Glycol dehydration unit

The dehydration unit at Acheson is described briefly by Lock (1997). At Acheson they dehydrate about 13 x 103 Sm3/d of acid gas (90% C02 and 10% H2S) in a glycol dehydration unit. This dehydration unit operates at about 1500 kPa. 

The treated gas leaving the M D E A unit will require downstream dehydration since the pipeline gas specifications require a minimum water dew point. This is best achieved with a conventional TEG glycol dehydration unit, as the gas is very lean without condensable hydrocarbons. 

The emission of BTEX components from glycol dehydration units is strictly regulated in most countries. In the U.S., benzene emissions are limited to 1 ton/year (900 kg/year). Mitigation of BTEX emissions is an important component in the design of a dehydration system. Correctly estimating the quantity of absorbed BTEX and understanding the factors that affect absorption levels is critical. 

Finally, it should be noted that in the operation of a glycol dehydration unit, the desired outcome is to meet the water content specification for the outlet gas, e.g. 7 lbs H20/MMSCF (112 kg/10 Sm ). When using the graphs in this paper, different operating points (temperature, pressure and circulation ratio) will produce different outlet water eontents. Make sure that the operating points you are using to estimate BTEX absorption ean also meet the water specification. 

Three process requirements must be met for gas to be dried in a standard glycol dehydration unit ... 

Figure 11-13. Diagram of glycol dehydration unit used in air conditioning service. Gifford, 1957)...

Two additional steps were taken to minimize corrosion downstream of the glycol dehydrator unit. One was the use of a product-gas scrubber to minimize glycol entrainment in the gas stream, and the other was the use of a second inhibitor that was added to the dried-gas stream. This material was of the polyethanolrosinamine-type consisting of 70% solution in isopropyl alcohol of a mixture of 90% ethoxylated rosinamine (II moles ethylene oxide with each mole of rosinamine) and 10% free rosinamine. This inhibitor was injected at the rate of 0.1 gal/day for a gas volume of 60 MMsef/day. As a result of the above measures, the corrosion rate of coupons suspended in the dried-gas line decreased from almost 30 mils ear to as low as 0.2 mil/year during about 4 years of testing. 

An alert on hydrocarbon emissions from glycol dehydration units issued by 77te American Petroleum Institute, in connection with their Specification for Glycol-Type Gas Dehydration Units (1990), contains a mass balance for a 10 MMscfd TEG unit operating at 800 psia and 130°F with a feed gas containing 100 ppm benzene. The study indicates that 10% (3 tons per year) of the benzene is absorbed and discharged in the regenerator vapor stream. In this... 

Bentley. M. T., 1991, The Basics of Operating Glycol Dehydration Units, presented at the 1991 AlChE Spring National Meeting, April 1-11, Houston, TX. 

Herrin, J. P., 1990, Solving Glycol Dehydration Unit Operating Problems by Use of Process Fundamentals, Proc. Laurance Reid Gas Conditioning Conf., University of Oklahoma, Norman, OK, p. 1. 

The glycol dehydration unit is extensively used in the oil and gas industry to produce dehydrated gas. The saturated gas, if left without treatment, can cause major problems, including ... 

A glycol dehydration unit is most commonly used in the industry because of the following advantages over solid desiccant ... 

The glycol dehydration unit is comparatively cheaper to install. 

The basic scheme is presented in Figure 5.1. The glycol dehydration unit can be installed either up- or downstream of the compressor. The following advantages/disadvantages need to be considered before finalizing the location. 

---