CN105854479A - Ammonia-process flue gas desulfurization device and method achieving efficient aerosol removal - Google Patents

Abstract

The invention provides an ammonia-based flue gas desulfurization device for removing aerosols with high efficiency. The ammonia-based flue gas desulfurization device includes a pretreatment device, a desulfurization tower device, an electric demisting device, and a flue gas discharge device in sequence from bottom to top. A pre-mist removal device is provided between the outlet of the desulfurization tower device and the electric demisting device. The pre-mist removal device is composed of a packing layer and a water washing device. The flushing spray nozzle of the water washing device is located between the packing layer and the desulfurization tower device. Between the beams of the exit. The present invention also installs a set of water-washing trays between the outlet of the desulfurization tower device and the pre-demister device. The present invention also provides an ammonia-based flue gas desulfurization method, the particle emission concentration of the original desulfurization device after demisting after transformation is reduced from 45.7mg/ ^Nm3 to 9.8mg/ ^Nm3 after transformation, meeting the requirement of ultra-low emission.

Description

An ammonia-based flue gas desulfurization device and method for removing aerosols with high efficiency

technical field

The invention belongs to the field of chemical industry, and in particular relates to an ammonia flue gas desulfurization device and method for removing aerosol with high efficiency.

Background technique

Ammonia desulfurization technology, as a green desulfurization technology that meets the requirements of circular economy, has attracted more and more attention from the industry. The by-product of ammonia flue gas desulfurization is ammonium sulfate, which is a fertilizer containing nitrogen and sulfur, and has a broad market demand. More and more self-provided thermal power plants in the chemical industry use ammonia desulfurization technology to treat boiler flue gas, especially the factories that produce synthetic ammonia. In the production process, waste ammonia water is generated, and waste ammonia water is used as a desulfurizer to produce ammonium sulfate fertilizer by-product. Treat waste with waste and turn waste into treasure.

At present, most of the ammonia-based desulfurization post-stages that are routinely put into operation only have folding plate demisters. Although SO ₂ depends on the forced addition of ammonia to meet the standard, it is difficult for the detection concentration of fog droplets and particulate matter at the chimney detection port to reach the true sense. Most of the emission standards are still in the state of billowing smoke. Common questions are:

(1) Chimney rain, PM2.5 aerosol plume tailing is obvious, the duration is long, and the environment is polluted;

(2) Ammonium sulfate falls with the entrainment of acid mist, corrodes production and living facilities, and affects the life of the factory area and nearby residents;

(3) The escape of ammonia is serious, and the loss of ammonium salt is large, which affects the economical operation of the desulfurization system.

With the continuous improvement of environmental protection requirements, the existing desulfurization devices need to consider the new requirements and margin guarantees brought about by the subsequent improvement of environmental protection standards, and gradually increase to require that the air pollutant emissions of new units are in principle close to or reach the emissions of gas turbine units. Limits (that is, under the condition of a reference oxygen content of 6%, the emission concentrations of smoke, sulfur dioxide, and nitrogen oxides are not higher than 10, 35, and 50 mg/Nm ³ respectively).

Due to the volatility of ammonia as a desulfurization absorbent, ammonia-based desulfurization tail gas will form ammonia aerosols, which are not easily captured. The particle size distribution of these aerosols ranges from about 0.01 to 1 μm. The wet electrostatic precipitator (fog) has its adaptability to the particle size range, and has a high removal efficiency for particles larger than 1 micron. There are different fractional removal efficiencies in collection theory.

CN 201969475 U discloses an absorption tower for ammonia flue gas desulfurization, including an absorption main tower, and the absorption main tower includes an oxidation crystallization section and a desulfurization absorption section, and is characterized in that a dedusting and quenching tower is set, according to the flow direction of flue gas , the dedusting and quenching tower is set before the absorption main tower, the reverse spray nozzle is set in the dedusting and quenching tower, the oxidation crystallization section is set at the lower part of the main tower of the absorption tower, the agitator is set in the oxidation crystallization section and connected to the compressed air source, and the desulfurization absorption section is set On the upper part of the main tower of the absorption tower, a gas distributor, at least one packing layer and a spraying device are arranged in the desulfurization absorption section. The device is disposed above the packing layer. Although this technology discloses the use of packing layers, the packing layers here are only used as ordinary filter devices, and there is no technical improvement for the electrostatic demisting device, and the setting position does not bring beneficial effects for dust removal.

CN 201454393 U discloses a novel ammonia-based flue gas desulfurization device. The purified flue gas is discharged from the top of the desulfurization tower, including three independent absorption liquid circulation systems. The lower and middle circulation pipelines are provided with raw material ammonia inlets, so that the desulfurization tower There is always a deamination section for recovering medium ammonia. The flow section of the flue gas inlet is rectangular, the ratio of the length of the long side of the rectangle to the diameter of the tower body is 0.55-0.95, the area of the flue gas inlet is 0.20-0.40 of the area of the tower body; the flow section of the flue gas outlet is rectangular or circular, and the flue gas outlet The area is 0.15-0.40 of the tower body area. This technology also discloses that spray pipes, packing layers and air bubbling pipes are arranged in the desulfurization tower. Although the technology can stabilize the airflow to a certain extent, the effect of flue gas treatment is still not ideal.

CN103920371A discloses an absorption tower, including an absorption device, which is characterized in that: a cooling and humidifying device is connected to the top of the absorption device, and an electric demisting device is connected to the top of the cooling and humidifying device; the absorption device and the cooling and humidifying device A first coupling port is set between the cooling and humidifying device, and a second coupling port is set between the cooling and humidifying device and the electric demisting device; the first and second coupling ports are flanged or welded; the absorption device is composed of the upper It includes a liquid separation device, a desulfurization absorption section, and a liquid storage section in sequence. The liquid separation device is provided with a circulating absorption liquid inlet, and the liquid storage section is provided with a circulating absorption liquid outlet. The lower part of the desulfurization absorption section is provided with a flue gas The gas inlet; the absorption device also includes a defoaming layer and a packing layer; the cooling and humidifying device includes an upper gas-liquid separation plate and a lower gas-liquid separation plate, and a cooling liquid outlet is set near the upper gas-liquid separation plate, A cooling liquid inlet is set near the lower gas-liquid separation plate, and multiple pipes are set between the upper and lower gas-liquid separation plates. The upper part of the pipes is provided with a humidifying liquid inlet, and the humidifying liquid is connected externally; the electric demisting A flue gas outlet is provided on the top of the device. Although this technology includes an electric demisting device and a packing layer, the packing layer is arranged in the absorption tower, and the air flow of the flue gas is not adjusted.

Contents of the invention

In order to solve the above problems, the present invention adds a water washing device and a packing layer on the basis of the original desulfurization system to improve the desulfurization capacity, reduce the generation of aerosols, strengthen the collection and washing of fine aerosols, increase the particle size, and improve the wet type. Aerosol removal efficiency of electrostatic precipitator. Without changing the equipment of the electrostatic demister, the treatment capacity of the electrostatic demister is improved through the pretreatment measures for the flue gas. Ensure that the particulate matter index at the desulfurization outlet falls to the ultra-low emission standard.

The invention provides an ammonia-based flue gas desulfurization device for removing aerosols with high efficiency. The ammonia-based flue gas desulfurization device is provided with a pretreatment device, a desulfurization tower device, an electric demisting device, and a flue gas discharge device in sequence from bottom to top. It is characterized in that a pre-mist removal device is provided between the outlet of the desulfurization tower device and the electric demisting device, and the pre-mist removal device is composed of a packing layer and a water washing device, and the water washing device includes a flushing spray nozzle. The flushing spray nozzle is located between the packing layer and the beam at the outlet of the desulfurization tower device.

In this plan, a packing layer and a water washing device are added before the outlet of the desulfurization tower and the wet electrostatic precipitator of the electric demisting device. Get further washing before entering the electric demister, through the effect of atomized liquid droplets, further increase the collision frequency between aerosol particles to condense, improve the dissolution and absorption of aerosol particles in the aqueous solution, and the water washing device in the pre-demister device The water is fresh and clean water, which is different from the circulating water in the desulfurization tower. The circulating water contains more impurities, and the cleaning effect on the flue gas is not good. Therefore, after being washed and sprayed by the water washing device in the pre-demister device, the flue gas can Get further washes.

The scrubbing flue gas passes through the packing layer to intercept and filter large-particle droplets, and at the same time further increases the gas-liquid mass transfer on the packing surface to reduce the carrying of fine particles in the flue gas.

After spray washing and packing filtration, the flue gas enters the electric demister again to remove residual water mist and particulate matter, and improve the comprehensive removal efficiency of the electric demister for particulate matter.

Preferably, the water washing device includes 5 to 500 flushing spray nozzles, and the flushing spray nozzles are evenly distributed on the flue cross section.

Preferably, a set of water-washing tray towers is installed between the outlet of the desulfurization tower device and the pre-demister device, and the water-washing tray towers sequentially include water-washing trays, water-washing packing layers, and water-washing spray layers from bottom to top, and the water-washing trays A swirl air cap is uniformly arranged inside, and the swirl air cap includes a swirl sub-piece and a swirl plate, the swirl sub-piece is located at the lower end of the swirl plate, and a tray is arranged under the swirl air cap.

The present invention also provides an ammonia-based flue gas desulfurization method. The flue gas passes through the desulfurization tower to remove sulfur dioxide after the flue gas is dedusted by the pretreatment device; The washing flue gas after spraying and washing by the water washing device enters the packing layer for filtration; after spraying washing and packing filtration, the flue gas enters the wet electrostatic precipitator of the electric demisting device, and the purified tail gas is discharged by the flue gas discharge device.

The present invention also provides an ammonia flue gas desulfurization method, which is characterized in that the flue gas passes through the desulfurization tower to remove sulfur dioxide after being dedusted by the pretreatment device; The flue gas coming out of the water washing tray is sprayed and washed by the water washing device in the pre-demister device, and the washed flue gas after being sprayed and washed by the water washing device enters the packing layer for filtration; after spray washing and packing filtration, The flue gas enters the wet electrostatic precipitator of the electrostatic demisting device, and the exhaust gas is discharged by the flue gas discharge device after purification.

Preferably, a set of water-washing tray towers is installed between the outlet of the desulfurization tower device and the pre-demister device, and the water-washing tray towers sequentially include water-washing trays, water-washing packing layers, and water-washing spray layers from bottom to top, and the water-washing trays A swirl air cap is uniformly arranged inside, and the swirl air cap includes a swirl sub-piece and a swirl plate, the swirl sub-piece is located at the lower end of the swirl plate, and a tray is arranged under the swirl air cap.

The washing tray tower is divided into 3 parts: the washing spray layer, the spray water source uses fresh process water, which is provided by the ground washing tank, preferably, the washing spray layer is 1 to 5 layers; the washing tray, the water washing tray The water collection system adopts a uniform structure of multiple swirl air caps. The flue gas enters the air cap from the middle of a single air cap from bottom to top. After demisting by the swirl plate, the flue gas exits from the upper part of the air cap, and the bottom of the tray collects spray washing water. Return to the washing tank to balance the water volume in the washing tank system. The entire gas cap is evenly distributed in the tower body, the layout is reasonable, the airflow passes through evenly, and no bias flow occurs; the water-washed packing layer is set between the spray layer and the water-washed tray for gas-liquid mass transfer and rectification, and the flue gas passes through The airflow after the water-washing tray is uniform, and when passing through the pre-mist removal device, it can be washed stably and more efficiently for the second time and filter large particles.

Preferably, the filler of the filler layer is iso-saddle ring ceramics, and the packing height of the filler layer is 250-350 mm.

Preferably, the porosity of the filler layer is 0.8-0.9m ³ /m ³ .

Preferably, the electrostatic demisting device is a wet electrostatic precipitator, using a pulsed high-voltage power supply, with a stable pulse voltage amplitude and steep upswings, which can effectively increase the product of the peak voltage and the average voltage, increase the driving speed, and improve the dust removal efficiency; The electrode line of the wet electrostatic precipitator adopts 2205/titanium rigid electrode.

The working principle of the wet electrostatic precipitator: through the electrostatic control device and the DC high-voltage generator, the high-voltage direct current is sent to the wet electrostatic precipitator, and a strong electric field is formed between the corona wire (cathode) and the collecting plate (anode). The discharge electrode generates corona discharge, which ionizes the air molecules and generates a large number of electrons and positive and negative ions instantly. When the particles in the flue gas pass through the space, they are forced to be charged, and the particles condense and move directionally under the action of the electric field force to achieve the purpose of capture. The wet electrostatic precipitator can efficiently remove 0.01-100μm aerosol fine particles, and realize the efficient removal of liquid or solid particles, aerosols, SO ₃ , etc. in the flue gas.

Preferably, the filling of the packing layer is iso-saddle ring ceramics, and the packing height of the packing layer is 300 mm.

Preferably, the secondary voltage of the wet electrostatic precipitator is greater than 70kV, and the secondary current is greater than 500mA. The removal effect of the wet electrostatic precipitator on particulate matter is related to the power supply parameters. The higher the secondary voltage and the greater the secondary current, the more significant the removal of particulate matter. The concentration of particulate matter at the outlet is also lower.

Beneficial effects of the present invention;

After adding a water-washing packing washing and demister device before the electric demister at the outlet of the absorption tower, and installing a set of water-washing trays between the outlet of the desulfurization tower device and the pre-demister device, the ammonia and sulfuric acid entrained in the flue gas will be eliminated. Ammonium is used for washing to reduce the entrainment of flue gas. The emission concentration of particulate matter in the flue gas has been significantly reduced, and the aerosol removal efficiency has been significantly improved. The emission concentration of particulate matter from the original desulfurization device after demisting was reduced from 45.7mg/Nm ³ to 9.8mg/Nm ³ after the transformation, meeting the ultra-low emission requirements Requirements, effectively solve the technical problem of flue gas particulate matter up to the standard or even ultra-low emission, greatly reduce the investment cost and save land.

Description of drawings

Figure 1 is a diagram of an ammonia-based flue gas desulfurization device with a pre-demisting device added, where 1 represents a desulfurization tower, 2 represents a pre-demisting device, and 3 represents an electric demisting device;

Fig. 2 is the enlarged view of pre-mist removal device, wherein 21 represents packing layer, 22 represents washing device, 221 represents flushing spray nozzle, and 11 represents the crossbeam detached from tower outlet;

Fig. 3 is the layout diagram of the water washing device, wherein 22 represents the water washing device, and 213 represents the supporting grid plate;

Fig. 4 is the diagram of the ammonia method flue gas desulfurization device that has increased the water-washing tray tower, wherein 4 represents the water-washing tray tower, 41 represents the water-washing tray, 42 represents the water-washing packing layer, and 43 represents the water-washing spray layer;

Fig. 5 is the layout drawing of water washing tray, wherein 414 is a swirl gas cap;

Fig. 6 is an A-A sectional view of the water washing tray in Fig. 5, wherein 411 is a tray, 412 is a swirl component, and 413 is a swirl plate.

detailed description

The specific embodiment of the present invention is described further below:

Example

The ammonia-based flue gas desulfurization device includes a pretreatment device, a desulfurization tower device, an electric demisting device, and a flue gas discharge device from bottom to top.

After a transformation: a pre-mist removal device 2 is installed between the desulfurization tower device 1 and the electric demister device 3. The pre-mist removal device 2 is composed of a packing layer 21 and a water washing device 22. The washing spray nozzle 221 of the water washing device is located in the packing layer Between the layer and the beam 11 at the outlet of the desulfurization tower device.

The design parameters of the packing layer device are shown in Table 1:

Table 1 Design parameters of packing layer device

The flue gas is dedusted by the pretreatment device and then passes through the desulfurization tower to remove sulfur dioxide; the flue gas from the outlet of the desulfurization tower is sprayed and washed by the water washing device in the pre-demister device, and the washed flue gas after being sprayed and washed by the water washing device enters the packing Layer filtration; after spray washing and filler filtration, the flue gas enters the wet electrostatic precipitator of the electrostatic demisting device to capture residual fog particles and aerosol smoke, and the purified tail gas is discharged from the flue gas discharge device.

After the secondary transformation: a set of washing tray tower 4 is installed between the outlet of the desulfurization tower device and the pre-demister device. The washing tray tower includes washing tray 41, washing packing layer 42, and washing spray layer 43 from bottom to top. , the swirl air cap 414 is evenly distributed in the water washing tray, and the swirl air cap 414 includes a swirl sub-piece 412 and a swirl plate 413, and the swirl sub-piece is located at the lower end of the swirl plate, below the swirl air cap 414 A tray 411 is also provided.

The technical parameters of the washing tray are as shown in Table 2:

Table 2 Process parameters of water washing tray

After the flue gas is dedusted by the pretreatment device, it passes through the circulating water of the desulfurization tower to remove sulfur dioxide; then the flue gas passes through the washing tray tower for washing, and then passes through the washing tray. , The flue gas enters the gas cap from the middle of the single gas cap from bottom to top, and the flue gas exits from the upper part of the gas cap after demisting by the swirl plate, and the spray washing water is collected at the bottom of the tray and returned to the washing tank to balance the water volume of the washing tank system. The entire gas cap is evenly distributed in the tower body, the layout is reasonable, the air flow passes through evenly, and there will be no bias flow; the water-washed packing layer is set between the spray layer and the water-washed tray for gas-liquid mass transfer and rectification, and the flue gas passes through After washing the tray tower, the aerosol in the flue gas is removed, and the airflow is uniform. When passing through the pre-demister device, it can be washed stably and more efficiently for the second time and filter large particles; the flue gas coming out of the washing tray tower is again The water washing device in the pre-demister device performs spray washing, and the washed flue gas after spraying and washing by the water washing device enters the packing layer for filtration; after spray washing and packing filtration, the flue gas enters the electric demisting device wet electrostatic precipitator The device collects residual fog particles and aerosol smoke, and the exhaust gas is discharged from the smoke exhaust device after purification.

Comparison of the effects before and after the two changes, the specific data is shown in Table 3:

Table 3 Comparison of effects before and after modification of ammonia flue gas desulfurization unit

serial number project name unit Transformation of the former After a renovation After the second transformation 1 Device size t/h 220 220 220 2 Standard flue gas volume Nm ³ /h 270000 270000 270000 3 coal sulfur content % 1.0 1.0 1.0 4 Inlet flue gas temperature ℃ 125 125 125 5 Inlet flue gas _SO2 concentration mg/ ^Nm3 2000 2000 2000 6 outlet flue gas temperature ℃ 50 50 50 7 Outlet flue gas SO ₂ concentration mg/ ^Nm3 ≤200 ≤50 ≤35 8 Ammonia concentration at outlet mg/ ^Nm3 ≤8 ≤8 ≤8 9 Export solid particle concentration mg/ ^Nm3 80 ≤15 ≤10 10 Liquid to gas ratio L/ ^Nm3 2.8 5.2 5.6 11 Desulfurization efficiency % ≥95 96-99 96-99 12 Ammonia utilization % ≥96.5 ≥96.5 ≥96.5 13 Oxidation efficiency % ≥98 ≥98 ≥98 14 Mother liquor concentration % 35-38 35-38 35-38 15 Desulfurization system resistance Pa 880 ≤1400 ≤1400

From the above results, it can be seen that the emission concentration of solid particles in flue gas after furnace desulfurization is ≤10mg/Nm ³ , and the emission concentration of SO ₂ is ≤35mg/Nm ³ . The removal efficiency has been significantly improved, and the particulate matter emission concentration after the demisting of the original desulfurization device is reduced from 45.7mg/Nm ³ to 9.8mg/Nm ³ after the transformation, which meets the requirements of ultra-low emission and effectively solves the problem of flue gas particulate matter reaching the standard or even ultra-low emission technical difficulties, greatly reducing investment costs and saving land.

According to the disclosure and teaching of the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiment. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims (5)

1. high efficiency removes an aerocolloidal ammonia type flue gas desulfurizing apparatus, and described ammonia type flue gas desulfurizing apparatus is the most successively Pretreatment unit, desulfurizer device, electric demister, smoke discharging device are set, it is characterised in that described desulfurizer device goes out Being provided with pre-demister between mouth and electric demister, described pre-demister is made up of packing layer and water washing device, described water Cleaning device includes rinse spray nozzle, and described rinse spray nozzle is between the crossbeam that packing layer and desulfurizer device export.

Device the most according to claim 1, it is characterised in that described water washing device includes 5～500 rinse spray sprays Mouth, described rinse spray nozzle is evenly distributed on flue cross section.

Device the most according to claim 1 and 2, it is characterised in that between desulfurizer device outlet and pre-demister Installing a set of washing tower tray tower, washing tower tray tower includes washing tower tray, washing packing layer, washing spraying layer the most successively, The uniform eddy flow gas cap that arranges in described washing tower tray, described eddy flow gas cap includes eddy flow component and spiral board, described eddy flow component Being positioned at spiral board lower end, eddy flow gas cap is provided with pallet further below.

4. the ammonia type flue gas desulfurizing method of a device according to claim 1 or claim 2, it is characterised in that flue gas is through pre-place Sulfur dioxide is removed through desulfurizing tower after reason device dedusting；The flue gas exporting out from desulfurizing tower is by the washing pre-demister Device carries out spray washing, and the washing flue gas after water washing device spray washing enters back into packing layer and filters；Through spray washing After filtering with filler, flue gas enters back into electric demister wet electrical dust precipitator, and after purification, tail gas is discharged by smoke discharging device.

5. the ammonia type flue gas desulfurizing method of a device according to claim 3, it is characterised in that flue gas fills through pretreatment Sulfur dioxide is removed through desulfurizing tower after putting dedusting；The flue gas exporting out from desulfurizing tower is de-through washing tower tray tower washing again Dirt；From washing tower tray tower out after flue gas carried out spray washing by the water washing device pre-demister again, through water washing device Washing flue gas after spray washing enters back into packing layer and filters；After spray washing and filler filter, flue gas enters back into electricity and removes Mist device wet electrical dust precipitator, after purification, tail gas is discharged by smoke discharging device.