The laboratory exhaust gas treatment system is a specialized environmental protection system that collects, purifies, and processes toxic, harmful, flammable, and explosive gases (such as volatile organic compounds VOCs, acidic gases, alkaline gases, sulfur/nitrogen-containing gases, etc.) generated during laboratory operations. It ensures these gases meet national emission standards (such as the Comprehensive Emission Standard for Air Pollutants GB 16297) before being released. This system is crucial for the health of laboratory personnel, the safety of surrounding environments, and environmental compliance, and is widely used in fields such as chemistry, pharmaceuticals, materials, and environmental testing.
System Design Key Standards and Specifications
The laboratory exhaust treatment system must strictly comply with national environmental protection standards (GB 16297, GB 37822 "Control Standard for Unorganized Emission of Volatile Organic Compounds") and industry regulations. The key design points are as follows:
1. Exhaust gas collection design standards
Capture Efficiency: Local exhaust (such as lab bench operations) requires a swivel exhaust hood (inlet air velocity ≥0.5m/s, hood mouth distance from exhaust source ≤30cm), and the cabinet exhaust (such as a fume hood) must maintain cabinet negative pressure (-5~-15Pa), with a capture efficiency ≥90%.
Pipe Design:
Pipe material must match the waste gas type (use PP pipe / FRP pipe for acidic waste gases, galvanized steel pipe / stainless steel pipe for organic waste gases to avoid corrosion or swelling).
Pipe velocity control: Acidic/alkaline waste gas ≤ 15m/s, VOCs waste gas ≤ 12m/s (to prevent excessive velocity causing pipe wear or waste gas retention).
Avoid dead ends: Use large-radius elbows (R≥3D, where D is the pipe diameter) at pipe bends, and connect branch pipes to main pipes with 45° offsets.
2. Design Standards for Main Purification Unit
Absorber Tower Design
Filling Material Selection: Polypropylene Pall Ring for acidic waste gas, ceramic filling for alkaline waste gas; filling layer height ≥ 1.5m.
Liquid to Gas Ratio: Acidic waste gas treatment liquid to gas ratio ≥ 2L/m³, alkaline waste gas ≥ 1.5L/m³.
Design of Activated Carbon Adsorption Tower
Activated Carbon Filling Quantity: Based on the exhaust air volume and concentration, the empty tower flow rate ≤ 0.8 m/s, and residence time ≥ 1.5 s.
Safety Design: The adsorption tower must be equipped with a explosion-proof valve and a CO concentration detector.
Catalytic combustion unit design:
Catalyst Selection: Ant poison-resistant catalyst required for treating sulfur/chlorine VOCs; space velocity ≤ 15,000 h⁻¹.
Preheat Temperature: During cold start, the exhaust gas needs to be preheated to the catalyst ignition temperature, using electric heating or waste heat recovery heating.
3. Emission and Safety Design Standards
Exhaust pipe requirements: The exhaust pipe height must be at least 3m higher than the laboratory roof, and at least 50m away from surrounding sensitive areas, with an exhaust velocity of no less than 5m/s.
Monitoring and Alarm
Exhaust outlets must be equipped with online monitoring devices.
Gas concentration detectors must be installed before and after the purification unit, and they need to be linked with the fan and valves.
Emergency Design: A bypass pipeline must be set up in the system.
IV. Routine Maintenance and Security Management
Regular maintenance content
Daily Inspection:
Check fan operating status.
Check the level of the absorption tower.
View online monitoring data.
Weekly Maintenance:
Clean the pre-treatment unit's filter.
Calibrate gas concentration detectors.
Monthly / Quarterly Maintenance:
Replace activated carbon.
Check catalyst activity.
Clean absorbent tower packing.
2. Safety Operating Procedures
Prior to starting the waste gas treatment system, the pretreatment unit must be activated first, followed by the fan to prevent untreated waste gas from being directly discharged.
When replacing activated carbon/catalyst, protective gear must be worn, and the used activated carbon/catalyst should be handled as hazardous waste by a qualified unit.
In the event of exhaust gas leakage, immediately shut down the equipment, close the exhaust source, activate emergency ventilation, and restart the system after the leakage is eliminated.
Regularly conduct emergency drills to ensure personnel are proficient in shutdown, evacuation, and rescue procedures.
3. Environmental Compliance Requirements
Regularly commission third-party testing agencies to sample and analyze exhaust emissions from exhaust outlets, issue test reports, and ensure compliance with emission standards.
Establish and maintain an operation and maintenance ledger, retaining it for at least 3 years for potential environmental inspection.
If there is a significant change in the composition or airflow of the laboratory waste gases, the treatment process must be re-evaluated, and the system may need to be modified if necessary, to prevent purification failure due to "mismatch."
