A low-temperature plasma catalytic electrode, its preparation method, low-temperature plasma catalytic reactor and method for treating NH3 in flue gas

Abstract

The present invention belongs to the field of environmental protection, and in particular relates to a low-temperature plasma catalytic electrode, a preparation method thereof, a low-temperature plasma catalytic reactor, and a method for treating NH3 in flue gas. The low-temperature plasma catalytic electrode provided by the present invention comprises: a low-temperature plasma electrode substrate, a catalyst carrier layer composited on the surface of the low-temperature plasma electrode substrate, and a catalyst active component loaded on the catalyst carrier layer. The method for treating NH3 in flue gas provided by the present invention comprises the following steps: after the flue gas is subjected to dust removal, washing, condensation demisting, and heat exchange and heating in sequence, it enters the low-temperature plasma catalytic reactor described in the above technical solution to carry out a plasma catalytic degradation reaction to obtain purified flue gas after NH3 is removed. The present invention applies low-temperature plasma in-situ catalytic technology to the removal of ammonia from flue gas, which has many advantages such as low energy consumption, high efficiency, and low operating and maintenance costs.

Description

Technical Field

[0001] The present invention belongs to the field of environmental protection, and in particular relates to a low-temperature plasma catalytic electrode, a preparation method thereof, a low-temperature plasma catalytic reactor and a method for treating NH3 in flue gas. Background Art

[0002] Ammonia pollution is widespread in everyday industrial and agricultural production. Significant amounts of ammonia pollutants are generated and emitted in numerous fields, including ammonia synthesis, urea synthesis, livestock farming, industrial flue gas denitrification, and semiconductor manufacturing. Ammonia, due to its high volatility and irritation, is highly soluble in water, exerting a strong irritating effect on the human body and potentially impacting human health. Furthermore, large quantities of ammonia molecules enter the ambient air, where they combine with water molecules and participate in complex atmospheric chemical reactions, forming ammonium salt particles, which in turn exacerbate PM2.5 pollution in the ambient air. Common methods and measures for ammonia control in the industrial sector include physical absorption, chemical absorption, membrane separation, and thermal catalysis.

[0003] Physical absorption is a commonly used method for recovering high-concentration ammonia. It utilizes the physical property of ammonia's solubility ratio of 700:1 in water. Soft water or dilute ammonia solution is used in a spray tower or other device to absorb the ammonia. The resulting ammonia solution is then recycled through steps such as distillation and rectification. Chinese patent CN202022306435.2 discloses an ammonia-containing tail gas absorption tower and a supporting energy recovery system. This utilizes a boiling ammonia tail gas recovery tower to allow the ammonia-containing tail gas to meet the water film on the boiling plate, creating a boiling effect. This transforms the existing passive scrubbing into active scrubbing, enhancing the tail gas scrubbing effect and improving tail gas treatment efficiency.

[0004] The chemical absorption method is based on the physical absorption method, replacing soft water or dilute ammonia with an acidic absorbent for acid-base neutralization and absorption, thereby producing nitrogen fertilizer with lower added value for recycling. Chinese patent CN202022989583.9 discloses an ammonia removal system and ammonia product preparation equipment. Dilute phosphoric acid is used as an absorbent to absorb ammonia gas in an ammonia scrubber to produce diammonium phosphate. The diammonium phosphate solution is purified by a purification device or an acid removal device and then deaminated by a deammonification device to produce high-concentration ammonia gas and monoammonium phosphate solution. The monoammonium phosphate solution is recycled into the ammonia scrubber to absorb ammonia gas.

[0005] Membrane separation is a process that utilizes the different permeation rates of gas molecules to enrich, concentrate, and separate them using a separation membrane. Chinese patent CN201811206221.9 discloses a method that utilizes the difference in osmotic pressure and permeation rate between gaseous ammonia and non-condensable hydrogen / nitrogen through a pervaporation membrane, as well as the phase change that occurs on both sides of the pervaporation membrane, to obtain high-purity liquid ammonia from the permeation side of the membrane. The method also utilizes the change in adsorption capacity of the gas flowing out of the non-permeation side during the adsorption and desorption cycle in a pressure swing adsorption (PSA) process, and vaporizes, cryogenically distills, adsorbs, and purifies the liquid ammonia to produce an electronic-grade ammonia product. This allows for high-purity, high-yield recovery of ammonia, which can then be returned to the LED-MOCVD process for use.

[0006] The thermal catalytic method uses ammonia as a reducing gas, which undergoes a redox reaction with an oxidizing gas under the action of a thermal catalyst to produce nitrogen. CN101554587A discloses a low-temperature ammonia selective oxidation catalyst used to eliminate ammonia pollution generated in industrial, agricultural, transportation, and construction processes. It selectively catalytically oxidizes ammonia into pollution-free nitrogen and water at relatively low temperatures. The catalyst achieves a 100% ammonia conversion rate at temperatures above 160°C, with a nitrogen selectivity approaching 80%. CN114425416A The catalyst prepared by the present invention has good NH3 conversion and N2 selectivity over a wide temperature window of 200-300°C.

[0007] The above-mentioned NH3 treatment methods generally have problems such as high energy consumption, low efficiency, and high operation and maintenance costs, and need to be further optimized. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a low-temperature plasma catalytic electrode, a preparation method thereof, a low-temperature plasma catalytic reactor and a method for treating NH3 in flue gas. The present invention applies low-temperature plasma in-situ catalytic technology to flue gas ammonia removal, which has many advantages such as low energy consumption, high efficiency, and low operation and maintenance costs.

[0009] The present invention provides a low-temperature plasma catalytic electrode, comprising: a low-temperature plasma electrode substrate, a catalyst carrier layer composited on the surface of the low-temperature plasma electrode substrate, and a catalyst active component loaded on the catalyst carrier layer.

[0010] Preferably, the catalyst support layer is made of ceramic; and the thickness of the catalyst support layer is 50 to 1000 μm.

[0011] Preferably, the catalyst active component is one or more of Fe, Cu, Mn, Co, Ce, V, Mo, Zr, Pt and Ag; the loading amount of the catalyst active component on the catalyst support layer is 20 to 50 mg / cm 2 .

[0012] The present invention provides a method for preparing the low-temperature plasma catalytic electrode described in the above technical solution, comprising the following steps:

[0013] a) Using thermal spraying technology, the catalyst support material is sprayed onto the surface of the low-temperature plasma electrode substrate to form a catalyst support layer;

[0014] b) using thermal spraying technology to spray the catalyst active components onto the catalyst support layer to obtain a low-temperature plasma catalytic electrode.

[0015] The present invention provides a low-temperature plasma catalytic reactor, wherein the discharge electrode in the low-temperature plasma catalytic reactor is the low-temperature plasma catalytic electrode described in the above technical solution or the low-temperature plasma catalytic electrode prepared by the preparation method described in the above technical solution.

[0016] The present invention provides a method for treating NH3 in flue gas, comprising the following steps:

[0017] After the flue gas has been subjected to dust removal, washing, condensation demisting and heat exchange heating in sequence, it enters the low-temperature plasma catalytic reactor described in the above technical solution to undergo plasma catalytic degradation reaction to obtain purified flue gas after NH3 removal.

[0018] Preferably, a plurality of the low-temperature plasma catalytic reactors are included, and the plurality of the low-temperature plasma catalytic reactors are switched and used during the NH3 treatment process.

[0019] Preferably, the method further includes the following steps: when the low-temperature plasma catalytic reactor is switched to a standby state, flushing the discharge electrode thereof.

[0020] Preferably, the method further comprises the following steps: collecting the waste water from flushing the discharge electrode, settling the waste water, and using the supernatant for the next flushing operation.

[0021] Preferably, the method further comprises the following steps: after completing the flushing, the low-temperature plasma catalytic reactor is subjected to forced air drying.

[0022] Compared with the prior art, the present invention provides a low-temperature plasma catalytic electrode, a preparation method thereof, a low-temperature plasma catalytic reactor, and a method for treating NH3 in flue gas. The low-temperature plasma catalytic electrode provided by the present invention comprises: a low-temperature plasma electrode substrate, a catalyst carrier layer composited on the surface of the low-temperature plasma electrode substrate, and a catalyst active component loaded on the catalyst carrier layer. The present invention directly sets the catalyst on the surface of the low-temperature plasma electrode, which is a true low-temperature plasma in-situ catalysis. The catalyst acts directly on the plasma discharge interval and can participate in the plasma catalytic reaction process to the greatest extent, with high catalytic efficiency. Moreover, since there is no need to set up an additional catalyst bed, the equipment footprint and manufacturing cost can be reduced.

[0023] The method for treating NH3 in flue gas provided by the present invention comprises the following steps: after the flue gas is subjected to dust removal, washing, condensation demisting and heat exchange heating in sequence, it enters the low-temperature plasma catalytic reactor described in the above technical solution to carry out plasma catalytic degradation reaction to obtain purified flue gas after NH3 is removed. The present invention effectively ensures the normal occurrence of the low-temperature plasma catalytic reaction through the dust removal process, and effectively removes dust pollutants in the flue gas at the same time; through the washing, condensation demisting and heat exchange heating processes, it realizes the removal of moisture in the flue gas and the recycling of condensed water, solving the "colored plume" problem caused by excessively high flue gas temperature in traditional water washing and acid washing processes; driven by the electric field force, the gas is ionized to form a plasma state, and an ammonia degradation reaction occurs on the catalytic coating on the surface of the low-temperature plasma electrode. The NH3 treatment method provided by the present invention has many advantages such as low energy consumption, high efficiency, and low operation and maintenance costs, and has broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0025] Figure 1 This is a flow chart of the flue gas treatment system provided by an embodiment of the present invention.

[0026] Explanation of the accompanying drawings: 1 is a dust collector, 2 is a pre-wash cooling tower, 3 is a condensing demister, 4 is a flue gas heat exchanger, 5a is a first low-temperature plasma catalytic reactor flushing equipment, 5b is a second low-temperature plasma catalytic reactor flushing equipment, 6a is a first low-temperature plasma catalytic reactor, 6b is a second low-temperature plasma catalytic reactor, 7a is a first static sedimentation tank, 7b is a second static sedimentation tank, 8a is a first high-voltage power supply, 8b is a second high-voltage power supply, 9a is a first fresh air fan, and 9b is a second fresh air fan. DETAILED DESCRIPTION

[0027] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] The present invention provides a low-temperature plasma catalytic electrode, comprising: a low-temperature plasma electrode substrate, a catalyst carrier layer composited on the surface of the low-temperature plasma electrode substrate, and a catalyst active component loaded on the catalyst carrier layer.

[0029] In the catalytic electrode provided by the present invention, the component of the catalyst support layer is preferably ceramic, more preferably alumina ceramic; the thickness of the catalyst support layer is preferably 50 to 1000 μm, specifically 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, 600 μm, 650 μm, 700 μm, 750 μm, 800 μm, 850 μm, 900 μm, 950 μm or 1000 μm, and most preferably 500 μm.

[0030] In the catalytic electrode provided by the present invention, the catalytic active components are one or more of Fe, Cu, Mn, Co, Ce, V, Mo, Zr, Pt and Ag. In one embodiment provided by the present invention, the catalytic active components are Mn and Fe, and the mass ratio of Mn to Fe is preferably (5-15):1, specifically 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1; in another embodiment provided by the present invention, the catalytic active components are Mn and Ag, and the mass ratio of Mn to Ag is preferably (80-120):5, specifically 80:5, 85:5, 90:5, 95:5, 100:5, 105:5, 110:5, 115:5 or 120:5. In the present invention, the loading amount of the catalytic active components on the catalyst support layer is preferably 20-50 mg / cm 2 , specifically 20mg / cm 2 , 23mg / cm 2 , 25mg / cm 2 , 27mg / cm 2 、30mg / cm 2 、32mg / cm 2 、35mg / cm 2、37mg / cm 2 , 40mg / cm 2 , 42mg / cm 2 , 45mg / cm 2 , 47mg / cm 2 or 50 mg / cm 2 , most preferably 20 mg / cm 2 .

[0031] The present invention also provides a method for preparing the low-temperature plasma catalytic electrode described in the above technical solution, comprising the following steps:

[0032] a) Using thermal spraying technology, the catalyst support material is sprayed onto the surface of the low-temperature plasma electrode substrate to form a catalyst support layer;

[0033] b) using thermal spraying technology to spray the catalyst active components onto the catalyst support layer to obtain a low-temperature plasma catalytic electrode.

[0034] In the preparation method provided by the present invention, in step a), the thermal spraying technology includes but is not limited to supersonic plasma thermal spraying, atmospheric plasma thermal spraying, low-pressure plasma thermal spraying, vacuum plasma thermal spraying or arc thermal spraying, preferably supersonic plasma thermal spraying; the catalyst support material is preferably alumina ceramic; the catalyst support material is preferably a powder material, and its particle size is preferably 200-500 mesh, specifically 200 mesh, 225 mesh, 250 mesh, 275 mesh, 300 mesh, 325 mesh, 350 mesh, 375 mesh, 400 mesh, 425 mesh, 450 mesh, 475 mesh or 500 mesh; the thickness of the catalyst support layer has been introduced above and will not be repeated here.

[0035] In the preparation method provided by the present invention, in step b), the thermal spraying technology includes but is not limited to supersonic plasma thermal spraying, atmospheric plasma thermal spraying, low-pressure plasma thermal spraying, vacuum plasma thermal spraying or arc thermal spraying, preferably supersonic plasma thermal spraying or atmospheric plasma thermal spraying; the catalyst active component is preferably a powder material, and its particle size is preferably 10 to 90 μm, specifically 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm or 90 μm; the loading amount of the catalyst active component on the catalyst support layer has been introduced above and will not be repeated here.

[0036] The present invention also provides a low-temperature plasma catalytic reactor, in which the discharge electrode is the low-temperature plasma catalytic electrode described in the above technical solution or the low-temperature plasma catalytic electrode prepared by the preparation method described in the above technical solution.

[0037] In the low-temperature plasma catalytic reactor provided by the present invention, the discharge mode of the reactor is preferably corona discharge, single dielectric barrier discharge or double dielectric barrier discharge, more preferably corona discharge.

[0038] The present invention also provides a method for treating NH3 in flue gas, comprising the following steps:

[0039] After the flue gas has been subjected to dust removal, washing, condensation demisting and heat exchange heating in sequence, it enters the low-temperature plasma catalytic reactor described in the above technical solution to undergo plasma catalytic degradation reaction to obtain purified flue gas after NH3 removal.

[0040] In the treatment method provided by the present invention, the NH3 concentration in the flue gas is preferably 5 to 50 mg / m 3 , specifically 5mg / m 3 , 10mg / m 3 , 15mg / m 3 , 20mg / m 3 , 25mg / m 3 , 30mg / m 3 , 35mg / m 3 , 40mg / m 3 45mg / m 3 or 50 mg / m 3 The dust content in the flue gas is preferably 10 to 100 mg / m 3 , specifically 10 mg / m 3 , 20mg / m 3 , 30mg / m 3 , 40mg / m 3 , 50mg / m 3 , 60mg / m 3 , 70mg / m 3 , 80mg / m 3 , 90mg / m 3 or 100 mg / m 3 The initial flue gas temperature is preferably 70-150°C, specifically 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C.

[0041] In the treatment method provided by the present invention, the flue gas is preferably first used as a heat source to participate in the heat exchange and heating process before dust removal, so as to realize the recovery and utilization of the flue gas waste heat and the initial cooling of the flue gas.

[0042] In the treatment method provided by the present invention, the dust removal is preferably carried out in a dust collector, and the type of the dust collector is preferably an electrostatic precipitator, a wet electrostatic precipitator, a bag dust collector, an electric bag dust collector, a cyclone dust collector or a ceramic filter cartridge, and more preferably an electrostatic precipitator; the dust content of the flue gas after the dust removal is completed is preferably ≤20mg / m 3 .

[0043] In the treatment method provided by the present invention, the washing is preferably carried out in a pre-wash cooling tower; the material of the pre-wash cooling tower includes but is not limited to stainless steel, fiberglass or polypropylene; the flue gas temperature after the washing is preferably ≤60°C, more preferably ≤50°C, and even more preferably ≤45°C.

[0044] In the treatment method provided by the present invention, the condensation demisting is preferably performed in a condensation demister; the condensation demister is preferably filled with packing; the packing includes but is not limited to structured packing or bulk packing, preferably bulk packing; the packing is preferably made of ceramic, metal, or plastic, preferably metal; the flue gas temperature after the condensation demisting is preferably ≤40°C, more preferably ≤35°C, and even more preferably ≤30°C. In the present invention, the overflow port of the condensation demister is preferably connected to the pre-wash cooling tower via a pipeline, and the condensed water generated in the condensation demister can be directly returned to the pre-wash cooling tower by gravity through the overflow port.

[0045] In the treatment method provided by the present invention, the heat exchange and temperature rise is preferably carried out in a heat exchanger, the cold side of the heat exchanger is the flue gas after condensation and demisting, and the hot side is preferably the original flue gas; the flue gas temperature after completing the heat exchange and temperature rise is preferably ≥50°C, more preferably ≥60°C.

[0046] In the treatment method provided by the present invention, a high-voltage power supply is provided to match the low-temperature plasma catalytic reactor, for providing electrical energy for discharge of the reactor.

[0047] In the treatment method provided by the present invention, the residence time of the flue gas in the low-temperature plasma catalytic reactor is preferably 5 to 20 s, specifically 5 s, 6 s, 7 s, 8 s, 9 s, 10 s, 11 s, 12 s, 13 s, 14 s, 15 s, 16 s, 17 s, 18 s, 19 s or 20 s.

[0048] In the treatment method provided by the present invention, it is preferred to include multiple low-temperature plasma catalytic reactors, that is, a multi-channel design, and multiple low-temperature plasma catalytic reactors are switched during the NH3 treatment process. In the present invention, the number of low-temperature plasma catalytic reactors is preferably 2 to 5, more preferably 2; the frequency of switching is preferably 8 to 72 hours / time, specifically 8 hours / time, 12 hours / time, 16 hours / time, 20 hours / time, 24 hours / time, 28 hours / time, 32 hours / time, 36 hours / time, 40 hours / time, 44 hours / time, 48 hours / time, 52 hours / time, 56 hours / time, 60 hours / time, 64 hours / time, 68 hours / time or 72 hours / time, and most preferably 24 hours / time.

[0049] The treatment method provided by the present invention preferably further comprises the step of flushing the discharge electrode when the low-temperature plasma catalytic reactor is switched to a standby state. In the present invention, the flushing is preferably performed in a low-temperature plasma catalytic reactor flushing device, which preferably utilizes a gas-liquid two-phase flow to clean the surface of the discharge electrode.

[0050] The treatment method provided by the present invention preferably further comprises the following steps: collecting the flushing wastewater from flushing the discharge electrode, settling it, and using the supernatant for the next flushing operation. In the present invention, the collection and sedimentation of the flushing wastewater are preferably carried out in a static sedimentation tank.

[0051] In the treatment method provided by the present invention, it is preferred that the following steps are further included: After the flushing is completed, the low-temperature plasma catalytic reactor is subjected to air drying. In the present invention, the air drying is preferably performed using a fresh air blower.

[0052] The technical solution provided by the present invention includes at least the following key points:

[0053] 1) After heat exchange, the original flue gas goes through dust removal, washing, condensation and demisting, heat exchange and heating, in-situ low-temperature plasma discharge catalysis and other links in sequence to achieve energy-saving and efficient integrated flue gas dust removal and deamination treatment.

[0054] 2) Using in-situ loading technology, the catalyst carrier is first thermally sprayed onto the surface of the low-temperature plasma electrode to form a dense and rough catalyst carrier with high bonding strength. After the carrier adheres to the electrode surface, it forms an insulating dielectric layer, which can effectively increase the discharge voltage. Then, through a re-spraying process, the catalyst active components are thermally sprayed onto the surface of the catalyst carrier and rapidly condensed, thereby generating nano-scale catalyst active component particles and realizing the occurrence of the in-situ plasma discharge catalytic reaction process.

[0055] 3) The waste heat recovery technology is used to heat the flue gas entering the low-temperature plasma catalytic reactor and reduce its relative humidity, thereby avoiding condensed water adhering to the surface of the plasma discharge electrode, thereby greatly improving the discharge efficiency and reducing phenomena such as creepage, spark discharge, and partial discharge.

[0056] 4) Dust removal technology is used to remove dust from the flue gas entering the system, reducing the dust content in the flue gas, thereby reducing the deposition and adhesion of dust on the surface of the plasma discharge electrode, and reducing the performance degradation caused by dust shielding the active sites on the catalyst surface.

[0057] 5) A low-temperature plasma catalytic reactor flushing device, a static sedimentation tank, and a fresh air blower were used. Periodic spray cleaning operations were performed based on the dust deposition on the surface of the catalytic electrode in the low-temperature plasma catalytic reactor. The water used for spray cleaning was returned to the static sedimentation tank for static stratification, and the upper layer of clear water after stratification was used for the next spray cleaning operation. The reactor was then dried with air through a fresh air blower connected to the reactor to ensure that there was no residual moisture inside the reactor when it was in contact with the flue gas.

[0058] 6) Multiple low-temperature plasma catalytic reactors are used for rotational switching operations. When the catalytic electrode surface in the currently operating low-temperature plasma catalytic reactor reaches the preset cleaning time, the valve switches to another low-temperature plasma catalytic reactor to always keep the low-temperature plasma catalytic reaction occurring.

[0059] The technical solution provided by the present invention includes at least the following advantages:

[0060] 1) Traditional ammonia treatment processes such as physical absorption, chemical absorption, and membrane separation only enrich and concentrate ammonia and require a recovery process to achieve ammonia emission reduction. The recovery process requires high-energy-consuming process steps such as evaporation or pressurized liquefaction. The technology of the present invention is a degradation and treatment process for ammonia molecules, without high-energy-consuming process steps.

[0061] 2) Compared with traditional physical absorption and chemical absorption ammonia treatment processes, the technology of the present invention adopts a closed treatment process, in which cooling and water removal are completed inside the equipment. Condensed water and clean water can be reused in the process, and the amount of ammonia-containing wastewater generated and the water consumption are both less than those of the absorption method.

[0062] 3) Traditional thermal catalysis usually requires temperatures between 160 and 400°C to degrade and remove ammonia molecules, and this method consumes a huge amount of energy. The technical advantage of the present invention is that the reaction path can be carried out at room temperature or low temperature, without the need for additional heat source. The heat source used for heating can come from the heat of the original flue gas itself, which is energy-saving and environmentally friendly.

[0063] 4) Compared with traditional processes, the ammonia-containing waste gas treatment process proposed in the present invention can be applied to the treatment of ammonia-containing waste gas with different temperatures, different dust contents, different dust types, and different flue gas humidity. It can effectively avoid the "colored plume" caused by the contact between high-temperature flue gas and the absorbent, effectively avoid the difficulty of crystallization purification caused by dust impurities, and effectively avoid the increase in pressure drop caused by dust and droplet blockage on the separation membrane surface.

[0064] 5) Compared with traditional processes, the low-temperature plasma catalytic electrode proposed in the present invention directly ionizes the gas passing between the electrodes under the action of a high-voltage electric field, forming a plasma state. Under the action of the catalyst on the electrode surface, the ionized intermediates of substances such as ammonia molecules, oxygen molecules, and water molecules interact with each other, and electrons are transferred, thereby realizing the redox reaction of ammonia, getting rid of the need for a heat source in thermal catalysis.

[0065] For the purpose of greater clarity, the present invention is described in detail with reference to the following examples.

[0066] Example 1

[0067] This embodiment provides a system for treating NH3 in flue gas. The devices in the system include: a dust collector 1, a pre-wash cooling tower 2, a condensing demister 3, a flue gas heat exchanger 4, a first low-temperature plasma catalytic reactor flushing device 5a, a second low-temperature plasma catalytic reactor flushing device 5b, a first low-temperature plasma catalytic reactor 6a, a second low-temperature plasma catalytic reactor 6b, a first static sedimentation tank 7a, a second static sedimentation tank 7b, a first high-voltage power supply 8a, a second high-voltage power supply 8b, a first fresh air fan 9a, and a second fresh air fan 9b. The specific working process of the system is as follows:

[0068] A) Turn on the equipment units flue gas heat exchanger 4, dust collector 1, pre-wash cooling tower 2, condenser demister 3, first low-temperature plasma catalytic reactor 6a, and first high-voltage power supply 8a in sequence;

[0069] B) The original flue gas is cooled once after passing through the hot side and cold side flue gas of the flue gas heat exchanger 4 for heat recovery and then enters the dust collector 1 for dust removal;

[0070] C) The flue gas after dust removal enters the pre-wash cooling tower 2 to achieve secondary cooling of the flue gas and further remove impurities such as dust in the flue gas;

[0071] D) The flue gas after cooling and dust removal enters the condensation demister 3 and is cooled three times. The droplets and condensed water entrained in the gas are intercepted and collected here. The collected water flows into the pre-wash cooling tower 2 through the overflow port of the condensation demister 3;

[0072] E) The dehumidified flue gas enters the cold side of the flue gas heat exchanger 4 and exchanges heat with the hot side of the flue gas heat exchanger 4 to achieve re-heating of the dehumidified flue gas, thereby reducing the relative humidity of the flue gas;

[0073] F) The heated flue gas enters the first low-temperature plasma catalytic reactor 6a, where it undergoes an in-situ low-temperature plasma discharge catalytic reaction to achieve room-temperature ionization and catalysis of ammonia molecules in the flue gas;

[0074] G) After the first low-temperature plasma catalytic reactor 6a has completed its operation, the second low-temperature plasma catalytic reactor 6b is opened to allow the flue gas to enter it, and then the second high-voltage power supply 8b is turned on to begin ammonia treatment; the first low-temperature plasma catalytic reactor 6a and the first high-voltage power supply 8a are closed, and the first low-temperature plasma catalytic reactor flushing device 5a is allowed to operate;

[0075] H) The first low-temperature plasma catalytic reactor flushing device 5a is turned on, and water is sprayed from the gas-liquid two-phase flow nozzle to clean the surface of the discharge electrode in the first low-temperature plasma catalytic reactor 6a, thereby preventing dust and dirt from shielding the catalyst surface and thus reducing the catalytic efficiency. The wastewater flows from the bottom drain port of the first low-temperature plasma catalytic reactor 6a into the first static sedimentation tank 7a for recycling;

[0076] 1) The wastewater is allowed to stand in the first static sedimentation tank 7a. After separation, the supernatant is returned to the first low-temperature plasma catalytic reactor flushing device 5a for the next cleaning;

[0077] J) After the first low-temperature plasma catalytic reactor 6a is cleaned, the first fresh air blower 9a is turned on to introduce clean air into the first low-temperature plasma catalytic reactor 6a to dry the equipment, thereby preventing the occurrence of creepage and electrical continuity on the surface of the low-temperature plasma discharge electrode;

[0078] K) After the operation time of the second low-temperature plasma catalytic reactor 6b ends, the system switches to the first low-temperature plasma catalytic reactor 6a and repeats steps G), H), I), and J).

[0079] Example 2

[0080] In the system provided in Example 1, the treatment of NH3 in the simulated flue gas is carried out, and the specific contents are as follows:

[0081] The simulated flue gas is a mixture of ammonia and air (the concentration of ammonia is 10 mg / m 3 ), the flue gas volume is 20000Nm 3 / h, the initial flue gas temperature is 100℃, and the dust addition amount is 50mg / Nm 3The discharge mode of the low-temperature plasma catalytic reactor is corona discharge. In the preparation of the catalytic electrode, supersonic plasma thermal spraying is used to melt and spray 325-mesh aluminum oxide ceramic powder onto the electrode surface to prime the substrate. The ceramic coating thickness is 500 μm. Subsequently, atmospheric low-temperature plasma thermal spraying is used to melt and spray 10-30 μm Mn / Fe (mass ratio 9:1) alloy powder onto the electrode surface substrate. The loading amount is 20 mg / cm 2 After the original flue gas passes through the electrostatic precipitator, the dust concentration drops to 10mg / Nm 3 After passing through the pre-wash cooling tower, the flue gas temperature drops to 50°C; after passing through the condensing demister, the flue gas temperature drops to 35°C; after passing through the flue gas heat exchanger, the flue gas temperature rises to 60°C; the flue gas enters the low-temperature plasma catalytic reactor, where it stays for 10 seconds. The ammonia concentration after purification is 2.3 mg / Nm 3 , the removal efficiency can reach 77%.

[0082] Example 3

[0083] In the system provided in Example 1, the treatment of NH3 in the simulated flue gas is carried out, and the specific contents are as follows:

[0084] The simulated flue gas is a mixture of ammonia and air (the concentration of ammonia is 20 mg / m 3 ), the flue gas volume is 20000Nm 3 / h, the initial flue gas temperature is 100℃, and the dust addition amount is 50mg / Nm 3 The discharge mode of the low-temperature plasma catalytic reactor is corona discharge. In the preparation of the catalytic electrode, supersonic plasma thermal spraying is used to melt and spray 325-mesh aluminum oxide ceramic powder onto the electrode surface to form a base substrate. The ceramic coating thickness is 1000 μm. Subsequently, atmospheric low-temperature plasma thermal spraying is used to melt and spray 45-90 μm Mn / Fe (mass ratio 9:1) alloy powder onto the electrode surface substrate. The loading amount is 30 mg / cm 2 After the original flue gas passes through the electrostatic precipitator, the dust concentration drops to 10mg / Nm 3 After passing through the pre-wash cooling tower, the flue gas temperature drops to 50°C; after passing through the condensing demister, the flue gas temperature drops to 35°C; after passing through the flue gas heat exchanger, the flue gas temperature rises to 60°C; the flue gas enters the low-temperature plasma catalytic reactor, where it stays for 10 seconds. The ammonia concentration after purification is 3.8 mg / Nm 3 , the removal efficiency can reach 81%.

[0085] Example 4

[0086] In the system provided in Example 1, the treatment of NH3 in the simulated flue gas is carried out, and the specific contents are as follows:

[0087] The simulated flue gas is a mixture of ammonia and air (the concentration of ammonia is 20 mg / m 3 ), the flue gas volume is 20000Nm 3 / h, the initial flue gas temperature is 100℃, and the dust addition amount is 50mg / Nm 3 The discharge mode of the low-temperature plasma catalytic reactor is corona discharge. In the preparation of the catalytic electrode, supersonic plasma thermal spraying is used to melt and spray 325-mesh aluminum oxide ceramic powder onto the electrode surface to prime the substrate. The ceramic coating thickness is 500 μm. Subsequently, atmospheric low-temperature plasma thermal spraying is used to melt and spray 15-30 μm Mn / Ag (mass ratio 95:5) alloy powder onto the electrode surface substrate. The loading amount is 20 mg / cm 2 After the original flue gas passes through the electrostatic precipitator, the dust concentration drops to 10mg / Nm 3 After passing through the pre-wash cooling tower, the flue gas temperature drops to 50°C; after passing through the condensing demister, the flue gas temperature drops to 35°C; after passing through the flue gas heat exchanger, the flue gas temperature rises to 60°C; the flue gas enters the low-temperature plasma catalytic reactor, where it stays for 10 seconds. The ammonia concentration after purification is 1.2 mg / Nm 3 , the removal efficiency can reach 94%.

[0088] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for treating NH3 in flue gas, characterized in that: The following steps are involved: After the flue gas has been subjected to dust removal, washing, condensation demisting and heat exchange heating, it enters the low-temperature plasma catalytic reactor for plasma catalytic degradation reaction to obtain purified flue gas after NH3 removal; The discharge electrode in the low-temperature plasma catalytic reactor is a low-temperature plasma catalytic electrode; The low-temperature plasma catalytic electrode comprises: a low-temperature plasma electrode substrate, a catalyst support layer composited on the surface of the low-temperature plasma electrode substrate, and a catalyst active component supported on the catalyst support layer; the catalyst support layer is composed of ceramic; the thickness of the catalyst support layer is 50 to 1000 μm; the catalyst active component is one or more of Fe, Cu, Mn, Co, Ce, V, Mo, Zr, Pt and Ag; the loading amount of the catalyst active component on the catalyst support layer is 20 to 50 mg / cm 2 ; The low-temperature plasma catalytic electrode is prepared according to the following steps: a) using thermal spraying technology to spray a catalyst support material onto the surface of a low-temperature plasma electrode substrate to form a catalyst support layer; b) using thermal spraying technology to spray a catalyst active component onto the catalyst support layer to obtain a low-temperature plasma catalytic electrode.

2. The treatment method according to claim 1, characterized in that: It comprises a plurality of low-temperature plasma catalytic reactors, which are switched and used during the NH3 treatment process.

3. The treatment method according to claim 2, characterized in that: The following steps are also included: When the low-temperature plasma catalytic reactor is switched to a standby state, its discharge electrode is flushed.

4. The treatment method according to claim 3, characterized in that: The following steps are also included: The waste water from rinsing the discharge electrode is collected and precipitated, and the supernatant is used for the next rinsing operation.

5. The treatment method according to claim 3, characterized in that: The following steps are also included: After the flushing is completed, the low-temperature plasma catalytic reactor is dried by air blast.

Images