WO2022095148A1

WO2022095148A1 - Method for applying membrane separation apparatus to ammonia desulfurization

Info

Publication number: WO2022095148A1
Application number: PCT/CN2020/130916
Authority: WO
Inventors: 罗静; 谭强; 卜兴军; 徐建东; 张军
Original assignee: 江南环保集团股份有限公司; 江苏新世纪江南环保股份有限公司
Priority date: 2020-11-03
Filing date: 2020-11-23
Publication date: 2022-05-12
Also published as: CN112354332B; CN112354332A

Abstract

Provided is a method for applying a membrane separation apparatus (24) to ammonia desulfurization, comprising an ammonia desulfurization apparatus and a membrane separation apparatus (24). The ammonia desulfurization apparatus comprises an absorption tower (1), the absorption tower (1) using circulation fluid desulfurization, and a water washing circulation fluid (10) washes the desulfurized flue gas. The circulation fluid of the ammonia desulfurization apparatus is fed into the membrane separation apparatus (24) for treatment, and the composition, temperature, and pH of the circulating absorption solution in each section of the ammonia desulfurization apparatus are controlled; after treatment, the concentrated solution is returned to the ammonia desulfurization apparatus, and the clear liquor from the membrane separation apparatus (24) is sent to a process water (15) system or to a water washing cycle (10).

Description

A method for applying a membrane separation device to ammonia desulfurization

technical field

The invention belongs to the technical field of environmental protection, and in particular relates to a method for applying a membrane separation device to ammonia desulfurization.

Background technique

All countries in the world emit sulfur dioxide to varying degrees. China's sulfur dioxide emissions are huge, which has a huge impact on the environment and society. In 2017, the total emission of sulfur dioxide was 8.754 million tons, which caused huge economic losses and seriously affected China's ecological environment and people's health.

At present, there are hundreds of mature desulfurization technologies, among which the wet desulfurization process is the most widely used, accounting for about 85% of the world's total installed desulfurization capacity. Common wet flue gas desulfurization technologies include limestone-gypsum method, double alkali method, sodium carbonate method, ammonia method, and magnesium oxide method. Ammonia desulfurization is a wet desulfurization process that uses ammonia as an absorbent. This method can produce ammonium sulfate fertilizer at the same time as desulfurization. It is a green flue gas treatment solution with low energy consumption, high added value, and resource recycling. In the chemical industry, a large amount of waste ammonia water is produced in the production process, so the use of ammonia desulfurization for boiler tail gas in the chemical industry has its unique advantages.

For flue gas with high water content, such as flue gas above 8%, the absorption temperature needs to be controlled in order to effectively control ammonia escape and aerosols. A large amount of condensed water is generated while controlling the temperature, which causes the water in the system to be unbalanced, and the product needs to be obtained by an evaporative crystallization process. The larger the dosage, the less economical the device will be.

In order to ensure that the particulate matter at the outlet meets the emission requirements, such as the ultra-low emission requirement of less than 5mg/Nm ³ , it is necessary to control not only the generation of aerosols, but also the washing effect of the washing section. However, it is necessary to increase the amount of fresh process water replenishment, which will not only cause water resource consumption, but also may cause water imbalance in the desulfurization system, or even unable to carry out saturated crystallization in the tower or increase in the amount of evaporative crystallization water outside the tower, increasing operating costs. .

The clogging of absorption pipes and nozzles is a key factor affecting the long-term stable operation of ammonia desulfurization. For example, when the hardness of the process make-up water is relatively high, calcium and magnesium ions will scale in the absorption section with high pH and block the nozzles and pipes, affecting the stable operation of the device. It is very important to control the hardness of the supplementary liquid in the absorption section-water washing circulating liquid to avoid scaling.

The flue gas ammonia desulfurization process has the following technical difficulties:

1. System water balance

The water content and temperature in the flue gas entering the desulfurization system affect the desulfurization absorption temperature and desulfurization effect. For flue gas with high temperature and high water content, a cooling system needs to be set up to control the desulfurization temperature to achieve high desulfurization effect. At the same time of cooling, a large amount of water is precipitated in the flue gas, which reduces the concentration of the absorption liquid and affects the desulfurization effect.

2. Control the blockage of pipes and nozzles in the absorption section

The desulfurization system needs process water, and the quality of process water in different regions is not the same. The high hardness of the water will increase the hardness of the absorption circulating fluid, and under high pH conditions, scale will block the pipes and nozzles, which will affect the stable operation of the device and the desulfurization effect.

3. Recovery of ammonia entrained in tail gas

Unlike other alkaline substances, ammonia is volatile. The traditional countercurrent contact absorption tower, whether it is a spray tower, a packed tower or a tray tower, in order to ensure the desulfurization efficiency and the final emission index, at the contact point located at the top of the absorption zone, the pH value of the solution is the highest, and the SO ₂ concentration in the gas phase lowest, the concentration of ammonia in the gas phase will be highest. This means that the amount of ammonia overflowing the desulfurization tower with the tail gas will be large. This results in both wasted loss of ammonia and new pollution.

The above problems are an important reason why the ammonia method has not been well developed for a long time in the past. For the problem of aerosol and ammonia escape, efficient water washing is a very effective auxiliary method while controlling the generation of aerosols in the absorption process. The concentration of ammonia and ammonium sulfate in the circulating water washing is an important factor affecting the washing effect. The conventional technology adopts increasing the replacement amount of fresh water to reduce the concentration of ammonia and ammonium sulfate, which not only causes waste of water resources, but also affects the water balance of the system. The method controls the ammonia concentration and ammonium sulfate concentration in the circulating liquid.

The Chinese invention patent application with application number _CN02136906.2 proposes a method and device for removing and recovering SO2 in flue gas, and the concentration of ammonium sulfite is controlled between 0.1-5% (wt), preferably 0.5-2.0% In order to create the most favorable conditions for oxidation, reduce the energy consumption and investment of oxidation, and ensure high desulfurization efficiency, the absorption liquid ammonia/sulfur ratio = 1.3-1.8 (molar ratio), and the absorption gas/liquid ratio is 2000-5000 (volume ratio), the ammonium sulfate solution is concentrated by the heat of the hot flue gas, the temperature of the hot flue gas is reduced to 50-55 ° C, and the concentration of ammonium sulfate can be increased to 40-50% (wt), sent to the ammonium sulfate crystallizer, and processed into commercial products Ammonium sulphate fertilizer. The oxidation section is provided with a vertical separation plate, so that the unoxidized ammonium sulfite solution and the oxidized ammonium sulfate solution are separated as much as possible without back mixing. This method does not pay attention to the control of ammonia escape and aerosol generation during the absorption process, and a reheater is required to eliminate white smoke.

The Chinese invention patent application with application number CN201510680578.0 proposes an ammonia process double-cycle desulfurization, denitrification and dust removal system, including a washing absorption tower (1) and an oxidation circulation tank (9); Water mist section (2), enhanced ammonia mist removal section (3), absorption liquid demisting section (4), secondary absorption section (5), primary absorption section (6), washing and cooling section (7); When the flue gas enters the first-stage absorption section (6), an ammonium sulfate solution containing ammonium nitrate with a density of 1.1 to 1.15 kg/L and a pH of 6.5 to 7 is used as the absorption liquid to mainly remove SO ₂ ; When the gas enters the secondary absorption section (5), an ammonium sulfate solution containing ammonium nitrate with a density of 1.05-1.1 kg/L and a pH value of _5.5-6 is used as the absorption liquid to assist in the removal of SO2. The technical process is complicated, the ammonia is excessive in the absorption process, and the aerosol and ammonia escape seriously.

The Chinese invention patent application with application number CN201611207184.4 proposes a process for saving water and controlling aerosols in the ammonia desulfurization process. The boiler flue gas enters the desulfurization tower, and the spray liquid is effective for the flue gas containing SO ₂ entering the desulfurization tower. For spray absorption, the spray liquid adopts ammonium sulfate/ammonium sulfite solution with a concentration of 5-35%, and then contacts the cooling water on the packing layer through the packing layer, and then contacts with the water washing spray layer, and the cooling water at the bottom of the packing layer The water falls into the washing liquid accumulation tray and returns to the cooling tower, and then enters the washing pool and is pumped to the washing spray layer for recycling; Absorb (NH ₄ ) ₂ SO ₄ particles, SO ₂ , NH ₃ substances in the boiler flue gas, and the saturated water vapor in the boiler flue gas uses the (NH ₄ ) ₂ SO ₄ particles as the nucleus to condense and form water droplets to capture the boiler smoke (NH ₄ ) ₂ SO ₄ particles in the gas can reduce aerosols, so that the concentration of particulate matter in the boiler flue gas discharged from the ammonia desulfurization process is lower than 30 mg/m ³ . This process adopts low temperature water washing process, although it can strengthen the control of ammonia escape and aerosol, but the energy consumption of low temperature water washing is high, and the concentration of particulate matter in clean flue gas is less than 30mg/m ³ , which cannot meet the latest emission standards.

The Chinese invention patent application with publication number CN109111009A discloses a patent for zero discharge of waste water. The waste water produced by desulfurization is used by adding alkali to remove ammonia in the waste water and entering the denitration system for utilization. Enter the spray drying tower for drying and desalination. The invention is a wastewater treatment membrane separation system developed for zero discharge of calcium desulfurization wastewater.

The Chinese invention patent application with publication number CN108793569A discloses a patent for zero discharge of wastewater - a disc tube membrane treatment system and method for desulfurization wastewater with high ammonia nitrogen and high organic matter, including desulfurization absorption tower outlet pipe, adjustment tank, pre-sedimentation tank, hydrogen Calcium oxide dosing device, organic sulfur dosing device, coagulant dosing device, coagulant dosing device, #1 reaction tank, #1 clarifier, NaClO dosing device, aeration reaction tank, clarifier, NaOH Dosing device, microfiltration system, disc type nanofiltration system, disc type reverse osmosis system, preheater, condensate tank, crystallizer and steam compressor, etc., realize centralized treatment of desulfurization wastewater and zero discharge of desulfurization wastewater .

SUMMARY OF THE INVENTION

The present invention aims at the major technical problem that the prior art does not fully grasp the key of ammonia desulfurization technology, and fails to systematically control ammonia escape and aerosol; meanwhile, for flue gas with high water content, in the process of desulfurization, the water balance of the system is affected, resulting in energy consumption Increase; high hardness make-up water scales in the desulfurization stage, which affects the stable operation of the system; based on the systematic study of ammonia desulfurization technology, the present invention focuses on controlling the causes of ammonia escape and aerosol generation, enhancing the washing effect, and reducing the water washing circulating fluid. Ion concentration and consumption, saving energy. By adding a membrane separation device, the water washing circulating liquid, the pre-washing circulating liquid, the absorbing circulating liquid and the concentrated circulating liquid are purified, effectively controlling the escape of ammonia and aerosol, reducing the consumption of water and saving energy, and the technology of the present invention is formed. Program.

The technical scheme of the present invention adopts the following technical means, which can be used alone or in combination:

A membrane separation device applied to ammonia desulfurization, the membrane separation device can be an ultrafiltration device, a nanofiltration device, a reverse osmosis device or a combination thereof, preferably a nanofiltration device. A pretreatment device is provided in the membrane separation device, and precipitation, multi-media filtration, ultrafiltration, and/or temperature and pH adjustment measures can be adopted. The ammonia desulfurization absorption tower in the technical solution of the present invention includes a cooling and cooling section, an absorption section, and a water washing and defogging section. The membrane separation device is connected with one or more of the water washing and demisting section, the cooling and cooling section, and the absorption section. One or more sections of circulating liquid in the absorption tower are provided with cooling and cooling facilities, and the exhaust gas temperature of the absorption tower is 40-60°C, preferably 45-55°C.

When the membrane separation system is connected with the cooling and cooling section, the pre-washing circulating liquid in the cooling and cooling section is processed, the concentrated liquid pipeline is connected with at least one of the absorption section and the ammonium sulfate post-system, and the clear liquid is connected with at least one of the process water system and the washing circulating liquid. .

When the membrane separation device is connected with the water washing and defogging section, the water washing circulating liquid in the water washing and defogging section is treated, the concentrated liquid pipeline is connected with at least one of the absorption section and the cooling and cooling section, and the clear liquid is connected with the process water system or the water washing circulating liquid pipeline.

When the membrane separation device is connected with the absorption section, the circulating liquid in the absorption section is processed, the concentrated liquid pipeline is connected with the cooling and cooling section, and the clear liquid is connected with the water washing and defogging section/process water system.

The present invention is better for flue gas with high water content, and the water content of the flue gas is ≥8%, preferably ≥12%, and more preferably ≥15%.

The sum of the concentrations of ()ammonium sulfite and ammonium bisulfite in the washing circulation liquid is 0.01-30g/L, preferably 0.1-10g/L, more preferably 0.3-5g/L; the hardness of the washing circulation liquid ₍ calculated as CaCO3) 1-4mmol/L, preferably 1.5-2.5mmol/L.

At least one of the cooling and cooling section, the absorption section, and the water washing and demisting section is connected to the cooling equipment through a circulating pipeline, and the temperature of the flue gas is controlled to 30-60 °C, preferably 40-55 °C.

Before the prewashing liquid of the cooling and cooling section enters the membrane separation device, add ammonia to adjust the pH to be >2, preferably 3-7; the pH of the membrane separation liquid is 2-7, and the temperature is 10-55 ℃. The preferred pH is 3-6, and the temperature is 30-50°C.

The combination scheme of the present invention is described as follows, including but not limited to the following description scheme:

(1) a kind of method that membrane separation is applied to ammonia process desulfurization, comprises the steps:

The flue gas enters from the cooling and cooling section, and is cooled and cooled in the cooling and cooling section, the water in the flue gas is condensed and separated, the absorption section absorbs sulfur dioxide, and the water is washed to remove the entrained aerosols such as ammonia and sulfate.

Part of the pre-washing liquid is taken out and sent to the membrane separation device for concentration and separation, the concentrated liquid is returned to the absorption section, and the clear liquid is reused as process water.

Control the temperature of the pre-wash circulating fluid to 30-60°C, preferably 40-55°C.

(2) a kind of method that membrane separation is applied to ammonia process desulfurization, comprises the steps:

The flue gas enters from the cooling and cooling section, and is cooled and cooled in the cooling and cooling section, the absorption section absorbs sulfur dioxide, and the water washing and defogging section is washed to remove entrained aerosols such as ammonia and sulfate, and then discharged.

Take out part of the washing circulating liquid and send it to the membrane separation device for concentration and separation. The concentrated liquid is returned to the absorption section, and the clear liquid is returned to the water washing and defogging section or reused as process water.

(3) a kind of method that membrane separation is applied to ammonia process desulfurization, comprises the steps:

The flue gas enters from the cooling and cooling section, cools down in the cooling and cooling section, absorbs sulfur dioxide in the absorption section, washes with water to remove mist and removes entrained aerosols such as ammonia and sulfate, and then discharges.

Part of the pre-washing circulating liquid and the washing circulating liquid are taken out and sent to the membrane separation device for concentration and separation. The concentrated liquid is returned to the absorption section, and the clear liquid is reused as process water.

(4) a kind of method that membrane separation is applied to ammonia process desulfurization, comprises the steps:

The flue gas enters from the cooling and cooling section, and is cooled and cooled in the cooling and cooling section and the absorption section, the absorption section absorbs sulfur dioxide, and the water washing and defogging section is washed to remove entrained aerosols such as ammonia and sulfate, and then discharged.

A part of the absorption circulating liquid is taken out and sent to the membrane separation device for concentration. The concentrated liquid is sent to the cooling and cooling section, and the clear liquid is sent to the water washing and demisting section or reused as process water.

The temperature of the absorption circulating liquid (concentrated circulating liquid) is controlled to be 30-60°C, preferably 40-55°C.

(5) a membrane separation method applied to ammonia desulfurization, comprising the steps:

Part of the circulating liquid in the cooling and cooling section is taken out and sent to the membrane separation device for concentration.

The method realized by the present invention is as follows:

1. The gas purification process includes a gas pre-washing cycle and a fine particle washing cycle, and the circulating liquid in the gas purification process includes a pre-washing circulating liquid and a fine particle washing circulating liquid. The pre-washing circulating fluid is mainly used to purify the flue gas initially and control the aerosol generation in the desulfurization process. The fine particulate matter washing circulating fluid can further ensure the desulfurization efficiency, and at the same time, control the fine particulate matter of the flue gas, and finally ensure the emission of particulate matter and free ammonia. qualified.

2. Control the absorption conditions, reduce the flue gas temperature, and control the absorption temperature at 30-60 °C to minimize the escape of ammonia and aerosols generated during the absorption process.

3. Set up a membrane separation device, which includes pre-washing circulating liquid membrane separation, water-washing circulating liquid membrane separation and absorption liquid membrane separation. The flue gas condensed water is purified into process water by pre-washing/concentrating circulating liquid membrane separation, and the circulating liquid is purified and reused to reduce the water replenishment of the desulfurization system. Through absorption/concentration liquid membrane separation, the amount of evaporative crystallization evaporated water is reduced and energy consumption is saved.

4. By cooling the cooling liquid, the flue gas temperature at the outlet of the cooling and cooling section is reduced, the absorption efficiency of the desulfurization absorption section is improved, and the ammonia escape and aerosol generation generated in the absorption process are reduced;

5. Reduce the hardness in the washing circulating liquid through the water washing/absorption circulating liquid membrane separation, and reduce the scaling problem of the pipes and nozzles in the high pH environment of the absorption circulating.

6. For flue gas with high water content, by cooling the pre-wash circulating fluid and separating membranes, a large amount of water in the flue gas is prevented from being cooled in the absorption stage, and the concentration of ammonium sulfate in the absorption liquid is reduced, thereby reducing the energy consumption of the subsequent ammonium sulfate system .

7. By controlling the best membrane separation conditions such as pH, temperature, membrane material, etc., the best membrane separation effect can be obtained.

Through diligent work, the inventor found and realized the best way to realize the above technical solution is to set up a membrane separation device and combine it with an absorption tower. The separation device purifies at least one section of the absorption liquid, controls the composition, concentration, temperature and pH of the absorption liquid, and controls the escape of ammonia and aerosols. Temperature cooling measures are provided in the absorption liquid. The purified water can be reused as process water to save desulfurization water.

Reduce flue gas temperature by setting heat exchangers in pre-wash circulating fluid or concentrated circulating fluid.

Finally, the present invention solves the above technical problems through the following technical solutions.

A method for applying membrane separation to ammonia desulfurization. On the basis of a desulfurization tower, a membrane separation device is added. The desulfurization tower controls the absorption reaction temperature to 30-60°C by pre-washing and cooling the flue gas. An absorption circulating liquid is used for purification operation, and the composition, concentration, temperature and PH of the absorption circulating liquid are controlled to achieve efficient desulfurization and dust removal while controlling ammonia escape and aerosol. Through membrane separation, at least one of the pre-washing circulating liquid, the absorption circulating liquid and the water-washing circulating liquid is purified, and the composition, concentration, temperature and pH of the circulating liquid are controlled, so that the circulating liquid can fully wash the flue gas and further control the escape of ammonia and aerosols. The excess pre-washing circulating liquid is separated by the membrane and used for process water replenishment. At the same time, the condensation and precipitation of water in the flue gas in the absorption section is avoided, the concentration of ammonium sulfate in the absorption liquid is reduced, and the system energy consumption after ammonium sulfate is increased.

The absorption reaction temperature is 30-60°C, preferably 40-55°C, and optimally 45-53°C.

The sum of the concentrations of ammonium sulfate, ammonium sulfite and ammonium hydrogen sulfite in the water washing circulating liquid is 0.01-30 g/L, preferably 0.1-10 g/L, more preferably 0.3-5 g/L.

The concentration of the absorption circulating liquid is 15-35%, preferably 20-30%.

Ammonia is added to adjust the pH of the prewash before entering the membrane separation device. PH>2, preferably PH 5-8.

The water content and absorption temperature of the flue gas are controlled by the circulating liquid cooling device. The cooling methods include air cooling, water cooling, and ice machine cooling. The cooling equipment includes tubular heat exchangers, evaporative coolers, air coolers, and plate heat exchangers. Plate heat exchangers are preferred in areas with excess circulating water/primary water.

Description of drawings

FIG. 1 is a schematic diagram of Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram of Embodiment 2 of the present invention.

FIG. 3 is a schematic diagram of Embodiment 3 of the present invention.

FIG. 4 is a schematic diagram of Embodiment 4 of the present invention.

FIG. 5 is a schematic diagram of Embodiment 5 of the present invention.

FIG. 6 is a schematic diagram of Comparative Example 6. FIG.

1. Absorption tower; 2. Oxidation equipment; 3. Water washing circulation tank; 4. Cooling and cooling section; 5. Absorption section; 6. Water washing and defogging section; 7. Absorption of circulating liquid; Gas inlet; 10. Washing circulating liquid; 11. Gas-liquid separator; 12. Pre-washing circulating liquid; 13. Ammonia; 14. Oxidizing air; 15. Process water; 16. Ammonium sulfate post-treatment system; 17. Evaporative crystallization system ; 18, heat exchange equipment; 19, solid-liquid separation equipment; 20, centrifuge; 21, drying equipment; 22, packaging machine; 23, finished ammonium sulfate; 24, membrane separation device.

Example

Embodiment 1: A kind of method and device that membrane separation is applied to ammonia desulfurization

As shown in Figure 1, the device is composed of a desulfurization tower and a membrane separation device. The flue gas enters from the cooling and cooling section 4, is cooled and washed to 50 ℃ by the pre-washing circulating liquid 12, and then is washed and desulfurized by the absorption circulating liquid 7 in the absorption section 5, and washed with water. The mist section 6 is discharged by the water washing circulating liquid 10 to remove fine particles; the pre-washing circulating liquid 12 is mainly flue gas condensate, the pre-washing circulating liquid is purified by the membrane separation device 24, the clear liquid goes to the process water main pipe, and the concentrated liquid goes to the absorption oxidation system .

The absorption circulating liquid 7 is oxidized in the oxidation system, and the solutions with different components are extracted from different positions or different devices of the oxidation equipment 2 of the oxidation system and circulated respectively.

The water washing and defogging section 6 is supplemented by process water 15 .

The water content and absorption temperature of the flue gas are controlled by the heat exchange device 18 .

Part of the absorption circulating liquid 7 is sent to the ammonium sulfate post-processing system 16 through the evaporation and crystallization system 17, and the finished ammonium sulfate product 23 is obtained through solid-liquid separation, centrifugation, drying and packaging.

The main flue gas and operating conditions are as follows: flue gas volume 2100000Nm ³ /h, temperature 158°C, water content 21.6%, SO ₂ concentration 6800mg/Nm ³ . The flow rate of pre-washing circulating fluid 12 is 10000m ³ /h. The cooling device on the circulating pipeline cools the circulating fluid to 48℃. After spraying the flue gas, the flue gas temperature is 50℃; the water in the flue gas condenses and separates out and enters the circulation together. In the liquid, the excess circulating liquid 172.5m ³ /h enters the membrane separation device, and the PH is adjusted to 4 with ammonia water, then enters the multi-media filtration, nanofiltration membrane, reverse osmosis separation system, and the clear liquid enters the process water main pipe for other units or use. After washing with water, the recovery rate of clear liquid is 85%, and the concentrated liquid enters the absorption section.

The flow rate of the absorption circulating liquid 7 is 15000m ³ /h; the flow rate of the washing circulating liquid 10 is 3400m ³ /h. The absorption liquid is sent to the evaporative crystallization system, and the evaporated condensed water is sent to the washing circulation tank or discharged to the outside. After the wet ammonium sulfate is dried, the ammonium sulfate finished product 23 is obtained and the output is 30t/h.

The temperature of the flue gas at the outlet of the cooling and cooling section 4 is controlled to be 50°C, and the concentration of ammonium sulfate in the water washing circulating liquid 10 is controlled below 0.5%.

Using this method, the net flue gas outlet 8 ammonia escape index is 3mg/Nm ³ , the dust content is 5mg/Nm ³ , the SO ₂ content is 35mg/Nm ³ , and the evaporated water volume is 116t/h.

Embodiment 2: A kind of method and device that membrane separation is applied to ammonia desulfurization

As shown in Figure 2, the device is composed of a desulfurization tower and a membrane separation device. The flue gas enters from the cooling and cooling section 4, is cooled and washed by the pre-washing circulating liquid 12, and then is washed and desulfurized by the absorption circulating liquid 7 in the absorption section 5, and washed with water. Demisting section 6 The fine particles are removed by the washing circulating liquid 10 and then discharged;

The flue gas is cooled to a suitable temperature by the pre-wash circulating fluid 12 .

The absorption circulating liquid 7 is oxidized in the oxidation system 2, and the solutions with different components are extracted from different positions of the oxidation equipment of the oxidation system or from different equipment to be circulated respectively.

The water washing and defogging section 6 is replenished by the process water 15, and the water washing circulating liquid 10 is purified by the membrane separation device 24 and returned to the water washing tank 3 or to the process water main pipe, and the concentrated liquid is absorbed and oxidized to the system.

A cooling device is provided on the pre-washing circulating pipeline, and the cooled concentrated circulating liquid is used for spraying, and the water content and absorption temperature of the flue gas are controlled by the heat exchange equipment 18 .

After part of the water washing circulating liquid is processed by the membrane separation device 24, it goes to the process water main pipe in the clear night, and the concentrated liquid goes to the absorption and oxidation system. Part of the pre-washing circulating liquid 12 is sent to the ammonium sulfate post-processing system 16 through the evaporation and crystallization system 17, and the finished ammonium sulfate product 23 is obtained through solid-liquid separation, centrifugation, drying and packaging.

The flue gas parameters and operating conditions are as follows: 2100000Nm ³ /h, temperature 158°C, water content 21.6%, SO ₂ concentration 6800mg/Nm ³ .

The flow rate of the pre-washing circulating fluid 12 is 10000m ³ /h, the temperature of the circulating fluid after cooling by the cooling device is 48°C, the temperature of the flue gas after spraying is 50°C, the flow rate of the absorption circulating fluid 7 is 15000m ³ /h, and the flow rate of the washing circulating fluid 10 is 3400m ³ / h. 71m ³ /h of water washing circulating liquid enters the membrane separation device, which adopts multi-media filtration and nanofiltration membrane separation system. After membrane separation, 60 m ³ /h of clear liquid is returned to the washing circulation tank or the process water main pipe, and the concentrated liquid enters the oxidation circulation tank; cooling The solution in the cooling section is sent to the evaporative crystallization system, and the evaporated condensed water goes to the washing circulation tank or is discharged outside. The output of ammonium sulfate finished product 23 is 30t/h.

The temperature of the flue gas at the outlet of the cooling and cooling section 4 is controlled to be 50°C, and the concentration of ammonium sulfate in the water washing circulating liquid 10 is controlled below 0.3%.

Using this method, the ammonia escape of the net flue gas outlet 8 is less than 3 mg/Nm ³ , the dust content is less than 4 mg/Nm ³ , the SO ₂ content is 35 mg/Nm ³ , and the evaporation of the evaporative crystallization system 17 is 213 t/h.

Embodiment 3: A kind of method and device that membrane separation is applied to ammonia desulfurization

As shown in Figure 3, the device consists of a desulfurization tower and a membrane separation device. The flue gas enters from the cooling and cooling section 4, is cooled and washed to 50 ℃ by the pre-washing circulating liquid 12, and then is washed and desulfurized by the absorption circulating liquid 7 in the absorption section 5, and washed with water. The mist section 6 is discharged by the water washing circulating liquid 10 to remove fine particles; the pre-washing circulating liquid 12 is mainly flue gas condensate. system.

The absorption circulating liquid 7 is oxidized in the oxidation system, and the solutions with different components are extracted from different positions of the oxidation equipment 2 of the oxidation system or different equipment for circulation respectively.

The water washing and defogging section 6 is replenished by the process water 15. After the water washing circulating liquid 10 is purified by the membrane separation device 24, the clear liquid is returned to the water washing tank 3 or the process water main pipe, and the concentrated liquid is absorbed and oxidized.

The main flue gas and operating conditions are as follows: flue gas volume 2100000Nm ³ /h, temperature 158°C, water content 21.6%, SO ₂ concentration 6800mg/Nm ³ . The flow rate of pre-washing circulating fluid 12 is 10000m ³ /h. The cooling device on the circulating pipeline cools the circulating fluid to 48℃. After spraying the flue gas, the flue gas temperature is 50℃; the water in the flue gas condenses and separates out and enters the circulation together. In the liquid, the excess circulating liquid 173m ³ /h enters the membrane separation device, and the PH is adjusted to 4 with ammonia water, and then enters the multi-media filtration, nanofiltration membrane, reverse osmosis separation system, and the clear liquid enters the process water main pipe for other units or for use. Wash and replenish water, the recovery rate of clear liquid is 85%, and the concentrated liquid enters the absorption section.

The flow rate of the absorption circulating liquid 7 is 15000m ³ /h; the flow rate of the washing circulating liquid 10 is 3400m ³ /h. 71m ³ /h of water washing circulating liquid enters the membrane separation device, 60 m ³ /h of clear liquid after membrane separation returns to the washing circulating tank, and the concentrated liquid enters the oxidation circulating tank; the solution in the absorption section is sent to the evaporation and crystallization system, and the evaporated condensed water goes to the washing circulating tank or Efflux. The output of ammonium sulfate finished product 23 is 30t/h.

The temperature of the flue gas at the outlet of the cooling section 4 in the cold zone is controlled to be 50°C, and the concentration of ammonium sulfate in the water washing circulating fluid 10 is controlled below 0.3%.

Using this method, the ammonia escape index of the net flue gas outlet 8 is 3 mg/Nm ³ , the dust content is 4 mg/Nm ³ , the SO ₂ content is 35 mg/Nm ³ , and the evaporation of the evaporative crystallization system 17 is 67 t/h.

Embodiment 4: A kind of method and device that membrane separation is applied to ammonia desulfurization

As shown in Figure 4, the device is composed of a desulfurization tower and a membrane separation device. The flue gas enters from the cooling and cooling section 4, is cooled and washed by the pre-washing circulating liquid 12, and then is cooled and washed by the absorption circulating liquid 7 in the absorption section 5. At the same time, desulfurization, water washing and demisting Section 6 is discharged by washing circulating liquid 10 to remove fine particles;

The flue gas is cooled to a suitable temperature by the prewashing circulating liquid 12 and the absorption circulating liquid 7 . A cooling device is provided on the absorption circulation pipeline, and the cooled concentrated circulating liquid is used for spraying, and the water content and absorption temperature of the flue gas are controlled by the heat exchange equipment 18 .

The absorption circulating liquid 7 is oxidized in the oxidation system 2, and the solutions with different components are extracted from different positions of the oxidation equipment of the oxidation system or from different equipment to be circulated respectively. After part of the absorption circulating liquid 7 is concentrated through the membrane separation device 24, the purified water goes to the process water main pipe, and the concentrated liquid goes to the cooling and cooling section.

The water washing and defogging section 6 is supplemented by process water 15 .

Part of the pre-washing circulating liquid 12 is sent to the ammonium sulfate post-processing system 16 through the evaporation and crystallization system 17, and the finished ammonium sulfate product 23 is obtained through solid-liquid separation, centrifugation, drying and packaging.

The flow rate of pre-wash circulating liquid 12 is 10000m ³ /h, the flow rate of absorption circulating liquid 7 is 15,000m ³ /h, and the flow rate of water washing circulating liquid 10 is 3400m ³ /h. 50°C. 143m ³ /h of the absorption circulating liquid enters the membrane separation device, which adopts multi-media filtration, nanofiltration membrane and reverse osmosis separation system. After membrane separation, 57 m ³ /h of clear liquid is returned to the process water main pipe, and the concentrated liquid enters the cooling and cooling section with a concentration of 26 %; The solution in the cooling and cooling section is sent to the evaporative crystallization system, and the evaporative condensed water is sent to the washing circulation tank or discharged outside. The output of ammonium sulfate finished product 23 is 30t/h.

Using this method, the ammonia escape index of the net flue gas outlet 8 is 3 mg/Nm ³ , the dust content is 5 mg/Nm ³ , the SO ₂ content is 35 mg/Nm ³ , and the evaporation of the evaporative crystallization system 17 is 206 t/h.

Embodiment 5: A kind of method and device that membrane separation is applied to ammonia desulfurization

As shown in Figure 5, the device is composed of a desulfurization tower and a membrane separation device. The flue gas enters from the cooling and cooling section 4, is cooled and washed by the pre-washing circulating liquid 12, and then is washed and desulfurized by the absorption circulating liquid 7 in the absorption section 5, and washed with water in the demisting section 6 The fine particles are removed by the washing circulating liquid 10 and then discharged;

The flue gas is cooled to a suitable temperature by the pre-wash circulating fluid 12 . A cooling device is provided on the pre-washing circulating pipeline, and the cooled pre-washing circulating liquid is used for spraying, and the water content and absorption temperature of the flue gas are controlled by the heat exchange equipment 18 .

The water washing and defogging section 6 is supplemented by process water 15 .

After part of the pre-washing circulating liquid is processed by the membrane separation device 24, it goes to the process water main pipe in the clear night, and the concentrated liquid goes to the evaporation and crystallization system 17. After evaporation and crystallization, it is sent to the ammonium sulfate post-processing system 16, and the finished product 23 of ammonium sulfate is obtained through solid-liquid separation, centrifugation, drying and packaging.

The flow rate of the pre-washing circulating fluid 12 is 10000m ³ /h, the temperature of the circulating fluid after cooling by the cooling device is 48°C, the temperature of the flue gas after spraying is 50°C, the flow rate of the absorption circulating fluid 7 is 15000m ³ /h, and the flow rate of the washing circulating fluid 10 is 3400m ³ / h. 263m ³ /h of concentrated circulating liquid enters the membrane separation device, which adopts multi-media filtration, nanofiltration membrane and reverse osmosis separation system. After membrane separation, 171m ³ /h of clear liquid returns to the washing circulation tank or process water main pipe, and the concentrated liquid enters the evaporation and crystallization system 17. The concentration is 25%, evaporate the condensed water to wash the circulation tank or discharge it out. The output of ammonium sulfate finished product 23 is 30t/h.

Using this method, the 8 ammonia escape index of the net flue gas outlet is 3mg/Nm ³ , the dust content is 4mg/Nm ³ , the SO ₂ content is 35mg/Nm ³ , and the evaporation of the evaporative crystallization system is 92t/h.

Example 6: Comparative Example

As shown in Figure 6, the device is composed of a conventional desulfurization tower. The flue gas enters from the cooling and cooling section 4, is cooled and washed by the pre-washing circulating liquid 12, and then is washed and desulfurized by the absorption circulating liquid 7 in the absorption section 5, and the water washing and demisting section 6 is washed and circulated by water. Liquid 10 is discharged after removing fine particles;

The water washing and defogging section 6 is replenished by the process water 15, and the water washing circulating liquid is sprayed with water to remove aerosols and particulate matter.

The flow rate of pre-washing circulating liquid 12 is 10000m ³ /h, the temperature of flue gas after spraying is 66°C, the flow rate of absorption circulating liquid 7 is 15000m ³ /h, and the flow rate of washing circulating liquid 10 is 3400m ³ /h. The output of ammonium sulfate finished product 23 is 30t/h. In addition, the external supplementary water volume is 87t/h.

The temperature of the flue gas at the outlet of the cooling section 4 is controlled to be 66°C, and the tower is saturated with crystallization. Using this method, the net flue gas outlet 8 has a ammonia escape of 10mg/Nm ³ , a dust content of 25mg/Nm ³ , and a SO ₂ content of 100mg/Nm ³ .

Claims

A method for applying a membrane separation device to ammonia desulfurization is characterized in that: the membrane separation device is applied to the purification of circulating liquid of the ammonia desulfurization device.
The method of claim 1, wherein the membrane separation device comprises an ultrafiltration device, a nanofiltration device, a reverse osmosis device or a combination thereof.
The method of claim 1, wherein the membrane separation device is provided with pretreatment equipment, including sedimentation, sand filtration, ultrafiltration, and/or temperature and pH adjustment equipment.
The method of claim 1, further comprising a desulfurization tower, the desulfurization tower includes a cooling and cooling section, an absorption section, a water washing and demisting section, and the membrane separation device is connected to any one or more sections of the desulfurization tower; Any one or more sections in the desulfurization tower are connected, and the clear liquid is connected with the desulfurization tower water washing and demisting section or the process water system.
The method according to claim 4, characterized in that, at least one section of the desulfurization tower is provided with cooling and cooling equipment, and the exhaust gas temperature is 40-60 °C.
The method of claim 4, wherein the water content of the flue gas entering the desulfurization tower is ≥8%, preferably ≥12%, more preferably ≥15%.
The method according to claim 4, characterized in that, before the circulating liquid enters the membrane separation device, ammonia is added to adjust pH>2, preferably 3-7.
The method of claim 1, wherein the operating temperature of the membrane separation device is 10-55°C, preferably 30-50°C.
A method for applying a membrane separation device to ammonia desulfurization, including an ammonia desulfurization device and a membrane separation device, the ammonia desulfurization device includes an absorption tower, the absorption tower uses a circulating liquid for desulfurization, and the circulating liquid is washed with water to wash the desulfurized flue gas, which is It is characterized in that: the circulating liquid of the ammonia desulfurization device is sent to the membrane separation device for treatment, the concentrated liquid is returned to the ammonia desulfurization device after treatment, and the clear liquid of the membrane separation device is sent to the process water system or the water washing circulating liquid.
The method of claim 9, wherein the sum of the concentrations of ()ammonium sulfite and ammonium hydrogen sulfite in the washing circulating liquid is 0.01-30 g/L.
The method according to claim 9, characterized in that, the hardness (calculated as CaCO 3 ) of the water washing circulating liquid is 1-4 mmol/L, preferably 1.5-2.5 mmol/L.
The method according to claim 1, characterized in that, the membrane separation device is used for treating water washing circulating liquid, pre-washing circulating liquid, absorption circulating liquid or concentrated circulating liquid.
A method for purifying circulating liquid of ammonia process desulfurization, comprising the following steps:

1) The flue gas after preliminary purification is washed with the circulating liquid to remove SO 2 in the flue gas, and the flue gas is discharged after further washing with the circulating liquid and demisting;

2) Sending part of the circulating liquid to the membrane separation device for purification, the purified concentrated liquid is returned to the circulating liquid, and the clear liquid is sent to the process water system or used as the replenishment of the washing circulating liquid;

3) By adjusting the water replenishment amount and water quality of the washing circulating liquid, the sum of the concentrations of ()ammonium sulfite and ammonium bisulfite in the washing circulating liquid is controlled to be 0.01-30 g/L.
The method of claim 13, wherein the water content of the flue gas entering the desulfurization tower is ≥8%, preferably ≥12%, more preferably ≥15%.
The method according to claim 13, characterized in that, the membrane separation device is used for treating water washing circulating liquid, pre-washing circulating liquid, absorption circulating liquid or concentrated circulating liquid.