Biomass conversion provides coal comfort30 May 2019
What do you do with a large and expensive recently commissioned state of the art supercritical coal fired plant to prevent it from becoming a stranded asset in the not too distant future? Conversion to (hopefully) sustainable biomass – partially or even fully – is one option. Rotterdam’s Maasvlakte is the site of not one but two such modern coal plants and both are pursuing the biomass route.
Uniper’s 1100 MW Maasvlakte Power Plant 3 (MPP3) expects to enter the commercial phase of its biomass cofiring conversion after the next scheduled outage (due May/June 2019). New biomass co-firing assets at the site (unloading facility, conveyors, silos, mills, burners, etc) are in the final stages of commissioning. Initially, it is planned to operate at an average level of 15% energy equivalent co-firing, as per the plant’s environmental permit limits. The plant will cofire “certified (ie, sustainable” industrial grade wood pellets, along with its existing fuel of hard coal (and some meat and bone meal wastes).
The converted plant will be part of the Port of Rotterdam’s “biobased cluster”, supplying heat (steam) and cooling water to nearby businesses, as well as providing low-temperature residual heat from its cooling water system for LNG regasification nearby.
Meanwhile, at Engie’s 800 MW Maasvlakte coal fired plant a major EU funded study, called ARBAHEAT, is underway looking at the feasibility of converting it to a 100% biomass fuelled combined heat and power facility, running on Arbacore, a fuel with coal-like properties produced by steam treating biomass using a process being developed Norwegian start- up Arbaflame (majority owned by Norwegian investment company Pemco).
The Arbacore fuel would be produced on site using process heat from the power plant.
The ARBAHEAT demonstration project encompasses:
- Transformation of the plant into a CHP facility. This will be demonstrated initially by delivering a small proportion of the power plant’s heat output to an on-site biomass treatment process, while envisaging large-volume heat delivery to nearby industry as the next step. This would provide renewable local heat, taking the overall efficiency of the plant from 46% electricity-only to 70-90% in CHP mode.
- Production of biomass feedstock. An integrated Arbaflame thermal pre-treatment process will enable utilisation of diverse sustainable biomass feedstock. This will minimise investment and operating cost while broadening the possibilities in term of geographical feedstock sourcing and quality. The Arbaflame thermal biomass upgrading process delivers biomass fuel with handling and milling characteristics approaching that of coal, allowing conversion to biomass with minimal adaptations to the existing power plant. The demonstration plant will be designed to allow maximum flexibility when it comes to upscaling the technology for future replication.
- Integration into the power plant. The biomass pre-treatment and heat delivery system will be physically integrated within the existing power plant. Elimination of several cost and energy intensive steps (steam production, pelletising) will be investigated, leading towards a more cost-effective final design. It is hoped this demonstration of an integrated low-cost concept for large-scale application will pave the way towards “subsequent multiplication in commercial industrial projects, thus increasing the EU capacity for renewable power and heat generation.” The renewable ARBAHEAT solution “therefore has the potential to significantly contribute to the replacement of fossil-fuel in the heat and power sectors and increase the decarbonisation of the energy market.”
The four year long project (which kicked off in October 2018) is being funded under the EU’s Horizon 2020 research & development framework. The total cost is estimated at € 26 million euro, of which the EU is contributing €19 million. The co-ordinator is PNO Consultants BV (funded by an EU contribution of € 446 468) and the participants are: Arbaflame, with EU funding of € 9 710 050; Engie Energie Nederland, EU funding € 5 512 218; TNO (Netherlands), EU funding € 1 826 421); Sintef (Norway), EU funding € 808 750; Vrije Universiteit Brussel (Belgium), EU funding € 630 250; Universitetet i Bergen (Norway), EU funding € 328 489; and the Port of Rotterdam Authority.
Arbaflame and Arbacore
Compared with normal biomass pellets Arbacore pellets are more water resistant and have a higher energy density, with almost the same burning characteristics as coal, facilitating their use in power plants and significantly reducing the costs of converting existing coal-fired power plants to biomass, says Arbaflame (company slogans: “Revolutionise your plant by keeping it the same”; “Keep the power station, lose the coal”).
Although parts of the steam treatment technology and the resulting biomass pellets have been previously tested by Arbaflame at around 15 other power plants, and a commercial scale project was implemented at the now permanently closed Thunder Bay facility in Canada (see panel, below), demonstrating the cost-effective integration of the technology into an existing modern power plant has never before been done to the extent contemplated in the ARBAHEAT project. “A successful demonstration of this concept will establish an impressive showcase for other EU coal-fired power plants or even other bio-energy plants”, says Arbaflame CEO, Håkon Knappskog.
European ambitions to limit CO2 emissions have “a significant impact on the operation of coal-fired power plants and on the required balancing power to support the grid supplementary to solar and wind energy”, notes Arbaflame. Retrofitting modern existing coal-fired power plants with the ARBAHEAT concept could offer a significant contribution to the realisation of decarbonisation targets in Europe by adding sustainable heat and power flexibility and the state of the art Engie power plant is seen as the perfect candidate for this first demonstration project because of its size and strategic location in the port of Rotterdam. “The plant can play an important role...not only supplementing wind and solar but also in providing heat. However, at this moment there is no viable business case to convert a coal-fired power plant into a 100% sustainable and flexible biomass plant. A successful demonstration will allow the delivery of large amounts of sustainable electricity and heat to the surrounding area”, says Jeroen Schaafsma of Engie.
Arbacore is produced using a “steam explosion process” in which the wood fibres are broken down and lignin, the binding agent in wood, is released (a process similar to torrefaction). The Arbacore pellets are almost black, with a film that makes them water-resistant, which facilitates outside storage and handling.
“During pulverisation, the particles become so fine that they are more similar to coal than the regular white pellets”, says Arbaflame, which estimates that Arbacore pellets contain “about 40% more energy per cubic meter than traditional white pellets, which...saves money throughout the supply chain.” At the same time, “their fire risk and potential for self-ignition is virtually non-existent”, which is a major issue with white pellets, which require the plant to be protected against “a clearly enhanced fire risk.”
Because Arbacore shares many of the properties of coal – and can be transported, sorted and handled in the same way – coal biomass co-firing, or a complete switch to renewable energy production becomes “easy, cheap and fast”, claims Arbaflame. “Only slight modifications are required to use existing equipment for, eg, pulverisation and combustion.”