NTU NEA Waste to Energy Research Facility
Figure 1. The waste-to-energy (WTE) research facility will be a test bed and demonstrator for new and emerging WTE technologies. Source: NTU.
The waste is dried and gasified as it moves down the furnace. About 85% of the waste converts to syngas — mostly carbon monoxide and hydrogen. This flows to a secondary combustion chamber where it’s burned to heat a boiler to generate steam. The steam then drives a turbine that generates electricity for the campus.
Meanwhile, 12% of the material leaves the bottom of a furnace as slag, a glass-like material that has potential as a construction material, and metal alloy granules that can be recycled.
The exhaust flue gas from the boiler is then treated with slaked lime and activated carbon and passed through a bag filter before being discharged as clean gas to atmosphere. Disposable fly ash makes up the remaining 3%.
In Singapore’s context, slagging gasification technology has potential to complement the current mass burn technology as it can treat diverse mixed-waste streams that can’t be handled by the incinerators because they typically operate at around 800°C.
According to NTU president professor Subra Suresh, the research facility’s use of university waste is well aligned with the NTU smart campus vision and will be a living testbed for advanced technology-enabled solutions aimed at tackling some of the most pressing challenges Singapore and the world are facing. “It will enable our scientists to scale up promising ideas from lab prototypes into practical engineering solutions for sustainable waste management,” he adds.
The plan now is for NTU scientists and engineers from the university’s Nanyang Environment and Water Research Institute (NEWRI) to spend several years collaborating with industry and academic partners on various research projects aimed at developing and testing emerging WTE technologies.
The research facility is designed specifically to simplify test bedding of new technologies in a plug-and-play style. Municipal solid waste also has the capability to process diverse feeds such as incineration bottom ash and sludge.
Provisions exist for evaluating the cleaning and upgrading of syngas to run a gas engine or turbine for higher energy recovery efficiencies, utilization of slag in engineering applications, novel flue-gas-treatment modules for reduced emissions, low-grade heat recovery and using a gas separation membrane to extract oxygen from air. These technologies, if proven successful and implemented, could enable more energy and materials to be recovered from waste, thereby prolonging the lifespan of the Semakau landfill.