US2353752A - Preparing coal for conversion into metallurgical coke - Google Patents

Description

July 18, 1944. c. oT'ro 2,353,752

l -PREPARING COAL FOR CONVERSION INTO METALLURGEICAL COKE Filed aan. s. 1941 yAT'roRlxlEY I QQ BY s' s! M e i improved method of preparing low massa July is', 1944 PBEPABING COAL FOB CONVERSION INTO BIETALLUBGICAL KE cui om, mman-es, N. Y., mimimruel nslining Corporation, Dover, Del., a corporation of Delaware Application :um s, mnssrm No. 312,9 schim. (ci. 21H5) The present invention comprises improvementsin the preparation of coal for conversion into metallurgical coke. At the present time substantially al1 metallurgical coke produced in this country is formed by coking dry, unwashed, comminuted coal. in coking chambers or retorts into which the coal is charged while in-its dry condition, in which it has a moisture content of less than three per cent, and ordinarily'after it has been subjected to a crushing or breaking operation of such character that seventy to eighty per cent of the coal will pass through a. screen having openings three'millimeters square, and not more than about thirty to forty per cent of the coal will pass through a screen having openings lmethod of giving a substantial moisture content to comminuted coal to be coked,l said method being useful in preparing high volatile coal and low volatile coal for coking. Another and important object of the invention is to provide an volatile expanding coal for retort coking.

I have discovered that in producing metallurgical coke from low volatile coals known as expanding coals, it is advantageous to depart from the usual practice in preparing such coals for coking by increasing the flnen'ess of the coal and by suitably wetting the coal. When prepared f for coking in accordance with the present invention, a low volatile, expanding coal cokes with to prevent the distillation gases from sweeping an objectionable amount of coal dust out of the coking chamber, without giving rise to seriously n objectionable consequences.

tion of water to the coal in amounts -sufiicient to give the coal a, moisture content in excess o! about eleven per cent willincrease the carbonization heat per pound of coal required, and will create some risk of injurious contact with the hot coking chamber walls of water oozingout of the coal charged into the coking chamber.

A mass of finely sub-divided coal will hold a greater volume of water than a mass of coal less nely divided, and in practice it is diilicult to uniformly wet coal as finely divided as is the expanding coal prepared for oven charging in accordance with the present invention by directly adding to it the amount of water needed to give it a moisture content of from six to eleven per cent. In the preferred form of the present V invention, I wet and subdivide the coal by the "following procedure; namely, I screen the dry consequence of the wetness of the iinely divided coal, th'e'distillation gases formed in the coking operation do not carry obiectionably large amounts of coal dust out of the coking chamber and into the associated gas collecting apparatus, as they would do lii' dry, unwashed coal' were similarly sub-divided, but not wetted, before being charged into the coking chamber.

Inv my preferred method of preparing unwashed, expanding coal for conversion into metallurgical coke, I subject the coal to a crushing or breaking action effective to reducethe coal to such ilneness that about seventy per cent of the coal will pass through a screen having apertures two millimeters square, and wet the coal by thoroughly mixing with the coal enough water to give the coal a moisture content of not less of the coal may be made considerably greater than the minimum of about six per cent needed than about six per cent. 'I'he moisture content coal, after it has been subjected to a crushing or breaking operation effective to reduce the coal to such neness that something like half of the coal will pass through a screen having apertures two millimeters square, to separate the particles of coal too coarse to pass through said screen from the nner coal particles, and then add to all or a portion of the coarser particles of coal th`e amount of water needed to increase the moisture content of the total mass of coal to its desired value of not less than about six per centand usually not greater than about eleven per cent. After the coarser coal particles are thus wetted, I mix theml with the ijlner coal particles separated from the coarser particles in the screening operation. and further sub-divide the coal in the mixture by a grinding and crushing action which reduces4 the coal to the desired iinal degree of ilneness and which distributes the water carried into the mixture bythe coarser coal particles with suitable uniformity throughout the sub-divided coal mass. y

In adding the water to the coarser coal particles and then increasing the ilneness of the 'coal and distributing the added water throughout the coal mass by a crushing and grinding operation,

I take advantage of the fact that it is compara,

tively easy to eifect a suitably uniform distribution of the water through the final, ilnely subdivided mass of coal, by transferring moisture from the coarser, wetted 'particles to the dry, ilner particles in the course of said crushing and grinding operation, whereas it is diilicult to However, the addidirectlyaddasmallamoimtotwatertaand dlh'iblltii'hfhemunlfotmitymmuhlcui:camsornnelydiviser!esmlpurticles.

Ihavealsodiscoveredtbatinpreparingdmunwashed, high volatile, non-expanding coal ior conversion into metallurgical coke, it is practically desirable to add water to the coal in amounts sufilcient--to increase its moisture contentto from about six to nine per oent,.as this permits the time required for coking coll chllled into I kl0 ing chamber to be reduced without giving rise to the formation oi graphite deposits on the coking chamber walls. v

As those skilled in the art understand, a reduction in the time taken in coking coal of any particular composition and condition requires an increase in the temperature o! the cokingchamber heating walls, and in com high volatile, dry coal prepared for coking in the usual manne any increase in the heatingwalltemperature above/ its customary value tends to the deposit on the v l coking chamber walls of carbon in the -iorm of graphite cracked out of the distillation products evolved from the coal. The removal of such c graphite deposits is troublesome, and they not only interfere with the discharge of the nnlshed coke, but decrease the effective heat conductivity of the coklng chamber heating walls and thereby increase the carbonization heat per pound of coal required and prevent the reduction in the time required for coking a charge from being as great as it otherwise would be. I' The addition of water tothe dry. high volatile coal has the eiiect of reducingthe maximumdistillation gas temperatures and of increasing the amount of steam in the dis- 35,l

tillation gases and minimizes the said tendency of an increase in coking chamber wall tempera- -tures to result in graphite deposits on the .furnace chamber walls. Furthermore, an increase inthe moisture content oi! the coal up to or slightly above 40 nine per cent will not signiiicantly increase the carbonization heat required per pound of coal, since such an amount of water will be vaporlzed by v heat which is abstracted from the distillation gases, and which,` but for such vaporizing action and the resultant cooling eiiect on the distillation gases, would be carried out of thecoking chamber as sensible heat in the gases.

In mparing highvolatlle, non-expanding coal 'for coking in accordance with the present in- 50 vention, it is not necessary to sub-divide the coal more ilnely than has heretofore been customary and in some' cases it is practically possible to add the water needed to bring the moisture content oi such coal up to nine per cent or so without i'ol- 55 lowing the preferred procedure hereinbetore described of preparing low volatile, expanding coal for coking by adding water directly to coarser coal particles and then mixing said particles with i'lnercoal particles and crushing and grinding the mixso ture. Such preferred procedure may advantageously be employedfin manycases, however, in preparing high volatile. non-expanding coals for coking in accordance with the present invention,

The use oi the present invention has important 05 con a hun volatile, non

Y Por example, in coking such aooal chargein a coking chamber having an average width of seveniorcokinginaeccrdancewiththepreseatmven- 7s oven chambers in which it is formed, but also materially reduces the maximum stressesto which coking chamber walls are subjected by the charge during the coking and coke removing operations.

when is formed of low volatile. expanding coal prepared for coking in the usual In the one ilgure oi the accompanying drawing, I-have diagrammatically illustrated, by way of' example, one form of apparatus adapted for use in the practice of the present invention, though those skilled in the art will understand that the invention may be carried out by the use of apparatus of very diil'erent form.

In the drawing, A represents an initial coal breaker or. grinding machine which may be of any usual form adapted to sub-divide run-of-'themine coal into particles about half of which will. and about half of which willnot, pass through a screen having openings two or three millimeters square. The coal breaker A receives runofthe mine coal through an inlet chute A' and discharges broken coal through an outlet A. The latter leads to the inlet of a coal screening device B havingan outlet B' for the coarser coal particles which will not pass a screenhaving apertures two or three millimeters square, and having a separate outlet B1l for coal ilne enough to pass said screen. The coal discharged through the outlet B' passes into a coal wetting device C having an inlet C' through which wateris passed into admixture with the entering coal at a suitcreases the tineness of the coal and elects a suitably uniform mixture of the wetted coal received i'romthe outlet Cz of the coal moistener withv the finer coal received through the outlet B of the coal molstener device B. The device D may well be a hammer mill of usual form, or it may be any other usual or suitable coal disintegrator, adapted to effect the desired sub-division of the coal and distribution throughout the sub-divided coal of the water on the coal particles received from the coal wetting device C. To insure that the amount of coal passing through the coal mostener will not be too large-to beI properly wetted inthe moistener C. an adjustable diverter switch B may be provided to pass more or less oi' the coal received by the'outlet B' away from the device C and into the outlet B.

As is well known tothose skilled in the art. metallurgical coke needs to have a relatively strong structure-such as can be obtained by socalled -high temperature carbonization in which order .of 1800 1". or above. Such structural strength is not obtained by so-called low-tem- 'perature carbonisation of coal in which the maximum temperature of the coke or "char" produced is of the'order of 900-1000 I'. In preparing high volatile, non-expanding coal in accordance with the present invention for conversion into metallurgical coke I may in some cases advantageously increasethestructuralstrengthoi'thecoke formed by addingto the'coal onel per cent or so ot a suitable, inorganic. binder material,- such'as the said portion of the coal containing relatively y clay which may be mixed with the water added to the coal to give the latter the desired moisture content.

While in accordance with the provisions of the statutes, I have illustrated and `described the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention, as set forth in the appended claims and that in some cases certain features of my invention may be used to advantage without a corresponding use oi other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent,is:

l. The method of preparing dry. crushed coal for conversion into metallurgical coke by high temperature carbonization. which consists in separatinfg the coal into two portions. one of which ciently large to hold the amount oi water needed to increase the averagemcisture content of said coal portions to not less than about six per cent and not more than about eleven percent, and the second oi which portions contains relatively fine particles. adding said amount ot water to contains relatively coarse particles and is sufil-'4 coarse particles. and mixing the two coal portions and increasing the neness of the mixture by a crushing and grinding action.

2. Thev method specified in claim 1 in which the coal mixture subjected to the said crushing and grinding action is thereby reduced to such 'iineness that not less than about seventy per cent of the coal will pass through a screen having apertures two millimeters square.

3. The method of preparing dry, crushed, low

volatile, expanding coal'for conversion into metal-y lurgical rcoke byhigh temperature carbonization.

which consists in separating the coal into two por.. l

tions, one of which contains relatively coarse particles and is sulciently large to hold the amount4 and grinding action and thereby so increasing the iineness of the mixture, that about seventy per cent of the coal wii pass through a screen having twomillimeters square. i

CARL O'I'I'O.

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