In an earlier post, Plasma Gasification-Municipal Waste as a Power Source, we highlighted this process as an effective way to create energy from waste. I received news from Emerson’s Barbara Hamilton that the Industrial Energy consulting and global project services teams have been working on a project expected to come on line in 2014.
The plant is being built near an existing landfill and is expected to divert 350,000 tonnes of waste from the landfill each year. It is designed to produce approximately 49 megawatts (MW) through oxygen assisted plasma gasification of approximately 950 metric tons per day of processed municipal solid waste (MSW) supplied from a nearby recycling facility.
Raw MSW will be processed by the Recycler to remove recyclable materials, such as ferrous and nonferrous metals, glass, and some plastics, and will then be shredded to approximately 300 x 300 mm (12 inch) average size and delivered to this facility via walking floor heavy goods vehicle (HGV).
The MSW will be further processed to reduce its size and increase its density, mixed with a bed support material, (metallurgical coke or anthracite coal), and a fluxant, (limestone), and then introduced into the vertical cylindrical gasifier, via feed screw injectors. As the material moves downward in the atmospheric pressure gasifier, it is heated by electric plasma torches to bulk temperatures in excess of 1200ºC.
Barbara explained that most of the carbon in the waste reacts with controlled amounts of oxygen introduced immediately above the plasma torches to produce carbon monoxide. Some of the carbon reacts with water present in the waste or steam introduced into the gasifier to produce hydrogen. The product syngas is partially quenched as it exits from the top of the gasifier vessel. Inorganic and inert materials exit the bottom of the gasifier as slag, which is quenched in a water bath, and conveyed onto trucks for offsite disposal by the Recycler.
The syngas produced will undergo a series of process operations to further quench, scrub, cool, compress, and remove particulates—hydrogen chloride, ammonia, sulphur, and any trace mercury from the syngas to make it suitable as fuel for two combustion gas turbines. The gas turbine generators will produce electricity, and the heat from each turbine’s exhaust is recovered as steam in heat recovery steam generators (HRSG).
An auxiliary boiler combusts any fuel beyond the capacity of the gas turbines. Steam produced via the auxiliary boiler is combined with the steam produced in the HRSG’s to feed a steam turbine, which will produce additional power. The exhaust gas of the auxiliary boiler and the HRSG’s is catalytically treated to remove NOx.
Barbara described the global Emerson team members in this project with people from Costa Rica, India, Romania, United Kingdom, and United States. Project functions included project management, process automation system and safety instrumented system design and execution, procurement, document control, integration, and testing.
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