Proceedings World Bioenergy 2010

NEW INSIGHTS IN THE ASH MELTING BEHAVIOUR AND IMPROVEMENT OF BIOMASS ENERGY
PELLETS USING FLOUR BOND
J. van Soest, J. Renirie, S. Moelchand, M. Schouten, A. van der Meijden, J. Plijter
Meneba B.V., www.meneba.com
Brielselaan 115, 3081 AB Rotterdam, The Netherlands.
Tel. +31 104238130, Fax. +31 104238299, J.vanSoest@meneba.com
ABSTRACT: New insight was obtained in the effect of ash composition on the ash melting behavior. It was shown that
there is a good correlation between the amount of calcium (Ca), silicon (Si) and potassium (K) contents of the ash and the
ash melting temperature (Tmelt) of bio-energy products like wood, agro- and sludge pellets (n=164). Using PCA and
linear regression analyses led to a good prediction of the Tmelt by using an easy to use formula:
Ln [Tmelt] = 7,24 -0,33*Si-0,70*K+1,28*K*Ca (variance accounted for is 72%)
The new formula gives much better predictions of ash Tmelt of wood pellets and other solid bio-energy or biofuel
products than previous fits. As expected Ca plays an important positive role. K and Si sink the Tmelt. Other metals play a
less dominant role, such as iron (Fe), aluminium (Al) and magnesium (Mg). The new insight was put into practice by
showing that by adding FlourBond®, a pressing aid high in Ca, the Tmelt of wood pellet ash can be increased. It is
envisaged that an elevated ash Tmelt reduces the risk of slagging of solid biofuels.
Keywords: pellets, ash, biomass production, biomass characteristics, sintering
1 INTRODUCTION
Wood pellet combustion is nowadays known as a
reliable and comfortable heating system. However,
the pellets have to be of high quality to ensure stable
and long-­‐term usage of the heaters. The pellets have
to be made according to strict quality criteria as put
down in the Önorm or DIN+ or ENplus [1]. It is
important to control the pellet properties such as
water content, hardness, abrasion, fines, ash content
and heating value. In particular ash melting behaviour
can create problems in ovens such as corrosion,
erosion and slagging [2-­‐7].
Some of the pellet properties can be improved by
using pressing aids, such as starch or rye meal. Pure
starches can be very expensive and rye meal, corn
grits or lower quality starches can result in high ash
content and melting temperature and severe slagging
beside resulting in worse processing and pellet
abrasion properties. Therefore, development of a, for
the pellet market dedicated, cheap multifunctional
pressing aid has become of great importance.
New insight has been obtained in the behavior of
pressing aids in the production of wood pellets. On the
basis of this a novel multifunctional pressing aid was
developed with a high calcium content (FlourBond®)[8].
It was shown that free flowing properties were improved
making the product easier to use in the pellet factory and
control dosage level. The output of the pellet presses
could be enhanced resulting in lower energy usage. The
pellet properties were improved at lower contents than
with currently used pressing aids such as most starches.
The pressing aid is readily available and an excellent
performing alternative for expensive starches.
In this detailed study, the properties of ash from
pellets produced in industrial conditions with various
pressing aids were investigated. The study includes the
effect of the new pressing aid with high calcium content
on pellet ash properties. A broad range of pellets (n=35)
were made on different industrial presses based on
various wood resources (containing both soft and hard
woods, see figure 1). The ash melting behavior and
composition were studied and compared with data from
literature on the ash composition and melting behavior of
various pellets and other bio-energy products [9-20]. The
total data set consisted of 164 products.
Figure 1: Various pellets
2 MATERIALS AND METHODS
Various wood pellets (n=35) were made based on
miscellaneous wood resources (soft, hard and mixed
woods as well as fresh and waste woods). Pellets were
made using various presses and pressing aids, including
FlourBond. Ash (composition and melting behavior) was
characterized according to the following DIN standards:
v Water content DIN CEN/TS 14774-3: 2004-11
v Ash content DIN CEN/TS 14775: 2004-11
v Ash composition DIN 51729 part 1 & 11 (as Oxide)
v Ash melting DIN CEN/TS 15370-1
Other ash melting data were taken from literature [9-
19]. A large data set was obtained of in total 164
products. Beside wood pellets, the data set contains
products consisting of woods, grasses, hay, straw, cereal
based products, whole crop products, sludge, municipal
and food processing waste products, and waste streams
from chemical industry such as paper and textile.
From the raw data the metal compositions were
calculated expressed as % of the total ash and as mg/kg
of the bio-energy products or wood pellet. The sintering
(SST), softening (DT), hemispheric (HAT) and flowing
(FT) temperatures were used to characterize the ash
melting behavior.
3 RESULTS AND DISCUSSION
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