Proceedings of the Coal Mine Dust Conference, Morgantown, West Virginia, October 8-10, 1984. Peng, SS, ed., Morgantown, WV: West Virginia University, 1984 Oct; :101-109
These early field tests indicate that the use of foam through the longwall shearer drums offers significant potential for respirable dust suppression at the face. The two tests reported were performed under widely varying conditions. In both cases there were significant reductions in the dust levels at the operator position. In Mine No.1, the total dust concentrations decreased 49 percent near the operator, compared to 10 percent in the similar location in Mine No.2, but the coal production in the second mine was 30 percent higher. The second mine also had a significant contribution of dust from roof support movements, and did not have very effective foam delivery from the drum nozzles. It may be concluded from these tests that the success of foam production at the face depends on the size of the plumbing circuit in the shearer. A minimum of 3/4-in.-dia (19-rnrn) lines is desirable, to deliver an adequate amount of foam through the drums. Also, even spaced foam nozzles along the scrolls of the drum are preferable to pick face foaming. The fewer outlets permit a high discharge pressure and reduce the likelihood of clogged nozzles. The cost of the chemical foaming agent used at these mines was $12.15 per gallon. In the first mine, with an average coal production of 1,200 tons/shift, and a 400:1 water-to-chemical ratio, the cost per ton was about $0.25. In the second mine, with a water-to-chemical ratio of 180:1 and coal production of 1,900 tons/ shift, the cost computed to $0.71/ton. In both cases an effective working time of 250 min/shift is assumed. (Of course, in this mine the cost drops to $0.45/ton for the shift that produce 3,000 tons.) In the second mine, however, even if a part of the increased productivity is attributed to the foam, the cost of $0.71/ton may well be tolerated. Further, in both mines the water consumption was significantly reduced -- from 80 gpm to 40 gpm in Mine No.1, and from 110 gpm to 80 gpm in Mine No.2. This resulted in a drier coal and hence a higher heating value. Besides, it is safe to state that the chemical agent costs will drop markedly when it is produced and sold in bulk. The cost given above was that paid for the relatively small quantities used during these two tests. The mine operators as well as face crews in both mines were enthusiastic about the use of the foam. The workers in the first mine noticed occasional skin irritation, but there were no such complaints at the second mine. However, alternative foams that do not have such effect, will be investigated in future tests. It may be surmised that although these two tests cannot be claimed to be conclusive, further testing of this system, to optimize the various parameters, is justified. The scheme may not be a panacea for the coal industry's dust problems, but it certainly offers considerable promise.
Proceedings of the Coal Mine Dust Conference, Morgantown, West Virginia, October 8-10, 1984