Production Of Fines Research Articles

Shreddability of pizza Mozzarella cheese predicted using physicochemical properties

This study used rheological techniques such as uniaxial compression, wire cutting, and dynamic oscillatory shear to probe the physical properties of pizza Mozzarella cheeses. Predictive models were built using compositional and textural descriptors to predict cheese shreddability. Experimental cheeses were made using milk with (0.25% wt/wt) or without denatured whey protein and renneted at pH 6.5 or 6.4. The cheeses were aged for 8, 22, or 36d and then tested at 4, 13, or 22°C for textural attributes using 11descriptors. Adding denatured whey protein and reducing the milk renneting pH strongly affected cheese mechanical properties, but these effects were usually dependent on testing temperature. Cheeses were generally weaker as they aged. None of the compositional or rheological descriptors taken alone could predict the shredding behavior of the cheeses. Using the stepwise method, an objective selection of a few (<4) relevant descriptors made it possible to predict the production of fines (R2=0.82), the percentage of long shreds (R2=0.67), and to a lesser degree, the adhesion of cheese to the shredding blade (R2=0.45). The principal component analysis markedly contrasted the adhesion of cheese to the shredding blade with other shredding properties such as the production of fines or long shreds. The predictive models and principal component analysis can help manufacturers select relevant descriptors for the development of cheese with optimal mechanical behavior under shredding conditions.

An Analysis of the Slow Compression Breakage of Coal Using Microfocus X-Ray Computed Tomography

The degradation of coal and the production of coal fines during handling and transport is a serious problem in processes that depend on closely sized large particles. To minimize the production of fines, a fundamental understanding of coal breakage is required, so, to clarify the complex nature of coal breakage, a series of experiments was conducted to determine the influence of the internal physical coal structures on compression breakage characteristics. The structures investigated are the cleat and layered structure of coal and the mineral inclusions. Samples of uniform size and shape were prepared from a large block of South African Waterberg coal. The samples were analyzed nondestructively using microfocus x-ray computed tomography then wrapped in cling film and mechanically compressed while the pressure applied was measured. The virtual three-dimensional volume tomograms of the initial sample and the progeny were compared and the changes qualitatively analyzed. Conclusions were drawn as to where the fatal cracks initialized and how the cracks propagated. Particle-size distributions were done to quantify the extent of breakage versus the breakage strength of the sample. It was found that, of all the internal structures, the inherent crack distribution has the biggest influence on breakage and breakage patterns of coal.

Testing the influence of high-voltage mineral liberation on grain size, shape and yield, and on fission track and 40Ar/39Ar dating

Mineral liberation and separation are fundamental for modern thermochronology. The fragmentation of rocks by high-voltage electrical pulses, called electrical fragmentation, is a new technology, only available since the development of a lab-sized machine a few years ago. The proposed advantages (e.g. disintegration along grain boundaries) compete with suspected negative effects of the locally occurring high temperatures (up to 104K) on the physical properties of the liberated minerals. Comparison of electrical fragmentation with conventional mechanical fragmentation (jaw crusher) revealed similar amounts of liberated apatite and zircon from the same quantity of granite, but 45% production of fines (<80μm) for mechanical fragmentation versus 5% for electrical fragmentation. Electrical fragmentation yielded larger-sized apatite grains (180–250μm) compared to 80–125μm for mechanical liberation, but no differences in shape factors (elongation, roundness, compactness). The liberation of idiomorphic crystals from coarse-grained rocks is ameliorated by the new method, as shown by the liberation of mm-sized idiomorphic biotite crystals from granite. Degassing curves of 40Ar from electrically and mechanically liberated biotites from the same sample are nearly identical (maximum difference: six percentage points); 40Ar/39Ar ages of biotites from three samples (two mechanically, one electrically fragmented) from the same intrusion are identical within 2σ error. Length measurements of apatite fission tracks gave identical results within 2σ error regardless of fragmentation method used. In summary, the positive aspects of electrical fragmentation have been confirmed in this study, while effects negative for thermochronology are not observed.

Effects of slurry pool volume on milling efficiency

In wet milling, the presence of a pool of slurry is generally the result of mill overfill. The effects of overfilling on milling kinetics have been examined. Assessment of milling efficiency has also been made.To this end, batch grinding tests were carried out at 75% of critical speed. A laboratory mill, filled with 20mm balls, was used for the tests. Two levels of ball volumetric filling were considered: J=20 and 30%. Slurry filling U was varied from 1.5 to 3.0 with reference to 20% ball filling. Equal masses of slurry were also used for a 30% ball filling which made slurry filling U change accordingly. Net power draw was measured throughout the experimentation.It was found that product size distribution is a definite function of slurry filling U. Graphical analysis of the results suggests that the voids within the media charge should be completely filled with slurry without allowing the formation of the pool. This way, optimal output shall be expected. Moreover, mill power drop due to slurry pooling did not result in a proportional decrease in the production of fines.

An Experimental Study on Characterizing Coal Bed Methane (CBM) Fines Production and Migration of Mineral Matter in Coal Beds

Drilling through coal beds and high initial fluid production rates can lead to shear and compressive failure of coal, resulting in the creation of coal fines. In overbalanced drilling, these fines mix with the drilling fluid and are carried into the near-wellbore zone. During initial water production, the fines are transported to the producing wellbore through the coal beds. Both transport processes result in blocked cleats and pores in the near-wellbore, high-pressure drop zone, reducing permeability and lowering production rates of gas and water. Excessive fines production will also lead to excessive wear and plugging of equipment. The objective of this study was to characterize a set of coal fines from a coal bed methane (CBM) field, with the aim of understanding their origin and character toward their effective management in the field. This study focused on fines originating from horizontal and vertical wells drilled in the Moranbah CBM field in Queensland, Australia, where the horizontal drilling process was suspected of creating excessive fines. We divided this study into two parts; in the first, we prepared fines from four different coal cores sourced from a nearby vertical well and characterized them. In the second, field fines collected over time from vertical wells connected to horizontal wells were characterized, with a novel technique called comparative quantitative X-ray diffraction (CQ-XRD) to establish organic-to-mineral ratios. We also report on key differences in CQ-XRD-derived mineralogy between field fines and core-derived lab fines; changes to particle size and helium-derived density over time; petrography and proximate ash yield of the four cores; and comparisons in water properties of field formation water with lab leachate water.

Effects of ultrasonic pretreatment on quantity and composition of bacterial DNA recovered from granular activated carbon used for drinking water treatment

Effects of ultrasonic pretreatment on bacterial DNA recovery from granular activated carbon (GAC) were investigated. GAC (Calgon F400), biologically activated, was sampled from an actual drinking water plant. Different ultrasonic energy densities (0–400 J·cm−3) were applied with agitation (250 rpm for 30 min), and recovered bacterial DNA was quantified using quantitative PCR. Energy density was linearly correlated with the concentration of carbon fines produced from GAC during ultrasonication. Ultrasonication alone had no effect on DNA recovery at ≤60 J·cm−3, but a strongly adverse effect at >67 J·cm−3 due to the produced carbon fines. Agitation along with ultrasonication strongly enhanced the bacterial DNA recovery when ≤40 J·cm−3 was applied, although it did not affect the production of carbon fines. Ribosomal tag pyrosequencing was used to compare recovered bacterial communities (0, 20 and 30 J·cm−3 with or without agitation). Ultrasonication allowed for obtaining a more diverse and richer bacterial community from GAC, compared with the control. Agitation did not show a positive effect on community organization (richness and diversity). Consistently, canonical correspondence analysis indicated that the energy density was associated with the relative abundances of particular bacterial members (P < 0.05), while agitation did not. Correspondence analysis revealed that the recovered bacterial communities were grouped according to the applied energy densities. In conclusion, ultrasonication and agitation influence the recovered DNA in quality and quantity, respectively, and carbon fines as a by-product by ultrasonication interfere with the DNA recovery.

Operation with Combined Oxides of Manganese and Silica as Oxygen Carriers in a 300 Wth Chemical-looping Combustion Unit

Chemical-looping combustion is a carbon capture technology which has received increased attention during the last years. The technology is based on fuel oxidation with oxygen provided by solid oxygen carrier particles. In this study two such oxygen carrier materials have been examined in a continuously circulating chemical-looping reactor system designed for a thermal power of 300W. The two materials consisted of manganese and silica oxides, with an addition of titania in one of them. The oxygen carrier particles were produced by spray drying, followed by calcination and sintering. Both materials released gas phase oxygen in inert atmosphere at 800-950°C, with the highest concentration at 1.8% observed at 850°C. The oxygen carrier consisting of only manganese and silica gave the highest fuel conversion for both syngas and natural gas. Full fuel conversion was achieved at 950°C for syngas and at 900°C for natural gas with this oxygen carrier material. The fuel conversion increased with temperature for both materials. The material consisting of only manganese and silica suffered from severe attrition and could only be operated for seven hours with fuel. The addition of titania increased the mechanical stability of the particles considerably, and this material was operated for 24h with fuel. No large production of fines was observed with this material. Combined oxides of manganese and silica are shown to be promising as oxygen carriers for chemical- looping. The mechanical stability can be increased by adding titanium to the MnSi material. The composition would however need to be further examined to optimize the performance of the oxygen carrier.

Analysis of ball mill grinding operation using mill power specific kinetic parameters

With a view to developing a sound basis for the design and scale-up of ball mills, a large amount of data available in the literature were analyzed for variation of the two key mill performance parameters: power specific values of the ‘absolute breakage rate of the coarsest size fraction’, S*, and ‘absolute rate of production of fines’, F*, with some of the important operating and design variables such as the mill speed, ball load, particle load, ball diameter and mill diameter. In general, values of both the mill performance parameters were found to vary significantly with the mill operating conditions. The nature and relative magnitude of variation for the two parameters also differed significantly. Moreover, the effect of any particular variable on the S* and F* values was found to be significantly different for different sets of operating conditions. It has been emphasized that, as the purpose of grinding is to produce fine particles, the mill design and scale-up work should be based mainly on the F* parameters. Moreover, it is not correct to regard the S* values to be independent of the mill design and operating variables as a general rule, especially for a fine analysis of the performance of the grinding systems.

Introduction to the use of the attainable region method in determining the optimal residence time of a ball mill

The application of the attainable region (AR) technique to the analysis of ball milling is currently limited to batch data. This paper introduces the use of the technique in continuous milling.To this end, a platinum-bearing ore (less than 850μm in size) was used and its breakage characteristics were measured by means of standard batch milling tests. The breakage parameters were scaled up to an industrial mill. This enabled the extension of the AR methodology to full-scale milling. However, the analysis was limited to two simple transport models: plug-flow and well-mixed mills without exit classification. Following this, the importance of controlling the residence time of the mill optimally was appreciated.Initial findings showed that milling conditions should be tailored to the desired product size requirements. The lower and upper limits in which the maximum production of fines should lie were also identified. Finally, mill speed was found to be pivotal in controlling the retention time of particles inside the mill.

Experimental micro-mechanics of granular media studied by x-ray tomography: recent results and challenges

Combining x-ray tomography and three-dimensional (3D) image analysis has finally opened the way for experimental micro-(geo)mechanics, allowing access to different scales of interest. When these correspond to a scale that has been imaged at high spatial resolution, high-quality measurements can be obtained (e.g. 3D displacements and rotations of individual grains of sand sample under load). However, there are issues when the scale of interest is smaller, for example the characterisation of grain-to-grain contacts (their orientations and evolution) or production of fines by grain breakage. This paper presents a short selection of new grain-scale measurements obtained using existing techniques. The challenges associated with smaller scale measurements on the same images are also discussed through a few examples from ongoing work.

Physical properties of pizza Mozzarella cheese manufactured under different cheese-making conditions

The effect of manufacturing factors on the shreddability and meltability of pizza Mozzarella cheese was studied. Four experimental cheeses were produced with 2 concentrations of denatured whey protein added to milk (0 or 0.25%) and 2 renneting pH values (6.4 or 6.5). The cheeses were aged 8, 22, or 36d before testing. Shreddability was assessed by the presence of fines, size of the shreds, and adhesion to the blade after shredding at 4, 13, or 22°C. A semi-empirical method was developed to measure the matting behavior of shreds by simulating industrial bulk packaging. Rheological measurements were performed on cheeses with and without a premelting treatment to assess melt and postmelt cheese physical properties. Lowering the pH of milk at renneting and aging the cheeses generally decreased the fines production during shredding. Adding whey protein to the cheeses also altered the fines production, but the effect varied depending on the renneting and aging conditions. The shred size distribution, adhesion to the blade, and matting behavior of the cheeses were adversely affected by increased temperature at shredding. The melting profiles obtained by rheological measurements showed that better meltability can be achieved by lowering the pH of milk at renneting or aging the cheese. The premelted cheeses were found to be softer at low temperatures (<40°C) and harder at high temperatures (>50°C) compared with the cheeses that had not undergone the premelting treatment. Understanding and controlling milk standardization, curd acidification, and cheese aging are essential for the production of Mozzarella cheese with desirable shreddability and meltability.

Size-Exclusion Colloidal Transport in Porous Media--Stochastic Modeling and Experimental Study

Suspension, colloidal, and emulsion flow in rocks with particle size-exclusion may have a strong effect on the reservoir and on the well behavior during fines migration and production, drilling-fluid invasion into oil- or gas-bearing formations, or injection of seawater or produced water. The stochastic microscale equations for size-exclusion colloidal transport in porous media (PM) are derived. The proposed model includes the following new features: It accounts for the accessible flux in the expression for capture rate, it accounts for the increase of inlet concentration caused by the injected particles entering only the accessible area, and it accounts for the dilution of effluent accessible flux in the overall flux of the produced suspension.

Mechanically Induced Fracture-Face Skin—Insights From Laboratory Testing and Modeling Approaches

Summary In the context of this work, a new formation-damage mechanism is proposed—the mechanically induced fracture-face skin (FFS). This new mechanism results from mechanical interactions between the proppants and the reservoir rock caused by the increasing stress on the rock/proppant system during production. Proppant embedment into the fracture face and proppant crushing lead to fines production and may impair the fracture performance. To achieve sustainable, long-term productivity from a reservoir, it is indispensable to understand the hydraulic and mechanical interactions in rock/proppant systems. In this study, permeability measurements on sandstones with propped fractures under stress using various flow cells were performed, allowing localization and quantification of the mechanical damage at the fracture face. The laboratory experiments identified a permeability reduction at the fracture face of up to 90%. The mechanical damage at the rock/proppant interface began immediately with loading of the rock/proppant system and for fracture-closure stresses less than 35 MPa; the damage was localized at the fracture face. Microstructure analysis identified quartz-grain crushing, fines production, and pore-space blocking at the fracture face, causing the observed mechanically induced FFS. At higher stresses, damage and embedment of the ceramic proppants reduce the fracture permeability further. Numerical modeling of the rock/proppant system identified highly inhomogeneous stress distributions in the granular system of grains and proppants. High tensile-stress concentrations beneath the area of contact between quartz grains and proppants were observed, even at small differential stress applied to the rock/proppant system. These high-stress concentrations were responsible for the early onset of damage at the fracture face. Therefore, even low differential stresses, which are expected under in-situ conditions, may affect the productivity of a hydraulically fractured well.

Effect of Seeding on Metal Ion Recovery from Wastewater by Reactive Crystallization of Metal Carbonates

AbstractReactive crystallization for separation and recovery of divalent metal ions from wastewater using a semi‐batch crystallizer has been developed. In this process, metal carbonates are produced by reacting metal sulfate solution with sodium carbonate solution. Nickel and copper ions are crystallized under particular initial pH conditions but the product shapes are not regular. Consequently, sphere seeds have been used as nucleus‐generating agents and their growth mechanism has been examined. When providing a particular amount of seeds before crystallization, metal substances piled up on the surface of the seeds, maintaining the form sphere, and the production of fines was restricted. The metal removal rate through reactive crystallization was ∼99.9 % on average. This operation proved to be suitable for application in industrial wastewater treatment and for recycling of metal materials.

Skin Due to Fines Mobilization, Migration, and Straining During Steady-State Oil Production

Permeability decline during core floods with high rates has been widely reported in the literature. It has often been explained by the lifting, migration, and subsequent plugging of pores by fine particles, which has been observed in numerous core flood tests. The phenomena have been connected to well productivity impairment during fines production that also has been widely observed in oilfields. The authors derive a formula for skin factor based on the modified particle detachment model with maximum retention function. The mobilized fines capture by the rock is assumed to be instant at the large reservoir scale, so skin factor drops at the beginning of production and remains constant. The fines migration induced skin is shown to increase with increase of rate and initial attached fines concentration.

Environmental factors affecting geotextile filter design in coal refuse impoundments

The US Mine Safety and Health Administration (MSHA) issued the Second Edition of Engineering and Design Manual for Coal Refuse Disposal Facilities prepared by D'Appolonia in 2009. This second edition provides design guidance on the use of nonwoven geotextiles for drainage applications when replacing graded granular filters in coal waste impoundments. Coal refuse is susceptible to slaking that produces an increase in fine particles which may lead to geotextile clogging. This article presents the results of research which investigated the effects of slaking on the hydraulic conductivity of permeated refuse specimens in order to identify parameters influencing the design criterion for selecting candidate nonwoven geotextiles for drainage applications. Permeability tests were performed on refuse–geotextile samples at different compaction energies and varying moisture contents, followed by post-grain size distribution (GSD) tests. Conclusions indicate that (i) the k soil of the acid-permeated refuse samples is one order of magnitude higher than the k soil of the water-permeated refuse samples and was attributed to fine particle aggregation. Any potential increase in the k soil due to continued particle aggregation may approach a failure criterion where the soil permeability is too high. The long-term effects of low-pH groundwater may cause an increase in refuse permeability, leading to criterion failure due to particle aggregation; (ii) comparisons of the coarse coal GSDs for the pre- and post-compacted, water-permeated specimens showed an increase in the production of particle fines due to slaking at critical indices.

Chemical-looping combustion of solid fuels – Operation in a 10 kW unit with two fuels, above-bed and in-bed fuel feed and two oxygen carriers, manganese ore and ilmenite

Chemical-looping combustion (CLC) is a combustion concept with inherent separation of CO2. The process uses a solid oxygen carrier, which consists of metal oxide, to transfer the oxygen from air to fuel. The chemical-looping combustor used in the present experiments features two interconnected fluidized beds; a fuel reactor (FR) and an air reactor (AR). In the FR, fuel is gasified with steam whereupon gasification products react with the oxygen carrier to form, ideally, CO2 and H2O. This study concerns CLC of solid fuels in a continuously operating 10kW unit using two natural ores as oxygen carrier: (a) ilmenite, an iron–titanium mineral and (b) a manganese ore containing smaller amounts of Fe, Al and Si. The fuel feed was re-designed in order to increase contact between oxygen carrier and fuel. The new in-bed fuel feed was found to significantly improve gas conversion, mainly caused by increased contact between the oxygen carrier and volatile gases released in the fuel chute. Two fuels were used to evaluate the effect of fuel feed; a bituminous coal and a pet coke. The in-bed fuel feed was used when ilmenite and manganese ore were compared. The use of a manganese ore as oxygen carrier was shown to significantly enhance the rate of char gasification and also improve gas conversion. A concern with the manganese ore is the large production of fines.

Designing a lactose crystallization process based on dynamic metastable limit

In the dairy industry, lactose crystallization during refining typically generates a large number of fines (<100μm), which greatly reduces the efficiency of downstream processes. To overcome this problem, a strategy to minimize fines production was developed. On lab scale units, lactose crystals were produced from three crystallizers (draft-tube baffled, anchor and paddle) operated with three cooling profiles (at different region inside metastable zone (MSZ)). Computational fluid dynamics was used to simulate the flow profile. Among all combinations investigated, anchor crystallizer (lowest shear) operated at slow cooling rate (in upper MSZ) produces the largest crystals with minimal fines. Then, the design strategy was applied in industrial scale crystallizer. The 13h cooling profile created for operation in the medium MSZ region successfully produced crystals with 28% less fines than the typical process. Therefore, depending on the crystallizer design and operational region (in MSZ), production of fines can be minimized.

EFFECTS OF FINES MIGRATION ON WELL PRODUCTIVITY DURING STEADY STATE PRODUCTION

Well clogging and productivity decline have been widely observed in oil, gas, and artesian wells producing reservoir fines. The phenomenon has been explained by the lifting, migration, and subsequent plugging of the pores by the fine particles, finally resulting in permeability decrease. This has been observed in numerous core flood tests and field cases. In this work, the new basic equations for the detachment of fine particles, their migration, and size exclusion, causing the rock permeability decline, have been derived. The analytical model, developed for the regime of steady-state production with the gradual accumulation of strained particles, exhibits the linear skin factor growth versus the amount of produced reservoir fines. The modeling data are in good agreement with the well production history. The model allows predicting well productivity decline due to fines production based on short-term production data.

Cone milling of compacted flakes: Process parameter selection by adopting the minimal fines approach

Cone mill was well studied for milling of wet agglomerates. This study evaluated the effects of various process parameters of cone milling roller compacted flakes on the granules produced. Impeller sidearm shapes, screen surface profiles and impeller speeds were studied. Impeller speed was found to play a major role in determining the granule attributes. Besides this, median size, size distribution and percent fines of a milled granule population were mainly determined by the size reduction mechanisms of different impellers and screens. Pre-breaking followed by shearing and slicing of flakes inside the milling chamber was primarily responsible for determining the size, size distribution and percent fines of milled granules. The pre-breaking action could be achieved using teethed round sidearm impeller and lowered the need for screen-based size reduction, thus generating less fines. The shearing and slicing of flakes due to the raised impaction edges of the grater screen also helped to minimize the production of fines. Therefore, the lowest percentage of fines was observed when the teethed round sidearm impeller was used with a grater screen. The results indicated that fines can be reduced considerably with the judicious selection of a suitable impeller and screen combination in the cone mill.