INFLUENCE OF FLY ASHES ON MASS TRANSFER
TAGUTCHOU Jean-Philippe, ESTEL Lionel, LEDOUX Alain, WANG Maxime
INSA de ROUEN – LSPC – St Etienne du Rouvray 76801, France
jean-philippe.tagutchou@insa-rouen.fr, lionel.estel@insa-rouen.fr,
alain.ledoux@insa-rouen.fr, maxime.wang@insa-rouen.fr
Abstract
Nowadays, the consideration of gas or liquid emissions takes a growing place in the design of
industrial plants. In the special case of hazardous waste coming from industrial sources,
incineration is one of the most common thermal treatments (E.T. Oppelt 1987). Indeed
incineration appears to be an effective way to convert hazardous waste into a nonhazardous
form while greatly decreasing its volume. Incineration of waste materials converts the waste
into ash, flue gas, and heat.
The problems associated with incineration are high capital and operating costs, and the
disposal of ash, which may contain hazardous substances. The ash is mostly formed by the
inorganic constituents of the waste, and may take the form of solid lumps or particulates
carried by the flue gas. Since the particles solidify while suspended in the exhaust gases, fly
ash particles are generally spherical in shape and range in size from 0.5 µm to 100 µm (Y.
Mamane et al. 1986). Fly ashes are generally highly heterogeneous, consisting of a mixture of
glassy particles with various identifiable crystalline phases such as quartz, mullite, and
various metal oxides. In addition, incinerating wastes can cause mercury and dioxin air
pollution (H.A. Razak et al. 2009; K.P. Naikwadi et al. 1993). The flue gases must be cleaned
of gaseous and particulate pollutants before they are dispersed into the atmosphere. Modern
incinerators include pollution mitigation equipment such as flue gas cleaning.
In a previous study (I. Aouini et al. 2009) we have evaluate the sustainability of carbon
dioxide alkanolamine capture from incinerator flue gas including reuse option. The process
target is to provide a CO2 stream with commercial purity and minimum investing and
operating cost. We select monoethanolamine (MEA) as the solvent as it is the most
appropriate for low CO2 partial pressure extraction.
In this paper we study the influence of fly ash fine particles on gas-liquid contactors in this
carbon dioxide capture process. Indeed we observe the presence of submillimetric fine
particles that rise with the flue gases and pass through the devices of upstream filtering
(electrostatic precipitators).
With reference samples of ash or direct samples from smokes of incineration, we try to
identify how these particles modify the phenomena of mass transfer at the gas-liquid
interface. Surface and interfacial tension are measured by the pendant drop method from
ambient to elevated temperatures [5°C ; 80°C] for different mixtures [10% ; 50%] and carbon
dioxide loading. In this method, geometry of a pendant drop is analyzed optically with
Young-Laplace drop shape analysis. A drop of liquid is hanging from a syringe needle then it
will assume a characteristic shape and size from which the surface tension can be determined.
These measurements allow to determine how quickly do contactors decrease in performance
and what chemical or physical treatments are considered suitable.
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