Dry Mill Research Articles

Dry mill route for synthesis of single phase bulk and e-beam growth of thin films of Cu2ZnSnSe4 for photovoltaic applications

In this present work, we have evaluated a reliable and simple route for synthesis of single-phase Cu2ZnSnSe4 (CZTSe) bulk material through dry ball milling method from elemental precursors (Cu, Zn, Sn, Se) in argon atmosphere. At every single hour of dry milling process, evolution towards single phase CZTSe and corresponding secondary phase depletion were studied in detail using X-ray diffraction (XRD) and Raman spectroscopy analyses. Rietveld refinement of XRD data, high-resolution TEM and selected area electron diffraction (SAED) analyses of milled CZTSe were done to confirm the phase purity. Optical and hall measurements have been carried out to compare the viability of dry milling method with conventional synthesis process. Thin films have been grown by electron beam evaporation method wherein the dry milled powder was used as source material. Thin films grown at ∼100 °C were subsequently vacuum annealed at ∼480 °C and characterized using XRD, Raman spectroscopy, optical absorption analysis and photoresponse measurements to check the compatibility of the films for photovoltaic applications.

Advanced comminution modelling: Part 2 - Mills

This second part paper explores rock breakage mechanisms, the life cycle of rocks in mills and the strong influence of end walls on charge motion within mills. We present recent advances in particle-based modelling of mills for comminution focused around wear and the effect of slurry and slurry phase grinding. Three mill scenarios are considered:1.Media flow and the resulting wear evolution of the belly and end wall liners and the resulting change in mill performance for a full industrial scale dry ball mill (modelled using DEM)2.Axial slurry transport and mixing in a wet overflow industrial scale ball mill (modelled using fully coupled DEM and SPH)3.Effect of mill speed on slurry and solid charge motion and the resulting grinding of fine particles in a 1.8 m diameter wet Hardinge pilot mill (modelled using fully coupled DEM and SPH with advection-diffusion-population balance equations solved for the slurry size distribution for each SPH particle)These demonstrate the nature and level of fidelity that is now possible to include in particle-scale comminution models. They provide insights into the critical importance of curtain flows generated by the end walls of tumbling mills, on wear behaviour on liners, on the structure of slurry pools and mill discharge and on the adverse effect on grinding of increasing mill speed.

Screening of bacterial and fungal strains for cellulase and xylanase production using distillers’ dried grains with solubles (DDGS) as the main feedstock

Bioenergy is one of the most promising solutions for the environmental problems of using non-renewable energy resources. Bioethanol is a form of bioenergy produced from food crops, such as corn, wheat, and sugarcane. Distillers’ dried grains with solubles (DDGS) is the by-product of corn and wheat ethanol production in the dry mill process and has a high nutritional profile. The undigested carbohydrate components in DDGS and proteins can be utilized as the feedstock to produce microbial cellulases and xylanases as the value-added products. Currently, several bacterial and fungal strains are used to produce such enzymes by using expensive feedstocks for commercial preparations. In this study, several bacterial and fungal strains have been evaluated to explore the potential of hydrolyzed DDGS as the main feedstock for these hydrolytic enzymes production. Maximum cellulase production of 0.592 IU/ml was observed for Aspergillus niger (NRRL 1956) on the eighteenth day and stable high production of xylanase of 34.8 IU/ml was obtained for Aspergillus niger (NRRL 567) on day twelfth during shake-flask fermentation. Hydrolytic enzyme production by Bacillus subtilis (NRRL NSR352, DSM 17766, and NF1) was relatively lower (0–0.261 IU/ml for cellulase and 1.2–5.2 IU/ml for xylanase) than the fungal enzyme production. In conclusion, this study demonstrated that hydrolyzed DDGS can be an alternative economical substrate for A. niger strains to produce cellulase and xylanase, respectively. The next phases of the study should further optimize the production of cellulase and xylanase in terms of growth parameters and medium components by using bench-top bioreactors.

THE CONVERSION OF THE MOISTURE-STABILITY WASTE-PAPERS WITH POLYMERIC COVERING. 1. BREAK-ING-UP OF THE WASTE-PAPER

Breaking-up of waste-paper with polyurethan and polyaziridin was studied. Paper moisture-stability is 49–51%. The waste paper reduced to the degree size of the particles 5–8 mm in the dry grind mill and chemical processing under higher temperature (to 70 °C) by sodium persulfate and hydroxide solution; duty of water 6. Cooking duration varied from 1 to 5 hours, solution strength of persulfate sodium – from 2 to 12%, hydroxide sodium – from 0.5 to 3% from the mass of bone-dry waste-paper. The secondary fiber received by breaking-up of the pulp in the hydropulper. The dependency degree of breaking-up, losses of the cellulose and liquor pH from the cooking variable factors approximated by the regression equations of the second order, which used for graphic presentation results. At the most importance of the all variable factors the cooks ended in the acid medium with pH 3 under practically full persulfate and hydroxide sodium consumption; at that the degree of the breaking-up more than 80% was reached, losses of the cellulose under the all conditions remained within the range of 12.6–14.6%. The necessary operations of the breaking-up: crush the dry waste-paper; the cooking of the waste-paper with sodium persulfate and hydrate; breaking-ap of the waste-paper in the hydropulper; washing the stringy mass by water; the hydrodynamic milling.

Dry and Wet Ball Mill Syntheses of Sb2Se3 from Its Constituent Elements

Binary antimony selenide (Sb2Se3) compound was synthesized by the mechanical alloying of constituent elements. Both dry and wet mill syntheses methods were applied. Dry milling was done in Ar atmosphere. Wet milling was done using toluene and n-butyl alcohol as a process control agent (PCA). It was found that Sb2Se3 phase was formed using toluene as PCA, whereas usage of n-butyl alcohol led to the formation of mixed phases consisting of Sb2Se3 and unreacted antimony and selenium. Single phase Sb2Se3 was obtained in 6 h and 13 h, respectively, through dry and wet milling, which was confirmed by x-ray diffraction (XRD) and Raman spectroscopy studies. Diffused reflectance spectroscopy studies of as-milled Sb2Se3 yielded direct band gap values of 1.10 eV and 1.18 eV for dry and wet milled samples, respectively. Particle-induced x-ray emission studies revealed that there is no impurity present in the compound and confirmed near stoichiometry. High-resolution transmission electron microscopy observations showed d spacing values of 0.28 nm for dry and toluene milled samples that corresponds to the (221) plane. The milled Sb2Se3 was used as source material and thin films were grown using the e-beam evaporation method. The as-grown films were characterized using XRD, Raman spectroscopy that showed a single phase nature of the films and optical transmission spectra analysis yielding a band gap of 1.29 eV. Electrical resistivity of the films was measured using a two probe method showing a resistivity of 1.6 × 107 Ω cm. Hot point probe measurement indicated that the as-grown Sb2Se3 films are p-type in nature.

Increasing drying efficiency by modifying the design of feed chute of the Gol-e-Gohar pelletizing plant ball mill

Pelletizing plant of the Gol-E-Gohar mining and industrial company consists of a burner, a dry ball mill (6.2 m × 13 m), and an air separator. The ball mill consists of a 2 m-long drying and an 11 m-long grinding chambers. The iron ore concentrate is fed to the drying chamber by a feed chute. It was found that when the feed moisture content increased from 1.3% to 3.5%, the throughput decreased by 12% (35 t/h) indicating a low performance of the dryer. Monitoring the wear rate of flights for a period of 12 months showed that the first 0.8 m (59%) length of the dryer length did not experience any wear. To overcome this problem, various feed chute designs with different geometries were simulated by the KMPCDEM© software. With the aim of arriving at a proper material trajectory, where the total length of the dryer is used, a new feed chute was selected. The simulation results indicated that if the height of the feed chute is increased from 1.60 to 2.26 m and the slope is increased from 45 to 48 degrees the material arrives at the first 0.48 m of the drying chamber. In this manner, the unused part of the drying chamber decreases from 59% to 36% of the length. After installation of the new feed chute during a period of three months, the throughput increased by 36 t/h.

In situpretreatment during distillation improves corn fiber conversion and ethanol yield in the dry mill process

Thein situpretreatment andin situconversion of corn fiber increased cellulose conversion and the overall ethanol yield.

On the Relationship between Exposure to Particles and Dustiness during Handling of Powders in Industrial Settings

Exposure to ceramic powders, which is frequent during handling operations, is known to cause adverse health effects. Finding proxy parameters to quantify exposure is useful for efficient and timely exposure assessments. Worker exposure during handling of five materials [a silica sand (SI1), three quartzes (Q1, Q2, and Q3), and a kaolin (K1)] with different particle shape (prismatic and platy) and sizes (3.4-120 µm) was assessed. Materials handling was simulated using a dry pendular mill under two different energy settings (low and high). Three repetitions of two kilos of material were carried out per material and energy conditions with a flow rate of 8-11 kg h-1. The performance of the dustiness index as a predictor of worker exposure was evaluated correlating material's dustiness indexes (with rotating drum and continuous drop) with exposure concentrations. Significant impacts on worker exposure in terms of inhalable and respirable mass fractions were detected for all materials. Mean inhalable mass concentrations during background were always lower than 40 µg m-3 whereas during material handling under high energy settings mean concentrations were 187, 373, 243, 156, and 430 µg m-3 for SI1, Q1, Q2, Q3, and K1, respectively. Impacts were not significant with regard to particle number concentration: background particle number concentrations ranged between 10 620 and 46 421 cm-3 while during handling under high energy settings they were 20 880 - 40 498 cm-3. Mean lung deposited surface area during background ranged between 27 and 101 μm2 cm-3 whereas it ranged between 22 and 42 μm2 cm-3 during materials handling. TEM images evidenced the presence of nanoparticles (≤100 nm) in the form of aggregates (300 nm-1 µm) in the worker area, and a slight reduction on mean particle size during handling was detected. Dustiness and exposure concentrations showed a high degree of correlation (R2 = 0.77-0.97) for the materials and operating conditions assessed, suggesting that dustiness could be considered a relevant predictor for workplace exposure. Nevertheless, the relationship between dustiness and exposure is complex and should be assessed for each process, taking into account not only material behaviour but also energy settings and workplace characteristics.

Surface property variations in flotation performance of calcite particles under different grinding patterns

Based on the working principles of particle bed comminution, particles produced by high-pressure grinding rolls (HPGR) have surface properties different from particles produced by other grinding patterns, which exert great influence on mineral flotation. Flotation performances of calcite particles under different grinding patterns involving the use of HPGR, a jaw crusher, a dry ball mill, a wet ball mill, and a wet rod mill were studied using single mineral flotation tests. The surface properties of the particles under different grinding patterns were characterized to determine the flotation performance variation in terms of specific surface area, particle size distribution, AFM, XPS, and zeta potential. The results show that particles ground by HPGR exhibited improved flotation performance within the lower range of grinding fineness in both NaOL and dodecyl amine flotation systems compared to the particles prepared using other grinding patterns. Specific surface area, particle size distribution, surface roughness, Fe(III) contamination, binding energy, and zeta potential are greatly influenced by grinding patterns, which is the main cause of the flotation performance variation.

INTRODUKSI PROSES PENGOLAHAN PANGAN BERBASIS TANAMAN HORTIKULTURA UNTUK PEMBERDAYAAN MASYARAKAT DESA WUNUT KABUPATEN KLATEN

Wunut Village is located in Tulung Sub-District, Klaten Regency which has the horticultural potential such as tomato and chili. But the huge potential has not been able to lift the economy of the village community. Therefore the community devotion team of Department of Food Science and Technology, Faculty of Agriculture, Sebelas Maret University chose Wunut Village as the target village. The problems faced by farming communities in Wunut Village are (1) production of chili and tomatoes are abundant, but the selling price is relatively low; (2) the large number of poor people; (3) lack of knowledge and community insight about entrepreneurship in the field of food; (4) interest in entrepreneurship is still lacking in society; And (5) the difficulty of marketing the resulting product. The solutions offered by the community devotion team are through training activities and the introduction of tomato processing technology into “torakur”; Training and introduction of production process technology of shredded pepper; Entrepreneurship training and food industry management; Information technology-based marketing training and direct selling strategies. In order to support these activities, aids were also provided to improve the quality of the chakra and the resulting chili pepper. Equipment provided in the form of cabinet dryer, dry mill, and packer sealer. The result of this activity in the form of introduction of tomato processing technology into “torakur”, and processing of chili into shredded chili has been done well, with products that can be accepted by society and have a big prospect to be developed.<br />Keywords:entreprenuership, quality, torakur, shredded chili, Wunut Village

Phytochemical analysis and acaricidal activity of Aloe arborescens Mill. extracts against Rhipicephalus (Boophilus) microplus

The indiscriminate use of chemical acaricides has allowed Rhipicephalus (Boophilus) microplus to develop resistance to several active principles. However, botanical extracts have been tested as an alternative method to control those ticks. This experiment studied the chemical fingerprint and acaricidal effect of fresh and dry Aloe arborescens Mill. extracts on R. (B.) microplus. The acaricidal activity of extracts was assessed using in vitro assays with engorged females, and phytochemical characterization was performed by infrared (IR) spectroscopy and high-performance liquid chromatography (HPLC). The results showed that fresh and dry A. arborescens extracts prepared with the solvents pure ethanol, ethanol-dichloromethane binary mixture, and ethanol-dichloromethane-acetone ternary mixture, contained water-soluble tannins and had a strong effect on the reproductive parameters of R. (B.) microplus demonstrated by a marked decreased in the number of eggs laid and in the larvae hatching rate (p < 0.05, p < 0.01, p < 0.001). In conclusion, A. arborescens Mill. has components with acaricidal activity against R. (B.) microplus, and phytotherapy with extracts of this plant may be used as an alternative method of R. (B.) microplus control.

Processing of Moringa leaves as natural source of nutrients by optimization of drying and grinding mechanism

AbstractIn this study, Moringa leaves were processed in two steps (1) drying and (2) grinding. In the first step, leaves were dried with different drying treatments including conventional, laboratory and advanced methods to optimize drying conditions in terms of maximum nutrients preservation and color quality. During the second step, leaves were ground with three different grinding mills including hammer, dry, and cutter mills to study the effect of grinding mechanism in combination with particles size and moisture content on the flowability of the powder. The flowability was measured using conventional and advanced methods including Carr Index and Cohesion Index. Oven drying at 50 °C was found to be the optimum conditions in terms of maximum nutrients and color preservation of Moringa leaves. The grinding mechanism having a substantial impact on the flowability of the powder produced in different types of mills. The effect of moisture content and particle size on Moringa leaves powder was also investigated and found that moisture content directly affects the flowability of Moringa leaves powder followed by particles size and shape. We have also noted powder sample prepared by the impact mechanism (hammer mill) with particle size 50 µm and moisture content 5% having appreciable flowability as compared to the samples processed by cutting (dry mill) and shattering (cutter mill) mechanisms. This study conveys an ultimate understanding regarding processing (drying and grinding) of Moringa leaves powder.Practical ApplicationsDried Moringa is restricted to use as dietary purposes because of its unpleasant taste, which becomes further bitter after drying procedure. Therefore, powder of Moringa leaves can be processed into different forms such as tablet, capsules and cereal formulations. For this purpose, a comprehensive study has been carried out to increase the understanding of drying and flow characteristics of Moringa (leaves and powder) using different drying and grinding mechanisms. The findings of this study regarding drying treatments, nutrients preservation, flowability and different grinding mechanisms can also be applied to other herbs and leaves. A correlation between Carr Index and Cohesion Index established successfully. This study will be helpful to conduct further research in food processing because Carr Index is simple and easy to measure as compared to Cohesion Index that requires both texture and powder flow analyzers.

The efficiency of copper ore comminution: A thermodynamic exergy analysis

This study analyzes the exergy efficiency of comminution using a laboratory sized dry ball mill and a copper mineral ore from central Chile. In this research, we develop a minimum work index from uniaxial compression tests results on the ore fitted to Morrell’s comminution energy equation using Hukki’s constant mineral parameter. An exergy analysis is then performed on a laboratory sized dry ball mill by considering the surface energy variation for different ore sizes, the obtained Hukki-Morrell fitted relationship from the compression tests of the ore and the minimum inertial energy required during a dry-ball milling process. The theoretical minimum work needed to crush the rock is first calculated by comparing the difference in surface energy between the incoming ore and the outgoing crushed rock. However, this analysis (based on the creation of new surfaces) suggests an impractical low minimum work of little use as a benchmark. Instead, use of the Hukki-Morrell relationship evaluated at the resulting ore particle sizes suggests a practical benchmark. Using this benchmark for the laboratory’s dry ball mill process renders an efficiency of approximately 3%. One could use the heat from the outgoing crushed ore to, theoretically perform work, but the heat flows through at a low temperature that this change would only increase the efficiency to 3.1%. We also consider the inertial energy needed to drive the ball mill employing it as a new benchmark for our efficiency calculation. The latter raises the efficiency of the dry ball milling to an average 23%. Finally, electrical energy measurements and inertial calculations on operating an empty versus loaded ball mill suggest that the efficiency could be increased by ensuring correct machinery scaling (diameter of the drum shell), ball load and a properly maintained transmission system.

P-57 乾式粉砕機タンデムリングミルおよび湿式粉砕機マイクロスによる粉砕物の特性比較 リグニン分解酵素ラッカーゼによるリグニン分解が糖化に及ぼす影響

P-57 乾式粉砕機タンデムリングミルおよび湿式粉砕機マイクロスによる粉砕物の特性比較 リグニン分解酵素ラッカーゼによるリグニン分解が糖化に及ぼす影響

横型乾式ビーズミルを用いた微粉砕および所要動力と粒子径の関係

Dry bead mills are believed to contribute significantly to the shortening of drying processes and reduction of required production space, as well as the energy costs reductions that result from these improvements. In this study, we used a dry bead mill to perform grinding test on silica sand, alumina, and activated carbon. We investigated the impact various dry bead mill conditions had on grinding, and explored the dry grinding potential of bead mills. We found a regular relationship between the median diameter and the power, and that this tended to match previous reports. We also demonstrated that within the scope of this experiment, tip speed, bead filling, and the feed rate were not factors that affected the energy efficiency.

Laboratory Characterization of Cemented Tailings Paste Containing Crushed Waste Rocks for Improved Compressive Strength Development

This paper aims at investigating some physical and mechanical characteristics of cemented tailings paste incorporating different amounts of crushed waste rocks (hereinafter called paste aggregate fill, PAF) for underground stope filling. Different mixture formulations were prepared with three classes of crushed waste rocks (or aggregate) grain size, namely 0/10, 0/15 and 0/20 mm. The amount of crushed waste rocks in the PAF mixtures ranges from 10 to 50% by volume (% v/v) (or 8–45% by mass, %m) of dry mill tailings and crushed waste rocks. The results show that the addition of crushed waste rocks in cemented tailings paste mixtures allows a significant unconfined compressive strength (UCS) development after 28 and 90 days of curing. The highest UCS was obtained from the mixtures containing 50% v/v of crushed waste rocks of class of size 0/15 mm. The PAF mixtures with the coarser crushed waste rocks (class of size of 0/20 mm) exhibit some particles segregation.

Optimization of Particle Size and Specific Surface Area of Pellet Feed in Dry Ball Mill using Central Composite Design

Objective: The dimensional properties of iron ore pellet feed including specific surface area and particle size distribution in the ball mill was studied using response surface area method. Methods/Statistical analysis: The effect of the operational parameters of dry ball mill including ball charge (20-40%), grinding time (30-50 min) and balling distribution (Small, Mixed and Large) on dimensional properties of pellet feed was meticulously examined and optimized using response surface methodology based on Central Composite Design (CCD). Responses were 80% passing size (D80) and Blaine (BL). A total of 30 grinding experiments were designed and carried out in the CCD method. Regression models and response surfaces were obtained for each response. Findings: The results predicted by these models showed good agreement with experimental values. In the studied range it was deduced that D80 is decreased and BL increased when grinding time and ball charge increased. Also, the production of fine particles improved using balling distribution of level B (mix balls), instead of one ball size distribution. 3D graphs were applied to visually evaluate each parameter effect on responses. The optimum conditions of ball mill operational parameters to reach the best pellet feed for each blast furnace burden and direct reduction iron (DRI) pellet feed were revealed using CCD optimization. The predicted values BL and D80 were found to be in a reasonable agreement with the experimental values, with R2 as correlation factor being 0.91 and 0.92 for BL and D80, respectively. Improvements: The optimum condition for having a suitable blast furnace burden was: Ball distribution level B, Ball charge= 21.8-22.4 %, Grinding time= 40.1-42.9 min. Also, the optimal condition for DRI pellet feed preparation was: Ball distribution level B, Ball charge= 21.8-22.1 %, Grinding time= 42.1-44.6 min.

Integrated biovalorization of wine and olive mill by-products to produce enzymes of industrial interest and soil amendments

An integral and affordable strategy for the simultaneous production of lignin-modifying and carbohydrate active enzymes and organic amendment, with the aid of a saprobe fungus was developed by using olive oil and wine extraction by-products. The polyporal fungus Trametes versicolor was cultivated in soy or barley media supplemented with dry olive mill residue (DOR) as well as with grape pomace and stalks (GPS) in solid state fermentation (SSF). This strategy led to a 4-fold increase in the activity of laccase, the principal enzyme produced by SFF, in DOR-soy media as compared to controls. T. versicolor managed to secrete lignin-modifying enzymes in GPS, although no stimulative effect was observed. GPS-barley media turned out to be the appropriate medium to elicit most of the carbohydrate active enzymes. The reuse of exhausted solid by-products as amendments after fermentation was also investigated. The water soluble compound polymerization profile of fermented residues was found to correlate with the effect of phytotoxic depletion. The incubation of DOR and GPS with T. versicolor not only reduced its phytotoxicity but also stimulated the plant growth. This study provides a basis for understanding the stimulation and repression of two groups of enzymes of industrial interest in the presence of different carbon and nitrogen sources from by-products, possible enzyme recovery and the final reuse as soil amendments.

Evaluating composting and co-composting kinetics of various agro-industrial wastes

Agro-industrial wastes are posing serious challenges for the agro-industries. Composting and co-composting of such wastes will lead to converting such wastes into a useful product that will serve as a soil conditioner. The present research investigated the kinetics of composting and co-composting of several agro-industrial wastes. Seven pilot scale composting and co-composting piles of substrates from grain dust (GD), coffee-processing waste (CPW) and olive mill waste (OMW) were tested. Temperature and moisture content of the piles were monitored during the composting process and adjusted whenever necessary. The biodegradation kinetics was found to be of first order for all composting and co-composting piles. As judged by the value of the reaction rate constant, and the temperature of the piles, the biodegradability of the grain dust was the highest among all composting piles, followed by the coffee-processing residue and finally the fresh olive mill waste. As for the co-composting, the highest degradability was noticed in the pile that was composed of grain dust and coffee-processing waste followed by that of grain dust mixed with dry olive mill waste, and then followed by coffee-processing waste and dry olive mill waste and finally by grain dust with fresh olive-processing waste. Composting and co-composting of agro-industrial wastes is a low cost and an environmentally friendly waste management option for solving the problem of the disposal of such waste. The study revealed that all piles followed first-order kinetics with different biodegradability rates.

Life Cycle Performance of Cellulosic Ethanol and Corn Ethanol from a Retrofitted Dry Mill Corn Ethanol Plant

This study conducts a life cycle assessment of a simulated dry mill corn ethanol facility in California’s Central Valley retrofitted to also produce ethanol from corn stover, a cellulosic feedstock. The assessment examines three facility designs, all producing corn ethanol and wet distiller’s grains and solubles as a co-product: a baseline facility with no cellulosic retrofit, a facility retrofitted with a small capacity for stover feedstock, and a facility retrofitted for a large capacity of stover feedstock. Corn grain is supplied by rail from the Midwest, while stover is sourced from in-state farms and delivered by truck. Two stover feedstock supply scenarios are considered, testing harvest rates at 25 or 40 % of stover mass. Allocation is required to separate impacts attributable to co-products. Additional scenarios are explored to assess the effect of co-product allocation methods on life cycle assessment results for the two fuel products, corn ethanol and stover ethanol. The assessment tracks greenhouse gas (GHG) emissions, energy consumption, criteria air pollutants, and direct water consumption. The GHG intensity of corn ethanol produced from the three facility designs range between 61.3 and 68.9 g CO2e/MJ, which includes 19.8 g CO2e/MJ from indirect land use change for Midwestern corn grain. The GHG intensity of cellulosic ethanol varies from 44.1 to 109.2 g CO2e/MJ, and 14.6 to 32.1 g CO2e/MJ in the low and high stover capacity cases, respectively. Total energy input ranges between 0.60 and 0.71 MJ/MJ for corn ethanol and 0.13 to 2.29 MJ/MJ for stover ethanol. This variability is the result of the stover supply scenarios (a function of harvest rate) and co-product allocation decisions.