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Environmental protection scientific and technological achievements in coal-to-oil production by Ningxia Coal Industry Group have passed evaluation / Author/Source: Coal Chemical Engineering Journal, Date: 2021-08-08, Clicks: 16. Recently, the project titled “Research on Intelligent Control and Key Domestic Technologies for Energy Conservation and Emission Reduction in Ultra-large Power Islands and Multi-level Steam Pipeline Networks”, submitted by Ningxia Coal Industry Group’s Coal-to-Oil Company, passed the evaluation of scientific and technological achievements at the autonomous region level. Over the course of 4 years of hard work, innovation, and research and development, the project achieved significant breakthroughs in areas such as the optimization of control systems for \"multi-furnace, multi-machine, multi-grade steam networks\", the localization of ultra-high temperature temperature reduction and pressure reduction devices, as well as innovative techniques for incorporating low-calorific value flare gas generated in coal indirect liquefaction processes. Major advancements were also made in terms of key equipment and energy-saving measures, resulting in the development of advanced, safe, green, intelligent, and economical power units for coal indirect liquefaction. The evaluation committee believes that this project has reached an internationally advanced level in terms of the optimization control technologies for multiple furnaces, machines, and grades, as well as for the recovery and blending of fuel gases with complex and variable characteristics and low-quality, unstable flow rates. As the requirements for environmental protection parameters of flue gas at the boiler outlet become increasingly stringent, in order to meet the standards for emissions related to desulfurization and denitrification during normal production, it is necessary to optimize the existing desulfurization and denitrification processes, as well as to refine the control strategies for these processes based on the current equipment. As the steam generation, heat production, and power generation units for upstream processes in large-scale coal indirect liquefaction projects, the steady operation of the power station over long periods provides high-quality steam for the downstream stages, thereby being essential for the plant to operate at full capacity efficiently. The project developed a control and optimization system for large-scale coal chemical power plants featuring \"multiple boilers, multiple machines, and multi-level steam pipelines.\" It introduced advanced control algorithms suitable for processes such as boiler combustion, desulfurization and denitrification, as well as steam temperature and pressure reduction in multi-level main piping systems, thereby addressing control challenges related to multivariable coupling, large time lags, and time-varying conditions in complex operating scenarios. The mathematical model linking the environmental protection control parameters of the boiler fleet to the indicators of complex operating conditions was established. By integrating this mathematical model with traditional PID control principles, the problem of the inability of the boiler desulfurization and denitrification control systems to function properly under different coal qualities and complex operating conditions was resolved. This improved the accuracy of control over environmental protection parameters (with average fluctuations of less than 5 mg/m3 for SO2 and NOx), while also reducing ammonia consumption in the system (saving 4,500 tons of liquid ammonia per year). The key technologies for reliable sealing and structural integrity of high-performance special control valves were studied, enabling the localization of a process that combines a 16-stage integrated labyrinth block with a separate integral pressure-reducing nozzle. This approach addressed issues such as internal component erosion and excessive vibration in steam valves used in the coal chemical industry under high pressure differences. The process technology for integrating the low calorific value fuel gas generated as a by-product of large-scale coal indirect liquefaction projects into boilers for co-firing was explored. The combustion strategy for matching fuel gas with complex dynamic composition to coal was optimized, and the bottleneck related to finding the optimal ratio of fuels with different caloric values was overcome. As a result, energy-saving and environmental protection goals were achieved: 486,040 tons of coal were saved annually, and the amount of solid ash produced was reduced by 122,480 tons per year. At present, the 10 desulfurization systems and 20 denitration systems in the coal-to-oil power plants can achieve long-term, stable operation with the automatic control of ammonia supply valves. Through exploration and research on the optimization of the control circuits for the desulfurization and denitrification systems in boiler installations, and by integrating APC optimization techniques with advanced control algorithms, it has been possible to ensure that the environmental parameters related to these systems meet the required standards. This approach also helps to reduce the overall ammonia consumption of the systems, providing a valuable reference for the application of such systems in other projects and offering significant guidance and insights.