Mathematical modelling of a semi-dry SO2 scrubber based on a Lagrangian-Eulerian approach.

Semi-dry desulfurization is an efficient means of SO2 removal from the effluent gases from electrolysis cells in aluminum smelters. These gases are at low temperature and contain low concentrations of SO2, as opposed to thermal power plants. The removal is carried out by injecting powdered alkaline sorbent, hydrated lime (solid particles), into the SO2-containing gas (gas phase) in the presence of humidity. The reaction is controlled by the adsorption of SO2 onto the surface of lime. This study involves the mathematical modelling of a lab-scale scrubber using a Lagrangian-Eulerian approach in order to analyze the desulfurization efficiency. The model was validated based on experimental data. A parametric study was carried out to investigate the effects of particle size, sorbent amount, and relative humidity (RH) on the desulfurization efficiency. The results show that the particle size is the most important parameter; as the particle size decreases, the desulfurization efficiency increases. However, using finer particles may increase the process cost. The loss in SO2 capture efficiency due to the use of coarser particle size could be compensated by increasing the relative humidity (RH) of the gas, another key parameter of the process.

Impact of Pitch Modification on Anode Properties: Effect of Additive Type.

Aluminum is one of the major industries in Canada. The main challenges facing the aluminum industry are carbon loss, energy use, greenhouse gas emissions, cell performance, and production costs, especially for high-amperage cells. The quality of carbon anodes plays a major role in the stability of cell operation and energy consumption. Anodes are made from petroleum coke, rejected green and baked anodes and butts, as well as coal tar pitch, which binds all of the particles. Although the industry depends on a steady supply of high-quality anodes, the availability of quality anode raw materials-coke and pitch-has decreased. A means of improving raw material quality is to modify their properties. In this work, using two additives, low- and high-quinoline insoluble (LQI and HQI) pitches were modified. These additives enrich the surface functional groups of the pitch, thereby increasing coke-pitch interactions. Various additive concentrations and pitch percentages were assessed. It is found that the choice of additive type has a marked effect on pitch properties, with different additives improving different pitches. Additive 1 is suitable for the HQI pitch, whereas additive 2 modifies the LQI pitch better. Anode properties are improved by modifying one of the pitches, whereas modifying the other pitch affects the anode quality to a lesser extent. Thus, the results showed that the modification of an already good-quality pitch (LQI pitch) does not significantly affect the anode quality. On the other hand, the modification of the inferior-quality pitch (HQI pitch) improved the anode quality and decreased the optimum pitch percentage necessary to obtain good anodes compared to the percentage of the LQI pitch needed. This would help decrease the anode production cost. The wettability tests give an indication of if the additive has the potential to improve the coke-pitch interactions, but it cannot predict the effect of pitch percent.

Effect of carbon anode production parameters on anode cracking.

Carbon anodes are used in the electrolytic production of aluminum. The quality of anodes is directly related to the production cost, carbon and energy consumption, and environmental emissions. It is desired that the anodes have high density, low porosity/cracks, low electrical resistivity as well as low air and CO2 reactivities. Low resistivity of anodes reduces energy required to produce aluminum during electrolysis. The presence of cracks and pores increases the anode electrical resistivity. Therefore, it is important to know how and when the pores and cracks form during the anode production so that the necessary actions could be taken to prevent their formation. A study was carried out to investigate the effect of different anode production parameters such as anode composition, type of raw material used, time and top-former bellow pressure of vibro-compactor, green anode cooling medium, and heating rate used during baking on the crack formation. The anodes are fabricated at the carbon laboratory of University of Quebec at Chicoutimi (UQAC) and characterized by measuring their properties (density, electrical resistivity, and surface crack density). The anode properties, hence the anode quality, were correlated with the anode production parameters. Also, their tomographic analysis was carried out to visualize and quantify the internal cracks.

The Effect of Novel Synthetic Methods and Parameters Control on Morphology of Nano-alumina Particles.

Alumina is an inorganic material, which is widely used in ceramics, catalysts, catalyst supports, ion exchange and other fields. The micromorphology of alumina determines its application in high tech and value-added industry and its development prospects. This paper gives an overview of the liquid phase synthetic method of alumina preparation, combined with the mechanism of its action. The present work focuses on the effects of various factors such as concentration, temperature, pH, additives, reaction system and methods of calcination on the morphology of alumina during its preparation.