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.

A method for controlling discharges of nitrogen compounds in the production of cellulose carbamate (CCA). Microcrystalline cellulose is produced from chemical pulp produced at a pulp mill, such that the chemical pulp is subjected to acid hydrolysis at an elevated temperature to form microcrystalline cellulose (MCC) and hydrolysate, and the MCC is reacted with urea to produce cellulose carbamate whereby ammonia is released. The microcrystalline cellulose production and the cellulose carbamate production are integrated into the pulp mill having a flue gas system such that carbon dioxide from the flue gases is reacted with released ammonia to produce urea, which is used in the carbamate production.

A method for controlling discharges of nitrogen compounds in the production of cellulose carbamate (CCA). Microcrystalline cellulose is produced from chemical pulp produced at a pulp mill, such that the chemical pulp is subjected to acid hydrolysis at an elevated temperature to form microcrystalline cellulose (MCC) and hydrolysate, and the MCC is reacted with urea to produce cellulose carbamate whereby ammonia is released. The microcrystalline cellulose production and the cellulose carbamate production are integrated into the pulp mill having a flue gas system such that carbon dioxide from the flue gases is reacted with released ammonia to produce urea, which is used in the carbamate production.

According to an example aspect of the present invention, there is provided a process for the conversion of cellulosic waste material into a recycled cellulose product comprising the steps of cooking the waste material in a cooking liquor to remove lignin from the waste material and provide a delignified pulp, dissolving the delignified pulp in an ionic liquid to provide a spinning dope suitable for dry jet-wet spinning in an ionic liquid solution, and subjecting the spinning dope to a further processing step to provide a recycled cellulose product, said further step selected from the group of spinning cellulose fibers for use in textiles from the solution, extruding a film product for use in packaging, regenerating the dope as a hydrogel and regenerating the dope as an aerogel.

The disclosed technology includes a membrane-based device configured to concentrate black liquor, which results from papermaking. Certain embodiments may comprise a nanofiltration membrane configured to remove lignin from black liquor, and the nanofiltration membrane may include a first macroporous polymer substrate and a first graphene oxide membrane covering the first macroporous polymer substrate. Some embodiments may comprise a reverse osmosis membrane, which may include a second macroporous polymer substrate and a second graphene oxide membrane covering the second macroporous polymer substrate.

The disclosed technology includes a membrane-based device configured to concentrate black liquor, which results from papermaking. Certain embodiments may comprise a nanofiltration membrane configured to remove lignin from black liquor, and the nanofiltration membrane may include a first macroporous polymer substrate and a first graphene oxide membrane covering the first macroporous polymer substrate. Some embodiments may comprise a reverse osmosis membrane, which may include a second macroporous polymer substrate and a second graphene oxide membrane covering the second macroporous polymer substrate.

A method for removing hydrogen sulphide ions (HS.sup.−) from a liquor (300) of a pulp mill process, the method comprising pumping the liquor (300) to an injector arrangement (710) using a pump arrangement (720) such that the pumping of the liquor (300) through a jet nozzle (115) generates suction at a gas inlet (130), whereby reagent gas (310) is mixed with the liquor (300), and letting out the treated liquor (300) from the injector arrangement (710) to a vessel (200). In this way, the liquor (300) is treated to form at least partly treated liquor (300). A corresponding use of an injector arrangement. A system for performing the method.

The present invention relates to processes for extracting lignin from black liquor. In particular, processes for both extracting acidic lignin and extracting alkaline lignin from black liquor are disclosed, comprising: precipitating lignin by acidification of black liquor; adjusting the temperature to above 60° C.; cooling; separation; and displacement washing and/or washing by ion exchange.

The present invention relates to novel lignin-derived compounds and compositions comprising the same and their use as redox flow battery electrolytes. The invention further provides a method for preparing said compounds and compositions as well as a redox flow battery comprising said compounds and compositions. Additionally, an assembly for carrying out the inventive method is provided.

The present invention relates to fractions of high purity lignin which are thermally stable, and to methods of producing said fractions from lignocellulosic material.