After petroleum, coal remains the world’s next most important fossil energy source. In 2010 it accounted for 30% of global primary energy consumption [DERA, 2010], while in Germany just under 40% of domestic power generation came from coal. Indeed in 2009 every fourth kilowatt hour of power consumed in Germany came from brown coal [DEBRIV, 2010.02] and domestic mineral coal production is on the decrease due to the loss of subsidies in 2018. In contrast, significantly more mineral coal than brown coal is produced globally. Flue gases formed through the burning of coal needs to be scrubbed in an ecologically responsible way - in flue gas desulphurisation plants (FGD). Gypsum is a by-product of the FGD process – about 7 million tonnes are produced annually worldwide [BVK]. This base material is required in the construction and cement industry in very large quantities, for example in the manufacture of drywall/plasterboard. VACUBELT filter cloths for vacuum belt filter systems have been developed by German company GKD – Gebr. Kufferath AG specifically to meet the demanding conditions for FGD gypsum dewatering in large coal power stations.
In 2007, 5.5 gigatonnes (5.5 billion tonnes) of hard coal (hard brown coal, mineral coal and anthracite coal) and 0.98 gigatonnes of soft brown coal were produced throughout the world. China is the country that produces the most hard coal (2.5 gigatonnes), followed by the USA (0.97 gigatonnes), India (0.45 gigatonnes), Australia (0.32 gigatonnes) and South Africa (0.24 gigatonnes) [DERA, 2010]. As well as increasing production volumes, newly constructed power stations, station expansions and renovations are also booming. It is the aim of these activities to increase the efficiency of coal conversion into electricity, while continuing to decrease emissions through improved technologies for dedusting, denitrifying and desulphurising flue gases. One of these power stations of the future is in Neurath, Germany, in the form of two new brown coal power station blocks. Each of these power station blocks has a gross output of 1,100 megawatts and an efficiency factor of more than 43%. Its optimised plant technology is basically in line with the blocks already in place, but the new ones make much better use of the fuel. As a result, efficiency is increased by about 31% compared with the existing plants. Consequently, gas and dust emissions are also reduced. For example, in the flue gas desulphurisation plant, more than 90% of the sulphur dioxide is separated and transformed into gypsum slurry. This is then condensed and the 60-65°C gypsum suspension is dewatered in vacuum belt filters in a continuous process. This operation imposes tough demands on the mechanical, thermal and chemical capacity of the filter belts used. conveyor belt filter
GKD has also supplied more than 15 power stations in the USA, with an output volume of 1-2.7 gigawatts, with over 35 VACUBELT belts on average every year. The all-monofilament VACUBELT 2015 is the most common belt size, and is 50 etres long and 3 metres wide. But the two-ply belt types are being used in the USA as well, such as the VACUBELT 2025 with staple fibres and the VACUBELT 2035 with multifilament weft wires. In South Africa the Kusile mineral coal power station, 100 kilometres east of Johannesburg, was equipped with high-performance VACUBELT 2015 belts in 2011. With 4,800 megawatts of rated output, Kusile is ranked among the largest coal power stations in the world.
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