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Juma Haydary

Abstract

In this work, the gasification of a fraction of municipal solid waste, MSW, generally separated from inorganic materials and biodegradable components, the so-called refuse-derived fuel (RDF), was studied using material characterisation methods, and the modelling of an industrial scale process was presented. The composition of RDF was determined by the separation of a representative sample into its basic components (paper, foils, hard plastics, textiles). All RDF components as well as a representative mixed sample of the RDF were studied using a thermogravimetric analysis (TGA), elemental analysis and bomb calorimetry to determine their proximate and elemental compositions, and a higher heating value. An industrial scale gasification process was studied by mathematical modelling and computer simulations. All techniques, gasification with air, gasification with oxygen, and gasification with both oxygen and steam were investigated under different conditions. The RDF conversion of 100 % was achieved by the gasification with air at the air to RDF mass ratio of 3.2. The gas heating value was 4.4 MJ/Nm3. The gasification of RDF using oxygen enables the production of gas with the heating value of around 10 MJ/Nm3 at the oxygen to RDF mass ratio of 0.65. By increasing the steam to the RDF mass ratio, the contents of H2 and CO2 increased, while the content of CO, reactor temperature and the gas heating value decreased.

Open access

Patrik Šuhaj, Jakub Husár and Juma Haydary

Abstract

Approximately 1 300 Gt of municipal solid waste (MSW) are produced worldwide every year. Most of it is disposed of in landfills, which is very hazardous for the environment. Up to 10 % of produced MSW are incinerated. However, incineration is not very effective and requires specific conditions for preventing emissions. Gasification and pyrolysis are more effective processes which can be used not only for heat and electricity generation but also for fuel and valuable chemicals production. MSW can be transformed into refuse-derived fuel (RDF) which has higher heat of combustion. Synthesis gas produced by RDF gasification can be utilised in methanol production. Methanol is a very lucrative chemical which can be used as renewable liquid fuel or as a reagent in organic syntheses. Gasifier design and process optimisation can be done using a reliable mathematical model. A good model can significantly decrease the number of experiments necessary for the gasification process design. In this work, equilibrium model for RDF gasification was designed in Aspen Plus environment and the flow of oxygen and steam as gasification agents were optimised to achieve the highest theoretical methanol yield. Impact of the recycle of unreacted steam and produced tar on the methanol yield was evaluated. The highest theoretical methanol yield (0.629 kgMEOH/kgRDF) was achieved when the steam and tar recycle were switched on, the ratio between oxygen and RDF feed was 0.423 kg/kg and that between the steam and RDF feed was 0.606 kg/kg. In this case, fresh steam represented only 12 % of the total steam fed to the reactor, the rest consisted of recycled steam. Optimal gasifier temperature was 900 °C.