Design for economical operation, minimum operating labor and minimum maintenance for labor and supplies are virtually inseparable. Each consideration has a vital bearing on the other.
The units involved most ordinarily for any type coal preparation plant will number as a minimum the following:
- Hoppering R.O.M. Coal
- Dewatering or Drying
The feeder should be simple and rugged and of a type which will not spill material. The old flat plate reciprocating feeder is a good one in addition to some of the new vibratory types.
Belt conveyors are probably the most economical from a maintenance standpoint on labor and supplies. Great strides have been made in the past few years with the development of cable and pipe frame belt conveyors for both underground and preparation plant use.
There are of course, situations where a belt conveyor is not applicable. Where it becomes necessary to use a metal apron or flight conveyor, we have a wide range of new metals from which to design a long life, low maintenance conveyor.
Most run of mine coal requires breaking to a given size before preparation. From the labor and supply maintenance view the rotary breaker is perhaps the lowest cost unit on the market. Most rotary breakers are of heavy construction and are designed to withstand a lot of abuse.
After selecting the type of washer required for a given job, one can specify from a great selection of metals, rubber and plastics for long life at those places in the various units where the greatest wear can be expected to occur.
Dewatering or drying coal covers a broad field depending on the degree of dryness required. This function can be simple dewatering by vibrator or reciprocating dewatering screens, centrifuging, or heat drying of coarse or fine coal or both.
After the coal is sized, cleaned, dried, separated or recombined, it must be loaded out either in railroad cars, belts or barges.
A simple plant containing the various units just reviewed can be operated from one central control panel in a majority of the cases. The physical arrangement of the various units should be planned in design to take advantage of gravity wherever possible.