Gas Dehydration
Tri-ethylene glycol (TEG) is most commonly used to remove water from natural gas on land or platforms at sea. Wet natural gas and lean TEG are contacted countercurrently in the absorber to reduce the water content of the gas to pipeline specifications. The absorber is usually vertical to allow proper glycol flow with sufficient gas/liquid contact and operates at the pressure of the incoming gas. Rich TEG is either first transferred to a flash separator or sent directly to the regenerator, which consists of a still column and a reboiler. The reboiler normally operates at a temperature of 350°F to 400°F providing a TEG concentration of 98.7%. TEG is occasionally replaced when it becomes fouled with contaminants such as heavy hydrocarbons, well-treating chemicals, corrosion products, degradation products and salts. The presence of these contaminants may result in fouled equipment, foaming and poor dehydration, which cannot be overcome by increasing the recirculation rate. Gas dehydration by TEG requires less frequent reclamation since very little soluble salt is carried into the glycol system. The presence of acid gases and TEG degradation rate will determine purification frequency. The patented EET process may be also integrated in a slipstream configuration as shown in Fig. 5 for larger dehydrators where electric supply is available for removal of salts and degradation products. Treatment of a slipstream has the advantages of minimizing equipment size, costs, and operating energy with partial removal of the salts and degradation products only to the extent needed to avoid problems in the reboiler.
Industrial Heat Transfer Fluids
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