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.

The present invention relates to a method for treating green liquor in a green liquor treatment arrangement, wherein the method comprisesadding (101) a flocculation agent to green liquor to form flocculated green liquor,supplying (102) the flocculated green liquor to a clarifying vessel for separating flocculated green liquor into flocculated matter and clear green liquor,removing (103) flocculated matter through a sludge outlet, andremoving (104) clear green liquor from the clarifying vessel, wherein the method further comprisesmeasuring (201) a flocculation of the green liquor, wherein said measuring takes place after adding the flocculation agent but before supplying the flocculated green liquor to the clarifying vessel. The invention also relates to a green liquor treatment device.

A system for producing aqueous sulphuric acid is provided, the system including a first heat exchanger configured to cool aqueous sulphuric for producing cooled aqueous sulphuric acid; a pre-cooling unit comprising an inlet or inlets for receiving the gas containing sulphur trioxide and the cooled aqueous sulphuric acid, an outlet for letting out aqueous sulphuric acid and the gas containing sulphur trioxide, and a first nozzle for spraying the cooled aqueous sulphuric acid onto the gas containing sulphur trioxide. The system further includes a condensation tower comprising a first inlet for receiving the cooled gas containing sulphur trioxide and aqueous sulphuric acid from the pre-cooling unit and means for circulating the aqueous sulphuric acid within the condensation tower by spraying. An associated method and pre-cooling unit suitable for cooling gas comprising sulphur trioxide from at least 400 C. to at most 150 C. are also provided.

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.

A method of recycling a by-product generated in a papermaking process including, pulverizing a by-product produced in a papermaking process to prepare a pulverized product, burning the pulverized product to prepare a burned product, hydrating the burned product to prepare a hydrate; and manufacturing paper from the hydrate and a paper slurry is provided, which allows reuse of by-products generated in conventional papermaking processes such as lime mud and lime kiln CaO, which is environmentally friendly as well as cost-effective, and also the level of whiteness of the by-products such as lime mud and lime kiln CaO generated in a papermaking process can be improved to that of a high-grade raw material, making it possible to also improve the whiteness of paper.

A system (100) for producing aqueous sulphuric acid. The system (100) comprises a first heat exchanger (410) configured to cool water and/or aqueous sulphuric for producing cooled water and/or cooled aqueous sulphuric acid; a pre-cooling unit (200) configured to pre-cool some gas containing sulphur trioxide, the pre-cooling unit (200) comprising an inlet or inlets (212, 214) for receiving [i] the gas containing sulphur trioxide and [ii] the cooled water and/or the cooled aqueous sulphuric acid, an outlet (216) for letting out aqueous sulphuric acid and the gas containing sulphur trioxide, and a first nozzle (220) for spraying the cooled water and/or the cooled aqueous sulphuric acid onto the gas containing sulphur trioxide to cool the gas containing sulphur trioxide. The system further comprises a condensation tower (300) comprising a first inlet (302) for receiving the cooled gas containing sulphur trioxide and aqueous sulphuric acid from the pre-cooling unit (200) and means (320) for circulating the aqueous sulphuric acid within the

This application discloses exemplary processes and systems for reducing mineral ring accumulation in calcination kiln. The processes and systems comprise inserting non-condensable gases (NCGs) in a preheating zone of a calcination kiln, upstream of the burner end. The pre -heating zone may be characterized by temperatures ranging from 1,300 F. to 1,750 F. The system may desirably comprise a plenum for inserting the NCGs into the rotating calcination kiln at the pre-heating zone.

A system and process is disclosed for treating foul condensate such as foul condensate produced in a Kraft pulp mill. Foul condensate is directed through a steam stripper to produce a clean condensate that is partially evaporated by a volatile rich vapor stream produced by the steam stripper in the course of treating the foul condensate. Vapor produced by the evaporation of the clean condensate is directed to one or more electrically driven mechanical vapor re-compressors that produce the steam that is used in the steam stripper.

A method for obtaining particulate calcium carbonate exhibiting improved brightness and color and having uniformity of size such that when the particles are formed in the causticization process in a kraft pulp mill, the time required to separate the particles from liquors in which they are suspended is minimized and the amount of liquor recovered is maximized, with minimal dilution by water used for washing. The method includes the steps of a) slaking calcium oxide in water or an alkaline liquor containing as dissolved species predominantly sodium hydroxide; b) mixing the slaked lime with green liquor from a kraft pulping process to complete a causticization reaction that produces white liquor and lime mud; c) separating the lime mud from the white liquor; and d) milling a portion of the lime mud for use as a white mineral pigment in applications where such pigments are typically used.

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.