Search

CN-122006465-A - Micro-ozone synergistic low-temperature catalysis method

CN122006465ACN 122006465 ACN122006465 ACN 122006465ACN-122006465-A

Abstract

The application relates to the technical field of waste gas treatment, and particularly discloses a micro-ozone synergistic low-temperature catalysis method which comprises the steps of uniformly mixing tail gas containing SO 2 with micro-ozone (5-50 ppmv), enabling the mixed gas to sequentially pass through a composite bed layer consisting of a transition metal oxide low-temperature oxidation layer, a mist blocking condensation layer and an active carbon layer, enabling the SO 2 to be efficiently oxidized into SO 3 at low temperature by utilizing active oxygen generated by decomposing ozone on the surface of a catalyst, realizing synergistic removal of sulfuric acid mist and SO 3 through condensation, adsorption and chemical fixation, simultaneously ensuring that residual ozone is thoroughly decomposed, dynamically adjusting ozone addition amount by a closed-loop control strategy taking the concentration of SO 2 and the axial temperature difference DeltaTr of the bed layer as main control variables, and realizing stable ultralow emission of SO 2 which is less than 10 mg/Nm3 and O 3 which is less than 0.1 ppmv. The method realizes high-efficiency deep purification of SO 2 under the low-temperature condition, and has the advantages of low energy consumption, no ozone escape, strong impact load resistance and stable and safe operation.

Inventors

  • LU CHAOJIN
  • BAI ZHISHAN
  • WANG GUANQING

Assignees

  • 华东理工大学

Dates

Publication Date
20260512
Application Date
20260317

Claims (10)

  1. 1. The low-temperature catalysis method is characterized by comprising the following steps of: s1, uniformly mixing tail gas containing SO 2 with ozone, wherein the addition amount of the ozone is 5-50 ppmv of the dry basis volume of the tail gas; S2, enabling the mixed gas in the S1 to sequentially pass through a composite bed layer consisting of a transition metal oxide low-temperature oxidation layer, a mist blocking and condensing layer and an active carbon layer in the low-temperature catalytic polishing device, wherein: the transition metal oxide layer is used for oxidizing SO 2 into SO 3 , and the transition metal oxide layer and the activated carbon layer are used for decomposing the surface of O 3 to generate surface active oxygen to the catalyst SO as to regenerate active sites; the mist blocking and condensing layer is used for capturing and condensing sulfuric acid mist drops and fine particles in the gas; The activated carbon layer is used for carrying out physical adsorption and chemical fixation on the generated SO 3 and sulfuric acid mist and decomposing and intercepting residual ozone; S3, on-line monitoring the concentration of the outlet SO 2 and the axial temperature difference delta Tr of the composite bed layer, dynamically adjusting the ozone adding amount based on a closed-loop control method taking the concentration of the outlet SO 2 and the delta Tr as main control variables, enabling the outlet SO 2 to reach the emission limit value less than or equal to 10 mg/Nm3, and enabling the tail exhaust O 3 to be less than 0.1 ppmv.
  2. 2. The method for catalyzing micro-ozone cooperatively at low temperature according to claim 1, wherein the ozone adding amount is 10-25 ppmv in steady state operation, and when SO 2 load impact is detected, the ozone adding amount is increased to 50-60 ppmv, and the high adding duration is less than 10 minutes.
  3. 3. The method for collaborative low temperature catalysis of micro-ozone according to claim 1, wherein the closed loop control method in S3 comprises the following steps: S31, collecting the concentration of an outlet SO 2 , the multi-point temperature T (z) of a bed layer, the pressure drop delta P and the dew point of incoming gas, wherein the outlets SO 2 and delta Tr are closed-loop main variables, and the concentration of acid mist, the delta P and the dew point margin are limiting or interlocking variables; S32, filtering and carrying out boundary inspection to obtain SO 2 error SO 2err , extracting bed temperature difference delta Tr, heat peak position and recovery time T rec , and calculating d (SO 2out )/dt; S33, according to O 3 , setting = PI [ w 1 ·SO 2err + w 2 ·ΔT rerr + w 3 ·d(SO 2 )/dt ] and superposing the adaptive limiting of the dew point margin and the delta P growth rate, generating an O 3 set value; S34, when O 3out is more than or equal to 0.2 ppmv, the duration is more than or equal to 60S, or the dew point margin is less than 5 ℃ or the delta P increase rate exceeds a threshold value, safety interlocking is executed, namely, O 3 =0 is forced, the ozone destruction unit is fully opened, and meanwhile, the heat purging and the alarm are maintained; S35, in the start-stop process, the unlocking O 3 is firstly added when the temperature of the bed layer is more than or equal to 100 ℃, and the stop is firstly carried out after O 3 is firstly cut off and the destruction unit is kept on line for 10-15 min.
  4. 4. The method for synergic low-temperature catalysis by micro-ozone according to claim 1, wherein the transition metal oxide low-temperature oxidation layer is filled with multi-metal composite oxide, the mass fraction of active components is 5-20 wt%, and the form is honeycomb, bar-shaped or spherical.
  5. 5. The method for low-temperature catalysis assisted by micro-ozone according to claim 1, wherein the activated carbon layer is columnar or granular activated carbon, has a specific surface area of 800-1200 m < 2 >/g, and is modified by alkali metal or alkaline earth metal or aminated.
  6. 6. The method for preparing the micro-ozone synergistic low-temperature catalysis according to claim 1, wherein the mist blocking and condensing layer is a fiber mat or a wire mesh.
  7. 7. The method for low-temperature catalytic co-operation of micro-ozone according to claim 1, wherein in S1, the low-temperature catalytic polishing apparatus comprises: A tail gas inlet and a mixed rectifying section; the ozone adding branch comprises an ozone generator, a mass flow controller, an online ozone analyzer and a valve group, and an ozone safe destroying unit connected with the main path in parallel; The composite reaction bed layer module is internally provided with the transition metal oxide low-temperature oxidation layer, the mist blocking condensation layer and the active carbon layer in sequence; The online monitoring unit is used for detecting the concentration of the outlet SO 2 , the concentration of the outlet ozone, the concentration of the acid mist, the pressure drop delta P of the bed layer and the multi-point temperature of the bed layer in real time; The control unit is in signal connection with the mass flow controller, the ozone destroying unit and the on-line monitoring unit and is used for outputting control instructions according to the closed-loop control method.
  8. 8. The method for low-temperature catalysis by combining trace ozone as claimed in claim 7, wherein the shell and the inner liner of the low-temperature catalysis polishing device are made of acid-resistant materials or coatings, and the lowest temperature of the inner wall of the shell is ensured not to be lower than the dew point of incoming gas by +10 ℃ during operation.
  9. 9. The method of claim 7, wherein the composite bed is of a cylinder type or drawer type replaceable structure, and comprises an independently replaceable transition metal oxide low-temperature oxidation module, a mist blocking and condensing module and an active carbon module, and each module has a positioning, material mixing preventing and sealing structure.
  10. 10. The method for low-temperature catalysis in cooperation with micro-ozone, as claimed in claim 7, wherein the low-temperature oxidation layer of transition metal oxide has a pore volume larger than that of the activated carbon layer for mist resistance and blocking resistance, and the low-temperature oxidation layer of transition metal oxide has a particle size larger than that of the activated carbon layer for improving the residence and fixation efficiency of mixed gas.

Description

Micro-ozone synergistic low-temperature catalysis method Technical Field The application relates to the technical field of waste gas treatment, in particular to a low-temperature catalysis method by cooperation of micro-ozone. Background In the industries of sulfuric acid, smelting, coal/gas burning, chemical industry and the like, trace SO 2 (usually 5-300 mg/Nm3, and the impact can reach 500-1000 mg/Nm 3) and SO 3 are still remained in tail gas after main treatment processes (such as double-alkali method, wet absorption and conversion-absorption) to form sulfuric acid mist. To meet increasingly stringent ultra low emission standards, efficient end point deep purification techniques are required. The prior art has the defects that high-temperature catalytic oxidation needs to be operated at a temperature of above 350 ℃, the energy consumption is high, the system is slow to start and stop, the adaptability to tail gas temperature fluctuation is poor, a complex absorption system is needed after SO 3 is generated, the wet deep absorption can be operated under mild conditions, but the problems of secondary pollution of waste water/sludge, equipment corrosion, limited acid mist removal efficiency and the like exist, the instant impact response to SO 2 concentration is delayed, the Activated Carbon (AC) absorption can absorb SO 2 and acid mist at low temperature, the absorption capacity is limited, the regeneration is difficult after saturation, the low-temperature oxidation capability of SO 2 by pure physical absorption is weak, and the bed pressure drop is easy to rapidly rise due to dust and acid mist accumulation. The direct oxidation of ozone can oxidize SO 2 into easier-to-handle SO 3, but the independent addition of ozone can easily cause side reactions, secondary pollution and material aging caused by ozone escape, and the accurate control of the reaction process is lacking, SO that the ozone utilization rate is low. Therefore, development of a deep SO 2 removal technology which can efficiently and stably operate at low temperature, has strong impact load resistance, low energy consumption and no secondary pollution risk is needed. Disclosure of Invention The application provides a low-temperature catalysis method by combining trace ozone, which aims to solve the problem that sulfuric acid mist formed by SO 2 and SO 3 is still remained after the existing tail gas treatment. The application provides a micro-ozone synergistic low-temperature catalysis method, which adopts the following technical scheme: a micro-ozone synergistic low-temperature catalysis method comprises the following steps: S1, uniformly mixing tail gas containing SO 2 with ozone, wherein the addition amount of the ozone is 5-50 ppmv of the dry basis volume of the tail gas; S2, enabling the mixed gas in the S1 to sequentially pass through a composite bed layer consisting of a transition metal oxide low-temperature oxidation layer, a mist blocking and condensing layer and an active carbon layer in the low-temperature catalytic polishing device, wherein: the transition metal oxide layer is used for oxidizing SO 2 into SO 3, and the transition metal oxide layer and the activated carbon layer are used for decomposing the surface of O 3 to generate surface active oxygen to the catalyst SO as to regenerate active sites; the mist blocking and condensing layer is used for capturing and condensing sulfuric acid mist drops and fine particles in the gas; The activated carbon layer is used for carrying out physical adsorption and chemical fixation on the generated SO 3 and sulfuric acid mist and decomposing and intercepting residual ozone; S3, on-line monitoring the concentration of the outlet SO 2 and the axial temperature difference delta Tr of the composite bed, dynamically adjusting the ozone adding amount based on a closed-loop control method taking the concentration of the outlet SO 2 and the delta Tr as main control variables, SO that the outlet SO 2 reaches the emission limit value less than or equal to 10 mg/Nm3, and the tail discharge O 3 is less than 0.1 ppmv. By adopting the technical scheme, the invention constructs a multistage cooperative purification path of ozone cooperative catalytic oxidation-fog droplet coagulation-adsorption fixation/ozone destruction, and introduces intelligent closed-loop control based on key parameters at the tail end, and the method combines trace ozone as a controllable active oxygen source with a low-temperature catalyst, SO that the high-efficiency and directional oxidation of trace SO 2 is realized at low temperature, and the defects of high energy consumption, limited adsorption capacity of active carbon and no oxidation capability of the traditional high-temperature catalysis are overcome; the introduction of closed loop control enables the whole process to have self-adaptive capacity, can keep optimal ozone utilization efficiency and purification effect under different loads, and achieves the purposes