Gypsum from FGD is a by-product of a process that was introduced initially to purify emissions containing sulphur dioxide (SO₂). It is found most often in power plants that burn fossil fuels – in particular coal – and has since the 1970s benefited from increased regulation of airborne emissions. Consequently FGD installations – and global volumes of synthetic gypsum production – is concentrated in North America, Western Europe and Japan, where regulations are tightest.
FGD-gypsum also has the advantage that it generally has high purity and is often of better quality than mined gypsum.
Exclusive data from the new Smithers Apex study The Future of Gypsum: Market Forecasts to 2026 shows that world output of by-product gypsum has now topped 30 million tonnes annually. This represents 8.5% of a global market Smithers pegs at 350 million tonnes (2016), with an overall value of $2.1 billion.
The study demonstrates how worldwide demand for all gypsum grades will grow at 9.6% year-on-year for 2016-2026, to yield a total demand of 531 million tonnes in 2026. This will push the overall market value to over $3.1 billion at that time.
Smithers Apex's analysis goes on to identify the key market and technical factors for why the proportion of by-product gypsum consumed as a share of overall gypsum consumption will continue to grow across the next decade.
A key consideration for FGD-gypsum production is the scrubber technology fitted to the flues of power plants that remove SO₂ and allow its conversion into gypsum.
Scrubber technology has advanced over the years. The previous model of multiple modules is now being superseded by single modules that can support a large boiler. In modern wet scrubbing systems, the flue gas first passes through a fly ash removal process – which can be either an electrostatic precipitator or a wet-scrubber – and from there it passes to an SO₂ absorber.
The latest scrubber systems carry an improved spray nozzle that is designed to channel flue gases, and can thus achieve 98% SO₂ removal, with no packing or trays necessary. Developments are also underway in gas reheating units or more corrosion-resistant materials to reduce the wear caused by SO₂ gas on FGD equipment.
Radiation and dewatering
One FGD process that could see wider deployment in future is radiation technology – using a beam of electrons fired into the flue gas to oxidise the SO₂, as ammonia is added to the gas. This simultaneously reduces the nitrogen content of flue gas and creates ammonium sulphate, which as a fertiliser is a second saleable by-product.
Another area of concentration is improving the variable quality of the microcrystalline structure of synthetic gypsum. This can affect its dewatering properties and greatly impact its sell-on value for industries, such plasterboard manufacture.
The US provides an exemplar for how FGD gypsum can transform a national market. In 2008, synthetic gypsum already accounted for 54% – 9.6 million tonnes – of domestic US gypsum production.
The FGD gypsum market with the greatest potential for expansion in the US is agriculture. Agricultural markets for FGD gypsum are somewhat opportunistic, and tend to develop primarily in agricultural regions close to sources of the material, or at sites where the utility fabricating the material encounters high disposal costs. The amount of FGD-gypsum available for agricultural applications worldwide will probably exceed 8 million tonnes per year by 2018.
China already dominates the world gypsum supply market with a network of mines and strong local demand from the construction and other industries. In 2014 raw production in China stood at around 132,000 tonnes – or 53.6% of global output.
In the coming years an ambitious Chinese air quality improvement programme, featuring the installation of 300 FGD units, will gradually change the picture. China has already overtaken the US in terms of installed FGD capacity, despite the increased retrofitting in the US forced by the Clean Air Interstate Rule and the Cross-State Air Pollution Rule.
India is also at the initial stage of introducing a new air quality programme. Most of those commissioned are limestone wet scrubbers, but 155 appear to be spray-dry scrubbers.
FGD aligns with many goals of the new green economy, in that it converts a damaging industrial emission into an inert, but valuable product. Furthermore the impact of using FGD-derived gypsum can be significantly lower than that for mining and transporting virgin gypsum.
Gypsum from FGD is not the only alternative to mining the mineral. Two other emergent solutions are:
- Recyclate from demolished housing
- Descaling industrial plant.
The former is arising due to greater official pressure to recycle as much waste as possible and minimise waste of all types sent to landfill. In the US however, due to the potential of contamination from lead paint, legislation excludes recovered gypsum from use in construction board, which favours FGD-sourced gypsum.
The second, less well-known method involves descaling the inside of boilers and large-diameter pipework in industrial facilities. This yields a supply of pure gypsum, but the overall volume such processes can yield is limited.
The long view
One future limiting factor for by-product gypsum is the broader climate change initiatives aimed at reducing the number of coal-fired power stations, the main source of FGD gypsum. This will lead to a long-term decline in power generation from fossil fuels; unless the promise of clean coal technology, carbon capture, or other techniques are developed and commercialised effectively.
While existing power stations may add FGD production units if not already equipped, few new coal-fired power stations will be built in Europe or North America, and it is safe to assume there will eventually be a similar reduction in the boom economies of China and India. Significant reduction in the overall supply of FGD gypsum may not happen for decades, but it is a long-term consideration.
This is true especially as to justify the cost of construction of a new plasterboard plant linked to an FGD-equipped power plant, an FGD gypsum supply of 20 years or more must be assured. The industry in consequence has taken to signing long-term contracts with power companies.
These trends and their overall impact on world gypsum supply are contextualised and quantified in-depth in the Smithers Apex report – The Future of Gypsum: Market Forecasts to 2026. This is available for purchase now.