1. Introduction - Firenze University Press

Te 1000
mp
era
900
tur 800
e
[°C 700
]
600
Temperatuur, °C
500
400
300
200
100
Stoom Steam>electricity > elektriciteit
met With voorverwarming;
preheating, potential
Potentieel 191 GJ/h 191 GJ/h
0 Stoom Steam>electricity > elektriciteit
0 zonder 50 voorverwarming;
100 150
Without preheating,
Potentieel 180 GJ/h
200 250
Enthalpy, GJ/h
300 350 400 450
potential 191 GJ/h
Fig 4. Grand composite curve of the pinch analysis
294
Base_case
Case 1 - mod. reactor pre-heat
Case 2 - no reactor preheat
voorverwarming Preheating above boven pinch pinch point
verbetert does not increase electricity
elektriciteitspotentieel potential
niet
The pinch analysis learns that there is an excess of heat. No heat source is required except for the
zinc ore. The aim of the pinch analysis is, therefore, to maximise the amount of steam that can be
used for power production. Nyrstar has a high power consumption, which is required during the
entire year. The potential for energy saving is 180 GJ per hour without reactor preheating or 191 GJ
per hour if the reactor is preheated.
Two scenarios for heat integration have been made. In scenario 1 the thermal energy saving is 73
GJ per hour leading to an electrical potential of 4.6 MWe and an investment of € 1.8 million. In
scenario 2 the thermal energy saving is 92 GJ per hour leading to an electrical potential of 5.3 MWe
with an associated investment of € 2.1 million
3.2.3. Process intensification
The results of the process intensification scan are solutions or solution directions, and thereby differ
from regular analyses.
The process intensification scan suggests to increase the understanding of the processes in the
boiler, by completing the mass and energy balances, making a chemical analysis of the scaling in
the bed and determining the effect of the process parameters on the bed. On the basis of this
information an improved redesign of the roaster and boiler can be made.
For the gas cleaning section a process simulation study is suggested. For the long term new
technologies can be considered. The leaching and purification section have different steps, which
occur at different pH. It is proposed to investigate the possibilities of using membranes to extract
water, when the pH needs to be decreased, i.e. acidity increased. It is expected that the process will
become more stable and easier to control. Demands on the material of the membrane will be an
important research parameter.