CN211255331U

CN211255331U - Two-stage energy-saving evaporation system with zero discharge of desulfurization wastewater

Info

Publication number: CN211255331U
Application number: CN201921910605.9U
Authority: CN
Inventors: 侯晶晶; 崔一尘; 赵凯; 吴一帆; 李明霞
Original assignee: Beijing Bootes Electric Power Sci Tech Co ltd
Current assignee: Beijing Bootes Electric Power Sci Tech Co ltd
Priority date: 2019-11-07
Filing date: 2019-11-07
Publication date: 2020-08-14
Anticipated expiration: 2029-11-07

Abstract

A two-stage energy-saving drying system with zero discharge of desulfurization waste water comprises a spray drying tower 1, a denitration system 2, a filter 3, a fluidized bed 4, a heat exchanger 5, a dust remover 6, a concentration tower 7, an atomizer 8, a flue gas uniform distributor 9, a demister 10, air 11, a dried material 12, humidified air 13 and desulfurization waste water 14. The filter sets up behind the deNOx systems and between the spray drying tower, the fluidized bed sets up between spray drying tower and heat exchanger, the heat exchanger setting is between spray drying tower and dust remover, the concentration tower setting is between heat exchanger and spray drying tower, flue gas equipartition ware and atomizer all set up the top at the spray drying tower, the defroster setting is at the top of concentration tower, the air gets into from the fluidized bed bottom, the evaporation to dryness material is discharged from the fluidized bed below. The system has the advantages of simple process flow, low dominant running cost, high thermal efficiency and good economic benefit, can effectively reduce the influence of ash content on a drying system, reduce the decomposition of heat-sensitive salts, reduce the evaporation load of a spray drying tower and realize waste heat recovery of waste gas.

Description

Two-stage energy-saving evaporation system with zero discharge of desulfurization wastewater

Technical Field

The utility model belongs to coal fired power plant desulfurization waste water treatment field, concretely relates to energy-conserving evaporation to distillation system of two-stage of desulfurization waste water zero release.

Background

In a limestone-gypsum wet boiler flue gas desulfurization system of a large-scale thermal power plant, in order to ensure the desulfurization efficiency and maintain the chloride ion balance of the system, partial desulfurization wastewater needs to be discharged. The traditional desulfurization wastewater treatment process mainly adopts a physical and chemical method, the treatment process is complex, high-salt wastewater is discharged, the number of configured equipment is large, and the operation and maintenance cost is high. With the continuous enhancement of the environmental protection of the country, the zero emission of the desulfurization wastewater needs to be gradually realized, which provides a serious challenge for the sustainable development of the coal boiler field.

At present, the technologies mainly studied for realizing zero discharge of desulfurization wastewater mainly comprise evaporative crystallization, flue direct injection and spray drying tower technologies, wherein the evaporative crystallization technology has higher investment and operation cost; the flue direct injection technology has the problems that incomplete evaporation exists, the flue is corroded, the comprehensive use of the fly ash is influenced, and the stable operation of subsequent equipment and a system is influenced; the spray drying tower technology has less influence on the operation of the system, the process is simple, the investment is low, the dominant operation cost is low, the technology is gradually developed into the mainstream technology in the zero emission field, but ash in high-temperature flue gas can be accumulated in equipment or a pipeline, the operation safety is influenced, if a high-temperature heat source is used for heating air firstly, and then the air is used for evaporating and drying the desulfurization wastewater, although the accumulation of ash is avoided, the heat efficiency is not high, the desulfurization wastewater is not concentrated and reduced in amount and is directly sprayed into the drying tower, the evaporation load of a spray dryer can be increased, the treatment capacity of the desulfurization wastewater is reduced, the temperature of crystallized salt is low, the waste heat can be ignored, but the temperature of tail gas is slightly higher. Chinese patent No. CN208327447U discloses a processing apparatus of high salt waste water, utilizes the high temperature flue gas heated air behind the deNOx systems, and the air after the heating is reused to evaporate the high salt waste water that contains, can effectively avoid the influence of ash content to the evaporation to dryness system in the flue gas, but the thermal efficiency reduces and the introduction of a large amount of air can exert an influence to dust removal and desulfurization system load.

Disclosure of Invention

The utility model aims at providing an energy-conserving evaporation to dryness system of two-stage of desulfurization waste water zero release, process flow is simple, and the dominant running cost is low, can effectively reduce the influence of ash content to the evaporation to dryness system, reduces the decomposition of heat sensitive salt, reduces the evaporation load of spray drying tower, improves the throughput of desulfurization waste water, realizes the waste heat recovery of waste gas, and the thermal efficiency is high, can realize better economic benefits.

In order to solve the above problem, the utility model adopts the following technical scheme: a two-stage energy-saving evaporation system with zero emission of desulfurization waste water is arranged between a denitration system and a dust remover and comprises a spray drying tower 1, a denitration system 2, a filter 3, a fluidized bed 4, a heat exchanger 5, a dust remover 6, a concentration tower 7, an atomizer 8, a flue gas uniform distributor 9, a demister 10, air 11, evaporation materials 12, humidified air 13 and desulfurization waste water 14, wherein the filter is arranged between the back of the denitration system and the spray drying tower, the fluidized bed is arranged between the spray drying tower and the heat exchanger, the heat exchanger is arranged between the spray drying tower and the dust remover, the concentration tower is arranged between the heat exchanger and the spray drying tower, the flue gas uniform distributor and the atomizer are both arranged at the top of the spray drying tower, the demister is arranged at the top of the concentration tower, the air enters from the bottom of the fluidized bed, the evaporation materials are discharged from the lower part of the fluidized bed, and the, humidified air is discharged from the top of the concentrating tower.

And (3) extracting part of the high-temperature flue gas after the denitration system enters a filter, filtering ash in the high-temperature flue gas, wherein the ash filtering efficiency is 80% -99%, and reducing the influence of the ash on a drying system. The spray drying tower is primary drying, the fluidized bed is secondary drying outside the tower, the heat efficiency of the spray drying tower is improved while the water content of crystallized salt is reduced, high-temperature flue gas enters from the top of the tower through a flue gas uniform distributor in the spray drying tower, desulfurization wastewater is atomized into fine fog drops through an atomizer arranged at the top of the tower, the high-temperature flue gas and the desulfurization wastewater flow downwards in a parallel flow mode, heat transfer and mass transfer as well as evaporative crystallization are carried out simultaneously, crystallized salt is discharged from the bottom of the tower and enters the fluidized bed, and tail gas is discharged from the side part of the bottom of the tower; in the fluidized bed, air enters from the bottom of the fluidized bed and is discharged from the top, crystallized salt is further dried, and the evaporated material is discharged from the bottom of the fluidized bed. Recovering waste heat of tail gas from air discharged from the top of the fluidized bed in a heat exchanger, wherein the heat exchanger is a dividing wall type heat exchanger, the tail gas after waste heat recovery enters a dust remover, and hot air enters a concentration tower; in the concentration tower, hot air and desulfurization wastewater are in countercurrent contact, and the temperature difference between the air and the desulfurization wastewater and the partial pressure difference of water vapor are utilized to cool and humidify the hot air and heat and concentrate the desulfurization wastewater.

In the two-stage energy-saving evaporating system with zero discharge of desulfurization wastewater, the atomizer is a rotary atomizer or a two-fluid atomizer, the atomized particle size is 20-300 μm, the specific surface area of the desulfurization wastewater is increased, preferably 60-200 μm, and the nozzle is made of hard alloy.

In the two-stage energy-saving evaporation-to-dryness system with zero discharge of desulfurization wastewater, the concentration tower is a plate tower or a bubble tower, the top of the tower is provided with a demister for removing small fog drops in hot air, the hot air enters from the lower part of the concentration tower and is discharged from the top through the demister, the desulfurization wastewater enters from the upper part and is discharged from the bottom, and the hot air and the desulfurization wastewater tower are in countercurrent contact.

Compared with the prior art, the utility model filters the ash in the high-temperature flue gas through the filter, and the ash is used as the heat source for drying the desulfurization wastewater, so that the ash accumulation and scaling of the tower wall of the spray drying tower can be effectively avoided; through two-stage drying of the spray drying tower and the fluidized bed, the heat efficiency of the spray drying tower is improved while the water content of crystallized salt is reduced, and the heat-sensitive salts are prevented from being decomposed to generate HCL (hydrochloric acid) by the parallel flow of high-temperature flue gas and desulfurization wastewater in the drying tower, so that CL (chlorinated polyethylene) is avoided^-Enrichment in a desulfurization system; the heat exchanger realizes the full utilization of the low-temperature flue gas waste heat; through the concentration tower, the temperature of hot air is reducedAnd the concentrated desulfurization wastewater enters a spray drying tower, so that the treatment capacity of the desulfurization wastewater is increased, the evaporation load of the spray drying tower is reduced, and the service life of a drying system is prolonged.

Drawings

Fig. 1 is the utility model discloses a two-stage energy-conserving evaporation to dryness system of desulfurization waste water zero release's schematic diagram, wherein 1 is the spray drying tower, 2 is deNOx systems, 3 is the filter, 4 is the fluidized bed, 5 is the heat exchanger, 6 is the dust remover, 7 is the concentration tower, 8 is the atomizer, 9 is the flue gas uniform distributor, 10 is the defroster, 11 is the air, 12 is the evaporation to dryness material, 13 is the humid air, 14 is desulfurization waste water.

Detailed Description

The present invention will be further explained with reference to the following embodiments, and features in the embodiments and embodiments of the present invention can be combined with each other without conflict. It should be noted that modifications and variations can be made to the present invention by those skilled in the art without departing from the principles of the present invention, but these modifications and variations also fall within the scope of the claims of the present invention.

As shown in fig. 1, the two-stage energy-saving drying system with zero emission of desulfurization wastewater comprises a spray drying tower 1, a denitration system 2, a filter 3, a fluidized bed 4, a heat exchanger 5, a dust remover 6, a concentration tower 7, an atomizer 8, a flue gas uniform distributor 9, a demister 10, air 11, a dried material 12, humidified air 13 and desulfurization wastewater 14, wherein a heat source of the spray drying tower is high-temperature flue gas extracted from a flue behind the denitration system, the temperature of the flue gas is 300-360 ℃, the flue gas enters the filter to filter ash in the flue gas, the filtering efficiency of the ash is 80-99%, and the influence of the ash on the drying system is reduced; high-temperature flue gas enters from the top of the spray drying tower through the flue gas uniform distributor, flows downwards together with atomized droplets of desulfurization wastewater, and simultaneously conducts heat transfer, mass transfer, evaporation and crystallization, so that decomposition of heat-sensitive salts can be effectively avoided, crystallized salt is discharged from the bottom of the tower and enters the fluidized bed, the water content of the crystallized salt is 6% -10%, tail gas is discharged from the side part of the bottom of the tower, and the exhaust temperature of the tail gas is 140-180 ℃; discharging crystallized salt from the bottom of a spray drying tower into a fluidized bed, allowing air to enter from the bottom of the fluidized bed, allowing the air to pass through a bed layer at a speed of 0.7-2 m/s, discharging the crystallized salt from the top of the fluidized bed and allowing the crystallized salt to enter a heat exchanger, further drying the crystallized salt, and discharging a dried material from the bottom of the fluidized bed, wherein the water content of the dried material is 2% -6%; recovering waste heat of tail gas from air discharged from the top of the fluidized bed in a heat exchanger, wherein the heat exchanger is a dividing wall type heat exchanger, the tail gas after waste heat recovery enters a dust remover, and hot air enters a concentration tower; before entering a spray drying tower, desulfurization wastewater is heated and concentrated through a concentration tower, hot air enters from the lower part of the concentration tower, humidified air is discharged from the top, desulfurization wastewater enters from the upper part and is discharged from the bottom to enter an atomizer in the spray drying tower, the desulfurization wastewater is in countercurrent contact in the concentration tower, the temperature of the hot air is reduced and humidified by utilizing the temperature difference between the hot air and the desulfurization wastewater and the partial pressure difference of water vapor, the desulfurization wastewater is heated and concentrated, the temperature of the desulfurization wastewater after being heated is 50-90 ℃, and the evaporation load of the spray drying tower is reduced.

Example 1: 50000m high-temperature flue gas with the temperature of 350 ℃ is extracted from a flue behind a denitration system³The flue gas enters a filter, the dust filtration efficiency is 95 percent, and then the flue gas enters a spray drying tower through a flue gas uniform distributor; the treatment capacity of the desulfurization wastewater at 20 ℃ is 3000kg/h, the desulfurization wastewater is in countercurrent contact with hot air for recovering tail gas waste heat in a concentration tower, the temperature is raised to 70 ℃, the solid content is raised from 3.9% to 9.8%, and the desulfurization wastewater after temperature rise concentration is atomized into 150 mu m fine fog drops by a rotary atomizer and enters a spray drying tower; in the drying tower, high-temperature flue gas and atomized droplets of desulfurization wastewater flow downwards in a parallel flow mode, heat and mass transfer and evaporative crystallization are carried out simultaneously, tail gas is discharged from the side part of the bottom of the tower, the temperature of the tail gas is 170 ℃, the water content of crystallized salt is 6%, the crystallized salt is discharged from the bottom of the tower and enters a fluidized bed for secondary drying, and the water content of a evaporated product is reduced to 2.5%.

Example 2: 50000m high-temperature flue gas with the temperature of 350 ℃ is extracted from a flue behind a denitration system³The flue gas enters a filter, the dust filtration efficiency is 95 percent, and then the flue gas enters a spray drying tower through a flue gas uniform distributor; the treatment capacity of the desulfurization waste water at 20 ℃ is 3000kg/h, the desulfurization waste water is in countercurrent contact with hot air for recovering the waste heat of tail gas in a concentration tower,the temperature is increased to 63 ℃, the solid content is increased to 7.1 percent from 3.9 percent, and the desulfurized wastewater after temperature rise and concentration is atomized into 90 mu m fine fog drops by a double-fluid atomizer and enters a spray drying tower; in the drying tower, high-temperature flue gas and the atomized fog drops of the desulfurization wastewater flow downwards in a parallel flow mode, heat and mass transfer and evaporative crystallization are carried out simultaneously, tail gas is discharged from the side part of the bottom of the tower, the temperature of the tail gas is 165 ℃, the water content of crystallized salt is 5%, the crystallized salt is discharged from the bottom of the tower and enters a fluidized bed for secondary drying, and the water content of a evaporated product is reduced to 2%.

Claims

1. A two-stage energy-saving evaporation system with zero emission of desulfurization waste water comprises a spray drying tower (1), a denitration system (2), a filter (3), a fluidized bed (4), a heat exchanger (5), a dust remover (6), a concentration tower (7), an atomizer (8), a flue gas uniform distributor (9), a demister (10), air (11), evaporation materials (12), humidified air (13) and desulfurization waste water (14), and is characterized in that the filter is arranged between the back of the denitration system and the spray drying tower, the fluidized bed is arranged between the spray drying tower and the heat exchanger, the heat exchanger is arranged between the spray drying tower and the dust remover, the concentration tower is arranged between the heat exchanger and the spray drying tower, the flue gas uniform distributor and the atomizer are both arranged at the top of the spray drying tower, the demister is arranged at the top of the concentration tower, air enters from the bottom of the fluidized bed, and the evaporation materials are discharged from the lower, the desulfurization waste water enters from the upper part of the concentration tower, and the humidified air is discharged from the top of the concentration tower.

2. The two-stage energy-saving evaporation system with zero emission of desulfurization wastewater as claimed in claim 1, wherein the spray drying tower is primary drying, the fluidized bed is secondary drying outside the tower, the moisture content of crystallized salt of the primary drying is 6% -10%, and the moisture content of evaporated material of the secondary drying is 2% -6%.

3. The two-stage energy-saving evaporation system with zero emission of desulfurization wastewater as claimed in claim 1, wherein the filter is arranged between the rear part of the denitration system and the spray drying tower, and is used for filtering ash in the high-temperature flue gas to obtain clean high-temperature flue gas, and the ash filtering efficiency is 80% -99%.

4. The two-stage energy-saving evaporation system with zero emission of desulfurization waste water of claim 1, wherein the heat exchanger is a dividing wall type heat exchanger, and the temperature reduction range of tail gas is 20-30 ℃.

5. The two-stage energy-saving evaporation system with zero emission of desulfurization waste water of claim 1, wherein the concentration tower is a plate tower or a bubble tower, a demister is arranged at the top of the tower to remove small fog drops in hot air, the hot air enters from the lower part of the concentration tower and is discharged from the top through the demister, the desulfurization waste water enters from the upper part and is discharged from the bottom, the hot air and the desulfurization waste water tower are in countercurrent contact, the hot air is cooled and humidified, the desulfurization waste water is heated and concentrated, and the temperature of the desulfurization waste water after being heated is 50-90 ℃.