Solvent Recovery Systems

Operating under vacuum lowers the boiling point of the solvent, allowing recovery at lower temperatures. This reduces energy consumption, prevents thermal degradation of heat-sensitive solvents, and minimizes the risk of ignition when working with flammable vapors.

Liquid ring vacuum pumps are the most common choice because they can safely handle condensable solvent vapors, tolerate liquid carryover, and, when paired with a compatible seal liquid, avoid creating an ignition source, which is critical when recovering flammable solvents.

This is a liquid ring pump configured to run in a closed loop using the process solvent (or a compatible liquid) as the seal fluid instead of water, so no water contamination occurs and the seal liquid itself becomes part of the recovered product stream.

A condenser is typically placed between the process and the vacuum pump to knock out the bulk of the solvent vapor as liquid before it reaches the pump. This reduces the size of the required vacuum pump, improves recovery efficiency, and protects the pump from excessive liquid carryover.

Any non-condensables (air leakage, inert gas blankets, or reaction byproducts) pass through the condenser and are handled by the vacuum pump, which is why the pump must be sized not just for vapor load but also for these residual gases.

Cooler seal liquid allows for a deeper vacuum and reduces solvent loss (less solvent flashes off into the pump’s exhaust), so colder cooling or chilled water results in better performance.

Common causes include seal liquid temperature running too high (increasing vapor pressure and solvent carryover into the exhaust), undersized condensers, air in-leakage diluting the vapor stream, and inadequate separator sizing allowing liquid entrainment out of the system.

This depends on the solvent’s material compatibility, but cast iron, carbon steel, and stainless steel are most common. Where particularly aggressive solvents are present, specialty materials such as hastelloy can be used.

A gas-liquid separator downstream of the pump discharge separates the exhaust gas from the liquid phase, and in solvent-sealed systems, recovered solvent collects with the sealant in the separator or in a separate condensate receiver.