Recovery of transient medium-grade heat in temperature swing adsorption natural gas dehydration processes

Abstract

Temperature swing adsorption (TSA) is a mature technology for various liquids and gases processing, notably used for natural gas dehydration. During the operation of TSA dehydration systems, considerable amount of transient medium-grade heat is generated, and it is often dissipated to the atmosphere. This study intends to enhance the thermal performance of TSA processes by recovering the discontinued medium-grade heat through an organic Rankine cycle (ORC). TSA steps were adjusted, optimized, ORC equipment were selected and sized to meet the Oil & Gas industry standards. Zeotropic mixtures were used as working fluids. Results indicate that rich propane liquefied petroleum gas exhibits better performance, compared to rich butane liquefied petroleum gas. Operating its turboexpander under optimized conditions could generate 1.2 MW of power and could ensure an efficiency of 26%. Three shell and tube heat exchangers having a total surface of 145 m2, connected in series was found to be the best configuration of its evaporation section. Besides, machinery average cost represents 61% of ORC equipment cost. While, the evaporator constitutes only 14%. Key economic factors predict a rate of return that reaches 35% and a pay-out period of 5.5 years at electricity price equals to 0.100 $/kWh