Method for obtaining information on quality of combustion of a liquor in a chemical recovery boiler and a method for controlling a chemical recovery boiler

A method for controlling a chemical recovery boiler, the method comprising:

• entering a value of a first input parameter to a computational model configured to determine, based on the value of the first input parameter, a value of the quality of combustion of liquor in the chemical recovery boiler,
• at a first time, running the computational model to obtain a first modelling result,
• measuring, from the chemical recovery boiler, a value indicative of carryover to obtain a measurement result,
• comparing the first modelling result with [a] the measurement result or [b] a result derived from the measurement result, to obtain a primary comparison result based on the value indicative of carryover,
• adjusting the value of the first input parameter based on the primary comparison result to obtain an adjusted value of the first input parameter,
• entering the adjusted value of the first input parameter to the computational model,
• at a second time, running the computational model with the adjusted value of the first input parameter to obtain information on quality of combustion of the liquor in the chemical recovery boiler, and
• controlling, in the chemical recovery boiler, at least one parameter selected from the group consisting of:
• a temperature of black liquor or brown liquor that is fed into the furnace of the chemical recovery boiler, and
• a pressure of the black or brown liquor that is fed into the furnace of the chemical recovery boiler,
• using the information on the quality of combustion of the liquor in the chemical recovery boiler.