Owing to its coal content, Colloidal Fuel is heavier, while oil is lighter than water. The character of the composite is such that it may be stored under a water seal and its fire may be quenched with water. The feature is of vast importance since an oil fire cannot be extinguished with water, and hence the rules governing the use of fuel oil are justifiably drastic. Not less than 6.4% of all fires are caused by "Fuel Oil," according to the records of the National Fire Prevention Association.
The Board of Standards and Appeals of New York City adopted a set of rules, which became effective December 1, 1919, to admit liquid fuel into the city. Rule 1 contains the following provision : "The term 'oil used for fuel purposes' under these rules includes any liquid or mobile mixture, substance or compound derived from or including petroleum." The rule is phrased so as to admit Colloidal Fuel, which is a liquid or mobile mixture including petroleum. Colloidal Fuel is also in an exceptionally favorable situation under the Tenta tive Regulations of the National Fire Protection Association, adopted on November 3, 1919. These set the standard in the United States and Canada. "Oil burning equipments are those using only liquids having a flash pdint above 150° F. closed cup tester." The word "liquids" as selected includes the new fuel. Section 1, Paragraph A, "For liquids of 20° Baume and below, tanks may be of concrete," and Section 4, Paragraph 34, states : "Where it is necessary to heat oil in storage tanks in order to handle it, the oil shall not be heated to a temperature higher than 40° F. below the flash point, closed cup." This excludes several varieties of fuel_ oils which require preheating over or close to their flash point in order to flow. This is not the case in the Coloidal Fuel. The Laboratory of the National Board of Fire Underwriters has certified that Grade 13, a typical example of the new fuel, had a flash point of 266° F. and Grade 15 had 273.2° F. Grades 13 and 15 were preheated in practice to about 130° F and 180° F. respectively. The apparent ignition temperature was 779° F. and 788° F. respectively, while neither gave off volatiles at room temperature or at 104° F., nor gave evidence of heating. It is for these reasons that Coloidal Fuel enjoys!, unusual safety features.
The combining of pulverized coal with oil and of tar with oil to make a liquid fuel has in the past had inventive devotees. As, however, petroleum does not ordinarily dissolve coal or tar, the problem was how to overcome the comparatively rapid and uncon trollable separation or settling out or sedimentation of some of the components. The present success was born immediately of the war efforts and was conceived to meet the possible shortage of liquid fuel in the Allied Navies.
The art of suspending as colloids in liquid hydrocarbons certain carbonaceous substances has been long practised. Lubri cants are in use made of less than 1% of Acheson graphite of 2.1
specific gravity reduced so that the size of the particles is about 75µ t.c (within colloidal limits) and suspended in oil by the addi tion of gallotannic acid. Colloids of charcoal and lampblack are known. It is also reported that if coal is reduced under high pres sure or high speed disk-grinding and lengthy trituration in oil, the coal may be brought into the state of stable combustible colloid.
Suspension of high percentages of particles above colloidal sizes is found to be, however, quite without precedent. So also the pepfization of carbonaceous matter in liquid hydrocarbons, producing a stable composite, is new. No prior art exists for producing a stable fuel of oils having carbonaceous matter as natural impurities, like the asphaltum and free carbon found in pressure still oil. In another field, that of rendering stable a compound of two or more unmixable or partly mixable liquid hydrocarbons for fuel needs, any prior art is also of little record. Many liquid hydrocarbons will mix. Others and these of the important burning liquid hydrocarbons have till this time proved obdurate to union—for instance, fuel oil and tar have heretofore refused to mix or have mixed only partially. Emulsions have been made of non-mixing liquid hydrocarbons for use in creosot ing and disinfecting, but no such emulsions much less suspensions concerning unmixing liquid hydrocarbons for use as fuels have heretofore been created.
Up to 40% by weight of pulverized coal can be suspended with 60% by weight of oil, making liquid Colloidal Fuel. Up to 75% of carbon can be incorporated in the mobile pastes. Mobile gels can be made from either the liquids or the pastes. Colloidal Fuel may be a combination of any two or more of the forms.• It will be understood, therefore, that between these States in varying blends and degrees of load, a large number of fuels either liquid or mobile, may be produced. Further, several of the forms have a natural tendency to transform themselves. For instance, liquid Colloidal Fuel stabilized for liquidity during a definite period of say, days or months, tends later to gel from the bottom of the container up. At that stage, the viscosities of the lower or gel stratum will be different from that of the thinner upper stratum. The fuel, nevertheless, has not given up the influence of its treat ment. It remains atoinizable, even though the gel be denser. In both layers and in the intermediate layers also, all the constituents are present and synchronize in burning. The gel thus formed is easily restored to a liquid state by heat or stirring or pumping. Sometimes even a tap upon the wall of the container will restore pristine liquid form. The colloidalizing treatment while arti ficially stabilizing the composite promotes also a gel formation. Conversely, the creation of a gel even in, early stages helps to stabilize the compound since particles with more difficulty precipi tate in a gel.