A wet purification method and device for coal oxygen-enriched fly ash molten tail gas

Abstract

A wet purification method and device for coal oxygen-enriched fly ash melting tail gas, belonging to the field of purification technology. The high-temperature tail gas released by the coal oxygen-enriched fly ash melting furnace is cooled to below 120-150°C by a quench tower; enters the water scrubber in turn for pre-dust removal, acid removal, and cooling to below 80°C; passes through a wet electrostatic precipitator for deep dust removal; passes through an oxidation absorption tower for denitration, desulfurization, and mercury removal, and cools to 50-70°C; passes through an alkali scrubber for further deacidification, and finally the purified tail gas is discharged into a chimney through an induced draft fan; the wastewater discharged from the water scrubber and the oxidation absorption tower is purified separately to obtain metal chlorides, sulfates, and nitrates for recycling. The present invention can fully and effectively give play to the advantages of integrated coordinated treatment of deacidification, denitration, mercury removal, and dust removal, so as to achieve standard flue gas and even ultra-clean emissions; wastewater purification treatment obtains reusable salts to achieve resource utilization.

Description

Technical Field

[0001] The invention relates to a wet purification method and device for coal oxygen-enriched fly ash molten tail gas, belonging to the technical field of purification. Background Art

[0002] After the incineration of domestic waste, fly ash of 2%-5% of the original waste will be produced. The fly ash contains a large amount of volatile heavy metals such as mercury, lead, chromium, and highly toxic substances such as dioxins. The state stipulates that fly ash is hazardous waste and must be specially treated. At present, the commonly used treatment methods are: cement solidification method, chemical treatment method, and melt solidification method. Among them, the melt solidification method has the advantages of reduction, harmlessness, and resource utilization, and has become the most promising treatment method. The melt solidification method forms a stable glass phase at high temperature (greater than 1300°C), which greatly reduces the possibility of heavy metal dissolution. However, the melting of fly ash is accompanied by the problem of secondary pollution emissions of tail gas. The exhaust gas contains a large amount of sulfur dioxide, hydrogen chloride, nitrogen oxides, alkali salts and heavy metals. There are two ways of melt solidification: fuel melting and electric heat melting. The tail gas purification process of fly ash melting in resistance furnace generally adopts the process of "water spray cooling + dry / wet deacidification". For the tail gas of coal oxygen-enriched fly ash melting, since coal powder is used in the fly ash melting process and the melting furnace temperature is high, the tail gas not only contains the above-mentioned pollutants, but also releases more nitrogen oxides and dust. The current purification process cannot completely solve the secondary pollution of tail gas, especially high nitrogen oxides (NOx up to 1000mg / m 3 ), high dust (up to 20g / m 3 ), the problem of heavy metal elemental mercury being difficult to capture and remove is prominent. Therefore, for this tail gas with many types of pollutants, high concentration, high temperature and difficult capture, an effective, reliable and low-investment tail gas purification process route is needed to completely solve the emission problem of the above pollutants. Summary of the invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides a wet purification method and device for coal oxygen-enriched fly ash molten tail gas.

[0004] A wet purification method for coal oxygen-enriched fly ash melting tail gas comprises the following steps: high-temperature tail gas released from a coal oxygen-enriched fly ash melting furnace is cooled to below 120-150°C by a quench tower; it enters a water scrubber in sequence for pre-dust removal, acid removal, and cooling to below 80°C; it passes through a wet electrostatic precipitator for deep dust removal; it passes through an oxidation absorption tower for denitration, desulfurization, and mercury removal, and is cooled to 50-70°C; it passes through an alkali scrubber for further acid removal, and finally the purified tail gas is discharged into a chimney through an induced draft fan; waste water discharged from the water scrubber and the oxidation absorption tower is purified to obtain metal chlorides, sulfates, and nitrates for recycling.

[0005] The high-temperature exhaust gas is released from the upper part of the fly ash melting furnace, enters the quenching tower and is instantly cooled to 120-150℃, enters the water washing tower for pre-dust removal, acid removal, and cooling to below 80℃, enters the wet electrostatic precipitator for deep dust removal, enters the oxidation absorption tower for denitrification, deacidification, and demercuration, and is cooled to 50-70℃, and then enters the alkali washing tower to further remove residual acid gas. Finally, the purified exhaust gas is discharged into the chimney through the induced draft fan.

[0006] The water washing tower, oxidation absorption tower and alkali washing tower are respectively provided with the first circulating water pump, the second circulating water pump and the third circulating water pump. The circulating liquid is sprayed from the top of the tower through the nozzle, and after being fully contacted with the tail gas, it flows into the liquid storage tank at the bottom of the tower, and then is sent to the nozzle at the top of the tower through the circulating pumps of the first circulating water pump, the second circulating water pump and the third circulating water pump to realize continuous circulation spraying. The wastewater from the wet electrostatic precipitator and the alkali washing tower is respectively transported by the first wastewater delivery pump and the second wastewater delivery pump to the liquid storage tank of the water washing tower and the oxidation absorption tower to realize the gradient reuse of water resources. The wastewater from the water washing tower and the oxidation absorption tower is respectively discharged by the first wastewater discharge pump and the second wastewater discharge pump to the first wastewater storage tank and the second wastewater storage tank. After preliminary sorting, it finally enters the wastewater purification section for purification and resource utilization.

[0007] The first replenishing pump, the second replenishing pump and the third replenishing pump are arranged to replenish cooling water, NaClO2 / NaClO oxidant + sodium hydroxide lye and sodium hydroxide lye to the quencher, the oxidation absorption tower and the alkali washing tower respectively, so as to ensure that the pollutants in the exhaust gas are fully oxidized, absorbed and captured.

[0008] The heat released by cooling the exhaust gas and the heat generated by the dissolution of the acidic gas are transferred to the circulating liquid. The system heat is removed by setting the first cooling water heat exchanger and the second cooling water heat exchanger on the circulating pipelines of the water scrubber and the oxidation absorption tower. The heat exchanger is a tubular heat exchanger, and the cold medium uses 25℃-32℃ industrial cooling water to maintain the operating temperature of 80℃ for the water scrubber and 50-70℃ for the oxidation absorption tower.

[0009] A wet purification method and device for coal oxygen-enriched fly ash melting tail gas, the upper part of the fly ash melting furnace is connected to the top of the quencher, the bottom of the quencher is connected to the top of the water washing tower, the upper part of the water washing tower is connected to the lower part of the wet electrostatic precipitator, the upper part of the wet electrostatic precipitator is connected to the lower part of the oxidation absorption tower, the upper part of the oxidation absorption tower is connected to the lower part of the alkali washing tower, the upper part of the alkali washing tower is connected to the induced draft fan, the induced draft fan is connected to the chimney, the first liquid replenishment pump is connected to the quencher, the first cooling water heat exchanger is respectively connected to the first circulating water pump and the water washing tower, the other end of the first circulating water pump is connected to the quencher, the first cooling water heat exchanger is respectively connected to the first circulating water pump and the water washing tower, and the other end of the first circulating water pump is connected to the quencher. The first end is connected to the water washing tower, the first wastewater delivery pump is respectively connected to the water washing tower and the first wastewater storage tank, the first wastewater discharge pump is respectively connected to the water washing tower and the wet electrostatic precipitator, the second wastewater delivery pump is respectively connected to the oxidation absorption tower and the second wastewater storage tank, the second cooling water heat exchanger is connected to the oxidation absorption tower, the second circulating water pump is respectively connected to the second cooling water heat exchanger, the second liquid replenishment pump and the oxidation absorption tower, the second wastewater discharge pump is respectively connected to the oxidation absorption tower and the alkali washing tower, and the third circulating water pump is respectively connected to the alkali washing tower and the third liquid replenishment pump.

[0010] The advantages of the present invention are:

[0011] (1) Effectively play the advantages of integrated synergistic treatment of deacidification, denitrification, demercurization and dust removal, with low investment, space saving, and effectively achieve flue gas compliance and even ultra-clean emissions.

[0012] (2) The gas-liquid two-phase quenching device operates in parallel flow inside the device, which effectively reduces the risk of scaling and clogging of the cooling water nozzle while ensuring high heat and mass transfer efficiency.

[0013] (3) In view of the characteristics of the pollutants and high concentrations in the exhaust gas, a multi-channel and multi-layer process setting such as water washing, alkaline washing, dust removal, oxidation absorption, etc. is used to deeply remove the pollutants to ensure that the pollutants meet the standards or even achieve ultra-clean emissions.

[0014] (4) The water scrubber uses a Venturi water film dust collector design, which not only removes HCl from the exhaust gas, but also removes most of the smoke dust. It can also further cool the exhaust gas to below 80°C, achieving the multi-effects of dust removal, acid removal, and cooling, and meeting the requirements of optimal process operating parameters and deep purification of subsequent equipment.

[0015] (5) Wet electrostatic precipitator is used to remove fine dust, with a dust removal efficiency of up to 99%. For tail gas with high dust content, the dust content is guaranteed to be 30mg / m 3 The following emission standards are met.

[0016] (6) The oxidation absorption tower uses NaClO2 as the oxidant, which can achieve the simultaneous removal of NO / SO2 / Hg in one tower. In order to reduce the cost of using the oxidant, NaClO2 can be mixed with NaClO, which has similar chemical properties and is inexpensive, and the removal is carried out using a NaClO2 / NaClO composite absorption liquid.

[0017] (7) The water washing tower, oxidation absorption tower and alkali washing tower are all equipped with circulating pumps to extract liquid from the liquid storage tank and then send it to the nozzle on the top of the tower for continuous circulation, which greatly improves the heat and mass transfer and capture efficiency in the tower and realizes energy and water saving of the system to the greatest extent.

[0018] (8) The excess wastewater from the wet electrostatic precipitator and the alkaline washing tower is respectively fed into the liquid storage tanks of the water washing tower and the oxidation absorption tower for further recycling, thus realizing the rational utilization of water resources in the system in different levels and gradients.

[0019] (9) The wastewater from the water washing tower and the oxidation absorption tower is purified separately to obtain chloride, sulfate and nitrate respectively, realizing resource utilization.

[0020] The present invention can fully and effectively bring into play the advantages of integrated coordinated treatment of deacidification, denitrification, demercurization and dust removal to achieve compliance with flue gas standards or even ultra-clean emissions; wastewater purification treatment obtains reusable salts to achieve resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] When considered in conjunction with the accompanying drawings, the present invention can be more completely and better understood and many of the accompanying advantages can be easily known by referring to the detailed description below, but the drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention, as shown in the figure:

[0022] Figure 1 It is a schematic diagram of the structure and process of the present invention.

[0023] The present invention is further described below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0024] Obviously, many modifications and changes made by those skilled in the art based on the purpose of the present invention belong to the protection scope of the present invention.

[0025] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when an element or component is said to be "connected" to another element or component, it may be directly connected to the other element or component, or there may be an intermediate element or component. The term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

[0026] It should be understood by those skilled in the art that unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art.

[0027] To facilitate the understanding of the embodiments, further explanations will be given below, and each embodiment does not constitute a limitation of the present invention.

[0028] Example 1: Figure 1 As shown, a wet purification device for coal oxygen-enriched fly ash melting tail gas includes a garbage fly ash melting furnace 1, a quencher 2, a water washing tower 3, a wet electrostatic precipitator 4, an oxidation absorption tower 5, an alkali washing tower 6, an induced draft fan 7, a chimney 8, a first cooling water heat exchanger 9, a second cooling water heat exchanger 10, a first circulating water pump 11, a second circulating water pump 12, a third circulating water pump 13, a first wastewater storage tank 21, a second wastewater storage tank 22, a first wastewater delivery pump 14, a second wastewater delivery pump 16, a first wastewater discharge pump 15, a second wastewater discharge pump 17, a first liquid replenishment pump 18, a second liquid replenishment pump 19, and a third liquid replenishment pump 20.

[0029] The upper part of the fly ash melting furnace 1 is connected to the top of the quencher 2, the bottom of the quencher 2 is connected to the top of the water washing tower 3, the upper part of the water washing tower 3 is connected to the lower part of the wet electrostatic precipitator 4, the upper part of the wet electrostatic precipitator 4 is connected to the lower part of the oxidation absorption tower 5, the upper part of the oxidation absorption tower 5 is connected to the lower part of the alkali washing tower 6, the upper part of the alkali washing tower 6 is connected to the induced draft fan 7, the induced draft fan 7 is connected to the chimney 8, the first liquid replenishment pump 18 is connected to the quencher 2, the first cooling water heat exchanger 9 is respectively connected to the first circulating water pump 11 and the water washing tower 3, the other end of the first circulating water pump 11 is connected to the water washing tower 3, the first wastewater delivery pump 14 is connected to the water washing tower 3 and the first wastewater storage tank 21 respectively, the first wastewater discharge pump 15 is connected to the water washing tower 3 and the wet electrostatic precipitator 4 respectively, the second wastewater delivery pump 16 is connected to the oxidation absorption tower 5 and the second wastewater storage tank 22 respectively, the second cooling water heat exchanger 10 is connected to the oxidation absorption tower 5, the second circulating water pump 12 is connected to the second cooling water heat exchanger 10, the second liquid replenishment pump 19 and the oxidation absorption tower 5 respectively, the second wastewater discharge pump 17 is connected to the oxidation absorption tower 5 and the alkali washing tower 6 respectively, and the third circulating water pump 13 is connected to the alkali washing tower 6 and the third liquid replenishment pump 20 respectively.

[0030] Example 2: Figure 1 As shown, a wet purification method and device for coal oxygen-enriched fly ash molten tail gas comprises the following steps:

[0031] The high-temperature tail gas is released from the upper part of the fly ash melting furnace 1, enters the quenching tower 2 and is instantly cooled to 120-150°C, enters the water washing tower 3 for pre-dust removal, acid removal, and cooling to below 80°C, enters the wet electrostatic precipitator 4 for deep dust removal, enters the oxidation absorption tower 5 for denitration, deacidification, and demercuration, and is cooled to 50-70°C, and then enters the alkali washing tower 6 to further remove residual acid gas. Finally, the purified tail gas is discharged into the chimney 8 through the induced draft fan 7.

[0032] The water washing tower 3, the oxidation absorption tower 5 and the alkali washing tower 6 are respectively provided with the first circulating water pump 11, the second circulating water pump 12 and the third circulating water pump 13. The circulating liquid is sprayed from the top of the tower through the nozzle, and after being fully contacted with the tail gas, it flows into the liquid storage tank at the bottom of the tower, and then sent to the nozzle at the top of the tower through the circulating pumps of the first circulating water pump 11, the second circulating water pump 12 and the third circulating water pump 13 to realize continuous circulation spraying. The wastewater from the wet electrostatic precipitator 4 and the alkali washing tower 6 is respectively transported to the liquid storage tanks of the water washing tower 3 and the oxidation absorption tower 5 by the first wastewater delivery pump 14 and the second wastewater delivery pump 16 to realize the gradient reuse of water resources. The wastewater from the water washing tower 3 and the oxidation absorption tower 5 is respectively discharged to the first wastewater storage tank 21 and the second wastewater storage tank 22 by the first wastewater discharge pump 15 and the second wastewater discharge pump 17. After preliminary sorting, it finally enters the wastewater purification section for purification and resource utilization.

[0033] The first replenishing pump 18, the second replenishing pump 19 and the third replenishing pump 20 are arranged to replenish cooling water, NaClO2 / NaClO oxidant+sodium hydroxide lye and sodium hydroxide lye to the quencher 2, the oxidation absorption tower 5 and the alkali washing tower 6 respectively, so as to ensure that the pollutants in the exhaust gas are fully oxidized, absorbed and captured.

[0034] The heat released by cooling the tail gas and the heat generated by dissolving the acidic gas are transferred to the circulating liquid, and the system heat is taken out by setting the first cooling water heat exchanger 9 and the second cooling water heat exchanger 10 on the circulating pipelines of the water scrubber 3 and the oxidation absorption tower 5. The heat exchanger is a tubular heat exchanger, and the cold medium is 25℃-32℃ industrial cooling water to maintain the optimal operating temperature of 80℃ for the water scrubber 3 and 50-70℃ for the oxidation absorption tower 5.

[0035] Example 3: Figure 1 As shown, a wet purification method and device for coal oxygen-enriched fly ash molten tail gas,

[0036] The steps include:

[0037] (1) The coal oxygen-rich fly ash molten tail gas is cooled to below 120-150℃ in a quench tower; it enters a water scrubber for pre-dust removal, acid removal, and cooling to below 80℃; it is deeply dusted by a wet electrostatic precipitator; it is denitrated, desulfurized, and demercured in an oxidation absorption tower, and cooled to 50-70℃; it is further deacidified in an alkali scrubber, and the purified tail gas is discharged into the chimney through an induced draft fan;

[0038] (2) The wastewater discharged from the water scrubber and the oxidation absorption tower is purified and treated respectively to obtain metal chloride, sulfate and nitrate for recycling;

[0039] The quenching tower is selected from an empty tower or a Venturi tower. The water washing tower is selected from a Venturi water film dust collector. The wet electrostatic dust collector uses the electrostatic principle to remove dust.

[0040] The oxidation absorption tower uses sodium chlorite solution or a mixture of sodium chlorite and sodium hypochlorite as an oxidant to remove SO2, NOx and mercury from the tail gas, thereby realizing integrated desulfurization, denitrification and demercurization.

[0041] The absorbent in the alkali washing tower is an alkaline solution, sodium hydroxide or sodium carbonate solution, which removes residual acidic substances such as HCl and SO2.

[0042] Wastewater purification treatment includes the following operations in sequence: sedimentation, flocculation, separation and drying.

[0043] Example 4: Figure 1 As shown, a wet purification method and device for coal oxygen-enriched fly ash molten tail gas can effectively solve the secondary pollution problem of fly ash molten tail gas and achieve standard or even ultra-clean emission of tail gas.

[0044] A wet purification method and device for coal oxygen-enriched fly ash molten tail gas, comprising the following steps:

[0045] (1) The coal oxygen-rich fly ash molten tail gas is cooled to below 120-150℃ in a quench tower; it enters a water scrubber for pre-dust removal, acid removal, and cooling to below 80℃; it passes through a wet electrostatic precipitator for deep dust removal; it passes through an oxidation absorption tower for denitration, desulfurization, and mercury removal, and is cooled to 50-70℃; it passes through an alkali scrubber for further acid removal, and the purified tail gas is discharged into the chimney through an induced draft fan;

[0046] (2) Purifying the wastewater discharged from the water scrubber and oxidation absorption tower to obtain metal chlorides, sulfates, and nitrates for recycling;

[0047] The quenching device is selected from a water spray cooling empty tower or a Venturi quenching tower. With water spray cooling, the high-temperature exhaust gas enters the quenching device from top to bottom, and the cooling water is sprayed from the nozzle at high speed into the air flow in the forward direction. The gas and liquid phases directly contact and collide to form a turbulent flow zone with high efficiency mixing, which strengthens the heat and mass transfer, and reduces the high-temperature flue gas (greater than 1300℃) to below 120-150℃ in a very short time.

[0048] The water scrubber has three functions: (1) pre-dust removal; (2) removal of acidic gas HCl; (3) further cooling the exhaust gas to below 80°C to meet the requirements of the optimal operating temperature of subsequent equipment. The water scrubber uses a Venturi water film dust collector. When the flue gas enters the Venturi tube, it first passes through the contraction tube, where the flue gas velocity gradually increases and reaches the highest value at the throat. The water droplets sprayed from the throat water spray device are impacted by the high-speed flue gas and atomized into fine water droplets of 100 to 200 microns, filling the entire throat. Due to the high relative velocity between the water droplets and the dust particles, the dust particles fully collide and contact with the small water droplets, and absorb the water droplets and condense into larger particles. After the exhaust gas reaches the diffusion tube, the velocity gradually decreases, and then enters the centrifugal water film dust collector. The larger particles carried by the exhaust gas are separated under the action of centrifugal force and flow into the lower wastewater pool. The purified exhaust gas is discharged from the top of the centrifugal water film dust collector, realizing wet dust removal of the exhaust gas.

[0049] At the same time, the water scrubber also has the function of acid washing. The tail gas and the water mist sprayed from the nozzle are fully mixed at the throat, and the acidic gas in the tail gas that is highly soluble in water dissolves in the water droplets and then enters the centrifugal water film dust collector. The separated water droplets are discharged from the bottom of the tower along with the particulate matter. Due to the large difference in the solubility of HCl and SO2 in water, at 80°C, the solubility of HCl is 38g / 100mL and the solubility of SO2 is 3.4g / 100mL. The water scrubber mainly removes HCl from the tail gas first, and then removes SO2 gas in the subsequent oxidation absorption tower and alkali scrubber.

[0050] The water washing tower is arranged downstream, and the tail gas enters from the top of the Venturi tower, passes through the venturi throat, and then is separated by the separator and discharged from the top; the circulating water is sprayed from the top of the Venturi through the nozzle, and after passing through the throat and fully contacting with the tail gas, it flows into the liquid storage tank at the bottom of the tower. The storage liquid is sent to the nozzle at the top of the tower through the circulating pump to achieve continuous spraying, and the excess wastewater is discharged to the wastewater purification process section by the wastewater delivery pump. The tail gas is cooled to release heat and the acid gas is dissolved to generate heat, and the system heat is taken out by setting a cooling water heat exchanger. The heat exchanger is a tubular heat exchanger, the working medium in the tube is 25℃-32℃ industrial cooling water, and the working medium outside the tube is the circulating liquid that needs to be cooled. The cooled circulating liquid cools the tail gas below 80℃ to meet the needs of the optimal process operating temperature of the subsequent equipment.

[0051] Wet electrostatic precipitator is an electrostatic precipitator that uses water spray or overflow water to form a layer of water film on the surface of the dust collecting electrode to achieve plate cleaning. Since the dust removal efficiency of the Venturi water film dust collector is generally 60%-80%, and the original dust content of the tail gas is as high as 20g / m3, it is necessary to add a wet electrostatic precipitator to further reduce the dust content of the tail gas. The wet electrostatic precipitator has a small air flow resistance and can remove fine dust with a dust removal efficiency of up to 99%, which can well ensure that the smoke dust is below 30mg / m3 and even meets the standard or even ultra-clean emissions. The dust-containing wastewater captured by the wet electrostatic precipitator is collected in the liquid storage tank of the water washing tower for recycling.

[0052] The oxidation absorption tower is mainly used to remove NOx, SO2 and heavy metal mercury from the tail gas. Oxidants are used to oxidize low-valent NO / SO2 into high-valent NO2 / SO3; and to convert the hard-to-capture elemental Hg 0 Oxidized into divalent mercury compounds that are easily soluble in water, greatly enhancing the capture and removal rate of mercury. NO2 / SO3 / Hg after oxidation 2+ , and finally eliminated through neutralization reaction to produce salt or acid.

[0053] Main reactions:

[0054] 2SO2+NaClO2+2H2O——2H2SO4+NaCl,

[0055] 4NO+3NaClO2+2H2O——4HNO3+3NaCl.

[0056] The oxidation absorption tower is arranged in countercurrent, with tail gas entering from the bottom of the tower and discharged from the top of the tower; the oxidation absorption liquid is sprayed in from the top of the tower through the nozzle, and after passing through the oxidation absorption layer and fully contacting with the tail gas, it flows into the liquid storage tank at the bottom of the tower; the oxidation absorption liquid in the liquid storage tank is sent to the nozzle at the top of the tower again through the circulation pump to realize continuous circulation spraying. Excess wastewater is discharged to the wastewater purification process section through the wastewater delivery pump. According to the emission requirements, one or more oxidation absorption layers can be set; the oxidant is NaClO2 solution or NaClO2 / NaClO mixed solution, which is used to oxidize NOx, SO2 and mercury in the tail gas; the absorption liquid is a dilute NaOH solution, which is used to neutralize and absorb the generated nitric acid, sulfuric acid and other acidic substances, and the pH value of the circulating liquid is controlled at 4-5 to achieve the best oxidation absorption efficiency.

[0057] The heat from cooling the tail gas in the oxidation absorption tower and the heat generated by the dissolution of the acidic gas are both used to remove the system heat through the cooling water heat exchanger installed on the circulating pipeline. The heat exchanger uses a tubular heat exchanger. The working fluid inside the tube is 25-32℃ industrial cooling water, and the working fluid outside the tube is circulating liquid. The tail gas can be further cooled to 50-70℃, which is the optimal reaction temperature of the oxidation absorption circulating liquid.

[0058] The alkali washing tower is mainly used to remove residual SO2 and other acidic gases in the tail gas, which can reduce the concentration of acidic gases in the gas phase to a very low value to meet the emission requirements. The alkali solution used in the alkali washing tower can be sodium hydroxide solution or sodium carbonate solution. According to different emission requirements, the alkali washing tower can use a single-stage or multi-stage packed tower. The alkali washing tower adopts a countercurrent layout, and the tail gas enters from the bottom of the tower and is discharged from the top of the tower; the alkali solution is sprayed from the top of the tower through the nozzle, and after the filler is fully in contact with the tail gas, it flows into the liquid storage tank at the bottom of the tower. The alkali solution in the liquid storage tank is sent to the nozzle at the top of the tower through a circulating pump to achieve continuous spraying, and the excess wastewater converges to the liquid storage tank of the oxidation absorption tower for recycling and reuse.

[0059] The discharged wastewater from the water washing tower and the oxidation absorption tower is discharged to the wastewater storage tank through the wastewater discharge pump respectively, and then passes through the respective wastewater purification treatment devices for neutralization, precipitation, flocculation, separation, and removal of heavy metals and suspended solids in the wastewater. The final concentrated brine is passed through the evaporation crystallizer to obtain chloride, sulfate, and nitrate. The water washing tower is mainly chloride or acid; the oxidation absorption tower is mainly nitrate or sulfate. These salts can be recycled and used in industry, such as dyeing auxiliaries in the printing and dyeing industry.

[0060] As described above, the embodiments of the present invention are described in detail, but it is obvious to those skilled in the art that many variations are possible without departing from the inventive point and effect of the present invention. Therefore, all such variations are also included in the protection scope of the present invention.

Claims

1. A wet purification method for coal oxygen-enriched fly ash molten tail gas, characterized in that: The high-temperature tail gas is released from the upper part of the oxygen-enriched fly ash melting furnace, enters the quench tower and instantly cools down to 120-150℃, enters the water scrubber for pre-dust removal, acid removal, and cooling to below 80℃, enters the wet electrostatic precipitator for deep dust removal, enters the oxidation absorption tower for denitration, acid removal, and mercury removal, and cools down to 50-70℃, and then enters the alkali scrubber to further remove residual acid gas. Finally, the purified tail gas is discharged into the chimney through the induced draft fan; the wastewater discharged from the water scrubber and the oxidation absorption tower is purified separately to obtain metal chloride and sulfate and nitrate for recycling; the water washing tower, oxidation absorption tower and alkali washing tower are respectively provided with the first circulating water pump, the second circulating water pump and the third circulating water pump. The circulating liquid is sprayed into the tower from the top through the nozzle, and after being fully contacted with the tail gas, it flows into the liquid storage tank at the bottom of the tower, and then is sent to the nozzle on the top of the tower through the first circulating water pump, the second circulating water pump and the third circulating water pump to realize continuous circulation spraying. The wastewater of the wet electrostatic precipitator is transported to the liquid storage tank of the water washing tower by the first wastewater discharge pump, and the wastewater of the alkali washing tower is transported to the liquid storage tank of the water washing tower by the second wastewater discharge pump. The wastewater is sent to the liquid storage tank of the oxidation absorption tower to realize the gradient reuse of water resources. The wastewater from the water washing tower is discharged to the first wastewater storage tank by the first wastewater delivery pump, and the wastewater from the oxidation absorption tower is discharged to the second wastewater storage tank by the second wastewater delivery pump. After preliminary sorting, it finally enters the wastewater purification section for purification and resource utilization. The first replenishment pump, the second replenishment pump, and the third replenishment pump are set to replenish cooling water, NaClO2 / NaClO oxidant + sodium hydroxide lye, and hydrogen to the quencher, oxidation absorption tower, and alkali washing tower respectively. Sodium oxide alkali solution is used to ensure that the pollutants in the exhaust gas are fully oxidized, absorbed and captured. The exhaust gas is cooled and the heat released and the dissolution heat of the acidic gas are transferred to the circulating liquid. The first cooling water heat exchanger and the second cooling water heat exchanger are set on the circulating pipelines of the water scrubber and the oxidation absorption tower to bring out the system heat. The heat exchanger is a tubular heat exchanger, and the cold medium is 25℃-32℃ industrial cooling water to maintain the operating temperature of 80℃ for the water scrubber and 50-70℃ for the oxidation absorption tower. The water scrubber is designed with a Venturi water film dust collector.

2. A device for wet purification of coal oxygen-enriched fly ash molten tail gas according to claim 1, characterized in that: The upper part of the fly ash melting furnace is connected to the top of the quencher, the bottom of the quencher is connected to the top of the water washing tower, the upper part of the water washing tower is connected to the lower part of the wet electrostatic precipitator, the upper part of the wet electrostatic precipitator is connected to the lower part of the oxidation absorption tower, the upper part of the oxidation absorption tower is connected to the lower part of the alkali washing tower, the upper part of the alkali washing tower is connected to the induced draft fan, the induced draft fan is connected to the chimney, the first liquid replenishment pump is connected to the quencher, the first cooling water heat exchanger is respectively connected to the first circulating water pump and the water washing tower, the other end of the first circulating water pump is connected to the water washing tower, the first The wastewater delivery pump is respectively connected to the water washing tower and the first wastewater storage tank, the first wastewater discharge pump is respectively connected to the water washing tower and the wet electrostatic precipitator, the second wastewater delivery pump is respectively connected to the oxidation absorption tower and the second wastewater storage tank, the second cooling water heat exchanger is connected to the oxidation absorption tower, the second circulating water pump is respectively connected to the second cooling water heat exchanger, the second liquid replenishment pump and the oxidation absorption tower, the second wastewater discharge pump is respectively connected to the oxidation absorption tower and the alkali washing tower, and the third circulating water pump is respectively connected to the alkali washing tower and the third liquid replenishment pump.

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