retort the heating zone may be maintained either by combustion or by the passage of highly heated gases therethroughl In the form of apparatus shown in the drawing hot producer gas or other suitable heated gases may be introduced into the retort by means of tuyre 8. Air and/or steam may be introduced in o the retort through the tuyere Ill where the combustion type of internally heated retort is employed to aid in complete combustion and to effect the control of temperature at the combustion zone.

' When a temperature of approximately 750 de- 5 grees F. is attained in the retort and by any method of heating, the plastic film forms which has been indicated diagrammatically at It in the form of a truncated cone. This film separates the uncoked coal from the formed coke at the center. The coke which is fed through pipe 6 forms a center core which maintains the top of the plastic cone l3 vented so thatthe gases formed within the cone may readily escape asindicated by the arrows. In this invention this cone is employed to keep the gases formed each side of the cone separated until they. reach a point where their temperature has fallen to a value where no harm results from their intermixturex. In other words, the low temperature volatiles formed outside of the plastic cone do not mix with the high temperature volatiles formed within the plastic zone until they get above the upper end of the cone at which time they may be \mixed without degradation of the low temperature oils. The center core of coke maintains the top of the plastic -cone vented permitting easy escape of the gases formed within the cone. The heated gases rising through the upper portion of -the retort through the pre'heating zone act to pre-heat'the fresh incoming coal in the preparation for coking before they are withdrawn through the connection 5. The incoming coal is normally pre-heated sufllciently to avoid all condensation of water and oil within the heating zone.

Previous attempts to improve the notoriously, inefilcient methods of producing coke have been directed more with a view to adapting the particular coals to a given retort rather than to 40 modifying the retort or the operation thereof to produce the proper conditions for efilcient production of high grade coke. It will be apparent that the present method is directed to an improved method of operating coking retorts to 4,5 adapt the method to the raw material to produce the desired operation and results.

In prior practice, one dimculty of operating coking retorts has resided in the fact that uniform operating conditions could not be maintained. As is well known in the operation of coking retorts, of either theinternally or the externally heated type, a plastic film formed which effectively sealed off the cross sectional area of the retort. This film is produced by the melting of the coal when it attains a temperature of the order of 750 degrees F. under which condition it is forming into coke. This film is highly resistant to gas flow and prevents the attainment of the proper through-put of heated gases necessary 6 to the production of high grade coke. This film continually breaks through and heals up, varying the resistance to flow of the heating gases and destroying the smooth operation. This film has taken the form of an inverted or dependent 66 plastic cone around which the heated gases ascended without proper diffusion through the fuel column.

This invention is carried on in a continuous internally heated retort in such away that what 70 was formerly a dependent cone now becomes an upright cone which is vented at the top and maintained vented so that the heating gases will flow against a substantially constant resistance,

namely, that formed by the fuel only. 76

' cone and the gaseous products are taken of! near or at the top of the column so that they must flow upwardly through the top of the column which is composed of fresh, incoming coal. The heated gases leaving the heating zone flow upwardly through-the coal and pre-heat it. This is a tremendously important feature of this invention, because it enables the production of high grade coke at a maximum rate.

By venting the top of the cone and by introducing the heating gases at the base of the heating zone, at the proper temperature and volume,

it is possible to pro-heat the coal to approximately 700 regress F. (near or at its melting temperature) before it reaches the heating zone. This requires that the heating gases enter the preheating zone at about 900 degrees F. and leave the retort at about 200 degrees F. with the fresh coal entering at about 60 degrees F., and with a proper volume of heating gases these results can be obtained. It is only by venting the top of the cone that it is now possible to increase the volume of the through-put to a value where these tem-' perature conditions can be uniformly attained and maintained. It requires a large volume of gas per ton of coal to produce these results which amount can only be put through the retort when the top of the cone is vented. This would be roughly 50,000 cubic feet of gas per ton, having an entering temperature of the order of 1120 degrees F.

With this invention about 80% of the heat of carbonization of the coal is supplied thereto in the pro-heating zone and before melting starts, leaving approximately 20% to be added to the fuel in the heating zone. The pre-heating zone acts similar to a reflux condenserfor all oils except the'pitch fraction which alone undergoes destructive distillation as it descends into the heating zone. The result is, that the coal is uniformly saturated which is a necessary condition for the production of uniform coke structure. Furthermore, this method of operation prevents swelling of the coal which is so disastrous to proper operation.

With this method, when dealing with weakly coking coals where stronger coke structure is required, the temperature of the heating gases would be raised and the volume per ton reduced, thereby reducing the amount of pro-heat. The result would be the return of the heavier pitch residues to the coking zone to augment the coke forming constituents in the coal. Thus the coke quality would be improved at the expense of the oil yield. This is illustrative of the fact that the retort controls are varied to suit the coal as distinguished from the present practice where the coals are blended or otherwise treated to suit the retort.

It is important to note that the key to uniform strong coke formation is the absence of re-vaporization at the coking zone which is made possible by pro-heat.

At this point it is interesting to note that a portion of the gaseous products after having the oils condensed therefrom and washed, maybe delivered back into the retort through the tu- The height of the eone\lii is determined by the coal throughput, the volume of the heated gases and the heat potential thereof; the lower the coal through-put, the shorter the cone; the greater the volume of the through-put heating 5 gases, the shorter the cone, and the ,lower the po-- 'tential of the heating gases, the shorter the cone.

through-put of the heating gases can be main- 1-5 tained either by increased heat potential and less volume. or by larger volume at less heat potential. The plastic zone terminates at the point where the temperature of the coking fuels falls below 750 degrees The tube 6 is made vertically adjustable so that the upper end of the cone l t has been maintained vented regardless of its vertical extent.

1 While coke is preferably fed through tube t because it does not contaminate the finished product, it is apparent that lumps of any non-melting substance could be used for this purpose such as rock and the like. The center core of coke is fed downwardly continuously with the fresh incoming fuel to maintain a gas pervious center core at ancitbeyond the point where the coal begins to me As the coke and other residue descends below the heating zone, it is cooled by discharging steam, or any neutral gas into it through pipe l2 and its attached nozzle. By cooling the coke in a zone below the heating zone, by the introduction of a gas, the gas is super-heated as it rises through the heating zones and mixes with the hot products produced in the heating zone to thereby t0 form a vehicle for suitably distributing heat in both the heating and pro-heating zones. The coked product is finally discharged after cooling from the retort through the discharge mechanism.

Another advantage of this method and apparat5 tus which causes the formation of the plastic cone as'shown is that the cone of coke within the plastic film is surrounded by a compacted cup of coal so that the coke is continuously sub- Jected to pressure. As aresult the coke cannot expand and deteriorate as in the case of previous apparatus where the cone is inverted so that the coke is in the form of an outside cup with a center core of coal. I In all continuous retorts the retorts are ta- 5 pered to facilitate easy discharge. This invention allows any taper desired without disturbing the coke during formation. The loose coal is continuously taking up the extra space made by the taper and does not allow the coke to swell; that is, does not make the coke too porous.

From the foregoing description it will be apparent that this invention resides in certain forms of apparatus and principles of operation which may be embodied by those skilled in the art in other ways without departure from the invention.

I do not, therefore, desire to be strictly limited to the disclosure as given for purpose of illustration but rather to the scope of the appended claims.

What I seek to secure by United States Letters Patent is:

1. A method of coking coal in a continuous internally heated retort comprising feeding coal into the retort to form a column thereof, ig-

niting the column at one end to form a combustion zone, forcing oxygen bearing gases into the combustion zone to maintain it and coke the coal, introducing coke into the central portion of the column above the combustion zone to form a core for the column, removing the gases generated in the column from the top, thereof,

said gases passing through coal column, and removing the residue from the bottom of the column, whereby an upstanding plastic film of conical shape of melted coal is formed and maintained vented at the apex of the coke core.

2. A method of coking coal in a continuous internally heated retort comprising feeding coking coal into the retort to form a column thereof, discharging coke into the retort to form a central core for the column of coal, introducing gases heated above the fusion temperature into the column to form a heating zone in the column, removing the gases generated in or introduced into the column from the top thereof and shielding the coke core to make it gas impervious to a point below the top of the column, whereby an upstanding plastic conical film of melted coal isformedvented attheapexby theookecorc and gases generated or introduced within the film flow upwardly throughthe vented 'top of the film and through the unshielded part of core into and upwardly through the column to the I point of gas removal from the column.

3. A method of destructively distilling coking coal in a continuous internally heated retort to control the compactness of the coke formed and uniformity of the oil yield comprising feeding lo coking coal into the retort to form a column thereof, maintaining a fusion zone at the base of the column with heated gases, feeding coke in a column into the coal column centrally thereof to form a gas pervious core therefor, removing the 15 gases from the retort at the top of the coal column, shielding the coke core to vary the length of the gas pervious portion and controlling the amount of heated gas and the amount of shielding of the coke core, whereby a maximum amount to of pre-heating of the coal column occurs before the coal reaches the fusion zone.

ARTHUR WOODWARD WARNER.

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