A continuous monitoring pretreatment system for waste gas non-methane hydrocarbon
By combining gradient heat tracing pipelines and self-cleaning filters, the problems of gas composition distortion and pipeline blockage in the exhaust gas non-methane total hydrocarbon monitoring system are solved, achieving stable transmission of gas composition and accurate monitoring.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- JIANGSU LANCHAUNG INFORMATION TECH SERVICESCO LTD
- Filing Date
- 2025-07-16
- Publication Date
- 2026-07-24
AI Technical Summary
In existing waste gas non-methane total hydrocarbon monitoring systems, uneven heating in the sampling pipeline leads to localized condensation or high-temperature decomposition of the gas, resulting in distorted composition. Traditional filtration devices require frequent shutdowns to replace filter elements and are not thoroughly cleaned, leading to pipeline blockage.
The system employs a gradient heat tracing pipeline and a self-cleaning filter. The gradient heat tracing pipeline creates a temperature gradient field by winding the heat tracing tape in stages, preventing gas condensation or high-temperature pyrolysis. The self-cleaning filter achieves automatic cleaning through three-stage filtration and backflushing of the gas path, ensuring the stability of gas composition and unobstructed pipeline flow.
Thermodynamic equilibrium of gas components during transmission is achieved, avoiding gas composition distortion and pipeline blockage, and improving monitoring accuracy and system stability.
Smart Images
Figure CN224553218U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of non-methane total hydrocarbon monitoring technology in waste gas, and particularly relates to a pretreatment system for continuous monitoring of non-methane total hydrocarbons in waste gas. Background Technology
[0002] In the monitoring of volatile organic compounds (VOCs) in organized waste gas, production processes often involve the emission of VOCs at varying temperatures and with different compositions. Monitoring instruments require multiple emissions for effective monitoring. Therefore, ensuring the composition of the detected gas remains unchanged necessitates high-temperature heating of the gas pipeline, large-particle filtration, and a pretreatment system to control and process the entire gas path to maintain pipeline cleanliness. However, in existing waste gas non-methane total hydrocarbon monitoring systems, uneven heating in the sampling pipeline often leads to localized condensation or high-temperature decomposition of the gas, resulting in distorted composition. Furthermore, traditional filtration devices require frequent shutdowns to replace filter elements, and incomplete backflushing cleaning further exacerbates pipeline blockage due to particulate matter accumulation. Summary of the Invention
[0003] Purpose of the invention: In order to overcome the shortcomings of the existing technology, this utility model provides a pretreatment system for continuous monitoring of non-methane total hydrocarbons in exhaust gas. Through gradient heating and self-cleaning filtration, it avoids gas composition distortion and pipeline blockage, thereby improving monitoring accuracy.
[0004] Technical solution: To achieve the above objectives, this utility model provides a continuous monitoring and pretreatment system for non-methane total hydrocarbons in exhaust gas, comprising a PLC control unit, a high-temperature sampling pump, a gradient heat tracing pipeline, a self-cleaning filter device, a high-temperature chamber, and a solid-state relay group.
[0005] The gradient heat tracing pipeline runs through the high-temperature chamber, with its inlet connected to the outlet of the self-cleaning filter and its outlet connected to the inlet of the high-temperature sampling pump.
[0006] The input terminal of the solid-state relay group is electrically connected to the digital output module of the PLC control unit, and the output terminal is electrically connected to the gradient heat tracing pipeline, the high-temperature chamber and the high-temperature sampling pump respectively.
[0007] The backflush solenoid valve of the self-cleaning filter is electrically connected to the PLC control unit through the control relay in the solid-state relay group.
[0008] Furthermore, the gradient heat tracing pipe route includes, from the inside out, an air duct, a heat tracing tape, an insulation layer, and a heat tracing temperature sensor; the heat tracing tape is wrapped around the outer wall of the air duct, and its winding density gradually decreases along the airflow direction to form a temperature gradient field; the detection end of the heat tracing temperature sensor is embedded in the insulation layer, and the signal output end is connected to the PLC control unit.
[0009] Furthermore, the high-temperature chamber is equipped with a temperature sensor, the signal output of which is connected to a PLC control unit.
[0010] Furthermore, the high-temperature chamber is equipped with a hot air circulation fan, the air outlet of which is directly opposite the outlet section of the gradient heat tracing pipeline where the heat tracing tape is wrapped, forming an auxiliary heat tracing air curtain.
[0011] Furthermore, the solid-state relay group includes a first relay electrically connecting the PLC control unit to the heating cable, a second relay electrically connecting the PLC control unit to the heater of the high-temperature chamber, a third relay electrically connecting the PLC control unit to the high-temperature sampling pump, and a fourth relay electrically connecting the PLC control unit to the backflush solenoid valve of the self-cleaning filter device.
[0012] Furthermore, the self-cleaning filtration device comprises a three-stage filtration unit consisting of a cyclone separator, a sintered metal filter element, and a polytetrafluoroethylene membrane filter layer arranged sequentially along the airflow direction.
[0013] Furthermore, the self-cleaning filter is equipped with a backflush air path, which is connected to a compressed air source through a backflush solenoid valve.
[0014] Furthermore, the metal sintered filter element and the polytetrafluoroethylene membrane filter layer are detachably connected by a connector.
[0015] Beneficial Effects: This invention utilizes a gradient heat tracing pipeline design, where the density of the heat tracing cable gradually decreases along the airflow direction, naturally creating a temperature gradient field within the pipeline that smoothly transitions from high to medium temperatures. The high-density winding at the inlet section ensures instantaneous and complete gas vaporization, preventing liquid component residue; the sparse winding at the outlet section maintains a moderate temperature, effectively suppressing the risk of high-temperature decomposition. Furthermore, hot air compensates for heat loss at the pipeline's end, completely eliminating the risk of condensation. This gradient heat tracing structure keeps the gas components in thermodynamic equilibrium throughout the transmission process, fundamentally solving the dual distortion problems of gas decomposition and condensation caused by traditional uniform heating. Attached Figure Description
[0016] Figure 1 This is a system block diagram of the present invention;
[0017] Figure 2 This is a schematic diagram of the gradient heat tracing pipeline structure;
[0018] Figure 3 This is a schematic diagram of a self-cleaning filter device.
[0019] Figure 4 This is a structural block diagram showing the electrical connections of the PLC control unit, solid-state relay group, high-temperature sampling pump, heating tape, high-temperature chamber, and backflush solenoid valve. Detailed Implementation
[0020] The present invention will be further described below with reference to the accompanying drawings.
[0021] like Figure 1 As shown, a continuous monitoring and pretreatment system for non-methane total hydrocarbons in exhaust gas includes a PLC control unit 1, a high-temperature sampling pump 2, a gradient heat tracing pipeline 3, a self-cleaning filter device 4, a high-temperature chamber 5, and a solid-state relay group 6. The gradient heat tracing pipeline 3 passes through the high-temperature chamber 5, with its inlet connected to the outlet of the self-cleaning filter device 4 and its outlet connected to the inlet of the high-temperature sampling pump 2. The input terminal of the solid-state relay group 6 is electrically connected to the digital output module of the PLC control unit 1, and its output terminal is electrically connected to the gradient heat tracing pipeline 3, the high-temperature chamber 5, and the high-temperature sampling pump 2, respectively. The backflush solenoid valve 45 of the self-cleaning filter device 4 is electrically connected to the PLC control unit 1 through the control relay in the solid-state relay group 6. A hard connection is achieved by using a solid-state relay resistor 6, eliminating the command delay of traditional bus communication. This enables rapid response for heating temperature regulation, sampling start / stop, and backflush triggering. Furthermore, the backflush action is directly driven by the current cylinder of the PLC, relay, and solenoid valve, avoiding malfunctions caused by fluctuations in the solenoid valve's voltage, such as premature or delayed backflush. This ensures accurate and controllable residence time of gas in the pipeline, maintaining the chemical stability of non-methane total hydrocarbons.
[0022] like Figure 2 As shown, the gradient heat tracing pipeline 3 includes, from the inside out, a gas guide pipe 31, a heat tracing tape 32, an insulation layer 33, and a heat tracing temperature sensor 34. The heat tracing tape 32 is wound around the outer wall of the gas guide pipe 31, with its winding density gradually decreasing along the airflow direction to form a temperature gradient field. It is wound at a high density at the inlet, preferably 8 turns / cm, and at a low density at the outlet, preferably 4 turns / cm, to achieve a power density gradient distribution through the difference in resistance per unit length. Therefore, at the inlet section, the high power density rapidly vaporizes liquid volatile organic compounds, while at the outlet section, the low power density continuously undergoes high-temperature decomposition, keeping the gas within the thermodynamic safety window of 120~180℃ throughout the entire process. The detection end of the heat tracing temperature sensor 34 is embedded in the insulation layer 33, and the signal output end is connected to the PLC control unit 1. The heat tracing temperature sensor 34 fits tightly against the pipe wall, thereby reducing side temperature errors and preventing distortion in gas volume calculations caused by temperature drift from the source.
[0023] The high-temperature chamber 5 is equipped with a temperature sensor 51 to monitor the temperature inside the chamber in a timely manner, and its signal output terminal is connected to the PLC control unit 1.
[0024] Because the tracing tape 32 at the outlet section is sparsely wound, heat loss may occur, leading to condensation points at the end. To avoid this, in this invention, a hot air circulating fan 52 is installed inside the high-temperature chamber 5. Its outlet is directly opposite the winding area of the tracing tape 32 at the outlet section of the gradient heat tracing pipeline 3, forming an auxiliary heat tracing air curtain. This compensates for the radial heat loss caused by the sparse winding at the outlet section and completely eliminates condensation points at the end. The winding density of the tracing tape 32 in the outlet section is 3~5 turns / cm, and the starting position of this section is less than or equal to 30 cm from the outlet of the gradient heat tracing pipeline 3. Experimental results show that when the winding density of the inlet section is 8 turns / cm, the maintained temperature is 182±3℃, and no hot air assistance is required; when the winding density of the outlet section is 5 turns / cm, the maintained temperature is 126±5℃, and hot air assistance is required; when the winding density of the outlet section is 3 turns / cm, the maintained temperature is 118±8℃, and hot air assistance is required.
[0025] like Figure 4 As shown, the solid-state relay group 6 includes a first relay 61 electrically connecting the PLC control unit 1 to the heating cable 32, a second relay 62 electrically connecting the PLC control unit 1 to the heater of the high-temperature chamber 5, a third relay 63 electrically connecting the PLC control unit 1 to the high-temperature sampling pump 2, and a fourth relay 64 electrically connecting the PLC control unit 1 to the backflush solenoid valve 45 of the self-cleaning filter device 4. There is no shared circuit between the output terminals of each relay and the actuator, achieving fault-safe isolation. For example, when the heating cable 32 is short-circuited, only the first relay 61 melts, while the high-temperature sampling pump 2 and the backflush solenoid valve 45 can still operate.
[0026] like Figure 3 As shown, the self-cleaning filtration device 4 comprises a three-stage filtration unit arranged sequentially along the airflow direction: a cyclone separator 41, a sintered metal filter element 42, and a polytetrafluoroethylene (PTFE) membrane filter layer 43. The cyclone separator 41 filters particles larger than or equal to 10 micrometers, the sintered metal filter element 42 intercepts particles from 1 to 10 micrometers, and the PTFE membrane filter layer 43 captures aerosols smaller than 1 micrometer, achieving a step-by-step interception and filtration effect with good filtration efficiency and avoiding clogging.
[0027] like Figure 1 and Figure 3 As shown, the self-cleaning filter device 4 is equipped with a backflush air path 44, which is connected to a compressed air source 46 through a backflush solenoid valve 45. The PLC control unit 1 triggers the backflush execution command based on time periodically, and the airflow is pulsed back from the polytetrafluoroethylene membrane filter layer 43 to the cyclone separator 41.
[0028] like Figure 3 As shown, the metal sintered filter element 42 and the polytetrafluoroethylene membrane filter layer 43 are detachably connected by a connector 47, which is preferably a mounting bolt.
[0029] In summary, this invention, through the structural design of a gradient heat tracing pipeline, achieves a gradual decrease in the density of the heat tracing cable along the airflow direction, naturally forming a temperature gradient field within the pipeline that smoothly transitions from high to medium temperatures. Specifically, the high-density winding at the inlet section ensures instantaneous and complete gas vaporization, preventing the residue of liquid components; the sparse winding at the outlet section maintains a moderate temperature, effectively suppressing the risk of high-temperature decomposition. Furthermore, hot air compensates for heat loss at the pipeline end, completely eliminating the risk of condensation. This gradient heat tracing structure keeps the gas components in thermodynamic equilibrium throughout the transmission process, fundamentally solving the dual distortion problem of gas decomposition and condensation caused by traditional uniform heating.
[0030] like Figure 1 As shown, the focus of this utility model is the pretreatment before gas monitoring. Before pretreatment, a rotor flow meter 1.2 is included, and after pretreatment, a chromatograph 1.1 is included. The standard gas enters the pretreatment system through the rotor flow meter 1.2, and then enters the chromatograph for calibration. After calibration, under the power of the high-temperature sampling pump 2, the sample gas is introduced through the rotor flow meter 1.2 into the sample gas storage chamber 1.3 of the high-temperature chamber 5 to the required volume of gas. The sample gas then enters the three-way pipe 1.4 through the self-cleaning filter device 4 and the gradient heating pipeline 3. The two outlets of the three-way pipe 1.4 are divided into two gas paths. The first gas path leads to the chromatograph 1.1 through the pneumatic valve 1.5, and the second gas path leads to the outside of the high-temperature chamber 5 through the manual valve 1.6, which is to vent the gas.
[0031] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.
Claims
1. A continuous monitoring and pretreatment system for non-methane total hydrocarbons in exhaust gas, characterized in that: It includes a PLC control unit (1), a high-temperature sampling pump (2), a gradient heat tracing pipeline (3), a self-cleaning filter device (4), a high-temperature chamber (5), and a solid-state relay group (6). The gradient heat tracing pipeline (3) runs through the high temperature box (5), with its inlet connected to the outlet of the self-cleaning filter device (4) and its outlet connected to the inlet of the high temperature sampling pump (2). The input terminal of the solid-state relay group (6) is electrically connected to the digital output module of the PLC control unit (1), and the output terminal is electrically connected to the gradient heat tracing pipeline (3), the high temperature box (5) and the high temperature sampling pump (2) respectively. The backflush solenoid valve (45) of the self-cleaning filter device (4) is electrically connected to the PLC control unit (1) through the control relay in the solid-state relay group (6).
2. The waste gas non-methane total hydrocarbon continuous monitoring and pretreatment system according to claim 1, characterized in that: The gradient heat tracing pipeline (3) includes, from the inside out, an air duct (31), a heat tracing tape (32), an insulation layer (33), and a heat tracing temperature sensor (34); the heat tracing tape (32) is wrapped around the outer wall of the air duct (31), and its winding density gradually decreases along the airflow direction to form a temperature gradient field; the detection end of the heat tracing temperature sensor (34) is embedded in the insulation layer (33), and the signal output end is connected to the PLC control unit (1).
3. The waste gas non-methane total hydrocarbon continuous monitoring and pretreatment system according to claim 2, characterized in that: The high-temperature chamber (5) is equipped with a temperature sensor (51), whose signal output terminal is connected to the PLC control unit (1).
4. The waste gas non-methane total hydrocarbon continuous monitoring and pretreatment system according to claim 3, characterized in that: The high-temperature box (5) is equipped with a hot air circulation fan (52), whose air outlet is directly opposite the tracing area of the outlet section of the gradient heat tracing pipe (3) and the tracing tape (32) to form an auxiliary heat tracing air curtain.
5. The waste gas non-methane total hydrocarbon continuous monitoring and pretreatment system according to claim 2, characterized in that: The solid-state relay group (6) includes a first relay (61) electrically connecting the PLC control unit (1) to the heating cable (32), a second relay (62) electrically connecting the PLC control unit (1) to the heater of the high-temperature chamber (5), a third relay (63) electrically connecting the PLC control unit (1) to the high-temperature sampling pump (2), and a fourth relay (64) electrically connecting the PLC control unit (1) to the backflush solenoid valve (45) of the self-cleaning filter device (4).
6. The waste gas non-methane total hydrocarbon continuous monitoring and pretreatment system according to claim 1, characterized in that: The self-cleaning filter device (4) includes a three-stage filtration unit consisting of a cyclone separator (41), a sintered metal filter element (42), and a polytetrafluoroethylene membrane filter layer (43) arranged sequentially along the airflow direction.
7. The waste gas non-methane total hydrocarbon continuous monitoring and pretreatment system according to claim 6, characterized in that: The self-cleaning filter device (4) is provided with a backflush air passage (44), which is connected to a compressed air source (46) through a backflush solenoid valve (45).
8. The waste gas non-methane total hydrocarbon continuous monitoring and pretreatment system according to claim 6, characterized in that: The metal sintered filter element (42) and the polytetrafluoroethylene membrane filter layer (43) are detachably connected by a connector (47).