Abstract : To improve the control level and combustion efficiency of the original boiler, the control system was upgraded. The upgraded system adopts an upper and lower computer control mode, connected via industrial Ethernet. The upper computer is a DELL PC, and the lower computer is a GE 90-30 controller. The forced draft, induced draft, and coal feed are controlled by frequency converters. The three variables—drum water level, steam flow, and feedwater—form a control branch with drum water level as the main control loop. The combustion control system is divided into three control systems: forced draft control, steam pressure control, and furnace negative pressure control. After the upgrade, annual savings of 499,800 yuan were achieved. Keywords: Chain grate boiler; combustion efficiency; drum water level; forced draft; steam pressure; furnace negative pressure; control system; frequency converter. Our company currently has 8 boilers, including 6 chain grate boilers and 2 circulating fluidized bed boilers. In the past, the control systems of chain grate boilers mostly used conventional instrument control, and the control of air volume, coal feed, etc., was done manually. The disadvantages of this control method are high labor intensity for workers and low boiler combustion efficiency. Therefore, in 2002, our company upgraded the control system of the No. 6 20T/h chain grate boiler. [b]1 Problems with the original control system[/b] (1) High labor intensity for employees. Due to the use of conventional instrument control, a large amount of data cannot be recorded in real time. The operators must perform a lot of manual recording and constantly manually change the air volume damper and the speed of the grate. All of these greatly increase the labor intensity of the operators. (2) The boiler cannot burn economically. The original control system relies entirely on the experience of the operators to manually adjust the air volume and coal feed rate, and cannot change the air volume and coal feed rate in a timely manner according to the changes in steam flow and pressure. (3) Waste of electricity. The air volume of the boiler fan is adjusted by changing the size of the damper. In this way, when the fan is under low load and the flow rate is low, there is a waste of electricity. Many years of experience have told us that the method of using throttling adjustment not only consumes a lot of electricity, but is also inconvenient to operate. [b][align=center]For details, please click: Energy-saving transformation of chain grate boiler control system[/align][/b]