An Economical and Environmentally Responsible Breakthrough in Lime Processing

This project has been Calx Energetics' main endeavour since 2011. All the other technologies developed by Calx Energetics are used in this process.
The Calx Energetics lime production process de-carbonates limestone (calcium carbonate) to produce hydrated lime (calcium hydroxide). The process uses an efficient and economical multi-stage chemical pathway, rather than calcining, to achieve the removal of carbon dioxide from the limestone. It has many environmental, operational and fiscal advantages over existing calcining technologies.

The low temperature lime decarbonisation process is driven by heat, and a range of suitable sources can deliver heat as low as 300ºC. Suitable heat sources include solar collector troughs, open gas turbine exhaust, industrial heat recovery, mining heat recovery (eg. sulphuric acid plant) and nuclear reactors.

Advantages and Unique Features

  • Currently used kiln technology releases the carbon dioxide from the decomposition of limestone into the atmosphere mixed with the general flue gases, and the cement and lime industry currently contributes around 8% of anthropological carbon emissions. In the Calx Energetics low temperature decarbonisation process, the carbon dioxide is emitted as a stream with only water vapour, and can be easily collected, dehydrated, compressed and stored. Our design allows for full capture of the carbon dioxide, which becomes a profitable by-product of the process. With the growing world market for carbon dioxide and carbon dioxide credits, there is potential for considerable income from this output.
  • The size and purity of the source rock is unimportant. The process can take any size or quality of rock, including existing sub-sized limestone from waste heaps, friable limestone, and unclassified quarry product.
  • The chemical pathway allows for the removal of valuable and/or  non-desired impurities (eg iron, magnesium, arsenic, lead, thorium), which have the potential to provide an additional revenue stream.
  • The calcium hydroxide produced is sized and has high surface area. As no high-temperature process is involved, no sintering ever occurs, and indeed since the hydroxide is directly produced, subsequent de-hydroxide steps produce a fine, reactive calcium oxide. Due to the impurity removal, this lime is exceptionally pure, making it highly suitable for uses in water treatment and food production.
  • The Calx Energetics low temperature lime decarbonisation process offers higher profitability as the result of a range of variables. Reduced operational costs are achieved through substitution of high-energy fossil fuels with cheaper, low-temperature alternatives, reduced bulk for transportation, processing product closer to the end-use site and/or stock-feed source, and lower overall energy requirements combined with higher energy efficiency. Increased gross income is the result of higher quality product and the sale of the carbon dioxide by-product.
  • The process can be used in small, low-capacity plants without the disadvantage of scale-related energy inefficiencies. A Calx Energetics plant can operate efficiently on as little as 30 tonnes per day and capex per tonne capacity is much lower than kiln technology. Large-scale production is a simple matter of duplication of units in parallel.

Suitable Applications and Target Industries

The existing pre-pilot plant is providing the data to refine the design for the pilot plants. Currently the pre-pilot is mounted in a 6m (20ft) shipping container and is transportable.

The plant design, offering efficient smaller outputs and transportability, enables the end users of lime, such as paper pulp, sugar mills, water treatment plants, and mines, to produce lime on site. Localised production, made possible by the feed-stock tolerance of the process, reduces transport costs and environmental impact, thus the low temperature lime decarbonisation process is particularly useful in more remote locations. However, existing lime and cement producers would be well served by the reduced environmental impact and carbon credit capacity of our process. One of our potential pilot partners is also interested in the process to reduce a 30-year stockpile of undersized and waste rock, and for them it is a very cost-effective way add capacity.

Lime stockpile

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