A Case Study of the Supercritical CO2-Brayton Cycle at a Natural Gas Compression Station

Rafał Kowalski,Mariusz Łaciak,Tomasz Włodek,Adam Szurlej,Szymon Kuczyński

doi:10.3390/en13102447

Abstract

Heat losses caused by the operation of compressor units are a key problem in the energy efficiency improvement of the natural gas compression station operation. Currently, waste heat recovery technologies are expensive and have low efficiency. One of these technologies is organic Rankine cycle (ORC) which is often analyzed in scientific works. In this paper, the authors decided to investigate another technology that allows for the usage of the exhaust waste energy—the supercritical Brayton cycle with CO2 (S-CO2). With a thermodynamic model development of S-CO2, the authors preformed a case study of the potential S-CO2 system at the gas compressor station with the reciprocating engines. By comparing the values of selected S-CO2 efficiency indicators with ORC efficiency indicators at the same natural gas compression station, the authors tried to determine which technology would be better to use at the considered installation. Investigations on parameter change impacts on the system operation (e.g., turbine inlet pressure or exhaust gas cooling temperatures) allowed to determine the direction for further analysis of the S-CO2 usage at the gas compressor station. When waste heat management is considered, priority should be given to its maximum recovery and cost-effectiveness.

Highlights

Due to the constant global increase in energy demand in various forms, humanity is more and more willingly looking for solutions that will reduce the energy consumption at the stage of production and transportation
Assuming a constant heat flux to be in internal efficiency has a greater impact on the waste heat utilization rate (WHUR) than decrease in percent of waste heat transferred to the system, the smaller enthalpy at the main heat exchanger inlet causes that the CO2 transferred to CO2 (PWHT)
The increase of WHUR is much more significant when the temperature velocity in the exchanger must be lower, and the mass stream. When it comes to the increase difference between CO2 and flue gases in the heat exchanger decreases. This is due to the fact that in the mass stream of CO2 with the growth of exhaust gases temperature at the heat exchanger outlet, both cycle efficiency (CE) and percent of waste heat transferred to CO2 (PWHT) grow with the temperature difference drop

Summary

Introduction

Due to the constant global increase in energy demand in various forms, humanity is more and more willingly looking for solutions that will reduce the energy consumption at the stage of production and transportation. In the case of natural gas transmission, it is assumed that the process that requires the consumption of the largest amount of energy is compression of natural gas—compressor stations may be responsible even for 50% of total cost of gas transmission [1]. From the point of view of managing the energy efficiency of the natural gas compression station, the heat losses caused by the operation of compressor units are a key problem. One of the available options is waste heat recovery with the use of a system based on the organic Rankine cycle (ORC). This technology is often analyzed in scientific works e.g., [2,3,4,5].

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Conclusion