Treatment system for NOx in flue gas treated by organic waste gas heat storage combustion method

Abstract

The utility model discloses a system for treating NOx in flue gas treated by an organic waste gas heat storage combustion method. The system comprises an RTO combustion chamber, an oxidation reactor and an absorption reactor, the output end of the bottom of the RTO combustion chamber is connected with the oxidation reactor, and the output end of the oxidation reactor is connected with the aeration head on the lower portion of the absorption reactor. According to the system, low-concentration NOx (the main component is NO) in tail gas is deeply removed through combination of oxidation and absorption, meanwhile, escape of ozone generated in the reaction process can be effectively controlled, and secondary pollution and potential harm to downstream equipment are avoided.

Description

Technical Field

[0001] The invention relates to the field of chemical environmental protection, and in particular to a system for treating NOx in flue gas after treatment of organic waste gas by thermal storage combustion in the field of chemical environmental protection. Background Art

[0002] Volatile organic compounds (VOCs) usually refer to various organic compounds with a boiling point of 50°C to 260°C at room temperature. They are important precursors to the formation of fine particulate matter (PM2.5) and ozone (O3) in the atmosphere, and are very harmful to the atmospheric environment and human health. my country attaches great importance to the prevention and control of VOCs, and has promulgated relevant standards and specifications such as the "Comprehensive Emission Standards for Air Pollutants" and the "Technical Specifications for the Treatment of Industrial Organic Waste Gas by Regenerative Combustion", forming a relatively complete standard system, and the requirements for the treatment of VOCs are becoming more and more stringent. In recent years, VOCs treatment technology has made great progress, and some new technologies have been applied in treatment projects and have achieved positive results. Among them, the regenerative combustion method (RTO) is one of the main technologies for the treatment of VOCs at present, and has been widely used in the treatment of VOCs in Japan, the United States, Europe and my country. The purification efficiency of RTO in treating VOCs is relatively high, and multi-chamber and rotary RTO can reach more than 98%, and two-chamber RTO can reach 95%. In general, a two-chamber RTO can be selected; if there are higher requirements for treatment efficiency (greater than 98%) or the emission limits of some industries are strict, a multi-chamber RTO can be selected; when there are restrictions on floor space, a rotary RTO can be selected. The heat recovery efficiency of RTO is also relatively high (up to 95%). Therefore, the application of RTO in the field of organic waste gas treatment in my country has increased year by year, especially in recent years, with the increasingly stringent environmental protection requirements and the continuous advancement of VOCs treatment, the technology has developed rapidly.

[0003] RTO treats VOCs by high-temperature combustion. The combustion chamber is an important component of RTO, which largely determines the removal efficiency and compliance of RTO. The lining material of the combustion chamber is generally refractory insulation materials such as ceramic fiber, which can withstand a high temperature of 1200°C for a short time. The combustion temperature mainly refers to the temperature that the combustion chamber may reach. In addition to being related to the composition, properties and content of the exhaust gas, it is also related to the heat enthalpy of the exhaust gas entering and leaving the combustion chamber, the combustion calorific value of the exhaust gas pollutants, and the heat transfer process inside and outside the combustion chamber. The combustion temperature is generally between 760°C and 980°C. According to the HJ1093-2020 "Technical Specifications for Industrial Organic Waste Gas Treatment Engineering by Regenerative Combustion Method" promulgated by the Ministry of Ecology and Environment on January 14, 2020, the combustion temperature in the combustion chamber should generally be higher than 760°C. This combustion process will generate a small amount of NOx (the main component is NO). Although the NOx concentration in the exhaust gas is not high (usually less than 50 mg / Nm3), it still needs to be further treated in some cases to meet more stringent NOx emission requirements (less than 20 mg / Nm3 or even lower).

[0004] There are many types of NOx treatment or denitrification technologies in gas, including selective catalytic reduction technology (SCR), selective non-catalytic reduction technology (SNCR), etc. However, most of the existing technologies are for the treatment of high-concentration NOx in conventional flue gas represented by boilers and industrial furnaces, which can meet the ultra-clean emission requirements (50mg / Nm3), but have high requirements for reaction window temperature, working conditions, etc. When treating low-concentration NOx, there are inappropriate reaction window temperature, complex system, and potential hazards of ammonia escape (corrosion and blockage of downstream equipment, secondary pollution, etc.), which are not suitable for the needs of RTO for efficient treatment of small-volume, low-concentration NOx in organic waste gas tail gas. Existing or implemented patented technologies are:

[0005] Patent No. CN201710367686.1 discloses an arsenic-resistant SCR denitrification catalyst and a preparation method thereof. The arsenic-resistant ability of the SCR denitrification catalyst is improved by appropriate additives, and the life of the SCR denitrification catalyst is extended. However, its reaction window temperature is above 300°C, the operating temperature is relatively high, the system is complex, and there is a small amount of ammonia escape, which has a certain impact on downstream equipment and the environment.

[0006] Patent No. CN201910379422.7 discloses a low-temperature SCR denitrification catalyst and a preparation method thereof. The catalyst maintains excellent SCR denitrification activity in a wide temperature window of 180 to 400°C, and the nitrogen oxide removal rate is over 60%. However, the temperature requirement for the flue gas is still relatively high, and it is difficult to directly treat flue gas close to normal temperature. In addition, there is a small amount of ammonia escape, which has a certain impact on downstream equipment and the environment.

[0007] Patent No. CN201410252283.9 discloses a flue gas SNCR denitrification control device and a control method for its use, which can adjust the optimal working mode of the denitrification device according to the monitoring of changes in boiler operating conditions. However, its denitrification operating temperature is about 850-1100°C, which cannot directly treat nitrogen oxides in low-temperature flue gas, and there is a small amount of ammonia escape, which has a certain impact on downstream equipment and the environment.

[0008] Patent No. CN202010022341.4 discloses a system and method for indirect low-temperature plasma activation reduction denitrification, which utilizes the low-temperature plasma activation reaction characteristics combined with reduced sulfur to reduce and remove NOx in flue gas. The reduction reaction device includes a reaction tower, a reduced sulfur storage tank, a bag filter, etc. The system is complex and is not suitable for the treatment of lower concentration NOx gases. Utility Model Content

[0009] The technical problem to be solved by the present invention is to provide a system for treating NOx in flue gas after the treatment of organic waste gas by thermal storage combustion method, which deeply removes low-concentration NOx in the tail gas through oxidation combined with absorption, and at the same time adopts ozone decomposition measures to effectively control the escape of residual ozone after the reaction, thereby avoiding secondary pollution and potential harm to downstream equipment.

[0010] The purpose of the present invention can be achieved through the following technical solutions:

[0011] A system for treating NOx in flue gas after treatment by thermal storage combustion of organic waste gas, the system comprises an RTO combustion chamber, an oxidation reactor and an absorption reactor; the output end at the bottom of the RTO combustion chamber is connected to the oxidation reactor, and the output end of the oxidation reactor is connected to the aeration head at the bottom of the absorption reactor.

[0012] In the technical solution of the utility model: an ultraviolet irradiation unit is arranged in the inner chamber of the oxidation reactor, and an ozone catalytic decomposition filter is arranged at the right end of the ultraviolet irradiation unit.

[0013] In the technical solution of the utility model: the ultraviolet irradiation unit is composed of an ultraviolet lamp, a first electrode line, a controller and a second electrode line which are connected in sequence end to end.

[0014] In the technical solution of the utility model: a valve is arranged on the branch pipe connecting the oxidation reactor and the absorption reactor.

[0015] In the technical solution of the utility model: an aeration head is arranged at the end of the branch pipe.

[0016] In the technical solution of the utility model: the top of the absorption reactor is provided with a clean smoke outlet, and the bottom is provided with an absorption liquid outlet.

[0017] In the technical solution of the utility model: the bottom of the RTO combustion chamber is respectively provided with an input pipeline for organic waste gas and / or an input end for purge air.

[0018] In the technical solution of the utility model: the ultraviolet irradiation unit is located upstream of the oxidation reactor (close to the inlet end of the oxidation reactor), and the ozone catalytic decomposition filter is located downstream of the oxidation reactor (close to the outlet end of the oxidation reactor).

[0019] In the technical solution of the utility model: the ultraviolet irradiation unit inside the oxidation reactor is connected to an external controller through an electrode line.

[0020] In the technical solution of the utility model: the connecting pipeline is divided into a plurality of branch pipes after entering the oxidation reactor, and an aeration head is arranged at the end of the branch pipe, and the aeration head is located below the liquid level of the absorption liquid in the oxidation reactor.

[0021] In the technical solution of the utility model: the absorption liquid in the oxidation reactor is water, and a small amount of sodium hydroxide or other alkaline substances can be added to enhance the absorption effect, or other alkaline solutions can be directly used.

[0022] The connecting pipeline is divided into several branch pipes after entering the oxidation reactor. An aeration head is arranged at the end of the branch pipe. The aeration head is located below the absorption liquid level in the oxidation reactor.

[0023] In the technical solution of the utility model: a valve (check valve) is provided on the connecting flue between the oxidation reactor and the absorption reactor to prevent the liquid in the absorption reactor from flowing back to the upstream oxidation reactor.

[0024] In the technical solution of the utility model: a clean smoke outlet is arranged at the top of the absorption reactor, and an absorption liquid outlet is arranged at the bottom.

[0025] A method for treating NOx in flue gas after the treatment of organic waste gas by thermal storage combustion method using the above system is disclosed. The method comprises the following steps: introducing flue gas from an RTO combustion chamber into an oxidation reactor through an original flue gas pipeline; the insoluble NO in the flue gas reacts with the highly active ozone generated by an ultraviolet irradiation unit in the oxidation reactor and is oxidized into more soluble NO2; the flue gas after the reaction continues to flow through an ozone catalytic decomposition filter in the oxidation reactor, and the unreacted residual O3 in the flue gas is decomposed; the flue gas enters an absorption reactor through a connecting pipeline and then enters the absorption reactor through an aeration head, and the NO2 in the flue gas is absorbed by an absorption liquid; and the clean flue gas is discharged through a clean flue gas outlet.

[0026] In the technical solution of the utility model, the RTO combustion chamber is a rotary heat storage combustion or a fixed two-chamber type. The beneficial effects of the present invention are:

[0027] 1. A system for treating NOx in flue gas after the treatment of organic waste gas by thermal storage combustion is provided. Low-concentration NOx (the main component is NO) in the tail gas is deeply removed by oxidation combined with absorption. At the same time, the escape of ozone generated in the reaction process can be effectively controlled to avoid secondary pollution and potential harm to downstream equipment.

[0028] 2. The highly active substance ozone (O3) is generated through ultraviolet radiation, which can oxidize NO into more soluble NO2 at room temperature, avoiding the requirement of excessively high flue gas temperatures for denitrification processes such as SCR and SNCR, and the amount of ozone generated can be flexibly adjusted by the controller.

[0029] 3. The small amount of residual O3 that has not reacted in the flue gas after the reaction is decomposed by the ozone catalytic decomposition filter, eliminating ozone escape, avoiding secondary pollution and potential harm to downstream equipment.

[0030] 4. The flue gas enters the absorption reactor and comes into contact with the absorption liquid for absorption. The aeration head aerates and mixes the gas fully, and the NO2 absorption effect is good.

[0031] 5. A valve is installed on the connecting flue between the oxidation reactor and the absorption reactor to prevent the liquid in the absorption reactor from flowing back to the upstream oxidation reactor, which is safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the process flow for treating NOx in flue gas after the rotary thermal storage combustion is used to treat organic waste gas.

[0033] Figure 2 It is a schematic diagram of the process flow of treating NOx in flue gas after treatment by the fixed two-chamber type organic waste gas thermal storage combustion method. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto:

[0035] like Figure 1 , a treatment system for NOx in flue gas after treatment by heat storage combustion method for organic waste gas, the system comprises an RTO combustion chamber 1, an oxidation reactor 3 and an absorption reactor 10; the output end at the bottom of the RTO combustion chamber 1 is connected to the oxidation reactor 3, and the output end of the oxidation reactor 3 is connected to the aeration head 9 at the bottom of the absorption reactor 10. An ultraviolet irradiation unit 4 is provided in the inner chamber of the oxidation reactor 3, and an ozone catalytic decomposition filter 5 is provided at the right end of the ultraviolet irradiation unit 4. The ultraviolet irradiation unit 4 is composed of an ultraviolet lamp 401, a first electrode line 402, a controller 404 and a second electrode line 403 connected end to end in sequence. A valve 7 is provided on the branch pipe 8 connecting the oxidation reactor 3 and the absorption reactor 10. An aeration head 9 is provided at the end of the branch pipe 8. A clean flue gas outlet 11 is provided at the top of the absorption reactor 10, and an absorption liquid outlet 12 is provided at the bottom. The bottom of the RTO combustion chamber 1 is respectively provided with an input pipeline for organic waste gas and an input end for purge air.

[0036] Specifically, the insoluble NO in the flue gas of the system reacts with the highly active ozone O3 generated by the ultraviolet irradiation unit 4 in the oxidation reactor 3, and is oxidized into more soluble NO2; the flue gas after the reaction continues to flow through the ozone catalytic decomposition filter 5 in the oxidation reactor 3, and the residual O3 in the flue gas that has not reacted is decomposed; the flue gas is introduced into the absorption reactor 10 through the connecting pipe 6, and then through the branch pipe 8, and finally through the aeration head 9 into the absorption reactor 10 to contact with the absorption liquid, and the NO2 in the flue gas is absorbed by the absorption liquid; the clean flue gas is discharged through the clean flue gas outlet 11. A valve 7 is provided on the connecting flue 6 between the oxidation reactor 3 and the absorption reactor 10, and an absorption liquid outlet 12 is provided at the bottom of the absorption reactor 10.

[0037] The ultraviolet lamp 401 of the ultraviolet irradiation unit 4 inside the oxidation reactor 3 is connected to the controller 404 through electrode wires 402 and 403 , and the amount of ozone generated can be flexibly adjusted by the controller 404 .

[0038] A method for treating NOx in organic waste gas tail gas by using the above system using a thermal storage combustion method, the method comprising the following steps:

[0039] Step 1: The flue gas to be treated from the RTO combustion chamber 1 is introduced into the oxidation reactor 3 through the original flue gas pipeline 2;

[0040] Step 2: The ultraviolet irradiation unit 4 in the oxidation reactor 3 generates highly active ozone O3, and NO in the flue gas reacts with O3, and NO is oxidized to more soluble NO2;

[0041] Ozone is produced when oxygen molecules (O2) in the gas absorb ultraviolet light of a specific wavelength (185nm):

[0042] O2+hr→O+O

[0043] O2+O+M→O3+M

[0044] Among them, hr is the ultraviolet light quantum, and M is an inert object, such as the reactor wall, nitrogen, carbon dioxide gas molecules, etc.

[0045] The advantages of producing ozone by ultraviolet radiation are that it is insensitive to humidity and temperature, has good repeatability, and the ozone output and concentration are easy to adjust.

[0046] Step 3: After passing through the ultraviolet irradiation unit 4, the flue gas continues to flow backward through the ozone catalytic decomposition filter 5, and the unreacted residual O3 is decomposed by the ozone catalytic decomposition filter 5;

[0047] Ozone is highly oxidizing and corrosive to metals such as aluminum, zinc, and lead. It also has a strong corrosive effect on non-metallic materials such as polyvinyl chloride plastics. It needs to be controlled during use. This system uses an ozone catalytic decomposition filter to decompose residual ozone.

[0048] Step 4: The flue gas passing through the ozone catalytic decomposition filter 5 is introduced into the absorption reactor 10 through the connecting pipe 6 and then enters the absorption reactor 10 through the aeration head 9 to contact with the absorption liquid, and the NO2 in the flue gas is absorbed by the absorption liquid;

[0049] Step 5: The clean flue gas is finally discharged through the clean flue gas outlet (11).

[0050] The ultraviolet irradiation unit 4 generates highly active ozone (O3) by ultraviolet irradiation, and oxidizes NO into more soluble NO2 at room temperature; the unreacted residual O3 in the flue gas after the reaction is decomposed by the ozone catalytic decomposition filter 5, and no ozone escapes, thereby avoiding secondary pollution and potential harm to downstream equipment.

[0051] Ozone generated by the ultraviolet irradiation unit 4 can achieve oxidation of NO at room temperature, avoiding the requirement of too high flue gas temperature for denitrification processes such as SCR and SNCR, and the amount of ozone generated can be flexibly adjusted by the controller 404; the flue gas enters the absorption reactor 10 and is contacted with the absorption liquid for absorption, the aeration head 9 is fully aerated, and the gas-liquid mixed absorption effect is good, that is, low-concentration NO in the tail gas can be deeply removed through oxidation combined with absorption.

[0052] The initial parameters of the exhaust gas after the organic waste gas is treated by rotary thermal storage combustion are listed in Table 1.

[0053] Table 1 Flue gas parameters after a rotary thermal storage combustion treatment of organic waste gas

[0054] project content Remark <![CDATA[Flue gas volume, Nm 3 / h]]> 11000 Smoke temperature, ℃ 43.0 Oxygen concentration, % 20.1 Pressure, KPa -0.62 Gauge pressure humidity,% 1.9 <![CDATA[Concentration of nitrogen oxides, mg / Nm 3 > 21.0 <![CDATA[Soot, mg / Nm 3 > 0

[0055] From the table above, we can see that the flue gas flow rate after a rotary thermal storage combustion treatment of organic waste gas is about 11000Nm 3 / h, the flue gas temperature is about 43℃, and the nitrogen oxide content is about 21mg / Nm 3 After being treated by this system, the NOx content in the clean flue gas can be reduced to 8mg / Nm 3 , low-concentration NOx can be effectively removed without heating the flue gas; ozone in the clean flue gas is negligible, avoiding secondary pollution and potential harm to downstream equipment.

Claims

1. A system for treating NOx in flue gas after treatment by thermal storage combustion of organic waste gas, characterized in that: The system comprises an RTO combustion chamber (1), an oxidation reactor (3) and an absorption reactor (10); the output end at the bottom of the RTO combustion chamber (1) is connected to the oxidation reactor (3), and the output end of the oxidation reactor (3) is connected to an aeration head (9) at the bottom of the absorption reactor (10); wherein an ultraviolet irradiation unit (4) is provided in the inner chamber of the oxidation reactor (3), and an ozone catalytic decomposition filter (5) is provided at the right end of the ultraviolet irradiation unit (4).

2. The system for treating NOx in flue gas after treatment by thermal storage combustion of organic waste gas according to claim 1 is characterized in that: The ultraviolet irradiation unit (4) comprises an ultraviolet lamp (401), a first electrode line (402), a controller (404), and a second electrode line (403) which are connected end to end in sequence.

3. The system for treating NOx in flue gas after treatment by thermal storage combustion of organic waste gas according to claim 1 is characterized in that: A valve (7) is provided on the branch pipe (8) connecting the oxidation reactor (3) and the absorption reactor (10).

4. The system for treating NOx in flue gas after treatment by thermal storage combustion of organic waste gas according to claim 3 is characterized in that: An aeration head (9) is provided at the end of the branch pipe (8).

5. The system for treating NOx in flue gas after treatment by thermal storage combustion of organic waste gas according to claim 1 is characterized in that: The top of the absorption reactor (10) is provided with a clean flue gas outlet (11), and the bottom of the absorption reactor (10) is provided with an absorption liquid outlet (12).

6. The system for treating NOx in flue gas after treatment by thermal storage combustion of organic waste gas according to claim 1 is characterized in that: An organic waste gas input pipeline and / or a purge air input end are respectively provided at the bottom of the RTO combustion chamber (1).

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