Precautions for using catalytic combustion equipment

Catalytic combustion equipment (CO), as the core environmental protection equipment for treating VOCs (volatile organic compounds (based on actual reports), must strictly follow the four core principles of "pretreatment control, catalytic reaction control, system maintenance, and safety protection" to ensure safe and stable operation, and avoid catalytic deactivation, equipment damage, and even safety accidents caused by improper operation. The following are detailed usage precautions:

1、 Preprocessing system: Confirm that the intake meets the catalytic reaction requirements (core prerequisite)

The core of catalytic combustion is the reaction between the catalyst and VOCs. If the intake contains impurities, dust, or excessive substances, it can directly cause catalyst poisoning, blockage, or equipment failure. Therefore, the pre-treatment process needs to be strictly controlled:

1. Intake concentration control (to prevent "flying temperature" and catalyst overload)

Strictly prohibit excessive concentration of intake: The intake concentration of VOCs must be controlled below 25% of the lower explosive limit (such as toluene with a lower explosive limit of 1.2%, the intake concentration must be ≤ 0.3%). If the concentration is too high (such as sudden emissions causing a sudden increase in concentration), it will cause excessive heat release in the catalytic reaction, leading to a sharp rise in the catalytic bed temperature (i.e. "flying temperature"), exceeding the catalyst tolerance temperature (such as precious metal catalysts with a tolerance temperature usually ≤ 400 ℃), causing long-term deactivation of the catalyst, and even burning of equipment.

Concentration monitoring and regulation: An "online VOCs concentration monitor" needs to be installed at the equipment inlet. When the concentration exceeds the set threshold (such as 20% of the lower explosive limit), the "dilution fan automatically starts" (fresh air is introduced to reduce concentration) or the "intake valve automatically closes" is triggered, and the front-end production equipment is linked to reduce VOCs emissions.

2. Filter impurities and dust in the intake (prevent catalyst blockage/poisoning)

Need to install pre-processing device:

If the treated exhaust gas contains dust (such as paint mist in spray painting exhaust gas, paper powder in printing exhaust gas), a "dry filter" (such as primary effect+medium effect filter cotton) or "wet spray tower" should be pre installed to confirm that the intake dust concentration is ≤ 10mg/m ³ (dust will cover the catalyst surface, block active sites, and cause a decrease in catalytic efficiency);

If the treated exhaust gas contains halogens and heavy metals (such as chlorine containing solvents and lead containing paint exhaust gas), it needs to be pre treated with an "adsorption tower (such as activated carbon adsorption)" or a "chemical neutralization device" to prevent such substances from reacting with catalysts (such as platinum and palladium) and causing "catalyst poisoning" (irreversible, requiring catalyst replacement).

3. Intake temperature control (to prevent catalyst deactivation at low temperatures)

Preheating temperature meets the standard: Catalytic reactions need to be carried out above the "ignition temperature" (such as toluene ignition temperature of about 250 ℃, benzene ignition temperature of about 300 ℃). If the intake temperature is too low (such as ambient temperature exhaust gas), the exhaust gas needs to be preheated to above the ignition temperature (usually preheated to 300-350 ℃) through "electric heating/gas heating", and then passed into the catalytic bed;

Avoid over temperature shock: The intake temperature should not exceed the "high tolerance temperature" of the catalyst (such as ceramic supported catalyst ≤ 450 ℃, metal supported catalyst ≤ 500 ℃). A "temperature sensor" should be installed at the inlet of the catalytic bed to trigger "cooling fan on" or "intake cut-off" when the temperature exceeds the limit.

2、 Catalytic reaction system: Real time monitoring of core parameters (confirming effectiveness)

1. Catalytic bed temperature monitoring (key among key)

Normal reaction temperature: The catalytic bed temperature should be stable at "ignition temperature+50-100 ℃" (such as when treating toluene, the catalytic bed temperature should be controlled at 300-350 ℃), and the temperature fluctuation range should be ≤± 20 ℃ (if the temperature is too low, the catalytic efficiency will decrease, and VOCs cannot be completely decomposed; Excessive temperature leads to catalyst sintering deactivation;

Exception handling:

If the temperature suddenly rises (such as exceeding 400 ℃): immediately turn on the "inert gas purge" (such as nitrogen) or "cold air dilution", and close the intake valve to check whether the "flying temperature" is caused by the excessive intake concentration;

If the temperature drops sharply (such as below 200 ℃): Check whether the preheating device is faulty (such as damaged electric heating tubes, blocked gas valves), or if the intake air suddenly increases (diluting the reaction temperature), and stop the machine for maintenance.

2. Catalytic efficiency monitoring (verifying treatment effectiveness)

Monitoring indicators: Through the "Import and Export VOCs Concentration Detector", confirm that the export VOCs concentration meets local environmental standards (such as ≤ 20mg/m ³, please refer to the project environmental impact assessment requirements for details);

Abnormal investigation: If the outlet concentration exceeds the standard, first check whether the "intake concentration is too high" and whether the pre-treatment is ineffective (such as insufficient air flow caused by clogged filter cotton), and then check whether the "catalyst is deactivated" (if the catalytic bed temperature is normal but the efficiency decreases, it may be due to catalyst poisoning or aging).

3. Air volume and flow rate control (protecting reaction adequacy)

Airspeed control: The "airspeed" (the ratio of exhaust gas volume to catalyst volume per unit time) of catalytic combustion equipment needs to be controlled within the design range (usually 10000-20000H ⁻¹). If the airspeed is too high (the air volume is too large), it will cause the exhaust gas to stay in the catalytic bed for too short a time (less than 0.5 seconds), resulting in insufficient reaction; Low airspeed (insufficient airflow) can lead to uneven temperature distribution in the catalytic bed and local overheating;

Adjustment method: Adjust the air volume through the linkage between the "inlet air valve" and the "induced draft fan frequency conversion" to confirm stable flow rate (the airflow velocity in the catalytic bed is usually ≤ 1m/s).

3、 Equipment maintenance: Extend service life and avoid sudden failures

1. Catalyst maintenance (core consumables, determining equipment efficiency)

Regular inspection: Stop the machine every 3-6 months to check the status of the catalyst. If there is obvious dust accumulation or clumping on the surface of the catalyst, use "low-pressure compressed air (pressure ≤ 0.2MPa)" to blow and clean it in reverse (do not use water washing to prevent the catalyst from becoming damp and ineffective);

Life management: The design life of the catalyst is usually 2-3 years (which can be extended to 4 years if the intake conditions are good). When there is a continuous decrease in catalytic efficiency (outlet concentration exceeds the standard and cannot be effectively cleaned) or a continuous increase in catalytic bed temperature to meet the standard (such as from 300 ℃ to 380 ℃), the catalyst needs to be replaced (attention should be paid to "matching the catalyst model with the exhaust gas composition" when replacing, such as using sulfur resistant catalysts for treating sulfur-containing exhaust gas).

2. Maintenance of pre-treatment equipment (to prevent impurities from entering the catalytic system)

Filter cotton/filter bag replacement: The initial efficiency filter cotton should be replaced every 1-2 weeks, and the medium efficiency filter cotton should be replaced every 1-2 months (adjusted according to the intake dust concentration, if the filter cotton pressure difference exceeds 500Pa, it needs to be replaced immediately);

Spray tower maintenance: If a wet spray tower is installed in advance, it is necessary to check the pH value of the circulating water every week (to maintain neutrality and avoid acid-base corrosion of equipment), and clean the filling inside the tower every month (to prevent blockage of the filling and a decrease in air volume).

3. Electrical and pipeline maintenance (ensuring stable operation of the protection system)

Electrical system: Check monthly whether the "electric heating tube, temperature sensor, pressure sensor" are normal (such as whether the heating tube is damaged and whether the sensor values are accurate), calibrate the "online monitoring instrument" (VOCs concentration meter, thermometer) quarterly, and confirm the authenticity of the data;

Pipeline system: Check the sealing of the "intake valve, exhaust valve, offline valve" every week (after closing the valve, apply soapy water to the interface and observe if there is any leakage), and check the "gas pipeline (if it is gas preheating)" for leaks every 3 months (using a dedicated leak detector for detection) to avoid explosions caused by gas mixing with VOCs.

4、 Anran Protection: Refusing Fire and Explosion Risks (Top Priority)

1. Explosion proof measures (based on actual reports) (based on actual reports) (VOCs are flammable and explosive substances that need to be strictly implemented)

Explosion proof level of equipment (based on actual reports) (based on actual reports): Catalytic combustion equipment must comply with the "Ex d IIB T4 Ga" explosion proof level (based on actual reports) (based on actual reports) (selected according to the explosion level for handling VOCs, such as handling Class IIA substances such as ethanol and acetone, the level can be appropriately reduced, but it must comply with national standards), and the equipment casing, fan, and motor must be explosion-proof (based on actual reports) (based on actual reports) type;

Explosion relief device: Install "explosion relief discs" (explosion pressure ≤ 0.15MPa) on the catalytic bed, intake pipeline, and exhaust pipeline. When the pressure in the system suddenly rises (such as local explosion), the explosion relief discs will rupture and release pressure to avoid equipment explosion;

Inert gas protection: Before starting the system (especially after starting or shutting down for more than 24 hours), nitrogen should be used to blow the pipeline and catalytic bed (blowing time ≥ 5 minutes), and residual air in the pipeline should be discharged (to avoid mixing VOCs with air to form explosive mixtures).

2. Fire and emergency measures

On site fire protection: "Dry powder fire extinguishers (ABC type)" and "carbon dioxide fire extinguishers" should be equipped around the equipment (water is prohibited for extinguishing fires, as VOCs are mostly oil substances and water can cause the fire to spread), and the fire extinguishers should be placed prominently and easily accessible within the effective period;

Emergency shutdown: Set up an "emergency shutdown button" (one should be set up next to the equipment and one in the control room). In case of emergency situations such as "catalyst bed overheating (exceeding 500 ℃)", "VOCs concentration exceeding the lower explosive limit (exceeding 30%)", "pipeline leakage", etc., immediately press the emergency shutdown button, cut off the intake and heating sources, and start inert gas purging.

3. Personnel operate safely

Certified on duty: Operators must undergo specialized training, be familiar with equipment principles, operating procedures, and safety regulations, and hold a "Special Equipment Operation Certificate" to work;

Protective equipment: When entering the equipment site (such as inspecting pre-treatment devices, replacing filter cotton), it is necessary to wear "gas masks (if VOCs have irritating odors)", "protective gloves", and "goggles" to avoid direct contact with useless substances;

Prohibition of illegal operations: It is strictly prohibited to open the "catalytic bed maintenance door" and "pre-treatment device cover plate" while the equipment is running; It is strictly prohibited to stack flammable and explosive materials (such as paint, solvent drums) around the equipment.

summary

The use of catalytic combustion equipment should revolve around "meeting pre-treatment standards, stable reaction parameters, timely maintenance, and good sales performance". By monitoring core indicators such as intake concentration, temperature, and catalytic efficiency in real time, regularly checking the status of catalysts and pre-treatment devices, and strictly following safety operating standards, the long-term effectiveness of the equipment can be confirmed, meeting environmental requirements while avoiding accidents.