Veolia prepares an energy by-product of coal combustion in the Třebovice power plant in the north-east of the country for reuse in the production of industrial abrasives.
In the Czech Republic, electricity is still largely supplied by coal-fired power plants. The coal is burned in a boiler; the heat that is generated boils water, which then turns into steam, activating a turbine that generates electricity. This old industrial process is still in used in a large number of countries. But what is new is applying the circular economy to it. Explanation.
When coal is burned, molten slag is formed in the wet-bottom boiler furnace . It is a mixture of aluminum oxide left after the coal has been burned at high temperature. Traditionally, power plants throw away this slag, which then congests landfills. But it is a by-product that can be recovered! In the Czech Republic, in the Třebovice plant in the north-east of the country, Veolia produces nearly 10,000 tonnes of molten slag every year and ensures its reuse.
Sandblasting and grit blasting
How does it work? The molten slag is recovered from the furnaces and then soaked in a water bath. It crystallizes in the form of glassy granules, which are then ground into tiny particles. Once processed, the slag has optimum hardness and density and so can be used as a substitute for the natural materials used during sandblasting or grit blasting.
These two industrial techniques are used in stripping - abrasives are projected at high speed using compressed air. Microbeads are used to clean and smooth a surface by removing anything that has been applied to it. For example, blasting a car body to strip the paint.
Traditionally when sandblasting or grit blasting industries use a mixture of sand and crystalline silica, a substance that is very harmful to health if inhaled - but slag microbeads contain no harmful components.
Turning the slag into abrasive microbeads solves two problems at a stroke - it reduces the volume of waste from coal-fired power plants that thermal power plants in the Czech Republic disposed of in landfills, and it provides an effective and harmless substitute for industrial stripping processes. The circular economy has plenty of tricks up its sleeve!
Find out more: