A dual-alkali FGD process technology in the transformation of a smoke flue gas dust removal device is: ①SO2 desulfurization efficiency ≥80%; ② dust concentration ufh≤100 mg / m3; ③ desulfurized fluid closed cycle, do not Secondary pollution occurs; 4 operation and operation of desulfurization and dust removal system does not affect the operation and maintenance of the original production equipment; 5 fully utilize the original equipment to save investment; 6 desulfurization and dust removal system runs stably for a long period of time, and management and maintenance are convenient.
1. Selection of desulfurization process The main industrial processes currently used for flue gas desulfurization include dry process, semi-dry process and wet process. Comparison of various desulfurization processes
Comparison of various general desulfurization processes in the world
1.1 Dry desulfurization Dry desulfurization is a traditional process. The common method is to spray calcium, lime/limestone, metal absorption, etc. into the furnace. The desulfurization efficiency is generally not high (<50%), and affects the operation of the boiler body, resulting in a decrease in the output of the boiler, which is currently less used in industry.
1.2 Semi-dry desulfurization The semi-dry method uses more in-column spray method, that is, lime is made into lime slurry, and SO2 absorption is carried out in the tower. Since the water in the lime slurry evaporates quickly, the reaction is basically a gas-solid phase reaction. The absorption reaction rate of SO2 is slow, the requirement for lime is very high, the cost of desulfurizer is high, the reaction efficiency of calcium injection is low, Ca/S is relatively large, generally above 1.5, and the dust removal pressure of subsequent systems is large. not much.
1.3 Wet Desulfurization Wet desulfurization is the most widely used desulfurization method, accounting for more than 80% of total desulfurization. Wet desulfurization can be divided into limestone/lime method, ammonia method, sodium alkali method, sodium calcium double alkali method, metal oxidation method and basic aluminum sulfate method according to different desulfurization raw materials.
(1) Limestone/lime method The limestone method is to crush limestone into 200-300 mesh lime powder to form a lime slurry, which is sprayed and atomized into contact with the flue gas in the absorption tower to react calcium carbonate with sulfur dioxide. Calcium sulfate to achieve the purpose of desulfurization. The process requires a limestone comminution system and a limestone pulping system. Because limestone is insoluble and has low reactivity, it is necessary to increase the liquid-gas ratio (liquid-gas ratio is usually greater than 20) to increase the efficiency of desulfurization by increasing the spray amount of the absorption liquid, so the operation cost is high. The lime method uses lime powder instead of limestone, and the lime activity is greatly higher than that of limestone to improve the desulfurization efficiency. The main problem with the lime method is that the inside of the tower is prone to fouling, causing blockage of the gas-liquid contactor (head or tray).
(2) Soda-alkali method The sodium-alkali method uses an alkaline substance such as sodium carbonate or sodium hydroxide to absorb sulfur dioxide in the flue gas, and can produce a high concentration of sulfur dioxide gas or sodium sulfite. The method has the advantages of non-volatile absorbent, high solubility, high activity, and no clogging of the absorption system, and is suitable for the treatment of high concentration of sulfur dioxide in the flue gas, but the recycling process of the by-product is complicated, the investment is high, and the running cost is high. Disadvantages.
(3) Ammonia method The ammonia method uses ammonia water as an absorbent for sulfur dioxide, and sulfur dioxide reacts with ammonia to form ammonium sulfite, ammonium hydrogen sulfite and ammonium sulfate which is partially produced by oxidation. The ammonia method can be classified into an ammonia-acid method, an ammonia-ammonium sulfite method, and an ammonia-ammonium sulfate method depending on the method of the absorption liquid regeneration.
Main features of ammonia desulfurization: 1 high desulfurization efficiency (same as sodium alkali method), absorbent ammonia source is convenient, by-product can be used as agricultural fertilizer, but the fertilizer is acidic fertilizer, low in nitrogen content, easy to cause soil compaction in long-term use. 2 Because ammonia is volatile, the consumption of absorbent is increased, and the utilization rate of desulfurizer is not high. 3 Desulfurization has certain requirements on the concentration of ammonia. If the concentration of ammonia is too low, it not only affects the desulfurization efficiency, but also the water circulation system is huge, so that the operation The cost increases; 4 the concentration increases, which will inevitably lead to an increase in evaporation and affect the working environment; 5 ammonia easily reacts with the sulfur dioxide in the purified flue gas to form an aerosol, so that the flue gas cannot reach the standard discharge.
The ammonia recovery process is difficult and the investment cost is high. It needs to be equipped with an acid production system or a crystallization recovery system (neutralizer, crystallizer, dewatering machine, dryer, etc.), so the system is complicated, the equipment is numerous, and the management and maintenance requirements are high. In addition, environmentally friendly water bodies have higher requirements for ammonia nitrogen and are prone to secondary pollution of ammonia and nitrogen.
(4) Metal oxide method A commonly used metal oxide method is a magnesium oxide method. Magnesium oxide reacts with sulfur dioxide to obtain magnesium sulfite and magnesium sulfate. The calcination can re-decompose magnesium oxide to regenerate the absorbent, and at the same time, recover the pure sulfur dioxide gas, and the desulfurizing agent can be recycled. Since the activity of magnesium oxide is higher than that of lime water, the desulfurization efficiency is also higher than that of the lime method. The disadvantage of the metal oxide method is that the magnesium oxide recovery requires crystallization, separation, evaporation, calcination and other processes, and the process is complicated; however, if the disposal method is directly adopted, a large amount of soluble magnesium salt will enter the water body to cause secondary pollution, and the overall operation cost is high. In addition, the pipeline of the system is easy to scale, and when the water hardness is high, the pipeline is more blocked.
(5) Nacalcium double alkali method Sodium calcium double alkali method (sodium carbonate/calcium hydroxide) combines the advantages of lime method and sodium alkali method, and utilizes sodium salt to be easily soluble in water and has high reactivity, and is inside the absorption tower. The sodium base absorbs sulfur dioxide, and the absorbed desulfurization liquid enters the alkali regeneration tank and is regenerated by using cheap lime, so that the sodium ions are recycled and utilized. The process combines the characteristics of the lime method and the sodium-base method, and not only solves the disadvantage of easy scaling in the lime tower, but also has the advantages of high absorption efficiency by the sodium-alkali method. The by-product of desulfurization is calcium sulfite or calcium sulfate (after oxidation). Calcium sulphite formulated synthetic resin can produce new composite material calcium plastic, or oxidize it to form gypsum, or directly mix with fly ash, can increase the plasticity of fly ash, enhance the strength of coal ash as paving underlayer cushion material . Compared with magnesium oxide, calcium salts are not polluting, so there is no secondary pollution of waste residue.
This transformation uses the sodium-calcium double alkali method as the desulfurization process for the renovation project.
2 Sodium-calcium double-alkali desulfurization principle 2.1 Advantages The sodium-calcium double-base method uses soda ash start-up, sodium-base absorption of SO2 and lime regeneration. Compared with the limestone method and other wet desulfurization processes, the nanocalcium double alkali method has the following advantages: 1 sodium alkali absorbent has high reaction activity, fast absorption speed, small liquid-gas ratio, low operating cost; 2 sodium-based clean absorption in the tower The absorption capacity of the absorbent and the absorption product is large, and the regeneration and precipitation separation outside the tower can greatly reduce the scale inside the tower and the pipeline; 3 the sodium and alkali recycling, the loss is small, the running cost is low; 4 the absorption process has no waste water discharge, the absorption liquid The salt does not accumulate and the concentration is stable; 5 the waste residue is non-toxic, the solubility is very small, no secondary pollution; 6 lime as a regenerant, safe and reliable, low cost; 7 nozzle, water pump, pipeline is not blocked; 8 liquid phase specific gravity during operation No increase, easy to separate and separate from water, can greatly reduce the investment in the pool; 9 easy to operate, the system can run in a long cycle.
2.2 Desulfurization process Na2Co3+SO2→Na2SO3+CO2↑ (1)
2NaoH+SO2→Na2SO3+H2O↑ (2)
Na2SO3+SO2+H2O→2NaHSO3 (3)
The above three formulas vary depending on the pH of the absorption liquid: (1) is the absorption initiation reaction; (2) is the main reaction (pH=9), and when the basicity is reduced to neutral or even acidic (5<PH<9), then according to (3) react.
Regeneration process:
2NaHSO3+Ca(OH)2→Na2SO3+CaSO3↓+2H20 (4)
Na2SO3+Ca(OH)2→NaOH+CaSO3↓ (5)
In the lime slurry (the lime reaches the supersaturation condition), the neutral NaHSO3 reacts with the lime to release [Na+], and the resulting [SO32-] continues to react with the lime. The CaSO3 formed in the reaction is in the form of a hemihydrate. Precipitated, so that [Na+] can be regenerated, and the absorption liquid restores the absorption capacity of SO2 and is recycled.
It can be seen from the above reaction that the sodium base is only used for the start-up reaction, and the consumption in actual operation is not large, and the main desulfurizer is lime.
Second, dust removal process:
1. Gravity dust removal method:
Different from the density of dust and gas, the dust naturally settles from the airflow by its own gravity to achieve the purpose of separating or trapping particles in the dusty gas flow. The disadvantage is that the dust removal efficiency is extremely low, and it is generally used in small boilers.
2 , inertial force dust removal method:
The inertial flow of dust and gas in motion is different, so that the dust is separated from the airflow. The general method for achieving inertial separation in practical applications is to cause the dust-containing airflow to impinge on the baffle, causing a sharp change in the direction of the airflow. The dust particles in the airflow have a large inertia and cannot be sharply turned with the airflow, and are separated from the airflow.
Inertial dust collectors are suitable for the removal of non-tacky, non-fibrous dust. The structure of the device is simple and the resistance is small; but the separation efficiency is low, and only coarse dust particles of 10-20 μm or more can be collected, and can only be used for the first stage dust removal in the multi-stage dust removal.
3 , centrifugal force dust removal method:
By using the flow velocity of the dust-containing gas, the airflow is continuously rotated in a certain direction in the dust removing device, and the particles obtain centrifugal force in the rotation of the airflow, thereby causing the particles to separate from the airflow. Commonly used dust removal devices include cyclone dust collectors and cyclone dust collectors. The most commonly used ones are cyclone dust collectors. The cyclone dust collectors have high dust removal efficiency and have good dust removal efficiency for particles larger than 5μm. It is suitable for the removal of non-viscous and non-fibrous dust, and can be used for dust removal and purification of high-temperature flue gas. Therefore, it is widely used in boiler flue gas dedusting, multi-stage dust removal and dust removal.
4 , wet dust removal method:
The liquid (usually water) is used to wash the dust-containing gas, and the formed liquid film, droplets or bubbles are used to trap the dust particles in the gas. The dust particles are discharged with the liquid, and the gas is purified. The liquid film, droplets or bubbles are mainly passed through inertia. Collision, the diffusion of fine dust particles, the agglomeration of the liquid film and droplets to humidify the dust particles and the adhesion to the dust particles, to achieve the purpose of capturing dust particles in the exhaust gas.
The wet dust collector has high dust removal efficiency, especially the high energy wet scrubber, which can maintain high dust removal efficiency when removing dust particles below 0.1μm. The wet scrubber has high efficiency and good safety for purifying high temperature, high humidity, flammable and explosive gases. The wet dust remover removes the dust particles in the exhaust gas, and at the same time removes the harmful and toxic gaseous pollutants in the exhaust gas through the absorption of the liquid, and has a better desulfurization effect. It is suitable for non-stick and non-fibrous.
5 , filter dust removal method:
The filter type dust removal is to make the dust-containing gas pass through the porous filter material, and the dust particles in the gas are intercepted to purify the gas. The filter material filters the dust-containing gas, and is divided into internal filtration and external filtration according to the dust filtration method. The filter material of the filter dust collector is to screen the particles through the pores of the filter material, and the particles collide with the inertial collision in the air movement, the diffusion of fine particles, and the combined effects of electrostatic attraction and gravity sedimentation to achieve dust removal. the goal of.
At present, the filter dust removal device is a bag type dust collector. The structure is to hang several circular or elliptical filter bags in the dust collection chamber of the dust collector. When the dusty airflow passes through the bag wall of the filter bags, the dust particles are The wall of the bag is trapped and collected on the inner or outer wall of the bag to be trapped.
Bag type dust collectors can be divided into mechanical vibrating bag type dust collectors, airflow back blowing bag type dust collectors, gas ring back blowing bag type dust collectors, and pulse jet bag type dust collectors according to different cleaning methods. Pulse jet bag filter. The pulse jet bag filter has the advantages of large gas volume, high efficiency, less damage to the filter bag, and is widely used in large and medium dust removal projects.
The bag filter is a high-efficiency dust collector, which has a strong trapping effect on fine dust. It is widely used in the dust removal of various industrial waste gases, but it is not suitable for the treatment of oily, watery and cohesive dust, and it is also uncomfortable. For the treatment of high temperature dusty gas, there is no desulfurization effect.
6 , electric dust removal method:
Electrostatic precipitator is the separation of solid particles or liquid particles from a gas stream by the action of electrostatic force (Coulomb force) generated by a high voltage electric field. The electric field should be a high-voltage direct current non-uniform electric field, the discharge electrode constituting the electric field is a linear electrode having a large surface curvature, and the dust collector is a plate-shaped electrode or a tubular electrode having a large area.
When a high DC voltage is applied between the discharge electrode and the dust collecting pole, the uneven electric field formed between the two poles makes the electric field intensity near the electrode large. When the voltage is applied to a certain value, the discharge electrode generates corona discharge and generates A large number of electrons and anions migrate to the dust collecting pole under the action of an electric field force. Neutral gas molecules easily capture these electrons or anions to form negative ions during migration. When these negatively charged particles collide with the dust particles in the gas stream and attach to them, the dust particles are negatively charged. The charged dust is driven to the dust collecting pole by the Coulomb force in the electric field, and the dust particles are deposited on the surface of the dust collecting pole and deposited on the dust collecting pole. When the dust is deposited to a certain thickness, it is eliminated by mechanical vibration.
The equipment commonly used in electric dust removal is an electric precipitator. The electrostatic precipitator is a high-efficiency dust collector with a dust removal efficiency of over 99%. It has excellent fine dust collection performance. The minimum particle size can be up to 0.05μm, and any dust removal efficiency from inefficient to efficient can be obtained as required. . The electrostatic precipitator has low resistance and low energy consumption allows operation in the range of 250-350 °C.
The electric dust removal equipment is huge and covers a large area. It requires operators to have a high technical level, high equipment investment, and no desulfurization effect.
Third, the selection of dust removal and desulfurization equipment According to the above various desulfurization and dust removal methods analysis and on-site investigation and consultation of the Aluminum Electrolysis Experimental Factory of Chinalco Zhengzhou Research Institute, our factory chose to use a high-efficiency desulfurization and dust removal integration technology SLTC-1.3 Desulfurization and dust removal treatment of 4t/h coal-fired chain boiler flue gas.
Bag dust collector dust bag
1. Selection of desulfurization process The main industrial processes currently used for flue gas desulfurization include dry process, semi-dry process and wet process. Comparison of various desulfurization processes
Comparison of various general desulfurization processes in the world
| Serial number | Adopting process | Desulfurization rate% | Desulfurization cost | Secondary pollution | Remarks |
| 1 | Calcination in the furnace | 50% lower | Lower | no | Reduced furnace thermal efficiency |
| 2 | Tower spray method | 70% lower | medium | no | Unstable and easy to block |
| 3 | Limestone/lime method | Higher | medium | no | Gypsum, easy to scale |
| 4 | Sodium alkali method | high | high | no | Suitable for high concentration sulfur dioxide recovery |
| 5 | Ammonia method | Higher | Higher | Light pollution | Recycling system complex |
| 6 | Metal oxide method | high | Higher | Direct discharge | Higher recycling costs |
| 7 | Sodium calcium double base method | Higher | low | no | Sodium alkali cycle absorption |
1.2 Semi-dry desulfurization The semi-dry method uses more in-column spray method, that is, lime is made into lime slurry, and SO2 absorption is carried out in the tower. Since the water in the lime slurry evaporates quickly, the reaction is basically a gas-solid phase reaction. The absorption reaction rate of SO2 is slow, the requirement for lime is very high, the cost of desulfurizer is high, the reaction efficiency of calcium injection is low, Ca/S is relatively large, generally above 1.5, and the dust removal pressure of subsequent systems is large. not much.
1.3 Wet Desulfurization Wet desulfurization is the most widely used desulfurization method, accounting for more than 80% of total desulfurization. Wet desulfurization can be divided into limestone/lime method, ammonia method, sodium alkali method, sodium calcium double alkali method, metal oxidation method and basic aluminum sulfate method according to different desulfurization raw materials.
(1) Limestone/lime method The limestone method is to crush limestone into 200-300 mesh lime powder to form a lime slurry, which is sprayed and atomized into contact with the flue gas in the absorption tower to react calcium carbonate with sulfur dioxide. Calcium sulfate to achieve the purpose of desulfurization. The process requires a limestone comminution system and a limestone pulping system. Because limestone is insoluble and has low reactivity, it is necessary to increase the liquid-gas ratio (liquid-gas ratio is usually greater than 20) to increase the efficiency of desulfurization by increasing the spray amount of the absorption liquid, so the operation cost is high. The lime method uses lime powder instead of limestone, and the lime activity is greatly higher than that of limestone to improve the desulfurization efficiency. The main problem with the lime method is that the inside of the tower is prone to fouling, causing blockage of the gas-liquid contactor (head or tray).
(2) Soda-alkali method The sodium-alkali method uses an alkaline substance such as sodium carbonate or sodium hydroxide to absorb sulfur dioxide in the flue gas, and can produce a high concentration of sulfur dioxide gas or sodium sulfite. The method has the advantages of non-volatile absorbent, high solubility, high activity, and no clogging of the absorption system, and is suitable for the treatment of high concentration of sulfur dioxide in the flue gas, but the recycling process of the by-product is complicated, the investment is high, and the running cost is high. Disadvantages.
(3) Ammonia method The ammonia method uses ammonia water as an absorbent for sulfur dioxide, and sulfur dioxide reacts with ammonia to form ammonium sulfite, ammonium hydrogen sulfite and ammonium sulfate which is partially produced by oxidation. The ammonia method can be classified into an ammonia-acid method, an ammonia-ammonium sulfite method, and an ammonia-ammonium sulfate method depending on the method of the absorption liquid regeneration.
Main features of ammonia desulfurization: 1 high desulfurization efficiency (same as sodium alkali method), absorbent ammonia source is convenient, by-product can be used as agricultural fertilizer, but the fertilizer is acidic fertilizer, low in nitrogen content, easy to cause soil compaction in long-term use. 2 Because ammonia is volatile, the consumption of absorbent is increased, and the utilization rate of desulfurizer is not high. 3 Desulfurization has certain requirements on the concentration of ammonia. If the concentration of ammonia is too low, it not only affects the desulfurization efficiency, but also the water circulation system is huge, so that the operation The cost increases; 4 the concentration increases, which will inevitably lead to an increase in evaporation and affect the working environment; 5 ammonia easily reacts with the sulfur dioxide in the purified flue gas to form an aerosol, so that the flue gas cannot reach the standard discharge.
The ammonia recovery process is difficult and the investment cost is high. It needs to be equipped with an acid production system or a crystallization recovery system (neutralizer, crystallizer, dewatering machine, dryer, etc.), so the system is complicated, the equipment is numerous, and the management and maintenance requirements are high. In addition, environmentally friendly water bodies have higher requirements for ammonia nitrogen and are prone to secondary pollution of ammonia and nitrogen.
(4) Metal oxide method A commonly used metal oxide method is a magnesium oxide method. Magnesium oxide reacts with sulfur dioxide to obtain magnesium sulfite and magnesium sulfate. The calcination can re-decompose magnesium oxide to regenerate the absorbent, and at the same time, recover the pure sulfur dioxide gas, and the desulfurizing agent can be recycled. Since the activity of magnesium oxide is higher than that of lime water, the desulfurization efficiency is also higher than that of the lime method. The disadvantage of the metal oxide method is that the magnesium oxide recovery requires crystallization, separation, evaporation, calcination and other processes, and the process is complicated; however, if the disposal method is directly adopted, a large amount of soluble magnesium salt will enter the water body to cause secondary pollution, and the overall operation cost is high. In addition, the pipeline of the system is easy to scale, and when the water hardness is high, the pipeline is more blocked.
(5) Nacalcium double alkali method Sodium calcium double alkali method (sodium carbonate/calcium hydroxide) combines the advantages of lime method and sodium alkali method, and utilizes sodium salt to be easily soluble in water and has high reactivity, and is inside the absorption tower. The sodium base absorbs sulfur dioxide, and the absorbed desulfurization liquid enters the alkali regeneration tank and is regenerated by using cheap lime, so that the sodium ions are recycled and utilized. The process combines the characteristics of the lime method and the sodium-base method, and not only solves the disadvantage of easy scaling in the lime tower, but also has the advantages of high absorption efficiency by the sodium-alkali method. The by-product of desulfurization is calcium sulfite or calcium sulfate (after oxidation). Calcium sulphite formulated synthetic resin can produce new composite material calcium plastic, or oxidize it to form gypsum, or directly mix with fly ash, can increase the plasticity of fly ash, enhance the strength of coal ash as paving underlayer cushion material . Compared with magnesium oxide, calcium salts are not polluting, so there is no secondary pollution of waste residue.
This transformation uses the sodium-calcium double alkali method as the desulfurization process for the renovation project.
2 Sodium-calcium double-alkali desulfurization principle 2.1 Advantages The sodium-calcium double-base method uses soda ash start-up, sodium-base absorption of SO2 and lime regeneration. Compared with the limestone method and other wet desulfurization processes, the nanocalcium double alkali method has the following advantages: 1 sodium alkali absorbent has high reaction activity, fast absorption speed, small liquid-gas ratio, low operating cost; 2 sodium-based clean absorption in the tower The absorption capacity of the absorbent and the absorption product is large, and the regeneration and precipitation separation outside the tower can greatly reduce the scale inside the tower and the pipeline; 3 the sodium and alkali recycling, the loss is small, the running cost is low; 4 the absorption process has no waste water discharge, the absorption liquid The salt does not accumulate and the concentration is stable; 5 the waste residue is non-toxic, the solubility is very small, no secondary pollution; 6 lime as a regenerant, safe and reliable, low cost; 7 nozzle, water pump, pipeline is not blocked; 8 liquid phase specific gravity during operation No increase, easy to separate and separate from water, can greatly reduce the investment in the pool; 9 easy to operate, the system can run in a long cycle.
2.2 Desulfurization process Na2Co3+SO2→Na2SO3+CO2↑ (1)
2NaoH+SO2→Na2SO3+H2O↑ (2)
Na2SO3+SO2+H2O→2NaHSO3 (3)
The above three formulas vary depending on the pH of the absorption liquid: (1) is the absorption initiation reaction; (2) is the main reaction (pH=9), and when the basicity is reduced to neutral or even acidic (5<PH<9), then according to (3) react.
Regeneration process:
2NaHSO3+Ca(OH)2→Na2SO3+CaSO3↓+2H20 (4)
Na2SO3+Ca(OH)2→NaOH+CaSO3↓ (5)
In the lime slurry (the lime reaches the supersaturation condition), the neutral NaHSO3 reacts with the lime to release [Na+], and the resulting [SO32-] continues to react with the lime. The CaSO3 formed in the reaction is in the form of a hemihydrate. Precipitated, so that [Na+] can be regenerated, and the absorption liquid restores the absorption capacity of SO2 and is recycled.
It can be seen from the above reaction that the sodium base is only used for the start-up reaction, and the consumption in actual operation is not large, and the main desulfurizer is lime.
Second, dust removal process:
1. Gravity dust removal method:
Different from the density of dust and gas, the dust naturally settles from the airflow by its own gravity to achieve the purpose of separating or trapping particles in the dusty gas flow. The disadvantage is that the dust removal efficiency is extremely low, and it is generally used in small boilers.
2 , inertial force dust removal method:
The inertial flow of dust and gas in motion is different, so that the dust is separated from the airflow. The general method for achieving inertial separation in practical applications is to cause the dust-containing airflow to impinge on the baffle, causing a sharp change in the direction of the airflow. The dust particles in the airflow have a large inertia and cannot be sharply turned with the airflow, and are separated from the airflow.
Inertial dust collectors are suitable for the removal of non-tacky, non-fibrous dust. The structure of the device is simple and the resistance is small; but the separation efficiency is low, and only coarse dust particles of 10-20 μm or more can be collected, and can only be used for the first stage dust removal in the multi-stage dust removal.
3 , centrifugal force dust removal method:
By using the flow velocity of the dust-containing gas, the airflow is continuously rotated in a certain direction in the dust removing device, and the particles obtain centrifugal force in the rotation of the airflow, thereby causing the particles to separate from the airflow. Commonly used dust removal devices include cyclone dust collectors and cyclone dust collectors. The most commonly used ones are cyclone dust collectors. The cyclone dust collectors have high dust removal efficiency and have good dust removal efficiency for particles larger than 5μm. It is suitable for the removal of non-viscous and non-fibrous dust, and can be used for dust removal and purification of high-temperature flue gas. Therefore, it is widely used in boiler flue gas dedusting, multi-stage dust removal and dust removal.
4 , wet dust removal method:
The liquid (usually water) is used to wash the dust-containing gas, and the formed liquid film, droplets or bubbles are used to trap the dust particles in the gas. The dust particles are discharged with the liquid, and the gas is purified. The liquid film, droplets or bubbles are mainly passed through inertia. Collision, the diffusion of fine dust particles, the agglomeration of the liquid film and droplets to humidify the dust particles and the adhesion to the dust particles, to achieve the purpose of capturing dust particles in the exhaust gas.
The wet dust collector has high dust removal efficiency, especially the high energy wet scrubber, which can maintain high dust removal efficiency when removing dust particles below 0.1μm. The wet scrubber has high efficiency and good safety for purifying high temperature, high humidity, flammable and explosive gases. The wet dust remover removes the dust particles in the exhaust gas, and at the same time removes the harmful and toxic gaseous pollutants in the exhaust gas through the absorption of the liquid, and has a better desulfurization effect. It is suitable for non-stick and non-fibrous.
5 , filter dust removal method:
The filter type dust removal is to make the dust-containing gas pass through the porous filter material, and the dust particles in the gas are intercepted to purify the gas. The filter material filters the dust-containing gas, and is divided into internal filtration and external filtration according to the dust filtration method. The filter material of the filter dust collector is to screen the particles through the pores of the filter material, and the particles collide with the inertial collision in the air movement, the diffusion of fine particles, and the combined effects of electrostatic attraction and gravity sedimentation to achieve dust removal. the goal of.
At present, the filter dust removal device is a bag type dust collector. The structure is to hang several circular or elliptical filter bags in the dust collection chamber of the dust collector. When the dusty airflow passes through the bag wall of the filter bags, the dust particles are The wall of the bag is trapped and collected on the inner or outer wall of the bag to be trapped.
Bag type dust collectors can be divided into mechanical vibrating bag type dust collectors, airflow back blowing bag type dust collectors, gas ring back blowing bag type dust collectors, and pulse jet bag type dust collectors according to different cleaning methods. Pulse jet bag filter. The pulse jet bag filter has the advantages of large gas volume, high efficiency, less damage to the filter bag, and is widely used in large and medium dust removal projects.
The bag filter is a high-efficiency dust collector, which has a strong trapping effect on fine dust. It is widely used in the dust removal of various industrial waste gases, but it is not suitable for the treatment of oily, watery and cohesive dust, and it is also uncomfortable. For the treatment of high temperature dusty gas, there is no desulfurization effect.
6 , electric dust removal method:
Electrostatic precipitator is the separation of solid particles or liquid particles from a gas stream by the action of electrostatic force (Coulomb force) generated by a high voltage electric field. The electric field should be a high-voltage direct current non-uniform electric field, the discharge electrode constituting the electric field is a linear electrode having a large surface curvature, and the dust collector is a plate-shaped electrode or a tubular electrode having a large area.
When a high DC voltage is applied between the discharge electrode and the dust collecting pole, the uneven electric field formed between the two poles makes the electric field intensity near the electrode large. When the voltage is applied to a certain value, the discharge electrode generates corona discharge and generates A large number of electrons and anions migrate to the dust collecting pole under the action of an electric field force. Neutral gas molecules easily capture these electrons or anions to form negative ions during migration. When these negatively charged particles collide with the dust particles in the gas stream and attach to them, the dust particles are negatively charged. The charged dust is driven to the dust collecting pole by the Coulomb force in the electric field, and the dust particles are deposited on the surface of the dust collecting pole and deposited on the dust collecting pole. When the dust is deposited to a certain thickness, it is eliminated by mechanical vibration.
The equipment commonly used in electric dust removal is an electric precipitator. The electrostatic precipitator is a high-efficiency dust collector with a dust removal efficiency of over 99%. It has excellent fine dust collection performance. The minimum particle size can be up to 0.05μm, and any dust removal efficiency from inefficient to efficient can be obtained as required. . The electrostatic precipitator has low resistance and low energy consumption allows operation in the range of 250-350 °C.
The electric dust removal equipment is huge and covers a large area. It requires operators to have a high technical level, high equipment investment, and no desulfurization effect.
Third, the selection of dust removal and desulfurization equipment According to the above various desulfurization and dust removal methods analysis and on-site investigation and consultation of the Aluminum Electrolysis Experimental Factory of Chinalco Zhengzhou Research Institute, our factory chose to use a high-efficiency desulfurization and dust removal integration technology SLTC-1.3 Desulfurization and dust removal treatment of 4t/h coal-fired chain boiler flue gas.
Bag dust collector dust bag
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