Organic Rankine cycle |
Egyptian gas compression project demonstrates the benefits
Implementation of organic Rankine cycle (ORC) technology, which turns waste heat into useful power, represents a smart way to aid progress towards decarbonisation. A pioneering first of a kind project developed by Turboden plus partners will see the deployment of a 28 MWe ORC system – the largest high temperature ORC installation ever built – in GASCO’s Dahshour compression station in Egypt. Coupled to two 10 MWe EMD (electric motor driven) compressor trains working in island mode, the new installation increases compression capacity by 25% without any additional fuel consumption
The project has its origins in the need to meet the increasing demand for natural gas in Egypt and the call from the Egyptian Ministry of Petroleum, which has drawn up plans for natural gas network expansion and development including energy efficiency improvements.
GASCO (Egyptian Natural Gas Holding Company) owns and operates the large natural gas compression station (Figure 1) in the outskirts of the small town of Dahshour, just south of Cairo.
The goal of the compression station is to pump natural gas extracted from the Mediterranean to the southern part of Egypt, to meet growing demand from large combined cycle plants and emerging industries. Specifically, GASCO wanted to increase the Dahshour gas compression capacity by around 652 MMSCFD, roughly 70% of existing capacity. The traditional approach to meeting GASCO’s requirements would have been the installation of new gas turbine trains operating in open cycle mode to power mechanical compressors to pump the gas through the pipeline. Despite being reliable and field proven, this scheme wastes a significant amount of energy (as well as releasing a huge amount of CO2
) and
moreover literally burns gas that could be otherwise sold to the market.
Indeed, from an energy management point of view, compressor stations represent one of the biggest energy consumers for a pipeline and the cost of compression can reach up to 50% of total transmission costs.
A promising way to enhance process efficiency therefore involves recovering compressor driver wasted heat and converting it into mechanical or electrical energy. Building on its long track record in organic Rankine cycle technology (more than 400 ORC turbines installed), Turboden (a Mitsubishi Heavy Industries Group company) responded by developing a first of its kind solution consisting of an ORC coupled with electric motor driven (EMD) compressors. This increases pumping capacity by converting waste heat into electric power, thus avoiding gas consumption.
Dahshour compression station upgrade
The Dahshour gas compression upgrade will include the installation of a new gas turbine and a heat recovery system rather than installing two new gas turbines.
The ORC system will be powered by heat recovered from four of the gas turbines at site. One of the old GE gas turbine trains will be used as a spare in case of emergency.
Above: Figure 1. GASCO’s Dahshour compressor station
The 28 MW gross produced by the ORC system (two ORC units, each rated at 16 MVA) will feed two new electric motor driven compressor trains, avoiding the need for new gas turbine trains. The power produced by the ORC system will also cover the remaining electrical loads of the compressor station, without importing electricity from the national grid, thus making it electrically self-sufficient.
Figure 2 shows a Turboden ORC power plant located in New Mexico, USA, while Figure 3 shows a Turboden ORC turbine. Figure 4 provides an overall aerial view of the ORC system, gas turbines and heat recovery units at the Dahshour gas compressor station, while Figure 5 focuses on the ORC units at Dahshour.
Left: Figure 2. Example of an ORC power plant
Above: Figure 3. Turboden ORC turbine 18 | July/August 2021 |
www.modernpowersystems.com
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