US1678379A - Coal briquette and process of making it - Google Patents

Description

Patented .luly 24.1, 1m28.

U ll 'll if] u all GEORGE ALBERT CHAPMAN, F FOREST HILLS, AND EETOFT WRAY WILKINSON, OF QUEENS VILLAGE, NEWl YORK, ASSIGNORS TO MINERALS SEPARATION NORTH AMERICAN CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF MARYLAND..

COAL BRIQUETTE AND PROCESS 0E MAKING: IT.

"No Drawing.

This'invention relates to coal.' briquettes and processesof making them, and is herein illustrated in part as applied to the production of briquettes from high ash coal and vfrom coal ashes such as are found on city dumps.

Inthe briquetting methods hither-to used it has usually been `deemed necessary to dry the coal in rotary driers until it contained less than 1% of moisture. It has also been deemed necessary to limit the crushingof the coal to a minimum amount because it has been deemed necessary to keepth'e total sur face of the coal particles as small as possible, thus reducing the amount of binder required to coat the surface of the particles Coarse crushing has resulted in retaining in l the coarse particles much of the ash which would be mechanically freed by fine crushing and could then be separated by suitable methods of coal concentration. Such processes therefore cannot commercially `convert the high-ash waste of coal mines into valuable fuels in competition with the good coal generally marketed. Usually the hot, dry, coarse-crushed coal as it comes from the drier has been mixed with hot oil or tar or asphaltic binder in a mixer which had to be kept hot. The mixed hot material. has usually been cooled slightly, pressed 1n a briquettc press and then baked in an oven to set? the binder and drive olf some of the volatiles from the binder.

The briquettes thus produced from American coals have usually proved unsatisfactory for the, American market. Those containing upwards of t'en per cent of oil or asphalt usually have been quite smoky, while those containing smaller amounts of binder have been objectionable because the binder has failed to mix uniformly With the coal, some coal particles having too much binder and others having too little or none at all, resulting in a dusty b1iquette,-tliat isone which goes largely into dust when it breaks, becaust the uncoated particles or insul'lieiently coated particles have no tendency to stick together. As a result the briquette loses its integrity in burning and the particles which are practically unbound fall apart as dust. Iudomestic fires this dust falls through the grates, passing into the ash as unburned carbon, With the result that the ashes left bv` burning the briquettes hitherto made Application 1aed March 1? ,1926. serial no. 95,45el'. l

in dusty briquettes which as above noted are wasteful and unsatisfactory.

According to the present invention these and others objections are overcome. Moreover it is found possible to crush the coal hne and yet use a relatively small amount of binder. ,The process therefore is Well adapted to produce valuable fuel fromhigh ash Waste coal which can be crushed fand' concentrated as well as fine `Wastecoalyboth of which are now generally rcgardedas useless, and which gencrallyrhave not been capable of* p rolitable utilization in commercial briquettmg processes with lAmerican coals for lthe American market. The coal is usual ly crushed to liner than ten-mesh and frequently even to less than thirty-five mesh. depending on the quality and ash content of the coal. This fine crushing frees many par ticles of coal from included or adhering ash, and thus facilitates the separation ot' the pure coal from the ash by the froth-tlota tion process. l/V'here the coal is concentrated by froth-flotation there is usually employed in this process a soluble. mineral-frothing agent, such as. cresylic acid, and also an oil, Which for example, may be a tar oil or coke oven tar or topped petroleum.

The crushed coal With the flotation agents is agitated in sufficient water to make a freely flowing pulp with the result that the coal floats. If little oil has been used the separate coal particles are carried in bubbles which float in the form of a froth., If larger amounts of oil have been used the coal will become agglomerated and the agglomerates may be floated or may be sunk.

Usually it has been found preferable to concentrate theV coal by frotli-iotation, `thus enabling the purified coal to be separated from the bulk of the pulp by removing the floating coal, thus easily and economically separating -the coal from the bulk of the Water of the pulp and from the ash which remains behind in the pulp Water. It may be advantageous to concentrate the coal by added in the aie Well agglomerated by an 'agglomerates of f. t0 Vthereafter reduce froth-flotation With a little oil and then add more oil to agglomerate the coal. 'lhis may reduce the Water associated with the coal from say 200% to say 35%.

A large proportion of the oil necessary for binding purposes in the production of briquettes is often thus disseminated by agitation in the presence of Water, thus effecting a uniform distribution of it on the surface of the coal particles. Usually this extra oil has the advantage of facilitating the draining of the Water away from the coal to be briquetted. The oil in some cases may be form of emulsion, especially with heavy oils, or tars which play the part of oils, and the emulsion may be made with laundry soap or other emulsifying agent before adding it to the pulp.

lt has been found advantageous to add to the aqueous pulp, in general, not more than about 2% or 5% of oil measured on the Weight of the coal. The rest of the oily or other binding agent is usually mixed later with the dried or partly dried pulp, as in a paddle or dough mixer. It is preferable that air or gas be present in th pulp when adding the binder to the pulp or causing the binder to'coat the coal particles in the pulp.

One great advantage of adding a substantial part of the binder in the pulp so that the coal is coated with it by agitation in Water, is that all of the particles of coal seem to be almost uniformly coated With the binder and thus, in the presence of sufficient binder, are certain to adhere or stick to each other and produce a practically .dustless briquette. Moreover if the coal particles oily material such as oil, tar or pitch, the coal'particles and the agglomerates become Water-repellent and Water runs away from the coated coal and from the agglomerates, and is practically free of coal. i

Owing to the fact that the agglomerates are Water-repellent they may be drained by leaving them in heaps, although it is usually preferable .te drain them by special draining appliances such for example as a cocoa matting in the form of a continuous belt. Frequently the best results are obtained When the agglomerates are drained by means of a continuous suction or centrifugal filter. Sometimes it is possible to obtain the coal in the form of hard shotlike granules, especially when the agitation is accompanied by a minimum of aeration. Such shotlike granules may be freed from Water by centrifuging. The drying operation usually reduces the moisture contained to somewhere between 15% and 25%. It is not found necessary to dry the agglomerates to the extent that has hitherto been deemed necessary in drying the materials for briquetting, but it is usually advantageous the contained moisture,

either by heat or by pressure, to'between 5% and 10%. The moisture may be expelled by pressing these agglomerates in a mold which is provided With narrow drainage openings or slots, since the agglomerates usually do not flow through such openings under pressures running up to two tons or more per square inch. The continuous lscrevv press as of the type used for pressing oil from seeds may be used where large capacity is not required. l

To produce astrong briquette from the agglomerates containing from one to five or sometimes more per cent of oily material, the oil-coated coal particle or agglomei'ates are preferably mixed with a further quantity of binder, which `may be melted or crushed pitch, or Mexican fuel oil7 or any one of a large number of oily materials, or sulphite cellulose liquor residues. It will be noted that these materials are substantially ashless. Vhen coal particles are already oilcoated, either by this process or in other Ways, there is little difliculty in uniformly coating them With a further` quantity of oily material. It has been found possible to mix in uniformly as littleas two or three per cent additionall oil in a paddle mixer ora dough mixer, either hot or cold depending upon the material, and in this Way add the amount of additional oil or oily material necessaryto make good and uniform briquettes. For reasons of economy the total oil or oily material needed as binder 'to make good briquettes is kept as small as possible. Forv other reasons it has been found advisable to keep the oily material below 10% to 12%, depending on the nature and coarseness of the coal. If more than that amount is used the coal has an oily feel,

and the unbaked briquctte is too soft 0r mushy. v

By properly adjusting the percentage of total binder and the percentage of moisture it has been found possible to obtain oilcoated coal particles which may be pressed into briquettes such as the ordinary pillowbriquettes that Will not stick in the mold and vwill burn Without breaking, will be dustless, and Will bear handling by the automatlic machinery used for the handling of coa Usually the briquettes after being formed in the molds are too soft to bear such han- (lling, ing at a temperature high enough to drive ofi some of the volatiles from the oil or other binder and yet not high enough to actually have the effect of producing coke. rIlhis renso they are usually hardened by bakders the briquettes smokeless -and odorless,

thus fitting them foi' sale in the most exactingmarkets. ally obtained by baking at temperatures above 300o F. and ultimately reaching about These results have been usu- 500o F., but, generally, not much exceeding 13p the latter ligure, although with some oils temperatures ultimately reaching 650O F. for a short time have been found to be most satisfactory. The baking of pillow-briquettes reaching a thickness of an inch and a quarter has usually required one and one-half to two hours at the temperatures named.

Single briquettes would sustain a crushing weight of 125 pounds when properly made.

lt is found that briquettes of fine coal made as above described bear rough handling and burn better than do similar briquettes made of coarser coal. 'It has been found that a properly made domestic fire of such fine coal pillow-briquettes will burn for twenty-four hours Without apparentv Ydiminutionv of volume if left undisturbed,

i ous structure of the ash is such that air passes through it and burns out the carbon of the coal so that the ashv of briquettes burned in ordinary domestic; 'stoves contained as little or two to three per cent of unburned carbon.

lt was found that the different oily materials lost different amounts when` the briquettes were baked and that relatively larger. amounts of oily materials had to be used as binder where their volatile content was high. @ne sample of Mexican fuel oil lost 45% on baking'.

It was found that some coals, and particularly the coal contained in the ashes of a city ash dump, did not take up enough oil or oily binder to form satisfactory agglomerates when agitated with the oil or oily binder in an aqueous pulp. It was found however that very good agglomerates could be made from such coals by adding a small amount, say one to three per cent of oil or oily binder in the aqueous pulpf The further binder needed to make the, briquettes was added by mixing in the additional binder with `the fairly well dried agglomerates after removal .from the pulp.

In recovering coal from the. ashes of a New York city dump it was found that 25% to 30% of the ashes were fines which passed through 28 mesh screen and that these fines contained only a few per vcent of coal. Accordingly in most runs the finespwere separated and rejected before grinding the ashes to 20 to 35 mesh preparatory tocon centration. l

Example 1.-Ashes from a New York city ash dump screened and ground as above were suhjectedto froth-flotation treatment `with a suit-able soluble frothing agent and with oily material, and then further oily material was added until about four or live 'per cent ofoily material on the coal present had been added. The partly drained Wet concentrate cointained abouti-32% of water. To 125 pounds of this concentrate (estimated to contain 100 pounds of solids) 'were added three pounds of finely ground pitch, and the whole mixture was put through an Anderson eXpeller to reduce the water content to approximately ten per cent. The discharge from the Anderson expeller was further mixed and then briquetted. The resulting briquettes were baked at a suitable temperature to make them practically smokeless. rlhe nished briquettes, after cooling, were tested as to Atheir water absorbing quality by immersion in water for about twenty hours,V and it was found that they absorbed only from ll/2% to. 6% of water. l

Similar concentrates were agitated in a .pulp in a standard minerals separation machine with between 41% and (i1/2% of gas house coal tar to form agglomerates. These wereseparated from muchof the pulp water, by flotation, drained on burlap to further reduce the water to' 32.8%, and then put through an Anderson expeller to reduce the water to 9%. The resulting cake was fed directly to a Belgian roll briquetting machinehand the resulting briquettes baked for one and one-half hours at about 500o F. The resulting briquettes were excellent. After cooling they were tested by immersion in water for twenty hours and it was found they had absorbed from 1.7% to 1.9% water and showed no signs of disintegrating and were hard.

No determinations of ash content: were made during this run, but such determinations were made in connection with another V substantially similar run in which the ashes were passed over a sixteen-mesh screen to separa-te out the lines. The material retained on the sixteen mesh screen was fed to a standard ball mill to be ground for fio'-v tation feed. The fine material was passed through a Dori' classifier adjusted so that the overflow carried about .two per cent of material largersthan 35 mesh. This overliow constitutedtlie mill tailings. The coarse material from the classifier passed to the ball mill along with the coarse material from the sixteen-mesh screen and constituted the llotation feed. The flotation feed was ground in the ball mill so that 82% of it passed a hmesh screen and this contained 67.5% of as The dotation `was effected in a series of six minerals separation positive-feed subaeration vessels. The feed to flotation averaged about a .ton and a half of, solids per hour. To the material in the ball mill was i material fed to the mill.

added an emulsion of Mexican. fuel oil and Water containing of oil and a fraction of a per cent of laundry soap so .that thev oil fed amounted to 22.8 pounds per hour, together with about 1.1 pounds of crosylic acid per hour. A further 0.4 pound of cresylic acid per hour was fed to the first agitating vessel. The froth. overflow from this vessel was fed to the fifth vessel in the serieswhich, together with the sixth vessel, retreated the froth overflow.. The. tailings from the. first vessel passed successively through the second, third and fourth vessels and the fioat therefrom was returned to the first vessel. The tailings from the sixth vessel were returned to and divided between the second and third Vessels. Together With them was fed the overflow from the thickener in which the concentrate obtained from the fifth and sixth vessels was thickened. The flotation tailings from the fourth vessel werercturned to the mill feed so that they passed through the sixteenmeshscreen and thereafter were treated as part of the raw The finished' concentrate coming from the thickener contained 15% ash, which .was reduced by fil tration to 13%.

Eau/malle 2.-A high ash coal from St. Clair Coal Company, St. Clair, Pennsylvania,'\vas ground in a ball mill so that all but 1.2% passed twenty mesh and 52.2% passed one hundred mesh. This was fed at the rate of from three-fourths of a ton to 'a tonrv and a h alf per hour to a minerals separation positive-feed subaeration machine of six cells. In the froth-flotation concentrating operation coal tar was added to the aqueous pulp at the rate of 7.6 pounds per hour together' with pine oil at the rate of one quarter pound per hour, oxidized petroleum at the rate of 4.5 pounds per hour, cresylic acid at the rate of 3.6 pounds per hour, and a Mexican fuel oil emulsion containing about one third Water and a very little soap, 1.47 pounds per hour. The original ash content i of the/coal, 27.5%, was reduced in the conyce centrate to 14.75%. This concentrate. was agitated in a minerals separation standard machine and coke oven coal tar Was added at the rate of 61.8 pounds per hour to form agglome-rates. The agglomerates were overfloived and after filtration contained from 13.5% to 17.5% of water and Were further dewatercd by passing them through an Anderson expeller and the product Was then mixed in a C. P. Day Company dough mixer with rather more than five per cent (com-4 puted on the coal present) of coke oven tar. to make a total estimated binder of about nine per cent on the coal present in' the agglomerates. The resulting material Was made into briquettcs which were baked aty a suitable temperature. Tested in a standard type of domestic grate they V4Were found to be smokeless, they burned Well, and they retained their shape during burning. The resulting ashes contained an average of two totwo and one-half per cent of unburned carbon as contrasted with unburned carbon contained in the ashes of briquettes produced by prior art processes of about 50%.

Eample 3.-High ash coa-l sludge from the Philadelphia and Reading Coal and Iron Company containing 27.75% of ash Was fed to a standard type ball mill together With an emulsion containing Mexican fuel oil and a little laundry soap so that the oil fed amounted to 13 pounds per ton. With this material which was about 35 mesh or finer was fed 2.8 pounds of cresylic acid per ton so that there was a total feed of agents With the coal amounting to' about 15.8 pounds per ton of material fed. Froth fiotation Waseffected in a minerals separation `positive-feed subaeration machine having eight cells. There Was added at the first cell an additional 1.05 pounds of cresylic acid per ton of solids in the feed. The concentrate from the first two eellswas fed to the seventh cell which, Atogether With the eighth cell, was used as a cleaner. The tailings from the second cell passed through the third, fourth,

flotation tails, while the overflow from these latter cells was returned as middlings to the feed atthe first cell. An additionaly 0.25 pound of eresylic acid per ton of solids in the feed was added at the fifth cell. The over flow from the eighth cell,\ constituted a cleaned concentrate. The concentrates were heaped up, the product of several similar runs being mixed together.

The ash content averaged about 11.0%. These were dried to about 7% of Water and mixed in a dough mixer with additional 9% of Mexican fuel oil and then made into pillow briquettes in a set of 4-pocket Mashek briquetting rolls (Belgian type). The briquettes did not stick to the` rolls and there wasl very little breakage of them. The briquettes were baked `for one hour and a half at a temperature rising to something over 500o F.. This yielded excellent briquettes which burned with so little smoke that it was not noticeable except upon careful examination.

Having thus described the invention,`what is claimed is:

1. A baked briquette consisting of uncoked anthracite coal substantially passing 10 mesh and bound by a. binder which consists largely ofthe residue of oil which is less then ten per cent on the coal, said briquette being adapted when burned in a deep mass in a grate to leave an ash containing less than ten per cent of unconsumed carbon andl of' uncoked line anthracite coal bound together b y a substantially ashless binder which is less than ten per cent on the coal,

- said briquette being substantially free ol dust than ten per cent on the coal, said briqucttebeing'substantially free of dust when broken and burnahlc in a gratewithout substantial softening so as to leave an ash containing less than ten per cent of iinconstuned carbon.

4l. A strong coal baked briquctte consisting o'l' uncoked anthracite coal passing l0 mesh bound together by4 a binder which consists largely ot' the residue of banked oil which is less than ten per cent on thc coal, said briquette being burnable in a grate Without substantial softening so as to leave an ash containing less t-han ten per -cent ot unconsuined carbon, and absorbing less than seven per cent of its Weight of Water upon prolonged immersion in water.

5. The process of making coal briquettes which consists in treating line. coal to coat it With a substantially uniform coating consisting oi' oily mate-rial in too small amount to serve as a binder, and then mixing the oilcoated coal, with further substantially ashless binder, and forming it into briquettes.

G. The process of making coal briquettes which consists in agitating an aqueous pulp ot line coal with an oily reagent to produce oil-coated coal agglomerates, separating the agglomerates from the pulp and from excess Water, mixing with -furthe-r oily substantially ashlcss binder, and forming it into briquettes.

7. rlhe process ci making coal briquettes which consists in agitating an aqueous pulp oii'the impure coal with a mineral-trothing agent and with an oily reagent to produce oil-coated coal particles, separating the particles from thenpulp and. lrom excess Water, mixing with further substantially ashless binding material, and forming it into briquettcs. I

S. llhe process of making coal briqucttes which consists in agitat-ing an aqueous pulp ol impure coal with a miueral-'trothing 'agent and with an oily reagent to produce floating A l'oil-coated coal agglomeraties, separating the agglomcrates from the pulp and from excess Water, mixing with further substantially ashless binder, and forming it'. into briquettes.

0. The process ot' making coal briquettes Which consists in agitating an aqueous pulp of fine coal with an oily reagent to produce oil-coated coal particles, separating the,particles from the pulp and from excess Water,

mixing with further substantially ashless binding material, forming the briquettes, and baking the briqucttes at a tempera-ture reaching the neighborhood of ()O F.

l0. lhe process ot making coal briquettes which consists in agitating an aqueous pulp of the impure coal with a mineral-frothing agent andfwith an oily reagent to produce floating oil-coated coal particles, separating the iiarticlcs from the pulp and `from excess Water and its contained ash, mixing With further substantially ashless binding inaterial, and forming it into briquettes.

ll. 'lhc process ot making coal briquettcs which consists in agitating an aqueous pulp of the impure coal with a mineral-frothing agent and with an oily reagent to produce floating oil-coated coal particles, separating the particles from the pulp and from. excess water and its contained ash, 'mixing with Jfurther substantially ashless binding inatcrial, forming the briquettesand baking thc briquettes at a temperature reaching the neighborhood oi2 50() o F. v

l2. rlhe process of making coal briquettes which consists .in agitating a pulp of the lcoal with an oily reagent adapted to serve as binder to produce float-ing agglomerates, overl'lowing the agglomerates from the pulp to separate them from .most of the excess Water', further vdewatering the agglomeratcs, mixing the agglomeratcs with further bind.- er, and then forming the mixture into briquettes.

13. .The process of making briquettes from impure coal which consists in agitating a pulp of the impure coal With a mineralfrothing agent to produce a. floating coal concentrate, agitating the coal concentrate lwith an oily reagent adapted to serve as binder to produce floating agglomerates, overflowing the aggloinerates from the pulp to separate them from most of the excess Water, further dewatering the agglomerates, mixing the agglomerates with further binder, forming the mixture into briquettes, and baking the briquettes. y

la. The process of making coal briquettes which consists in agitating, an aqueous pulp ot impure coal With a mineral-frothing agent to produce a floating concentrate supported by bubbles, adding oily material which is adapted/"to serve as a binder, and further agit-ating to produce agglomerates of oil-coated coal, removing from the agglomerates the excess Water, mixing further binder with the relatively dry agglomerates',l molding the briquettes, and baking the briquettes.v f

l5. The process of making coal briquettes which consists in agitating an aqueous pulp of impure coal with a mincral-frothing agent to produce a floating concentrate supported by bubbles, adding oily material which is adapted to serve as a binder, and

further4 agitating to produce agglomerates of oil-coated coal, removing from the agglomerates the excess Water, mixing further oily binder with the relatively dry agglom-v as a binder, and further agitating to produce agglomeraties ofoil-coated coal, removing from the agglomerates the excess Water, mixing further binder with the relatively dry agglomerates, `molding the briquettes, and baking the briquettes. I

17. The process of Vmaking coal briquettes which consists in agitating an aqueous pulp of impure coal with a mineral-frothing agent and with an oil to produce a fioating concentrate supported by bubbles, adding more oily material which is adapted to serve as a binder, and further agitating to produce agglomerates of oilcoated coal, removing from the agglomerates the excess-water, mixing further oily binder with the relatively dry agglomerates,v molding the briquettes, and baking the briquettes.

18. The process of making coal briquettes .from ashes Which consists in separating out the finer ashes, grinding the coarser ashes to free coal particles from adherent ash, agitating an aqueous pulp of the ground ashes ticles, separating the float from the pulpA and `vfrom excess Water and its contained ash, mixing with further substantially ashless binding material, forming the mixture into briquettes and baking them to produce almost or absolutely smokeless briquettes.

19. The process of making coal briquettes from ashes which consists in separating out the finer ashes, grinding the coarser ashes to free coal particles from adherent ash, agi- .tating an aqueous pulp of the ground ashes with a mineral-frothing agent and with an oily agent to produce floating oil-coated particles, separating the fioat from the pulp and from excess Water and its contained ash, mixing with further substantially ashless oily` binding material, forming the' mixture into briquettes and baking them to produce almost or absolutely smokeless briquettes.

In testimony Whereoiwe have alixed our signatures to this. specification.

GEGRGE ALBERT CHAPMAN. ELTOFT WRAY VILKINSON.