Power generation from hard coal produces mineral by-products such as fly ash, bottom ash and gypsum, which are marketed by Uniper subsidiary BauMineral. Bottom ash has now been certified as the last by-product from the Datteln 4 power station. This secures the disposal of the power station and the supply of customers in the UK.
For the marketing of power station by-products, it plays a major role whether they are to be regarded as by-products according to their name or whether they are to be classified as waste.
If the materials are classified as waste, their qualities as building materials quickly fade into the background. Most building material manufacturers, such as concrete plants, are not allowed to accept and process waste due to a lack of permits. In general, significantly higher environmental compatibility requirements are placed on waste, and in many cases it can also only be stored in explicitly designated areas that have to meet increased construction requirements. As a result, power station by-products, if classified as waste, cannot be recycled or can only be recycled with great restrictions.
For by-products, on the other hand, sales revenues can usually be generated if their material properties make them useful for certain applications, for example as concrete components. This is the case for hard coal fly ash, bottom ashes and FGD gypsum.
The gypsum from the Datteln 4 power station has already been marketed since the end of 2020, and since the beginning of this year BauMineral has also been supplying customers with hard coal fly ash from there. As the last power station by-product, the bottom ash has now also received a certificate based on the harmonized EU standard DIN EN 13055-1.
Certified bottom ash from the Scholven, Heyden, Wilhelmshaven and Maasvlakte power stations has been marketed by BauMineral in the block making industry in England for more than 20 years. There, it is used for the production of masonry blocks which, in addition to their CO2-neutrality, are characterized by lower weight and better thermal insulation compared to blocks made of gravel concrete.
"After certification, the first two ships could now start their voyage to the UK with the bottom ash "Grobalith D4". This was also important for maintaining the business relationship with customers there”, says Mario Gladisch, who is responsible for sales at BauMineral.
The reason for this is that the energy transition is leading to a significant reduction in the use of hard coal-fired power stations. This also greatly reduces the volume of by-products. The marketing of Grobalith D4 prevents customers from looking for alternatives and entering into contractual commitments elsewhere.
Mario Gladisch: "Incidentally, the customer supplied with the bottom ash from Datteln was recently awarded the "BES 6001 Excellent Status" because it only uses concrete raw materials from reliable sources and trustworthy partners. An award we are pleased about together with our customer!"
Coal contains gangue, also referred to as ballast. Depending on their fineness, the non-combustible particles remain as bottom ash or coal fly ash when coal is burned in dry-fired boilers. Bottom ash is used in road construction or as a substitute for natural sand in concrete.
Fly ash is filtered out of the flue gases during the flue gas cleaning. Non-combustible elements of coal in the flue gas are negatively charged and are routed through an electrical field. There they are drawn to a positively charged electrode and brushed off. In the construction industry, fly ash can be used as a filler in concrete.
The sulfur present in the coal oxidizes during combustion to sulfur dioxide. This reacts with calcium hydroxide in the flue gas desulfurization plant (FGD) to produce gypsum and water. FGD gypsum can completely replace natural gypsum in the production of plasterboard and gypsum plasters.
