Simulation and optimization of refrigeration cycle in NGL recovery plants with exergy-pinch analysis

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.

Section: Resultsmentioning

confidence: 85%

“…A thermodynamic loss within a process can be caused by a loss of flow through a system boundary or by internal exergy destruction. The exergetic analysis has been applied with great success by many authors in different literatures …”

Section: Introductionmentioning

confidence: 99%

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

Safarvand

Aliazdeh

Giri

et al. 2014

“…Normally, kinetic exergy and potential exergy are negligible. High‐pressure propane recovery processes are closed, with no material exchange with the environment; thus, the chemical exergy of the processes can be considered zero . The exergy analysis of all processes is used mainly in the calculation and comparison of physical exergy.…”

Section: Study Conditions and Methodsmentioning

confidence: 99%

“…High-pressure propane recovery processes are closed, with no material exchange with the environment; thus, the chemical exergy of the processes can be considered zero. 20 The exergy analysis of all processes is used mainly in the calculation and comparison of physical exergy. A pressure of 101.325 kPa and a temperature of 298 K are regarded as the environmental reference state.…”

Section: Exergy Analysis Methodsmentioning

confidence: 99%

The improvement and analysis of the high‐pressure propane recovery process

Jiang

Zhang

Jing

et al. 2018

The recovery of propane from high‐pressure natural gas is an effective approach to increasing the economic benefits of the gas field. Currently, the high‐pressure absorber (HPA) process is the most common process available for recovering high‐pressure natural gas liquid. We have proposed two improved processes based on the HPA process for propane recovery from high‐pressure natural gas: revised HPA and HPA recycle liquid (HPARL) processes. Through the optimization algorithm, the three processes were optimized with the lowest unit energy consumption as the objective. The optimization results show that the HPARL process has a substantial energy‐saving advantage when the feed pressure is sufficiently high under lean gas conditions, whereas the HPARL process requires greater cooling capacity than the HPA and revised HPA processes under rich gas conditions to ensure recovery. The exergy analysis of the processes under the optimized conditions shows that the main exergy loss in the three processes originates from the deethanizer and that the exergy loss difference caused by the deethanizer in each process is derived from the first stage and the eighth stage. Because of the extensive exergy loss at the first stage of HPARL, this process has the highest deethanizer exergy loss under all conditions. The exergy efficiency difference among the three processes is very small under different conditions.

“…The exergy destruction rate

((), {\overset{I}{true}}_{HE})

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

{\dot{I}}_{HE} = \sum {\dot{m}}_{in} e_{in} - \sum {\dot{m}}_{out} e_{out}

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 .…”

Section: Exergy Analysismentioning

confidence: 99%

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

Shehata

Bhran

Shoaib

et al. 2019

Nowadays, gas processing for natural gas liquids (NGLs) recovery is becoming of great interest. However, many of the present NGLs recovery units in operation do not give the desired revenue. This study focuses on the retrofitting of an existing NGLs plant constructed in Egypt for maximizing LPG product recovery due to its high economic value. Various alternatives have been suggested to maximize LPG recovery, while achieving the same cooling target and ethane recovery in terms of power consumption and additional capital cost. The economic study shows that replacing the existing pure propane refrigerant used to recover C 5 + (pentane and heavier) in the existing plant by a mixed refrigerant type is the best retrofitting technique. Furthermore, the exergy of the whole NGL unit was studied to evaluate the exergetic performance of all suggested upgrading methods. Regarding the upgraded plant, the butanes and propane recoveries were increased by 13% and 7%, respectively, with 15.95% increase in LPG overall recovery. In addition, the solutions of operational problems that may appear in the glycol injection system, propane refrigeration facilities, and de-ethanizer unit facilities when switching from single refrigerant to mixed refrigerant have been taken into consideration.