阅读说明：本技术 无水亚硫酸钠的制备方法及系统 (Preparation method and system of anhydrous sodium sulfite ) 是由 吴昊泉 邵雷 吴林 李涛 于 2020-10-16 设计创作，主要内容包括：本发明涉及本申请提供了一种无水亚硫酸钠的制备方法,包括：采用包含碳酸钠的第一混合溶液吸收制酸烟气,得到包含亚硫酸氢钠和硫酸钠的第二混合溶液；在第二混合溶液中以预定添加速率加入第一混合溶液,搅拌后得到预中和溶液,预中和溶液的体积与第二混合溶液的体积之比为1:2～2:3,预中和溶液的pH值为6.5～7；在预中和溶液中以预定添加速率加入氢氧化钠溶液,反应后得到pH值为10～10.2的中和溶液；将中和溶液加热至75～85℃并保温,使中和溶液中结晶析出固态物,直至固态物的固含量为30～40％；将包含固态物的中和溶液进行离心和干燥,得到无水亚硫酸钠。本发明提供的无水亚硫酸钠的制备方法省去了无水亚硫酸钠制备工艺中常见的物料浓缩步骤,能够大幅度降低能耗,降低生产成本。(The invention relates to the application and provides a preparation method of anhydrous sodium sulfite, which comprises the following steps: absorbing acid making flue gas by adopting a first mixed solution containing sodium carbonate to obtain a second mixed solution containing sodium bisulfite and sodium sulfate; adding the first mixed solution into the second mixed solution at a preset adding rate, and stirring to obtain a pre-neutralized solution, wherein the volume ratio of the pre-neutralized solution to the second mixed solution is 1: 2-2: 3, and the pH value of the pre-neutralized solution is 6.5-7; adding a sodium hydroxide solution into the pre-neutralization solution at a preset adding rate, and reacting to obtain a neutralization solution with the pH value of 10-10.2; heating the neutralization solution to 75-85 ℃, and preserving heat to crystallize out a solid in the neutralization solution until the solid content of the solid is 30-40%; the neutralized solution containing solids was centrifuged and dried to give anhydrous sodium sulfite. The preparation method of the anhydrous sodium sulfite provided by the invention omits the common material concentration step in the anhydrous sodium sulfite preparation process, can greatly reduce energy consumption and reduce production cost.)

1. A preparation method of anhydrous sodium sulfite is characterized by comprising the following steps:

absorbing acid making flue gas by adopting a first mixed solution containing sodium carbonate to obtain a second mixed solution containing sodium bisulfite and sodium sulfate;

adding the first mixed solution into the second mixed solution at a preset adding rate, and stirring to obtain a pre-neutralized solution, wherein the volume ratio of the pre-neutralized solution to the second mixed solution is 1: 2-2: 3, and the pH value of the pre-neutralized solution is 6.5-7;

adding a sodium hydroxide solution into the pre-neutralization solution at a preset adding rate, and reacting to obtain a neutralization solution with the pH value of 10-10.2;

heating the neutralization solution to 75-85 ℃, and preserving heat to crystallize out a solid substance from the neutralization solution until the solid content of the solid substance is 30-40%;

centrifuging and drying the neutralized solution containing the solids to obtain anhydrous sodium sulfite.

2. The method of claim 1, wherein the first mixed solution comprises distilled water, a centrifuged mother liquor and sodium carbonate; said centrifugation mother liquor is obtained from said step of centrifuging said neutralized solution comprising said solids; the mass fraction of sodium carbonate in the first mixed solution is 40% -45%, and the Baume degree is 48-52.

3. The method for preparing anhydrous sodium sulfite according to claim 1, wherein the step of absorbing the acid making flue gas by using the first mixed solution containing sodium carbonate comprises:

separating solid particles in the initial acid making flue gas to obtain the acid making flue gas;

introducing the acid making flue gas into a primary absorption reaction kettle to obtain a second mixed solution and first tail gas;

and introducing the first tail gas into a secondary absorption reaction kettle, wherein the secondary absorption reaction kettle contains the first mixed solution, and the first mixed solution discharged from the secondary absorption reaction kettle is conveyed to the primary absorption reaction kettle.

4. The method for producing anhydrous sodium sulfite according to claim 1 or 3, wherein the mass fraction of sodium bisulfite in the second mixed solution is 40 to 42% NaHSO₃The mass fraction of the sodium sulfate is 0-3%.

5. The method of claim 1, wherein the step of obtaining a preneutralized solution after stirring comprises:

adding 0.002m into the second mixed solution³Adding the first mixed solution at an addition rate of/s, and keeping the temperature of the second mixed solution at 55-65 ℃;

and stirring the second mixed solution at a stirring speed of 20-30 revolutions per minute until the pre-neutralization solution is obtained.

6. The method of claim 1, wherein the step of adding sodium hydroxide solution to the pre-neutralized solution at a predetermined addition rate comprises:

adding 0.002m to the pre-neutralization solution³Adding the sodium hydroxide solution at an addition rate of/s, and keeping the temperature of the preneutralized solution at 35-45 ℃;

and stirring the pre-neutralization solution at a stirring speed of 30-40 revolutions per minute until the neutralization solution is generated.

7. The method of claim 1, wherein the step of centrifuging and drying the neutralized solution containing the solids to obtain anhydrous sodium sulfite comprises:

centrifuging the neutralized solution containing the solid to obtain a wet product, and carrying out pneumatic conveying and drying on the wet product;

the pneumatic conveying drying process comprises the following steps:

exchanging heat between the dry air and the acid making flue gas at the temperature of 260-280 ℃ in an external heat exchanger to heat the temperature of the dry air to 160 ℃;

the temperature of the drying air is raised to 190-200 ℃ through a multi-stage heating resistor, and the wet product is dried; the temperature of the tail air for conveying and drying the air flow is controlled to be above 80 ℃.

8. A preparation system of anhydrous sodium sulfite, which is used for implementing the preparation method of anhydrous sodium sulfite according to any one of claims 1 to 7, and comprises an alkali dissolving tank, a primary absorption reaction kettle, a secondary absorption reaction kettle, a dust remover, a tail gas absorption tower, a transfer kettle, a neutralization kettle, a thickening kettle, a centrifuge and a dryer;

the alkali dissolving tank is connected with the secondary absorption reaction kettle;

the secondary absorption reaction kettle, the dust remover and the transfer kettle are respectively connected with the primary absorption reaction kettle;

the alkali dissolving tank, the secondary absorption reaction kettle, the transfer kettle and the neutralization kettle are respectively connected with the tail gas absorption tower;

the transfer kettle, the alkali dissolving tank and the thickening kettle are respectively connected with the neutralization kettle;

the centrifuge is respectively connected with the thickening kettle, the alkali dissolving pool and the dryer.

Technical Field

The invention relates to the field of chemical production, in particular to a preparation method and a system of anhydrous sodium sulfite.

Background

The anhydrous sodium sulfite is a white powdery chemical raw material, and is widely applied to the production and preparation of reagents such as artificial fiber stabilizers, lignin removal agents in the paper industry, deoxidizing agents in the dye bleaching industry, oxygen inhibitors in the tanning industry, photographic developers, food additives, fruit preservatives and the like.

At present, the smoke gas contains sulfur dioxide in acid making by smelting, and if the sulfur dioxide is directly discharged into the air, the environment is polluted, and the smoke gas also has great harm to the health of human bodies. If sulfur dioxide in the acid making flue gas can be utilized to prepare sodium sulfite, not only the recycling of waste gas is realized, the cost is saved, but also the more important effect of environmental protection is played. The main methods for preparing anhydrous sodium sulfite include a sulfur dioxide soda ash method, a sulfur dioxide caustic soda method, a sulfur dioxide sodium chloride method, a sodium metabisulfite method, a mirabilite lime method and the like. The sulfur dioxide soda ash method has wide raw material source and mature technology, but the purity is not high. When the sodium sulfite with high purity is produced, a complex purification post-treatment process is needed, the energy consumption is high, the production cost is high, and the large-scale and long-time application of the method is severely limited.

Disclosure of Invention

In view of the above, it is necessary to provide a method and a system for preparing anhydrous sodium sulfite, which address at least one of the above-mentioned problems.

In a first aspect, the present application provides a method for preparing anhydrous sodium sulfite, comprising the following steps:

absorbing acid making flue gas by adopting a first mixed solution containing sodium carbonate to obtain a second mixed solution containing sodium bisulfite and sodium sulfate;

adding the first mixed solution into the second mixed solution at a preset adding rate, and stirring to obtain a pre-neutralized solution, wherein the volume ratio of the pre-neutralized solution to the second mixed solution is 1: 2-2: 3, and the pH value of the pre-neutralized solution is 6.5-7;

adding a sodium hydroxide solution into the pre-neutralization solution at a preset adding rate, and reacting to obtain a neutralization solution with the pH value of 10-10.2;

heating the neutralization solution to 75-85 ℃, and preserving heat to crystallize out a solid substance from the neutralization solution until the solid content of the solid substance is 30-40%;

centrifuging and drying the neutralized solution containing the solids to obtain anhydrous sodium sulfite.

In certain implementations of the first aspect, the first mixed solution includes distilled water, centrate, and sodium carbonate; said centrifugation mother liquor is obtained from said step of centrifuging said neutralized solution comprising said solids; the mass fraction of sodium carbonate in the first mixed solution is 40% -45%, and the Baume degree is 48-52.

With reference to the first aspect and the foregoing implementations, in certain implementations of the first aspect, the step of absorbing the acid making flue gas with the first mixed solution containing sodium carbonate includes:

separating solid particles in the initial acid making flue gas to obtain the acid making flue gas;

introducing the acid making flue gas into a primary absorption reaction kettle to obtain a second mixed solution and first tail gas;

and introducing the first tail gas into a secondary absorption reaction kettle, wherein the secondary absorption reaction kettle contains the first mixed solution, and the first mixed solution discharged from the secondary absorption reaction kettle is conveyed to the primary absorption reaction kettle.

With reference to the first aspect and the foregoing implementation manners, in certain implementation manners of the first aspect, the mass fraction of the sodium bisulfite in the second mixed solution is 40% to 42% NaHSO₃The mass fraction of the sodium sulfate is 0-3%.

With reference to the first aspect and the foregoing implementations, in certain implementations of the first aspect, the step of obtaining a preneutralized solution after stirring includes:

adding 0.002m into the second mixed solution³Adding the first mixed solution at an addition rate of/s, and keeping the temperature of the second mixed solution at 55-65 ℃;

and stirring the second mixed solution at a stirring speed of 20-30 revolutions per minute until the pre-neutralization solution is obtained.

With reference to the first aspect and the foregoing implementations, in certain implementations of the first aspect, the step of adding the sodium hydroxide solution to the pre-neutralization solution at a predetermined addition rate includes:

adding 0.002m to the pre-neutralization solution³Adding the sodium hydroxide solution at an addition rate of/s, and keeping the temperature of the preneutralized solution at 35-45 ℃;

and stirring the pre-neutralization solution at a stirring speed of 30-40 revolutions per minute until the neutralization solution is generated.

With reference to the first aspect and the foregoing implementations, in certain implementations of the first aspect, the step of centrifuging and drying the neutralized solution containing the solids to obtain anhydrous sodium sulfite comprises:

centrifuging the neutralized solution containing the solid to obtain a wet product, and carrying out pneumatic conveying and drying on the wet product;

the pneumatic conveying drying process comprises the following steps:

exchanging heat between the dry air and the acid making flue gas at the temperature of 260-280 ℃ in an external heat exchanger to heat the temperature of the dry air to 160 ℃;

the temperature of the drying air is raised to 190-200 ℃ through a multi-stage heating resistor, and the wet product is dried; the temperature of the tail air for conveying and drying the air flow is controlled to be above 80 ℃.

In a second aspect, the present application provides a system for preparing anhydrous sodium sulfite, the system is used for implementing the method for preparing anhydrous sodium sulfite described in the first aspect of the present application, the system comprises an alkali dissolving tank, a primary absorption reaction kettle, a secondary absorption reaction kettle, a dust remover, a tail gas absorption tower, a transfer kettle, a neutralization kettle, a thickening kettle, a centrifuge and a dryer;

the alkali dissolving tank is connected with the secondary absorption reaction kettle;

the secondary absorption reaction kettle, the dust remover and the transfer kettle are respectively connected with the primary absorption reaction kettle;

the alkali dissolving tank, the secondary absorption reaction kettle, the transfer kettle and the neutralization kettle are respectively connected with the tail gas absorption tower;

the transfer kettle, the alkali dissolving tank and the thickening kettle are respectively connected with the neutralization kettle;

the centrifuge is respectively connected with the thickening kettle, the alkali dissolving pool and the dryer.

The technical scheme provided by the embodiment of the invention has the following beneficial technical effects:

according to the preparation method of the anhydrous sodium sulfite provided by the invention, through neutralization operation in two stages, the second mixed solution containing the sodium bisulfite and the sodium sulfate obtained after absorbing the flue gas generated in acid making generates the neutralized solution, the neutralized solution is utilized to crystallize and separate out solid substances, and the anhydrous sodium sulfite is obtained after centrifugation and drying, so that the common material concentration step in the preparation process of the anhydrous sodium sulfite is omitted, the energy consumption can be greatly reduced, and the production cost can be reduced.

Additional aspects and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

FIG. 1 is a schematic flow chart of a method for preparing anhydrous sodium sulfite according to an embodiment of the present invention;

FIG. 2 is a schematic flow chart of a method for absorbing flue gas generated during acid making with the first mixed solution according to an embodiment of the present invention;

FIG. 3 is a schematic view of a structural framework and a process flow of a system for preparing anhydrous sodium sulfite according to an embodiment of the present invention;

FIG. 4 is a schematic flow chart of a method of a pre-neutralization step according to an embodiment of the present invention;

FIG. 5 is a flowchart illustrating a neutralization step according to an embodiment of the present invention.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Possible embodiments of the invention are given in the figures. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein by the accompanying drawings. The embodiments described by way of reference to the drawings are illustrative for the purpose of providing a more thorough understanding of the present disclosure and are not to be construed as limiting the present invention. Furthermore, if a detailed description of known technologies is not necessary for illustrating the features of the present invention, such technical details may be omitted.

It will be understood by those skilled in the relevant art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It is to be understood that the term "and/or" as used herein is intended to include all or any and all combinations of one or more of the associated listed items.

The technical solution of the present invention and how to solve the above technical problems will be described in detail with specific examples.

In an embodiment of the first aspect of the present application, there is provided a method for preparing anhydrous sodium sulfite, as shown in fig. 1, the method comprising the steps of:

s100: absorbing the acid making flue gas by adopting a first mixed solution containing sodium carbonate to obtain a second mixed solution containing sodium bisulfite and sodium sulfate.

S200: and adding the first mixed solution into the second mixed solution at a preset adding rate, and stirring to obtain a pre-neutralized solution, wherein the volume ratio of the pre-neutralized solution to the second mixed solution is 1: 2-2: 3, and the pH value of the pre-neutralized solution is 6.5-7.

S300: and adding a sodium hydroxide solution into the pre-neutralization solution at a preset adding rate, and reacting to obtain a neutralization solution with the pH value of 10-10.2.

S400: and heating the neutralization solution to 75-85 ℃, and preserving heat to crystallize out a solid in the neutralization solution until the solid content of the solid is 30-40%.

S500: the neutralized solution containing solids was centrifuged and dried to give anhydrous sodium sulfite.

The preparation method of the anhydrous sodium sulfite provided by the invention comprises at least five steps, and two stages of neutralization operation are carried out, so that the second mixed solution containing the sodium bisulfite and the sodium sulfate, which is obtained after the acid making flue gas is absorbed, generates the neutralized solution, the neutralized solution is utilized to crystallize and separate out solid matters, and the anhydrous sodium sulfite is obtained after centrifugation and drying, thereby omitting the common material concentration step in the anhydrous sodium sulfite preparation process, greatly reducing the energy consumption and the production cost.

Optionally, in one implementation manner of the embodiment of the first aspect of the present application, the first mixed solution in S100 includes distilled water, centrifugal mother liquor and sodium carbonate; centrifuging the mother liquor obtained from the step of centrifuging the neutralized solution containing solids; the mass fraction of sodium carbonate in the first mixed solution is 40% -45%, and the Baume degree is 48-52. Wherein the distilled water can also be replaced by tap water to achieve cost reduction. Tap water, centrifugal mother liquor and a small part of kettle washing water are mixed with industrial sodium carbonate to prepare supersaturated sodium carbonate solution with a certain content, wherein the content of the sodium carbonate solution is 40-45%, and the Baume degree is 48-52. The blending amount of the centrifugal mother liquor and the kettle washing water is strictly controlled in the production process, and meanwhile, the auxiliary detection is realized by controlling the addition amount of sodium carbonate and Baume degree.

In the actual production process, a production reaction kettle, such as a transfer kettle, a neutralization kettle and the like, is cleaned, the obtained cleaned solution can influence the environment if being directly discharged, and the solution can be reused because of containing a small amount of effective reaction components, so that the production cost can be reduced, and the influence on the environment in the production process can be reduced as much as possible. The centrifugal mother liquor is a solution remaining after the neutralization solution obtained in S500 is subjected to solid separation, and can be reused in the continuous production process, but the centrifugal mother liquor is not generated in the first preparation process of the first mixed solution, and therefore, the centrifugal mother liquor is not used temporarily.

Optionally, with reference to the foregoing implementation manners, in some more specific implementation manners of embodiments of the first aspect, as shown in fig. 2, the step of absorbing the acid making flue gas with the first mixed solution containing sodium carbonate specifically includes:

s110: and separating solid particles in the initial acid making flue gas to obtain the acid making flue gas.

S120: and introducing the acid making flue gas into a primary absorption reaction kettle to obtain a second mixed solution and first tail gas.

S130: and introducing the first tail gas into a secondary absorption reaction kettle, wherein the secondary absorption reaction kettle contains a first mixed solution, and the first mixed solution discharged from the secondary absorption reaction kettle is conveyed to a primary absorption reaction kettle.

The refining acid making flue gas obtained in the production process is firstly filtered by a dust remover to remove 98-99% of solid particles, and the dust remover can be a bag-type dust remover. The solid particles are then sent to a non-ferrous metal smelting system for harmless treatment or recycling. The main reaction gas component SO in the flue gas after dust removal₂About 9 to 12 percent of the total content of the components, and the gas amount is about 10559Nm³H, wherein the content of impurity sulfuric acid mist is less than or equal to 30mg/Nm³，Nm³Refers to a volume of gas at 0 degrees celsius at 1 standard atmosphere.

As shown in fig. 3, the first mixed solution (which may be referred to as alkaline water) is first introduced into the second-stage absorption reaction kettle, and then is put into the first-stage absorption reaction kettle from the second-stage absorption reaction kettle. The dedusted acid making flue gas enters a primary absorption reaction kettle, and is fully absorbed by alkaline water in the primary absorption reaction kettle through aeration operation. Flue gas (namely the first tail gas) output from the first-stage absorption reaction kettle enters the second-stage absorption reaction kettle again for aeration absorption, and tail gas of the second-stage absorption reaction kettle enters the tail gas absorption tower and is discharged after the tail gas reaches the standard after treatment. And controlling the pH value of the reaction end point of the solution in the tail gas absorption tower to be 8-8.5, and returning the mature absorption liquid obtained in the tail gas absorption tower to an alkali pool to be used for preparing alkaline water.

The pH value of the reaction end point of the liquid in the first-stage absorption reaction kettle is 4-4.1, after the reaction end point is reached, the aeration is continued for 10 minutes, and the main component of the second mixed solution is NaHSO with the mass fraction of 40% -42%₃0 to 3 mass percent of Na₂SO₄. Of course, the second mixed solution is not only a chemical solution, but may also include some solid materials, and the second mixed solution is transferred into a transfer kettle, and the temperature in the transfer kettle is controlled to be about 85 ℃.

The main chemical reaction in the first-stage absorption reaction kettle is as follows:

Na₂CO₃+SO₂＝Na₂SO₃+CO₂，Na₂SO₃+SO₂+H2O＝2NaHSO₃。

optionally, with reference to the embodiment of the first aspect and the foregoing implementation manners, in another implementation manner of the embodiment of the first aspect, as shown in fig. 4, the step of obtaining the preneutralized solution after stirring includes:

s210: adding 0.002m into the second mixed solution³Adding the first mixed solution at an addition rate of/s, and keeping the temperature of the second mixed solution at 55-65 ℃.

S220: and stirring the second mixed solution at a stirring speed of 20-30 revolutions per minute until a pre-neutralization solution is obtained.

As shown in fig. 5, the step of adding the sodium hydroxide solution into the pre-neutralization solution at a predetermined addition rate specifically includes:

s310: 0.002m into the preneutralized solution³Adding sodium hydroxide solution at a rate of addition/s, maintaining the temperature of the preneutralized solution at 35 ℃ to45℃。

S320: and stirring the pre-neutralization solution at a stirring speed of 30-40 revolutions per minute until a neutralization solution is generated.

The reaction in the neutralization kettle is mainly divided into two steps. Firstly, the second mixed solution is pumped into the neutralization kettle from the transfer kettle, and the second mixed solution can be added to one half of the volume of the neutralization kettle in the actual production process, and the total volume of the neutralization kettle is 12m³. The alkaline water is slowly added, namely the alkaline water is continuously added at a certain adding rate, and when the adding rate of the alkaline water is too high, a large amount of bubbles can be quickly generated in the kettle. In the second mixed solution at 6m³In grades, the addition rate may be 0.002m³And s. The temperature is controlled at about 60 ℃, and the rotation speed in the neutralization kettle is adjusted to 20-30 r/min. When a large amount of bubbles are generated in the neutralization kettle and the liquid level in the neutralization kettle reaches three-fourths of the total volume of the neutralization kettle, the addition of the alkaline water is stopped until the reaction end point is reached. After the reaction end point of the pre-neutralization operation is reached, the materials in the kettle are continuously stirred for 30 minutes at a stirring speed of 20-30 revolutions per minute.

The second stage, neutralization. Sodium hydroxide solution with a mass fraction of 32% is slowly added, and the addition rate can be referred to the pre-neutralization reaction. If the rate of addition of the sodium hydroxide solution is too fast, the local temperature rise in the kettle may be too fast, resulting in a locally large amount of crystallization. The temperature in the neutralization reaction is controlled to be 35-45 ℃, and the rotating speed is adjusted to be 30-40 r/min. The reaction temperature is low compared to the preneutralization stage, while the stirring speed is relatively high. And when the solution in the neutralization kettle reaches the reaction end point of the second stage, namely the pH value is controlled to be 10-10.2, continuously stirring for 10 minutes, and then quickly transferring the solution into the thickening kettle.

The neutralization kettle adopts jacket heat exchange, circulating cooling water is introduced into the jacket, and the reaction temperature in the kettle is regulated and controlled by controlling the flow rate of the introduced cooling water. The main chemical reactions occurring in the neutralization kettle are:

2NaHSO₃+Na₂CO₃＝2Na₂SO₃+H₂O+CO₂，

NaHSO₃+NaOH＝Na₂SO₃+H₂O。

in order to produce solid sodium sulfite in a specified container instead of directly crystallizing in the neutralization kettle, the solution in the neutralization kettle is transferred into the thickening kettle, so that the crystallization is completed in the thickening kettle. In the thickening kettle, the stirring speed is 10-20 r/min, and the temperature is controlled at 75-85 ℃. The thickening kettle adopts jacket heat exchange, the temperature of steam introduced into the jacket is 110 ℃, heat preservation operation is performed in the thickening kettle, the stirring speed is reduced, and crystal growth is facilitated. When the solid content in the thickening kettle reaches 30-40%, transferring the substances in the thickening kettle to a centrifugal drying system.

The first mixed solution, the second mixed solution and the pre-neutralized solution and the neutralized solution described in this application are not purely chemically uniform and stable mixtures, and only such designations are used to describe the substances involved in or formed during the production of anhydrous sodium sulfite, which named mixtures may include solid substances produced or not dissolved in the corresponding stages.

Alternatively, in certain implementations of embodiments of the first aspect, the step of centrifuging and drying the neutralized solution containing solids to obtain anhydrous sodium sulfite comprises: and centrifuging the neutralized solution containing the solid substances to obtain a wet product, and carrying out pneumatic conveying and drying on the wet product.

The pneumatic conveying drying process comprises the following steps: the dry air exchanges heat with the acid making flue gas with the temperature of 260-280 ℃ in the external heat exchanger, so that the temperature of the dry air is heated to 160 ℃. The temperature of the drying air is raised to 190-200 ℃ through a multi-stage heating resistor, and the wet product is dried; the temperature of the tail air of the air flow conveying drying is controlled to be above 80 ℃.

Centrifuging to obtain mother liquor containing Na₂SO₃The content is 20-25%, the content of Na2SO4 is 1-5%, the obtained wet product enters a sodium sulfite drying system, the drying air exchanges heat with the 280 ℃ sulfur dioxide flue gas in an external heat exchanger, the temperature is heated to 160 ℃, and the temperature is raised to 190 ℃ and 200 ℃ through multi-stage electric heating resistance, and the drying is carried out. The temperature of the dry inlet air is controlled to be 190-200 ℃, and the temperature of the tail air is controlled to be above 80 ℃.The content of the anhydrous sodium sulfite product obtained after drying is more than 97 percent. Through the crystal growth of the thickening kettle and the separation and drying of the centrifugal drying system, the grain size of the obtained anhydrous sodium sulfite crystal is more uniform and the grain size distribution is more concentrated compared with the traditional process.

In a second aspect, the present application provides a system for preparing anhydrous sodium sulfite, the system for preparing anhydrous sodium sulfite is used for implementing the method for preparing anhydrous sodium sulfite described in the first aspect of the present application, and the system for preparing anhydrous sodium sulfite comprises an alkali dissolving tank, a primary absorption reaction kettle, a secondary absorption reaction kettle, a dust remover, a tail gas absorption tower, a transfer kettle, a neutralization kettle, a thickening kettle, a centrifuge and a dryer. As shown in fig. 3, wherein the alkali dissolving tank is connected with the secondary absorption reaction kettle. The secondary absorption reaction kettle, the dust remover and the transfer kettle are respectively connected with the primary absorption reaction kettle. The alkali dissolving tank, the secondary absorption reaction kettle, the transfer kettle and the neutralization kettle are respectively connected with the tail gas absorption tower. The transfer kettle, the alkali dissolving tank and the thickening kettle are respectively connected with the neutralization kettle. The centrifugal machine is respectively connected with the thickening kettle, the alkali dissolving pool and the dryer.

The technical scheme provided in the embodiment of the second aspect of the invention has the following beneficial technical effects:

through one-level absorption reation kettle and second grade absorption reation kettle, fully absorb sulfur dioxide in the system acid flue gas and other flue gases that produce among the absorption process, the flue gas that produces can also enter into the tail gas absorption tower and carry out waste gas standard treatment in the absorption process. The new tail gas generated in the transfer kettle and the neutralization kettle can also enter the tail gas absorption tower and be absorbed. In addition, the liquid produced by the preparation system of the sewage sodium sulfite in the process of generating the sodium sulfite can be recycled, a concentration device is not required to be arranged, the process of material concentration is omitted, and the energy consumption can be greatly reduced. The application provides a preparation system is at the in-process of production sodium sulfite, and the discharge to reach standard is collected to the overall process tail gas, and is friendly to the environment, and the overall process waste water becomes raw materials recycle, and is friendly to the environment.

Those of skill in the art will appreciate that the various operations, methods, steps in the processes, acts, or solutions discussed in this application can be interchanged, modified, combined, or eliminated. Further, other steps, measures, or schemes in various operations, methods, or flows that have been discussed in this application can be alternated, altered, rearranged, broken down, combined, or deleted. Further, steps, measures, schemes in the prior art having various operations, methods, procedures disclosed in the present application may also be alternated, modified, rearranged, decomposed, combined, or deleted.

The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless otherwise specified.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

In the description herein, particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

It should be understood that, although the steps in the flowcharts of the figures are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and may be performed in other orders unless explicitly stated herein. Moreover, at least a portion of the steps in the flow chart of the figure may include multiple sub-steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, which are not necessarily performed in sequence, but may be performed alternately or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

The foregoing is only a partial embodiment of the present application, and it should be noted that, for those skilled in the art, several modifications and decorations can be made without departing from the principle of the present application, and these modifications and decorations should also be regarded as the protection scope of the present application.