Abstract : This paper introduces the process flow of the alkali recovery combustion section, and completes the design and hardware and software implementation of subsystems such as black liquor conditioning, forced draft and induced draft, boiler water supply, combustion process control and interlock protection. A frequency converter is applied to achieve fine-tuning of the forced draft and induced draft, resulting in significant energy savings and greatly reducing operating costs. Keywords: Alkali recovery; Frequency conversion control; Forced draft and induced draft control; Combustion process control; Interlock protection 0 Introduction The black liquor concentrated in the evaporation section is sent to the direct contact evaporator in the combustion section, where it is further concentrated to 65%-70% using flue gas and waste heat for combustion. In the black liquor solids, 70% is combustible organic matter and 30% is inorganic matter. The purpose of the combustion section is to: recover chemicals for reuse in production; recover the heat generated by the combustion of organic matter as steam for use in subsequent sections; reduce the supplemented sodium sulfate to Na₂S during combustion; and reduce the pollution of waste gas to the environment. The tasks of the automatic control system in the combustion section are: ① to stabilize the boiler outlet steam pressure; ② to ensure the economy of the combustion process; and ③ to maintain a constant negative pressure in the furnace. If the furnace negative pressure is too low, flames are easily ejected from the furnace, affecting environmental hygiene and potentially endangering the safety of equipment and operators. If the negative pressure is too high, the furnace air leakage increases, increasing the power consumption of the induced draft fan and the heat loss carried away by the flue gas. This paper designs an automatic control system for the combustion process based on the technological characteristics and requirements of the alkali recovery combustion section. In this system, both the forced draft and induced draft are controlled by frequency converters, allowing for fine-tuning of the forced draft and induced draft volumes. This ensures stable and continuous combustion of the concentrated black liquor fed into the furnace and the stability of the steam pressure, while also guaranteeing the safe, economical, and efficient operation of the alkali recovery furnace. [b][align=center]For more details, please click: Design and Application of Automatic Control System for Alkali Recovery Combustion Section[/align][/b]