 |
|
IPSI Enhanced NGL Recovery Process
(U.S. Patent No. 5,992,175 Issued 11/30/1999)
This recently patented process offers significant enhancements to state-of-the-art NGL recovery processes. This process developed by IPSI utilizes a slip stream from or near the bottom of the distillation column (demethanizer) as a mixed refrigerant. The mixed refrigerant is totally or partially vaporized, providing refrigeration for inlet gas cooling otherwise normally accomplished using a costly external refrigeration system, including compressors, condensers, refrigerant accumulators, economizers and refrigerant storage. The vapor generated from this "self-refrigeration" cycle is specifically tailored to enhance separation efficiency, then is recompressed and recycled back to the bottom of the tower where it serves as a stripping gas. The innovation not only reduces or eliminates the need for inlet gas cooling via external refrigeration, but also provides the following enhancements to the demethanizer operation:
- Lowers the temperature profile in the tower, thereby permitting better energy integration for inlet gas cooling via reboilers, resulting in reduced heating and refrigeration requirements.
- Reduces and/or eliminates the need for external reboiler heat, thereby saving fuel plus refrigeration.
- Enhances the relative volatility of the key components in the tower when operated at a typical pressure, thereby improving separation efficiency and NGL recovery; or alternatively allows increased tower pressure at a typical recovery efficiency, thereby reducing the residue gas compression requirements.
It is noteworthy that the simplicity of the self-refrigeration scheme can be adapted to most leading NGL recovery technologies to enhance the operational efficiency and reduce capital and operating costs of those processes regardless of the original licensor. Moreover, it can be configured into a simple add-on skid particularly suitable for retrofitting plants to enhance NGL recovery and/or increase gas plant capacity at original recovery levels without additional residue gas compression.
While the Process Enhancement scheme is widely applicable, it offers significant advantages as applied to gas processing plants (existing or new) with the following characteristics:
- The inlet gas is relatively rich in NGL’s and requires refrigeration to obtain required liquid recoveries.
- Inlet gas pressure is in the intermediate to high ranges, (above 400 psi with the residue gas delivered at the same pressure as the inlet gas
- There is a benefit to maintaining recovery levels when the inlet gas drops in pressure and/or becomes richer over time.
- There is an incentive to improve NGL recoveries in existing plants by adding four or five pieces of equipment as a retrofit package.
- There is a need to process up to 20% more gas in an existing gas plant without sacrificing NGL recovery levels or adding additional residue gas compression. (This is by far the highest ROI achievable using this technology.)
IPSI offers this technology under license in addition to industrial design and testing services.
Figure 3: IPSI Enhanced NGL Recovery ProcessSM
