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EU Eyes Waste Heat

Dec. 13, 2020
Several projects aim to reduce the impact of energy-intensive processes

The latest CORDIS results pack — a roundup of research funded by the European Union (EU) into promising technologies for reducing the impact of energy-intensive industrial processes — spotlights efforts to enable taking greater advantage of waste heat.

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The brochure focuses on eight cutting-edge projects covering topics as diverse as new generation organic Rankine cycle (ORC) systems, novel heat exchange and thermal energy storage technologies, and innovative heat pump technologies.

Spanish research foundation Technalia, San Sebastián, Spain, is coordinating two of the projects.

The first, Indus3Es, focuses on recovering low-quality waste heat, which the report notes often is neither practical nor economically viable for process companies today.

The report points out that, overall, a large portion of waste heat in the chemical and other energy-intensive industries has a temperature below 200°C. Yet, economically viable heat-recovery technologies have been limited primarily to medium-to-high-temperature waste-heat sources.

Under Indus3Es, a low-cost system based on absorption heat transfers (AHTs) has been developed to maximize heat recovery at temperatures below 150°C. Turkey-based petrochemical company Tüpraş has installed and demonstrated the system.

“The AHT developed within Indus3Es effectively recovers and revalues low-temperature waste heat at competitive costs. Using a waste steam of around 100°C, it produces a higher temperature stream, becoming reusable in refinery operations. Overall, it leverages about 50% of low-temperature heat that would otherwise be discharged to the atmosphere,” explains researcher Asier Martinez-Urrutia.

Essentially, an AHT operates in the reverse way to absorption chillers. Both consist of a condenser, an evaporator, an absorber and a generator. The difference is that the absorber and evaporator now operate at a high pressure and the condenser and generator at a low pressure.

The payback period of the 200-kW system in Turkey is estimated to be under 10 years, which the researchers point out is a very positive value for a first capacity level prototype. They are now looking to develop systems that work at much bigger scales: a 1-MW AHT would reduce payback to two years, for example.

Also coordinated by Technalia is the TASIO project, which focuses on exploiting waste heat recovery technologies based on the ORC.

In this version of the Rankine cycle, an organic fluid is used instead of water. Vapor from the fluid, which has a much lower boiling point than water, powers a turbine that can be directly coupled to a generator to produce electricity or to a compressor to compress air for mechanical work. It differs from a typical ORC arrangement which uses indirect exchange of heat to the organic fluid via a heat transfer fluid.

As project manager Pedro Egizabal notes in the report, TASIO was the first application of direct-heat-exchange-based ORC technology to energy-intensive industries.

“The benefits of eliminating the intermediate heat transfer fluid, makes the process simpler, enhances heat transfer efficiency and reduces maintenance costs,” he says.

The TASIO team successfully demonstrated the technical and economic feasibility of the direct heat exchange ORC technology to produce up to 2 MW of electric capacity in an operating cement plant.

The system also reduced water consumption as a high-pressure pump provided water to cool the waste gas.

In addition, a small-scale demonstrator validated a 15-kW ORC module to generate compressed air.

Finally, researchers conducted feasibility and cost analyses associated with applying ORC technology to a pilot plant for the treatment of petrochemical sludge.

The report notes that fundamental to this project’s success was new coating/steel substrate combinations for production of components for the higher-temperature conditions relative to a conventional ORC.

(Editor’s Note: For more ORC applications, see December 2020’s Energy Saver column, “Consider ORCs for Waste Heat Recovery.”)

A briefer mention is made of the ongoing DryFiciency project, which aims to develop technically and economically feasible ways to upgrade low-temperature idle waste heat streams into process heat supply at temperature levels of up to 160°C. This project focuses on industrial drying and dehydration processes applications. Its key technical elements include high-temperature vapor compression heat pumps: two closed-loop heat pumps for air-drying processes and an open-loop heat pump for steam drying processes.

Currently, three European process companies are demonstrating DryFiciency under real operational industrial drying processes.

In conclusion, the CORDIS report notes that while the use of such technologies will enhance the competitiveness and sustainability of all energy-intensive industries, they will require support from policy makers for further adoption.

Read an online edition of the full report. 

Seán Ottewell is Chemical Processing's editor at large. You can email him at [email protected].

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