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Development of a fuel flexible and highly efficient ultra low emission residential-scale boiler with coupled heat recuperation based on flue gas condensation

Periodic Reporting for period 2 - FlexiFuel-CHX (Development of a fuel flexible and highly efficient ultra low emission residential-scale boiler with coupled heat recuperation based on flue gas condensation)

Reporting period: 2017-07-01 to 2018-12-31

The FlexiFuel-CHX project aimed at the development of a new fuel-flexible and highly efficient residential biomass heating technology. The technology should be developed for a capacity range of 20 to 130 kW (fuel power) and thus be an attractive solution for a wide range of residential-scale heating applications. It should be based on an existing small-scale fixed-bed updraft gasifier directly coupled with a gas burner and a hot water boiler.
The further enlargement of the fuel spectrum applicable in the gasifier from wood pellets and wood chips to forest residues, SRF (short rotation forestry, e.g. willow, poplar), miscanthus, olive stones, almond shells, vineyard and olive tree prunings and agro-pellets played a central role. Moreover, a Low-NOx gas burner was developed with the aim to reduce NOx emissions (also for N-rich fuels). A hot water fire tube boiler was developed which is able to cope with a broad range of biomass fuels. Last but not least a novel fuel flexible flue gas condensation technology with an integrated condensate neutralisation stage and an automatic cleaning system was developed, which is tailored to the demands of condensing flue gases from the combustion of a wide fuel spectrum also comprising fuels with elevated S and Cl contents.
At first an advanced fuel database for a thorough characterisation of the fuels of interest has been set up. Then, as basis for widening the applicable feedstock range, investigations on ash formation in the updraft gasifier with special respect to ash melting and K-behaviour and on the effects of the addition of inorganic additives to influence ash formation have been carried out.
Two work packages have been dedicated to the development of the key components, the fuel-flexible gasifier and the condenser. The work has been performed stepwisely aiming at the development of basic technologies at the beginning of the project and of advanced versions during the second project half. Thus, a fuel flexible fuel feeding system, the gasifier and the Low-NOx-gas burner have been developed and the control system has been adapted accordingly. Moreover, the boiler, the condenser, the condenser cleaning system and the condensate neutralisation system have been developed using a, for small-scale biomass combustion plants, totally new approach regarding condenser design in order to achieve a very compact solution with a very high thermal efficiency.
A first series of three basic testing plants and a second series of three advanced testing plants has been constructed, manufactured and commissioned. Two comprehensive testing phases at three sites each, one with the basic and one with the advanced testing plants have been performed. A detailed data and experience exchange with the development-related work packages guaranteed for a steady stepwise further development of the technology.
This work was accompanied by market studies, impact assessments and techno-economic evaluations, which have been performed in a two phase approach that allowed for considering the results of preliminary studies already during the development phase of the advanced testing plants. The final market studies, impact assessment and techno-economic evaluations, published at project end then also confirmed, that the new technology resulted in a product with high market opportunities and high potentials for positive impacts on the European energy system and the environment.
All technical aspects as well as the market related, environmental and economic framework conditions formed the basis for working out an optimised system integration, a final system design and a scale-up and scale down of the new technology in the anticipated power range. This work, accompanied by related risk assessments, forms the basis for a quick and efficient exploitation of the project results by introducing the new technology into the market after project end.
With the work performed, all objectives of the project could be reached.
With its ambitious approach the project aimed to achieve a significant step beyond the present state-of-the-art and thus bears a high innovation potential. The new technology provides for the first time the possibility to apply various qualities of cost-efficient biomass fuels in the small capcity range at almost zero gaseous, particulate matter (PM) as well as reduced NOX emission levels. By an innovative condenser design the temperature difference between the return of the heating water cycle and the flue gas temperature is reduced to less than 5°C and, thus, total efficiencies of up to 113% (net calorific value / NCV based) were possible.
Accordingly, based on preceding techno-economic analyses, the impact assessment (IA) performed present lower greenhouse gas emission levels than almost all other scenarios for state-of-the-art biomass boilers and especially against oil and gas condensing boilers. Comparing the analysed technology scenarios strongly requires looking at respective total annual efficiencies and fuel types. In that respect, the FlexiFuel-CHX scenario performs better for fuel consumption reduction than the other biomass boiler scenarios. Derived from the techno-economic analyses, over the whole period scrutinized and across all applications the new technology appears to be also the option that incurs the lowest long-term cumulated overall costs, despite initially different product prices.
All improvements of existing or new biomass heating systems also have to consider the specific properties of each installation, such as e.g. correct dimensioning, frequency of use, fuel availability, etc. Therefore, typically more properly trained and certified employees are required for upgrading or installing advanced heating systems with high efficiencies and low emissions. Otherwise, the benefits of better technology could be offset by losses and failures due to improper installation. For that reason, within the IA there have been also complementary considerations about socio-economic effects. Thus, with rising sales numbers and the increasing degree of complexity of efficient appliances, there is consequently also a higher demand for qualified personnel among manufacturers, for certification bodies and for the whole biomass supply chain. Accordingly, positive overall turnover and additional job creation effects in the EU, especially for SMEs, can be expected.
Considered together, all the insights gained in the Impact Assessment give some meaningful indications on the most prominent aspects to be considered for the long-range impacts of the project. Assuming the full market potential for small-scale systems to be fulfilled, improvements by the new FlexiFuel-CHX technology could have large positive EU-wide environmental and socio-economic effects: A high emission reduction potential is given EU wide, the Low-NOx boiler also contributes clearly to NOX emission reduction, the FF-CHX technology also contributes to lower fuel demand on an EU level due to the high efficiency, shows the lowest auxiliary electricity consumption of all biomass boilers investigated, the lowest greenhouse gas emissions, as well as large turnover and additional job creation potentials in the EU, especially for small and medium-sized enterprises (SMEs).
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