Common Problems and Solutions of Zeolite Rotors (Zeolite Molecular Sieve Rotors)

The molecular sieve adsorption rotor system utilizes the continuous process of adsorption - desorption - concentration and incineration to treat and purify VOCs exhaust gas. It has the advantages of wide application range, high safety, and stable operation. However, in different practical application scenarios, the exhaust gas composition is complex, and there are easily occurrences of high-boiling-point VOCs residue polymerization and smoldering phenomena.

1. High-boiling-point VOCs residue polymerization

When high-boiling-point VOCs substances are present in the exhaust gas treatment, if the desorption heat is insufficient and the adsorbate is not completely desorbed, the adsorbate will accumulate and remain near the adsorption short in a short period of time. Over time, this will lead to polymerization, thereby blocking the adsorption position of the zeolite and reducing the adsorption efficiency in that area. To ensure that the high-boiling-point VOCs adsorbed in the zeolite can be completely desorbed, the following suggestions are given:

(1) Install a front-end equipment for removing high-boiling-point VOCs substances

To avoid the difficulty in desorption caused by the adsorption of high-boiling-point VOCs substances, a pre-filter cloth or activated carbon filter, an orifice dehumidifier or condenser can be added before the exhaust gas enters the adsorption rotor to remove high-boiling-point VOCs substances.

(2) Increase the heat capacity of desorption

Method one is to increase the desorption temperature, which is recommended to be controlled between 180-200℃, with a maximum not exceeding 220℃, to avoid excessive residual heat that leads to incomplete cooling and affects the effect of the adsorption section; another method is to increase the desorption regeneration air volume and reduce the concentration ratio, which can achieve a sufficient desorption and regeneration effect.

(3) Regularly perform maintenance and cleaning with clean water

When cleaning, attention should be paid to the water quality. If there is a large amount of calcium, magnesium ions in the water, it may form carbonate in the zeolite, blocking the honeycomb-shaped pores of the zeolite rotor; while chloroform in the water may occupy the adsorption position of the zeolite and hinder the adsorption efficiency of VOCs; in addition, trace heavy metal substances in the water may poison the zeolite. Therefore, it is recommended to use a high-pressure nozzle to form fine mist droplets of the cleaning water and use the clean air in the cooling section of the system as the gas carrier.

(4) Regularly perform high-temperature desorption and regeneration

Regular high-temperature desorption treatment will effectively remove the components of high-boiling-point VOCs substances and also achieve the effect of activating the zeolite rotor. The desorption temperature is generally most suitable at 300℃.

2. Occurrence of smoldering phenomenon

When the desorption condition is at 180-200℃, if the system stops abnormally without airflow circulation and without external oxygen supply, the VOCs components in the exhaust gas and the high-boiling-point substances polymerized on the rotor will react with the oxygen in the zeolite and the original residual oxygen in the rotor channels and zeolite pores through catalytic reaction, forming heat and causing smoldering phenomenon, which will damage the zeolite structure. To prevent the occurrence of smoldering phenomenon, it is recommended to use pure gas (such as nitrogen) as the protection gas when the system stops abnormally, and the best solution to prevent the continuous occurrence of smoldering phenomenon is to use a water spray device.