Abstract In this work, a high limestone content waste was evaluated as a potential material for CO2 capture. The influence of calcination conditions on the CO2 capture capacity was evaluated using 5 cycles of calcination-hydration-carbonation reactions. A Central Composite Design of Experiments was set using calcination temperatures and time as variables. The response evaluated was the CO2 capture measured by thermogravimetric analysis. The results indicate that both calcination temperature and time influence the CO2 capture capacities in the initial cycles but, after a large number of cycles, the effect becomes less relevant. The optimum calcination temperature did not change significantly between cycles - about 893 °C in the first and 850 °C in the fourth cycle. However, the optimum calcination time decreased from 40.1 min in the first to 22.5 min in the fourth cycle. The maximum CO2 capture capacity declines over the reaction cycles due to the sorbent sintering, which becomes more noticeable. Moreover, the waste used in this work is suitable for separating CO2 from flue gas, achieving more than 0.2 g/g of capture capacity after five cycles.

Filtering hydrocyclone is a device that was developed and patented by the Particulate System Research Group at the Federal University of Uberlandia. This equipment consists of a hydrocyclone whose conical section is replaced by a conical filtering wall. Thus, during the operation of these devices, besides the underflow and overflow streams, there is another stream of liquid, resulting from the filtrate produced in the porous cone. In the present work, the influence of some geometric variables of a filtering hydrocyclone was analyzed by an experimental and CFD study. The geometric variables analyzed were underflow orifice diameter (D U) and vortex finder length (ℓ). Data from a conventional hydrocyclone of the same configuration were also obtained. The results indicated that the performance of hydrocyclones is significantly influenced by the conical filtering wall. The incorporation of the filtering medium decreased the Euler numbers and increased the total efficiency of the hydrocyclones. Depending on the specific functions of the separator (as a classifier or concentrator) the best values of D U and ℓ were also found for the filtering hydrocyclone.

Determination of the size distribution of solid particles is fundamental for analysis of the performance several pieces of equipment used for solid-fluid separation. The main objective of this work is to compare the results obtained with two traditional methods for determination of the size grade distribution of powdery solids: the gamma-ray attenuation technique (GRAT) and the LADEQ test tube technique. The effect of draining the suspension in the two techniques used was also analyzed. The GRAT can supply the particle size distribution of solids through the monitoring of solid concentration in experiments on batch settling of diluted suspensions. The results show that use of the peristaltic pump in the GRAT and the LADEQ methods produced a significant difference between the values obtained for the parameters of the particle size model.

The filtering hydrocyclone is a solid-liquid separation device patented by the Chemical Engineering Department at the Federal University of Uberlândia, which consists of a hydrocyclone whose conical section was replaced by a conical filtering wall. The objective of this work is to compare the performances of the filtering hydrocyclones designed by Bradley and by Rietema. The experimental results obtained with the filtering hydrocyclones under the same operational conditions as those used with the conventional device allow the conclusion that performance of the Bradley and Rietema types is significantly influenced by the filtering medium. Rietema's filtering hydrocyclones had a lower volumetric feed flowrate than the conventional device and Bradley's filtering hydrocyclones showed increases in this same variable. In both designs, overall efficiency was influenced by the underflow-to-throughput ratio.