阅读说明：本技术 一种烟气脱硫法生产焦亚硫酸钠的工艺及装置 (Process and device for producing sodium metabisulfite by flue gas desulfurization method ) 是由 王杰 于 2021-07-30 设计创作，主要内容包括：本发明公开了一种烟气脱硫法生产焦亚硫酸钠的工艺及装置,所述工艺采用含量为85％以上的工业亚硫酸钠吸收烟气,控制吸收液终点pH值至3.9-4.1时生成NaHSO-3,经析晶得到焦亚硫酸钠；所述吸收液为Na-2SO-3溶液,所述析晶母液与吸收液混合。本发明所述工艺采用简单可行的方法有效的降低了硫酸盐的析出,提高了焦亚硫酸钠的产出,有力推动了烟气脱硫法制备焦亚硫酸钠的工业化。(The invention discloses a process and a device for producing sodium metabisulfite by a flue gas desulfurization method, wherein the process adopts industrial sodium sulfite with the content of more than 85 percent to absorb flue gas, and generates NaHSO when the pH value of the end point of absorption liquid is controlled to be 3.9-4.1 3 Crystallizing to obtain sodium pyrosulfite; the absorption liquid is Na 2 SO 3 And the crystallization mother liquor is mixed with the absorption liquid. The process provided by the invention effectively reduces the precipitation of sulfate by adopting a simple and feasible method, improves the output of sodium metabisulfite, and powerfully promotes the industrialization of preparing the sodium metabisulfite by a flue gas desulfurization method.)

1. A process for producing sodium pyrosulfite by a flue gas desulfurization method is characterized in that absorption liquid is used for absorbing flue gas to generate NaHSO₃Crystallizing to obtain sodium pyrosulfite; the absorption liquid is Na₂SO₃And the crystallization mother liquor is mixed with the absorption liquid.

2. The process of claim 1, wherein the absorption produces NaHSO₃The pH of (A) is 3.9-4.1.

3. The process according to claim 1, wherein the absorption liquid is selected from the group consisting ofIndustrial Na₂SO₃The content is more than 85 wt%.

4. The process according to claim 1, wherein the Baume degree of the absorption liquid is 54 to 56 degrees.

5. The process of claim 1, wherein sodium metabisulfite magma is added during the crystallization.

6. The production device of the process of claim 1, which comprises an absorption liquid tank (1), a synthesis kettle (2), a thickening kettle (3) and a centrifuge (4) which are communicated in sequence; the overflow output pipe of the thickening kettle (3) and the mother liquor output pipe of the centrifuge (4) are respectively communicated with the absorption liquid tank (1); the flue gas enters the synthesis kettle (2) from the lower part, is output from the upper part after being desulfurized, and the absorption liquid enters the synthesis kettle (2) from the upper part, absorbs sulfur dioxide, is output from a desulfurization liquid discharge pipe (21) arranged at the lower part and enters the thickening kettle (3).

7. The production plant according to claim 6, wherein the synthesis tank (2) comprises a plurality of tanks connected in series.

8. The production apparatus according to claim 7, wherein the synthesis kettle (2) is provided with a pH control interlock system, and when the pH of the desulfurization solution in the final synthesis kettle is 3.9-4.1, the desulfurization solution is output and enters the thickening kettle (3).

Technical Field

The invention relates to the technical field of sodium metabisulfite preparation, in particular to a process and a device for producing metabisulfite by a flue gas desulfurization method.

Background

Existing wet method for preparing Na₂S₂O₅The production technology adopts more than 98 percent of Na₂CO₃With SO₂Reaction to form Na₂S₂O₅And (5) producing the product. This production process produces large amounts of CO₂The gas, and during the soda input, releases a large amount of heat, raising the temperature of the absorption liquid (65 ℃), and a violent reaction takes place, generating a large amount of bubbles, due to the increase in temperature, a part of the SO₃ ^2-Decompose to release SO₂Gas, CO produced thereby₂And SO₂The mixed gas generates great harm to human body.

In addition, a large amount of heat released during soda ash dissolving can make the temperature of the alkali liquor reach 60-70 ℃, and the subsequent reaction process is also an exothermic reaction, so that the absorption synthesis is realizedThe temperature of the kettle is always maintained at 70-80 ℃, which is not beneficial to the reaction and is easy to cause SO₃ ^2-Decomposition, reduction of absorption efficiency, and increase of NaHSO in solution due to over-high discharge temperature₃Solubility of (NaHSO at 45 ℃ C.)₃Has a solubility of 46.3%, NaHSO at 80 ℃₃51.46%) which reduces the one pot yield. In addition, a large amount of CO is produced during the reaction₂Gas causes the whole solution to boil badly in the synthesis cauldron, leads to the material solution to be stained with the wall, and the material is stained with the wall scale deposit to a series of problems that lead to, such as: the pipe blockage leads to low production efficiency, labor force increase and product quality problems caused by scaling and falling.

Currently, Na₂CO₃Cost ratio of Na₂SO₃Higher price, low grade (more than 85 wt%) Na₂SO₃Na with bad market prospect and low grade₂SO₃Is easily oxidized into Na under the influence of a plurality of factors₂SO₄The components greatly reduce the availability of the product, thereby being easy to become solid waste. In fact, Na₂SO₃The following reaction can also take place as a desulfurization absorbent:

Na₂SO₃+SO₂+H₂O＝2NaHSO₃

but because sulfite ions are very easily oxidized, new impurities are introduced, and industrial low-grade Na is adopted₂SO₃Middle and higher content of Na₂SO₄High solubility, difficult removal, affecting the purity of sodium metabisulfite and supplying Na₂SO₃Production of Na as a desulfurization absorbent₂S₂O₅A new bottleneck is brought.

Disclosure of Invention

The first purpose of the invention is to provide a process for producing sodium metabisulfite by a flue gas desulfurization method; the second purpose of the invention is to provide a production device for producing sodium metabisulfite by a flue gas desulfurization method. The above object is to solve one of the problems occurring in the prior art described above.

In view of this, the scheme of the invention is as follows:

a process for preparing sodium pyrosulfite by flue gas desulfurization method uses absorption liquid to absorb flue gas to generate NaHSO₃Crystallizing to obtain sodium pyrosulfite; the absorption liquid is Na₂SO₃And the crystallization mother liquor is mixed with the absorption liquid.

Further, the absorption produces NaHSO₃The pH of (A) is 3.9-4.1.

Further, the absorption liquid adopts industrial Na₂SO₃The content is more than 85 wt%.

Further, the Baume degree of the absorption liquid is 54-56 degrees.

Further, sodium metabisulfite crystal slurry is added in the crystallization process.

A production device of the process comprises an absorption liquid tank, a synthesis kettle, a thickening kettle and a centrifuge which are sequentially communicated; the overflow liquid output pipe of the thickening kettle and the mother liquid output pipe of the centrifuge are communicated with the absorption liquid tank; the flue gas enters the synthesis kettle from the lower part, is output from the upper part after being desulfurized, and the absorption liquid enters the synthesis kettle from the upper part, absorbs sulfur dioxide, is output from a desulfurization liquid discharging pipe arranged on the lower part and enters the thickening kettle.

Furthermore, the synthesis kettle comprises a plurality of synthesis kettles which are connected in series in sequence.

And further, the synthesis kettle is provided with a pH control interlocking system, and when the pH of the desulfurization solution in the final synthesis kettle is 3.9-4.1, the desulfurization solution is output and enters the thickening kettle.

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

1. the production process recycles the mother liquor, improves the yield, provides a reduction protective agent for the desulfurization process, effectively inhibits sulfite ions from being oxidized, and reduces the precipitation of sulfate; in addition, the sodium sulfite is used as the absorption liquid, so that a large amount of heat generated in the alkali dissolving and absorption processes of the sodium carbonate is effectively avoided, and the absorption temperature is reduced, so that the sodium metabisulfite is separated out when the absorption is saturated; by controlling the pH value, the solubility of sulfate radical is increased, and the separation of sodium pyrosulfite is facilitated.

2. The process cost of the inventionLow cost, high efficiency, low grade sodium sulfite as absorbent, low cost and avoiding generating a large amount of CO₂The problems of influencing desulfurization absorption and influencing quality due to high content of sodium sulfate; the obtained product has high yield and content, and overcomes the defect that the prior art uses industrial low-grade Na through a simple desulfurization absorption process₂SO₃It is difficult to produce high-quality Na₂S₂O₅The technical bias of the method greatly promotes the industrialization of producing the sodium metabisulfite by the flue gas desulfurization absorption method.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a schematic diagram of a device for producing pyrosulfurous acid by using a flue gas desulfurization method.

Detailed Description

In order to make the objects, technical solutions and advantageous effects of the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and the detailed description. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

The invention provides a process for producing sodium pyrosulfate by flue gas desulfurization, and a flow chart is shown in figure 1.

The process comprises the following steps:

1. preparing an absorption liquid: the content of Na is more than 85wt percent₂SO₃Mixing the product with mother liquor generated in the production process according to a certain proportion to form NaHSO₃、Na₂SO₃And Na₂S₂O₅Controlling the Baume degree to be 54-56 degrees, and preparing the mixed solution for later use;

2. and (3) desulfurization reaction: beating the prepared suspensionPutting the suspension into a multi-stage synthesis kettle, wherein the suspension and the next-stage synthesis kettle sequentially come out from top to bottom and contain incompletely absorbed SO₂Carrying out absorption reaction on the gas; controlling the gas-liquid ratio to make the pH value of the slurry in the last stage synthetic kettle reach 3.9-4.1;

3. thickening and crystallizing: and (4) feeding the slurry subjected to desulfurization and absorption into a thickening kettle, feeding the slurry into a centrifugal system for solid-liquid separation, and returning the thickening kettle overflow liquid and centrifugal mother liquor to be used for absorption liquid preparation.

SO used in the production of the invention₂The gas is the purified flue gas in the smelting process, and SO in the flue gas₂The concentration is 7-9%, and the temperature is controlled at 50 ℃ after cooling. The flue gas is absorbed at different stages in sequence and then is mixed with Na in the suspension₂SO₃Reaction to produce NaHSO₃；

In order to improve the separation efficiency of the centrifugal machine in the centrifugal drying stage, the synthesized crystal mush is firstly put into a thickening kettle, the solid content at the bottom of the mush is improved, then the mush enters the centrifugal machine for solid-liquid separation, and thickening overflow liquid and centrifugal mother liquid are circularly used as absorption liquid for preparation.

The tail gas after multistage absorption is absorbed by alkali liquor and treated by dust, SO that SO in the tail gas₂Less than 30mg/Nm³The dust content is lower than 8mg/Nm³And is discharged into the atmosphere.

The principle of the invention is as follows:

in Na₂SO₃Introducing SO into the solution₂The NaHSO is generated when the pH value is between 3.9 and 4.1₃Solution, reaction formula as follows:

Na₂SO₃+SO₂+H₂O＝2NaHSO₃①；

as NaHSO in solution₃When the supersaturated concentration is reached, Na is precipitated₂S₂O₅Crystallization, reaction formula is as follows:

2NaHSO₃＝Na2S₂O₅+H₂O②；

the overall reaction formula of the two-step reaction is:

Na₂SO₃+SO₂＝Na₂S₂O₅③。

in the process, more than 85 wt% of Na is utilized₂SO₃Production of Na₂S₂O₅Due to industrial Na₂SO₃The content of sodium sulfate is high, so that it is necessary to control the sodium sulfate component in the solution, and the invention utilizes partial sulfate radical as H when the pH value is about 4.0₂SO₄And HSO₄ ^-The sodium sulfate exists in a form and has higher solubility in water, so that the precipitation of the sodium sulfate is reduced, and the influence on the precipitation of a product is reduced; in addition, the overflow liquid generated in the subsequent thickening process and the mother liquid generated in the crystallization process are recycled in the absorption liquid, so that a small amount of Na contained in the overflow liquid and the mother liquid can be effectively recycled₂S₂O₅、NaHSO₃On the one hand, the material recycling can be realized to improve the yield, and on the other hand, the introduced Na₂S₂O₅Can effectively inhibit SO as reduction protective agent₃ ^2-In the presence of SO₂Or free oxygen is oxidized to SO₄ ^2-The production and the precipitation of the by-product sodium sulfate are reduced. Therefore, the adoption of the pH control method and the mother liquor circulation method overcomes the defect that the prior art uses industrial low-grade Na through a simple desulfurization absorption process₂SO₃It is difficult to produce high-quality Na₂S₂O₅The technical prejudice of (1).

The invention also provides a production device of the process, as shown in fig. 1, comprising: 1. an absorption liquid tank; 2. a synthesis kettle; 3. a thickening kettle; 4. a centrifuge; 21, a desulfurization liquid discharge pipe; 22, a desulfurized flue gas output pipe.

The bottom of the absorption liquid tank 1 is communicated with an upper feeding pipe of the synthesis kettle 2, a lower discharging pipe of the synthesis kettle 2 is communicated with the thickening kettle 3, and a discharging pipe of the thickening kettle 3 is communicated with a feeding hole of the centrifugal machine 4 through a centrifugal pump. And mother liquor discharge pipes at the bottom of the centrifugal machine 4 are respectively communicated with the absorption liquid tank, so that mother liquor obtained in the production of the centrifugal machine 4 is circulated to the absorption liquid tank for use.

Wherein, the synthesis kettle 2 is a common desulfurization synthesis kettle, countercurrent absorption is carried out in a mode of lower air inlet and upper feeding, absorption liquid is discharged from a desulfurization liquid discharge pipe 21 arranged at the lower part, and desulfurization flue gas leaves the synthesis kettle 2 from a desulfurization flue gas output pipe 22 arranged at the upper part; in addition, the synthesis kettle 2 can be designed into a multi-stage series connection mode, so that countercurrent absorption (gas phase circulates from low to high, liquid phase circulates from high to low, three stages of synthesis kettles are arranged in the figure, but the height relation of the synthesis kettles at all stages is not shown) is met, and the desulfurization absorption effect is improved. The thickening tank 3 can be a common thickener, the suspension liquid flows in from a central liquid feeding groove, and the mother liquid overflows from the periphery and is discharged from an outflow groove.

According to the production process, in the production device, the pH value in the synthesis kettle 2 is gradually reduced, the desulfurization liquid discharge pipe of the final-stage synthesis kettle is provided with a pH interlocking control system, and when the pH value is within the range of 3.9-4.1, the desulfurization liquid leaves the synthesis kettle 2 and enters the next procedure; on the contrary, the desulfurization solution is circularly absorbed in the final-stage synthesis kettle until the pH value is reduced to the target range.

According to the common design knowledge in the field, the production device of the present invention is further provided with valves for opening and closing the pipeline, a flow meter (not shown in the figure) and a pump for transferring materials.

It is to be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", and the like, as used herein, refer to an orientation or positional relationship illustrated in the drawings for convenience and simplicity of description only and are not intended to indicate or imply that the referenced device or component must have a particular orientation, be constructed and operated in a particular orientation, and are not to be construed as limiting the present invention.

Specifically, as shown in fig. 1, the mother liquor in the thickening kettle 3 and/or the centrifuge 4 is mixed with the absorption liquid Na in the absorption liquid tank 1₂SO₃Mixing, then entering the synthesis kettle 2 from the upper part, and leading the smelting flue gas to enter the synthesis kettle 2 from the side surface of the lower part to perform mass transfer and reaction with the absorption liquid in a counter-current manner. The flue gas firstly enters a first-stage synthesis kettle, and part of Na₂SO₃In the presence of SO₂Post-reaction to form NaHSO₃Unreacted Na₂SO₃Enters the upper part of the second-stage synthesis kettle from the desulfurization liquid discharge pipe 21 to continue countercurrent repeated suctionAnd (4) recovering and desulfurizing, wherein the flue gas enters the lower part of the second-stage synthesis kettle along a desulfurized flue gas output pipe 22 at the upper part for repeated desulfurization, and finally the desulfurization solution in the third-stage synthesis kettle enters the thickening kettle when the pH value reaches 3.9-4.1. In addition, when the pH value of the desulfurization solution in the three-stage synthesis kettle is not within the range of 3.9-4.1, the desulfurization solution is continuously circularly absorbed in the three-stage synthesis kettle until the pH value is within the range of 3.9-4.1, then the desulfurization solution enters the thickening kettle 3 for thickening to obtain crystal suspension, and then the crystal suspension enters the centrifuge 4 under the action of the transfer pump to remove mother liquor, so that the finished product can be obtained through drying and crushing procedures. The overflow liquid generated by the thickening kettle 3 and the mother liquid generated by the centrifuge 4 are mixed with the absorption liquid in the absorption liquid tank 1 through a delivery pump to realize circulation.

By adopting the process or the device, the invention can produce the product with the content of more than 96.5 wt% by controlling the feeding ratio of the smelting flue gas and the absorption liquid and the reasonable design of the absorption efficiency. Therefore, the industrialization of preparing the sodium pyrosulfite by a flue gas desulfurization method is promoted by adopting the low-grade sodium sulfite as the desulfurization absorbent.

The invention is not limited solely to that described in the specification and embodiments, and additional advantages and modifications will readily occur to those skilled in the art, so that the invention is not limited to the specific details, representative apparatus, and illustrative examples shown and described herein, without departing from the spirit and scope of the general concept as defined by the appended claims and their equivalents.