A RTO waste gas treatment system and method using electric heating

Abstract

The present invention provides an RTO waste gas treatment system and method using electric heating, the system comprising an adsorption unit, an RTO direct-fired furnace, a desorption unit and an exhaust pipe, the air intake main pipe of VOCs waste gas is connected to a VOCs concentration detector, the VOCs concentration detector is connected to the adsorption unit through an adsorption pipe, and is connected to the RTO direct-fired furnace through a first air intake pipe, the adsorption unit is connected to the exhaust pipe through an adsorption unit exhaust pipe, and a main exhaust fan is arranged on the adsorption unit exhaust pipe; the RTO direct-fired furnace is connected to the exhaust pipe through an RTO exhaust pipe, and a direct-fired fan is arranged on the RTO exhaust pipe; the desorption unit is connected to the adsorption unit through a desorption pipe, and the adsorption unit is connected to the RTO direct-fired furnace through a second air intake pipe; a plurality of silicon carbon rods are arranged in the combustion chamber of the RTO direct-fired furnace to provide a combustion temperature for the combustion chamber; the system also comprises a PLC control device to control various working conditions.

Description

Technical Field

[0001] The invention relates to an RTO waste gas treatment system and method using electric heating, belonging to the technical field of organic waste gas treatment. Background Art

[0002] Volatile organic compounds (VOCs) generally refer to organic compounds with a saturated vapor pressure greater than 70Pa at room temperature and a boiling point below 260°C at normal pressure, or all organic compounds with a vapor pressure greater than or equal to 10Pa at 20°C and are volatile. VOCs are important precursors to secondary pollutants such as fine particulate matter (PM2.5) and ozone (O3), which in turn cause atmospheric environmental problems such as haze and photochemical smog.

[0003] Regenerative thermal combustion (RTO) technology is a common technology in the treatment of organic waste gas. Its principle is that combustible organic waste gas undergoes thermal oxidation reaction at 760℃~1000℃ to produce carbon dioxide and water, etc. The waste gas is first heated to a temperature close to the thermal oxidation temperature by a thermal storage body, and then enters the combustion chamber for thermal oxidation. The temperature of the oxidized gas increases, and the organic matter is basically converted into carbon dioxide and water. The purified gas passes through another thermal storage body, and the temperature drops. It is discharged after meeting the national emission standards. The regenerative ceramic packed bed heat exchanger in the RTO equipment can recover heat energy to the maximum extent, with a heat recovery rate of more than 95%. No or a small amount of fuel is used when treating VOCs.

[0004] RTO devices can usually be designed with two, three, multiple or single chambers for rotation. This technology has the characteristics of high treatment effect and high energy consumption. It mainly uses natural gas combustion to oxidize and decompose organic waste gas at high temperature. However, some users are far away from the natural gas pipeline network and need to go through relevant account opening procedures and pay expensive account opening fees. Therefore, electric heating is used as a substitute.

[0005] However, in the RTO device using electric heating in the prior art, since a fin-type alloy material resistance wire is used, and the thermal oxidation temperature in the RTO device is usually required to be around 800°C, the metal resistance wire will produce oxidation and large thermal deformation when heated to such a high temperature and cause short circuit or open circuit, and the heating element needs to be set at the top of the combustion chamber, and the fin-type electric heating wire will bend and fall off. Danger; further, due to the high temperature operation of the metal resistance wire, part of the heat is transferred to the external heating box, and the external heating box may also cause open circuit due to insufficient heat dissipation, so the existing RTO devices using electric heating have great safety hazards. Summary of the invention

[0006] The purpose of the present invention is to provide an RTO waste gas treatment system and method using electric heating for enterprises operating at various concentrations, which can adopt a variable air volume operation process, achieve effective resource utilization, and achieve huge economic benefits and environmental protection. The system and method of the present invention are suitable for the treatment of VOCs organic waste gas with large air volume, unstable production conditions and no recovery value.

[0007] The technical solution of the present invention is as follows:

[0008] The present invention first provides an RTO waste gas treatment system using electric heating, the system comprising an intake manifold, an adsorption unit, an RTO direct-fired furnace, a desorption unit and an exhaust pipe, wherein the intake manifold of the system is connected to a VOCs concentration detector, the VOCs concentration detector is connected to the adsorption unit through an adsorption pipeline, and is connected to the RTO direct-fired furnace through a first intake pipeline, the adsorption unit is connected to the exhaust pipe through an adsorption unit exhaust pipeline, and a main exhaust fan is provided on the adsorption unit exhaust pipeline, the main exhaust fan is used to provide power to make the waste gas in the intake manifold The gas enters the adsorption unit, and the gas treated by the adsorption unit is discharged to the exhaust pipe through the adsorption unit exhaust pipe; the RTO direct-fired furnace is connected to the exhaust pipe through the RTO exhaust pipe, and a direct-fired fan is arranged on the RTO exhaust pipe, and the direct-fired fan is used to provide power, so that the exhaust gas in the intake manifold enters the RTO direct-fired furnace, and the gas treated by combustion in the RTO direct-fired furnace is passed into the exhaust pipe; the desorption unit is connected to the adsorption unit through the desorption pipe, and the adsorption unit is connected to the RTO direct-fired furnace through the second intake pipe.

[0009] According to the technical solution of the present invention, the VOCs concentration detector of the system is respectively connected to the adsorption pipe of the adsorption unit and the first air intake pipe connected to the RTO direct-fired furnace, and valves are provided on both; and the first air intake pipe and the second air intake pipe are respectively connected to the RTO air intake pipe of the RTO direct-fired furnace; and a valve is also provided on the second air intake pipe.

[0010] According to the technical solution of the present invention, the VOCs concentration detector of the system is connected to the air intake main pipe of the system and a dry filter is provided to filter particulate matter in the VOCs waste gas to be treated.

[0011] According to the technical solution of the present invention, the desorption unit can be connected to the RTO direct-fired furnace through a heat extraction pipeline and extract heat from the RTO direct-fired furnace; further, a regulating valve is provided on the heat extraction pipeline.

[0012] According to the technical solution of the present invention, the desorption unit can also introduce clean air through a second air supply duct, and an air supply valve is provided on the second air supply duct.

[0013] According to the technical solution of the present invention, the adsorption unit is an activated carbon box for adsorbing VOCs waste gas; and the desorption unit is a mixing tank for providing a desorption temperature for the desorption process of the activated carbon in the adsorption unit.

[0014] According to the technical solution of the present invention, in one embodiment, the adsorption unit can be configured as a plurality of activated carbon boxes connected in parallel, and in the adsorption condition, after the activated carbon box adsorbs for a predetermined time, the activated carbon box is switched to the desorption condition, and a new activated carbon box is connected for exhaust gas adsorption.

[0015] According to the technical solution of the present invention, the desorption process of the adsorption unit is as follows: the clean air introduced from the outside and the air entering the desorption unit from the heat extraction pipe of the RTO direct-fired furnace are mixed in the mixing tank of the desorption unit, and are transported to the adsorption unit through the desorption pipe, so that the substances adsorbed in the activated carbon of the adsorption unit are desorbed; and, in the adsorption unit, the gas formed after desorption of the fixed bed activated carbon can be introduced into the RTO direct-fired furnace through the second air intake pipe for further combustion treatment.

[0016] According to the technical solution of the present invention, the system also includes a PLC control device, which is electrically connected to the VOCs concentration detector and can receive signals from the VOCs concentration detector. The PLC control device can also be connected to the pipeline valve in the system to control the exhaust gas treatment conditions of the system.

[0017] According to the technical solution of the present invention, in the RTO direct-fired furnace, the upper area is the heating zone, that is, the combustion chamber of the RTO direct-fired furnace, and a plurality of silicon carbon rods are arranged in the combustion chamber to provide combustion temperature for the combustion chamber of the RTO direct-fired furnace.

[0018] According to the technical solution of the present invention, in one embodiment, both ends of the silicon carbon rods in the combustion chamber have wiring terminals, and the wiring terminals are connected to an external heating box through wires to electrically heat the plurality of silicon carbon rods.

[0019] The system is provided with an induced draft fan at the connection terminals where the external heating box of the RTO direct-fired furnace is connected to the two ends of the silicon carbon rod, and the pipeline of the induced draft fan is sealed. The induced draft fan is used to cool the connection terminals during the heating of the silicon carbon rod.

[0020] According to the technical solution of the present invention, in one embodiment, the silicon carbon rod in the combustion chamber is arranged to penetrate the upper part of the RTO direct-fired furnace from front to back, and one end of the silicon carbon rod is fixed and the other end is movably connected, so that the silicon carbon rod can have deformation space.

[0021] According to the technical solution of the present invention, in one embodiment, chamber A, chamber B and chamber C are arranged at the lower part of the combustion chamber of the RTO direct-fired furnace, and heat storage bodies are respectively arranged in the middle of chamber A, chamber B and chamber C.

[0022] According to the technical solution of the present invention, the chamber A, chamber B and chamber C of the RTO direct-fired furnace are independent of each other, and the upper parts of chamber A, chamber B and chamber C are all connected to the combustion chamber.

[0023] According to the technical solution of the present invention, the lower parts of the chamber A, chamber B and chamber C of the RTO direct-fired furnace are respectively the air intake and exhaust ducts of the RTO direct-fired furnace, and the air intake and exhaust ducts of the chamber A, chamber B and chamber C are respectively provided with air inlets and exhaust ports, that is, the lower part of each chamber is provided with an air inlet and an exhaust port, and the air inlet and the exhaust port are respectively provided on both sides of the chamber A, chamber B and chamber C.

[0024] According to the technical solution of the present invention, the air inlet pipe of the RTO direct-fired furnace is respectively connected to the air inlets of the chambers A, B and C, and a valve is provided at each air inlet. The RTO exhaust pipe of the RTO direct-fired furnace is respectively connected to the exhaust ports of the chambers A, B and C, and a valve is provided at each exhaust port.

[0025] According to the technical solution of the present invention, the air intake and exhaust ducts at the lower parts of the chambers A, B and C of the RTO direct-fired furnace are also provided with air supply ports, and the first air supply duct of the system is respectively connected to the air supply ports of the chambers A, B and C; and a valve is provided at each air supply port; a purge fan is provided on the first air supply duct, and the purge fan is used to introduce clean air into the air supply ports of chambers A, B or C, so that impurities dropped by the exhaust gas in the combustion chamber of the RTO direct-fired furnace during the combustion process can return to the combustion chamber to continue burning, and can cool the heat storage body in chambers A, B or C.

[0026] According to the technical solution of the present invention, the system can continuously heat the RTO direct-fired furnace so that the combustion chamber of the RTO direct-fired furnace is always maintained in the range of 760°C-850°C.

[0027] According to the technical solution of the present invention, the air intake and exhaust ducts at the lower parts of chambers A, B and C of the RTO direct-fired furnace can be operated in the following order:

[0028] First, the air inlet of the RTO direct-fired furnace is connected to the valve at the air inlet of chamber A, and the VOCs waste gas is passed into the RTO direct-fired furnace from chamber A, and moves upward, passes through the heat storage body of chamber A, and reaches the combustion chamber for combustion treatment; the valve at the air supply port of chamber B is opened, and the valve at the exhaust port of chamber C is opened, and the waste gas after combustion treatment enters chamber C from the combustion chamber, passes through the heat storage body of chamber C for cooling, and is discharged from the exhaust port of chamber C;

[0029] Second, the valve at the air inlet of the RTO direct-fired furnace connected to the C chamber is opened, and the VOCs waste gas is passed into the RTO direct-fired furnace from the C chamber, and moves upward, passes through the heat storage body of the C chamber, and reaches the combustion chamber for combustion treatment; the valve at the air supply port of the A chamber is opened, and the valve at the exhaust port of the B chamber is opened, and the waste gas after combustion treatment enters the B chamber from the combustion chamber, passes through the heat storage body of the B chamber for cooling, and is discharged from the exhaust port of the B chamber;

[0030] Third, the air inlet pipe of the RTO direct-fired furnace is connected to the valve at the air inlet of chamber B, and the VOCs waste gas is passed into the RTO direct-fired furnace from chamber B, and runs upward, passes through the heat storage body of chamber B, and reaches the combustion chamber for combustion treatment; the valve at the air supply port of chamber C is opened, and the valve at the exhaust port of chamber A is opened, and the waste gas after combustion treatment enters chamber A from the combustion chamber, passes through the heat storage body of chamber A for cooling, and is discharged from the exhaust port of chamber A.

[0031] According to the above operation process, the inlet temperature of the RTO direct-fired furnace is always kept at 20-30°C, the exhaust temperature is always kept at 70-80°C, and the combustion chamber of the RTO direct-fired furnace is always kept in the range of 760°C-850°C.

[0032] According to the technical solution of the present invention, the PLC control device is used to determine whether the exhaust gas of the intake manifold enters the adsorption condition or the direct combustion condition according to the monitoring result of the intake concentration of the intake manifold by the VOCs concentration detector; and adjust the valves of the adsorption pipeline and the first intake pipeline according to different working conditions; so that the exhaust gas enters the adsorption unit or the RTO direct combustion furnace. Furthermore, the PLC control device can also intelligently control the air volume of the main exhaust fan and the direct combustion fan.

[0033] According to the technical solution of the present invention, the PLC control device can also control the opening of the regulating valve on the heat extraction pipe of the RTO direct-fired furnace according to the temperature feedback displayed by the thermometer on the mixing tank, so as to control the temperature of the desorbed gas provided in the mixing tank of the desorption unit, so that the desorbed gas entering the adsorption unit is maintained at 130°C.

[0034] According to the technical solution of the present invention, the PLC control device can also detect the content of combustible gas in the adsorption unit through a combustible gas probe. Once the concentration of the combustible gas is close to 0, the adsorption unit completes the desorption work.

[0035] According to the technical solution of the present invention, when the concentration of organic waste gas in the intake manifold is low, the system enters the adsorption condition and adopts the adsorption unit for adsorption treatment; when the concentration of organic waste gas in the intake manifold is high, the system enters the direct combustion condition and adopts the RTO direct combustion furnace for combustion treatment; and after the adsorption reaches the predetermined time, the system enters the desorption condition, switches the activated carbon box of the adsorption unit, and desorbs the activated carbon box saturated with adsorption; since the desorption process takes a long time, during the desorption process, when the concentration of organic waste gas in the intake manifold is still low, desorption and adsorption are carried out simultaneously; when the concentration of organic waste gas in the intake manifold is high, desorption and direct combustion are carried out simultaneously; when the desorption condition ends, the system enters the cooling condition and cools the adsorption unit; and when both desorption and direct combustion end, the system enters the insulation condition. Specifically, the system of the present invention can also work under the following conditions:

[0036] Normal working conditions:

[0037] When the PLC control device receives the VOCs exhaust gas concentration of 300mg / m 3 When the temperature is below 400 °C, the valve of the adsorption pipe is opened, and the main exhaust fan is started to run, and its running frequency is, for example, 42 Hz. This is because the fan generally does not work at full frequency (50 Hz), which can protect the equipment. The exhaust gas from the intake manifold enters the activated carbon box of the adsorption unit through the adsorption pipe for adsorption; and in the system of the present invention, the activated carbon box is set to be connected in parallel, and two or more activated carbon boxes can be opened at the same time for adsorption treatment. After the activated carbon box is saturated with adsorption, the PLC control device switches the activated carbon box according to the predetermined adsorption time, and at the same time, the saturated activated carbon box is desorbed.

[0038] When the concentration of VOCs is 400mg / m 3 When the temperature reaches 0.1°C or above, the valve of the first air inlet duct is opened, and the direct-fired blower is started to operate; the exhaust gas from the air inlet main pipe enters the combustion chamber of the RTO direct-fired furnace through the first air inlet duct for combustion treatment.

[0039] More specifically, when the concentration of VOCs is 400 mg / m 3 -600mg / m 3When it is within the range, the direct-fired fan is operated at 38Hz; optionally, when the concentration of organic waste gas in the RTO direct-fired furnace cannot reach the temperature for complete oxidation, it can be compensated by further electric heating. At the same time, by operating at a slightly lower frequency, the waste gas treatment can be guaranteed to meet the standards while meeting the production requirements.

[0040] When the concentration of VOCs is 650mg / m 3 -850mg / m 3 When it is within the range, the direct-fired fan is operated at 42Hz and treated by the RTO direct-fired furnace; optionally, when the temperature does not reach the temperature for complete oxidation, it is compensated by further electric heating. At the same time, through normal frequency operation, the exhaust gas treatment is guaranteed to meet the standards while meeting the production requirements.

[0041] When the concentration of VOCs is 900mg / m 3 When the above conditions are met, the direct-fired fan is operated at 45 Hz and can also be operated by further electric heating auxiliary heat source.

[0042] When the concentration of VOCs does not rise to the above range, it will operate under the original working conditions; this can ensure that the system will not frequently switch working conditions due to concentration fluctuations to ensure the stability of equipment operation; because the concentration change is a momentary value, if the production workshop keeps shaking around this concentration, it will cause frequent switching of valves. Therefore, the designed concentration range is an interval, and the concentration exceeds 400mg / m 3 , and it takes 1 minute to switch to direct combustion conditions; when the concentration is continuously lower than 300mg / m 3 , and it must last for a full minute before it can be switched to the adsorption state.

[0043] Desorption and direct combustion conditions:

[0044] When the activated carbon adsorption of the adsorption unit reaches the set adsorption time, the high-temperature gas taken out from the RTO direct-fired furnace and the clean air introduced into the second air supply pipe are mixed in the mixing tank by opening the regulating valve of the heat extraction pipe and the air supply valve of the second air supply pipe, and are transported to the activated carbon box of the adsorption unit through the desorption pipe. The adsorbed activated carbon is thermally desorbed, and the temperature of the desorbed gas is controlled at 130°C. The hot air entering the adsorption unit through the desorption pipe can desorb the substances adsorbed in the activated carbon, and the desorption operation is performed in the adsorption unit. The desorbed gas is connected to the RTO direct-fired furnace through a second air intake pipe; under the operation of the direct-fired fan, the desorbed gas and the exhaust gas entering from the air intake manifold are sent into the RTO direct-fired furnace for combustion, and the PLC control device can control the valve opening of the second air intake pipe according to the combustion temperature in the RTO direct-fired furnace. Once the concentration of the desorbed gas is too high, causing the furnace in the RTO direct-fired furnace to overheat, the valve opening of the second air intake pipe is reduced to reduce the delivery of the desorbed gas to ensure the furnace temperature.

[0045] Desorption and adsorption conditions:

[0046] When the exhaust gas concentration in the air intake main is very low, the system is in adsorption condition and an adsorption unit is used for adsorption treatment. At this time, since the first air intake duct of the RTO direct-fired furnace is closed and only the second air intake duct is open, the frequency of the direct-fired fan is reduced to 20HZ to ensure the air volume requirement of the desorbed gas, and the desorption temperature is also controlled at 130°C to ensure the desorption of activated carbon in the fixed bed.

[0047] Cooling conditions:

[0048] After the desorption of the activated carbon box in the adsorption unit is completed, the regulating valve of the heat extraction pipe of the desorption unit is closed, so that the clean cold air in the mixing tank passed through the second air supply pipe directly enters the activated carbon box, and the temperature of the activated carbon box is reduced to below 50°C. The cooled exhaust gas enters the RTO direct-fired furnace through the second air intake pipe for combustion treatment.

[0049] Insulation conditions:

[0050] When the desorption of the system is completed and the system is in the adsorption state, the first air inlet duct and the second air inlet duct of the RTO direct-fired furnace are both in a closed state. At this time, clean air is introduced into the air inlet duct of the RTO direct-fired furnace, and the direct-fired fan is operated at a frequency of 10 Hz to keep the RTO direct-fired furnace warm.

[0051] According to the technical solution of the present invention, optionally, the PLC control device further includes an over-temperature alarm unit, and the system can include a temperature alarm condition:

[0052] When the temperature in the activated carbon box exceeds 150°C, there will be a risk of spontaneous combustion; when the regulating valve of the heat extraction pipeline fails, causing the gas temperature in the activated carbon box to exceed 140°C, the over-temperature alarm unit will sound an alarm, and the PLC control device will close the valve for the gas to enter the activated carbon box, and at the same time open the solenoid valve of the nitrogen pipeline arranged in the activated carbon box, and automatically close after the PLC control device determines that the temperature of the activated carbon box has dropped to 60°C.

[0053] The over-temperature alarm unit of the PLC control device can also be used to alarm when the RTO direct-fired furnace is over-heated. The temperature of a normal RTO direct-fired furnace is controlled between 760°C and 850°C. When its temperature exceeds 950°C, it is considered that the RTO direct-fired furnace is in an over-temperature condition. This condition generally occurs during the desorption process due to the excessively high concentration of the desorbed organic waste gas. Therefore, the PLC control device controls the valve opening of the second air inlet pipe through the anemometer of the desorption pipe to control the concentration of the desorbed waste gas entering the RTO direct-fired furnace. If it still increases, the desorption regulating valve of the RTO direct-fired furnace is opened to discharge part of the high-temperature gas in the RTO furnace into the atmosphere to ensure the normal operation of the furnace.

[0054] According to the technical solution of the present invention, the adsorption unit includes but is not limited to a fixed bed made of adsorbents such as granular activated carbon, activated carbon fiber, molecular sieve, silica gel, activated alumina, organic polymer materials, etc.; the fixed bed can make the air distribution of the adsorption unit uniform, so that the adsorption efficiency of the adsorption unit is higher.

[0055] According to the technical solution of the present invention, the adsorption efficiency of the adsorption unit can normally reach 90%-95% in the initial stage; as the adsorption proceeds, the adsorption efficiency will become lower and lower, and when it reaches about 85%, it needs to be desorbed.

[0056] The present invention also provides a method for treating RTO waste gas, the method using the system according to the present invention, the method comprising the following steps:

[0057] Step 1: Use a VOCs concentration detector to detect the concentration of VOCs exhaust gas in the intake manifold. The PLC control device makes a judgment based on the concentration detected by the VOCs concentration detector. When the concentration is above 300 mg / m 3 When the system enters the adsorption state, the valve of the adsorption pipe is opened and the main exhaust fan starts to run; the exhaust gas from the air intake manifold enters the activated carbon box of the adsorption unit through the adsorption pipe for adsorption, and the adsorbed gas is passed into the exhaust pipe through the adsorption unit exhaust pipe of the adsorption unit under the action of the main exhaust fan;

[0058] Step 2: When the PLC control device determines that the concentration of VOCs exhaust gas is 400 mg / m 3 When the temperature is higher than 0.040°C, the system enters the direct-fired working state, at which time the valve of the first air intake pipe is opened, and the direct-fired fan starts to run; the exhaust gas from the air intake manifold enters the combustion chamber of the RTO direct-fired furnace through the first air intake pipe for combustion treatment, and the frequency of the direct-fired fan is adjusted according to the change of the intake air concentration during the treatment process; the treated gas is passed into the exhaust pipe through the RTO exhaust pipe of the RTO direct-fired furnace;

[0059] Step three: after the activated carbon box of the adsorption unit has been adsorbed for a predetermined time, the activated carbon box is switched, and the activated carbon box that is saturated with adsorption is desorbed, and the system enters the desorption condition; at this time, the air supply valve of the second air supply duct is opened, and the regulating valve of the heat extraction duct is opened, and the clean air introduced from the second air supply duct and the air entering the desorption unit from the heat extraction duct of the RTO direct-fired furnace are mixed in the mixing tank of the desorption unit to form a desorbed gas, and the desorbed gas is transported to the adsorption unit through the desorption duct to desorb the adsorbed substances in the fixed bed of the adsorption unit; and the valve of the second air inlet duct is opened, and the gas generated after desorption in the adsorption unit is introduced into the RTO direct-fired furnace through the second air inlet duct for further combustion treatment;

[0060] Step 4: Under the desorption condition, when the VOCs exhaust gas concentration of the intake manifold is at 300 mg / m 3 and below, the step 1 and the step 3 are performed simultaneously; and when the adsorption condition and the desorption condition are performed simultaneously, the direct-fired blower operates at a low frequency; when the VOCs exhaust gas concentration of the intake manifold is at 400 mg / m 3 When the temperature is higher than 0.1°C, the step 2 and the step 3 are performed simultaneously, and when the direct-fired working condition and the desorption working condition are performed simultaneously, the direct-fired fan operates at a normal frequency;

[0061] Step 5: After the desorption is completed, the system enters the cooling state, the regulating valve of the heat extraction pipeline of the RTO direct-fired furnace is closed, and the clean cold air in the temperature mixing tank is introduced into the activated carbon box through the second air supply pipeline, and the temperature of the activated carbon box is reduced to below 50°C, and the cooled exhaust gas is introduced into the RTO direct-fired furnace through the second air intake pipeline for combustion treatment;

[0062] Step six: After the desorption of the adsorption unit is completed and the system is in the adsorption condition, the first air inlet duct and the second air inlet duct of the RTO direct-fired furnace are both in a closed state. At this time, the system enters the insulation condition, clean air is introduced into the air inlet duct of the RTO direct-fired furnace, and the direct-fired fan is operated at a frequency of 10 Hz to insulate the RTO direct-fired furnace.

[0063] The beneficial effects of the present invention are:

[0064] The waste gas treatment system of the present invention adopts silicon carbon rods for electric heating in the RTO direct-fired furnace, so that the temperature of the RTO direct-fired furnace is always controlled within the range of 760°C-850°C, so that the RTO direct-fired furnace runs stably, and compared with the fin-type electric heating wire, the thermal deformation of the silicon carbon rod is smaller; and the use of silicon carbon rods for electric heating will not cause short circuit or open circuit, and the safety is high.

[0065] According to the technical solution of the present invention, an induced draft fan is provided at the connection terminals at both ends of the silicon carbon rod connected to the external heating box of the RTO direct-fired furnace, and the pipeline of the induced draft fan is sealed. The induced draft fan is used to cool down the connection terminals during the heating of the silicon carbon rod, thereby further improving the safety during the electric heating process.

[0066] According to the technical solution of the present invention, the silicon carbon rod in the combustion chamber is arranged to penetrate the upper part of the RTO direct-fired furnace, and one end of the silicon carbon rod is fixed and the other end is movably connected, so that the silicon carbon rod has a deformation space. In addition, the multiple silicon carbon rods arranged in the RTO direct-fired furnace are easy to replace; and the use of electric heating can save energy, which is very suitable for environments with insufficient natural gas.

[0067] According to the technical solution of the present invention, the waste gas treatment system and method are controlled by a PLC control device, and different working conditions are used for waste gas treatment according to different intake concentrations of VOCs waste gas, so that the system can realize automatic working condition switching, and according to the system of the present invention, the desorbed gas can be introduced into the RTO direct-fired furnace for further combustion treatment; multiple working conditions are realized in parallel to improve the waste gas treatment efficiency; and in the process of RTO direct-fired treatment, the frequency of the direct-fired fan is controlled according to the step concentration changes, which can save energy on the one hand and use less power consumption to meet the operation of the RTO direct-fired furnace to maintain the economical and reliable operation of the equipment, while taking into account the air volume required for production to achieve efficient operation of the waste gas treatment system under different working conditions, thereby reducing costs and having great economic benefits.

[0068] According to the technical solution of the present invention, the adsorption unit includes but is not limited to a fixed bed made of adsorbents such as granular activated carbon, activated carbon fiber, molecular sieve, silica gel, activated alumina, organic polymer materials, etc.; the fixed bed can make the air distribution of the adsorption unit uniform, so that the adsorption efficiency of the adsorption unit is higher. In addition, according to the technical solution of the present invention, the direct combustion treatment of exhaust gas using an electrically heated RTO direct combustion furnace can provide a stable temperature range, which is more efficient than the exhaust gas treatment of the RCO catalytic furnace and saves the trouble of replacing the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0070] Figure 1 is a schematic diagram of the overall structure of the system according to the present invention;

[0071] Figure 2 It is a schematic diagram of pipeline connection of the RTO direct-fired furnace in the system of the present invention;

[0072] Figure 3 It is a schematic diagram of pipeline connection of the RTO direct-fired furnace in the system of the present invention;

[0073] Figure 4 It is a schematic diagram of the internal structure of the RTO direct-fired furnace in the system of the present invention;

[0074] Among them, 1. dry filter; 2. VOCs concentration detector; 3. adsorption unit; 4. RTO direct-fired furnace; 5. desorption unit; 6. exhaust chimney; 7. heat storage body; 8. direct-fired fan; 9. main exhaust fan; 10. purge fan; 11. adsorption duct; 12. first air intake duct; 13. second air intake duct; 14. desorption duct; 15. RTO air intake duct; 16. first air supply duct; 17. RTO exhaust duct; 18. adsorption unit exhaust duct; 19. second air supply duct; 20. air intake main pipe. DETAILED DESCRIPTION

[0075] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0076] Embodiment 1:

[0077] A specific embodiment of the present invention is described in detail below in conjunction with the accompanying drawings, but no limitation is imposed on the claims of the present invention.

[0078] This embodiment first provides an RTO waste gas treatment system using electrical heating, see Figure 1As shown, the system includes an intake manifold 20 for VOCs waste gas, an adsorption unit 3, an RTO direct-fired furnace 4, a desorption unit 5 and an exhaust pipe 6, wherein the intake manifold 20 of the system is connected to a VOCs concentration detector 2, the VOCs concentration detector 2 is connected to the adsorption unit 3 through an adsorption pipe 11, and is connected to the RTO direct-fired furnace 4 through a first intake pipe 12, the adsorption unit 3 is connected to the exhaust pipe 6 through an adsorption unit exhaust pipe 18, and a main exhaust fan 9 is provided on the adsorption unit exhaust pipe 18, the main exhaust fan 9 is used to provide power to allow the exhaust gas in the intake manifold 20 to enter the adsorption unit 3 , and discharges the gas treated by the adsorption unit 3 to the exhaust pipe 6 through the adsorption unit exhaust pipe 18; the RTO direct-fired furnace 4 is connected to the exhaust pipe 6 through the RTO exhaust pipe 17, and a direct-fired fan 8 is arranged on the RTO exhaust pipe 17, and the direct-fired fan 8 is used to provide power, so that the exhaust gas in the air intake manifold 20 enters the RTO direct-fired furnace 4, and the gas treated by combustion in the RTO direct-fired furnace 4 is passed into the exhaust pipe 6; the desorption unit 5 is connected to the adsorption unit 3 through the desorption pipe 14, and the adsorption unit 3 is connected to the RTO direct-fired furnace 4 through the second air intake pipe 13.

[0079] According to the technical solution of the present invention, the VOCs concentration detector 2 of the system is respectively connected to the adsorption pipe 11 of the adsorption unit 3 and the first air intake pipe 12 connected to the RTO direct-fired furnace 4, and valves are provided on both; and the first air intake pipe 12 and the second air intake pipe 13 are respectively connected to the RTO air intake pipe 15 of the RTO direct-fired furnace 4; and a valve is also provided on the second air intake pipe 13.

[0080] According to the technical solution of the present invention, the VOCs concentration detector 2 of the system is connected to the air intake manifold 20 of the system and a dry filter 1 is provided on the system to filter particulate matter in the VOCs waste gas to be treated.

[0081] According to the technical solution of the present invention, the desorption unit 5 can be connected to the RTO direct-fired furnace 4 through a heat extraction pipeline and extract heat from the RTO direct-fired furnace 4; further, a regulating valve is provided on the heat extraction pipeline.

[0082] According to the technical solution of the present invention, the desorption unit 5 can also be supplied with clean air through the second air supply duct 19, and an air supply valve is provided on the second air supply duct 19 for supplying clean air.

[0083] According to the technical solution of the present invention, the adsorption unit 3 is an activated carbon box for adsorbing VOCs waste gas; and the desorption unit 5 is a mixing temperature tank for providing a desorption temperature for the desorption process of the activated carbon in the adsorption unit 3.

[0084] According to the technical solution of the present invention, in one embodiment, the adsorption unit 3 can be configured as a plurality of activated carbon boxes connected in parallel, and in the adsorption condition, after the activated carbon box adsorbs for a predetermined time, the activated carbon box is switched to the desorption condition, and a new activated carbon box is connected for exhaust gas adsorption.

[0085] According to the technical solution of the present invention, the desorption process is as follows: the clean air introduced from the second air supply duct 19 and the heat extraction gas entering the desorption unit 5 from the heat extraction duct of the RTO direct-fired furnace 4 are mixed in the mixing tank of the desorption unit 5 to form a desorbed gas, and are transported to the adsorption unit 3 through the desorption duct 14 to desorb the substances adsorbed in the activated carbon of the adsorption unit 3; and, in the adsorption unit 3, the gas formed after desorption of the activated carbon in the fixed bed can be introduced into the RTO direct-fired furnace 4 through the second air inlet duct 13 for further combustion treatment.

[0086] According to the technical solution of the present invention, the system also includes a PLC control device, which is electrically connected to the VOCs concentration detector 2 and can receive signals from the VOCs concentration detector. The PLC control device can also be connected to the pipeline valve in the system to control the exhaust gas treatment conditions of the system.

[0087] According to the technical solution of the present invention, in the RTO direct-fired furnace 4, the upper area is the heating zone, that is, the combustion chamber of the RTO direct-fired furnace, and a plurality of silicon carbon rods are arranged in the combustion chamber, such as Figure 4 As shown, it is used to provide combustion temperature for the combustion chamber of the RTO direct-fired furnace 4.

[0088] According to the technical solution of the present invention, in one embodiment, both ends of the silicon carbon rods in the combustion chamber have wiring terminals, and the wiring terminals are connected to an external heating box through wires to electrically heat the plurality of silicon carbon rods.

[0089] The system is provided with an induced draft fan at the connection terminals where the external heating box of the RTO direct-fired furnace is connected to the two ends of the silicon carbon rod, and the pipeline of the induced draft fan is sealed. The induced draft fan is used to cool the connection terminals during the heating of the silicon carbon rod.

[0090] In one embodiment, the silicon carbon rod in the combustion chamber is arranged to penetrate the upper part of the RTO direct-fired furnace from front to back, and one end of the silicon carbon rod is fixedly connected and the other end is movably connected, so that the silicon carbon rod can have deformation space.

[0091] In one embodiment, if Figure 1As shown, the lower part of the combustion chamber of the RTO direct-fired furnace 4 is provided with chamber A, chamber B and chamber C, and heat storage bodies 7 are respectively provided in the middle of the chambers A, B and C.

[0092] The chamber A, chamber B and chamber C of the RTO direct-fired furnace are independent of each other, and the upper parts of chamber A, chamber B and chamber C are all connected to the combustion chamber.

[0093] The lower parts of the chamber A, chamber B and chamber C of the RTO direct-fired furnace are respectively the air intake and exhaust ducts of the RTO direct-fired furnace, and the air intake and exhaust ducts of the chamber A, chamber B and chamber C are respectively provided with air inlets and exhaust ports, that is, the lower part of each chamber is provided with an air inlet and an exhaust port, and the air inlet and exhaust ports are respectively provided on both sides of the chamber A, chamber B and chamber C.

[0094] like Figure 2 Shown and Figure 3 As shown, the RTO air inlet pipe 15 of the RTO direct-fired furnace is respectively connected to the air inlets of the chambers A, B and C, and a valve is provided at each air inlet. The RTO exhaust pipe 17 of the RTO direct-fired furnace 4 is respectively connected to the exhaust ports of the chambers A, B and C, and a valve is provided at each exhaust port.

[0095] The air intake and exhaust ducts at the lower parts of the chambers A, B and C of the RTO direct-fired furnace are also provided with air supply ports, and the first air supply duct 16 of the system is respectively connected to the air supply ports of the chambers A, B and C; and a valve is provided at each air supply port; a purge fan 10 is provided on the first air supply duct, and the purge fan is used to introduce clean air into the air supply ports of chambers A, B or C, so that impurities dropped by the exhaust gas in the combustion chamber of the RTO direct-fired furnace during the combustion process can return to the combustion chamber to continue burning, and can cool the heat storage body in chambers A, B or C.

[0096] The system can use silicon carbon rods to continuously heat the RTO direct-fired furnace 4, so that the combustion chamber of the RTO direct-fired furnace 4 is always maintained in the range of 760°C-850°C.

[0097] The air inlet and exhaust ducts at the lower parts of chambers A, B and C of the RTO direct-fired furnace 4 can be operated in the following order:

[0098] First, the air inlet of the RTO direct-fired furnace is connected to the valve at the air inlet of chamber A, and the VOCs waste gas is passed into the RTO direct-fired furnace from chamber A, and moves upward, passes through the heat storage body of chamber A, and reaches the combustion chamber for combustion treatment; the valve at the air supply port of chamber B is opened, and the valve at the exhaust port of chamber C is opened, and the waste gas after combustion treatment enters chamber C from the combustion chamber, passes through the heat storage body of chamber C for cooling, and is discharged from the exhaust port of chamber C;

[0099] Second, the valve at the air inlet of the RTO direct-fired furnace connected to the C chamber is opened, and the VOCs waste gas is passed into the RTO direct-fired furnace from the C chamber, and moves upward, passes through the heat storage body of the C chamber, and reaches the combustion chamber for combustion treatment; the valve at the air supply port of the A chamber is opened, and the valve at the exhaust port of the B chamber is opened, and the waste gas after combustion treatment enters the B chamber from the combustion chamber, passes through the heat storage body of the B chamber for cooling, and is discharged from the exhaust port of the B chamber;

[0100] Third, the air inlet pipe of the RTO direct-fired furnace is connected to the valve at the air inlet of chamber B, and the VOCs waste gas is passed into the RTO direct-fired furnace from chamber B, and runs upward, passes through the heat storage body of chamber B, and reaches the combustion chamber for combustion treatment; the valve at the air supply port of chamber C is opened, and the valve at the exhaust port of chamber A is opened, and the waste gas after combustion treatment enters chamber A from the combustion chamber, passes through the heat storage body of chamber A for cooling, and is discharged from the exhaust port of chamber A.

[0101] According to the above operation process, the inlet temperature of the RTO direct-fired furnace is always kept at 20°C-30°C, the exhaust temperature is always kept at 70°C-80°C, and the combustion chamber of the RTO direct-fired furnace is always kept in the range of 760°C-850°C.

[0102] According to the technical solution of the present invention, the PLC control device is used to determine whether the exhaust gas of the intake manifold enters the adsorption condition or the direct combustion condition according to the monitoring result of the intake concentration of the intake manifold by the VOCs concentration detector; and adjust the valves of the adsorption pipeline and the first intake pipeline according to different working conditions; so that the exhaust gas enters the adsorption unit or the RTO direct combustion furnace. Furthermore, the PLC control device can also intelligently control the air volume of the main exhaust fan and the direct combustion fan.

[0103] According to the technical solution of the present invention, the PLC control device can also control the opening of the regulating valve on the heat extraction pipe of the RTO direct-fired furnace according to the temperature feedback displayed by the thermometer on the mixing tank, so as to control the temperature of the desorbed gas provided in the mixing tank of the desorption unit, so that the desorbed gas entering the adsorption unit is maintained at 130°C.

[0104] According to the technical solution of the present invention, the PLC control device can also detect the content of combustible gas in the adsorption unit through a combustible gas probe. Once the concentration of the combustible gas is close to 0, the adsorption unit completes the desorption work.

[0105] According to the technical solution of the present invention, the adsorption unit includes but is not limited to a fixed bed made of adsorbents such as granular activated carbon, activated carbon fiber, molecular sieve, silica gel, activated alumina, organic polymer materials, etc.; the fixed bed can make the air distribution of the adsorption unit uniform, so that the adsorption efficiency of the adsorption unit is higher.

[0106] According to the technical solution of the present invention, the adsorption efficiency of the adsorption unit can normally reach 90%-95% in the initial stage; as the adsorption proceeds, the adsorption efficiency will become lower and lower, and when it reaches about 85%, it needs to be desorbed.

[0107] Embodiment 2

[0108] This embodiment provides a method for treating RTO waste gas, the method adopts the RTO waste gas treatment system described in Embodiment 1, and the method includes:

[0109] Step 1: Use a VOCs concentration detector to detect the concentration of VOCs exhaust gas in the intake manifold. The PLC control device makes a judgment based on the concentration detected by the VOCs concentration detector. When the concentration is above 300 mg / m 3 When the system enters the adsorption state, the valve of the adsorption pipe is opened and the main exhaust fan starts to run; the exhaust gas from the air intake manifold enters the activated carbon box of the adsorption unit through the adsorption pipe for adsorption, and the adsorbed gas is passed into the exhaust pipe through the adsorption unit exhaust pipe of the adsorption unit under the action of the main exhaust fan;

[0110] Step 2: When the PLC control device determines that the concentration of VOCs exhaust gas is 400 mg / m 3 When the temperature is higher than 0.040°C, the system enters the direct-fired working state, at which time the valve of the first air intake pipe is opened, and the direct-fired fan starts to run; the exhaust gas from the air intake manifold enters the combustion chamber of the RTO direct-fired furnace through the first air intake pipe for combustion treatment, and the frequency of the direct-fired fan is adjusted according to the change of the intake air concentration during the treatment process; the treated gas is passed into the exhaust pipe through the RTO exhaust pipe of the RTO direct-fired furnace;

[0111] Step three: after the activated carbon box of the adsorption unit has been adsorbed for a predetermined time, the activated carbon box is switched, and the activated carbon box that is saturated with adsorption is desorbed, and the system enters the desorption condition; at this time, the air supply valve of the second air supply duct is opened, and the regulating valve of the heat extraction duct is opened, and the clean air introduced from the second air supply duct and the air entering the desorption unit from the heat extraction duct of the RTO direct-fired furnace are mixed in the mixing tank of the desorption unit to form a desorbed gas, and the desorbed gas is transported to the adsorption unit through the desorption duct to desorb the adsorbed substances in the fixed bed of the adsorption unit; and the valve of the second air inlet duct is opened, and the gas generated after desorption in the adsorption unit is introduced into the RTO direct-fired furnace through the second air inlet duct for further combustion treatment;

[0112] Step 4: Under the desorption condition, when the VOCs exhaust gas concentration of the intake manifold is at 300 mg / m 3 and below, the step 1 and the step 3 are performed simultaneously; and when the adsorption condition and the desorption condition are performed simultaneously, the direct-fired blower operates at a low frequency; when the VOCs exhaust gas concentration of the intake manifold is at 400 mg / m 3 When the temperature is higher than 0.1°C, the step 2 and the step 3 are performed simultaneously, and when the direct-fired working condition and the desorption working condition are performed simultaneously, the direct-fired fan operates at a normal frequency;

[0113] Step 5: After the desorption is completed, the system enters the cooling state, the regulating valve of the heat extraction pipeline of the RTO direct-fired furnace is closed, and the clean cold air in the temperature mixing tank is introduced into the activated carbon box through the second air supply pipeline, and the temperature of the activated carbon box is reduced to below 50°C, and the cooled exhaust gas is introduced into the RTO direct-fired furnace through the second air intake pipeline for combustion treatment;

[0114] Step six: After the desorption of the adsorption unit is completed and the system is in the adsorption condition, the first air inlet duct and the second air inlet duct of the RTO direct-fired furnace are both in a closed state. At this time, the system enters the insulation condition, clean air is introduced into the air inlet duct of the RTO direct-fired furnace, and the direct-fired fan is operated at a frequency of 10 Hz to insulate the RTO direct-fired furnace.

[0115] According to the exhaust gas treatment system described in Example 1, when the concentration of organic waste gas in the intake manifold is low, the system enters an adsorption condition and uses an adsorption unit for adsorption treatment. When the concentration of organic waste gas in the intake manifold is high, the system enters a direct combustion condition and uses an RTO direct combustion furnace for combustion treatment. After the adsorption reaches a predetermined time, the system enters a desorption condition, switches the activated carbon box of the adsorption unit, and desorbs the activated carbon box that is saturated with adsorption. Since the desorption process takes a long time, during the desorption process, when the concentration of organic waste gas in the intake manifold is still low, desorption and adsorption are carried out simultaneously. When the concentration of organic waste gas in the intake manifold is high, desorption and direct combustion are carried out simultaneously. When the desorption condition ends, the system enters a cooling condition and cools the adsorption unit. And, when both desorption and direct combustion end, the system enters a heat preservation condition. Specifically, the system of the present invention can also work under the following conditions:

[0116] Normal working conditions:

[0117] When the PLC control device receives the VOCs exhaust gas concentration of 300mg / m 3 When the temperature is below 400 °C, the valve of the adsorption pipe is opened, and the main exhaust fan is started to run, and its running frequency is, for example, 42 Hz. This is because the fan generally does not work at full frequency (50 Hz), which can protect the equipment. The exhaust gas from the intake manifold enters the activated carbon box of the adsorption unit through the adsorption pipe for adsorption; and in the system of the present invention, the activated carbon box is set to be connected in parallel, and two or more activated carbon boxes can be opened at the same time for adsorption treatment. After the activated carbon box is saturated with adsorption, the PLC control device switches the activated carbon box according to the predetermined adsorption time, and at the same time, the saturated activated carbon box is desorbed.

[0118] When the concentration of VOCs is 400mg / m 3 When the temperature reaches 0.1°C or above, the valve of the first air inlet duct is opened, and the direct-fired blower is started to operate; the exhaust gas from the air inlet main pipe enters the combustion chamber of the RTO direct-fired furnace through the first air inlet duct for combustion treatment.

[0119] More specifically, when the concentration of VOCs is 400 mg / m 3 -600mg / m 3 When it is within the range, the direct-fired fan is operated at 38Hz; optionally, when the concentration of organic waste gas in the RTO direct-fired furnace cannot reach the temperature for complete oxidation, it can be compensated by further electric heating. At the same time, through low-frequency operation, the waste gas treatment is guaranteed to meet the standards under the premise of meeting production.

[0120] When the concentration of VOCs is 650mg / m 3 -850mg / m 3When it is within the range, the direct-fired fan is operated at 42Hz and treated by the RTO direct-fired furnace; optionally, when the temperature does not reach the temperature for complete oxidation, it is compensated by further electric heating. At the same time, through normal frequency operation, the exhaust gas treatment is guaranteed to meet the standards while meeting the production requirements.

[0121] When the concentration of VOCs is 900mg / m 3 When the above conditions are met, the direct-fired fan is operated at 45 Hz and can also be operated by further electric heating auxiliary heat source.

[0122] When the concentration of VOCs does not rise to the above range, it will operate under the original working conditions; this can ensure that the system will not frequently switch working conditions due to concentration fluctuations to ensure the stability of equipment operation; because the concentration change is a momentary value, if the production workshop keeps shaking around this concentration, it will cause frequent switching of valves. Therefore, the designed concentration range is an interval, and the concentration exceeds 400mg / m 3 , and it takes 1 minute to switch to direct combustion conditions; when the concentration is continuously lower than 300mg / m 3 , and it must last for a full minute before it can be switched to the adsorption state.

[0123] Desorption and direct combustion conditions:

[0124] When the activated carbon adsorption of the adsorption unit reaches the set adsorption time, the high-temperature gas taken out from the RTO direct-fired furnace and the clean air introduced into the second air supply pipe are mixed in the mixing tank by opening the regulating valve of the heat extraction pipe and the air supply valve of the second air supply pipe, and are transported to the activated carbon box of the adsorption unit through the desorption pipe. The adsorbed activated carbon is thermally desorbed, and the temperature of the desorbed gas is controlled at 130°C. The hot air entering the adsorption unit through the desorption pipe can desorb the substances adsorbed in the activated carbon, and the desorption operation is performed in the adsorption unit. The desorbed gas is connected to the RTO direct-fired furnace through a second air intake pipe; under the operation of the direct-fired fan, the desorbed gas and the exhaust gas entering from the air intake manifold are sent into the RTO direct-fired furnace for combustion, and the PLC control device can control the valve opening of the second air intake pipe according to the combustion temperature in the RTO direct-fired furnace. Once the concentration of the desorbed gas is too high, causing the furnace in the RTO direct-fired furnace to overheat, the valve opening of the second air intake pipe is reduced to reduce the delivery of the desorbed gas to ensure the furnace temperature.

[0125] Desorption and adsorption conditions:

[0126] When the exhaust gas concentration in the air intake main is very low, the system is in adsorption condition and an adsorption unit is used for adsorption treatment. At this time, since the first air intake duct of the RTO direct-fired furnace is closed and only the second air intake duct is open, the frequency of the direct-fired fan is reduced to 20HZ to ensure the air volume requirement of the desorbed gas, and the desorption temperature is also controlled at 130°C to ensure the desorption of activated carbon in the fixed bed.

[0127] Cooling conditions:

[0128] After the desorption of the activated carbon box in the adsorption unit is completed, the regulating valve of the heat extraction pipe of the desorption unit is closed, so that the clean cold air in the mixing tank passed through the second air supply pipe directly enters the activated carbon box, and the temperature of the activated carbon box is reduced to below 50°C. The cooled exhaust gas enters the RTO direct-fired furnace through the second air intake pipe for combustion treatment.

[0129] Insulation conditions:

[0130] When the desorption of the system is completed and the system is in the adsorption state, the first air inlet duct and the second air inlet duct of the RTO direct-fired furnace are both in a closed state. At this time, clean air is introduced into the air inlet duct of the RTO direct-fired furnace, and the direct-fired fan is operated at a frequency of 10 Hz to keep the RTO direct-fired furnace warm.

[0131] According to the technical solution of the present invention, optionally, the PLC control device further includes an over-temperature alarm unit, and the system can include a temperature alarm condition:

[0132] When the temperature in the activated carbon box exceeds 150°C, there will be a risk of spontaneous combustion; when the regulating valve of the heat extraction pipeline fails, causing the gas temperature in the activated carbon box to exceed 140°C, the over-temperature alarm unit will sound an alarm, and the PLC control device will close the valve for the gas to enter the activated carbon box, and at the same time open the solenoid valve of the nitrogen pipeline arranged in the activated carbon box, and automatically close after the PLC control device determines that the temperature of the activated carbon box has dropped to 60°C.

[0133] The over-temperature alarm unit of the PLC control device can also be used to alarm when the RTO direct-fired furnace is over-heated. The temperature of a normal RTO direct-fired furnace is controlled between 760°C and 850°C. When its temperature exceeds 950°C, it is considered that the RTO direct-fired furnace is in an over-temperature condition. This condition generally occurs during the desorption process due to the excessively high concentration of the desorbed organic waste gas. Therefore, the PLC control device controls the valve opening of the second air inlet pipe through the anemometer of the desorption pipe to control the concentration of the desorbed waste gas entering the RTO furnace. If it still increases, the desorption regulating valve of the RTO direct-fired furnace is opened to discharge part of the high-temperature gas in the RTO furnace into the atmosphere to ensure the normal operation of the furnace.

[0134] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An RTO waste gas treatment system using electrical heating, characterized in that: The system includes an air intake main pipe, an adsorption unit, an RTO direct-fired furnace, a desorption unit and an exhaust pipe, wherein the air intake main pipe of the system is connected to a VOCs concentration detector, the VOCs concentration detector is connected to the adsorption unit through an adsorption pipe, and is connected to the RTO direct-fired furnace through a first air intake pipe, the adsorption unit is connected to the exhaust pipe through an adsorption unit exhaust pipe, and a main exhaust fan is provided on the adsorption unit exhaust pipe, the main exhaust fan is used to provide power, so that the exhaust gas in the air intake main pipe enters the adsorption unit, and the gas adsorbed by the adsorption unit is discharged to the exhaust pipe through the adsorption unit exhaust pipe; the RTO direct-fired furnace is connected to the exhaust pipe through the RTO exhaust pipe, and a direct-fired fan is provided on the RTO exhaust pipe, the direct-fired fan is used to provide power, so that the exhaust gas in the air intake main pipe enters the RTO direct-fired furnace, and the gas after combustion treatment in the RTO direct-fired furnace is passed into the exhaust pipe; the desorption unit is connected to the adsorption unit through a desorption pipe, and the adsorption unit is connected to the RTO direct-fired furnace through a second air intake pipe; The system further includes a PLC control device, which is electrically connected to the VOCs concentration detector and can receive signals from the VOCs concentration detector, and the PLC control device can also be connected to a pipeline valve in the system to control the exhaust gas treatment working condition of the system; In the RTO direct-fired furnace, the upper area is the combustion chamber of the RTO direct-fired furnace, and a plurality of silicon carbon rods are arranged in the combustion chamber to provide combustion temperature for the combustion chamber of the RTO direct-fired furnace; Furthermore, each silicon carbon rod is arranged to penetrate the upper part of the RTO direct-fired furnace from front to back, and one end of the silicon carbon rod is fixed, and the other end is movably connected, so that the silicon carbon rod can have a deformation space; Each silicon carbon rod has a terminal at both ends, and the terminal is connected to an external heating box through a wire to electrically heat the plurality of silicon carbon rods; An induced draft fan is provided at the connection terminals at both ends of the silicon carbon rod connected to the external heating box of the RTO direct-fired furnace, and the pipeline of the induced draft fan is sealed. The induced draft fan is used to cool the connection terminals during the heating of the silicon carbon rod.

2. The system according to claim 1, characterized in that The VOCs concentration detector of the system is connected to the adsorption pipe of the adsorption unit and the first air intake pipe connected to the RTO direct-fired furnace, and valves are respectively provided; and a valve is provided on the second air intake pipe.

3. The system according to claim 1, characterized in that The desorption unit is connected to the RTO direct-fired furnace through a heat extraction pipeline and extracts heat from the RTO direct-fired furnace; a regulating valve is provided on the heat extraction pipeline; The desorption unit can also be supplied with clean air through a second air supply duct, and an air supply valve is arranged on the second air supply duct.

4. The system according to claim 1, characterized in that The adsorption unit can be configured as a plurality of activated carbon boxes connected in parallel, and in the adsorption condition, after the activated carbon box adsorbs for a predetermined time, the activated carbon box is switched to the desorption condition, and a new activated carbon box is connected to adsorb the exhaust gas.

5. The system according to claim 1, characterized in that The desorption process of the adsorption unit is as follows: the clean air introduced from the second air supply duct and the heat-taking gas introduced into the desorption unit from the heat-taking duct of the RTO direct-fired furnace are mixed in the mixing tank of the desorption unit to form a desorbed gas, which is transported to the adsorption unit through the desorption duct to desorb the substances adsorbed by the activated carbon in the fixed bed of the adsorption unit; and the gas formed after desorption in the adsorption unit can be introduced into the RTO direct-fired furnace through the second air inlet duct for combustion treatment.

6. The system according to claim 1, characterized in that The RTO direct-fired furnace has chamber A, chamber B and chamber C arranged at the lower part of the combustion chamber, and heat storage bodies are arranged in the middle of chamber A, chamber B and chamber C respectively; The A chamber, B chamber and C chamber of the RTO direct-fired furnace are independent of each other, and the upper parts of the A chamber, B chamber and C chamber are connected to the combustion chamber; the lower parts of the A chamber, B chamber and C chamber are the air intake and exhaust ducts of the RTO direct-fired furnace, and the air intake ports, exhaust ports, and air supply ports are respectively provided in the air intake and exhaust ducts of the A chamber, B chamber and C chamber.

7. A method for treating RTO waste gas using electric heating, characterized in that: The method adopts the system according to any one of claims 1 to 6, and the method comprises the following steps: Step 1: Use a VOCs concentration detector to detect the concentration of VOCs exhaust gas in the intake manifold. The PLC control device makes a judgment based on the concentration detected by the VOCs concentration detector. When the concentration is above 300 mg / m 3 When the system enters the adsorption state, the valve of the adsorption pipe is opened and the main exhaust fan starts to run; the exhaust gas from the air intake manifold enters the activated carbon box of the adsorption unit through the adsorption pipe for adsorption, and the adsorbed gas is passed into the exhaust pipe through the adsorption unit exhaust pipe of the adsorption unit under the action of the main exhaust fan; Step 2: When the PLC control device determines that the concentration of VOCs exhaust gas is 400 mg / m 3 When the temperature is higher than 0.040°C, the system enters the direct-fired working state, at which time the valve of the first air intake pipe is opened, and the direct-fired fan starts to run; the exhaust gas from the air intake manifold enters the combustion chamber of the RTO direct-fired furnace through the first air intake pipe for combustion treatment, and the frequency of the direct-fired fan is adjusted according to the change of the intake air concentration during the treatment process; the treated gas is passed into the exhaust pipe through the RTO exhaust pipe of the RTO direct-fired furnace; Step three: after the activated carbon box of the adsorption unit has been adsorbed for a predetermined time, the activated carbon box is switched, and the activated carbon box that is saturated with adsorption is desorbed, and the system enters the desorption condition; at this time, the air supply valve of the second air supply duct is opened, and the regulating valve of the heat extraction duct is opened, and the clean air introduced from the second air supply duct and the air entering the desorption unit from the heat extraction duct of the RTO direct-fired furnace are mixed in the mixing tank of the desorption unit to form a desorbed gas, and the desorbed gas is transported to the adsorption unit through the desorption duct to desorb the adsorbed substances in the fixed bed of the adsorption unit; and the valve of the second air inlet duct is opened, and the gas generated after desorption in the adsorption unit is introduced into the RTO direct-fired furnace through the second air inlet duct for combustion treatment; Step 4: Under the desorption condition, when the VOCs exhaust gas concentration of the intake manifold is at 300 mg / m 3 and below, the step 1 and the step 3 are performed simultaneously, and when the adsorption condition and the desorption condition are performed simultaneously, the direct-fired blower operates at a low frequency; when the VOCs exhaust gas concentration of the intake manifold is at 400 mg / m 3 When the temperature is higher than 0.1°C, the step 2 and the step 3 are performed simultaneously, and when the direct-fired working condition and the desorption working condition are performed simultaneously, the direct-fired fan operates at a normal frequency; Step 5: After the desorption is completed, the system enters the cooling state, the regulating valve of the heat extraction pipeline of the RTO direct-fired furnace is closed, and the clean cold air in the temperature mixing tank is introduced into the activated carbon box through the second air supply pipeline, and the temperature of the activated carbon box is reduced to below 50°C, and the cooled exhaust gas is introduced into the RTO direct-fired furnace through the second air intake pipeline for combustion treatment; Step six: After the desorption of the adsorption unit is completed and the system is in the adsorption condition, the valves of the first air inlet pipe and the second air inlet pipe of the RTO direct-fired furnace are closed. At this time, the system enters the insulation condition, clean air is introduced into the air inlet pipe of the RTO direct-fired furnace, and the direct-fired fan is operated at a low frequency to insulate the RTO direct-fired furnace.

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