Dry gas from TEG overhead KO drum flows to Gas/Gas Exchanger where it is cooled by Low Temperature Separator overhead stream.
The Gas/Gas Exchanger is a special Printed Circuit Heat Exchanger design. The exchanger is protected by strainers in order to avoid oversized particles entering Sales Gas Metering Skid.
JT valves provides cooling of the gas stream. The dew point conditioning unit is designed to achieve a hydrocarbon dew point of 13 degC at 400 psig.
As traces of liquid may be carried over from the Low Temperature Separator in gas phase, therefore a 3 degC margin is provided in the design, maintaining the hydrocarbon dew point under the specification.
The cold gas flows into the Low Temperature Separator where the condensed hydrocarbon is accumulated. The condensed hydrocarbon is then combined with compressed gas entering the 2nd Stage Flash Gas Compressor Suction Scrubber.
The Low Temperature Separator is a cold insulated vessel equipped with level control and safety devices.
Metering
The purpose of the flow metering system is to measure the gas flow for commercial purposes.
Sales gas metering package includes the following:
- Flow Metering system
- Gas Chromatograph
- Miscellaneous component, like isolation valve, tube JB, etc.
One of the options is utilizing senior orifice meter. The flow meter is designed and constructed in accordance for AGA Report No 2. To compesate the flow readings, Pressure and Temperature transmitters are provided on each stream.
The capacity of each flow meter is based upon the plant throughput capacity, Three orifice plates are supplied for each stream to provide the maximum possible accuracy during turndowns in gas sales.
An Online gas chromatograph is installed to continually measure the sales gas composition. The componens to be measure are C1 through C6+, CO2, and N2.
The gas chromatograph analyses the gas and transmits the composition data to the individual stream flow computer. The stream flow computer will compute the GHV of the gas being supplied.