Study on the interchangeability between low calorific value coalbed methane blended with hydrogen, dimethyl ether and natural gas

Abstract

China is rich in coal-bed methane resources, but the utilization rate is very low, especially the low calorific value coal-bed methane, because of its methane concentration cannot meet the requirements of direct utilization, it must be discharged into the atmosphere, resulting in serious energy waste and environmental pollution. In this paper, the interchangeability of hydrogen, dimethyl ether and low calorific value coalbed methane mixtures with natural gas, as well as the influence of blending proportion on the interchangeability were studied by AGA index method and Weaver index method respectively. The results show that: An increasing number of the blending proportion of hydrogen in low calorific value coalbed methane can promote the heat load index and air ejection index to meet the requirements of interchangeability, reduce the tendency of lifting and yellow tipping, increase the tendency of flashback and incomplete combustion; while increasing the blending proportion of methane in low calorific value coalbed methane can also promote the heat load index and air ejection index to meet the requirements of interchangeability, and at the same time, it reduces the tendency of lifting, but increases the tendency of flashback and incomplete combustion, and the possibility of yellow tipping. What’s more, because of the low calorific value of hydrogen, the heat load index is always unable to meet the interchange requirements, the dimethyl ether was introduced into the mixture, and the interchangeability between low calorific value coalbed methane blended with hydrogen, dimethyl ether and natural gas was studied as well. When the blending proportion of hydrogen is controlled at 20%, in order to meet the interchangeability requirements, the blending proportion of dimethyl ether should be controlled to 60%, but some measures should be taken to prevent flashback, such as appropriately reducing the diameter of fire hole.