What values should be assigned to K1 and K2 for the three-parameter control of the waste heat boiler?

Firstly, this scheme is not a typical drum level + feedwater flow cascade system that introduces steam flow; the output of the level controller is sent to the feedwater flow control valve to adjust the feedwater flow, and the level controller is determined by the steam flow and feedwater flow. 1. The setpoint for the level controller is provided by the output of an adder; the expression for this adder is not accurate. Assuming that the output of the adder is Is, it should be Is=K1*IB-K2*IC+I0. In the formula: Is: setpoint of the level controller ； IB: Steam flow transmitter output ； IC: Output of the feedwater flow rate transmitter ； I0: Adder bias, namely the designed value of the drum liquid level. 2. Adder coefficients. The adder coefficients follow the principle of ΣKi=0. Therefore, the signs of K2 and K3 are opposite. 3. The values of K1 and K2 are determined by the false level effect (i.e., the evaporation effect, which is influenced by the boiler’s structure and combustion conditions), and they range roughly between 0.5 and 0.8. 4. Under normal circumstances, K1 and K2 are equal; taking into account boiler feedwater losses, K2 can be slightly greater than K1. 5. Three-weight control process: Stabilization process, where the steam flow rate (mass flow rate) equals the feedwater flow rate (mass flow rate); since the coefficients for each are equal but have opposite signs, they cancel each other out, and the level controller has an I0 setpoint ； Dynamic process: A sudden increase in steam flow (mass flow rate) leads to a sudden rise in the drum liquid level (false level). The increase in the steam flow signal within the adder cancels out the increase in the liquid level signal, thereby overcoming the false level caused by the increased steam flow. As the steam flow increases (while the feedwater flow remains unchanged), the drum level gradually drops, causing the level controller to generate a deviation and increase the feedwater flow. An increase in feedwater pressure leads to an increase in feedwater flow, causing a sudden drop in the drum level (a false level). The increase in the feedwater flow signal inside the adder counteracts the decrease in the level signal, thereby overcoming the false level resulting from the increased feedwater flow. As the feedwater flow rate increases (while the steam flow rate remains unchanged), the drum level rises gradually, causing the level controller to generate a deviation and thus reduce the feedwater flow rate.

Firstly, this scheme is not a typical drum level + feedwater flow cascade system that introduces steam flow; the output of the level controller is sent to the feedwater flow control valve to adjust the feedwater flow, and the level controller is determined by the steam flow and feedwater flow. 1. The setpoint for the level controller is provided by the output of an adder; the expression for this adder is not accurate. Assuming that the output of the adder is Is, it should be Is=K1*IB-K2*IC+I0. In the formula: Is: setpoint of the level controller ； IB: Steam flow transmitter output ； IC: Output of the feedwater flow rate transmitter ； I0: Adder bias, namely the designed value of the drum liquid level. 2. Adder coefficients. The adder coefficients follow the principle of ΣKi=0. Therefore, the signs of K2 and K3 are opposite. 3. The values of K1 and K2 are determined by the false level effect (i.e., the evaporation effect, which is influenced by the boiler’s structure and combustion conditions), and they range roughly between 0.5 and 0.8. 4. Under normal circumstances, K1 and K2 are equal; taking into account boiler feedwater losses, K2 can be slightly greater than K1. 5. Three-weight control process: Stabilization process, where the steam flow rate (mass flow rate) equals the feedwater flow rate (mass flow rate); since the coefficients for each are equal but have opposite signs, they cancel each other out, and the level controller has an I0 setpoint ； Dynamic process: A sudden increase in steam flow (mass flow rate) leads to a sudden rise in the drum liquid level (false level). The increase in the steam flow signal within the adder cancels out the increase in the liquid level signal, thereby overcoming the false level caused by the increased steam flow. As the steam flow increases (while the feedwater flow remains unchanged), the drum level gradually drops, causing the level controller to generate a deviation and increase the feedwater flow. An increase in feedwater pressure leads to an increase in feedwater flow, causing a sudden drop in the drum level (a false level). The increase in the feedwater flow signal inside the adder counteracts the decrease in the level signal, thereby overcoming the false level resulting from the increased feedwater flow. As the feedwater flow rate increases (while the steam flow rate remains unchanged), the drum level rises gradually, causing the level controller to generate a deviation and thus reduce the feedwater flow rate.