Flowsheet development for the steam gasification of animal manure with subsequent CO₂capturing using CaO: An Aspen Plus® modelling study

Animal manure is one of the important wastes present in the state of Qatar and worldwide. The aim of the current investigation is to develop a flowsheet model for the steam gasification of animal manure with CaO for CO2 capturing using Aspen Plus through the Gibbs-free energy minimisation model. The effect of the three key variables, namely, the temperature (600°C-800°C), the steam/manure ratio of (0.5-2), and the CaO/manure ratio of (0-2) on syngas production was analysed. The CO2 content reduced from 19 to less than 1 vol% and the H2 increased from 66 vol% to 98 vol% by varying the CaO/manure ratio from 0-2 at a high temperature of 700°C and steam/manure ratio of 1.5. Whereas the CO2 reduced from 15 vol% to 11 vol% at an elevated temperature of 850°C. The cost of H2/kg is $40.44/kg with CaO and $43.17/kg without CaO showing the benefits of its usage. The calculated rate of return and payback period for the manure gasification without CaO utilisation demonstrate higher values than the case with CaO utilisation at approximately 56.60% and 1.77 years compared to 49.02% and 2.04 years, respectively.