US2231513A - Liquid fuel - Google Patents

Description

Patented Feb. 11, 1941 1 I LIQUID FUEL Albert L. Stillman, Plainfield, N. J., assignor to Fuel Research Corporation, a corporation of Delaware No Drawing. Application November 5, 1938,

1 Serial No. 238,973

7 Claims. (Cl. 44-8) This invention relates to improvements in the erratic motion which the mass of certain finely production of suspensions of coal inoil and has divided solid particles effects when suspended in for its principal object to provide a substantially certain fluid media and which for any particle stable suspension of coal particles in hydrocarbon that is moving continues more or less indefinitely liquid which will be suitable for combustion in in such media. Chemists are not agreed as to 5 furnaces adapted for the burning of oil fuel and the cause of this movement but it is applicant's other industrial uses, such as, a carburetant in belief which is in line with the theory advanced the carbureting of water gas, a binder for coal by Arthur F. Taggart, T. C. Taylor and A. F.

briquettes and, in general, for all those purposes Knoll in their paper issued as Technical Publiwhere 100% oil is now employed but which may cation No. 312 by the American Institute of Min 10 be replaced by the suspension of this invention. ing and Metallurgical Engineers, that it is due In view of the economy which may be realized to a chemical action, a partial ionization of the by a product of this type because of the relative minute solid particles by the liquid media. As cheapness of solid fuel,. previous attempts havea result of the reaction, it is believed that the been made to produce a satisfactory fuel of coal non-anchored ions on the surfaces of the particles 5 and oil and while such prior fuels have been are gradually replaced by less soluble ions from satisfactory as fuels they possessed other disadthe liquid media and during this change of the vantages which offset the economies derived from surfaces of the particles from arelatively soluble supplementing the oil by coal. For example, it to a relatively insoluble state which takes place is a matter of experience that when coal and oil at random over the entire surfaces of the par- 20 are mixed together as they have been in the past, ticles, an unbalanced or constantly changing the coal will in time settle to the bottom of the .mean pull is exerted on each of the particles container. Such segregation of the coal renders thereby inducing theparticles to move erratically the mixture useless for the purpose for which it in the liquid media. The essentials for this was intended as it cannot be conveniently movement are believed to be, first, that the pain. 25 pumped and several methods were adopted for ticle be of a chemical composition that is, seethe purpose of maintaining the coal in sus- 0nd, capable of being ionized to a sufficient but pension, or in other words, to insure the stanot too great an extentin the liquid media so as bility of the mixture. One of these methods was to cause the particles to move erratically in such to keep the mix in a state of constant agitation media and, third, that the particles be sufilciently 30 by mechanical means. If the mixture was used small to be maintained in suspension by such as a fuel, especially for marine purposes where movement. the fuel is required to stand long periods of stor- Coal is known to have been formed from vegeage without precipitation, the use of mechanical table matter more or less consolidated by the agitators was too expensive and their bulk too action of heat and pressure. As a result of the 35 cumbersome for ship bunkers or fuel storage coalification process the originally relatively simstations. Another method that was devised was ple molecules are condensedand polymerized to to add to the coal-oil mixture a stabilizer, usually form a much more complex coal molecule whose a coagulant such as casein or starch. The dischemical composition ranges over wide limits, advantage of thm method however is that the depending on the-nature of the original vegeta- 40 use of a coagulant, forming as it does a gel tion, on the conditions in the early stages of its of the mix, causes the viscosity of the mixture to deposition and on the magnitude of the natural become extremely high thereby making preheatforces to which the deposit was later subjected. ing and pumping of the mixture difficult and in- Investigations of the reactions of coal with simcreasing the expense of dispensing the coal in ple chemical reagents, however, have tended to 45 the carrying medium. prove that the coal molecule contains as an essen- I have found that a satisfactory oil and coal tial element of structure, the six-membered carmixture which will remain substantially stable bon ring characteristic of aromatic compounds for a long period without the necessity of in- (The Chemical: Coal by H. H. Lowry, published corporating a coagulant in the mix or using a by the Coal Research Laboratory, Carnegie Insti- 50 mechanical agitator, can be obtained if a certute of Technology, February, 1934). While all tain proportion of the coal particles is made sufcoal molecules may have the same essential ficiently small and is sufficiently soluble in the chemical structure, I have found that coals of the oil to produce the phenomenon known as semi-bituminous type which have a high grind- Brownian Movement. This movement is an ability, namely a grindability 'about.85 on the 55 Hardgrove scale, are best suited for the purposes of this invention. Bituminous coals may also be satisfactorily used but they should preferably be first heated to the softening point so that they swell and become porous before subjecting them to the grinding operation. The preheating of such coals should be carried to temperatures approximating 350 F. in order to add to percent grindability to thecoal which is then preferably ground by a dry-grinding proc- 'ess.

I have found that good results are obtained by mixing with'a coal of the above indicated type a hydrocarbon liquid-used as liquid fuel (cracked fuel oil). This type of oil is capable of so partially ionizing small particles of bituminous and semi-bituminous coal as to produce the phenomenon above described. The size of the particles at which such movement begins is about .007 millimeter, that is to say, '7 microns. The move.. ment increases in intensity as the particle size decreases and I prefer for the purposes of the invention to reduce the size of the particles to 5 microns as I have found that best results are obtained within practical limits at that size. By grinding the coal and oil mixture together until at least 30 to 50% of the coal particles have been reduced to at least the size of 7 microns and preferably of 5 microns I have found that the mixture will be in a state of microscopic agitation throughout its bulk' and that the agitation of the smaller particles will be suflicient to maintain the larger particles in suspension, permanently, the latter remaining equally distributed in a stable state throughout the mixture.

In order that a better understanding of the invention may be obtained, the following example is given by way of illustration:

carbon bisulfide.

coal particles which are of micron size. As a specific test, 100 cu. cm. of the mix is removed from the grinder and the coal extracted with The coal is then screened to determine whether it will all go through a 325 mesh screen. If the coal screens as indicated, a portion of it is placed under a microscope to determine the percent of micron size. I have found that a stable mixture of the coal and oil is formed when at least 30% by weight of the coal has been reduced to at least a size of 7 microns and preferably 5 microns and from a practical viewpoint coal particles small enough to produce the r Brownian Movement will be present in the mixture in efficient proportion to accomplish the purposes of the invention if the proportion of coal particles in the mixture which have been reduced to less than 10 micron size is at least approximately 50% of the coal. In other words, a coal ground to pass 100% through a 325 mesh and having at least 50% by weight of its particles under 10 microns in size will usually have at least 30% of its particles capable of producing Brownian movement of suflicient intensity to stabilize the larger particles of coal. Best practical results, however, are attained if the proportion of coal particles in the mixture under 10 micron size is approximately from to of the coal. The resulting. mixture willhave a viscosity which is well within the standards of the United States Government for Bunker C fuel oil and can therefore be used with present equipment. The ignition point of the mixture is approximately 425 F. which makes it desirable for use in low rating furnaces.

While I have referred to-Pocahontas and lower Kittaning coal in the foregoing example it will be understood that any satisfactory bituminoui to 70% by weight of a fuel oil having a chemical composition such that it reacts with the coal particles to cause those particles capable of partaking of Brownian movement to move erratically therein and of from approximately 60 to 30% by weight of coal of the bituminous type which has been subjected to a grinding action in the presence of the oil so that it passes 100% through a sieve of about 325 mesh, a substantial portion of said coal particles being of a size as to render them in and of themselves incapable of remaining in permanent suspension in the oil and at least 30% by weight of the coal particles being less than 7 microns but being greater'than colloidal in size and producing in the oil Brownian movement of suflicient intensity to stabilize the larger particles of coal without the aid of other agents.

2. A stable liquid fuel having coal particles equally distributed throughout the fuel and composed of a mixture of approximately from 40 to 60% by weight of a fuel oil having a chemical composition such that it reacts with the coal giparticles to cause those particles capable of Dar.-

taking of Brownian movement to move erratically therein and of approximately from 60 to 40% by weight of coal of high grindability, at least30% by weight of the coal particles being less than 5 microns but being greater than colloidal in size and the balance of the coal particles being greater than 5 microns in size but not substantially greater than 325 mesh, the major portion of the coal particles above 5 microns in size being in and of themselves incapable of remaining in permanent suspension in the oil and the particles 7 of coal under 5 microns in size producing in the oil Brownian movement of sumcient intensity to stabilize the larger particles of coal without the aid of other agents.

3. A stable liquid fuel having coal particles equally distributed throughout the fuel and composed of a mixture of. approximately from 40 to 70% by weight of a fuel oil having a chemical composition such that it reacts with 'the coal particles to cause those particles capable of partaking of Brownian movement to move erratically therein and of approximately from 60 to 30% by weight of a coal of the bituminous type having a grindabllity above 85 on the Hardgrove scale, at least 50% of the coal particles being less than 10 microns but greater than colloidal in size and the balance of the coal particles being greater than 10 microns in size but small enough to pass 100% through a sieve of 325 mesh, the coal particles above 10 microns in size being in and of themselves incapable of remaining in permanent suspension in the oil and the particles of coal under 10 microns in size including an amount of coal particles sumciently small to produce in the oil Brownian movement of sufficient intensity to stabilize the other particles of coal without the aid ofother agents.

4. A stable liquid fuel having coal particles equally distributed throughout the fuel and composed of a mixture of approximately from 40 to 60% by weight of Bunker fuel oil and of approximately from 60 to 40% by weight of a bituminous coal having a high grindability, said coal being pulverized so that it passes 100% through a sieve of 325 mesh, a substantial portion of said coal particles being of a size as to render them in and of themselves incapable ofiremaining in permanent suspension in the oil, and from 30 to 50% by weight of the coal particles being less than from 5 to 7 microns but greater than colloidal in size and producing'in the oil Brownian movement of sufficient intensity to stabilize the larger particles of coal without the aid of other agents. g

5. The method of manufacturing a stable liquid fuel which comprises mixing a coal of the bituminous type having a high grindability, with a fuel oil having a chemical composition such that it reacts with the coal particles to cause those particles capable of partaking of Brownian movement to move erratically therein, until the percentage of coal particles in the mix is greater than 30% but not substantially greater than 60% by weight of the mix, then subjecting the coal in the presence of the oil to 'a grinding action and continuing such grinding action until approximately all of the coal particles are less than 325 mesh but include a substantial proportion of particles of a size as to render them of themselves incapable of remaining in permanent suspension in the oil and until at least 30% by weight of such coal particles are less than '7 microns but greater than colloidal in size and are capable of producing in the oil Brownian movement of sufficient intensity to stabilize the larger particles of coal without the aid of added stabilizing agents.

6. The method of manufacturing a stable liquid fuel which comprises mixing a fuel oil of the order of Bunker 0 fuel oil with particles of coal until the percentage of coal particles in the mix is greater than 30% but not greater than 60% by weightof the mix, then subjecting the coal in the presence of the oil to a grinding action and continuing such grinding action until approximately all of the coal particles are less than 325 mesh but include a substantial proportion .ofparticles of a size as to render them of themselves incapable of remaining in permanent suspension in the oil and until at least 30% by weight of the coal particles are less than? 'microns but greater than colloidal in size and are capable of producing in the oil Brownian movement of suiiicient intensity to stabilize the particles of coal above 7 microns in size without A the aid of added stabilizing agents.

325 mesh, a substantial portion of said coal particles being of a size as to render them bfthemselves incapable of remaining in permanent suspension'in the oil and approximately 30% of said coal particles being less than '7 microns in size and producing in the oil Brownian movement of such intensity as to stabilize the larger particles of coal in the oil without the aid of other agents.

ALBERT L; 'STIILMAN.