The use of thermal plasma technology for treating air pollution control residues

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Courtesy of Waste Advantage Magazine

Energy from waste (EFW) is an exciting industry to be in right now in the UK. As pointed out by Euston Ling and Dr. Adam Read's article 'The Shifting Landscape for Renewable Energy in the UK' {Waste Advantage Magazine, June 2011), the EFW capacity in the UK is set to grow strongly in the next 10 years, with some commentators predicting a three-fold increase in EFW capacity from the current 4 million tons per year to 12 million tons per year by the year 2020. This spectacular rate of growth is driven by a combination of tighter environmental regulations in the EU, which are forcing a higher diversion of waste away from landfill, and the move towards greater use of renewable energy. It also reflects the fairly low starting point of the UK, which historically has lagged behind many other countries in the proportion of wastes that it sends to EFW facilities.

This growth in EFW plant capacity is leading to a corresponding increase in the generation of Air Pollution Control (APC) residues, making it one of the fastest growing waste sectors in the UK. For example, the amount of APC residue generated in the UK from municipal solid waste (MSW) alone rose from around 170,000 tons per year in 2006 to around 190,000 tons per year in 2009, while the proportion of MSW being incinerated rose from around 7 percent to 12 percent over the same period.

APC residues are generated in the exhaust gas cleaning systems of EFW plants and typically represent 2 to 5wt percent of the input waste material. They are a highly alkaline hazardous waste, containing volatile heavy metals, dioxins, furans, chlorine and a high soluble salt content, which means they are classified officially as 'hazardous waste' in the EU. As a result, unlike bottom ash from EFW plants and fly ash from more traditional coal-fired power stations, much of which can be processed into aggregate or used as fillers for concrete, APC residues are generally disposed of in a hazardous waste landfill.

APC Residue Treatment : From Disposal to Recovery
The problem with this solution is that a landfill is increasingly unsustainable and legislation has moved to reinforce this. Not only has this led to a large reduction in the hazardous waste landfill capacity in the UK, but it will also result in landfill taxes rising year by year until they reach £80 ($125) per ton by 2014, with plenty of evidence that they will keep on rising beyond this point. As a result (and perhaps somewhat ironically), the very regulatory and landfill tax incentives that have made EfW plants more economically favorable are the exact same ones that are also making it more difficult and expensive to landfill the APC residue that they generate.

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