Effect of TiO2 content in slag on Ti content in molten steel

A calculation model of activity for CaO–SiO2–MgO–Al2O3–TiO2 slag is established according to molecular-ion coexistence theory of slag structure to calculate the activities of Al2O3, SiO2, and TiO2 in the slag. The possibility of TiO2 reduction in the slag during refining is analyzed by thermodynamics and verified by laboratory and industrial experiments. Both theoretical analysis and laboratory experimental results show that the content of TiO2 in the ladle slag significantly influences the Ti content in molten steel. When the content of the dissolved aluminum in molten steel is 0.030–0.050%, the TiO2 content in the ladle slag should be controlled below 0.3% to prevent TiO2 reduction. The critical content of TiO2 decreases with an increasing amount of the dissolved aluminum in molten steel. In addition, silicon should be used as a deoxidizer during diffused deoxidization because aluminum as a deoxidizer would lead to the reduction of TiO2. The industrial experiments confirm the results of the laboratory experiments and thermodynamics analysis.

Monitoring the Caustic Dissolution of Aluminum Alloy in a Radiochemical Hot Cell Using Raman Spectroscopy

Chemical processing of highly radioactive materials commonly takes place in heavily shielded hot cells. The remote, real-time monitoring of chemical processing streams via optical spectroscopic techniques in hot cells may be particularly useful. Here, we describe the implementation of Raman spectroscopy and chemometric analysis to monitor the dissolution of aluminum-clad targets containing irradiated aluminum–neptunium oxide cermet pellets in caustic solutions in a hot cell environment. Partial least squares regression analysis was used to generate calibration models to quantify the concentration of dissolved aluminum, nitrate, and hydroxide in solutions within the radiochemical hot cell. This work explored a systematic approach to optimize a matrix of calibration standards using a D-optimal experimental design. The Design of Experiments-based regression model, in comparison to more traditional analytical approaches, was found to be the more practical method for building calibration models, with fewer samples, to obtain informative analytical data from Raman spectra.

Thermodynamic modeling of cerium reduction from slags of the CaO-SiO2-Ce2O3-15%Al2O3-8%MgO system by dissolved aluminum in the metal

Thermodynamic modeling of cerium reduction from slags of the CaO – SiO2 – Ce2O3 system containing 15% Al2O3 and 8% MgO by dissolved aluminum in the metal at temperatures of 1550 and 1650 °C was performed using the HSC 6.1 Chemistry software package (Outokumpu), based on minimizing Gibbs energy and variational principles of thermodynamics using the method of simplex planning lattices (mass% is indicated in this expression and hereinafter). When constructing the planning matrix, the following restrictions were imposed on the variable components of the CaO-SiO2-Ce2O3-Al2O3-MgO system: CaO/SiO2 = 2-5; 15% Al2O3; 8% MgO and 1-7% Ce2O3. As a result of imposing restrictions on the change of components in the system, the studied region is represented by a local simplex in the form of two concentration triangles whose vertices are the pseudo-components Y1, Y2, Y3 and Y4. It was found that depending on the temperature of the metal, the basicity of the slag and the cerium oxide content in the steel, containing 0.06% carbon, 0.25% silicon and 0.05% aluminum, goes from 0.055 to 16 ppm cerium. The positive influence of the temperature factor, slag basicity and cerium oxide content in the studied range of chemical composition on the cerium reduction process is explained from the standpoint of the phase composition of the formed slags and the thermodynamics of cerium reduction reactions. When the metal is kept under slag with a basicity of 2.0, containing 1.0% cerium oxide, it passes into the metal at a temperature of 1550 °C to 0.055 ppm cerium. An increase in the temperature of the system to 1650 °C is accompanied by a slight increase in the concentration of cerium, reaching no more than 0.085 ppm. The most noticeable increase in the cerium content in the metal is observed with an increase in the slag basicity. It is noted that the shift of slags containing 7.0% cerium oxide to the region increased to 5.0 basicity provides, in the temperature range 1550-1650 °C, the equilibrium cerium content in the metal at the level of 12-16 ppm.

Influence of Dissolved-Aluminum Concentration on Sulfur-Oxidizing Bacterial Activity in the Biodeterioration of Concrete

ABSTRACTSeveral studies undertaken on the biodeterioration of concrete sewer infrastructures have highlighted the better durability of aluminate-based materials. The bacteriostatic effect of aluminum has been suggested to explain the increase in durability of these materials. However, no clear demonstration of the negative effect of aluminum on cell growth has been yet provided in the literature. In the present study, we sought to investigate the inhibitory potential of dissolved aluminum on nonsterile microbial cultures containing sulfur-oxidizing microorganisms. Both kinetic (maximum specific growth rate) and stoichiometric (oxygen consumption yield) parameters describing cells activity were accurately determined by using respirometry measurements coupled with modeled data obtained from fed-batch cultures run for several days at pH below 4 and with increasing total aluminum (Altot) concentrations from 0 to 100 mM. Short-term inhibition was observed for cells poorly acclimated to high salinity. However, inhibition was significantly attenuated for cells grown on mortar substrate. Moreover, after a rapid adaptation, and for an Altotconcentration up to 100 mM, both kinetic and stoichiometric growth parameters remained similar to those obtained in control culture conditions where no aluminum was added. This argued in favor of the impact of ionic strength change on the growth of sulfur-oxidizing microorganism rather than an inhibitory effect of dissolved aluminum. Other assumptions must therefore be put forward in order to explain the better durability of cement containing aluminate-based materials in sewer networks. Among these assumptions, the influence of physical or chemical properties of the material (phase reactivity, porosity, etc.) might be proposed.IMPORTANCEBiodeterioration of cement infrastructures represents 5 to 20% of observed deteriorations within the sewer network. Such biodeterioration events are mainly due to microbial sulfur-oxidizing activity which produces sulfuric acid able to dissolve cementitious material. Calcium aluminate cement materials are more resistant to biodeterioration compared to the commonly used Portland cement. Several theories have been suggested to describe this resistance, and the bacteriostatic effect of aluminum seems to be the most plausible explanation. However, results reported by the several studies on this exact topic are highly controversial. This present study provides a comprehensive analysis of the influence of dissolved aluminum on growth parameters of long-term cultures of sulfur-oxidizing bacterial consortia sampled from different origins. Kinetic and stoichiometric parameters estimated by respirometry measurements and modeling showed that total dissolved-aluminum concentrations up to 100 mM were not inhibitory, but it is more likely that a sudden increase in the ionic strength affects cell growth. Therefore, it appears that the bacteriostatic effect of aluminum on microbial growth cannot explain the better durability of aluminate based cementitious materials.

Impact of addition of ca on clogging of SEN and magnetic properties of non-oriented silicon steel

The submerged entry nozzle (SEN) clogging has been happening during continuous casting (or CC for short) for nonoriented silicon steel. To solve the problem, the paper studied a flow rate through SEN, a node attached to one of them, and the impact on the clogging. The results showed that when SEN is clogged seriously, the casting speed has to decrease below the target casting speed and that SEN clogging can be predicted by comparing the actual value and the theoretical one of a casting speed. Al2O3 and its composite inclusions caused the SEN clogging and the addition of Ca can solve SEN clogging during CC of the silicon steel both theoretically and practically. Furthermore, the impact of the addition of Ca on the magnetic properties of the steel were analyzed. The results showed that the core loss and the magnetic induction of the silicon steel decreased by using the addition of Ca, which generated more dissolved Aluminum, and the addition of Ca generated more harmful textures, which reduced the magnetic induction.