A resource treatment method for catalytic cracking flue gas desulfurization wastewater

Abstract

A resource treatment method for the flue gas desulfurization wastewater of fluid catalytic cracking, belonging to the technical field of wastewater treatment. The treatment method of the present invention for the flue gas desulfurization wastewater of fluid catalytic cracking includes steps such as aeration oxidation, carbon dioxide neutralization reaction, flocculation precipitation, evaporation concentration, double decomposition reaction, concentration separation, centrifugal separation, evaporation in an ammonia stripping tower, concentration in an evaporation kettle, and centrifugal separation. The present invention prepares sodium bicarbonate that can be recycled for desulfurization through a double decomposition reaction with the sodium sulfate in the flue gas desulfurization wastewater of fluid catalytic cracking, and the by-product is ammonium sulfate, which is used as a fertilizer; the products are sodium bicarbonate and ammonium sulfate with economic value, truly realizing a closed-loop of resource utilization from "waste" to "product"; no new "three wastes" such as waste residue, waste gas, and wastewater are generated, achieving zero discharge of wastewater in the entire desulfurization system; reducing the treatment cost; completely solving the problem of the disposal of the flue gas desulfurization wastewater of fluid catalytic cracking.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly relates to a method for resource treatment of flue gas desulfurization wastewater from catalytic cracking. Background Art

[0002] Flue gas desulfurization wastewater from catalytic cracking is the wastewater generated during the desulfurization treatment of the flue gas produced by a catalytic cracking unit in the process of petroleum refining. This kind of wastewater usually has the following characteristics:

[0003] 1. High salinity: It contains a large amount of inorganic salts, such as sulfates, chlorides, etc.

[0004] 2. High hardness: The content of hardness ions such as calcium ions and magnesium ions is relatively high.

[0005] 3. Complex pollutants: It will contain heavy metal ions, organic substances, suspended solids, etc.

[0006] Therefore, it is relatively difficult and costly to treat flue gas desulfurization wastewater from catalytic cracking. Common treatment methods include physicochemical methods (such as precipitation, filtration, adsorption, etc.), biological methods, and membrane separation technologies, etc. These methods aim to reduce the pollutant concentration in the wastewater to make it meet the discharge standards and reduce environmental pollution.

[0007] Among them, in the highly saline desulfurization wastewater, the main components are sodium sulfate and sodium sulfite. Due to its high salinity characteristics, it will cause problems such as the death of nitrifying bacteria in the sewage treatment system. Therefore, it cannot be normally discharged to the factory sewage treatment system for disposal, which has caused a great operation burden and obstacle to the operation of the entire device.

[0008] Currently, the commonly used treatment methods generally adopt means such as membrane concentration and MVR evaporation to extract the salts in the wastewater in solid form, obtain wastewater with a low salt concentration, and then send it to the sewage treatment plant for disposal. The extracted solid waste salt is treated as solid waste. This treatment method not only has a high cost, but also increases the types of waste, and the treatment of solid waste salt also increases the burden on the enterprise.

[0009] Therefore, it is necessary to develop a more economical and practical desulfurization wastewater treatment method to produce waste that can be resourcefully utilized, so as to solve the problem of desulfurization wastewater treatment and reduce costs. Summary of the Invention

[0010] In view of the problems existing in the existing treatment methods for the desulfurization wastewater of catalytic cracking flue gas, such as high difficulty, high cost, large amount of waste produced, and difficulty in realizing resource utilization, the present invention provides a resource treatment method for the desulfurization wastewater of catalytic cracking flue gas. The sodium sulfate in the desulfurization wastewater of catalytic cracking flue gas is prepared into sodium bicarbonate that can be recycled for desulfurization through a metathesis reaction, and the by-product is ammonium sulfate, which is used as a fertilizer; not only does it increase the economy of the entire desulfurization process, making the environmental protection project no longer a simple consumption project; at the same time, it realizes zero discharge of wastewater in the entire desulfurization system and solves the difficult problem of difficult disposal of high-salt desulfurization wastewater. The specific technical solution is as follows:

[0011] A resource treatment method for the desulfurization wastewater of catalytic cracking flue gas, the method comprising the following steps:

[0012] S1: Aerate and oxidize the desulfurization wastewater of catalytic cracking flue gas to oxidize sodium sulfite in the desulfurization wastewater of catalytic cracking flue gas into sodium sulfate, obtaining waste liquid A;

[0013] S2: Introduce carbon dioxide gas into waste liquid A, and the alkaline substances in waste liquid A react with carbon dioxide in an acid-base neutralization reaction to generate carbonate (HCO3 - +OH-→H2O+CO3 2- ), until the pH of waste liquid A is 6.5 - 7.2, stop introducing carbon dioxide, end the reaction, and obtain neutral waste liquid B;

[0014] S3: Add a flocculant to neutral waste liquid B, carry out flocculation precipitation, and then use a filter press for solid-liquid separation to obtain filter residue C and sodium sulfate aqueous solution D;

[0015] S4: Carry out vacuum evaporation and concentration on sodium sulfate aqueous solution D to obtain condensed water and sodium sulfate;

[0016] S5: By mass ratio, ammonium bicarbonate: condensed water: sodium sulfate = (1 - 1.5): (3 - 5): (1 - 1.5), first dissolve ammonium bicarbonate in condensed water, and then add sodium sulfate for a metathesis reaction to obtain reaction liquid E;

[0017] S6: Concentrate and separate reaction liquid E by a thickener to obtain supernatant F and concentrated liquid G containing solid crystals; solid-liquid separation of concentrated liquid G by a centrifuge to obtain centrifugate H and filter cake I, and dry filter cake I;

[0018] Evaporate supernatant F and centrifugate H by an ammonia stripping tower to obtain liquid J and gas K. Gas K contains ammonia and carbon dioxide, and gas K is recycled and introduced into waste liquid A in S2 for absorption;

[0019] S7: After the liquid J is quenched, it is concentrated in an evaporation kettle, and the mixed salt M is crystallized by cooling and separated by centrifugation to obtain the centrifugate L and the mixed salt M. After the mixed salt M is dried, it is sent to step S5 for repeated reaction;

[0020] S8: The centrifugate L is evaporated in an evaporation kettle to crystallize ammonium sulfate.

[0021] In S1 of the above method, the specific parameters of the aeration oxidation are as follows: aeration volume: the volume of the air introduced is 0.8 times to 1.5 times the volume of the flue gas desulfurization wastewater from fluid catalytic cracking per hour; aeration time: 3h to 4h; dissolved oxygen concentration: 2mg / L to 4mg / L; bubble diameter: 1mm to 5mm; pressure: 0.01MPa to 0.05MPa.

[0022] In S3 of the above method, the main component of the filter residue C is the catalyst used in the production of flue gas desulfurization from fluid catalytic cracking. The filter residue C is used to merge with the waste catalyst replaced by the flue gas desulfurization production device of fluid catalytic cracking and is recycled by the waste catalyst recycling manufacturer.

[0023] In S3 of the above method, the flocculant is sodium polyacrylate with a molecular weight of 8 million daltons.

[0024] In S4 of the above method, the condensed water is the water collected after the water vapor generated by vacuum evaporation and concentration is condensed, and is recycled.

[0025] In S5 of the above method, the parameters of the double decomposition reaction are: temperature 30°C to 40°C, reaction time 2h to 3h.

[0026] In S6 of the above method, the filter cake I contains sodium bicarbonate, and the filter cake I is recycled for the flue gas desulfurization reaction of fluid catalytic cracking.

[0027] In S7 of the above method, the quenching is to adjust the pH to 7 to 8 with sodium carbonate; the temperature of the evaporation kettle concentration is 75°C to 80°C; the evaporation kettle concentration also obtains the condensed water collected after the evaporation-generated water vapor is condensed, and is recycled.

[0028] In S8 of the above method, the temperature of the evaporation is 75°C to 80°C; the evaporation also obtains the condensed water collected after the water vapor is condensed, and is recycled.

[0029] In S8 of the above method, the ammonium sulfate is used as a fertilizer for resource utilization.

[0030] In the above method, the recycling of the condensed water includes adding water for the double decomposition reaction and replenishing water for the production of flue gas desulfurization from fluid catalytic cracking.

[0031] A resource treatment method for the desulfurization wastewater of catalytic cracking flue gas according to the present invention has the following beneficial effects compared with the prior art:

[0032] 1. The present invention uses an aeration oxidation method to oxidize sodium sulfite into sodium sulfate, which can improve the extraction rate of sodium sulfate and further improve the extraction rate of sodium bicarbonate.

[0033] 2. The desulfurization is carried out under alkaline conditions. Therefore, there is a small amount of unreacted sodium hydroxide in the desulfurization wastewater of catalytic cracking flue gas. It is necessary to adjust the pH value of the waste liquid to 6.5 - 7.2 by means of acid adjustment. The best acid adjustment scheme is to introduce carbon dioxide gas into the waste liquid, so that the alkali liquid and carbon dioxide undergo an acid-base neutralization reaction to generate carbonate (HCO3 - +OH-→H2O+CO3 2- ). Carbon dioxide is used as a raw material in the conversion process, enabling the subsequent generated gas K to be recycled and absorbed to participate in the reaction, which contributes to "carbon emission reduction" to a certain extent.

[0034] 3. According to the properties of the catalyst base material, the present invention uses a specific flocculant to well separate the catalyst used in the production of catalytic cracking flue gas desulfurization. The separated catalyst is used to merge with the waste catalyst replaced by the catalytic cracking flue gas desulfurization production device and is recycled by the waste catalyst recycling manufacturer, realizing the reuse of the catalyst.

[0035] 4. The sodium sulfate obtained by the present invention through vacuum evaporation and concentration undergoes a double decomposition reaction with ammonium bicarbonate and condensed water, and then is concentrated and separated by a thickener. After solid-liquid separation by a centrifuge, a sodium bicarbonate product can be obtained, which can be recycled for use in the catalytic cracking flue gas desulfurization reaction, realizing the resource recovery and utilization of sodium bicarbonate.

[0036] 5. After the double decomposition reaction liquid is concentrated and separated by a thickener to obtain the supernatant by-product, it is evaporated by an ammonia distillation tower. The obtained gas contains ammonia and carbon dioxide, which can be recycled and introduced into the acid-base neutralization reaction to participate in the reaction, achieving zero tail gas emission.

[0037] 6. The residual liquid after evaporation in the ammonia distillation tower is conditioned and then concentrated by an evaporation kettle and centrifugally separated to obtain the mixed salt M, which can participate in the cyclic reaction. The centrifugate is evaporated by an evaporation kettle and crystallized to obtain ammonium sulfate, which can be recycled as fertilizer, realizing resource utilization.

[0038] 7. The distilled water generated during the whole treatment process can be recycled and reused, including adding water for the double decomposition reaction and supplementing water for the production of catalytic cracking flue gas desulfurization, achieving zero sewage discharge.

[0039] In summary, the raw materials of the method of the present invention are the wastes generated by desulfurization, and the products are sodium bicarbonate and ammonium sulfate with economic value, truly realizing the closed-loop resource utilization from "waste" to "product"; no new "three wastes" such as waste residue, waste gas, and waste water are generated, and the environmental benefits are obvious; the treatment cost is reduced; the disposal problem of the catalytic cracking flue gas desulfurization waste water is completely solved. Detailed implementation manners

[0040] The present invention will be further described below in conjunction with specific implementation cases, but the present invention is not limited to these embodiments.

[0041] Example 1

[0042] A resource treatment method for catalytic cracking flue gas desulfurization waste water, the method comprising the following steps:

[0043] S1: Aerate and oxidize the catalytic cracking flue gas desulfurization waste water to oxidize sodium sulfite in the catalytic cracking flue gas desulfurization waste water into sodium sulfate, obtaining waste liquid A;

[0044] The specific parameters of the aeration oxidation are as follows: aeration volume: the volume of the introduced air is 1.2 times the volume of the catalytic cracking flue gas desulfurization waste water per hour; aeration time: 3.5 h; dissolved oxygen concentration: 3 mg / L; bubble diameter: 1 mm - 5 mm; pressure: 0.03 MPa;

[0045] S2: Introduce carbon dioxide gas into waste liquid A, and the alkaline substances in waste liquid A react with carbon dioxide in an acid-base neutralization reaction to generate carbonate (HCO3 - +OH-→H2O+CO3 2- ), until the pH of waste liquid A is 6.8, stop introducing carbon dioxide, end the reaction, and obtain neutral waste liquid B;

[0046] S3: Add a flocculant to neutral waste liquid B, perform flocculation precipitation, and then use a filter press for solid-liquid separation to obtain filter residue C and sodium sulfate aqueous solution D; the main component of filter residue C is the catalyst used in the catalytic cracking flue gas desulfurization production, and filter residue C is used to merge with the waste catalyst replaced by the catalytic cracking flue gas desulfurization production device and is recycled by the waste catalyst recycling manufacturer;

[0047] S4: Perform vacuum evaporation and concentration on the sodium sulfate aqueous solution D to obtain condensed water and sodium sulfate; the condensed water is the water collected after the water vapor generated by vacuum evaporation and concentration is condensed, and is recycled, including being used for adding water in the double decomposition reaction and for making up water in the catalytic cracking flue gas desulfurization production;

[0048] S5: According to the mass ratio, ammonium bicarbonate: condensed water: sodium sulfate = 1:3:1, first dissolve ammonium bicarbonate in the condensed water, and then add sodium sulfate for a double decomposition reaction. After reacting at 35 °C for 2 h, obtain reaction liquid E;

[0049] S6: The reaction liquid E is concentrated and separated by a thickener to obtain a supernatant liquid F and a concentrated liquid G containing solid crystals; the concentrated liquid G is separated by a centrifuge to obtain a centrifugate H and a filter cake I, and the filter cake I is dried; the filter cake I contains sodium bicarbonate, and the filter cake I is recycled for use in the catalytic cracking flue gas desulfurization reaction;

[0050] The supernatant liquid F and the centrifugate H are evaporated by an ammonia distillation tower to obtain a liquid J and a gas K. The gas K contains ammonia and carbon dioxide, and the gas K is recycled and introduced into the waste liquid A in S2 for absorption;

[0051] S7: The pH of the liquid J is adjusted to 7.5 with sodium carbonate, and it is concentrated at 78 °C by an evaporation kettle, and mixed salt M is crystallized by cooling. After centrifugal separation, a centrifugate L and the mixed salt M are obtained. After the mixed salt M is dried, it is sent to step S5 for repeated reaction; the evaporation kettle concentration also obtains condensed water collected after the evaporated water vapor is condensed, and it is recycled, including being used for adding water in the double decomposition reaction and for supplementing water in the catalytic cracking flue gas desulfurization production;

[0052] S8: The centrifugate L is evaporated at 80 °C by an evaporation kettle to crystallize ammonium sulfate, and the ammonium sulfate is used as a fertilizer for resource utilization; the evaporation also obtains condensed water collected after the evaporated water vapor is condensed, and it is recycled, including being used for adding water in the double decomposition reaction and for supplementing water in the catalytic cracking flue gas desulfurization production.

[0053] The flocculant used in this example is sodium polyacrylate, with a molecular weight of 8 million Daltons, provided by Daqian Environmental Protection Technology Co., Ltd.

[0054] A resource treatment method for the wastewater from catalytic cracking flue gas desulfurization in this example has good use effects, can obtain sodium bicarbonate, and is recycled for use in the catalytic cracking flue gas desulfurization reaction; the by-product is ammonium sulfate, which can be used as a fertilizer; the distilled water and gas generated can participate in the reaction cyclically; this method not only increases the economy of the entire desulfurization process, making the environmental protection project no longer a simple consumption project; at the same time, it realizes zero discharge of wastewater in the entire desulfurization system, and no new "three wastes" such as waste residue, waste gas, and wastewater are generated, completely solving the problem of disposing of the wastewater from catalytic cracking flue gas desulfurization.

[0055] Example 2

[0056] A resource treatment method for the wastewater from catalytic cracking flue gas desulfurization, the method includes the following steps:

[0057] S1: Aerate and oxidize the wastewater from catalytic cracking flue gas desulfurization to oxidize sodium sulfite in the wastewater from catalytic cracking flue gas desulfurization into sodium sulfate to obtain waste liquid A;

[0058] The specific parameters of aeration oxidation are as follows: aeration volume: the volume of the air introduced is 0.8 times the volume of the wastewater from catalytic cracking flue gas desulfurization per hour; aeration time: 3 h; dissolved oxygen concentration: 2 mg / L; bubble diameter: 1 mm - 5 mm; pressure: 0.01 MPa.

[0059] S2: Carbon dioxide gas is introduced into waste liquid A, and the alkaline substances in waste liquid A undergo an acid-base neutralization reaction with carbon dioxide to form carbonates (HCO3 - +OH-→H2O+CO3 2- ), until the pH of waste liquid A reaches 6.5, then stop introducing carbon dioxide and end the reaction to obtain neutral waste liquid B.

[0060] S3: A flocculant is added to neutral waste liquid B. After flocculation and precipitation, a filter press is used for solid-liquid separation to obtain filter residue C and sodium sulfate aqueous solution D; the main component of filter residue C is the catalyst used in catalytic cracking flue gas desulfurization production. Filter residue C is used to be combined with the waste catalyst replaced from the catalytic cracking flue gas desulfurization production device and recycled by the waste catalyst recycling manufacturer.

[0061] S4: The sodium sulfate aqueous solution D is concentrated by vacuum evaporation to obtain condensed water and sodium sulfate; the condensed water is the water collected after the steam generated by vacuum evaporation and condensation, and is recycled, including being used for adding water in the metathesis reaction and for supplementing water in catalytic cracking flue gas desulfurization production.

[0062] S5: By mass ratio, ammonium bicarbonate: condensed water: sodium sulfate = 1:3:1. First, dissolve ammonium bicarbonate in the condensed water, and then add sodium sulfate for a metathesis reaction. After reacting at 30 °C for 2 h, reaction liquid E is obtained.

[0063] S6: Reaction liquid E is concentrated and separated by a thickener to obtain supernatant F and concentrated liquid G containing solid crystals; concentrated liquid G is separated by a centrifuge to obtain centrifugate H and filter cake I, and filter cake I is dried; filter cake I contains sodium bicarbonate and is recycled for use in the catalytic cracking flue gas desulfurization reaction.

[0064] Supernatant F and centrifugate H are evaporated in an ammonia stripping tower to obtain liquid J and gas K. Gas K contains ammonia and carbon dioxide and is recycled and introduced into waste liquid A in S2 for absorption.

[0065] S7: The pH of liquid J is adjusted to 7 with sodium carbonate, and it is concentrated in an evaporation kettle at 75 °C, and mixed salt M is crystallized out by cooling. After centrifugal separation, centrifugate L and mixed salt M are obtained. After drying, mixed salt M is sent to step S5 for repeated reaction; the evaporation kettle concentration also obtains condensed water collected after the steam generated by evaporation and condensation, which is recycled, including being used for adding water in the metathesis reaction and for supplementing water in catalytic cracking flue gas desulfurization production.

[0066] S8: The centrifuged liquid L is evaporated at 75 °C in an evaporation kettle to crystallize ammonium sulfate, which is used as a fertilizer for resource utilization; the evaporation also produces condensed water collected after the steam is condensed, which is recycled, including being used for adding water in the metathesis reaction and for water replenishment in the production of catalytic cracking flue gas desulfurization.

[0067] The flocculant used in this example is sodium polyacrylate with a molecular weight of 8 million Daltons, provided by Daqian Environmental Protection Technology Co., Ltd.

[0068] The resource treatment method for the wastewater from catalytic cracking flue gas desulfurization in this example has good use effects, can obtain sodium bicarbonate for recycling in the catalytic cracking flue gas desulfurization reaction; the by-product is ammonium sulfate, which can be used as a fertilizer; the distilled water and gas produced can participate in the reaction in a cycle; this method not only increases the economy of the entire desulfurization process, making the environmental protection project no longer a simple consumption project; at the same time, it realizes zero discharge of wastewater in the entire desulfurization system, without generating new "three wastes" such as waste residue, waste gas, and wastewater, and completely solves the problem of disposing of the wastewater from catalytic cracking flue gas desulfurization.

[0069] Example 3

[0070] A resource treatment method for the wastewater from catalytic cracking flue gas desulfurization, the method comprising the following steps:

[0071] S1: Aerate and oxidize the wastewater from catalytic cracking flue gas desulfurization to oxidize sodium sulfite in the wastewater from catalytic cracking flue gas desulfurization into sodium sulfate, obtaining waste liquid A;

[0072] The specific parameters of the aeration oxidation are as follows: aeration volume: the volume of the air introduced is 1.5 times the volume of the wastewater from catalytic cracking flue gas desulfurization per hour; aeration time: 4 h; dissolved oxygen concentration: 4 mg / L; bubble diameter: 1 mm - 3 mm; pressure: 0.05 MPa;

[0073] S2: Introduce carbon dioxide gas into waste liquid A, and the alkaline substances in waste liquid A undergo an acid-base neutralization reaction with carbon dioxide to generate carbonate (HCO3 - + OH- → H2O + CO3 2- ), until the pH of waste liquid A is 7.2, stop introducing carbon dioxide, end the reaction, and obtain neutral waste liquid B;

[0074] S3: Add a flocculant to neutral waste liquid B, after flocculation precipitation, use a filter press for solid-liquid separation to obtain filter residue C and an aqueous sodium sulfate solution D; the main component of filter residue C is the catalyst used in the production of catalytic cracking flue gas desulfurization, and filter residue C is used to merge with the waste catalyst replaced by the catalytic cracking flue gas desulfurization production device, and is recycled and reused by the waste catalyst recycling manufacturer;

[0075] S4: The aqueous sodium sulfate solution D is concentrated by vacuum evaporation to obtain condensed water and sodium sulfate; the condensed water is the water collected after the water vapor generated by vacuum evaporation and concentration is condensed, and is recycled, including being used for adding water in the double decomposition reaction and for replenishing water in the production of catalytic cracking flue gas desulfurization;

[0076] S5: By mass ratio, ammonium bicarbonate: condensed water: sodium sulfate = 1.5:5:1.5. First, dissolve ammonium bicarbonate in the condensed water, and then add sodium sulfate for a double decomposition reaction. After reacting at 40 °C for 3 h, the reaction solution E is obtained;

[0077] S6: The reaction solution E is concentrated and separated by a thickener to obtain a supernatant F and a concentrated solution G containing solid crystals; the concentrated solution G is separated by solid-liquid separation using a centrifuge to obtain a centrifugate H and a filter cake I, and the filter cake I is dried; the filter cake I contains sodium bicarbonate, and the filter cake I is recycled for use in the catalytic cracking flue gas desulfurization reaction;

[0078] The supernatant F and the centrifugate H are evaporated using an ammonia distillation tower to obtain a liquid J and a gas K. The gas K contains ammonia and carbon dioxide, and the gas K is recycled and introduced into the waste liquid A in S2 for absorption;

[0079] S7: The pH of the liquid J is adjusted to 8 with sodium carbonate, and it is concentrated at 80 °C using an evaporation kettle, and mixed salt M is crystallized by cooling. After centrifugal separation, a centrifugate L and the mixed salt M are obtained. After the mixed salt M is dried, it is sent to step S5 for repeated reaction; the evaporation kettle concentration also obtains condensed water collected after the evaporation-generated water vapor is condensed, and is recycled, including being used for adding water in the double decomposition reaction and for replenishing water in the production of catalytic cracking flue gas desulfurization;

[0080] S8: The centrifugate L is evaporated at 80 °C using an evaporation kettle to crystallize ammonium sulfate, and the ammonium sulfate is used as a fertilizer for resource utilization; the evaporation also obtains condensed water collected after the water vapor is condensed, and is recycled, including being used for adding water in the double decomposition reaction and for replenishing water in the production of catalytic cracking flue gas desulfurization.

[0081] The flocculant used in this example is sodium polyacrylate, with a molecular weight of 8 million Daltons, provided by Daqian Environmental Protection Technology Co., Ltd.

[0082] A method for resource treatment of catalytic cracking flue gas desulfurization wastewater in this example has good use effects, can obtain sodium bicarbonate, and is recycled for use in the catalytic cracking flue gas desulfurization reaction; the by-product is ammonium sulfate, which can be used as a fertilizer; the distilled water and gas generated can participate in the reaction cyclically; this method not only increases the economy of the entire desulfurization process, making the environmental protection project no longer a simple consumption project; at the same time, it realizes zero discharge of wastewater in the entire desulfurization system, without generating new "three wastes" such as waste residue, waste gas, and wastewater, and completely solves the problem of disposing of catalytic cracking flue gas desulfurization wastewater.

[0083] Example 4

[0084] A resource treatment method for the flue gas desulfurization wastewater of catalytic cracking, the method comprising the following steps:

[0085] S1: Aerate and oxidize the flue gas desulfurization wastewater of catalytic cracking to oxidize sodium sulfite in the flue gas desulfurization wastewater of catalytic cracking into sodium sulfate, obtaining waste liquid A;

[0086] The specific parameters of the aeration oxidation are as follows: aeration volume: the volume of the introduced air is 0.8 times the volume of the flue gas desulfurization wastewater of catalytic cracking per hour; aeration time: 4 h; dissolved oxygen concentration: 2 mg / L; bubble diameter: 1 mm - 4 mm; pressure: 0.05 MPa;

[0087] S2: Introduce carbon dioxide gas into waste liquid A, and the alkaline substances in waste liquid A undergo an acid-base neutralization reaction with carbon dioxide to generate carbonate (HCO3 - +OH-→H2O+CO3 2- ), until the pH of waste liquid A is 6.6, then stop introducing carbon dioxide to end the reaction, obtaining neutral waste liquid B;

[0088] S3: Add a flocculant to neutral waste liquid B, perform flocculation precipitation, and then use a filter press for solid-liquid separation to obtain filter residue C and sodium sulfate aqueous solution D; the main component of filter residue C is the catalyst used in the production of flue gas desulfurization of catalytic cracking, and filter residue C is used to merge with the waste catalyst replaced by the flue gas desulfurization production device of catalytic cracking and is recycled by the waste catalyst recycling manufacturer;

[0089] S4: Perform vacuum evaporation and concentration on sodium sulfate aqueous solution D to obtain condensed water and sodium sulfate; the condensed water is the water collected after the steam generated by vacuum evaporation and concentration is condensed, and is recycled, including being used for adding water in the double decomposition reaction and for making up water in the production of flue gas desulfurization of catalytic cracking;

[0090] S5: By mass ratio, ammonium bicarbonate: condensed water: sodium sulfate = 1.2:4:1.2. First, dissolve ammonium bicarbonate in condensed water, and then add sodium sulfate for double decomposition reaction. After reacting at 32 °C for 2 h, obtain reaction liquid E;

[0091] S6: Concentrate and separate reaction liquid E by a thickener to obtain supernatant F and concentrated liquid G containing solid crystals; perform solid-liquid separation on concentrated liquid G by a centrifuge to obtain centrifugate H and filter cake I, and dry filter cake I; filter cake I contains sodium bicarbonate, and filter cake I is recycled for use in the flue gas desulfurization reaction of catalytic cracking;

[0092] Supernatant F and centrifugate H are evaporated by an ammonia stripping tower to obtain liquid J and gas K. Gas K contains ammonia and carbon dioxide, and gas K is recycled and introduced into waste liquid A in S2 for absorption;

[0093] S7: Adjust the pH of liquid J to 7.2 with sodium carbonate, concentrate it in an evaporation kettle at 76 °C, cool and crystallize to obtain mixed salt M, and centrifuge to separate to obtain centrifugate L and mixed salt M. After the mixed salt M is dried, it is sent to step S5 for repeated reaction; the evaporation kettle concentration also obtains condensed water collected after the evaporated water vapor is condensed, which is recycled, including the water added in the double decomposition reaction and the water replenished in the production of catalytic cracking flue gas desulfurization;

[0094] S8: Evaporate the centrifugate L in an evaporation kettle at 78 °C to crystallize ammonium sulfate, and the ammonium sulfate is used as a fertilizer for resource utilization; the evaporation also obtains condensed water collected after the water vapor is condensed, which is recycled, including the water added in the double decomposition reaction and the water replenished in the production of catalytic cracking flue gas desulfurization.

[0095] The flocculant used in this example is sodium polyacrylate, with a molecular weight of 8 million Daltons, provided by Daqian Environmental Protection Technology Co., Ltd.

[0096] A resource treatment method for catalytic cracking flue gas desulfurization wastewater in this example has good use effects, can obtain sodium bicarbonate and recycle it for catalytic cracking flue gas desulfurization reaction; the by-product is ammonium sulfate, which can be used as a fertilizer; the distilled water and gas generated can participate in the reaction in a cycle; this method not only increases the economy of the entire desulfurization process, making the environmental protection project no longer a simple consumption project; at the same time, it realizes zero discharge of wastewater in the entire desulfurization system, without generating new "three wastes" such as waste residue, waste gas, and wastewater, and completely solves the problem of disposing of catalytic cracking flue gas desulfurization wastewater.

[0097] Example 5

[0098] A resource treatment method for catalytic cracking flue gas desulfurization wastewater, the method includes the following steps:

[0099] S1: Aerobically oxidize the catalytic cracking flue gas desulfurization wastewater to oxidize sodium sulfite in the catalytic cracking flue gas desulfurization wastewater into sodium sulfate to obtain waste liquid A;

[0100] The specific parameters of the aerobic oxidation are as follows: aeration volume: the volume of the introduced air is 1.4 times the volume of the catalytic cracking flue gas desulfurization wastewater per hour; aeration time: 3.5 h; dissolved oxygen concentration: 3.5 mg / L; bubble diameter: 2 mm - 5 mm; pressure: 0.04 MPa;

[0101] S2: Introduce carbon dioxide gas into waste liquid A, and the alkaline substances in waste liquid A undergo an acid-base neutralization reaction with carbon dioxide to generate carbonate (HCO3 - +OH- → H2O + CO3 2- ), until the pH of waste liquid A is 7.0, stop introducing carbon dioxide, end the reaction, and obtain neutral waste liquid B;

[0102] S3: Add a flocculant to the neutral waste liquid B. After flocculation precipitation, use a filter press for solid-liquid separation to obtain filter residue C and sodium sulfate aqueous solution D. The main component in the filter residue C is the catalyst used in the production of catalytic cracking flue gas desulfurization. The filter residue C is used to be combined with the waste catalyst replaced from the catalytic cracking flue gas desulfurization production device and recycled by the waste catalyst recycling manufacturer;

[0103] S4: Carry out vacuum evaporation and concentration on the sodium sulfate aqueous solution D to obtain condensed water and sodium sulfate. The condensed water is the water collected after the steam generated by vacuum evaporation and concentration is condensed, and is recycled, including being used for adding water in the double decomposition reaction and for making up water in the production of catalytic cracking flue gas desulfurization;

[0104] S5: By mass ratio, ammonium bicarbonate: condensed water: sodium sulfate = 1.4:4.5:1.4. First, dissolve ammonium bicarbonate in the condensed water, and then add sodium sulfate for double decomposition reaction. After reacting at 38 °C for 3 h, obtain reaction liquid E;

[0105] S6: Concentrate and separate the reaction liquid E with a thickener to obtain supernatant F and concentrated liquid G containing solid crystals. The concentrated liquid G is separated by solid-liquid separation with a centrifuge to obtain centrifugate H and filter cake I, and the filter cake I is dried. The filter cake I contains sodium bicarbonate, and the filter cake I is recycled for use in the catalytic cracking flue gas desulfurization reaction;

[0106] The supernatant F and the centrifugate H are evaporated in an ammonia distillation tower to obtain liquid J and gas K. The gas K contains ammonia and carbon dioxide, and the gas K is recycled and introduced into the waste liquid A in S2 for absorption;

[0107] S7: Adjust the pH of the liquid J to 7.8 with sodium carbonate, concentrate it at 78 °C in an evaporation kettle, cool and crystallize the mixed salt M, and carry out centrifugal separation to obtain centrifugate L and mixed salt M. After the mixed salt M is dried, it is sent to step S5 for repeated reaction; The evaporation in the evaporation kettle also obtains the condensed water collected after the steam generated by evaporation is condensed, and is recycled, including being used for adding water in the double decomposition reaction and for making up water in the production of catalytic cracking flue gas desulfurization;

[0108] S8: The centrifugate L is evaporated at 80 °C in an evaporation kettle to crystallize ammonium sulfate, and the ammonium sulfate is used as a fertilizer for resource utilization; The evaporation also obtains the condensed water collected after the steam is condensed, and is recycled, including being used for adding water in the double decomposition reaction and for making up water in the production of catalytic cracking flue gas desulfurization.

[0109] The flocculant used in this embodiment is sodium polyacrylate with a molecular weight of 8 million Daltons, provided by Daqian Environmental Protection Technology Co., Ltd.

[0110] A resource treatment method for the flue gas desulfurization wastewater in fluid catalytic cracking has good use effects, can obtain sodium bicarbonate, which is recycled for the flue gas desulfurization reaction in fluid catalytic cracking; the by-product is ammonium sulfate, which can be used as fertilizer; the distilled water and gas generated can participate in the reaction in a cycle; this method not only increases the economy of the entire desulfurization process, making the environmental protection project no longer a simple consumption project; at the same time, it realizes zero discharge of wastewater in the entire desulfurization system, without generating new "three wastes" such as waste residue, waste gas and wastewater, and completely solves the disposal problem of the flue gas desulfurization wastewater in fluid catalytic cracking.

Claims

1. A resource treatment method for catalytic cracking flue gas desulfurization wastewater, characterized in that, The resource treatment method includes the following steps: S1: Aerate and oxidize the flue gas desulfurization wastewater from fluid catalytic cracking, oxidize sodium sulfite in the flue gas desulfurization wastewater from fluid catalytic cracking into sodium sulfate, and obtain waste liquid A; S2: Introduce carbon dioxide gas into waste liquid A, carry out an acid-base neutralization reaction between the alkaline substances in waste liquid A and carbon dioxide to generate carbonates, stop introducing carbon dioxide until the pH of waste liquid A is 6.5 - 7.2, end the reaction, and obtain neutral waste liquid B; S3: Add a flocculant to neutral waste liquid B, carry out flocculation precipitation, and then use a filter press for solid-liquid separation to obtain filter residue C and sodium sulfate aqueous solution D; S4: Carry out vacuum evaporation and concentration on sodium sulfate aqueous solution D to obtain condensed water and sodium sulfate; S5: By mass ratio, ammonium bicarbonate: condensed water: sodium sulfate = (1 - 1.5):(3 - 5):(1 - 1.5), first dissolve ammonium bicarbonate in condensed water, and then add sodium sulfate for a double decomposition reaction to obtain reaction liquid E; S6: Concentrate and separate reaction liquid E using a thickener to obtain supernatant F and concentrated liquid G containing solid crystals; carry out solid-liquid separation on concentrated liquid G using a centrifuge to obtain centrifugate H and filter cake I, and dry filter cake I; Supernatant F and centrifugate H are evaporated using an ammonia stripping tower to obtain liquid J and gas K. Gas K contains ammonia and carbon dioxide, and gas K is recycled and introduced into waste liquid A in S2 for absorption; S7: After liquid J is conditioned, it is concentrated using an evaporation kettle, cooled to crystallize mixed salt M, and centrifugally separated to obtain centrifugate L and mixed salt M. After mixed salt M is dried, it is sent to step S5 for repeated reaction; S8: Centrifugate L is evaporated using an evaporation kettle to crystallize ammonium sulfate.

2. The resource treatment method for the catalytic cracking flue gas desulfurization wastewater according to claim 1, characterized in that, In S1, the specific parameters of the aeration oxidation are as follows: aeration volume: the volume of air introduced is 0.8 times to 1.5 times the volume of the flue gas desulfurization wastewater from fluid catalytic cracking per hour; aeration time: 3h - 4h; dissolved oxygen concentration: 2mg / L - 4mg / L; bubble diameter: 1mm - 5mm; pressure: 0.01MPa - 0.05MPa.

3. The resource treatment method for the catalytic cracking flue gas desulfurization wastewater according to claim 1, characterized in that, In S3, the flocculant is sodium polyacrylate with a molecular weight of 8 million Daltons; the main component in filter residue C is the catalyst used in the production of flue gas desulfurization from fluid catalytic cracking. Filter residue C is used to merge with the waste catalyst replaced by the flue gas desulfurization production device from fluid catalytic cracking and is recycled by the waste catalyst recycling manufacturer.

4. A resource treatment method for catalytic cracking flue gas desulfurization wastewater according to claim 1, characterized in that, In S4, the condensed water is the water collected after the steam generated by vacuum evaporation and concentration is condensed, and is recycled.

5. The resource treatment method for the catalytic cracking flue gas desulfurization wastewater according to claim 1, characterized in that, In S5, the parameters of the double decomposition reaction are: temperature 30°C - 40°C, reaction time 2h - 3h.

6. The resource treatment method of catalytic cracking flue gas desulfurization wastewater according to claim 1, characterized in that In S6, filter cake I contains sodium bicarbonate, and filter cake I is recycled for the flue gas desulfurization reaction from fluid catalytic cracking.

7. The resource treatment method of the catalytic cracking flue gas desulfurization wastewater according to claim 1, characterized in that, In S7, the conditioning is to adjust the pH to 7 - 8 using sodium carbonate; the temperature of the evaporation kettle concentration is 75°C - 80°C; the evaporation kettle concentration also obtains the condensed water collected after the steam generated by evaporation is condensed, and is recycled.

8. A resource treatment method for catalytic cracking flue gas desulfurization wastewater according to claim 1, characterized in that, In S8, the temperature of the evaporation is 75°C - 80°C; the evaporation also obtains the condensed water collected after the steam is condensed, and is recycled.

9. The resource treatment method for the catalytic cracking flue gas desulfurization wastewater according to claim 1, characterized in that, In S8, the ammonium sulfate is utilized for fertilizer resource recovery.

10. A resource treatment method for catalytic cracking flue gas desulfurization wastewater according to claim 4, 7 or 8, characterized in that The recycling of the condensed water includes water addition for the metathesis reaction and water make-up for the catalytic cracking flue gas desulfurization production.