Circular fluid energy mill
TL;DR: In this paper, an operational matrix was established with its elements representing the particular angle between the nozzles giving maximum performance for a given nozzle size and grinding pressure, and the results and observations were used of to develop a circular fluid energy mill, which can be an efficient alternative to the existing mills.
Abstract: The griding chamber of an elliptical fluid energy mill was subjected to further investigations. An operational matrix was established with its elements representing the particular angle between the nozzles giving maximum performance for a given nozzle size and grinding pressure. After estimating the breakage function values for different grinding chamber conditions, it was found advisable, for the best performance with respect to the energy sent in, to follow the diagonal operation in the matrix, with the nozzles being arranged in an ascending order of sizes and descending order for grinding pressures. The effects of the feeder nozzle pressure and the uptake height were analysed by following the process of attaining steady state and by monitoring the pressure difference across the downtake. The results and observations were made use of to develop a circular fluid energy mill, which can be an efficient alternative to the existing mills. The design is patented by the authors under Indian Patent Act.
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TL;DR: In this paper, a methodology for characterising grinding kinetics is developed based on a new criterion, ''the residual fraction'' to represent the performance of a grinding process, applied to pseudo-batch grinding of hydrargillite in a fluidised bed opposed jet mill Alpine 100 AFG.
Abstract: A methodology for characterising grinding kinetics is developed based on a new criterion, `the residual fraction' to represent the performance of a grinding process. This is applied to pseudo-batch grinding of hydrargillite in a fluidised bed opposed jet mill Alpine 100 AFG. It appears to give an adequate representation and a simple mathematical expression for the change in particle size distribution with time. Approximate values of breakage and selection matrices are then calculated on the basis of previous studies, showing that the breakage function is not normalisable over the whole range of particle size. These results are used to propose a fragmentation mechanism for hydrargillite which includes cleavage of the larger particles and destructive breakage of the fine particles.
61 citations
TL;DR: In this article, the effect of the three major operating variables of a circular fluid energy mill, namely the grinding nozzle pressure, grinding nozzle size and the material feed rate on the breakage distribution parameter of the mill, were analysed using G-H solution for the size-discretised batch grinding equation.
Abstract: Modeling and simulation of any comminution process are based on the two mechanistic-phenomenological concepts, namely the breakage function or the breakage distribution function and the selection function or the breakage rate function. For a realistic and mathematical representation of any grinding process, the characteristics of these functions with respect to the operational variables of a given comminution system are the prime requisite. For the present work, the effect of the three major operating variables of a circular fluid energy mill, namely the grinding nozzle pressure, grinding nozzle size and the material feed rate on the breakage distribution parameter of the mill, were analysed using G–H solution for the size-discretised batch grinding equation. The parameter values were estimated for four grinding nozzle pressures, four grinding nozzle sizes and four material feed rates using the ground product size distribution after each pass, for six successive passes through the grinding chamber of a circular fluid energy mill. The parameter values could be related to particle size with the sum of two power functions equation. The behaviour of the coefficients of these equations were analysed and characterised with respect to the operating variables.
15 citations
TL;DR: In this article, the effect of material hardness on the breakage process of a circular fluid energy mill was analyzed by estimating breakage parameters using the G-H solution for the size discretized batch grinding equation, with corrections to account for the deviation from first-order kinetics during the initial stages of grinding and a back-calculation scheme.
Abstract: Towards analyzing the breakage behavior of materials with respect to their physical properties in the context of simulation and modeling of the process of comminution in a circular fluid energy mill, the present work was taken up to characterize the effect of material hardness on the breakage process of the mill. The breakage parameters of a range of materials, chosen based on their hardness, were analyzed by estimating them using the G-H solution for the size discretized batch grinding equation, with corrections to account for the deviation from first-order kinetics during the initial stages of grinding and a back-calculation scheme. All the operating variables of the mill were kept the same while collecting the primary breakage data using a single-size feed for six successive passes through the grinding chamber of the mill. The breakage distribution values could be related to particle size with the sum of two power function equations, while the breakage rate could be expressed as a power function of the dimensionless particle size and the top size interval disappearance. The coefficients of these functions for different materials indicated inconsistent behavior with respect to the hardness for softer materials, while medium and harder minerals showed specific trends.
11 citations
TL;DR: In this article, a disk centrifuge-type pneumatic classifier was developed, with a classifier nozzle introduced at a specific location inside the classifier so that the suction created out of the expansion of air through this nozzle can be used for the on-line control of the product fineness.
Abstract: Innovation of novel grinding systems like fluid energy grinding and fluidized bed grinding for the production of contamination-free, ultra-fine powder products necessitated an equally effective integral classification system for controlling the fineness of the products. Towards maintaining the high standards of purity of the product, it was found advisable to dispense with mechanical classifiers for such grinding systems. It is to facilitate this idea that a disk centrifuge-type pneumatic classifier was developed, with a classifier nozzle introduced at a specific location inside the classifier so that the suction created out of the expansion of air through this nozzle can be used for the on-line control of the product fineness and the classifier can be incorporated in any of the fluid energy-based grinding systems. The performance of the classifier was tested by mounting it on the grinding chamber of a circular fluid energy mill and by collecting the data for estimating the classification functions of particles, at different suction levels and material loading. A two-parameter model was used to relate the variation of the classification function with particle size and the coefficients of the model were characterized with the operating conditions.
2 citations
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TL;DR: The distribution of primary breakage products in laboratory mills can be estimated by batch grinding for short times by manipulating the data, and the second and third methods correcting for secondary breakage are given.
Abstract: The distribution of primary breakage products in laboratory mills can be estimated by batch grinding for short times. Three methods are given for manipulating the data, the second and third methods correcting for secondary breakage. Method III is the most accurate, but since it uses the specific rates of breakage of the various sizes in the correction procedure it is necessary to have experimental or theoretical estimates of these values. A general computer program is given for the computations.
190 citations
TL;DR: In this paper, experimental optimization studies were carried out with the design and operating variables of an elliptical fluid energy mill in order to explore the possibilities of improving its grinding efficiency, and it was noticed that the performance of the mill varied with the locations of the nozzles around the outer periphery of the grinding chamber.
Abstract: Experimental optimization studies were carried out with the design and operating variables of an elliptical fluid energy mill in order to explore the possibilities of improving its grinding efficiency. It was noticed that the performance of the mill varied with the locations of the nozzles around the outer periphery of the grinding chamber and for a given nozzle size there was a particular spacing between the nozzles giving maximum product fineness. The data collected from the experiments carried out with different heights of the uptake and downtake had indicated that, for a range of grinding nozzle pressures, a circular configuration for the mill with no uptake and downtake yielded better results. The pressure difference across the downtake pipe was monitored using a water manometer while the system was attaining steady state and it was found that the performance of the mill at steady state was very sensitive to the pressure conditions across the downtake pipe.
4 citations