At constant pressure, the water content of the inlet gas increases as the inlet gas temperature increases. For example, at 1,000 psia and 80°F gas holds about 34 Ib/MMscf, while at 1,000 psia and 120°F it will hold about 104 Ib/MMscf. At the higher temperature, the glycol will have to remove over three times as… Read More »
The commonly available glycols and their uses are: 1. Ethylene glycol—High vapor equilibrium with gas so tend to lose to gas phase in contactor. Use as hydrate inhibitor where it can be recovered from gas by separation at temperatures below 50° F. 2. Diethylene glycol—High vapor pressure leads to high losses in contactor. Low decomposition… Read More »
Since there is a large difference between the boiling point of triethylene glycol (546°F) and water (212°F), the still column can be relatively short (10 to 12 ft of packing). The glycol liquid in the reboiler is heated to 340°F to 400°F to provide the heat necessary for the still column to operate. Higher temperatures… Read More »
On larger streams filter separators are used as inlet scrubbers to further reduce glycol contamination and thus increase the life of the glycol charge. Due to their cost, filter separators are not normally used on streams less than approximately 50 MMscfd. Often on these smaller units a section in the bottom of the contactor is… Read More »
Most glycol dehydration processes are continuous. That is, gas and glycol flow continuously through a vessel (the “contactor” or “absorber”) where they come in contact and the glycol absorbs the water. The glycol flows from the contactor to a “reboiler” (sometimes called “reconcentrator” or “regenerator”1) where the water is removed or “stripped” from the glycol… Read More »
By far the most common process for dehydrating natural gas is to contact the gas with a hygroscopic liquid such as one of the glycois. This is an absorption process, where the water vapor in the gas stream becomes dissolved in a relatively pure glycol liquid solvent stream. Glycol dehydration is relatively inexpensive, as the… Read More »
The first step in evaluating and/or designing a gas dehydration system is to determine the water content of the gas. The water content of a gas is dependent upon gas composition, temperature, and pressure. For sweet natural gases containing over 70% methane and small amounts of “heavy ends,” the McKetta-Wehe pressure-temperature correlation, as shown in… Read More »
Gas dehydration is the process of removing water vapor from a gas stream to lower the temperature at which water will condense from the stream. This temperature is called the “dew point” of the gas. Most gas sales contracts specify a maximum value for the amount of water vapor allowable in the gas. Typical values… Read More »
Amine systems are extremely corrosive due to the acid-gas concentrations and the high temperatures. It is important that all carbon steel exposed to the amine be stress-relieved after the completion of welding on the particular piece. A system fabricated from stress-relieved carbon steel for DEA solutions, as recommended, will not suffer excessive corrosion. For MEA… Read More »
Due to side reactions and/or degradation, a variety of contaminants will begin to accumulate in an amine system. The method of removing these depends on the amine involved. When MEA is used in the presence of COS and CS2, they react to form heat-stable salts. Therefore, MEA systems usually include a reclaimer, The reclaimer is… Read More »