AHF section tail gas desulfurization method

Abstract

The invention relates to the technical field of desulfurization processes, in particular to an AHF section tail gas desulfurization method. The method comprises the following steps: firstly, treating the AHF section tail gas through a desulfurizing tower and an alkaline washing tower in sequence, then discharging, conveying waste slurry obtained by the desulfurizing tower to a settling pond, carrying out solid-liquid separation, preparing obtained solids into filter cakes through a filter press, conveying waste liquid obtained by the alkaline washing tower to a comprehensive treatment workshop, and treating to complete the desulfurization of the AHF section tail gas; wherein the desulfurization rate of the AHF section tail gas is greater than or equal to 95%. According to the invention, the quality of the anhydrous hydrogen fluoride finished product can be improved, the corrosion of equipment is reduced, the inspection and maintenance frequency is shortened, the emission of harmful gases is reduced, the environment-friendly competitiveness is improved, and a better market environment is provided for the benign competition of enterprises.

Description

Technical Field

[0001] This invention relates to the field of desulfurization technology, and in particular to a method for desulfurizing tail gas in the AHF section. Background Technology

[0002] Traditionally, fluorite powder reacts with sulfuric acid in an external rotary kiln to produce anhydrous hydrogen fluoride. The fluorite powder, mostly derived from fluorite ore after screening, is primarily composed of calcium fluoride, with small amounts of calcium carbonate, silicon dioxide, sulfides, and other impurities. The sulfides and concentrated sulfuric acid in the fluorite powder undergo different transformations under varying temperatures and proportions, leading to the generation of sulfur dioxide gas. SO2 is a colorless gas with a strong, pungent odor, harmful to human respiratory systems and plants, and, along with nitrogen oxides, is a major pollutant contributing to acid rain. The presence of moisture in the raw materials and during reactions within the rotary kiln, if not properly handled, exacerbates the corrosion rate of the rotary kiln under high temperatures. In severe cases, this can lead to the leakage of anhydrous hydrogen fluoride gas, further exacerbating environmental pollution.

[0003] Hydrogen fluoride (AHF) is a basic raw material for many fluorochemical products, with wide applications and large demand. However, because hydrogen fluoride is a highly toxic and heavily regulated hazardous chemical, its production involves gas, solid, and liquid phases, making production quite challenging. Traditional production processes and equipment, as well as the addition of new equipment, all inevitably increase the investment in production.

[0004] Therefore, it is necessary to conduct further research on the existing processes to improve the quality of anhydrous hydrogen fluoride products, reduce equipment investment, reduce exhaust emissions, and enhance environmental competitiveness. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a method for desulfurizing tail gas from an AHF (Air-to-Fuel) production line. This invention involves passing the sulfur dioxide-containing gas from the tail gas of the AHF production unit, after absorption, through a calcium hydroxide desulfurization tower. The slurry from the absorption reaction is pumped into a filter press to form a filter cake. The waste liquid obtained from the sodium hydroxide alkaline washing tower is then sent to a comprehensive treatment workshop for further processing. This process removes the vast majority of sulfur dioxide from the gas, ensuring it meets emission standards.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] This invention provides a method for desulfurization of tail gas in an AHF process, comprising the following steps:

[0008] The tail gas from the AHF section (a light component gas mainly composed of SiF4) is treated sequentially by a desulfurization tower and an alkaline scrubbing tower before being discharged (achieving a sulfur dioxide emission standard of ≤100 mg / m³). 3The waste slurry obtained from the desulfurization tower is sent to the sedimentation tank. After solid-liquid separation, the obtained solid is made into filter cake by a pressure filter. The waste liquid obtained from the alkali washing tower is sent to the comprehensive treatment workshop for treatment. Most of the sulfur dioxide is removed from the gas, and the desulfurization of the tail gas of the AHF section is completed. The desulfurization rate of the tail gas of the AHF section is ≥95%.

[0009] In one embodiment of the present invention, the desulfurization tower uses 5-10 wt% calcium hydroxide slurry as the desulfurization liquid.

[0010] Preferably, the desulfurization tower has several layers of first spraying components arranged parallel to each other at the top for spraying calcium hydroxide slurry; the bottom of the desulfurization tower is provided with a stirring circulation tank to prevent solid sediment from accumulating in the bottom of the desulfurization tower.

[0011] More preferably, the first spray assembly has three layers arranged in parallel at intervals.

[0012] Preferably, the pH in the stirring circulation tank is controlled at 6-7.

[0013] In one embodiment of the present invention, a sodium hydroxide solution of ≤2wt% is used as the alkaline washing liquid in the alkaline washing tower.

[0014] Preferably, the pH value of the alkaline washing solution is controlled to be >7.

[0015] Preferably, the top of the alkaline washing tower is provided with several layers of second spray components for spraying alkaline washing liquid at parallel intervals.

[0016] More preferably, the second spray assembly is provided with three layers spaced parallel to each other.

[0017] Preferably, the clear liquid obtained after solid-liquid separation is used for the preparation of solutions in the desulfurization tower and the alkali washing tower.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention utilizes existing production facilities and adds a tail gas desulfurization device. It can reduce SO2 emissions in the tail gas using only calcium hydroxide slurry and sodium hydroxide solution, thus more effectively controlling the SO2 emission value of the equipment tail gas. This invention can improve the quality of anhydrous hydrogen fluoride products, reduce equipment corrosion, shorten maintenance frequency, reduce the emission of harmful gases, enhance environmental competitiveness, and provide a better market environment for healthy competition among enterprises. Detailed Implementation

[0020] The present invention will now be described in detail with reference to specific embodiments.

[0021] Unless otherwise specified, the structures or components used in the following embodiments are conventional structures or components in the art, the reagents used are commercially available reagents, and the detection methods and means used are conventional detection methods and means in the art.

[0022] Example 1

[0023] This embodiment provides a method for desulfurization of tail gas in an AHF process, including the following steps:

[0024] The tail gas of the AHF section (light component gas mainly composed of SiF4) is treated sequentially by the desulfurization tower and the alkaline washing tower before being discharged. The waste slurry obtained from the desulfurization tower is sent to the sedimentation tank. After solid-liquid separation, the obtained solid is made into filter cake by a pressure filter. The obtained clear liquid is used to prepare the desulfurization tower solution (calcium hydroxide slurry) and the alkaline washing tower solution (sodium hydroxide solution) to complete the desulfurization of the tail gas of the AHF section.

[0025] In this embodiment, the tail gas from the AHF section enters the desulfurization tower through the inlet of the desulfurization tower bottom. The top of the desulfurization tower is equipped with three parallel spraying components for spraying calcium hydroxide slurry (using 5-10 wt% calcium hydroxide slurry as the desulfurization liquid). The calcium hydroxide slurry is sprayed from top to bottom to react with sulfur dioxide in the tail gas from the AHF section (absorbing sulfur dioxide in the tail gas from the AHF section). The bottom of the desulfurization tower is equipped with a stirring circulation tank to enhance the reaction and prevent solid precipitation in the bottom of the desulfurization tower (the pH in the stirring circulation tank is controlled at 6-7; if the pH is too high, scaling is likely to occur; if the pH is too low, sulfur dioxide is likely to precipitate).

[0026] The gas treated by the desulfurization tower enters the alkaline washing tower through the bottom inlet of the alkaline washing tower. The top of the alkaline washing tower is equipped with three parallel and spaced second spray components for spraying alkaline washing liquid (≤2wt% sodium hydroxide solution is used as alkaline washing liquid in the alkaline washing tower (pH value >7)). The alkaline washing liquid is sprayed from top to bottom and reacts with the gas treated by the desulfurization tower to absorb the trace amounts of sulfur dioxide that were not treated by the desulfurization tower.

[0027] The calcium hydroxide slurry is stored in a first preparation tank, which is connected to the inlet of the desulfurization tower via a first discharge pump. The calcium hydroxide slurry is a mixed solution of calcium hydroxide and water (including the clear liquid obtained after solid-liquid separation). When the liquid level in the first preparation tank reaches a low level, calcium hydroxide and water are simultaneously added to the preparation tank in a set ratio. When the liquid level reaches a high level, the addition of calcium hydroxide and water is stopped.

[0028] The sodium hydroxide solution is a mixed solution of sodium hydroxide mother liquor (≤32% sodium hydroxide solution) and water (including the clear liquid obtained after solid-liquid separation). The sodium hydroxide mother liquor and water are transported to the feed inlet of the alkali washing tower by a circulating pump.

[0029] In this embodiment, the sulfur dioxide content of the AHF section tail gas treated by the desulfurization tower and alkali washing tower is ≤100mg / m³. 3 The desulfurization rate is 95%.

[0030] Comparative Example 1

[0031] This comparative example provides a desulfurization method for the tail gas of the AHF section, which is the same as that in Example 1 except for the following:

[0032] The desulfurization solution in the desulfurization tower is a sodium hydroxide solution of ≤2wt%, and the alkaline washing solution in the alkaline washing tower is a calcium hydroxide slurry of 5-10wt%.

[0033] In this comparative example, the sulfur dioxide content of the tail gas from the AHF section, after treatment by the desulfurization tower and alkali scrubbing tower, is ≤100 mg / m³. 3 The desulfurization rate is 95%, but the cost is 4 times higher than that of Example 1.

[0034] Comparative Example 2

[0035] This comparative example provides a desulfurization method for the tail gas of the AHF section, which is the same as that in Example 1 except for the following:

[0036] The desulfurization liquid in the desulfurization tower is a calcium hydroxide slurry of 2-5 wt%.

[0037] In this comparative example, the tail gas from the AHF section treated by the desulfurization tower and the alkali washing tower had a desulfurization rate of 90%, which was worse than the desulfurization rate in Example 1.

[0038] Comparative Example 2

[0039] This comparative example provides a desulfurization method for the tail gas of the AHF section, which is the same as that in Example 1 except for the following:

[0040] The desulfurization liquid in the desulfurization tower is a calcium hydroxide slurry of 10-15 wt%.

[0041] In this comparative example, the tail gas from the AHF section treated by the desulfurization tower and the alkali washing tower achieved a desulfurization rate of 95%, but the cost increased by 1.5 times compared to Example 1.

[0042] Comparative Example 3

[0043] This comparative example provides a desulfurization method for the tail gas of the AHF section, which is the same as that in Example 1 except for the following:

[0044] The alkaline washing solution in the alkaline washing tower is a 1 wt% sodium hydroxide solution.

[0045] In this comparative example, the tail gas from the AHF section treated by the desulfurization tower and the alkali washing tower achieved a desulfurization rate of 93%, which is slightly worse than the desulfurization rate in Example 1.

[0046] Comparative Example 4

[0047] This comparative example provides a desulfurization method for the tail gas of the AHF section, which is the same as that in Example 1 except for the following:

[0048] The alkaline washing solution in the alkaline washing tower is a 4 wt% sodium hydroxide solution.

[0049] In this comparative example, the tail gas from the AHF section treated by the desulfurization tower and the alkali washing tower achieved a desulfurization rate of 97%, but the cost increased by 2 times compared to Example 1.

[0050] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the interpretation of the present invention, without departing from the scope of the invention, should be within the protection scope of the present invention.

Claims

1. A method for desulfurization of tail gas in an AHF process, characterized in that, Includes the following steps: The tail gas from the AHF section is treated sequentially by a desulfurization tower and an alkaline scrubbing tower before being discharged. The waste slurry obtained from the desulfurization tower is sent to a sedimentation tank. After solid-liquid separation, the obtained solid is processed into filter cake by a filter press. The waste liquid obtained from the alkaline scrubbing tower is sent to the comprehensive treatment workshop for treatment, thus completing the desulfurization of the tail gas from the AHF section. The desulfurization rate of the tail gas from the AHF section is ≥95%.

2. The method for desulfurization of tail gas in an AHF section according to claim 1, characterized in that, The desulfurization tower uses 5-10 wt% calcium hydroxide slurry as the desulfurization liquid.

3. The method for desulfurization of tail gas in an AHF section according to claim 2, characterized in that, The desulfurization tower has several layers of first spray components arranged parallel and spaced apart at the top of the tower for spraying calcium hydroxide slurry. The bottom of the desulfurization tower is equipped with a stirring circulation tank to enhance the reaction and prevent solids from accumulating in the bottom of the desulfurization tower.

4. The method for desulfurization of tail gas in an AHF section according to claim 3, characterized in that, The first spray assembly has three layers arranged in parallel at intervals.

5. The method for desulfurization of tail gas in an AHF section according to claim 3, characterized in that, The pH in the stirring circulation tank should be controlled at 6-7.

6. The method for desulfurization of tail gas in an AHF section according to claim 1, characterized in that, In the alkaline washing tower, a sodium hydroxide solution of ≤2wt% is used as the alkaline washing liquid.

7. The method for desulfurization of tail gas in an AHF section according to claim 6, characterized in that, Control the pH value of the alkaline washing solution to be greater than 7.

8. The method for desulfurization of tail gas in an AHF section according to claim 6, characterized in that, The top of the alkaline washing tower is provided with several layers of second spray components for spraying alkaline washing liquid at parallel intervals.

9. A method for desulfurizing tail gas in an AHF section according to claim 8, characterized in that, The second spray assembly has several layers arranged in parallel at intervals.

10. A method for desulfurizing tail gas in an AHF section according to claim 1, characterized in that, The clear liquid obtained after solid-liquid separation is used for the preparation of solutions in the desulfurization tower and alkali washing tower.