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Neutralisation of aggressive process water
The cement components may raise the pH value in the process water up to 14. By adding acids, e.g. hydrochloric acid, the pH value is reduced to a neutral level. Carbon dioxide (CO2) is increasingly applied to neutralise alkaline process water. Dissolved in water, CO2 produces carbonic acid. Carbon dioxide has many advantages compared to mineral acids, because it prevents the salination of wastewater with chlorides, sulphates, etc. In addition, its flat neutralisation curve practically rules out the over-acidification of the wastewater. Using carbon dioxide is also much safer than handling aggressive acids, and corrosion problems are largely prevented.
The use of a loop-type bubble column optimises the introduction and contact time of CO2 with the process water, which enables efficient use.
However, process water also occurs when using acids, e.g. when acidifying concrete or stone surfaces. This also has to be neutralised. The use of alkaline remnant water with cement components is expedient. Alkaline solutions like caustic soda can be applied additionally.