When treating volatile organic compounds (VOCs), switching valves are core components of industrial RTO regenerative incineration systems, fulfilling the critical task of directing exhaust gas flow and controlling the switching between the combustion chamber and the regenerator. However, due to frequent operation, high temperatures, and the corrosive nature of exhaust gas, switching valves are prone to internal and external leakage, mechanical jamming, or corrosion damage. This can lead to untreated exhaust gas discharge, reduced purification efficiency, and even system shutdown. To ensure the safe operation of industrial RTO regenerative incineration systems in the event of switching valve failure, a comprehensive protection system must be established, encompassing design optimization, safety interlocks, emergency control, and maintenance management.
The sealing performance of switching valves directly impacts exhaust gas treatment effectiveness. Internal leakage typically results from a loose seal after the valve disc closes, allowing exhaust gas, under pressure, to bypass the regenerator and furnace and be discharged directly, causing VOC emissions to exceed standards. External leakage arises from wear on the sealing packing caused by the reciprocating motion of the valve stem, allowing exhaust gas to leak through the packing into the atmosphere and cause environmental pollution. To address these issues, high-precision machining and assembly processes are required to ensure the flatness of the valve plate and sealing end faces, as well as the concentricity of the valve stem installation, thereby minimizing sealing gaps. Furthermore, wear- and corrosion-resistant sealing materials, such as special rubber or metal sealing rings, should be selected, and wear parts should be regularly replaced to maintain long-term sealing performance.
High temperatures and corrosion are the main causes of switching valve failure. In industrial RTO regenerative incineration systems, the outer side of the high-temperature side of the reversing valve connects to the flue gas outlet duct, where temperatures can reach 300°C; the outer side of the low-temperature side of the reversing valve connects to the flue gas inlet duct, where temperatures can also reach 200°C. If the exhaust gas contains corrosive components such as halogenated hydrocarbons, high temperatures can accelerate corrosion of the valve stem and disc, leading to a decrease in sealing performance. Therefore, valve materials must be heat- and corrosion-resistant, such as stainless steel or nickel-based alloys, and the inner wall of the valve body must be treated with anti-corrosion treatment. Furthermore, installing a pretreatment device in the exhaust gas inlet duct to remove particulate matter and corrosive gases can extend the valve's service life.
Mechanical failure is another risk associated with switching valve operation. Valve stem sticking is often caused by insufficient clearance or impurity intrusion, while valve plate deformation stems from material creep under prolonged high-temperature conditions. To avoid these problems, valve structural design should be optimized, such as using self-lubricating bearings or guide sleeves to reduce resistance to valve stem movement. Furthermore, filters should be installed at the valve inlet to prevent impurities from entering the valve cavity. Deformed valve plates should be promptly replaced or repaired to ensure a tight valve closure.
Safety interlocks and emergency controls are key to system safety. Industrial RTO regenerative incineration systems should be equipped with concentration detectors to monitor VOC concentrations in exhaust gas in real time. When high gas concentrations are detected, the system should trigger an interlock shutdown mechanism: the exhaust emergency discharge valve opens, the exhaust shut-off valve closes, the fresh air valve opens, and the main fan operates at a reduced airflow rate to ensure low-concentration gas enters the furnace and avoid explosion risks. Furthermore, explosion relief devices, such as explosion relief doors and venting discs, should be installed on the furnace roof and buffer tank to mitigate damage caused by explosions. Explosion relief doors should close automatically to ensure the system can quickly resume normal operation after explosion relief.
Routine maintenance and inspection are effective means of preventing failures. Companies should establish a regular maintenance system and conduct comprehensive inspections of switching valves, including leak testing, stem movement flexibility testing, and corrosion assessments. They should also develop emergency response plans, clearly define personnel responsibilities, and equip personnel with emergency equipment such as chemical protective suits, heat-insulating suits, and gas masks. Regular emergency drills should be conducted to enhance personnel's response capabilities and ensure prompt action in the event of a switching valve failure, ensuring safe system operation.
