Pyrolysis-catalytic steam/dry reforming of processed municipal solid waste for control of syngas H2:CO ratio

Abstract

The production of syngas from the pyrolysis-catalytic reforming of processed municipal solid waste in the form of refuse derived fuel has been investigated experimentally using a two-stage fixed bed reactor with a 10 wt% Ni–Al2O3 catalyst. The reforming gases used were a combination of steam and carbon dioxide (dry reforming). The main focus of the research was to manipulate the H2:CO ratio in the syngas for targeted end-use applications by optimizing the process conditions, including the input steam/CO2 reforming gas ratio. The experimental results showed that at higher steam:CO2 ratios, there was a marked increase in H2 yield due to the endothermic nature of the steam and CO2 reforming processes. The catalytic reforming temperature also had a major influence on H2 yield, with increasing temperature raising the hydrogen yield to a maximum of ∼41.0 mmol gRDF−1 at 955 °C catalyst temperature. The H2:CO molar ratio was also affected by the process variables and were interdependent on them. For example, the influence of an increase in the catalytic reforming temperature as the content of steam in the reforming gas input was also increased, produced a maximum H2:CO molar ratio of ∼4.7:1 achieved at an input steam:CO2 ratio of 75:25 and a catalyst temperature of 700 °C. Whereas, at higher CO2 content in the reforming gas, the product H2:CO ratio was ∼1:1. Also, for a steam:CO2 input ratio of 50:50, the H2:CO ratio produced was ∼2:1 and for higher steam content in the reforming gas the product H2:CO was ∼3:1. Design of Experiments (DoE) modelling was carried out using the experimental data to identify the process conditions that would produce a target syngas H2:CO molar ratio of 1:1 and 2:1. The predicted optimised process conditions from the DoE modelling produced experimental results close to the targeted syngas H2:CO molar ratios, thereby validating the DoE model.