Energy Analysis of the New Dual-Pressure Low-Temperature Distillation Process for Natural Gas Purification Integrated with Natural Gas Liquids Recovery

The global natural gas demand is expected to rise continuously over the next decades, compelling industries to study and develop new natural gas purification processes, such as those using low-temperature, in order to allow the profitable exploitation of low-quality gas reserves (with high contents of CO 2 and/or H 2 S) that up to some years ago were not considered suitable for their commercialization. When dealing with natural gas, not only are acidic gases present in the main stream but also hydrocarbons heavier than methane (ethane, propane, n -butane, etc.). These substances may have to be removed from the produced gas for the dew point control of the sales gas or to manage its BTU content. Moreover, they are widely used for petrochemical productions and their recovery can be profitable for natural gas producers. In this work, an energy analysis is carried out in order to assess the energy requirements for the recovery of Natural Gas Liquids (NGLs) during natural gas purification at low-temperatures. The results are compared with the ones obtained when traditional processes (amine units + dehydration + demethanizer) are used for the same purpose, in order to define the trade-off between the two technologies, extended to the overall production chain, under different possible feed stream compositions. The complete natural gas production chain has been studied. The energy requirements for the considered process units for both the traditional and the low-temperature schemes have been calculated by means of detailed process simulations in Aspen Hysys V7.3 or by means of rules of thumb (when possible). Results prove the feasibility of low-temperature purification processes when dealing with gases having high amounts of acidic compounds and different concentrations of NGLs.