Two-Step Aqueous Carbonation of Solid Residues

Much along the same lines as the process described above, as proposed by Katsuyama et al. [57], Geerlings et al. recently described a process for producing CaC03 from various solid residues [58]. In this patent, two examples of the described process were described, one utilizing paper bottom ash and one steel slag, although neither example provided a reaction rate for the precipitation step. 

The extraction of calcium took place inside a water-filled, stirred reactor for 15 min, which resulted in a calcium hydroxide concentration of 1.1 gT1 for paper bottom ash and 0.46gT1 for steel slag. The formed hydroxide slurry was separated from the solids and carbonated by injecting it with C02 at a rate of 25 ml min-1. However, the feasibility of the process should be investigated with a cost and environmental assessment before any firm conclusions can be drawn, as was also the case for a process described by Gorset et al. [59]. 

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