Redox treatment system for treating NOx-containing waste gas

Abstract

The invention provides an oxidation and reduction treatment method and process for treating NOX-containing waste gas, and is characterized in that the waste gas treatment method comprises the following steps: (1) tail gas oxidation, (2) gas washing, and (3) urea solution preparation and maintaining.The catalytic oxidation capacity of a microwave electrodeless ultraviolet waste gas treatment platform is utilized to oxidize NOx into gas with NO and NO2 accounting for a certain proportion, and the NOx and the NO2 are subjected to oxidation and reduction treatment. According to the treatment method, the capacity of removing the particulate matter and the NOx at a time is achieved, the structure is simple, the construction cost is low, secondary pollution is avoided, and the method is suitable for industrial production. The device can be widely used for treating various acid mist waste gases and acid gases such as sulfur oxides (SOx), nitrogen oxides (NOx), carbon oxides (CO and CO2), cyanide (HCN) and the like discharged in the production process of industrial departments such as chemical industry, light industry, printing and dyeing, medicine, steel, machinery, electronics, instruments, electroplating and the like, and can be used for treating the acid gases such as the sulfur oxides (SOx), the nitrogen oxides (NOx), the carbon oxides (CO and CO2), the cyanide (HCN) and the like.

Description

Technical Field

[0001] The present invention relates to the field of waste gas treatment, and in particular to a redox treatment system for treating waste gas containing NOx. Background Art

[0002] The treatment of NOx-containing waste gas usually adopts the SCR process, that is, under the action of a catalyst, NH3 is used to reduce NOx to N2. This process has high construction costs, expensive and highly toxic catalysts, and ammonia slip often occurs in order to achieve ultra-low NOx emissions. At the same time, the system has large wind resistance and high operating costs. The traditional absorption method generally uses ozone oxidation to oxidize NO, which accounts for about 95% of NOx, into NO2, and then uses alkaline solution absorption or acidic urea solution absorption. Alkaline solution absorption will produce impurities and require further treatment. Acidic urea solution absorption will produce a reduction reaction to reduce the mixture of NO and NO2 to N2. This process only consumes urea and does not produce secondary pollution. However, due to the unsatisfactory effect of traditional ozone oxidation, that is, the subsequent acidic urea absorption tower is too large, the system cost is high, and the treatment effect is not ideal. Summary of the invention

[0003] The purpose of the present invention is to provide a NOx redox treatment system to solve the problems of high system operating cost and unsatisfactory treatment effect in the prior art when treating NOx-containing waste gas, so as to solve the shortcomings of the prior art.

[0004] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0005] The present invention provides an oxidation-reduction treatment system for treating NOx-containing waste gas, characterized in that the system comprises a waste gas collection module, a gas-liquid separation module, a MW-LEP oxidation module, a dissolving tank, a circulation pool, a reduction absorption tower, a fan, a chimney, and a control module. The waste gas collection module is connected to the gas-liquid separation module, the gas-liquid separation module is connected to the MW-LEP oxidation module, the dissolving tank is connected to the circulation pool, the circulation pool is connected to the reduction absorption tower, the reduction absorption tower is connected to a fan, and the fan is connected to the chimney.

[0006] Furthermore, the MW-LEP treatment module may also be added with oxidants such as air, water vapor and hydrogen peroxide, and the molar ratio of the oxidant to NOx is 0.5-2.

[0007] Furthermore, the MW-LEP processing module is used to oxidize NOx to a molar ratio of NO:NO2 in the range of 0.4-0.6.

[0008] Furthermore, the reduction absorption tower is used to scrub the oxidized tail gas, and a supergravity scrubber or a spray tower may be used.

[0009] Furthermore, the tower body material of the reduction absorption tower is glass fiber reinforced polystyrene, and the filler in the tower is plastic stepped rings.

[0010] Furthermore, the absorption liquid temperature is about 30°C and does not exceed 50°C at most.

[0011] Furthermore, the concentration of the urea solution in the circulation tank should be maintained between 6% and 15%, and the pH value of the urea solution should be between 2 and 6.

[0012] Furthermore, the control system is used to control the concentration and pH value of the urea solution, and its control process includes the following steps: (1) measuring and controlling the concentration of the urea solution, (2) measuring and controlling the pH value of the urea solution, and (3) after the urea solution refluxes, measuring the volume of the solution, and calculating and adding an appropriate amount of urea.

[0013] Further, the urea dosage is calculated using the following method:

[0014] 6NO2+4(NO2)2CO—7N2+4CO2+8H2O

[0015] 6NO+2(NO2)2CO—5N2+2CO2+4H2O

[0016] 2NO+2NO2+2H2O+(NH2)2CO—2N2+CO2+3H2O

[0017] According to the total concentration of NOx in the flue gas, and the ratio of NO to NO2 (for combustion exhaust gas, NO usually accounts for 95% of the total NOx), the amount of urea used is calculated according to the above three reaction equations, as well as the change in urea solution concentration over time, to determine the amount and time of urea addition.

[0018] Furthermore, 0.04%-0.5% of a surfactant, such as LAO-30, may be added to the urea solution.

[0019] Beneficial effects of the present invention: The present invention provides a redox treatment system for treating waste gas containing NOx, characterized in that the system includes: a waste gas collection module, a gas-liquid separation module, a MW-LEP oxidation module, a dissolving tank, a circulating pool, a reduction absorption tower, a fan, a chimney, and a control module. The waste gas collection module is connected to the gas-liquid separation module, the gas-liquid separation module is connected to the MW-LEP oxidation module, the dissolving tank is connected to the circulating pool, the circulating pool is connected to the reduction absorption tower, the reduction absorption tower is connected to a fan, and the fan is connected to the chimney. This patent utilizes the catalytic oxidation ability of the microwave electrodeless ultraviolet waste gas treatment platform to first oxidize NOx into gases with a certain proportion of NO and NO2, and then absorb them with an acidic urea solution. It can not only efficiently reduce NOx to N2 for removal, but also remove particulate matter at the same time. The system is equipped with a sludge treatment system, which can immediately clear the sludge in the acidic urea solution, and automatically detect the concentration of the urea solution and replenish it in time. Compared with traditional treatment methods, this system has the ability to remove NOx and particulate matter in exhaust gas at one time, with the advantages of simple system structure, low construction cost, small footprint, stability and reliability, low operating cost and no secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings in the specification without paying creative work.

[0021] Figure 1 Schematic diagram of a redox system for treating NOx-containing waste gas provided in an embodiment of the present invention

[0022] Legend: 1-Gas collection hood 2-Gas-liquid separator 3-Dissolution tank 4-Circulation pool 5-Reduction absorption tower 6-Blower 7-Chimney 8-MW-LEP treatment equipment DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the embodiment of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, rather than all the embodiments. The components of the embodiment of the present invention described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiment of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but only represents the selected embodiment of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0024] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the products of the invention in this specification are usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limitations on the present invention. In addition, the terms "first", "second", "third" and the like are only used to distinguish descriptions, and cannot be understood as indicating or implying relative importance. In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] Figure 1 A schematic diagram of a redox system for treating NOx-containing waste gas provided by one embodiment of the present invention; Figure 1 The present application is described in detail with reference to the embodiments.

[0026] The present invention provides a redox treatment system for treating NOx-containing waste gas. The system comprises: a waste gas collection module, a gas-liquid separation module, a MW-LEP oxidation module, a dissolving tank, a circulation pool, a reduction absorption tower, a fan, a chimney, and a control module. The waste gas collection module is connected with the gas-liquid separation module, the gas-liquid separation module is connected with the MW-LEP oxidation module, the dissolving tank is connected with the circulation pool, the circulation pool is connected with the reduction absorption tower, the reduction absorption tower is connected with a fan, and the fan is connected with the chimney.

[0027] Furthermore, the MW-LEP treatment module may also be added with oxidants such as air, water vapor and hydrogen peroxide, and the molar ratio of the oxidant to NOx is 0.5-2.

[0028] Furthermore, the MW-LEP processing module is used to oxidize NOx into NO:NO2 in a molar ratio ranging from 0.4 to 0.6.

[0029] It should be noted that the tail gas containing NOx is oxidized by microwave electrodeless ultraviolet (MW-LEP) tail gas oxidation equipment to NO: NO2 (molar ratio) = 0.4-0.6; in the oxidation process, in order to enhance the oxidation effect, air (O2), water vapor and H2O2 vapor can be added, and the molar ratio of the added oxidant to NOx is 0.5-2;

[0030] The chemical reaction that occurs is: NOx+O2→NO2.

[0031] Furthermore, the reduction absorption tower is used to scrub the oxidized tail gas, and a supergravity scrubber or a spray tower may be used.

[0032] Furthermore, the tower body material of the reduction absorption tower is glass fiber reinforced polystyrene, and the filler in the tower is plastic stepped rings.

[0033] Furthermore, the absorption liquid temperature is about 30°C and does not exceed 50°C at most.

[0034] It should be noted that the temperature of the absorption liquid is around 30°C and can reach up to 50°C, and the temperature has no significant effect on the absorption efficiency.

[0035] Furthermore, the concentration of the urea solution in the circulation tank should be maintained between 6% and 15%, and the pH value of the urea solution should be between 2 and 6.

[0036] It should be noted that the scrubbing liquid uses a urea solution, wherein the urea concentration is 6%-15%. During the scrubbing process, the mixed gas of NO and NO2 is reduced to N2 by urea;

[0037] The chemical reaction occurring during the scrubbing process is: 2NO+2NO2+2H2O+(NH2)2CO—2N2+CO2+3H2O.

[0038] After the urea solution reduces the NO and NO2 mixed gas, it will be consumed and needs to be replenished at any time. When the concentration of the urea solution is lower than 6%, urea can be added to make its concentration reach 15%. In this process, in order to increase the absorption rate of the urea solution to the NO and NO2 mixed gas, sulfuric acid can be added to make the pH of the urea solution within the range of 2-6; 0.04%-0.5% of a surfactant, such as LAO-30, can also be added.

[0039] Furthermore, the control system is used to control the concentration and pH value of the urea solution, and its control process includes the following steps: (1) measuring and controlling the concentration of the urea solution, (2) measuring and controlling the pH value of the urea solution, and (3) after the urea solution refluxes, measuring the volume of the solution, and calculating and adding an appropriate amount of urea.

[0040] Further, the urea dosage is calculated using the following method:

[0041] 6NO2+4(NO2)2CO—7N2+4CO2+8H2O

[0042] 6NO+2(NO2)2CO—5N2+2CO2+4H2O

[0043] 2NO+2NO2+2H2O+(NH2)2CO—2N2+CO2+3H2O

[0044] According to the total concentration of NOx in the flue gas, and the ratio of NO to NO2 (for combustion exhaust gas, NO usually accounts for 95% of the total NOx), the amount of urea used is calculated according to the above three reaction equations, as well as the change in urea solution concentration over time, to determine the amount and time of urea addition.

[0045] Furthermore, 0.04%-0.5% of a surfactant, such as LAO-30, may be added to the urea solution.

[0046] The present invention provides a redox treatment system for treating waste gas containing NOx, the system comprising: a waste gas collection module, a gas-liquid separation module, a MW-LEP oxidation module, a dissolving tank, a circulation pool, a reduction absorption tower, a fan, a chimney, and a control module. The waste gas collection module is connected to the gas-liquid separation module, the gas-liquid separation module is connected to the MW-LEP oxidation module, the dissolving tank is connected to the circulation pool, the circulation pool is connected to the reduction absorption tower, the reduction absorption tower is connected to a fan, and the fan is connected to the chimney. The present invention utilizes the catalytic oxidation ability of a microwave electrodeless ultraviolet waste gas treatment platform to first oxidize NOx into gases each accounting for a certain proportion of NO and NO2, and then absorbs them with an acidic urea solution, which can not only efficiently reduce NOx to N2 for removal, but also remove particulate matter at the same time. The system is equipped with a sludge treatment system, which can immediately clear the sludge in the acidic urea solution, and automatically detect the concentration of the urea solution and replenish it in time. Compared with traditional treatment methods, this system has the ability to remove NOx and particulate matter in exhaust gas at one time. It has a simple system structure, low construction cost, small footprint, stability and reliability, low operating cost, and no secondary pollution. It can be widely used in the treatment of various acid mist exhaust gases and acidic gases such as sulfur oxides (SOx), nitrogen oxides (NOx), carbon oxides (CO, CO2), and cyanide (HCN) emitted in the production process of chemical, light industry, printing and dyeing, medicine, steel, machinery, electronics, instrumentation, and electroplating industries.

Claims

1. An oxidation treatment system for treating NOx-containing waste gas, characterized in that: The system includes: a waste gas collection module, a gas-liquid separation module, a MW-LEP oxidation module, a dissolution tank, a circulation pool, a reduction absorption tower, a fan, a chimney, and a control module. The waste gas collection module is connected to the gas-liquid separation module, the gas-liquid separation module is connected to the MW-LEP oxidation module, the dissolution tank is connected to the circulation pool, the circulation pool is connected to the reduction absorption tower, the reduction absorption tower is connected to a fan, and the fan is connected to the chimney.

2. The oxidation treatment system for treating NOx-containing waste gas according to claim 1, characterized in that: The MW-LEP treatment module may also be added with oxidants such as air, water vapor and hydrogen peroxide, and the molar ratio of the oxidant to NOx is 0.5-2.

3. The oxidation treatment system for treating NOx-containing waste gas according to claim 2, characterized in that: The MW-LEP processing module is used to oxidize NOx to a molar ratio of NO:NO2 in the range of 0.4-0.

6.

4. The oxidation treatment system for treating NOx-containing waste gas according to claim 1, characterized in that: The reduction absorption tower is used to wash the oxidized tail gas, and a supergravity washing device or a spray tower can be used.

5. The oxidation treatment system for treating NOx-containing waste gas according to claim 4, characterized in that The tower body material of the reduction absorption tower is glass fiber reinforced polystyrene, and the filler in the tower is plastic stepped rings.

6. The oxidation treatment system for treating NOx-containing waste gas according to claim 4, characterized in that: The absorption liquid temperature is about 30°C and does not exceed 50°C at most.

7. The oxidation treatment system for treating NOx-containing waste gas according to claim 1, characterized in that: The concentration of the urea solution in the circulation tank should be maintained between 6% and 15%, and the pH value of the urea solution should be between 2 and 6.

8. The oxidation treatment system for treating NOx-containing waste gas according to claim 1, characterized in that: The control system is used to control the concentration and pH value of the urea solution, and its control process includes the following steps: (1) measuring and controlling the concentration of the urea solution, (2) measuring and controlling the pH value of the urea solution, and (3) after the urea solution refluxes, measuring the volume of the solution, and calculating and adding an appropriate amount of urea.

9. The oxidation treatment system for treating NOx-containing waste gas according to claim 8, characterized in that: The urea dosage is calculated using the following method: 6NO2+4(NO2)2CO—7N2+4CO2+8H2O 6NO+2(NO2)2CO—5N2+2CO2+4H2O 2NO+2NO2+2H2O+(NH2)2CO—2N2+CO2+3H2O According to the total concentration of NOx in the flue gas, and the ratio of NO to NO2 (for combustion exhaust gas, NO usually accounts for 95% of the total NOx), the amount of urea used is calculated according to the above three reaction equations, as well as the change in urea solution concentration over time, to determine the amount and time of urea addition.

10. The oxidation treatment system for treating NOx-containing waste gas according to claim 1, characterized in that : 0.04%-0.5% of a surfactant, such as LAO-30, may also be added to the urea solution.

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