1. Sources

The present Combustion File is part of the cluster of CFs produced within the literature survey phase of the industrial sponsored research and development project PowerFlam1 and is confidential to the participants registered for that project.

This CF is specifically concerned with the research project:

R. Cenni, F. Frandsen, Th. Gerhardt, H. Spliethoff, K.R.G. Hein (1998): Study on trace metal partitioning in pulverized combustion of bituminous coal and dry sewage sludge, which is published within Journal of Waste Management Vol.18, pp. 433-444.

2. Background

·         This combustion file is concerned with the provision of combustion related data to the sponsors.

·         In this html file the source of the data is summarised in section 4 below, in order to give the reader a general overview of the way the data was collected.

·         Fuel and related data, prepared for calculation, are presented in individual Microsoft Excel Worksheets, all contained within a Workbook.

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·         The data in these worksheets are protected – thus the reader cannot change the worksheet without knowledge of the protection password.

·         However the reader can copy and paste the data into his/her own project work book as required – at this point the accuracy and integrity of the data becomes the responsibility of the reader. Included in this workbook are copies of the abstract and synopsis for reference purposes.

·         All credits and sources, and where necessary, instructions/advice for data use, are presented in this html file. These are not necessarily reproduced in the Excel Work Sheets.

3. Abstract

A study of the influence of co-firing of dry municipal sewage sludge on the behavior of the metals Cr, Hg, Mn, Ni, Pb, Zn during pulverized coal combustion is presented. Sewage sludge contains higher concentrations of the metals listed above than the reference coal, but a lower concentration of Cl, that enhances the volatility of many metals. Experiments were performed in a semi-industrial scale pulverized fuel combustion chamber (500 kW). Ash was collected at four locations: bottom hopper (T=850 K), air preheater (T=750 K), cyclone (T=620 K), and bag filter (T=480 K). From the bottom hopper to the filter, the particle size decreased and ash particles were progressively enriched in volatile elements. Mass balances of the metals were performed and the enrichment trends on the ash collected at the different locations were calculated. Increasing the sewage sludge share in the blend caused a significant increase in the recovery rate in the solid phase. In spite of that, the calculated concentrations in the flue gas of Hg and Zn increased. Sewage sludge co-firing influences the combustion process and the post-combustion environment in many ways. This study focuses on the effect of the different flue gas composition on the condensation temperature of metal species. The system was modeled by assuming thermodynamic equilibrium. The results indicated that the increasing recovery of Zn might be caused by enhanced condensation and the increasing recovery of Hg by adsorption on ash particles. The increasing recovery of the other metals seemed referable to failure in vaporization and it cannot be studied with an equilibrium approach.

A second conference paper of the same material is referenced below.

R. Cenni, F. Frandsen, Th. Gerhardt, H. Spliethoff, K.R.G. Hein (1998): Study on metal species partitioning along the flue gas path in combustion of bituminous coal and dry sewage sludge. Int. Conf. on Incineration and Thermal Treatment Technologies. May 11-5, Salt Lake City, Utah, USA.

4. Synopsis