With the deteriorating environment in today's world, people’s environmental awareness is also increasing. In order to save resources and energy, reduce pollution loads, reduce deforestation, forestation, and the recycling of waste paper has attracted increasing attention. The recycled pulp is high in opacity and uniform in fibrous structure, and can meet the quality requirements of most papers. It can be used for papermaking without having to be beaten. The paper has less fluff, flatness, and wide applicability. Now recycled pulp has been used to make high quality paper. The deinking principle of waste paper is to use deinking agent to reduce the surface tension of the printing ink on waste paper, thereby producing various functions such as wetting, penetrating, emulsifying and dispersing. The comprehensive effect makes the ink detached from the paper surface. The purpose of deinking is to restore the waste paper fiber even more than the original whiteness, degree of cleanliness, flexibility and other characteristics of the original fiber, so that the paper pulp has a good papermaking performance, and achieve the required product indicators to ensure product quality . The deinking process is generally divided into three steps: disintegrating the fibers; removing the ink from the fibers; and removing the ink from the fiber suspension.
1 Deinking method
The conventional deinking process includes a flotation method, a washing method, a combination of flotation and washing, and a short range method. The flotation method uses a mechanism in which different particles have different surface properties to perform deinking; the washing process utilizes hydraulic force for separation, the pulp suspension is screened through sieves or screens, water is entrained with oil particles and removed; flotation and washing are combined The method integrates the advantages of both flotation and washing methods and is now used by many manufacturers; the short-path method is used to process waste paper with a relatively small amount of ink, it only deinks in the pulper and disperses the good waste pulp into storage. The slurry tank was then screened, purified and washed according to normal procedures. For the flotation method, the particle size of the ink particles is preferably 20 to 40 μm. For the washing method, the smaller the size of the oil particles, the better, and preferably less than 5 μm.
In addition, there are many other methods of deinking. Enzymatic deinking mostly uses cellulase and hemicellulase as enzyme preparations. Studies abroad have shown that neutral cellulases are more effective than acidic conditions, and that purely alkaline cellulases can also achieve good whiteness. Enzymes and surfactants used in enzymatic deinking of non-contact printing wastepaper are shared, greatly improving Deinking efficiency. Waste paper and mechanical pulp are mixed and deinked to achieve whiteness of up to 60% ISO. Agglomeration and deinking method Agglomeration agents are used to agglomerate the flake-shaped toners that have been peeled off during the pulping process into spherical particles with a density of more than 400 μm, and then purify them by screening. The ultrasonic deinking method utilizes sound waves greater than 16 Hz for deinking. In addition, there are solvent deinking, steam explosion deinking, steam explosion and magnetic deinking with deinking method.
2 Deinking agent
Surfactants used in the deinking agent include anionic surfactants and nonionic surfactants. Anionic deinking agents include potassium soaps, sulfonated oils, linear alkyl benzene sulfonates, sodium fatty alcohol sulfates, dioctyl sulfosuccinate sodium salts, fatty alcohol polyoxyethylene ether sulfate sodium salts, and the like. Non-ionic deinking agents include alkyl phenol polyoxyethylene ethers, polyethers, polyoxyethylene sorbitan fatty acid esters, and the like.
The deinking effect of different types of deinking agents is as follows: deinking agent formulated with an anionic surfactant and a nonionic surfactant> a nonionic surfactant deinking agent> an anionic surfactant deinking agent> Traditional NaOH or NaSiO3. The chemical aids used in the flotation process include NaO äº iii å¹” å¹” å¹” å¹” 〠ã€, surfactants, chelating agents, trapping agents and adsorbents.
Flotation deinking should use high alcohol alcohol polyoxyethylene ether with good foaming effect and good ink dispersion effect, but it is easy to be degraded under high alkaline conditions, the activity is decreased, and the flocculation ability of ink and impurities is limited. Fatty acid salts have good chelating ability for metal ions and can effectively trap and float ink by electrostatic attraction. The deinking agent obtained by compounding fatty acid polyoxyethylene ester and fatty acid soap has strong flotation and flocculation ability. The chemical aids used in the washing method include NaOH, NaSiO3, a surfactant, a chelating agent, a dispersant, and an ink reprecipitation inhibitor. The washing process mainly uses non-ionic surfactants and requires less foam. Commonly used AEO-9, OP-10, JEC, Tween-80, phosphodiester and so on. Domestic research on the application of multi-component surfactants in waste paper has been conducted in various ways. The XQ series deinking agent, HD series deinking agent and FCS five-component deinking agent have been developed. Deinking agent, and good deinking effect. Washing method, deinking agent can be directly added to the pulper. Flotation method, deinking agent can be directly added to the pulper, can also be added at the entrance of the flotation tank.
Recent studies have shown that the addition of surfactants from the top of the flotation tower in a spray manner is conducive to the establishment of a stable foam layer, to obtain a higher ink removal rate, which can effectively reduce or even avoid the adsorption of surfactant on the fiber pollution, but also reduce due to Adsorption caused fiber and bubble surface changes in fiber loss and water loss.
3 Stickies problem
The problem of stickies in the recycling of waste paper is a very important issue. These substances are characterized by stickiness, lipophilicity, deformation, surface electronegativity, etc. They tend to coalesce into large particles during the pulping and papermaking process. , Deposited in a variety of ways on the surface of the device or left in the paper, creating obstacles, eventually leading directly or indirectly to a decline in product quality and yield. Stickies are mainly derived from various synthetic organic materials such as hot melts, pressure-sensitive papers, coating adhesives, and sizing agents in waste paper. The stickies in waste paper recycling can be divided into primary stickies and secondary stickies according to the forms and behaviors existing in the slurry system.
One-time adhesives refer to hot melts, pressure-sensitive paper additives, etc. Secondary adhesives undergo physical and chemical changes with changes in external conditions, which are more difficult to control and more serious than primary glues. The addition of cationic additives, the evaporation of water, the incorporation of air, the action of the fluid shear force, and the presence of inorganic fillers destabilize the sticky particles, generating a wetting effect and depositing on the surface of the device. To prevent the problem of stickies, we must first strengthen the sorting of raw materials and try to avoid mixing the substances that cause the problem into the system. For substances that are already present in the system, either the dispersion is strengthened so that it does not produce sedimentation, and it adsorbs on the fibers. As the sheet is carried out of the system, chemicals are added to make it coagulate, which is removed in the screening purification. It is worth noting that flotation is also one of the effective ways to remove stickies.
4 Deinking waste water treatment
The waste water discharged from the waste paper deinking workshop contains colored substances, heavy metals, TSS (total solids content) and may contain PCBS. The pressurized air floatation method and air floatation filter method can be used to treat the waste water, and the deinking waste of the flotation tank should be treated separately. Non-deinking recycled paper mills can easily achieve closed loops, and deinking recycled paper mills have difficulties in achieving closed loops due to the addition of many chemicals in the production process. It is technically feasible to design a closed-cycle deinking facility, but the cost of the facility is high and it is currently not economically reasonable. Nano-TiO2 was also used for deinking pulp wastewater treatment.
The nano-ultrafine TiO2 has very strong oxidizing ability under the irradiation of ultraviolet light, which can directly degrade most of the organic matters to generate non-toxic and odorless carbon dioxide, water and some simple inorganic substances, so as to achieve the purpose of one-time degradation of inorganic substances. . The chemical composition of the waste paper pulp residue is complex, organic matter accounts for 70% to 90%, and inorganic matter and metal impurities account for about 10% to 30%. Organic substances include plastics, fine fibers, rags, cotton yarns, fast food boxes, discarded discs, and various organic pigments and adhesives from printing inks; inorganic substances are mainly added in papermaking fillers, coatings, and pulp and paper processes. Other inorganic salts. Paper-making deinking sludge of waste paper has the characteristics of high organic content, large quantity and concentration. However, the organic matter in the deinked sludge is easily thermally chemically cracked. The sludge can be treated by landfill and incineration. The landfill method is simple and easy to invest, but it occupies a large amount of land resources, and it easily causes new environmental pollution. The thermal efficiency of the incineration method is low, and in the combustion process, a highly toxic two-port evil spirit is found. In the waste residue treatment process, its use in other aspects can be developed. U.S. uses slime as an ingredient to produce light-weight pellets for construction, and it works well. New York Mining Technology Co., Ltd. of the United States applied for a patent on the recovery of inorganic fillers from paper deinking plant residues. The patent oxidizes the residue at a high temperature and then adds the calcium hydroxide slurry to the reactor to blow in carbon dioxide to generate PCC.
5 Deinking effect evaluation
Typical methods for evaluating the deinking effect include a whiteness method, an image method, and an ER IC method (effective residual ink particle concentration method). The whiteness method measures the difference in whiteness of two types of unprinted and printed newsprint. Since the measured whiteness is measured at a wavelength of 457 nm, it cannot represent only the influence of black ink particles on whiteness because other color qualities will have a certain influence. The image method used the method of measuring the dust spot (area) to measure the ink ion area (unit: mm2/m2). However, the image method does not detect ink particles of 8 μm or less. The effect of such particles on the deinking effect is indicated by the background reflection.
Not only ink particles but also other types of dust are detected by the image method. The ERIC method is an effective residual ink particle concentration method. It can detect the concentration of ink particles (in mg/kg) with a diameter of 1 μm or less. It uses the near infrared wavelength (950 ~ 1000nm) to determine the absorption coefficient of deinked pulp, and then calculate the concentration of ink particles in the pulp. It can more accurately measure the true black ink particle concentration in the deinked pulp without being affected by other factors. The measurement is performed at 950 nm or 1000 nm, which is not affected by the lignin and dye in the deinked pulp.
1 Deinking method
The conventional deinking process includes a flotation method, a washing method, a combination of flotation and washing, and a short range method. The flotation method uses a mechanism in which different particles have different surface properties to perform deinking; the washing process utilizes hydraulic force for separation, the pulp suspension is screened through sieves or screens, water is entrained with oil particles and removed; flotation and washing are combined The method integrates the advantages of both flotation and washing methods and is now used by many manufacturers; the short-path method is used to process waste paper with a relatively small amount of ink, it only deinks in the pulper and disperses the good waste pulp into storage. The slurry tank was then screened, purified and washed according to normal procedures. For the flotation method, the particle size of the ink particles is preferably 20 to 40 μm. For the washing method, the smaller the size of the oil particles, the better, and preferably less than 5 μm.
In addition, there are many other methods of deinking. Enzymatic deinking mostly uses cellulase and hemicellulase as enzyme preparations. Studies abroad have shown that neutral cellulases are more effective than acidic conditions, and that purely alkaline cellulases can also achieve good whiteness. Enzymes and surfactants used in enzymatic deinking of non-contact printing wastepaper are shared, greatly improving Deinking efficiency. Waste paper and mechanical pulp are mixed and deinked to achieve whiteness of up to 60% ISO. Agglomeration and deinking method Agglomeration agents are used to agglomerate the flake-shaped toners that have been peeled off during the pulping process into spherical particles with a density of more than 400 μm, and then purify them by screening. The ultrasonic deinking method utilizes sound waves greater than 16 Hz for deinking. In addition, there are solvent deinking, steam explosion deinking, steam explosion and magnetic deinking with deinking method.
2 Deinking agent
Surfactants used in the deinking agent include anionic surfactants and nonionic surfactants. Anionic deinking agents include potassium soaps, sulfonated oils, linear alkyl benzene sulfonates, sodium fatty alcohol sulfates, dioctyl sulfosuccinate sodium salts, fatty alcohol polyoxyethylene ether sulfate sodium salts, and the like. Non-ionic deinking agents include alkyl phenol polyoxyethylene ethers, polyethers, polyoxyethylene sorbitan fatty acid esters, and the like.
The deinking effect of different types of deinking agents is as follows: deinking agent formulated with an anionic surfactant and a nonionic surfactant> a nonionic surfactant deinking agent> an anionic surfactant deinking agent> Traditional NaOH or NaSiO3. The chemical aids used in the flotation process include NaO äº iii å¹” å¹” å¹” å¹” 〠ã€, surfactants, chelating agents, trapping agents and adsorbents.
Flotation deinking should use high alcohol alcohol polyoxyethylene ether with good foaming effect and good ink dispersion effect, but it is easy to be degraded under high alkaline conditions, the activity is decreased, and the flocculation ability of ink and impurities is limited. Fatty acid salts have good chelating ability for metal ions and can effectively trap and float ink by electrostatic attraction. The deinking agent obtained by compounding fatty acid polyoxyethylene ester and fatty acid soap has strong flotation and flocculation ability. The chemical aids used in the washing method include NaOH, NaSiO3, a surfactant, a chelating agent, a dispersant, and an ink reprecipitation inhibitor. The washing process mainly uses non-ionic surfactants and requires less foam. Commonly used AEO-9, OP-10, JEC, Tween-80, phosphodiester and so on. Domestic research on the application of multi-component surfactants in waste paper has been conducted in various ways. The XQ series deinking agent, HD series deinking agent and FCS five-component deinking agent have been developed. Deinking agent, and good deinking effect. Washing method, deinking agent can be directly added to the pulper. Flotation method, deinking agent can be directly added to the pulper, can also be added at the entrance of the flotation tank.
Recent studies have shown that the addition of surfactants from the top of the flotation tower in a spray manner is conducive to the establishment of a stable foam layer, to obtain a higher ink removal rate, which can effectively reduce or even avoid the adsorption of surfactant on the fiber pollution, but also reduce due to Adsorption caused fiber and bubble surface changes in fiber loss and water loss.
3 Stickies problem
The problem of stickies in the recycling of waste paper is a very important issue. These substances are characterized by stickiness, lipophilicity, deformation, surface electronegativity, etc. They tend to coalesce into large particles during the pulping and papermaking process. , Deposited in a variety of ways on the surface of the device or left in the paper, creating obstacles, eventually leading directly or indirectly to a decline in product quality and yield. Stickies are mainly derived from various synthetic organic materials such as hot melts, pressure-sensitive papers, coating adhesives, and sizing agents in waste paper. The stickies in waste paper recycling can be divided into primary stickies and secondary stickies according to the forms and behaviors existing in the slurry system.
One-time adhesives refer to hot melts, pressure-sensitive paper additives, etc. Secondary adhesives undergo physical and chemical changes with changes in external conditions, which are more difficult to control and more serious than primary glues. The addition of cationic additives, the evaporation of water, the incorporation of air, the action of the fluid shear force, and the presence of inorganic fillers destabilize the sticky particles, generating a wetting effect and depositing on the surface of the device. To prevent the problem of stickies, we must first strengthen the sorting of raw materials and try to avoid mixing the substances that cause the problem into the system. For substances that are already present in the system, either the dispersion is strengthened so that it does not produce sedimentation, and it adsorbs on the fibers. As the sheet is carried out of the system, chemicals are added to make it coagulate, which is removed in the screening purification. It is worth noting that flotation is also one of the effective ways to remove stickies.
4 Deinking waste water treatment
The waste water discharged from the waste paper deinking workshop contains colored substances, heavy metals, TSS (total solids content) and may contain PCBS. The pressurized air floatation method and air floatation filter method can be used to treat the waste water, and the deinking waste of the flotation tank should be treated separately. Non-deinking recycled paper mills can easily achieve closed loops, and deinking recycled paper mills have difficulties in achieving closed loops due to the addition of many chemicals in the production process. It is technically feasible to design a closed-cycle deinking facility, but the cost of the facility is high and it is currently not economically reasonable. Nano-TiO2 was also used for deinking pulp wastewater treatment.
The nano-ultrafine TiO2 has very strong oxidizing ability under the irradiation of ultraviolet light, which can directly degrade most of the organic matters to generate non-toxic and odorless carbon dioxide, water and some simple inorganic substances, so as to achieve the purpose of one-time degradation of inorganic substances. . The chemical composition of the waste paper pulp residue is complex, organic matter accounts for 70% to 90%, and inorganic matter and metal impurities account for about 10% to 30%. Organic substances include plastics, fine fibers, rags, cotton yarns, fast food boxes, discarded discs, and various organic pigments and adhesives from printing inks; inorganic substances are mainly added in papermaking fillers, coatings, and pulp and paper processes. Other inorganic salts. Paper-making deinking sludge of waste paper has the characteristics of high organic content, large quantity and concentration. However, the organic matter in the deinked sludge is easily thermally chemically cracked. The sludge can be treated by landfill and incineration. The landfill method is simple and easy to invest, but it occupies a large amount of land resources, and it easily causes new environmental pollution. The thermal efficiency of the incineration method is low, and in the combustion process, a highly toxic two-port evil spirit is found. In the waste residue treatment process, its use in other aspects can be developed. U.S. uses slime as an ingredient to produce light-weight pellets for construction, and it works well. New York Mining Technology Co., Ltd. of the United States applied for a patent on the recovery of inorganic fillers from paper deinking plant residues. The patent oxidizes the residue at a high temperature and then adds the calcium hydroxide slurry to the reactor to blow in carbon dioxide to generate PCC.
5 Deinking effect evaluation
Typical methods for evaluating the deinking effect include a whiteness method, an image method, and an ER IC method (effective residual ink particle concentration method). The whiteness method measures the difference in whiteness of two types of unprinted and printed newsprint. Since the measured whiteness is measured at a wavelength of 457 nm, it cannot represent only the influence of black ink particles on whiteness because other color qualities will have a certain influence. The image method used the method of measuring the dust spot (area) to measure the ink ion area (unit: mm2/m2). However, the image method does not detect ink particles of 8 μm or less. The effect of such particles on the deinking effect is indicated by the background reflection.
Not only ink particles but also other types of dust are detected by the image method. The ERIC method is an effective residual ink particle concentration method. It can detect the concentration of ink particles (in mg/kg) with a diameter of 1 μm or less. It uses the near infrared wavelength (950 ~ 1000nm) to determine the absorption coefficient of deinked pulp, and then calculate the concentration of ink particles in the pulp. It can more accurately measure the true black ink particle concentration in the deinked pulp without being affected by other factors. The measurement is performed at 950 nm or 1000 nm, which is not affected by the lignin and dye in the deinked pulp.
1. High-strength steel body, more stable
2. Precision feed platform, a stable paper transport, to ensure perfect print quality.
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4. industrial piezo printheads, high-precision, low noise, low wear, unattended printing operations;
5 .one brushless servo motor control technology, precise trails, eliminate broken;
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11.VSDT advanced variable droplet control technology and high fault feathering technology, to ensure that the fine reproduction of fine details.
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