S. P. Long and C. V Beale with contributions from P. K. Farage. Agronomy ... in determining the operating conditions of the conversion plant and the disposal of.
m
I
(/)
l
)>
~
-
3:
o
-
o
m
(/)-l
m o
o z
.OJ
r-
m
)>
I
n
~
Contents
Authors and contributors Priface
Published by James &James (Science Publishers) Ltd, 35- 37 William Road, London NWl 3ER, UK
VI lX
© 200 l The authors and contributors
l
Origins and Taxonomy of Miscanthus L. Scally, T. Hodkinson and M. B. Jones
The moral rights of the authors have been asserted.
2
Resource Capture by Miscanthus S. P. Long and C. V Beale with contributions from P. K. Farage
IO
3
Agronomy of Miscanthus D. G. Christian and E. Haase with contributions from C. Dalianis, J. C. Clifton-Brown and S. Cosentino
21
Ali righ ts reserved. No part of this book may be reproduced in any form or by any means electronic or mechanical, including photocopying, recording or by any information storage and retrieval system without permission in writing from the copyright holder and the publisher. A catalogue record for this book is available from the British Library.
·l
4
Miscanthus Productivity ]. C. Clifton-Brown, S. P. Long and U.j0rgensen with contributions from S. A. H umphries, K.-U. Schwarz and H . Schwarz
46
5
Miscanthus Breeding and lmprovement U. j 0rgensen and H.·:J. Muhs with contributions from N. El Bassam, A. Eppel-Hotz, C. Petrini andJ. C. Clifton-Brown
68
6
Harvesting and Storage of Miscanthus N. El Bassam and W Huisman
86
7
Utilisation of Miscanthus P. Visser and V Pignatelli with contributions from U.j0rgensen and ]. F. Santos Oliveira
109
8
Economics of Miscanthus Production M. Bullard
155
9
Environmental Aspects of Miscanthus Production ]. F. Santos O liveira with contributions from P. D uarte, D. G. Christian, A. Eppel-H otz and A. L. Fernando
172
Bibliography Index
179 189
ISBN 1-9029 16-07-7 Printed in the UK by The Cromwell Press Cover photos courtesy of Dr I. Lewandowski, University of Hohenheim, Stuttgart.
B. Schwarz,
6 Haruesting and Storage of Misc~nthus'
108
Year . - - - - Yariety
7
Utilisation qf Miscanthus by P Visser and V. Pignatelli
Harvest method (Hm)
with contributions from U. j0rgensen and F Santos Oliveira
J.
Sociallimitations
per hr/day per day
Julian day Areato be harvested
7 .l lntroduction Value lost mass
Cropm Harvest method Crop yield
Cy, t/ha Eoutput Energy output in kJ/t
E input
Figure 6.1 7. Optimisation mode/ to calculate harvest time and total chain costs for uarious haruesting, drying and storage scenarios.
from a number of sub-models concerning crop moisture content, trafficability, shoot regrowth, workability, time loss, machine costs, drying in storage, soil damage and yield loss. The mode! outputs are costs (NLG) and energy input of the whole chain. Various scenarios of different harvesting, drying and storage systems will be chosen and calculations will be made for all years so that the variation of the calculated costs and energy input can be examined and statistically described. The results should then give an insight into the costs and the variation in the costs that can be expected in the future for these scenarios (assuming no weather change in the future).
Miscanthus was introduced into Europe in 1935 and has primarily been used as an ornamental plant since then (Jones et al., 1994; Jorgensen, 1996). However, more recently, research results from severa! European countries have encouraged the development of a range of commerciai uses for it. Energy production and paper pulp production were the fìrst end uses which were considered for Miscanthus, but the feasibility of other end uses is also being examined. These potential end uses include utilisation in building materials and also in the bioremediation of contaminateci soil. This chapter outlines the different options for the utilisation of Miscanthus-harvested biomass.
7. 2 Energy Production One of the potential end uses of Miscanthus is as a fuel for energy production. The energy production alternatives which have been examined are co-combustion with coal, and combustion in farm heating plants. These two alternatives are outlined below.
7.2.1 Chemical and Physical Characterisation If Miscanthus is to be used as a fu el for energy production, it is important to know the chemical composition of the biomass itself and its ashes. BTG has carried out an investigation as part of the Miscanthus Productivity Network to determine the physical and chemical characteristics of Miscanthus. The results of this research will be of use in determining the operating conditions of the conversion plant and the disposal of the ash. BTG analysed a sample of Miscanthus (sample l) in 1994 for its chemical and physical characteristics, another sample (sample 2) was analysed in 1995. Sample 2 had been used in droptube furnace experiments. Two further Miscanthus samples (samples 3 and 4) were analysed by MIDTKRAIT (A/S Midtkraft Energy Company, Skodstrup, Denmark) during large scale co-combustion t~sts in Denmark. In addition, data on the chemical and physical characteristics of Miscanthus have been found in the
Vzsser and Pignatelli
7 Utilisatwn qf Miscanthus
110
Table 7.1 . Pf!ysical and chemical characteristics qfMiscanthus. Parameter
Sample l*
Gross calorific value (MJ kg'" 1) 19.05 on dry basis 16.78 on wet basis N et calorific value (MJ kg'" 1) on dry basis 15.37 on wet basis, as received 11.9 Moisture content (%, wet basis) 11.2 Fixed carbon (%) 86.3 Volatile content (%) 2.6 Ash content (%) Chemical composition (%,dry basis) 49.5 c 7.47 H 39.3 0.17 s 0.61 N 0.49 CL Heavy metals (mg kg'" 1, dry basis) 3.9 Pb < 0.8 Cd 2.1 Cu < 0.02 Hg 2.1 Cr 48 Zn 2.0 Ni 500 MWcl). The factors which affect the conversion of pulverised coal inside a combustor can be interpreted and understood if the process is locally probed to measure relevant parameters such as temperature, velocity and local composition of the gas and solid phase. The sections below describe the co-combustion of biomass with coal through the use of a droptube reactor and the implementation of large-scale co-combustion experiments.
Droptube Experim.ents on Co-combustion with Goal
1020 1090 1120
Samples analysed for BTG, according to characterisation standards recommended by IEA. Samples analysed by MIDTKRAFT Chemistry Department Laboratory. Source: Kristensen, 1997.
Choosing a power station as an experimental set-up for research is difficult because of the scale of operation (>500 MWcl). In order to overcome this prob1em BTG designed and constructed a droptube reactor for carrying out well controlled biomass devolati1isation experirnents with operational conditions that resemb1e those of a pulverised coal combustion reactor. A mathematical mode! was also developed to predict biomass dècomposition in the droptube reactor. The goal of the mode! was to describe the processes which occur inside a pu1verised coal combustion station and to determine if biomass contributes to the flame formation 'inside the combustion chamber.
7 Utilisation qf Miscanth~s
112
The droptube reactor simulated the environment inside a pulverised coal combustion chamber. Default values for the experimental conditions such as temperature, particle residence time and gas phase composition were derived from pulverised coal combustion literature. The biomass particle diameter and type of biomass were independent variables defined during the experiments. Operating Conditions of the Droptube Reactor The reactor temperatures varied from 800- 1400°C. A custornised biomass belt feeder was designed to allow a continuous biomass feeding rate of l g h- 1 (in order to study the thermal decomposition rate of single particles). Prior to each droptube reactor experiment the biomass particles were size-reduced using a hammermill, the material was then size-classified with a vibrating sieve stack where three biomass particle size classes were obtained. These were ClassI (0.6- 1.0 mm), Class II (1.0-2.0 mm), and Class III (2.0-2.8 mm). The experimental conditions employed in the reactor may be summarised as follows: • • • • •
temperature: l 000, 1200, 1300 or 1400 oc oxygen concentration: 20% voi p artide size class: 0.5- 1, 1- 2, or 2- 3 mm tube length: 0.4, 0.8, 1.2, or 1.6 m biomass type: willow, poplar, Miscanthus or reed
Visser and Pignatelli
113
Table 7.2. Parameter ualues used in mathematical rrwdelfor thmnal decomposition qf willow particles. Parameter
Unit of measurement
Value
Willow particle shape Willow particle diameter (dP) Willow particle length (LP) Willow density Willow heat capacity Willow heat conductivity Heat of reaction Ultimate char mass fraction Gas phase medium Gas phase temperature
cylindrical 1.3 7.0 470 1335 0.122 0.5 0.1 air 1573
mm mm kg m-J J ~
