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\"Let Flowers Bloom in the Chimneys\" – The Path to Success in the Industrialization of Coalbed Methane Separation and Liquefaction Technologies, Science Times, August 20, 2007. Authors: Wang Jing, Zheng Qianli. Coalbed methane: The dream of an emerging industry. On the afternoon of August 8th, before heading to Shanxi, a colleague warned me not to expect to see blue skies and white clouds there – this important coal-producing province in China is grayish all 365 days of the year. But upon arriving in Yangquan, Shanxi, in the evening, under the gray sky, the journalists heard a wonderful idea that could not be heard elsewhere: “We want flowers to bloom out of the chimneys!” The person who said this was Liu Ning, chairman of the private enterprise Beijing Zan Cheng International Investment Co., Ltd. Is he talking in his sleep? Can his dream come true? In the following interview, the reporter found that Liu Ning’s dreams were gradually coming true. Liu Ning explained that Beijing Zanhe International Investment Co., Ltd. has primarily focused on operating commercial real estate and developing cultural projects, and has reaped substantial returns in recent years. The company also wishes to invest in projects that bring social benefits and long-term advantages; therefore, since 2004 it has been focusing on the development and application of coalbed methane (commonly known as \"gas\"). It collaborated with a design firm in an attempt to remove oxygen from oxygen-containing coalbed methane using combustion, but the results were not satisfactory yet it did not give up. He said, “When I learned online that the low-temperature distillation technology developed by the Institute of Physical Chemistry of the Chinese Academy of Sciences could be applied to the development and utilization of coalbed methane, I immediately contacted the relevant personnel at that institute.” Soon, I discussed with Zhang Wu, an associate researcher at the institute, how the key low-temperature technologies in his research team could be used as a solution for the low-temperature separation and liquefaction of oxygen-containing coalbed methane. Everyone believes that this technology can enable the simultaneous separation and liquefaction of coalbed methane. We hit it off almost immediately. One party provides the funding, while the other contributes labor, and work on the experiments begins right away. ” Why are they optimistic about the development of oxygen-containing coalbed methane technology? Liu Xinhou, director of the Institute of Physical and Chemical Technology at the Chinese Academy of Sciences, explained that the coalbed methane industry is an emerging industry that has risen worldwide over the past 20 years. Coalbed methane is a type of methane gas that exists in an adsorbed state, is formed and stored in coal seams and their surrounding rocks, with a calorific value of over 8100 kcal per cubic meter ； Similar to the composition of conventional natural gas, coalbed methane is primarily composed of over 95% methane; the remaining 5% consists generally of carbon dioxide or nitrogen. Natural gas is also mainly made up of methane, with the other components varying considerably ； Their uses are the same as well; they are both high-quality energy sources and chemical raw materials that can be transported and used together. The difference between them is that coalbed methane essentially contains no heavy hydrocarbons with two or more carbon atoms, and it is free of inorganic impurities at the time of production; natural gas, on the other hand, generally contains large amounts of heavy hydrocarbons with two or more carbon atoms, and it also contains inorganic impurities at the time of production ； It exists in different forms underground: coalbed methane is primarily present in the coal seams in the form of large molecular clusters adsorbed there, whereas natural gas exists mainly as free gas in sandstones or limestones. Therefore, the development and utilization of coalbed methane can not only prevent coal mine gas accidents and improve safety in coal mining, but also turn a potential hazard into an asset by making effective use of the coalbed methane generated during coal extraction. This can help improve China’s energy structure to some extent, increase the supply of clean gaseous energy, and compensate for the shortcomings in the geographical distribution and supply volume of conventional natural gas in the country. Senior experts have long argued that the 21st century will be an era of significant development for coalbed methane, which is the most practical and reliable alternative to conventional natural gas in China. Furthermore, the development and utilization of coalbed methane can effectively reduce greenhouse gas emissions and improve the atmospheric environment. According to United Nations statistics, China emits 19 billion cubic meters of methane into the atmosphere each year as a result of coal mining, which accounts for about one-third of the country’s total methane emissions from industrial activities; this issue has drawn widespread attention from the international community. The development and utilization of coalbed methane are of great significance for improving the environment. Dreams come true: Low-temperature distillation as a promising approach. According to Zhang Wu, in order to develop and utilize coalbed methane, there are currently four main technologies under research internationally: pressure swing adsorption, membrane separation, combustion deoxygenation, and low-temperature separation. Through years of research, scientists have discovered that the pressure swing adsorption method involves carrying out the adsorption process at high pressures, and then reducing the pressure to cause the adsorbate to desorb, with a portion of the product gas being used as the desorption purge gas. The adsorption process takes place under pressure, while regeneration washing is generally carried out at atmospheric pressure. Pressure swing adsorption has advantages such as low energy consumption, short desorption time, and easy operation. However, its product recovery rate is relatively low, at only 40%–50%. This is because there are voids in the adsorption layer, and the product gas stored in these voids is released and lost during the desorption phase. Additionally, a portion of the product gas must be used for flushing purposes. There is a conflict between product purity and recovery rate; increasing the recovery rate leads to a decrease in purity. Therefore, this method is not economical for the separation of oxygenated coalbed methane. Membrane separation methods have many advantages: no phase change is required, the equipment is simple, it occupies little space, and it can operate continuously. However, the permeability of various gas components through the film varies; the amount of permeation is related to the permeation coefficient of each component, to the area of the permeable membrane, and also to the partial pressure difference of the gas components on either side of the membrane. It results in losses of product gas during separation, and excessive pressure poses safety risks to the mixture, making it unsuitable for use in coal mines. Compared with the first two methods, the combustion method achieves more thorough deoxygenation, allowing the oxygen content to be reduced to below 0.5%. The downside is that the equipment is relatively complex, and it also increases the levels of CO2, CO, SO2, and H2S in the feed gas during the combustion process. Coalbed methane usually contains very little CO2, only 0.2%–0.5%, and some types contain no sulfides at all; CO2 can be removed simultaneously with dehydration using molecular sieves. If combustion-based deoxidation is used, after deoxidization, an additional set of complex alcohol-amine acid-removal equipment for removing CO2 and sulfides is required. This not only increases capital investment and energy consumption but also makes operation more difficult, making it unsuitable for use in coal mines. The principle of the low-temperature separation method is to first condense the gas mixture into a liquid, and then separate the components based on their different evaporation temperatures; it is the most suitable approach for separating oxygen-containing coalbed methane. Firstly, this approach yields the highest purity of the separated product ； Secondly, this approach is relatively safe; the separation process takes place at low pressure and low temperature, so combustion and explosion are unlikely to occur even when in the range where methane can ignite and explode ； Third, this approach is the most economical, as to produce liquefied natural gas (LNG), it is necessary to reduce the temperature of the feed gas to the temperature at which methane liquefies. During this cooling process, low-temperature separation can be carried out to simultaneously separate and remove oxygen and nitrogen, without the need for additional energy consumption for their removal. Other methods either require increased energy consumption or result in the loss of some of the feed gas; some also increase the level of acidic gases, raising the costs associated with gas purification. Moreover, they can only remove oxygen and not nitrogen simultaneously. The low-temperature separation method can simultaneously separate and remove oxygen and nitrogen. Yang Kejian, a researcher at the Institute of Physics and Chemistry, Chinese Academy of Sciences, who has filed an **invention patent**, told reporters that the critical temperature of methane is 190.7 K; in other words, it must be at least -82.45°C and under a pressure of 46.4 bar for it to turn into a liquid. At atmospheric pressure, its liquefaction temperature is -161.5°C. Therefore, the liquefaction of coalbed methane can only be achieved at low temperatures. The refrigeration and liquefaction processes for coalbed methane are similar to those of natural gas, including cascade refrigeration-liquefaction cycles, mixed-refrigerant refrigeration-liquefaction cycles, and refrigeration-liquefaction cycles with expanders. Oxygen-containing coalbed methane usually has very low pressure, only a slight positive pressure; during the liquefaction and separation process, some pure nitrogen can be produced, which is sufficient to compensate for any leaks in the refrigerant used in the nitrogen refrigeration cycle. Incentive policies: Accelerating the development of emerging industries. Once the experiments in the laboratory are completed, Beijing Zanxing International Investment Company and the Institute of Physical and Chemical Technology of the Chinese Academy of Sciences hope to apply these results further in coal mines. They seek third parties across the country to collaborate on scaling up laboratory technologies to pilot scale. However, a few years ago, their laboratory technologies struggled to gain corporate support. This is because few coal mines were familiar with this technology, and at that time **there was no emphasis on energy conservation and emission reduction as there is today. For coal mining enterprises, using this technology is much more difficult than simply digging for coal and selling it, and it also requires training a group of technical personnel. In recent years, as calls for environmental improvement have grown and the central government has paid increased attention to this issue, relevant departments in our country have formulated a series of policies at various levels and from different perspectives to encourage the development of the coalbed methane industry. As stipulated in Article 35 of the Coal Law of the People’s Republic of China, \"**coal mining enterprises are encouraged to develop and utilize coalbed methane\"” ； The Ministry of Finance and the **State Taxation Administration have introduced preferential VAT policies, stipulating that for joint ventures between Chinese and foreign parties engaged in the extraction of onshore coalbed methane, a 5% VAT is levied on a physical basis, with no input tax credits allowed ； For the value-added tax on self-operated onshore coalbed methane extraction, a policy of levy first and then refund is applied; that is, a tax rate of 13% is imposed, with 8 percentage points refunded. In 2007, Beijing Zansheng International Investment Company and the Institute of Physical Chemistry of the Chinese Academy of Sciences finally reached an agreement with Shanxi Yangmei Group to jointly carry out experiments on an industrial facility capable of processing 4,300 cubic meters of coalbed methane per day. Through the joint efforts of all three parties, the Twin Towers experimental facility in Yangquan, Shanxi was completed in July 2007, with technicians carrying out adjustments on each individual piece of equipment. “On the morning of August 4, the first joint debugging was carried out. The nitrogen compressor has started up, and the turbine expander has begun pre-cooling. At around 8 p.m., the temperature of the cryogenic tank and separation tower of the coalbed methane testing equipment dropped below minus 170 degrees Celsius, and oxygen-containing coalbed methane with a methane content of 35% was began to be fed into the tower ； At 10 p.m., the methane column began to accumulate liquid. The analyzer for measuring the concentration of liquid methane in the device showed a gradual increase in methane concentration; when the concentration stabilized at 100%, the testers present cheered... Such a new type of testing device was able to produce qualified liquefied natural gas on the first attempt at testing, and this is the result of the hard work of all the members of the project team, as well as the strong support from local authorities at all levels and the active cooperation of various partner organizations!” Zhang Wu, who remained at the experiment site, described the situation to the reporters with great excitement. This is the industrialized technology for the separation and liquefaction of oxygenated coalbed methane, which was successfully tested in China for the first time on August 8th and attracted widespread media attention. It is reported that the three parties involved in the cooperation will develop larger-scale coalbed methane facilities as quickly as possible. It is foreseeable that in the near future, the cutting-edge technologies of scientists, combined with the insightful investment of businesses, will enable the widespread use in coal mines of technologies for developing and utilizing coalbed methane, which bring significant economic and social benefits. Coal mines will no longer emit greenhouse gases that pollute the atmosphere, and instead, the most imaginative ‘flowers’ will bloom across the earth.