CN112299626A

CN112299626A - Method for purifying flue gas at tail of sintering machine and cooperatively treating waste water

Info

Publication number: CN112299626A
Application number: CN201910692538.6A
Authority: CN
Inventors: 杨本涛; 王兆才; 魏进超; 叶恒棣; 李勇; 刘昌齐; 崔泽星
Original assignee: Zhongye Changtian International Engineering Co Ltd
Current assignee: Zhongye Changtian International Engineering Co Ltd
Priority date: 2019-07-30
Filing date: 2019-07-30
Publication date: 2021-02-02

Abstract

The invention provides a method for realizing zero discharge of washing wastewater by using tail flue gas of a sintering machine as a heat source and simultaneously realizing treatment of waste in the tail flue gas of the sintering machine. The method adopts the high-temperature waste gas from the tail of the sintering machine as a heat source to treat the salt-containing wastewater, and has the advantages of low investment of evaporation equipment, small occupied area, high heat utilization rate and reliable operation compared with the method adopting the medium-temperature waste gas from a large flue as a heat source. Meanwhile, the flue gas containing pollutants contacts with the salt-containing wastewater, so that the concentration of the pollutants in the flue gas can be reduced, the subsequent flue gas purification treatment load is reduced, the salt-containing wastewater is evaporated to obtain crystallized salt, and zero discharge of the wastewater is realized.

Description

Method for purifying flue gas at tail of sintering machine and cooperatively treating waste water

Technical Field

The invention relates to a flue gas treatment and wastewater treatment method, in particular to a sintering machine tail flue gas purification and wastewater synergistic treatment method, and belongs to the field of resource environment protection and waste heat utilization.

Background

The sintering machine can generate a large amount of hot waste gas in the sintering process and contains a large amount of heat energy, and the flue gas generated by the sintering machine is gathered in a large flue through each air box through a main exhaust fan and is discharged after being purified. The waste gas temperature in each air box is different, and the heat distribution is characterized in that the waste gas temperature of the machine head air box is low, and the waste gas temperature of the machine tail air box is high. Generally, the exhaust gas temperature of a tail air box can reach more than 200 ℃, the conventional exhaust gas utilization mode is used for power generation or ignition of a steam boiler, the utilization rate of the exhaust gas heat is low, and the investment cost is high. In addition, because the hot waste gas of the tail air box of the sintering machine contains pollutants such as dust, sulfur dioxide, fluoride, chloride and the like with higher concentration, when the conventional high-temperature sintering hot waste gas is used for waste heat power generation, a large amount of dust can abrade equipment such as a steam boiler and the like to cause equipment damage, and the sulfur dioxide, the fluoride and the chloride in the flue gas can aggravate equipment corrosion. Therefore, in order to avoid the damage of the steam boiler, the requirement for corrosion prevention and abrasion prevention is generally high, thereby increasing the cost of the steam boiler.

In addition, a large amount of salt-containing wastewater, such as flue gas wet desulphurization and denitration wastewater, activated carbon desorption gas pickling and washing wastewater and the like, can be generated in steel smelting and other production processes, and the defects of high cost and long flow are caused by adopting the traditional step-by-step treatment technology. At present, the 'zero discharge' of the waste water is realized by adopting waste water evaporation and crystallization, and the technology is simple and convenient and has low cost. The crystallization product is formed in the evaporation process of the waste water in a typical homogeneous nucleation growth process, so that the crystallization product is fine, the dedusting and recycling difficulty of the crystallization product is increased, and the crystallization salt can enter a subsequent system.

For example, activated carbon SRG gas scrubbing removes impurities, which produces large amounts of acidic scrubbing wastewater. The components are complex, the wastewater is newly emerged, and no reference technology exists at home and abroad. Aiming at the wastewater, the company develops a wastewater zero discharge technology through independent research and development in the past, and the patent name is as follows: a zero discharge treatment method and a device for acidic flue gas washing wastewater.

At present, the process for converting sulfur dioxide into sulfuric acid mainly comprises the steps of absorbing low-concentration sulfur dioxide by using a solid adsorbent or liquid, and then enriching the sulfur dioxide into high-concentration sulfur dioxide by resolution for preparing sulfuric acid. In order to ensure the quality of sulfuric acid and the stability of an acid making system, a washing method is often adopted to wash and remove impurities from the analytic gas, so that a large amount of acidic flue gas washing wastewater is generated.

Since the stripping gas often contains a large amount of sulfur dioxide, it is dissolved into water during the washing process, so that the washing wastewater is generally acidic. The washing wastewater components are easily affected by sulfur dioxide flue gas, an adsorbent and a desorption process, so that the washing wastewater components are various, and the impurities in the desorption gas are complex and high in concentration, so that the washing wastewater components are particularly complex.

Through earlier stage research, the acid-making wastewater is determined to be mainly complex wastewater containing elemental sulfur, suspended matters, metals, ammonia nitrogen, fluorine and chlorine and organic pollutants. However, at present, the wastewater is not effectively treated, and a reference technology is not available at home and abroad.

In addition, in the prior art, the solution is adjusted to be high alkaline to completely precipitate metal ions, and then ammonia nitrogen is treated. However, under high alkali conditions, the metal cations are easy to form stable complexes with ammonia nitrogen, so that the removal rate of the metal cations and the ammonia nitrogen is reduced. In addition, the solution is in a high-alkali state, and although metal cations can be precipitated, ammonia nitrogen can be converted into free ammonia in high alkalinity, so that the ammonia can be separated out from a liquid phase, and a large amount of ammonia can escape. However, adjusting the solution to a lower alkalinity is not conducive to complete precipitation of the metal cations. In order to effectively solve the above-mentioned contradiction and realize the effective removal of metal cations and ammonia nitrogen, a novel cleaning treatment technology is urgently needed to be developed.

In conclusion, in consideration of the serious waste of heat energy of tail hot waste gas of the sintering machine and the requirement of evaporative crystallization heat of zero discharge of waste water in the sintering process, a method for purifying tail flue gas of the sintering machine and utilizing waste heat is developed, and the problems of recycling of sintering waste water energy, reducing of waste gas amount and zero discharge of waste water can be effectively solved.

Disclosure of Invention

Aiming at the problems that the tail flue gas of the sintering machine has higher temperature in the prior art, and the equipment is seriously abraded and corroded in the waste heat utilization process of the tail flue gas of the sintering machine due to the existence of pollutants such as sulfur dioxide, fluoride, chloride and the like in the tail flue gas of the sintering machine at present; meanwhile, the acidic washing wastewater is characterized by containing simple substance sulfur, suspended matters, metals, ammonia nitrogen, fluorine and chlorine and organic pollutants. The invention provides a method for realizing zero discharge of washing wastewater by using tail flue gas of a sintering machine as a heat source and simultaneously realizing treatment of waste in the tail flue gas of the sintering machine. The method adopts the high-temperature waste gas from the tail of the sintering machine as a heat source to treat the salt-containing wastewater, and has the advantages of low investment of evaporation equipment, small occupied area, high heat utilization rate and reliable operation compared with the method adopting the medium-temperature waste gas from a large flue as a heat source. Meanwhile, the flue gas containing pollutants contacts with the salt-containing wastewater, so that the concentration of the pollutants in the flue gas can be reduced, the subsequent flue gas purification treatment load is reduced, the salt-containing wastewater is evaporated to obtain crystallized salt, and zero discharge of the wastewater is realized.

According to the first embodiment provided by the invention, a method for purifying tail flue gas of a sintering machine and cooperatively treating waste water is provided.

A method for purifying tail flue gas of a sintering machine and cooperatively treating waste water comprises the following steps:

1) the bellows export and the flue gas branch connection of sintering machine bottom, wherein: connecting a flue gas branch pipe connected with an air box at the tail part of the sintering machine to a bypass flue gas pipeline, and connecting a flue gas branch pipe connected with the rest (except the tail part) air boxes of the sintering machine to a flue gas large pipeline;

2) mixing the salt-containing wastewater with the flue gas in the bypass flue gas pipeline, wherein the salt-containing wastewater absorbs pollutants in the flue gas in the bypass flue gas pipeline, and the flue gas in the bypass flue gas pipeline evaporates the salt-containing wastewater to form low-temperature flue gas containing crystallized salt;

3) carrying out dust removal treatment on the low-temperature flue gas containing the crystalline salt through a dust remover to realize separation of the crystalline salt and the low-temperature flue gas and obtain the crystalline salt and the low-temperature flue gas; and conveying the low-temperature flue gas to a flue gas large pipeline.

In the invention, the salt-containing wastewater is acidic flue gas washing wastewater; preferably, the salt-containing wastewater is one or more of flue gas wet desulphurization and denitration wastewater, activated carbon SRG sulfur-rich gas pickling wastewater and plant membrane concentration wastewater.

Preferably, the flue gas in the flue gas large pipeline is discharged after being purified.

In the invention, the step 2) is specifically as follows:

201) and (3) wet washing: washing the acidic flue gas by a wet method through a wet method washing device to obtain acidic flue gas washing wastewater;

202) acid filtration: carrying out acidic filtration on the acidic flue gas washing wastewater by an acidic filtration device to obtain suspended substance precipitate and clear liquid;

203) clear liquid flocculation: introducing the clear liquid obtained in the step 202) into a flocculation precipitation device, and adding mixed alkali to flocculate and precipitate the clear liquid to obtain metal-containing sludge and salt-containing wastewater;

204) mixing the salt-containing wastewater with the alkali liquor, then mixing the mixed liquid of the salt-containing wastewater and the alkali liquor with the flue gas in the bypass flue gas pipeline, absorbing pollutants in the flue gas in the bypass flue gas pipeline by the mixed liquid of the salt-containing wastewater and the alkali liquor, and evaporating the mixed liquid of the salt-containing wastewater and the alkali liquor by the flue gas in the bypass flue gas pipeline to form low-temperature flue gas containing crystallized salt.

Preferably, the flue gas branch pipe connected with the air box at the tail part of the sintering machine is respectively connected to the bypass flue gas pipeline and the flue gas large pipeline through a three-way switching valve. Wherein: the sintering machine tail bellows means 1 to 10 bellows, preferably 2 to 8 bellows, more preferably 3 to 6 bellows near the sintering machine tail.

Preferably, the method further comprises: step 4) adjusting the flue gas flow in the bypass flue gas pipeline, which specifically comprises the following steps:

401) calculating the heat required by wastewater treatment: detecting the amount of the mixed solution of the salt-containing wastewater and the alkali liquor as M_{Water (W)}，m³H; detecting the initial temperature of the mixed solution as T_{Water (W)}DEG C; thereby, the heat quantity Q to be absorbed for treating the mixed liquid_{Water (W)}Comprises the following steps:

Q_{water (W)}＝M_{Water (W)}×C_{Water (W)}×ΔT_{Water (W)}+M_{Water (W)}×r_{Water (W)}＝M_{Water (W)}×(r_{Water (W)}+C_{Water (W)}×(100-T_{Water (W)})) (1)

In formula (1): r is_{Water (W)}Is the heat of vaporization of the mixed liquor, J/m³；C_{Water (W)}Is the specific heat capacity of water, J/(m)³·℃)；

402) Calculating the required flue gas amount of the bypass flue gas pipeline (L2): setting the amount of flue gas entering the bypass flue gas pipeline (L2) as M_{Cigarette with heating means}，m³H; whereby the heat Q released by the flue gas entering the bypass flue gas duct (L2)_{Cigarette with heating means}Comprises the following steps:

Q_{cigarette with heating means}＝C_{Cigarette with heating means}×M_{Cigarette with heating means}×ΔT_{Cigarette with heating means}＝C_{Cigarette with heating means}×M_{Cigarette with heating means}×(T_{Cigarette with heating means}-T_{Is provided with}) (2)

In formula (2): t is_{Cigarette with heating means}The temperature of the flue gas entering the bypass flue gas duct (L2) is DEG C; t is_{Is provided with}Setting the temperature of the evaporated flue gas at DEG C; c_{Cigarette with heating means}Is the specific heat capacity of the flue gas, J/(m)³·℃)；

Heat Q released by the flue gas entering the bypass flue gas duct (L2)_{Cigarette with heating means}For evaporation flow of M_{Water (W)}The mixed solution of the salt-containing wastewater and the alkali liquor can be obtained:

k×C_{cigarette with heating means}×M_{Cigarette with heating means}×(T_{Cigarette with heating means}-T_{Is provided with})＝M_{Water (W)}×(r_{Water (W)}+C_{Water (W)}×(100-T_{Water (W)})) (3)

Obtaining the following components:

wherein: k is a heat exchange coefficient, and the value of k is 0.1-1, preferably 0.5-0.99, and more preferably 0.7-0.98;

the flue gas branch pipe connected with the tail air box of the sintering machine is adjusted to pass through a three-way switching valve, so that the amount of flue gas entering a bypass flue gas pipeline is M_{Cigarette with heating means}。

Preferably, T is_{Is provided with}The temperature is 100-160 ℃, and the value is preferably within the range of 110-140 ℃.

In the invention, the mixing of the mixed liquid of the salt-containing wastewater and the alkali liquor and the flue gas in the bypass flue gas pipeline is as follows: atomizing the mixed solution of the salt-containing wastewater and the alkali liquor, and spraying the atomized mixed solution into a bypass flue gas pipeline; or, the mixed liquid of the salt-containing wastewater and the alkali liquor is conveyed to a drying tower, the mixed liquid of the salt-containing wastewater and the alkali liquor is atomized in the drying tower, meanwhile, the bypass flue gas pipeline is connected to the drying tower, and the mixed liquid of the salt-containing wastewater and the alkali liquor and the flue gas in the bypass flue gas pipeline are mixed in the drying tower.

Preferably, the method further comprises: 5) metal recovery: the metal-containing sludge obtained in the step 203) is passed through a metal recovery device to recover metals.

Preferably, step 203) further comprises an oxidation step. The method specifically comprises the following steps: oxidizing the clear liquid obtained in the step 202) by an oxidation device, then introducing the oxidized clear liquid into a flocculation precipitation device, adding mixed alkali, and performing a weak alkali flocculation precipitation process to flocculate and precipitate the clear liquid to obtain the metal-containing sludge and the salt-containing wastewater.

In the present invention, the oxidation treatment employs one or more of chemical oxidation, electrochemical oxidation, ultraviolet catalytic oxidation, air oxidation, or chemical oxidation.

In the invention, the acidic flue gas contains SO₂、NO_xOne or more of dust, fluoride, chloride, VOCs and heavy metals.

Preferably, the acid flue gas is derived from a complex gas containing sulfur dioxide generated in the steel, electric, colored, petrochemical, chemical or building material industries.

Preferably, the volume content of the sulfur dioxide in the acid flue gas is 0.01-10%, preferably 0.03-8%, and more preferably 0.05-5%.

Preferably, the temperature of the acidic flue gas is 100-300 ℃, preferably 120-250 ℃, and more preferably 130-200 ℃.

In the present invention, in step 201), the solution used for the wet washing is an acidic solution.

Preferably, the pH value of the acidic solution is 0 to 7, preferably 1 to 6, and more preferably 2 to 5.

Preferably, the acidic solution is dilute sulfuric acid or dilute hydrochloric acid; in the wet washing process, the volume flow ratio of the acidic flue gas to the acidic solution is 1: 10-100, preferably 1: 20-80, and more preferably 1: 30-60.

In the present invention, in step 202), the acidic filtration specifically is: the suspended matters in the wastewater are removed by utilizing the gravity settling action or the interception action of a filter.

Preferably, the concentration of the suspension in the acid-filtered clear solution is 0 to 100mg/L, preferably 1 to 80mg/L, and more preferably 2 to 50 mg/L.

Preferably, the acidic flue gas washing wastewater comprises one or more of suspended matters, metal ions, ammonia nitrogen, fluorine and chlorine and organic pollutants.

Preferably, the metal ions are one or more of iron, copper, lead, calcium, zinc, cadmium, cobalt, nickel and aluminum.

In the present invention, in step 203), the flocculation precipitation is specifically: adding mixed alkali into the clear liquid, adjusting the pH value to be alkalescent, and flocculating and precipitating the clear liquid with weak alkali to obtain metal-containing sludge and salt-containing wastewater.

Preferably, the pH of the serum is adjusted to 7-10, preferably 7.2-9, more preferably 7.5-8.5.

Preferably, the mixed alkali is a mixture of soluble hydroxide and soluble carbonate, or a mixture of soluble hydroxide and soluble bicarbonate; more preferably, the mixed alkali is a mixture of one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide and one or more of sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate.

In the invention, in step 204), the mixing of the mixed solution of the salt-containing wastewater and the alkali liquor and the flue gas in the bypass flue gas pipeline specifically comprises: the mixed solution of the salt-containing wastewater and the alkali liquor is dispersed into small fog drops through an atomizer, and the particle size of the small fog drops is 10-100 microns, preferably 15-80 microns, and more preferably 20-50 microns.

Preferably, the alkali liquor is one or more of soluble hydroxide, soluble carbonate and soluble bicarbonate, and is preferably sodium hydroxide.

Preferably, the addition amount of the alkali liquor is 0 to 0.5 times, preferably 0.01 to 0.25 times, and more preferably 0.05 to 0.1 times of the amount of the clear liquor.

In the invention, dry dedusting is adopted in the dedusting treatment in the step 3). The dust remover is preferably an electric dust remover, a bag-type dust remover, a cyclone dust remover or a ceramic dust remover, and is preferably a cyclone dust remover.

Preferably, after the dust removal treatment, the crystallized salt is discharged from a solid outlet of the dust remover.

According to the invention, the flue gas of the tail of the sintering machine is used for treating the salt-containing wastewater, the salt-containing wastewater is subjected to alkali regulation treatment, the salt-containing wastewater is alkaline, pollutants such as dust, sulfur dioxide, fluoride and chloride in the exhaust gas discharged by the tail bellows can be well absorbed, and the pollutants with corrosiveness are removed by treating the tail flue gas with the salt-containing wastewater, so that the subsequent waste heat utilization is facilitated, the damage of the dust to equipment such as a steam boiler is avoided, and the corrosion of the equipment by the corrosive pollutants such as sulfur dioxide, fluoride and chloride is also avoided.

In addition, high-temperature flue gas discharged by a tail air box of the sintering machine is used for evaporating salt-containing wastewater by using the heat of the flue gas, so that the salt in the wastewater is recycled, and the crystallized salt is obtained; the evaporated flue gas is changed into low-temperature flue gas, and the low-temperature flue gas is conveyed back to the flue gas large pipeline and is combined to carry out waste heat utilization and purification treatment. In addition, the dust in the high-temperature flue gas discharged by the tail air box of the sintering machine is used as a 'nucleus' in the evaporation and crystallization process of the salt-containing wastewater, so that the formation and growth of crystallized salt are facilitated.

In the invention, steel, electricity and color are adoptedIn industries such as petrochemical industry, chemical industry or building materials, the used raw materials are various, and the flue gas containing various pollutants is often generated, wherein the flue gas contains SO₂NOx, dust, VOCs, heavy metals, and the like. The multi-pollutant flue gas is subjected to adsorption treatment, and an adsorbent (such as activated carbon) adsorbing the multi-pollutants is subjected to desorption treatment and is recycled; in the process of desorption, the generated desorption gas is washed, a large amount of wastewater is generated in the washing process, and the desorption gas washing wastewater is not effectively treated, so that the environment is seriously polluted. The invention utilizes the heat of the flue gas discharged by the tail air box of the sintering machine to treat the waste water generated in the processes of analyzing, analyzing gas treatment and the like. The method has the advantages of synergistic treatment of flue gas and wastewater, low operation cost, less equipment investment, clean treatment and effective control of secondary pollution, and realizes zero discharge of wastewater. In the invention, all the wastewater to be treated is evaporated by the waste heat of the flue gas discharged by the tail air box of the sintering machine, then is dedusted and is conveyed to the purification treatment system for treatment, thereby realizing zero discharge of the wastewater.

In the invention, the flue gas generated by conveying the sintering machine is divided into two parts, the flue gas exhausted by the air box at the tail of the sintering machine enters the bypass flue gas pipeline, and the flue gas exhausted by the other air boxes is conveyed through the flue gas large pipeline. And the waste water is dried and crystallized through the flue gas in the bypass flue gas pipeline, and then the flue gas and waste water mixed gas obtained by mixing the part of waste water and the flue gas is conveyed to a flue gas large pipeline for subsequent treatment through dust removal treatment.

The invention provides a method for purifying tail flue gas of a sintering machine and utilizing waste heat, which has the following technical processes and technical principles:

1) high-temperature hot exhaust gas regulation: and (4) analyzing and calculating according to the temperature characteristics of the hot waste gas and the heat demand of the evaporation water amount, determining the required hot waste gas amount, and adjusting a three-way switching valve on a tail air box flue gas pipeline, thereby obtaining the subsequent required flue gas.

2) Adjusting alkali of wastewater: because high-salinity wastewater generally contains a large amount of fluorine and chlorine, and tail flue gas of a sintering machine is weakly acidic, in order to prevent hydrogen fluoride, hydrogen chloride and the like from being generated in the evaporation process of the wastewater, the wastewater needs to be adjusted to be alkaline. In addition, the wastewater is adjusted to be alkaline, so that the hardness of the wastewater is reduced, heavy metals are removed, the scaling of subsequent equipment is avoided, and the enrichment of heavy metal precipitates is realized.

3) Wastewater atomization and drying: because the small liquid drops are easy to evaporate and dry, the waste water can be atomized by an air compressor or a high-speed centrifuge after being pressurized by the air compressor, the atomized mist drops with small grain size of 10-100 microns are contacted with hot waste gas, and because the grain size is small, the specific surface area is large, the mass transfer rate is high, the heat of the flue gas can be quickly absorbed, and the drying and crystallization are realized. The waste water is contacted with the hot waste gas in a way of arranging a separate drying tower or directly contacting in a flue of the hot waste gas.

4) Purifying the tail smoke pollutants: as the wastewater needs to be adjusted to be alkaline before drying, pollutants such as dust, sulfur dioxide, fluoride, chloride and the like in the tail flue gas can react with the alkali liquor to be removed. And the dust in the tail flue gas can be recovered through subsequent crystallization and is captured and removed by a dust remover. The subsequent treatment difficulty of the tail flue gas is reduced.

5) Crystal nucleation and growth: the dust in the tail flue gas can provide crystal nucleus for the waste water drying crystallization precipitation process, and the heterogeneous nucleation growth degree is generally greater than the homogeneous nucleation according to the crystallization nucleation principle. Therefore, under the induction of dust, crystal salt particles formed by drying and crystallizing the wastewater can be enlarged, and the subsequent dedusting and recycling are facilitated.

6) Crystal recovery and disposal: after the solution is evaporated, the solid mainly comprises sulfate, chloride and fluoride salt, and is conventional inorganic salt, and can be recovered and removed by a conventional dust remover. In addition, because the waste water has removed the heavy metal in advance, the crystalline salt after drying does not contain the heavy metal, reduce the hazardness of the crystalline salt.

In the invention, aiming at the characteristic that the acid washing wastewater in the prior art is complex wastewater containing elemental sulfur, suspended matters, metals, ammonia nitrogen, fluorine and chlorine and organic pollutants; removing suspended matters in the wastewater through acidic filtration; removing metal ions by flocculation precipitation; then, substances such as fluorine, chlorine and the like are recovered through drying, and organic substances are removed; the method can effectively treat the acidic washing wastewater, realizes the reduction of heavy metal hazardous waste, and avoids the blockage of equipment by elemental sulfur, the zero discharge of the wastewater, the low dust viscosity and the no bag pasting phenomenon; the resources are recovered and reused, and the environment is protected.

In the invention, 1) acidic flue gas washing wastewater is subjected to acidic filtration to obtain suspended substance precipitate and clear liquid; 2) adding mixed alkali into the filtered supernatant, adjusting the pH value of the wastewater to be alkalescent, and forming a precipitate by metal ions; filtering to obtain filter residue containing metal ion precipitate and salt-containing wastewater; 3) the salt-containing wastewater is mixed with flue gas discharged by a tail air box of a sintering machine in a bypass flue through an atomizer, the drying and crystallization are realized by utilizing the waste heat of the flue gas, and simultaneously, a certain amount of alkali liquor is added into the atomizer to adjust the fog drops of the wastewater to be high-alkalinity; 4) and recovering the crystallized salt generated after drying by using a dust remover, and discharging the crystallized salt from the system.

In the present invention, acidic precipitation/acidic filtration: the nature that the suspended matter is easy to settle is utilized, and the suspended matter is filtered in the acidity by the gravity action and the acidic filter under the acidic condition. Carbon powder blockage is prevented by acidic filtration; the sulphur colloid is prevented from dissolving to form sodium thiosulphate and is decomposed on drying.

In the present invention, flocculation weak base precipitation: adjusting the wastewater to be alkalescent by adopting mixed alkali, wherein the pH value is less than or equal to 10; the metal cation will react with OH^-、CO₃ ^2-Or HCO₃ ^-And the like, to form insoluble substances. And the precipitate is settled by adding a flocculating agent, so that the metal cations in the wastewater are removed, and the hardness of the wastewater is reduced. Heavy metals are precipitated to prevent the heavy metals from entering into crystallized salt, so that hazardous waste reduction is realized; meanwhile, the flocculation precipitation process adopts mixed alkali, so that a weak alkali environment is ensured, and ammonia volatilization and formation of a metal ammonia nitrogen complex are avoided.

In the invention, the wastewater atomization and alkali regulation: because the small liquid drops are easy to evaporate and dry, the waste water is atomized into 10-100 mu m particle size after being pressurized by an air compressor, and the drying speed of the waste water is improved. Meanwhile, ammonia is easy to escape from the wastewater under high alkali, so that the workshop environment is worsened and the recovery rate of ammonia nitrogen is low. The purpose of adopting atomization alkali regulation is to quickly regulate the pH value of small drops of atomized wastewater to be more than or equal to 10 in a closed space, realize the conversion of ammonia nitrogen into free ammonia and simultaneously avoid ammonia escape caused by open alkali regulation. Drying by using the waste heat of the flue gas in the flue; high-alkali atomization is adopted, which is beneficial to recycling ammonia gas; alkaline drying to prevent formation of high viscosity ammonium bisulfate and other by-products.

In the present invention, the crystallization recovery: after the solution is evaporated, the solid mainly comprises sulfate, chloride and fluoride salt, is conventional inorganic salt, and can be recovered and removed by adopting a dust removal material with the filter diameter of less than 1 mu m. Commonly used dust removal materials include cloth bags, ceramics, metal membranes, and the like. After the suspended matters in the wastewater are removed by acidic filtration, the wastewater is changed into small-particle acidic fog drops by an atomizer, and the acidic fog drops are in contact with atomized alkali liquor quickly and have neutralization reaction to form alkaline liquid drops due to small particle size, large specific surface area and high mass transfer rate, and the dry crystallization is realized by quickly absorbing the heat of the flue gas. Because the heavy metal is removed by the weak base flocculation precipitation, the dried crystallized salt does not contain the heavy metal, the harmfulness of the crystallized salt is reduced, and the harmless treatment of fluorine and chlorine is realized.

In the present invention, fluorine and chlorine are harmless: fluorine and chlorine in the flue gas are easily adsorbed by the activated carbon, and then desorbed at high temperature and enter the washing wastewater. Because the solubility of the fluorine chloride salt in water is reduced along with the reduction of the temperature, the method adopts the reduction of the solution temperature to separate out the fluorine chloride salt crystals after the heavy metal and ammonia nitrogen in the wastewater are removed. The problems of co-precipitation with heavy metals and difficult crystallization of ammonium salt are avoided, the harmfulness of the crystallized salt is reduced, and harmless treatment of fluorine and chlorine is realized.

In the invention, after wet washing, the generated acidic washing wastewater comprises carbon powder in a suspended state and a wastewater solution containing metal ions; the part of the acidic washing wastewater is subjected to acidic filtration to separate suspended matters (such as carbon powder) in the wastewater to obtain carbon powder, and the part of the carbon powder can be recycled through a carbon powder recycling process, for example, a re-granulation process is adopted to obtain large-particle activated carbon, and then the large-particle activated carbon is recycled to an adsorption tower. The wastewater after the suspended matter is separated contains metal ions (or metal salts) which are clear liquid; and (3) subjecting the clear liquid to a flocculation precipitation process, adding mixed alkali into the clear liquid to enable most heavy metal ions in the clear liquid to form precipitates, introducing the precipitates into the metal-containing sludge, and then recovering metals from the metal-containing sludge to obtain a pure metal recovered material which can be sold or used for other purposes. The salt-containing wastewater obtained after the flocculation and precipitation process is characterized in that an alkali solution is added into the salt-containing wastewater, after atomization, the heat of flue gas discharged by a tail air box of a sintering machine is utilized for drying, metal ions which are not precipitated in the flocculation and precipitation process are crystallized in the salt-containing wastewater after drying, and the heat generated by adding alkali solution into the salt-containing wastewater to form clear liquid and the heat generated by mixing the alkali solution through a flue gas conveying pipeline is utilized for drying. The volatile matter is pollution-free matter. The crystalline salt can be sold or used for other purposes, resulting in economic value. The crystal salt is sulfate, chloride or fluoride.

In the invention, the SRG gas refers to the enriched flue gas discharged after being analyzed by the desorption tower. The SRG gas (or SRG flue gas) has high temperature, high dust content and SO₂High content, high water content, complex smoke impurity components and the like. In the art, SRG gas is also referred to simply as sulfur-rich gas; used for being conveyed to an acid making system for making acid.

According to the waste water amount to be treated, the invention accurately controls the amount of flue gas entering the bypass flue gas pipeline from the tail air box of the sintering machine, so that the flue gas entering the bypass flue gas pipeline can just treat the waste water. If the flue gas introduced into the bypass flue gas pipeline is too little, the wastewater treatment is incomplete, and the significance of the invention is lost; if the flue gas that introduces bypass flue gas pipeline is too much, will make the flue gas in the bypass flue gas pipeline surplus, handle waste water and need not surplus flue gas, because the flue gas in the bypass flue gas pipeline all need handle through the dust remover, consequently, the too much work load that will increase the dust removal of flue gas that introduces bypass flue gas pipeline, and is also stricter to the requirement of dust remover, has increased the input cost. According to the invention, the amount of the flue gas introduced into the bypass flue gas pipeline is accurately controlled, so that the part of the flue gas can just treat the wastewater to be treated, and the extra workload of dust removal is not increased. And removing the flue gas introduced into the bypass flue gas pipeline, and continuously conveying the residual flue gas to a waste heat utilization device and/or a purification device through a flue gas large pipeline.

In the invention, the waste water is mixed with the flue gas in the bypass flue gas pipeline, so that the waste water is mixed with the flue gas to form mixed gas of the flue gas and the waste water; the purpose of treating the wastewater is achieved. Because the wastewater contains metal ions, chloride ions, fluoride ions, sulfate ions and other substances, after the wastewater is conveyed to the bypass flue gas pipeline, the wastewater can be dried by utilizing the flue gas in the bypass flue gas pipeline, so that ions in the wastewater form crystal salt; such as chloride, fluoride, sulfate, and the like; in the mixed gas of the flue gas and the waste water after mixing, because ions are contained in the waste water before forming crystallized salt, the crystallized salt is discharged from a solid outlet of a dust remover through dust removal treatment; the crystallized salt is recovered and can be sold or used for other purposes, resulting in economic value. Therefore, the technical scheme of the invention not only treats the wastewater containing impurities, but also can recover by-product crystalline salt to generate economic value; in addition, the waste water sprayed into the bypass flue gas pipeline also plays a role in removing corrosive pollutants in flue gas discharged by a tail air box of the sintering machine.

In the invention, the heat quantity required by the wastewater treatment is calculated according to the wastewater quantity to be treated, the temperature of the wastewater, the temperature of the flue gas in the bypass flue gas pipeline and the temperature required by the wastewater evaporation (the set temperature according to the process experience). The heat required by the wastewater treatment is provided by the flue gas in the bypass flue gas pipeline, and the amount of the flue gas entering the bypass flue gas pipeline can be accurately calculated according to the temperature of the original flue gas; therefore, through adjustment and control, the amount of the flue gas entering the bypass flue gas pipeline can just completely treat the wastewater, and the surplus condition can not exist, so that the load of dust removal treatment can not be additionally increased; in addition, through accurate control, the temperature of the flue gas entering the adsorption tower can be controlled within a temperature range suitable for activated carbon adsorption treatment.

In the invention, the wastewater is obtained from SRG gas generated by activated carbon thermal regeneration, and is subjected to wet washing by a wet washing device to obtain high-sulfur gas and acidic washing wastewater. Wherein: the high-sulfur gas is subjected to a sulfur resource recycling process to recover sulfur resources. Preferably, the acidic washing wastewater is subjected to acidic filtration to obtain clear liquid and carbon powder. The clear liquid is conveyed to a bypass flue gas pipeline.

Preferably, alkali liquor is added into the obtained clear liquid, the clear liquid is atomized by an atomizer, the mixture of the atomized clear liquid and the alkali liquor is input into a flue gas conveying pipeline to be dried by flue gas, then crystallization is carried out, the flue gas is dedusted by a deduster, and simultaneously (trapped) crystallized salt is obtained.

In the invention, the acidic flue gas washing wastewater comprises one or more of suspended matters, metal ions, ammonia nitrogen, fluorine and chlorine and organic pollutants. Preferably, the metal ions are one or more of iron, copper, lead, calcium, zinc, cadmium, cobalt, nickel and aluminum.

In the present invention, the desorption gas, i.e. SRG gas, is washed by wet method, so that a part of carbon powder attached in the SRG gas enters the wastewater along with the desorption gas, and metal ions are dissolved in the water. The sulfur-containing gas is still gaseous, the high-sulfur gas is collected, sulfur resources are recovered through a sulfur resource recycling process, and the remaining extremely small part of sulfur-containing tail gas is conveyed to a flue gas conveying pipeline and then treated by an adsorption tower. Realizing zero emission of the polluted gas.

Preferably, mixed alkali is added into the obtained clear liquid, the pH of the clear liquid is adjusted to be alkalescent, and the metal-containing sludge and the salt-containing wastewater are obtained through weak alkali flocculation precipitation. Preferably, the pH of the serum is adjusted to 7-10, preferably 7.2-9, more preferably 7.5-8.5.

In the invention, the mixed alkali is OH-containing^-And CO₃ ^2-A mixture of constituents, or containing OH^-And HCO₃ ^-A mixture of components. Preferably, the mixed base is a mixture of a lyotropic hydroxide and a lyotropic carbonate, or a mixture of a lyotropic hydroxide and a lyotropic bicarbonate. More preferably, the mixed alkali is a mixture of one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide and one or more of sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate.

Generally, the lower part of the sintering machine is provided with 18 to 48 windboxes, preferably 20 to 36 windboxes, and more preferably 24 to 32 windboxes.

In the present invention, the heat of vaporization r of the mixed liquid_{Water (W)}Is (2.0 to 2.5) × 10⁵J/m³(ii) a The value in general process is 2.25 multiplied by 10⁵J/m³. Specific heat capacity of water C_{Water (W)}Is 4.2X 10⁶J/(m³C.g. to be prepared into a preparation. Specific heat capacity C of flue gas_{Cigarette with heating means}Is (300-350) J/(m)³DEG C.); the value is 330.36J/(m) in general process³·℃)。

In the invention, the temperature T of the flue gas entering the bypass flue gas pipeline_{Cigarette with heating means}Typically 200 ℃ and 300 ℃, preferably 210 ℃ and 260 ℃ nuclei, e.g., 220 ℃.

Compared with the prior art, the technical scheme of the invention has the following beneficial technical effects:

1. the invention carries out reasonable design aiming at the respective characteristics of hot waste gas and waste water of the sintering air box, and realizes the high-efficiency utilization of waste heat and the zero discharge of waste water.

2. Sintering machine tail bellows exhaust flue gas is through waste heat utilization, and flue gas temperature can reduce by a wide margin, and consequently, hot exhaust gas volume can reduce by a wide margin, can know according to the gas state equation (pV equals nrT), effectively reduces the total amount of exhaust gas that the sintering was discharged, effectively reduces later stage dust removal, SOx/NOx control purification workshop section construction cost and working costs.

3. When hot waste gas discharged from an air box at the tail of a sintering machine contacts with waste water, pollutants such as dust, sulfur dioxide, fluoride, chloride and the like in the hot waste gas can react with substances in the waste water to be removed cooperatively, for example, the sulfur dioxide, the fluoride and the chloride can be absorbed by alkali liquor, and the dust can be removed by a dust remover used in the method, so that the concentration of the pollutants in flue gas can be reduced, and the difficulty and the pressure of subsequent treatment can be reduced.

4. The dust in the hot waste gas used in the invention is large-particle iron oxide dust, which can provide crystal nucleus for the formation of the waste water crystallization product, so that the crystallization process is changed from homogeneous nucleation growth to heterogeneous nucleation growth, which is beneficial to improving the particle of the crystal salt and improving the dust removal and recovery efficiency of the subsequent crystallization product.

5. The method adopts the tail high-temperature hot waste gas of the sintering machine as a heat source, and has the advantages of low investment of evaporation equipment, small occupied area, high heat utilization rate and reliable operation compared with the method adopting the middle-temperature hot waste gas of a large flue as a heat source.

Drawings

FIG. 1 is a flow chart of the method for purifying flue gas at the tail of a sintering machine and co-processing waste water according to the invention;

FIG. 2 is a flow chart of salt-containing wastewater treatment in the method for purifying flue gas at the tail of a sintering machine and co-treating wastewater according to the invention;

FIG. 3 is a process flow chart of the method for purifying flue gas at the tail of a sintering machine and co-processing waste water, which comprises the treatment of salt-containing waste water;

FIG. 4 is a flow chart of the apparatus for the method of co-processing the flue gas purification and the waste water at the tail of the sintering machine according to the present invention;

FIG. 5 is a schematic structural diagram of a device for purifying flue gas at the tail of a sintering machine and cooperatively treating wastewater according to the present invention.

Reference numerals:

1: sintering machine; 101: an air box; 2: a dust remover; 3: a wet scrubbing apparatus; 4: an acidic filtration unit; 5: a flocculation precipitation device; 6: a drying tower; 7: a metal recovery device; 8: an oxidation unit; l1: a flue gas branch pipe; l2: a bypass flue gas duct; l0: a flue gas large pipeline.

Detailed Description

The technical solution of the present invention is illustrated below, and the claimed scope of the present invention includes, but is not limited to, the following examples.

Example 1

1) The outlet of the air box 101 at the bottom of the sintering machine 1 is connected with a flue gas branch pipe L1, wherein: a flue gas branch pipe L1 connected with an air box 101 at the tail of the sintering machine 1 is connected to a bypass flue gas pipeline L2, and a flue gas branch pipe L1 connected with the rest (other than the tail) air boxes 101 of the sintering machine is connected to a flue gas large pipeline L0;

2) mixing the salt-containing wastewater with the flue gas in the bypass flue gas pipeline L2, absorbing pollutants in the flue gas in the bypass flue gas pipeline L2 by the salt-containing wastewater, and evaporating the salt-containing wastewater by the flue gas in the bypass flue gas pipeline L2 to form low-temperature flue gas containing crystal salt;

3) carrying out dust removal treatment on the low-temperature flue gas containing the crystal salt through a dust remover 2 to realize separation of the crystal salt and the low-temperature flue gas and obtain the crystal salt and the low-temperature flue gas; the low temperature flue gas is conveyed to a flue gas large pipeline L0.

Example 2

1) The outlet of the air box 101 at the bottom of the sintering machine 1 is connected with a flue gas branch pipe L1, wherein: connecting flue gas branch pipes L1 connected with 5 air boxes 101 at the tail of the sintering machine 1 to a bypass flue gas pipeline L2, and connecting flue gas branch pipes L1 connected with the rest air boxes 101 (except for 5 air boxes at the tail) of the sintering machine to a flue gas large pipeline L0;

201) and (3) wet washing: washing the acidic flue gas by a wet method through a wet method washing device 3 to obtain acidic flue gas washing wastewater;

202) acid filtration: carrying out acidic filtration on the acidic flue gas washing wastewater through an acidic filtration device 4 to obtain suspended matter precipitate and clear liquid;

203) clear liquid flocculation: introducing the clear liquid obtained in the step 202) into a flocculation precipitation device 5, and adding mixed alkali to flocculate and precipitate the clear liquid to obtain metal-containing sludge and salt-containing wastewater;

204) mixing the salt-containing wastewater with alkali liquor, mixing a mixed solution of the salt-containing wastewater and the alkali liquor with the flue gas in the bypass flue gas pipeline L2, absorbing pollutants in the flue gas in the bypass flue gas pipeline L2 by the mixed solution of the salt-containing wastewater and the alkali liquor, and evaporating the mixed solution of the salt-containing wastewater and the alkali liquor by the flue gas in the bypass flue gas pipeline L2 to form low-temperature flue gas containing crystallized salt;

The acidic flue gas contains SO₂、NO_xDust, fluoride, chloride, VOCs and heavy metals. The solution adopted by the wet washing is an acidic solution, and the pH value of the acidic solution is 4; the acid solution is dilute sulfuric acid; acidic cigaretteThe gas washing wastewater comprises suspended matters, metal ions, ammonia nitrogen, fluorine and chlorine and organic pollutants. The flocculation precipitation specifically comprises the following steps: adding mixed alkali into the clear liquid, and adjusting the pH value to 8; the mixed alkali is sodium hydroxide and sodium carbonate.

In this example, the concentration of the suspension in the supernatant after acidic filtration was 1 mg/L. And removing heavy metal ions in the clear liquid after the acid washing through flocculation and precipitation, wherein the metal ions enter the metal-containing sludge. And drying the salt-containing wastewater through a flue gas pipeline to obtain crystalline salt. Realizing zero discharge of waste water.

Example 3

Example 2 was repeated except that the flue gas branch pipes L1 connected to the 10 windboxes 101 at the tail of the sintering machine 1 were connected to the bypass flue gas pipeline L2 and the flue gas large pipeline L0, respectively, by three-way switching valves.

The method further comprises the following steps: step 4) adjusting the flue gas flow in the bypass flue gas pipeline L2, which specifically comprises the following steps:

Obtaining the following components:

wherein: k is a heat exchange coefficient, and the value of k is 0.9; t is_{Is provided with}The temperature was 130 ℃.

The flue gas branch pipe L1 connected with the tail air box 101 of the sintering machine 1 is adjusted to pass through a three-way switching valve, so that the amount of flue gas entering a bypass flue gas pipeline L2 is M_{Cigarette with heating means}。

Example 4

Example 3 was repeated except that the mixing of the mixed liquor of the salt-containing wastewater and the alkali liquor with the flue gas in the bypass flue gas pipeline L2 was as follows: and atomizing the mixed solution of the salt-containing wastewater and the alkali liquor, and spraying the atomized mixed solution into a bypass flue gas pipeline L2.

Example 5

Example 3 was repeated except that the mixing of the mixed liquor of the salt-containing wastewater and the alkali liquor with the flue gas in the bypass flue gas pipeline L2 was as follows: the mixed liquid of the salt-containing wastewater and the alkali liquor is conveyed to the drying tower 6, the mixed liquid of the salt-containing wastewater and the alkali liquor is atomized in the drying tower 6, meanwhile, the bypass flue gas pipeline L2 is connected to the drying tower 6, and the mixed liquid of the salt-containing wastewater and the alkali liquor and the flue gas in the bypass flue gas pipeline L2 are mixed in the drying tower 6.

Example 6

Example 5 was repeated except that the method further included: 5) metal recovery: the metal-containing sludge obtained in step 203) is passed through a metal recovery apparatus 7 to recover metals.

Example 7

Example 6 was repeated except that the oxidation process was also included in step 203). The method specifically comprises the following steps: oxidizing the clear liquid obtained in the step 202) by an oxidation device 8, then introducing the oxidized clear liquid into a flocculation precipitation device 5, adding mixed alkali, and performing a weak alkali flocculation precipitation process to flocculate and precipitate the clear liquid to obtain the metal-containing sludge and the salt-containing wastewater. The oxidation treatment is electrochemical oxidation.

In the embodiment, the clear liquid after acid washing is subjected to an oxidation process to remove COD in the clear liquid, so that organic matter components in the clear liquid are greatly reduced; then removing heavy metal ions in the waste water by flocculation precipitation. The metal-containing sludge is subjected to a metal recovery process to enrich and recover metals, so that economic value is directly generated. The ammonia-containing flue gas after drying treatment is circulated to an adsorption tower for treatment, and zero discharge of waste water and waste gas is realized.

Example 8

Example 7 is repeated, except that in step 204), the mixing of the mixed solution of the salt-containing wastewater and the alkali liquor and the flue gas in the bypass flue gas pipeline L2 is specifically as follows: the mixed solution of the salt-containing wastewater and the alkali liquor is dispersed into small fog drops through an atomizer, and the particle size of the small fog drops is 30 mu m. The alkali liquor is sodium hydroxide.

Example 9

Example 8 was repeated except that the dust removal treatment in step 3) was dry dust removal. The dust collector 2 is a cyclone dust collector. After the dust removal treatment, the crystallized salt is discharged from the solid outlet of the dust remover 2.

By adopting the method of the embodiment 9, the flue gas discharged from the tail bellows of the sintering machine is used for treating SRG gas washing wastewater, and the process conditions and the detection results are as follows:

Claims

1. a method for purifying tail flue gas of a sintering machine and cooperatively treating waste water comprises the following steps:

1) the outlet of the air box (101) at the bottom of the sintering machine (1) is connected with a flue gas branch pipe (L1), wherein: connecting a flue gas branch pipe (L1) connected with an air box (101) at the tail part of the sintering machine (1) to a bypass flue gas pipeline (L2), and connecting a flue gas branch pipe (L1) connected with the rest (other than the tail part) air boxes (101) of the sintering machine to a flue gas large pipeline (L0);

2) mixing the salt-containing wastewater with the flue gas in the bypass flue gas pipeline (L2), absorbing pollutants in the flue gas in the bypass flue gas pipeline (L2) by the salt-containing wastewater, and evaporating the salt-containing wastewater by the flue gas in the bypass flue gas pipeline (L2) to form low-temperature flue gas containing crystallized salt;

3) carrying out dust removal treatment on the low-temperature flue gas containing the crystallized salt through a dust remover (2) to realize separation of the crystallized salt and the low-temperature flue gas and obtain the crystallized salt and the low-temperature flue gas; the low temperature flue gas is conveyed to a flue gas large pipeline (L0).

2. The method of claim 1, wherein: the salt-containing wastewater is acidic flue gas washing wastewater; preferably, the salt-containing wastewater is one or more of flue gas wet desulfurization and denitrification wastewater, activated carbon SRG sulfur-rich gas pickling and washing wastewater and plant membrane concentration wastewater; and/or

And the flue gas in the flue gas large pipeline (L0) is discharged after being purified.

3. The method of claim 2, wherein: the step 2) is specifically as follows:

201) and (3) wet washing: washing the acidic flue gas by a wet method through a wet method washing device (3) to obtain acidic flue gas washing wastewater;

202) acid filtration: carrying out acidic filtration on the acidic flue gas washing wastewater through an acidic filtration device (4) to obtain suspended matter precipitate and clear liquid;

203) clear liquid flocculation: introducing the clear liquid obtained in the step 202) into a flocculation precipitation device (5), adding mixed alkali to flocculate and precipitate the clear liquid, and obtaining metal-containing sludge and salt-containing wastewater;

204) the method comprises the steps of mixing salt-containing wastewater with alkali liquor, mixing a mixed solution of the salt-containing wastewater and the alkali liquor with flue gas in a bypass flue gas pipeline (L2), absorbing pollutants in the flue gas in the bypass flue gas pipeline (L2) by the mixed solution of the salt-containing wastewater and the alkali liquor, and evaporating the mixed solution of the salt-containing wastewater and the alkali liquor by the flue gas in the bypass flue gas pipeline (L2) to form low-temperature flue gas containing crystallized salt.

4. The method of claim 3, wherein: a flue gas branch pipe (L1) connected with an air box (101) at the tail part of the sintering machine (1) is respectively connected to a bypass flue gas pipeline (L2) and a flue gas large pipeline (L0) through a three-way switching valve; wherein: the tail air box (101) of the sintering machine (1) refers to 1-10 air boxes (101) close to the tail of the sintering machine (1), preferably 2-8 air boxes (101), and more preferably 3-6 air boxes (101).

5. The method of claim 4, wherein: the method further comprises the following steps: step 4) adjusting the flue gas flow in the bypass flue gas pipeline (L2), which specifically comprises the following steps:

Q_{cigarette with heating means}＝C_{Cigarette with heating means}×M_{Cigarette with heating means}×ΔT_{Cigarette with heating means}＝C_{Cigarette with heating means}×M_{Cigarette with heating means}×(T_{Cigarette with heating means}-T_{Is provided with}) (2)，

In formula (2): t is_{Cigarette with heating means}To the temperature of the flue gas entering the bypass flue gas duct (L2),℃；T_{is provided with}Setting the temperature of the evaporated flue gas at DEG C; c_{Cigarette with heating means}Is the specific heat capacity of the flue gas, J/(m)³·℃)；

k×C_{cigarette with heating means}×M_{Cigarette with heating means}×(T_{Cigarette with heating means}-T_{Is provided with})＝M_{Water (W)}×(r_{Water (W)}+C_{Water (W)}×(100-T_{Water (W)})) (3)，

Obtaining the following components:

a flue gas branch pipe (L1) connected with an air box (101) at the tail part of the sintering machine (1) is adjusted to pass through a three-way switching valve, so that the amount of flue gas entering a bypass flue gas pipeline (L2) is M_{Cigarette with heating means}；

6. The method according to any one of claims 3-5, wherein: mixing the mixed solution of the salt-containing wastewater and the alkali liquor with the flue gas in the bypass flue gas pipeline (L2) as follows: atomizing the mixed solution of the salt-containing wastewater and the alkali liquor, and spraying the atomized mixed solution into a bypass flue gas pipeline (L2); or the mixed liquid of the salt-containing wastewater and the alkali liquor is conveyed to the drying tower (6), the mixed liquid of the salt-containing wastewater and the alkali liquor is atomized in the drying tower (6), the bypass flue gas pipeline (L2) is connected to the drying tower (6), and the mixed liquid of the salt-containing wastewater and the alkali liquor is mixed with the flue gas in the bypass flue gas pipeline (L2) in the drying tower (6).

7. The method according to any one of claims 3-6, wherein: the method further comprises the following steps: 5) metal recovery: the metal-containing sludge obtained in the step 203) is processed by a metal recovery device (7) to recover metals; and/or

Step 203) also comprises an oxidation process; the method specifically comprises the following steps: oxidizing the clear liquid obtained in the step 202) by an oxidation device (8), then introducing the oxidized clear liquid into a flocculation precipitation device (5), adding mixed alkali, and performing a weak alkali flocculation precipitation process to flocculate and precipitate the clear liquid to obtain the metal-containing sludge and the salt-containing wastewater.

8. The method of claim 7, wherein: the oxidation treatment adopts one or more of chemical oxidation, electrochemical oxidation, ultraviolet catalytic oxidation, air oxidation or medicament oxidation; and/or

The acidic flue gas contains SO₂、NO_xOne or more of dust, fluoride, chloride, VOCs and heavy metals; preferably, the acid flue gas is derived from a complex gas containing sulfur dioxide generated in the steel, electric, colored, petrochemical, chemical or building material industries; the volume content of sulfur dioxide in the acidic flue gas is 0.01-10%, preferably 0.03-8%, and more preferably 0.05-5%; the temperature of the acidic flue gas is 100-300 ℃, preferably 120-250 ℃, and more preferably 130-200 ℃.

9. The method according to any one of claims 3-8, wherein: in step 201), the solution adopted by the wet washing is an acid solution; preferably, the pH value of the acidic solution is 0-7, preferably 1-6, and more preferably 2-5; preferably, the acidic solution is dilute sulfuric acid or dilute hydrochloric acid; in the wet washing process, the volume flow ratio of the acidic flue gas to the acidic solution is 1: 10-100, preferably 1: 20-80, and more preferably 1: 30-60; and/or

In step 202), the acidic filtration specifically comprises: removing suspended matters by utilizing the self gravity settling action or the filter interception action of the suspended matters in the wastewater; the concentration of suspended matters in the clear liquid after acidic filtration is 0-100 mg/L, preferably 1-80 mg/L, and more preferably 2-50 mg/L; the acidic flue gas washing wastewater comprises one or more of suspended matters, metal ions, ammonia nitrogen, fluorine and chlorine and organic pollutants; preferably, the metal ions are one or more of iron, copper, lead, calcium, zinc, cadmium, cobalt, nickel and aluminum.

10. The method according to any one of claims 3-9, wherein: in step 203), the flocculation precipitation is specifically: adding mixed alkali into the clear liquid, and adjusting the pH value to be alkalescent so as to flocculate and precipitate the weak alkali in the clear liquid and obtain metal-containing sludge and salt-containing wastewater; preferably, the pH of the serum is adjusted to 7-10, preferably 7.2-9, more preferably 7.5-8.5; preferably, the mixed alkali is a mixture of soluble hydroxide and soluble carbonate, or a mixture of soluble hydroxide and soluble bicarbonate; more preferably, the mixed alkali is a mixture of one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide and one or more of sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate; and/or

In the step 204), the mixing of the mixed solution of the salt-containing wastewater and the alkali liquor and the flue gas in the bypass flue gas pipeline (L2) is specifically as follows: dispersing the mixed solution of the salt-containing wastewater and the alkali liquor into small fog drops through an atomizer, wherein the particle size of the small fog drops is 10-100 microns, preferably 15-80 microns, and more preferably 20-50 microns; preferably, the alkali liquor is one or more of soluble hydroxide, soluble carbonate and soluble bicarbonate, and is preferably sodium hydroxide; preferably, the addition amount of the alkali liquor is 0-0.5 times, preferably 0.01-0.25 times, and more preferably 0.05-0.1 times of the amount of the clear liquor; and/or

The dust removal treatment in the step 3) adopts dry dust removal, and the dust remover (2) is preferably an electric dust remover, a bag-type dust remover, a cyclone dust remover or a ceramic dust remover, and is preferably a cyclone dust remover; after the dust removal treatment, the crystallized salt is discharged from a solid outlet of the dust remover (2).