Abstract
Agglomeration of bed sand is a common problem during combustion of biofuels with high ash content in fluidized bed boilers. Former studies have shown that co-combustion of biofuels with sewage sludge increases the agglomeration temperature. Sewage sludge has a low heating value and high ash content. It would therefore be better to use sludge as an additive to the combustion than as a co-combusted biofuel. In this study the trigging value of sludge addition to the combustion of some biofuel was investigated. The effect of adding sludge with different precipitation chemicals, iron sulphate and aluminium sulphate, was investigated. The biofuels used for the experiments were bark, refused derived fuel (RDF) and a mixture of wood and straw, 75/25 % on energy basis. All experiments were carried out in a laboratory scale fluidized bed reactor. Analyses of chemical composition of bed sand and SEM/EDX analyses were performed after the combustion. Eventually agglomeration tests were performed in order to find the agglomeration temperature of the samples. Some of the samples sintered during the combustion and were not tested for the agglomeration temperature. SEM/EDX showed that all samples of bed sand contained sand particles with more or less coatings. In some cases the
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Citation Formats
Andersson, Kajsa, and Gervind, Pernilla.
Prevention of Bed Agglomeration Problems in a Fluidized Bed Boiler by Finding the Trigging Value of Sewage Sludge Dosage Added to Combustion of Biofuels.
Sweden: N. p.,
2009.
Web.
Andersson, Kajsa, & Gervind, Pernilla.
Prevention of Bed Agglomeration Problems in a Fluidized Bed Boiler by Finding the Trigging Value of Sewage Sludge Dosage Added to Combustion of Biofuels.
Sweden.
Andersson, Kajsa, and Gervind, Pernilla.
2009.
"Prevention of Bed Agglomeration Problems in a Fluidized Bed Boiler by Finding the Trigging Value of Sewage Sludge Dosage Added to Combustion of Biofuels."
Sweden.
@misc{etde_1011589,
title = {Prevention of Bed Agglomeration Problems in a Fluidized Bed Boiler by Finding the Trigging Value of Sewage Sludge Dosage Added to Combustion of Biofuels}
author = {Andersson, Kajsa, and Gervind, Pernilla}
abstractNote = {Agglomeration of bed sand is a common problem during combustion of biofuels with high ash content in fluidized bed boilers. Former studies have shown that co-combustion of biofuels with sewage sludge increases the agglomeration temperature. Sewage sludge has a low heating value and high ash content. It would therefore be better to use sludge as an additive to the combustion than as a co-combusted biofuel. In this study the trigging value of sludge addition to the combustion of some biofuel was investigated. The effect of adding sludge with different precipitation chemicals, iron sulphate and aluminium sulphate, was investigated. The biofuels used for the experiments were bark, refused derived fuel (RDF) and a mixture of wood and straw, 75/25 % on energy basis. All experiments were carried out in a laboratory scale fluidized bed reactor. Analyses of chemical composition of bed sand and SEM/EDX analyses were performed after the combustion. Eventually agglomeration tests were performed in order to find the agglomeration temperature of the samples. Some of the samples sintered during the combustion and were not tested for the agglomeration temperature. SEM/EDX showed that all samples of bed sand contained sand particles with more or less coatings. In some cases the coatings seemed to consist of one dense inner layer and one more porous outer layer. From SEM/EDX and chemical composition analyses it was found that the total amount of phosphorous in the bed sand samples was increased with an increased addition of sludge in all experiments. The concentration of phosphorous was especially higher in the outer layers/coatings. It was also found that elements from the sludge seem to get caught by a sticky layer at the bed sand surface and form a non-sticky or less sticky layer that prevents agglomeration. The total amount of aluminium was increased with an increased addition of sludge for the wood/straw samples, while it increased with an increased amount of combusted fuel for the RDF cases. A tendency of a higher concentration of aluminium in the bed sand could be seen in the samples precipitated with aluminium sulphate than the samples precipitated with iron sulphate. The total amount of potassium in the bed sand was only little increased during the combustion for all experiments. The experiments showed that for the wood/straw samples an addition of 2wt% sludge was enough to increase the bed agglomeration temperature with about 100 deg C and an addition of 6wt% sludge gave an even better effect. For RDF an addition of 6wt% sludge was necessary to give any effect. Sludge precipitated with aluminium sulphate gave a better effect than sludge precipitated with iron sulphate}
place = {Sweden}
year = {2009}
month = {Jul}
}
title = {Prevention of Bed Agglomeration Problems in a Fluidized Bed Boiler by Finding the Trigging Value of Sewage Sludge Dosage Added to Combustion of Biofuels}
author = {Andersson, Kajsa, and Gervind, Pernilla}
abstractNote = {Agglomeration of bed sand is a common problem during combustion of biofuels with high ash content in fluidized bed boilers. Former studies have shown that co-combustion of biofuels with sewage sludge increases the agglomeration temperature. Sewage sludge has a low heating value and high ash content. It would therefore be better to use sludge as an additive to the combustion than as a co-combusted biofuel. In this study the trigging value of sludge addition to the combustion of some biofuel was investigated. The effect of adding sludge with different precipitation chemicals, iron sulphate and aluminium sulphate, was investigated. The biofuels used for the experiments were bark, refused derived fuel (RDF) and a mixture of wood and straw, 75/25 % on energy basis. All experiments were carried out in a laboratory scale fluidized bed reactor. Analyses of chemical composition of bed sand and SEM/EDX analyses were performed after the combustion. Eventually agglomeration tests were performed in order to find the agglomeration temperature of the samples. Some of the samples sintered during the combustion and were not tested for the agglomeration temperature. SEM/EDX showed that all samples of bed sand contained sand particles with more or less coatings. In some cases the coatings seemed to consist of one dense inner layer and one more porous outer layer. From SEM/EDX and chemical composition analyses it was found that the total amount of phosphorous in the bed sand samples was increased with an increased addition of sludge in all experiments. The concentration of phosphorous was especially higher in the outer layers/coatings. It was also found that elements from the sludge seem to get caught by a sticky layer at the bed sand surface and form a non-sticky or less sticky layer that prevents agglomeration. The total amount of aluminium was increased with an increased addition of sludge for the wood/straw samples, while it increased with an increased amount of combusted fuel for the RDF cases. A tendency of a higher concentration of aluminium in the bed sand could be seen in the samples precipitated with aluminium sulphate than the samples precipitated with iron sulphate. The total amount of potassium in the bed sand was only little increased during the combustion for all experiments. The experiments showed that for the wood/straw samples an addition of 2wt% sludge was enough to increase the bed agglomeration temperature with about 100 deg C and an addition of 6wt% sludge gave an even better effect. For RDF an addition of 6wt% sludge was necessary to give any effect. Sludge precipitated with aluminium sulphate gave a better effect than sludge precipitated with iron sulphate}
place = {Sweden}
year = {2009}
month = {Jul}
}