CDE – Clay processing for the cement industry

by Dr Allistair Wilkinson, Sustainable Materials Expert at CDE 

Dr Allistair Wilkinson is a Sustainable Materials Expert at CDE Group, specialising in industrial decarbonization, circularity and the development of low-carbon construction materials. With a background spanning cement manufacturing, industrial innovation and academic research, he focuses on turning emerging technologies and underutilized resources into practical, scalable solutions for the construction materials industry.

BACKGROUND

The cement industry is responsible for approximately 8% of total global CO2 emissions annually. This is largely due to high temperature processing of limestone as the main raw material in the production of clinker. Clay, typically shale, can also account for approximately 10% of the raw material used in cement production, providing important chemical compounds necessary for producing high-quality clinker.

CDE have been pioneering the washing of soils to recycle aggregate and sand. Our technology has been developed over the last 20 years to remove clay through scrubbing, attrition and Hydrocyclone technologies. Until recently there has been limited industrial interest in the filter cake in which clay is the dominant constituent.

SOLUTIONS

“Every cement plant should have a wash plant”

Significant quantities of overburden are generated annually by the cement industry. Overburden typically contains approximately 20% clay with the remaining constituents being sand and gravel. We can process this material, extracting sand and gravel which is suitable for sale or for use within an existing vertical integration business model. The residual material from the process is clay-rich with clay minerals accounting for up to 50% of the filter cake. This material will be suitable for use as a raw material in the clinker manufacturing process, reducing demand for virgin raw materials and reducing material travel distances as clay quarries are typically located further from the cement plant than the limestone quarry.

As well as processing waste materials generated on site, most cement plants will be permitted to receive and process a wide range of waste materials. A wash plant located within the cement plant quarry would allow for increased quantities of excavation wastes, demolition wastes and similar to be processed with the flexibility to recover useful sand and gravels for sale or use while using the residual filter cake as a raw material for clinker production. In addition to the benefits associated with overburden processing, a gate fee for such received material can also be factored into the RoI calculations, improving the payback period.

CALCINED CLAY

Supplementary cementitious materials (SCMs) are widely used in the cement industry and regarded as a significant means of reducing the embodied CO2 per tonne of cement product. Typical SCMs include limestone fines, fly ash and GGBS but each of these have significant downsides associated with their use either in terms of reactivity or availability of material. Calcined clay is widely regarded as an alternative to traditional SCMs. Rather than utilising the filter cake generated from a wash plant located on site, this material may be suitable for calcination. This will have a significant impact on the availability of suitable clay globally, potentially accelerating adoption of the technology and having a meaningful impact on decarbonisation of the cement industry.

CDE plants create clay (from soil/overburden), this enables wider adoption of calcined clay technology 

In this area, CDE have an advantage over our competitors. We have the technology available to process these materials while our team has in depth knowledge of cement chemistry and raw materials.Our team has hands on experience of producing calcined clay using low grade clays and cement blends with up to 50% calcined clay at an industrial scale. These opportunities are not limited to the cement industry, but this is the area we are likely to be able to make the greatest impact both in terms of decarbonization and business development.