Performance of Separation Processes for Precipitated Calcium Carbonate Produced with an Innovative Method from Steelmaking Slag and Carbon Dioxide

Abstract

In this work, experiments were performed to determine the filterability of calcium carbonate produced with an alternative calcium carbonate production concept. The concept uses steelmaking slag as raw material and has potential to fix CO2 emissions and utilize steelmaking slag, simultaneously. As calcium carbonate is precipitated in a solution containing ammonium chloride, calcium chloride, and ammonia, the product needs to be washed and hence filtered. In this work, different separation processes, including washing, filtering, and drying, were tested on two calcium carbonate slurries produced from steel converter slag and CO2 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. The order of maximum filtration rates achievable of the calcium carbonate slurries was determined by experimental work. 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 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. Pressure filtration gave a high capacity (400-460 kg/m 2 h) and a low cake residual moisture content (12-14 wt-%). Vacuum filtration gave slightly higher filtration rates (500-610 kg/m 2 h at the lowest residual chloride contents of the cakes), but the cake residual moisture also stayed higher (25-26 wt-%). 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. 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.

Penghilangan Kadar Klorine pada Precipitate Calcium Carbonate (PCC) dengan Proses Pencucian dan Filtrasi

“…Oleh karena itu, perlu adanya proses tambahan untuk menghilangkan zat-zat aditif yang masih terkandung di dalam produk PCC supaya tidak menimbulkan efek toksik dan merugikan bagi konsumen PCC. Efek toksik yang dihasilkan oleh pelarut dan zat aditif seperti NH4Cl dapat dihilangkan dengan proses pencucian dan penyaringan, diantaranya Pressure Filtration Test dan Vacuum Filtration (Teir, Auvinen, et al, 2016). Penelitian yang berhubungan dengan penghilangan kadar klorin pada PCC masih sedikit yang dilakukan.…”

Synthesis of High-Purity and Stable Vaterite Via Leaching–Carbonation of Basic Oxygen Furnace Slag

“…Numerous studies have successfully extracted calcium ions from BOFS using acid (CH 3 COOH, HCl, H 2 SO 4 ) and ammonium salts (NH 4 Cl, NH 4 NO 3 , (NH 4 ) 2 SO 4 ), followed by a subsequent set of aqueous carbonation to produce PCC, − with some studies advancing to pilot-scale experimentation. − Compared with acid, NH 4 Cl exhibits a higher selectivity for Ca leaching, pH buffering properties, and a higher carbonation conversion rate, which is a more suitable leaching agent for indirect carbonation of BOFS . However, the Ca leaching ratio from the NH 4 Cl solution is lower (<60%) due to its weaker acidity, and the NH 3 overflow further reduces the Ca leaching efficiency .…”

Calcium Carbonate Particle Formation through Precipitation in a Stagnant Bubble and a Bubble Column Reactor

“…An alternative method of producing micron-sized CaCO 3 is through the precipitation of the particles in solution referred to as precipitated calcium carbonate (PCC). The particle purity, yield, and particle characteristics generated via this method are generally seen as superior to those of GCC. , Two main methods are employed to produce PCC particles: (i) a liquid–liquid system using a direct reaction between Ca 2+ and CO 3 2– and (ii) a gas–liquid system which involves the bubbling of CO 2 gas into a solution containing Ca 2+ ions such as Ca­(OH) 2 − or CaCl 2 in the presence of ammonium hydroxide/amine solutions. − …”

“…The particle purity, yield, and particle characteristics generated via this method are generally seen as superior to those of GCC. 3,5 Two main methods are employed to produce PCC particles: (i) a liquid− liquid system using a direct reaction between Ca 2+ and CO 3 2−6 and (ii) a gas−liquid system which involves the bubbling of CO 2 gas into a solution containing Ca 2+ ions such as Ca(OH) 2 7−12 or CaCl 2 in the presence of ammonium hydroxide/amine solutions. 13−15 The focus of this paper is on the utilization of the latter method using CaCl 2 as the calcium source, as Ca(OH) 2 is sparingly soluble in water (1.6 g/L at 20 °C) which can lead to excessive carbonation times (∼100 min) without the use of additional additives.…”