CN114832596B - Method and device for preparing ammonia by active molecule oxidation flue gas double-circulation denitration - Google Patents
Method and device for preparing ammonia by active molecule oxidation flue gas double-circulation denitration Download PDFInfo
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- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/48—Sulfur compounds
- B01D53/50—Sulfur oxides
- B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
- B01D53/502—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound characterised by a specific solution or suspension
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- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
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- B01D2258/0283—Flue gases
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Abstract
The invention provides a method and a device for preparing ammonia by active molecule oxidation flue gas double-circulation denitration, and relates to the field of flue gas treatment denitration wastewater treatment and flue gas denitration. The method comprises the following steps: the flue gas containing nitrogen oxide sequentially enters a flue reactor and a wet washing absorption tower, and is O from an active molecule generator 3 Oxidizing the flue gas by molecules, and absorbing the nitrogen oxides into nitrate solution by wet alkali washing; the absorbed nitrate-containing alkaline washing liquid is processed by an ammonia-making electrolytic tank to generate ammonia, the ammonia is removed through an ammonia outlet tower, and the alkaline liquor is diluted by make-up water and then regenerated and enters a wet washing absorption tower for recycling. The invention reduces the emission of flue gas denitration wastewater by active molecule oxidation, and reduces the emission of flue gas pollutants NO x Conversion to NH 3 The recycling of pollutants is realized, the alkali liquor and the oxygen in the system are recycled, the consumption of the alkali liquor and the oxygen is reduced, and the energy consumption is reduced. Denitration efficiency is more than 95 percent, NH 3 The conversion rate reaches more than 80 percent, and the method has great environmental and economic benefits.
Description
Technical Field
The invention relates to the field of flue gas denitration wastewater treatment and flue gas denitration, in particular to a method and a device for preparing ammonia by active molecule oxidation flue gas double-circulation denitration.
Background
The burning such as solid useless, waste liquid, waste gas in the chemical production produces a large amount of air pollutants, including nitrogen oxide etc. for guaranteeing to burn flue gas emission up to standard, reduces the pollution to the air, must handle the pollutant of flue gas.
At present, the main application technologies for flue gas denitration are SNCR (selective non-catalytic reduction) and SCR (selective catalytic reduction) technologies. The SNCR is suitable for directly spraying a reducing agent into the flue gas under the condition that the flue gas temperature is 850-1150 ℃, and reducing nitrogen oxides in the flue gas into N through thermochemical reaction 2 And water, can go on without the catalyst, investment and running cost are lower, but denitration efficiency is lower, along with emission standard's stricter day by day, solitary SNCR can't satisfy the denitration requirement gradually. In SCR, a catalyst is used for reducing nitrogen oxides in flue gas through a reducing agent in a lower temperature range (180-420 ℃), so that the denitration efficiency is higher, but the investment and operation costs are higher, the system is complex, and the occupied space is large.
Using reactive molecules O 3 The technology of oxidizing flue gas and then performing wet absorption becomes a flue gas denitration technology for researching hot in recent years, and the principle method is as follows: first of all with the active molecule O 3 Oxidizing low-valence indissolvable nitrogen oxide NO and the like in the flue gas into high-valence soluble NO 2 、N 2 O 5 、NO 3 And (3) waiting for the nitrogen oxides, then absorbing and fixing the high-valence nitrogen oxides into the slurry by using water or alkali liquor, and using the generated nitrate solution as wastewater or after evaporation and crystallization. In order to ensure the absorption efficiency of the high-valence nitrogen oxides in the flue gas, the method needs to add an absorbent to react with the high-valence nitrogen oxides, and the consumption of the absorbent is high. The absorbed nitrate solution has low value, is troublesome to treat and generates a large amount of wastewater to discharge. Generation of reactive molecule O 3 The process of (2) consumes a large amount of oxygen and has large energy consumption.
Such as CN102716650 discloses an O 3 A microbial oxidative decomposition denitration apparatus using O 3 Most NO in the flue gas is oxidized and sprayed to absorb nitrate, and partial nitrogen oxide is converted into N through microbial denitrification after being oxidized into nitrate by microbes 2 . A reactive molecule O is provided in CN104941410 3 A low-temperature two-step oxidized flue gas sulfur and nitrate integrated removal method is characterized in that a wet washing tower is used for absorbing oxidized nitrogen oxides in flue gas, and washed waste slurry is subjected to sulfur and nitrogen element recovery in a mode of evaporation crystallization after filter pressing.
Reactive molecule O 3 The technology of wet absorption after oxidizing flue gas generates a large amount of nitrate-containing waste liquid, and for the problem of disposal of the nitrate-containing waste liquid, CN111924985A discloses a synchronous treatment device and method for flue gas desulfurization waste water and denitration waste water based on the synergistic effect of microorganisms, but nitrogen elements in the waste liquid are finally discharged in a nitrogen form, and high-value utilization is not performed. CN109592834A discloses a flue gas wet flue gas desulfurization denitration waste water resourceful treatment process system and method, and it adopts chloride ion to exchange nitrate radical particle, and later evaporation crystallization prepares nitrate crystal, has additionally increased the energy consumption of chlorine ion solution processing after the exchange. CN113526621A proposes a method and an apparatus for treating a waste liquid containing nitrate, which utilizes an electrolysis method to convert iron ions into ferrous ions through electric synergy so as to effectively decompose nitrate, but requires that a cathode electrolyte contains iron ions, i.e. inorganic iron salt needs to be added, and nitrate is decomposed into nitric oxide, which cannot solve the problem of nitrogen oxide pollution.
The present invention is directed to the reactive molecule O 3 The problems of difficult treatment of the low-temperature oxidation flue gas denitration wastewater, high oxygen and absorbent consumption, high energy consumption and the like are solved by adopting a mode of carrying out catalytic electrolysis on the absorption slurry to prepare ammonia, so that the low-value nitrate wastewater is converted into NH with high added value 3 Meanwhile, the washing tower absorbs the slurry for regeneration and recycling, and oxygen is regenerated and used for generating active molecules, so that the running supplement investment of the absorbent and the discharge of waste water are reduced, and the energy consumption of the system is reduced.
Disclosure of Invention
The invention provides a method and a device for preparing ammonia by electrolyzing denitration waste water of active molecule oxidation flue gas, aiming at solving the problems of difficult treatment of the denitration waste water of the active molecule oxidation and high denitration operation cost and low yield, and the method and the device can convert nitrogen oxides in the flue gas into high-value NH 3 Meanwhile, the wastewater discharge is reduced, the consumption of an absorbent and oxygen is reduced, and the energy consumption of a system is reduced.
The technical scheme of the invention is as follows:
one of the purposes of the invention is to provide a method for preparing ammonia by active molecule oxidation flue gas double-circulation denitration, which is characterized by comprising the following steps:
the active molecule generator generates active molecule O through discharge reaction 3 Diluting active molecules and then feeding the diluted active molecules into an active molecule denitration flue reactor;
the flue gas to be treated enters an active molecule denitration flue reactor and reacts with active molecule O 3 Reaction, NO in the flue gas x Oxidizing the flue gas into high-valence nitrogen oxides, and feeding the oxidized flue gas into a wet scrubbing absorption tower;
the wet washing absorption tower adopts alkaline solution for spraying absorption, the alkaline solution and the flue gas perform countercurrent reaction, high-valence nitrogen oxides in the flue gas are absorbed and reacted into corresponding nitrates, the flue gas after the absorption reaction enters a subsequent flue gas treatment device, and the absorbed nitrate-containing alkali liquor enters an ammonia-making electrolytic cell;
in the ammonia-making electrolytic cell, the nitrate-containing alkali liquor is catalytically electrolyzed, and at the anode end of the electrolytic cell, the O produced by electrolysis 2 The foam is removed and then is used by an active molecule generator; at the cathode end of the electrolytic cell, nitrate ions are electro-reduced to NH under the condition of catalyst 3 While H is 2 Formation of OH from O molecule - Concentrating and regenerating the alkali liquor; electrolyte in NH 3 The ammonia enters the bottom of an ammonia outlet tower after the concentration reaches a certain degree;
rich in NH 3 The electrolyte is heated in an ammonia outlet tower by using NH 3 Low solubility in alkaline solution, NH 3 After the temperature of the solution is raised, the NH is distilled off 3 And (4) taking the deaminated concentrated alkali liquor as a product out of the system, diluting the deaminated concentrated alkali liquor at the tower bottom to a set concentration by using make-up water, and then re-entering a wet washing tower for absorption.
As a preferable scheme of the invention, the raw material of the active molecule generator is liquid oxygen or pure oxygen, wherein the raw material of the active molecule generator is provided by the anode of the ammonia-making electrolytic cell and is supplemented by one or more of a liquid oxygen source, a pure oxygen source or oxygen produced by an air separation device.
As a preferred scheme of the invention, the temperature of the flue gas to be treated entering the active molecule denitration flue reactor is 60-160 ℃. The flue gas to be treated comes from a front-end treatment process, wherein the flue gas contains nitrogen oxides, and the nitrogen oxides in the flue gas must be treated in order to ensure that the flue gas reaches the standard and is discharged.
As the preferred scheme of the invention, in order to ensure the absorption effect of the high-valence nitrogen oxides, carrying out heavy plantation in a wet washing absorption tower at a liquid-gas ratio of more than or equal to 5L/Nm, wherein a spraying layer is not less than 2 layers, and the retention time of flue gas is more than 2s; the alkaline washing solution is alkali solution formed by metals such as Na, K, ca, mg, ba, zn and the like, the source of the alkaline solution is mainly concentrated alkaline solution from the bottom of the ammonia tower, the concentrated alkaline solution is diluted by supplementing water for regeneration circulation, the mass percentage concentration is 3 to 40 percent, and the temperature of the alkaline solution after absorption is 40 to 100 ℃.
As a preferable scheme of the invention, NO is adopted as the cathode of the ammonia-making electrolytic cell 3 - -NH 3 A selective catalyst; the temperature of the electrolyte of the ammonia-making electrolytic cell is selected to be 40-120 ℃; the anode and the cathode of the ammonia-making electrolytic cell are separated by adopting a diaphragm, and the electrolysis escaping gas is respectively collected. More preferably, the catalyst is a metal-containing catalyst, and more preferably a mono-or multi-component catalyst containing Cu, ni, fe, ru, co, rh, or the like; faraday efficiency is more than or equal to 90 percent, and N reduces NH 3 The selectivity is more than or equal to 85 percent. By electrolytic reaction to NO 3 - +2H 2 O→NH 3 +OH - +2O 2 。
As a preferred scheme of the invention, the ammonia outlet tower is heated by indirect steam, the temperature of the outlet gas at the top of the tower is 70-150 ℃, and a condensation reflux device is arranged at the top of the tower, so that the water content of the outlet gas is reduced.
As the preferred scheme of the invention, the supplementary desalted water or new alkali liquor is added into the alkali liquor at the bottom outlet of the ammonia tower to dilute the regenerated alkali liquor, and the supplementary liquid amount is used for producing NH by electrolysis 3 1 to 2 times of the amount.
As a preferred embodiment of the present invention, the active molecule O of the active molecule generator 3 The two parts respectively enter the front section and the last section of the active molecule denitration reactor to participate in the reaction.
As a preferred embodiment of the present invention, when the sulfur content in the flue gas is high, for example, SO in the flue gas x vol%/NO x The volume percent is more than or equal to 2 percent, at the moment, the alkali liquor containing the nitrate at the bottom of the wet washing absorption tower after absorption is subjected to sulfuric acid removal through a crystallization separation deviceAnd then the salt enters an ammonia-making electrolytic cell for electrolysis.
As the preferable scheme of the invention, the top of the ammonia outlet tower is provided with a reflux condenser, and ammonia gas with moisture content less than or equal to 1% is generated as a product after the ammonia gas at the top of the ammonia outlet tower is subjected to water vapor removal through the reflux condenser.
Another objective of the present invention is to provide an active molecule oxidation flue gas dual cycle denitration ammonia production device, which comprises:
an active molecule generator for generating active molecule O by discharge reaction 3 Diluting active molecules generated by an active molecule generator and then entering an active molecule denitration flue reactor;
flue reactor for denitration by active molecule 3 NO in the flue gas x Oxidizing the flue gas into high-valence nitrogen oxide, and feeding the oxidized flue gas into a wet scrubbing absorption tower;
the wet washing absorption tower adopts alkaline solution to spray from the tower top to react with the flue gas in a countercurrent way, high-valence nitrogen oxides in the flue gas are absorbed and reacted into corresponding nitrate, the flue gas after the absorption reaction enters a subsequent flue gas treatment device, and the absorbed nitrate-containing alkali liquor enters an ammonia-making electrolytic tank;
an ammonia-producing electrolytic cell for catalytically electrolyzing nitrate-containing alkaline solution under alkaline condition to produce O at the anode end of the electrolytic cell 2 The foam is removed and then is used by an active molecule generator; at the cathode end of the electrolyzer, nitrate ions are electro-reduced to NH under the condition of a catalyst 3 While H is 2 Formation of OH from O molecule - Concentrating and regenerating the alkali liquor; electrolyte in NH 3 The ammonia enters the bottom of an ammonia outlet tower after the concentration reaches a certain degree; and
ammonia outlet tower rich in NH 3 The electrolyte is heated in the ammonia outlet tower by using NH 3 Low solubility in alkaline solution, NH 3 After the temperature of the solution is raised, the NH is distilled off 3 And (4) discharging the concentrated alkali liquor from the bottom of the deaminated tower out of the system as a product, diluting the concentrated alkali liquor to a set concentration by using make-up water, and then re-entering the wet washing tower for absorption.
As a preferred scheme of the invention, when the sulfur content in the flue gas isAt higher levels, e.g. SO in flue gas x vol%/NO x The volume percent is more than or equal to 2 percent, and the device is also provided with a crystallization separation device; and after being absorbed by the nitrate at the bottom of the wet washing absorption tower, the alkali liquor containing the nitrate is subjected to sulfate removal by a crystallization separation device and then enters an ammonia production electrolytic cell for electrolysis.
Compared with the prior art, the invention can realize the resource utilization of the flue gas denitration treatment, converts nitrogen oxides with pollution harm in the flue gas into high-value ammonia gas, simultaneously circularly regenerates the alkali washing waste liquid, reduces the wastewater discharge amount of the active molecule denitration unit, simultaneously circularly regenerates oxygen in the electrolysis process, successfully realizes the double-circulation regeneration of the oxygen and alkali liquor, can realize the resource utilization of the flue gas denitration only by supplementing proper amount of oxygen and desalted water (or alkali liquor), and conforms to the concept of green chemistry. The alkali liquor is concentrated and regenerated in the electrolysis process, so that the alkalinity of the ammonia-rich solution is improved, the ammonia gas is favorably evaporated, and the heating energy consumption of the ammonia outlet tower is reduced. The denitration efficiency of the system can reach more than 95%, the ammonia conversion rate can reach more than 80%, and the system has great environmental and economic benefits.
Drawings
FIG. 1 is a first process flow diagram of the present invention (no sulfur in the flue gas, no sulfate enrichment in the system).
Fig. 2 is a schematic diagram of the apparatus corresponding to fig. 1.
FIG. 3 is a second process flow diagram of the present invention (high sulfur content in flue gas, adding a sulfate separation device).
Fig. 4 is a schematic diagram of the apparatus corresponding to fig. 3.
Reference numerals are as follows: 1-flue reactor, 2-active molecule generator, 3-wet washing absorption tower, 4-ammonia-making electrolytic tank, 5-ammonia-discharging tower, 6-reflux condenser, 7-mixing tank, 8-active molecule dilution fan, 9-demister, 10-circulating pump, 11-washing absorption tower liquid-discharging pump, 12-electrolytic tank liquid-discharging pump, 13-mixing tank liquid-discharging pump, 14-crystallization separation device and 15-separation device liquid-discharging pump.
Detailed Description
The invention will be further illustrated and described with reference to specific embodiments. The described embodiments are merely exemplary of the disclosure and are not intended to limit the scope thereof. The technical characteristics of the embodiments of the invention can be correspondingly combined without mutual conflict.
The embodiment of the invention illustrates two typical but non-limiting devices for producing ammonia by active molecular oxidation flue gas dual-cycle denitration, as shown in fig. 2 and 4, respectively, wherein fig. 2 is directed to the case of no sulfur in the flue gas, and fig. 1 is a process flow diagram corresponding to the device in fig. 2; FIG. 4 is a process flow diagram corresponding to the apparatus of FIG. 4, in view of the situation of high sulfur content in the flue gas.
As shown in fig. 2, the active molecule oxidation flue gas dual-cycle denitration ammonia production apparatus of the embodiment includes: a flue reactor 1, an active molecule generator 2, a wet washing absorption tower 3, an ammonia-making electrolytic bath 4 and an ammonia outlet tower 5.
Wherein the content of the first and second substances,
reactive molecule denitration flue reactor 1 utilizes reactive molecule O 3 NO in the smoke x Oxidizing the flue gas into high-valence nitrogen oxide, and feeding the oxidized flue gas into a wet scrubbing absorption tower.
The active molecule generator 2 generates active molecules O by a discharge reaction 3 And the active molecules generated by the active molecule generator are diluted and then enter the active molecule denitration flue reactor.
The wet washing absorption tower 3 adopts alkaline solution to spray from the top of the tower to react with the flue gas in a countercurrent way, high-valence nitrogen oxides in the flue gas are absorbed and reacted into corresponding nitrates, the flue gas after the absorption reaction enters a subsequent flue gas treatment device, and the absorbed nitrate-containing alkali liquor enters an ammonia-making electrolytic cell.
The ammonia-making electrolytic tank 4 carries out catalytic electrolysis on the nitrate-containing alkali liquor under the alkaline condition, and O generated by electrolysis is arranged at the anode end of the electrolytic tank 2 The foam is removed and then is used by an active molecule generator; at the cathode end of the electrolytic cell, nitrate ions are electro-reduced to NH under the condition of catalyst 3 While H is 2 Formation of OH from O molecule - Concentrating and regenerating the alkali liquor; electrolyte in NH 3 The ammonia enters the bottom of the ammonia tower after the concentration reaches a certain degree.
The ammonia outlet tower 5 pairs are rich in NH 3 In the presence of an electrolyteLine heating with NH 3 Low solubility in alkaline solution, NH 3 After the temperature of the solution is raised, the NH is distilled off 3 And (4) taking the deaminated concentrated alkali liquor as a product out of the system, diluting the deaminated concentrated alkali liquor at the tower bottom to a set concentration by using make-up water, and then re-entering a wet washing tower for absorption.
The apparatus of the present invention is described below as divided into an active molecule oxidation flue gas denitration apparatus and a two-cycle regeneration electrolysis ammonia production apparatus.
The active molecular oxidation flue gas denitration device mainly comprises a flue reactor 1, an active molecular generator 2, a wet washing absorption tower 3 and the like, and NO is contained at 60-160 ℃ from the front-stage process x The flue gas enters a flue reactor 1, an oxygen source generates active molecules O through an active molecule generator 2 3 The diluted flue gas is sprayed into a flue reactor 1 to be mixed with flue gas after being diluted by a dilution fan 8, nitrogen oxides in the flue gas are oxidized into high-valence nitrogen oxides, the oxidized flue gas enters from the lower part of a wet scrubbing absorption tower 3, the high-valence nitrogen oxides are absorbed by alkali liquor sprayed from the top of the tower, and a nitrate solution is formed and enters a subsequent double-circulation regeneration electrolysis ammonia production device. The flue gas passes through a demister 9 arranged at the upper part of the tower after being washed and absorbed by a wet method, and the flue gas enters a post-treatment device after liquid drops are removed.
The double-circulation regeneration electrolysis ammonia production device mainly comprises an ammonia production electrolytic tank 4, an ammonia outlet tower 5, a mixing tank 7 and the like, when the sulfur content of the flue gas is high (SO in the flue gas) x vol%/NO x vol% 2%) and a sulfate crystallization separator 14 (shown in FIG. 4).
Pumping out the absorbed alkali liquor containing nitrate from the bottom of the wet washing absorption tower 3, feeding the alkali liquor into an ammonia production electrolytic tank 4, or removing sulfate through a crystallization separation device 14, feeding the alkali liquor into the ammonia production electrolytic tank 4, and discharging NO 3 - -NH 3 Under the action of the selective catalyst, nitrate ions in the solution are electrolyzed to generate ammonia, hydroxide ions in the solution are regenerated at the same time, the ammonia enters the ammonia outlet tower 5 along with the solution, and meanwhile, oxygen molecules generated by the anode of the ammonia preparation electrolytic cell 4 escape from the solution.
The ammonia-containing solution is evaporated in the ammonia outlet tower 5 under the heating condition, the ammonia in the solution is evaporated, water vapor in a gas phase is removed under the action of the reflux condenser 6, meanwhile, a small amount of gas escaped from the cathode of the ammonia-making electrolytic cell 4 also enters the top of the ammonia outlet tower 5 for purification, and an ammonia gas product with the moisture content less than or equal to 1% is produced at the top of the tower. The alkali liquor after ammonia removal enters a mixing tank 7, supplementary water is added to supplement water lost in the electrolysis process, or the supplementary alkali liquor is added to supplement alkali lost in the denitration process when a sulfate separation device is arranged, and the alkali liquor is generated into qualified alkali liquor after passing through the mixing tank 7 and enters the wet washing absorption tower 3 again for absorption.
In a preferred embodiment of the invention, the liquid-gas ratio of the wet washing absorption tower is more than or equal to 5L/Nm, the spraying layer is not less than 2 layers, and the smoke retention time is more than 2s; the alkaline washing solution is alkaline solution formed by metals such as Na, K, ca, mg, ba, zn and the like, the source of the alkaline solution is mainly used for the cyclic regeneration of a subsequent device, the mass percentage concentration is 3 to 40 percent, and the temperature of the alkaline solution after absorption is 40 to 100 ℃.
In a preferred embodiment of the invention, the cathode of the ammonia-producing electrolytic cell is made of NO 3 - -NH 3 The catalyst is preferably a metal-containing catalyst, more preferably a mono-or multi-component catalyst containing Cu, ni, fe, ru, co, rh, etc., the Faraday efficiency is more than or equal to 90%, and N reduces NH 3 The selectivity is more than or equal to 85 percent; the electrolyte is alkaline electrolyte, and the temperature is selected to be 40-120 ℃; the anode and the cathode of the electrolytic cell are separated by adopting a diaphragm, and electrolysis escaping gases are respectively collected. By electrolytic reaction to NO 3 - +2H 2 O→NH 3 +OH - +2O 2 。
In a preferred embodiment of the invention, indirect steam heating is preferentially selected for the ammonia outlet tower, the temperature of the outlet gas at the top of the tower is 70-150 ℃, and a condensation reflux device is arranged at the top of the tower to reduce the water content of the outlet gas.
In a preferred embodiment of the invention, the regenerated alkali liquor is diluted by adding supplementary desalted water or fresh alkali liquor into the outlet alkali liquor at the bottom of the ammonia tower, the supplementary water and the concentrated alkali liquor can be mixed in the form of a mixing tank, a pipeline mixer and the like, and the quantity of the supplementary water is the quantity for producing NH by electrolysis 3 1 to 2 times of the amount.
Example 1
As shown in fig. 1 and 2The flue gas with the temperature of 60 to 160 ℃ after the front section treatment enters a flue reactor 1 and reacts with active molecules O generated by an active molecule generator 2 3 Mixing, and converting nitrogen oxides in the flue gas into high-valence nitrogen oxides through oxidation reaction. The oxidized flue gas enters a wet washing absorption tower 3, alkali liquor is uniformly sprayed from the top of the tower to absorb high-valence nitrogen oxides in the flue gas into solution containing nitrate, and the flue gas is subjected to liquid drop removal by a demister 9 and then enters a rear-section flue gas treatment device. The absorbed nitrate-containing solution enters an ammonia production electrolytic tank 4, nitrate ions are converted into ammonia molecules through catalytic electrolysis, the ammonia-containing solution enters an ammonia outlet tower 5, ammonia is evaporated under heating, and ammonia with the moisture content less than or equal to 1% is generated as a product after water vapor is removed through a reflux condenser 6. The alkali liquor after deamination enters a mixing tank 7, and after water is supplemented, qualified alkali liquor is generated and enters the wet washing absorption tower 3 again for alkali washing of flue gas.
By this device, NO in the flue gas x The denitration efficiency is more than or equal to 95 percent, and simultaneously, an ammonia product is generated, so that the resource utilization of the smoke pollutants is realized. The denitration waste water is regenerated into qualified alkali liquor for recycling, and the waste water discharge in the flue gas treatment device is reduced. And in the ammonia preparation process, the alkali liquor is regenerated, and the oxygen is also regenerated circularly, so that the oxygen consumption of the active molecule generator is reduced. The alkali liquor characteristics are adapted to the ammonia discharging conditions, and the heat consumption of the ammonia discharging tower is reduced.
Example 2
As shown in figures 3 and 4, flue gas with the temperature of 60 to 160 ℃ after the front-stage treatment (SOx vol%/NOx vol% in the flue gas is 2) enters a flue reactor 1 and reacts with active molecules O generated by an active molecule generator 2 3 Mixing, and converting nitrogen oxides in the flue gas into high-valence nitrogen oxides through oxidation reaction. The oxidized flue gas enters a wet washing absorption tower 3, slaked lime alkali liquor is uniformly sprayed from the top of the tower to absorb high-valence nitrogen oxides in the flue gas into solution containing nitrate, and the flue gas is subjected to liquid drop removal by a demister 9 and then enters a rear-section flue gas treatment device. The absorbed nitrate-containing solution enters a crystallization separation device 14, calcium sulfate crystals enriched in the solution are separated, and a gypsum product is generated after subsequent treatment. The solution after the sulfur removal enters an ammonia production electrolytic tank 4 and is converted into nitrate ions through catalytic electrolysisThe ammonia solution is converted into ammonia molecules, the ammonia-containing solution enters an ammonia outlet tower 5, ammonia is evaporated under heating, and ammonia gas with the moisture content less than or equal to 1% is generated as a product after water vapor is removed by a reflux condenser 6. The alkali liquor after deamination enters a mixing tank 7, and after water is supplemented, qualified alkali liquor is generated and enters the wet washing absorption tower 3 again for alkali washing of flue gas.
By this device, SOx and NO in the flue gas x The waste gas is removed, the denitration efficiency is more than or equal to 95 percent, and meanwhile, a gypsum product and an ammonia product are generated, so that the resource utilization of the smoke pollutants is realized. The denitration waste water is regenerated into qualified alkali liquor for recycling, and the waste water discharge in the flue gas treatment device is reduced. And in the ammonia preparation process, the alkali liquor is regenerated, and the oxygen is also regenerated circularly, so that the oxygen consumption of the active molecule generator is reduced. The alkali liquor characteristics are adapted to the ammonia discharging conditions, and the heat consumption of the ammonia discharging tower is reduced.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
Claims (9)
1. A method for preparing ammonia by active molecule oxidation flue gas double-circulation denitration is characterized by comprising the following steps:
the active molecule generator generates active molecule O through discharge reaction 3 Diluting active molecules and then feeding the diluted active molecules into an active molecule denitration flue reactor; the raw material of the active molecule generator is provided by the anode of the ammonia-making electrolytic cell;
the flue gas to be treated enters an active molecule denitration flue reactor and reacts with active molecule O 3 Reacting to remove NO in the flue gas x Oxidizing the flue gas into high-valence nitrogen oxide, and feeding the oxidized flue gas into a wet scrubbing absorption tower;
the wet washing absorption tower adopts alkaline solution for spraying absorption, the source of the alkaline solution is mainly that concentrated alkaline solution at the bottom of the ammonia tower is diluted by supplementing water for regeneration circulation, and the mass percentage concentration is 3-40%; the alkaline solution and the flue gas are in counter-current reaction, high-valence nitrogen oxides in the flue gas are absorbed and reacted into corresponding nitrates, the flue gas after the absorption reaction enters a subsequent flue gas treatment device, and the absorbed nitrate-containing alkali liquor enters an ammonia-making electrolytic cell; the temperature of the alkali liquor after absorption is 40 to 100 ℃;
in the ammonia-making electrolytic cell, the nitrate-containing alkali liquor is catalytically electrolyzed, and at the anode end of the electrolytic cell, the O produced by electrolysis 2 The foam is removed and then is used by an active molecule generator; at the cathode end of the electrolytic cell, nitrate ions are electro-reduced to NH under the condition of catalyst 3 While H is 2 Formation of OH from O molecule - Concentrating and regenerating the alkali liquor; the temperature of the electrolyte of the ammonia-making electrolytic cell is selected to be 40-120 ℃; electrolyte in NH 3 The ammonia enters the bottom of the ammonia outlet tower after the concentration reaches a certain degree;
rich in NH 3 The electrolyte is heated in an ammonia outlet tower by using NH 3 Low solubility in alkaline solution, NH 3 After the temperature of the solution is raised, the NH is distilled off 3 And (4) taking the deaminated concentrated alkali liquor as a product out of the system, diluting the deaminated concentrated alkali liquor at the tower bottom to a set concentration by using make-up water, and then re-entering a wet washing tower for absorption.
2. The method for preparing ammonia by dual-cycle denitration of active molecular oxidation flue gas as claimed in claim 1, wherein the raw material of the active molecular generator is liquid oxygen or pure oxygen, wherein one or more of a liquid oxygen source, a pure oxygen source or oxygen produced by an air separation device is adopted for supplement supply.
3. The active molecule oxidation flue gas double-circulation denitration ammonia production method according to claim 1, wherein the temperature of flue gas to be treated entering an active molecule denitration flue reactor is 60-160 ℃.
4. The method for preparing ammonia through dual-cycle denitration by active molecular oxidation flue gas according to claim 1, wherein liquid-gas ratio in the wet scrubbing absorption tower is not less than 5L/Nm, spraying layers are not less than 2 layers, and flue gas residence time is more than 2s.
5. The active molecule oxidation flue gas double-circulation denitration ammonia production method according to claim 1, wherein NO is adopted as a cathode of the ammonia production electrolytic cell 3 - -NH 3 A selective catalyst; the anode and the cathode of the ammonia-making electrolytic cell are separated by adopting a diaphragm, and the electrolysis escaping gas is respectively collected.
6. The active molecular oxidation flue gas double-cycle denitration ammonia production method according to claim 1 or 2, wherein the catalyst is preferably a metal catalyst containing one or more of Cu, ni, fe, ru, co, rh; faraday efficiency is more than or equal to 90 percent, and N reduces NH 3 The selectivity is more than or equal to 85 percent.
7. The active molecule oxidation flue gas double-circulation denitration ammonia production method according to claim 1, wherein indirect steam heating is selected for the ammonia outlet tower, the temperature of the outlet gas at the top of the tower ranges from 70 ℃ to 150 ℃, and a condensation reflux device is arranged at the top of the tower to reduce the water content of the outlet gas.
8. The method for preparing ammonia by active molecular oxidation flue gas double-circulation denitration according to claim 1, wherein supplementary demineralized water or new alkali liquor is added into the alkali liquor at the bottom outlet of the ammonia outlet tower to dilute the regenerated alkali liquor, and the supplementary liquid is used for producing NH by electrolysis 3 1 to 2 times of the amount.
9. The method for preparing ammonia by active molecule oxidation flue gas double-cycle denitration according to claim 1, wherein active molecule O of active molecule generator 3 The two parts respectively enter the front section and the last section of the active molecule denitration reactor to participate in the reaction.
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