Methane contents and release rates measured using the methane rating system

摘要

Methane Rating was developed from a need in South Africa to measure coal seam gas contents, as well as emission rates into the cutting zone for mechanical miners. These are then combined and compared to the average and normal conditions to provide a risk analysis tool for continuous miner operations.The last two years have seen widespread acceptance of Methane Rating as a practical and simple means of identifying seam gas contents and emission rates during mining, and of rating the changing methane conditions. The system uses proven direct methods of methane measurement to quantity the contents and emissions, combined with an innovative rating system. Each new result is compared with the expected average or normal conditions to determine its Methane Rating between 1 and 5.The present South African national database of over 300 individual samples shows methane contents can normally be expected between 0,14 m~3/t and 1,6 m~3/t, with emission rates during coal cutting of 20 ?/t/min to 82 ?/t/min.The highest risk rated mines are presently in the Secunda and eastern Witbank areas, with the lowest risk rated mines to the west of Witbank.