#Calcium chloride precipitation series

Therefore, GCC has a broad distribution of shapes and sizes, which reduces their optical performance ( Clark, 1992). Ground calcium carbonate (GCC) is manufactured by grinding high quality limestone to very small sizes and is mostly used as a pigment, included as an externally applied coating in coated papers. However, both filtration technologies seem suitable for filtering and washing calcium carbonate prepared with the studied method as a residual chloride content as low as 10 ppm of the filtered solids can be achieved with quite a small amount of washing water and the filtration rate is fast.Ĭalcium carbonate is the most commonly used filler material in paper making ( Naydowski et al., 2001). As the vacuum filtration tests used a filter cloth with higher permeability than that of the pressure filtration tests, a slightly higher filtration rate was expected. Vacuum filtration gave slightly higher filtration rates (500–610 kg/m 2h at the lowest residual chloride contents of the cakes), but the cake residual moisture also stayed higher (25–26 wt-%). Pressure filtration gave a high capacity (400–460 kg/m 2h) and a low cake residual moisture content (12–14 wt-%). The filtered cakes were analyzed by their residual moisture content, chloride content, and conductivity, and the filtrates by their residual solids content, chloride content, and conductivity.

#Calcium chloride precipitation series

The tests included pressure filtration and vacuum filtration and the test series contained altogether 21 different filtration cycles with varying combinations of filtering, washing, and drying steps. The order of maximum filtration rates achievable of the calcium carbonate slurries was determined by experimental work. In this work, different separation processes, including washing, filtering, and drying, were tested on two calcium carbonate slurries produced from steel converter slag and CO 2 by a laboratory-scale pilot facility, with the aim of obtaining a solid product with a low chloride content using a minimum amount of washing water. As calcium carbonate is precipitated in a solution containing ammonium chloride, calcium chloride, and ammonia, the product needs to be washed and hence filtered. The concept uses steelmaking slag as raw material and has potential to fix CO 2 emissions and utilize steelmaking slag, simultaneously.

In this work, experiments were performed to determine the filterability of calcium carbonate produced with an alternative calcium carbonate production concept. 4Outotec Research Center, Pori, Finland.3Department of Energy Technology, School of Engineering, Aalto University, Espoo, Finland.2Outotec Dewatering Technology Center, Lappeenranta, Finland.1VTT Technical Research Centre of Finland Ltd., Espoo, Finland.