Production Of Precipitated Calcium Carbonate (PCC) Using Malaysian Limestone Based Materials Via Continuous Production Technique
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Date
2010-04
Authors
Ismail, Roniza
Journal Title
Journal ISSN
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Publisher
Universiti Sains Malaysia
Abstract
In present commercial practice, precipitated calcium carbonate (PCC) is normally manufactured by reacting the „milk of lime‟ with carbon dioxide (CO2) in a stirred tank batch reactor system. The drawback of this technique is PCC could not be produced uninterrupted for the required quantity in a real time process continuously. Thus, two newly designed lab scale reactors i.e. tall tubular and sprayed-mist are used in this study to produce PCC in continuous mode. The main aim is to investigate the operating variables that control the PCC synthesis using these continuous techniques as well as to evaluate the properties of the resulted PCC. High purity local limestone is used as a starting material and needs to be prepared involving 3 main processes which are calcinations, slaking and recarbonation. The uniqueness of the tall tubular reactor is the feed flow rate and the recarbonation took place while suspension is moving up the tube that afterwards will discharge via the outlet continuously as products (PCC). Meanwhile, the sprayed-mist technique capabled to increase the surface area of the reactant by converting „milk of lime‟ into fine mists, thus enhanced the recarbonation process. However, the operating variable settings (reactant concentration, CO2 gas flow rate and feed flow rate) are different from each technique which depends on the reactor design. Tall tubular reactor is able to cope with wide range of reactant concentration (0.2M to 1.0M) and gas flow rate between 100 to 600 ml/min. In contrast, sprayed-mist reactor is suitable to precipitate PCC at lower reactant concentration (between 0.1M to 0.2M) with the extremely high gas flow rate (>1000 ml/min). The properties of the resulted PCC like crystal morphology, particle size distribution, specific surface area and purity are also determined. The results showed that both techniques be able to manufacture higher purity of PCC successfully with various morphologies and characteristics. PCC with morphologies that varied from rhombohedral, prismatic to scalenohedral shape in the size range between 100 to 600 nm can be produced via tall tubular reactor in the predetermined setting. Meanwhile, sprayed-mist technique tends to produce PCC with rhombohedral shape/ morphology in the size range of 200 to 1500 nm. All PCC products have calcite morphology even the morphology are looked different. To conclude, these new innovations are capable to produce PCC that fulfilled the industrial requirements for various applications what can be further improved.
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Keywords
Precipitated calcium carbonate (PCC) is normally manufactured , by reacting the „milk of lime‟ with carbon dioxide