Optimization for Gas Plant Processes Utilizing Aspen Economic Analyzer Techno-Economics

The high quality of natural gas depends on three main important parameters; hydrocarbon dew point, water dew point, and cricondentherm. Controlling these parameters play an important role to get sales of gas that meets the specification of gas pipeline transmission to be below the pipeline operating conditions.

The process facilities of a gas plant covering the LTS trains and LPG production units to control the specification of natural gas using the J-T expansion technique in two schemes (with or without a mechanical refrigeration unit). This paper comprises two main parts; the first part is to simulate the process of an existing natural gas plant in Egypt that produce natural gas, condensate, and LPG.using steady-state model Aspen HYSYS to select the optimum operating conditions to meet the specification of gas pipelines transmission. The second part comprises the techno-economic study for gas plant processes using Aspen Process Economic Analyzer to select the optimum scheme depending on the profitability index and payout period and also the capital and operating cost; and compare two schemes (with and without refrigeration) from the economic point of view.

The results of scheme 1 (without refrigeration) showed that increasing the differential pressure of Joule – Thomson valve from 12 bar to 24 bar causes a decrease in hydrocarbon dew point, water dew point from -1 °C to -26 °C and from 0 °C to -18 °C, respectively using composition (C1). It is observed that the optimum differential pressure shall be higher than 12 bar.

The techno-economic study observed that scheme (1 & 3) using Joule - Thomson is the optimized configuration in the gas plant which achieves the economic parameters when compared to scheme (2). However, the design of gas plant process using scheme (3) achieved a cost saving of around $ 5,722,550 as it is more economic and profitable in case of producing natural gas only rather than producing natural gas and LPG together. Accordingly, it is recommended to use scheme 3 through using J-T valve without refrigeration unit as it is the most economical scheme.