Increasing permeability of coal seams using the phase energy of liquid carbon dioxide

Carbon dioxide (CO2) is a major greenhouse gas, and it is also an energy source that can be utilized. This paper describes a new technology designed to increase the permeability of coal seams using the phase energy of CO2. The technology, named as liquid carbon dioxide phase change fracturing technology, is classified as physical blasting. The kernel of this technology is the blasting system, which consists of release tube containing release holes, cutting plate, liquid storage tube containing heating pipe, guide tube and detonator following the order from the top to the bottom. By starting the detonator, special chemicals in the heating pipe begin to react and a lot of heats then are released instantly to heat the liquid carbon dioxide in liquid storage tube. This process brought about the phase change of carbon dioxide and then caused the dramatically expansion of the volume of carbon dioxide. When the pressure of carbon dioxide in the liquid storage tube exceeds the strength of the cutting plate, the cutting plate is damaged and high pressure carbon dioxide enters the release tube and acts on the coal body. The sphere of influence of this technology in coal seams was studied by the numerical study. Then, a large-scale industrial experiment using the technology was conducted in an underground coal mine in China based on the modeling results. Application of this technology could not only improve the efficiency of coal seam gas extraction but could also turn carbon dioxide into energy to improve energy efficiency. (C) 2017 Elsevier Ltd. All rights reserved.