阅读说明：本技术 一种用于氢氧化镁悬浮液生产的脱钙方法及其应用 (Decalcification method for producing magnesium hydroxide suspension and application thereof ) 是由 张明磊 刘其锋 王芝洪 徐松林 郑艳 于 2020-04-15 设计创作，主要内容包括：本发明提供一种用于氢氧化镁悬浮液生产的脱钙方法,所述方法包括：浆料制备、脱钙；所述脱钙,对所述氢氧化镁悬浮液生产过程中的所述浆料进行脱钙处理。本发明还提供一种用于氢氧化镁悬浮液生产的脱钙方法的应用。本发明的有益效果：脱钙方法简单、可靠,脱钙效果稳定,钙脱除率高达74.6~90.5%,反应时间仅需2~4h；其CaO(干基含量)≤0.5%；静置七天后,其上层、中层、下层固含量变化率不超过2%,悬浮效果好；用于烟气脱硫中时,废渣少,节省废渣处理成本；用于烟气脱硫中时,整个洗涤脱硫系统运转稳定,其脱硫效果不会随运转时间增长而下降；可采用化工副产品为原料,对环境保护有积极意义。(The invention provides a decalcification method for producing a magnesium hydroxide suspension, which comprises the following steps: preparing slurry and decalcifying; and the decalcification is to perform decalcification treatment on the slurry in the production process of the magnesium hydroxide suspension. The invention also provides an application of the decalcification method for producing the magnesium hydroxide suspension. The invention has the beneficial effects that: the decalcification method is simple and reliable, the decalcification effect is stable, the calcium removal rate is as high as 74.6-90.5%, and the reaction time is only 2-4 h; CaO (dry basis content) is less than or equal to 0.5 percent; after standing for seven days, the solid content change rate of the upper layer, the middle layer and the lower layer is not more than 2 percent, and the suspension effect is good; when the catalyst is used for flue gas desulfurization, the waste residue is less, and the waste residue treatment cost is saved; when the washing desulfurization system is used for flue gas desulfurization, the whole washing desulfurization system operates stably, and the desulfurization effect of the washing desulfurization system cannot be reduced along with the increase of the operation time; chemical by-products can be used as raw materials, which has positive significance for environmental protection.)

1. A decalcification process for the production of a magnesium hydroxide suspension, comprising: preparing slurry and decalcifying; and the decalcification is to perform decalcification treatment on the slurry in the production process of the magnesium hydroxide suspension.

2. The decalcifying method for magnesium hydroxide suspension production according to claim 1, wherein the slurry is prepared by taking a substance containing magnesium hydroxide or magnesium oxide as a raw material and dispersing the substance in water; the raw materials are as follows: the ratio of the weight parts of the water is 10-30: 68-88.

3. The decalcifying method for magnesium hydroxide suspension production according to claim 1, wherein the slurry has a CaO content of 1.5 to 5% and a particle diameter D50 of 1 to 3 μm.

4. The decalcification method for producing the magnesium hydroxide suspension according to claim 1, wherein the decalcification is carried out by adding water into the slurry under stirring, diluting the solid content of the slurry to 4-8%, then adding decalcification agent, heating the slurry to 80-90 ℃, and reacting for 2-4 h under heat preservation;

stirring at the stirring speed of 90-120 RPM;

the decalcifying agent is magnesium chloride.

5. The decalcifying process for the production of a magnesium hydroxide suspension according to claim 2, wherein the magnesium hydroxide containing substance is brucite.

6. The decalcifying process for the production of a magnesium hydroxide suspension according to claim 2, wherein the magnesium oxide containing material is a crude magnesium oxide, the crude magnesium oxide being one of: prepared by calcining magnesite, hydromagnesite and brucite.

7. The decalcifying method for magnesium hydroxide suspension production according to claim 4, wherein the amount of the decalcifying agent added is 2 to 4 times the content of CaO in the slurry.

8. The decalcifying method for the production of a magnesium hydroxide suspension according to claim 4, wherein the magnesium chloride content is 5 to 95% and the balance is water.

9. The application of the decalcification method for producing the magnesium hydroxide suspension is characterized in that the slurry subjected to the decalcification treatment is prepared into the magnesium hydroxide suspension, and the calcium content in the magnesium hydroxide suspension is less than 0.5 percent.

Technical Field

The invention relates to the field of magnesium hydroxide suspension, in particular to a decalcification method for producing magnesium hydroxide suspension and application thereof.

Background

Magnesium hydroxide, white amorphous powder. The suspension of magnesium hydroxide in water is called magnesium hydroxide emulsion, abbreviated as magma, and is also called caustic magnesite, light calcined magnesite, etc. The magnesium hydroxide is colorless hexagonal column crystal or white powder, is insoluble in water and alcohol, is soluble in dilute acid and ammonium salt solution, and has weak alkalinity in water solution. The solubility in water was small, but the water-soluble fraction was completely ionized, and the concentration of the saturated aqueous solution was 1.9 mg/l (18 ℃). Since the natural mineral brucite of magnesium hydroxide is rich in natural content and its chemical properties are close to those of aluminum, users began to replace aluminum chloride with magnesium hydroxide for use in fragrance products. The method is mainly used for analytical reagents, pharmaceutical industry, flue gas desulfurization, wastewater treatment and the like.

Magnesium desulfurization converts magnesium oxide into magnesium hydroxide suspension through hydrolytic digestion, the magnesium hydroxide suspension is reversely absorbed with flue gas in a desulfurizing tower, SO2 and SO3 in the flue gas are converted into magnesium sulfate liquid through acid-base neutralization reaction, and then the magnesium sulfate liquid is subjected to post-treatment. In recent years, based on the good characteristics of magnesium hydroxide or magnesium oxide for flue gas desulfurization, along with the enhancement of the law enforcement of environmental protection policies, the magnesium hydroxide or magnesium oxide is more and more widely used as a desulfurizing agent, and the usage amount of the magnesium hydroxide or magnesium oxide is gradually increased.

Among them, there are many methods for synthesizing magnesium hydroxide, mainly including magnesium salt precipitation method and hydration method. The magnesium salt precipitation method consumes a large amount of acid and alkali, is complex in subsequent treatment and high in cost, and is not suitable for synthesizing environment-friendly magnesium hydroxide slurry. The hydration method mainly takes magnesium oxide as a raw material, and generates magnesium hydroxide by hydration reaction with water at a certain temperature, and has the advantages of simple process and low cost, thereby being widely adopted.

The applicant finds that in the application of using the existing magnesium hydroxide suspension as the washing liquid to carry out desulfurization treatment on the flue gas, the desulfurization effect of the whole washing desulfurization system is seriously reduced after the whole washing desulfurization system is operated for a period of time, not only the treated flue gas can not reach the emission standard, but also the problems of serious scaling phenomenon in a circulating box, reduction of the circulating flow rate of the washing liquid, deterioration of the backflow effect of the washing liquid, reduction of the pump efficiency, deterioration of the spraying effect, non-standard post-treatment of waste liquid and the like can occur. The research of the applicant finds that CaO in the magnesium hydroxide suspension is the most direct factor causing the phenomenon, the small amount of CaO in the magnesium hydroxide suspension can cause the magnesium hydroxide suspension to have a large amount of waste residues after the magnesium hydroxide suspension is used for treating flue gas, the waste residues are easy to deposit at the bottom of equipment, and can block pipelines, a spraying system and a circulating system of the equipment after long-term operation, so that the working pressure of a post-treatment unit is increased, the whole system is difficult to maintain at the later stage, and a large amount of funds and manpower are wasted. In the prior art, the decalcification treatment of the magnesium hydroxide cannot achieve a good effect, the decalcification effect is unstable, and the calcium content in the magnesium hydroxide is high and cannot be effectively removed all the time.

CN104891534A discloses a method for preparing high-purity high-activity magnesium hydroxide by calcium-containing magnesium hydroxide, which comprises the steps of adding a calcium remover and a dispersant into agglomerated magnesium oxide to prepare dispersed high-purity magnesium hydroxide; the patent has the following defects: the decalcification method has complicated steps, long reaction time for obtaining a good decalcification effect, and unstable decalcification effect, and cannot meet the standard control requirement of industrial production.

CN101698490A discloses a method for preparing magnesium hydroxide, which is to modify magnesium hydroxide suspension by a specific process method to obtain a nano-scale magnesium hydroxide, so as to overcome the problem of blockage of a rotating packed bed in the production of magnesium hydroxide. The patent has the following defects: the prepared nano-scale magnesium hydroxide has high calcium content, and when the nano-scale magnesium hydroxide is used in flue gas desulfurization, the phenomena of washing liquid precipitation and slag bonding are serious, and the number of waste slag particles is large, so that the problem of the reduction of the overall desulfurization effect of a desulfurization system cannot be solved.

CN106115748B discloses a method for preparing superfine magnesium hydroxide slurry by a wet method, which prepares a superfine magnesium hydroxide suspension by adding raw materials such as a specific grinding aid, a dispersing agent, a surfactant and the like. The patent has the following defects: the superfine magnesium hydroxide suspension produced by the method has high calcium content, and when the superfine magnesium hydroxide suspension is used for flue gas desulfurization, the problems of serious washing liquid precipitation and slagging phenomena, more waste residue particles and reduced desulfurization effect exist.

In summary, the existing decalcification method for preparing magnesium hydroxide suspension and the application thereof have the following technical problems:

(1) the existing decalcification process for the magnesium hydroxide suspension is complicated, long in reaction time, low in decalcification rate and unstable in decalcification effect, and cannot meet the standard control requirements of industrial production.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention provides a decalcification method for producing magnesium hydroxide suspension, which aims to realize the following purposes:

(1) the method for decalcifying the magnesium hydroxide suspension is simple and reliable in process, short in reaction time, high in calcium decalcification rate and stable in decalcification effect;

in order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a decalcification process for the production of a magnesium hydroxide suspension comprising: preparing slurry and decalcifying; and the decalcification is to perform decalcification treatment on the slurry in the production process of the magnesium hydroxide suspension.

Preparing the slurry, namely taking a substance containing magnesium hydroxide or magnesium oxide as a raw material, and dispersing the substance in water to prepare the slurry; the raw materials are as follows: the ratio of the weight parts of the water is 10-30: 68-88.

In the slurry, the content of CaO is 1.5-5%, and the particle size D50 is 1-3 μm.

Adding water into the slurry under the stirring state, diluting the solid content of the slurry to 4-8%, then adding a decalcifying agent, heating the slurry to 80-90 ℃, and reacting for 2-4 hours in a heat preservation manner;

stirring at the stirring speed of 90-120 RPM;

the decalcifying agent is magnesium chloride.

The substance containing magnesium hydroxide is brucite.

The magnesium oxide-containing substance is a magnesium oxide crude product, and the magnesium oxide crude product is one of the following substances: prepared by calcining magnesite, hydromagnesite and brucite.

The adding amount of the decalcifying agent is 2-4 times of the CaO content in the slurry.

The magnesium chloride content is 5-95%, and the balance of water.

Preparing the slurry subjected to decalcification treatment into a magnesium hydroxide suspension, wherein the calcium content in the magnesium hydroxide suspension is less than 0.5%.

Compared with the prior art, the invention has the beneficial effects that:

(1) the decalcification method is simple and reliable, the decalcification effect is stable, the calcium removal rate is as high as 74.6-90.5%, the reaction time is only 2-4 h, and the reaction time is shortened in comparison with the prior art;

(2) the magnesium hydroxide suspension has low calcium content, and CaO (dry basis content) is less than or equal to 0.5 percent;

(3) after the magnesium hydroxide suspension is kept still for seven days, the solid content change rate of the upper layer, the middle layer and the lower layer is not more than 2 percent, and the suspension effect is good.

(4) When the magnesium hydroxide suspension is used for flue gas desulfurization, the waste residues are less, and the waste residue treatment cost is saved;

(5) when the magnesium hydroxide suspension is used for flue gas desulfurization, the desulfurization effect is good, the S/C value of the treated tail gas is less than 4.3, and the emission effect that the S content in fuel oil is less than 0.1 percent is achieved;

(6) when the magnesium hydroxide suspension liquid is used in flue gas desulfurization, the whole washing desulfurization system operates stably, and the desulfurization effect of the washing desulfurization system cannot be reduced along with the increase of the operation time;

(7) the magnesium hydroxide suspension liquid is not easy to generate phenomena such as precipitation, scaling and the like;

(8) the magnesium hydroxide suspension liquid has rich raw materials, can be produced by taking chemical byproducts as raw materials, has high cost performance and has positive significance for environmental protection.

Detailed Description

In order to more clearly understand the technical features, objects, and effects of the present invention, specific embodiments of the present invention will now be described.