An equilibrium calculation tool with development potential for predicting phosphorus recovery from sewage sludge in entrained-flow gasifiers

• Published in: Chemical engineering research & design 2023-09, Vol.197, p.53-64
• Main Authors: Askarizadeh, Hossein, Lotfollahzadeh, Arash, Wolfersdorf, Christian, Pielsticker, Stefan, Kneer, Reinhold
• Format: Article
• Language: English
• Subjects: Chemical equilibrium calculator; Entrained flow gasifier; Gibbs free energy minimization; Sensitivity analysis; Sewage sludge gasification
• ISSN: 0263-8762
• DOI: 10.1016/j.cherd.2023.07.008

Gasification of industrial residues and sewage sludge from wastewater treatment plants aims to recover phosphorus and to contribute to the reduction of greenhouse gas emissions. One novel method for the recovery, co-opted from the Wöhler process, is the mobilisation of phosphorus into the gas phase in entrained flow gasifiers and the subsequent separation. In this regard, a chemical equilibrium calculation tool is developed in this study to predict gasifier performance and find optimum conditions for a set of input parameters. The calculation is based on the non-stoichiometric formulation of the Gibbs free energy minimization problem. With a maximum root-mean-square error of 0.31 vol% in the gas composition, the equilibrium tool predictions are in good agreement with available experimental data. The tool is then used to carry out sensitivity analyses on the performance of a multi-fuel-conversion (MFC) pilot plant in Niederaußem, an entrained-flow gasifier with 850 kW thermal input of a mixture of sewage sludge and dried lignite. The sensitivity analysis shows oxygen followed by the fuel mixture and steam influence significantly the gasifier performance by changing O/C and H/C ratios. [Display omitted] •A chemical equilibrium calculator based on the minimization of Gibbs free energy for analysing entrained-flow gasifiers.•Forward calculation approach starting from inlet conditions and energy balance to analyse gasifier performance.•Backward calculation approach starting from the raw gas composition at the reactor outlet to analyse gasifier performance.•Accurate results with significantly shorter computation time compared to computational fluid dynamics (CFD) simulations.•Sensitivity analysis to determine the influence of various parameters on the gasifier performance.