Optimum operating conditions for existing natural gas compression station

Abstract

There has been continuous evolution of NG treatment processes to meet the ever– increasing demands of electricity generation and various manufacturing sectors. Our focal point is the booster compression station of an existing gas plant which consists of two centrifugal compressors. The objective of the presented work is to debottleneck both compressor trains to increase its capacity and to study the effect of the proposed modifications on the downstream dehydration package that using adsorption by silica gel fixed beds. The presented modifications are adding two slip steams to the gas/gas heat exchangers, the first one to be installed on tube side and the second one on shell side, each slip stream will accommodate 160 MMscf/d. These will give the compression station an important advantage as the capacity of each train will increase from 450 to 610 MMscf/d per train that means we can got a gain of 320 MMscf/d per both trains to be added to the national gas grid at Egypt. The adsorption performance changed after adding both slip streams where the operating parameters of the inlet gas have changed such as temperature and pressure. The simulations for both cases existing and modifying compression station were conducted using Aspen- HYSYS simulation program. The simulation results shows that fuel gas consumption of both compressors driver gas turbines has increased from 6880 to 10000 Kw that equal 45.0% equivalent to 2.25 MMscf/d (1.125 MMscf/d per each) compared to compressed gas capacity increment by 35.5 % that equal 320 MMscf/d. Adsorption calculation for hydration beds shows that pressure drop per each bed increased from 0.66 to 1.19 bar but still within limit (Max 1.25 bar) and adsorbed water for each bed has increased from 1260 to 2850 lb H2O that equal 1590 lb H2O or 126 % while the bed should hold 6500 lb H2O.