Inlet Moisture Considerations |
Startup Assistance & Field Service | Pressure Storage & Facilities Design & Procurement Statement
Inlet Moisture Considerations
Inlet gas moisture (water) content control is required to maintain continuous operation of the gas conditioning process. It is crucial that only a properly dehydrated inlet gas be fed to the skid inlet to avoid ice and hydrate problems.
Dew Point Control recommends the following precautions to help prevent hydrate and ice formation:
- When operating at cold separator temperatures of 35 degrees or higher:
When operating at cold separator temperatures below 35 degrees:
- Dehydrated gas fed to the DPC unit should have no more than 7#/MMSCF of water content.
- Methanol injection is not normally needed with a properly operating glycol unit, although it is recommended that methanol be injected for one shift per week to keep the system “clean.”
- Dehydrated gas fed to the DPC unit should have no more than 3#/MMSCF water content, requiring, in most cases, stripping gas on the re-concentrator reboiler, an eight tray contactor, and a reboiler temperature of no less than 385 degrees.
- Methanol injection is recommended to keep unit clear of hydrates and ice when operating below 35 degrees.
- When the unit chills the gas to the vicinity of hydrate formation or ice formation temperature, methanol must be injected using the DPC provided on-skid pump. When using DPC’s high efficiency methanol injection system, methanol flow should be set at 2.5 pounds of methanol per pound of inlet water by setting the strokes per minute of the injection pump. (1.2 gallons of methanol per MMSCF of 3# gas)
- Because of the potential for a freeze blockage in the unit, it is strongly recommended that a pressure controlled unit bypass be installed across the inlet and outlet piping to permit continuous gas delivery to the pipeline until skid operation can be restored to normal. If the pipeline will not permit offspec gas to flow for startup or thawing, or other system troubleshooting, then provision should be made to safely dispose of the off-spec gas during these periods, such as a flare or vent stack located safely at the edge of the facility and away from any exposure to neighboring personnel, residents, houses, businesses, etc.
DPC will work with the Lessee to recommend or provide additional controls and devices to meet specific or unique requirement for any location.