Pearls in Mud
The Korea Research Institute of Chemical Technology announced on April 16 that its resource separation and recovery research team led by Dr. Kim Jeong-hoon developed a hybrid purification technology for membrane separation with which the methane gas given off by landfills can be purified to the point of being usable as a vehicle fuel.
Landfill gas is characterized by its high content of nitrogen and low concentration of methane. As such, even developed countries have failed at high-purity refinement, and used it mainly in post-combustion generation, which is rarely economical.
The research team developed a new purification technology in order to apply it to the low-grade gas mixed with impurities such as carbon dioxide, nitrogen, oxygen, siloxane, hydrogen sulfide, and moisture. With the technique, impurities can be selectively removed from the gas so the resultant material can be employed in CNG vehicle fuel at a methane purity of at least 95 percent (caloric value of 9,000 kcal/m3) and a recovery rate of up to 88 percent.
The purity and recovery rate can be increased when the technique is applied to the methane gas generated from livestock wastewater, food garbage and sewage sludge containing high-concentration methane without nitrogen. In this case, the methane purity and recovery rate can exceed 95 percent and 90 percent each using the separation membrane process alone. The purified material can be used in city gas or vehicle fuel. It will also reduce the greenhouse gas emissions from methane. At present, methane has a global warming index of 21, second on the list.
“The new technique has a lot of advantages over existing absorption and adsorption methods, for example, less expensive plant facility costs, simpler operation and higher eco-friendliness with no wastewater generated,” said the head of the research team, adding, “We are expecting that it will be able to increase its presence in the field of methane gas purification.”