Utslippsfri energi: Utvikling av effektiv tofase varmepumpe for industriell dampproduksjon

Fossil fuels are the most common energy source in the process industry today and contribute to significant greenhouse gas emissions. At the same time a large amount of excess heat is available, however the temperature of this heat is too low for direct use in the industry. High temperature heat pumps are identified as a strong candidate to substitute fossil fuel based steam production, reducing both emissions and specific energy consumption. Current technology is however limited to small temperature lifts or large-scale thermal capacities and do not cover real industrial demands. Free2Heat has developed a validated concept for high-temperature heat pumps. The central part in a heat pump is the compressor, and the main objective has been to design, develop and test a robust and sustainable two-phase compressor for an open-loop heat pump, a so-called MVR (Mechanical Vapor Recompression) system, to recover waste heat and upgrade it to a higher temperature level, e.g. to create industrial steam. Industrial waste heat streams often consist of several phases such as steam and water, and often contain air and other contaminants. Requirements for a robust, efficient, temperature-resistant and flexible heat pump thus require the development of a compressor solution that can compress multiple phases. Through Free2Heat, Tocircle has developed, built and tested a compressor that meets these requirements. The compressor handles two phase flow (gas and liquid) and exploits this feature by injecting liquid into the compression chamber to control the discharge temperature. This means that unnecessary superheating of the working medium is avoided, thus enabling high delivery temperatures and a more efficient heat pump process. The compressor handles high pressure ratios, and since temperature control is done by liquid injection, there is no need for inter- or aftercoolers, and the required compression can be done in one stage. In addition, the compressor is oil-free (does not contaminate the steam with lubricants), and there is also no need for oil separation equipment in the heat pump. Together, this means a robust and simple heat pump, well suited for the recovery of waste heat streams. In Free2Heat, the working fluid is water/steam (R718), and the injected liquid is also water, which evaporates through compression, increasing the amount of steam delivered. In the first part of the project, Sintef and Tocircle explored possible applications for a steam compressor. Those with the greatest potential were further analyzed, and based on these findings, design parameters such as temperature range and required performance for a new-generation two-phase compressor were defined. A relevant application was heat recovery from superheated steam drying processes. The use of superheated steam for drying of moist masses is considered very effective, but also energy intensive. By capturing the moisture evaporating from the mass in the form of atmospheric steam, compressing this steam directly in an open-loop heat pump to increase pressure and temperature, and returning it as a heat source to the drying process, the energy consumption is significantly reduced. Bioretur AS is a Norwegian company with proprietary technology for superheated steam drying Bioretur’s dryers are primarily used for drying fish sludge, but other applications are also being considered. Bioretur was taken on as a partner in Free2Heat, and a collaboration started to implement Tocircle's MVR solution in Bioretur's dryer. The first version of Tocircle's new compressor was built in 2021, and enables delivery of steam at 150 - 180°C. Initial testing was done in Tocircle's test facility in Glomfjord, and the design parameters were verified against the requirements of Bioretur's dryers. Tocircle then designed the MVR plant in which the compressor was to operate, and this was also built and tested in Glomfjord. In parallel with the construction, a new opportunity was found to demonstrate the technology at a clients site; Scanship AS operates a biomass dryer at the Lindum waste management facility outside Drammen, and was interested in testing new technology to recover waste heat from the dryer. The MVR plant was installed and started up at Lindum in the spring of 2022 and operated as a pilot plant for the rest of the year. During this period, stable operation of the MVR plant together with the dryer was achieved, enabling drying with the MVR plant as the only heat source. Several potential customers visited the facility at Lindum to see the MVR in operation, and in December 2022 the Minister of Petroleum and Energy, Terje Aasland, also visited and received an introduction to the technology. The main purpose of Free2Heat has thus been fulfilled, and it was considered that a new demonstration period in one of Bioretur's facilities within the project period was not necessary. The collaboration between Bioretur and Tocircle instead continues around commercial applications.

For Tocircle: Prosjektet har resultert i et attraktivt produkt som ved prosjektavslutning kan tilbys kommersielt. Det har også skapt mye interesse blant potensielle kunder, og bidrar dermed til Tocircle kan ta steget fra ren teknologiutvikling til regulær lønnsom drift. Dette vil i sin tur bl.a. bety økt antall arbeidsplasser både i Nordland og Oslo-området. For Bioretur: Samarbeidet i Free2Heat gir Bioretur mulighet til å tilby sine anlegg med integrert løsning for gjenvinning av overskuddsvarme, og dermed redusere både utslipp og energikostnader, hvilket gir et betydelig konkurransefortrinn. For samfunnet generelt: Industrielle høytemperatur varmepumper regnes som en viktig teknologi for å muliggjøre overgang fra fossile brennstoff til elektrisk energi i varmekrevende prosesser. Teknologien som er tatt frem i Free2Heat vil bidra til dette skiftet, og dermed redusere utslipp og kostnader/ressurser til både energi og energirelatert infrastruktur

Prosjektet svarer på EnergiX-utlysningen for området Energibruk og konvertering, og muliggjør økt utnyttelse av spillvarme og mer energieffektive produksjonsmetoder og prosesser for helt nye industrisegmenter. I dag blir energien til prosessindustrien i hovedsak levert fra fossildrevne energikilder (f.eks. fyr- eller gasskjeler) som bidrar betydelig til utslipp av klimagasser. Samtidig er temperaturen på overskuddsenergien fra ulike prosesstrinn for lav for direkte gjenvinning og gjenbruk. Forskning har identifisert industriens behov for høytemperatur varmepumper som kan erstatte dampproduksjon fra fossildrevne energikilder og redusere spesifikt energiforbruk. Det tekniske potensialet til en industriell varmepumpe i området 100 til 150°C er estimert til 172 TWh/år i EU, med et markedspotensiale for 4400 anlegg og et verdiskapningspotensial mellom 13 200 og 35 200 MNOK. Kapasitetsbehovet for termiske systemer ligger i effektområdet 0,5-4 MW. Høytemperatur varmepumper kan integreres i termiske prosesser hvor damp ofte er varmebærer, hvor produksjonen leverer overskuddsdamp som benyttes direkte i varmepumpen, og leveres tilbake til prosessen etter temperaturløft. Dagens teknologi er begrenset til små temperaturløft eller svært store termiske kapasiteter, og dekker ikke industriens behov. Free2Heat skal utvikle en validert konsept for høytemperatur varmepumper. Hovedmålet er utvikling av en robust og bærekraftig tofase varmepumpe som kan implementeres i en åpen varmepumpekrets, slik at spillvarme fra termisk prosesser kan gjenvinnes og oppgraderes til et høyere temperaturnivå. Spillvarmestrømmer i industrien består ofte av flere faser som for eksempel damp og vann, og inneholder også ofte luft og andre forurensninger. Krav til en robust, effektiv, temperaturbestandig og fleksibel varmepumper krever dermed utvikling av en kompressorløsning som kan komprimere flere faser. Ved utviklingen av to-fase varmepumper vil Tocircle bli ledende i verden på dette området.