According to an example aspect of the present invention, there is provided a method of replacing with sodium make-up chemicals sodium losses caused by outflows in a pulp mill which employs a kraft process for producing cellulosic pulp, wherein the pulp mill includes a unit for conversion of sulphurous compounds, which is fed with sulphurous substances of the kraft process to convert said sulphurous substances into oxidized sulphurous compounds, said method comprising using sodium sulphate possibly together with other sodium salts as the main make-up chemical, to achieve an essentially sodium hydroxide free feed of sodium make-up chemicals, and at least a part of the sulphur contained in the sodium sulphate make-up chemical being used for producing oxidized sulphurous compounds in said unit for conversion of sulphurous compounds.

A process for the isolation of lignin from black liquor and modification of lignin for use in many plastic applications is disclosed. The isolation of lignin consists of removing all of the non-lignin components from black liquor solution. The non-lignin components including but not limited to organic acids, sugars, and inorganic materials can be removed using either solvent extraction or ion-exchange resin or a combination of both methods. The isolated lignin is water soluble. The non-lignin components can be further isolated and sold or reused in the pulping or lignin isolation processes. The isolated lignin can be further modified in order to meet the needs of the desired plastic application.

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.

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.

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. The method comprises entering the adjusted value of the first input parameter to the computational model, and at a second time, running the computational model to obtain the information on quality of combustion of the liquor in the chemical recovery boiler.

The invention relates to a process for the isolation of components from plant material of Miscanthus. The process comprises three subsequent extractions. The first extraction yields an extract comprising one or more compounds selected from the group of antioxidants, polyphenols, proteins, sterols, acids, alcohols, ketones, aldehydes and aromatic compounds. Thereafter, the plant material is subjected to two extractions with a metal hydroxide (e.g. NaOH), the first performed at a lower pH than the second. These steps yield a sugar fraction and a lignin fraction, respectively. Finally, from the residue after the third extraction, cellulose is isolated.

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 a process for the controlling the sodium and sulfur levels in a pulp mill, comprising the steps of: a) providing a pulp mill stream comprising sulfide and having a total alkali concentration of at least 2 Molar; b) supplying a portion of the pulp mill stream to a reactor comprising sulfide oxidizing bacteria and removing sulfide from the pulp mill stream by subjecting said stream to sulfide oxidizing bacteria in the presence of oxygen, and at a pH in the range 8 to 11, to oxidize the sulfide to elemental sulfur, c) withdrawing from the reactor a treated pulp mill stream comprising sulfur, wherein the portion of the pulp mill stream is mixed with a portion of the sulfide oxidizing bacteria present in the reactor prior to supplying the pulp mill stream to the reactor in step b).

Disclosed is a process for reducing slag in a black liquor recovery boiler, the process comprising: injecting and burning black liquor in a boiler by contacting it with primary air and secondary air; introducing a slag-reducing chemical into the gases above the injection locations through interlaced, tangential or concentric secondary, tertiary, and/or quarternary air ports.

A method for transforming a black liquor, comprising the following steps: a) supplying a black liquor, b) gasifying the black liquor by means of supercritical water gasification in the presence of a hydrogenated carbon-free fuel, by means of which reaction products are formed, c) cooling the reaction products, by means of which a gaseous mixture is obtained which comprises at least methane and a green liquor comprising at least sulphur in the form of NaHS, Na.sub.2S and H.sub.2S.