► An alternative production process for precipitated calcium carbonate is studied. ► Calcium is extracted selectively from steel converter slag with aqueous solvents. ► Process kinetics being ...estimated, slag particle size is of high importance. ► Levels of Ca2+, CO32- and NH3/NH4+ are key parameters in CaCO3 precipitation. ► Regarding process chemistry, the system can also be operated in continuous mode.
A novel process for precipitated calcium carbonate production and carbon dioxide mineralization is studied. The process consists of two steps; firstly calcium is selectively extracted from steelmaking slags with an ammonium salt solution, secondly the dissolved calcium is allowed to react with carbon dioxide and is thus precipitated as calcium carbonate. Temperatures between 20 and 70°C and atmospheric pressure are used. To gain information of the effects of different process parameters on the reaction rates in both process steps a kinetic modeling study is performed and validated with experimental results. Calcium extraction rate is found to mainly depend on the particle size and chemical properties of the slag. Concentration of the ammonium salt solvent has an effect as well, while the extraction temperature hardly affects the kinetics. Rate of carbonate precipitation depends mainly on carbon dioxide flow through the reactor, mixing of the solution, size of gas bubbles and also strongly on the concentration of ammonia in the solution. Since the steelmaking slag is a heterogeneous feedstock and it will require continuous adjustments on the process, the kinetic model is used to preliminary predict the reaction rates in extraction and carbonation steps in continuously working reactors. It is found that depending on the slag properties residence times starting from 1h can be used in extraction. For carbonation, the model does not include changes in particle morphology, but regarding the overall calcium conversion 30min would be a long enough residence time in the studied cases. Dividing the extraction in two or more stages would also shorten the total processing time.
Today, regulations and consumer awareness demand production technologies with minimum impact on the environment and maximum utilization of available resources. In the field of lipids, two well-known ...technologies for avoiding the use of organic solvents and chemicals stand out: supercritical (Sc) fluids and short path distillation (SPD). To date, both technologies involve high operating costs that have limited their application to selected high value-added products which are high temperature sensitive. However, improvements in process control and materials make further implementation of these techniques possible. In this chapter, an integrative review has been carried out with the aim of compiling the literature on the application of these technologies to lipid extraction, micronization and fractionation of liquid mixtures. Special attention has been paid to the separation of compounds by both technologies: deacidification, partial purification of acylglycerol compounds, isolation of unsaponifiable compounds and separation of toxic and polluting compounds.
A novel process for precipitated calcium carbonate production and carbon dioxide mineralization is studied. The process consists of two steps; firstly calcium is selectively extracted from ...steelmaking slags with an ammonium salt solution, secondly the dissolved calcium is allowed to react with carbon dioxide and is thus precipitated as calcium carbonate. Temperatures between 20 and 70 degree C and atmospheric pressure are used. To gain information of the effects of different process parameters on the reaction rates in both process steps a kinetic modeling study is performed and validated with experimental results. Calcium extraction rate is found to mainly depend on the particle size and chemical properties of the slag. Concentration of the ammonium salt solvent has an effect as well, while the extraction temperature hardly affects the kinetics. Rate of carbonate precipitation depends mainly on carbon dioxide flow through the reactor, mixing of the solution, size of gas bubbles and also strongly on the concentration of ammonia in the solution. Since the steelmaking slag is a heterogeneous feedstock and it will require continuous adjustments on the process, the kinetic model is used to preliminary predict the reaction rates in extraction and carbonation steps in continuously working reactors. It is found that depending on the slag properties residence times starting from 1 h can be used in extraction. For carbonation, the model does not include changes in particle morphology, but regarding the overall calcium conversion 30 min would be a long enough residence time in the studied cases. Dividing the extraction in two or more stages would also shorten the total processing time.
