Application of Regenerative Thermal Oxidizer in Coating Industry

2026-04-13

The coating process is an important surface treatment step in industrial production. However, during processes such as spraying, leveling, and drying, a large amount of Volatile Organic Compounds (VOCs) is generated. The main components include methyl isobutyl ketone, n-butyl acetate, n-butanol, ethylene glycol, butyl ether, toluene, xylene, trimethylbenzene, etc. If these waste gases are discharged directly without effective treatment, they will cause serious harm to the environment and human health.

Waste gas in coating workshops mainly comes from spray booths, leveling rooms, and drying ovens. Among them, the waste gas from drying ovens and leveling rooms is characterized by small air volume and high concentration, while the waste gas from spray booths is characterized by large air volume and low concentration. After water scrubbing treatment, it still contains a certain amount of moisture and paint mist particles that are not completely removed, making it more difficult to treat.

1. Overview of Waste Gas Treatment Routes in the Coating Industry

1.1 Mainstream Treatment Route for Spray Booth Waste Gas
Recommended process route:
Filtration system + rotary concentrator (zeolite wheel) + Regenerative Thermal Oxidation technology
Technical characteristics:
This combined process can effectively handle the characteristics of large air volume and low concentration in spray booth exhaust. First, multi-stage filtration removes residual paint mist; then the rotary concentrator adsorbs and concentrates VOCs; finally, the gas enters the RTO for high-efficiency purification.
This route offers high purification efficiency, and emission concentration can be stably controlled below 30 mg/m³. It is currently the recommended technical route for high emission standards.

1.2 Treatment Route for Drying Oven Waste Gas
Recommended process route:
High-temperature filtration + regenerative thermal oxidation technology
Technical characteristics:
Due to the high temperature and high concentration of drying oven exhaust, high-temperature filtration is used to remove particulates, after which the gas directly enters the RTO for oxidation decomposition.
This process is simple, has high heat-recovery efficiency, and can achieve ultra-low emissions below 30 mg/m³. It is an ideal solution for drying process exhaust treatment.

2. Introduction of Various Treatment Equipment

Water Scrubbing Device
The water scrubbing spray booth is an improved process designed to solve the problem of clogging in traditional water circulation systems.
Working principle:
Outdoor air is filtered through the top filters and enters the spray booth, forming a uniform downward airflow. After passing through the working area, the exhaust fan draws the dust-laden gas into the water scrubber beneath the floor grating. A water curtain formed by the overflow tray is atomized under high-speed airflow and fully contacts the exhaust gas, capturing most paint mist particles in water and achieving preliminary purification.

Filtration Device
The main function of the filtration system is to deeply purify the exhaust gas after water scrubbing, ensuring it meets the requirements for subsequent concentration equipment.
The mainstream process adopts a four-stage filtration system: G4 + F5 + F7 + F9. This gradient filtration design effectively removes residual particles of different sizes and protects downstream equipment such as the rotary concentrator.

Rotary Concentrator (Zeolite Rotor)
The core function of this device is to achieve efficient concentration of large air volumes and low-concentration exhaust gases.
Through adsorption–desorption principles, low-concentration VOCs are concentrated into high-concentration, low-volume gas, significantly reducing the size and energy consumption of downstream incineration equipment.
Low-concentration exhaust gas can be concentrated 8–30 times by the zeolite rotor, and the air volume is reduced to 1/8–1/30 before entering the RTO. When the gas passes through the rotor, VOCs are adsorbed by the zeolite, and purified gas is discharged. Then, a small volume of high-temperature air is used to desorb the VOCs, which are finally sent to the RTO for treatment.
Applicable range of zeolite rotor:
Flow rate per unit: 10,000–200,000 m³/h
Waste gas concentration: <1000 mg/m³
Treatment efficiency: ≥95%

Rotary Regenerative Thermal Oxidizer (RTO)
The system is divided into 12 zones: 5 inlet zones, 5 outlet zones, 1 purge zone, and 1 isolation zone.
A rotary air distribution valve is installed at the bottom of the furnace. With special contact-type rubber sealing technology, the airflow is reliably distributed at the bottom of the furnace. Similar to a 12-cylinder engine, it continuously cycles through intake, purge, exhaust, and isolation processes.
The rotary RTO can also be equipped with waste heat recovery systems (thermal oil, hot air, hot water, steam, etc.) to meet different process heating demands.
Applicable range of RTO:
Flow rate per unit: 3,000–100,000 m³/h
Purification efficiency: ≥99.5%
Thermal efficiency: ≥96%

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Social Benefits

Using a zeolite rotor combined with a rotary Regenerative Thermal Oxidizer system for coating exhaust gas treatment can achieve the following effects:

VOCs emissions ≤30 mg/m³, meeting national and local emission standards;
Effective removal of odors in the exhaust gas.
Significant reduction of total exhaust emissions through the use of a zeolite rotor.