US2268989A - Process for improving fuel - Google Patents

Description

l.. cj KARRICK PROCESS FOR IMPROVINGYFUEL Jan. 6,' 1942.

Filed April 17, 195e 4'burning in charcoal braziers.

Patented Jan. 6, 1942 UNITED STATES PATENT OFFICE raocass Fon IMPROVING FUEL Lewis o. Kwiek, sau Lake city, man Application Api-11 17,1936, serial No. '14,835

I (Cl. 2oz-15) n Claims.

aceous materials `so that the coal will yield a.

reactive easily ignited form of solid smokeless lump fuel which is very well suited to burning in all types of household heating and cooking.

equipment, and also is excellently adapted vto l The invention is especially adapted to the treatment of mixed sizes of coals which have been crushed to the sizes used in power plants, and thereby produce domestic fuel in the lump sizes that are found to be most popular in all domestic uses.

I have discovered a method for the treatment of dust-free graded sizes of coal, all being treated simultaneously in the same chamber or retort, while applying the thermochemical principles lignites. The tendencyy of the Utah coals to become weak lstructurally during this softening stage, and fall to pieces if not held together,

is a unique property which is made use of in this process. AI have found that the smaller` klumps of coal will become soft to the center within this range of temperature but the. largest lumps are not uniformly soft to the center for the reason that the change from the rigid coal stage into the rigid coke state is a gradual and progressive transition through the softened stage,

' and atno time, if the heating is rapid, is the that cause 'the formation of a series of sizes of -dense lumps of chemically reactive fuel, also coal loils that can be easily refined into high antiknock gasoline and other oil products, and fuel gases of both high and low heating value. At the same time I make use of thermal principles that produce economies in cost of heating while carrying out the treatments, so that the fuel cost is low. A new heat-exchange step is used in the treatment by which I have found it unnecessary to construct and maintain costly steam superheaters, and yet -I am able to use highlyheated superheated steam which enables this process to yield the afore-mentioned unusual products from coals. The process has been found to produce from Utah coals, or other partiallylcoking coals, large yields of low-heating value gases for industrial needs, and at the same time a less amount of gas with heating value as high as natural gas. Steam and electric power are produced simultaneously with the above treatment, by the heat cycles through which the combustion gases and'steam, used in the processing,

are routed. The apparatus required in this coal-` temperature thev same throughout the large lumps. Thus the large lump is always hard at its surface, part'way in, or at the-center, and

smallest lumps are therefore placed at the top t of the retort and nearest to the source of-heat. This treatment causes by my process all of the lumps of coal, regardless of size, to become quite dense and hard while still observing' the thermo? chemical conditions that produce reactive carbon with simultaneous evolution of high quality oil and gases. These points are more fully described in my U. S. Patent No. 2,011,054.

Since some of the above types of coals are more compressible than others,'or they may vary somewhat from the same coal seam,-it is found to be desirable to apply means: of controlling the pressure throughout the mass of coal undergoing treatment. 'Ihis is accomplished-by interposing within the coal mass an unyielding member or members which isunaiected by the comfluid passing between the lumps.

range of temperatures. These types of coals do not -fuse as do the ordinary coking coals, nor do they disintegrate like sub-bituminous coal or pressibility or compacting of thev coal mass. Sev` eral forms of apparatus for accomplishing this step are fully described in my copending application for U. S. Patent, Serial No. 701,838, now Patent No. 2,165,143, and one form is shown in the accompanying drawing which forms a part of this application for patent. l

I have found that it is very much better to treat the non-coking or partially-coklrlg typesl of coals' in large batches with a heat-carrying This makes possible the speeding up of the 'distilling time over that which. would be required if the coal were heated in ovens surrounded'with combustion ple manner, and important Y,economies are obtained. Y

In carrying out this process the coal such as is l normally deliveredto power plant or industrial plants, say dust to Z-inch, is screened into a continuous series of sizes with minimum steps between screens. The dust to say y-inchis sent to bunkers for' use as heating-fuel for the process, and the remaining dust-free lumps are charged into a tall shaft retort chamber with the smallest lumps at the top and the largest lumps at the bottom -of the charge. 'Ihe coal in the chamber,

consisting of a column of graduated lumps, is heated by passing hot gases downwardly through v the chamber between the lumps. The temperature of the gases is kept below 1150 F. while carrying on the low temperature 'carbonizatiom but if producer gas or water gas is desired from the rapid gas generation will follow.

I have found that substantially neutral combustion gases may be used Vfor the heat-carrying fluid provided their temperature is not excessively high. It is the top layer of coal only that would suffer by excessive gas temperature inasmuch as layers of coal lower down in the retort will receive their heat gradually as the rise in temperature of the superposed coal permits hotter and hotter gases to pass down through the charge. I provide means, however, for preventing overheating of the coal until after the oilforming. volatiles are removed, after which the combustion gases are increased in temperature in order that producer gas is formed from the top layers of small-sized lumps of coal.

I have also found that superheated steam is a very desirable heating medium for distilling the lumps of coal. I'his heat-carrying uid has the advantage of any of the other gases mentioned in that there is no diiuent gas mixed with thel rich coal gases, and thusgas as rich as natural gas (900'to 1100 B. t, u. per cubic foot) may-be obtained from treating Utah coals with this process. i In this invention I provide means for obtaining superheated steam without the necessity of installing superheaters which are rather costly to install and to maintain.

'I'his invention will be understood from the description in connection withthe accompanying drawing. Figure 1 is a side elevation partly in section and partly broken away showing an illustrative embodiment of the invention. Crushed coal is screenedA into a series of closely spaced sizes by a screening plant not shown, the dust to say %inch size being subsequently -fed into stoker hopper I from which it is burned' under the boilersof steam plant 2. The sized dustfree coal lumps yare deposited into bins provided for the different sizes, and from these bins the coal is deposited into retort 3 by means of chutes A or charging larries,-also not shown.

` process then the temperature is increased and.

assautsside of neck l is pipe connection and valve i Y through; which the gases' and vapors are drawn by exhauster i. 'Ihe top of retort chamber 3 is of steel plate covered with insulation, and passing down through the top is loading pipe 1 provided with gas-tight door I. This loading pipe extends about one third to one half the height of the retort. Within the 'top of the retort chamber is a built-in checker work of ilre brick I which illls the space down to the lower extremity ofthe loading pipe 1.l Leading out, of one side ofthe top of tire retort is conduit Il and gate ,I I', leading into the side of the lsteam plant stack I2. -A damper or gate Il is provided in the stack just above the connection with the conduit Il. Also, leading into the top of the retort chamber is steam line and valve I4. At the bottom of loading pipe I is hung the coal-supporting members I5 which may be large link chain with lateral extension members Il.

downward component of weight to a small portion of the actual weight of the coal column, also part of the weight of the coal is resolved into a horizontal stress, The supporting members I5 are placed'near enough together throughout the coal charge that their space is not more than three times the average diameter` of the contacting lumps of coal. This is a safe spacing but need not be adhered to, in fact some of our coals do not require more than occasional lateral suption gases.`

Exhauster fan i may also deliver the gases, oil

and water vapors into fractionating condensers,

Il and I9. Condenser Il is maintained at a temperature vabove the condensing temperature ofthe water vapor. I have found that this procedure permits condensation of the oils that are heavier than water in condenser I l, and thereafter the balance of the oils and all of the water is condensed in condenser Il, thus permitting the oil and water to be separated by decantation.

A number, at least two, retorts may advantageously be operated simultaneously from the same heat'sources, originating with the combustion gases of the steam plant and from the steam generated therein. To do this another connection is made to stack I2, like conduit Il, and leading into the top of another retort. Also, the same condensing and cooling system will serve both units, the exhauster i being connectedv through manifold 2l to the diiferent retort outlets l.

When the coal is charged into the retort as described above, gate II is opened, damper Il is closed, gates-l and 4 are closed, then exhauster l is started.. The hot products of combustion from stack I2' are drawn into the retort and down through the coal charge v ia the checkerwork 9. As soon as the checkerwork reaches about '100 F. at its bottom the top layer of coal will begin to distil, and as the heating continues and the top temperature rises the heating zone moves downwardly throughthe coal while the These extension4 members are so spaced that the lumps of coal which arch against these members limit the the lower layers of coal. I have found that when the coal has been distilled 'of its oil-yielding volatiles down to about the middle of the retort, the combustion `gases from the steam plant may be shut oif and diverted into another retort. Thereupon the steam valve I4 isopened, gate Il having been closed, and the incoming steam passes through the highly heated checkerwork wherecoal takes place. After the drying of the coal a4 larger flow of the combustion gases may be use d to effect the distillation of the coal part way down the retort height, During this stage of the treatment I have found that it is desirable to use a small amount of excess air in order that some combustion of the top layers of semi-coke takes place, thereby heating the reacting carbon and carbon dioxide to a. point at which the producer reaction takes place; this causes, thereby, the generation of producer gas instead of permitting the coal gases to Ibe diluted with incombustible combustion gases. It should be noted that the producer gas is formed from the relatively low `value semi-coke in the smallest pieces. When the top half, or thereabouts, is distilled by the heat of the stack gases, the superheated steam complet/es the distillation to the bottom of the charge. During this last stage the gases formed from the coal are free of any diluents of any kind and, from Utah coals,"will have a fuel value of 1,000 B. t. u. per cubic foot or higher. The gases from the two stages of heating, that with the stack gases and that with thesuperheated steam, are of very different heating value and have their advantageous fields of uses. 'I'herehot gases are continuously serving to preheat v fore they should be stored in separate gas holders.

It should be noted further that during the last stage of distilling, with the superheated steam, that cooling or dry-quenching has been progressing as the top heat of the charge is being transferred into the bottom of thev retort. Consequently when the charge is completely distilled the steam should be permitted to flow into the top o`f the retort until theentire body of semicoke is cooled to 400 F. or less as at this temperature this reactive semi-coke will not take fire. Preferably, the steam used-in the treatment is steam coming from an engine or other power generator, that is, bled steam that has already provided Work energy.

I claim:

l. The process of preparing an improved fuel` from Utah type coal comprising forming a column of lumps of said coal within a vertical retort, passinghot gases of combustion downwardly through said column to partially carbonize said lumps, discontinuing the ilow of said hot gases of combustion and passing steam heated to a temperature below that of the said hot ga'ses of combustion downwardly through said column to complete the carbonization of said lumps;

2. The process of preparing` an improved fuel from Utah type coal comprising forming a column of lumps of said coal within a vertical retort, p hot gases of lcombustion through a heat accumulator'andl thereafter said gases downwardly through said kcolumn to partiallycarbonize said lumps, discontinuing the iiow or said gases and passing steam heated to a temperature below that of the said gases through said heat accumulator and thereafter passing said steam downwardly through said column to completethev carbonization of said 3. The process of preparing an improved fuel from Utah type coal comprising forming'a column of lumps of said coal within a vertical retort. passing hot gases of combustion through a heat accumulator and thereafter passing said gases downwardly through said column to partially carbonize said lumps, discontinuing ther flow of said gases and passing steam heated to a temperature below that of the said gases through said heat accumulator and thereafter passing said steam downwardly through said column to complete the carbonization of said lumps, said heat accumulator being brick checkerwork, whereby said heat accumulator is heated lto a high temperature by said hot gases of combustion and said steam is superheated during passage through said heat accumulator.

4. The process of preparing an improved'fuel from-Utah type coal comprising forming a column oflumps of said coal within a vertical retort, said lumps being of graduated size within the column with lumps of progressively smaller size being positioned at progressively higher points within said retort, passing hot gases 'of combustion downwardly through said column to partially carbonize said lumps, discontinuing the -ow ofsaid hot gases of combustion and passing steam heated t'o a temperature below that of the said hot gases of combustion downwardly through said column to complete the carbonization of said lumps.

5. The process of preparing an improved fuel from Utah type coal comprising forming a column of lumps of said coal within a vertical retort, said lumps being of graduated size within the column with lumps of progressively smaller size being positioned at progressively higher points within said retort, passinghot gases of combustion through a heat accumulator and thereafterA passing said gases downwardly through said column to partially carbonize said lumps, discontinuing the ilow of said gases and passing steam heated to a temperature below that of the said gases through said heat accumulatorA and thereafter passing said 'steam downwardly through sai'd column to complete the carbonizav tion of said 1umps. v

6. The process of preparing an improved fuel Vfrom Utah type coal comprising forming a column of lumps of said coal within a vertical retort, said lumps being of graduated size Within the column with lumps of progressively smaller size being positioned at progressively higher points within said retort, passing hot gases of combustion through a, heat accumulator` and thereafterpassing said gases downwardly through said column to partially carbonize said lumps,

discontinuing the flow of said gases and passing steam heated to a temperature below that of the 'I said gases throughsaid heat accumulator and thereafter passing said steam downwardly through said column to complete the carboniza tion of said lumps, said heat accumulator being brick checkerworlr, whereby said heat accumugases of combustion and said steam 'is superheat- 'ed during passage through said heat accumulator.

7. The process of preparing an improved fuel 4from Utah type coal comprising forming a body end of said body and being progressively larger` at points therein farther from said end, introducing hot gases of combustion into said end' and 1am is heated to a high temperature by said not l passing said gases through said body to partially carbonize said lumps, discontinuingthe flow of said gases and introducing steam heated to a temperature below that of said gases into saidend and passing said steam through said body to complete the carbonization of the lumps.

y 8. The process of preparing an improved fuel tinuing the ow of said gases, passing steam' heated to a temperature below that of said gases through said heataccumulator, thereafter introducing said steam into saidend and passing said steam through said body to complete the carbonization of said lumps.

9. The process of preparing an improved fuel from Utah type coal comprising forming a body of lumps of said coal in graduated sizes within a retort, the size of the lumps being smallest at one end of said body and being progressively larger at points therein farther from said end, passing hoty gases of combustion through a heat accumulator, thereafter introducing said gases into said end and passing said gases through said body to partially carbonize said lumps, discontinuing the ow of said gases, passing steam heated to' a temperature below that of said gases through said heat accumulator; thereafter introducing said steam into said end and 4passing said steam through said body to complete the carbonization of said lumps, said heat accumulator being brick checkerwork, whereby said heat accumulator is heated to a high temperature by said hot gases of combustion and said steam is superheated during passage through said heat accumulator.

10. The process of forming improvediuell products by carbonizing. graded sizes of Utah type coal, which comprises separating said coal into a series of sizes, with the dust removed, and the coal introduced into a vertical retort, with the largest lumps at the bottom, supporting said coal throughout its height and reducing its downward and internal pressure, passing hot combustion gases downwardly through the layers of coal in such a manner that said gases contactsfirst the small lumps of coal and last the largest lumps to remove part of the volatile materials, disoontinu- 1 ing the hot combustion gases and introducing steam into said retort from the top end thereof, passing said steam down through the coal to com'- plete the distillation thereof with the contained heat of the partly distilled coal.

LEWIS C. KARRICK.

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