Coke cleaning method of plasma reactor

Abstract

The invention relates to the technical field of low-temperature plasmas, and discloses a decoking method of a plasma reactor. The method is implemented in an organic waste gas treatment system, the organic waste gas treatment system is provided with more than two plasma reactors, and the method comprises the following steps: when at least one plasma reactor needs decoking treatment, introducing organic waste gas into the normally working plasma reactor for plasma waste gas treatment, the obtained organic waste gas tail gas is introduced into a plasma reactor needing decoking for decoking treatment, and then the obtained decoking tail gas is circularly and sequentially introduced into the normally working plasma reactor and the plasma reactor needing decoking for treatment; and the decoking process is completed until the total hydrocarbon concentrations of the gases at the gas inlet end and the gas outlet end of the plasma reactor needing decoking are basically consistent. The technical scheme provided by the invention realizes effective removal of coking substances in the reactor and in the pore channels of the catalyst or the filler.

Description

Technical Field

[0001] This invention relates to the field of low-temperature plasma technology, and more specifically to a method for descaling a plasma reactor. Background Technology

[0002] For industrial applications with large gas volume and low concentration (<3000 mg / m³) 3 VOCs waste gas, which has no recycling value, has attracted great interest from researchers and manufacturers both domestically and internationally due to its simple process and convenient operation and management. However, the treatment of VOCs using this process often results in the generation of various byproducts, also known as coking compounds. These coking compounds are polycyclic aromatic hydrocarbons with molecular weights of 300-1000, ranging in color from light yellow to brownish-yellow, and have a viscous texture. The accumulation of these coking compounds within the reactor tube walls directly poses safety hazards. Furthermore, when low-temperature plasma is used in conjunction with catalysts or packing materials, coking compounds accumulate within the pores of the catalyst or packing material, causing pore blockage, catalyst deactivation and reduced lifespan, and a significant decrease in treatment efficiency.

[0003] To address the safety hazards posed by the accumulation of coking deposits, two methods exist for removal: physical and chemical. Physical methods remove coking deposits by dissolving or scraping without damaging their chemical structure. Chemical methods remove coking deposits by disrupting their chemical structure to generate new substances. Patent application CN104056829B discloses a continuous coking removal method for a thermal plasma reactor. During the pyrolysis reaction, a decoking gas is continuously introduced, reacting with the coking deposits to complete the removal. The decoking gas is carbon dioxide or a mixture of carbon dioxide and hydrogen. The decoking gas is introduced tangentially along the inner wall of the reactor. This decoking method does not significantly affect the flow rate and composition of the pyrolysis gas, can be performed continuously, is suitable for different types of thermal plasma reactors, and has a significant removal effect on coking deposits of different properties and contents. However, this patent can only remove coking deposits whose main component is carbon, and cannot remove coking deposits composed of yellowish-brown organic matter. Furthermore, under low-temperature plasma application conditions, the method provided by this patent cannot be directly applied to remove coking deposits within the catalyst pore structure.

[0004] Therefore, there is an urgent need to develop a decoking method for plasma reactors that can remove coke, which is composed of yellowish-brown organic matter, from the reactor and the pores of the catalyst or packing material. This would extend the service life of the reactor and catalyst, reduce subsequent maintenance and operating costs, and ensure the long-term stable operation of the equipment. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem in existing technologies that fail to clean coke within the catalyst pore structure during the cleaning of low-temperature plasma reactors and catalyst or packing pores. This invention provides a method for cleaning coke from plasma reactors. The technical solution utilizes a CO2 and H2O atmosphere under low-temperature plasma conditions to react with the coke organic matter adhering to the reactor and catalyst pore structure, generating new gaseous substances, including CO, H2, and C2-C5 small molecule hydrocarbons. These gaseous substances leave the adhering surface with the gas flow, thereby achieving the removal of coke from the reactor and catalyst or packing pores. This extends the service life of the reactor and catalyst, reduces operating costs, ensures long-term stable operation of the equipment, and eliminates the need for additional cleaning equipment, resulting in no secondary pollution such as wastewater or waste gas.

[0006] To achieve the above objectives, the present invention provides a method for decoking a plasma reactor, which is implemented in an organic waste gas treatment system having two or more plasma reactors. The method includes:

[0007] When at least one plasma reactor requires decoking, organic waste gas is introduced into the normally operating plasma reactor for plasma waste gas treatment, and the resulting organic waste gas tail gas is introduced into the plasma reactor requiring decoking for decoking treatment. Then, the resulting decoking tail gas is circulated back and forth between the normally operating plasma reactor and the plasma reactor requiring decoking for treatment until the total hydrocarbon concentration at the inlet and outlet of the plasma reactor requiring decoking is basically the same, at which point decoking is completed. The residence time of the gas in the plasma reactor requiring decoking is longer than that in the normally operating plasma reactor, and the discharge power of the decoking treatment is higher than that of the plasma waste gas treatment.

[0008] Preferably, the residence time of the gas in the plasma reactor requiring descaling is 1-10 times that in the normally operating plasma reactor, and more preferably 1.5-6 times.

[0009] Preferably, the discharge power of the descaling treatment is 1.1-3 times that of the discharge power of the plasma exhaust gas treatment.

[0010] Preferably, the organic waste gas is air mainly containing CO2 and H2O.

[0011] Preferably, the organic waste gas treatment system includes: a first plasma reactor, a second plasma reactor, a first inlet pipeline, a first outlet pipeline, a second inlet pipeline, a second outlet pipeline, a first descaling pipeline, and a second descaling pipeline.

[0012] Preferably, when the first plasma reactor and the second plasma reactor are in normal operating condition, the organic waste gas enters the first plasma reactor and the second plasma reactor through the first inlet pipeline and the second inlet pipeline, respectively, and the organic waste gas tail gas obtained after plasma waste gas treatment is discharged through the first outlet pipeline and the second outlet pipeline, respectively.

[0013] Preferably, when the first plasma reactor is operating normally and the second plasma reactor requires descaling, the gas stream after being treated by the plasma exhaust gas of the first plasma reactor is introduced into the second plasma reactor through the first descaling pipeline, and the gas stream after being treated by the descaling process of the second plasma reactor is introduced into the first plasma reactor through the second descaling pipeline.

[0014] Preferably, when the second plasma reactor is operating normally and the first plasma reactor requires descaling, the gas stream after being treated by the plasma exhaust gas of the second plasma reactor is introduced into the first plasma reactor through the first descaling pipeline, and the gas stream after being treated by the descaling process of the first plasma reactor is introduced into the second plasma reactor through the second descaling pipeline.

[0015] Preferably, the first coke removal pipeline is equipped with a valve and a first gas component concentration detector, and the second coke removal pipeline is equipped with a valve and a second gas component concentration detector. The first gas component concentration detector and the second gas component concentration detector are used to detect at least one of the following in the gas stream: total hydrocarbon concentration, non-methane total hydrocarbon concentration, CO2 concentration, and CO concentration.

[0016] Preferably, the first gas outlet pipeline is equipped with a valve and a third gas component concentration detector, and the second gas outlet pipeline is equipped with a valve and a fourth gas component concentration detector. The third gas component concentration detector and the fourth gas component concentration detector are used to detect at least one of the following in the gas stream: total hydrocarbon concentration, non-methane total hydrocarbon concentration, CO2 concentration, and CO concentration.

[0017] Preferably, during the decoking process, when the total hydrocarbon concentration measured by the first gas component concentration detector is inconsistent with the non-methane total hydrocarbon concentration or the total hydrocarbon concentration measured by the second gas component concentration detector is inconsistent with the non-methane total hydrocarbon concentration, the discharge power of the normally operating plasma reactor is increased, or the flow rate of the gas stream in the first decoking pipeline (12) and the second decoking pipeline (11) is reduced.

[0018] Preferably, the decoking process includes: increasing the discharge power of the plasma reactor that needs decoking, and / or extending the residence time of the gas stream in the plasma reactor that needs decoking, until the total hydrocarbon concentration of the gas stream discharged from the outlet of the plasma reactor that needs decoking is stable.

[0019] Preferably, when the degradation rate of non-methane total hydrocarbons in the plasma reactor is 1 / 2 to 2 / 3 of the degradation rate of non-methane total hydrocarbons under optimal operating conditions, the plasma reactor is determined to be a plasma reactor that requires decoking.

[0020] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0021] (1) According to the plasma reactor decoking method of the present invention, the tail gas of plasma exhaust gas treatment is circulated into the plasma reactor to remove the coking in the reactor and the catalyst or packing channel. The decoking tail gas is then introduced into the plasma reactor for harmless degradation again, which extends the service life of the reactor and catalyst, reduces the cost of use, and ensures the long-term stable operation of the equipment.

[0022] (2) The decoking method of the plasma reactor according to the present invention does not require additional decoking equipment, and there is no secondary pollution such as wastewater and waste gas, which reduces the cost of later maintenance and treatment of secondary pollution.

[0023] (3) The decoking mode is turned on or off based on the non-methane total hydrocarbon degradation rate and total hydrocarbon concentration. The electrical parameters of the plasma reactor and the pipeline flow parameters used in the decoking mode are controlled according to the concentration of each component of the tail gas, thereby reducing the maintenance and use costs of the plasma reactor and ensuring the long-term stable operation of the equipment.

[0024] The technical solution of this invention can be applied to all equipment that contains at least two parallel plasma reactors for treating low-concentration VOCs, odorous gases, etc. The technical solution of this invention can be applied to industries that emit organic waste gases, such as petrochemicals, spraying, printing and dyeing, municipal wastewater treatment, and pharmaceuticals. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the organic waste gas treatment system described in this invention.

[0026] Explanation of reference numerals in the attached figures

[0027] I. First plasma reactor; II. Second plasma reactor; 01. First inlet pipeline; 02. First outlet pipeline; 03. Second inlet pipeline; 04. Second outlet pipeline; 11. Second coke removal pipeline; 12. First coke removal pipeline; 21. Third gas component concentration detector; 22. First gas component concentration detector; 23. Second gas component concentration detector; 24. Fourth gas component concentration detector; A. First inlet; B. First outlet; C. Second inlet; D. Second outlet; E. Coke removal tail gas inlet; F. Organic waste gas outlet; G. Coke removal tail gas outlet; H. Organic waste gas inlet. Detailed Implementation

[0028] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] The decoking method for the plasma reactor described in this invention is implemented in an organic waste gas treatment system having two or more plasma reactors. The method includes:

[0031] When at least one plasma reactor requires decoking, organic waste gas is introduced into the normally operating plasma reactor for plasma waste gas treatment, and the resulting organic waste gas tail gas is introduced into the plasma reactor requiring decoking for decoking treatment. Then, the resulting decoking tail gas is circulated back and forth between the normally operating plasma reactor and the plasma reactor requiring decoking for treatment until the total hydrocarbon concentration at the inlet and outlet of the plasma reactor requiring decoking is basically the same, at which point decoking is completed. The residence time of the gas in the plasma reactor requiring decoking is longer than that in the normally operating plasma reactor, and the discharge power of the decoking treatment is higher than that of the plasma waste gas treatment.

[0032] According to the method described in this invention, the tail gas from the treatment of organic waste gas using low-temperature plasma is circulated into the plasma reactor to remove coking materials inside the reactor and in the channels of the catalyst or packing material. The decoking tail gas can then be treated again with plasma for harmless degradation. The decoking process produces no secondary pollution, extends the service life of the reactor and catalyst, reduces subsequent maintenance and operating costs, and ensures long-term stable operation of the equipment.

[0033] In the method described in this invention, when the total hydrocarbon concentration of the gas at the inlet and outlet of the plasma reactor that needs to be de-coked is stable and the deviation is less than 3%, it can be determined that the total hydrocarbon concentration of the gas at the inlet and outlet of the plasma reactor that needs to be de-coked is basically the same.

[0034] In the method described in this invention, the plasma reactor can be a low-temperature plasma reactor; the low-temperature plasma unit within the low-temperature plasma reactor employs a dielectric barrier discharge. The electrodes within the plasma reactor can be conductive metals, specifically, at least one of copper, iron, and tungsten, preferably iron. The barrier dielectric material within the plasma reactor can be at least one of quartz, corundum, ceramic, and nylon, preferably quartz. The plasma reactor can include a coaxially arranged central high-voltage electrode, a ground electrode, and a plasma reaction tube. The outer diameter of the central high-voltage electrode can be 7-10 mm, the inner diameter can be 5-7 mm, and the central high-voltage electrode can be a quartz tube. The ground electrode is located outside the plasma reaction tube and can be a copper sheet. The outer diameter of the plasma reaction tube can be 15-18 mm, the outer diameter of the plasma reaction tube can be 13-15 mm, the discharge gap of the plasma reaction tube can be 1-5 mm, and the plasma reaction tube can be a quartz tube.

[0035] In the method described in this invention, the minimum basic configuration of the plasma reactor can be a cylindrical type and / or a staged type, preferably a cylindrical type. The plasma reactor can be filled with a packing agent and / or a catalyst. The catalyst can be a noble metal and / or a transition metal oxide; the noble metal can be at least one of gold, platinum, palladium, rhodium, silver, and ruthenium; the transition metal oxide can be at least one of chromium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, and zinc oxide, preferably manganese oxide. The catalyst support can be at least one of activated carbon, molecular sieve, zeolite, alumina, and MOFs, preferably a molecular sieve. When the minimum basic configuration of the plasma reactor is a cylindrical type, the packing agent and / or catalyst in the plasma reactor can be inside and / or outside the plasma zone; when the minimum basic configuration of the plasma reactor is a staged type, the packing agent and / or catalyst in the plasma reactor can be outside the plasma zone.

[0036] In the method described in this invention, the residence time of the gas in the plasma reactor requiring descaling can be 1-10 times, preferably 1.5-6 times, the residence time of the gas in the normally operating plasma reactor. The residence time can be the time required for the gas to pass through the entire plasma zone. When the plasma reactor does not contain a packing agent or catalyst, the residence time of the organic waste gas in the plasma reactor requiring descaling is 1-10 times, preferably 2-6 times; when the plasma reactor contains a packing agent or catalyst, the residence time of the organic waste gas in the plasma reactor requiring descaling is 1-10 times, preferably 1-5 times. In the above preferred embodiments, by controlling the residence time of the gas in the plasma reactor, a good descaling effect is ensured.

[0037] In the method described in this invention, the discharge power of the descaling treatment can be 1-3 times, preferably 1.5-3 times, the discharge power of the plasma exhaust gas treatment. The discharge power of the descaling treatment can be within the rated power range of the driving power supply. The discharge power of the descaling treatment and the discharge power of the plasma exhaust gas treatment refer to the discharge power of the same plasma reactor when performing descaling treatment and plasma exhaust gas treatment. The plasma driving power supply of the plasma reactor can be a high-frequency sinusoidal AC power supply, the frequency of which can be 6-8kHz. When the plasma reactor performs plasma exhaust gas treatment, the voltage amplitude of the high-frequency sinusoidal AC power supply can be 25-30kV; when the plasma reactor performs descaling treatment, the voltage amplitude of the high-frequency sinusoidal AC power supply can be 30-36kV.

[0038] In the method described in this invention, the organic waste gas tail gas can be air mainly containing CO2 and H2O. The concentration of CO2 can be 0.05%-0.6%, preferably 0.1%-0.5%. Under low-temperature plasma conditions, the CO2 in the organic waste gas tail gas reacts with coking deposits attached to the reactor and the catalyst pore structure to generate new gaseous substances. These new gaseous substances contain at least one of CO, H2, and C2-C5 small molecule hydrocarbons. The new gaseous substances leave the attached surface with the gas flow, thereby achieving the effect of removing coking deposits. The gas passage of the organic waste gas tail gas is the same as that of the organic waste gas, and both the organic waste gas tail gas and the organic waste gas are distributed throughout the entire space within the plasma reactor.

[0039] In the method described in this invention, the organic waste gas treatment system may include: a first plasma reactor I, a second plasma reactor II, a first inlet pipeline 01, a first outlet pipeline 02, a second inlet pipeline 03, a second outlet pipeline 04, a first descaling pipeline 12, and a second descaling pipeline 11. At least one of the first plasma reactor I and the second plasma reactor II is a normally operating plasma reactor, and the others are normally operating plasma reactors or plasma reactors requiring descaling.

[0040] In the method described in this invention, when the first plasma reactor I and the second plasma reactor II are in normal working condition, the organic waste gas enters the first plasma reactor I and the second plasma reactor II through the first inlet pipeline 01 and the second inlet pipeline 03, respectively. The organic waste gas tail gas obtained after plasma waste gas treatment is discharged through the first outlet pipeline 02 and the second outlet pipeline 04, respectively. The organic waste gas treatment system is in organic waste gas degradation mode, and the first plasma reactor I and the second plasma reactor II are connected in parallel.

[0041] In the method described in this invention, when the first plasma reactor I is operating normally and the second plasma reactor II requires decoking treatment, the gas stream after plasma waste gas treatment by the first plasma reactor I is introduced into the second plasma reactor II through the first decoking pipeline 12, and the gas stream after decoking treatment by the second plasma reactor II is introduced into the first plasma reactor I through the second decoking pipeline 11. The organic waste gas treatment system is in the decoking mode for the second plasma reactor II.

[0042] In the method described in this invention, when the second plasma reactor II is operating normally and the first plasma reactor I needs to be decoked, the gas stream after being treated by the plasma exhaust gas of the second plasma reactor II is introduced into the first plasma reactor I through the first decoking pipeline 12, and the gas stream after being treated by the decoking gas of the first plasma reactor I is introduced into the second plasma reactor II through the second decoking pipeline 11. The organic exhaust gas treatment system is in the decoking mode of the first plasma reactor I.

[0043] In the method described in this invention, a valve and a first gas component concentration detector 22 are installed on the first coke removal pipeline 12, and a valve and a second gas component concentration detector 23 are installed on the second coke removal pipeline 11. The first gas component concentration detector 22 and the second gas component concentration detector 23 are used to detect at least one of the following in the gas stream: total hydrocarbon concentration, non-methane total hydrocarbon concentration, CO2 concentration, and CO concentration. The first gas component concentration detector 22 and the second gas component concentration detector 23 are mainly used to detect the total hydrocarbon concentration and non-methane total hydrocarbon concentration in the gas stream, and to adjust the gas stream flow rate and the discharge power of the plasma reactor according to the total hydrocarbon concentration and non-methane total hydrocarbon concentration in the gas stream.

[0044] In the method described in this invention, a valve and a third gas component concentration detector 21 are installed on the first gas outlet pipeline 02, and a valve and a fourth gas component concentration detector 24 are installed on the second gas outlet pipeline 04. The third gas component concentration detector 21 and the fourth gas component concentration detector 24 are used to detect at least one of the following concentrations in the gas stream: total hydrocarbon concentration, non-methane total hydrocarbon concentration, CO2 concentration, and CO concentration. The third gas component concentration detector 21 and the fourth gas component concentration detector 24 are mainly used to detect the non-methane total hydrocarbon concentration, CO2 concentration, and CO concentration in the gas stream. Based on the non-methane total hydrocarbon concentration in the gas stream, it is determined whether the plasma reactor is a plasma reactor that requires decoking. Based on the CO2 concentration and CO concentration in the gas stream, the decoking effect is evaluated, and the flow rate of the gas stream and the discharge intensity of the plasma reactor are adjusted.

[0045] In the method described in this invention, in order to ensure the best decoking effect, during the decoking process, when the total hydrocarbon concentration measured by the first gas component concentration detector 22 is inconsistent with the non-methane total hydrocarbon concentration or the total hydrocarbon concentration measured by the second gas component concentration detector 23 is inconsistent with the non-methane total hydrocarbon concentration, it is preferable to increase the discharge power of the normally operating plasma reactor, or preferably to reduce the flow rate of the gas stream in the first decoking pipeline (12) and the second decoking pipeline (11).

[0046] In the method described in this invention, the decoking process includes: increasing the discharge power of the plasma reactor requiring decoking, and / or extending the residence time of the gas stream in the plasma reactor requiring decoking until the total hydrocarbon concentration of the gas stream discharged from the outlet of the plasma reactor requiring decoking stabilizes. Extending the residence time of the gas stream in the plasma reactor requiring decoking can be achieved by reducing the valve opening, thereby adjusting the flow rate of the gas stream in the plasma reactor requiring decoking.

[0047] In the method described in this invention, when the non-methane total hydrocarbon degradation rate of the plasma reactor is 1 / 2 to 2 / 3 of the optimal operating state non-methane total hydrocarbon degradation rate, the plasma reactor is determined to be a plasma reactor requiring decoking. The optimal operating state refers to a non-methane total hydrocarbon concentration in the organic waste gas tail gas being less than 60 mg / m³. 3 .

[0048] In the organic waste gas treatment system of the present invention, the system has two or more plasma reactors, specifically two, three, four or more. In practical applications, when the organic waste gas treatment system is in organic waste gas degradation mode, the more plasma reactors there are, the better the organic waste gas degradation performance of the system. However, this also increases the difficulty of voltage control and the system design cost. Considering both organic waste gas degradation performance and cost, the preferred number of plasma reactors is two. When the organic waste gas treatment system is in decoking mode, at least one plasma reactor is a normally operating plasma reactor, and the remaining plasma reactors are either normally operating plasma reactors or plasma reactors requiring decoking.

[0049] In some embodiments, the decoking method of the plasma reactor described in this invention is implemented in an organic waste gas treatment system, where the organic waste gas treatment system has two plasma reactors, such as... Figure 1 As shown, when the first plasma reactor I is operating normally and the second plasma reactor II requires decoking, the method includes: introducing organic waste gas into the first plasma reactor I through the first inlet pipeline 01 and the first inlet A for plasma waste gas treatment; sequentially introducing all or part of the obtained organic waste gas tail gas through the organic waste gas tail gas outlet F, the first decoking pipeline 12 and the organic waste gas tail gas inlet H into the second plasma reactor II for decoking treatment; sequentially introducing the obtained decoking tail gas through the decoking tail gas outlet G, the second decoking pipeline 11 and the decoking tail gas inlet E into the first plasma reactor I; and then cyclically introducing the first plasma reactor I and the second plasma reactor II for treatment until the total hydrocarbon concentration at the inlet and outlet of the second plasma reactor II is basically the same, that is, when the total hydrocarbon concentration measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 is basically the same, the decoking ends.

[0050] In other embodiments, the decoking method of the plasma reactor described in this invention is implemented in an organic waste gas treatment system, where the organic waste gas treatment system has two plasma reactors, such as... Figure 1As shown, when the second plasma reactor II is operating normally and the first plasma reactor I requires decoking treatment, the method includes: introducing organic waste gas into the second plasma reactor II through the second inlet pipeline 03 and the second inlet C for plasma waste gas treatment; sequentially introducing all or part of the obtained organic waste gas tail gas through the organic waste gas tail gas inlet H, the first decoking pipeline 12 and the organic waste gas tail gas outlet F into the first plasma reactor I for decoking treatment; sequentially introducing the obtained decoking tail gas through the decoking tail gas inlet E, the second decoking pipeline 11 and the decoking tail gas outlet G into the second plasma reactor II; and then cyclically introducing the first plasma reactor I and the second plasma reactor II for treatment until the total hydrocarbon concentration at the inlet and outlet of the first plasma reactor I is basically the same, that is, when the total hydrocarbon concentration measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 is basically the same, the decoking ends.

[0051] In other embodiments, the decoking method of the plasma reactor described in this invention is implemented in an organic waste gas treatment system. When the organic waste gas treatment system has three plasma reactors, one first plasma reactor I is operating normally and two second plasma reactors II require decoking treatment, the method includes: introducing organic waste gas into the first plasma reactor I through the first inlet pipeline 01 and the first inlet A for plasma waste gas treatment; sequentially introducing all or part of the obtained organic waste gas tail gas through the organic waste gas tail gas outlet F, the first decoking pipeline 12 and the organic waste gas tail gas inlet H into the second plasma reactor II for decoking treatment; sequentially introducing the obtained decoking tail gas through the decoking tail gas outlet G, the second decoking pipeline 11 and the decoking tail gas inlet E into the first plasma reactor I; and then cyclically introducing the first plasma reactor I and the second plasma reactor II for treatment until the total hydrocarbon concentration at the inlet and outlet of the second plasma reactor II is basically the same, that is, when the total hydrocarbon concentration measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 is basically the same, the decoking ends.

[0052] The following examples further illustrate the descaling method for the plasma reactor described in this invention. These examples are implemented based on the technical solution of this invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of this invention is not limited to the following examples.

[0053] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0054] The decoking methods for plasma reactors in Examples 1, 2, and Comparative Example 1 are described below. Figure 1 The organic waste gas treatment system shown has two plasma reactors. Specifically, the system includes a first plasma reactor I, a second plasma reactor II, a first inlet pipeline 01, a first outlet pipeline 02, a second inlet pipeline 03, a second outlet pipeline 04, a first coke removal pipeline 12, and a second coke removal pipeline 11. The first coke removal pipeline 12 is equipped with a valve and a first gas component concentration detector 22. The second coke removal pipeline 11 is equipped with a valve and a second gas component concentration detector 23. The first outlet pipeline 02 is equipped with a valve and a third gas component concentration detector 21. The second outlet pipeline 04 is equipped with a valve and a fourth gas component concentration detector 24. The third gas component concentration detector 21, the fourth gas component concentration detector 24, the first gas component concentration detector 22, and the second gas component concentration detector 23 are used to detect at least one of the following in the gas stream: total hydrocarbon concentration, non-methane total hydrocarbon concentration, CO2 concentration, and CO concentration. The first plasma reactor I and the second plasma reactor II are coaxial dual-quartz dielectric barrier plasma reactors. Each coaxial dual-quartz dielectric barrier plasma reactor includes a central high-voltage electrode, a ground electrode, and a plasma reaction tube arranged coaxially. The central high-voltage electrode is a quartz tube with an outer diameter of 8 mm and an inner diameter of 6 mm, filled with iron powder, and connected to a high-voltage power supply. The plasma reaction tube is a quartz tube with an outer diameter of 16 mm and an inner diameter of 14 mm, with a discharge gap of 3 mm. The ground electrode, tightly wrapped around the outside of the plasma reaction tube, is a 6 cm long copper sheet.

[0055] Example 1

[0056] When the organic waste gas treatment system is in the organic waste gas degradation mode, the plasma reactor is driven by a high-frequency sinusoidal AC power supply with a frequency of 7kHz and a voltage amplitude of 28kV. 500ppm benzene / air is introduced into the plasma reactor at a flow rate of 0.4L / min. After continuous discharge for 10 minutes, brownish-yellow byproducts adhere to the inner wall of the quartz tube outside the plasma discharge zone and the outer wall of the quartz tube of the inner high-voltage electrode in the second plasma reactor II. The non-methane total hydrocarbon degradation rate of the second plasma reactor II is 1 / 2 to 2 / 3 of the optimal operating rate, indicating that the second plasma reactor II requires decoking. The non-methane total hydrocarbon degradation rate of the first plasma reactor I is greater than 2 / 3 of the optimal operating rate, indicating that the first plasma reactor I is operating normally. When the organic waste gas treatment system is in the decoking mode for the second plasma reactor II, the second plasma reactor II is driven by a high-frequency sinusoidal AC power supply with a frequency of 7kHz and a voltage amplitude of 32kV. 500 ppm benzene / air is introduced into the first plasma reactor I at a flow rate of 0.4 L / min through the first inlet pipe 01 and the first inlet A for plasma exhaust gas treatment. The resulting CO2 / air with a CO2 concentration of 0.2% is then introduced into the second plasma reactor II at a flow rate of 0.4 L / min through the organic exhaust gas outlet F, the first decoking pipe 12, and the organic exhaust gas inlet H for decoking treatment. This process is then repeated sequentially between the first plasma reactor I and the second plasma reactor II until the total hydrocarbon concentrations measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 are essentially the same, at which point decoking is complete. The CO concentration in the decoking exhaust gas measured by the second gas component concentration detector 23 is 0.11%.

[0057] Example 2

[0058] The method of Example 1 is followed, except that the CO2 / air with a CO2 concentration of 0.2% and a flow rate of 0.4 L / min is replaced with the CO2 / air with a CO2 concentration of 0.2% and a flow rate of 0.1 L / min. The CO concentration in the coking tail gas is measured to be 0.34% by the second gas component concentration detector 23.

[0059] Comparative Example 1

[0060] The organic waste gas treatment system in this comparative example was implemented according to Example 1. The second plasma reactor II was driven by a high-frequency sinusoidal AC power supply with a frequency of 7kHz and a voltage amplitude of 32kV. CO2 / air with a CO2 concentration of 0.2% was introduced into the first plasma reactor I at a flow rate of 0.4L / min through the first inlet pipeline 01 and the first inlet A for plasma waste gas treatment. The resulting gas was then sequentially introduced into the second plasma reactor II at a flow rate of 0.4L / min through the organic waste gas tail gas outlet F, the first decoking pipeline 12, and the organic waste gas tail gas inlet H for decoking treatment. This process was then repeated sequentially between the first plasma reactor I and the second plasma reactor II until the total hydrocarbon concentrations measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 were essentially the same, indicating that decoking was complete. The CO concentration in the decoking tail gas measured by the second gas component concentration detector 23 was 0.03%.

[0061] Example 3

[0062] The organic waste gas treatment system in this embodiment is implemented according to Embodiment 1, except that the plasma discharge zone wrapped by the ground electrode is filled with SiO2 glass spheres with a diameter of 1-1.5 mm.

[0063] When the organic waste gas treatment system is in the organic waste gas degradation mode, the plasma reactor is driven by a high-frequency sinusoidal AC power supply with a frequency of 7kHz and a voltage amplitude of 28kV. 500ppm benzene / air is introduced into the plasma reactor at a flow rate of 0.4L / min. After continuous discharge for 10 minutes, brownish-yellow byproducts adhere to the inner wall of the quartz tube outside the plasma discharge zone of the second plasma reactor II, the outer wall of the quartz tube of the inner high-voltage electrode, and the surface of some glass spheres. When the organic waste gas treatment system is in the decoking mode for the second plasma reactor II, the second plasma reactor II is driven by a high-frequency sinusoidal AC power supply with a frequency of 7kHz and a voltage amplitude of 32kV. 500 ppm benzene / air is introduced into the first plasma reactor I at a flow rate of 0.4 L / min through the first inlet pipe 01 and the first inlet A for plasma exhaust gas treatment. The resulting CO2 / air with a CO2 concentration of 0.2% is then introduced into the second plasma reactor II at a flow rate of 0.4 L / min through the organic exhaust gas outlet F, the first decoking pipe 12, and the organic exhaust gas inlet H for decoking treatment. This process is then repeated sequentially between the first plasma reactor I and the second plasma reactor II until the total hydrocarbon concentrations measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 are essentially the same, at which point decoking is complete. The CO concentration in the decoking exhaust gas measured by the second gas component concentration detector 23 is 0.15%.

[0064] Example 4

[0065] The method of Example 3 is followed, except that the CO2 / air with a CO2 concentration of 0.2% and a flow rate of 0.4 L / min is replaced with the CO2 / air with a CO2 concentration of 0.2% and a flow rate of 0.1 L / min. The CO concentration in the coking tail gas is measured to be 0.36% by the second gas component concentration detector 23.

[0066] Example 5

[0067] The method of Example 3 is followed, except that the CO2 / air with a CO2 concentration of 0.2% and a flow rate of 0.4 L / min is replaced with the CO2 / air with a CO2 concentration of 0.2% and a flow rate of 0.05 L / min. The CO concentration in the coking tail gas is measured to be 0.28% by the second gas component concentration detector 23.

[0068] Comparative Example 2

[0069] The organic waste gas treatment system in this comparative example was implemented according to Example 3. The second plasma reactor II was driven by a high-frequency sinusoidal AC power supply with a frequency of 7kHz and a voltage amplitude of 32kV. CO2 / air with a CO2 concentration of 0.2% was introduced into the first plasma reactor I at a flow rate of 0.4L / min through the first inlet pipeline 01 and the first inlet A for plasma waste gas treatment. The resulting gas was then sequentially introduced into the second plasma reactor II at a flow rate of 0.4L / min through the organic waste gas tail gas outlet F, the first decoking pipeline 12, and the organic waste gas tail gas inlet H for decoking treatment. This process was then repeated sequentially between the first plasma reactor I and the second plasma reactor II until the total hydrocarbon concentrations measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 were essentially the same, indicating that decoking was complete. The CO concentration in the decoking tail gas measured by the second gas component concentration detector 23 was 0.05%.

[0070] Example 6

[0071] The organic waste gas treatment system in this embodiment is implemented according to Embodiment 1, except that two cascade plasma discharge disks are vertically arranged in the plasma reactor along the airflow direction.

[0072] When the organic waste gas treatment system is in organic waste gas degradation mode, the plasma driving power supply for the plasma reactor is a high-frequency sinusoidal AC power supply with a frequency of 7kHz and a voltage amplitude of 25kV. The discharge power of plasma reactors I and II is 2kW each. The total hydrocarbon concentration is 1000mg / m³. 3 (i.e., non-methane total hydrocarbons are 1000 mg / m³) 3VOCs waste gas containing benzene and toluene is introduced into the plasma reactor at a flow rate of 10 L / min (residence time 10 s). Depending on the concentration ratio of benzene and toluene, the degradation rate of non-methane total hydrocarbons in the VOCs waste gas ranges from 80% to 98%, and the CO2 concentration ranges from 2800 to 3400 mg / m³. 3 (0.16%-0.19%). After one month of operation, brownish-yellow coking byproducts adhered to the inner wall and discharge disk electrodes of the second plasma reactor II. The accumulation of coking byproducts reduced the degradation efficiency of the plasma generator; the non-methane total hydrocarbon degradation rate of the second plasma reactor II was 45%, indicating that the second plasma reactor II required decoking. When the organic waste gas treatment system was in the decoking mode for the second plasma reactor II, the second plasma reactor II was driven by a high-frequency sinusoidal AC power supply with a frequency of 7kHz and a voltage amplitude of 25kV. The total hydrocarbon concentration was 1000mg / m³. 3 (i.e., non-methane total hydrocarbons are 1000 mg / m³) 3 VOCs waste gas containing benzene and toluene is introduced into the first plasma reactor I at a flow rate of 10 L / min (residence time 10 s) through the first inlet pipeline 01 and the first inlet A for plasma waste gas treatment. The resulting CO2 / air mixture with a CO2 concentration of 0.19% is then sequentially introduced into the second plasma reactor II through the organic waste gas tail gas outlet F, the first decoking pipeline 12, and the organic waste gas tail gas inlet H for decoking treatment. This process is then repeated sequentially between the first plasma reactor I and the second plasma reactor II. The discharge power of the second plasma reactor II is increased from 2 kW to 3 kW until the total hydrocarbon concentrations measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 are essentially the same, at which point decoking is complete. The CO concentration in the decoking tail gas measured by the second gas component concentration detector 23 is 0.05%.

[0073] Comparative Example 3

[0074] The organic waste gas treatment system in this comparative example was implemented according to Example 6, except that the total hydrocarbons were 1000 mg / m³. 3 (i.e., non-methane total hydrocarbons are 1000 mg / m³) 3 The VOCs waste gas containing benzene and toluene was converted to 3400 mg / m³. 3 (That is, 0.19%) CO2 concentration. The CO concentration in the coke exhaust gas was measured to be 0.03% by the second gas component concentration detector 23.

[0075] Example 7

[0076] The organic waste gas treatment system in this embodiment is implemented according to Embodiment 6, except that the obtained CO2 / air with a CO2 concentration of 0.19% is sequentially introduced into the second plasma reactor II through the organic waste gas tail gas outlet F, the first decoking pipe 12, and the organic waste gas tail gas inlet H for decoking treatment. Then, it is circulated sequentially into the first plasma reactor I and the second plasma reactor II for treatment. The discharge power of the second plasma reactor II is still maintained at 2kW, and the residence time of the gas stream in the plasma reactor requiring decoking is extended (flow rate of 5L / min, residence time of 20s) until the total hydrocarbon concentration measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 is basically the same, at which point decoking is completed. The CO concentration in the decoking tail gas measured by the second gas component concentration detector 23 is 0.07%.

[0077] Comparative Example 4

[0078] The organic waste gas treatment system in this comparative example was implemented according to Example 7, except that the total hydrocarbons were 1000 mg / m³. 3 (i.e., non-methane total hydrocarbons are 1000 mg / m³) 3 The VOCs waste gas containing benzene and toluene was converted to 3400 mg / m³. 3 (That is, 0.19%) CO2 concentration. The CO concentration in the coke exhaust gas was measured to be 0.034% by the second gas component concentration detector 23.

[0079] Example 8

[0080] The organic waste gas treatment system in this embodiment is implemented according to Embodiment 6, except that the obtained CO2 / air with a CO2 concentration of 0.19% is sequentially introduced into the second plasma reactor II through the organic waste gas tail gas outlet F, the first decoking pipe 12, and the organic waste gas tail gas inlet H for decoking treatment. Then, it is circulated sequentially into the first plasma reactor I and the second plasma reactor II for further treatment. The discharge power of the second plasma reactor II is increased to 3kW, and the residence time of the gas stream in the plasma reactor requiring decoking is extended (flow rate 5L / min, residence time 20s) until the total hydrocarbon concentration measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 is basically the same, at which point decoking is completed. The CO concentration in the decoking tail gas measured by the second gas component concentration detector 23 is 0.12%.

[0081] Comparative Example 5

[0082] The organic waste gas treatment system in this comparative example was implemented according to Example 8, except that the total hydrocarbons were 1000 mg / m³. 3 (i.e., non-methane total hydrocarbons are 1000 mg / m³) 3The VOCs waste gas containing benzene and toluene was converted to 3400 mg / m³. 3 (That is, 0.19%) CO2 concentration. The CO concentration in the coke exhaust gas was measured to be 0.04% by the second gas component concentration detector 23.

[0083] Example 9

[0084] The organic waste gas treatment system in this embodiment is implemented according to Embodiment 8, except that the discharge power of the second plasma reactor II is increased to 3kW, and the residence time of the gas stream in the plasma reactor requiring decoking is extended (flow rate of 5L / min, residence time of 20s). If, after treatment, the total hydrocarbon concentration measured by the first gas component concentration detector 22 or the second gas component concentration detector 23 is found to be inconsistent with the non-methane total hydrocarbon concentration, the discharge power of the first plasma reactor I is increased to 3kW, or the flow rate of the gas stream in the first plasma reactor I is reduced to 5L / min, i.e., the residence time is 20s. The flow rate of the gas in the second plasma reactor II remains 5L / min, and the residence time remains 20s, until the total hydrocarbon concentration measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 are basically consistent, at which point decoking is completed. The CO concentration in the decoking tail gas measured by the second gas component concentration detector 23 is 0.20%.

[0085] Comparative Example 6

[0086] The organic waste gas treatment system in this comparative example was implemented according to Example 9, except that the total hydrocarbons were 1000 mg / m³. 3 (i.e., non-methane total hydrocarbons are 1000 mg / m³) 3 The VOCs waste gas containing benzene and toluene was converted to 3400 mg / m³. 3 (That is, 0.19%) CO2 concentration. The CO concentration in the coke exhaust gas was measured to be 0.06% by the second gas component concentration detector 23.

[0087] Example 10

[0088] The organic waste gas treatment system in this embodiment is implemented according to Embodiment 6, except that the obtained CO2 / air with a CO2 concentration of 0.19% is sequentially introduced into the second plasma reactor II through the organic waste gas tail gas outlet F, the first decoking pipe 12, and the organic waste gas tail gas inlet H for decoking treatment. Then, it is circulated sequentially into the first plasma reactor I and the second plasma reactor II for further treatment. The discharge power of the second plasma reactor II is increased to 6kW, and the residence time of the gas stream in the plasma reactor requiring decoking is extended (flow rate 2L / min, residence time 50s) until the total hydrocarbon concentration measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 is basically the same, at which point decoking is completed. The CO concentration in the decoking tail gas measured by the second gas component concentration detector 23 is 0.21%.

[0089] Example 11

[0090] The organic waste gas treatment system in this embodiment is implemented according to Embodiment 6, except that the obtained CO2 / air with a CO2 concentration of 0.19% is sequentially introduced into the second plasma reactor II through the organic waste gas tail gas outlet F, the first decoking pipe 12, and the organic waste gas tail gas inlet H for decoking treatment. Then, it is circulated sequentially into the first plasma reactor I and the second plasma reactor II for treatment. The discharge power of the second plasma reactor II is not only increased to 3kW, but the residence time of the gas stream in the plasma reactor requiring decoking is also extended (flow rate of 1.6L / min, residence time of 62s) until the total hydrocarbon concentration measured by the first gas component concentration detector 22 and the second gas component concentration detector 23 is basically the same, at which point decoking is completed. The CO concentration in the decoking tail gas measured by the second gas component concentration detector 23 is 0.20%.

[0091] Since CO2-containing atmosphere reacts with coke adhering to the reactor and catalyst pore structure under low-temperature plasma conditions to generate CO, the CO concentration of the coke removal tail gas can represent the effect of coke removal. The higher the CO concentration of the coke removal tail gas, the better the removal effect of coke in the reactor and catalyst or packing pores.

[0092] The embodiments of the decoking method for the plasma reactor described in this invention effectively remove coke from the reactor and from the catalyst or packing pores.

[0093] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for removing char from a plasma reactor, characterized in that, This method is implemented in an organic waste gas treatment system having two or more plasma reactors, and the method includes: When at least one plasma reactor needs decoking, organic waste gas is introduced into the normally operating plasma reactor for plasma waste gas treatment, and the resulting organic waste gas tail gas is introduced into the plasma reactor that needs decoking for decoking treatment. Then, the resulting decoking tail gas is circulated back into the normally operating plasma reactor and the plasma reactor that needs decoking for treatment until the total hydrocarbon concentration at the inlet and outlet of the plasma reactor that needs decoking is basically the same, at which point decoking is completed. The residence time of the gas in the plasma reactor requiring descaling is longer than that in the normally operating plasma reactor, and the discharge power of the descaling treatment is higher than that of the plasma exhaust gas treatment.

2. The method according to claim 1, characterized in that, The residence time of the gas in the plasma reactor requiring descaling is 1-10 times that in the normally operating plasma reactor, preferably 1.5-6 times.

3. The method according to claim 1 or 2, characterized in that, The discharge power of the descaling treatment is 1.1-3 times that of the discharge power of the plasma exhaust gas treatment.

4. The method according to claim 1, characterized in that, The organic waste gas exhaust gas is air mainly containing CO2 and H2O.

5. The method according to any one of claims 1-4, characterized in that, The organic waste gas treatment system includes: a first plasma reactor (I), a second plasma reactor (II), a first inlet pipeline (01), a first outlet pipeline (02), a second inlet pipeline (03), a second outlet pipeline (04), a first coke removal pipeline (12), and a second coke removal pipeline (11); When the first plasma reactor (I) and the second plasma reactor (II) are in normal working condition, the organic waste gas enters the first plasma reactor (I) and the second plasma reactor (II) through the first inlet pipeline (01) and the second inlet pipeline (03) respectively, and the organic waste gas tail gas obtained after plasma waste gas treatment is discharged through the first outlet pipeline (02) and the second outlet pipeline (04) respectively. When the first plasma reactor (I) is operating normally and the second plasma reactor (II) needs decoking treatment, the gas stream after plasma exhaust treatment of the first plasma reactor (I) is introduced into the second plasma reactor (II) through the first decoking pipeline (12), and the gas stream after decoking treatment of the second plasma reactor (II) is introduced into the first plasma reactor (I) through the second decoking pipeline (11). When the second plasma reactor (II) is operating normally and the first plasma reactor (I) needs decoking treatment, the gas stream after being treated by the plasma exhaust gas of the second plasma reactor (II) is introduced into the first plasma reactor (I) through the first decoking pipeline (12), and the gas stream after being treated by the decoking treatment of the first plasma reactor (I) is introduced into the second plasma reactor (II) through the second decoking pipeline (11).

6. The method according to claim 5, characterized in that, The first coke removal pipeline (12) is equipped with a valve and a first gas component concentration detector (22), and the second coke removal pipeline (11) is equipped with a valve and a second gas component concentration detector (23). The first gas component concentration detector (22) and the second gas component concentration detector (23) are used to detect at least one of the total hydrocarbon concentration, non-methane total hydrocarbon concentration, CO2 concentration and CO concentration in the gas stream.

7. The method according to claim 5 or 6, characterized in that, The first gas outlet pipeline (02) is equipped with a valve and a third gas component concentration detector (21), and the second gas outlet pipeline (04) is equipped with a valve and a fourth gas component concentration detector (24). The third gas component concentration detector (21) and the fourth gas component concentration detector (24) are used to detect at least one of the following in the gas stream: total hydrocarbon concentration, non-methane total hydrocarbon concentration, CO2 concentration and CO concentration.

8. The method according to claim 6, characterized in that, During the decoking process, when the total hydrocarbon concentration measured by the first gas component concentration detector (22) is inconsistent with the non-methane total hydrocarbon concentration, or when the total hydrocarbon concentration measured by the second gas component concentration detector (23) is inconsistent with the non-methane total hydrocarbon concentration, the discharge power of the normally operating plasma reactor is increased, or the flow rate of the gas stream in the first decoking pipeline (12) and the second decoking pipeline (11) is reduced.

9. The method according to any one of claims 5-8, characterized in that, The decoking process includes: increasing the discharge power of the plasma reactor that needs decoking, and / or extending the residence time of the gas stream in the plasma reactor that needs decoking, until the total hydrocarbon concentration of the gas stream discharged from the outlet of the plasma reactor that needs decoking is stable.

10. The method according to any one of claims 1-8, characterized in that, When the degradation rate of non-methane total hydrocarbons in the plasma reactor is 1 / 2 to 2 / 3 of the degradation rate under optimal operating conditions, the plasma reactor is determined to be a plasma reactor that requires decoking.

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