Zeolite Adsorption and Desorption

Technology Introduction

In industries such as printing, coating, and electronics manufacturing, the treatment of low-concentration volatile organic compounds (VOCs) exhaust gas has always been a challenge for environmental protection. Traditional single technologies (such as direct combustion or activated carbon adsorption) have problems including high energy consumption, high operating costs, poor safety, or secondary pollution. The combined process of zeolite adsorption concentration + catalytic combustion achieves efficient purification and resource utilization of low-concentration exhaust gas through the synergistic effect of "adsorption-desorption-combustion," becoming one of the mainstream solutions for industrial exhaust gas treatment today.n be widely used in the following industries such as power, metallurgy, cement and chemistry, and so on.

Adsorbent Materials: Activated carbon adsorption and desorption can be adopted in certain scenarios.

1. The main material of honeycomb molecular sieve is natural zeolite, an inorganic microporous material composed of SiO2, Al2O3, and alkali metals or alkaline earth metals; 

2. It has uniform micropores, with pore sizes comparable to general molecular sizes, an internal pore volume accounting for 40-50% of the total volume, and a specific surface area of 300-1000 m²/g; 

3. Due to the uniform pore size distribution, significant variations in structure and composition, it features high temperature resistance, non-flammability, good thermal stability, and hydrothermal stability.

Adsorption Principle:

1.Select adsorption according to the geometric size and shape of the molecule Molecular sieves have a honeycomb structure, with cavity diameters generally 

between 0.6~1.5nm, pore sizes about 0.3~1nm, and uniformly arranged channels within the crystal. The uniform pore size and the regular framework structure of the molecular sieve determine its shape-selective adsorption. 

2.Select adsorption according to the polarity, unsaturation, and polarizability of the molecule Due to differences in polarity, unsaturation, and polarizability of the adsorbate 

molecules, their interaction strength with the molecular sieve and diffusion rate inside the molecular sieve vary. Since zeolite molecular sieves themselves are polar substances with a strong internal electrostatic field, molecules with stronger polarity or easier polarization are more easily adsorbed.

Desorption Principle :

The desorption uses hot air as the desorption medium, and this hot airflow comes entirely from the residual heat after catalytic combustion within the system. The concentrated 

organic waste gas after desorption enters the catalytic combustor for purification treatment, requiring no additional energy, greatly reducing operating costs. For the same treatment volume, it is about 1/20 of the direct catalytic combustion method and 1/10 of the molecular sieve adsorption.

Principle of Catalytic Combustion Technology:

1. The exhaust gas enters the heat exchanger under the action of the main fan, and the gas is heated.

2. The exhaust gas enters the catalytic bed. If the temperature after heat exchange does not reach the catalytic temperature, electric heating or a burner is used to heat the exhaust gas until it reaches the catalytic temperature, then it enters the catalyst.

3. Under the action of the catalyst, the organic substances in the exhaust gas are oxidized and decomposed, purified into carbon dioxide and water, and release heat; the released heat enters the hot side of the heat exchanger to heat the exhaust gas. 

4. The purified exhaust gas is discharged in compliance with standards.

Technical advantages

High Purification Efficiency: Purification efficiency is high, usually reaching 95%~99% or above.

High Concentration Efficiency: Large volume, low concentration waste gas is concentrated into small volume, high concentration waste gas, greatly reducing the investment and operating costs of subsequent treatment equipment.

Stable Operation: Zeolite is heat-resistant and non-combustible; the system operates safely and reliably with a long service life.

Humidity Interference Resistance: Hydrophobic zeolite has weak adsorption of water vapor, suitable for waste gas environments with relatively high humidity.

Continuous Automated Operation: The rotor continuously rotates, with adsorption and desorption occurring simultaneously, enabling unattended operation.

Complete Decomposition: Directly converts organic substances into CO₂ and H₂O, with no secondary pollution (provided that post-treatment is adequate).

Application areas

Especially suitable for large volume, low concentration organic waste gas treatment, such as:

Printing and coating industries

Automotive painting and furniture painting industries

Electronics and semiconductor industries

Petrochemical and pharmaceutical industries