In discussing the open storage dust problem and possible solutions, one obvious question arises – what are the economics of placing large bulk storage under cover? Several known, practical, workable solutions to the open storage dust problem are described. These include the following which will be dealt with in some detail:
A. Open pile surface crusting agents
B. Open pile surface moistening systems
C. Dust control at the transfer points – (dust suppression and collection)
As might be expected, this artificial surface crust traps the loose, small particles by means of a chemical bonding agent on the face of the pile. By spraying such a bonding agent over the pile surface, a thin solid crust is formed (about 3/8″), which will normally last from several months to a year depending on conditions. As an example of the crust durability. These crusting agents are normally applied by a conventional tank-truck sprayer system which is loaded with the liquid crusting agent, which travels around the perimeter of the piles, applying the crusting agent to the surface.
One of the organic polymer type systems offered is the Johnson-March SP-301 system. The vendor states that it can maintain a crust up to one year’s time. The generalized application recommendation is about one gallon of concentrate per one hundred square feet. (To solve for specific proportions accurately, lab testing of the bulk material by the vendor is offered.) Assuming the above preliminary recommendation for coverage, and based on an F.O.B. factory price of $1.15 to $1.30 per gallon, the material cost is about 1.2¢ per sq.ft. of pile surface.
For more permanent storage of coal of more than a year’s time, & large flat top compacted pile is often formed. Successful coverage of the surface has been accomplished with commercially available “road tar” liquid using conventional highway type tank trucks with horizontal spray bars behind, which operate on the flat top of the pile.
As an alternate to the chemical crusting solution, another successful system involves using a cheaper raw material with more frequent applications. This approach requires wetting the sides of the pile with a water spray. In actual practice, the water seems to form a thin, wet crust on the surface.
As part of this sane installation at the unit-train car dumper a wetting agent is sprayed on the coal discharge through five fixed and one movable spray headers to complete the effective dust control. All of the air inside the doubly enclosed dumper is exhausted to two Peabody scrubbers rated at 55,000 cfm capacity. The conveyor belts are covered and equipped with dust suppression systems at the transfer points. Any wetting agent carried on the coal out to the storage pile obviously assists this previously described pile wetting.
