Chinese technologists have developed a new industrial device to purify methane from the coal-bed gas, finding a solution to reduce a big chunk of China's greenhouse gas emission.

    Yang Kejian, a veteran technologist at the Technical Institute of Physics and Chemistry under the Chinese Academy of Sciences (CAS), led his research team to develop the device, which is used for sucking coal-bed gas, a combination of methane, oxygen and nitrogen, and producing highly-purified methane, a clean energy equivalent to natural gas.

    As key steps of their experiment, Yang and his team installed two sets of such device on two different coal pits in Yangquan and Jincheng, both big coal fields in north China's Shanxi Province.

    With the device like a huge refrigerator, the technologists freeze the combined coal-bed gas under 200 degrees Celsius below zero, and separate methane, oxygen and nitrogen from each other thanks to their different evaporation points, Yang said in an interview with Xinhua on Saturday.

    "The technology not only produces commercialized methane, but also help reduce greenhouse effect resulting from randomly emitting methane to the air," Yang said.

    The usually combined coal-bed gas, which is highly explosive if aggregating to a certain density, also poses deadly threat to coalminers.

    Coal mine explosions were often triggered by the gas. No coal mining companies have found ways better than pumping the coal-bed gas out of pits and letting it melt in the air.

    Statistics show that China has the world's biggest reserve of coal-bed gas, three times that of the United States. But unlike Americans, most of the precious coal-bed gas has not been collected or utilized.

    The Yangquan coal mines, one of the country's largest 13 coal production bases, accounted for one fifth of the total coal-bed gas emission. Therefore, Yang and his team negotiated with Yangquan Coal Company for a test on the experimental device.

    All the three major components of the coal-bed gas could be effectively used, said Zhang Wu, chief architect and leading engineer for the experimental project.

    "We got 99 percent purified methane which could be directly packaged for consumers, oxygen is okay for certain purposes or just being released into the air, and nitrogen is used for adding coolant," Zhang said.

    After comparing other techniques in separating methane from the mingled gas, Zhang said he feels confident of the low-temperature fractionation method they are employing. With computerized analyses, the research team built more than 10 models for the best possible choice. They have made every effort to ensure safety of the process while the chilled gas was heated again in the 20 meter-high metal-made fractionating tower, which is still prone to trigger explosion.

    A Beijing-based venture capital company financed the green-energy project. The private company invested roughly 10 million yuan (1.32 million U.S. dollars) in the two experimental devices.

    All participating parties into the test, including the CAS institute, the coal companies, and the venture capital company, are discussing to build a plant manufacturing the methane product. The proposed joint company is aimed at churning out 20,000 tons of liquidized methane annually.

    Zhang estimated profits of the business will be high. He calculated that the cost for producing every cubic meter of purified methane will be 1.5 yuan and its commercial price in big cities is usually higher than two yuan.