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Gas turbine efficiency enhancement using waste heat powered absorption chillers in the oil and gas industry.

Author(s) : POPLI S., RODGERS P., EVELOY V.

Type of article: Article

Summary

In hot climates, the efficiency of energy-intensive industrial facilities utilizing gas turbines for power generation, such as oil refineries and natural gas processing plants (NGPPs), can be enhanced by reducing gas turbine compressor inlet air temperature. This is typically achieved using either evaporative media coolers or electrically-driven mechanical vapor-compression chillers. However, the performance of evaporative media coolers is constrained in high relative humidity (RH) conditions, such as encountered in the Middle East and tropical regions, and such coolers require demineralized water supply, while electrically-driven mechanical vapor-compression chillers consume a significant amount of electric power. In this study, the use of gas turbine exhaust gas waste-heat powered, single-effect water-lithium bromide (H2O-LiBr) absorption chillers is thermo-economically evaluated for gas turbine compressor inlet air cooling scheme, with particular applicability to Middle East NGPPs. The thermodynamic performance of the proposed scheme, integrated in a NGPP, is compared with that of conventional evaporative coolers and mechanical vapor-compression chillers, in terms of key operating parameters, and either demineralized water or electricity consumption, respectively. The results show that in extreme ambient conditions representative of summer in the Persian Gulf (i.e., 55 °C, 80% RH), three steam-fired, single-effect H2OeLiBr absorption chillers utilizing 17 MW of gas turbine exhaust heat, could provide 12.3 MW of cooling to cool compressor inlet air to 10°C. In the same ambient conditions, evaporative coolers would only provide 2.3 MW cooling capacity, and necessitate consumption of approximately 0.8 kg/s of demineralized water to be vaporized. In addition, mechanical vapor-compression chillers would require an additional 2.7 MW of electric energy to provide the same amount of cooling as H2OeLiBr absorption chillers. The additional electricity generated through gas turbine compressor inlet air cooling using the waste heat powered absorption refrigeration scheme is of approximately 5264 MWh per year, compared to 1774 MWh for evaporative cooling. When integrated with other plant process cooling applications, the proposed scheme would not only permit to both meet gas turbine compressor inlet air cooling loads throughout the year, including peak summer loads, but also provide other process cooling during off-peaks time periods. The economic paypack period of the waste heat recovery scheme is estimated to range from 1.3 to 3.4 years for a three-chiller system based on present and project utility prices for NGPPs in the United Arab Emirates. This study suggests that waste heat absorption refrigeration is an attractive solution to enhance electrical power generation in Middle East NGPPs through gas turbine inlet air cooling, both in terms of thermodynamic and economic feasibility. This strategy would also reduce plant natural gas consumption for power generation, hence production costs and emissions.

Details

  • Original title: Gas turbine efficiency enhancement using waste heat powered absorption chillers in the oil and gas industry.
  • Record ID : 30006108
  • Languages: English
  • Source: Applied Thermal Engineering - vol. 50 - n. 1
  • Publication date: 2013/01
  • DOI: http://dx.doi.org/10.1016/j.applthermaleng.2012.06.018

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