A method to be used in conjunction with a single-stage or multi-stage process for leaching ash originating from the recovery boiler of a pulp mill, particularly when the ash contains a significant amount of carbonate, wherein calcium compounds, such as calcium oxide (CaO) or calcium hydroxide (Ca(OH).sub.2), are employed as additives in one or more leaching stages, a liquid fraction formed in the leaching process is utilized outside the main chemical recovery cycle, such as a substitute for purchased sodium hydroxide in the bleaching line of the pulp mill, and a solids fraction may be mixed with a black-liquor stream of the mill or subjected to further processing to separate calcium compounds for recycle.

A method and arrangement for separating tall oil products from a black liquor-containing boiling liquid that has been drained off, was produced within a kraft mill chip digester, and includes a fibrous cellulose material in a mixture with the black liquor and tall oil products, and where the boiling liquid is separated in a separation unit arranged to mechanically separate the boiling liquid into a fibrous cellulose material and a mixture of mixed black liquor and tall oil products, where the mixture of boiling liquid and tall oil products is brought to a separation tank, the separation tank being a gravity separation tank, and adapted to be emptied in a discontinuous manner of the tall oil product collected and concentrated therein, the tall oil products being floated on top of and above a fraction of mixed black liquor, where the tall oil products is brought to a centrifugal separator.

The present invention relates to a process for the extraction of valuable components from a tannin-rich bark raw-material, by carrying out an alkaline cooking step, followed by acid precipitation to separate the valuable components from the remaining bark pulp. The invention also relates to the use of said process on a bark side stream of a chemical pulping plant, whereby the liquor remaining after the extraction of the present process is returned to a stream of the wood pulping process, typically to a black liquor stream, while the spent pulp can be processed further, e.g. by bleaching to give dissolved pulp.

The invention provides a unique, efficient and cost-effective process for the recovery of acid from acid-rich solutions. The process of the invention utilizes a strong oxidizer, such as Caro's acid, to disintegrate or render insoluble organic or inorganic materials such as carbohydrates and complexes thereof contained in acid-rich solutions, to make efficient and simple the separation and recovery of the acid solution. The acid recovered thus obtained is free of organic matter, and containing nearly all of the acid originally contained in the acid-rich solution.

Related to are a device and a method for performing continuous carbonation and impurity removal for xylose mother liquor. The device includes an alkali addition unit, a continuous carbonating unit, a discharge controlling unit, a CO.sub.2 supply station, a vapor station and an after-carbonation tank, wherein the alkali addition unit is configured to add Ca(OH).sub.2 alkaline liquid into xylose mother liquor, the continuous carbonating unit is configured to introduce CO.sub.2 supplied from the CO.sub.2 supply station into the alkali-added xylose mother liquor to perform carbonation and mixing so as to remove impurities such as colloid and pigment in xylose mother liquor, the discharge controlling unit is configured to introduce CO.sub.2 supplied from the CO.sub.2 supply station and vapor transported from the vapor station into the carbonated xylose mother liquor so as to control and stabilize a pH value of the carbonated xylose mother liquor, and the after-carbonation tank is configured to collect and temporarily store the carbonated and impurity-removed xylose mother liquor so as to prepare for a next procedure. Further, a method using the device is disclosed. According to the device and the method, the pH of xylose mother liquor is continuously regulated and stabilized and continuous feeding and discharge are performed with highly automated device so as to achieve continuous and uninterrupted production, and thus facilitate improving the production efficiency.

Embodiments described herein relate generally to graphene oxide membranes for fluid filtration and more specifically to graphene oxide membranes having tunable permeability, rejection rate, and flux. Some embodiments of the graphene oxide membranes disclosed herein are characterized as having a flux of at least about 2.5×10.sup.−4 gallons per square foot per day per psi with a 1 wt % lactose solution at room temperature, and a lactose rejection rate of at least 50% with a 1 wt % lactose solution.

Process for upgrading effluent treatment plants for pulp and paper production processes, where salts are removed from the effluent for water reuse and chemical recovery. The process comprises a first dialysis system for salt removal, a second treatment system for recovery or re-concentration, and optionally a post-treatment of the re-concentrate preventing liquid discharges to the environment. In the first system, a reversible electrodialysis or reversible pulsed step is carried out, separating the salts from the effluent, which are sent to the second treatment system to concentrate the salts (re-concentrate) or transform them into useful chemicals for the same process (recovery). Chemical recovery is achieved by electrodialysis with bipolar membranes or metathesis, to reduce the re-concentrate stream, which cannot be reused in the same plant. Lastly, this stream may be treated by spray drying, crystallization or evaporation.

Process for upgrading effluent treatment plants for pulp and paper production processes, where salts are removed from the effluent for water reuse and chemical recovery. The process comprises a first dialysis system for salt removal, a second treatment system for recovery or re-concentration, and optionally a post-treatment of the re-concentrate preventing liquid discharges to the environment. In the first system, a reversible electrodialysis or reversible pulsed step is carried out, separating the salts from the effluent, which are sent to the second treatment system to concentrate the salts (re-concentrate) or transform them into useful chemicals for the same process (recovery). Chemical recovery is achieved by electrodialysis with bipolar membranes or metathesis, to reduce the re-concentrate stream, which cannot be reused in the same plant. Lastly, this stream may be treated by spray drying, crystallization or evaporation.

The disclosure belongs to the technical field of papermaking technology and waste comprehensive utilization, and specifically relates to a method for preparing biomechanical unbleached pulp from wheat straw and full utilization of by-products thereof. In the present disclosure, wheat straw is used as raw materials for pulping, and treated by hot water, then a trace of KOH is added, the temperature of the wheat straw after heat saturation and softening is adjusted, alkaline compound enzymes is added for biological treatment, and refining of wheat straw is performed at last. The mechanical pulp meets the production requirements for unbleached packaging paper and paper-based materials, meanwhile, the by-products are recycled to prepare a biomass compound fertilizer, turning solid waste into treasures, and realizing a high value full utilization of wheat straw. Thus a good practical application value and a broad application prospect are performed.

The present disclosure relates to a method for preparing an unbleached biomechanical pulp from straws and full utilization of by-products, which belongs to the technical field of papermaking technology and waste comprehensive utilization. In the present disclosure, straw as raw material for pulping is treated with steam, then a small amount of KOH is added, the straw is softened by hydrothermal saturation, then the temperature of the straw is adjusted, alkaline compound enzymes are added for biological treatment, and finally the straw is refined, where the prepared mechanical pulp can meet the requirements of producing unbleached packaging paper and paper-based materials. At the same time, the by-products are recycled to prepare biomass compound fertilizer, which turns solid waste into treasure and realizes the high-value full utilization of wheat straw. Therefore, it has good practical application value and broad application prospects.