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An investigation of lime addition to fuel as a countermeasure to bed agglomeration for the combustion of non-woody biomass fuels in a 20kWth bubbling fluidised bed combustor

Chi, Hetian; Pans, Miguel A.; Sun, Chenggong; Liu, Hao

An investigation of lime addition to fuel as a countermeasure to bed agglomeration for the combustion of non-woody biomass fuels in a 20kWth bubbling fluidised bed combustor Thumbnail


Authors

Hetian Chi

Miguel A. Pans

Chenggong Sun

HAO LIU LIU.HAO@NOTTINGHAM.AC.UK
Professor of Energy Engineering



Abstract

The unique fuel flexibility of fluidised bed system facilitates the combustion of low quality solid fuels such as agricultural residues, but may suffer from serious bed agglomeration problems especially when operating at the high end of the typical fluidised bed combustion temperature range (800–900 °C). In this study, a 1.5 wt% lime addition to biomass fuels was investigated as a countermeasure to agglomeration for the combustion of pelletised wheat straw and miscanthus in a 20 kW bubbling fluidised bed (BFB) combustor using quartz sand as the bed material. Comparing to the widely studied agglomeration countermeasures such as bed additives and alternatives, the lime addition to fuel can provide a continuous on-site agglomeration counter action. Without lime addition, defluidisation as a result of bed agglomeration occurred once the bed temperature reached 860 °C and 877 °C for miscanthus and wheat straw respectively. However, with the lime addition, stable combustion could be achieved at 900 °C for both fuels with a substantially prolonged operation time. The obtained agglomerates were characterised using CAMSIZER, XRD and SEM/EDX and the results showed that the presence of lime in the fuel could significantly reduce the agglomerates size by forming high melting point calcium silicates/phosphates which hinder the K-rich molten substance attachment and result in heterogeneous coating layers in the agglomerates. The results of this study clearly indicate that using lime as fuel additive can realise the combustion of the problematic non-woody biomass fuels by considerably reducing the bed agglomeration propensity in practical fluidised bed combustion plants.

Citation

Chi, H., Pans, M. A., Sun, C., & Liu, H. (2019). An investigation of lime addition to fuel as a countermeasure to bed agglomeration for the combustion of non-woody biomass fuels in a 20kWth bubbling fluidised bed combustor. Fuel, 240, 349-361. https://doi.org/10.1016/j.fuel.2018.11.122

Journal Article Type Article
Acceptance Date Nov 22, 2018
Online Publication Date Dec 14, 2018
Publication Date Mar 15, 2019
Deposit Date Feb 8, 2019
Publicly Available Date Feb 8, 2019
Journal Fuel
Print ISSN 0016-2361
Electronic ISSN 1873-7153
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 240
Pages 349-361
DOI https://doi.org/10.1016/j.fuel.2018.11.122
Keywords Biomass combustion; Fluidised bed; Lime addition; Agglomeration; Additive to fuel
Public URL https://nottingham-repository.worktribe.com/output/1367394
Publisher URL https://www.sciencedirect.com/science/article/pii/S0016236118320179
Additional Information This article is maintained by: Elsevier; Article Title: An investigation of lime addition to fuel as a countermeasure to bed agglomeration for the combustion of non-woody biomass fuels in a 20kWth bubbling fluidised bed combustor; Journal Title: Fuel; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.fuel.2018.11.122; Content Type: article; Copyright: © 2018 The Authors. Published by Elsevier Ltd.