Preventing gas and dust explosions at the working coal face remains one of the major challenges in mines but Age Mining’s Dr Albert Dawood said usual practices of diluting gas in coal mines were not only ineffective but also expensive.
These practices included blowing large quantities of air at speeds of 4-5m per second across the face, using excessive amounts of water and installing expensive dust scrubbers on cutting machines.
Dawood, who has a PhD in pick tip geometry and coal cutting mechanics, said one of the outcomes of using high cutting forces was an increase in the probability of frictional ignition induced by mechanical fiction.
Evidence for this came from mining experience, laboratory research and recent Age Mining trials.
“The cutting system geometry, the rake, clearance and the apex angles of a tungsten carbide tip and the angle of attack for the pick all play a major role in coal dust and gas explosions in underground mines,” Dawood said.
“The optimal tip and cutting drum geometry prevents the build-up of forces, thus reducing the production of dust and the probability of frictional ignition. Additionally, this will have a substantial effect on the machine noise and vibration.”
Dawood said a number of factors affected underground coal dust and gas explosions.
“There is no standard for this important part of the machine to provide guidelines for appropriate selection and testing techniques for the cutting system used in the mines,” he said.
“There is no definition for the blunted pick in the Australian coal mine industry.”
Dawood added that the respirable coal dust exposure standard, established in 1982, did not take into consideration the percentage of quartz content in the coal seam.
“To date, the coal mining industry is using the same exposure standard in spite of the higher production of coal and increased respirable dust generation,” he said.
The development of such standards would provide an important tool for mining industry authorities to ensure the mine working environment was protected during coal mining production, he said.
Dawood noted that in general the coal mining industry did not undertake risk assessments for the product on the cutting head used in underground coal mines.