Solvent Recovery Unit | Direct Condensation | DEC.SRU_RSC™
What Is Direct Condensation Solvent Recovery?
Direct condensation is an industrial solvent recovery process that uses a condenser to cool the solvent-laden gas stream. The cooled gas stream then condenses the solvent, which is collected in a receiver. Direct condensation is a simple and effective process that is well-suited for a variety of solvents.
How Does DEC.SRU_RSC™ Work?
The efficiency of direct condensation depends on the following factors:
- The boiling point of the solvent
- The concentration of the solvent in the gas stream
- The cooling capacity of the condenser
From Solvent-Laden Air to Recovered Solvent
Simple Direct Condensation
Direct condensation is a relatively low-cost and safe process: the main costs associated with direct condensation are the cost of the condenser and the cost of the energy used to cool-down the SLA gas stream.
The feasibility of DEC.SRU_RSC™ direct condensation is influenced by both the boiling points of the solvents and the concentration in the SLA stream (the higher the concentration of the solvent in the SLA stream, the more efficient the direct condensation process will be).
Cryogenic Condensation with Liquid Nitrogen
The cryogenic condensation solvent recovery process is ideal for low flow rates (typically < 2.000 Nm³/h) and high concentrations of VOC ( > 0,5% vol).
- Refrigerant
- Liquid nitrogen (LN2)
- Recommended flow rate
- < 2,000 Nm³/h
- Recommended VOC concentration
- > 0.5% vol
- Footprint
- Compact, skid-mounted (DEC-SMS™)
Using liquid nitrogen as the refrigerant, the cryo-condensation process is designed to cool the effluent in a process stream to very low temperatures, thanks to the use of advanced heat exchangers, which are characterized by high fractionating capacities of vapors and gases.
The stream effluent is separated by decreasing the vapor pressure as a function of the vapor/liquid and vapor/solid equilibrium. The VOC is recovered for reuse in the process (directly or after distillation) or as a fuel (DEC.WTE™ - Waste To Energy module), while the nitrogen is cycled back into the process for purging and blanketing operations.
The cryo-condensation units are usually very compact, requiring a relatively small footprint, and are skid mounted (DEC-SMS™ (Smart Modular System)), lowering installation and start-up costs. The system design minimizes moving parts, reducing maintenance and repair.
When Is Direct Condensation Preferred?
Direct condensation is generally considered where solvent concentration and gas flow make condensation economically and technically attractive. For larger solvent-laden air flows, DEC.SRU_RSG™ and DEC.SRU_RSV™ activated-carbon systems may provide a more appropriate recovery solution.
| Technology | Typical Flow Range | VOC Concentration | Best Suited For |
|---|---|---|---|
| DEC.SRU_RSC™ • Simple Direct Condensation | Varies with solvent boiling point & cooling capacity | Efficiency increases with concentration | High-boiling, high-concentration solvent streams |
| DEC.SRU_RSC™ • Cryogenic Condensation (LN2) | < 2,000 Nm³/h | > 0.5% vol | Low-flow, high-concentration VOC streams |
| DEC.SRU_RSG™ • Activated Carbon, N2 (TSA) Regeneration | 5,000 – 1,000,000 Nm³/h | Wider concentration range | Larger solvent-laden air (SLA) flows |
| DEC.SRU_RSV™ • Activated Carbon, Steam (TSA) Regeneration | 5,000 – 1,000,000 Nm³/h | Wider concentration range | Larger solvent-laden air (SLA) flows |
For higher flow rates (5.000 ÷ 1.000.000 Nm³/h), please check solvent recovery systems based on activated carbon, steam or nitrogen desorption (DEC.SRU_RSV™ and DEC.SRU_RSG™).
Solvent and Process Selection
Once condensed, the recovered solvent can be reused without further treatment or further processed through DEC.ADM™ dehydration modules (e.g. to separate water from humidity) and/or through a DEC.DST™ distillation unit.
Downstream Refinement Options
VOC Emission Control After Condensation
Depending on the type of solvent(s) to be recovered and the level of VOC emission control requested at the stack of the system, a disposable activated carbon filter (DEC.XFU_AFU™) or a concentration system (DEC.XBC™) may be required for further VOC abatement, prior to exhaust at stack.
Stack-Ready Emission Control
Industrial Applications
DEC.SRU_RSC™ direct condensation is used across process industries to recover a wide range of solvents — for example NMP (N-Methyl-2-pyrrolidone) recovery, shown above. DEC Solvent Recovery Units (SRUs) are available in both modular layout (DEC-SMS™ • Smart Modular System, pre-built and pre-tested at our workshops) or in full customizable version (DEC-CBS™ • Custom Built System, with on-site erection).
Related Resources
If you are looking for a reliable and efficient solvent recovery unit, DEC.SRUs™ (Solvent Recovery Units) are DEC.SRUs™ are engineered with different recovery processes, configurations and options to meet specific application requirements. Feel free to contact DEC: we can help you assess your needs and recommend the best SRU for your operation.
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FAQs • Frequently Asked Questions
solvent recovery | direct condensation ♻️ DEC.SRU_RSC™
What is direct condensation and how does DEC.SRU_RSC™ work?
Direct condensation is an industrial solvent recovery process that uses a condenser to cool the solvent-laden gas stream. The cooled gas stream then condenses the solvent, which is collected in a receiver. Direct condensation is a simple and effective process that is well-suited for a variety of solvents.
What factors affect the efficiency of direct condensation?
The efficiency of direct condensation depends on the boiling point of the solvent, the concentration of the solvent in the gas stream, and the cooling capacity of the condenser.
When should cryogenic condensation with liquid nitrogen be used instead of simple direct condensation?
Cryogenic condensation using liquid nitrogen (N2) as the refrigerant is ideal for low flow rates (typically below 2,000 Nm³/h) and high concentrations of VOC (above 0.5% vol). For higher flow rates, from 5,000 up to 1,000,000 Nm³/h, activated-carbon-based solvent recovery systems (DEC.SRU_RSV™ steam regeneration or DEC.SRU_RSG™ nitrogen regeneration) are recommended instead.
How does DEC.SRU_RSC™ direct condensation compare to activated-carbon solvent recovery?
Direct condensation is generally considered where solvent concentration and gas flow make condensation economically and technically attractive. For larger solvent-laden air flows, DEC.SRU_RSG™ and DEC.SRU_RSV™ activated-carbon systems may provide a more appropriate recovery solution.
Is pricing available for a DEC.SRU_RSC™ direct condensation system?
DEC.SRU_RSC™ systems are custom-engineered, quote-based equipment with no fixed list price. Each system is sized and priced after DEC's engineering team evaluates the customer's solvent, flow rate and VOC concentration requirements. Contact DEC to request a project-specific quote.
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