Abstract
Mathematical modelling of wet oxidation of excess sludge A mathematical model enabling a quantitative description of wet oxidation of excess sludge in continuous bubble columns is proposed. The model consists of mass and heat transfer kinetic equations and material and heat balance equations of gas and liquid phases flowing through the absorber. The equations of material and heat balance refer to a parallel, co- current flow of gas and liquid phase and take into account a complex chemical reaction in the liquid phase core. The proposed model was used in a numerical simulation of wet oxidation in a bubble absorber for different process conditions: flow rate and composition of the gas and liquid phase, temperature and pressure, and different heights and diameters of the column.
Highlights
Management of sludge generated in wastewater treatment plants is a serious problem in Poland
The process is characterised by high efficiency because it enables over 80% reduction of total organic carbon (TOC) in the suspension and complete dissolution of biomass which forms a solid phase of the sludge[1]
BALANCE EQUATION FOR THE BUBBLE COLUMN A mathematical description was formulated under the following assumptions (Fig. 2): – the process is steady and adiabatic – the flow of phases corresponds to the model of plug flow with axial dispersion – the chemical reaction takes place in the liquid phase core only – the temperatures of liquid core and interfacial area are the same – the column diameter and total height as well as all parameters of streams flowing to this column are known
Summary
A mathematical model enabling a quantitative description of wet oxidation of excess sludge in continuous bubble columns is proposed. The model consists of mass and heat transfer kinetic equations and material and heat balance equations of gas and liquid phases flowing through the absorber. The equations of material and heat balance refer to a parallel, co- current flow of gas and liquid phase and take into account a complex chemical reaction in the liquid phase core. The proposed model was used in a numerical simulation of wet oxidation in a bubble absorber for different process conditions: flow rate and composition of the gas and liquid phase, temperature and pressure, and different heights and diameters of the column. Presented at VII Conference Wasteless Technologies and Waste Management in Chemical Industry and Agriculture, Miêdzyzdroje, 12 – 15 June, 2007
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