TABLE OF CONTENTS Natural, associated, or tail gas usually contains water, in liquid and/or vapor form, at source and/or as a result of sweetening with an aqueous solution. Operating experience and thorough engineering have proved that it is necessary to reduce and control the water content of gas to ensure safe processing and transmission. The major reasons for removing the water from natural gas are as follow.
Natural gas in the right conditions can combine with liquid or free water to form solid hydrates that can plug valves fittings or even pipelines.
Water can condense in the pipeline, causing slug flow and possible erosion and corrosion.
Water vapor increases the volume and decreases the heating value of the gas.
Sales gas contracts and/or pipeline specifications often have to meet the maximum water content of 7 lb H 2O per MMscf.
Pipeline drips installed near wellheads and at strategic locations along gathering and trunk lines will eliminate most of the free water lifted from the wells in the gas stream. Multistage separators can also be deployed to ensure the reduction of free water that may be present. However, removal of the water vapor that exists in solution in natural gas requires a more complex treatment. This treatment consists of "dehydrating" the natural gas, which is accomplished by lowering the dew point temperature of the gas at which water vapor will condense from the gas.
There are several methods of dehydrating natural gas. The most common of these are liquid desiccant (glycol)...
