Stable blend of coal and diesel oil

A stable dispersion of powdered coal in petroleum oil comprising: PA1 5-50% by weight of pulverized coal; PA1 45-90% by weight of diesel oil or Fuel Oil No. 2; and PA1 5-20% by weight of ethanol. This dispersion is particularly useful as a liquid fuel.

BACKGROUND OF THE INVENTION 
Diesel Oil and Fuel Oil No. 2 are distillate oils produced in petroleum 
refineries principally for use as internal combustion engine fuels. These 
oils are low in specific gravity and low in viscosity. Attempts to make 
stable dispersions of pulverized coal in such oils has been accomplished 
only by adding large amounts of water and several glycols such as 
ethyleneglycol, polypropyleneglycol, polyethyleneglycol, etc. Such large 
amounts of water and glycols materially reduce the heating value of the 
composition, and make its commercial value substantially less. 
It is an object of this invention to provide a stable dispersion of coal in 
diesel oil without the necessity of employing large amounts of water and 
glycols. It is another object of this invention to provide a blend of coal 
and diesel oil as an internal combustion engine fuel. It is desirable that 
such a fuel should have low viscosity and stability so that it can be 
pumped and stored at ambient temperature. Still other objects will appear 
from the more detailed description of this invention which follows. 
BRIEF SUMMARY OF THE INVENTION 
This invention provides a stable dispersion of powdered coal in petroleum 
oil comprising 5-50% by weight of pulverized coal, 45-90% by weight of 
diesel oil or Fuel Oil No. 2; and 5-20% by weight of ethanol. A specific 
embodiment of this composition comprises 10-20% by weight of coal, 65-80% 
by weight of diesel oil, 10-20% by weight of ethanol, and 0.1-0.5% by 
weight of a surfactant.

BRIEF DESCRIPTION OF THE DRAWINGS 
The novel features believed to be characteristic of this invention are set 
forth with particularity in the appended claims. The invention itself, 
however, both as to its organization and method of operation, together 
with further objects and advantages thereof, may best be understood by 
reference to the following description taken in connection with the 
accompanying drawing in which: 
FIG. 1 is a graphic illustration of the comparative stabilities of several 
compositions of coal and diesel oil. 
DETAILED DESCRIPTION OF THE INVENTION 
The composition of this invention includes three required components and 
one optional component. 
The first required component is diesel oil or a similar fraction called 
Fuel Oil No. 2. These are distillate oils produced in refining crude 
petroleum oil. The oils intended to be included have a flash point of 
about 110.degree.-170.degree. F., an A.P.I. of about 30-40, and a Saybolt 
Universal Viscosity of about 35-38 at 100.degree. F. These oils are 
intended to be included in the term "diesel oil" as used herein. 
The second component is pulverized coal. The particle size of the coal 
should be about 25-40 microns which is about 350-325 mesh in U.S. Sieve 
Series. The type of coal, anthracite or bituminous, is not important to 
this invention since any type will work. 
The third component is ethanol. Generally, ethanol is available 
commercially as "absolute" which is substantially 99-100% ethanol made 
from any source, e.g. natural gas, catalytic synthesis, biomass 
conversion, etc. or "denatured" which is absolute ethanol treated with a 
toxic substance such as methanol, pyridine, or formaldehyde to make it 
unfit for human consumption. Generally the "denatured" ethanol will also 
contain 1-10% water. 
The optional component is a surfactant which is compatible with the blend 
of diesel oil, coal, and ethanol. The usual types of surfactants, e.g. 
sulfonates, compounds with polyalkylene oxide chains, etc. are useful for 
this purpose. Particularly useful surfactants are TRS 10-80 (Witco 
Chemicals) and Pluronic F108 (BASF-Wyandotte). 
In FIG. 1 several compositions of this invention are compared to a similar 
composition solely of coal and diesel oil, by graphically showing how 
stable the dispersions are with respect to time. The dispersion of coal in 
diesel oil separates with the coal particles settling to about one-half of 
the total original volume in approximately 30 minutes. The addition of 
ethanol to such a dispersion in accordance with this invention increases 
that settling time to about 70 minutes when the ethanol is "absolute" and 
to about 100 minutes when the ethanol is "denatured". When either of the 
surfactants, TRS 10-80 or Pluronic F-108 is present in the dispersion 
employing denatured ethanol, the dispersion remains stable over long 
periods of time i.e. no settling after as much as 6 days of standing. Thus 
remarkable improvement is achieved with these specific compositions. 
The viscosity of the coal-diesel oil-ethanol-surfactant mixture is not 
significantly higher than the viscosity of the diesel oil itself. The 
mixtures exhibit viscosities of about 10-15 cp at ambient temperatures. 
The compositions of this invention in their broadset aspects contain 5-50% 
by weight of pulverized coal, 45-90% by weight of diesel oil or Fuel Oil 
No. 2, and 5-20% by weight of ethanol. If a surfactant is employed, its 
concentration is 0.1-0.5% by weight of the total composition. The 
preferred compositions contain 10-20% by weight of pulverized coal, 65-80% 
by weight of diesel oil, 10-20% by weight of denatured ethanol, and 
0.25-0.5% by weight of TRS 10-80 or Pluronic F-108. 
This invention provides an opportunity to obtain a stable coal-diesel oil 
mixture with a wide range of coal concentrations. The lower concentrations 
of coal have been difficult to produce in the past due to the low specific 
gravity and low viscosity of the diesel oil. Stable mixtures with low coal 
concentrations are especially useful as internal combustion engine fuel. 
Because of the presence of ethanol, which itself is a good fuel, the 
stocks of diesel oil will be extended, providing a commercial advantage 
during this time when petroleum crude oil is increasing in cost. The 
presence of a small amount of water in the denatured alcohol will provide 
better combustion since water-in-oil emulsions are known to enhance 
burning efficiency. The higher concentrations of coal in diesel oil are 
particularly useful as fuels for industrial and utility boilers, and as 
fuel for modified internal combustion engines. 
While the invention has been described with respect to certain specific 
embodiments, it will be appreciated that many modifications and changes 
may be made by those skilled in the art without departing from the spirit 
of the invention. It is intended, therefore, by the appended claims to 
cover all such modifications and changes as fall within the true spirit 
and scope of the invention.