Rotary Calcination Research Articles

Oxidative wear behaviors of Inconel 625 alloy in a simulated rotary calcination furnace environment at 600 and 800 ℃

This study investigates the oxidative wear behaviors of Inconel 625 alloy in a simulated rotary calcination furnace environment at 600 and 800 ℃. Results show that both the coefficient of friction and wear loss increase with temperature from 600 °C to 800 °C. At 600 °C, the alloy exhibits strong resistance to oxidative wear, due to the formation of an intact oxide scale composed of Ni-Cr-O and Cr-rich layers. However, the oxide scale formed at 800 °C features a coarser grain structure, coupled with increased wear debris, leads to higher surface roughness and coefficient of friction. The oxide scale at 800 ℃ has poor effectiveness in protecting the substrate, being more prone to spallation and contributing to greater wear loss.

Milligrams to Kilograms - Scaling Production of Cobalt Free Lithium Excess Cathode Materials through Rotary Calcination

Both Tesla and the Government of the United States have listed the elimination of cobalt and the resilience of the battery cathode supply chain as critical issues in need of advancement 1,2. This investigation answered this call to action through scaling the production of a high-performance cobalt free lithium excess cathode material using rotary calcination. The cathode in this investigation is of the chemical series Li[NixLi(1/3-2x/3)Mn(2/3-x/3)]O2 (where x = 0.25), and to our knowledge this marks the first time an investigation has demonstrated the scaling of this class of materials. In order to achieve the several orders of magnitude increase in production scale the precursor feedstock for rotary calcination required comparison of sol-gel, Pechini, and solid-state precursors routes. Viability of each precursor synthesis route required comparison of synthesis time, synthesis complexity, Thermogravimetric Analysis, Dynamic Scanning Calorimetry, X-Ray Diffraction of intermediate and final materials, as well as Galvanostatic cycling of final cathode materials. Modification and controlled decomposition of sol-gel processing was ultimately used for the scaled production of precursor powders. Once the precursor feedstocks were fed through the rotary kiln we used X-Ray Diffraction, X-Ray Fluorescence, Galvanostatic Testing, and Scanning Electron Microscopy of resultant materials to optimize rotary calcination conditions to find the pareto optimal conditions that allowed for maximized material quality, and output, with minimized energy and time costs. These materials were also compared to our baseline material, which was made in a box furnace in ambient conditions over the course of 24 hours. Synthesis conditions were also modified to allow for the inclusion rapid water quenching of final scaled material to ensure material quality.Sources: F. C. for A. Batteries, National blueprint for lithium batteries 2021–2030, (2021).E. Musk and R. Denholm, UPDATES TO 2020 ANNUAL MEETING OF STOCKHOLDERS AND BATTERY DAY EVENT, (2020).

GENERALIZED MATHEMATICAL MODEL OF PHYSICAL FIELDS OF TECHNOLOGICAL REDISTRIBUTIONS OF MANUFACTURING ELECTROGRAPHITE PRODUCTS

A generalized mathematical model of the physical fields of the main technological redistributions of electrographite products is developed, which is based on a continuous-discrete approach to the description of nonlinear behavior of solids, liquids and gases, and bulk media. It is shown that the continuous formulation of physical processes in the technology of carbongraphite production is based on the Euler frame of reference and may include the following equations: conservation of mass, momentum and energy, electrical conductivity in the vortex-free approximation of electric potential and transport of chemical components of combustion reactions. The discrete formulation of physical processes in bulk materials used in the technology of production of carbon graphite products is based on the Lagrangian frame of reference and may include the following equations: translational and rotational motion and energy. The application of the generalized mathematical model for construction or refinement of mathematical and numerical models of separate redistributions for performance of the numerical analysis of physical fields and parameters of processes and the equipment on examples of pressing of "green" electrode preparations and theoretical research of effective thermophysical properties of loose carbonaceous materials. On the basis of the developed generalized statement, the complex of separate mathematical models of such redistributions of production of electrographite production as: calcination of carbonaceous materials in electrocalciners, gasification of carbonaceous materials in the equipment of rotary calcination furnaces is also formulated and specified, burning and graphitization of electrographite blanks. Bibl. 40, Fig. 4.

Measurement of the residence time distribution of a cohesive powder in a flighted rotary kiln

The rotary kiln is an essential device in chemical and metallurgical industries, with applications in a wide range of solids manufacturing processes. In particular, in the preparation of industrial chemical catalysts, the kiln has become a popular reactor for continuous calcination of catalysts ranging from millimeter-sized extrudates to micron-sized powders. As granular and powder flow behaviors are difficult to characterize, the design and scale-up of rotary calcination processes are often performed empirically. The goal of this research is to improve the fundamental understanding of powder flow in rotary kilns to aid in optimization of the continuous calcination process. For successful calcination to occur, the residence time of the particles must exceed the time required for heating and subsequent treatment. For uniform treatment of the feed, the particles must also exhibit low axial dispersion. In this work, the mean residence time and axial dispersion coefficient for a cohesive fluid catalytic cracking powder were determined in a pilot plant kiln by measuring the residence time distribution. This study utilized a pulse test developed by Danckwerts. Results were fit to the Taylor solution of the axial dispersion model and compared to the Sullivan prediction for mean residence time. It was found that the mean residence time decreases as the feed rate, kiln incline, and rotation rate increase. It was also found that the axial dispersion coefficient increases with speed of rotation and angle of incline. However, the axial dispersion coefficient decreases as the feed rate is increased.

The effect of operating conditions on the residence time distribution and axial dispersion coefficient of a cohesive powder in a rotary kiln

While continuous rotary calcination is a widely used thermal treatment in large-scale catalyst manufacturing, the process's heat and mass transfer mechanisms remain a challenge to characterize and to predict. Thus, the goal of this research is to improve fundamental understanding of rotary calcination to aid in the creation of a scientific methodology for process design and scale-up. For successful calcination to occur, the residence time of the particles must exceed the time required for heating and calcination at a set temperature. The optimal residence time therefore depends on both of these competing time scales, each of which is function of feed material properties, kiln geometry and kiln operating conditions. For uniform treatment of the feed, the particles must also exhibit low axial dispersion. In this work, the residence time distribution and axial dispersion coefficient for a dry cohesive fluid cracking catalyst powder were measured in a pilot plant kiln using a tracer study developed by Danckwerts. Results were successfully matched to the Taylor fit of the axial dispersion model and the Sullivan prediction for mean residence time. It was found that an increase in feed rate, kiln incline and rotary speed decreased mean residence time and overall axial dispersion. Such results have been established previously for free-flowing material like millimeter-sized extrudates, but have not been previously reported for the cohesive powders such as the one used in our work. As in free-flowing material, the axial dispersion coefficient was found to vary with kiln conditions. The values of the axial dispersion coefficients were lower for the powder than for free-flowing material, showing a dependency of axial dispersion on material properties as well as bulk flow behavior.

Measurement of residence time distribution in a rotary calciner

Rotary calcination is widely used in catalyst manufacturing and many other industrial processes. In this article, the influence of operational variables and material properties on the mean residence time (MRT), hold up, and axial dispersion was investigated in a pilot plant rotary calciner. Residence time distributions (RTD) of spherical, cylindrical, and quadrilobe catalyst particles were measured and contrasted. The Saeman's model was successfully applied to predict the experimental bed depth and the MRT as particles flowed through the calciner. It was observed that increasing the feed rate did not significantly affect the MRT. Results for the different particles indicated that cylinders and quadrulobes exhibited less axial dispersion than spheres due to the decreased flowability. A reliable method was developed to provide a reasonable RTD prediction in rotary calcination systems. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4068–4076, 2013

Modeling of the behavior of liquid radwastes in a rotary calcination furnace

A rotary calcination furnace is used at the first stage of a two-stage facility for immobilizing liquid radwastes and comprises a heated rotary tube inclined at a small angle with respect to the horizontal plane. As they move along the furnace, the wastes fed into it are heated, the liquid phase evaporates, and the solid phase remaining after evaporation undergoes chemical changes (calcination) during subsequent motion. The objective of the present work is to develop a model for determining the size of the heating, evaporation and calcination zones.

Predictive controller design for multivariable process system based on support vector machine model

Based on the predictive control principle and support vector machine theory, this paper presents an intelligent predictive control scheme to solve the control difficulties of industry process with multi-variables. As an example, the rotary kiln calcination is the most important part of cement production including complicated physical and chemical reaction processes with large inertia, pure hysteresis, non-linearity and strong coupling characteristics. Considering the need of advanced process control in cement industry, the main control system structure includes three control loops as the pressure control loop, the burning zone control loop and the back-end of kiln temperature control loop. Based on the analysis of PID and generalised predictive control algorithm, the performance index of generalised predictive control algorithm is restructured into PID form. By analysis of the experimental data, the non-linear regression model based on SVM is introduced. The control algorithm using SVM model is simulated in two cases to derive the responses of system compared with the ordinary PID control algorithm. The simulation results of typical step responses of control variables using the presented control scheme show the effectiveness of the control scheme with better response time and tracking performance compared to traditional PID control.

Alumina production method as a factor in the properties of dense corundum refractories

Experimental batches ofα-alumina containing mineralizing additives were produced at various calcination temperatures in the rotary calcination kilns of the Dneprovsk Aluminum Plant.

Influence of some conditions of calcination on the reactivity of calcium sulphate hemihydrate

AbstractA study has been made of the influence of temperature and of some other conditions in the calcination of gypsum on the properties of the product. No anhydrite was detected in the product of still calcination carried out at temperatures up to 200°, but calcination at 143° and above in a rotary calciner leads to appreciable rates of transformation to anhydrite. The formation of anhydrite appears to be catalysed by water vapour, and initiated to some extent by friction of the grains.The reactivity of the product of still calcination of the sample of gypsum studied appeared to be independent of the duration of calcinations taking more than 10 h., and was at a minimum for calcination at about 150°. The reactivity of the product of rotary calcination varied in a more complicated manner. In general, the higher the temperature of preparation the greater was the reactivity of hemihydrate. Anhydrite appears to offer favourable sites for the formation of gypsum nuclei and its formation tends to be associated with a more reactive product. However, it is evident that mechanisms other than the formation of anhydrite produce sites for the nucleation of gypsum and this matter is discussed.