Analysis on the MSW thermal degradation processes

The waste to renewable energy source has become a priority in the wastes treatment field.
The research goal is not only the wastes destruction but also a better thermal energy
recovery from the processes. The municipal solid waste presents a high heterogeneity degree
from the dimensional point of view, form and its components specific weight of as well as
thermal-chemical characteristics. That’s why there are many treatment methods, each one
with its own particularities.
For a better understanding of the phenomenon during thermal degradation processes both
under pyrolysis or atmospheric pressure gasification stages we first accomplished a
laboratory scale series of experiments in a tubular reactor, on small quantities (5 – 10 grams)
of reconstituted urban wastes. For the validation of the obtained data on more representative
samples we extended the experiment to an original industrial scale pilot installation that
enables the continuous thermal treatment of 10 – 50 waste kilograms per hour under oxidant
or non-oxidant atmosphere (on choice) and at variable temperature between 400 °C – 1100 ºC.
The residential time of the treated sample in the installation and the flow conditions can be set
independently. The installation reproduces the incinerators or the pyrolysis / gasification
reactor process conditions and provides complete information on the wastes thermal
degradation kinetics and on the pollutant emissions. The particularity of the device consists in
the product advancing piston – like flow system based on the bed vibration. The product
particles in the bed have a translation movement without any layer shift. Therefore the
particles distribution in a given product bed section is the same all along the installation from
the feeding inlet to the extraction. That characteristic enables us to extrapolate and compare
the laboratory results of the fixed bed treatment to the industrial pilot continuously treatment
applied on the same product: reconstituted municipal solid waste, one of the most
heterogynous solid wastes in mixture.
The main targets were the sample mass reduction rate, the resulting gases composition, the
samples mechanical behavior for different temperature levels, residential time, treatment
atmosphere conditions and different steam flow rates (in the gasification process). The results
were compared to an established reference – the incineration.
The paper presents the research and results on the degradation mechanisms of MSW treated
samples in those two equipments from the Science Division CNRS, Department of Industrial
Methods, University of Technology Compiègne, France.