A process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system

Abstract

The present invention provides a process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system, belonging to the technical field of wet-process phosphoric acid preparation. The process comprises the following steps: S1. passing a mixed flue gas from the bottom of a first tower into a primary absorption and regeneration tower, while a washing liquid, after being treated by a heater, enters the primary absorption and regeneration tower from the top of the first tower. The washing liquid temperature is controlled at 40-50°C, and the mixed flue gas and the washing liquid are in countercurrent contact; S2. The mixed flue gas is discharged from the top of the first tower and enters a secondary absorption and regeneration tower from the bottom of a second tower. The washing liquid enters the secondary absorption and regeneration tower from the top of the second tower, and the mixed flue gas and the washing liquid are in countercurrent contact; S3. The mixed flue gas enters a mist separator from the top of the second tower, is treated by the mist separator, and is then discharged. This process can significantly remove hydrogen sulfide gas from the mixed flue gas, while also reducing the organic gas methyl isobutyl ketone in the mixed flue gas, thereby improving the waste gas treatment effect.

Description

Technical Field

[0001] The present invention relates to the technical field of wet-process phosphoric acid preparation, and in particular to a process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system. Background Art

[0002] The purified phosphoric acid operation department at Wengfu Zijin Co., Ltd. uses sodium sulfide for arsenic removal during its production process. During the arsenic removal process, the added sodium sulfide first reacts with phosphoric acid to produce hydrogen sulfide gas. This hydrogen sulfide then reacts with arsenous acid to form As₂S₃ and As₂S₅ precipitates. The remaining hydrogen sulfide gas enters the purified phosphoric acid purification system.

[0003] Because solvent extraction is used in the production process of purified phosphoric acid, and the extractant is methyl isobutyl ketone, a flammable and volatile organic solvent, the flue gas from the purification system is rich in methyl isobutyl ketone organic gas, hydrogen sulfide, fluoride, etc. The flue gas composition is complex and the composition fluctuates greatly, making flue gas treatment very difficult.

[0004] The flue gas is scrubbed for hydrogen sulfide using a tower spray scrubber and a high-gravity hydrogen sulfide scrubber (the scrubbing fluid is liquid caustic soda). However, due to the complex and fluctuating composition of the flue gas and the low removal efficiency of the spray scrubber and high-gravity scrubber, the hydrogen sulfide content remains high after treatment. Furthermore, the sodium sulfide solution generated by the reaction of sodium hydroxide (the scrubbing fluid) with hydrogen sulfide poses a risk of leakage. Sodium sulfide is a hazardous chemical that rapidly generates highly toxic hydrogen sulfide gas when in contact with acid, posing a significant safety hazard. Currently, there is no process for efficiently removing hydrogen sulfide from the production process with a low risk factor. Summary of the Invention

[0005] To overcome the problems existing in the related art, the purpose of the present invention is to provide a process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system. The process can significantly remove hydrogen sulfide gas from mixed flue gas, while also reducing the organic gas methyl isobutyl ketone in the mixed flue gas, thereby improving the waste gas treatment effect.

[0006] A process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system.

[0007] The steps include:

[0008] S1. The mixed flue gas enters the primary absorption and regeneration tower from the bottom of the first tower. At the same time, the scrubbing liquid, after being treated by the heater, enters the primary absorption and regeneration tower from the top of the first tower. The scrubbing liquid temperature is controlled at 40-50°C. The mixed flue gas and scrubbing liquid contact in a countercurrent manner.

[0009] S2. The mixed flue gas is discharged from the top of the first tower and enters the secondary absorption and regeneration tower from the bottom of the second tower. The scrubbing liquid enters the secondary absorption and regeneration tower from the top of the second tower. The mixed flue gas and the scrubbing liquid are in contact in a countercurrent manner.

[0010] S3. The mixed flue gas enters the entrainment separator from the top of the second tower and is discharged after being processed by the entrainment separator;

[0011] By setting up a two-stage absorption and regeneration treatment, the mixed flue gas can be purified to the maximum extent while taking into account economic and energy-saving considerations; the washing liquid is heated before entering the first-stage absorption and regeneration tower, and the temperature is controlled within a certain range to ensure that the washing liquid does not crystallize when the ambient temperature is low; the small droplets entrained in the mixed flue gas are captured by the mist separator and then discharged.

[0012] In the preferred technical solution of the present invention, in the first-stage absorption and regeneration tower and the second-stage absorption and regeneration tower, the mixed flue gas flow rate and the washing liquid flow rate are both mixed flue gas flow rate (Nm 3 / h): washing liquid flow (m 3 / h) is (20-40):1, negative pressure 900-1100pa;

[0013] In a preferred technical solution of the present invention, the washing liquid comprises the following components in parts by weight:

[0014]

[0015] The washing liquid also includes sodium hydroxide solution, and the amount of sodium hydroxide solution added is to control the pH value of the washing liquid to be 9-10.

[0016] The scrubbing liquid treatment mechanism involves countercurrent contact between the mixed flue gas and the scrubbing liquid in the primary and secondary absorption regeneration towers. The overall process proceeds as follows: H2S + 1 / 2O2 → H2O + S°. This reaction occurs in a water-based solution and is catalyzed by the scrubbing liquid. This reaction can be divided into two parts: absorption and regeneration, as shown below:

[0017] Absorption part

[0018]

[0019]

[0020] HS - +2Fe 3+ →2Fe 2+ +H + +S (3)

[0021] The total equation of the absorption part (Equations 1, 2, and 3 superimposed)

[0022] H2S(g)+2Fe 3+ →2H + +S+2Fe 2+ (4)

[0023] Regeneration part

[0024]

[0025] 1 / 2O2(l)+H2O+2Fe2+→2OH-+2Fe3+ (6)

[0026] The total equation of the regeneration part (Equations 5 and 6 superimposed)

[0027] 1 / 2O2(g)+H2O+2Fe 2+ →2OH - +2Fe 3+ (7)

[0028] The improved Claus reaction equation is obtained by superimposing equations 4 and 7:

[0029] H2S+1 / 2O2→H2O+S°.

[0030] The concentrations of methyl isobutyl ketone and fluoride in the mixed flue gas are also reduced, and fluoride is dissolved in the scrubbing liquid. 2+ In the presence of hydroxyl radicals with strong oxidizing ability, hydroxyl radicals are generated to achieve the degradation of organic matter, that is, methyl isobutyl ketone is catalytically oxidized to inorganic carbon dioxide gas and water through catalytic oxidation reaction;

[0031] The scrubbing liquid has high efficiency in washing mixed flue gas once, and the removal rate of hydrogen sulfide after washing is 87.3-92.9%, and the removal rate of organic gas methyl isobutyl ketone after washing is 9.6-11%.

[0032] In a preferred technical solution of the present invention, the concentration of the hydrogen peroxide solution is 25-30%.

[0033] In a preferred technical solution of the present invention, the concentration of the sodium hydroxide solution is 45-50%.

[0034] In a preferred technical solution of the present invention, the weight ratio of the ethylenediaminetetraacetic acid, sodium salt of nitrilotriacetic acid and nonylphenol ethoxylate is in the range of 1:(6-8):(1-2).

[0035] In a preferred technical solution of the present invention, in S1, the washing liquid is discharged from the bottom of the first tower, and after being processed by the first-stage jet pump and the heater in sequence, it re-enters the first-stage absorption and regeneration tower from the top of the first tower;

[0036] In order to prevent water and hydrocarbons from condensing in the primary absorption and regeneration tower, the washing liquid is maintained at a higher temperature (40-50℃) to maintain the water balance of the system. The circulating washing liquid is heated by the heater and then recycled to ensure the treatment effect of the system solution on acid gas. At the same time, it avoids the situation where the washing liquid crystallizes and causes system blockage when the ambient temperature is low. While controlling the washing liquid temperature in the primary absorption and regeneration tower, it can also avoid the washing liquid temperature in the secondary absorption and regeneration tower being too low.

[0037] In a preferred technical solution of the present invention, in S2, the washing liquid is discharged from the bottom of the second tower, and after being processed by the secondary jet pump, it re-enters the secondary absorption and regeneration tower from the top of the second tower.

[0038] In a preferred technical solution of the present invention, the sulfur generated in the first-stage absorption and regeneration tower settles at the bottom of the first tower and is pumped to the filter press through a first-stage sulfur slurry pump;

[0039] The elemental sulfur generated in the primary absorption and regeneration tower is transported to the filter press for solid-liquid separation. The solid by-product sulfur paste can be processed for external value, and the filtrate can be recycled and reused as washing liquid.

[0040] In a preferred technical solution of the present invention, the sulfur generated in the secondary absorption and regeneration tower settles at the bottom of the second tower and is pumped to the filter press through a secondary sulfur slurry pump;

[0041] The elemental sulfur generated in the secondary absorption and regeneration tower is transported to the filter press for solid-liquid separation. The solid by-product sulfur paste can be processed for external value, and the filtrate can be recycled and reused as washing liquid.

[0042] In a preferred technical solution of the present invention, air is introduced into the bottom of the first absorption and regeneration tower and the bottom of the second absorption and regeneration tower respectively through a blower;

[0043] In a preferred technical solution of the present invention, air is introduced into the bottom of the first absorption and regeneration tower and the bottom of the second absorption and regeneration tower respectively through a blower and a tower bottom distributor in sequence;

[0044] Air from the blower is introduced into the first-stage absorption regeneration tower and the second-stage absorption regeneration tower respectively, and enters the tower evenly through the bottom distributor to oxidize the divalent iron ions in the washing liquid; at the same time, it can reduce the concentration of the mixed gas and improve the purification effect.

[0045] The beneficial effects of the present invention are:

[0046] The present invention provides a process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system. The process can significantly remove hydrogen sulfide gas from mixed flue gas while also reducing methyl isobutyl ketone (MIBK) in the mixed flue gas. After the mixed flue gas passes through a primary absorption and regeneration tower and a secondary absorption and regeneration tower for secondary washing, the hydrogen sulfide removal rate is 99.80-99.90%, and the methyl isobutyl ketone (MIBK) removal rate after washing is 18.6-21.7%, thereby improving the waste gas treatment effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The present invention provides a flow chart of a process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system.

[0048] Reference numerals:

[0049] 1. Primary absorption and regeneration tower; 2. Secondary absorption and regeneration tower; 3. Mist and entrainment separator; 4. Primary jet pump; 5. Secondary jet pump; 6. Primary sulfur slurry pump; 7. Secondary sulfur slurry pump; 8. Filter press; 9. Heater; 10. Blower. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a", "the" and "the" used in the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and encompasses any or all possible combinations of one or more associated listed items.

[0052] It should be understood that although the present invention may use terms such as "first", "second", and "third" to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other.

[0053] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0054] The raw materials used in the following examples and comparative examples are as follows:

[0055] Ethylenediaminetetraacetic acid: Shandong Wanhua Tianhe New Materials Co., Ltd.

[0056] Ferric amine: Shandong Wanhua Tianhe New Materials Co., Ltd.

[0057] Nitrilotriacetic acid sodium salt: Shandong Xinhe New Materials Co., Ltd.;

[0058] Nonylphenol ethoxylate: Shenzhen Ruijit Biotechnology Co., Ltd.;

[0059]

[0060] Preparation of the washing liquids of Examples 1-5 and Comparative Examples 1-3: Mix and stir the corresponding components in the examples uniformly;

[0061] Table 1 Parameters of Examples 1-5 and Comparative Examples 1-3

[0062]

[0063] 100 L of mixed flue gas from a wet-process phosphoric acid purification system was passed into 10 L of the scrubbing liquids prepared in Examples 1-5 and Comparative Examples 1-3, and the hydrogen sulfide concentration and the organic gas methyl isobutyl ketone concentration of the mixed flue gas were measured before and after the addition.

[0064] The above examples and comparative examples all passed the following performance tests:

[0065] 1. Detect the hydrogen sulfide concentration in the mixed flue gas before and after the scrubbing liquid is introduced according to GB / T14678-1993;

[0066] 2. Detect the concentration of organic gas methyl isobutyl ketone in the mixed flue gas before and after the scrubbing liquid is introduced according to KSM1982-2007;

[0067] Table 2 Data of Examples and Comparative Examples

[0068]

[0069]

[0070] Example 6

[0071] S1. The mixed flue gas enters the primary absorption and regeneration tower from the bottom of the first tower. At the same time, the scrubbing liquid, after being treated by the heater, enters the primary absorption and regeneration tower from the top of the first tower. The scrubbing liquid temperature is controlled at 45°C. The mixed flue gas and scrubbing liquid are in countercurrent contact.

[0072] In S1, the washing liquid is discharged from the bottom of the first tower, and after being processed by the first-stage jet pump and the heater, it re-enters the first-stage absorption regeneration tower from the top of the first tower;

[0073] The sulfur generated in the first-stage absorption and regeneration tower settles at the bottom of the first tower and is pumped to the filter press through the first-stage sulfur slurry pump;

[0074] S2. The mixed flue gas is discharged from the top of the first tower and enters the secondary absorption and regeneration tower from the bottom of the second tower. The scrubbing liquid enters the secondary absorption and regeneration tower from the top of the second tower. The mixed flue gas and the scrubbing liquid are in contact in a countercurrent manner.

[0075] In S2, the washing liquid is discharged from the bottom of the second tower, and after being processed by the secondary jet pump, it re-enters the secondary absorption regeneration tower from the top of the second tower;

[0076] The sulfur generated in the secondary absorption and regeneration tower settles at the bottom of the second tower and is pumped to the filter press through the secondary sulfur slurry pump;

[0077] Air is introduced into the bottom of the first absorption and regeneration tower and the bottom of the second absorption and regeneration tower respectively through a blower;

[0078] In the first-stage absorption regeneration tower and the second-stage absorption regeneration tower, the mixed flue gas flow rate and the washing liquid flow rate are both mixed flue gas flow rate (Nm 3 / h): washing liquid flow (m 3 / h) is 30:1, negative pressure 1000pa;

[0079] S3. The mixed flue gas enters the entrainment separator from the top of the second tower and is discharged after being processed by the entrainment separator;

[0080] The washing liquid used was the washing liquid prepared in Example 2.

[0081] Example 7

[0082] The difference from Example 6 is that the washing liquid adopts the washing liquid prepared in Example 3; the remaining steps are the same as those in Example 6;

[0083] Example 8

[0084] The difference from Example 6 is that the washing liquid adopts the washing liquid prepared in Example 4; the remaining steps are the same as in Example 6;

[0085] Example 9

[0086] The difference from Example 6 is that the washing liquid adopts the washing liquid prepared in Example 5; the remaining steps are the same as those in Example 6;

[0087] Comparative Example 4

[0088] The difference from Example 6 is that the temperature of the S1 washing solution is controlled at 60°C, and the remaining steps are the same as those in Example 6;

[0089] Comparative Example 5

[0090] The difference from Example 6 is that the temperature of the S1 washing solution is controlled at 30°C, and the remaining steps are the same as Example 6;

[0091] Comparative Example 6

[0092] The difference from Example 6 is that in the first-stage absorption and regeneration tower and the second-stage absorption and regeneration tower, the mixed flue gas flow rate and the washing liquid flow rate are both, the mixed flue gas flow rate (Nm 3 / h): washing liquid flow (m 3 / h) is 10:1, negative pressure 1000pa;

[0093] Comparative Example 7

[0094] The difference from Example 6 is that in the first-stage absorption and regeneration tower and the second-stage absorption and regeneration tower, the mixed flue gas flow rate and the washing liquid flow rate are both, the mixed flue gas flow rate (Nm 3 / h): washing liquid flow (m 3 / h) is 50:1, negative pressure 1000pa;

[0095] The mixed flue gas from the wet-process phosphoric acid purification system was introduced into the processes of Examples 6-9 and Comparative Examples 4-7. After treatment in the primary absorption and regeneration tower and the secondary absorption and regeneration tower, the hydrogen sulfide concentration and the organic gas methyl isobutyl ketone concentration of the mixed flue gas were measured before and after the introduction.

[0096] The above examples and comparative examples all passed the following performance tests:

[0097] 1. Detect the hydrogen sulfide concentration in the mixed flue gas before and after two washes in accordance with GB / T14678-1993;

[0098] 3. Detect the concentration of organic gas methyl isobutyl ketone in the mixed flue gas before and after two washes in accordance with KSM1982-2007;

[0099] Table 2 Data of Examples and Comparative Examples

[0100]

[0101] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments. The embodiments of the present application have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The choice of terms used in this article is intended to best explain the principles of the embodiments, practical applications or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system, characterized in that: The steps include: S1. The mixed flue gas enters the primary absorption and regeneration tower from the bottom of the first tower. At the same time, the scrubbing liquid, after being treated by the heater, enters the primary absorption and regeneration tower from the top of the first tower. The scrubbing liquid temperature is controlled at 40-50°C. The mixed flue gas and scrubbing liquid contact in a countercurrent manner. S2. The mixed flue gas is discharged from the top of the first tower and enters the secondary absorption and regeneration tower from the bottom of the second tower. The scrubbing liquid enters the secondary absorption and regeneration tower from the top of the second tower. The mixed flue gas and the scrubbing liquid are in contact in a countercurrent manner. S3. The mixed flue gas enters the entrainment separator from the top of the second tower and is discharged after being processed by the entrainment separator; The washing liquid comprises the following components in parts by weight: Also included is a sodium hydroxide solution, the amount of sodium hydroxide solution added is to control the pH value of the washing liquid to 9-10; The concentration of the hydrogen peroxide solution is 25-30%; The weight ratio of the ethylenediaminetetraacetic acid, the sodium salt of nitrilotriacetic acid and the nonylphenol ethoxylate is in the range of 1:(6-8):(1-2).

2. The process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system according to claim 1, characterized in that: In S1, the washing liquid is discharged from the bottom of the first tower, and after being processed by the first-stage jet pump and the heater in sequence, it re-enters the first-stage absorption regeneration tower from the top of the first tower.

3. The process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system according to claim 1, characterized in that: In S2, the washing liquid is discharged from the bottom of the second tower, and after being processed by the secondary jet pump, it re-enters the secondary absorption and regeneration tower from the top of the second tower.

4. The process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system according to claim 1, characterized in that: The sulfur generated in the first-stage absorption and regeneration tower settles at the bottom of the first tower and is pumped to the filter press through the first-stage sulfur slurry pump.

5. The process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system according to claim 1, characterized in that: The sulfur generated in the secondary absorption and regeneration tower settles at the bottom of the second tower and is pumped to the filter press through the secondary sulfur slurry pump.

6. The process for efficiently removing hydrogen sulfide from a wet-process phosphoric acid purification system according to claim 1, characterized in that: Air is introduced into the bottom of the first absorption and regeneration tower and the bottom of the second absorption and regeneration tower respectively through a blower.

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