Streamlining production in South Africa

Since 2011, Cimprogetti has been actively involved in the design, installation, and commissioning of two regenerative lime kilns with a capacity of 600 tpd in South Africa. Over the years, Cimprogetti has offered extensive services to the client, including technical and engineering support to achieve the best kiln performance, and ensuring adherence to lime product specifications.

The assistance provided covered several areas, including conducting detailed geological field surveys of the quarry, offering expert advice on representative sampling techniques, providing comprehensive laboratory support for sample analysis, and optimising kiln performance through process refinement. This article will provide a summary of the methodological approach used in these steps.

Geological settings and quarry survey

As part of the initial technical assistance, the geological survey was conducted at the limestone quarry, which is managed by the client and located a few miles from the lime plant. This deposit consists of one of the oldest carbonate platforms worldwide. Remarkably, the raw material used to feed the regenerative kilns dates back to the Archean Era, approximately 2500 million years ago.

As described in the literature, this geological unit exhibits a thickness of several hundred meters and is characterised by grey massive or coarsely stratified limestones, occasionally interspersed with finely stratified graphite-rich black shales. Structurally, the deposit is remarkably well-preserved, with minimal tectonic activity observed. The predominant geological characteristic is a gentle warping that extends across the majority of the craton. Effectively, the limestone observed in the quarry displays a parallel plan stratification, and the strata exhibit a dip at an approximate angle of 10 – 15° towards the west, without any visible faulting present.

Mining operations focus on extracting a portion of deposit with a thickness of around 50 m. Specifically, five distinct benches, each approximately 10 m high, are being mined: bench 2P, 3P, 4P1, 4P2, and 4S. Among these, only benches 2P, 4P1, and 4P2 contain high-grade limestone that meets the requirements for quicklime. Material from the other benches is stored and utilised for various industrial applications, such as aggregates for concrete, road subbases, and other byproducts.

Mining operations consist of a progressive reduction of the quarry steps located in a pit below ground level. The extraction process begins by removing the weathering hat, also known as the overburden. Following this, the benches themselves are blasted as the subsequent step in the process.

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Read the article online at: https://www.worldcement.com/special-reports/16082023/streamlining-production-in-south-africa/