Wet process combined desulfurization and denitrification carbon sequestration device and method

Abstract

According to the wet-process combined desulfurization, denitrification and carbon sequestration device and method, a conventional stepped independent removal mode is adopted, desulfurization, denitrification and carbon sequestration operations are sequentially carried out, SO2 generated by an original limestone / gypsum wet-process desulfurization technology is eliminated by developing a stricter SO2 removal technology, nitric oxide in flue gas enters a water body by adopting a two-step method of firstly oxidizing and then absorbing, and the desulfurization and denitrification carbon sequestration is realized. Total nitrogen in the water body is removed by a biological denitrification technology, so that harmless nitrogen is generated and discharged; carbon dioxide in flue gas enters a water body by adopting an alkali liquor absorption method, and then calcium ions are subjected to chemical precipitation to generate calcium carbonate to solidify the carbon dioxide. The removal rate of pollutants in the flue gas can be controlled by controlling the concentration of the sodium hypochlorite solution, the concentration of sodium hydroxide and the liquid-gas ratio, and low energy consumption and low consumption are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental governance, and specifically relates to a wet combined desulfurization, denitrification and carbon fixation device and method. Background Art

[0002] my country's energy and electricity demand is growing rapidly. Because my country's energy structure has long been dominated by coal, fossil fuel consumption is increasing. According to relevant data from the National Bureau of Statistics, my country's coal consumption accounted for 56.0% of total energy consumption in 2021. Considering the uncertain international situation, my country's coal energy dominance is unlikely to change in the future. As an important fuel for thermal power plants, coal will emit a large amount of flue gas during its combustion process, and the flue gas is accompanied by a high concentration of SO 2 , NO and a large amount of CO 2 , where SO 2 , NO can cause equipment corrosion or form acid rain, while CO 2 It will indirectly cause natural disasters such as global warming and glacier melting. Therefore, it is necessary to remove SO from the flue gas of coal-fired power plants. 2 , NO and CO 2 It is extremely important to prevent and control environmental pollution and respond to climate change.

[0003] Tail flue gas purification is the most commercialized industrial flue gas treatment method. Post-combustion flue gas desulfurization (FGD) technology can be divided into three categories: wet, semi-dry and dry. Among them, wet desulfurization is the most widely used, including limestone / gypsum method, magnesium oxide method and seawater washing method, and limestone / gypsum wet desulfurization technology occupies the mainstream. Post-combustion flue gas denitrification technology mainly includes SNCR non-selective reduction method and SCR selective catalytic reduction method, and SCR denitrification technology with medium-high temperature and high dust layout occupies the mainstream. Post-combustion flue gas decarbonization (PCC) technology mainly includes absorption separation method, adsorption separation method, membrane separation method and low-temperature separation method, and is currently in the trial demonstration stage. Existing studies have shown that coupling the desulfurization system based on post-combustion purification technology with the decarbonization system to achieve synergistic removal has great application prospects, and wet chemical treatment methods have become the first choice for this type of synergistic removal technology due to their advantages of high removal efficiency, wide application range and strong flexibility, but the technology of coupling wet desulfurization, denitrification and decarbonization systems to achieve complete purification of flue gas has not been reported. At the same time, the current mainstream limestone / gypsum wet flue gas desulfurization technology is effective in removing SO 2 At the same time, a large amount of CO 2 , which is not conducive to CO 2 Emission reduction: The mainstream flue gas SCR technology for denitrification will produce a large amount of waste catalysts and other adverse effects. In addition, when SCR denitrification technology uses urea as a reducing agent, carbon dioxide will be produced when urea is decomposed, which removes nitrogen oxides but increases carbon dioxide emissions. Summary of the invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a wet combined desulfurization, denitrification and carbon fixation device and method, which is developed from the following aspects:

[0005] 1. Use the conventional cascaded separate removal method to carry out desulfurization, denitrification and carbon fixation operations in sequence, and eliminate the CO2 generated by the original limestone / gypsum wet desulfurization technology by developing more stringent SO2 removal technology;

[0006] Second, the two-step method of first oxidation and then absorption is adopted to allow nitrogen oxides in the flue gas to enter the water body, and then the total nitrogen in the water body is removed by biological denitrification technology to generate harmless nitrogen gas emissions without consuming reducing agents (liquid ammonia, urea, etc.);

[0007] 3. Use alkali solution absorption method to make carbon dioxide in flue gas enter water body, and then use calcium ions to chemically precipitate calcium carbonate to solidify carbon dioxide;

[0008] 4. Recycle the oxidation absorption liquid used for desulfurization and denitrification and the alkaline absorption liquid used for carbon fixation to reduce material consumption and lower operating costs;

[0009] 5. Collect and reuse hydrogen, a by-product of the production process of the oxidation absorption liquid used in desulfurization and denitrification, to reduce energy consumption.

[0010] This is achieved specifically through the following technical solutions:

[0011] Wet combined desulfurization, denitrification and carbon fixation device, the device includes:

[0012] Oxidation absorption tower: the bottom of the tower has an oxidation slurry pool, a first dual-fluid atomizing nozzle is arranged above the oxidation slurry pool inside the oxidation absorption tower, a first demister is arranged on the upper part of the oxidation absorption tower, the gas side of the first dual-fluid atomizing nozzle is introduced with compressed air through a pipeline, and the liquid side of the first dual-fluid atomizing nozzle is connected with the oxidation slurry pool through a pipeline; the waste raw flue gas to be treated enters the oxidation absorption tower in two ways, one way is directly introduced into the oxidation absorption tower through a pipeline, and the other way is introduced into the oxidation slurry pool through the first Venturi jet tube and discharged through the bubbling port;

[0013] Alkali liquid absorption tower: the bottom of the tower has an alkali liquid slurry pool, a second double-fluid atomizing nozzle is arranged above the alkali liquid slurry pool inside the alkali liquid absorption tower, a second demister is arranged on the upper part of the alkali liquid absorption tower, the gas side of the second double-fluid atomizing nozzle is connected to a Roots blower through a pipeline, and the liquid side of the second double-fluid atomizing nozzle is connected to the alkali liquid slurry pool through a pipeline; the flue gas treated by the oxidation absorption tower enters the alkali liquid absorption tower through two routes from the top outlet of the oxidation absorption tower through a pipeline, one route is connected to the Roots blower, and the other route enters the alkali liquid slurry pool through the second Venturi jet tube and is discharged through the bubbling port;

[0014] Oxidation and sulfur fixation integrated device: used for the preparation and recycling of oxidation absorption liquid, connected to the calcium sulfate filter press and oxidation slurry tank through pipelines;

[0015] Carbon fixation reaction triple box: used for the preparation and recycling of alkali solution, connected to the calcium carbonate filter press and biochemical reaction device through pipelines.

[0016] Furthermore, a first reaction tank, a second reaction tank, a third reaction tank and a chlorine-making tank with a built-in chlorine-making electrode are sequentially arranged in the integrated oxidation and sulfur-fixing device. The bottom of the integrated oxidation and sulfur-fixing device is connected to the calcium sulfate filter press through a pipeline and a calcium sulfate slurry discharge pump arranged on the pipeline. The chlorine-making tank is connected to the first venturi jet tube through a pipeline and an oxidation absorption liquid supply pump arranged on the pipeline; the first reaction tank is connected to the oxidation slurry tank through a pipeline and a sodium sulfate slurry discharge pump arranged on the pipeline. A first agitator and a calcium hydroxide addition channel are also arranged in the first reaction tank.

[0017] Furthermore, the carbon fixation reaction triple box includes a reaction tank A, a reaction tank B, a reaction tank C and an alkaline solution tank which are arranged in sequence. The bottom of the carbon fixation reaction triple box is connected to a calcium carbonate filter press through a pipeline provided with a calcium carbonate slurry discharge pump. The upper end of the reaction tank A is connected to the calcium carbonate filter press through a pipeline, and is provided with a calcium hydroxide addition pipeline and a second agitator. The biochemical reaction device pumps the biochemical reaction clear liquid into the reaction tank A through a biochemical reaction clear liquid discharge pump arranged on the pipeline. The alkaline slurry tank is connected to the second Venturi jet tube through a pipeline provided with an alkaline absorption liquid supply pump.

[0018] Furthermore, the waste-containing raw flue gas contains sulfur dioxide, nitrogen monoxide and carbon dioxide.

[0019] A method for wet combined desulfurization, denitrification and carbon fixation using the above device comprises the following steps:

[0020] 1) Sodium chloride solution is introduced into the chlorine production pool in the integrated oxidation and sulfur fixation device, and the chlorine production electrode is energized to produce a sodium hypochlorite solution with a concentration of 0.2-0.8%, and the hydrogen generated is collected and discharged harmlessly from the discharge port or recovered to support combustion;

[0021] 2) The sodium hypochlorite solution prepared in step 1) is used as an absorption liquid to countercurrently contact with the original flue gas, absorb sulfur dioxide in the original flue gas, form a rich liquid containing sodium sulfate, and enter the oxidation slurry pool. At the same time, the nitrogen monoxide in the original flue gas is oxidized into nitrogen dioxide and the nitrogen dioxide and the carbon dioxide in the original flue gas are separated by gas and liquid in the first demister, and then the gas enters the alkali liquid absorption tower;

[0022] 3) In the alkali solution absorption tower, sodium hydroxide solution is used as the absorption liquid to contact with the original flue gas in countercurrent. The sodium hydroxide solution reacts with the original flue gas to absorb nitrogen dioxide and carbon dioxide, forming a rich liquid containing sodium nitrate, sodium nitrite and sodium carbonate, which enters the alkali solution slurry pool. The pollutants in the flue gas are treated and discharged.

[0023] Furthermore, in step 2), the rich liquid of sodium sulfate in the oxidation slurry pool is pumped into the first reaction pool of the oxidation and sulfur-fixing integrated device through a sodium sulfate slurry discharge pump, reacts with the added calcium hydroxide in the first reaction pool to generate calcium sulfate precipitate, and the calcium sulfate precipitate is transported to a calcium sulfate filter press through a calcium sulfate slurry discharge pump for solid-liquid separation, the solid is discharged or reused to replace natural gypsum, and the filtrate is reused in the first reaction pool.

[0024] Furthermore, the supernatant produced by the reaction in the first reaction tank enters the second reaction tank and the third reaction tank from the overflow port in sequence to further precipitate solid matter, and the precipitation effect is further enhanced by the first inclined tube arranged in the second reaction tank and the first sand filter arranged in the third reaction tank. Finally, the supernatant containing sodium chloride enters the chlorine production tank for repeated utilization to prepare sodium hypochlorite solution.

[0025] Furthermore, in step 3), the rich liquid containing sodium nitrate, sodium nitrite and sodium carbonate entering the alkaline liquid slurry pool is pumped to the biochemical reaction device through the sodium carbonate slurry discharge pump for reaction to remove nitrate, and the generated nitrogen and oxygen are discharged. The rich liquid rich in sodium carbonate is transported to the reaction tank A of the carbon fixation reaction triple box through the biochemical reaction clear liquid discharge pump for further treatment.

[0026] Furthermore, calcium hydroxide is added to reaction tank A to react with sodium carbonate to generate calcium carbonate precipitate, and is transported to a calcium carbonate filter press by a calcium carbonate slurry discharge pump for solid-liquid separation, solids are discharged or reused to replace natural limestone, and the filtrate is recycled to reaction tank A, and the supernatant enters reaction tank B and reaction tank C in sequence through the overflow port to further precipitate solid matter, and the precipitation effect is enhanced by a second inclined tube arranged in reaction tank B and a second sand filter arranged in reaction tank C, and finally the supernatant containing sodium hydroxide enters the alkali liquid pool and is recycled to the alkali liquid absorption tower through an alkaline absorption liquid supply pump.

[0027] The biological denitrification of the present invention is used for flue gas denitrification treatment, and the wet carbon fixation is used for flue gas carbon dioxide emission reduction treatment. Both the oxidant and the absorbent can be recycled, saving costs. Although it is a wet process, there is no wastewater discharge, and the solid by-products can be comprehensively utilized. In principle, the main pollutants in flue gas (SO 2 / NO / CO 2 ) can achieve complete purification. In fact, the removal rate of pollutants in the flue gas can be controlled by controlling the concentration of sodium hypochlorite solution, sodium hydroxide concentration and liquid-gas ratio, achieving low energy consumption and low consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0029] In the figure, 1-oxidation absorption tower, 101-oxidation slurry pool, 102-first dual-fluid atomizing nozzle, 103-first demister, 104-first venturi jet tube, 2-alkali solution absorption tower, 201-alkali solution slurry pool, 202-second dual-fluid atomizing nozzle, 203-second demister, 204-Roots blower, 205-second venturi jet tube, 3-oxidation and sulfur fixation integrated device, 301-first reaction pool, 302-second reaction pool, 303-third reaction pool, 304-chlorine production electrode, 305-chlorine production pool, 306-calcium sulfate slurry discharge pump, 307-oxidation absorption tower, 308-calcium sulfate slurry discharge pump, 309-oxidation absorption tower, 310-alkali solution slurry pool, 311-alkali solution slurry pool, 312-alkali solution slurry pool, 313-alkali solution slurry pool, 314-alkali solution slurry pool, 315-alkali solution slurry pool, 316-alkali solution slurry pool, 317-alkali solution slurry pool, 318-alkali solution slurry pool, 319-alkali solution slurry pool, 320-alkali solution slurry pool, 321-alkali solution slurry pool, 322-alkali solution slurry pool, 323-alkali solution slurry pool, 324-alkali solution slurry pool, 325-alkali solution slurry pool, 326-alkali solution slurry pool, 327-alkali solution slurry pool, 328-alkali solution slurry pool, 3 Liquid collection supply pump, 308-sodium sulfate slurry discharge pump, 309-first agitator, 310-first inclined tube, 311-first sand filter, 4-calcium sulfate filter press, 5-carbon fixation reaction triple box, 501-reaction tank A, 502-reaction tank B, 503-reaction tank C, 504-alkali liquid tank, 505-calcium carbonate slurry discharge pump, 506-second agitator, 507-biochemical reaction clear liquid discharge pump, 508-alkaline absorption liquid supply pump, 509-sodium carbonate slurry preparation pump, 510-second inclined tube, 511-second sand filter, 6-calcium carbonate filter press, 7-biochemical reaction device. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings in order to better understand the technical solution.

[0031] Flue gas flow:

[0032] 1.1 Press Figure 1 In the process, a 5% concentration sodium chloride solution is introduced into the integrated oxidation and sulfur fixation device 3 through the input port;

[0033] 1.2 Power is supplied to make the chlorine-making electrode 304 in the integrated oxidation and sulfur fixation device 3 work and produce a sodium hypochlorite solution, and at the same time, the hydrogen generated thereby is collected and discharged harmlessly from the discharge port or recycled for combustion support;

[0034] 1.3 The sodium hypochlorite solution prepared in step 1.2 is transported to the first venturi jet tube 104 via the oxidation absorption liquid supply pump 307;

[0035] 1.4 The first venturi jet tube 104 absorbs a certain flow of waste flue gas and is connected to the bubbling port of the oxidation absorption tower 1 through the outlet jet port;

[0036] 1.5 After the oxidation absorption liquid is introduced into the oxidation absorption tower 1, the liquid level in the tower is controlled to a height of 2-4 meters;

[0037] 1.6 After the liquid level in the oxidation absorption tower 1 reaches the control value, the input port is opened to allow compressed air to enter the gas side of the first dual-fluid atomizing nozzle 102. The liquid side of the first dual-fluid atomizing nozzle 102 is connected to the oxidation slurry pool 101 at the lower part of the oxidation absorption tower 1, and enters the nozzle by self-priming, and finally forms atomized spray liquid in the tower;

[0038] 1.7 While implementing step 1.1, a 20% concentration sodium hydroxide solution is introduced into the carbon fixation reaction triple box 5 through the input port;

[0039] 1.8 The sodium hydroxide solution added to the carbon fixation reaction triple tank 5 in step 1.7 is transported to the second venturi jet tube 205 through the alkaline absorption liquid supply pump 508;

[0040] 1.9 The second venturi jet tube 205 absorbs a certain flow of waste flue gas and is connected to the bubbling port of the alkali solution absorption tower 2 through the outlet jet port;

[0041] 1.10 After the alkaline absorption liquid is passed into the alkaline liquid absorption tower 2, the liquid level in the tower is controlled to a height of 2-4 meters;

[0042] 1.11 After the liquid level in the alkali liquid absorption tower 2 reaches the control value, the Roots blower 204 is turned on, the inlet of the Roots blower 204 is connected to the top outlet of the oxidation absorption tower 1, the outlet of the Roots blower 204 is connected to the gas side of the second double-fluid atomizing nozzle 202, and the liquid side of the second double-fluid atomizing nozzle 202 is connected to the alkali liquid slurry pool 201 at the bottom of the alkali liquid absorption tower 2, and enters the nozzle by self-priming, and finally forms an atomized spray liquid in the tower;

[0043] 1.12 After steps 1.6-1.11 are completed, the original flue gas containing pollutants (SO2\NO\CO2) is introduced into the air inlet at the lower part of the oxidation absorption tower 1 to enter the tower and contact with the spray liquid in the tower;

[0044] 1.13 The original flue gas and the spray liquid in the oxidation absorption tower 1 undergo gas-liquid contact reaction and then enter the first demister 103 for gas-liquid separation. The flue gas is discharged from the top of the oxidation absorption tower 1 and enters the alkali liquid absorption tower 2 to enter the next flue gas treatment process link;

[0045] 1.14 The flue gas discharged from the top of the oxidation absorption tower 1 enters the alkali solution absorption tower 2 through two paths: one is connected to the air inlet of the Roots blower 204, and the other is connected to the air intake of the second venturi jet tube 205;

[0046] 1.15 The flue gas discharged from the top of the oxidation absorption tower 1 undergoes gas-liquid contact reaction with the spray liquid in the alkali liquid absorption tower 2 and then enters the second demister 203 for gas-liquid separation. The flue gas (clean flue gas) is discharged from the exhaust port at the top of the alkali liquid absorption tower 2.

[0047] Calcium sulfate slurry process

[0048] 1.1 When the salt concentration in the oxidation slurry tank 101 reaches 5000-10000 mg / l, the sodium sulfate slurry discharge pump 308 is started, the pump inlet is connected to the oxidation slurry tank 101, and the pump outlet is connected to the first reaction tank 301 of the oxidation and sulfur fixation integrated device 3;

[0049] 1.2 After the slurry transported by the sodium sulfate slurry discharge pump 308 to the integrated oxidation and sulfur fixation device 3 reaches the first reaction tank 301 of the integrated oxidation and sulfur fixation device 3, calcium hydroxide is added from the upper inlet and the first agitator 309 is started;

[0050] 1.3 After the solid content in the first reaction tank 301 of the integrated oxidation and sulfur fixation device 3 reaches 15-30%, the calcium sulfate slurry discharge pump 306 discharges the slurry to the calcium sulfate filter press 4;

[0051] 1.4 The slurry with low solid content overflowing from the first reaction tank 301 of the oxidation-solidification device 3 enters the second reaction tank 302 of the oxidation-solidification device 3 to further precipitate solid matter, and passes through the first inclined pipe 310 to enhance the precipitation effect;

[0052] 1.5 The slurry with a lower solid content overflowing from the second reaction tank 302 of the oxidation-solidification device 3 enters the third reaction tank 303 of the oxidation-solidification device 3 to further precipitate solid matter, and passes through the first sand filter 311 to make the solid content of the slurry lower than 10 mg / l;

[0053] 1.6 The slurry overflowing from the third reaction tank 303 of the oxidation-solidification device 3 is a sodium chloride solution, which enters the chlorine production tank 305 of the oxidation-solidification device 3 and is prepared into a sodium hypochlorite solution by the chlorine production electrode 304;

[0054] 1.7 The sodium hypochlorite solution produced in the oxidation-solidification integrated device 3 is transported to the first venturi jet tube 104 by the oxidation-absorbing liquid supply pump 307 and then enters the oxidation-absorbing tower 1 to form an oxidation-absorbing liquid circulation;

[0055] 1.8 The calcium sulfate filter press 4 performs solid-liquid separation on the slurry with a solid content of 15-30%, and the separated filtrate is recycled to the first reaction tank 301 of the integrated oxidation and sulfur fixation device 3. The separated solid is calcium sulfate and is discharged from the discharge port or comprehensively utilized.

[0056] Calcium carbonate slurry process:

[0057] 1.1 When the salt concentration in the alkali liquid slurry pool 201 reaches 3000-5000 mg / l, the sodium carbonate slurry discharge pump 509 is started, the pump inlet is connected to the alkali liquid slurry pool 201, and the pump outlet is connected to the biochemical reaction device 7;

[0058] 1.2 The slurry transported to the biochemical reaction device 7 by the sodium carbonate slurry discharge pump 209 undergoes a series of biochemical reactions to remove total nitrogen from the slurry, and the total nitrogen produces nitrogen gas that is harmlessly discharged from the discharge port;

[0059] 1.3 The clear liquid of the biochemical reaction device 7 is discharged by the biochemical reaction clear liquid discharge pump 207 to the reaction tank A501 of the carbon fixation reaction triple box 5;

[0060] 1.4 After the slurry transported to the carbon fixation reaction triple tank 5 by the biochemical reaction clear liquid discharge pump 207 reaches the reaction tank A501 of the device, calcium hydroxide is added from the inlet above the reaction tank A501, and the second agitator 506 is started;

[0061] 1.5 After the solid content of the reaction tank A501 of the carbon fixation reaction triple box 5 reaches 15-30%, the slurry is discharged from the calcium carbonate slurry discharge pump 505 to the calcium carbonate filter press 6;

[0062] 1.6 The slurry with low solid content overflowing from the reaction tank A501 of the carbon fixation reaction triple box 5 enters the reaction tank B502 of the carbon fixation reaction triple box 5 to further precipitate the solid matter, and passes through the second inclined tube 510 to enhance the precipitation effect;

[0063] 1.7 The slurry with a lower solid content overflowing from the reaction tank B502 of the carbon fixation reaction triple box 5 enters the reaction tank C503 of the carbon fixation reaction triple box 5 to further precipitate solid matter, and passes through the second sand filter 511 to make the solid content of the slurry less than 10 mg / l;

[0064] 1.8 The slurry overflowing from the reaction tank C503 of the carbon fixation reaction triple tank 5 is a sodium hydroxide solution and enters the alkali liquid tank 504 of the carbon fixation reaction triple tank 5;

[0065] 1.9 The sodium hydroxide solution in the alkali liquid pool 504 of the carbon fixation reaction triple box 5 is transported to the second venturi jet tube 205 by the alkaline absorption liquid supply pump 508 and then enters the alkali liquid absorption tower 2 to form an alkaline absorption liquid circulation;

[0066] 1.10 The calcium carbonate filter press 6 performs solid-liquid separation on the slurry with a solid content of 15-30%. The separated filtrate is recycled to the reaction tank A501 of the carbon fixation reaction triple box 5. The separated solid is calcium carbonate and is discharged from the discharge port or comprehensively utilized.

[0067] The present invention uses sodium hypochlorite oxidant to absorb SO 2 It also oxidizes NO and uses alkaline absorption liquid to absorb CO 2 The double tower process and the combined method of removing nitrogen oxides by biological denitrification, wherein the concentration of sodium hypochlorite oxidant solution is controlled at 0.2-0.8%, and the liquid-gas ratio is controlled at 2-5; the oxidation absorption tower 1 adopts air atomization to improve the gas-liquid contact effect and oxygenation to promote NO rapid oxidation technology, and the oxidation absorption tower adopts bubbling and spraying oxidation absorption technology at the same time. The present invention is not only applicable to the flue gas purification treatment of coal-fired thermal power plants, but also to the flue gas purification treatment of all kinds of industrial boilers using fossil fuels.

[0068] The working principle of the wet desulfurization, denitrification and carbon fixation of the present invention is as follows:

[0069] The chemical reactions involved are:

[0070] Absorption oxidation reaction:

[0071] Desulfurization: SO 2 +3NaClO+H 2 O→Na 2 SO 4 +NaCl+2HClO ①

[0072] Oxidation: 2NO+2HClO+H 2 O→2NO 2 +H 2 O+2HCl②

[0073] Denitrification / Carbon: 6NaOH+2NO 2 +CO 2 +H 2 O→NaNO 3 +NaNO 2 +2Na 2 CO 3 +4H 2 O③

[0074] Precipitation reaction:

[0075] Desulfate: Na 2 SO 4 +Ca(OH) 2 + 2HCl → CaSO 4 ↓+2NaCl+2H 2 O④

[0076] Decarbonation (carbon fixation): Na 2 CO 3 +Ca(OH) 2 →CaCO 3 ↓+2NaOH⑤

[0077] Biological denitrification reaction:

[0078] N0 3 -→NO 2 -→NO→N 2 O→N 2 ↑+O 2 ↑ ⑥

[0079] NaNO 3 +NaNO 2 +2Na 2 CO 3 +4H 2 O+4CO 2 →6Na 2 CO 3 +4H 2 O+N 2 ↑+O 2 ↑ ⑦

[0080] Oxidation absorption liquid production reaction:

[0081] NaCl+H 2 O=Electricity=NaClO+H2↑⑧

[0082] Flue gas system working process:

[0083] A. Containing SO 2 \NO\CO 2 The original flue gas containing pollutants is sent to the oxidation absorption tower 1. In this process, sodium hypochlorite solution (relative to SO 2 Excess) as the absorption liquid and countercurrently contact with the original flue gas (part of the flue gas enters through bubbling), and absorbs the SO in the original flue gas according to the reaction of formula ①② 2 , forming a rich liquid containing sodium sulfate and entering the oxidation liquid slurry pool 101, while oxidizing NO in the original flue gas into NO 2 Enter the next process link for further processing.

[0084] B. The NO-containing 2 / CO 2 The flue gas is sent to the alkali liquid absorption tower 2. In this process, sodium hydroxide solution (relative to CO 2 Excess) as the absorption liquid and countercurrently contact with the original flue gas, absorbing NO in the original flue gas according to the reaction of formula ③ 2 / CO 2, forming a rich solution containing sodium nitrate, sodium nitrite and sodium carbonate, which enters the alkali liquid slurry pool 201, and the pollutants in the flue gas are treated and discharged.

[0085] Working process of oxidation absorption tower slurry system:

[0086] A. The rich liquid containing sodium sulfate in the oxidation slurry pool 101 enters the integrated oxidation and sulfur fixation device 3, in which calcium hydroxide is added to react according to formula ④ to generate calcium sulfate. The calcium sulfate precipitated from the integrated oxidation and sulfur fixation device 3 is separated into solid and liquid by a filtering device, and the solid is discharged or reused to replace natural gypsum, and the filtrate is reused to the inlet of the integrated oxidation and sulfur fixation device 3.

[0087] B. The supernatant of the oxidation and sulfur fixation integrated device 3 enters the chlorine production pool 305 to produce sodium hypochlorite solution according to formula ⑧ and is recycled to the oxidation absorption tower 1. The generated hydrogen is discharged or collected and recycled for combustion.

[0088] Working process of slurry system of alkali liquid absorption tower:

[0089] A. The rich liquid containing sodium nitrate, sodium nitrite and sodium carbonate in the alkali liquid slurry pool 201 of the alkali liquid absorption tower 2 enters the biochemical reaction device 7 to remove nitrate according to formula ⑥⑦ to form nitrogen and oxygen for discharge, while the rich liquid rich in sodium carbonate enters the carbon fixation reaction triple box 5 for further treatment.

[0090] B. Calcium hydroxide is added to the carbon fixation reaction triple box 5 to generate calcium carbonate according to formula ⑤. The calcium carbonate precipitated in the carbon fixation reaction triple box 5 is separated into solid and liquid by a filtering device. The solid is discharged or reused by the lime / slaked lime production enterprise instead of natural limestone, and the filtrate is recycled to the inlet of the carbon fixation reaction triple box 5.

[0091] C. The supernatant from the carbon fixation reaction triple tank 5 is recycled to the alkali solution absorption tower 2.

Claims

1. Wet combined desulfurization, denitrification and carbon fixation device, characterized in that: The device includes: An oxidation absorption tower (1) is provided with an oxidation slurry pool (101) at its bottom, a first dual-fluid atomizing nozzle (102) is arranged inside the oxidation absorption tower (1) above the oxidation slurry pool (102), a first demister (103) is arranged at the top of the oxidation absorption tower (1), compressed air is introduced into the gas side of the first dual-fluid atomizing nozzle (102) through a pipeline, and the liquid side of the first dual-fluid atomizing nozzle (102) is connected to the oxidation slurry pool (101) through a pipeline; the waste raw flue gas to be treated enters the oxidation absorption tower (1) in two ways, one way is directly introduced into the oxidation absorption tower (1) through a pipeline, and the other way is introduced into the oxidation slurry pool (101) through a first venturi jet tube (104) and discharged through a bubbling port; An alkali liquid absorption tower (2) is provided with an alkali liquid slurry pool (201) at its bottom, a second dual-fluid atomizing nozzle (202) is arranged above the alkali liquid slurry pool (201) inside the alkali liquid absorption tower (2), a second demister (203) is arranged at the top of the alkali liquid absorption tower (2), the gas side of the second dual-fluid atomizing nozzle (202) is connected to a Roots blower (204) through a pipeline, and the liquid side of the second dual-fluid atomizing nozzle (202) is connected to the alkali liquid slurry pool (201) through a pipeline; the flue gas treated by the oxidation absorption tower (1) enters the alkali liquid absorption tower (2) through two paths through the pipeline from the top outlet of the oxidation absorption tower (1), one path is connected to the Roots blower (204), and the other path enters the alkali liquid slurry pool (201) through a second Venturi jet pipe (205) and is discharged through a bubbling port; The integrated oxidation and sulfur fixation device (3) is used for preparing and recycling the oxidation absorption liquid and is connected to the calcium sulfate filter press (4) and the oxidation slurry pool (101) through pipelines; Carbon fixation reaction triple box (5): used for preparation and recycling of alkali solution, and connected to a calcium carbonate filter press (6) and a biochemical reaction device (7) through pipelines.

2. The wet combined desulfurization, denitrification and carbon fixation device according to claim 1, characterized in that The integrated oxidation and sulfur fixation device (3) is provided with a first reaction tank (301), a second reaction tank (302), a third reaction tank (303) and a chlorine production tank (305) with a built-in chlorine production electrode (304) in sequence. The bottom of the integrated oxidation and sulfur fixation device (3) is connected to the calcium sulfate filter press (4) via a pipeline and a calcium sulfate slurry discharge pump (306) arranged on the pipeline. The chlorine production tank (305) is connected to the first venturi jet tube (104) via a pipeline and an oxidation absorption liquid supply pump (307) arranged on the pipeline. The first reaction tank (301) is connected to the oxidation slurry tank (101) via a pipeline and a sodium sulfate slurry discharge pump (308) arranged on the pipeline. The first reaction tank (301) is also provided with a first agitator (309) and a calcium hydroxide addition channel.

3. The wet combined desulfurization, denitrification and carbon fixation device according to claim 1, characterized in that The carbon fixation reaction triple box (5) comprises a reaction tank A (501), a reaction tank B (502), a reaction tank C (503) and an alkali liquid tank (504) which are arranged in sequence. The bottom of the carbon fixation reaction triple box (5) is connected to a calcium carbonate filter press (6) via a pipeline provided with a calcium carbonate slurry discharge pump (505). The upper end of the reaction tank A (501) is connected to the calcium carbonate filter press (6) via a pipeline, and is provided with a calcium hydroxide addition pipeline and a second agitator (506). The biochemical reaction device (7) pumps the biochemical reaction clear liquid into the reaction tank A (501) via a biochemical reaction clear liquid discharge pump (507) provided on the pipeline. The alkaline slurry tank (201) is connected to a second Venturi jet tube (205) via a pipeline provided with an alkaline absorption liquid supply pump (508).

4. The wet combined desulfurization, denitrification and carbon fixation device according to claim 1, characterized in that The waste flue gas contains sulfur dioxide, nitrogen monoxide and carbon dioxide.

5. A method for wet combined desulfurization, denitrification and carbon fixation using the device according to any one of claims 1 to 4, characterized in that The following steps are involved: 1) Sodium chloride solution is introduced into the chlorine production pool (305) in the integrated oxidation and sulfur fixation device (3), and the chlorine production electrode (304) is energized to produce a sodium hypochlorite solution with a concentration of 0.2-0.8%, and the hydrogen generated is collected and discharged harmlessly from the discharge port or recovered to support combustion; 2) The sodium hypochlorite solution prepared in step 1) is used as an absorption liquid to countercurrently contact with the original flue gas, absorb sulfur dioxide in the original flue gas, form a rich liquid containing sodium sulfate, and enter the oxidation slurry pool (101), and at the same time, oxidize the nitrogen monoxide in the original flue gas into nitrogen dioxide and separate the nitrogen monoxide and carbon dioxide in the original flue gas through the first demister (103), and then the gas enters the alkali liquid absorption tower (2); 3) In the alkali solution absorption tower (2), sodium hydroxide solution is used as the absorption liquid to countercurrently contact with the original flue gas. The sodium hydroxide solution reacts with the original flue gas to absorb nitrogen dioxide and carbon dioxide, forming a rich liquid containing sodium nitrate, sodium nitrite and sodium carbonate, which enters the alkali solution slurry pool (201). The pollutants in the flue gas are treated and then discharged.

6. A wet combined desulfurization, denitrification and carbon fixation method as claimed in claim 5, characterized in that In step 2), the sodium sulfate rich liquid in the oxidation slurry tank (101) is pumped into the first reaction tank (301) of the oxidation and sulfur fixation integrated device (3) through the sodium sulfate slurry discharge pump (308), and reacts with the added calcium hydroxide in the first reaction tank (301) to generate calcium sulfate precipitate, which is transported to the calcium sulfate filter press (4) through the calcium sulfate slurry discharge pump (306) for solid-liquid separation, and the solid is discharged or reused to replace natural gypsum, and the filtrate is reused in the first reaction tank (301).

7. A wet combined desulfurization, denitrification and carbon fixation method as claimed in claim 6, characterized in that The supernatant produced by the reaction in the first reaction tank (301) enters the second reaction tank (302) and the third reaction tank (303) from the overflow port in sequence to further precipitate solid matter, and the precipitation effect is further enhanced by the first inclined tube (310) arranged in the second reaction tank (302) and the first sand filter (311) arranged in the third reaction tank (303). Finally, the supernatant containing sodium chloride enters the chlorine production tank (305) for repeated use to prepare sodium hypochlorite solution.

8. A wet combined desulfurization, denitrification and carbon fixation method as claimed in claim 5, characterized in that In step 3), the rich liquid containing sodium nitrate, sodium nitrite and sodium carbonate entering the alkaline liquid slurry pool (201) is pumped to the biochemical reaction device (7) through the sodium carbonate slurry discharge pump (509) for reaction to remove nitrate, and the generated nitrogen and oxygen are discharged. The rich liquid rich in sodium carbonate is transported to the reaction pool A (501) of the carbon fixation reaction triple box (5) through the biochemical reaction clear liquid discharge pump (507) for further treatment.

9. A wet combined desulfurization, denitrification and carbon fixation method as claimed in claim 8, characterized in that Calcium hydroxide is added to the reaction tank A (501) to react with sodium carbonate to generate calcium carbonate precipitate, and the precipitate is transported to the calcium carbonate filter press (6) through the calcium carbonate slurry discharge pump (505) for solid-liquid separation. The solid is discharged or reused to replace natural limestone. The filtrate is recycled to the reaction tank A (501). The supernatant enters the reaction tank B (502) and the reaction tank C (503) in sequence through the overflow port to further precipitate solid matter. The precipitation effect is enhanced by the second inclined tube (510) arranged in the reaction tank B (502) and the second sand filter (511) arranged in the reaction tank C (503). Finally, the supernatant containing sodium hydroxide enters the alkali liquid pool (504) and is recycled to the alkali liquid absorption tower (2) through the alkaline absorption liquid supply pump (508).

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