CoalSwitch – is it the holy grail?

24 February 2017



Enabling coal-fired power plants to burn biomass without extensive retro-fitting has long been the ‘holy grail’ of power generation. Active Energy Group has started planning a new production facility that will allow it commercialise a drop-in biomass fuel that might warrant such a description. Staff report


The CoalSwitch wood fibre fuel product, still glowing after a triumphant testing phase with the University of Utah, is described by its maker as nothing less than a revolutionary game changer for the renewable energy industry. Elsewhere, the achievement has been described as finding the Holy Grail of biomass, an assessment that derives from a single important quality – that it can be a drop in replacement for coal, or mixed in any ratio, in existing coal-fired power stations globally without reducing performance or creating the need for expensive modifications of the combustion system or exhaust.

Now, to promote its aim of targeting the American market, with its huge coal burn and tough clean air legislation, AEG has started planning the construction of a new production facility in North America. The new facility is a manufacturing scale-up for CoalSwitch, which was recently tested and endorsed by Rocky Mountain Power, a unit of US utility PacifiCorp, at the University of Utah. According to Active Energy, test results proved that CoalSwitch behaves better than coal in every respect, in the handling of feedstock to the plant and as a drop-in replacement for coal. RMP will conduct commercial testing of the CoalSwitch product at one of its Utah facilities as soon as production at the new plant gets under way.

Expanding production

In order to expedite construction of the 35 000 tonne per annum plant, Active Energy has delivered a $6 million five-year unsecured loan facility. “This is a landmark moment for AEG,” said Richard Spinks, its CEO. “The funding unlocks our ability to commercialise our revolutionary and proven CoalSwitch technology and will enable us to generate meaningful revenues within the USA, which is set to be one of our core geographic markets.”

First viable offering

Although measures in Europe, the USA and elsewhere have had an effect – global coal use decreased by 2.3% in 2015, and is expected to stay flat – there are still at least 2300 coal fired power plants worldwide and to date, the only methods available commercially to reduce substantially the emissions they produce, in particular carbon dioxide, have been to install exhaust scrubbers, which is very expensive, or to modify them to burn renewable fuels, generically known as biomass.

AEG CoalSwitch is the world’s first ‘drop- in’ biomass fuel that can directly replace coal completely – or be co-fired at high percentages – in industrial power plants, without requiring any furnace, logistics, handling or storage modifications.

And, helpfully, it possesses comparable energy release levels to coal, and has similar handling and friability characteristics.

It is the result of seven years of extensive research and development, for which seventeen ‘greenfield’ patents have already been filed, and enables coal-fired power plant owners to significantly reduce pollution levels and greenhouse gas emissions, while complying with new emissions regulations.

The manufacturing technology, which has not been revealed, is said to work with any plant- or wood-based biomass material, including previously unusable forest waste, sawmill waste (contaminated sawdust and offcuts) and industrial timber by removing contaminants in an organic process that leaves no harmful residues.

Other advantages are listed as high volume throughput, lower production costs, the ability to supply the feedstock as pellets, granules, briquettes or bales and greatly reduced storage, handling and distribution costs, as the final product is water-resistant.

AEG CoalSwitch – a joint venture of AEG and Biomass Energy Enhancements LLC, the process inventors – intends soon to start up a ‘build-own-operate-toll’ business model, under which the company will construct a network of advanced demountable fuel manufacturing facilities close to large-scale biomass raw material sources.

Test results

The University of Utah announced its results in March last year. It reported on CoalSwitch’s technical and commercial viability for use a standalone fuel – or co-fired in high concentrations with coal in coal-fired power plants – and confirmed that it provides significant environmental and commercial advantages for industrial power generators.

The five-day testing process, at the university’s 100 kW combustor in its Industrial Combustion & Gasification Research Facility, recorded the energy output, flame stability and behaviour, furnace reaction, depositions (fouling and slagging) and emissions produced by CoalSwitch biomass fuel (in this case, derived from low-grade aspen/ poplar feedstock) during combustion. It includedreal-timeanalysisandinterpretation of its combustion, particle and deposition characteristics; and compared the results to those achieved with Illinois Number 6 coal (a typical feedstock used for industrial power generation in the US) and a CoalSwitch/Illinois coal 50/50 mix under the same test conditions.

The 50/50 blend was a much higher concentration of biomass material than it has previously been possible to use in existing coal-fired plants without causing significant slagging and fouling issues in their boilers.

The university confirmed the potential of CoalSwitch fuel for the power generation industry, and judged that it delivered significant financial and environmental benefits over current Biomass fuel solutions. Key findings included:

  • CoalSwitch fuel burned at near-identical temperatures to coal – 2170°F compared to 2220°F. This confirmed that it can be co-fired with coal in power plants without any hardware furnace modifications, that it produces an equivalent energy output, and can improve the efficiency at which the coal component of the blended feedstock burns.
  • CoalSwitch fuel burned more efficiently than coal, and produced far less ash.
  • The ash content in CoalSwitch was 1.69%, compared to 9.42% for the pure coal. The carbon content within that ash was the same for both fuels but there was a 40-55% reduction from the CoalSwitch/coal blend in the ‘staged’ combustion conditions typically used in industrial power plant boilers to control NOx emissions.
  • CoalSwitch fuel burned cleaner than coal, and when co-fired with coal generated less sulphur dioxide than the coal alone. In addition the CoalSwitch fuel was essentially free of both potassium and sodium, so there would be little fouling, and showed coal-like levels of particulates except for a much lower level of ultrafine particles. However, there was a noticeable reduction in ultrafine particles with the CoalSwitch/coal blend, likely due to the reduction in sulphur levels. Together, these properties demonstrated that the fuel can significantly outperform existing biomass fuels in terms of slagging and fouling, and can reduce the impact of coal in a fuel mix that contains it. 

Biomass
Biomass CoalSwitch test rig at the University of Utah


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