Aspen Plus Simulation of Power Generation Using Turboexpanders in Natural Gas Pressure Reduction Stations

Document Type : Original Article

Authors
Bijan Hejazi 1
Fatollah Farhadi 2
1 Chemical Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
2 Chemical & Petroleum Engineering Department, Sharif University of Technology, Tehran, Iran
Abstract
This paper investigates the economic feasibility of installing a turboexpander in parallel with the throttling valve of a city gate station for the purpose of distributed electricity generation through exergy recovery from pressurized natural gas. The preheating requirements for preventing hydrate formation due to pressure reduction are provided by the combustion of a small fraction of the outlet natural gas stream. As a case study, the simulation of Tehran No.2 City Gate Station demonstrates an exergy loss of more than 36.5 million kWh per year for the present throttling valves. Thermo-economic analyses gives the optimum operating conditions for electricity generation through a turboexpander. Optimization of preheating temperature leads to an exergy recovery of >60%, cost to generate electricity of <$0.04/kWh, and discounted payback period of around ~4 years. Simulation results can be used for designing an automatic preheating temperature control system to optimize exergy recovery via turboexpander under the variable operating conditions of a pressure reduction station.

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Article Title Persian

شبیه سازی تولید توان الکتریکی با استفاده از توربین‌های انبساطی در ایستگاه‌های تقلیل فشار گاز طبیعی با استفاده از نرم افزار Aspen Plus

Authors Persian

بیژن حجازی 1
فتح ا... فرهادی 2
1 استادیار گروه مهندسی شیمی، دانشکده مهندسی، دانشگاه فردوسی مشهد، مشهد، ایران
2 استاد دانشکده مهندسی شیمی و نفت، دانشگاه صنعتی شریف، تهران، ایران
Abstract Persian

این مقاله امکان سنجی اقتصادی تولید برق پراکنده از بازیافت اکسرژی جریان گاز طبیعی تحت فشار از طریق نصب توربین انبساطی به موازات شیر فشار شکن در ایستگاه تقلیل فشار شهری را مورد مطالعه قرار می دهد. احتیاجات پیش گرمایشی مورد نیاز برای جلوگیری از تشکیل هیدرات بر اثر افت فشار توسط احتراق کسر کوچکی از جریان گاز طبیعی خروجی تامین می گردد. به عنوان مطالعه موردی، شبیه سازی ایستگاه دروازه شهری شماره ۲ شهر تهران بیانگر اتلاف اکسرژی بیش از ۳۶/۵ میلیون کیلووات ساعت در سال توسط شیرهای فشار شکن موجود است. آنالیزهای ترمودینامیکی و اقتصادی، شرایط عملیاتی بهینه برای تولید برق توسط توربین انبساطی را بدست می دهند. بهینه سازی دمای پیش گرمایش منجر به بیش از ۶۰ درصد بازیافت اکسرژی، هزینه برق تولیدی کمتر از 0.04 دلار بر کیلووات ساعت و زمان بازگشت سرمایه حدود 4 سال می گردد. از نتایج شبیه سازی ها می توان برای طراحی سیستم کنترل خودکار دمای پیش گرمایش به منظور بهینه سازی بازیافت اکسرژی توسط توربین انبساطی تحت شرایط عملیاتی متغیر ایستگاه تقلیل فشار گاز استفاده نمود. 

Keywords Persian

گاز طبیعی
ایستگاه تقلیل فشار
توربین انبساطی
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Journal of Gas Technology
Volume 6, Issue 1 - Serial Number 6
September 2021
Pages 14-29