Importance of Benchmarking, Parametric Assessment for Capacity Enhancement

Abstract It is very important to benchmark the plant performance and check existing unit adequacy in detail to ensure integrity and operating flexibility for the potential capacity enhancement. In this study 110% capacity enhancement of existing acid gas removal unit and NGL units are targeted with higher ethane recovery and the study is conducted to identify any bottlenecks / limitations. The digital twin model is developed in performing the adequacy checks with digital databank of the existing facilities. Bench marking simulations and parametric study is carried out to clearly demonstrate the plant performance in terms of product quality, major equipment performance, duty, utility (refrigerant, steam requirement) and available margin on equipment. The detailed process simulation model developed with rigorous modelling of Column internals, Exchangers, compressors, expanders, steam turbines, pumps etc. The calculation routines for adequacy check of all type of separators, molecular sieves beds, piping, inline instruments are built in the excel digital twin concept. The approach of rating mode of simulation and results transfer from HYSYS to excel digital twin completes adequacy check quickly in details. Based on one-year operating data, processing capacity limits of process trains are established for different range of feed compositions anticipated. Process simulation and detailed equipment level adequacy checks has been performed for benchmarked plant performance as well as increase in feed gas throughputs to the maximum limits in steps. The parametric study identified the potential capacity enhancement of existing AGRU and NGL units is possible up to 110% compared to original design for various compositional cases simulated. The study established the maximum CO2 concentration in the treated gas from acid gas removal unit shall be limited less than 1% to avoid potential freezing issues in NGL unit for the targeted ethane recovery level. NGL unit capacity and ethane recovery levels are limited by the richness of the gas, a nomogram is developed indicating the maximum through put that could be achieved with respect to C2+ content in the feed gas for the targeting ethane recovery levels. The propane refrigerant compressors in the unit were limiting the process capacity for the targeted recovery levels. Few minor debottlenecking measures were identified in AGRU units to ensure the plant safe operating limits. The detailed study ensured safe operation, integrity and no HSE concerns. This study helped in maximizing overall asset utilization and supporting the revenue stream in terms of more gas throughput and higher NGL recovery. The detailed digital twin modelling approach adopted along with the simulation data integration to perform calculations helped to do the detailed study to complete quickly with all the necessary information.