Application of Vacuum Pumps for VOCs Treatment Equipment

In VOCs treatment, the core function of vacuum pumps is to generate negative pressure to extract high‑concentration organic vapor for waste gas collection, vacuum desorption and solvent recovery. For common high‑air‑volume and low‑concentration VOCs, only induced draft fans are generally used. Vacuum pumps are not equipped on all VOCs equipment; they are only adopted for specific processes.

1. VOCs Processes Equipped with Vacuum Pumps

Adsorption‑vacuum desorption process (activated carbon / molecular sieve adsorption & recovery)

This is the most typical application scenario of vacuum pumps for VOCs equipment. When the adsorbent reaches saturation, vacuum desorption is applied instead of hot nitrogen purging. The vacuum pump evacuates the adsorption tank to lower the boiling point, desorbs organic components adsorbed on the material, extracts high‑concentration VOCs gas and feeds it into a condenser to condense into liquid solvent for recovery. Common models: liquid‑ring vacuum pump, Roots‑liquid‑ring vacuum unit, dry screw vacuum pump.

Closed waste gas collection for process equipment (reactors, storage tanks, distillation and devolatilization processes)

In chemical, coating and resin production, VOCs are generated from reactors, discharging and vacuum devolatilization. The equipment chamber is kept under negative pressure. The vacuum pump directly draws organic waste gas volatilized from the process and delivers it to condensation and absorption units to prevent VOCs leakage.

Difference: Ordinary gas collection uses fans to draw gas from pipelines; vacuum pumps create negative pressure inside closed vessels.

Condensation‑recovery VOCs units

For high‑concentration condensable organic waste gas, vacuum pumps maintain negative pressure in the condensation system, reduce the dew point of organics and improve solvent recovery efficiency, mostly used for organic solvent recovery applications.

Vapor recovery equipment

For tank vapor recovery, vacuum pumps are used in some processes to extract volatile oil vapor from tank farms.

2. VOCs Equipment Normally Without Vacuum Pumps

Spray scrubber, UV photo‑oxidation catalysis, RCO/RTO thermal oxidation, activated carbon hot‑air desorption. Waste gas for such equipment runs under slight negative / slight positive pressure with large air flow. Only centrifugal induced draft fans are required, and vacuum pumps are not needed.

Key point: Induced draft fans handle large‑volume waste gas at atmospheric pressure; vacuum pumps serve closed chambers for low‑flow and high‑concentration organic vapor.

3. Vacuum Pump Selection Guidelines for VOCs Working Conditions

Medium characteristics: organic vapor, partially condensable and solvent‑laden; explosion‑proof design is preferred.

Liquid‑ring vacuum pump: low cost, tolerates a small amount of condensable vapor. Disadvantage: it produces VOC‑containing wastewater which requires auxiliary wastewater treatment. Suitable for medium‑concentration scenarios where wastewater generation is acceptable.

Dry vacuum pump (dry screw type): no working fluid, no wastewater output, high purity of recovered solvent; higher cost. Suitable for high‑value‑solvent recovery projects requiring zero wastewater.

Roots‑liquid‑ring unit: higher ultimate vacuum, applied to processes requiring high‑vacuum desorption.

Material: wetted parts in contact with organic vapor shall resist organic solvent corrosion; motors must be explosion‑proof.

4. Points Prone to Confusion

Vacuum pumps convey gas (VOCs vapor); centrifugal pumps only transport spray liquid and cooling liquid and cannot extract waste gas.

Vacuum desorption ≠ hot‑air desorption: hot‑air desorption uses fans, while vacuum desorption requires vacuum pumps.