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Waste Heat Recovery in Industrial Drying Processes

Periodic Reporting for period 2 - DryFiciency (Waste Heat Recovery in Industrial Drying Processes)

Reporting period: 2018-03-01 to 2019-10-31

The industrial sector accounts for 25% of the total final energy consumption in EU-28 in 2015, of which 12% to 25 % is attributable to industrial drying. Drying and dehydration processes are currently primarily fossil-fired, generating large volumes of low grade waste heat that are not or only minimally utilized. Hence, industrial drying offers large potential for improved energy efficiency, reduction of fossil carbon emissions, and increased competitiveness by introducing advanced energy efficiency technologies.

The overall objective of the DryFiciency project is to lead the European energy intensive industry to high energy efficiency and a reduction of fossil carbon emissions by means of waste heat recovery and its valorization through means of high temperature heat pump technology. The project mainly focuses on industrial drying and dehydration processes in the food, ceramic and waste management industry. The results are also of relevance for other sectors such as e.g. pulp & paper.

The consortium elaborates techno-economic solutions for upgrading idle waste heat streams into process heat supply at temperature levels up to 160 °C. The key elements are three advanced high temperature vapor compression heat pumps: two closed loop heat pumps for air drying processes, and an open loop heat pump for steam driven drying processes. The technology shall be widely replicable and adaptable to both newly built installations as well as for retrofitting. The DryFiciency solutions will be demonstrated under real production conditions in industrial drying processes of three leading European companies.
Process parameters for the selected drying brick, starch and sludge processes were determined. Schematic integration schemes were developed. Boundary conditions and capacities for the integration of the three demonstrators and their full scale configurations were defined. Key performance indicators were elaborated to allow a comparable evaluation of the demonstrators e.g. coefficient of performance of the HP dryers, CO2 emissions avoided and production costs reduced. The performance and associated impact of the solutions is assessed and validated during the demonstration phase.

Crucial components for the high temperature HP systems were developed. For the closed loop case, all screw compressor parts were analyzed and adapted to the requirements of the high temperature application. Four compressors were assembled and tested before delivery to the HP manufacturer. A novel lubricant was developed to be used with the refrigerant OpteonMZ based on an extensive development series with detailed testing at >160°C. The required quantities of the lubricant for the test runs were produced.

Four cycle configurations were modeled and analyzed on component level. A twin cycle water-to-water HP was selected as the most suitable configuration in terms of efficiency and operability. Two HP prototypes were finally constructed by an experienced SME, that won the corresponding public tender. The HP for starch drying was equipped with two adapted screw compressors; the one for brick drying with eight novel piston compressors.
For the open loop HP, an electric and oil-free steam turbo compressor was developed allowing temperature lifts of up to 50K in a two-stage vapor compression cycle. The compressors are designed in a compact and cost-efficient way. Several compressor concepts and prototypes were developed and tested, leading finally to a concept using a traction drive gear box. Two compressor prototypes were assembled, and successfully tested under air and steam conditions. For dimensioning of the open loop system, detailed numerical simulations were performed. The HP was designed, dimensioned and constructed based on real operating conditions at the demo-site. Finally, the open loop system was installed at a test rig, and tested successfully with the novel two-stage steam turbo compressor prototypes up to 155°C.
At all three demo-sites, space and infrastructural requirements for the HP integration were evaluated. Operational schedules were planned and aligned to the respective drying processes; control strategies were developed. Components, services, and infrastructural facilities were sourced and installed. For the open loop, batch dryers were designed, optimized and partly built. The two closed loop HP were fully integrated into their drying processes. At the open loop case, construction work is ongoing. Finally, commissioning work started for the brick drying process with first promising results for the closed loop HP.

For the demo-phase, data acquisition systems were developed on conceptional level including weekly reporting and interactive data visualization. Implementation work started at both closed loop demo-sites; the system was successfully tested in real operation for one of them during commissioning.
Communication tools were developed for popular communication channels and other means of dissemination. Relations to end-users, multipliers, R&D community, policy makers, and general public were successfully built up:
• External Experts Advisory Board
• 6 scientific papers
• presentations at more than 30 events
• market potential analysis for high temperature HP
• end-user online survey
• training concept for the main target groups (end-users and multipliers)
The three demonstrators are the first high temperature HP implemented in real industrial environments (TRL7) aiming to reach supply temperature of up to 160°C. The two closed loop HP systems use a novel non-flammable, non-toxic refrigerant with a minimum global warming potential. Adapted screw and piston compressors and a fine-tuned lubricant are applied. The ambition of the open loop system lies in the development of a cost-efficient multi-stage compression system for steam. It is based on an oil-free, fully integrated turbo compressor allowing supply temperatures of up to 155°C.

The core results at the end of the project include three fully functional industrial HP systems integrated in industrial environments and validated on component and system level to achieve the following:

• Energy savings of sensible heat of 40 to 80%.
• Primary energy savings ranging from approx. 3.200 to 13.000 MWh/a.
• CO2 reductions ranging from approx. 800 t-CO2/a to 2800 t-CO2/a.
• Improved energy efficiency from 55 to 80%.
• Cost reduction from 4% to 20% / kg product.

In addition, business models, appropriate IP protection and exploitation/investment plans are developed to ensure post project roll out of the HP.
The DryFiciency project has the potential to cover the full range of industrial drying processes and can therefore act as key enabler for market uptake of the novel high temperature HP technologies for most energy intensive industries within the EU. In line with the EU 2030 climate and energy targets and the Energy Efficiency Directive (2012/27/EU) DryFiciency will reduce CO2 emission significantly and increase the energy efficiency in energy intensive industrial processes. Furthermore, DryFiciency will support the industry in complying with the new F-Gas Regulation limiting the total amount of fluorinated gases sold.