MONICALC - process research for more sustainable kaolin calcination

Outotec recently participated as the lead partner in the MONICALC Innovation Project being run by the EIT RawMaterials, initiated and funded by the EIT, European Institute of Innovation and Technology, a body of the EU. Focusing on kaolin production, the project brought together six partners and aimed to demonstrate the feasibility of the controlled use of diversified energy in calcination.

Partnering to develop an integrated monitoring system and advanced process control

Developing a kaolin production process that ensured high quality while reducing energy use required the expertise and close cooperation of all the partners in the consortium. Imerys, the world’s largest kaolin producer, provided the industrial-scale plant for testing and implementing the MONICALC process.

French software company Predict developed an integrated monitoring system that receives data from multiple sources during the production process, including the distributed control system, online sensors, and lab analytic measurements. Collecting and consolidating data from the whole production chain meant that bottlenecks and disturbances could be identified at an early stage.

Finland’s Aalto University, together with Imerys, developed an off-line prototype for an advanced control system for the multiple-hearth furnace calciner. This control system is key as it has the potential to optimize the operational condition of the furnace with the aim of reducing energy consumption, increasing plant capacity, and ensuring that the product-quality specifications are met.

To get instant feedback on product quality, an infrared sensor using advanced evaluation algorithms was developed by the University of Delft in the Netherlands. The quality parameter of aluminum solubility content is directly calculated from the infrared spectrum measurement values, which could lead to the introduction of an automated system.

The University of Exeter in the UK investigated the optimal scraper configuration of the internal rabble arms in the multiple-hearth furnace, which is key to ensuring better product quality. They built a small-scale model to test the distribution of the material in the different stages, which in turn could be used to predict material flow and residence time.

Cutting the carbon footprint of kaolin production Outotec tested fluidized bed technology for kaolin calcination. Fluidized bed calciners have shown several advantages in other processes, for example alumina production, in recent decades. The results showed that fluidized bed calcination has significantly lower energy consumption than older technology.

In order to further reduce the environmental impact of kaolin production, Outotec tested diversified energy sources – in this case pelletized sewage sludge – to fuel the calcination process. To ensure product quality even with a biomass-based fuel, a hot-gas cleaning system was used to prevent tar condensation and the need for further cleaning stages.

Experiments performed at Outotec’s Research Center showed that, depending on the product quality requirements, acceptable quality in the fuel gas can be achieved with gas-cleaning equipment like cyclones and hot electrostatic precipitators, which have the advantage of lower pressure drop and low operating and maintenance costs.

A promising result with wider implications The result of the integrated process investigated in the MONICALC project is the potential to increase process efficiency and decrease energy consumption and therefore the CO2 emissions in kaolin calcination. The products and concepts developed as part of the project can be adapted to produce other minerals as well, which is good news not only for the mining and minerals industry, but also for society as a whole.