The continuous and stable operation of the gasifier at Datang Keqi Coal-to-Natural Gas Company has exceeded 255 days!
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As of May 18, the 228# gasifier at Datang Keqi Coal-to-Natural Gas Company, China’s first coal-to-gas demonstration project, has been in continuous operation for 255 days, running steadily. The company’s 16 gasification units operate on a schedule of \"14 units in operation, 1 unit in standby, and 1 unit under maintenance,\" allowing continuous operation. Three of these gasification units have been in continuous operation for more than 200 days, exceeding last year’s record of 183 days and setting the best performance record for such gasification units in the industry. Overcoming challenges to ensure continuous operation: The gas chemical processing unit is the key component in coal chemical processes; ensuring its stable operation is essential for achieving full-capacity operation. However, for a considerable period of time, the gasifier was a persistent problem that hindered the stable operation of the facility. In the early stages of operation, corrosion of the inner wall jacket of the furnace caused by lignite components once raised doubts about the safety of operating the coal pulverization pressurized gasification furnace. As a **pilot project, there was very little experience to draw on. The company began by analyzing the corrosion mechanisms within the gasifier’s jacket, conducted thorough research, and compared various methods before ultimately adopting a nickel-based surfacing technique to address the corrosion issue on the inner walls of the gasifier, thereby ensuring that its operational requirements could be met. Experience has shown that the maximum continuous operating time for a single furnace can exceed 240 days, and no corrosion has occurred in the jacket since self-repair operation was implemented.
Special studies on eliminating potential hazards: Over time, waste heat boilers that had accumulated more than 10,000 hours of operation began to experience tube bundle leaks, with the frequency of such leaks increasing over time. To address this issue, the company conducted specialized research on leaks in the waste heat boiler tubes, and implemented measures in areas such as the internal structure of the waste heat boiler, the support for the coarse coal gas pipelines, and the water temperature in the low-pressure boiler. By collecting, comparing, and analyzing various data such as process operation parameters, operating methods, equipment structure, and raw materials, they ultimately linked issues such as waste boiler tube bundle leakage to the method of adding chemicals to boiler water and the quality of wastewater discharged from the boiler. They then proposed a solution titled \"Eliminating the impact of boiler water pH on equipment by changing the method of adding chemicals to boiler water.\" After the implementation of this solution, the previous situation of an average of 40 leaks per year was completely resolved; currently, the waste heat boiler tubes have remained leak-free for over 500 consecutive days, thereby eliminating yet another major safety hazard that had been hindering the achievement of required performance standards. Through extensive testing and efforts, the average service life of the upper and lower valves for coal locking has reached 340 days, while that of the upper and lower valves for ash locking is 300 days – both figures represent leading levels in China. This helps ensure the safe, stable, long-term, and high-load operation of the equipment.
In-depth efforts to overcome technical challenges: To ensure a steady supply of raw coal, Datang Keqi Coal-to-Natural Gas Company continues to expand its sources of coal procurement; yet different types of coal pose new challenges for the gasification furnaces. The company conducts in-depth analysis of the impact of differences in the parameters of various coal types on gasification furnaces, formulates different blending strategies based on the type of coal and laboratory test data, and optimizes the combined operation mode of the vibrating screens in a rational manner. The focus of gasifier operation lies in prediction and anticipation; meanwhile, by optimizing operational parameters, the precision of production processes and the standardization of on-site operations are improved. This has enabled seamless transition between different co-firing methods, thereby reaching the boundary conditions for mass production using coal. To further improve the economic efficiency and stability of the gasification furnace’s operation, the company adopted lean production management as a strategy, and subsequently carried out various technical improvements such as optimizing the steam-to-oxygen ratio in the gasification furnace, increasing pressure, and controlling the residual carbon content in the ash. After several years of experimentation, the oxygen-to-gas ratio was reduced from 7.0 kilograms per standard cubic meter to 6.0 kilograms per standard cubic meter, thereby decreasing the amount of wastewater generated. The increase in the pressure of the gasifier led to a 3% increase in the yield of by-products, while the residual carbon content in the ash decreased from 7% as designed to 3.5%. These technical advancements have significantly improved the economic viability of the project. From January to April this year, Datang Coal-to-Gas achieved a profit of 22.14 million yuan. In April, the average daily output of natural gas was 4.03 million standard cubic meters, exceeding the designed daily output of 4 million standard cubic meters.