Impact Mill Research Articles

Current outlook and future research needs for harvest weed seed control in North American cropping systems.

Harvest weed seed control (HWSC) comprises a set of tools and tactics that prevents the addition of weed seed to the soil seed bank, attenuating weed infestations and providing a method to combat the development and spread of herbicide-resistant weed populations. Initial HWSC research efforts in North America are summarized and, combined with the vast area of crops suitable for HWSC, clearly indicate strong potential for this technology. However, potential limitations exist that are not present in Australian cropping systems where HWSC was developed. These include rotations with crops that are not currently amenable to HWSC (e.g. corn), high moisture content at harvest, untimely harvest, and others. Concerns about weeds becoming resistant to HWSC (i.e. adapting) exist, as do shifts in weed species composition, particularly with the diversity of weeds in North America. Currently the potential of HWSC vastly outweighs any drawbacks, necessitating further research. Such expanded efforts should foremost include chaff lining and impact mill commercial scale evaluation, as this will address potential limitations as well as economics. Growers must be integrated into large-scale, on-farm research and development activities aimed at alleviating the problems of using HWSC systems in North America and drive greater adoption subsequently. © 2020 Society of Chemical Industry.

Scale-up procedure of parameter estimation in selection and breakage functions for impact pin milling

This paper presents a scale-up procedure of parameter estimation in the selection function and breakage function from single particle impact breakage to inform the predictions at the process scale of an impact pin mill. The selection and breakage functions used in population balance model (PBM) for particle breakage in the literature are briefly reviewed. Single particle breakage tests are conducted in a vertical impact tester subject to varying impact velocities. The single particle breakage results further serve to provide the database for the parameter estimation in Vogel and Peukert model (Vogel and Peukert, 2005). The estimated parameters in the particle level are upscaled in an impact pin mill using the population balance model, which is implemented in the software gPROMS (Process Systems Enterprise, UK) (gPROMS® 4.1 Release Notes, 2016). The impact milling tests were carried out in an impact pin mill UPZ100 subject to four feed rates, providing the dataset for model validation. The sensitivity analysis of the PBM parameters was conducted to help identify their leverage on the particle size distribution. The scale-up procedure by specifying the parameters from single particle level to the process level of PBM demonstrates an approach to help predict the size reduction process subject to the prevailing mechanism in an impact pin mill and other milling processes alike.

Influence of humidifying on charged characteristic in ultrafine pulverization of sulfur

The accumulation of static electricity is a big headache in the industry of sulfur ultrafine pulverization, as the fluidized sulfur powder charged with electricity will change the flow behavior, causing particles aggregation and lowered pulverization efficiency, which will impede the pneumatic transmission and collection system or even trigger the fire blast. In order to effectively reduce the accumulation of static electricity in the dry pulverization process of sulfur, LNI-330A impact mill was utilized to prepare −200-mesh sulfur powder, aiming to explore the influence of absolute humidity and wet basis moisture content on charge-to-mass ratio of the sulfur powder. The results show that the charge-to-mass ratio of sulfur powder decreased with the increase of the absolute humidity, and the formula implying the relation of the charge-to-mass ratio with relative humidity and the temperature was converted: Q=A1-A21+edxζ(a+Ae-tb)+A2. Increased wet basis moisture content could also lower the charge-to-mass ratio, e.g. raising the wet basis moisture content of sulfur powder from 0 to 1.469% could lower the charge-to-mass ratio by 80.91%, and direct humidification of sulfur could better lower the charge-to-mass ratio of sulfur powder than increasing absolute humidity. This study provides a feasible method for reducing of static electricity in the process of the ultrafine pulverization to promote safety and pollution reduction in chemical engineering production.

Optimization of the powder state to enhance the enrichment of functional mung bean protein concentrates obtained by dry separation

To increase the purity and yield of mung bean protein concentrates obtained by dry separation, the state of the powder was optimized from the milling to air classification processes. Relatively coarse milling (rotator frequency 40 Hz) by a full-scale airflow impact mill generated sufficient detached protein bodies while not overly damaging the starch granules. Subsequently, a higher classifier wheel frequency (50–70 Hz), an induced-draft fan frequency (50–70 Hz), and a lower feed rate (1.0–6.0 kg/h) reduced the cut point and fish-hook effect, thereby contributing to the improvement of protein separation efficiency. Under optimal conditions designed by response surface methodology (RSM), the protein concentrates with separation efficiency 84.0 ± 4.4% and superior free radical scavenging capacity when compared with original flour and protein isolate (wet) was obtained. These results provide insight into the critical parameters affecting powder state, thus facilitating the development of a dry separation method to fractionate mung bean protein.

Effects of milling methods on rheological properties of fermented and non-fermented dough

Abstract The rheological properties of wheat flour are very important for the production of bakery products, and the milling methods greatly influence the rheological properties. In this paper, we measured the particle size distributions, damaged starch contents, granular morphology, and pasting properties of the wheat flour, also carried out the uniaxial elongation test, the texture profile analysis, and rheological properties of the dough to evaluate effects of two milling methods, i.e. impact mill (IM) and hammer mill (HM), on the rheological properties of wheat flour and dough. The results showed that milling methods had no significant effects on flour pasting temperature (except the flour H3 obtained by HM grinding three times) and springiness of dough. Flour samples milled by IM had a lower damaged starch content, higher trough viscosity, higher final viscosity and higher values of setback compared to samples processed by HM. After repeated milling of IM, the damaged starch content of the endosperm granules could be controlled below 1% (P

Experiments and modeling of mine soil inertization through mechano-chemical processing: from bench to pilot scale using attritor and impact mills.

Mechano-chemical treatment has been recognized to be a promising technology for the immobilization of heavy metals (HMs) in contaminated soils without the use of additional reagents. Despite this, very few studies aiming to investigate the applicability of this technology at full scale have been published so far. In this study, a quantitative approach was developed to provide process design information to scale-up from laboratory- into pilot-scale mechano-chemical reactors for immobilizing heavy metals in contaminated mining soil. In fact, after preliminary experiments with laboratory-scale ball mills, experiments have been carried out by taking advantage of milling devices suited for pilot-scale applications. The experimental data of this work, along with literature ones, have been quantitatively interpreted by means of a mathematical model allowing to describe the effect of milling dynamics on the HM immobilization kinetics for applications at different scales. The results suggest that the mechanical process can trigger specific physico-chemical phenomena leading to a significant reduction of HMs leached from mining soils. Specifically, after suitably prolonged processing time, HM concentration in the leachate is lowered below the corresponding threshold limits. The observed behavior is well captured by the proposed model for different HMs and operating conditions. Therefore, the model might be exploited to infer design parameters for the implementation of this technique at the pilot and full scale. Moreover, it represents a valuable tool for designing and controlling mechano-chemical reactors at productive scale.

A DEM-PBM multiscale coupling approach for the prediction of an impact pin mill

Despite many attempts to establish material grindability in a milling process, it remains very difficult to predict the milling performance. In this study, impact milling tests were carried out under varying operational conditions in a UPZ100 impact pin mill. The product size distribution and fineness of milled alumina particle are reported and analyzed. A multiscale framework coupling discrete element method (DEM) and population balance model (PBM) is proposed to predict the milling performance of the mill. The impact velocity and impact frequency information from DEM is utilized to inform the mill operation parameters of the PBM model at the process scale, whilst the material grindability parameters are evaluated using constrained optimization to match a milling test. The predictions of the product size distribution show very good agreement with the experimental results. This indicates that the multiscale model is promising for optimizing the design and operation of mills.

The nutritional components and physicochemical properties of brown rice flour ground by a novel low temperature impact mill

A low temperature impact mill (LTIM) was created and used for grinding brown rice. The nutritional components and physicochemical properties of the resulting flour were investigated and compared with those ground by traditional wet colloid mill (CM) and dry high-speed universal grinder (HUG). It was found that LTIM produced a fine flour with unimodal particle size distribution, and well retained non-starch nutrients. Especially, the phenolic content of flour prepared by LTIM was two times higher than that prepared by CM. LTIM also led to less damaged starch content than HUG. The damaged starch content related well with the thermal and gel hydration properties. Interesting, comparing the particle size distribution before and after enzymolysis, it was found that LTIM could pulverize dietary fiber of brown rice efficiently. The results from this study indicated that the LTIM may provide a promising technology for pulverizing brown rice thus open its new applications.

Life Cycle Assessment of Resource Recovery from Waste Electrical and Electronic Equipment: A Case Study of Tantalum Recovery by Chain-Using Drum-Typed Impact Mill

Life Cycle Assessment of Resource Recovery from Waste Electrical and Electronic Equipment: A Case Study of Tantalum Recovery by Chain-Using Drum-Typed Impact Mill

Fate of Weed Seeds after Impact Mill Processing in Midwestern and Mid-Atlantic United States

Abstract Harvest weed seed control (HWSC) technology such as impact mills that destroy weed seeds in seed-bearing chaff material during grain crop harvest, has been highly effective in Australian cropping systems. However, the impact mill has never been tested in soybeans and weeds common to soybean production systems in the Midwest and Mid-Atlantic US. We conducted stationary testing of Harrington Seed Destructor (HSD) impact mill and winter burial studies during 2015-2016 and 2017-2018 to determine (i) the efficacy of the impact mill to target weed seeds of seven common weeds in Midwestern and five in Mid-Atlantic US, and (ii) the fate of impact mill processed weed seeds after winter burial. The impact mill was highly effective in destroying seeds of all the species tested, with 93.5-99.8% weed seed destruction in 2015 and 85.6-100% in 2017. The weak relationships (positive or negative) between seed size and seed destruction by impact mill, and high percentage of weed seed destruction by impact mill across all seed sizes indicate that the biological or practical effect of seed size is limited. The impact mill-processed weed seeds that retained at least 50% of their original size, labeled as potentially viable seed (PVS), were buried for 90 d over winter to determine the fate of weed seeds after winter burial. At 90 d after burial (DAB), the impact mill processed PVS were significantly less viable than unprocessed control seeds, indicating that impact mill processing physically damaged the PVS and promoted seed mortality over winter. A very small fraction (< 0.4%) of the total weed seed processed by the impact mill remained viable after winter burial. The results presented here demonstrate that the impact mill is highly effective in increasing seed mortality and could potentially be used as a HWSC tactic for weed management in this region.

Seed retention of winter annual grass weeds at winter wheat harvest maturity shows potential for harvest weed seed control

AbstractDowny brome, feral rye, and jointed goatgrass are problematic winter annual grasses in central Great Plains winter wheat production. Integrated control strategies are needed to manage winter annual grasses and reduce selection pressure exerted on these weed populations by the limited herbicide options currently available. Harvest weed-seed control (HWSC) methods aim to remove or destroy weed seeds, thereby reducing seed-bank enrichment at crop harvest. An added advantage is the potential to reduce herbicide-resistant weed seeds that are more likely to be present at harvest, thereby providing a nonchemical resistance-management strategy. Our objective was to assess the potential for HWSC of winter annual grass weeds in winter wheat by measuring seed retention at harvest and destruction percentage in an impact mill. During 2015 and 2016, 40 wheat fields in eastern Colorado were sampled. Seed retention was quantified and compared per weed species by counting seed retained above the harvested fraction of the wheat upper canopy (15 cm and above), seed retained below 15 cm, and shattered seed on the soil surface at wheat harvest. A stand-mounted impact mill device was used to determine the percent seed destruction of grass weed species in processed wheat chaff. Averaged across both years, seed retention (±SE) was 75% ± 2.9%, 90% ± 1.7%, and 76% ± 4.3% for downy brome, feral rye, and jointed goatgrass, respectively. Seed retention was most variable for downy brome, because 59% of the samples had at least 75% seed retention, whereas the proportions for feral rye and jointed goatgrass samples with at least 75% seed retention were 93% and 70%, respectively. Weed seed destruction percentages were at least 98% for all three species. These results suggest HWSC could be implemented as an integrated strategy for winter annual grass management in central Great Plains winter wheat cropping systems.

MODELING AND CALCULATION OF GRINDING AND CLASSIFICATION OF MIXTURE OF DISSIMILAR COMPONENTS IN CLOSED MILLING CIRCUIT

It is shown that the developed earlier model of joint grinding of dissimilar particulate solids based on the discrete models of the Boltzmann equation does not take into account the possible size and density classification of particles and the operating of technological equipment in a closed milling circuit. It is substantiated that the problem of improving the efficiency of separation of mixture components, based on the analysis of their treatment in a closed milling circuit is an actual problem in the field. Theoretical investigations were based on the discrete models of the Boltzmann equation and the methods of their solution related to the technology of treatment of dissimilar components mixture. A special program for measurements and experimental data treatment obtained at the laboratory fluidized bed jet mill and the impact mill was developed for the experimental investigations. In the course of computational and experimental study a mathematical model of classification of dissimilar components was proposed and tested as well as the algorithm of its implementation into the general model of a closed milling circuit. The computational investigations were carried out to estimate the model sensitivity to the input parameters disturbance. The directions of improving the efficiency of the objective component separation in the closed milling circuit with the fluidized bed jet mill are found. The developed model the closed milling circuit for grinding dissimilar particulate solids can be used in engineering practice with acceptable accuracy. It can be used to estimate the possible enrichment of particulate solids mixtures and to define the optimal technological conditions of their separation with taking into account the limitations on the objective product impurity. The paths are outlined and the order of selection of the parameters of the grinding processes and the classification for effective separation of the components of the mixture are shown.

Increasing tensile strength by reducing particle size for extrudate-based tablet formulations

The effect of milled extrudate particle size on tablet tensile strength was investigated in this study. Parameters used for milling with a hammer impact mill were investigated to give different particle size milled extrudate. Mill screen type and aperture size were varied, along with mill rotor speed and extrudate feed rate to the mill. The results showed that reducing the mill screen aperture size, increasing the mill rotor speed and decreasing the extrudate feed rate led to a reduction in the milled extrudate particle size. Milling using a reduced screen aperture size caused a narrowing of the particle size distribution. A smaller milled extrudate particle size resulted in tablets of a higher tensile strength. This along with a narrowing of the particle size distribution resulted in more uniform tablets, hence less weak points for cracks to propagate, and a stronger tablet.

INVESTIGATION OF INFLUENCE OF COMPLEXACTIVATION ON RHEOTECHNOLOGICAL CHARACTERISTICSOF CERAMIC MASSES

in the work, rheological characteristics of ceramic masses based on loam with ash, mechanical-and complex activated loam with ash are investigated.Joint mechanical activation of loam with ash was carried out in a mixer-activator, operating on the principle of a centrifugal impact mill. Complex activation includes joint mechanical activation of loam with ash, followed by treatment with surface active additive -PO-PB-7 in an amount of 0.1%.When determining the plastic strength of the masses on the basis of mechanical-, complexlyactivated and non-activated (original) loam with ash (in an amount of from 0 to 75%), optimal compositions of the masses were found.It was found that the plastic strength of the complex activated ceramic masses increases. The coefficient of sensitivity increases in mechanical-and complexly activated loams, and decreases with the introduction of ash, which predetermines the possibility of intensifying the drying process of samples based on complexly activated clay-ash mass.It has been established that the masses on the basis of complexly activated clay-ash raw turn into structural-mechanical type I with improved rheological properties

COMPUTATIONAL AND EXPERIMENTAL STUDY OF JOINT GRINDING OF DISSIMILAR COMPONENTS IN A CIRCULATING FLUIDIZED BED JET MILL

At joint grinding, classification and mixing of dissimilar particulate solids, not only the total content of each in a mixture is the point of researcher’s interest but also the particle size distribution in each component. It is particularly important for enrichment and purification of components at their joint grinding and classification. Tracers of different type (radioactive, colored, etc.) are commonly used for this purpose. However, such methods are available not for any materials due to technological, financial and sanitary limitations. An alternative simple and easy available approach to investigate the particle size distributions in a mixture is proposed. It is based on application of soluble tracers and can be used in the case of selective solution of one of the components in a chosen solvent. Such method to define the particle size distribution can be interesting for the chemical and other industries. A laboratory impact mill was used for experimentation and identification of the model of joint grinding of a components mixture. This part of the research allowed obtaining and testing the method to define the particle size distributions in the binary mixture of components one of which was solvable in water, and another one was not. The developed method was used for grinding kinetics of joint grinding of two dissimilar components. The conducted research allowed developing a conception of modeling of the selective grinding of dissimilar components mixture. The computational analysis showed that the proposed model with calibrating parameters obtained from the experiments allows describing the process of selective grinding of a dissimilar components mixture with the accuracy that is acceptable for engineering practice. It allows using the model for practical estimation of the objective components enrichment and defining the optimal conditions for dissimilar components separation.

INVESTIGATION OF PROCESS OF NATURAL GRAPHITE SPHEROIDIZATION

In this paper, the process of spheroidization of natural graphite powders on an original impact-reflecting mill with internal separation of particles was investigated. It was established that the process of spheroidization of natural graphite by impact depends both on the intensity and duration of mechanical activation. For the type of mill used, the critical linear velocity of the impact elements of the mill rotor, at which the graphite particles can be spheroidized, is 45 m/s. An increase in the linear rotational speed of the mill (intensity of impact) leads to a decrease in the average particle size, an increase in particle roundness, but significantly increases product losses. In the process of mechanical activation by impact, it is possible to increase the coefficient of roundness of the graphite particles to an average value of 0.8-0.9, which leads to compaction of graphite powders. The presence of ash impurities has a negative effect on the ability of natural graphite powders to compact. A mechanism is proposed for the process of spheroidization of graphite particles in a shock-reflecting mill. According to the proposed mechanism, at first, small-sized graphite plates are detached and deformed due to impact. As the free energy accumulates, agglomeration of deformed particles into spheres takes place. With increasing processing time, the surface of the particles is smoothed due to their friction with each other and against the wall of the mill. Powders of spherical graphite obtained by the proposed method have shown the possibility of their use as an anode material of lithium-ion batteries. The type of equipment investigated has made it possible to reduce the required number of pieces of equipment from 20 to 12 impact mills per line in comparison with foreign analogues.
 For citation:
 Yudina T.F., Blinichev V.N., Bratkov I.V., Gushchina Т.V., Melnikov A.G. Investigation of process of natural graphite spheroidization. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 9-10. P. 48-52

Population balance modeling applied to the milling of pharmaceutical extrudate for use in scale-up

This study modeled the particle size distribution (PSD) of pharmaceutical extrudates after milling by developing a so-called time-discrete population balance model (PBM). The PBM, which models size reduction as a series of breakage events, was formulated so that the model parameters separate the effect of material properties and milling process conditions. Because of this novel aspect, the PBM should have excellent predictive capability with specific applications in technology transfer and scale-up. To investigate this application, copovidone extrudate produced by the hot-melt extrusion process was milled using a lab-scale continuous impact mill (Fitz Mill). The effect of impeller speed and classification screen size on PSD of the extrudate was investigated. The PBM with parameters obtained by fitting lab-scale PSD data was then applied to model the PSD of the extrudate following milling by a pilot-scale continuous impact mill (Hosokawa mill). The study found that the parameters determined at the lab-scale can be used to model PSDs at the pilot-scale and may be generally applied to similar classification-type impact mills. Since technology transfer and scale-up can be material and time consuming, this approach may offer significant benefits to the pharmaceutical industry for the development of milling processes.

Generation of low ash fine clean coal powder by autogenous grinding process powder technology

Crushing and grinding process in mineral processing industry is high energy consuming but it is essential for generating required sized ore with improved liberation, which enhances the process efficiency of physical cleaning of ore. Due to the presence of various minerals in lump of ore, breakage mechanism plays a major role in liberation of different materials, which is solely depends on the type of force applied for crushing and grinding. In conventional crushing and grinding equipment, high impact and attrition forces are applied on the ore lump, which breaks the grain mixture homogeneously, but mineral cleaning enhances when there is a breakage through grain boundaries and not through the grains.Coal is a carbonaceous ore contains maceral and minerals with different properties. Due to the presence of high mineral content, the mineral beneficiation process is adopted where the liberation of inorganic minerals plays key role. As coal is a soft material, use of impact mills generates coal with homogeneous distribution of minerals. In this paper, Autogenous grinding method explored for coal to study the effect on liberation of coal and it was observed that, autogenous grinding helps in improving the liberation of minerals. Experiments also revealed that, the autogenous grinding produces clean coal fines with low ash percentage(16.5% ash clean coal from 24.4% ash feed coals) directly without washing. It was also observed from petrographic study that liberation of coal improved in comparison with conventional grinding process. This is due to the breakage of the coal particles through the coal and mineral boundary.

On the separation and recycling behaviour of textile reinforced concrete: an experimental study

This paper presents the results of recent experiments on the recyclability of the textile components in textile reinforced concrete (TRC). TRC as a multi-component system often contains organic ingredients such as carbon fibres and polymer impregnations. Consequently, the recycling of TRC is not trivial and has not yet been sufficiently clarified until now. In this study, an impregnated, bi-axially reinforced, and warp-knitted textiles made of carbon fibres was used in combination with a fine grained concrete. Flexural tests on TRC specimens containing recycled epoxy-impregnated carbon reinforcement were performed, whereby the recycling was simulated by a pre-treatment of the carbon fibre material in a jaw crusher. The results showed a pronounced decrease in flexural strength compared to untreated carbon reinforcement. Moreover, three different crushing methods were investigated with respect to their influence on the recovery of styrene-butadiene-rubber impregnated carbon textiles. Besides jaw crushing and impact milling, crushing with a hammer mill showed the best degree of purity but also caused the highest mechanical damage to the textile. The impact of material, structure of the composite and crushing methods on the separation behaviour could be deduced from the experiments.

Protein enrichment of defatted soybean flour by fine milling and electrostatic separation

Abstract Defatting and dry fractionation of soybean flour by the combination of impact milling and tribo-electrostatic separation was investigated to prepare protein–enriched soybean flour. Defatting is crucial to facilitate dry milling required for dry fractionation. Both organic solvent extraction and oil pressing were suitable as defatting methods although oil pressing compacted the tissue structure visually. Moderate impact milling (classifier wheel speed of 3000 rpm) effectively liberated protein bodies while eliminating agglomeration of small particles. Electrostatic separation was conducted with varying charging tube configurations. We found higher yields in the separation with a spiral charging tube design than with a slit design. The soy flour was enriched in protein from 37 g/100 g to 45 g/100 g dry basis by defatting. During electrostatic separation a soy protein enrichment of 15% was achieved and a yield of 62% of the protein was recovered from the defatted soy flour. Industrial applications The production of soy protein isolates and soy protein concentrates with wet fractionation consumes a lot of water and energy. Meanwhile, the ingredients lose their native state and part of their functionality due to the harsh processing conditions. This study proposed a dry fractionation method combining fine milling and electrostatic separation for the preparation of soybean protein-enriched fractions retaining the native state of the protein. Although the proposed dry fractionation for protein-enriched fractions from oilseeds is promising, still challenges are ahead for upscaling the process, being efficient and safe in its operation.