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Fate of phosphorus and potassium in single-pellet thermal conversion of forest residues with a focus on the char composition

Hedayati, Ali and Lestander, Torbjörn and Rudolfsson, Magnus and Thyrel, Mikael and Ohman, Marcus (2021). Fate of phosphorus and potassium in single-pellet thermal conversion of forest residues with a focus on the char composition. Biomass and Bioenergy. 150 , 106124
[Research article]

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Abstract

The phosphorus and potassium contents of the char obtained from thermal conversion of forest residues can limit its utilization as an alternative fuel and reducing agent to substitute coal/coke in the steelmaking industry. In this study, ash transformation and release of K and P during single-pellet thermal conversion of different types of forest residues (i.e., bark, twigs, and bark+twigs) were investigated with the aid of a vertical tube furnace (Macro-TGA) at different temperatures (i.e., 600, 800, and 950 degrees C) and within and after different fuel conversion stages, i.e., devolatilization and char gasification. The residual char before and after full devolatilization, and ash after char gasification were characterized by SEM-EDS, XRD, and ICP-OES with the support of thermochemical equilibrium calculations. The concentrations of K (7970-19500 mg/kg) and P (1440-4925 mg/kg) in the char produced after devolatilization were more than four times higher than in coke and pulverized coal frequently used in metallurgical processes. A low amount of P and K (<= 15%) were released from all fuels. K and P were evenly distributed within the char residues, and no crystalline compounds containing K and P were found. In ash residues of bark, K was found in K2Ca2(CO3)3, and K2Ca(CO3)2. K in ash residues from twigs and bark+twigs was mainly found in the amorphous part of ash, most likely in the form of K-Ca rich silicates. Apatite was found as the main P crystalline compound in all ashes at all temperatures. Estimations show that a release of more than 80% is needed for the studied forest residual assortments to reach K and P concentrations typical of blast furnace coals and cokes.

Authors/Creators:Hedayati, Ali and Lestander, Torbjörn and Rudolfsson, Magnus and Thyrel, Mikael and Ohman, Marcus
Title:Fate of phosphorus and potassium in single-pellet thermal conversion of forest residues with a focus on the char composition
Series Name/Journal:Biomass and Bioenergy
Year of publishing :2021
Volume:150
Article number:106124
Number of Pages:12
Publisher:PERGAMON-ELSEVIER SCIENCE LTD
ISSN:0961-9534
Language:English
Publication Type:Research article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 405 Other Agricultural Sciences > Renewable Bioenergy Research
Keywords:Char, Forest residues, Ash transformation, Potassium, Phosphorus, Thermal conversion, Macro-TGA, Single pellets
URN:NBN:urn:nbn:se:slu:epsilon-p-112754
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-112754
Additional ID:
Type of IDID
DOI10.1016/j.biombioe.2021.106124
Web of Science (WoS)000663554100008
ID Code:24847
Faculty:S - Faculty of Forest Sciences
Department:(S) > Department of Forest Biomaterials and Technology
Deposited By: SLUpub Connector
Deposited On:12 Jul 2021 12:29
Metadata Last Modified:12 Jul 2021 12:31

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