[Denmark] PhD Scholarship in Fly Ash and Deposit Formation when Firing Biodust with and without Additives
Application Deadline : 20th September 2011
Background
This particular position deals with the formation of ashes and deposits in boilers fired with biomass in suspension. In Denmark, heat and power (CHP) production from biomass has traditionally been based on dedicated grate-fired units, and co-firing of straw and coal in suspension-fired power stations. But, in order to achieve the European targets on reduction of greenhouse gases and increasing use of renewable energy in 2020, utilization of 100 % biomass in high-efficient suspension-fired power stations has becomed an attractive solution. Compared to traditional grate-fired units, suspension-fired units have a higher electrical efficiency and load flexibility, which can better compensate e.g. the foreseeing increasing wind power production in Denmark. Since biomass is fundamentally different from coal, in terms of fuel properties and combustion behavior, dust-firing of biomass may raise several technical challenges, such as flame stability and burnout, ash deposition and corrosion, deactivation of SCR catalyst, and ash utilization. Most of these issues are linked to the the fate of inorganic species in biomass. One approach to minimize potential ash related operational problems during biodust-firing is to apply additives, which can convert flame-volatilized inorganic species (like KCl, NaCl) to less harmful chemical species.
Project objective
It is the objective of the project to provide an improved understanding of the behavior of biodust fired in suspension with respect to fly ash and deposit formation and the effect of additives on these phenomena. This will include a experiments conducted under well-controlled conditions in the CHEC entrained flow reactor, eventually combined with full-scale sampling at power stations. The PhD project will be coordinated with other GREEN research activities in order to provide tools supporting the efforts of the power plant companies Vattenfall and DONG Energy, increase the amount of biomass utilized on Danish power stations.
Project description
The final content of the PhD will be planned by the student, supervisors and power plant company project participants. The project will contain the following subtasks;
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Conduct a thorough literature survey covering; characterization of solid biofuels, combustion of biofuels, release of critical ash-forming elements incl. K, S and Cl, formation of aerosols, fly ash and deposits, and effects of additives on ash transformations in modern biodust fired utility boilers.
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Conduct combustion tests on the selected biodust in the CHEC entrained flow reactor (EFR) in order to evaluate the quality of the experiments and the combustion performance of the tested biodust.
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Define potential additives to be applied together with biodust in the EFR.
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Conduct combustion tests on selected biodust-additive blends in the EFR.
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Conduct combustion tests with collection of fly ash particles when firing KCl and additive in the EFR, in order to deduce K-interactions in these systems.
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Eventually, conduct full-scale tests in order to confirm lab-scale results.
The PhD project is part of the GREEN project and will be coordinated with other GREEN research activities.
Qualifications
Candidates must hold a M.Sc.-degree in Chemical Engineering, or a similar degree at an equivalent academic level. Fluent speaking and writing in English is a must.
Approval and enrolments
The scholarships for the PhD degree are subject to academic approval, and the candidates will be enrolled in one of the general degree programs of DTU. For information about the general requirements for enrolment and the general planning of the scholarship studies, please see theDTU PhD Guide.
