CN108930971A - A kind of tail gas white-smoke-removing device and method of wet desulphurization, denitration - Google Patents

Abstract

The invention discloses a wet desulfurization and denitrification tail gas white smoke removal device and method. The device comprises boilers or kilns, wet desulfurization devices or wet denitrification devices, mist eliminators, heat exchangers, post- stage demister and chimney, the method comprises the following steps: 1) tail gas after wet desulfurization or denitrification and low-temperature gas carry out heat exchange through a heat exchanger to obtain tail gas after heat exchange and gas after heat exchange respectively; (2) step ( 1) The tail gas obtained after heat exchange is passed through the post-stage demister to remove the condensed mist droplets, and then mixed with the gas obtained in step (1) to become flue gas with low relative humidity and discharged from the chimney. The invention improves the energy utilization rate of the system, effectively prevents problems such as white smoke from the chimney of tail gas after wet desulfurization or denitrification, chimney rain, misty rain, etc., and has good economic value and environmental protection value.

Description

A device and method for removing white smoke from tail gas by wet desulfurization and denitrification

Technical field:

The invention relates to the technical field of industrial waste gas purification, in particular to a wet desulfurization and denitrification tail gas white smoke removal device and method.

Background technique:

At present, people's requirements for the environment are increasing day by day. In order to meet the requirements of environmental protection, it is necessary to desulfurize and denitrify industrial waste gas. The commonly used methods are wet desulfurization and denitrification. The flue gas temperature after wet desulfurization and denitrification is generally 45-65°C. At the same time, after the absorption tower or reactor is humidified, the treated gas also contains water mist in addition to the extremely high humidity. After passing through the chimney, the temperature drops further and contains more water mist. The ambient temperature is lower than that of the exhaust smoke, and the sharp drop in temperature increases the water mist contained in the exhaust smoke, forming white smoke. The general way to remove white smoke is to use a flue gas heater (GGH) to increase the temperature of the smoke and reduce or remove the white smoke. However, GGH generally works within the acid dew point, which is likely to cause corrosion and dust accumulation and blockage, resulting in equipment failure and system failure. Some also use the heat of high-temperature flue gas to heat the air, but the corrosion and dust accumulation of the heat exchanger still exist. Therefore, many enterprises dismantle the original GGH and use it. However, the flue gas after desulfurization treatment has high humidity and low temperature, which may easily cause the fan to carry water and vibrate. At the same time, the condensate in the flue gas is corrosive, which will cause serious corrosion to the flue and chimney behind the desulfurization and denitrification absorption towers, shorten the service life of the equipment, and affect the stability and safety of the system. The liquid droplets entrained by the flue gas will cause white smoke and chimney rain to appear in the chimney, causing smoke and rain to fall, causing secondary public nuisance.

Invention content:

The purpose of the present invention is to provide a wet desulfurization and denitrification tail gas white smoke removal device and method, which has a simple structure and extremely low energy consumption, and most of the required heat is obtained from wet flue gas, which improves the energy utilization rate of the system , achieved the purpose of reducing the humidity of tail gas after wet desulfurization and denitrification, effectively prevented the problems of white smoke from the tail gas chimney of wet desulfurization and denitrification, chimney rain, and smoky rain, and solved the air leakage existing in the use of GGH in the prior art , Clogging, scaling and corrosion problems, but also solve the problem of fan running with water.

The present invention is achieved through the following technical solutions:

A wet desulfurization, denitrification tail gas white smoke removal method, the method comprises the following steps:

(1) After wet desulfurization or denitrification, the tail gas and low-temperature gas are exchanged through a heat exchanger to obtain heat-exchanged tail gas and heat-exchanged gas, respectively;

(2) The heat-exchanged tail gas obtained in step (1) is passed through the post-stage demister to remove the condensed mist droplets, and then mixed with the gas obtained in step (1) to become flue gas with low relative humidity and discharged from the chimney.

In particular, the wet desulfurization and denitrification tail gas white smoke removal method includes the following steps:

(1) After wet desulfurization or denitrification, the tail gas and low-temperature gas are exchanged through a heat exchanger to obtain heat-exchanged tail gas and heat-exchanged gas, respectively;

(2) The heat-exchanged gas obtained in step (1) generates a power pressure head and heats up through a blower;

(3) The heat-exchanged tail gas obtained in step (1) passes through the post-stage demister to remove the condensed mist droplets, and then mixes with the gas obtained in step (2) to become flue gas with low relative humidity and discharge it from the chimney.

The low temperature gas is preferably air.

The heat exchanger is provided with a purging device.

In addition to the ordinary folding plate type, gull type, cyclone, and wire mesh, the post-stage demister also has an electrostatic dust removal structure.

The tail gas temperature of wet desulfurization and denitrification is about 45-65 ℃, and the relative humidity is close to saturation. The gas with low absolute humidity is heated until the temperature is close to the exhaust gas after heat exchange, and then the power head is raised by the blower, and the temperature is also raised at the same time. The temperature is closer to the exhaust gas after heat exchange, and then mixed with the exhaust gas after heat exchange to remove droplets , so that the relative humidity of the tail gas is reduced. At this time, the discharge from the chimney can reduce or solve the phenomenon of white smoke from the chimney, and at the same time reduce the corrosion of the chimney and reduce the cost of chimney anticorrosion.

The invention also protects a device for removing white smoke from tail gas of wet desulfurization and denitrification, the device includes sequentially connected boilers or kilns, wet desulfurization devices or wet denitrification devices, demisters, heat exchangers, post-stage The demister and the chimney also include the blower; the low-temperature gas is exchanged through the heat exchanger and then the blower is mixed with the tail gas after the heat exchange that removes the mist droplets through the post-stage demister and discharged from the chimney. At low temperatures, the air has relatively low absolute humidity.

In particular, the wet desulfurization and denitrification tail gas removal device is also equipped with an environmentally friendly booster fan.

The environment-friendly booster fan is installed in front of the wet desulfurization device or wet denitrification device or in the pipeline after gas mixing.

More specifically, an air preheater and a dust collector are installed in front of the wet desulfurization device or wet denitrification device, and an ejector is arranged in front of the chimney.

More preferably, the environmental booster fan is preferably installed after the ejector, and a post-stage dust collector is also installed between the mist eliminator and the heat exchanger.

The beneficial effects of the present invention are as follows:

(1) The present invention has simple structure and extremely low energy consumption. Firstly, the temperature of desulfurization and denitrification tail gas is lowered to reduce the absolute humidity in the tail gas. Mixing with the tail gas that removes the mist droplets after heat exchange reduces the relative humidity of the tail gas. At this time, discharging from the chimney can reduce or solve the phenomenon of white smoke from the chimney, and at the same time reduce the corrosion of the chimney and reduce the cost of chimney anticorrosion. The required energy is mainly provided by wet desulfurization and denitrification tail gas, which greatly reduces the demand for energy, and the operating cost is lower than other low-temperature flue gas treatment systems (MGGH) and flue gas heat exchangers (GGH) or the same operating cost can be reached better effect.

(2) Part of the flue gas heat before desulfurization and denitrification can be recovered for other aspects (such as air preheater, economizer, etc.). At the same time, there is no problem of cooling part of the flue gas heat exchange before desulfurization and denitrification to the acid dew point temperature, avoiding the problem of ash accumulation and blockage that is difficult to solve for this part of the heat exchanger. After desulfurization and denitrification, the flue gas heat exchanger (heater) has a very low dust content after passing through the dust collector, wet desulfurization device, and mist eliminator.

(3) The present invention can further reduce the tail gas temperature of desulfurization and denitrification, and can condense a part of water and dissolved sulfur dioxide, sulfur trioxide and nitrogen oxides into liquid to reduce the content of sulfur dioxide, sulfur trioxide and nitrogen oxides in the tail gas , improve the efficiency of desulfurization and denitrification, and meet higher environmental protection requirements. At the same time, reduce the burden of wet desulfurization device or wet denitrification device, reduce the use of desulfurization agent or denitrification agent and the water consumption of wet desulfurization or wet denitrification process, and reduce the equipment cost and operating cost of wet desulfurization device or wet denitrification device. Compared with other water spray cooling flue gas, the water-saving effect is more prominent, and at the same time, the heat of the flue gas is used to heat the gas with low humidity to reduce the humidity of the exhaust gas.

In a word, the present invention has simple structure, extremely low energy consumption, and most of the required heat is obtained from wet flue gas, which improves the energy utilization rate of the system and achieves the purpose of reducing the humidity of low-temperature tail gas after wet desulfurization and denitrification. It effectively prevents the problems of white smoke from the exhaust chimney after wet desulfurization and denitrification, chimney rain, and misty rain, and solves the problems of air leakage, ash blocking, scaling and corrosion in the existing technology of GGH, and also solves the problem of fan The problem of running with water is mainly used for the wet flue gas treatment of thermal power plants and industrial kilns after wet desulfurization and denitrification, which has good economic value and environmental protection value.

Description of drawings:

Fig. 1 is the structural representation of embodiment 1;

Fig. 2 is the structural representation of embodiment 2;

Among them, 1. Boiler or kiln; 2. Air preheater (coal economizer); 3. Dust collector; 4. Environmental booster fan; 5. Wet desulfurization device or wet denitrification device; 6. Demister ; 7. Heat exchanger (heater); 8. Post-stage demister; 9. Blower; 10. Ejector; 11. Chimney; 12. Post-stage dust collector.

Figure 3 is a psychrometric chart.

Detailed ways:

The following is a further description of the present invention, rather than a limitation of the present invention.

Example 1:

As shown in Figure 1, the device for removing white smoke from the tail gas of wet desulfurization, the device includes sequentially connected boiler or kiln 1, air preheater (coal economizer) 2, dust collector 3, environmental protection booster fan 4 , wet desulfurization device or wet denitrification device 5, demister 6, heat exchanger (heater) 7, post-stage demister 8, ejector 10 and chimney 11, and blower 9 in addition.

After the flue gas or exhaust gas discharged from the boiler or kiln 1 passes through the heat exchanger air preheater (economizer) 2 at the tail of the boiler or kiln to cool down, the dust content of the flue gas or exhaust gas is greatly reduced through the dust collector 3, which is environmentally friendly The booster fan 4 enters the wet desulfurization device or the wet denitrification device 5. After cooling and humidifying, the flue gas containing a large amount of water droplets passes through the demister 6 to remove the water droplets. At this time, the temperature of the flue gas or tail gas after the wet desulfurization or denitrification is At around 45-65°C, the relative humidity is close to saturation, and the flue gas or tail gas contains a large amount of water vapor, a large amount of latent heat of condensation and a small amount of fog droplets. The flue gas or tail gas after wet desulfurization or denitrification is exchanged with low-temperature gas with low absolute humidity, such as air at normal temperature, through the heat exchanger (heater) 7, and the heat exchanger is arranged in countercurrent. (Heater) 7 Recover the heat of the flue gas or tail gas after wet desulfurization or denitrification, which contains a large amount of latent heat of condensation, and the flue gas or tail gas after wet desulfurization or denitrification is cooled by a heat exchanger to obtain flue gas after heat exchange Or tail gas, low-temperature gas with low absolute humidity is heated by a heat exchanger, and the temperature rises to obtain heat-exchanged gas. After heat exchange, the temperature of flue gas or tail gas and heat-exchanged gas is close; The heat-exchanged gas obtained after heat exchange passes through the blower 9 to generate a power head and heat up, so that its temperature is basically close to that of the heat-exchanged flue gas or tail gas. After the heat exchange, the flue gas or exhaust gas passes through the post-stage demister 8 to remove the condensed mist droplets, and then mixes with the gas after the blower 9 heats up and passes through the ejector 10 to form a flue gas with low relative humidity, as shown in Figure 3 On the psychrometric diagram, the state changes from near state A to state B, and it is discharged into the atmosphere through the chimney 11, which can reduce or solve the phenomenon of white smoke from the chimney, and can also reduce chimney corrosion and reduce the cost of chimney anticorrosion.

Example 2:

As shown in Figure 2, the device for removing white smoke from tail gas of wet desulfurization, the device includes sequentially connected boiler or kiln 1, air preheater (economizer) 2, dust collector 3, wet desulfurization device or Wet denitrification device 5, mist eliminator 6, post-stage dust collector 12, heat exchanger (heater) 7, post-stage demister 8, ejector 10, environmental protection booster fan 4 and chimney 11, in addition to blower9. It is better to install the environmental booster fan behind the ejector.

After the wet desulfurization device or wet denitrification device 5 demister 6, add a post-stage dust collector 12 to further remove dust and liquid droplets in the flue gas or tail gas, and better solve the problem of dust accumulation in the heat exchanger. The mixed flue gas no longer contains mist droplets, will not cause the fan to run with water, and has low corrosion on the blades. The operating temperature of the fan is much lower than that before desulfurization and denitrification. At the same time, this part of the heat can be used to further increase the flue gas temperature. , so that the effect of solving white smoke is better. The state shown on the psychrometric diagram of FIG. 3 changes from near A to near point C, and is discharged into the atmosphere through the chimney 11 .

Claims (9)

1. a wet desulfurization, denitrification tail gas method for removing white smoke, is characterized in that, the method may further comprise the steps: (1) After wet desulfurization or denitrification, the tail gas and low-temperature gas are exchanged through a heat exchanger to obtain heat-exchanged tail gas and heat-exchanged gas, respectively; (2) The heat-exchanged tail gas obtained in step (1) is passed through the post-stage demister to remove the condensed mist droplets, and then mixed with the gas obtained in step (1) to become flue gas with low relative humidity and discharged from the chimney. 2. The method for removing white smoke from tail gas of wet desulfurization and denitrification according to claim 1, characterized in that the method comprises the following steps: (1) After wet desulfurization or denitrification, the tail gas and low-temperature gas are exchanged through a heat exchanger to obtain heat-exchanged tail gas and heat-exchanged gas, respectively; (2) The heat-exchanged gas obtained in step (1) generates a power pressure head and heats up through a blower; (3) The heat-exchanged tail gas obtained in step (1) passes through the post-stage demister to remove the condensed mist droplets, and then mixes with the gas obtained in step (2) to become flue gas with low relative humidity and discharge it from the chimney. 3. The method for removing white smoke from tail gas by wet desulfurization and denitrification according to claim 1 or 2, characterized in that the heat exchanger is provided with a purging device. 4. The method for removing white smoke from tail gas by wet desulfurization and denitrification according to claim 1 or 2, characterized in that the post-stage mist eliminator also has an electrostatic precipitator structure. 5. A device for removing white smoke from tail gas of wet desulfurization and denitrification, characterized in that the device comprises sequentially connected boilers or kilns, wet desulfurization devices or wet denitrification devices, mist eliminators, heat exchangers, The post-stage demister and chimney, in addition to the blower; the low-temperature gas is exchanged by the heat exchanger and then passed through the blower, and then mixed with the tail gas after heat exchange that removes the mist droplets by the post-stage demister and discharged from the chimney. 6. The device for removing white smoke from tail gas of wet desulfurization and denitrification according to claim 5, characterized in that an environmentally friendly booster fan is also provided. 7. The device for removing white smoke from tail gas of wet desulfurization and denitrification according to claim 6, characterized in that the environmentally friendly booster fan is installed in front of the wet desulfurization device or wet denitrification device or in the pipeline after gas mixing. 8. The device for removing white smoke from tail gas of wet desulfurization and denitrification according to claim 5 or 6, characterized in that an air preheater, a dust collector, and a chimney are arranged before the wet desulfurization device or the wet denitrification device. There is an ejector in front. 9. The device for removing white smoke from the tail gas of wet desulfurization and denitrification according to claim 8, characterized in that, the environmentally friendly booster fan is arranged behind the ejector, and there is also a device between the demister and the heat exchanger. Post-stage dust collector.