Method for treating industrial waste gas by co-production with phosphorus chemical production

Abstract

The invention discloses a method for treating industrial waste gas through co-production with phosphorus chemical production, and belongs to the technical field of air pollution prevention and control. The method comprises the following steps: (1) crushing and grinding phosphorite, and then mixing the ground phosphorite with water to prepare phosphorite slurry; (2) carrying out countercurrent contact on the phosphoric ore pulp obtained in the step (1) and smelting flue gas, carrying out smelting flue gas purification treatment, and collecting slurry I after purification treatment; (3) adding sulfuric acid into the slurry I obtained in the step (2), and stirring until the concentration of phosphoric acid in the slurry I reaches 5% or above according to P2O5, so as to obtain slurry II; and (4) conveying the slurry II obtained in the step (3) to a wet-process phosphoric acid production process for recycling to produce phosphoric acid. According to the invention, industrial waste gas purification treatment is carried out through co-production with phosphorus chemical industry production, and the resource utilization rate of low-grade phosphorite and other wastes can be improved, so that secondary pollution is reduced, and good purification treatment of waste gas with relatively complex pollutants is realized on the basis of low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of air pollution prevention and control, and relates to a method for co-producing and treating industrial waste gas in phosphorus chemical production. Background Art

[0002] Industrial waste gas refers to the general term for various pollutant-containing gases discharged into the air during fuel combustion and production processes in the factory area of a production unit. These pollutants directly discharged into the atmosphere will cause serious air pollution, and when the pollutants enter the human body, they will accumulate, thus directly harming human health. Therefore, generally speaking, industrial waste gas cannot be directly discharged into the air. It must be purified to reduce the pollutants to a safe level or remove the pollution before discharging relatively clean gas.

[0003] Smelting flue gas belongs to industrial waste gas. At present, the desulfurization and purification of smelting flue gas are mainly carried out by the limestone-gypsum method. However, on the one hand, a large amount of CO2 will be discharged during the desulfurization process of the limestone-gypsum method, and a large amount of by-product desulfurized gypsum will be generated. Among them, CO2 also belongs to industrial waste gas, and a large amount of emissions will also cause air pollution. And the by-product desulfurized gypsum is difficult to be utilized on a large scale. Most of the by-product desulfurized gypsum can only be piled up, occupying a large amount of land and possibly causing environmental pollution at the same time; on the other hand, when the smelting flue gas is purified by the limestone-gypsum method, it only has a good effect on SO2, and the purification effect is very limited. At the same time, because the limestone-gypsum method is mainly used for flue gas desulfurization, and the tail gas generated during the sulfuric acid production process mainly contains SO2, therefore, the limestone-gypsum method is usually also used in the purification process of sulfuric acid production tail gas, which is also likely to cause secondary environmental pollution.

[0004] Therefore, it is necessary to provide a method for co-producing and treating industrial waste gas in the phosphorus chemical industry to achieve a better purification effect on smelting flue gas and sulfuric acid production tail gas. At the same time, the resource utilization of waste is realized during the treatment process, which helps to reduce secondary pollution and is beneficial to saving treatment costs. Summary of the Invention

[0005] To overcome the problems in the background art, the present invention purifies industrial waste gas by using the phosphate rock slurry formed during the phosphoric acid production process, and the slurry formed after treatment can be returned to the phosphoric acid production process as a raw material for phosphoric acid production, thereby achieving a better purification effect on industrial waste gas (smelting flue gas, sulfuric acid production tail gas). Moreover, the treated slurry can be recycled in the phosphoric acid production process, realizing the resource utilization of waste, reducing secondary pollution. At the same time, the slurry is recycled in the phosphoric acid production process, which can replace part of the raw materials for phosphoric acid production, reducing the consumption of phosphoric acid production raw materials to a certain extent and being beneficial to saving the production cost of phosphoric acid. In addition, the industrial waste gas purification treatment of the present invention is closely combined with the phosphoric acid production process, without the need for additional complex operations, which is beneficial to saving the treatment cost.

[0006] To achieve the above object, the present invention is realized through the following technical solutions:

[0007] The industrial waste gas is non-ferrous smelting flue gas or sulfuric acid production tail gas, and the treatment method of the smelting flue gas includes the following steps:

[0008] (1) Crush and grind phosphate rock, and then mix the ground phosphate rock with water to make a phosphate rock slurry.

[0009] (2) Make the phosphate rock slurry obtained in the step (1) contact countercurrently with the smelting flue gas for smelting flue gas purification treatment, and collect the slurry I after purification treatment.

[0010] (3) Add sulfuric acid to the slurry I obtained in the step (2) and stir until the phosphoric acid concentration in the slurry I reaches more than 5% calculated as P2O5 to obtain slurry II. SO2, NO x As some of the pollutants contained in the smelting flue gas, after countercurrent contact with the phosphate rock slurry, H2SO4 and HNO3 will be generated. The generated H2SO4 and HNO3 will have an acidolysis effect on the phosphate rock in the phosphate rock slurry, generating phosphoric acid. Therefore, adding sulfuric acid to the slurry can increase the phosphoric acid concentration in the slurry, making the slurry meet the raw material requirements of the wet-process phosphoric acid production process before entering the wet-process phosphoric acid production process.

[0011] And since the acid for the acidolysis of the phosphate rock in the slurry comes from the purification treatment product, it is equivalent to reducing the amount of phosphate rock that needs to be acidolyzed in the original wet-process phosphoric acid production process. Therefore, the amount of acid used for acidolysis in the original wet-process phosphoric acid production process is also reduced, thereby achieving the purpose of reducing raw material consumption and saving costs.

[0012] (4) Feed the slurry II obtained in step (3) to the wet-process phosphoric acid production process for recycling to produce phosphoric acid. During the wet-process phosphoric acid production process, it includes a concentration process. The slurry is fed to the concentration process of the wet-process phosphoric acid production as the raw material of the concentration process and merged with the raw material of the original wet-process phosphoric acid production concentration process. Subsequently, the subsequent processes such as concentration of the wet-process phosphoric acid production can proceed normally.

[0013] Preferably, in step (1), the phosphate rock is ground to 200 mesh.

[0014] Preferably, in step (1), the concentration of the phosphate rock slurry is 20% - 40%.

[0015] Preferably, in step (2), both the phosphate rock slurry and the smelting flue gas are fed to a spray tower for countercurrent contact. The liquid-gas volume ratio of the phosphate rock slurry to the smelting flue gas in the tower is phosphate rock slurry:smelting flue gas = 0.005 - 0.03:1, the flow rate of the smelting flue gas is 0.5 - 3 m / s, and the purification treatment temperature is 20 - 60 °C.

[0016] Preferably, in step (2), before the phosphate rock slurry contacts the smelting flue gas countercurrently, 0.5% - 5% of the phosphorus mud based on the mass of the phosphate rock slurry is added to the phosphate rock slurry.

[0017] Preferably, the phosphorus mud is the solid waste generated during the yellow phosphorus production process.

[0018] Preferably, the phosphate rock is the original ore mined from the mine.

[0019] Preferably, the treatment method of the sulfuric acid production tail gas includes the following steps:

[0020] S1: Crush and grind the phosphate rock, and then mix the ground phosphate rock with water to make a phosphate rock slurry.

[0021] S2: Make the phosphate rock slurry obtained in step S1 contact the sulfuric acid production tail gas countercurrently, perform purification treatment on the sulfuric acid production tail gas, and collect the purified slurry III.

[0022] S3: Feed the slurry III obtained in step S2 to the wet-process phosphoric acid production process for recycling to produce phosphoric acid.

[0023] Preferably, in step S1, the phosphate rock is ground to 200 mesh, and the concentration of the phosphate rock slurry is 20% - 40%.

[0024] In step S2, both the phosphate rock slurry and the sulfuric acid production tail gas are fed to a spray tower for countercurrent contact. The liquid-gas volume ratio in the spray tower is phosphate rock slurry:sulfuric acid production tail gas = 0.005 - 0.03:1, the flow rate of the sulfuric acid production tail gas is 0.5 - 3 m / s, and the purification treatment temperature is 20 - 60 °C.

[0025] In step S3, the molar ratio of calcium element to the usage amount of sulfuric acid in the wet-process phosphoric acid production process in slurry III is calcium element: sulfuric acid = 1:1 to 2:1, and the concentration of sulfuric acid in the wet-process phosphoric acid production process is 20% to 30%. The main mineral of phosphorus is apatite, and apatite usually contains Ca element. Therefore, Ca element exists in the phosphate ore slurry. The pollutants in the sulfuric acid production tail gas are relatively single, mainly SO2. Thus, after the phosphate ore slurry and the sulfuric acid production tail gas are in countercurrent contact, H2SO4 and HNO3 will be obtained by reaction. Although sulfuric acid will have an acidolysis effect on the phosphate ore after being generated in the phosphate ore slurry, thereby consuming sulfuric acid, however, due to the large amount of SO2 existing in the sulfuric acid production tail gas, after the sulfuric acid in the phosphate ore slurry pre-decomposes the phosphate ore slurry, it still exists. When the slurry is transported to the acidolysis process of the wet-process phosphate ore production process, it can replace part of the sulfuric acid that needs to be added in the wet-process phosphoric acid production process, thereby saving part of the raw materials. At the same time, the sulfuric acid obtained from sulfuric acid production can be directly used for acidolysis of phosphate ore in the wet-process phosphoric acid production process.

[0026] Advantages of the present invention:

[0027] 1. The present invention has an excellent purification effect on smelting flue gas.

[0028] 2. The present invention enables the resource utilization of low-grade phosphate ore and improves the resource utilization rate of low-grade phosphate ore.

[0029] 3. By adding slime phosphorus to the phosphate ore slurry, the present invention not only realizes the resource utilization of slime phosphorus solid waste, achieving waste treatment with waste, but also strengthens the purification effect of the phosphate ore slurry on smelting flue gas.

[0030] 4. The present invention uses the phosphate ore slurry to purify industrial waste gas, and at the same time, the purified slurry can also be returned to the phosphoric acid production process as a raw material. The purification of industrial waste gas and the phosphochemical industry have excellent compatibility, have little impact on the normal production of phosphoric acid, have a small difficulty in process improvement and transformation, and have a small cost investment.

[0031] 5. Phosphate ore is relatively cheap compared with limestone. The present invention uses phosphate ore to prepare phosphate ore slurry for industrial waste gas purification treatment, which is beneficial to reducing the treatment cost.

[0032] 6. The process flow of the present invention is simple, has good compatibility with the phosphochemical industry, and is suitable for industrial promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a process flow schematic diagram of the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] The following further describes the present invention in detail with reference to specific embodiments, but the protection scope of the present invention is not limited to the content described.

[0035] Example 1

[0036] In this example, the smelting flue gas is purified by the following method:

[0037] (1) The as-mined phosphate rock ore is crushed and ground to 200 mesh, and the ground phosphate rock is mixed with water to prepare a phosphate rock slurry with a concentration of 20%.

[0038] (2) The phosphate rock slurry is transported to a spray tower, and at the same time, the smelting flue gas is also transported to the spray tower. The temperature inside the spray tower is set at 20 °C, the liquid-gas volume ratio is 0.005:1, and the smelting flue gas flow rate is 0.5 m / s. The smelting flue gas and the phosphate rock slurry are in countercurrent contact inside the spray tower. The smelting flue gas is purified, and the purified smelting flue gas is discharged normally, and the slurry obtained after purification is collected.

[0039] (3) Sulfuric acid is added to the collected slurry until the phosphoric acid concentration in the slurry reaches 10% (calculated as P2O5).

[0040] (4) The slurry is transported to the wet-process phosphoric acid production process for phosphoric acid production.

[0041] After the smelting flue gas is purified in this example, it meets the emission standards and can be discharged normally, in which the SO2 emission is less than 100 mg / m 3 , NO x emission is less than 50 mg / m 3 .

[0042] In this example, the quality of the finally prepared phosphoric acid is similar to that of the phosphoric acid prepared by the original wet-process phosphoric acid production process, indicating that transporting the slurry to the wet-process phosphoric acid production process will not have a negative impact on the normal production of phosphoric acid.

[0043] Example 2

[0044] In this example, the smelting flue gas is purified by the following method:

[0045] (1) The as-mined phosphate rock ore is crushed and ground to 200 mesh, and the ground phosphate rock is mixed with water to prepare a phosphate rock slurry with a concentration of 40%.

[0046] (2) The phosphate rock slurry is transported to a spray tower, and at the same time, the smelting flue gas is also transported to the spray tower. The temperature inside the spray tower is set at 50 °C, the liquid-gas volume ratio is 0.01:1, and the smelting flue gas flow rate is 3 m / s. The smelting flue gas and the phosphate rock slurry are in countercurrent contact inside the spray tower. The smelting flue gas is purified, and the purified smelting flue gas is discharged normally, and the slurry obtained after purification is collected.

[0047] (3) Add sulfuric acid to the collected slurry until the concentration of phosphoric acid in the slurry reaches 8% (calculated as P2O5).

[0048] (4) Transport the slurry to the wet-process phosphoric acid production process for phosphoric acid production.

[0049] The purification effect of the smelting flue gas in this example is similar to that in Example 1.

[0050] Example 3

[0051] The purification of the smelting flue gas in this example is carried out by the following method:

[0052] (1) Crush the as-mined phosphate rock ore from the mine, grind it to 200 mesh, mix the ground phosphate rock with water to prepare a phosphate rock slurry with a concentration of 30%, and add 0.5% of slime phosphorus (by mass of the phosphate rock slurry) to the phosphate rock slurry.

[0053] (2) Transport the phosphate rock slurry to the spray tower, and at the same time transport the smelting flue gas to the spray tower. Set the temperature in the spray tower to 60 °C, the liquid-gas volume ratio to 0.03:1, the flow rate of the smelting flue gas to 1.5 m / s. The smelting flue gas and the phosphate rock slurry conduct countercurrent contact in the spray tower. The smelting flue gas is purified, and the purified smelting flue gas is discharged normally, and the slurry obtained after purification is collected.

[0054] (3) Add sulfuric acid to the collected slurry until the concentration of phosphoric acid in the slurry reaches 9% (calculated as P2O5).

[0055] (4) Transport the slurry to the wet-process phosphoric acid production process for phosphoric acid production.

[0056] After the smelting flue gas is purified in this example, it meets the emission standard and can be discharged normally, where the SO2 emission is less than 90 mg / m 3 , NO x emission is less than 40 mg / m 3 . It shows that after adding slime phosphorus, the treatment effect of the phosphate rock slurry on the smelting flue gas has a slight improvement, and slime phosphorus has a promoting effect on the purification treatment of the smelting flue gas.

[0057] In this example, the quality of the finally prepared phosphoric acid is similar to that of the phosphoric acid prepared by the original wet-process phosphoric acid production process, indicating that transporting the slurry to the wet-process phosphoric acid production process will not have a negative impact on the normal production of phosphoric acid.

[0058] Example 4

[0059] This example uses the same method as Example 3 to purify the smelting flue gas, the difference is: add 3% of slime phosphorus to the phosphate rock slurry.

[0060] The purification effect of the smelting flue gas in this example is similar to that in Example 3.

[0061] Example 5

[0062] In this example, the same method as in Example 3 is used to purify the smelting flue gas, with the difference that 5% of muddy phosphorus is added to the phosphate rock slurry.

[0063] The purification effect of the smelting flue gas in this example is similar to that in Example 3.

[0064] Example 6

[0065] The purification of the sulfuric acid production tail gas in this example is carried out by the following method:

[0066] (1) The as-mined phosphate rock ore from the mine is crushed and ground to 200 mesh, and the ground phosphate rock is mixed with water to prepare a phosphate rock slurry with a concentration of 30%.

[0067] (2) The phosphate rock slurry is transported to the spray tower, and at the same time, the sulfuric acid production tail gas is also transported to the spray tower. The temperature inside the spray tower is set at 35 °C, the liquid-gas ratio is 0.007:1, and the gas flow rate is 2 m / s. The sulfuric acid production tail gas and the phosphate rock slurry are in countercurrent contact inside the spray tower. The sulfuric acid production tail gas is purified, and the purified sulfuric acid production tail gas is discharged normally, and the slurry obtained after purification is collected.

[0068] (3) The collected slurry is transported to the wet-process phosphoric acid production process. The sulfuric acid originally used in the wet-process phosphoric acid production process has a concentration of 25%, and the mass ratio of the originally used sulfuric acid to the transported slurry is approximately sulfuric acid:slurry = 1.2:1 (the molar ratio of calcium element to sulfuric acid in the slurry is 1:1.03).

[0069] After the smelting flue gas is purified in this example, it meets the emission standards and can be discharged normally, where the SO2 emission is less than 100 mg / m 3 , NO x emission is less than 50 mg / m 3 .

[0070] In this example, the quality of the finally prepared phosphoric acid is similar to that of the phosphoric acid prepared by the original wet-process phosphoric acid production process, indicating that transporting the slurry to the wet-process phosphoric acid production process will not have a negative impact on the normal production of phosphoric acid.

[0071] Example 7

[0072] The purification of the sulfuric acid production tail gas in this example is carried out by the following method:

[0073] (1) The as-mined phosphate rock ore from the mine is crushed and ground to 200 mesh, and the ground phosphate rock is mixed with water to prepare a phosphate rock slurry with a concentration of 20%.

[0074] (2) Transport the phosphoric ore pulp to the spray tower, and at the same time transport the sulfuric acid production tail gas to the spray tower. Set the temperature in the spray tower to 20°C, the liquid-gas ratio to 0.005:1, and the gas flow rate to 0.5 m / s. The sulfuric acid production tail gas and the phosphoric ore pulp are in countercurrent contact in the spray tower. The sulfuric acid production tail gas is purified, and the purified sulfuric acid production tail gas is discharged normally, and the slurry obtained after purification is collected.

[0075] (3) Transport the collected slurry to the wet-process phosphoric acid production process. The sulfuric acid originally used in the wet-process phosphoric acid production process has a concentration of 20%, and the mass ratio of the originally used sulfuric acid to the transported slurry is approximately sulfuric acid:slurry = 1.17:1 (the molar ratio of calcium element to sulfuric acid in the slurry is 1:1.2).

[0076] The purification treatment effect of the sulfuric acid production tail gas in this example is similar to that in Example 7.

[0077] Example 8

[0078] The sulfuric acid production tail gas is purified in this example by the following method:

[0079] (1) Crush the raw phosphoric ore mined in the mine and grind it to 200 meshes, and mix the ground phosphoric ore with water to prepare a phosphoric ore pulp with a concentration of 30%.

[0080] (2) Transport the phosphoric ore pulp to the spray tower, and at the same time transport the sulfuric acid production tail gas to the spray tower. Set the temperature in the spray tower to 60°C, the liquid-gas ratio to 0.03:1, and the gas flow rate to 3 m / s. The sulfuric acid production tail gas and the phosphoric ore pulp are in countercurrent contact in the spray tower. The sulfuric acid production tail gas is purified, and the purified sulfuric acid production tail gas is discharged normally, and the slurry obtained after purification is collected.

[0081] (3) Transport the collected slurry to the wet-process phosphoric acid production process. The sulfuric acid originally used in the wet-process phosphoric acid production process has a concentration of 30%, and the mass ratio of the originally used sulfuric acid to the transported slurry is approximately sulfuric acid:slurry = 1.94:1 (the molar ratio of calcium element to sulfuric acid in the slurry is 1:2).

[0082] The purification treatment effect of the sulfuric acid production tail gas in this example is similar to that in Example 7.

[0083] In summary, the present invention uses the phosphate ore pulp involved in the phosphate ore production process to purify the smelting flue gas and the tail gas of sulfuric acid production (industrial waste gas). Excellent purification treatment effects are achieved for both the smelting flue gas and the tail gas of sulfuric acid production. Moreover, the products after purification treatment can be smoothly used as raw materials in the wet-process phosphoric acid production process, enabling the industrial waste gas purification treatment method of the present invention to be closely integrated with the phosphochemical production and having little impact on the normal production of phosphoric acid. Thus, the resource utilization of low-grade phosphate ore and other wastes is realized, which helps to reduce secondary pollution and achieve industrial waste gas purification treatment with low cost and excellent effects.

[0084] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for co - processing industrial waste gas in phosphorus chemical production, characterized in that: The industrial waste gas is colored smelting flue gas or sulfuric acid production tail gas, and the treatment method of the smelting flue gas includes the following steps: (1) Crush and grind the phosphate rock, and then mix the ground phosphate rock with water to make a phosphate rock slurry; (2) Make the phosphate rock slurry obtained in the step (1) contact countercurrently with the smelting flue gas for purifying the smelting flue gas, and collect the slurry I after purification treatment; (3) Add sulfuric acid to the slurry I obtained in the step (2) and stir until the concentration of phosphoric acid in the slurry I reaches more than 5% based on P2O5 to obtain slurry II; (4) Transport the slurry II obtained in the step (3) to the wet-process phosphoric acid production process for recycling to produce phosphoric acid.

2. The method according to claim 1, wherein: In the step (1), the phosphate rock is ground to 200 meshes.

3. The method according to claim 1, wherein: In the step (1), the concentration of the phosphate rock slurry is 20% - 40%.

4. The method according to claim 1, wherein: In the step (2), both the phosphate rock slurry and the smelting flue gas are transported to a spray tower for countercurrent contact. The volume ratio of the liquid to the gas of the phosphate rock slurry to the smelting flue gas in the tower is phosphate rock slurry:smelting flue gas = 0.005 - 0.03:1, the flow rate of the smelting flue gas is 0.5 - 3 m / s, and the purification treatment temperature is 20 - 60 °C.

5. The method according to claim 1, wherein: In the step (2), before the phosphate rock slurry contacts the smelting flue gas countercurrently, add 0.5% - 5% of muddy phosphorus based on the mass of the phosphate rock slurry to the phosphate rock slurry.

6. The method according to claim 5, characterized in that: The muddy phosphorus is a solid waste generated during the production of yellow phosphorus.

7. The method according to any one of claims 1-6, characterized in that: The phosphate rock is the original ore mined from the mine.

8. The method according to claim 1, wherein: The treatment method of the sulfuric acid production tail gas includes the following steps: S1: Crush and grind the phosphate rock, and then mix the ground phosphate rock with water to make a phosphate rock slurry; S2: Make the phosphate rock slurry obtained in the step S1 contact countercurrently with the sulfuric acid production tail gas for purifying the sulfuric acid production tail gas, and collect the slurry III after purification treatment; S3: Transport the slurry III obtained in the step S2 to the wet-process phosphoric acid production process for recycling to produce phosphoric acid.

9. The method according to claim 8, wherein: In the step S1, the phosphate rock is ground to 200 meshes and the concentration of the phosphate rock slurry is 20% - 40%; In the step S2, both the phosphate rock slurry and the sulfuric acid production tail gas are transported to a spray tower for countercurrent contact. The volume ratio of the liquid to the gas in the spray tower is phosphate rock slurry:sulfuric acid production tail gas = 0.005 - 0.03:1, the flow rate of the sulfuric acid production tail gas is 0.5 - 3 m / s, and the purification treatment temperature is 20 - 60 °C; In the step S3, the molar ratio of calcium element to the amount of sulfuric acid used in the wet-process phosphoric acid production process in the slurry III is calcium element:sulfuric acid = 1:1 - 1:2, and the concentration of sulfuric acid in the wet-process phosphoric acid production process is 20% - 30%.

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