WO2013053109A1 - 氧化法去除废气中氮氧化合物、硫氧化物和汞的工艺及其设备 - Google Patents

氧化法去除废气中氮氧化合物、硫氧化物和汞的工艺及其设备 Download PDF

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WO2013053109A1
WO2013053109A1 PCT/CN2011/080670 CN2011080670W WO2013053109A1 WO 2013053109 A1 WO2013053109 A1 WO 2013053109A1 CN 2011080670 W CN2011080670 W CN 2011080670W WO 2013053109 A1 WO2013053109 A1 WO 2013053109A1
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exhaust gas
split
pipe
gas
hydrogen peroxide
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PCT/CN2011/080670
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English (en)
French (fr)
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熊靓
朱核光
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Xiong Liang
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Priority to US13/881,614 priority Critical patent/US9126143B2/en
Priority to PCT/CN2011/080670 priority patent/WO2013053109A1/zh
Priority to CN201180043916.XA priority patent/CN103209755B/zh
Publication of WO2013053109A1 publication Critical patent/WO2013053109A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation 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
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/60—Simultaneously removing sulfur oxides and nitrogen oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation 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
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/64—Heavy metals or compounds thereof, e.g. mercury
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation 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
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/76—Gas phase processes, e.g. by using aerosols
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/10—Oxidants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/10—Oxidants
    • B01D2251/106—Peroxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/60—Heavy metals or heavy metal compounds
    • B01D2257/602—Mercury or mercury compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation 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
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation 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
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B01D53/507—Sulfur oxides by treating the gases with other liquids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation 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
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/54—Nitrogen compounds
    • B01D53/56—Nitrogen oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
    • B01J19/10—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing sonic or ultrasonic vibrations
    • Y—GENERAL 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Definitions

  • the present invention relates to nitrogen oxides (NOx) and sulfur oxides (SOx) in flue gas and other industrial waste gases. And mercury removal process and equipment, belonging to the field of industrial waste gas treatment and environmental protection technology.
  • the treatment of exhaust gases such as flue gas generated in the combustion process and its similar chemical processes is a very important aspect in the field of air pollution control.
  • the common feature of this type of exhaust gas is that the temperature is relatively high (usually above 100 °C), containing relatively high concentrations of nitrogen oxides, sulfur oxides and a small amount of metal oxides or metal vapors.
  • Part of the NOx is derived from the oxidation of nitrogenous compounds in the fuel, partly from the oxidation of nitrogen in the air.
  • the total nitrogen oxides usually account for about 90% of NO, and the rest are mainly NO 2 .
  • Sulfur oxides are mainly derived from the oxidation of sulfides in fuels, with the exception of a small fraction of SO 3 , mostly SO 2 .
  • Metal oxides are mainly derived from the oxidation of metal compounds contained in fuels. Most of the metal oxides are mixed into the ash after cooling, and do not enter the atmosphere, and are mainly low-boiling metals that can enter the atmosphere and harm the environment. Steam, such as zero-order metallic mercury.
  • the main methods currently used are wet, dry and mixed methods.
  • the dry desulfurization process removes SOx by spraying SOx adsorption and absorption materials such as powdered limestone (CaCO 3 ), lime (CaO) or hydrated lime (Ca(OH) 2 ) into the flue of the furnace or the furnace.
  • SOx adsorption and absorption materials such as powdered limestone (CaCO 3 ), lime (CaO) or hydrated lime (Ca(OH) 2 ) into the flue of the furnace or the furnace.
  • the reaction efficiency is low, and a large amount of adsorption/absorption materials are needed, and the removal efficiency is generally less than 70%; when the adsorbent material is sprayed into the combustion furnace, it is easy to cause scaling on the surface of the boiler heat exchanger, and Frequently clean the heat exchanger surface.
  • the adsorbed material after the reaction increases the concentration of solid particles in the flue gas, which makes it difficult to remove dust from the flue gas. It is necessary to increase the humidity or inject SO 3 to increase the dust removal effect.
  • the adsorbent material after the reaction is mixed into the combustion ash. It is very difficult to recycle.
  • the wet desulfurization process absorbs SOx by using a wet scrubbing device.
  • the washing liquid is usually treated with an alkali solution (NaOH or Ca(OH) 2 ); the exhaust gas and the washing liquid are in sufficient contact, so that the SOx is absorbed into the alkaline liquid to be removed.
  • the process generally achieves a removal efficiency of more than 90%, and the resulting sulfate and sulfite can be recycled as by-products.
  • the main disadvantage is that the equipment cost is higher than the dry method, and a part of the water will be lost to the flue gas; at the same time, a certain amount of waste water will be generated, which requires additional treatment.
  • the denitrification of flue gas can be carried out by selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), oxidation, and adsorption absorption.
  • SCR selective catalytic reduction
  • SNCR selective non-catalytic reduction
  • oxidation oxidation
  • adsorption absorption oxidation absorption
  • the selective catalytic reduction method reduces NOx to N 2 by the action of a catalyst by injecting ammonia into the flue and passing it through the catalyst layer together with the flue gas. This reaction requires a temperature of around 300 ° C, so ammonia filling and catalyst installation must be close to the boiler outlet and before the precipitator.
  • the catalyst is usually a transition metal oxide such as V 2 O 5 , Fe 2 O 3 , CuO or the like. The process is relatively simple, the removal efficiency is high, and the removal rate of 80% or more is generally achieved.
  • the disadvantage is that the catalyst is expensive; since the catalyst layer must be installed before the dust removal device, the catalyst layer must be cleaned and replaced frequently; at the same time, ammonia is an unstable and irritating compound, and there are safety hazards in storage and transportation; Removal of the effect generally requires the appropriate addition of ammonia gas, which brings the risk of ammonia leakage, and leakage of ammonia into the environment will have a serious impact on the atmospheric environment.
  • the selective non-catalytic reduction method adds the reducing agent ammonia or urea to the combustion furnace to reduce NOx to N 2 at a high temperature of about 1000 °C. Although this method is simple in process, it does not need to use a catalyst, but the removal effect is low, generally less than 70%.
  • the adsorption or absorption method employs an activated carbon adsorbent or an organometallic chelate absorbent such as iron diamine tetraacetate (Fe II EDTA ) and ethylene diamine cobalt ( Co ( en ) 3 ) 2+ to adsorb or absorb NOx.
  • an activated carbon adsorbent or an organometallic chelate absorbent such as iron diamine tetraacetate (Fe II EDTA ) and ethylene diamine cobalt ( Co ( en ) 3 ) 2+ to adsorb or absorb NOx.
  • Such methods can often remove SOx while removing NOx, and the removal efficiency is high, but the amount of adsorption/absorbent is large and expensive; and the regeneration of the adsorbent/absorbent is difficult, and the adsorbed or absorbed NOx or SOx is not converted. , still need to be processed after parsing.
  • Oxidation denitration method oxidant injected in the flue gas NO and NO 2 are more readily oxidized to dissolve in water or alkaline solution of NO 2, and NO 3, NO 2, and then the absorbed NO 3 is absorbed by the gas scrubbing device The liquid is decomposed to form nitrous acid (salt) or nitric acid (salt).
  • oxidizing agents are sodium hypochlorite, hydrogen peroxide, ozone and chlorine dioxide (ClO 2 ) (US Pat 7 , 628 , 967 B2 ) and chlorine (US Pat 4 , 619 , 608 and US Pat 6 , 447 , 740 ) and the like.
  • Oxidative denitration can achieve relatively high removal efficiency. Since the oxidant generally oxidizes SO 2 and metallic mercury, and the absorption and removal methods of NO 2 and NO 3 are the same as the absorption and removal methods of SO 2 and SO 3 , the oxidative denitration can simultaneously remove SO 2 and metallic mercury. However, the amount of the oxidizing agent, the reaction conditions, and the energy consumption are greatly affected by the type of the oxidizing agent and the manner in which the oxidizing agent is added.
  • ozone is a highly oxidizing gas that can only be produced on site and consumes a large amount of electrical energy.
  • sodium hypochlorite, chlorine dioxide and chlorine contain chlorine, which will increase the difficulty of wastewater treatment and the recycling of oxidation products to a certain extent, and also require a higher reaction temperature.
  • hydrogen peroxide does not cause new pollutants and affects the quality of by-products, it has a relatively low oxidation efficiency at normal temperatures, and it is necessary to add a large amount of hydrogen peroxide or increase the reaction temperature to achieve the desired effect.
  • the methods for removing mercury (elemental mercury and mercury ions) in flue gas mainly include oxidation method and activated carbon adsorption method, and oxidation method uses halogenated gas such as bromine gas, chlorine gas, iodine molecule and its compound (US Pat 6 , 878 , 358 B2 and US Pat 6 , 447 , 740 ) or elemental sulfur and sulfides including H 2 S , COS ( US Pat 6 , 972 , 120 B2 ) and Na 2 S 4 (EP 0 , 709 , 128 A2 ) react with mercury to form A mercury metal compound having a high freezing point or a good solubility in the liquid washing liquid, thereby causing mercury to be separated from the gas phase into the solid phase residue or the liquid phase residue.
  • halogenated gas such as bromine gas, chlorine gas, iodine molecule and its compound (US Pat 6 , 878 , 358 B2 and US Pat 6 , 447 , 740 ) or
  • U.S. Patent No. 6, 503, 470 also teaches the addition of sodium thiohydride (NaHS) or other sulfur compounds and mercury to form mercuric sulfide.
  • NaHS sodium thiohydride
  • US Pat. 6, 447, 740 mentions the addition of an alkali metal iodide salt to react with mercury ions to form a HgI 2 precipitate.
  • chlorine can be used to treat other gas components at the same time.
  • These reagents are specially designed for the removal of mercury, and have little help in removing other polluting components in the flue gas. These methods are costly if used alone for the removal of mercury.
  • the adsorption capacity of activated carbon for mercury is not very large, and it is generally necessary to treat the surface (such as fumigation with bromine or immersion with bromate) to obtain better treatment results.
  • US Pat. No. 7, Pat. No. 6,628,967 B2 proposes the use of a multi-stage washing process to simultaneously remove SOx from exhaust gases. , NOx and mercury, which are first absorbed by conventional lye to remove all or part of the SOx, and then injected with oxidant to oxidize NOx and remaining SOx to NOx and SOx with higher oxidation states. And use the lye to absorb the high oxidation state of SOx and NOx, and finally wash it with a conventional lye to remove residual NOx and SOx. .
  • the volatile metal mercury can be oxidized to ionic mercury in the oxidation stage to be removed in a subsequent water washing apparatus.
  • the oxidizing agent uses hydrogen peroxide, or a mixture of hydrogen peroxide and nitric acid, or a mixture thereof with nitric acid and chlorous acid, and various sodium or potassium salts of chloric acid.
  • the oxidant is added to the liquid wash solution for use.
  • known exhaust gas desulfurization processes such as dry, wet or mixed scrubbing processes only remove SOx Effective, it is impossible to realize off-sale and de-weighting metals at the same time; known exhaust gas denitration processes such as selective catalytic reduction, selective non-catalytic reduction, and adsorption absorption have problems such as high cost or unsatisfactory results. Either / It is difficult to regenerate the absorbent. At the same time as denitration, it is impossible to simultaneously desulfurize and de-metalize the metal, and it cannot be widely used in production.
  • Hydrogen peroxide as a denitrifying oxidant will not affect the purity of the eluted product, nor will it have a negative impact on the corresponding wastewater treatment.
  • a relatively high reaction temperature is required, and all the flue gas is required. Heating, which inevitably brings a lot of energy consumption, has an adverse effect on subsequent washing operations.
  • the application of the present invention is directed to the above problems existing in the process for denitration, desulfurization and removal of metallic mercury of exhaust gas, and provides a reaction condition capable of comprehensively performing denitration, desulfurization and mercury removal treatment on exhaust gas and overcoming high temperature.
  • the process described in the application of the present invention aims to optimize the use of an oxidant represented by hydrogen peroxide for denitration, overcome the high energy consumption problem caused by the reaction conditions requiring high temperature, and maximize the oxidizing ability and denitration of these oxidants.
  • the effect while achieving both desulfurization and mercury removal.
  • the idea of the application of the present invention is to split the exhaust gas, use the off-gas as the carrier gas of the oxidant, and heat it to the decomposition temperature of the oxidant to form a more oxidizing hydrogen and oxygen peroxide radical, and make these freedoms
  • the base is mixed with the unheated main exhaust gas along with the split exhaust gas, and reacts with a reducing gas such as NOx, SOx and mercury vapor in the exhaust gas to oxidize it into a higher oxidation state of NOx, SOx and mercury ions, which is partially generated.
  • NOx and SOx and water vapor in the exhaust gas produce products such as nitrous acid, nitric acid and sulfuric acid.
  • H2O2 +HO2• H2O + O2 + HO•
  • Hydrogen peroxide is thermally decomposed to produce hydroxyl radicals (HO•) and peroxyl radicals (HO2•), which in turn react with hydrogen peroxide to form new radicals.
  • This chain reaction occurs.
  • This allows hydrogen peroxide to be rapidly decomposed and produces a large amount of hydrogen and peroxygen radicals, which have a higher redox potential than H2O2 and can react more efficiently with NO, NO2 or SO2 or metallic mercury. .
  • these free radicals can also collide with each other and regenerate hydrogen peroxide and oxygen, so a dynamic equilibrium will be reached at a certain temperature. The higher the temperature, the equilibrium shifts toward the production of more free radicals until at a certain temperature. A saturated concentration of free radicals is reached or approached.
  • the use of hydrogen peroxide to oxidize the reducing gas in the exhaust gas does not require heating all of the gas to the (saturated) decomposition temperature of the hydrogen peroxide, and it is only necessary to heat the hydrogen peroxide to its decomposition temperature.
  • the concentration of hydrogen peroxide is preferably adjusted to below the saturated vapor concentration, which can greatly reduce the energy required to heat the entire reaction system.
  • the yield of free radicals can be maximized, and the purpose of reducing the reducing gas (NO, NO2 or SO2 and metallic mercury) in the exhaust gas at a low cost and high efficiency can be achieved.
  • An object of the present invention is to provide an apparatus for removing nitrogen oxides, sulfur oxides and mercury in an exhaust gas by an oxidation process, the apparatus comprising an exhaust gas main pipe, a branch pipe and an oxidant injection device, wherein
  • the inlet end and the outlet end of the split branch pipe are respectively opened between the upstream flue gas inlet and the downstream flue gas outlet of the exhaust gas main pipe, and the downstream flue gas outlet of the exhaust gas main pipe is connected to the washing device;
  • a control valve and a fan are arranged in the branch branch near the intake end to control and adjust the intake air amount and the flow rate of the branch branch pipe, and a heating reaction chamber is arranged at a position near the outlet end of the branch branch pipe, and a heater is arranged in the heating reaction chamber;
  • the oxidant injection device comprises an oxidant storage tank, a transfer pump and a transfer pipe.
  • the transfer pipe is opened downstream of the heater in the heating reaction chamber, and the heating reaction chamber is directly connected to the exhaust gas main pipe, and a diffusion distributor or a nozzle is arranged at the opening.
  • an air flow control valve may be disposed downstream of the exhaust gas main pipe located at the inlet of the diverting branch pipe for controlling the flow rate and flow rate of the gas in the diverting branch pipe.
  • the heater includes an electric heater.
  • the opening position of the conveying pipe in the oxidant injection device is set as close as possible to the inlet end in the heating reaction chamber, so that the injected oxidant can be sufficiently mixed in the branch pipe and the divided exhaust gas, sufficiently heated, and decomposed into more oxidizing ability. Hydrogen and peroxyl radicals.
  • the oxidizing agent includes hydrogen peroxide and other oxidizing agents capable of decomposing to form free radicals under high temperature conditions, and the oxidizing agent includes chlorine gas, ClO2, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, sodium salts thereof or Potassium salts, mixtures thereof, or mixtures thereof with their respective catalysts which promote decomposition.
  • the end of the delivery tube of the oxidant injection device is provided with a nozzle or an atomizing device, and the nozzle includes an ultrasonic nozzle (ultrasound) Nozzle) or venturi nozzle (Venturi
  • a filling pump may be added to the conveying pipe to provide power for the injection of the oxidant
  • an oxidant injection control valve is added to the conveying pipe for control The amount of hydrogen peroxide injected.
  • Venturi nozzles are designed according to the Venturi effect.
  • the so-called Venturi effect is a phenomenon in which the fluid pressure decreases as the fluid passes from a larger flow cross section into a smaller flow cross section.
  • the use of high velocity airflow and the negative pressure created by the flow of air through the narrow throat allows the liquid to be added to be drawn from the throat and thoroughly mixed with the gas, forming a spray at the downstream nozzle under the action of gas shear.
  • a heat exchange device may be added to transfer part of the heat of the mixed gas to the relatively low temperature split exhaust gas intake.
  • Another object of the present application is to provide a method for the removal of nitrogen oxides, sulfur oxides and mercury in an exhaust gas by oxidation using the apparatus described above, the method comprising the following process steps:
  • Exhaust gas split a split branch pipe is arranged between the upstream flue gas inlet and the downstream flue gas outlet of the main exhaust passage to divert the exhaust gas to be treated;
  • the flow rate of the split exhaust gas can be controlled and regulated by the air flow control valve provided on the main passage of the exhaust gas and the air flow control valve and the fan provided on the exhaust gas branch pipe.
  • the injected oxidant can be thoroughly mixed with the split exhaust gas. heating;
  • Reflux washing The split exhaust gas with high oxidizing free radicals flows back to the main exhaust pipe and is completely mixed with the exhaust gas in the main exhaust pipe, and the mixed exhaust gas reacts to the subsequent washing device.
  • the present application provides a method for removing nitrogen oxides, sulfur oxides and mercury in exhaust gas by using hydrogen peroxide, the method comprising the following process steps:
  • Exhaust gas split a split branch is provided between the upstream flue gas inlet and the downstream flue gas outlet of the exhaust passage main pipe to divert the exhaust gas to be treated;
  • the flow rate of the split exhaust gas can be controlled and regulated by the air flow control valve provided on the main passage of the exhaust gas and the air flow control valve and the fan provided on the exhaust gas branch pipe.
  • the injected hydrogen peroxide energy and the split exhaust gas are injected. Fully mixed, heated, and decomposed into more oxidizing hydrogen and peroxyl radicals;
  • Reflux washing The split exhaust gas with high oxidizing free radicals flows back to the main exhaust pipe and is completely mixed with the exhaust gas in the main exhaust pipe. After a reaction time of 0.4 to 5.0 seconds, the mixed exhaust gas enters the subsequent washing device.
  • the hydrogen peroxide is injected into the exhaust gas branch pipe through the oxidant injection device at a certain flow rate to be sufficiently mixed with the split exhaust gas, and stays in the heating reaction chamber for 0.2 to 4.0 seconds, preferably 0.5 to 1.0 second.
  • the heater provided on the exhaust pipe increases the temperature of the split exhaust gas to the optimum decomposition temperature of H2O2, at which time H2O2 is completely or partially decomposed into HO• and H. O2•etc.
  • step 2 of the above method a part of the hydrogen peroxide and the generated radical are immediately used to react with the reducing gas (NO, NO2, SO2 and Hg vapor) in the exhaust gas to be converted into a corresponding high oxidation state.
  • the oxides (NO2, NO3, SO3) and the second-order mercury ions (Hg2+), some of the acidic high-oxidation oxides react with the water vapor in the exhaust gas to form the corresponding acids (HNO2, HNO3, H2SO4), and the resulting inorganic The acid in turn promotes further decomposition of H2O2.
  • step 3 the remaining and newly generated free radicals and the remaining hydrogen peroxide are returned to the exhaust main pipe and the reducing gas (NO, NO2, SO2 and Hg steam) in the main exhaust gas together with the split exhaust gas to generate Corresponding high-oxidation oxides (NO2, NO3, SO3) and second-order mercury ions (Hg2+), some acidic high-oxidation oxides react with water vapor in the exhaust gas to form new acids (HNO2, HNO3, H2SO4) . Finally, all of the NO2, NO3, SO3, HNO2, HNO3, H2SO4 and mercury ions are removed in subsequent gas scrubbing units.
  • NO2, NO3, SO3, HNO2, HNO3, H2SO4 and mercury ions are removed in subsequent gas scrubbing units.
  • the injection flow rate of hydrogen peroxide can be determined by experiments.
  • the molar ratio of H2O2 to NOx in the raw exhaust gas ranges from 2 to 0.5:1, and the molar ratio of H2O2 to NOx is preferably 1:1. Since the presence of SO2 promotes the oxidation of NOx by H2O2, it is not necessary to consider the influence of SO2 concentration when determining the addition amount of hydrogen peroxide; and since the content of metallic mercury is generally much lower than that of NOx, it is not necessary to determine the addition amount of H2O2. Consider the effects of metallic mercury.
  • the optimum decomposition temperature of H2O2 is related to the composition of the exhaust gas and the composition of the H2O2 product used, and the presence or absence of a catalytic factor that promotes the decomposition of H2O2, and the general temperature is 200-600. In the range of °C, preferably 300 to 500 °C.
  • the ratio of the air volume of the split exhaust gas to the air volume of the mainstream exhaust gas is generally in the range of 0.5 to 50%, preferably 1 to 10%.
  • the optimum ratio of the split air volume to the mainstream air volume is determined by the ratio of the H2O2 concentration required for oxidizing NOx in the exhaust gas main pipe to the saturation concentration of H2O2 in the high temperature state of the exhaust gas branch pipe determined by the optimum molar ratio of H2O2 and NOx. .
  • the hydrogen peroxide injection device can be equipped with various nozzles or atomizing devices, including ultrasonic nozzles (ultrasound) Nozzle and Venturi nozzle (Venturi).
  • the nozzles are in the form of nozzles, so that H2O2 can be distributed in the form of steam or tiny droplets to the shunting exhaust gas flowing through, and partially or completely decomposed into a gas containing hydroxyl radicals, and the oxidizing gas passes through the second channel.
  • the nozzle or the diffusion device is mixed into the main exhaust pipe to react with the reducing gas contained in the main exhaust gas, oxidize the gas into a gas element of a higher oxidation state, and is removed into a subsequent washing device. The oxidation of the zero-order metallic mercury to the second-order mercury ions is also removed in subsequent liquid absorption.
  • the H2O2 used can be of high purity (eg containing H2O2) More than 80% of the aqueous solution may also be an aqueous solution having a relatively low purity (for example, a H2O2 concentration of 30%), which is required to have a concentration greater than 10%, since the boiling point of H2O2 is 150.2. °C, and the boiling point of water is 100 ° C, as long as the temperature of the gas is 150.2 Above °C, regardless of the H2O2 aqueous solution used, the relative concentration of H2O2 and water after gasification remains unchanged. If the temperature is further increased, more and more H2O2 will be decomposed and the relative concentration of water will increase due to water. The molecule is relatively stable, and it has little effect on the oxidative properties of H2O2 and its decomposition of hydroxyl radicals.
  • a certain amount of catalyst for promoting decomposition of H2O2 may be mixed in an aqueous solution of H2O2, including inorganic acids such as nitric acid, hydrochloric acid, sulfuric acid, and various iron or ferrous salts (iron or ferrous salts and H2O2).
  • the composition of the mixture is also known as Fenton's reagent (Fenton's Reagent)), the mixing ratio of these inorganic acid, iron salt or ferrous salt to H2O2 is less than or equal to 1:1, and the addition of these chemicals can promote the decomposition of H2O2 and generate hydroxyl radicals, thereby making H2O2 Decomposition occurs at lower temperatures. Since the addition of the above-mentioned catalyst for promoting the decomposition of H2O2 leads to instability of H2O2, these catalysts can be stored separately from H2O2 and mixed after both sides leave their respective storage tanks.
  • a heat exchange device can be used to transfer part of the heat of the outlet high-temperature gas to the relatively low-temperature branch gas exhaust gas, so that on the one hand, a part of the heat can be recovered to further reduce the energy consumption, and on the other hand, the gas after the oxidation reaction can be made.
  • the temperature is lowered to facilitate the operation of the subsequent gas scrubbing unit.
  • the method can be conveniently applied to the desulfurization device, and the effect of denitrification and de-heavy metal can be obtained by modifying the existing device;
  • the method can also be used for subsequent denitration and removal of heavy metals in the existing desulfurization device. Since hydrogen peroxide or hydrogen peroxide-based oxidant is used, the by-product obtained is relatively pure and is favorable for recycling.
  • FIG. 1 is a schematic structural view of an embodiment of the device according to the present application.
  • FIG. 2 is a schematic structural view of another embodiment of the device according to the present application.
  • FIG. 3 is a schematic structural diagram of still another embodiment of the device according to the present application.
  • 1 is the upstream flue gas inlet
  • 2 is the exhaust gas main pipe
  • 3 is the diverting branch pipe
  • 4 is the heating reaction chamber
  • 5 is the downstream flue gas outlet
  • 6 is the exhaust gas main control valve
  • 7 is the diverting branch pipe control valve
  • 8 is the fan
  • 9 is a heater
  • 10 is a diffusion distributor
  • 11 is an oxidant storage tank
  • 12 is a filling pump
  • 13 is a nozzle
  • 14 is an oxidant injection control valve
  • 15 is a venturi
  • 16 is a heat exchanger
  • 17 is a conveying pipe .
  • Examples 1-3 are various embodiments of an apparatus for removing nitrogen oxides, sulfur oxides, and mercury in an exhaust gas using an oxidation process as described in the present application.
  • the apparatus as shown in FIG. 1 includes an exhaust gas main pipe, a branch pipe branch and an oxidant injection device, wherein the intake end and the outlet end of the branch pipe branch 3 are respectively opened between the upstream flue gas inlet 1 and the downstream flue gas outlet 5 of the exhaust gas main pipe 2
  • the downstream flue gas outlet 5 of the exhaust gas main pipe 2 is connected to the washing device, and the diverting branch pipe control valve 7 and the fan 8 are provided at the intake end of the diverting branch pipe 3, and the exhaust gas main pipe control valve 6 is provided on the exhaust gas main pipe 2 for control And adjusting the intake air amount and the flow rate of the branch pipe 3,
  • the heating reaction chamber 4 is provided at the outlet end of the branch pipe 3, and the heater 9 is provided in the heating reaction chamber 4, and the oxidant injection device includes the oxidant tank 11 and the pipe 17
  • the conveying pipe 17 is opened downstream of the heater 9 in the heating reaction chamber 4, and the heating reaction chamber 4 is directly connected to the exhaust gas main pipe 2, and the opening is provided with a diffusion distributor 10.
  • the opening position of the conveying pipe 17 in the oxidizing agent injection device is set.
  • the injected oxidant can be sufficiently mixed and heated in the branch pipe and the split exhaust gas, and a nozzle is provided at the end of the transfer pipe 17 of the oxidant injection device.
  • a nozzle is provided at the end of the transfer pipe 17 of the oxidant injection device.
  • 13 may be an ultrasonic nozzle, in which case a filling pump 12 may be added to the delivery pipe 17 to provide power for the injection of the oxidant.
  • the apparatus of Fig. 2 has the same basic structure as that of Embodiment 1, except that the end of the delivery pipe 17 of the oxidant injection device is provided with a venturi for inhaling the oxidant, while the delivery pipe 17 is close to the oxidant storage.
  • the position of the tank 11 is provided with an oxidant injection control valve 14 for controlling the amount of hydrogen peroxide injected.
  • the flue gas of a power plant is treated by the invention, the total flue gas flow is 220,000 m3/h, and the flue gas contains SO2 1700 Mg/m3, NOx 1300 mg/m3, temperature 150 °C.
  • Set the flue gas split flow rate to 10% of the total flue gas flow, ie 22,000 M3 / hour; using the valve adjustment method to control the flow of the split flue gas; the split flue gas is heated to 500 ° C by electric heating; H2O2 is added in a ratio of H 2 O 2 to NOx molar ratio of 1:1, and the flow rate of the added H 2 O 2 is 324 Kg / hour; H2O2 is added by ultrasonic atomizer, the concentration of H2O2 in the split flue gas is about 14.7 g/m3.
  • H2O2 entering the heating section is quickly evaporated into a gas, which stays at about 0.8 in the high temperature section. In seconds, most of the H2O2 entering the heating section is decomposed into free radicals such as HO• and HO2•, and the free radicals formed by decomposition and their remaining hydrogen peroxide first occur with NOx, SOx and metallic mercury in the split flue gas. The reaction produces higher oxidation state NOx, SOx, second-order mercury ions, and part of nitric acid, nitrous acid and sulfuric acid.
  • the generated nitric acid, nitrous acid and sulfuric acid promote the oxidation activity of H2O2, so that the remaining H2O2 can be further decomposed into free
  • the newly formed and remaining free radicals are returned to the mainstream flue gas channel along with the split flue gas to oxidize with reducing substances such as NOx in the mainstream flue gas, and oxidize them to oxidation products of higher oxidation state.
  • Nitrogen oxide reacts with water vapor to form nitric acid and nitrous acid.
  • the temperature of the flue gas will be slightly higher than the intake temperature of the flue gas, about 170 ° C, after the condensation treatment, the temperature will reach below 100 ° C, and enter the flue gas washing device, NO2, NO3 in the flue gas, SO2, SO3, Hg2+, as well as nitric acid, nitrous acid, sulfuric acid, sulfurous acid, etc. are absorbed in the flue gas scrubbing device, and the flue gas scrubbing device can be used in a commercially available venturi washing device such as the venturi sold under the trademark ReitherM. A washing device, or a packed tower water scrubber.
  • the removal rate of NO reaches 90%
  • the removal rate of SO2 reaches 99%
  • the removal rate of metal mercury can reach over 90%.
  • the energy saving is about 90% compared to the method of warming all the flue gases.
  • the flow rate of the split flue gas is 1% of the total flow rate, that is, 2,200. M3/h, using split air pump and flow metering control device to control the flow of splitting flue gas; shunting flue gas is heated to 500 °C by electric heating method; H2O2 is added in a ratio of H2O2 to NOx molar ratio of 1:1, adding The flow of H2O2 is 324 Kg/h, sprayed with a venturi nozzle designed spray device (see Figure 2). The concentration of H2O2 in the split flue gas is about 147.
  • the saturated vapor pressure of H2O2 exceeds 1 atm at 500 °C, at which time the H2O2 concentration in the split flue gas (147 g/m3) is lower than the saturated vapor concentration at this time (greater than 200) g/m3).
  • H2O2 entering the heating section is quickly evaporated into a gas, which stays at about 0.5 in the high temperature section. Seconds, then enter the mainstream flue and mix with mainstream smoke.
  • the temperature of the flue gas after the reaction is almost the same as the inlet temperature of the flue gas, about 150 ° C, after the condensation treatment, the temperature reaches below 100 ° C, and enters the flue gas washing device to take NO 2 , NO 3 in the flue gas at this time.
  • the flue gas washing device uses a marketed venturi washing device such as the venturi washing device sold under the trademark Reither.
  • the removal rate of NO reaches 80%
  • the removal rate of SO2 reaches 99%
  • the removal rate of metal mercury reaches 80% or more.
  • the flow rate of the split flue gas is 30% of the total flow rate, that is, 66,000.
  • the regulating valve is used to adjust the flow rate of the splitter flue gas; the split flue gas is heated to 500 °C by electric heating method; H2O2 is added in a ratio of H2O2 to NOx molar ratio of 1:1, and the flow rate of the added H2O2 is 324. Kg/h, sprayed with an ultrasonic nozzle.
  • the concentration of H2O2 in the split flue gas is about 5 g/m3. H2O2 entering the heating section is quickly evaporated into a gas, which stays at about 0.5 in the high temperature section.
  • the reducing gas in the splitter flue gas is first oxidized, and the resulting inorganic acid promotes further decomposition of H2O2.
  • the remaining or newly formed hydrogen or oxygen peroxide radicals enter the mainstream flue and mix with the mainstream smoke.
  • the temperature of the flue gas after the reaction is about 255. °C. Due to the high temperature, the heat contained in the flue gas after the reaction is considered to be recovered, and part of the heat is transferred to the intake of the split flue gas through the heat exchanger (Fig. 3). After the heat exchange, the temperature of the split flue gas inlet is increased.
  • the temperature of the mixed flue gas drops to 230 ° C, after condensation treatment, the temperature reaches below 100 ° C, and enters the flue gas scrubbing device, NO2, NO3, SO2, SO3, Hg2+, nitric acid in the flue gas.
  • Nitrous acid, sulfuric acid, sulfurous acid and the like are absorbed in the flue gas washing device, and the flue gas washing device uses a commercially available venturi washing device.
  • the removal rate of NO is 90%, the removal rate of SO2 is 99%, and the removal rate of metal mercury is over 90%. Compared with the method of heating all the flue gas, energy can be saved by more than 80%.
  • the flue gas split flow rate is 10% of the total flue gas flow rate, that is, 22,000. M3/hour; valve and air pump are used to regulate and control the flow of splitter flue gas; ClO2 is used as oxidant.
  • ClO2 was prepared by the reaction of chlorous acid and concentrated hydrochloric acid. The split flue gas is heated to 500 ° C by electric heating; ClO2 is added in a ratio of ClO2 to NOx of 1:3, and the flow rate of ClO2 added is 229.

Abstract

本发明申请提供一种能够综合对废气进行脱硝、脱硫和脱汞处理，并且克服了高温的反应条件所带来的高能耗问题的工艺方法及其相应的配套设备。是通过将废气进行分流，利用分流废气作为氧化剂的载气，并将其加热至氧化剂的分解温度，形成氧化能力更强的氢氧和过氧氢氧自由基，并使这些自由基随分流废气一起与未加热的主流废气混合，并与废气中的NOx、SOx和汞蒸汽等还原性气体进行反应，使其氧化成更高氧化态的NOx、SOx和汞离子，所有的酸性产物以及汞离子在后续的气体洗涤装置中得以去除。所述的方法和设备由于只用一部分烟气作为氧化剂的载体，并使氧化剂等离子化，可以大大降低氧化法所需的能量，有效地去除NO2和SOx以及金属汞等还原性重金属。

Description

氧化法去除废气中氮氧化合物、硫氧化物和汞的工艺及其设备 Technical Field
本发明申请涉及烟气及其它工业废气中氮氧化合物（ NOx ）、硫氧化合物（ SOx ）和汞的去除工艺及其设备，属于工业废气处理与环境保护技术领域。
Background Art
燃烧过程及其相近的化工过程中所产生的烟气等废气的处理是在大气污染防治领域中非常重要的一个方面。这类废气的共同特点是温度比较高（通常都在 100°C 以上），含有浓度比较高的氮氧化物、硫氧化物以及少量金属氧化物或金属蒸汽。氮氧化物部分来自燃料中含氮化合物的氧化，部分来自于空气中氮气的氧化，总的氮氧化合物中 NO 通常占 90% 左右，其余的主要为 NO 2 。硫氧化物主要来自于燃料中硫化物的氧化，除少部分 SO 3 外，绝大部分为 SO 2 。金属氧化物主要来自于燃料中所含的金属化合物的氧化，绝大部分的金属氧化物冷却后即混合到灰分中，不进入大气环境中，能进入大气并危害环境的主要是低沸点的金属蒸汽，如零阶金属汞。
针对烟气中 SOx 的控制（即脱硫），目前主要采用的方法有湿法、干法及混合法等几类。干法脱硫工艺是通过在燃烧炉或燃烧炉后烟道里喷入粉状石灰石（ CaCO 3 ），石灰（ CaO ）或消石灰（ Ca(OH) 2 ）等 SOx 的吸附和吸收材料将 SOx 去除。该法虽然工艺简单，但反应效率低，需要用到大量的吸附 / 吸收材料，去除效率一般低于 70% ；当吸附材料喷入燃烧炉时还容易造成锅炉热交换器表面的结垢，需要频繁地清洗热交换器表面。反应后的吸附材料增加了烟气中的固体颗粒浓度，给烟气除尘造成困难，需要采取增加湿度或注入 SO 3 等办法来相应地提高除尘效果；此外，反应后的吸附材料混入燃烧灰分中使得其回收利用非常困难。
湿法脱硫工艺通过使用湿式洗涤（ wet scrubbing ）装置来吸收 SOx 。洗涤液通常采用碱液（ NaOH 或 Ca(OH) 2 ）；废气和洗涤液充分接触，使得 SOx 被吸收到碱性液体中得以去除。该法通常可以获得 90% 以上的去除效率，所产生的硫酸盐和亚硫酸盐可以作为副产物回收利用。主要缺点是设备成本比干法高，会损失一部分水到烟气中；同时会产生一定量的废水，需要额外的处理。除了以上的两种方法外，还有一种混合洗涤法，即洗涤液通过喷雾器以微小液滴的形式进入洗涤装置中，这种方式仅需少量液体洗涤液，因此也称为干式洗涤。该法的主要缺点是废气通过洗涤装置所需的压降比较大，从而造成较大的能耗；而且对气体的温度有一定的限制，一般要求进入洗涤装置的气体温度必须接近或低于被洗涤气体的饱和温度（ saturation temperature ）。
烟气的脱氮（也称为脱硝）可以采用选择性催化还原法（ selective catalytic reduction-SCR ）、选择性非催化还原法（ selective non catalytic reduction-SNCR ）、氧化法和吸附吸收法等方法。选择性催化还原法通过在烟道中注入氨并让其与烟气一起通过催化剂层，在催化剂的作用下氨气把 NOx 还原为 N 2 。此反应需要 300°C 左右的温度，因此氨的加注和催化剂的安装必须在靠近锅炉出口处及除尘器以前。催化剂通常为过渡金属氧化物如 V 2 O 5 、 Fe 2 O 3 和 CuO 等。此法工艺相对简单，去除效率高，一般可以达到 80% 以上的去除率。缺点是催化剂成本昂贵；由于催化剂层必须装在除尘装置以前，因此催化剂层必须经常清洗和更换；同时氨是不稳定有刺激性气味的化合物，保存及运输中存在安全隐患；为了保证较高的去除效果，一般需要适当过量地添加氨气，这会带来氨气泄漏的风险，而氨气泄漏到环境中会对大气环境造成严重的影响。选择性非催化还原法将还原剂氨或尿素添加到燃烧炉里面，在 1000 °C 左右的高温下把 NOx 还原成 N 2 。此法虽然工艺简单，无需利用催化剂，但去除效果较低，一般低于 70% 。使用尿素时在添加过程中不可避免地要注入一定量的水（水作为尿素的溶剂），水的蒸发会带来较大的能量损失。吸附或吸收法采用活性炭吸附剂或有机金属螯合物吸收剂如乙二胺四乙酸铁（ FeIIEDTA ）和乙二胺合钴（ Co （ en ） 3 ） 2+ 来吸附或吸收 NOx 。此类方法往往可以在去除 NOx 的同时去除 SOx ，去除效率较高，但吸附 / 吸收剂用量大，而且价格昂贵；还有吸附 / 吸收剂的再生困难，吸附或吸收的 NOx 或 SOx 无得到转化，在解析后仍然需要处理。
氧化法脱硝采用在烟气中注入氧化剂的方法把 NO 和 NO 2 分别氧化成更容易溶解于水或碱性溶液的 NO 2 和 NO 3 ，而后通过气体洗涤装置把 NO 2 和 NO 3 吸收到吸收液中去生成亚硝酸（盐）或硝酸（盐）。常用的氧化剂有次氯酸钠、过氧化氢、臭氧和二氧化氯（ ClO 2 ）（ US Pat 7 ， 628 ， 967 B2 ）和氯气（ US Pat 4 ， 619 ， 608 和 US Pat 6 ， 447 ， 740 ）等。次氯酸钠和过氧化氢在常温下为液体，它们一般是被混入到气体洗涤器的液相中得以使用，但也可单独喷淋使用。臭氧、 ClO 2 和氯气常温下为气体，它们一般被直接注入到气体中使用。氧化法脱硝可以达到比较高的去除效率。由于氧化剂一般都可以氧化 SO 2 和金属汞，同时 NO 2 和 NO 3 的吸收去除方法和 SO 2 和 SO 3 的吸收去除方法相同，因此氧化法脱硝可以同时实现去除 SO 2 和金属汞。但是，氧化剂的用量、反应条件及能耗等受氧化剂的种类和氧化剂的添加方式很大的影响。例如，臭氧是氧化活性很高的气体，只能在现场生产，需要消耗大量的电能。又如次氯酸钠、二氧化氯和氯气含有氯，会在一定程度上增加废水处理的难度和氧化产物的回收利用，同时也需要较高的反应温度。过氧化氢虽然不会造成新的污染物和影响到副产物质量，但它在通常温度下氧化效率相对较低，需要添加大量的过氧化氢或提高反应温度才能达到理想的效果。
目前去除烟气中汞（元素汞和汞离子）的方法主要有氧化法和活性炭吸附法，氧化法使用卤代气体如溴气、氯气、碘分子其化合物（ US Pat 6 ， 878 ， 358 B2 和 US Pat 6 ， 447 ， 740 ）或元素硫和硫化物包括 H 2 S 、 COS （ US Pat 6 ， 972 ， 120 B2 ）和 Na 2 S 4 （ EP 0 ， 709 ， 128 A2 ）等与汞反应来生成凝固点高或液体洗涤液中溶解性好的汞金属化合物，从而使汞脱离气相进入固相残渣或液相残液。美国专利 US Pat 6 ， 503 ， 470 也提到可以添加硫氢化钠（ NaHS ）或其它硫化合物和汞反应生成硫化汞。 US Pat 6 ， 447 ， 740 提到了添加碱金属碘盐来与汞离子反应生成 HgI 2 沉淀。这些反应试剂中除了氯气为常用氧化剂可以同时处理其它气体成分外，都是专门针对汞的去除的，对烟气中其它污染成分去除的帮助不大。这些方法若单独用于汞的去除，成本很高。而活性炭对汞的吸附能力不是很大，一般都要对其表面进行处理（如用溴气来薰蒸或用溴酸来浸渍）才能获得较好的处理效果。
美国专利 US Pat 7 ， 628 ， 967 B2 提出了用多段洗涤法来同时去除废气中的 SOx 、 NOx 和汞，即先用常规的碱液吸收去除全部或部分的 SOx ，然后注入氧化剂使得 NOx 和剩余的 SOx 被氧化成具有更高氧化态的 NOx 和 SOx ，并用碱液把生成的高氧化态的 SOx 和 NOx 吸收掉，最后再经过一道常规碱液洗涤去除残余的 NOx 和 SOx 。挥发性金属汞可以在氧化段被氧化成离子态的汞从而在后续的水洗装置中得以去除。氧化剂使用过氧化氢，或过氧化氢与硝酸的混合物，或其与硝酸与亚氯酸的混合物，以及各种氯酸的钠盐或钾盐。氧化剂添加到液体洗涤液中使用。该法虽然可以实现同时脱除 SOx 和 NOx 及汞，但显然工艺流程比较长。此外，该专利也没有具体说明氧化反应的条件。
由于过氧化氢常温下为液体，运输存储比较方便，只含有氢氧两种元素，不会带来有害副产物，因此使用过氧化氢作为氧化剂来进行废气脱硝具有较大的优势。 Collins 等 (2001) 揭示过氧化氢和 NO 的反应其最佳的温度为 500 °C 。在这一温度下 H 2 O 2 分解产生 HO 自由基， HO • 自由基和 H 2 O 2 进一步反应生成 HO 2 • 自由基，它是一种非常活泼的自由基；所需的 H 2 O 2 和 NO 的摩尔比为 1 ： 1 ，可以达到 90% 左右的去除率，而且二氧化硫的存在对 NOx 的去除不造成影响，相反还有促进作用，这为同时脱硫脱硝提供了非常有利的条件。但是该方法需要很高的反应温度，一般燃烧炉的出口经过换热器后的温度只有 150 °C 左右，因此要达到理想的脱硝效果，必须把烟气的温度大幅度提高到 500 °C ，这必然要消耗大量的能量。此外，温度提高对后续的洗涤作业产生不利的影响，因为保证洗涤高效进行的气体温度必须在被洗涤气体的露点以下。
综上所述，已知的废气脱硫工艺如干法、湿法或混合法洗涤工艺只对去除 SOx 有效，无法同时实现脱销和脱重金属；已知的废气脱硝工艺如选择性催化还原法、选择性非催化还原法、以及吸附吸收法都存在这样那样的问题，要么成本昂贵，要么效果不理想，要么吸附 / 吸收剂再生困难，在脱硝的同时也无法实现同时脱硫和脱重金属，在生产上无法大量推广使用。现有的氧化法脱硝工艺虽然可以同时兼顾脱硫和去除重金属汞，但其成本和效果除了取决于氧化剂的种类外，还很大程度上和氧化剂的使用方法有关。臭氧的发生需要消耗大量的电流，含氯的氧化剂如各类氯酸（高氯酸，氯酸，亚氯酸和次氯酸）及其钠盐或钾盐、氯气和二氧化氯会在洗脱液中引入含氯化合物，这对相应的废水处理和副产物回收造成不利影响，此外这些方法一般需要较高的反应温度或者进行超剂量的添加。
过氧化氢作为脱硝氧化剂，不会影响洗脱产品的纯度，也不会对相应的废水处理带来负面影响，但要达到理想的脱硝效果也需要比较高的反应温度，需要对所有的烟气进行加温，这样必然会带来很大的能耗，并对后续的洗涤作业产生不利的影响。
 Technical Problem
本发明申请即是针对目前在对废气脱硝、脱硫和去除金属汞的工艺方法中存在的上述问题，提供一种能够对废气综合进行脱硝、脱硫和脱汞处理，并且克服了高温的反应条件所带来的高能耗问题的工艺方法及其相应的配套设备。
本发明申请所述的工艺方法旨在优化使用以过氧化氢为代表的氧化剂来进行脱硝，克服由于需要高温的反应条件而带来的高能耗问题，最大限度地发挥这些氧化剂的氧化能力和脱硝效果，并同时实现脱硫和脱汞。
 Technical Solution
本发明申请的思路是将废气进行分流，利用分流废气作为氧化剂的载气，并将其加热至氧化剂的分解温度，形成氧化能力更强的氢氧和过氧氢氧自由基，并使这些自由基随分流废气一起与未加热的主流废气混合，并与废气中的NOx、SOx和汞蒸汽等还原性气体进行反应，使其氧化成更高氧化态的NOx、SOx和汞离子，部分生成的NOx和SOx与废气中的水蒸汽生成亚硝酸、硝酸和硫酸等产物，这些酸性产物的生成可以反过来促进H2O2的分解，所有的酸性产物以及汞离子在后续的气体洗涤装置中得以去除。当采用较大的废气分流时，加热的分流废气与未加热的主流废气混合后温度仍会有较大幅度上升，此时可采用热交换的方法把高温气体的部分热量传递给温度相对较低的废气进气，以便进一步降低能耗，同时使得氧化反应后气体的温度降低，这样有利于提高后续气体洗涤装置的洗涤效果。
采用过氧化氢H2O2氧化NO和NO2需要高温，这主要是因为只有在高温下，H2O2才会被大量的分解。Baldwin和Brattan（1961）揭示在520°C下60%左右的H2O2能得到分解，其分解反应如以下方程所示：
H2O2 = 2HO•
H2O2 + HO• = HO2• + H2O
H2O2 +HO2• = H2O + O2 + HO•
2HO2• = H2O2 + O2
过氧化氢受热分解产生氢氧自由基（HO•）和过氧氢氧自由基（HO2•），而这些自由基又能和过氧化氢反应生成新的自由基，这种链式反应的发生使得过氧化氢被很快的分解并产生大量的氢氧和过氧氢氧自由基，这些自由基具有比H2O2更高的氧化还原电位，可以更有效地与NO、NO2或SO2或金属汞反应。但是这些自由基也能够相互碰撞并重新生成过氧化氢及氧气，因此在某一温度下会达到一个动态平衡，温度越高，平衡向着生产更多自由基的方向转移，直至在某一温度下达到或接近自由基的饱和浓度。基于这样的认识，用过氧化氢来氧化废气中的还原性气体不需要把所有的气体都加热到过氧化氢的（饱和）分解温度，只需要把过氧化氢加热到其分解温度。但是为了降低分解所生成的自由基碰撞后重新变回到原始氧化态的分子，过氧化氢的浓度最好调整到其饱和蒸汽浓度以下，这样既可以大大降低加热整个反应体系所需的能量，又可以最大限度地保证自由基的生成产率，达到低成本高效率地氧化废气中还原性气体（NO、NO2或SO2和金属汞）的目的。
本发明申请的一个目的是提供一种利用氧化法去除废气中氮氧化合物、硫氧化物和汞的设备，所述的设备包括废气主管、分流支管和氧化剂注入装置，其中，
1. 分流支管的进气端和出口端分别开口于废气主管的上游烟气进口与下游烟气出口之间，废气主管的下游烟气出口连接洗涤装置；
2. 在分流支管内靠近进气端的位置设有控制阀和风机，控制和调节分流支管的进气量和流速，在分流支管接近出口端的位置设有加热反应室，在加热反应室内设有加热器；
3. 氧化剂注入装置包括氧化剂储槽、输送泵和输送管，输送管开口于加热反应室内加热器的下游，加热反应室直通废气主管内，开口处设有扩散分布器或喷嘴。
优选的，还可以在所述的废气主管位于所述的分流支管入口的下游设置气流控制阀，用于控制分流支管内气体的流量和流速。
进一步的，所述的加热器包括电加热器。
优选的，氧化剂注入装置中输送管的开口位置设在加热反应室内尽量靠近进气端的位置，使得注入的氧化剂能在支管内和分流废气充分混合、得到充分加热、并被分解为氧化能力更强的氢氧和过氧氢氧自由基。
所述的氧化剂包括过氧化氢以及其它能够在高温条件下分解形成自由基的氧化剂，这些氧化剂包包括氯气、ClO2、次氯酸、亚氯酸、氯酸、高氯酸、它们的钠盐或钾盐、它们的混合物，或它们与它们各自的促进分解的催化剂的混合物。
进一步的，所述氧化剂注入装置的输送管的末端设有喷嘴或雾化装置，所述的喷嘴包括超声波喷嘴（ultrasound nozzle）或文丘里喷嘴（Venturi nozzle），当使用超声波喷嘴时，在输送管上可以增设加注泵，为氧化剂的注入提供动力；当使用文丘里喷嘴时，在所述的输送管上增设氧化剂注入控制阀，用于控制过氧化氢的注入量。
文丘里喷嘴是根据文丘里效应设计而成的，所谓的文丘里效应是当流体从较大的过流断面进入较小的过流断面时其流体压力降低的现象。利用高速气流以及气流流经狭窄喉口所造成的负压可以使得需要添加的液体从喉口吸入并与气体充分混合，在气体剪切力的作用下，在下游的喷口形成喷雾。进一步的，当较大比例的废气由分流支管进行分流的时候，例如分流废气与主流废气的比例大于10%时，分流废气流回到主流管道与未加热的主流废气混合后使得混合气体的温度会有较大幅度的上升，此时可增设热交换装置，把混合气体的部分热量传递给温度相对较低的分流废气进气。
本发明申请的另一个目的是提供利用上述的设备进行氧化法去除废气中氮氧化合物、硫氧化物和汞的方法，所述的方法包括如下的工艺步骤：
1. 废气分流：在废气主通道的上游烟气进口与下游烟气出口之间设置分流支管来对需进行处理的废气进行分流；
2. 混合加热：分流废气的流量可以通过在废气主通道上设置的气流控制阀以及设在废气支管上的气流控制阀和风机来控制和调节，在加热反应室内，注入的氧化剂能和分流废气充分混合加热；
3. 回流洗涤：带有高氧化性自由基的分流废气流回废气主管道并和废气主管道内的废气进行完全混合，混合废气反应后进入后续洗涤装置。
具体的，本发明申请提供一种利用过氧化氢去除废气中氮氧化合物、硫氧化物和汞的方法，所述的方法包括如下的工艺步骤：
1. 废气分流：在废气通道主管的上游烟气进口与下游烟气出口之间设置分流支管来对需进行处理的废气进行分流；
2. 混合加热：分流废气的流量可以通过在废气主通道上设置的气流控制阀以及设在废气支管上的气流控制阀和风机来控制和调节，在加热反应室内，注入的过氧化氢能和分流废气充分混合，并得以加热，并被分解为氧化能力更强的氢氧和过氧氢氧自由基；
3. 回流洗涤：带有高氧化性自由基的分流废气流回废气主管道并和废气主管道内的废气进行完全混合，经过0.4~5.0秒的反应时间后，混合废气进入后续洗涤装置。
进一步的，在所述的方法中，过氧化氢以一定流量通过氧化剂注入装置注入废气支管与分流废气充分混合，并在加热反应室内停留0.2~4.0秒，优选0.5~1.0秒。设在废气支管上的加热器使得分流废气的温度提高到H2O2的最佳分解温度，此时H2O2被全部或部分地分解为HO•和H O2•等自由基。
在上述的方法步骤2中一部分过氧化氢及所产生的自由基被立即用于和分流废气中的还原性气体（NO、NO2、SO2及Hg蒸汽）反应，使其转化成相应的高氧化态的氧化物（NO2、NO3、SO3）及二阶汞离子（Hg2+），部分酸性高氧化态的氧化物和废气中的水蒸气反应生成相应的酸（HNO2、HNO3、H2SO4），这些生成的无机酸反过来又能促进H2O2的进一步分解。
在上述步骤3中，剩余的和新生成的自由基及剩余的过氧化氢随分流废气一起流回废气主管道与主流废气中的还原性气体（NO，NO2，SO2和Hg蒸汽）反应，生成相应的高氧化态的氧化物（NO2、NO3、SO3）及二阶汞离子（Hg2+），部分酸性高氧化态的氧化物和废气中的水蒸气反应生成新的酸（HNO2、HNO3、H2SO4）。最后，所有生成NO2、NO3、SO3、HNO2、HNO3、H2SO4及汞离子在后续的气体洗涤装置得以去除。
在上述的方法中，过氧化氢的注入流量可由试验来确定，H2O2与原废气中的NOx的摩尔比的取值范围为2~0.5：1，H2O2和NOx的摩尔比优选1：1。由于SO2的存在对H2O2氧化NOx有促进作用，所以在确定过氧化氢的添加量时不必考虑SO2浓度的影响；又由于金属汞的含量一般远低于NOx，因此确定H2O2的添加量时也不必考虑金属汞的影响。
在上述的方法中，H2O2的最佳分解温度受废气的成分以及所用的H2O2产品成分、有无促进H2O2分解的催化因子存在有关，一般温度在200~600 ℃范围内，优选300~500℃。分流废气的风量占主流废气风量的比例，一般在0.5~50%的范围内，优选为1~10%。分流风量占主流风量的最佳比例由前述H2O2和NOx的最佳摩尔比所确定的在废气主管内氧化NOx所需的H2O2的浓度与在废气支管内高温状态下H2O2的饱和浓度的比例来决定。
过氧化氢的注入装置可选用各种喷嘴或雾化装置，包括超声波喷嘴（ultrasound nozzle）及文丘里喷嘴（Venturi nozzle）等喷嘴形式，使得H2O2能以蒸汽或微小雾滴的形式分布到流经的分流废气中去，并部分或全部分解成含氢氧自由基的气体，这样的氧化气体再通过第二道喷嘴或扩散装置混入到废气主管道中去，与主流废气中所含的还原性气体发生反应，把这些气体氧化成更高级氧化态的气体分子，并进入后续的洗涤装置中得以去除。零阶金属汞则被氧化成二阶汞离子也在后续的液体吸收中得以去除。
所用的H2O2可以是纯度高（如含H2O2 80%以上）的水溶液，也可以是纯度比较低（如H2O2浓度为30%）的水溶液，要求其浓度大于10%，由于H2O2的沸点为150.2 ℃，而水的沸点为100℃，只要气体的温度为150.2 ℃以上，不管使用哪种H2O2的水溶液，气化后的H2O2和水的相对浓度保持不变，若温度进一步提高，越来越多的H2O2被分解，水的相对浓度会有所提高，由于水分子比较稳定，它对H2O2及其分解所产生的氢氧自由基的氧化性的影响不大。
作为一种选择，在H2O2的水溶液中也可混入一定量的促进H2O2分解的催化剂，包括硝酸、盐酸、硫酸等无机酸，和各类铁盐或亚铁盐（铁盐或亚铁盐与H2O2的混合物组成也称为芬顿试剂（Fenton’s reagent）），这些无机酸、铁盐或亚铁盐与H2O2的混合比例为摩尔小于或等于1：1，这些化学试剂的加入可以促进H2O2的分解并生成氢氧自由基，而从而使得H2O2的分解在较低的温度下发生。由于加入上述提到的促进H2O2分解的催化剂会导致H2O2不稳定，这些催化剂可以和H2O2分开储存，在双方离开各自的储罐后再混合。
当采用较大比例的废气分流的时候，如分流废气与主流废气的比例大于10%，分流废气流回到主流管道与未加热的主流废气混合后混合气体的温度会有较大幅度的上升，此时可采用热交换装置把出口高温气体的部分热量传递给温度相对较低的支流废气进气，这样，一方面可以回收一部分热量，进一步降低能耗，另一方面可以使得氧化反应后气体的温度降低，以利于后续气体洗涤装置的运行。
 Advantageous Effects
本发明申请所述的设备及工艺方法，具有以下的优点：
1、 由于只用一部分烟气作为氧化剂的载体，并使其等离子化，可以大大降低氧化法所需的能量，有效地去除NO2和SOx以及金属汞等还原性重金属；
2、 该方法可以方便的用于脱硫装置上，通过改造现有装置而获得脱硝和脱重金属的作用；
3、 该方法也可以单独用于既有脱硫装置后续的脱硝和去除重金属，由于使用过氧化氢或以过氧化氢为主的氧化剂，所获得的副产品比较纯，有利于回收利用。
 Description of Drawings
图1为本发明申请所述设备的一个实施例的结构示意图；
图2为本发明申请所述设备的另一个实施例的结构示意图；
图3为本发明申请所述设备的再一个实施例的结构示意图；
其中，1为上游烟气进口、2为废气主管、3为分流支管、4为加热反应室、5为下游烟气出口、6为废气主管控制阀、7为分流支管控制阀、8为风机、9为加热器、10为扩散分布器、11为氧化剂储槽、12为加注泵、13为喷嘴、14为氧化剂注入控制阀、15为文丘里管、16为热交换器、17为输送管。
 Mode for Invention
以下结合具体的实施方式，对本发明申请所述的工艺方法进行描述，目的是为了公众更好的理解本发明申请所述的技术内容，而不是对所述技术内容的限制，尽管本发明的主要内容如上所述，但本发明的技术内容并不限于这些，还包括对于本领域的普通技术人员来说显而易见的各种各样的改动和变通，这些改动或变通只要符合本发明的精神实质、特征和范畴，则都在本发明申请所要求保护的技术方案之内。
实施例1-3是本发明申请所述的利用氧化法去除废气中氮氧化合物、硫氧化物和汞的设备的不同实施例。
实施例1
如图1所述的设备包括废气主管、分流支管和氧化剂注入装置，其中，分流支管3的进气端和出口端分别开口于废气主管2的上游烟气进口1与下游烟气出口5之间，废气主管2的下游烟气出口5连接洗涤装置，在分流支管3的进气端设有分流支管控制阀7和风机8，同时在废气主管2上设有废气主管控制阀6，用于控制和调节分流支管3的进气量和流速，在分流支管3的出口端设有加热反应室4，在加热反应室4内设有加热器9，氧化剂注入装置包括氧化剂储槽11和输送管17，输送管17开口于加热反应室4内加热器9的下游，加热反应室4直通废气主管2内，开口处设有扩散分布器10，优选的，氧化剂注入装置中输送管17的开口位置设在加热反应室4尽量靠近进气端的位置，使得注入的氧化剂能在支管内和分流废气充分混合和加热，在所述氧化剂注入装置的输送管17的末端设有喷嘴13，例如可以是超声波喷嘴，此时在输送管17上可以增设加注泵12，为氧化剂的注入提供动力。
实施例2
如图2所述的设备，其基本结构与实施例1相同，区别在于所述的氧化剂注入装置的输送管17的末端设有文丘里管，用于吸入氧化剂，同时在输送管17靠近氧化剂储槽11的位置设有氧化剂注入控制阀14，用于控制过氧化氢的注入量。
实施例3
其结构如图3所示，基本结构与图1和图2相同，当较大比例（例如大于10%时）的废气由分流支管进行分流的时候，分流废气流回到主流管道与未加热的主流废气混合后使得温度会有较大幅度的上升，此时可增设热交换器16，把分流支管出口高温气体的部分热量传递给温度相对较低的分流支管废气进气端。
实施例4
对某一发电厂的烟气利用本发明进行处理，烟气总流量为220,000 m3/h，烟气中含有SO2 1700 mg/m3, 含NOx 1300 mg/m3, 温度为150 ℃。设定烟气分流流量为烟气总流量的10%，即22，000 m3/小时；采用阀门调节法控制分流烟气流量；分流烟气用电加热的方法加热至500℃；H2O2以H2O2与NOx的摩尔比1：1的比例投加，加入的H2O2的流量为324 kg/小时；H2O2的加入采用超声波雾化装置（ultrasound atomizer），在分流烟气中的H2O2的浓度约为14.7 g/m3。在500℃时H2O2饱和蒸汽压超过1大气压，因此H2O2浓度（14.7 g/m3）远低于此时的饱和蒸汽浓度。进入加热段的H2O2迅速得以蒸发成气体，在高温段停留约0.8 秒，使得大部分的进入加温段的H2O2被分解成HO•和HO2•等自由基，分解形成的自由基及其剩余的过氧化氢首先与分流烟气中的NOx，SOx及金属汞发生反应，生成更高氧化态的NOx、SOx、二阶汞离子、及部分硝酸、亚硝酸和硫酸，生成的硝酸、亚硝酸、硫酸促进了H2O2的氧化活性，使得剩余的H2O2得以进一步分解成自由基，新生成的和剩下的自由基随分流烟气一起返回主流烟气通道与主流烟气中的NOx等还原性物质发生氧化反应，并将它们氧化成更高氧化态的氧化产物，这些氮氧化物与水蒸汽反应部分生成硝酸和亚硝酸。此时的烟气温度会比烟气的进气温度略高，约在170℃左右，经过冷凝处理后使其温度达到100℃以下，并进入烟气洗涤装置，烟气中的NO2、NO3、SO2、SO3，Hg2+、还有硝酸、亚硝酸、硫酸、亚硫酸等在烟气洗涤装置中被吸收掉，烟气洗涤装置可采用已经市场化的文丘里洗涤装置如以商标ReitherM销售的文丘里洗涤装置，或填充塔水洗器。去除率NO达到90%，SO2的去除率达到99%，金属汞去除率可达到90%以上。对照使全部烟气加温的方法，节省能量约90%。
实施例5
类似实施例4中所描述的烟气，分流烟气的流量采用总流量的1%，即2，200 m3/h，采用分流空气泵和流量计量控制装置来控制分流烟气流量；分流烟气用电加热的方法加热至500℃；H2O2以H2O2与NOx的摩尔比1：1的比例投加，加入的H2O2的流量为324 kg/h，采用文丘里喷嘴设计的喷雾装置（见附图2）喷入。在分流烟气中的H2O2的浓度约为147 g/m3，在500°C时H2O2饱和蒸汽压超过1大气压，此时分流烟气中的H2O2浓度（147 g/m3）低于此时的饱和蒸汽浓度（大于200 g/m3）。进入加热段的H2O2迅速得以蒸发成气体，在高温段停留约0.5 秒，然后进入主流烟道与主流烟气进行混合反应。反应后的烟气温度几乎和烟气的进气温度相同，约150℃，经过冷凝处理后使其温度达到100℃以下，并进入烟气洗涤装置来把此时烟气中的NO2、NO3、SO2、SO3、Hg2+，还有硝酸、亚硝酸、硫酸、亚硫酸等吸收掉，烟气洗涤装置采用已经市场化的文丘里洗涤装置如以商标ReitherM销售的文丘里洗涤装置。去除率NO达到80%，SO2的去除率达到99%，金属汞去除率达到80%以上。对照使全部烟气加温的方法，可以节省能量95%以上。
实施例6
类似实施例4中所描述的烟气，分流烟气的流量采用总流量的30%，即66，000 m3/h，采用调节阀门调节分流烟气的流量；分流烟气用电加热的方法加热至500℃；H2O2以H2O2与NOx的摩尔比1：1的比例投加，加入的H2O2的流量为324 kg/h，采用超声波喷嘴喷入。在分流烟气中的H2O2的浓度约为5 g/m3。进入加热段的H2O2迅速得以蒸发成气体，在高温段停留约0.5 秒，此时分流烟气中的还原性气体首先被氧化，生成的无机酸促进H2O2的进一步分解。余下的或新生成的氢氧或过氧氢氧自由基进入主流烟道与主流烟气进行混合反应。反应后的烟气温度约255 ℃。由于温度很高，反应后烟气中所含的热量考虑回收，通过热交换器将其部分热量传递给分流烟气的进气（附图3），经过热交换后，分流烟气进口温度提高到接近220℃，混合烟气温度则降至230℃，经过冷凝处理后使其温度达到100℃以下，并进入烟气洗涤装置，烟气中的NO2、NO3、SO2、SO3，Hg2+、硝酸、亚硝酸、硫酸、亚硫酸等在烟气洗涤装置中被吸收掉，烟气洗涤装置采用已经市场化的文丘里洗涤装置。NO的去除率达到90%，SO2的去除率为99%，金属汞去除率达到90%以上。对照使全部烟气加温的方法，可以节省能量80%以上。
实施例7
类似实施例4中所描述的烟气，烟气分流流量为烟气总流量的10%，即22，000 m3/小时；采用阀门及空气泵调节和控制分流烟气流量；采用ClO2作为氧化剂。ClO2用亚氯酸和浓盐酸的反应来制备。分流烟气用电加热的方法加热至500℃； ClO2以ClO2与NOx的摩尔比1：3的比例投加，加入的ClO2的流量为229 kg/h；采用与实施例4类似的工艺流程，经文丘里洗涤器洗脱所生成的二氧化氮、三氧化氮、二氧化硫、三氧化硫、二阶汞、硝酸、亚硝酸、硫酸、盐酸， NOx去除率可达90%，SO2的去除率可达99%，金属汞去除率可达到90%以上。

Claims (22)

  1. 一种利用氧化法去除废气中氮氧化合物、硫氧化物和汞的设备，其特征在于：所述的设备包括废气主管、分流支管和氧化剂注入装置，其中，
    1) 分流支管的进气端和出口端分别开口于废气主管的上游烟气进口与下游烟气出口之间，废气主管的下游烟气出口连接洗涤装置；
    2) 在分流支管的进气端设有控制阀和风机，控制和调节分流支管的进气量和流速，在分流支管的出口端设有加热反应室，在加热反应室内设有加热器；
    3) 氧化剂注入装置包括氧化剂储槽和输送管，输送管开口于加热反应室内加热器的下游，加热反应室直通废气主管内，开口处设有扩散分布器。
  2. 根据权利要求1所述的设备，其特征在于：在所述的废气主管位于所述的分流支管入口的下游设置气流控制阀，用于控制分流支管内气体的流量和流速。
  3. 根据权利要求1所述的设备，其特征在于：所述的加热器包括电加热器。
  4. 根据权利要求1所述的设备，其特征在于：所述氧化剂注入装置中输送管的开口位置设在加热反应室靠近进气端的位置，使得注入的氧化剂能在支管内和分流废气充分混合加热。
  5. 根据权利要求1所述的设备，其特征在于：所述的氧化剂包括过氧化氢以及其它能够在高温条件下分解形成自由基的氧化剂。
  6. 根据权利要求5所述的设备，其特征在于：所述的能够在高温条件下分解形成自由基的氧化剂包括氯气、ClO2、次氯酸、亚氯酸、氯酸、高氯酸、它们的钠盐或钾盐、它们的混合物，或它们与它们各自的促进分解的催化剂的混合物。
  7. 据权利要求1所述的设备，其特征在于：所述氧化剂注入装置的输送管的末端设有喷嘴或雾化装置。
  8. 根据权利要求7所述的设备，其特征在于：所述的喷嘴包括超声波喷嘴或文丘里喷嘴，当使用超声波喷嘴时，在输送管上可以增设加注泵，为氧化剂的注入提供动力；当使用文丘里喷嘴时，在所述的输送管上增设氧化剂注入控制阀，用于控制过氧化氢的注入量。
  9. 应用权利要求1所述的设备进行氧化法去除废气中氮氧化合物、硫氧化物和汞的方法，其特征在于：所述的方法包括如下的工艺步骤：
    1) 废气分流：在废气通道主管的上游烟气进口与下游烟气出口之间设置分流支管来对需进行处理的废气进行分流；
    2) 混合加热：分流废气的流量可以通过在废气主通道上设置的气流控制阀以及设在废气支管上的气流控制阀和风机来控制和调节，在加热反应室内，注入的氧化剂能在分流支管内和分流废气充分混合加热；
    3) 回流洗涤：带有高氧化性自由基的分流废气流回废气主管道并和废气主管道内的废气进行完全混合，混合废气反应后进入后续洗涤装置。
  10. 根据权利要求9所述的方法，其特征在于：所述的方法包括如下的工艺步骤：
    1) 废气分流：在废气通道主管的上游烟气进口与下游烟气出口之间设置分流支管来对需进行处理的废气进行分流；
    2) 混合加热：分流废气的流量可以通过在废气主通道上设置的气流控制阀以及设在废气支管上的气流控制阀和风机来控制和调节，在加热反应室内，注入的过氧化氢能在分流支管内和分流废气充分混合加热，并被分解为氧化能力更强的氢氧和过氧氢氧自由基；
    3) 回流洗涤：带有高氧化性自由基的分流废气流回废气主管道并和废气主管道内的废气进行完全混合，经过0.4~5.0秒的反应时间后，混合废气进入后续洗涤装置。
  11. 根据权利要求10所述的方法，其特征在于：所述的方法中，过氧化氢以通过氧化剂注入装置注入废气支管与分流废气充分混合，并在加热反应室内停留0.2~4.0秒。
  12. 根据权利要求11所述的方法，其特征在于：过氧化氢在加热反应室内停留时间为0.5~1.0秒。
  13. 根据权利要求10所述的方法，其特征在于：在上述的方法中，过氧化氢的注入流量与原废气中的NOx的摩尔比为2.0~0.5：1。
  14. 根据权利要求13所述的方法，其特征在于：过氧化氢的注入流量与原废气中的NOx的摩尔比为1：1。
  15. 根据权利要求10所述的方法，其特征在于：在上述的方法中，过氧化氢的分解温度在200~600 ℃范围内。
  16. 根据权利要求15所述的方法，其特征在于：过氧化氢的分解温度在300~500℃的范围内。
  17. 根据权利要求10所述的方法，其特征在于：所述分流废气的风量占主流废气风量的比例为0.5~50%。
  18. 根据权利要求17所述的方法，其特征在于：所述分流废气的风量占主流废气风量的比例为1~10%。
  19. 根据权利要求10所述的方法，其特征在于：所用的过氧化氢是纯度在10%以上的水溶液。
  20. 根据权利要求10所述的方法，其特征在于：所述的过氧化氢水溶液中含有促进过氧化氢分解的催化剂。
  21. 根据权利要求20所述的方法，其特征在于：所述的催化剂包括无机酸或它们的铁盐或亚铁盐。
  22. 根据权利要求21所述的方法，其特征在于：所述的无机酸、铁盐或亚铁盐与过氧化氢的混合比例为摩尔比小于或等于1：1。
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