View Article as Single page
The compressed ethane-rich, mixed refrigerant stream is then cooled and partially condensed in the mixed refrigerant gas-gas exchanger. Cooling for this exchanger is provided by low-temperature mixed refrigerant and propane. The two-phase stream flows to the de-ethanizer reflux drum, a conventional two-phase gas liquid separator. This liquid is used to provide reflux to the de-ethanizer column, thereby completing the "open" cycle of the mixed refrigerant loop.
Noncondensable vapors, consisting mainly of methane, are directed back into the process via the de-ethanizer overhead separator and eventually exit the process into the residue gas stream or may be used as fuel.
The closed-loop propane refrigeration is of conventional natural gas industry design and construction. In a typical IPOR process, the process refrigeration temperature is in the range of –10° F. to –20° F.; other refrigerants, therefore, such as ammonia may be used as well.
For the LPG-recovery configuration above, product extraction efficiencies are excellent, with C3 recovery in the range of 95-99%+, with essentially 100% recovery of the C4+ fraction.
From a thermal efficiency perspective, the IPOR process requires about 15-40% less compression power than a comparable turboexpander design. As a result, plants using the IPOR technology will also have lower emissions and a smaller carbon footprint.
The process utilizes equipment and materials that are all well proven within the natural gas processing industry. Most of the unit can be of carbon steel or low-temperature carbon steel construction; typically the only major equipment item that requires stainless steel construction is the de-ethanizer overhead separator.
The only rotating equipment required for the IPOR process is the refrigerant compressor. The process requires no cryogenic turboexpander or light hydrocarbon pumps. As a result:
• Reliability and operability will be comparable to that of a conventional refrigeration process and should exceed that of a modern day turboexpander facility, given the fewer items of rotating equipment.
• The process offers superior economics for almost any feed-gas rate, from as low as 5 MMscfd to 1 bcfd+.
• Almost infinite turndown capacity is possible with an IPOR process, to feed-gas rates as low as 10% of design, limited only by the performance of in-line control instruments, i.e., control valves, meters, etc., unlike turboexpander designs, which suffer from an inherent loss of efficiency at reduced flows.
The process can be designed for a wide variety of feed-gas compositions, site conditions, and capacities. Ethane recovery can be incorporated into an IPOR process design, with ethane recoveries up to 80%, depending upon feed-gas composition. Equipment can be incorporated to allow for future ethane recovery, or the initial design can permit operation in ethane-rejection/ethane-recovery mode.
The process was developed based on proven technologies and equipment employed extensively in gas plants. All the equipment incorporated into the process design is well within the natural gas industry’s experience and capability. The low equipment count, small footprint, and process simplicity of the technology permit a compact layout and a high degree of modularization.
Marcellus plant
A recent study compared the IPOR process with modern turboexpander technology. Feedstock for the new plant is from the Marcellus shale, a region with limited existing oil and gas infrastructure and no existing ethane market. Demand for LPG in the region is strong, with extracted LPG sold into the local market.
As a result, the customer wanted to maximize LPG production. Due to the richness of the gas, some ethane extraction was required to meet the residue-gas pipeline specifications, with the ethane consumed within the plant as fuel. The field’s gathering system operated at low pressure, with residue gas delivered into an existing high pressure pipeline.
Displaying 3/6
View Article as Single page
