Flocculation and Filtration of Coal
Flotation Concentrates and Tailings
E. W. GIESEKE, Regional Metallurgist
Explosives and Mining Chemicals Department
American Cyanamid Company
Latrobe, Pennsylvania
Coal, our basic fuel, will become more important to national development
as time goes on. The last few years have seen the coal industry struggling for
survival under conditions not conducive to growth.
Coal preparation men are today confronted with problems brought about by
the changing coal markets, changing feed characteristics, and ever increasing
labor and supply costs. Small mines are finding it difficult to exist, and the
larger mines are rapidly changing to fully mechanized and automated operation
to survive. The "size consist" of the coal going to preparation plants has been
getting finer and finer and the problems facing the preparation plant personnel
are growing larger and larger. With new plants, facilities can be provided to
handle this plant feed, but with existing plants the problems are generally not so
simple. Here existing equipment must often be used to perform tasks far beyond
its rated capacity. In addition, various state conservation departments, water
commission boards, and other federal and state agencies are endeavoring to
eliminate stream pollution.
These problems, and many more not mentioned, have been forced on the
preparation engineer for reasons of economy and the public interest. In the matter of stream poUution, a determined effort is being made by the coal industry to
cooperate with the federal, state, and local agencies.
Economists predict it will be necessary to produce 600 to 700 million tons of
coal by 1970. Bear in mind that the greater proportion of this increased tonnage
will have to be processed in existing plants, and-you get an idea as to the problems facing the preparation engineer.
Methods presently in use for preparing fine coal do an acceptable job down
to 48 to 100 mesh. A large percentage of the -48 or -100 mesh fraction of the
tonnage of coal produced now is being sent to settling ponds or sold at a low
figure for reason of quality.
This has caused operators to turn to flotation. Building settling ponds and
impounding fines is a costly and at times impossible method of handling these
sizes. Recently a number of flotation plants have been instaUed to beneficiate
material finer than 48 mesh and these plants have demonstrated that flotation
can be successful and increase the plant realization.
Coal is a low cost commodity and processes for its beneficiation must be low
in cost. Flotation is such a process. It is easily adapted to handling fine coal,
requires little supervision when properly installed, and is economical to operate.
Flotation separates coal from refuse and fine clay. For reagents, several
combinations are used. Some plants use as much as 1.5 to three per cent light oil
while others use a mixture of light oil and a frother. Still other plants use only a
frother and get excellent results.
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