阅读说明：本技术 一种双氧水氧化漂白过程pH值稳定技术 (Technology for stabilizing pH value in hydrogen peroxide oxidation bleaching process ) 是由 李群 刘蓉蓉 胡恒 游紫 于 2019-10-18 设计创作，主要内容包括：本发明涉及一种双氧水氧化漂白过程pH值稳定技术,主要应用于纺织、造纸、食品等涉及碱性条件下双氧水漂白的多个领域中,本方法以氧化镁作为单一碱源替代常规双氧水漂白中的烧碱和硅酸钠等碱源和缓冲剂,利用氧化镁微溶并逐步转化为氢氧化镁的特性,为双氧水漂白提供稳定的pH值,起到pH缓冲液的作用。由于Mg(OH)<Sub>2</Sub>属于弱碱性化合物,使用MgO矿粉制备的悬浮液实测pH值在10.24左右,因此漂白初始pH值较低,具有更为缓和的碱抽提作用,漂白过程COD发生量相对较小,有利于减少污染物发生、降低料耗：用氧化镁取代硅酸钠,避免了硅引起的漂白废液黏度上升和设备结垢问题,同时从根本上避免了当前采用热泵或蒸发浓缩方法处理漂白废液过程中的硅干扰问题。(The invention relates to a technology for stabilizing the pH value in the hydrogen peroxide oxidation bleaching process, which is mainly applied to multiple fields of textile, papermaking, food and the like which relate to hydrogen peroxide bleaching under alkaline conditions. Due to Mg (OH) 2 Belongs to weakly alkaline compounds, the practical measurement of the pH value of a suspension prepared by using MgO mineral powder is about 10.24, so the initial bleaching pH value is lower, the bleaching process has a more moderate alkali extraction effect, the COD generation amount in the bleaching process is relatively smaller, and the reduction of pollution is facilitatedDyeing material generation and material consumption reduction: the magnesium oxide is used for replacing sodium silicate, so that the problems of viscosity rise of bleaching waste liquid and equipment scaling caused by silicon are solved, and the problem of silicon interference in the process of treating the bleaching waste liquid by adopting a heat pump or an evaporation concentration method at present is fundamentally solved.)

1. A technology for stabilizing the pH value in the hydrogen peroxide oxidation bleaching process takes high-yield pulping bleaching as an example, and the production process comprises the following steps:

(1) after being treated by screening, washing, steam preheating softening and the like, the raw material of the commodity wood chips enters a vertical pre-soaking device, stays for a period of time, enters a transfer screw-reaction bin, and then enters a first section high-concentration pulping machine to finish mechanical pulping;

(2) the wood chips which are preimpregnated and ground by a high-concentration mill enter a medium-concentration bleaching tower, and are added with a chemical 1 for screw pressing; then the pulp enters a high-concentration bleaching tower, and chemicals 2 are added to complete the bleaching of the pulp;

(3) dewatering and concentrating by using a screw press, performing low-concentration pulping in a second stage, and performing further mechanical grinding treatment on the paper pulp fibers to obtain paper pulp fibers;

(4) and (4) washing the bleached pulp, and conveying the pulp to a pulp storage tower through a medium concentration pump for later use.

The components of the chemical 1 and the chemical 2 and the weight percentage of the chemical 2 in terms of pulp absolute dry fiber are respectively as follows:

2. the method according to claim 1, wherein the magnesium oxide is used as a suspension with a concentration of 5-8%, and the magnesium oxide suspension is separately provided with a delivery pump and a delivery pipeline.

3. The method of claim 1, wherein: the parameter setting range of the operation unit of the pulping method is as follows:

pre-steaming the bin: the temperature range is 60-100 ℃; the retention time is 10-30 minutes

A vertical pre-soaking device: the temperature range is 60-100 ℃; the retention time is 3-5 minutes

Transfer screw-reaction chamber: the temperature range is 50-70 ℃; the retention time is 10-50 minutes

First-stage grinding: the concentration of the ground pulp is 20-40%; the grinding pressure is 0.05-0.5MPa

Bleaching in a medium-concentration bleaching tower: the temperature range is 60-100 ℃; the pulp concentration is 10-15%

Bleaching by a high-concentration bleaching tower: the temperature range is 60-100 ℃; the pulp concentration is 25-30%

And (3) secondary grinding: the concentration of the ground pulp is 1-10%; atmospheric pulping

Medium concentration pulp storage tower: the concentration of the pulp fiber is 10-20%.

Technical Field

The invention belongs to the field of application of oxydol oxidation bleaching industry in multiple industries such as textile, papermaking and food, and relates to a pH value control technology in the oxydol oxidation reaction process under alkaline conditions.

Background

The hydrogen peroxide bleaching technology has the advantages of high whiteness, good stability, less pollution and the like, and is widely applied to multiple industries such as papermaking, textile printing and dyeing, food and the like. However, the hydrogen peroxide bleaching process is usually carried out under the conditions of higher temperature or high alkali, for example, cotton fabrics are generally bleached under the conditions of 90 ℃ and pH value of 11.5; the temperature of a paper pulp fiber bleaching system is between 60 and 100 ℃, the initial pH can reach 13 to 14, and the paper pulp fiber bleaching system can cause serious damage to fibers and influence the fiber yield. At present, in the traditional domestic hydrogen peroxide bleaching process under alkaline conditions, caustic soda, sodium silicate and the like are still used as main bleaching chemicals, wherein the caustic soda provides the alkaline conditions required for bleaching, and the sodium silicate plays a role of a pH buffering agent, so that the problems of large initial and final pH value change in the bleaching process, equipment scaling, wastewater BOD and COD Cr load loading, anion garbage interference and the like can be caused. Because of the addition of sodium hydroxide, hydrogen peroxide is unstable and is easy to generate rapid ineffective decomposition, and the utilization rate of the hydrogen peroxide is greatly reduced. In the paper making industry, the presence of silicon can cause the viscosity of pulping waste liquid to rise, particularly the problems of serious scaling of equipment and the like, and the operation performance of a pulping system is influenced. In addition, because the initial pH of hydrogen peroxide bleaching is higher, part of alkali-soluble hemicellulose and caustic soda extract are dissolved out, the problems of higher pollution load of bleaching waste liquid, higher raw material consumption and low paper pulp yield are caused.

Therefore, researchers at home and abroad in recent years in the pulping and papermaking world firstly develop a method for preparing MgO or Mg (OH)₂The research work of pulping of hydrogen peroxide bleaching technology as an alkali source. The added magnesium oxide forms Mg (OH) in a hydration reaction₂Partially replacing NaOH as an alkali source and jointly using H₂O₂Bleaching provides the necessary pH conditions. Due to Mg (OH)₂The pH value of the suspension prepared by using MgO mineral powder is measured to be about 10.24, and when the suspension is used for bleaching hydrogen peroxide in a proportion of less than or equal to 30% instead of caustic soda, the pH value of the slurry at the inlet of a bleaching tower (after adding bleaching liquid medicine) is less than or equal to 11, and the pH value after bleaching is generally reduced to 8.0-8.5, and the suspension still has good bleaching effect. In 2006, the book "bleaching with high yield pulp hydrogen peroxide using magnesium alkali instead of sodium alkali" in journal of "paper making in China" at volume 25, phase 10, pages 47-50, published by late clever et al in the national emphasis laboratory of university of southern ChinaForeign research institutions since 1991-2005 related to MgO or Mg (OH)₂The research results of the application technology and the basic theory for replacing the traditional caustic soda in the high-yield pulp bleaching clearly point out that the foreign research and production examples prove that the Mg (OH) is utilized in the hydrogen peroxide bleaching₂Or MgO replaces NaOH to reduce the pollution of wastewater, but the research works discuss the stabilizing action and mechanism of the magnesium oxide on the pH value of a bleaching system in the hydrogen peroxide bleaching process, and no relevant research work is found in recent research works and production practices at home and abroad.

Compared with a hydrogen peroxide bleaching system based on caustic soda, the magnesium oxide bleaching system has the advantages of small change range of pH value in the bleaching process and high whiteness stability after bleaching. A large number of experiments prove that the pH value of a caustic soda bleaching system can be directly reduced to about 7 from 13-14 initially, while the pH value of the system is relatively stable when a magnesia method is reduced to about 8 from 10, and the whiteness of the pulp before and after bleaching is changed by less than 2% ISO. The reason is that the caustic soda belongs to strong alkali, the initial pH value is high, the oxidation reaction rate of hydrogen peroxide is high, the consumption is large, the hydrogen peroxide content in a reaction system at the later stage of bleaching is low, the reaction efficiency is reduced, and the magnesium oxide is weak in alkalinity and low in solubility, so that magnesium hydroxide is gradually formed in the reaction system through hydration reaction, and the reaction system is always stabilized in a low pH value range. Therefore, the reaction rate of the hydrogen peroxide is low, the consumption is low, the change of the hydrogen peroxide concentration in the whole bleaching process is small, the high oxidation reaction efficiency can be kept, and the better pulp whiteness can be obtained by using the relatively low hydrogen peroxide consumption.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a technology for stabilizing the pH value in the hydrogen peroxide oxidation bleaching process, which is mainly applied to multiple fields of textile, papermaking, food and the like which relate to hydrogen peroxide bleaching under alkaline conditions. Due to Mg (OH)₂Belongs to weakly alkaline compounds, and is a suspension prepared by using MgO mineral powderThe actual measurement of the pH value is about 10.24, so the bleaching initial pH value is low, the COD generation amount is relatively small, and the pollutant generation and material consumption reduction are facilitated; the magnesium oxide is used for replacing sodium silicate, so that the problems of viscosity rise of bleaching waste liquid and equipment scaling caused by silicon are solved, the problem of silicon interference in the process of treating the pulp waste liquid by adopting a heat pump or an evaporation concentration method at present is fundamentally solved, and favorable conditions are provided for subsequent treatment of the bleaching waste liquid.

Taking the bleaching production of wood raw materials as an example, the invention is implemented by the following technical scheme:

(1) after being treated by screening, washing, steam preheating softening and the like, the raw material of the commodity wood chips enters a vertical pre-soaking device, stays for a period of time, enters a transfer screw-reaction bin, and then enters a first section high-concentration pulping machine to finish mechanical pulping;

(2) the wood chips which are preimpregnated and ground by a high-concentration mill enter a medium-concentration bleaching tower, and are added with a chemical 1 for screw pressing; then the pulp enters a high-concentration bleaching tower, and chemicals 2 are added to complete the bleaching of the pulp;

(3) dewatering and concentrating by using a screw press, performing low-concentration pulping in a second stage, and performing further mechanical grinding treatment on the paper pulp fibers to obtain paper pulp fibers;

(4) and (4) washing the bleached pulp, and conveying the pulp to a pulp storage tower through a medium concentration pump for later use.

The components of the chemical 1 and the chemical 2 and the weight percentage of the chemical 2 in terms of pulp absolute dry fiber are respectively as follows:

the magnesium oxide is prepared into suspension for use, the concentration of the suspension is 5% -8%, and the magnesium oxide suspension is separately provided with a delivery pump and a delivery pipeline.

Furthermore, the parameter setting ranges of the operation units of the pulping method are as follows:

pre-steaming the bin: the temperature range is 60-100 ℃; the retention time is 10-30 minutes

A vertical pre-soaking device: the temperature range is 60-100 ℃; the retention time is 3-5 minutes

Transfer screw-reaction chamber: the temperature range is 50-70 ℃; the retention time is 10-50 minutes

First-stage grinding: the concentration of the ground pulp is 20-40%; the grinding pressure is 0.05-0.5MPa

Bleaching in a medium-concentration bleaching tower: the temperature range is 60-100 ℃; the pulp concentration is 10-15%

Bleaching by a high-concentration bleaching tower: the temperature range is 60-100 ℃; the pulp concentration is 25-30%

And (3) secondary grinding: the concentration of the ground pulp is 1-10%; grinding under normal pressure;

medium concentration pulp storage tower: the concentration of the pulp fiber is 10-20%.

Moreover, the high-yield pulp prepared by the pulping method has the following performance index ranges:

pulp yield: 85-90% of the wood chip amount of oven dry;

COD generation amount of the total drained pulp per ton of the pulping is less than 200 kg;

the proportion of the novel high-yield pulp in high-grade cultural paper such as A3 coated paper, high-grade double-sided offset paper and the like reaches about 30-40%.

The content of fine components in the paper pulp is as follows: 10% -40% of the amount of oven-dried pulp;

paper pulp freeness: 100-300ml CSF;

ISO brightness of pulp: 65-80% ISO;

bulk of the pulp: 1.9-3.0cm³/g；

And (3) breaking and growing of paper pulp: 2.5-3.5 km;

discharge water 15m per ton of pulp³Under the condition, the viscosity of the waste liquid is reduced by 20-30% compared with the traditional caustic soda hydrogen peroxide bleaching process.

Compared with the prior art, the invention has the following advantages:

1) the method is suitable for multiple fields relating to alkaline hydrogen peroxide bleaching technology, such as papermaking, textile printing and dyeing, food and the like, and solves the technical difficulties of high pollution and high consumption under the condition of weak alkaline bleaching;

2) the magnesium oxide is slightly soluble and gradually converted into magnesium hydroxide, so that sodium hydroxide is replaced, and sodium silicate is completely replaced to play a role of a buffer solution. The magnesium oxide has the characteristics of alkalescence and low solubility, so that the pH value is more stable in the bleaching process, and the hydrogen peroxide can keep higher oxidation reaction efficiency. In addition, the bleaching system has a low pH value at the beginning of bleaching, has the advantages of high whiteness stability and relatively small COD generation amount after bleaching, is beneficial to reducing the generation of pollutants, reducing the material consumption and reducing the influence on the consumption of wood raw materials;

3) the problem of viscosity rise of bleaching waste liquid caused by silicon and the problem of pipeline scaling caused by sodium silicate in the traditional chemical mechanical pulp bleaching production are effectively solved by replacing sodium silicate by percent;

4) the proportion of the novel chemi-mechanical pulp in the production of the high-grade cultural paper can be effectively improved, and the cost of the paper can be reduced.

Detailed Description

The present invention will be further described with reference to specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the present invention.