Waste Heat to Power Through Organic Rankine Cycle ORC Technology: Das Island Case Study

Abstract

Same as other energy-intensive industries, ADNOC LNG is looking at the development of energy-efficiency solutions aimed to improve production process sustainability while maintaining effectiveness and competitiveness. The conversion of waste heat into useful power represents a viable and profitable solution to hit these targets. The possibility to implement an ORC-based heat recovery system as a replacement of an open-cycle gas turbine in Das Island facility has been investigated. The study evolved in two main phases. The first one was aimed to identify the most suitable waste heat sources present on site. This included the quantification of the waste heat sources needed to achieve the forecasted power demand while complying with layout constrains. The second one was directed to the technical and economic analysis of different heat recovery configurations, in order to understand the best ORC solution. The outcome of the second phase constitutes the reference business case that will be used to compare the ORC with the alternative power production technology, i.e. an open-cycle gas turbine. With a view to the commissioning of new projects in Das Island and the resulting power consumption increase, ADNOC LNG was originally planning to cover this extra power demand by installing a new open-cycle gas turbine. Given the presence on site of other several open-cycle gas turbines, a waste-heat-to-power solution appeared to be an alternative and feasible solution. The ORC technology, thanks to the use of an organic working fluid, is able to recover the exhaust gas sensible heat and produce power, resulting in a simple power plant with extremely low operation and maintenance costs, high availability, simplicity of operation and no water consumption if an air-cooled condenser solution is selected. Depending on the combination of gas turbines considered for heat recovery in Das Island, the ORC power output can reach up to 30+ MW el., covering a not-negligible portion of Das Island electrical consumption and allowing considerable fuel savings, computed in 10 MMSCFD of fuel gas that can be saved and thus re-allocated to produce useful gas products. The study showed that the ORC solution is viable and can produce the required power at the allocated plot area, which was reserved for the open-cycle gas turbine. Das Island case study represents one of the first systematic analysis aimed at the integration of an ORC-based heat recovery system within an existing LNG facility. The results of the investigation appear very promising: with a computed LCOE < 30 USD/MWh and breakeven of 3 years, the ORC embodies a possible alternative to traditional power-production technologies. This type of project would be the first in the Region, making ADNOC LNG a pioneer of the technology.