The project will form an extension of research conducted by the U.S. Bureau of Mines in the late 1980’s on water-powered scrubbers. The current research will look at how water pressure to these scrubbers can be reduced while still achieving acceptable air movement and dust capture.

In the 1980’s, water-powered scrubbers were tested on a continuous miner to control dust that could be pulled by the conveyor back towards the miner and shuttle car operators.

“A water-powered scrubber was mounted in the conveyor throat of the continuous miner and pulled about 2500 cubic feet per minute (cfm) of air from under the boom of the miner. This air was cleaned at a 90% efficiency rate,” said NIOSH dust researcher Jay Colinet.

“The dust laden water was then dropped onto the coal on the conveyor coming through the miner to wet it additionally, so when it is transferred through to the shuttle car it produced less dust there also.”

The problem researchers found with this method was that it used about 1000 pounds per square inch (psi) of water pressure to move the required amount of air.

“Most mines didn’t have that sort of pressure available and if they did, it was too expensive with the cost of the high pressure pump and hoses. There was also the safety factor of high pressure, if for example, a hose broke.”

“We showed it worked but it was not adopted into practice because of the operational and expense issues.”

Researchers now want to induce similar amounts of air flow at lower water pressures. The proposed way of achieving this is through changing the design of the tubes to the scrubber.

Originally, the water scrubber had five tubes adjacent to one another and each tube was equipped with one high-pressure, spray nozzle to suck air into the tube. At operating pressures of 1000 psi, each tube moved nearly 500 cfm of air, totalling about 2500 cfm for the water-powered scrubber.

The new design will adopt multiple sprays in a single tube with the sprays operating at 250 psi or less.

“Because you have added additional sprays in the same tube you can get energy transfer benefits and move a similar amount of air with less water pressure,” Colinet said.

Initial tests have shown that two or three nozzles in one tube can move a similar quantity of air to that achieved with the high pressure systems.

Further tests will be completed in NIOSH’s dust chamber to evaluate the dust capture efficiency at the lower water pressures. If positive results are achieved from these dust tests, trials will be moved into the longwall dust gallery where a series of tubes will be tested on the shearer. Ultimately, in-mine testing will be conducted.