Integrated Process Design Optimization Accounting for Co-Digestion of Sludge and Municipal Solid Waste

The process simulation performed in the present study aimed at investigating energetically self-sufficient wastewater treatment plant of 500,000 population equivalents. To implement this, three different scenarios were evaluated using computational tools named GPS-X® and SuperPro®. They were designed based on municipal wastes recovery to energy generation and its utilisation within the facility. An anaerobic/anoxic/oxic process for biological treatment of wastewater was considered and mesophilic anaerobic digestion at different scenarios (1) primary sludge (PS) with waste activated sludge (WAS), (2) PS with thermally hydrolysed WAS, and (3) PS with WAS and organic fractions derived from municipal solid waste. The results from scenario 1 and scenario 2 showed only enough thermal energy to meet their demand (they reach only 44 and 52% of electrical self-sufficiency, respectively), while positive net thermal and electrical energy result in scenario 3 from codigestion of sewage sludge and the organic fraction of municipal solid waste. The main limitation of tools used is their lack of sensitivity to economies of scale and their dependence on real data used for process design to obtain more accurate results.

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Modelling of syngas production from municipal solid waste (MSW) for methanol synthesis

Acta Chimica Slovaca ◽

10.1515/acs-2017-0019 ◽

2017 ◽

Vol 10 (2) ◽

pp. 107-114 ◽

Cited By ~ 6

Author(s):

Patrik Šuhaj ◽

Jakub Husár ◽

Juma Haydary

Keyword(s):

Municipal Solid Waste ◽

Solid Waste ◽

Process Design ◽

Electricity Generation ◽

Liquid Fuel ◽

Process Optimisation ◽

Methanol Production ◽

Syngas Production ◽

Gasification Process ◽

Refuse Derived Fuel

AbstractApproximately 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.

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