FRIT-REC - flue gas dry-neutralization

The use of lime-based processes for treating flue gases is a widely-used technique in industries that produce acidic gases such as hydrogen chloride, sulphur dioxide and hydrogen fluoride. Calcium carbonate (chalk), calcium oxide (quicklime) or calcium hydroxide (hydrated lime) can be used to neutralise acidic gases and remove sulphur dioxide.

For instance, huge volumes of lime are used by the energy sector to abate CO2 emissions at power utilities. Coal-based power stations are retrofitted with flue gas desulphurization units where sulphur dioxide is transformed into gypsum. Similarly, incinerating municipal solid waste is a common and efficient way of reducing quantities of waste and recovering energy. However, the acid flue gases generated when combusting this fuel represent a pollution source that must be controlled. Again, lime-based neutralization processes are the most common technique. The characteristics of the process imply that large amounts of by-products can be produced as it is the case of synthetic gypsum at the coal-powered utilities. The secondary raw material is widely reused by the construction industry.

Similarly, the aim of the FRIT-REC project is the valorisation of an industrial by-product of the
flue gas dry-neutralization arising during the production of frits and enamels. The flue gases from smelting furnaces contain fluoride, which interact with lime particles through the process of dry-neutralization. Micronized fluorided lime (MFL) is the result.

Ca(OH)2 + 2HF → CaF2 + 2H2O

In the project, the chemical reaction between lime and HF (hydrofluoric acid) has been optimized. The injection of micronized lime into the reactor is adjusted according to the HF concentration in flue gases. Hence, optimal reaction rate and material consumption are guaranteed.

Furthermore, the implemented separation unit produce homogenized MFL that can be reused in the production of high quality ceramics. The whole amount of MFL is planned to be reused internally for the production of frits, enamels and specialized ceramic compounds.