MID MIX technique
Another interesting route with a low environmental impact for MID MIX is so-called dehydration. Using our own green energy, secondary CaO is produced from Neutral without any CO₂ emissions occurring in this process.
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The MID MIX technique has been patented worldwide. VSGM markets the MID MIX in large parts of Europe.
Application and capacity
The basic process
The processing sludge is converted to the product Neutral in a reactor by adding CaO. The installation consists of various components. From the supply buffer, dewatered sludge is pre-treated and then processed in two reactors. Here, CaO is added. Moisture is extracted through an exothermic reaction and various chemical and physical processes take place. The core processes that take place in the plant are soldigation and molecular encapsulation of heavy metals. The end product, Neutral, is cooled. The ventilation air from the process is treated in a bag filter and a scrubber. About 65% of the total input mass is converted into the final Neutral product. There is no residual product during the process that needs to be disposed of as waste.
End product Neutral
After processing sludge in the MID MIX, the circular building material Neutral is created. It consists of 80%-90% Calcium Hydroxide (Ca(OH)2) and 20%-10% Calcium Carbonate (CaCO3). Neutral can be used as an aggregate in construction, as a soil improver and as a substitute for primary building materials. However, there are two routes, using primary Neutral as a base, that have a very beneficial impact on the environmental score of the MID MIX process. The routes are Carbonation and Dehydration.
With Carbonation, primary Neutral is reacted with CO2 whereby the CO2 is permanently stored. Between 500 kg and 700 kg of CO₂ can be captured in 1,000 kg of Neutral. This CO₂ can be captured elsewhere and transported to a CO₂ conversion box. When installed next to a flue gas duct, CO₂ can be led directly to the box where the process takes place. In both cases, a hybrid/synthetic limestone flour is the end product. Carmeuse can apply the end product and therefore gives a 100% off-take guarantee of the carbonated Neutral.
In dehydration, primary Neutral is heated to 600˚C and CaO is recovered. This secondary and circular CaO can be re-used. The CaO then has no CO2 footprint.