Análise da hidroxilação de magnésia cáustica em moinho e reator CSTR

Abstract

Análise da hidroxilação de magnésia cáustica em moinho e reator CSTR Analysis of caustic magnesia hydroxilation in CSTR reactor and mil

Sedimentation and rheological behavior of reactive and non-reactive magnesium hydroxide pulps for industrial spray dryer processing

“…Preparation of magnesium hydroxide pulps: the HM pulps have been produced in a reactor mill under optimum operating conditions [18]: feed: caustic magnesia suspension varying from 25 to 30 wt% and 0.2 mol/L acetic acid (Labsynth, Brazil); initial temperature=25 °C; operating time=5 h. The reactor mill equipment had an internal volume corresponding to 2.0 L with a diameter of 0.12 m and a height of 0.18 m. Caustic magnesia came from two different Brazilian mineral sources: magnesia A with 91% of MgO and magnesia B with 99% of MgO. HM pulps left the reactor mill in the pH range from 11 to 12 (11.8 on average) and remained at this range due to the buffer effect of HM suspensions [18]. HM-A and HM-B pulps were produced for each test performed since they were reactive and hence could not be stored and/or processed for more than 3 h (stable time scale) at 25 °C.…”

“…Samples were taken from these pulps to determine: i) solid concentration, C s (=m s /m susp ), by measuring the sample mass (m susp ) and the solids mass (m s ), which was made after washing the sample with acetone R.G. (Labsynth, Brazil) and drying it in an oven (Med-Clave, LTE Scient., UK) at 120 °C for 2 h; ii) magnesium hydroxide concentration in dry basis, X HM =m HM /m s (HM mass/ solid mass), by calculating m HM as a sum of the HM mass generated by the MgO hydration reaction plus one already presented in the precursor sample [18]. Mass measurements were made in a high-precision analytical balance (AY220, Shimadzu, USA) in triplicate.…”

“…The spray dryer is suggested to replace the commonly used rotary dryer to be able to form HM powder with predefined characteristics. Using a lab reactor mill and caustic magnesia with 98.2% of MgO, the technical feasibility of performing the MgO hydration reaction and the particle comminution simultaneously has been confirmed reaching conversions of MgO to HM up to 5% higher than one obtained in a conventional caustic magnesia hydration route (CSTR) under the same operation conditions [18]. The feasibility of using the spray dryer for producing powder from these HM pulps requires knowledge of their sedimentation behavior, their rheology as well as their particle size distribution.…”

“…This problem affects the transportation, processing, and storage of concentrated HM pulps, so, it encourages new advances in producing HM powder with specific properties. A new route for HM production is proposed using an equipment that performs simultaneously the MgO hydration reaction and the particle comminution [18]. The spray dryer is suggested to replace the commonly used rotary dryer to be able to form HM powder with predefined characteristics.…”