System and method for treating flue gas by using organic waste gas

Abstract

The invention belongs to the field of waste gas treatment and emission reduction, and discloses a system and method for treating flue gas through organic waste gas, the system comprises an organic waste gas emission unit, a collection unit, an in-situ reduction unit and an emission unit which are sequentially connected, and the in-situ reduction unit comprises a reduction gas inlet, a flue gas inlet and a gas outlet; the reducing gas inlet is connected with an outlet of the collecting unit, the flue gas inlet is used for inputting flue gas, and the gas outlet is connected with an inlet of the discharging unit. The organic waste gas produced by a refinery enterprise is used for in-situ reduction of nitrogen oxide, the concentration of the nitrogen oxide in the flue gas is reduced by strengthening the in-situ reduction reaction after the nitrogen oxide is generated, a catalyst, ammonia and other reducing agents are not needed, the treatment cost is low, the subsequent nitrogen oxide treatment process is simplified, and the treatment effect is good. And the energy consumption input, the carbon emission and the ammonia use and escape amount in the treatment process are reduced.

Description

Technical Field

[0001] This application belongs to the field of waste gas treatment and emission reduction, and in particular relates to a system and method for treating flue gas using organic waste gas. Background Technology

[0002] Volatile organic compounds (VOCs) and nitrogen oxides (NOx) are the main precursors to particulate matter and have a significant impact on air quality. Refining and chemical enterprises are key sources of VOCs and NOx emissions. NOx mainly originates from flue gas from the equipment, while VOCs mainly originate from fugitive emissions.

[0003] Currently, NOx treatment technology mainly relies on low-temperature selective ammonia reduction (SCR). This technology primarily utilizes the selective reduction between ammonia and nitrogen oxides to convert nitrogen oxides into nitrogen and water, achieving compliance with NOx emission standards. This technology requires the additional injection of ammonia components into the flue gas, typically operates at temperatures between 250-450℃, and demands highly efficient catalysts. The technical requirements, supporting facilities, and conditions are relatively stringent, resulting in high investment costs.

[0004] VOCs treatment technologies mainly include two types: recovery and disposal. Recovery technologies include adsorption, absorption, condensation, and membrane separation, while disposal technologies include biological treatment, photocatalytic oxidation, thermal oxidation, catalytic oxidation, and low-temperature plasma. These different technologies have significantly different principles and process characteristics, and are applicable to specific scenarios. Under increasingly stringent emission standards, incineration technology will serve as the final unit in various treatment processes to achieve ultra-low VOCs concentrations. The trend will be to treat VOCs waste gas from refining processes by introducing it into heating furnaces and other devices.

[0005] Therefore, it is necessary to propose a method for treating nitrogen oxides using VOCs. This method involves collecting VOCs waste gas from fugitive sources in refining and chemical enterprises and transporting it to the tail gas incinerator of a sulfur plant. By controlling the area and residence time of VOCs waste gas entering the incinerator, the in-situ oxidation-reduction process between VOCs and NOx is enhanced by utilizing the thermal environment inside the furnace. This achieves effects such as NOx reduction and concentration reduction, and VOCs oxidation, thereby reducing the NOx concentration in the flue gas at the incinerator outlet, reducing the load on subsequent denitrification units, and ultimately reducing energy consumption and the amount of ammonia used. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, this application introduces the collected VOCs waste gas from the refining and chemical enterprise into the tail gas incinerator of the sulfur unit, and utilizes the special environment inside the furnace to achieve VOCs degradation and nitrogen oxide conversion, thereby achieving VOCs and NOx co-treatment and emission compliance.

[0007] The first objective of this application is to provide a system for treating flue gas using organic waste gas, comprising an organic waste gas emission unit, a collection unit, an in-situ reduction unit, and an emission unit connected in sequence.

[0008] The in-situ reduction unit includes a reducing gas inlet, a flue gas inlet, and a gas outlet. The reducing gas inlet is connected to the outlet of the collection unit, the flue gas inlet is used to input flue gas, and the gas outlet is connected to the inlet of the emission unit.

[0009] Furthermore, a pressurization unit is provided between the collection unit and the in-situ reduction unit to pressurize and treat the organic waste gas, thereby increasing the static pressure energy and kinetic energy of the organic waste gas.

[0010] Furthermore, a stable homogenizing unit is provided between the collection unit and the in-situ reduction unit. The stable homogenizing unit is filled with adsorption material as a stable homogenizing bed. The stable homogenizing bed is used to adsorb or desorb VOCs according to the concentration of VOCs in the exhaust gas.

[0011] Furthermore, a gas distribution and mixing unit is provided between the collection unit and the in-situ reduction unit to regulate the flow rate and concentration of organic waste gas.

[0012] Furthermore, the gas distribution and mixing unit is connected to a combustion air supply unit, which is used to adjust the concentration of organic waste gas in the gas distribution and mixing unit and to assist combustion.

[0013] Furthermore, the in-situ reduction unit is connected to an air supply unit, which is used to supply combustion air to the combustion zone of the in-situ reduction unit.

[0014] Furthermore, the in-situ reduction unit is connected to a gas supply unit, which is used to supply gas to the combustion zone of the in-situ reduction unit.

[0015] Furthermore, a cooling unit is provided between the in-situ reduction unit and the emission unit. The cooling unit uses a heat exchange medium to transfer heat, reduce the temperature of the gas discharged from the in-situ reduction unit, and recover heat.

[0016] Furthermore, a desulfurization unit is installed between the in-situ reduction unit and the emission unit. The desulfurization unit uses alkaline washing solvent to absorb acidic substances in the gas discharged from the cooling unit.

[0017] Furthermore, the desulfurization unit is connected to an absorbent lean solution supply unit, which is used to supply the desulfurization unit with alkaline washing solvent lean solution.

[0018] Furthermore, the desulfurization unit is connected to an absorbent rich solution storage unit, which is used to store the alkaline washing solvent rich solution discharged from the desulfurization unit.

[0019] Furthermore, flue gas includes flue gas generated during the combustion processes of oil refining units, chemical plants, and environmental protection facilities.

[0020] The second objective of this application is to provide a method for treating flue gas using organic waste gas, based on the above-described system for treating nitrogen oxides in flue gas.

[0021] The technical effects and advantages of this application are as follows:

[0022] 1. This application utilizes organic waste gas produced by refining and chemical enterprises for in-situ reduction of nitrogen oxides. By enhancing the in-situ reduction reaction after the formation of nitrogen oxides, the concentration of nitrogen oxides in the flue gas is reduced. No catalysts or reducing agents such as ammonia are required, resulting in low treatment costs. This simplifies the subsequent nitrogen oxide treatment process and reduces energy consumption, carbon emissions, ammonia usage, and escape during the treatment process.

[0023] 2. This application utilizes the oxidation of nitrogen oxides in high-temperature flue gas to achieve VOCs treatment, saving investment in VOCs treatment process construction, energy consumption, and carbon emissions.

[0024] 3. This application makes full use of existing equipment, reduces additional engineering work, has a high degree of compatibility with the original waste gas treatment process, has low investment costs, and can be flexibly adjusted according to different VOCs waste gas emission volume and concentration. It has the advantages of simple process, high operational flexibility, and easy operation.

[0025] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0026] Figure 1 This is a flowchart of a system for treating flue gas using organic waste gas, as described in this application.

[0027] Figure 2 This is a flowchart of a system for treating flue gas using organic waste gas, as described in Example 1.

[0028] Attached reference numerals: 1. Organic waste gas emission unit; 2. Collection unit; 3. Conveying pipeline; 4. Pressurization unit; 5. Stabilizing and homogenizing unit; 6. Gas distribution and mixing unit; 7. In-situ reduction unit; 8. Cooling unit; 9. Desulfurization unit; 10. Emission unit; 11. Combustion air supply unit; 12. Air supply unit; 13. Gas supply unit; 14. Lean absorbent solution supply unit; 15. Rich absorbent solution storage unit. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] Firstly, such as Figure 1 As shown, this application provides a system for treating flue gas using organic waste gas, including an organic waste gas emission unit 1, a collection unit 2, a pressurization unit 4, a stabilization and homogenization unit 5, a gas distribution and mixing unit 6, an in-situ reduction unit 7, a cooling unit 8, a desulfurization unit 9, and an emission unit 10 connected in sequence.

[0031] Specifically, the organic waste gas emission unit 1 includes a device for generating organic waste gas emissions from a refining and chemical enterprise. The VOCs-containing waste gas outlet of the organic waste gas emission unit 1 is connected to the inlet of the collection unit 2. The collection unit 2 is used to collect the waste gas discharged from the organic waste gas emission unit 1. The outlet of the collection unit 2 is connected to the inlet of the booster unit 4 via a conveying pipeline 3. The booster unit 4 is used to increase the static pressure energy and kinetic energy of the waste gas. The outlet of the booster unit 4 is connected to the inlet of the stabilizing and homogenizing unit 5 via a conveying pipeline 3. The stabilizing and homogenizing unit 5 is used to stabilize and homogenize the collected waste gas. The outlet of the stabilizing and homogenizing unit 5 is connected to the inlet of the gas distribution and mixing unit 6 via a conveying pipeline 3. The gas distribution and mixing unit 6 is used to adjust the flow rate and concentration of the organic waste gas according to the in-situ reduction requirements of nitrogen oxides. The gas outlet of unit 6 is connected to the reducing gas inlet of in-situ reduction unit 7 via pipeline 3. The flue gas inlet of in-situ reduction unit 7 is used to input the flue gas generated during the combustion process of oil refining units, chemical units, and environmental protection facilities. The gas outlet of in-situ reduction unit 7 is connected to the gas inlet of cooling unit 8 via pipeline 3. Cooling unit 8 uses a heat exchange medium to transfer heat, reduce the temperature of the gas discharged from in-situ reduction unit 7, and recover heat. The gas outlet of cooling unit 8 is connected to the gas inlet of desulfurization unit 9 via pipeline 3. Desulfurization unit 9 uses an alkaline washing solvent to absorb acidic substances in the gas discharged from cooling unit 8. The gas outlet of desulfurization unit 9 is connected to the inlet of emission unit 10 via pipeline 3. Emission unit 10 includes an emission stack or chimney for discharging the treated waste gas into the air.

[0032] In some embodiments of this application, the stable homogenizing unit 5 is filled with adsorbent material as a stable homogenizing bed. The VOCs components in the exhaust gas undergo adsorption concentration or desorption processes with the stable homogenizing bed. When the VOCs concentration in the incoming gas is high, some VOCs components are adsorbed by the stable homogenizing bed to achieve a concentration reduction effect. When the VOCs concentration in the incoming gas is low, some VOCs components are desorbed from the stable homogenizing bed to achieve a concentration increase effect. The exhaust gas flow rate, pressure, and VOCs concentration are stabilized.

[0033] like Figure 2 As shown, in some embodiments of this application, the gas distribution and mixing unit 6 is connected to the combustion air supply unit 11, which is used to adjust the concentration of organic waste gas in the gas distribution and mixing unit 6 and to assist combustion. The in-situ reduction unit 7 is connected to the air supply unit 12, which is used to supply combustion air to the combustion zone of the in-situ reduction unit 7. The in-situ reduction unit 7 is connected to the fuel gas supply unit 13, which is used to supply fuel gas to the combustion zone of the in-situ reduction unit 7. The desulfurization unit 9 is connected to the absorbent lean liquid supply unit 14 and the absorbent rich liquid storage unit 15. The absorbent lean liquid supply unit 14 is used to supply the alkaline washing solvent lean liquid to the desulfurization unit 9, and the absorbent rich liquid storage unit 15 is used to store the alkaline washing solvent rich liquid discharged from the desulfurization unit 9.

[0034] Secondly, this application discloses a method for treating flue gas using organic waste gas, based on the above-mentioned system for treating nitrogen oxides in flue gas.

[0035] To better illustrate this solution, the following embodiments are provided.

[0036] Example 1

[0037] Taking a sulfur recovery unit of a certain refining and chemical enterprise as an example (the sulfur recovery unit has a capacity of 250,000 tons per year), the flue gas emission of the tail gas incinerator of the sulfur recovery unit is 200-600 million cubic meters per hour, and the nitrogen oxide emission concentration is about 150 milligrams per cubic meter, which is close to the limit of exceeding the standard.

[0038] according to Figure 2The system shown uses other VOCs-generating devices near the sulfur recovery unit as organic waste gas emission unit 1. Waste gas collection unit 2 collects the VOCs generated by organic waste gas emission unit 1, and then, via pipeline 3 and pressurization unit 4, collects the VOCs in the waste gas into stabilization and homogenization unit 5. Here, the VOCs components in the waste gas are homogenized in terms of pressure, concentration, temperature, and composition. After stabilization and homogenization, the VOCs waste gas enters gas distribution and mixing unit 6 and is thoroughly mixed with combustion air generated by combustion air supply unit 11. The flue gas from the tail gas incinerator is also fed into the in-situ reduction unit 7 through the flue gas inlet. The organic waste gas entering this unit mixes thoroughly with the flue gas, and the VOCs components undergo an oxidation-reduction process with the nitrogen oxides in the flue gas. The nitrogen oxides are reduced to nitrogen and water by the VOCs molecules, and the VOCs components are oxidized to carbon dioxide and water. The flue gas after the reaction enters the cooling unit 8 for cooling and heat recovery. The cooled flue gas then enters the desulfurization unit 9 for sulfide removal. The desulfurized flue gas enters the chimney to achieve compliant emissions. Using the system and method of this application, the concentration of nitrogen oxides in the tail gas incineration of the sulfur recovery unit can be reduced by 40%-50%, resulting in a reduction of 10-30 tons / year of nitrogen oxide emissions from the sulfur recovery unit, and a reduction of 5-20 tons / year of VOCs emissions from refining. It is estimated that this will save 360,000-1,100,000 yuan in pollution discharge tax annually (pollutant equivalent is 0.5 kg, and each pollution equivalent of air pollutant costs 1.2 yuan).

[0039] In summary, by employing the nitrogen oxide treatment system and method of this application, and utilizing units such as waste gas collection, homogenization and concentration, oxidation-reduction, heat recovery, and desulfurization, it is possible to achieve compliant nitrogen oxide emissions from sulfur recovery equipment and harmless treatment of VOCs waste gas from refining and chemical enterprises. This significantly reduces the emissions of pollutants such as nitrogen oxides and VOCs, substantially lowers pollution discharge taxes, and significantly improves energy consumption and carbon emissions in the pollutant treatment process.

[0040] Finally, it should be noted that the above description is only a preferred embodiment of this application and is not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A system for treating flue gas using organic waste gas, characterized in that, The system includes an organic waste gas emission unit (1), a collection unit (2), an in-situ reduction unit (7), and an emission unit (10) connected in sequence. The in-situ reduction unit (7) includes a reducing gas inlet, a flue gas inlet, and a gas outlet. The reducing gas inlet is connected to the outlet of the collection unit (2), the flue gas inlet is used to input flue gas, and the gas outlet is connected to the inlet of the emission unit (10).

2. The system for treating flue gas using organic waste gas according to claim 1, characterized in that, A pressurization unit (4) is provided between the collection unit (2) and the in-situ reduction unit (7).

3. The system for treating flue gas using organic waste gas according to claim 1, characterized in that, A stable homogenizing unit (5) is provided between the collection unit (2) and the in-situ reduction unit (7). The stable homogenizing unit (5) is filled with adsorption material as a stable homogenizing bed. The stable homogenizing bed is used to adsorb or desorb VOCs according to the concentration of VOCs in the waste gas.

4. A system for treating flue gas using organic waste gas according to any one of claims 1-3, characterized in that, A gas distribution and mixing unit (6) is provided between the collection unit (2) and the in-situ reduction unit (7) to regulate the flow rate and concentration of organic waste gas.

5. A system for treating flue gas using organic waste gas according to claim 4, characterized in that, The gas distribution and mixing unit (6) is connected to a combustion air supply unit (11), which is used to adjust the concentration of organic waste gas in the gas distribution and mixing unit (6) and to assist combustion.

6. The system for treating flue gas using organic waste gas according to claim 1, characterized in that, The in-situ reduction unit (7) is connected to an air supply unit (12), which is used to supply combustion air to the combustion zone of the in-situ reduction unit (7).

7. A system for treating flue gas using organic waste gas according to claim 1 or 6, characterized in that, The in-situ reduction unit (7) is connected to a gas supply unit (13), which is used to supply gas to the combustion zone of the in-situ reduction unit (7).

8. A system for treating flue gas using organic waste gas according to claim 1, characterized in that, A cooling unit (8) is provided between the in-situ reduction unit (7) and the discharge unit (10). The cooling unit (8) uses a heat exchange medium to transfer heat, reduce the temperature of the gas discharged by the in-situ reduction unit (7), and recover heat.

9. A system for treating flue gas using organic waste gas according to claim 1, characterized in that, A desulfurization unit (9) is provided between the in-situ reduction unit (7) and the emission unit (10), and the desulfurization unit (9) uses an alkaline washing solvent to absorb acidic substances in the gas.

10. A system for treating flue gas using organic waste gas according to claim 9, characterized in that, The desulfurization unit (9) is connected to an absorbent lean solution supply unit (14), which is used to supply the desulfurization unit (9) with alkaline washing solvent lean solution.

11. A system for treating flue gas using organic waste gas according to claim 9 or 10, characterized in that, The desulfurization unit (9) is connected to an absorbent rich solution storage unit (15), which is used to store the alkaline washing solvent rich solution discharged from the desulfurization unit (9).

12. A system for treating flue gas using organic waste gas according to claim 1, characterized in that, The flue gas includes flue gas generated during the combustion processes of oil refining units, chemical units, and environmental protection facilities.

13. A method for treating flue gas using organic waste gas, characterized in that, The method is based on the system described in any one of claims 1-12 for treating nitrogen oxides in flue gas.

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