Process & Equipment Description

Inlet Separator:
Sour feed gas at a pressure range of 180-190 psig for LP modules and 1000 psig the HP module and temperature of 90-130 deg. F enters each gas treating module at the feed gas filter separators, D-*01. The purpose of this vessel is to separate the inlet fluids into the two phases. A second, and very important function, is to be able to handle any slugs of liquids from the pipeline system, without contaminating the exist vapor from the vessel with liquids. There are three filter separators in each Gas Treat Unit. The separators are divided into two (2) compartments. The first compartment contains filter elements and the other compartment contains vane de-misters.

The Sour Gas first contacts the filter elements to remove solids such as dirt and iron sulfide particles. The elements will also coalesce droplets of water and hydrocarbon. This operation is done to help minimize foaming in the DGA Contactor. Most of the liquid material drops out in the first compartment and little finds its way to the second compartment. The second section’s demister will remove any residual water entrained in the gas. Any increase in differential pressure indicates fouling of the filter which requires replacement when it reaches 15 psia.

Dew Point System:
The function of the dew point system is to remove heavy hydrocarbons from the sour gas before entering the contactor and coming into contact with the amine solvent. Heavy hydrocarbons especially aromatics dissolve in the amine solvent lowering its surface tension and causing foaming. It is desired to cool the sour gas to low temperatures however hydrate formation temperature is a limiting factor. As a result, it is a practice to chill the sour gas to about 5 F above its hydrate formation temperature.

Contactor:
The absorber or contactor is a vertical pressure vessel containing about 23 trays. The mass transfer of the acid gases from the gas to the sweetening solvent takes place in this vessel. The bulk of the absorption occurs on the first 2 to 5 trays in the bottom section of the tower. With amine-based solvents, the absorption is by chemical reaction, which is exothermic. This may increase the exit temperature of the solution by several degrees, depending on the concentration of the acid gases in the sour gas and the mole loadings. The rich solution leaves the bottom of the tower through a liquid level control and pressure letdown valve. Contactor operating pressures can very considerably; in the units operate at 180 psig where as the HPDGA unit operates at 1000 psig.