Exergy analysis of NGL recovery plant using a hybrid ACO_R‐BP neural network modeling: a case study

Abstract

The major objective of the study is to make exergy analysis of natural gas liquid (NGL) process more understandable by coupling it with the use of an artificial neural network modeling. The presented method permits to provide an energy diagnosis of the process under a wide range of operating conditions. As a case study, Siri Island NGL Recovery in Iran is considered. The Aspen Plus process simulator linked with MATLAB Software was used to obtain thermodynamic properties of the process streams and to perform exergy balances. The results are validated with industrial data. The exergy destruction and exergetic efficiency for the main system components and for the entire system were calculated. Major sources of irreversibility in the process are identified, and the best conditions for process improvement are presented. The simulation results reveal that the exergetic losses of the separation towers, heating/cooling equipment, and compression/expansion section obtain the highest rank among the other components of the plant. The results show that the overall exergetic efficiency of the system is about 61%. After proposing new operational conditions, another exergetic analysis was made that caused a decrease of 6% in the exergetic losses of the entire system. Then, the recorded and calculated data are used as inputs for the neural network. The results show that ACO R is highly effective to optimize the performance of the neural networks to predict overall exergy efficiency. This method was compared with other current methods, and the results indicated that the integrated n Ant Colony Optimization-Back Propagation (ACO R -BP) provides the least error on the testing dataset.

Advanced exergy analysis of the natural gas liquid recovery process

“…The exergy analysis method is a key issue for a better understanding the locations, causes, and magnitudes of process inefficiencies [7]. CEA is a useful technique to evaluate the performance of chemical processes [23].…”

“…This shows a promising future for its natural gas and NGL recovery industries. In this regard, Iran's natural gas production has rapidly increased over the past two decades, from 0.9 Tcf in 1991 to 1127.7 Tcf in 2018 [6,7].…”

“…High energy consumption is the most important problem of NGL production technologies, especially in the refrigeration cycles [14]. Exergy analysis in such plants allows determining the most inefficient parts of a process where energy is wasted [7]. Raising the quality level of energy consumption is logical to improve the efficiency of these plants [13].…”

Liquefied petroleum gas recovery enhancement via retrofitting the refrigeration system of an existing natural gas liquid plant

“…The exergy destruction rate for the original heat exchangers or the LNG unit heat exchangers is calculated as the difference of the exergies of the incoming and the outgoing streams as presented in Equation The exergetic efficiency of the heat exchangers is defined as the ratio of the increase in the cold streams exergy to the decrease in the hot streams exergy as illustrated in Equation .…”

“…The exergy destruction and exergetic efficiency of the column equipped with condenser at top and reboiler at the bottom could be estimated by using Equations and , respectively where , and are the vapor, liquid, and feed flowrate of the column (kg/s), respectively; e vap , e liq , and e feed are the specific vapor, liquid, and feed flow exergy (kJ/kg), respectively; and Q heat and Q cond are the heat transfer rate added to the reboiler and removed from the condenser (kW), respectively.…”