Colloidal Fuel is a composite whose particles are in three states of dispersion—solution, colloid and suspension. They give the characteristics of the 'three conditions. Some of the particles pass through a filter—many do not. Many are visible and meas urable under microscopic inspection. Others are - not. Some show active Brownian movement ; others show slower movement ; others no such motion at all. In considering the changes and stabilization under the treatment of Colloidal Fuel the division of the carbon surfaces must be noted. A cube of coal one centi meter on each side exposes a surface of six square centimeters. Such a cube pulverized so that 85% passes through a 200 mesh screen exposes surfaces of about 1872 square centimeters. The ratio of surface to volume has 1p&n multiplied over 300 times. Such a cube reduced to colloidal size (or .1µ diameter) develops a surface of 60 square meters—a multiplication of one hundred thousand. In Colloidal Fuel, most of the carbon particles are not reduced to colloidal sizes. Many remain much above these limits and above the colloidal borderlaii'd.
For the manufacture of the new fuel, the coal should be reduCed so that about 95% passes through a 100 mesh screen and 85% through a screen. A finer pulverization, while of advantage, is not essential to the process. Coarser particles than those cited above maybe temporarily or partly stabilized, serving sufficiently well certain fuel uses. For the reduction, mechanical, electric or chemical means may be used, but an ordinary coal pulverizing ball or tube mill is most economical.
To carry the load of a high percentage of carbon at normal and working temperatures the base oil employed should be in a certain range of viscosities which the treatment secures. While a lower viscosity does not hinder the creation of Colloidal Fuel, it lessens the load which the liquid hydrocarbon can stably carry. If the product sought is to be a gel or paste, the initial viscosity is of less concern. If the liquid medium provided is of over high viscosity to produce a liquid fuel with the percentage desired of load, a "cut back" can be introduced to lower viscosity. This "cut back" can be of another suitable hydrocarbon. If the me dium provided is of over low viscosity, the process is reversed and the viscosity is raised by introducing a liquid hydrocarbon which adjusts the density. Several other ways, of course, exist for securing the right viscosity, such as, for instance, heat and emulsification.
With the right quality of fixateur or peptizing agent, stability is most readily and satisfactorily secured through its use. Vary
ing the amount introduced makes adjustment simple. In general, the shorter the time, the less the degree of stability desired, the lower the temperature, the less the load and the finer the grinding, so much less fixateur or peptizing agent is needed. If a gel or paste is required, less of the agent is essential than if a liquid is sought. The introduction of more agent than is demanded 'for 'liquid stabilizing begets a tendency to early, complete and con sistent gellification. The amount of the agent therefore intro duced, must be a matter of knowledge from experimentation. It must be such a quantity and quality as will secure adequate stability at the temperature of storage and preheater. In practice, virtually, the maximum of a good quality of fixateur which has ever been employed to secure a stable liquid is an amount which adds 2% by weight of the essential substances to the fuel. The minimum producing an appreciable result is about .1%. Ordi narily between A% to 172% is used. Higher percentages of cer tain peptizers or stabilizers are required than of others: If gaseous means are used these percentages do not hold. Between these outer limits the quality of fixateur and peptizer for par ticular products has been very accurately determined by experi ence and the effects recorded of different percentages blended with various ratios and kinds of components of the Colloidal Fuel.
Colloidal Fuel carrying up to 40 percent of carbon is prac tically equivalent to the class of heavy oil in relation to handling to the preheater stage. At 68° F. its viscosity will hardly be below 65° Engler, except when only the carbon particles found in pressure still oil are stabilized. The viscosity ordinary will range between 160° and 350° Engler, depending upon the com ponents and other factors. At higher temperatures that obtain in the preheater, it behaves as do the lighter class of oils. Col loidal Fuel is really only a laden, stabilized oil and the problem of burning both is largely the same. Viscosity is under perfect control. The installations for burning oil, burn liquid Colloidal Fuel without any material change. Some slight modification is required for burning the pastes and gels since there must be suffi cient pressure to carry the fuel to the atomizer. / If the gel is broken up by pumping or if it becomes liquid in the preheater, pressure for conveying it alone is needed. Existing mechanical or steam, or air oil burners are adapted to Colloidal Fuel. Several varieties have been used.