The application of producer gas from biomass gasification for power generation through engines requires cleaning and conditioning. Wet scrubbing is often chosen to remove organic components (tars) and particulate matter and to cool the gas, resulting in the production of contaminated water. On the other hand, even for dry gas cleaning technologies, cooling still produces contaminated liquids. The serious environmental problems posed by such effluents can be faced only by adequate pre-treatments before discharge into urban network. The proposal is concerned with the development and optimisation of a technology for the purification of contaminated water from biomass gasification, which also allows energy to be recovered from the tarry pollutants. Currently, these are separated into a heavy fraction, not soluble in water and recycled back to the gasifier, and a light fraction, soluble in water that needs treatment. The treatment technology is based on supercritical wet oxidation/gasification (SCWO/G). The R&D activities proposed include experimentation at laboratory and pilot scale and mathematical modelling, both supporting evaluations for full scale (technical and economic) implementation .The overall objective is to evaluate the full scale application of supercritical wet oxidation/gasification (SCWO/G). Indeed liquid effluents from biomass gasification plants are too dilute to incinerate and yet too toxic to bio-treatment. The process under study refers to the aqueous oxidation/gasification of organic (and inorganic) materials at pressure and temperatures above the critical data for water.
More specific objectives are:
1. to characterise the chemical composition of waste water from updraft gasification of wood (in particular, light tar components which are soluble in water),
2. to apply and optimise SCWO/G of such waste water at laboratory and pilot scale,
3.to formulate kinetic and transport models for the SCWO/G process including validation and process simulation,
4. to provide a chemical characterisation of the effluent water from the SCWO/G process,
5. to extend the results of the analysis carried out for the effluents (of a wet gas cleaning process) from a 6 MWTH updraft wood-chips plant to other gasifier configurations and other gas cleaning technologies, based on literature information,
6. to provide a full scale evaluation of the process for both the technical (energetic and environmental) and the economic aspects.
The project will be carried out on 3 different levels:
1. The Laboratory Scale Unit (LSU - already existing 1 kg/h system, financed exclusively by some of the Partners) will be used to establish parameters for the thermo chemical mechanisms involved under various process conditions (retention times, temperature/pressure levels and influence of raw tar-water acidity and added carbon powder catalyst).
2. The Process Development Unit (PDU - which is in the process of being designed for a capacity of 60 kg/h, financed in part by a national Energy Agency) will be used for correlation with the mathematical model and tools to be developed, for optimisation of the SCWO/G processes and as a basis for up-scaling the process for full scale application.
3. A full-scale implementation layout (1000 kg/h of waste water), which will be used to evaluate the capital/operational cost and environmental impact of the technology.
Call for proposalData not available
Funding SchemeCSC - Cost-sharing contracts