The feed stream is first compressed in a liquid ring compressor. The compressor outlet is sent to an absorber, where the gas flows upward and is contacted with downward flowing liquid absorbent. Hydrocarbons are absorbed from the vapor into the liquid. The recovered hydrocarbon liquid stream exits from the bottom of the column and is returned to storage.
The absorber overhead gas is sent to the VaporSep membrane, which separates the stream into a hydrocarbon-depleted residue gas and a hydrocarbon-enriched permeate stream. The residue gas (containing < 10 g/Nm3, or as required by the customer) is vented. The hydrocarbon-enriched permeate stream, at low pressure, is recycled via a vacuum pump to the compressor inlet.
Jordan Technologies’ vapor recovery unit is supplied as a complete skid mounted package (single skid for units up to ~ 500 Nm3/hr, multiple skids for larger units) including feed compressor, vacuum pump, membrane, and absorber.
VaporSep membranes separate gas mixtures on the basis of solubility. Large hydrocarbon molecules with greater solubility in the membrane permeate much faster than smaller, less soluble molecules such as nitrogen, hydrogen, or methane. By comparison, conventional membranes separate gases on the basis of size. Small molecules are selectively permeated because they diffuse through the membrane more rapidly than large molecules.
VaporSep membranes are manufactured as flat sheets and rolled into spiral-wound modules. The feed gas enters the module and flows between the membrane sheets. Spacers on the feed side and the permeate side of the membrane sheets create flow channels. The hydrocarbon vapor that passes preferentially through the membrane flows inward to a central permeate collection pipe. The light gas (nitrogen, hydrogen or methane) is rejected by the membrane and exits as the residue.
VaporSep VRUs provide many important features and benefits:
- A better alternative for plants that handle petro-chemicals and chemicals
- Compatible with a wider range of hydrocarbons and various crudes
- Compact design; a smaller footprint compared to the equal sized carbon system
- Steady state process for constant flow design applications
- Fewer moving parts and control requirements compared to other technologies
- Inlet compressor eliminates process pressure drop issues; inherently safe design
- Skid mounted for easy installation, faster commissioning, lower installation costs and simpler transportation requirements
- Low maintenance, operation and replacement cost
- Proven technology with roughly 200 systems installed in the petrochemical, natural gas, and refining industry.