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INDUSTRIAL AND ENGINEERING CHEMISTRY
definite superiority of the constant-volume buret smoker over the constant pressure-time device. If the “suction” and consequent rate of flow through the cigaret be plotted against time during the puff, it will be seen that in the latter the flow rises to a maximum as the valve opens, depending upon the rapidity with which this is accomplished, remains constant until the valve begins to close, and then diminishes to zero as the valve closes. In the former, the flow quickly reaches a maximum and diminishes with the head of water in the buret. This behavior corresponds closely to the diminished suction in mouth puffing as the buccal cavity becomes filled with smoke. A graphical representation of this phenomenon is shown in Figure 5, the volume taken being the same in each case. Pfyl (IO)studied the smoking habits of several individuals in the effort to choose as realistic a rate as possible. The difficulty of obtaining such information under normal conditions is great and, when obtained, shows wide variation between individuals and between different times for the same individual. Also, the subjects under examination are apt to be nervous and smoke somewhat more vigorously than normally. Pfyl, as a result of his investigation, took a 40-cc.
839
puff of 2-second duration twice a minute; Pyriki (11) adhered to Pfyl’s rate. The present writers’ arbitrarily selected rate is a 35-cc. puff of %second duration taken once a minute. It is comparatively simple to correlate data so similarly obtained, when all the facts in the case are presented, and this has been done.
Literature Cited (1) (2) (3) (4) (5) (6)
(7) (8) (9)
(IO) (11) (12)
Baumberger, J. P., J . Pharmacal., 21, 23-34 (1923). Ibid., 21, 35-46. Ibid., 21, 47-57. Bogen, E., J . Am. Med. Assoc., 93, 1110-14 (1929). Jensen, C. O., and Haley, D. E . , J . Agr. Research, 51, 267-76 (1935). Kenyon, 0. A., “Theory and Facts of Cigarette Smoking,” p. 26, Louisville, Axton Fisher Tobacco Co., 1934. Kissling, R., “Handbuch der Tabakkunde, des Tabakbaues, und der Tabakfabrikation,” p. 344, Berlin, Paul Parey, 1905, Koperina, A. W., Biochem. Z . , 219, 258-76 (1930). Mulinos, M. G., and Osborne, R . L., Proc. Soc. Exptl. Biol. Med., 32, 241-5 (1934). Pfyl, B., 2. Untersuch. Lebensm., 66, 501-10 (1933). Pyriki, C., Chem.-Ztg., 58, 279 (1934). Wenusch, A., Ibid., 58, 206-7 (1934).
RECEIVED April 15, 1936.
COLLOIDAL FUEL DIFFERENT DAVID BROWNLIE 46, Grange Road, Ealing, London, W. 5, England
URING the recent years since the World War (1914-18) great attention has been given, particularly in Great Britain, to what is called “colloidal fuel.” I n nearly all cases, however, this name is grossly misleading, since the fuel is not in the true colloidal condition; that is, the solid particles are not in that extremely fine state of division where settling by gravity is impossible, as is the case in a “solution” of glue in water. Colloidal fuel may be defined as a mixture of finely pulverized coal, or other solid fuel, and a liquid fuel, such as petroleum oil, coal tar, lignite tar, or shale oil fractions, in such a condition that the solid particles will not separate out by gravity for a long period. About 30 to 50 per cent by weight of solid fuel is generally used so khat the mixture remains liquid, and the object is to substitute the product for oil fuel, whether for combustion by atomization a t burners or for internal combustion engines. The main advantage claimed is that a liquid fuel of equal heating value is obtained containing much less oil. Obviously colloidal fuel is of no practical value to countries such as the United States and Soviet Russia with abundant oil supplies, but may be irnportant to Great Britain, France, Germany, Japan, and other countries that possess little or no petroleum. The subject, however, is of considerable scientific interest in the field of fuel technology, and American fuel technolo-
gists have played a prominent part. Accordingly, the present contribution will attempt to give, for reference purposes, a concise description of all the colloidal fuel processes.
Methods of Manufacture Three general methods have been used in the manufacture of colloidal fuel. The first is to grind the coal or other solid fuel in the liquid fuel under such conditions-for example, with a colloid mill-that the coal is converted into the true colloidal condition and therefore cannot separate by gravity. This method, however, is not a t present commercially economical because of the high cost and general difficulties of colloidal grinding for the bulk production that would be necessary. Generally, therefore, the principle of a stabilizer or Jizateur is used, as well as a peptizer. That is, the coal or other solid fuel in the ordinary pulverized condition is merely mixed with the oil or tar fractions, and the stabilizer, generally a colloid, is added in small amount to delay a separation of the solid particles by gravity. The stabilizers have included soaps of all kinds, alkalies such 5ts sodium silicate, gelatin, glue, gum arabic, olein oil (sodium salt of sulfonated castor oil), dextrin, and stannic acid. Mostly, however, lime-rosin soap mixed with oil has been employed, the average composition being 84 per cent oil, 10 per cent rosin, 5 per cent lime,
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and 1 per cent water. This mixture is used in the colloidal fuel in an amount corresponding to about 0.5-1.5 per cent of rosin on the weight of the coal. In some cases the fiateur employed has been kept secret; hundreds of colloids can, of course, be used for the purpose. Coal tar or other carbonization tar fractions are generally employed as peptizers. It is remarkable that such fractions can be mixed intimately with petroleum fractions and stabilized by using pulverized coal as a stabilizer or jixateur; that is, a solid acts as a stabilizer for two liquids that otherwise will not mix. A typical colloidal fuel which is not too pasty, made on the peptizer principle, is 30 per cent coal, 10 per cent tar products, and 60 per cent petroleum products, with about 1 per cent lime-rosin soap as a Jixateur, although the latter is not essential. A third method is to adopt mechanical means, such as continually moving agitators in the store tanks, to prevent undue separation of the solid particles.
Nature of Colloidal Fuel A solid, such as coal, in a liquid, such as petroleum oil, may exist in three conditions-true solution, colloidal solution, and suspension. In a true solution, such as sodium chloride in water, the solid particles are less than 0.001 micron in size. In a colloidal solution, howerer, the individual particles of the solid in the liquid (such as coal in oil or glue in water) are within a range of 0.001 to 0.10 micron in size. Under such conditions the particles can be seen in the solution by the ultramicroscope but not by the ordinary microscope. Further, as already mentioned, particles of solid material in the colloidal solution will never separate by gravity on standing and are equal in this respect to those of a true solution. Simple suspension means a state where the solid particles in the liquid are larger than 0.10 micron and can easily be separated by means of filter paper or cloth. In a colloidal solution, however, the solid particles are much too large to pass through parchment, whereas, when the particles are in true solution, they go through the microscopic interstices of parchment as easily as the original liquid. When pulverized coal is ground with oil in an ordinary ball or roller mill for a reasonable length of time, the result is a very small proportion of true solution and some colloidal solution, but mostly simple suspension. Consequently the greater part of the coal particles separate by gravity in a few hours. The role of stabilizers or fizateurs is to delay this action; such a fuel is, of course, not in colloidal solution but is mostly in delayed suspension which is entirely different. The work that has been carried out in the field of colloidal fuel is described in order of date. No commercial success has yet been achieved by any process, mainly because the net cost of manufactureis too high in competition with petroleum, and the product gives more or less trouble in burners and pipes.
Smith and Munsell Method Great interest attaches to the patent of two Americans (4, which is one of the first references in the literature to colloidal fuel, It describes the manufacture of liquid fuel by pulverizing any solid fuel in the dry condition and mixing it with the liquid fuel for use a t burners, simple mechanical agitation being employed to prevent separation. The patentees believed they were the first to make an artificial liquid fuel composed of a mixture of solid particles and liquid, and apparently their claim is correct. The object was to produce a cheap and easily manipulated fuel for use in steam boilers, furnaces, gas manufacture, metallurgical operations, and other purposes. The inventors point out clearly that any solid fuel, such as coal, coke, charcoal, or oil shale, could be used, as well as any liquid; generally, a 50 to 50 mixture was preferred.
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They understood thoroughly, more than half a century ago, the principles of colloidal fuel, and one of their proposals was to carbonize coal a t the mines and mix the resulting tar with pulverized coal or other solid product to make colloidal fuel, Nothing is known, however, as to whether Smith and Munsell carried out this work on a large scale.
Spelman Method Another interesting early patent issued to an American (6) describes a “composite” fuel-that is, a mixture of pulverized solid fuel and crude petroleum or other liquid hydrocarbon in which pulverization of the solid takes place in the presence of the liquid, followed by the addition of a thinner such as alcohol or light hydrocarbons. The solid fuels preferred included anthracite or bituminous coal, but peat, charcoal, and sawdust could also be used. In addition to crude petroleum or similar inflammable liquids, reference was made to the utilization of molasses. No details, however, were given as to the method and degree of grinding the solid in the presence of the liquid, and it is possible that the resulting product was more or less in the true colloidal condition. Curiously enough, however, Spelman does not seem to have been concerned so much with producing a stable colloidal fuel as with preventing dust explosions by grinding dry solid coal; this was a serious problem about thirty years ago. Here again there is no record as to whether this method was carried out on a large scale, and obviously the idea of using molasses instead of heavy oil is an impracticable proposition as far as rapid and efficient combustion is concerned,
Plauson Process The practical pioneer of colloidal fuel, as well as the colloid mill, is Herman Plauson, an Estonian fuel technologist resident for a long time in Hamburg. His original British patent (3)was taken out in 1913 when he lived in Leningrad, and describes in lucid language the whole principle of the colloid mill and the manufacture of true colloidal fuel. Essentially his method is to grind pulverized coal, charcoal, or other solid fuel with liquids, especially hydrocarbons such as petroleum oil fractions, for a long period (about 1 to 2 hours), using two polished metal plates operating at high speed until the solid is reduced to the true .colloidal solution. In addition, Plauson describes the beneficial action of adding to the mixture a small amount (around 1to 3 per cent) of another colloid, such as soap, gelatin, and albumen, which enables the action to be considerably accelerated. This work was based on the Acheson process for the manufacture of colloidal graphite, as used for lubricants; Plauson also points out that other investigators have reduced metals to the colloidal condition. From this he developea the ides of converting solid fuel, such as coal, into the colloidal condition suspended in liquid fuel so that the product could be employed a t burners in place of oil or for internal combustion engines of the Diesel or other type.
Research by Submarine Defense Association This well-known work on colloidal fuel (with that of Plauson, the most important ever undertaken) was begun in New York in 1918, under the presidency of Lindon W. Bates, for the production of colloidal fuel from pulverized coal and heavy petroleum fractions using a stabilizer or Jixateur, and also if necessary according to the peptizer principle, with the addition of coal-tar fractions such as creosote. The object was to find a liquid fuel for the British Navy during the war in order to reduce the amount of petroleum that had to be taken across the Atlantic, in view of the activities of German submarines. The stabilizer used was lime-rosin soap, and gen-
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erally the fuel consisted of about 33 parts by weight of coal, first pulverized to pass through a 200-mesh screen, and 63 parts by weight of heavy petroleum fractions, along with 1 per cent rosin soap. When a peptizer was used, with or without a jixateur, usually 10 per cent of coal-tar fractions was added to the petroleum. Colloidal fuel of this type, with a heating value of 17,000 B. t. u. per pound, was used on a large scale during the period April to July, 1918, on the U. S. Navy scout vessel Gem, fitted with Normand water-tube boilers, but the war came to an end before the British Navy could take advantage of the work. Attempts were then made to develop the fuel in the United States for commercial use both on land and sea but without success. A large number of patents, dating from 1919, were taken out, and considerable differences of opinion exist as to the stability and general efficiency of the fuel.
In this case, however, the bulk of the liquid fuel, such as oil, was kept in a separate storage tank, and a very thick mixture of oil and pulverized coal was kept in another storage tank. When ready for use a t the burners, the thick product was then mixed with the oil in a third small tank p r o v i d e d w i t h agitators and was used direct before it had time to settle. Large-scale experimental work with this fuel was ca.rried out on one of the locomotives of the Great Central Railway in runs between Manchester and various other places. This work was also combined with pulverized fuel firing. In general the results were favorable, but the net cost of preparing the colloidal fuel was too high and the work was abandoned.
Coalinoil Process
Leadbeater Process
A mixture of pulverized coal and oil, using a stabilizer such as lime-rosin soap, was produced by Charles Jason Greenstreet, an American fuel technologist now resident in Great Britain. This fuel was called LLCoalinoil’land seems to be identical with the colloidal fuel of the Submarine Defense Association. According to patents dating from 1920, the principle is to mix coal or other solid fuel, pulverized to pass through a 200mesh screen, with heavy liquid fuel (petroleum or carbonization products) of around 22-25’ BB., and to use as a stabilizer or jixateur oleates, stearates, and palmitates (that is, soap) as well as paraffin wax or other wax substance. Greenstreet appears to have started work on the subject in 1918 and a t first tried to prevent separation by gravity of the solid particles from the liquid by blowing in hot air to cause thickening by oxidation. Later, about 1920, stabilizers were employed. The proportions given by Greenstreet are 20 to 35 parts of solid fuel, and 100 parts of liquid fuel, with 2 parts of soap. Later there was developed the Greenstreet process for the carbonization of colloidal fuel.
Some work on the manufacture of colloidal fuel was undertaken during 1921-22 by John W. Leadbeater a t the works of the Coal, Peat & Oil Company Ltd. of Earlstown (Lancashire). The general principle was to use the higher grade black peat from the bottom of bogs as a stabilizer or jixateur, along with a small amount of fatty substance such as tallow or soap. Several British patents were taken out in this connection; essentially the process consisted in using 5 to 10 parts of the wet black peat and 1 part of tallow or soap, added to a mixture of 30 parts of pulverized coal and 70 parts of petroleum oil or other liquid fuel. Nothing further has been heard of this process.
Calvert or Coloil Process Another method suggested in 1920 in Great Britain for the use of pulverized coal suspended in petroleum oil or other liquid fuel was that of George Calvert of Twickenham (London). This consisted in mixing the pulverized coal with the oil, giving a more or less simple suspension; the fuel was in special tanks provided with compressed-air equipment or other apparatus for continual agitation, neither colloidal grinding, stabilizers, or Jixateurs being used. It is claimed that by mechanical agitation, combined with a special design of pipe circuits and burners, no practical difficulty resulted from separation of the solid particles, but the process never reached the commercial stage.
United Coal Oil Corporation Process Another British colloidal fuel process was developed, dating from 1920, by a company called United Coal Oil Corporation Ltd., of London, with which was prominently associated Sir Sam Fay, formerly chief engineer of the Great Central Railway in Great Britain (now merged in the London and NorthEastern Railway Group). The basic principle, like that of the Coloil process, is the simple mixing of pulverized coal or other solid fuel with petroleum oil or other liquid fuel, combined with the use of a special arrangement of tanks, agitators, pipes, and burners, so as to prevent the solid particles from separating by mechanical means.
French Process A patent was taken out in 1923 by the Soci6t6 Anonyme des PBtroles, Houilles, et DBrives (5) and assigned to Emile B. 0. Bascou. The principle consists in using colloidal fuel, not for combustion at burners or in internal combustion engines, but for injecting into the charge of either low- or high-temperature carbonization retorts or ovens, in order to obtain a more dense solid fuel. For example, the colloidal fuel is made by grinding 100 parts of mazout (heavy petroleum fractions) and 30 parts of pulverized fuel, the temperature being raised to about 60’ C. to give increased fluidity. Then 15 to 20 per cent of the colloidal fuel is sprayed into the charge in the retorts or ovens, and a current of inert gas is passed through a t the same time.
Balcke Process Interesting work has been carried out by the Maschinenbau
A. G. Balcke of Bochum, Germany, in producing a product called Fliesskohle (flowing or liquid coal). Essentially this consists of finely divided coal (generally anthracite or anthracitic) suspended in heavy coal-tar fractions (usually anthracene oil) in the average proportion of 50 to 60 per cent coal and 40 to 50 per cent tar oil by weight. Full details including the date of origin cannot be obtained, but no stabilizer orfixateuris employed, and apparently grinding is carried out in some form of colloid mill. Whether this results in true colloidal grinding or only gives what may be termed a partial colloidal fuel is not known. The main point is that heavy carbonization tar oils are used, and not petroleum products, forming a smooth thick liquid of about 14,500 to 14,800 B. t. u. per pound with 3.5 per cent or less ash. Nothing is known as to how long this fuel will stand without separation of the coal particles by gravity. Performance tests on firing steam boilers are contained in a report issued by
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the Verein zur Ueberwaching der Kraftwirtschaft der Ruhrzechen (Association for the Scientific Control of Boiler Plants in the Ruhr Mines) of Essen, but no commercial development seems to have resulted, in spite of great interest in Germany in every method capable of reducing dependence upon imported petroleum.
doned, consisted of a small amount of paraffin wax. For this purpose the colloidal fuel had to be made by grinding the coal with hot oil to melt the wax so that each solid particle was covered with a film of wax, to delay separation by gravity. However, paraffin proved to be of little value in this connection.
Cunard Process
Processes for Carbonization of Coal-Oil Mixture
A great sensation was caused in Great Britain, starting in June, 1932, by hundreds of articles, notices, and letters (mostly rubbish) in the British press, concerning the production of a secret colloidal fuel by the Cunard Steam Ship Company Ltd. This fuel was first tested on one boiler of the Cunard oil-fired liner Scythia, which left Liverpool for New York June 11, 1932, but no detailed information has ever been made public concerning the results obtained. The matter has long since been forgotten by the daily press but finally the British patent appeared in 1934 (2). The essential claim is for the manufacture of colloidal fuel, without a jixateur or stabilizer, by mixing coal pulverized to pass through a 200-mesh screen, with petroleum oil or tar fractions that contain not less than 5 per cent, and preferably 6 per cent, fixed carbon. The latter is determined by heating a weighed proportion of the oil or tar for 7 minutes over a Bunsen burner flame in a fused-silica crucible under certain standard conditions. For the liquid fuel any product can be used so long as there is 5 or 6 per cent fixed carbon, such as cracked petroleum fuel oil or noncracked straight-run petroleum oil fractions blended with cracked fuel oil, or coaltar fractions containing a high proportion of fixed carbon Generally also bituminous coal is used (for example, 40 parts by weight with 60 parts of the cracked fuel oil), apparently made merely by mixing the pulverized coal with the oil. Whether the claims for stability by these methods can be substantiated is a matter of conjecture, and no large-scale development has yet taken place. Some of the statements made in the patent, however, are vague, including reference to passing the fuel through a "homogenizer." No explanation is given as to what this means, although it obviously refers to some kind of grinding; apparently neither a stabilizer nor a colloid mill is considered necessary.
Wyndham Mobile Fuel This invention (7) attracted considerable attention in the daily papers in South Wales in 1932. At that time the colloidal fuel was made from pulverized fuel, using a stabilizer or fiateur which was a t first kept secret. However, the British patent appeared in 1934, and the colloidal fuel in its present form consists in grinding pulverized coal with liquid fuel, such as petroleum oil or tar fractions, in a mill consisting of a pair of metal rollers almost in contact, driven in opposite directions at different speeds; one roller runs five times quicker than the other. No stabilizer is now employed, and apparently the liquid fuel is in the partially colloidal condition. It is also understood that a commercial-sized mill has been erected. The stabilizer or Jisateur originally used, and then aban-
An entirely new development in the field of colloidal fuel is concerned with various processes for the carbonization of coal-oil mixtures. The basic principle (1) is to heat a mixture, generally 50 to 50, of pulverized coal or other solid and liquid fuel, such as petroleum or coal-tar fractions or the mixed heavier oils from the process, to temperatures varying within a wide range-about 392'to 2000" F. (ZOO" to 1095" C.) -either at atmospheric or higher pressures which may reach 200-300 pounds per square inch. The claim is that by this means a higher yield of valuable light oil is obtained than if the coal and the liquid are heated separately. However, there is great difference of opinion about this claim. In two of these processes (Bluemner and the Carbonol or Woidich) the coal-oil mixture is heated to within a range of about 302' to 806" F. (150" to 430' C.) under pressure conditions up to several hundred pounds per square inch, in such a manner as to drive off only the light oils and leave a heavy thick liquid in which the solid particles are partly carbonized coal. Also the operation is carried out by forcing the coaloil mixture, using a pump in the circuit, between the narrow concentric space of two steel cylinders or pipes which are externally heated. It is claimed that this thick residual liquid is more or less in the true colloidal condition because of the extreme subdivision of the already finely pulverized coal particles obtained as the result of carbonization and partial solution of the bituminous content in the hot oil. Incidentally, the Bluemner process also includes in the circuit a simple form of colloid mill, but this is intended only to finish the subdivision of the partly carbonized particles; no reference to such supplementary treatment is made in the Woidich process. Therefore, according to these claims the manufacture of true colloidal fuels may be combined with low-temperature carbonization and the production of a high yield of light oil in a manner that involves practically no colloidal or other costly grinding.
Literature Cited (1) Brownlie, David, IND.ENGCEIEM.,28,629 (1936). (2) Cunard Steam Ship Co. Ltd., Adams, R. A., Holmes, F. C . V., and Perrin, A. W., British Patent 396,432(Aug. 2,1933). (3) Plauson, Herman, Ibid., 17,729(Aug. 3, 1913). (4) Smith, H. R.,and Munsell, H. M., U. S. Patent 219,181 (Feb. 24,1879). (5) Soc. Anon. des PBtroles, Houilles, et DBrivBs, British Patent 225,505(Nov. 28,1923). (6) Spelman, M. B., U. S. Patent 776,365 (Sept. 28,1904). (7) Wyndham, 9. L., British Patent 410,883 (original application. Deo. 8, 1932; issued May 31,1934). RECEIVED April 3, 1936
