Abstract: A method for controlling carryover in a chemical recovery boiler. The method comprises feeding black or brown liquor to a furnace of the chemical recovery boiler through an injection gun to burn the black or brown liquor. The chemical recovery boiler comprises a bullnose, which narrows the furnace, and a first superheater, of which at least a part is arranged at a higher vertical level than the bullnose. The method comprises measuring information indicative of a spatial temperature distribution on a cross section of the furnace, wherein the cross section is above the injection gun and below the first superheater; determining primary information indicative of carryover using the information indicative of the spatial temperature distribution on the cross section of the furnace; and controlling a temperature of the black or brown liquor that is fed to the furnace using the primary information. In addition, a system for performing the method.

Abstract: A method for managing and controlling nitrogen emission from a cyclic liquor flow system in a pulp mill (1), the pulp mill (1) comprising a recovery system (20) for recovering heat and chemicals from a pulping process (30), the recovery system (20) comprising a recovery boiler (8) and a nitrogen oxide scrubber (15), the nitrogen oxide scrubber (15) being arranged to remove nitrogen oxide from flue gas (16) from the recovery boiler (8), the method comprising the steps of: —exposing flue gas (16) from the recovery oiler (8) to an oxidizing agent, thereby oxidising nitrogen oxide in the flue gas (16) to higher nitrogen oxides; —contacting the flue gas (16) with an alkaline aqueous scrubber liquid (17) in the nitrogen oxide scrubber (15), thereby absorbing the nitrogen oxides in the scrubber liquid (17) and producing a nitrogen containing scrubber liquid (17); —introducing all or a part of the nitrogen containing scrubber liquid (17) into the cyclic liquor flow system.

Abstract: A method for controlling a chemical recovery boiler. The method includes measuring concentrations of sodium carbonate, sodium sulfide, and sodium sulfate from green liquor of the chemical recovery boiler, determining a target temperature for smelt, imaging at least an area of a char bed of the chemical recovery boiler, the area being close to a smelt spout, to obtain an image of the area, determining a measured temperature of the char bed using the image of the area. The method further includes determining that the measured temperature of the char bed is less than the target temperature for smelt, and controlling the chemical recovery boiler such that the temperature of the char bed increases. A chemical recovery boiler for the same.

Abstract: A method for obtaining information on quality of combustion of a liquor in a chemical recovery boiler. The method comprises 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 the liquor in the chemical recovery boiler, and at a first time, running the computational model to obtain a first modelling result. The method comprises 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; and adjusting the value of the first input parameter based on the primary comparison result to obtain an adjusted value of the first input parameter.

Abstract: A method for controlling carryover in a chemical recovery boiler. The method comprises feeding black or brown liquor to a furnace of the chemical recovery boiler through an injection gun to burn the black or brown liquor. The chemical recovery boiler comprises a bullnose, which narrows the furnace, and a first superheater, of which at least a part is arranged at a higher vertical level than the bullnose. The method comprises measuring information indicative of a spatial temperature distribution on a cross section of the furnace, wherein the cross section is above the injection gun and below the first superheater; determining primary information indicative of carryover using the information indicative of the spatial temperature distribution on the cross section of the furnace; and controlling a temperature of the black or brown liquor that is fed to the furnace using the primary information. In addition, a system for performing the method.

Abstract: Disclosed is a system for producing electricity, the system comprising a chemical recovery boiler adapted to supply superheated steam to a steam turbine driving a generator, the chemical recovery boiler comprising a first flue discharge channel with a first heat exchanger arrangement; and a lime kiln comprising a second flue discharge channel with a second heat exchanger arrangement; and a circulation for heat transfer medium between the said heat exchanger arrangements. Also disclosed is a method for producing electricity, wherein said heat transfer medium is circulated between said heat exchanger arrangements such that thermal energy may be transferred from the flue gases in the first flue charge channel and/or the second flue discharge channel into the feed water of the chemical recovery boiler and/or into a heat-consuming process.

Abstract: Disclosed is a system for producing electricity, the system comprising a chemical recovery boiler adapted to supply superheated steam to a steam turbine driving a generator, the chemical recovery boiler comprising a first flue discharge channel with a first heat exchanger arrangement; and a lime kiln comprising a second flue discharge channel with a second heat exchanger arrangement; and a circulation for heat transfer medium between the said heat exchanger arrangements. Also disclosed is a method for producing electricity, wherein said heat transfer medium is circulated between said heat exchanger arrangements such that thermal energy may be transferred from the flue gases in the first flue charge channel and/or the second flue discharge channel into the feed water of the chemical recovery boiler and/or into a heat-consuming process.

Abstract: The method in a recovery boiler comprises estimating the first melting temperature T0 of the fly ash depositing on heat transfer surfaces, the estimating being based on potassium (K) content of the fly ash; measuring or estimating the temperature Tss of superheated steam; evaluating a temperature difference TD1 between the first melting temperature T0 and the temperature Tss of the superheated steam, the temperature difference TD1 providing an estimate of the risk of corrosion; and selecting a control action for influencing the temperature difference TD1.

Abstract: The disclosed solution relates to recovering thermal energy from the operation of a dissolver of a chemical recovery boiler used in pulp manufacturing. According to the solution, a primary fluid circuit conveys green liquor from the dissolver to an external process such as causticizing and solvent such as weak white liquor back to the dissolver, and from this circuit solvent is diverted into a secondary fluid passageway comprising a heat exchanger which cools the solvent by recovering heat from it and transfers the heat to a heat-consuming process. After heat recovery, solvent may be used for further processes before it is at least partly conveyed back to the dissolver.

Abstract: The disclosed solution relates to recovering thermal energy from the operation of a dissolver of a chemical recovery boiler used in pulp manufacturing. According to the solution, a primary fluid circuit conveys green liquor from the dissolver to an external process such as causticizing and solvent such as weak white liquor back to the dissolver, and from this circuit solvent is diverted into a secondary fluid passageway comprising a heat exchanger which cools the solvent by recovering heat from it and transfers the heat to a heat-consuming process. After heat recovery, solvent may be used for further processes before it is at least partly conveyed back to the dissolver.

Abstract: The disclosed solution relates to recovering thermal energy from the operation of a dissolver of a chemical recovery boiler used in pulp manufacturing. According to the solution, a primary fluid circuit conveys green liquor from the dissolver to an external process such as causticizing and solvent such as weak white liquor back to the dissolver, and from this circuit solvent is diverted into a secondary fluid passageway comprising a heat exchanger which cools the solvent by recovering heat from it and transfers the heat to a heat-consuming process. After heat recovery, solvent may be used for further processes before it is at least partly conveyed back to the dissolver.

Abstract: A method for optimizing reduction and content of total titratable alkali of green liquor of a recovery boiler. The method comprises producing green liquor in a dissolving tank by conveying smelt and weak white liquor into the dissolving tank and measuring at least the contents of sodium sulphate, sodium hydroxide, sodium sulphide, and sodium carbonate of the green liquor. The method comprises controlling at least a process parameter of a recovery boiler to maximize the reduction of the recovery boiler and controlling the flow of the weak white liquor into the dissolving tank to optimize the content of total titratable alkali of the green liquor. In addition, a system for producing green liquor with optimized reduction and content of total titratable alkali. The system comprises a first sensor arrangement, a first and a second regulator, and a processing unit arrangement configured to perform the method.

Abstract: The method in a recovery boiler comprises estimating the first melting temperature T0 of the fly ash depositing on heat transfer surfaces, the estimating being based on potassium (K) content of the fly ash; measuring or estimating the temperature Tss of superheated steam; evaluating a temperature difference TD1 between the first melting temperature T0 and the temperature Tss of the superheated steam, the temperature difference TD1 providing an estimate of the risk of corrosion; and selecting a control action for influencing the temperature difference TD1.

Abstract: The disclosed solution relates to recovering thermal energy from the operation of a dissolver of a chemical recovery boiler used in pulp manufacturing. According to the solution, a primary fluid circuit conveys green liquor from the dissolver to an external process such as causticizing and solvent such as weak white liquor back to the dissolver, and from this circuit solvent is diverted into a secondary fluid passageway comprising a heat exchanger which cools the solvent by recovering heat from it and transfers the heat to a heat-consuming process. After heat recovery, solvent may be used for further processes before it is at least partly conveyed back to the dissolver.

Abstract: A method for optimizing reduction and content of total titratable alkali of green liquor of a recovery boiler. The method comprises producing green liquor in a dissolving tank by conveying smelt and weak white liquor into the dissolving tank and measuring at least the contents of sodium sulphate, sodium hydroxide, sodium sulphide, and sodium carbonate of the green liquor. The method comprises controlling at least a process parameter of a recovery boiler to maximize the reduction of the recovery boiler and controlling the flow of the weak white liquor into the dissolving tank to optimize the content of total titratable alkali of the green liquor. In addition, a system for producing green liquor with optimized reduction and content of total titratable alkali. The system comprises a first sensor arrangement, a first and a second regulator, and a processing unit arrangement configured to perform the method.