The technology readiness level of biomass gasification for medium power cogeneration applications reaches an industrial scale in Europe but locks in terms of biomass flexibility and process reliability still remain for ensuring its deployment.
The multiannual investment program for power generation in France involves the installation of 2300 MWe biomass power plants from 2009 to 2020. In this context, gasification appears to be a promising thermochemical upgrading of lignocellulosic biomass (ie, wood, forest and agricultural by-products, crops such as miscanthus) compared with the combustion in traditional boilers. Biomass, heated from the partial combustion of the pyrolysis products, is converted under air atmosphere in a fuel gas which can be valued, after purification, in an engine for cogeneration applications.<br />Among the techniques developed for medium power applications (1 to 10 MWe) and able of satisfying the typical needs of decentralized district heating networks, the bubbling fluidized bed technology is relevant towards technical, economic and environmental criteria. However, this pathway is today not entirely proven.<br />The GAMECO project aims at improving a biomass gasification reactor in bubbling fluidized bed developed by EQTEC (Spain) and includes objectives in terms of: i) flexibility extension of an existing process to value more varied biomass, ii) process reliability increase to promote its availability, iii) process scaling-up laws control to minimize the risk at industrial scale.<br />The outlooks join the maturation acceleration of a gasification process and improvement of its competitiveness for medium-term industrial deployment in certain French territories.<br />
The project structure is based on scientific study of technical locks in a bubbling fluidized bed gasifier: i) bed agglomeration from interactions of biomass inorganic compounds with the bed material, ii) presence of tars at the gasifier outlet controlled by the chemical reactions inside the gasifier, iii) biomass and bed material hydrodynamic (mixing laws and segregation). Work is carried out through modeling, experimentation at laboratory scale (0.1 – 4 kg/h) and test campaigns in an instrumented gasification pilot (50 kg/h). Criteria of similarity have been selected for approaching industrial conditions at laboratory scale.
The study includes five complementary tasks covering i) the agglomeration phenomena at both static and dynamic laboratory scale, ii) the mechanisms of tar production and degradation in ideal reactors with validation of kinetic schemes through pilot plant tests, iii) the gas-solid flow in cold model with validation through pilot plant tests, iv) detailed characterization of three ligno-cellulosic biomass (miscanthus, forest and agricultural biomass) at the pilot scale, v) identification of alternative and low-cost biomasses, available in France and suitable to the technology, as well as the technical-economic and environmental assessment of gasification technology integrating the complete process.
The first results concern the behavior of compounds involved in the gasification reactor. Crystalline and amorphous phases have been identified in miscanthus ashes, so revealing that the phase transition occurs at relatively low temperature. Besides, diffusion of iron from the bed material to the molten miscanthus ashes occurs at high temperature, so giving evidence of a strong chemical interaction between solids. The conversion kinetics of a tar compound (anisole) in gas phase has been characterized via the analysis of more than 20 products of reaction and a detailed kinetic model has been validated. The analysis of the chemical interactions between tar and the bed material has revealed the formation of various types of carbonaceous deposits according to the material and its size grading.
To allow the study of gas-solid hydrodynamics, a promising technique of solid particles activation has been developed to ensure a similarity between biomass particles placed in reactive conditions and particles in ambient conditions.
In addition, five alternative biomasses among around thirty have been selected on the basis of criteria consistent with the process, and including the pre-treatment costs and availability on the territory. Finally, the French potential of miscanthus chain has been estimated on the basis of economic and environmental criteria. The environmental impact of miscanthus harvest is limited by the good exploitative practices of NOVABIOM.
The experimental works will be pursued during the next period on all the devices, among which two original laboratory devices instrumented to allow the study, at high temperature and in dynamic fluidization conditions, on one hand of the interactions between the biomass inorganic compounds and the bed material, and on the other hand of the interactions between biomass and the bed material.
The final prospect of the project is to validate the extension of a gasification process in terms of flexibility and reliability through tests conducted on a gasification pilot plant implanted in Epinal. Results will be capitalized on the one hand in operational guides to go beyond the characterized locks, and on the other hand in an operating model of the gasification reactor.
A publication has been submitted to Journal of Chemical Engineering (analysis of interactions between the biomass inorganic compounds with the bed material). Six communications covering the project have been made in international conferences and also two communications in French conferences.
Air-blown fluidised bed biomass gasification is a well adapted technology for CHP applications. However, it is not mature yet. Despite promising pilot plants, CHP gasification needs further improvements to become the reference technology in the medium-size CHP market. This is the purpose of the GAMECO project, which aims at improving an existing technology by optimising its operation, increasing its feedstock flexibility and optimising its upscaling, based on a better understanding of the key points of biomass BFB gasification:
-Bed agglomeration risks with agricultural biomasses: interaction of biomass inorganics with different bed materials.
-Tar production minimisation: homogeneous and heterogeneous tar conversion kinetics
-Biomass particle hydrodynamics: with a focus on segregation and attrition
These 3 topics are studied through modelling, lab tests (<1 kg/h), and pilot tests (50 kg/h). Two main feedstocks will be used: miscanthus, which is one of the most promising energy crops and already commercially available in France and woody biomass, which is the largest part of available biomass for energetic purposes. Miscanthus will be used for studying agglomeration problems while woody biomass will be used as the reference fuel to study hydrodynamics as a function of the shape and the particle size. Concerning tar kinetics, they will be studied at the lab scale in controlled conditions and validated through the different gasification tests. Finally, other challenging biomasses – i.e. more difficult but cheaper - will be tested in the last phase of the project based on its learnings.
In order to ensure the success of this ambitious project, all the required actors from industry and experts from the public research sector are involved. The three bottlenecks identified will be assessed by three reputed laboratories in the concerning fields:
-Inorganic issues will be treated by Professor Poirier’s team at CEMHTI with high experience in this field as showed in previous projects (INORGANIQUES, SLUGAS,...).
-Thermochemistry issues, with a focus on tar kinetics, will be covered by FJV, and more precisely by the LRGP teams (LSGC+DCPR), joining the expertise of DCPR in detailed kinetic models and LSGC in biomass thermochemical conversion.
-Finally, efforts concerning the better understanding of biomass hydrodynamics in bubbling fluidised beds will be led by the team of Professor A. Delebarre, reputed expert in this field (FJV-Lemta).
These R&D efforts will be completed by FJV-Lermab at Epinal, which will provide their large experience in biomass pretreatment and thermochemical conversion technologies and in pilot-scale units operation.
Complementing these R&D centers, three actors from industry participate to this project: Novabiom, biomass producer and supplier specialised in energy crops, and more precisely in miscanthus, will provide its experience in order to assess the biomass supply concepts depending on the specifications at the reactor inlet. EQTEC will provide the latest version of its technology as a starting point of this project. EQTEC will also provide its vision and counsel as a technology developer and engineering company, sharing its previous experience acquired through the different gasification units they have delivered.
Finally, EDF will coordinate all these efforts and evaluate the technology based on different feedstocks. It will optimise the whole chain and will identify the best configurations for developing CHP projects based on this technology.
Monsieur Olivier AUTHIER (EDF RECHERCHE ET DEVELOPPEMENT) – email@example.com
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
EDF EDF RECHERCHE ET DEVELOPPEMENT
FJV / LRGP UNIVERSITE HENRY POINCARE NANCY I
CEMHTI CNRS - DR CENTRE POITOU-CHARENTES
EQTEC EQTEC Iberia
Help of the ANR 1,015,184 euros
Beginning and duration of the scientific project: - 48 Months