Waste gas treatment system capable of adjusting oxygen content and treatment method

Abstract

The invention relates to a waste gas treatment system capable of adjusting oxygen content and a treatment method, and relates to the field of environmental protection and waste gas treatment, the waste gas treatment system comprises a pretreatment device, an incineration device, a waste heat utilization device and an air return device. According to the system, a high-boiling-point organic solvent is condensed and discharged through the pretreatment device, pretreated waste gas is incinerated in the direct combustion furnace, the temperature in the furnace is controlled through the water spraying device and the incinerated tail gas return air amount, and water is heated and gasified through waste heat of tail gas to generate steam. The air return device controls the concentration of organic matter in the furnace and the temperature of the furnace body by adjusting the tail gas return air amount and the fresh air fan air amount, and efficient and safe treatment of waste gas and energy recovery are achieved.

Description

Technical Field

[0001] The present application relates to the technical field of waste gas treatment, and in particular to a waste gas treatment system and method capable of adjusting oxygen content. Background Art

[0002] The pollutant concentrations in waste gases from petrochemical storage tanks, ship unloading at docks, and oil and gas from automobile loading are high, especially the alkane content exceeds 80% and the hydrogen content is about 5%. At present, this type of waste gas is mainly treated by VCU or CEB process, but there are significant problems. First, since the waste gas itself does not contain oxygen, and the combustion process requires oxygen, it must be supplemented with air, which leads to a decrease in the waste gas concentration and may even put the waste gas concentration within the explosion limit, thus posing a safety risk. Secondly, the high concentration of organic matter and hydrogen in the waste gas will release a lot of heat during the combustion process, which can easily cause the furnace temperature to exceed the standard. Summary of the invention

[0003] The present application aims to overcome the above-mentioned technical problems and provide a waste gas treatment system and method with adjustable oxygen content, which can not only reduce the safety risks in the waste gas treatment process, but also effectively utilize the heat generated by the combustion of the waste gas. The present application provides a waste gas treatment system with adjustable oxygen content, comprising a pretreatment device, an incineration device, a waste heat utilization device and an emission device which are arranged in sequence; the pretreatment device is connected to a waste gas collection pipe, a gas-liquid separation mechanism is arranged in the pretreatment device, and the gas separated from the waste gas after being treated by the gas-liquid separation device is transported to the incineration device; the incineration device is provided with a burner for burning the waste gas, the incineration device is connected to a fresh air device, and the fresh air device is used to send the fresh air into the incineration device through a gas distribution pipeline; the waste heat utilization device is used to recover heat from the purified gas generated by the combustion, and the emission device comprises a three-way valve for connecting the purified gas of the waste heat utilization device, one end of the three-way valve is used to discharge the purified gas, and the other end of the three-way valve is connected to the gas distribution pipeline, the three-way valve is used to adjust the purified gas emission and the return air volume sent back to the incineration device, and the fresh air device can mix the fresh air with the purified gas and send the mixed air into the incineration device through the gas distribution pipeline.

[0004] Preferably, it also includes a water supply device, which includes a water inlet pipe and a water storage tank. The incineration device is provided with a water spray mechanism for cooling, and the water inlet pipe is connected to the water spray mechanism on the incinerator; the water storage tank connects the water to the waste heat utilization device through a water pump and performs heat exchange with the purified gas after combustion.

[0005] Preferably: the waste heat utilization device includes an economizer, a waste heat boiler and a superheater arranged in the incineration device, the superheater, the waste heat boiler and the economizer are arranged in sequence along the direction of the purified gas discharge, and the water in the water storage tank passes through the economizer, the waste heat boiler and the superheater in sequence to exchange heat with the purified gas.

[0006] Preferably: the incineration device is provided with a control system, and a temperature sensor, an oxygen content sensor, and a pressure sensor which can transmit signals to the control system. The control system controls the fresh air supply of the fresh air device, the return air volume of the purified air from the three-way valve, and the water spraying volume of the water spraying mechanism, and controls the furnace temperature of the incineration device to be 1150±100℃, and the waste gas stays in the furnace for 2 to 5s.

[0007] Preferably, the water spray mechanism is provided with two groups, a ventilation mechanism is provided between the two groups of water spray mechanisms, and the ventilation mechanism is connected with the fresh air device and the three-way valve.

[0008] Preferably: the fresh air device adopts a variable frequency fan, wherein the fresh air volume of the fresh air device can be set to 5 levels of wind speed, level 0 represents that the fresh air device is completely stopped, and level 5 represents that the fresh air device is running at the highest power; the return air volume of the purified air returned by the three-way valve to the incineration device can also be set to 5 levels, level 0 represents that the return air volume level of the three-way valve to the incineration device is 0, that is, the closed state, and level 5 represents the maximum return air volume of the purified air delivered by the three-way valve to the incineration device.

[0009] Preferably: when the exhaust gas flow rate is constant, the fresh air volume level of the fresh air device and the return air volume level of the three-way valve are arranged and combined, and the corresponding furnace temperature of the incineration device is used as the initial setting of the control system, so as to select a suitable combination of fresh air volume level and return air volume level according to the furnace temperature, air pressure, oxygen content and other conditions.

[0010] Preferably, a booster pump, a buffer tank and a return air valve are arranged in sequence on the return air duct connecting the three-way valve and the fresh air device, and the return air valve is located on the side of the buffer tank outlet. The return air valve is a pulse solenoid valve, and the control system controls the return air valve to open and close periodically, so that the fresh air and the purified air return air are mixed and then enter the furnace in a pulsed manner.

[0011] The present application also provides a waste gas treatment method, comprising the following steps: The first step is pretreatment: the waste gas is passed into the pretreatment device, and the waste gas is separated into gas and liquid through the transfer tank of the pretreatment device. The formed liquid can be discharged through the bottom of the transfer tank, and the separated gas is passed into the incineration device.

[0012] The second step is to ignite the waste gas: the gas is introduced into the incineration device, and fresh air is introduced into the incineration device, and the burner is used to ignite the waste gas; after the temperature of the incinerator rises to the target temperature, the waste gas is introduced, and the waste gas is burned in the furnace. When the waste gas concentration is low and cannot sustain combustion, the gas is supplemented to make the waste gas fully burn; The third step is temperature control: when the furnace temperature reaches the first temperature threshold, the tail gas generated by the combustion is purified and cooled, and part of the purified gas generated is returned to the incineration device to keep the furnace temperature near the second temperature threshold; when the furnace temperature drops and is lower than the first lower limit of the second temperature threshold, the return air volume of the purified gas is reduced; when the furnace temperature is higher than the upper limit of the second temperature threshold, the fresh air volume is reduced and the return air volume of the purified gas is increased; if the furnace temperature is still on an upward trend, water is sprayed into the furnace to cool it down; Step 4: Purify gas and denitrate. Urea is decomposed into ammonia at high temperature. Ammonia reacts with NOX generated in the incinerator to generate N2, which purifies NOX generated after combustion.

[0013] Step 5: Heat recovery: The waste heat utilization device recovers the waste heat from the exhaust gas generated by the combustion of waste gas, and the generated water vapor is used for other thermal needs of the factory area.

[0014] Step 6: Purified gas emission. After the tail gas is purified and cooled, part of the net gas is returned to the incineration device through the reflux pipe and the gas distribution pipe, and the rest is discharged through the chimney.

[0015] Preferably: in the second step, the target temperature is 1100°C, and in the third step, when the first temperature threshold in the temperature control step is set to 1000°C, the lower limit of the second temperature threshold is 1100°C and the upper limit is 1200°C.

[0016] In summary, the present invention has at least the following beneficial effects: 1. Since the present invention adopts the method of reintroducing the tail gas after the combustion of the waste gas into the incineration device, the mixing of the tail gas and the fresh air can not only control the oxygen content entering the incineration device and realize the precise adjustment of the furnace temperature, but also reduce the concentration of the waste gas so that it is no longer within the explosion limit, thereby significantly reducing the risk of explosion; 2. In the present invention, the furnace temperature is reduced by a water spray mechanism to avoid the temperature in the furnace from exceeding the standard, protect the incineration device, and extend the service life of the incineration device; 3. Direct combustion is adopted, and the temperature in the furnace is controlled at 1000-1200°C, and the waste gas stays in the furnace for 2-5s, so that the waste gas can be fully burned and harmful gases are reduced; 4. The waste heat utilization device exchanges heat with the high-temperature tail gas, and finally outputs superheated steam with a temperature of 300-400°C, thereby realizing the reuse of heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of the exhaust gas treatment system capable of adjusting the oxygen content in Example 1; Figure 2 This is a schematic diagram of the structure of the exhaust gas treatment system capable of adjusting the oxygen content in Example 2; Figure numerals: 1. pretreatment device; 2. incineration device; 21. first burner; 22. second burner; 23. water spray mechanism; 24. ventilation mechanism; 25. fresh air interface; 26. gas distribution pipeline; 3. waste heat utilization device; 31. superheater; 32. waste heat boiler; 33. economizer; 4. discharge device; 41. induced draft fan; 42. three-way valve; 43. chimney; 44. return air duct; 441. booster pump; 442. buffer tank; 443. reflux valve; 5. water supply device; 51. water inlet pipeline; 52. water storage tank; 6. fresh air device; 7. urea device; 71. urea tank; 72. urea pump. DETAILED DESCRIPTION

[0018] The following is combined with Figure 1 -Attached Figure 2 , further details of this application are given.

[0019] like Figure 1 As shown, this embodiment discloses a waste gas treatment system and treatment method capable of adjusting oxygen content, which mainly includes a pretreatment device 1, an incineration device 2, a waste heat utilization device 3 and an emission device 4 arranged in sequence. A close functional link is formed between the components, which effectively realizes the efficient treatment of waste gas and the reuse of energy, and improves the comprehensive benefits of the entire system.

[0020] In order to facilitate the understanding of this scheme, the waste gas referred to in this application is waste gas from petrochemical storage tanks, waste gas from unloading ships at docks, and waste gas from loading oil on cars, etc. The tail gas referred to in this application refers to the gas produced by the combustion of waste gas or a mixture of waste gas and fuel gas, and the purified gas referred to in this application refers to the gas after the tail gas has been purified and cooled. The pretreatment device 1 is used to receive and pretreat the waste gas. There are many types of waste gas. Various types of waste gas can be temporarily stored in storage tanks and then passed into the pretreatment device 1. Different storage tanks can be set for different waste gases. The storage tank is filled with porous materials such as granular activated carbon and zeolite molecular sieves, which are used to balance the concentration of waste gas. When the waste gas concentration is low, the waste gas is released from the surface of the adsorbent, and when it is high, the waste gas is absorbed. When the waste gas is treated, the storage tanks can be connected to the pretreatment device 1 separately, or all of them can be connected to the pretreatment device 1 at the same time; as another optional scheme, each medium with waste gas is directly passed into the pretreatment device 1.

[0021] The pretreatment device 1 includes a transfer tank. The first function of the transfer tank is to mix various types of waste gas to stabilize the gas properties. The second function is to separate the high-boiling point components in the waste gas through the gas-liquid separation mechanism in the transfer tank, separate the gas and liquid in the waste gas, and discharge the separated liquid from the bottom of the transfer tank to ensure that the waste gas entering the next treatment link is purer. The gas-liquid separation method can use a cyclone separator and a filter. A cyclone separator is a device that uses centrifugal force to separate suspended solid particles or droplets. An electrostatic precipitator or a wet scrubber can be used as an alternative. The filter can be made of a wire mesh or other materials, and a ceramic filter element can also be used as an alternative. Of course, another way to separate gas and liquid is to set up two groups of transfer tanks. Both groups of transfer tanks can be connected to the waste gas. One of the transfer tanks is pressurized to partially liquefy the waste gas and then separate the gas and liquid. The other group of transfer tanks normally transports the waste gas to the incineration device 2. By alternately connecting the two groups of transfer tanks to the incineration device 2, one group can use pressurization to achieve a better liquefaction effect, thereby achieving efficient gas-liquid separation.

[0022] The incineration device 2 adopts a direct-fired furnace, and the incineration device 2 supplies oxygen to the furnace through the gas distribution pipe 26. The incineration device 2 is equipped with two burners, namely the first burner 21 and the second burner 22. The fuel gas and the waste gas from the transfer tank are mixed and passed into the first burner 21. The second burner 22 is connected to the fuel gas alone. The second burner 22 plays the role of auxiliary combustion. After the temperature in the incineration device 2 rises to 1100°C, the waste gas is introduced, and the fuel gas supply is stopped. When the waste gas concentration is too low to sustain self-combustion, the fuel gas is supplemented to keep the waste gas fully burned; the incineration device 2 is equipped with a high-precision temperature sensor, oxygen content sensor, and pressure sensor; and when the furnace temperature reaches 10 When the temperature is between 00 and 1200°C, the fresh air supply is locked, and part of the purified gas generated after the exhaust gas is burned, purified and cooled is returned to the gas distribution pipe 26, thereby reducing the oxygen content to control the incinerator temperature. For example, when the furnace temperature reaches 1150°C, the fresh air supply is locked, and the purified gas return air volume is increased, thereby reducing the oxygen content in the furnace to lower the furnace temperature; if the furnace temperature is still rising significantly, water can be sprayed into the furnace to cool it down; and when the furnace temperature is lower than 1150°C, the purified gas return air volume is reduced or the fresh air volume is increased, and the furnace temperature is increased by increasing the oxygen content in the furnace to increase the combustion effect.

[0023] The specific incineration device 2 is also equipped with a ventilation mechanism 24 and a water spray mechanism 23 with a nozzle. The ventilation mechanism 24 is connected to the gas distribution pipeline 26, and fresh air or a mixture of fresh air and purified gas is introduced into the furnace through the gas distribution pipeline 26; the water spray mechanism 23 is used to spray water into the furnace for cooling. The ventilation mechanism 24 is annular, and the air outlets on the ventilation mechanism 24 are distributed in an annular shape. The water spray mechanism 23 is annular, and the nozzles on the water spray mechanism 23 are distributed in an annular shape. Through the synergistic effect of the water spray mechanism 23 and the ventilation mechanism 24, the furnace temperature can be stably controlled at 1000-1200°C. The optimal furnace temperature fluctuates around 1150°C, while ensuring that the residence time of the exhaust gas in the furnace reaches 2-5s, fully ensuring the reaction efficiency of the exhaust gas and oxygen, and generating harmless carbon dioxide and water. When the furnace temperature is greater than 1250°C, the system needs to be shut down to ensure safety.

[0024] The inlet and outlet pipes of the incineration device 2 are equipped with real-time detectors of flow rate, oxygen concentration, and organic matter concentration. These instruments can continuously monitor and feedback the incineration status in the furnace, and provide accurate data support for operators, so as to adjust the incineration parameters in time and ensure the optimization of the treatment effect. Specifically, the control system of the incineration device 2 dynamically adjusts the fresh air volume, purified gas return air volume, and cooling water supply in the furnace by detecting parameters such as furnace temperature, oxygen content, pressure, exhaust gas intake, and purified gas exhaust volume of the incineration device 2; for example, when the furnace temperature is lower than 1150°C, the water spray mechanism 23 can be closed or adjusted down to stop or reduce the supply of cooling water, and further, the purified gas return air volume is reduced to increase the oxygen content in the furnace, and the furnace temperature is increased by making the combustion in the furnace more intense in the above manner; and when the furnace temperature is higher than 1150°C, the purified gas return air volume is increased to reduce the oxygen content in the furnace to reduce the degree of combustion. If the furnace temperature rise trend is still obvious, the water spray device is opened or adjusted up to increase the supply of cooling water to increase the cooling effect. Through the above method, the furnace temperature fluctuates around 1150°C, keeping the furnace temperature within a reasonable range.

[0025] The high-temperature tail gas generated after the waste gas is burned in the incineration device 2 enters the waste heat utilization device 3 for cooling. The waste heat utilization device 3 makes full use of the waste heat of the tail gas generated by the incineration device 2. The waste heat utilization device 3 includes a waste heat boiler 32 and an economizer 33. Through the waste heat boiler 32, the high-temperature tail gas flows in the tube side, and water is introduced into the shell side for heat exchange. This design not only effectively reduces the temperature of the tail gas, but also heats the water to gasification, generating a large amount of steam. The temperature range of these steams is 200℃~300℃, which has a high utilization value and can be applied to other thermal needs of the plant area, thereby realizing the recycling and conservation of energy. The waste heat utilization device 3 includes a waste heat boiler 32 and an economizer 33. The waste heat boiler 32 and the economizer 33 further reduce the temperature of the purified gas when it is discharged by heat exchange with water, thereby realizing energy saving and emission reduction of this system.

[0026] An emission device 4 is also provided at the end of the economizer 33, and the emission device 4 includes an induced draft fan 41 and a chimney 43. The induced draft fan 41 can drive the exhaust gas in the incineration device 2 and the waste heat utilization device 3 to flow forward. A three-way valve 42 is provided at the end of the induced draft fan 41, and one end of the three-way valve 42 is connected to the chimney 43. The emission device 4 is a chimney 43, which is used for normal emission of purified gas, and the other end is connected to the gas distribution pipe 26. The refluxed purified gas is mixed with fresh air in a certain proportion and passed into the incineration device 2 through the gas distribution pipe 26 to provide reasonable oxygen for the combustion of the exhaust gas. The gas distribution pipe 26 is respectively connected to the first burner 21, or the second burner 22, and the ventilation mechanism 24. The function of the three-way valve 42 is to adjust the return air volume of the purified gas by changing the opening of the valve core. The purpose of the purified gas returning to the furnace is to reduce the concentration of the exhaust gas, so that the exhaust gas concentration is not within the explosion limit, reducing the risk of explosion. In addition, due to the mixing of the purified gas, the oxygen content of the gas distribution pipeline 26 entering the furnace is also reduced, so that the heat generated by the combustion of the exhaust gas is also reduced, so that the temperature of the exhaust gas combustion in the furnace can be better controlled. Therefore, this adjustment mechanism not only ensures the stability and safety of the incineration process, but also effectively controls the concentration and oxygen content of the outlet pollutants, making the entire exhaust gas treatment system more efficient and environmentally friendly.

[0027] A fresh air interface 25 is provided near the first burner 21 of the incineration device 2. The fresh air interface 25 is only connected to the fresh air device 6, and no purified gas is connected. It is suitable for the working conditions when the incineration device 2 is just started or the temperature is insufficient and needs to be quickly heated up, so that more oxygen can enter the furnace. An automatic control system is added to the incineration device 2. The system can automatically adjust the water spraying amount of the water spraying device, the purified gas return air volume of the three-way valve 42 and the air volume of the fresh air fan according to the real-time monitored data such as furnace temperature, furnace pressure, furnace oxygen content, exhaust gas intake flow, gas distribution pipeline intake volume, furnace exhaust flow, etc., thereby realizing intelligent control of the incineration process and further improving the efficiency and safety of waste gas treatment.

[0028] The fresh air device 6 adopts a variable frequency fan, so that the fresh air device 6 can adjust the appropriate fresh air intake volume according to the flow rate of the exhaust gas. In order to facilitate the control system to control the fresh air system, the fresh air volume of the fresh air device 6 can be set to 5 levels of wind speed, level 0 represents that the fresh air device 6 is completely stopped, and level 5 represents that the fresh air device 6 is running at the highest power. Correspondingly, the return air volume of the purified gas from the three-way valve 42 to the incineration device 2 can also be set to 5 levels, level 0 represents that the return air volume level of the three-way valve 42 to the incineration device 2 is 0, that is, the closed state, and level 5 represents the maximum return air volume of the purified gas delivered by the three-way valve 42 to the incineration device 2. The maximum return air volume referred to here does not mean that all the purified gas is returned to the incineration device 2. According to the actual operation of the system, the purified gas can be discharged normally through the chimney 43 to maintain the normal operation of this system. Through the system test before leaving the factory, under the condition of constant exhaust gas flow, the fresh air volume level and the purified gas return air volume level are arranged and combined to test the corresponding furnace temperature of the incineration device 2, which is used as the initial setting of the control system. The appropriate combination of fresh air volume level and purified gas return air volume level is selected according to the furnace temperature, air pressure, oxygen content and other conditions to achieve precise control of the furnace temperature.

[0029] The waste gas treatment system further includes a water supply device 5, which includes a water inlet pipe 51 and a water storage tank 52. The water inlet pipe 51 is used to provide softened water or deoxygenated and desalted water to the waste gas treatment system. The water inlet pipe 51 is connected to the water spraying mechanism 23 on the incineration device 2. The water spraying mechanism 23 has two groups, and the two groups of water spraying devices are arranged on both sides of the ventilation device. The water storage tank 52 is connected to the water inlet pipe 51 and can store a certain amount of water. The water in the water storage tank 52 is connected to the economizer 33 through a water pump and undergoes the first heat exchange with the tail gas in the economizer 33. The heated water after the heat exchange enters the waste heat boiler 32 for the second heat exchange, and the water is heated to form high-temperature saturated steam; a superheater 31 is arranged in the incineration device 2, and the superheater 31 is arranged between the ventilation mechanism 24 and the right water spray device. The saturated steam after the secondary heat exchange enters the superheater 31 in the incineration device 2 for the third heat exchange. The generated steam of 200-300°C can be used for other thermal needs of the plant. After three heat exchanges, the heat generated in the exhaust gas combustion process can be better recovered, and the temperature of the purified gas finally discharged can be lower, so that the purified gas emission meets environmental protection standards.

[0030] The waste gas treatment system also includes a urea device 7, which includes a urea tank 71 and a urea pump 72. The urea tank 71 is connected to the water inlet pipe 51. Water is added to the urea tank 71 and stirred by a stirring mechanism to dilute the urea to form a urea aqueous solution. The diluted urea is sent to the furnace of the incineration device 2 through the urea pump 72. The urea aqueous solution is sprayed into the furnace and decomposed into ammonia at high temperature. The ammonia reacts with nitrogen monoxide and nitrogen dioxide in the flue gas to generate nitrogen, thereby achieving the purpose of flue gas denitrification and purifying the tail gas generated by the incineration device 2. The purified gas generated after purification and cooling can enter the furnace again through the three-way valve 42, and can be purified again, so that the gas discharged from the chimney 43 is more likely to meet environmental protection requirements.

[0031] Example 2 like Figure 2 As shown, for the convenience of expression in the drawings, the same parts as the embodiment are omitted. This embodiment is based on embodiment 1, and a pressure pump 441, a buffer tank 442 and a return air valve 443 are arranged in sequence on the return air duct 44 connected to the three-way valve 42 and the fresh air device 6, and the return air valve 443 is located on the side of the buffer tank 442 where the air is discharged. The return air valve 443 is a pulse solenoid valve, and the control system controls the return air valve 443 to open and close periodically. When the incineration device 2 needs the purified air to return, the three-way valve 42 controls the purified air to connect to the return air duct 44, the pressure pump 441 is started, and when the air valve is closed, the buffer tank 442 stores energy, and when the return air valve 443 is opened, the buffer tank 442 releases pressure, so that the air pressure of the fresh air and the purified air in the return air duct 44 changes in a pulsed manner, and the fresh air and purified air entering the incineration device 2 in the return air duct 44 can stir the exhaust gas in the incineration device 2, so that the exhaust gas, the fresh air and the purified air are quickly mixed, so that the exhaust gas will not be locally gathered. And the gas distribution pipeline 26 is respectively connected to the first burner 21, the second burner 22, the ventilation mechanism 24, etc. The pulse air intake method can stir the gas in the incineration device 2 in all directions, and further make the exhaust gas, purified gas, and fresh air mix more quickly and evenly. In the above process, the amount of fresh air provided is balanced with the amount of exhaust gas, and the total amount of oxygen entering the incineration device 2 remains unchanged, and does not affect the combustion in the furnace. In addition, the furnace volume of the incineration device 2 is relatively large, and the pulse air intake method of the purified gas has a slight effect on the overall air pressure in the furnace, which can be ignored. The flow rate of the purified gas reflux to the incineration device 2 can be adjusted by changing the power of the booster pump 441.

[0032] This embodiment also adjusts the water supply device 5 in Embodiment 1. Before entering the economizer 33, the water supply device 5 first passes through the buffer tank 442 and the pressure pump 441 to dissipate heat from the buffer tank 442 and the pressure pump 441. Since heat is generated when the pressure pump 441 compresses the purified gas, the heat is taken away by the water supply device 5. As a result, the temperature of the purified gas is lower when the purified gas enters the gas distribution pipeline 26 from the buffer tank 442. When the incineration device 2 needs to be slightly adjusted, the furnace temperature can be slightly adjusted only through the ventilation mechanism 24.

[0033] Example 3 This embodiment also discloses a waste gas treatment method capable of adjusting oxygen content, which is implemented based on the waste gas treatment system. The specific steps are as follows: The first step is pretreatment: the waste gas is passed into the pretreatment device 1, and the waste gas is separated into gas and liquid through the transfer tank of the pretreatment device 1. The formed liquid can be discharged through the bottom of the transfer tank, and the separated gas is passed into the incineration device 2.

[0034] The second step is to ignite the waste gas: the fuel gas is introduced into the incineration device 2, and fresh air is introduced into the incineration device 2, and the burner is used to ignite the waste gas; the temperature of the incinerator rises to 1100°C, and the waste gas is introduced, and the waste gas burns in the furnace. When the waste gas concentration is low and cannot sustain self-combustion, fuel gas is added to ensure full combustion of the waste gas.

[0035] The third step is temperature control: when the furnace temperature approaches 1000℃, maintain the fresh air volume, purify the exhaust gas generated by combustion, and return part of the purified gas generated after cooling to the incineration device 2, so that the furnace temperature is kept in dynamic balance at 1150±100℃; when the furnace temperature drops and is lower than 1050℃, reduce the return air volume of purified gas, increase the combustion effect and raise the furnace temperature by increasing the oxygen content; when the furnace temperature exceeds 1200℃, reduce the fresh air volume and increase the return air volume of purified gas; if the furnace temperature is still on an upward trend, spray water into the furnace to cool it down; keep the furnace temperature at 1150±100℃.

[0036] Step 4: Purify gas and denitrate. Urea is decomposed into ammonia at high temperature. Ammonia reacts with NOX generated in the incinerator to generate N2, which purifies NOX generated after combustion.

[0037] Step 5: Heat recovery: The waste heat utilization device 3 recovers the waste heat from the tail gas generated by the combustion of the waste gas, and the generated water vapor is used for other thermal needs of the factory area.

[0038] Step 6: Purified gas discharge. After the tail gas is purified and cooled, part of the net gas is returned to the incineration device 2 through the reflux pipe and the gas distribution pipe 26, and the remaining part is discharged through the chimney 43.

[0039] In summary, the beneficial effects of this solution are: the purified gas after the exhaust gas is burned and purified is led back to the air inlet end of the incineration device 2, and the exhaust gas concentration is reduced by diluting the exhaust gas, so that the exhaust gas concentration is not within the explosion limit, thereby reducing the risk of explosion; the reduction in exhaust gas concentration also means that the heat generated by the exhaust gas combustion can also be reduced, which can more effectively control the temperature in the furnace.

[0040] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A waste gas treatment system capable of adjusting oxygen content, characterized in that: The invention comprises a pre-treatment device (1), an incineration device (2), a waste heat utilization device (3) and an emission device (4) which are arranged in sequence; the pre-treatment device (1) is connected to a waste gas collection pipe, a gas-liquid separation mechanism is arranged in the pre-treatment device (1), and the gas separated after the waste gas is treated by the gas-liquid separation device is transported to the incineration device (2); the incineration device (2) is provided with a burner for burning the waste gas, and the incineration device (2) is connected to a fresh air device (6), and the fresh air device (6) is used to send fresh air into the incineration device through a gas distribution pipeline (26). The waste heat utilization device (3) is used to recover heat from the purified gas generated by the combustion. The discharge device (4) includes a three-way valve (42) connected to the purified gas of the waste heat utilization device (3). One end of the three-way valve (42) is used to discharge the purified gas. The other end of the three-way valve (42) is connected to the gas distribution pipeline (26). The three-way valve (42) is used to adjust the discharge amount of the purified gas and the return air amount sent back to the incineration device (2). The fresh air device (6) can mix the fresh air with the purified gas and send it into the incineration device (2) through the gas distribution pipeline (26).

2. The exhaust gas treatment system with adjustable oxygen content according to claim 1, characterized in that: It also includes a water supply device (5), the water supply device (5) including a water inlet pipe (51) and a water storage tank (52); the incineration device (2) is provided with a water spray mechanism (23) for cooling, the water inlet pipe (51) is connected to the water spray mechanism (23) on the incinerator; the water storage tank (52) connects water to the waste heat utilization device (3) through a water pump and performs heat exchange with the purified gas after combustion.

3. The exhaust gas treatment system with adjustable oxygen content according to claim 2, characterized in that: The waste heat utilization device (3) comprises an economizer (33), a waste heat boiler (32), and a superheater (31) arranged in the incineration device (2); the superheater (31), the waste heat boiler (32), and the economizer (33) are arranged in sequence along the direction in which the purified gas is discharged; and the water in the water storage tank (52) passes through the economizer (33), the waste heat boiler (32), and the superheater (31) in sequence to perform heat exchange with the purified gas.

4. The exhaust gas treatment system with adjustable oxygen content according to claim 3, characterized in that: The incineration device (2) is provided with a control system, as well as a temperature sensor, an oxygen content sensor, and a pressure sensor capable of transmitting signals to the control system. The control system controls the fresh air supply of the fresh air device (6), the purified air return volume of the three-way valve (42), and the water spray volume of the water spray mechanism (23), and controls the furnace temperature of the incineration device (2) to be 1150±100°C and the waste gas to stay in the furnace for 2 to 5 seconds.

5. The exhaust gas treatment system with adjustable oxygen content according to claim 4, characterized in that: The water spray mechanism (23) is provided in two groups, and a ventilation mechanism (24) is provided between the two groups of water spray mechanisms (23). The ventilation mechanism (24) is connected to the fresh air device (6) and the three-way valve (42).

6. The exhaust gas treatment system with adjustable oxygen content according to claim 4, characterized in that: The fresh air device (6) adopts a variable frequency fan, wherein the fresh air volume of the fresh air device (6) can be set to 5 levels of wind speed, where level 0 represents that the fresh air device (6) is completely stopped, and level 5 represents that the fresh air device (6) is running at the highest power; the return air volume of the purified air returned by the three-way valve (42) to the incineration device (2) can also be set to 5 levels, where level 0 represents that the return air volume level of the three-way valve (42) to the incineration device (2) is 0, that is, the closed state, and level 5 represents the maximum return air volume of the purified air delivered by the three-way valve (42) to the incineration device (2).

7. The exhaust gas treatment system with adjustable oxygen content according to claim 6, characterized in that: When the exhaust gas flow rate is constant, the fresh air volume level of the fresh air device (6) and the return air volume level of the three-way valve (42) are arranged and combined, and the corresponding furnace temperature of the incineration device (2) is used as the initial setting of the control system, so that the appropriate combination of the fresh air volume level and the return air volume level is selected according to the furnace temperature, air pressure, oxygen content, etc.

8. The exhaust gas treatment system with adjustable oxygen content according to claim 1, characterized in that: A pressure pump (441), a buffer tank (442) and a return air valve (443) are provided in sequence on a return air duct (44) connected to the three-way valve (42) and the fresh air device (6). The return air valve (443) is located on the side of the buffer tank (442) where air is discharged. The return air valve (443) is a pulse solenoid valve. The control system controls the return air valve (443) to open and close periodically, so that fresh air and purified air return air are mixed and then enter the furnace in a pulsed manner.

9. A method for treating waste gas using the waste gas treatment system with adjustable oxygen content according to any one of claims 1 to 8, characterized in that: The steps include: The first step is pretreatment: the waste gas is introduced into the pretreatment device (1), and the waste gas is separated into gas and liquid through the transfer tank of the pretreatment device (1). The formed liquid can be discharged through the bottom of the transfer tank, and the separated gas is introduced into the incineration device (2); The second step is to ignite the waste gas: the fuel gas is introduced into the incineration device (2), and fresh air is introduced into the incineration device (2), and the waste gas is ignited by the burner; after the temperature of the incineration furnace rises to the target temperature, the waste gas is introduced, and the waste gas is burned in the furnace. When the waste gas concentration is low and cannot sustain combustion, the fuel gas is supplemented to ensure that the waste gas is fully burned; The third step is temperature control: when the furnace temperature reaches the first temperature threshold, the tail gas generated by the combustion is purified and cooled, and part of the purified gas generated is returned to the incineration device (2), so that the furnace temperature is maintained near the second temperature threshold; when the furnace temperature drops and is lower than the first lower limit of the second temperature threshold, the return air volume of the purified gas is reduced; when the furnace temperature is higher than the upper limit of the second temperature threshold, the fresh air volume is reduced and the return air volume of the purified gas is increased; if the furnace temperature is still on the rise, water is sprayed into the furnace to cool it down; Step 4: Purify gas to denitrate. Urea is decomposed into ammonia at high temperature. Ammonia reacts with NOX generated in the incinerator to generate N2, which purifies NOX generated after combustion. Step 5: Heat recovery: The waste heat utilization device (3) recovers the waste heat from the exhaust gas generated by the combustion of the waste gas, and the generated water vapor is used for other thermal needs of the plant area; Step 6: Purified gas emission. The net part of the tail gas produced after purification and cooling is returned to the incineration device (2) through the return pipe and the gas distribution pipe (26), and the remaining part is discharged through the chimney (43).

10. The waste gas treatment method according to claim 9, characterized in that: In the second step, the target temperature is 1100°C. In the third step, when the first temperature threshold in the temperature control step is set to 1000°C, the lower limit of the second temperature threshold is 1100°C and the upper limit is 1200°C.

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