Assessment of Power Generation Through Pressure Reduction in High Pressure Natural Gas Pipelines of SNGPL

Abstract

Natural resources of in Pakistan face limitations of its power system as the country currently uses 1,559 billion cubic feet of natural gases annually. The natural gas network consists of high pressure transmission pipelines that operate at pressures ranging between 600–1200 psig under exclusive management by two state-owned companies SNGPL (Sui Northern Gas Pipeline Limited) and SSGCL (Sui Southern Gas Company Limited). SMSs (Sales Metering Station) utilize Pressure Control Valves to reduce transmission pressure to distribution pressures typically set at 100-150 PSI so end users obtain the required pressures. At SMSs which are approximately 433 currently, SNGPL use Pressure control valves (PCVs) or throttle valves to execute isenthalpic expansion for natural gas pressure reduction without energy recovery. Natural gas stores high-pressure energy yet this stored energy remains untapped during the process. Under this framework Turbo Expanders (TEs) serve as an available control option at throttle valve stations throughout SMS locations. Natural gas turbines named Turbo expanders utilize pressure variability in natural gas channels to generate mechanical energy to activate electric generators or other mechanical devices. This research paper evaluates power generation capabilities and energy progressivity measures of the SNGPL SMSs facilities at Naughazi, Rawat and Ranial. This study determines the power generation capacity of these facilities by running simulations through Aspen HYSYS® software as well as some theoretically calculation and evaluation. The study demonstrates significant energy recovery capabilities that remain lost at SMSs locations through turbo expander implementation. The current 433 SMS locations within SNGPL's network demonstrate substantial untapped power generation potential according to this work which requires immediate loss reduction strategies. The simulation results produced by Aspen HYSYS® indicate that the three principal SMS sites currently transmitting and distributing Rawalpindi and Islamabad capital city of Pakistan could potentially generate 361.62 Megawatt per month through pressure-reducing stations within the SNGPL network. The research demonstrates that turbo expanders provide a path to integrate into SMS systems for harnessing this current energy waste which increases Pakistan's power generation efficiency.