Conference article

Simulation of Condensation in Compressed Raw Biogas Using Aspen HYSYS

Lars Erik Øi
Department of and Process, Energy and Environmental Technology, University College of Southeast Norway, Norway

Jon Hovland
SINTEF Tel-Tek, SINTEF Industry, Porsgrunn, Norway

Download articlehttp://dx.doi.org/10.3384/ecp1815331

Published in: Proceedings of The 59th Conference on Simulation and Modelling (SIMS 59), 26-28 September 2018, Oslo Metropolitan University, Norway

Linköping Electronic Conference Proceedings 153:5, p. 31-36

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Published: 2018-11-19

ISBN: 978-91-7685-494-5

ISSN: 1650-3686 (print), 1650-3740 (online)

Abstract

Raw biogas typically contains 60 % methane, 40 % CO2, small amounts of other components and is saturated with water. It is a question whether raw biogas can be compressed to high pressures without condensation. The aim of this work is to calculate the condensation limit under different conditions with varied temperature, pressure and gas composition using different equilibrium models. Traditionally, gas mixtures of methane, CO2 and water are calculated in a process simulation program with standard models like Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK). PR and SRK with the a-function replaced with a Twu a-function were also evaluated. For mixtures with only methane and CO2 (dry biogas) all the models gave similar results. Under normal ambient temperatures (above 0 °C), a dry mixture with more than 40 % methane will not give any condensation. For biogas saturated with water, the different models gave similar results up to about 70 bar when binary coefficients were included, but above this pressure there were significant deviations between the models. The PR and SRK with standard or Twu a-function gave reasonable results for the dew-point predictions, but above about 70 bar the uncertainty increases.

Keywords

CO2, methane, water, biogas, phase envelope, Aspen HYSYS

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