CN111135692A - Method and system for recycling waste slurry obtained by power plant boiler flue gas desulfurization and denitrating power plant boiler flue gas - Google Patents

Method and system for recycling waste slurry obtained by power plant boiler flue gas desulfurization and denitrating power plant boiler flue gas Download PDF

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Publication number
CN111135692A
CN111135692A CN201811308166.4A CN201811308166A CN111135692A CN 111135692 A CN111135692 A CN 111135692A CN 201811308166 A CN201811308166 A CN 201811308166A CN 111135692 A CN111135692 A CN 111135692A
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China
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flue gas
power plant
plant boiler
desulfurization
chlorate
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CN201811308166.4A
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Inventor
银波
武珠峰
范协诚
李西良
孙永仕
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Xinjiang Silicon Based New Material Innovation Center Co Ltd
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Xinjiang Silicon Based New Material Innovation Center Co Ltd
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/74General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/77Liquid phase processes
    • B01D53/78Liquid phase processes with gas-liquid contact
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/46Removing components of defined structure
    • B01D53/60Simultaneously removing sulfur oxides and nitrogen oxides
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2251/00Reactants
    • B01D2251/10Oxidants
    • B01D2251/108Halogens or halogen compounds
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2258/00Sources of waste gases
    • B01D2258/02Other waste gases
    • B01D2258/0283Flue gases
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Abstract

The invention discloses a method and a system for recycling waste slurry obtained by flue gas desulfurization of a power plant boiler and denitrating flue gas of the power plant boiler, wherein the method comprises the following steps: 1) preparing a chlorate solution by taking waste slurry obtained by power plant boiler flue gas desulfurization as a raw material; 2) and carrying out contact reaction on the chlorate solution and the flue gas of the power plant boiler in a denitration tower to remove the nitrogen oxide and the residual sulfur oxide in the flue gas of the power plant boiler. According to the method and the system for recovering the waste slurry obtained by the flue gas desulfurization of the power plant boiler and the flue gas denitration of the power plant boiler, the desulfurization and the denitration are performed on the filtered flue gas of the power plant, the waste slurry obtained by the flue gas desulfurization of the power plant boiler is recycled, chlorine in the waste slurry is recycled and converted into chlorate, the environmental pollution is avoided, the hidden danger of secondary pollution is reduced, and the cost for treating the flue gas of the power plant boiler is reduced.

Description

Method and system for recycling waste slurry obtained by power plant boiler flue gas desulfurization and denitrating power plant boiler flue gas
Technical Field
The invention belongs to the technical field of recovery of power plant boiler flue gas, and particularly relates to a method and a system for recycling waste slurry obtained by desulfurization of power plant boiler flue gas and denitration of power plant boiler flue gas.
Background
At present, the problem of air pollution in China is serious, increasingly strict air pollutant discharge standards are set by the nation, the management of pollution discharge and charge is strengthened, and the desulfurization and denitrification of coal-fired flue gas become an irreparable task for protecting the health and ecological environment of human bodies. At present, a plurality of methods for desulfurization and denitrification can be industrially classified into the following types: complex absorption method, NaClO2The method comprises an oxidation absorption method, a pulse corona plasma method, a urea simultaneous desulfurization and denitration technology and a chloric acid oxidation method, but the method has the technical problems of high implementation cost and easy secondary pollution when the flue gas of the power plant boiler is desulfurized and denitrated.
Disclosure of Invention
The invention aims to solve the technical problems in the prior art, and provides a method and a system for recycling waste slurry obtained by power plant boiler flue gas desulfurization and power plant boiler flue gas denitration, which not only carry out desulfurization and denitration on power plant filtered flue gas, but also recycle waste slurry obtained by power plant boiler flue gas desulfurization.
The technical scheme adopted for solving the technical problem of the invention is to provide a method for recovering waste slurry obtained by desulfurizing flue gas of a power plant boiler and flue gas of the power plant boiler, which comprises the following steps:
1) preparing a chlorate solution by taking waste slurry obtained by power plant boiler flue gas desulfurization as a raw material;
2) and carrying out contact reaction on the chlorate solution and the flue gas of the power plant boiler in a desulfurization and denitrification tower to remove the nitrogen oxide and the residual sulfur oxide in the flue gas of the power plant boiler.
The waste slurry obtained by the flue gas desulfurization of the power plant boiler comprises: 8-13 mas% of gypsum, 0.1-0.5 mas% of calcium carbonate, 0.5-2 mas% of inert impurities, 1-3 mas% of fly ash, 1-4 mas% of soluble salt and 73.5-86.4 mas% of water, wherein the content of chloride ions is 5000-30000 ppm.
The power plant boiler flue gas includes: solid-phase soot and gas-phase substances, the content of soot in the flue gas is 25-35 mas%. The content of sulfur oxide in the gas phase is 1500-3The content of nitrogen oxide is 750-900mg/Nm3
Preferably, the step 1) is specifically:
11) adding alkali liquor into waste slurry obtained by power plant boiler flue gas desulfurization, and adjusting to be neutral; preferably, the alkali liquor is one or more of sodium hydroxide solution, calcium hydroxide solution and potassium hydroxide solution.
12) Performing solid-liquid separation to obtain separated solid phase substance and liquid phase substance;
13) electrolyzing the liquid phase to respectively obtain separated chlorine and alkali solution;
14) mixing chlorine gas and alkali solution for reaction to obtain the chlorate solution. Preferably, the temperature of the mixing reaction is 60 to 80 ℃.
SO in flue gas2、SO3Dissolving in water to form H2SO3、H2SO4
The alkali solution in the step 11) is a calcium hydroxide solution, and the reaction in the step 11) is as follows:
H2SO4+Ca(OH)2=CaSO4+H2O
H2SO3+Ca(OH)2=CaSO3+H2O
the alkali solution in the step 11) is a sodium hydroxide solution, and the reaction in the step 11) is as follows:
H2SO4+NaOH=Na2SO4+H2O
H2SO3+NaOH=Na2SO3+H2O
the alkali solution in the step 11) is a potassium hydroxide solution, and the reaction in the step 11) is as follows:
H2SO4+KOH=K2SO4+H2O
H2SO3+KOH=K2SO3+H2O
preferably, a step m) is further included between the step 12) and the step 13): concentrating the liquid phase until the concentration of chloride ions is 20-100 g/L.
Preferably, the concentration method in the step m) is: separating the liquid phase by ion membrane for concentration; alternatively, the liquid phase is concentrated by evaporation.
Preferably, a step n) is further included between the step 13) and the step 14): and concentrating the alkali solution to 30-50 mas%.
Preferably, a step j) is further included between the step 1) and the step 2): the chloride in the chlorate solution is removed by cooling crystallization. The chlorate solution prepared in the step 1) is a sodium chlorate solution, the sodium chlorate solution comprises sodium chlorate and sodium chloride, wherein the concentration of the sodium chlorate is 7-10 mas%, and the concentration of the sodium chloride is 20-27 mas%.
Preferably, the solid phase in step 12) includes calcium sulfate and calcium sulfite, and the solid phase is subjected to oxidation treatment to obtain gypsum.
Preferably, the chlorate solution in the step 2) is subjected to a contact reaction with the flue gas of the power plant boiler to obtain a solution of chloride, chlorate, sulfate and nitrate, and the solution is subjected to spray evaporation to separate out miscellaneous salts in the solution to obtain a solution with less impurities, and the solution with less impurities is used for waste solid treatment or is discharged to a wastewater treatment process for treatment. The miscellaneous salt includes chloride, chlorate, sulfate, and nitrate.
Preferably, the tower kettle of the desulfurization and denitrification tower in the step 2) is connected with the top of the desulfurization and denitrification tower, the tower kettle liquid of the desulfurization and denitrification tower is introduced to the top of the desulfurization and denitrification tower to be used as the leacheate of the power plant boiler flue gas introduced into the desulfurization and denitrification tower, and the concentration of sodium chlorate in the tower kettle liquid of the desulfurization and denitrification tower is controlled to be 1-10 mas%.
The invention also provides a system for recycling waste slurry obtained by flue gas desulfurization of the power plant boiler and denitration of flue gas of the power plant boiler, which comprises the following steps:
the chlorate preparation device is used for preparing chlorate solution by taking waste slurry obtained by flue gas desulfurization of a power plant boiler as a raw material;
and the desulfurization and denitrification tower is connected with the chlorate preparation device, and the chlorate solution and the power plant boiler flue gas are introduced into the desulfurization and denitrification tower for contact reaction to remove the nitrogen oxide and the residual sulfur oxide in the power plant boiler flue gas.
Preferably, the chlorate production plant comprises:
the neutralization tank is used for introducing waste slurry obtained by power plant boiler flue gas desulfurization into the neutralization tank, and adding alkali liquor to adjust the waste slurry to be neutral;
the solid-liquid separator is connected with the neutralization tank and is used for carrying out solid-liquid separation to respectively obtain a separated solid-phase substance and a separated liquid-phase substance; the solid-liquid separator is a filter press or a vacuum filter.
The electrolytic cell is connected with the solid-liquid separator and is used for electrolyzing the introduced liquid phase substance to respectively obtain separated chlorine and alkali solution;
and the absorption tower is connected with the electrolytic cell, and chlorine and alkali solution are mixed and react in the absorption tower to obtain the chlorate solution.
Preferably, the chlorate production plant further comprises:
the first concentrator is arranged between the solid-liquid separator and the electrolytic cell, is respectively connected with the solid-liquid separator and the electrolytic cell, and is used for concentrating the liquid phase substance.
Preferably, the first concentrator is a first evaporator or a first ionic membrane separator. And simultaneously obtaining dischargeable purified water separated by the first ionic membrane separator. The concentration of the chloride ions in the dischargeable purified water is less than 1000 mg/L.
Preferably, the chlorate production plant further comprises:
and the second concentrator is arranged between the electrolytic cell and the absorption tower, is respectively connected with the electrolytic cell and the absorption tower, and is used for concentrating the alkali solution.
Preferably, the second concentrator is a second evaporator or a second ionic membrane separator.
Preferably, the system for recycling the waste slurry obtained by the flue gas desulfurization of the power plant boiler and denitrating the flue gas of the power plant boiler further comprises a desalter, wherein the desalter is arranged between the absorption tower and the desulfurization and denitrification tower, the desalter is respectively connected with the absorption tower and the desulfurization and denitrification tower, and the desalter is used for removing chloride in a chlorate solution through cooling crystallization.
Preferably, the system for recycling the waste slurry obtained by flue gas desulfurization of the power plant boiler and denitration of flue gas of the power plant boiler further comprises:
and the spray evaporator is connected with the desulfurization and denitrification tower and is used for carrying out spray evaporation on the solution of chloride, chlorate, sulfate and nitrate to separate out miscellaneous salts in the filtrate, wherein the miscellaneous salts comprise chloride, chlorate, sulfate and nitrate to obtain the solution with less impurities.
Preferably, the system for recycling the waste slurry obtained by the flue gas desulfurization of the power plant boiler and denitrating the flue gas of the power plant boiler further comprises a circulating pump, an inlet of the circulating pump is connected with a tower kettle of the desulfurization and denitrification tower, an outlet of the circulating pump is connected with the top of the desulfurization and denitrification tower, and the circulating pump pumps the tower kettle liquid of the desulfurization and denitrification tower into the top of the desulfurization and denitrification tower to be used as the leacheate for introducing the flue gas of the power plant boiler into the desulfurization and denitrification tower.
According to the method and the system for recycling the waste slurry obtained by the flue gas desulfurization of the power plant boiler and the flue gas denitration of the power plant boiler, the flue gas filtered by the power plant is subjected to desulfurization and denitration, the waste slurry obtained by the flue gas desulfurization of the power plant boiler is recycled, chlorine in the waste slurry is recycled and converted into chlorate, the environmental pollution is avoided, the hidden danger of secondary pollution is reduced, and the cost for treating the flue gas of the power plant boiler is reduced.
Drawings
Fig. 1 is a schematic structural diagram of a system for recycling waste slurry obtained by desulfurizing flue gas of a power plant boiler and denitrating flue gas of the power plant boiler in embodiment 2 of the present invention.
In the figure: 1-a neutralization tank; 2-a solid-liquid separator; 3-a first concentrator; 4-an electrolytic cell; 5-a cathode; 6-an anode; 7-a second concentrator; 8-an absorption tower; 9-a desalter; 10-a desulfurization and denitrification tower; 11-a circulation pump; 12-crystal separator.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Example 1
The embodiment provides a method for recovering waste slurry obtained by flue gas desulfurization of a power plant boiler and flue gas of the power plant boiler, which comprises the following steps:
1) preparing a chlorate solution by taking waste slurry obtained by power plant boiler flue gas desulfurization as a raw material;
2) and carrying out contact reaction on the chlorate solution and the flue gas of the power plant boiler in a desulfurization and denitrification tower to remove the nitrogen oxide and the residual sulfur oxide in the flue gas of the power plant boiler.
This embodiment still provides a system of useless thick liquid recycle that power boiler flue gas desulfurization obtained and power boiler flue gas denitration, includes:
the chlorate preparation device is used for preparing chlorate solution by taking waste slurry obtained by flue gas desulfurization of a power plant boiler as a raw material;
and the desulfurization and denitrification tower is connected with the chlorate preparation device, and the chlorate solution and the power plant boiler flue gas are introduced into the desulfurization and denitrification tower for contact reaction to remove the nitrogen oxide and the residual sulfur oxide in the power plant boiler flue gas.
According to the method and the system for recycling the waste slurry obtained by flue gas desulfurization of the power plant boiler and denitration of the flue gas of the power plant boiler, not only is desulfurization and denitration carried out on filtered flue gas of the power plant, but also the waste slurry obtained by flue gas desulfurization of the power plant boiler is recycled, so that chlorine in the waste slurry is recycled and converted into chlorate, the environmental pollution is avoided, the hidden danger of secondary pollution is reduced, and the cost for treating flue gas of the power plant boiler is reduced.
Example 2
As shown in fig. 1, this embodiment provides a system for waste slurry recycle and power plant boiler flue gas denitration that power plant boiler flue gas desulfurization obtained, includes:
the chlorate preparation device is used for preparing chlorate solution by taking waste slurry obtained by flue gas desulfurization of a power plant boiler as a raw material. The chlorate preparation facilities include:
the neutralizing tank 1 is used for introducing waste slurry obtained by power plant boiler flue gas desulfurization into the neutralizing tank, and adding alkali liquor to adjust the waste slurry to be neutral;
the solid-liquid separator 2 is connected with the neutralization tank 1, and the solid-liquid separator 2 is used for carrying out solid-liquid separation to respectively obtain a separated solid phase substance and a separated liquid phase substance; the solid-liquid separator 2 is a filter press or a vacuum filter. Specifically, the solid-liquid separator 2 in this embodiment is a vacuum filter.
The first concentrator 3 is arranged between the solid-liquid separator 2 and the electrolytic cell 4, the first concentrator 3 is respectively connected with the solid-liquid separator 2 and the electrolytic cell 4, and the first concentrator 3 is used for concentrating the liquid phase. The first concentrator 3 is a first evaporator or a first ionic membrane separator. Specifically, the first concentrator 3 in this embodiment is a first ion membrane separator. The first concentrator 3 is a first ion membrane separator because of the low concentration of ions in the liquid phase.
The electrolytic cell 4 is connected with the first concentrator 3, and the electrolytic cell 4 is used for electrolyzing the introduced liquid phase substance to respectively obtain separated chlorine and alkali solution;
and the second concentrator 7 is arranged between the electrolytic cell 4 and the absorption tower 8, the second concentrator 7 is respectively connected with the electrolytic cell 4 and the absorption tower 8, and the second concentrator 7 is used for concentrating the alkaline solution. The second concentrator 7 is a second evaporator or a second ionic membrane separator. Specifically, the second concentrator 7 in the present embodiment is a second evaporator. The second concentrator 7 is a second evaporator due to the higher concentration of the alkali solution.
And an absorption tower 8 connected to the second concentrator 7, wherein the chlorine gas and the alkali solution are mixed and reacted in the absorption tower 8 to obtain a chlorate solution.
The system of useless thick liquid recycle and power plant's boiler flue gas denitration that power plant's boiler flue gas desulfurization obtained in this embodiment still includes: and the desalter 9, the desalter 9 is arranged between the absorption tower 8 and the desulfurization and denitrification tower 10, the desalter 9 is respectively connected with the absorption tower 8 and the desulfurization and denitrification tower 10, and the desalter 9 is used for removing chloride in chlorate solution through cooling crystallization.
The system of useless thick liquid recycle and power plant's boiler flue gas denitration that power plant's boiler flue gas desulfurization obtained in this embodiment includes: the desulfurization and denitrification tower 10 is connected with the chlorate preparation device, and the chlorate solution and the flue gas of the power plant boiler are introduced into the desulfurization and denitrification tower 10 to carry out contact reaction so as to remove nitrogen oxides and sulfur oxides in the flue gas of the power plant boiler.
The system of useless thick liquid recycle and power plant's boiler flue gas denitration that power plant's boiler flue gas desulfurization obtained in this embodiment still includes: circulating pump 11, circulating pump 11's entry and the tower cauldron of SOx/NOx control tower 10 are connected, and circulating pump 11's export is connected with the top of the tower of SOx/NOx control tower 10, and circulating pump 11 is used as the leacheate that lets in the power boiler flue gas in SOx/NOx control tower 10 to the top of the tower of SOx/NOx control tower 10 with the tower cauldron liquid pump of SOx/NOx control tower 10.
The system for recycling the waste slurry obtained by the flue gas desulfurization of the power plant boiler and the flue gas denitration of the power plant boiler in the embodiment further comprises a spray evaporator 12 connected with the desulfurization and denitration tower 10, wherein the spray evaporator 12 is used for performing spray evaporation on a solution of chloride, chlorate, sulfate and nitrate to separate miscellaneous salts in filtrate, and the miscellaneous salts comprise the chloride, the chlorate, the sulfate and the nitrate to obtain a solution with less impurities.
In this embodiment, the waste slurry that power boiler flue gas desulfurization obtained includes: 8-13 mas% of gypsum, 0.1-0.5 mas% of calcium carbonate, 0.5-2 mas% of inert impurities, 1-3 mas% of fly ash, 1-4 mas% of soluble salt and 73.5-86.4 mas% of water, wherein the content of chloride ions is 5000-30000 ppm.
The power plant boiler flue gas includes: solid-phase soot and gas-phase substances, the content of soot in the flue gas is 25-35 mas%. The content of sulfur oxide in the gas phase is 1500-3The content of nitrogen oxide is 750-900mg/Nm3
The embodiment provides a method for recovering waste slurry obtained by flue gas desulfurization of a power plant boiler and flue gas of the power plant boiler, which comprises the following steps:
1) waste slurry obtained by power plant boiler flue gas desulfurization is introduced into the neutralization tank 1, and SO in the flue gas2、SO3Dissolving in water to form H2SO3、H2SO4Adding alkali liquor into the waste slurry in the neutralization tank 1, and adjusting to be neutral H2SO4+NaOH=Na2SO4+H2O、H2SO3+NaOH=Na2SO3+H2O; specifically, the alkali solution in this embodiment is a sodium hydroxide solution. The liquid phase includes chloride ion, calcium ion, sulfate ion, and sodium ion.
2) Conveying the neutral waste slurry into a vacuum filter through a conveying belt for solid-liquid separation to respectively obtain separated solid-phase substances and liquid-phase substances; the solid phase comprises calcium sulfate and calcium sulfite, and the gypsum is obtained by oxidizing the solid phase.
3) The liquid phase substance is introduced into a first ionic membrane separator to be concentrated until the concentration of chloride ions is 50g/L, water molecules in the liquid phase substance can pass through an ionic membrane in the first ionic membrane separator, the chloride ions, sodium ions, sulfate ions and calcium ions are blocked at one side of the ionic membrane, the concentrated liquid phase substance is a high-concentration mixed salt ion solution, simultaneously dischargeable purified water separated by the first ionic membrane separator is obtained, the concentration of the chloride ions in the dischargeable purified water is less than 50ppm, and the purified water can be reused.
4) Feeding the concentrated liquid phase substance into an electrolytic cell 4 for electrolysis to respectively obtain separated chlorine and alkali solution; the electrolytic cell 4 comprises a cathode 5, an anode 6 and an intermediate ionic membrane separator thereof.
On the electrodes, the discharge sequence on the anode 6 is: au coating3+>Ag+>Hg2+>Cu2+>Pb2+>Fe2+>Zn2+>H+>Al3+>Mg2+>Na+>Ca2+>K+(ii) a The discharge sequence on the cathode 5 is: s2->I->Br->Cl->OH->Containing oxygen acid radicals, thereby chlorine ions at the anode 6 of the electrolysis apparatusSub-discharging to generate chlorine; the hydrogen ions on the cathode 5 are discharged to generate hydrogen, and the hydrogen is communicated to a hydrogen storage tank to be stored. Meanwhile, strong alkaline electrolyte is obtained at the cathode 5 of the electrolysis device, and the main components of the electrolyte are sodium hydroxide and calcium hydroxide.
The chlorine element in the waste slurry obtained by the flue gas desulfurization of the power plant boiler is recycled, so that the environmental pollution is avoided, and meanwhile, the byproduct sodium chloride is a low-cost raw material for the electrolysis reaction.
5) And (3) introducing the electrolyte in the cathode 5 into a second evaporator, and concentrating the alkali solution in the electrolyte to 30 mas%.
6) The chlorine and the concentrated alkali solution are in countercurrent contact reaction in an absorption tower 8 to obtain chlorate solution. Specifically, the temperature of the mixing reaction was 70 ℃. The sodium chlorate is prepared by the reaction of electrolytic chlorine and hot sodium hydroxide, the process is simple, and the production cost is low.
Absorbing chlorine gas by using hot concentrated alkali solution to generate a sodium chlorate and sodium chloride mixed solution, wherein the mole ratio of sodium chlorate to sodium chloride in the mixed solution is 1:6 after absorption is finished, sodium chloride is continuously formed along with the generation of sodium chlorate in the absorption process, and when the amount of sodium chloride in the mixed solution exceeds the saturated solubility, the sodium chloride is separated out to form crystals; the absorption tower 8 is a filler absorption tower 8, the filler form comprises pall rings and Raschig rings, the top of the absorption tower 8 is provided with an absorption liquid spraying mechanism, and hot concentrated alkali liquor is uniformly distributed through the spraying mechanism and then is contacted with chlorine.
7) The chlorate solution is passed to a desalter 9 for cooling and crystallization to remove chloride in the chlorate solution. The sodium chlorate solution comprises sodium chlorate and sodium chloride, wherein the concentration of the sodium chlorate is 7-10 mas%, and the concentration of the sodium chloride is 20-27 mas%. Specifically, in this example, sodium chloride solution in sodium chlorate solution was removed by cooling crystallization, the solubility of sodium chlorate was 79.6g/100g water at 10 ℃ and the solubility of sodium chloride was 35.8g/100g water, and in the cooling crystallization process, when the concentration of sodium chlorate in the solution reached 20 mas%, 70 mas% or more of sodium chloride was precipitated to form sodium chloride solid. Specifically, in the sodium chlorate solution in this example, NaClO3Concentration 10 mas% and NaCl concentrationThe degree is 27.46 mas%, and the chloride in the chlorate solution is removed by cooling crystallization, thereby being beneficial to the reaction of nitric oxide in the boiler flue gas of the subsequent power plant and sodium chlorate to generate sodium chloride.
8) The chlorate solution without chloride and the flue gas of the power plant boiler are subjected to contact reaction in a desulfurization and denitrification tower 10 to remove the nitrogen oxide and the residual sulfur oxide in the flue gas of the power plant boiler, and the flue gas without the nitrogen oxide and the sulfur oxide can be directly discharged through the top of the desulfurization and denitrification tower 10. The sulfur oxide content in the flue gas at the top of the desulfurization and denitrification tower 10 is less than 50ppm, and the nitrogen oxide content is less than 50 ppm. And (3) carrying out contact reaction on the chlorate solution and the flue gas of the power plant boiler to obtain a solution of chloride, chlorate, sulfate and nitrate, and using the filtrate as the electrolysis raw material in the step 13), thereby realizing the recycling of chlorine, avoiding secondary pollution and reducing the cost. Specifically, in this embodiment, after the contact reaction occurs in the desulfurization and denitrification tower 10, a solution of sodium chloride, sodium chlorate, sodium sulfate, and sodium nitrate is obtained, and the solution is subjected to spray evaporation by the spray evaporator 12 to separate out impurity salts in the solution, so as to obtain a solution with less impurities, and the solution with less impurities is used for waste solid treatment or is discharged to a wastewater treatment process for treatment. The miscellaneous salt includes chloride, chlorate, sulfate, and nitrate.
The tower kettle of the desulfurization and denitrification tower 10 is connected with the top of the desulfurization and denitrification tower 10, the tower kettle liquid of the desulfurization and denitrification tower 10 is introduced to the top of the desulfurization and denitrification tower 10 to be used as the leacheate of the power plant boiler flue gas introduced into the desulfurization and denitrification tower 10, and the concentration of sodium chlorate in the tower kettle liquid of the desulfurization and denitrification tower 10 is controlled to be 1-10 mas%.
By the method, the flue gas discharged by the invention reaches the national exhaust emission standard, and the full-working-condition denitration of the boiler flue gas in the thermal power plant is realized.
In the contact reaction process, chlorate solution and nitric oxide and oxysulfide in the flue gas are subjected to gas-liquid contact reaction, the low-valence nitric oxide in the flue gas is oxidized into high-valence nitric oxide, the low-valence oxysulfide is oxidized into high-valence oxysulfide, chlorate ions are reduced into low-valence chloride ions, and the high-valence nitric oxide, the oxysulfide and sodium hydroxide are subjected to neutralization reaction to generate corresponding salts. The concentration range of the chlorate absorption liquid is 1-10 mas%, and the optimal absorption effect can be achieved through circulating absorption; and when the concentration of chlorate in the absorption liquid is lower than 1 mas%, conveying the absorption liquid to a subsequent recovery system for treatment.
According to the method and the system for recycling the waste slurry obtained by flue gas desulfurization of the power plant boiler and denitration of the flue gas of the power plant boiler, not only is desulfurization and denitration carried out on filtered flue gas of the power plant, but also the waste slurry obtained by flue gas desulfurization of the power plant boiler is recycled, so that chlorine in the waste slurry is recycled and converted into chlorate, the environmental pollution is avoided, the hidden danger of secondary pollution is reduced, and the cost for treating flue gas of the power plant boiler is reduced.
Example 3
This embodiment provides a method for recycling waste slurry obtained by desulfurizing flue gas of a power plant boiler and denitrating flue gas of a power plant boiler, which is performed by using the system in embodiment 2, and the differences from the method in embodiment 2 are as follows:
and 3) introducing the liquid phase substance into a first ion membrane separator in the step 3) for concentrating until the concentration of chloride ions is 20 g/L.
And 5) introducing the electrolyte in the cathode 5 into a second evaporator, and concentrating the alkali solution in the electrolyte to 50 mas%.
The temperature of the mixing reaction in step 6) was 80 ℃.
Example 4
This embodiment provides a method for recycling waste slurry obtained by desulfurizing flue gas of a power plant boiler and denitrating flue gas of a power plant boiler, which is performed by using the system in embodiment 2, and the differences from the method in embodiment 2 are as follows:
and 3) introducing the liquid phase substance into a first ion membrane separator in the step 3) for concentrating until the concentration of chloride ions is 100 g/L.
And 5) introducing the electrolyte in the cathode 5 into a second evaporator, and concentrating the alkali solution in the electrolyte to 40 mas%.
The temperature of the mixing reaction in step 6) was 60 ℃.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims (15)

1. A method for recycling waste slurry obtained by power plant boiler flue gas desulfurization and denitrating power plant boiler flue gas is characterized by comprising the following steps:
1) preparing a chlorate solution by taking waste slurry obtained by power plant boiler flue gas desulfurization as a raw material;
2) and carrying out contact reaction on the chlorate solution and the flue gas of the power plant boiler in a denitration tower to remove the nitrogen oxide and the residual sulfur oxide in the flue gas of the power plant boiler.
2. The method for recycling the waste slurry obtained by desulfurizing the flue gas of the power plant boiler and denitrating the flue gas of the power plant boiler according to claim 1, wherein the step 1) is specifically as follows:
11) adding alkali liquor into waste slurry obtained by power plant boiler flue gas desulfurization, and adjusting to be neutral;
12) performing solid-liquid separation to obtain separated solid phase substance and liquid phase substance;
13) electrolyzing the liquid phase to respectively obtain separated chlorine and alkali solution;
14) mixing chlorine gas and alkali solution for reaction to obtain the chlorate solution.
3. The method for recycling the waste slurry obtained by desulfurizing the flue gas of the power plant boiler and denitrating the flue gas of the power plant boiler according to claim 2, wherein a step m) is further included between the step 12) and the step 13): concentrating the liquid phase until the concentration of chloride ions is 20-100 g/L.
4. The method for recycling the waste slurry obtained by desulfurizing the flue gas of the power plant boiler and denitrating the flue gas of the power plant boiler according to claim 2, wherein a step n) is further included between the step 13) and the step 14): and concentrating the alkali solution to 30-50 mas%.
5. The method for recycling the waste slurry obtained by desulfurizing the flue gas of the power plant boiler and denitrating the flue gas of the power plant boiler according to claim 2, wherein a step j) is further included between the step 1) and the step 2): the chloride in the chlorate solution is removed by cooling crystallization.
6. The method for recycling the waste slurry obtained by desulfurizing the flue gas of the power plant boiler and denitrating the flue gas of the power plant boiler according to claim 2, wherein the solid phase in the step 12) comprises calcium sulfate and calcium sulfite, and the solid phase is subjected to oxidation treatment to obtain gypsum.
7. The method for recycling the waste slurry obtained by desulfurizing the flue gas of the power plant boiler and denitrating the flue gas of the power plant boiler according to any one of claims 2 to 6, wherein the chlorate solution in the step 2) is in contact reaction with the flue gas of the power plant boiler to obtain a solution of chloride, chlorate, sulfate and nitrate, and the solution is subjected to spray evaporation to separate out miscellaneous salts in the filtrate, wherein the miscellaneous salts comprise chloride, chlorate, sulfate and nitrate, so that a solution with less impurities is obtained.
8. The method for recycling the waste slurry obtained by the desulfurization of the power plant boiler flue gas and the denitration of the power plant boiler flue gas according to any one of claims 1 to 6, wherein the tower kettle of the desulfurization and denitration tower in the step 2) is connected with the top of the desulfurization and denitration tower, the tower kettle liquid of the desulfurization and denitration tower is introduced to the top of the desulfurization and denitration tower to be used as the leacheate for the power plant boiler flue gas introduced into the desulfurization and denitration tower, and the concentration of sodium chlorate in the tower kettle liquid of the desulfurization and denitration tower is controlled to be 1 to 10 mas%.
9. The utility model provides a system for useless thick liquid recycle that power boiler flue gas desulfurization obtained and power boiler flue gas denitration, its characterized in that includes:
the chlorate preparation device is used for preparing chlorate solution by taking waste slurry obtained by flue gas desulfurization of a power plant boiler as a raw material;
and the desulfurization and denitrification tower is connected with the chlorate preparation device, and the chlorate solution and the power plant boiler flue gas are introduced into the desulfurization and denitrification tower for contact reaction to remove the nitrogen oxide and the residual sulfur oxide in the power plant boiler flue gas.
10. The system for recycling the waste slurry obtained by desulfurizing the flue gas of the power plant boiler and denitrating the flue gas of the power plant boiler according to claim 9, wherein the chlorate preparing device comprises:
the neutralization tank is used for introducing waste slurry obtained by power plant boiler flue gas desulfurization into the neutralization tank, and adding alkali liquor to adjust the waste slurry to be neutral;
the solid-liquid separator is connected with the neutralization tank and is used for carrying out solid-liquid separation to respectively obtain a separated solid-phase substance and a separated liquid-phase substance;
the electrolytic cell is connected with the solid-liquid separator and is used for electrolyzing the introduced liquid phase substance to respectively obtain separated chlorine and alkali solution;
and the absorption tower is connected with the electrolytic cell, and chlorine and alkali solution are mixed and react in the absorption tower to obtain the chlorate solution.
11. The system for recycling the waste slurry obtained by desulfurizing the flue gas of the power plant boiler and denitrating the flue gas of the power plant boiler according to claim 10, wherein the chlorate preparing device further comprises:
the first concentrator is arranged between the solid-liquid separator and the electrolytic cell, is respectively connected with the solid-liquid separator and the electrolytic cell, and is used for concentrating the liquid phase substance.
12. The system for recycling the waste slurry obtained by desulfurizing the flue gas of the power plant boiler and denitrating the flue gas of the power plant boiler according to claim 10, wherein the chlorate preparing device further comprises:
and the second concentrator is arranged between the electrolytic cell and the absorption tower, is respectively connected with the electrolytic cell and the absorption tower, and is used for concentrating the alkali solution.
13. The system for recycling the waste slurry obtained by desulfurizing the flue gas of the power plant boiler and denitrating the flue gas of the power plant boiler according to claim 10, further comprising a desalter, wherein the desalter is arranged between the absorption tower and the desulfurization and denitrification tower, the desalter is respectively connected with the absorption tower and the desulfurization and denitrification tower, and the desalter is used for removing chloride in a chlorate solution through cooling crystallization.
14. The system for recycling the waste slurry obtained by desulfurizing the flue gas of the power plant boiler and denitrating the flue gas of the power plant boiler according to any one of claims 10 to 13, further comprising:
and the spray evaporator is connected with the desulfurization and denitrification tower and is used for carrying out spray evaporation on the solution of chloride, chlorate, sulfate and nitrate to separate out miscellaneous salts in the filtrate, wherein the miscellaneous salts comprise chloride, chlorate, sulfate and nitrate to obtain the solution with less impurities.
15. The system for recycling the waste slurry obtained by the flue gas desulfurization of the power plant boiler and the flue gas denitration of the power plant boiler as claimed in any one of claims 9 to 13, further comprising a circulating pump, wherein an inlet of the circulating pump is connected with a tower kettle of the desulfurization and denitration tower, an outlet of the circulating pump is connected with the top of the desulfurization and denitration tower, and the circulating pump pumps the tower kettle liquid of the desulfurization and denitration tower into the top of the desulfurization and denitration tower to be used as a leacheate for the flue gas of the power plant boiler introduced into the desulfurization and denitration tower.
CN201811308166.4A 2018-11-05 2018-11-05 Method and system for recycling waste slurry obtained by power plant boiler flue gas desulfurization and denitrating power plant boiler flue gas Pending CN111135692A (en)

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