(07-18-2013, 10:40 PM)ArtM72 Wrote: I suspect the free water and condensates are removed at the CSP, leaving the CO2 and lower molecular weight hydrocarbons like ethane and propane to be removed at the LNG plant. I doubt there is much of a problem mixing the dry gas in the pipeline from E/A with gas from the Highlands unless the Highlands gas has a significantly different composition than that from E/A. We know that E/A has very little H2S and its CO2 content is low as well. This is very good. I don't recall hearing of or seeing the specific mix of higher mw hydrocarbons, but that could likely change over time as the gas is drawn out of the formation. The question becomes whether there is sufficient flexibility designed into the LNG plant to handle the mix. I suspect there is no technical or capacity problem there, but possibly an item to be considered in negotiations. It might be that enough additional ethane, propane etc is "value added".
How it Works!
At the CSP the “liquid” water and hydrocarbon condensate is removed from the gas stream. The gas stream then contains water vapor and 3-6% CO2 and a trace of H2S (hydrogen sulfide) which will need to be removed before the gas is put into the pipeline. The water vapor will be removed at the CSP by bubbling the gas through a TEG (triethylene glycol) liquid and the CO2 and H2S will be removed by bubbling the gas through an Amine solution. The glycol and amine solutions are heated (regenerated) to drive off the impurities and water so that the liquid glycol and amine can be re-circulated for continuous reuse.
The hydrocarbon gases will be put into the pipeline at “pipeline specifications” of water content etc.
The hydrocarbon gases from Elk/Antelope will be very similar to the gas from the Exxon/OilSearch highlands fields and there will be no problem mixing them in the same pipeline or processing the gas in the same LNG train. Of course that will have to be true since the gas will all be in the same pipeline. If there is any worry about one of the gas streams being more valuable than the other the gas can be valued and sold by the BTU instead of the MCF before mixing the two streams.
The propane and butane can be removed at the LNG plant for local sale or the propane and ethane may be left with the LNG and sold as a higher BTU content LNG to the LNG buyer. The LNG will be mostly methane (CH4) but the ethane (C2H6) and propane (C3H8) will also be in liquid form at -164 degrees Centigrade. See
http://www.elmhurst.edu/~chm/vchembook/5...ngpts.html
LNG is stored and shipped near atmospheric pressure. When the LNG in the storage tank or ship reaches the boiling point of methane (-164 degrees centigrade) it is vented from the storage tank. The vented gas can be used for fuel, re-liquefied at the LNG plant, vented to the atmosphere or flared. Of course we do not want to vent it to the atmosphere or flare it except in case of an emergency.