Statistical Analysis and Technical Comparative Study of Coal-to-Natural Gas Projects

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Statistics and Technical Comparative Analysis of Coal-to-Natural Gas Projects Author/Source: Huahua Network – Coal Chemical Industry (Author: Wang Shoujian, Chief Engineer of China National Chemical Engineering Corporation) Date: 2018-03-16 Clicks: 14 As of June 2017, there were 4 coal-to-natural gas projects in operation in China, including the first phase of the Datang Keqi coal-to-natural gas project with an annual production capacity of 1.33 billion cubic meters, the first phase of the Qinghua Yili coal-to-natural gas project with an annual capacity of 1.375 billion cubic meters, the first phase of the HuiNeng Ordos coal-to-natural gas project with an annual capacity of 400 million cubic meters, and the ZheNeng Xintian Yili coal-to-natural gas pilot project with an annual capacity of 2 billion cubic meters. Among them, except that the product of the HuiNeng project is liquefied natural gas transported by tankers, the other 3 projects involve gaseous natural gas products that are sent through long-distance pipelines, as shown in Table 1. http://img.yf116.cn/image/img/20180316/1635365973643.jpg http://img.yf116.cn/image/img/20180316/1636265978652.jpg Based on the operation status of these projects that are already in use, the Datang Keqi and Qinghua Yili projects both have the capability to operate at high loads; however, due to limitations in the pipeline networks and at the consumption end, the actual load is only around half of that capacity. HuiNeng Engineering operates at full capacity, with LNG products being sold to regions in North China, Central China, East China, and the areas surrounding Inner Mongolia. The Zhejiang Energy Xintian project came online in April 2017 and is currently still in the production commissioning phase. This project is also constrained by the capacity and receiving price of the gas pipeline network, which has a significant impact on the production load. There are a total of 5 new coal-to-natural gas projects under the \"13th Five-Year Plan\" for the demonstration of advanced coal processing industries. As of June 2017, the Suxin New Energy Zhundong coal-to-natural gas project and the Beikong Ordos coal-to-natural gas project had been approved. The Xinjiang Ili coal-to-natural gas projects include those operated by Zhejiang Energy Xintian with a capacity of 2 billion cubic meters per year, as well as those operated by China Power Investment with the same capacity; the plant operated by Zhejiang Energy Xintian is already in operation, while the project managed by China Power Investment is still in the planning stage. The coal-to-natural gas project in Datong, Shanxi, and the coal-to-natural gas project in Huainan, Anhui, are still under planning. Affected by the decline in domestic natural gas prices, the progress of the aforementioned projects has been slow, with some projects already on hold. “During the 12th Five-Year Plan period, many coal-to-natural gas projects were approved by the National Development and Reform Commission and the Energy Bureau for preliminary work, but with the continuous decline in domestic natural gas prices, most of these projects have come to a standstill. Overall, affected by the decline in domestic natural gas prices, domestic coal-to-natural gas projects are facing severe challenges. The status of the proposed coal-to-natural gas projects is shown in Table 2. http://img.yf116.cn/image/img/20180316/1638235990376.jpg http://img.yf116.cn/image/img/20180316/1638575993733.jpg http://img.yf116.cn/image/img/20180316/1639265996693.jpg Selection of key technologies for coal-to-natural gas projects. Coal-to-natural gas is a process in which coal is used as raw material; through gasification, shift reaction, and purification steps, the syngas is brought to the right hydrogen-to-carbon ratio for methane synthesis, and then methaneation is used to produce natural gas. Typical coal-to-natural gas plants include process units such as air separation, coal gasification, shift reaction, desulfurization and decarbonization, refrigeration, methanation, compression at the initial station, natural gas drying, sulfur recovery, as well as coal gas and water separation and phenol and ammonia recovery (when fixed-bed pressurized gasification technology is used), along with the corresponding utility and auxiliary systems. The typical coal-to-natural gas process flow is shown in Figures 1 to 6. http://img.yf116.cn/image/img/20180316/1640346003459.jpg http://img.yf116.cn/image/img/20180316/164176006717.jpg http://img.yf116.cn/image/img/20180316/1641376009759.jpg http://img.yf116.cn/image/img/20180316/164286012858.jpg To date, four coal-to-natural gas plants have been put into operation in China. The process flows and technical choices for three of these plants—Datang Keqi, Qinghua Yili, and Zhejiang Energy Xintian—are similar: all use Saiding’s coal pulverization fixed-bed dry ash removal pressurized gasification method; the shift reaction is carried out using sulfur-resistant shift catalysts; purification is achieved through low-temperature methanol washing; sulfur recovery is accomplished via the Claus process; and methanation is carried out using imported technologies, either American David Technology or Danish Topsoe Technology. The Inner Mongolia HuiNeng coal-to-natural gas plant utilizes the multi-feed slurry gasification technology developed by the Northwest Research Institute; all conversion processes are sulfur-resistant types, purification is carried out using low-temperature methanol washing, and sulfur recovery is achieved through the Claus process as well as the Topsoe methanization technology from Denmark. The selection of key technologies for typical coal-to-natural gas projects is shown in Table 3. http://img.yf116.cn/image/img/20180316/1643146019420.jpg http://img.yf116.cn/image/img/20180316/1643536023373.jpg http://img.yf116.cn/image/img/20180316/1644396027970.jpg http://img.yf116.cn/image/img/20180316/164555603553.jpg http://img.yf116.cn/image/img/20180316/1646386039865.jpg http://img.yf116.cn/image/img/20180316/1647126043217.jpg http://img.yf116.cn/image/img/20180316/1647426046264.jpg Fixed-bed coal gasification under pressure is used; the gasifier can produce methane directly, which accounts for 12%-14% (by volume) of the total raw gas – that’s nearly 50% of the final natural gas product. In other words, almost 50% of the final product is generated directly by the gasifier, and it only needs to be purified and separated before it can be used as the final product. Therefore, fixed-bed coal crushing pressurized gasification has inherent advantages for coal-to-natural gas production. However, fixed-bed coal pulverization pressurized gasification operates at low temperatures, resulting in an incomplete gasification process that produces products such as tar, middle oil, and crude phenol; therefore, additional devices for gas-water separation and phenol-ammonia recovery are required for these substances to be extracted. Domestic coal-to-natural gas projects utilize domestic proprietary technologies for gas-water separation and phenol-amine recovery. Due to the significant difference between the coal quality specified in the design and the actual coal quality used in operation for the Datang Keqi project, after the project was put into operation, the capacity of the phenol-amine recovery unit was insufficient to handle the changes in processing volume and composition resulting from these variations in coal quality; accordingly, improvements were made later on. Furthermore, the wastewater treatment for the fixed-bed coal pulverization pressurized gasification process is quite challenging; it involves a high level of impurities, a lengthy treatment process, and requires greater investment in environmental protection measures. Fixed-bed coal crushing pressurized gasification uses lump coal as raw material; the large amount of pulverized coal generated in coal mines has no proper use, and can only be stored or sold at low prices. This imbalance between lump coal and pulverized coal poses certain challenges for coal-to-gas plants. Therefore, drawing on these experiences, later projects mostly adopted the \"dual gasification\" technology approach that combines fixed-bed coal gasification under pressure with fluidized-bed coal gasification under pressure. All the coal-to-gas projects that have been put into operation use imported methanization technology, while domestically developed methanization technology has not been applied due to delays in its industrialization process. The \"13th Five-Year Plan for Demonstration of Advanced Coal Processing Upgrades\" requires that all new coal-to-natural gas projects established during the \"13th Five-Year Plan\" period must carry out demonstrations of autonomous methanation technologies. Accordingly, the well-known domestic methanization technologies include: the methanization technology developed by the Dalian Institute of Chemical Physics, the methanization technology from the Datang Economic and Technical Research Institute, and the methanization technology from the Southwest Research Institute, among others.