TY - JOUR
T1 - Ash transformation and deposit build-up during biomass suspension and grate firing: Full-scale experimental studies
AU - Shafique Bashir, Muhammad
AU - Jensen, Peter Arendt
AU - Frandsen, Flemming
AU - Wedel, Stig
AU - Dam-Johansen, Kim
AU - Wadenbäck, JOhan
AU - Thaaning, Søren
PY - 2012
Y1 - 2012
N2 - An attractive option for reducing the net CO2 emissions is to substitute coal with biomass in large power plant
boilers. However, the presence of chlorine (Cl) and alkali metals (K, Na) in biomassmay induce large operational
problems due to ash deposit formation on the superheater tubes. The aim of this study was to investigate ash
transformation and deposition behavior in two biomass-fired boilers, firing wheat straw and/or wood. The influence
of strawfiring technology (grate and suspension) on the ash transformation, deposit formation rate and deposit
characteristics has been investigated. Bulk elemental analysis of fly ashes revealed that fly ash from
suspension firing of straw has high contents of Si, K and Ca, while fly ash from straw firing on grate was rich in
the volatile elements K, Cl and S. Investigations of deposit formation ratesweremade in the superheater and convective
pass regions of the boilers by use of an advanced online deposit probe. During straw firing on grate, the
measured deposit formation ratewas close to 38 g/m2/h. Data fromstraw suspension firing showed a deposit formation
rate of 41 g/m2/h. The deposit formation rates during straw suspension firing and straw grate firing were
on similar levels. This was observed even though the concentration of fly ash in the flue gas was significantly
higher during straw suspension firing. The influence of co-combustion of wood with straw on deposit formation
rate, probe heat uptake and deposit characteristicswas also investigated during suspension firing conditions. Data
from 35% straw suspension firing with wood showed a deposit formation rate of 33 g/m2/h for the first 12 h. The
deposit formation rate increased to 41 g/m2/h with 100% strawfiring. The probe heat uptake reduction up to 40 h
of exposure time was 3.0, 7.3, 8.4 and 16.5 kW/m2 during 35, 65, 80 and 100% straw firing, respectively.
AB - An attractive option for reducing the net CO2 emissions is to substitute coal with biomass in large power plant
boilers. However, the presence of chlorine (Cl) and alkali metals (K, Na) in biomassmay induce large operational
problems due to ash deposit formation on the superheater tubes. The aim of this study was to investigate ash
transformation and deposition behavior in two biomass-fired boilers, firing wheat straw and/or wood. The influence
of strawfiring technology (grate and suspension) on the ash transformation, deposit formation rate and deposit
characteristics has been investigated. Bulk elemental analysis of fly ashes revealed that fly ash from
suspension firing of straw has high contents of Si, K and Ca, while fly ash from straw firing on grate was rich in
the volatile elements K, Cl and S. Investigations of deposit formation ratesweremade in the superheater and convective
pass regions of the boilers by use of an advanced online deposit probe. During straw firing on grate, the
measured deposit formation ratewas close to 38 g/m2/h. Data fromstraw suspension firing showed a deposit formation
rate of 41 g/m2/h. The deposit formation rates during straw suspension firing and straw grate firing were
on similar levels. This was observed even though the concentration of fly ash in the flue gas was significantly
higher during straw suspension firing. The influence of co-combustion of wood with straw on deposit formation
rate, probe heat uptake and deposit characteristicswas also investigated during suspension firing conditions. Data
from 35% straw suspension firing with wood showed a deposit formation rate of 33 g/m2/h for the first 12 h. The
deposit formation rate increased to 41 g/m2/h with 100% strawfiring. The probe heat uptake reduction up to 40 h
of exposure time was 3.0, 7.3, 8.4 and 16.5 kW/m2 during 35, 65, 80 and 100% straw firing, respectively.
KW - Suspension-fired boiler
KW - Fly ash
KW - Wood
KW - Straw
KW - Grate-fired boiler
KW - Deposit formation rate
U2 - 10.1016/j.fuproc.2012.01.018
DO - 10.1016/j.fuproc.2012.01.018
M3 - Journal article
SN - 0378-3820
VL - 97
SP - 93
EP - 106
JO - Fuel Processing Technology
JF - Fuel Processing Technology
ER -