Coke oven gas ammonium phosphate washing ammonia fine removal device and method

Abstract

The application discloses a coke oven gas ammonia removal device and method, and belongs to the technical field of coke oven gas purification. The device comprises a phosphorus ammonium absorption section and a phosphoric acid absorption section located above the phosphorus ammonium absorption section. A circulating spray liquid pipeline is arranged in the phosphoric acid absorption section. A phosphoric acid tank and a circulating pump are arranged on the pipeline, so that the phosphoric acid solution is circulated and sprayed in the phosphoric acid absorption section to absorb residual ammonia in the coke oven gas. A short circuit pipe distributor is arranged between the phosphorus ammonium absorption section and the phosphoric acid absorption section, and is used for introducing excessive phosphoric acid solution in the phosphoric acid absorption section into the phosphorus ammonium absorption section. According to the method, the coke oven gas is introduced into the phosphoric acid absorption section after ammonia absorption by the phosphorus ammonium absorption section from bottom to top, residual ammonia is removed, and excessive phosphoric acid solution is supplemented to the phosphorus ammonium absorption section. According to the application, the ammonia content of the coke oven gas outlet can be reduced by means of cascade cooperation, the requirements of ultra-low emission and clean production can be met, and the phosphoric acid consumption can be reduced.

Description

Technical Field

[0001] This invention relates to the field of coke oven gas purification technology, and in particular to a device and method for removing ammonia from coke oven gas by washing with ammonium phosphate. Background Technology

[0002] Ammonium phosphate washing is a commonly used process for deammonium phosphate removal from coke oven gas. It uses ammonium phosphate solution as an absorbent to absorb ammonia from the gas and can produce anhydrous ammonia or concentrated ammonia water as needed for desulfurization and denitrification. This process has advantages such as a short process flow, small footprint, and good absorption selectivity, and is widely used in the coking industry.

[0003] In existing ammonium phosphate washing processes, the ammonia content in the coal gas after absorption by ammonium phosphate solution is generally 0.1 g / Nm³. 3 To further improve the purification depth, existing processes have optimized the absorption process to achieve an ammonia content of 0.05 g / Nm³ in the gas after the ammonia absorption tower. 3 The following. However, with increasingly stringent ultra-low emission requirements in the steel industry, the aforementioned export ammonia content is comparable to that of the ammonium sulfate process (export ammonia content is approximately 0.03 g / Nm³). 3 There is still a gap compared to other methods, making it difficult to meet the increasingly stringent requirements for clean production, and it will increase the operating costs of subsequent flue gas treatment.

[0004] In addition, in the existing ammonium phosphate washing process, acid mist entrained in the coal gas is easily carried out of the absorption device along with the coal gas, causing phosphoric acid and ammonium phosphate solution to enter the subsequent pipelines, resulting in high phosphoric acid consumption, severe corrosion of the subsequent pipelines by the coal gas, and the acid mist removal efficiency needs to be improved. Summary of the Invention

[0005] The problem this invention aims to solve is that the ammonia content at the outlet gas of existing ammonium phosphate washing processes is still too high, making it difficult to meet increasingly stringent requirements for ultra-low emissions and clean production. Furthermore, existing ammonium phosphate washing processes also suffer from high phosphoric acid consumption, severe corrosion of downstream pipelines by the coal gas, and the need to improve acid mist removal efficiency.

[0006] To solve the above-mentioned technical problems, the present invention provides a coke oven gas phosphate washing and ammonia removal device, including a phosphate absorption section and a phosphoric acid absorption section located above the phosphate absorption section. The phosphoric acid absorption section is provided with a circulating spray liquid pipeline, and the circulating spray liquid pipeline is provided with a phosphoric acid tank and a circulating pump, so that the phosphoric acid solution can be circulated and sprayed in the phosphoric acid absorption section to absorb residual ammonia in the gas. A short-circuit pipe distributor is provided between the phosphate absorption section and the phosphoric acid absorption section. The short-circuit pipe distributor is used to introduce excess phosphoric acid solution in the phosphoric acid absorption section into the phosphate absorption section.

[0007] Furthermore, the ammonium phosphate absorption section includes an ammonium phosphate rich solution absorption section and an ammonium phosphate poor solution absorption section, with the ammonium phosphate rich solution absorption section located below the ammonium phosphate poor solution absorption section.

[0008] Furthermore, a liquid cut-off plate is provided between the ammonium phosphate rich solution absorption section and the ammonium phosphate poor solution absorption section, and between the ammonium phosphate poor solution absorption section and the phosphoric acid absorption section.

[0009] Furthermore, a cooler is provided outside the ammonium phosphate absorption section to cool the absorbent liquid inside the ammonium phosphate absorption section.

[0010] Furthermore, an acid mist removal section is provided above the phosphoric acid absorption section to remove acid mist entrained in the coal gas.

[0011] Furthermore, the phosphoric acid tank is equipped with a replenishment port for replenishing fresh phosphoric acid and soft water.

[0012] The present invention also provides a method for removing ammonia from coke oven gas by washing with ammonium phosphate, comprising: passing coke oven gas from bottom to top into an ammonium phosphate absorption section, where it is contacted countercurrently with an ammonium phosphate solution to absorb ammonia in the gas; passing the gas treated by the ammonium phosphate absorption section into a phosphoric acid absorption section located above the ammonium phosphate absorption section, where it is contacted with a circulating sprayed phosphoric acid solution to absorb residual ammonia in the gas; and returning excess phosphoric acid solution in the phosphoric acid absorption section to the ammonium phosphate absorption section.

[0013] Furthermore, the ammonium phosphate absorption section includes an ammonium phosphate rich solution absorption section and an ammonium phosphate lean solution absorption section. The ammonium phosphate rich solution absorption section is used to absorb most of the ammonia in the coal gas, and the coal gas treated by the ammonium phosphate rich solution absorption section enters the ammonium phosphate lean solution absorption section.

[0014] Compared with the prior art, the beneficial effects of the present invention are: First, through the tiered combination of the ammonium phosphate absorption section and the phosphoric acid absorption section, after the ammonium phosphate absorption section absorbs most of the ammonia in the coal gas, the phosphoric acid absorption section uses a circulating sprayed phosphoric acid solution to deeply clean the residual ammonia. This reduces the ammonia content at the coal gas outlet, meeting increasingly stringent requirements for ultra-low emissions and clean production. The ammonia content at the coal gas outlet can reach 0.01-0.03 g / Nm³. 3 .

[0015] Secondly, excess phosphoric acid solution in the phosphoric acid absorption section is replenished to the ammonium phosphate absorption section via a short-circuit distributor, allowing the phosphoric acid solution to be recycled in a closed loop within the system. Simultaneously, an external cooler in the ammonium phosphate absorption section lowers the operating temperature of the coal gas, and an acid mist removal section is installed to control acid mist within the device. These measures work together to reduce phosphoric acid consumption (by approximately 10%) and minimize the amount of phosphoric acid and ammonium phosphate solution carried into subsequent pipelines by the coal gas, thus reducing the corrosiveness of the coal gas to these pipelines.

[0016] Third, the reduced ammonia content in the coal gas outlet can reduce the investment, land occupation, and operating costs of subsequent flue gas treatment and deep purification projects. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the coke oven gas phosphate washing and ammonia removal device provided in an embodiment of the present invention.

[0018] The markings in the diagram are as follows: 1. Ammonium phosphate rich solution absorption section, 2. Ammonium phosphate lean solution absorption section, 3. Phosphoric acid absorption section, 4. Acid mist removal section, 5. Ammonium phosphate rich solution pump, 6. Ammonium phosphate rich solution cooler, 7. Ammonium phosphate rich solution distributor, 8. Interruption tray one, 9. Ammonium phosphate lean solution pump, 10. Ammonium phosphate lean solution cooler, 11. Ammonium phosphate lean solution distributor, 12. Interruption tray two, 13. Phosphoric acid tank, 14. Phosphoric acid pump, 15. Phosphoric acid solution distributor, 16. Short-circuit pipe distributor, 17. Mist eliminator layer. Detailed Implementation

[0019] The present invention will be described below through embodiments. These embodiments are only for illustrating the present invention and are not intended to limit the scope of protection of the present invention.

[0020] Example 1: As Figure 1 As shown, this embodiment provides a coke oven gas ammonia washing and deammoniation device. The device, from bottom to top, comprises a rich ammonium phosphate (FP) solution absorption section 1, a lean FP phosphate (FP) solution absorption section 2, a phosphoric acid (P) solution absorption section 3, and an acid mist removal section 4. The rich FP phosphate (FP) solution absorption section 1 and the lean FP phosphate (FP) solution absorption section 2 can employ an air-spray structure or a packing structure. A liquid cut-off plate 8 is provided between the rich FP phosphate (FP) solution absorption section 1 and the lean FP phosphate (FP) solution absorption section 2, and a liquid cut-off plate 12 is provided between the lean FP phosphate (FP) solution absorption section 2 and the P) solution absorption section 3 to separate the liquids in adjacent absorption sections. The rich FP phosphate (FP) solution absorption section 1 has a rich FP phosphate (FP) solution circulation loop, including a rich FP phosphate (FP) solution pump 5, a rich FP phosphate (FP) solution cooler 6, and a rich FP phosphate (FP) solution distributor 7; the lean FP phosphate (FP) solution absorption section 2 has a lean FP phosphate (FP) solution circulation loop, including a lean FP phosphate (FP) solution pump 9, a lean FP phosphate (FP) solution cooler 10, and a lean FP phosphate (FP) solution distributor 11. The phosphoric acid absorption section 3 is equipped with a phosphoric acid circulation loop, including a phosphoric acid tank 13, a phosphoric acid pump 14, and a phosphoric acid solution distributor 15. A short-circuit pipe distributor 16 is also provided between the phosphoric acid absorption section 3 and the ammonium phosphate absorber section 2, connecting the phosphoric acid absorption section 3 to the ammonium phosphate absorber section below, and is used to introduce excess phosphoric acid solution from the phosphoric acid absorption section 3 into the ammonium phosphate absorber section. The acid mist removal section 4 is located above the phosphoric acid absorption section 3, and contains a mist-catching layer 17, which is a wire mesh demister.

[0021] In this embodiment, the inlet gas is coke oven gas, and the ammonia content of the coke oven gas is 3-14 g / Nm³. 3 The temperature is 45℃.

[0022] Coke oven gas enters the device from the lower part of the ammonium phosphate rich liquor absorption section 1. In the ammonium phosphate rich liquor absorption section 1, it comes into countercurrent contact with the ammonium phosphate rich liquor. Most of the ammonia in the coke oven gas is absorbed by the ammonium phosphate rich liquor, which then enters the ammonium phosphate rich liquor pump 5. Most of the ammonium phosphate rich liquor is cooled by the ammonium phosphate rich liquor cooler 6 and then circulated and sprayed. A small portion of the ammonium phosphate rich liquor leaves the device and enters the desorption device.

[0023] The coke oven gas, after being treated in the rich ammonium phosphate liquor absorption section 1, enters the lean ammonium phosphate liquor absorption section 2 via the liquid cut-off plate 8. There, it comes into countercurrent contact with the lean ammonium phosphate liquor cooled by the lean ammonium phosphate liquor cooler 10, reducing the ammonia content in the gas to 0.1 g / Nm³. 3 The lean ammonium phosphate solution consists of circulating spray solution and replacement solution returned from the desorption unit.

[0024] After being treated in the ammonium phosphate lean solution absorption section 2, the coke oven gas enters the phosphoric acid absorption section 3, where residual ammonia in the gas is deeply removed by the circulating sprayed phosphoric acid solution. The circulating phosphoric acid solution enters the phosphoric acid tank 13, where fresh phosphoric acid and soft water are added to refresh the phosphoric acid solution, and the phosphoric acid solution is absorbed in a closed loop via the phosphoric acid pump 14. Excess phosphoric acid solution in the phosphoric acid absorption section 3 is introduced into the ammonium phosphate absorption section below through the short-circuit pipe distributor 16.

[0025] Finally, the coke oven gas leaves the unit after the entrained acid mist is removed by the mist-catching layer 17 in the acid mist removal section 4. At this time, the temperature of the coke oven gas is 30-35℃.

[0026] In this embodiment, the ammonia content at the coal gas outlet can reach 0.01-0.03 g / Nm³. 3 Compared with the existing ammonium phosphate washing process, phosphoric acid consumption can be reduced by about 10%.

Claims

1. A coke oven gas phosphate washing and ammonia removal device, comprising a phosphate absorption section, characterized in that, It also includes a phosphoric acid absorption section located above the ammonium phosphate absorption section; the phosphoric acid absorption section is equipped with a circulating spray liquid pipeline, and the circulating spray liquid pipeline is equipped with a phosphoric acid tank and a circulating pump, which is used to circulate and spray the phosphoric acid solution in the phosphoric acid absorption section to absorb residual ammonia in the coal gas; a short-circuit pipe distributor is provided between the phosphoric acid absorption section and the ammonium phosphate absorption section, and the short-circuit pipe distributor is used to introduce excess phosphoric acid solution in the phosphoric acid absorption section into the ammonium phosphate absorption section.

2. The coke oven gas phosphate washing and ammonia removal device according to claim 1, characterized in that, The ammonium phosphate absorption section includes an ammonium phosphate rich solution absorption section and an ammonium phosphate poor solution absorption section, with the ammonium phosphate rich solution absorption section located below the ammonium phosphate poor solution absorption section.

3. The coke oven gas phosphate washing and ammonia removal device according to claim 2, characterized in that, Liquid cut-off plates are provided between the ammonium phosphate rich solution absorption section and the ammonium phosphate poor solution absorption section, as well as between the ammonium phosphate poor solution absorption section and the phosphoric acid absorption section.

4. The coke oven gas phosphate washing and ammonia removal device according to claim 1, characterized in that, It also includes a cooler located outside the ammonium phosphate absorption section, the cooler being used to cool the absorbent liquid within the ammonium phosphate absorption section.

5. The coke oven gas phosphate washing and ammonia removal device according to claim 1, characterized in that, It also includes an acid mist removal section, which is located above the phosphoric acid absorption section and is used to remove acid mist entrained in the coal gas.

6. The coke oven gas phosphate washing and ammonia removal device according to claim 1, characterized in that, The phosphoric acid tank is equipped with a replenishment port, which is used to replenish fresh phosphoric acid and soft water.

7. A method for removing ammonia from coke oven gas by washing with ammonium phosphate and ammonia concentrate, characterized in that, Includes the following steps: Coke oven gas is passed from bottom to top into the ammonium phosphate absorption section, where it comes into countercurrent contact with the ammonium phosphate solution to absorb ammonia from the gas. The coal gas treated by the ammonium phosphate absorption section is passed into the phosphoric acid absorption section located above the ammonium phosphate absorption section, where it comes into contact with the circulating sprayed phosphoric acid solution to absorb the residual ammonia in the coal gas; excess phosphoric acid solution in the phosphoric acid absorption section is returned to the ammonium phosphate absorption section.

8. The method for removing ammonia from coke oven gas by phosphate washing and ammonia refining according to claim 7, characterized in that, The ammonium phosphate absorption section includes an ammonium phosphate rich solution absorption section and an ammonium phosphate lean solution absorption section. The ammonium phosphate rich solution absorption section is used to absorb most of the ammonia in the coal gas. The coal gas treated by the ammonium phosphate rich solution absorption section enters the ammonium phosphate lean solution absorption section.

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