Abstract
The aim of this doctoral dissertation was to increase
the average grain size of the
milled layer from the present 5 mm up to 15 mm without
an increase in the power
demand of the miller by studying the present blade
models already used in peat
production and by developing new ones. If the target
of the research can be achieved,
the drying of peat will be improved by at least 20 %
and hence the hectare yield will be increased and the
production costs reduced.
The research was carried out in a laboratory by using
a milling machine simulator.
The miller types investigated were rotating pin and
screw millers already used in peat production, and new
plate and granulating millers. The
experiments were carried out
using medium and well humified Carex and
Carex/Sphagnum peats. The research
plans were made using test planning software, and the
results have been analysed by a multivariate method.
Models were compiled for four
miller and peat types,
and they show the effects of the milled layer and
driving parameters on the average
grain size and on the power demand of the miller.
The average grain size is increased with nearly all
the miller and peat types as the milling depth, milling
moisture content and the
driving speed of the miller areincreased, and as the
amount of the residual peat and the rotation speed of
the miller drum are decreased. The power demand of the
miller is increased as the driving speed, the rotation
speed of the miller drum, the amount of residual peat
and the milling depth are increased.
It was not possible to reach the target fully. The
best results were obtained using plate
and screw millers for all four peat types. The average
14 mm grain size was obtained in the case of medium
humified Carex and Carex/Sphagnum peats, as well as
with well-humified Carex peats while using the plate
miller. The average grain size of over
15 mm was obtained in the case of well and medium
humified Carex peats while using the screw miller. The
powe
r demand of the plate
miller is lowest,
being about
the same as that of the pin miller, but the power
demand of the screw miller
is
higher than that of the plate and pin millers.
On the basis of the average grain size and the power
and maintenance demands
of
the miller, the plate miller is the best. The
obtainable average grain size
of the plate
miller can be increased and the grain size
distribution and power demand
decreased
by reducing both the diameter and the rotation speed
of the miller drum. The
plate
miller can also be developed further in order to
obtain the grain size
target with all
peat types.
Original language | English |
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Qualification | Doctor Degree |
Awarding Institution |
|
Supervisors/Advisors |
|
Place of Publication | Espoo |
Publisher | |
Print ISBNs | 951-38-4411-0 |
Publication status | Published - 1994 |
MoE publication type | G4 Doctoral dissertation (monograph) |
Keywords
- peat millers
- power demand
- milling
- peat
- properties
- grain size
- decomposition
- fibers
- multivariate analysis
- simulators