A skid-mounted SUPERMAX shell and plate heat exchanger is helping a gas processing company achieve increased propane recovery and reduce sales gas gross heating value.
An Oklahoma-based pipeline company processes gas from a rich gas field to recover propane and heavier components. The process used also reduces the gross heating value (GHV) of the sales gas to a contractual maximum. As a result of increasing inlet gas production and also assays showing higher propane and longer chain hydrocarbon concentrations, it became necessary to reduce the chilling temperature to condense more of the propane and heavier components from the gas.
However, the existing refrigeration system and process equipment would not allow the pipeline operator to achieve the lower temperature without changing the refrigeration compression and equipment to operate in the vacuum, which was extremely costly and not practical. The company sought a more cost-efficient solution.
Modelling performed by the engineering department suggested that by adding another exchanger downstream of the chiller, the gas temperature could be reduced sufficiently to improve the propane recovery and lower the GHV of the sales gas. The model predicted that propane recovery would improve from 3% to 5%, depending on the refrigeration chiller load for flow rates of 184–240 MMscmd (6,500–8,500 MMscfd).
Sizing calculations showed that a shell and tube exchanger for the application would approximately measure 254mm in diameter by 4.6m long, but would require a major reconstruction of the original skid, which had an open area of 1m².
Looking for alternate HE technologies to avoid the extra cost of foundation work and skid modifications, the engineering team found that a Tranter SUPERMAX shell and plate heat exchanger featuring a footprint of only 0.5m² would be a perfect fit.
Following the installation, the SUPERMAX heat exchanger has been exceeding performance expectations, producing a colder temperature in the cold separator of -37°C as against the -30°C temperature achieved earlier without the exchanger. Propane recovery improved by 13%, resulting in a reduction of the sales gas GHV by 2% to contractual levels.