Energetic, exergetic, environmental and economic assessment of a novel control system for indirect heaters in natural ga

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Energetic, exergetic, environmental and economic assessment of a novel control system for indirect heaters in natural gas city gate stations Amir Ebrahimi‑Moghadam1,2 · Mahdi Deymi‑Dashtebayaz3 · Hosein Jafari3 · Amir Niazmand1 Received: 1 November 2019 / Accepted: 4 February 2020 © Akadémiai Kiadó, Budapest, Hungary 2020

Abstract  The energy consumption and greenhouse gases emissions in natural gas city gate stations are important issues in the natural gas industry. In order to improve efficiency, have a cleaner environment and achieve economic benefits, the present study aims to propose an optimal system for the indirect water bath heaters in natural gas city gate stations. The optimization procedure is carried out by designing a control system to gain an eligible discharge temperature for the heater based on the gas entry conditions to the city gate station. The controller calculates the temperature of hydrate formation in terms of passing gas pressure and gives this information to the torch of the heater for regulating fuel consumption. A comprehensive study is accomplished based on energy, exergy, environment and economic analysis for different pressure reduction stations. The results indicate that employing the proposed system decreases the amount of fuel consumption and greenhouse gases emissions along with increasing system efficiency. Analyzing the results reveals that using the proposed system leads to a maximum of 28.54% relative increment in the heater efficiency compared to the conventional system (at this condition, the heater efficiency of the conventional and proposed system is η = 36.12% to η = 46.43%, respectively). Furthermore, with choosing a heater with a capacity of 100,000 SCMH, it is possible to reduce the pollutants emissions and total costs down to 142.6 tons per year and 3,671,000 $ per year, respectively.

* Amir Ebrahimi‑Moghadam [email protected]; [email protected] 1



Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran

2



Department of Energy Technology, Aalborg University, Esbjerg, Denmark

3

Department of Mechanical Engineering, Center of Computational Energy, Hakim Sabzevari University, Sabzevar, Iran



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Graphic abstract

Pollutants

LPLTNG

HPHTNG

HPLTNG

Regulator Indirect water bath heater

Fire tube

Reducing fuel consumption for natural gas preheating Increasing the efficiency of heaters Reducing exergy destruction in system Reducing pollutants emissions Various cost savings HPLTNG: high pressure-low temperature natural gas HPHTNG: high pressure-high temperature natural gas LPLTNG: low pressure-low temperature natural gas

Keywords  City gate station · Water bath heater · Fuel consumption · Greenhouse gases emission · Techno-economic analysis List of symbols E Exergy (J) Ė Exergy rate (W) ē Specific exergy (kJ kmol−1) g Gravitational acceleration (m s−2) h Specific enthalpy (J kg−1) ṁ Mass flow rate (kg s−1) P Pressure (MPa) Q̇ Heat rate (W) R̄ Universal