CN1223399C

CN1223399C - Desulfurizing process and equipment with regeneratable sulfurizing agent

Info

Publication number: CN1223399C
Application number: CN 01115417
Authority: CN
Inventors: 郑智慧; 覃征远; 慎义勇
Original assignee: SHENZHEN KELEIN LANTIAN TECHNOLOGY Co Ltd
Current assignee: Shenzhen Kelein Lantian Technology Co., Ltd.
Priority date: 2001-04-24
Filing date: 2001-04-24
Publication date: 2005-10-19
Anticipated expiration: 2021-04-24
Also published as: CN1382518A

Abstract

The present invention provides a desulfurizing method and a desulfurizing device thereof for regenerating a desulfurizing agent. The present invention has the advantages of low investment, low operation cost, high desulfurizing efficiency and no secondary pollution and is particularly suitable for the occasions with low electricity price and wide occupied land areas.

Description

Desulfurization method and device with regenerable desulfurizer

The invention relates to a desulfurization method and a desulfurization device for removing sulfur dioxide in waste gas, in particular to a desulfurization method and a desulfurization device with a reproducible desulfurizing agent.

The exhaust gas exhausted from boilers and kilns commonly used in the industries of electric power, chemical industry, metallurgy and the like contains a large amount of sulfur dioxide, which causes serious pollution to the atmosphere and is a main pollution source formed by acid rain. At present, the research of flue gas desulfurization is actively developed at home and abroad, certain progress is made, and some desulfurization technologies and processes are applied and popularized in practical engineering. For example, the most commonly used lime/limestone-gypsum method utilizes the characteristic that lime or limestone can react with sulfur dioxide to perform wet desulfurization and washing on flue gas, thereby achieving the purpose of purifying the flue gas; there are other methods such as spray drying, electron beam, ammonia, and the like. However, the methods have the disadvantages that the final desulfurization by-product of the lime/limestone-gypsum method is gypsum which is restricted by the process and the market, cannot be commercialized and only occupies land to discard and stack, thus forming secondary pollution; in the method for regenerating the desulfurizer by electrolyzing sodium sulfate mentioned in some foreign documents, a large amount of by-product dilute sulfuric acid is difficult to treat, and the cost for purifying to commercial concentrated sulfuric acid is high. In other desulfurization process methods, some methods have high initial investment, some methods have high operation cost, some methods form secondary pollution, and some methods have low desulfurization efficiency. These disadvantages have largely restricted the development of the desulfurization environmental protection industry.

The invention aims to provide a desulfurizing method with regenerable desulfurizing agent, which has low investment, low operating cost, high desulfurizing efficiency and no secondary pollution, and is particularly suitable for occasions with low electricity price (such as thermal power station desulfurization and the like).

In order to achieve the purpose, the technical scheme of the invention is as follows:

the desulfurization method with the regenerable desulfurizing agent comprises the following steps:

(A) with NaOH, Na₂SO₃And NaCl is used as a desulfurizer to wash and desulfurize the waste gas;

(B) threshing deviceMixing the waste water after sulfur with gaseous HCl, SO₂Is replaced out;

(C) and (3) electrolyzing the replaced wastewater to regenerate NaOH, taking the generated mixed solution of NaOH and NaCl as a desulfurizing agent, leading back to the step (A) for recycling, leading hydrogen and chlorine generated in the electrolysis process into an HCl synthesis chamber to synthesize gas HCl, and leading back to the step (B) for recycling.

In a preferred embodiment of the present invention, after the step (a) is completed, the desulfurized wastewater is precipitated or filtered, and then the step (B) is performed.

The device for implementing the method of the invention comprises:

at least one desulfurization scrubber 1;

at least one SO₂Replacement chamber 4, the SO₂The displacement chamber 4 is connected to the desulfurization scrubber 1 by a first conduit 10 equipped with a shut-off valve 18;

at least one diaphragm electrolyzer 5, the anode chamber of the electrolyzer 5 being connected to the SO via a second conduit 11₂The displacement chamber 4 is connected and the cathode chamber of the electrolytic cell 5 is fed back to the desulfurization scrubber 1 through a third conduit 12;

at least one HCL synthesizing chamber 6 for introducing chlorine gas in the anode chamber of the electrolytic cell 5 through a fourth conduit 13 and hydrogen gas in the cathode chamber of the electrolytic cell 5 through a fifth conduit 14 into the HCL synthesizing chamber 6, the HCL synthesizing chamber 6 for introducing HCL in the HCL synthesizing chamber 6 into SO through a sixth conduit 15₂The chamber 4 is replaced.

In a preferred embodiment of the present invention, the apparatus further comprises:

at least one wastewater collection tank 2 connected to the bottom end of the desulfurization scrubber 1 through a seventh conduit 7;

at least one filter 3, into which filter 3 the waste water from the waste water collecting tank 2 is introduced through an eighth conduit 9 provided with a pump 17, the filter 3 being connected to the SO through a first conduit 10 provided with a shut-off valve 18₂The displacement chamber 4 is connected.

At least one intermediate tank 8 for introducing the solution in the cathodic compartment of the electrolyzer 5 into the intermediate tank 8 through a third conduit 12, the intermediate tank 8 being connected to the desulfurization scrubber 1 through a ninth conduit 16 equipped with a pump 19;

the top of the desulfurization scrubbing tower is provided with at least one gas outlet pipe 20, and the bottom of the desulfurization scrubbing tower is provided with at least one gas pipeline 21 to be treated.

Said intermediate tank 8 is provided with at least one supplementary conduit 23.

The SO₂The displacement chamber 4 is provided with at least one gas SO₂And a delivery tube 22.

By adopting the method and the device, the whole desulfurization and desulfurizing agent electrolysis regeneration process does not generate solid waste and secondary pollution, and the byproduct is high-purity SO₂The gas can be processed into various downstream products, so that the market demand is large and the commercial value is high; the high-concentration NaOH solution is adopted as a desulfurizer to carry out desulfurization, and the desulfurization efficiency is far higher than that of other common desulfurizers; in addition, the diaphragm electrolytic cell is adopted, so that the cost is low; the initial investment of the whole desulfurization and desulfurizer electrolysis regeneration system is relatively low; in the occasions with low electricity price, such as power station desulfurization occasions, especially under the condition of wide occupied area, the desulfurization operation cost is greatly lower than that of the prior common desulfurization process and method after the sales income of byproducts is deducted; in addition, it avoids the disadvantage of producing large amounts of dilute sulfuric acid which is difficult to handle in conventional sodium sulfate electrolytic regeneration processes.

FIG. 1 is a flow chart of the apparatus of the present invention.

The invention isexplained in more detail below with reference to the figures and examples:

using sodium hydroxide (NaOH) and sodium sulfite (Na)₂SO₃) And the mixed solution of sodium chloride (NaCl) is used as a desulfurizer (wherein NaCl does not participate in the desulfurization reaction), wet washing desulfurization is carried out on the flue gas to be treated, and the purified flue gas is discharged to the atmosphere. The desulfurization washing equipment can be any desulfurization tower which can use NaOH desulfurizing agent. Dioxygen in flue gasThe sulfur sulfide and the desulfurizing agent react as follows:

when CO is present in the flue gas₂Then, the following reaction takes place:

when the NaOH is completely consumed, Na₂SO₃Can be mixed with SO₂Further reaction takes place:

as can be seen, the desulfurized wastewater is Na₂SO₃、NaHSO₃And NaCl, and of course, depending on the composition of the flue gas, there may be some suspended solids and small amounts of other impurity ions such as SO in the desulfurization waste water₄ ^2-And the like.

In order to ensure better desulfurizing agent electrolytic regeneration efficiency and reduce electrolytic energy consumption, the concentration of the desulfurizingagent NaOH is as high as possible, preferably more than 10%, and the provided high-concentration NaOH can be used in a desulfurizing washing tower for multiple times in a self-circulation manner or in multiple-stage washing manner so as to ensure that the total consumption of the NaOH is changed into Na₂SO₃And NaHSO₃(ii) a However, NaOH is preferably not diluted, which may cause Na in the desulfurization waste water₂SO₃And NaHSO₃Is lower, thereby increasing the energy consumption of electrolysis.

Before entering the electrolytic bath, the desulfurization wastewater is filtered to separate out solid suspended matters in the wastewater as much as possible. The filtered desulfurization waste water is introduced into a replacement chamber for replacementIn the room, HCl is introduced, with Na₂SO₃And NaHSO₃Reaction is carried out:

the displacer HCl is derived fromHCl synthesis chamber. Replacement of chamber generated SO₂The gas needs to be led out. To reduce SO₂Dissolving in solution, heating or depressurizing the solution, but avoiding heating to near boiling, or SO₂The gas contains a large amount of water, which increases the difficulty of post-treatment.

By-product of high concentration of SO₂Introduction of SO₂The post-treatment process can prepare liquid sulfur dioxide or high-purity oleum. SO (SO)₂The post-treatment process is not within the scope of the present invention.

Is replaced by SO₂The desulfurized waste water after the desulfurization treatment mainly contains sodium chloride (NaCl).

The NaCl solution is led into an anode chamber of a diaphragm electrolytic cell to carry out electrolysis to regenerate a desulfurizer. The diaphragm electrolytic cell has low cost but occupies a wider area.

Introducing desulfurization wastewater into an anode chamber solution inlet of the electrolytic cell; the outlet of the cathode chamber is used for leading out concentrated NaOH and Na₂SO₃The mixed solution of (1). The following electrolytic reactions take place in the electrolytic cell:

concentrated NaOH and Na produced by electrolysis₂SO₃The mixed solution is used as a desulfurizer and is led into a desulfurization washing tower to complete the cycle process.

Chlorine and hydrogen generated by the anode chamber and the cathode chamber of the electrolytic cell are led into the HCl synthesis chamber to synthesize HCl. The chemical reaction is as follows:

the HCl produced is introduced into the displacement chamber as displaced SO₂And (4) using the method to complete the circulation process.

Since the solution is lost during the processes of desulfurization washing, filtration and the like, sodium ions and water are reduced, so that NaOH and water need to be supplemented in the whole desulfurization and desulfurizer regeneration system.

As shown in FIG. 1, the flue gas to be treated is introduced into a gas desulfurization scrubber 1 through a flue gas pipeline 21 to be treated, and NaOH and Na are added₂SO₃The mixed solution isThe main component of the desulfurizer is introduced into the desulfurization washing tower 1 through a ninth conduit 16 provided with a pump 19, and the desulfurizer reacts with sulfur dioxide in the flue gas, so that the purpose of desulfurization washing is achieved. The gas after washing and purification is led out through a gas outlet pipe 20;

the desulfurized product contains Na₂SO₃And NaHSO₃The waste water flows into the waste water collecting tank 2 via the seventh conduit 7 and is collected, via the eighth conduit 9 provided with the pump 17, into the filter 3, the filtered waste water being conducted to the SO via the first conduit 10 provided with the shut-off valve 18₂In the displacement chamber 4.

In SO₂In the replacement chamber 4, the desulfurization waste water from the filter 3 is mixed with HCl from the HCl synthesis chamber 6, SO₂Is displaced to form a gas from SO₂And the output of the delivery pipe 22.

The desulfurized waste water containing mainly dilute NaCl after the replacement is introduced into the anode chamber of the electrolytic cell 5 through the second conduit 11. Under the action of current, an electrolytic reaction is carried out, chlorine is generated in the anode chamber, and meanwhile, NaCl is partially consumed to form a dilute NaCl solution which is led out; hydrogen gas is generated in the cathode chamber, and NaOH and Na are simultaneously generated₂SO₃The mixed solution of (1). Hydrogen is led into the HCl synthesis chamber 6 through a fifth conduit 14 and chlorine is led into the HCl synthesis chamber 6 through a fourth conduit 13, and the effluent of the cathode chamber is taken as a desulfurizer and sent into an intermediate storage tank 8 through a third conduit 12, and then sent to the desulfurization washing tower 1 for recycling after being pressurized by a pump 19.

A small part of anode chamber effluent is led out by a pipeline and sent to a sulfate radical separation process.

Concentrated HCl, synthesized in the HCl synthesis chamber 6, is conducted to SO₂Replacement chamber 4 for replacing SO₂The application is recycling.

The supplementing water and NaOH or NaCl are supplemented to the intermediate tank 8 through the pipe 23 to supplement the decrease of the water and NaOH caused by the solution loss and the like.

Claims

1. A desulfurization method with renewable desulfurizing agents comprises the following steps:

(B) mixing the desulfurized wastewater with gaseous HCl, SO₂Is replaced out;

(C) and (3) electrolyzing the replaced wastewater to regenerate NaOH, taking the generated mixed solution of NaOH and NaCl as a desulfurizing agent, leading back to the step (A) for recycling, synthesizing gaseous HCl from hydrogen and chlorine generated in the electrolysis process, and leading back to the step (B) for recycling.

2. The desulfurization method with regenerable desulfurization agent according to claim 1, characterized in that after said step (A) is completed, the desulfurized waste water is precipitated or filtered and then subjected to said step (B).

3. An apparatus for implementing the method of claim 1, the apparatus comprising:

at least one desulfurization scrubber (1);

at least one SO₂A replacement chamber (4), the SO₂The displacement chamber (4) is connected to the desulfurization scrubber (1) by means of a first conduit (10) equipped with a shut-off valve (18);

at least one diaphragm electrolyzer (5), the anode chamber of the electrolyzer (5) being connected to the SO by a second conduit (11)₂The replacement chamber (4) is connected, and the cathode chamber of the electrolytic cell (5) leads the solution back to the desulfurization scrubber (1) through a third conduit (12);

at least one HCL synthesis chamber (6) for introducing chlorine gas in the anode compartment of the electrolytic cell (5) through a fourth conduit (13) and hydrogen gas in the cathode compartment of the electrolytic cell (5) through a fifth conduit (14) into the HCL synthesis chamber (6), the HCL synthesis chamber (6) for introducing HCL in the HCL synthesis chamber (6) into SO through a sixth conduit (15)₂A replacement chamber (4).

4. The apparatus of claim 3, further comprising:

at least one waste water collecting tank (2) connected to the bottom end of the desulfurization scrubber (1) through a seventh conduit (7);

at least one filter (3) into which the waste water from the waste water collecting tank (2) is introduced via an eighth conduit (9) provided with a pump (17), the filter (3) being connected to the SO via a first conduit (10) provided with a shut-off valve (18)₂The replacement chambers (4) are connected.

5. The apparatus of claim 3, further comprising:

at least one intermediate tank (8) to which the solution in the cathodic compartment of the electrolyzer (5) is introduced by means of a third conduit (12), the intermediate tank (8) being connected to the desulfurization scrubber (1) by means of a ninth conduit (16) equipped with a pump (19);

6. the apparatus according to claim 3, characterized in that the desulfurization scrubber is provided with at least one gas outlet duct (20) at the top and at least one gas duct (21) to be treated at the bottom.

7. The apparatus according to claim 5, characterized in that the intermediate tank (8) is provided with at least one supplementary conduit (23).

8. The apparatus of claim 3, wherein said SO₂The displacement chamber (4) is provided with at least one gas SO₂A delivery pipe (22).