US1783982A - Processing of coal and product thereof - Google Patents

Description

Der; 9, 1930.

`W. RUNGE ET AL l PROCESSING OF GOAL` ND PRODUCT THEREOF 1925 2 sheets-sheet '1 y Dec. 9,1930. RL'JNGEHETAL I 1,783,982

lPROCESSING 0F COAL ND PRODUCT THEREOF FiledJune 12, 1925 2 Sheets-Sheet 2 refait-sainte, 9, 1930 'UNITED STATES PATENT OFFICE WALTER. RUNGE, oF EAST ORANGE, NEW JERSEY, AND EDWIN A. PACKARD, E.-

. YONKERS, NEW YoEx, ASsrGNoES, BY MESNE ASSIGNMENTS, To INTERNATONAL.

V COAL CARBONIZATION COMPANY, A CORPORATION DELAWARE PROCESSING 0F COAL AND PRODUCT ATHEREOIE Ap'piication mealx'une i2, 1925. serial No. 36,590;

KThe invention relates to the processing of coal. It is particularly directed to the converting of coal into a form whereby it 1s readily attacked by oxygen thus facilitating 5 rapid and high temperature combustion.

. residue.

One advantage of the invention is that it` facilitates and furthers theemployment of a relatively small combust-ion chamber although the invention is no t limited to the use of the fuel in a'relatively small combustion chamber since the fuel is advantageously employed in'V any; present day furnace construction having suitable instrumentalities for feeding fuel thereto and for bringing the combustion supporting air to the fuel in any suitable manner. u

According to one aspect of the invention inely'divided coal is heat pretreated under conditions to drive olf only a small portion of4 its hydrocarbon volatile contents-leaving substantially all of the hydrocarbon volatile contents in the pretreated residue--and under conditions to lslightly increase the size ofthe coal particles. Thereafter' the pretreated residues are subjected to low temperature carbonizationunder conditions to convert many of the coal particles into relativelyhollow spheroids many ofwhich have what appears to beone or more Windows-visible under the microscope. The product or semlcoke thus obtained is thereafter crushedor further pulverized-so as to break up the cell-like structures or,spheroids in order to materially increase the surface area. of the Thereafter the treated residue is burned in anysuitable manner, preferably by burningthe crushed residue in suspenslon in any suitably constructed pnlverlzed burning fuel furnace, for example, a boiler fur-l nace.

The invention has various aspects as hereafter will be apparent from that which follows, andaccording to the broader aspects of the invention the pretreating prior 'to low temperature carbonization need not be elnployed.

Tir-order that the invention as to its fundamentals may be readily understood, a speciic mode of its realization will now be described, thisin reference to the accompanying drawings which constitute a part of this specification and in which drawings-'- f Figure 1 diagrammatically illustratesl a plant comprising an arrangement of coal processing apparatus-in association with a boiler furnace wherein there is burned the crushed ysemi-coke or pulverized product which is produced in accordance with the invention. i i A Figure 2 is a reproduction .of a micro-photograph of a particleof raw pulverizedcoal under a magnification of approximately v155 diameters and shows the angular nature of the particles or minute fragment of coal. In other words, 'itv will be noted that the coal fragment is delineated sharp lines and sharp edges.

Figure 3 vis a reproductionv of a microphoto-graph showing the appearance of a minute fragment of coal after heat pretreatment in a gaseous medium at approximately 650 degrees F. This reproduction of the micro-photo-graph was made under ay magnication of 155 diameters. be noted that the edges of the yfragment have become rounded due presumably to fusion and the fragment is solid and opaque. The general shape is spherical. This is illustrative of the appearance of the minute fragments of coal'after a hot gas pretreatment atv the approximatel temperature just specified.

Figure 4 is a reproduction of a microphoto-graph illustrative of a relatively hollow spheroid having a shell-like structure with Windows in the shell-like structure.

in many `respects by Here it will -l This is a particle of the product after the i uct illustrated in Figure 4. The crushed semi-coke of which the fragments of this figure are illustrative, is sometimes referred to asthe crushed semi-coke of the process or as the pulverized product becauseit has been subjected tothe crushing or pulverizing action of a mill subsequent toits production by the low temperature carbonization outlined.

Figures 2 to 5 inclusive illustrate step by step the processing of the coal in the instrumentalities` associatingly arranged according to Figure 1 prior tothe burning of liberate burning the crushed product (illustrated in Figure 5) in the boiler furnace indicated in Figure 1. There has been incorporated in the patent file as originally presented in the United States Patent Office, a set of microphoto-graphs duly labeled and which illustrates in refined detail actualfstructures realized from the performing of the invention prior to liling anappllcation for` patent in the United States Patent Oliice.

Figure 5 is merely illustrative" as to the 'shape and definition of the articles which may be obtained .'by the crus ing operation. The partsin Figure 5 have not been taken from actual specimens or in other words are not reproductions of micro-photo-graphs of specimens.` The pieces of Figure 5 are intendedl to illustrate how these small coke particles might be broken down by crushing in order to form greater air attacking s'urfaces than would be the case if the 'particles from which they were made were not crushed, all of this having in mind'the'artv of combustion when these broken up particles-are subjected to urning.v The pieces of Figure 5 are manife ly at a much enlarged scale.

The invention in this c se primarily revolves about the deliberate processing of finely divided coal so as to produce semicoke in finely divided form, the deliberate breaking up of this small coke into much smaller particles or fragments and the deof these small particles so as to take advantage of the results of the series of steps previously defined. i

l Referring now to the drawings in detail `1 indicates a pulverizing mill wherein the coal to be processed is initially pulverized .to the desired degree of tineness for example to a neness such that approximately will pass through a 200 mesh screen (a screen defined byfwires crossing at right angles to each other so as to form forty thousand openings per square inch) -and so that substantially all ,of the pulverized` coal will pass through a 40 mesh screenl- The pulverized coal is pneumatically conveyed to-a cyclone separator'2 where 1t is collected and from which it is conveyed to areceiving hopper 3 from which it is fed by a suitable means 4 into the top of la pretreating retort 5. Within this pretreating retort the pulverized coal in cloud-like formation moves VVdownwardly with delayed gravitation into and. counter to slowly rising hot pretreating gases'which 'are introduced in the lower regions of the retort as at 6. These pretreating gases are preferably, although not necessarily, heated air. When air isthus employed it constitutes a'hot oxidizing medium by which /the oxygen' content of the coal undergoing pretreatment is slightly increased. The pretreated pulverized coal ulti- `mately settles at the'bottom of the pretreatdefinition, the length of time the coal is treated in the different steps, and the apparatus,

therefor is described in detail in Patent No. 1,669,023, granted May 8, 1928, to Walter Runge, one of the applicants' herein. On page 3 of this Patent No. 1,669,023 is disclosed an example of the pretreating process, wherein the hot oxidizing gas, or air, is admitted to the retort at a temperature of approximately 800 degrees F. and leaves the upper portion of the retort at approximately 500 degrees F., thecoal being subjected to the4 action of the hot air for approximately thirty seconds, during which time all of the moisture and only a small portion of the hydrocarbon volatile content of the coal is removed. The tine. coal particles arev also slightly enlarged vin size. It will be understood, of course, that the above process will be modified to secure the desired results, depending on the character of the coal treated, length of ,the

retort,'etc. v

On page 4 of this Patent No. 1,669,023 is disclosed an `example of the method-.of carbonizing the pretreated coal, wherein it is stated that the process are su stantially chemically inert with respect tothe Vcoal undergoing carbonization.

-Thelhot gases for effecting the carbonization within the carbonizing retort 10 are vsupplied at the bottom thereof as at 11 and the temperatures of .these rising hot gases average approximately 1000 degrees F. The settling orgravitating of the coal undergoing the carbonlzing operation issuiiciently ldegases used in the carbonizingv layed by theupwardly moving hot gases to effect the desired degree of carbonization. or in other words, a s'ucient length of time to substantially reduce the hydrocarbon vola- -tile content of the coal and also a sufcient length of time toreduce the oxy en content of the coal below that which t e original coal possessed. 'i

It will be manifest that in the plant for realizing the invention suitable pipings and y other instrumentalities should be employed trated by Figures 2 to 5 inclusive. All the coal undergoing treatment is in relatively finely divided form being in the form of vminute fragments or particles and a typiying illustration of a fragment of raw pulverized coal is seen in Figure 2: Here it will be noted that the prominent.characteristics are thesharp lines and edges. f

When the fpulverized coal undergoes the hot pretreatment to wit underconditions such that `the averagetemperatures of the pretreating gases approximate' 650 degreesA F. it losesthese sharp edges vand they are replaced by relatively smooth rounded surfaces. Where the pretreating gases are hot oxidizing gases then the pretreated particles 'of'pulverized coal take on, as determined by chemical analysis, another characteristic in g1' that they have been oxidized by thel hot pretreating air so that for example, pulverized I coal having an initial oxygen content of71/% may after the pretreatment, have an oxygen content of 81/2%. The coal which has been thus pretreated and er having been subjected to the above men ioned low temperature carbonization, for e mple at temperatures averaging approxim tely 1000 degrees. F., and according to the process herein described becomes further changed as to its physical and structural characteristics as isclearly illustrated in Figure 4;

. A study of the product resulting from the' low temperature carbonization shows that it is semi-coke compound mainly of spheroids, as shown in Figurefl, most of which are relatively hollow and many of which have the appearance of windows in the surface thereof, which windows are not ap arent to the naked eye but with the aid o transmitted light are visible under the microscope.

It may not be desirablein all instances to subject the pulverized coal toa heat pretreatment prior to the carboniz'ation. Here again the product which has been produced ac cording to one aspect of the process is a semi-coke composed in main of spheroids which are relatively hollow and manylof which have windows. With theA direct low temperature carbonization however, the particles are, as a generalrule, slightly larger than in the instance where the particles are vproduced by the pretreatment which is followed by the low temperature carbonization. This is best discernible by-comparative, screen analysis of the raw pulverizedcoal, the product realized by the direct carbonization, and the product 'derivable by the dual process to wit the pretreating process which is followed by the 10W temperature carbonization. According to the process of this application one can take c oal having a hydrocarbon volatile content of, for example 34%, and an oxygen contentl of; approximately 7 to 10% and readily obtain therefrom the desired resulting semi-coke product. When a pretreatment is employed (although accord- Y ing to the broader aspects of the invention the pretreating or preheating is not necessarily employed) the steps of a specific aspect of the invention would include the following:l pulverizing the raw coal to a ineness such that approximately 55% to 65% .of the coal will pass through a 200 mesh screen and so that substantially all of the pulverized coal will pass through a 40 mesh screen, thereafter pretreating the pulverized coal by suspend-l ing the coal in the form of dust clouds in a current of slowly upwardly moving hot gases, preferably .but not necessarily hot oxidizing gases, at temperatures averaging approximately 650 degrees F. or even less, to 700 deees F., under conditions to dry the coal, to' slightly` reduce the hydrocarbon volatile content, to slightly lessen thedensity, to slightly increase .the oxygen content, to eliminate thesharp edges of the coal -fragments, and in general to round ofi' the outer surface of the coal fragments. This pretreatment is `followed by the separating of the treated particles from :the treating gases and lthe showeringv of the pretreated coal in the` form of dust clouds into and counter to a current of slowly upwardly moving hot carbonizing gases at temperatures averaging approximately 1000 degrees F., soasto produce a semi-coke product with less, slightly less,"

oxygen than in the original coal.' The semicoke thus produced by the direct action of hot carbonizing gases consists largely'ofparticles in the form of relatively hollow spheroids of high porosity and low density relative to that of the original coal. Many of the spheroids have a shell-like delining structure with -windows inthe surface thereof. The-'spheroids are of such size that 5% to 20% of the semi-coke will pass through a 200 mesh screen and such thatV practically all will pass a 10 mesh screen. The semi-cokethus produced is in fact 'a low temperature coke and may have a hydrocarbon volatile content of approximately 8% to 12%. f

A semi-coke produced by the direct carbonizing of raw pulverized coal in a current of slowly rising hot gases in the manner specified will possess substantially the same gene-ral characteristics as the semi-coke just described but in the instance of the direct production of the semi-cokewithout the pretreatment the spheroids would in general be somewhat larger than-:Mould be the Lcase if the pretreatment Werenot employed. The semi-coke resulting :from the two stage process, that is-the process-employing the pretreating as well as the carbonizing and the same is true' of the semi-coke of the4 single stage process, particularly if the carbonizing treatment is carried out in uniform and proper manner, will contain therein not' only the spheroids just described but also spheroids under conditions such that the oxygen of the air can readily'combine with the pulverized product as the Acombustion progresses. crushed cokeL or pulverized product such as obtained by the process herein outlined-has a relatively large number of projecting surfaces being more or less porous and of the' character to be readily attacked by the oxygen of the air thus facilitating rapid combustion and in fact relatively high temperature combustion within a localized zone if such is desired. This crushed product has al naturally increased surface area as compared with the semi-coke before crushing, moreover the crushing is such as to reduce the semicoke into fragments of a ineness such that approximately 60% will pass a- 200 mesh screen. f t

Applicants believe they are the rst to produce a pulverized or crushed semi-coke product herein described and that they are also the first to appreciate the advantage of producing such a product and burning the same ina furnace.

What is claimed is: f

1. The method of preparing coal for use in a pulverized fuel burning furnace comprising pulverizing coal, subjecting vthe pulverized coal to a' preliminary heat treatment in an'oxidizing atmosphere under conditions to drive off only a small percentage of the hydrocarbon volatile content but under conditions such that the treated coal particles lose the sharp edges and are by the preliminary heat treatment transformed from solids having sharp edges to solids having relatively smooth and rounded outer surfaces and by said preliminary heat treatment are also slightly increased in size, thereafter subject- A ing the treated pulverized 'coal to carbonization by suspending it in a gaseous medium substantially chemically inert with respect to the coaland in a carbonizing zone wherein ,the heat is suilicient to effect a low temperature carbonization and thereby driving 'olf a substantial portion of the hydrocarbon volatile-content of the coal and under conditions to produce semi-coke comprising in the main particles in the form of hollow spheroids, withdrawing `the semi-coke and then crushing it. 1

2. A method of preparing coal for use in a pulverized fuel burning furnace comprising subjecting pulverized coal to the heat treating action of hot oxidizing gases at temperatures averaging approximately 650 degrees F. so as to round 'thesurfaces of the coal particles andunder conditions to only slightly reduce its hydrocarbon volatile content and to slightly lessen its density, separating the treated coal from the treating gases, subjecting the separated treated coal to carbonization at temperatures averaging approximately 1000 degrees F. while suspended 'in hot gases substantially-chemically inert with respect to the coal so as to produce semicoke, separating the semi-coke thus produced from the carbonizing gasesand crushing the separated semi-coke.

3. A method of preparing coal foruse in a pulverized fuel burning furnace comprising pulveri'zing the coal, preliminarily subjecting the pulverized coal to the action of hotv oxidizingatmospheres at temperatures aver-- aging approximately 650 degrees F. so as to slightly increase the oxygencontent,`and under conditionstoslightly reduce its hydrocarbon volatile content, separating the oxidized coal from the oxidizing atmosphere,

beingsuch as to produce a semi-coke conf sisting largely of particles -in the form of relatively hollow spheroids with a shell-like defining structure and o f sizes such that practically all of the spheroids will pass a l0 mesh screen, separating the semi-coke thus produced from the treating gases and thereafter crushing the semi-coke.

4. A method of preparing coal for use in a, pulverized fuel burning furnace comprising pulverizing coal, pretreating the pulverized coal by subjecting it to a hot oxidizing l, atmosphere, but without substantially reducing its hydrocarbon volatile content, se a- 'rating the lpretreated cdal from the oxi -zing atmosphere, thereafter subjecting the pretreated coal tolow temperature carbonizationein a hot gaseous medium which is substantially chemically inert with respect to the coal within which the coal is suspended incassa and by whichlthe'coal is-directlyheatedidurl ing the carbonization -so as' to produce a semi-coke having an oxygen content less than -the oxygen 'content of the original' coal and with a substantially less hydrocarbon volatile content than that of the original coal, separating the semi-coke thus produced from the carbonizing gases and thereafter crushing the semi-coke.'

r 5. A finely divided coke product obtained by showering pulverized coal in a dust-like formation into a vertical retort the average temperatures of which approximate 650 degreesF. bypsubjectingthe coal thus showered to the pretreating action of a slowly and upwardly moving current of hot gases, by

separating the coa-1 thus pretreated, by sub-v jecting it to carbonization by showering it in a dust-like formation down a'vertical carbonizing retort wherein it is subjected to the carbonizing action of a slowly and upwardly movin current of gases which are substanr tially c emcally inert with respect to the coal the temperatures of which ases average approximately 1 000- degrees he carbonization being such as to produce semi-coke con-l sisting mostlyo-I` substantially hollow spheroids with shell-like defining-structures and the size of which is such that practically al1 of the semi-coke will pass a 10 mesh screen by separating; the semi-coke thus produced from the treating and resulting gases, by collecting the semi-coke as the solid residual of the process, and by crushing the semi-coke to a fineness such thatapproximately will pass a t 200 mesh screen.

In testimony whereof, we have hereunto signedl our names y l WALTER RUNGE. EDWIN A. PACKARD.

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