Device for producing sodium hydrogen sulfite by flue gas desulfurization through limestone method

Abstract

The utility model relates to a device for producing sodium hydrogen sulfite by flue gas limestone desulfurization, which comprises a desulfurization tower, a limestone slurry tank and a sodium sulfate dissolving tank, the desulfurization tower comprises an upper desulfurization section and a lower desulfurization section which are respectively a primary desulfurization section and a secondary desulfurization section; a first-stage desulfurization pipe and a second-stage desulfurization pipe are respectively arranged on the first-stage desulfurization section and the second-stage desulfurization section, and are connected with the limestone slurry tank through liquid inlet pipes; the sodium sulfate dissolving tank is connected with a liquid inlet of a first-stage desulfurization section in the desulfurization tower through a second liquid inlet pipe, meanwhile, the bottom of the first-stage desulfurization section in the desulfurization tower is connected with an inlet of a first liquid-solid separator through a liquid outlet pipeline, and a liquid outlet of the first liquid-solid separator is connected with a liquid inlet of the heat exchanger through a pipeline. A liquid outlet of the heat exchanger is connected with a sodium hydrogen sulfite crystallization tank through a pipeline; the device disclosed by the utility model is simple in structure, not only can ensure that the desulfurization efficiency meets the environment-friendly emission index, but also can produce a sodium hydrogen sulfite chemical product with a relatively high added value, and simultaneously solves the problem of treating sodium sulfate waste salt.

Description

Technical Field

[0001] The utility model relates to the technical field of flue gas purification, in particular to a device for producing sodium bisulfite by using a flue gas limestone method for desulfurization. Background Art

[0002] After more than two decades of rapid industrial flue gas treatment, my country's industrial flue gas purification rate has essentially reached 100%. Over 90% of this rate utilizes wet desulfurization technology using lime / limestone-gypsum. Lime / limestone, the desulfurizer, is abundantly available; simply mining and grinding it into powder is sufficient. This technology offers minimal circulation control points, is easy to operate, and offers stable desulfurization efficiency. However, its drawbacks include significant investment and high energy consumption. As the real estate industry declines as a major economic growth driver, the use of desulfurization gypsum is limited, with most disposal requiring landfill. Desulfurization equipment is considered an environmentally friendly project, with no positive economic returns.

[0003] Sodium sulfate (or Glauber's salt) is a bulk chemical product. my country has abundant sodium sulfate resources, and the chemical industry also produces a large amount of sodium sulfate waste salt that needs to be treated. It would be better if new uses could be found for it.

[0004] Sodium bisulfite is widely used in the bleaching of cotton fabrics and organic materials. It is also used as a reducing agent in the dye, papermaking, leather, and chemical synthesis industries. In the pharmaceutical industry, it is used as an intermediate in the production of analgin and aminopyrine. In food-grade products, it is used as a bleaching agent, preservative, and antioxidant. In water treatment, it is used to treat chromium-containing wastewater and as an electroplating additive. Demand for sodium bisulfite in my country has grown rapidly in recent years, and the market outlook is promising. Utility Model Content

[0005] In response to the problems existing in the existing technology, the utility model proposes a device for producing sodium bisulfite by using the limestone method for flue gas desulfurization. The device can not only ensure that the desulfurization efficiency meets the environmental emission indicators, but also produce sodium bisulfite chemical products with higher by-value-added, and also solve the problem of treating sodium sulfate waste salt.

[0006] The utility model provides a technical solution to the above technical problems: a device for producing sodium bisulfite by limestone desulfurization of flue gas is provided, comprising a desulfurization tower, a limestone slurry tank and a sodium sulfate dissolution tank, wherein the desulfurization tower comprises two upper and lower desulfurization sections, namely a primary desulfurization section and a secondary desulfurization section, wherein a primary desulfurization pipe and a secondary desulfurization pipe are respectively provided on the primary desulfurization section and the secondary desulfurization section, and both the primary desulfurization pipe and the secondary desulfurization pipe are connected to the limestone slurry tank via a liquid inlet pipe 1;

[0007] The sodium sulfate dissolution tank is connected to the liquid inlet of the first-level desulfurization section in the desulfurization tower through a second liquid inlet pipe, and the first-level desulfurization section is connected to the industrial flue gas pipeline. At the same time, the bottom of the first-level desulfurization section in the desulfurization tower is connected to the inlet of a liquid-solid separator through a liquid outlet pipeline. The liquid outlet of the liquid-solid separator is connected to the liquid inlet of the heat exchanger through a pipeline, and the liquid outlet of the heat exchanger is connected to the sodium bisulfite crystallization tank through a pipeline.

[0008] The technical solutions further defined in this utility model are:

[0009] Preferably, at least one layer of desulfurization sieve plate is provided in each desulfurization section, and a gas cap is provided between the two desulfurization sections.

[0010] Preferably, a limestone slurry delivery pump 6 and a sodium sulfate solution delivery pump 4 are respectively provided on the liquid inlet pipe 1 and the liquid inlet pipe 2.

[0011] Preferably, one side of the sodium bisulfite crystallization tank 13 is connected through a circulation pipeline, and the other side is connected to the second feed port of the liquid-solid separator 16 through a separation pipeline. The liquid outlet of the liquid-solid separator 16 transports the saturated solution to the first-level desulfurization section 2-1 in the desulfurization tower through a pipeline.

[0012] Preferably, an induced draft fan 1 is installed on the industrial flue gas duct 17 .

[0013] Preferably, a primary desulfurization circulation pump 9 and a secondary desulfurization circulation pump 10 are respectively provided on the primary desulfurization pipe and the secondary desulfurization pipe.

[0014] Preferably, one side of the secondary desulfurization section is connected to an air inlet pipe, and an oxidation blower 7 is installed on the air inlet pipe.

[0015] Preferably, the primary desulfurization section 2-1 and the secondary desulfurization section 2-2 are both connected to a process water pipe on the same side.

[0016] The beneficial effects of the utility model are as follows: the utility model performs two-stage wet flue gas desulfurization, the first-stage wet flue gas desulfurization controls the pH value to be 5.5--7, adopts industrial waste sodium sulfate as a replacement agent to produce sodium bisulfite and gypsum, the second-stage wet flue gas desulfurization controls the pH value to be 4.5--6, provides oxidizing air, oxidizes calcium sulfite to produce gypsum, the two-stage wet flue gas desulfurization slurries are combined, and solid-liquid separation is performed to obtain sodium bisulfite solution and gypsum, the sodium bisulfite solution is cooled, the sodium bisulfite is crystallized, and solid-liquid separation is performed again to obtain sodium bisulfite solid, which not only ensures that the desulfurization efficiency meets the environmental emission indicators, but also solves the problem of treating sodium sulfate waste salt, and also produces sodium bisulfite chemical products with higher by-value-added. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural diagram of the present utility model. DETAILED DESCRIPTION Example

[0018] The present embodiment provides a device for producing sodium bisulfite by limestone desulfurization of flue gas, comprising a desulfurization tower 2, a limestone slurry tank 5, and a sodium sulfate dissolution tank 3. The desulfurization tower 2 comprises two upper and lower desulfurization sections, namely a primary desulfurization section 2-1 and a secondary desulfurization section 2-2. Three layers of desulfurization sieve plates 23 and a demister 27 are provided in each desulfurization section. An air cap 24 is provided between the two desulfurization sections. A process water pipe is connected to the same side of the primary desulfurization section 2-1 and the secondary desulfurization section 2-2, both of which are located above the demister 27. A primary desulfurization pipe 19 and a secondary desulfurization pipe 18 are provided on the primary desulfurization section 2-1 and the secondary desulfurization section 2-2, respectively. A primary desulfurization circulation pump 9 and a secondary desulfurization circulation pump 10 are provided on the primary desulfurization pipe and the secondary desulfurization pipe, respectively. The primary desulfurization pipe 19 and the secondary desulfurization pipe 18 are both connected to the limestone slurry tank 5 via a liquid inlet pipe 20, and a limestone slurry delivery pump 6 is provided on the liquid inlet pipe 20.

[0019] The sodium sulfate dissolution tank 3 is connected to the liquid inlet of the first-level desulfurization section 2-1 in the desulfurization tower through the liquid inlet pipe 21. The liquid inlet pipe 2 is provided with a sodium sulfate solution delivery pump 4. The first-level desulfurization section 2-1 is connected to the industrial flue gas pipeline 17. The industrial flue gas pipeline 17 is equipped with an induced draft fan 1. At the same time, the bottom of the first-level desulfurization section 2-1 in the desulfurization tower is connected to the inlet of the liquid-solid separator 11 through the liquid outlet pipe 22. The liquid outlet of the liquid-solid separator 11 is connected to the liquid inlet of the heat exchanger 12 through a pipeline. The liquid outlet of the heat exchanger 12 is connected to the sodium bisulfite crystallization tank 13 through a pipeline. One side of the sodium bisulfite crystallization tank 13 is connected to the cooling water system through a circulating cooling water pipeline, and the other side is connected to the second feed port of the liquid-solid separator 16 through a separation pipeline. The liquid outlet of the liquid-solid separator 16 delivers the saturated solution to the first-level desulfurization section 2-1 in the desulfurization tower through a pipeline. One side of the secondary desulfurization section is connected to the air inlet pipe, and the air inlet pipe is equipped with an oxidation fan 7.

[0020] The principle of the utility model is as follows: after being pressurized by the induced draft fan, the flue gas enters the primary desulfurization section at the bottom of the desulfurization tower, and contacts the sodium sulfate solution, a desulfurization liquid pumped out by the primary desulfurization circulating pump. Most of the sulfur dioxide dissolves and reacts with the desulfurization liquid. After the preliminary desulfurization, the flue gas passes through the demister and the air cap, enters the primary desulfurization section at the top, and further contacts the desulfurization liquid pumped out by the secondary desulfurization circulating pump. The sulfur dioxide dissolves and reacts with the desulfurization liquid. Finally, the flue gas is defogged by the demister and discharged in compliance with the emission standards.

[0021] Primary wet flue gas desulfurization:

[0022] The removal principle of SO2 is as follows:

[0023] SO2+H2O→H2SO3

[0024] CaCO3+H2SO3→CaSO3·½H2O↓+½H2O+CO2 ↑

[0025] CaSO3·½H2O+H2SO3→Ca(HSO3)2+½H2O

[0026] Ca(HSO3)2+Na2SO4+2H2O→2NaHSO3+CaSO4·2H2O↓

[0027] Secondary wet flue gas desulfurization:

[0028] SO2+H2O→H2SO3

[0029] CaCO3+H2SO3→CaSO3·½H2O↓+½H2O+CO2 ↑

[0030] CaSO3+½O2+2H2O→CaSO4·2H2O↓

[0031] In the limestone slurry tank, limestone powder is mixed with process water and delivered to the primary and secondary desulfurization sections via limestone slurry pumps. In the primary desulfurization section, limestone reacts with sulfurous acid to form calcium sulfite, which then reacts with sulfurous acid to form calcium bisulfite. Calcium bisulfite reacts with sodium sulfate to form gypsum and sodium bisulfite. In the secondary desulfurization section, limestone reacts with sulfurous acid to form calcium sulfite, which then reacts with oxygen to form gypsum. The gypsum slurry is then drained to the primary desulfurization section, mixed with the primary desulfurization slurry, and discharged together. The discharged slurry passes through Liquid-Solid Separator 1 to separate the gypsum and sodium bisulfite solution. The filtrate is cooled to 5-20°C in a heat exchanger, allowing the sodium bisulfite to crystallize. The sodium bisulfite slurry passes through Liquid-Solid Separator 2 to separate the sodium bisulfite crystals and a saturated sodium bisulfite solution. The saturated solution is returned to the primary desulfurization section, where the sodium bisulfite crystals are dried and packaged.

[0032] In the sodium sulfate solution tank, sodium sulfate is mixed with process water and sent to the primary desulfurization section through the sodium sulfate solution delivery pump to react with calcium bisulfite to produce gypsum and sodium bisulfite.

[0033] In addition to the above embodiments, the present invention may also have other implementation methods. Any technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims

1. A device for producing sodium bisulfite by limestone flue gas desulfurization, comprising a desulfurization tower, a limestone slurry tank, and a sodium sulfate dissolution tank, characterized in that: The desulfurization tower includes two upper and lower desulfurization sections, namely a primary desulfurization section and a secondary desulfurization section. The primary desulfurization section and the secondary desulfurization section are respectively provided with a primary desulfurization pipe and a secondary desulfurization pipe, and the primary desulfurization pipe and the secondary desulfurization pipe are both connected to the limestone slurry tank through a liquid inlet pipe 1; The sodium sulfate dissolution tank is connected to the liquid inlet of the first-level desulfurization section in the desulfurization tower through a second liquid inlet pipe, and the first-level desulfurization section is connected to the industrial flue gas pipeline. At the same time, the bottom of the first-level desulfurization section in the desulfurization tower is connected to the inlet of a liquid-solid separator through a liquid outlet pipeline. The liquid outlet of the liquid-solid separator is connected to the liquid inlet of the heat exchanger through a pipeline, and the liquid outlet of the heat exchanger is connected to the sodium bisulfite crystallization tank through a pipeline.

2. The device for producing sodium bisulfite by limestone flue gas desulfurization according to claim 1, characterized in that: At least one layer of desulfurization sieve plate is provided in each desulfurization section, and a gas cap is provided between the two desulfurization sections.

3. The device for producing sodium bisulfite by limestone flue gas desulfurization according to claim 1, characterized in that: The first liquid inlet pipe and the second liquid inlet pipe are respectively provided with a limestone slurry delivery pump and a sodium sulfate solution delivery pump.

4. The device for producing sodium bisulfite by limestone flue gas desulfurization according to claim 1, characterized in that: One side of the sodium bisulfite crystallization tank is connected through a circulation pipeline, and the other side is connected to the second feed port of the liquid-solid separator through a separation pipeline. The liquid outlet of the liquid-solid separator transports the saturated solution to the secondary desulfurization section in the desulfurization tower through a pipeline.

5. The device for producing sodium bisulfite by limestone flue gas desulfurization according to claim 1, characterized in that: An induced draft fan is installed on the industrial flue gas duct.

6. The device for producing sodium bisulfite by limestone flue gas desulfurization according to claim 1, characterized in that: The primary desulfurization pipe and the secondary desulfurization pipe are respectively provided with a primary desulfurization circulation pump and a secondary desulfurization circulation pump.

7. The device for producing sodium bisulfite by limestone flue gas desulfurization according to claim 1, characterized in that: One side of the secondary desulfurization section is connected to an air inlet pipe, and an oxidation blower is installed on the air inlet pipe.

8. The device for producing sodium bisulfite by limestone flue gas desulfurization according to claim 1, characterized in that: The same side of the primary desulfurization section and the secondary desulfurization section are both connected to a process water pipe.

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