In a method for the continuous precipitation of lignin from black liquor black liquor is provided so as to flow as a pressurized flow in a reactor with a dwell time of less than 300 s. An acidifying agent selected from the group of carbon dioxide, acid and their combinations is led to the flow at one or more feeding sites to lower the pH of black liquor. The pH is allowed to decrease by the effect of the acidifying agent in the pressurized flow to the precipitation point of lignin, the pressure of the pressurized flow is abruptly released, and lignin particles are separated from black liquor.

An assembly for cleaning a smelt spout includes a cleaning head, a drive rod connected with the cleaning head, and a pneumatic or other drive connected to selectively extend or retract the drive rod. The drive rod may be connected with the cleaning head by a pivotal connection. The cleaning head may be bifurcated. The cleaning head may include a leading edge configured to engage and clean a spout opening from which smelt from a chemical reduction furnace flows to the spout. The assembly may further include a pivot point and, as the drive selectively extends the drive rod, torque about the pivot point produced by the cleaning head and an extending portion of the drive rod rotates the cleaning head downward to engage a smelt spout.

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 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 disclosure relates to a method for preparing unbleached biomechanical pulp by hot steam and biological enzyme treatment and full utilization of by-products thereof, and belongs to the technical field of papermaking technology and comprehensive utilization of waste. The present disclosure proposes a method for preparing high-strength unbleached biomechanical pulp, using whole wheat straw as a raw material, by using hot water in coordination with an alkaline biological enzyme to treat whole wheat straw, thereby meeting the requirements for the production of unbleached linerboard and paper-based materials, and recycling by-products thereof to prepare biomass compound fertilizers, which creates wealth from solid waste and realizes the high-value full utilization of wheat straw. The preparation method of the disclosure is simple, green, clean and efficient, and has good practical application value and broad application prospects.

The disclosure relates to a method for preparing unbleached biomechanical pulp by hot steam and biological enzyme treatment and full utilization of by-products thereof, and belongs to the technical field of papermaking technology and comprehensive utilization of waste. The present disclosure proposes a method for preparing high-strength unbleached biomechanical pulp, using whole wheat straw as a raw material, by using hot water in coordination with an alkaline biological enzyme to treat whole wheat straw, thereby meeting the requirements for the production of unbleached linerboard and paper-based materials, and recycling by-products thereof to prepare biomass compound fertilizers, which creates wealth from solid waste and realizes the high-value full utilization of wheat straw. The preparation method of the disclosure is simple, green, clean and efficient, and has good practical application value and broad application prospects.

The present invention is related to a method for: reducing metals content in a Kraft pulping process comprising adding magnesium to a black liquor that is returned to the pulping operation; reducing aluminum content in a pulping process by adding magnesium to the black liquor to provide a green liquor having a specific molar ratio of magnesium:aluminum; producing or treating a green liquor having a specific molar ratio of magnesium:aluminum by adding magnesium to the black, weak black, strong black liqueurs; and producing hydrotalcite by the addition of at least 0.04-5.0 mols of magnesium:aluminum present at the weak black, strong black liqueurs, or a combination thereof. It is also provided a pulp mill comprising a digester (1), a washer (2), an optionally pulp bleaching, a weak black liquor concentrator (4), among other parts.

The present invention is related to a method for: reducing metals content in a Kraft pulping process comprising adding magnesium to a black liquor that is returned to the pulping operation; reducing aluminum content in a pulping process by adding magnesium to the black liquor to provide a green liquor having a specific molar ratio of magnesium:aluminum; producing or treating a green liquor having a specific molar ratio of magnesium:aluminum by adding magnesium to the black, weak black, strong black liqueurs; and producing hydrotalcite by the addition of at least 0.04-5.0 mols of magnesium:aluminum present at the weak black, strong black liqueurs, or a combination thereof. It is also provided a pulp mill comprising a digester (1), a washer (2), an optionally pulp bleaching, a weak black liquor concentrator (4), among other parts.