Online gas pretreatment system

1、 System Overview

Online gas pretreatment systemIt is a crucial component in industrial process analysis, environmental monitoring, scientific research experiments, and other fields. Its main function is to perform a series of physical and chemical treatments on raw gas samples collected from process pipelines or environments to remove interfering components, adjust gas states (such as temperature, pressure, flow rate), and meet the strict requirements of subsequent analytical instruments (such as gas chromatographs, mass spectrometers, infrared gas analyzers, laser gas analyzers, etc.) for injection conditions, ensuring the accuracy, reliability, and stability of analytical data. This system directly affects the quality of analysis results and the service life of analytical instruments, and is a prerequisite for achieving continuous, online, and accurate monitoring.

2、 Core functions and roles

1. Sample collection and transmissionCollect representative samples from the target gas source (such as pipelines, reaction vessels, atmospheric environment) through appropriate sampling probes, and transport the samples to the pre-processing unit through insulated or heat tracing sampling pipelines. The sampling probe should consider characteristics such as anti clogging, corrosion resistance, and high temperature resistance, while the sampling pipeline should avoid loss, adsorption, or deterioration of the sample during transmission.

2. Filter and purifyRemove solid particles (such as dust and smoke), liquid droplets (such as water mist and oil mist), and harmful chemical components (such as corrosive gases, water vapor, high boiling point organic compounds, etc.) that may cause damage or interfere with the analysis results from gas samples. Common filtration and purification components include precision filters, membrane filters, adsorption traps (such as activated carbon, molecular sieves, silica gel), etc.

3. temperature controlHeat or cool the sample gas to the appropriate operating temperature for the analytical instrument. For example, for high boiling point components that are prone to condensation, it is necessary to perform heat tracing and insulation on the sampling pipeline and pretreatment components to prevent component condensation loss; For temperature sensitive analytical instruments, it may be necessary to cool down the sample.

4. Pressure and flow regulationStabilize the pressure and flow rate of the sample gas within the range required by the analytical instrument. Usually through pressure reducing valves, stabilizing valves, needle valves, and mass flow controllers（MFC）Or components such as flow meters can be used to ensure a constant flow rate and stable pressure of the sample entering the analytical instrument, thereby improving the repeatability of the analysis results.

5. Dehumidification and dryingWhen the sample gas contains excessive moisture, it can interfere with the analysis of many gas components (such as infrared spectroscopy)CO₂Laser method for measuring certain gases may cause damage to internal components of the instrument. Dehumidification methods include freeze-drying, adsorption drying (such as using desiccants), and membrane drying. The appropriate dehumidification method should be selected based on the characteristics of the sample and analysis requirements to avoid loss of the target analytical component.

6. Component separation and enrichment (specific requirements)In some complex sample analyses, it may be necessary to pre separate or enrich specific components in the sample to improve analysis sensitivity or eliminate mutual interference between components. This may involve chromatographic column pre separation and solid-phase microextraction（SPME）Waiting for technology.

7. System status monitoring and alarmSome advanced preprocessing systems also have real-time monitoring functions for key parameters such as temperature, pressure, flow rate, filter blockage status, desiccant saturation status, etc., and can issue alarm signals when the parameters exceed the set range to remind operators to perform maintenance.

3、 Main components

1. Sampling probe/samplerDirectly in contact with the sample source, responsible for collecting the original sample. Common types include insertion probes, extraction probes, and probes with filters.

2. Sampling pipelineConnect the sampling probe to the preprocessing unit, usually made of stainless steel or polytetrafluoroethylene（PTFE）Wait, some parts need to be accompanied by a heating belt.

3. filterIncluding pre filter (coarse filter) and precision filter (fine filter), used to remove particulate matter and droplets. The filter material includes metal mesh, ceramic, polytetrafluoroethylene membrane, etc.

4. Drying deviceSuch as freeze dryersNafionDrying tube, adsorption drying tower (equipped with silica gel, molecular sieve, activated alumina, etc.).

5. Temperature control deviceHeating belt, constant temperature box, heat tracing pipeline controller, cooler, etc.

6. Pressure and flow control componentsPressure reducing valve, stabilizing valve, back pressure valve, needle valve, rotor flowmeter, mass flow controller（MFC）Pressure gauges, etc.

7. Valves and Switching DevicesElectromagnetic valves and pneumatic valves are used to switch sample flow paths and calibrate gases/Zero gas switching, reverse blowing and other functions.

8. pumpWhen the sample pressure is insufficient, a sampling pump is needed to extract the sample; Or it can be used when accelerating the sample update speed and overcoming system resistance.

9. Preprocessing chassis/cabinetIntegrate most of the preprocessing components mentioned above, provide a unified installation and operation platform, usually with dust-proof, waterproof, explosion-proof and other characteristics, suitable for industrial site environments.

10. Control and Monitoring Unit：PLCControllers, touch screens, sensors (temperature, pressure, flow sensors), alarms, etc., achieve automated control and status monitoring.

4、 Key technical features

1. representativenessThe primary principle of pre-processing system design is to ensure that the collected and processed samples can truly represent the composition and state of the original gas, avoiding sample distortion.

2. efficiencyQuick response, able to promptly reflect changes in sample gas, with short system lag time.

3. Stability and reliabilityThe system runs stably, has a low failure rate, a long maintenance cycle, and adapts to the complex and changing environment of industrial sites (such as high temperature, high humidity, dust, vibration, corrosive gases, etc.).

4. low lossDuring the preprocessing process, the loss of target analysis components, especially trace components, should be minimized as much as possible.

5. High degree of automationEquipped with automatic calibration, automatic blowback (to remove filter dust), automatic drainage, fault self diagnosis and alarm functions, reducing manual intervention and lowering operation and maintenance costs.

6. modular designThe system adopts modular design for each functional unit, which facilitates flexible combination, upgrade, and maintenance replacement according to different application requirements.

7. AdaptableCapable of handling gas samples under different operating conditions, such as high-temperature flue gas, high humidity gas, high dust gas, high-pressure gas, gas containing corrosive components, etc., and meeting the interface requirements of different analytical instruments.

5、 Typical application areas

1. Industrial process gas analysisSuch as petrochemical, coal chemical, steel metallurgy, and power (coal-fired power plant flue gas monitoring)CEMS）Used in industries such as cement and semiconductor manufacturing for online monitoring of gas component content in the process, optimizing production processes, ensuring product quality, and ensuring production safety.

2. Automatic monitoring of ambient air qualityRegarding the atmospheric environmentSO₂TheNOxTheCOTheO₃ThePM₂.₅TheVOCsContinuous automatic monitoring of pollutants.

3. Fixed pollution source exhaust gas monitoringPollutants in the flue gas emitted by industrial enterprises, such as dustSO₂TheNOxTheCOTheVOCsConduct online monitoring to meet environmental regulations.

4. vehicle emissionIn automobile emission testing, the exhaust gas is pre treated before entering the analyzer.

5. Scientific research experimentUnder laboratory conditions, precise pretreatment of various gas samples is carried out to complete research work in conjunction with various analytical instruments.

6. medical fieldGas pretreatment for occasions such as anesthesia gas monitoring and respiratory gas analysis.

7. Security monitoring and emergency monitoringOnline monitoring and warning of toxic and harmful gases in confined spaces and hazardous areas.

6、 Selection and configuration principles

1. Clearly define the analysis object and objectivesSelect an appropriate pretreatment plan based on the gas composition, concentration range, detection limit requirements, etc. that need to be analyzed.

2. Understand the characteristics of the sampleDetailed understanding of the temperature, pressure, flow rate, humidity, dust content, corrosiveness, and presence of condensates of the original sample gas.

3. Requirements for analytical instrumentsDesign the pretreatment process based on the specific requirements of the subsequent analytical instruments for injection conditions (temperature, pressure, flow rate, cleanliness, dryness).

4. On site environmental conditionsConsider factors such as temperature, humidity, dust, explosion-proof rating, and space size at the installation site.

5. System reliability and maintenance costsChoose mature and reliable technologies and components, considering the maintenance cycle, maintenance difficulty, and consumables cost of the system.

6. Compliance with regulations and standardsFor specific fields such as environmental monitoring, the pre-treatment system must comply with the requirements of relevant national or industry standards.

7. Flexibility and ScalabilityThe system should have a certain degree of flexibility to adapt to changes in sample conditions or analysis requirements, and consider possible future functional extensions.

Online gas pretreatment systemAs a bridge connecting sampling points and analytical instruments, its performance directly affects the success or failure of the entire online analysis system. In practical applications, careful system design, reasonable equipment selection, and standardized operation and maintenance are necessary based on specific analysis requirements, sample characteristics, and site conditions to ensure long-term stable and reliable operation. This provides accurate and effective data support for production process optimization, environmental monitoring, safety assurance, and more.