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Thermochemistry: the key to minerals separation from biomass for fuel use in high performance systems

Abstract

Biomass use in high efficiency thermal electricity generation is limited not by the properties of the organic component of biomass, but by the behavior of the associated mineral matter at high temperatures. On a moisture and ash free basis biomass, which has an average formula of CH{sub 1.4}O{sub 0.6}N{sub 0.1}, has a relatively low heating value of 18.6 GJ/t. However, this would not limit its use in high efficiency combustion systems because adequate high temperatures could be reached to achieve high carnot cycle efficiencies. These high temperatures cannot be reached because of the fouling and slagging propensities of the minerals in biomass. The mineral composition is a function of soils and the growth habit of the biomass, however, the most important element is potassium, which either alone or in combinating with silica forms the basis of fouling and slagging behaviors. Growing plants selectively concentrate potassium in their cells, which along with nitrogen and phosphorus are the key macronutrients for plant growth. Annual plants tend to have very high potassium contents, although wood biomass exclusive of the living cambial layer (i.e. minus the bark, small branches, and leaves) has minimal potassium content and other nutrients. Under combustion conditions the potassium is  More>>
Authors:
Overend, R P [1] 
  1. National Renewable Energy Laboratory, Golden, CO (United States)
Publication Date:
Dec 31, 1996
Product Type:
Technical Report
Report Number:
VTT-SYMP-164
Reference Number:
SCA: 092000; PA: FI-98:003016; EDB-98:027704; SN: 98001896196
Resource Relation:
Other Information: PBD: 1996; Related Information: Is Part Of Power production from biomass II with special emphasis on gasification and pyrolysis R and DD; Sipilae, K.; Korhonen, M. [eds.] [VTT Energy, Espoo (Finland). Energy Production Technologies]; PB: 320 p.
Subject:
09 BIOMASS FUELS; BIOMASS; THERMOCHEMICAL PROCESSES; FOULING; REMOVAL; MINERALS; ASHES
OSTI ID:
570557
Research Organizations:
Technical Research Centre of Finland, Espoo (Finland)
Country of Origin:
Finland
Language:
English
Other Identifying Numbers:
Other: ON: DE98724226; ISBN 951-38-4555-9; TRN: FI9803016
Availability:
OSTI as DE98724226
Submitting Site:
FI
Size:
pp. 197-214
Announcement Date:
Apr 02, 1998

Citation Formats

Overend, R P. Thermochemistry: the key to minerals separation from biomass for fuel use in high performance systems. Finland: N. p., 1996. Web.
Overend, R P. Thermochemistry: the key to minerals separation from biomass for fuel use in high performance systems. Finland.
Overend, R P. 1996. "Thermochemistry: the key to minerals separation from biomass for fuel use in high performance systems." Finland.
@misc{etde_570557,
title = {Thermochemistry: the key to minerals separation from biomass for fuel use in high performance systems}
author = {Overend, R P}
abstractNote = {Biomass use in high efficiency thermal electricity generation is limited not by the properties of the organic component of biomass, but by the behavior of the associated mineral matter at high temperatures. On a moisture and ash free basis biomass, which has an average formula of CH{sub 1.4}O{sub 0.6}N{sub 0.1}, has a relatively low heating value of 18.6 GJ/t. However, this would not limit its use in high efficiency combustion systems because adequate high temperatures could be reached to achieve high carnot cycle efficiencies. These high temperatures cannot be reached because of the fouling and slagging propensities of the minerals in biomass. The mineral composition is a function of soils and the growth habit of the biomass, however, the most important element is potassium, which either alone or in combinating with silica forms the basis of fouling and slagging behaviors. Growing plants selectively concentrate potassium in their cells, which along with nitrogen and phosphorus are the key macronutrients for plant growth. Annual plants tend to have very high potassium contents, although wood biomass exclusive of the living cambial layer (i.e. minus the bark, small branches, and leaves) has minimal potassium content and other nutrients. Under combustion conditions the potassium is mobilized, especially in the presence of chlorine, at relative low temperatures and fouls heat transfer surfaces and corrodes high performance metals used, for example, in the high temperature sections of burners and gas turbines. Recent work has demonstrated the phenomenology of ash fouling, mainly by the potassium component of biomass, as well as identifying the key species such as KOH, KCl, and sulphates that are involved in potassium transport at temperatures <800 deg C. Techniques that separate the mineral matter from the fuel components (carbon and hydrogen) at low temperatures reduce or limit the alkali metal transport phenomena and result in very high efficiency combustion applications in combustors, gas turbines, and diesel engines. Gasification and various types of clean up systems as well as pyrolysis techniques are able to separate the minerals from the fuel component. The performance of these systems under investigation will be discussed. (orig.) 22 refs.}
place = {Finland}
year = {1996}
month = {Dec}
}