US2430085A - Process of preparing coal for use in colloidal fuels - Google Patents

Description

I Nov. 4, 1947. K. A. sPENcER ET'AL PROCESS OF PREPARING COAL FCR USEl IN COLLOIDAL FUELS I Filed July s, 1943 IN VEN TORS Patented Nov. 4, 1947 PROCESS oF PREPARING coAi. Foa USE 1N coLLomAL FUELS Kenneth A. Spencer, Kansas City, and Donald W. Machin, Lawrence, Kans., assignors to The Pittsburg-and Midway Coal Mining Company, Pittsburg, Kans., a corporation -of Missouri Application July 9, 1943, Serial No. 494,006

I This invention is concerned with a process of preparing coal for use in composite coal-oil fuels commonly referred to as colloidal fuels.

Examples of prior art processes may be found in the U. S. patents to L. W. Bates, No. 1,390,228; C. J. Greenstreet,-Nos. 1,431,225 and 1,623,241;

H. Plauson, No. 1,647,471; R. A. Adam, No. 1,939,-

587; and A. L. Stillman, No. 2,231,513.

The new process comprises the following principal steps: First, the step Aof far-reaching dehydration of previously de-ashed, i. e., Washed lump size coal prior to pulverization thereof; second, the step of withdrawing coal fines incident to dehydration and collecting such fines for use and intermixture with a suitablev fuel oil; third, pulverization of the dehydrated lump size coal in two separate and distinct operations; fourth, separation of the pulverized coal which furnishes in the form of undersize a selected product suitable for dispersion in the fuel oiland in the form of oversize a product which is re-circulated through the pulverizing apparatus; and fifth, uniting the coal nes extracted from the feed incident to dehydration with the selection nes obtained by the separation of the pulverized coal, and dispersing such fines in a suitable fuel oil.

The combination of these steps, and particularly the dehydration of the coal and the steps of feeding to the pulverizing and thence to the separating apparatus the previously dehydrated coal are important features which have a profound'effect on the all-important question of economy of producing the-colloidal fuel. The dehydration of the coal also aids the proper dispersion of the particles in the oil and thereby benefits the stability of the final product.

.cally indicatedf Auxiliary apparatus, such as` conveyors. elevators, feed' belts, drives, various control means, and the like are'omitted.

Washed, i. e., previously de-ashed, bituminous coal of a maximum lump size of about 3A in.

y1 claim. (C1. er1- 17) is fed to the drum II of a suitable heat drier. This drier may be of the rotary type as indicated in the drawing. The coal flows through the drier in the direction indicated by the arrow, and is subjectedto an air current, sweeping through the drum, which has been heated to a mean temperature of about 350 F. in a furnace I2. The feed of the coal and the speed of rotation of the drum are adjusted so as to subject the coal to the action. of the heated air current for a time sufficient to effect substantially complete removal of moisture, i. e., to a point when the moisture content is reduced to less than 1%.

The step of dehydrating coal of substantial lump size, as indicated, permits the application of higher temperatures, and longer treatment times than could beapplied with safety if the material were ground to appreciably smaller size. It may be mentioned at this point that we applied appreciably higher temperatures, up to 500 F., for short periods of time, without any ill effect. The mean'temperature was, however, as stated, 350 F. The process of removing the moisture is accelerated by this mode of operation, and the danger of combustion is eliminated. The treatment can be applied with available equipment of proved performance.

Air containing coal fines is withdrawn from the heat drier, by a suction fan I3, and is conducted into a dust precipitation chamber M. These coal fines are on the order of about 200 mesh, suitable for dispersion in the'oil. They are collected and either supplied to a sacker bin 2|, for storage,

or to a feeder device 20 for' mixing with the oil. l

The step of removing coal fines from the heat drier, as described, serves a double purpose. It contributes to the safety of the moisture removal operation Within the drier, and results in saving appreciable amounts of material for dispersion in the oil.

The moisture-free lump coal flows from the heat drier Il into and through the cooler l5 to .reduce its temperature to around F. The

The operation of the crusher is accelerated and is rendered economical by the dry condition of the material which is still at elevated temperature.

The by 1/4 in.,dehydrated coal is then fed to a suitable mill l1 which performs the -second and final pulverizing operation by reducing the coal to a. particle size of about 200 mesh. Any suitable mill may be used; the mill actually employed was a ball mill of well known structure.

The step of feeding substantially moisture-free material at elevated temperature to the mill I1 accelerates the nal pulverlzing 'operation and therefore contributes to the economy of the process. The pre-grinding of the lump size coal to a particle size of about 1/4 in. has been found best for the efilcent operation of the pulverizing mill.

'I'he dry pulverized material coming from the mill i1 is fed to an air separator i8 commonly referred to as a cyclone. Ths separator delivers two products, namely, the product of desired particle size of about 85% to 95%- through 200 mesh, which is either supplied to a sacker bin i9 for storage, or to the feeder device 20 for dispersion in the oil, and an oversize product which is recirculated through the pulverizer mill i1.

The step of feeding substantially moisturefree material to the cyclone separator accelerates and renders more accurate the sizing operation, resulting in a greater yield of selected nes per time unit, thereby adding to the economy of the process.

The discharge into the sacker bins i9 and 2i (a single bin may be used for receiving material from the separator i8 and also from the dust precipitator Il) is practiced when it is desired .to prepare coal for temporary storage and subsequent dispersion in the oil. The sacker bin is an ordinary bin or hopper which receives the pulverized material for discharge into storage sacks provided with moistureproof lining.

The process may also be continuous, and in this case, the pulverized material from the pre.- cipitator i4 and from the separator i8 is collected in a Vsuitable bin (not shown) and is then fed in measured, controlled amounts to the mixer 22, during the mixing operation, by means of the feeder 20. The latter may be an ordinary screw feeding device, as indicated. Its speed controls the amount of coal nes gradually supplied to the mixer.

The mixer 22 may be equipped with a propeller or a plurality of propellers, according to its size and the desired speed of processing. Heating coils may be provided within the mixer tank and supplied with steam in order to carry out the mixing at elevated temperatures between 150 F. and 200 F.

Oil is supplied' from the reservoir 23. Coal is gradually added, during mixing, in an amount to provide a final mix containing about 40% of coal by weight. Samples are taken during the initial mixing operation, and subjected to tests, so as to determine the proper dispersion of the coal particles in the oil and therewith the optimum mixing time for subsequent operation. The finished fuel is withdrawn from the tank 22 for storage or use.

A colloid mill 24 may be-used in place of the mixer 22, or may receive a rough mix, produced in the mixer 22 at a shorter mixing time, vflor homogenizlng.' Such operation is well known and need not be describedin detail. The iinished product is then withdrawn from the colloid /f'mill for storage or use.

The coal actually used in the above described process was washed bituminous coal. It

is, of course, clear that other coal, and various combustible solids, such as are mentioned in the prior art patents, may be employed equally well. The process was practiced with numerous kinds of fuel oils. Production was successfully carried out, using 6.0 A. P. I. residual fuel oil with a Saybolt Furol viscosity of 220 sec. No stabilizer was used and none appears to be required in this case. The fuel remained stable in testing, in storage, during transport in tank cars, and during large scale industrial combustion tests ordinary equipment provided for oil burning.

The process disclosed herein is not restricted to the use of heavy fuel oils such as mentioned. The combustible solids, prepared as described, may also be dispersed in lighter combustible liquids., Stabilizers may be employed if desired or required. l

The far-reaching, substantially complete removal of moisture benefits not only the economy of production, as previously explained; it is also believed to aid the dispersion of the coal particles in the oil and therewith to benefit the stabilization of the final product. This will be, understood when it is considered that coal containing moisture presents surfaces to the oil which` are moist and, therefore, lyophobic with respect to the oil. This means that these surfaces are liquid-repellent, producing a. system in which the dispersed phase has no attraction for the dispersion medium and therefore tends to separate; Coal that is practically completely dehydrated, such as is used in the present process will. on the other hand, assist lyosorption, i. e., the adhesion of the liquid to the solids, and will therefore tend to produce adsorption of solvent films upon the surfaces oi' the particles dispersed and suspended in the oil. It is believed that the dehydration of the coal, as previously described. accounts in part for the stability of the colloidal fuel produced.

Changes may be made within the scope and spirit of the following claim in which is pointed out what is considered new and desired to have protected by Letters Patent of the United States.

We claim: The process of preparing coal for use in colloidal fuels which consists of the following steps, in the sequence specified, namely, (1) taking lump size de-ashed bituminous coal within a size range from 0" to about 3A" and dehydrating such coal to a moisture content of less than 1% in the presence of heat ranging from about 350 F. to about 500 F.; (2) withdrawing during such dehydration nes which are about 200 mesh; (3) cooling the dehydrated coal to a temperature of about 100 F.; (4) pre-crushing the dehydrated and cooled coal at a temperature of about 100 F. retained therein to obtain particles of a size range from 0" to about 1/4"; (5) pulverizing the pre-crushed coal at a temperature of about- 100 F. retained therein to obtain a product of about 85% to 95% through 200 mesh; (6) separating from the pulverized product particles of about 200 mesh; and (7) intermixing the separated particles ofv about 200 mesh with the nes of about KENNETH A. SPENCER. DONALD W. MACHIN.

(References on following page) Number Name Date REFERENCES CITED 2,175,484 Rees oct. 1o, 1939 The following references are of record ln the 2,319,394 Erickson May 13, 1943 f'lle of this patent: 1,491,841 Bell Apr. 29, 1924 5 Newhouse Apr. Number v, Name Date FOREIGN PATENTS 1,390,231 Bates Sept. 6, 1921 Number Country Date gg? Frisch (i Fetb-l, 410,883 Great Britain May 31, 1934 1, 1 Townsen Oc 10 v 1,390,228 Bates sept. 6, 1921 OTHER REFERENCES 1,939,587 Adam Dec. 12, 1933 Pulverlzlng 200 Process Materials, pages 241-2 2,231,513 Stillman Feb. 11, 1941 of Chemical and Metallurgical Engneeerlng, vol- 1,458,106 McLaughlin June 5, 1923 ume 45, No. 5, May 1938. McGraw Hill Book i.

1,991,583 Stockton Feb. 19, 1935 15 Company, New York. (Copy in 241-30.)

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