Modelling Water Scrubbing Biogas Based Technology William Nock, Sonia Heaven, Charles Banks Faculty of Engineering and the Environment, University of Southampton Promotion of Biogas Upgrading and Bottling in India and European Union

Why do we need a model? Description of real life situations Tool to help design and operate a system Provide predictions on how a system will behave under different conditions “Everything should be made as simple as possible, but not simpler”- Albert Einstein

Promotion of Biogas Upgrading and Bottling in India and European Union Modelling Approach Equilibrium Based Models Rate Based Models 1D, 2D or 3D Steady state or dynamic model CFD Empirical design HETP and HTU/NTU

Promotion of Biogas Upgrading and Bottling in India and European Union Well mixed system with negligible directional concentration gradients Ideal Gas Law and ideal liquid flow Isothermal reactor Chemical reaction Which species should mass transfer consider Mass transfer liquid or gas side dominant? Modelling Assumptions

Promotion of Biogas Upgrading and Bottling in India and European Union Model Derivation L IN L OUT G OUT G IN Δz Q G, Z c G, Z Q G, Z+ΔZ c G, Z+ΔZ Q L, Z+ΔZ c L, Z+ΔZ Q L, Z c L, Z Q G, Z+ΔZ c G, Z+ΔZ c L, Z+ΔZ Q L, Z c L, Z

Promotion of Biogas Upgrading and Bottling in India and European Union Plug Flow Reactor Δz Q G, Z c G, Z Q L, Z+ΔZ Q G, Z+ΔZ c G, Z+ΔZ c L, Z+ΔZ Q L, Z c L, Z z+Δz z Accumulation = input – output – reaction

Promotion of Biogas Upgrading and Bottling in India and European Union Axial Dispersion Model Δz Q G, Z c G, Z Q L, Z+ΔZ Q G, Z+ΔZ c G, Z+ΔZ c L, Z+ΔZ Q L, Z c L, Z Accumulation = input – output – reaction

Promotion of Biogas Upgrading and Bottling in India and European Union Boundary Conditions Closed - Closed Open - Open

Promotion of Biogas Upgrading and Bottling in India and European Union Mass Transfer Theory Interface Bulk Gas Bulk Liquid Liquid Film Gas Film cGcG c Gi c Li cLcL

Promotion of Biogas Upgrading and Bottling in India and European Union Mass Transfer Theory cGcG Interface Bulk Gas (c G ) Bulk Liquid (c L ) Liquid Film Gas Film cLcL

Promotion of Biogas Upgrading and Bottling in India and European Union Empirical Correlations Henry’s Law Mass transfer coefficients Interfacial area Pressure drop Gas/ liquid holdup

Promotion of Biogas Upgrading and Bottling in India and European Union Finite Difference

Promotion of Biogas Upgrading and Bottling in India and European Union Finite Difference

Promotion of Biogas Upgrading and Bottling in India and European Union Summary Simple models often out perform more detailed models Assumptions need to be taken with care

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