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The purpose of this study was to evaluate the feasibility of using highly filled powders as electrostatically applied paper coatings. Powders prepared by two different methods were suitable for electrostatic deposition and they attached to the paper surface with a grounded backing. Pressing at elevated temperatures turned out to be a crucial process step for improving the adhesive and cohesive strengths of the powder coating layer on paper. Limited mechanical interlocking with the base paper and an uneven pressure profile were factors impairing the surface strength of the coated paper. On the other hand, factors such as higher polymer content, higher pressing temperature, pre-heating the paper prior to coating, and increasing the number of hot roll nips increased adhesion between the coating and the base paper. Powder coatings as such had uneven thickness, and they displayed a relatively broad pore size distribution.

Resource utilization of silicon is crucial to the sustainable reuse of the silicon-containing waste residues. In this study, a simple method to synthesize calcium silicate as paper filler with desirable particle size from the residues was proposed. Foil-shaped calcium silicate with the average particle size (APS) of about 10 μm and the span of below 1.2 was successfully synthesized. Compared with larger calcium silicate, the obtained product used as paper filler could greatly improve the bulk of paper while maintaining similar tensile strength. The online focused beam reflectance measurement (FBRM) was used to investigate the hydration of CaO and the formation of calcium silicate. It was found that the hydration of CaO in NaOH solution with the presence of silicate played a key role in synthesizing the 10 μm-sized calcium silicate. The formation of calcium silicate was speculated to be controlled by a liquid-liquid reaction.

In this work, new core-shell pigment based on precipitating a small amount of titanium dioxide on precipitated calcium carbonate (CC) were applied once as filler in paper sheet making and another time was mixed with chitosan as a coat on the papers. The prepared pigments were characterized to confirm their preparation. The mechanical and optical properties of both filled and coated paper sheets and their individual components (TiO 2 and CC) were performed to compare their effect on the paper sheets using SEM, TGA and UV aging.

A hierarchically porous nitrogen, oxygen-rich carbon material is developed by Mg(NO3)2 treatment of filter paper in a one-step pyrolysis. The obtained carbons exhibit high specific surface area (1031 m2 g−1), interconnected micro-, meso-, and macroporous conductive network and attractive heteroatom contents (2.84 at.% nitrogen and 13.82 at.% oxygen). The as-prepared carbon tested as anode for lithium ion batteries displays an excellent reversible capacity (1560 mAh g−1 at 0.1 A g−1), superior rate capability (501 mAh g−1 at 5 A g−1) and desired cycling performance (1538 mAh g−1 at 0.1 A g−1 and 1105 mAh g−1 at 1 A g−1after 100 cycles). Moreover, a full battery with an as-obtained carbon anode and a LiFePO4 cathode delivers a high discharge capacity of 165 mAh g−1 (the theoretical capacity of LiFePO4 was 170 mAh g−1) and good cyclability (156 mAh g−1 after 20 cycles).

The modification of low quality Egyptian kaolinite to be acceptable as a pigment for paper coating was reported in this work. Sedimentation, chemical bleaching, preparation of organo kaolinite and preparation of nano-kaolinite were the modification methods used in this study. The modified pigments were characterized using X-ray fluorescence, an X-ray diffractometer, Fourier-transform infrared spectroscopy and scanning electron microscopy. The original and modified kaolinites were applied in paper coating mixture. The results of XRF analysis showed that Fe 2 O 3 impurities reduced by using sodium dithionite from 0.41 to 0.25 (wt %). XRD data revealed shifting of basal space of kaolinite from 7.14 to 11.8 A with an intercalation ratio of 80% upon grinding with urea for 5 h. Meanwhile, IR spectra showed that NH–CO molecule (refer to urea molecule) exists in the intercalated kaolinite. The characteristic peak of kaolinite completely disappeared during dispersion of kaolinite–urea in paper coating suspension which showed the exfoliation of kaolinite–urea layers through the binder (nano-kaolinite). The SEM images of intercalated kaolinite–urea and exfoliated kaolinite/binder revealed thin flacks with particle size ranging from 500 nm and 300 nm, respectively. Nano-kaolinite caused a significant decrease in coated paper roughness and an increase in optical properties compared with the original and commercial kaolinite. Air permeability of coated paper increased and was better than commercial kaolinite. Although, nano-kaolinite reduced the mechanical properties of coated paper, it produced coated paper having print density and print gloss higher than the ones containing the original and commercial kaolinite.

In the present study, calcium sulphate pigment has been synthesized experimentally from commercial grade calcium chloride. The effect of various factors on the particle size of calcium sulphate formed in a wet process and its potential application as pigment in coating recipe has been investigated. The operating factors investigated include concentration of calcium chloride solution, temperature, addition of different rheology modifiers and their optimization. The particle shape and size distribution of synthesized calcium sulphate pigment have been studied through image analyzer, scanning electron microscope (SEM) and particle size analyzer. Significant improvement was observed in various coated paper properties like brightness, whiteness, gloss, stiffness, surface strength and water retention properties of coating color with respect to conventional ground calcium carbonate (GCC) coating pigment.

This paper is a response to the comment by Roberto Giustetto on our article entitled “Effect of grinding time on fabricating a stable methylene blue/palygorskite hybrid nanocomposite”. We thank Dr. Roberto Giustetto for his interest in our recently published work, and appreciate his comment because it offers us an opportunity to present additional discussions about our work. The relevant discussion about the effect of the grinding factors on the structure and stability of dye/PAL hybrid were further clarified.

To develop the physical properties of paper, it is necessary to prepare the cellulose fibres. This is done in wet mills or refiners. In these machines, the dilute fibre suspension is forced through a gap between two surfaces fitted with bars that move relatively to each other. Their fibre collection efficiency, together with the cyclic stresses, lead to particle breakage (fibre shortening), fibrillation and hydration. In this article, a model for the kinetics of particle breakage is proposed that links the weight-average fibre length to the energy per unit mass consumed by the solid phase and the average impact intensity. The experimental evidence shows the validity of the assumptions and supports this theory of physical comminution. The raw material–mill combination can be optimized and the shortening effect can be predicted under given mill conditions.

The papers presented in the sessions on fluidization and transport phenomena cover a wide range of subjects pertaining to fluid—particle systems. Examples of these subjects include bubble coalescence mechanisms, entrainment, pressure effects and chaos in bubbling and turbulent fluidized beds, wave phenomena and cluster structure in circulating fluidized beds, and spectral and fractal characteristics in gas—liquid—solid fluidized beds. In this summary paper, an overview based on these papers is given and salient results are highlighted.

This paper provides a summary of the Agglomeration and Size Enlargement session of the First International Particle Technology Forum held in Denver, CO, USA, August 17–19, 1994. The conference was sponsored by the recently formed Particle Technology Forum of the American Institute of Chemical Engineers. This first session on agglomeration and size enlargement brought together a cross-section of industries dealing with agglomeration processes. Represented were the areas of mineral processing, consumer products, ceramics, industrial chemicals, agricultural chemicals and fertilizers, biological materials, and pharmaceutical processing. The session focused on agitative granulation techniques including pan, fluidized bed, drum, and mixer granulation as well as compaction processes including tabletting, uniaxial compaction, and roll pressing. Two critical themes running throughout the session were (i) relating particle and formulation properties such as friction, plasticity, interfacial energy, and binder viscosity to bulk agglomeration behavior, and (ii) the incorporation of these relationships into process scale simulations. The aim of this endeavor was to share our different approaches to agglomeration processes and through this sharing achieve a cross-fertilization of ideas. It is hoped that this effort, and similar sessions to follow, will increase our understanding of agglomeration phenomena which can be utilized for the rational design and optimization of size enlargement processes as well as product design. This review paper summarizes the technical papers presented at this session as well as the subsequent discussion which followed (B.J. Ennis (ed.), Proc. 1st Int. Particle Technology Forum, Vol. 1, American Institute of Chemical Engineers, New York, pp. 155–286).

This paper provides a summary of the Control of Particulate Processes III Conference held January 24–29, 1993, in Santa Barbara, CA, USA. It is the third in a series of such conferences held by the Engineering Foundation. The purposes and goals behind the conference are highlighted, and the major points as well as unresolved challenges of the presentations are summarized. Despite the economic impact, insufficient attention is often paid to the difficulties associated with the processing of particles. It is clear that improved appreciation of particle science, engineering and technology and its practical application to manufacturing processes can have a profound effect on particle product quality, process simplification, manufacturing process operation, and new plant design and construction. The problem is that expertise to address these areas resides in no one discipline. A multidisciplinary team effort is required if real progress is to be made. In this paper we summarize such an attempt made towards this interdisciplinary gathering through the Santa Barbara Conference.

An overview of the contributions made at the Particle Technology Forum in the general context of multiphase flow research is presented. Recent developments in the measuring and computational simulation techniques have made significant inroads in the field. There is an increased interest on basic two-phase flow mechanisms, particularly for dense suspension flows. The numerical simulations are more sophisticated and closer to industrial design and applications. Rapidly changing technologies provide support for the non-intrusive instrumentation and on-line technology for two-phase flow. The necessity to combine experimental, theoretical and numerical simulation techniques in most research projects has highlighted the importance of a broader university education and the use of interdisciplinary research teams. Several open research issues have been identified.

The Wastewater Evaporation System (WES) was a reliable and economical way to treat desulfurization wastewater. However, the evaporation mechanism was not clear, and the evaporation product properties were lack of awareness. In this study, the evaporation and product properties were revealed by the single droplet drying (SDD) method and spray drying system. It was found that the evaporation process of wastewater involved the constant rate and falling rate period. The component of the evaporation product from the SDD and spray drying method were similar, mainly consisted of MgCl2, CaCl2, NaCl and CaSO4. Besides, the potential risks of WES were assessed. After wastewater evaporation, the Electrostatic Precipitator (ESP) removal efficiency was enhanced due to the aggregation of fine particles and the enhanced specific resistance. For the influence of WES on comprehensive fly ash utilization, the chloride mass fraction in the final product was lower than 0.06% and could meet strict regulations.

Particulate systems for functional ingredient development were obtained by fluidized bed drying of blackberry wastes. Fluidization behavior, drying characteristics, and physicochemical and functional properties were studied at different air temperatures (50, 60 and 70 °C) and an airflow rate of 6 m/s. Under these conditions, the blackberry waste -a heterogeneous and high-humidity material- could be successfully transformed into granulates under bubbling fluidization regime and without the use of inert material. The Page model was the most suitable to predict the blackberry waste drying behavior. Drying rate increased with temperature and the time to reach a granulate of aw

Due to the availability of high ash feedstocks and drift origin, Indian coal washeries face tremendous pressure in maintaining the clean coal yield and handling huge quantities of rejects. Since flotation rejects (tailings) discharged in the form of fine-sized (−500 μ) coal-water-slurry, handling and disposal is an environmental concern and it impacts mine sustainability. As conventional methods for extracting clean coal from tailings reported poor yields, a two-stage process i.e. wet-grinding followed by density-gradient-centrifugal separation was explored and optimized for recovering >80% of the carbon values. Clean coal of 19.2%–21.4% ash with >40% yield was obtained by density-gradient-centrifugation of different ultrafine size (−75 μ) coal-water-slurries at 50% pulp density. However, further reduction in clean coal ash by maintaining the yield was limited due to the hindrance in the movement of the high-ash coal particle caused by particle-particle interactions in a thick slurry. Hence, the pulp density of coal-water-slurry was optimized with the addition of extra water, which resulted in 15.1%–17.3% ash clean coal at an average yield of 54–58% from coal tailings having 34.9%–39.3% ash content. Optimization and kinetics of grinding and density-gradient-centrifugation were studied to check the effect of pulp density and other operating conditions. Ash reduction was mainly due to the removal of silica-based materials, where alumina to silica ratio was increased from 0.394 to 0.475. The petrographic analysis showed that the product coal was rich in macerals with ~60% of vitrinites and ~ 30% of inertinites.

Waste biomass powders are appealing to generate renewable energy and to reduce the dependence on fossil fuels, however, feeding reactors in processing is still a challenge. This paper examines the performance of a non-mechanical L-valve to feed dry and moist Spent Coffee Ground (SCG) powders into a circulating fluidized bed under a broad range of conveying and aeration flowrates. The L-valve performed as a robust feeder, providing stable solids circulation rate (WS) for most of the tested conditions. Solid mass flowrates were not affected by fluctuations in the riser air flowrate up to ±15%. We verified that the L-valve performance is limited by a deterioration of powders' flowability. Lower values of WS and narrower operating ranges were observed when feeding dry SCGs powders and samples containing fine particles. Nevertheless, the feeder can be considered a good option to handle SCGs with moisture content close to 30% w.b. and a mean particle size of 400 μm. This is an appealing result since the moisture content of SCGs burned in the soluble coffee industry ranges from 25 to 50%. Solids feeding was stable and operation was smooth in a range of 1.2

Increasing energy demand and high environmental pressure are calling for grading, quality-based classification and effective utilization of coal in China. Using fine classification and multistage pulverization liberation techniques, a typical inertinite-rich coal was used to study the migration characteristics of ash content, sulfur content and macerals of the classifier products. The results showed that the vitrinite and the inertinite contents obtained using fine classification technique reached the maximum of 61.5% and 73.3%, respectively, with enrichment efficiencies of 16.6% and 55.3%, respectively. In contrast, the maximum vitrinite and inertinite contents treated with the multistage pulverization liberation technique reached 58.9% and 82.8%, respectively, with enrichment efficiencies of 11.8% and 75.4%, respectively. A calculation model and a process model for the pulverization liberation of coal maceral were proposed. The maceral separation techniques developed in this study showed outstanding quality improvement and quality-based classification effects.

Insecticides based on Azadirachta indica have been demonstrated as useful in pest control and bioinsecticides that are microencapsulated can reduce the amount of product utilized, and minimize impacts on the environment and human health. The objective of this study was to optimize drying, and evaluate the release and degradation kinetics of microencapsulated extracts from A. indica seeds. The Box-Behnken model (33) and surface response methodologies were used to find the best spray drying conditions for the chosen variables. They were: in-let temperature of 160 °C, feed flow of 3.3 mL/min, and nozzle diameter of 0.7 mm. The drying efficiency and EE under these conditions were respectively 71.15% ± 2.18 and 56.88% ± 0.28. In the release kinetics study, the release time for Azadirachtin (100%) was 20h. The 50% photo-degradation time for Azadirachtin was 21.07 days. Our results support industrial scale-up studies, and can help application measures in the field.

The Jameson flotation cell is widely known to be efficient at fine coal recovery. However, it may be inefficient if the design parameters are not changed along with the difference in mineral floatability and working environment. In this paper, a pilot-scale Jameson Cell was modified for improving flotation separation of spodumene in high altitude area with low atmospheric pressure. The modified design parameters were the method of forming micro-bubbles by using a micro-porous tube instead of inducing air by the highly pressurized pulp, and the installation of a shower nozzle with three chokes at the end of downcomer. Micro-bubbles were formed by pressurized air passing through the micro-porous tube. Mineralization energy and dynamic turbulence intensity in separation tank were increased when the pressurized pulp passed through the chokes. Through these modified designs, the effects of low atmospheric pressure on generating micro-bubbles were eliminated, and the mineralization rate was improved in high altitude area. The usability and performance of this modified Jameson Cell was firstly assessed and confirmed on flotation of spodumene by a pilot-scale plant. The Li 2 O concentrate grade reached 4.60% with a recovery of 57.42% after a one rougher stage. Comparing with traditional mechanical flotation machine, the Li 2 O concentrate grade from the modified Jameson Cell increased by about 0.6% and the recovery increased by about 15%. Meanwhile, the power consumption per ton decreases from 2.27 kW ∗ h/t to 1.81 kW ∗ h/t.

The oxidation properties and flotation parameters of low-rank coal slimes from Shuilian mine were researched in this paper. Because coal slimes remain piled up for long periods outdoors, they are highly susceptible to oxidation, which makes it difficult for them to undergo flotation. Based on elemental analysis, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), different characteristics of fresh and oxidized coal slimes were compared. The results showed that coal slimes collected from Shuilian mine were characterized by high ash content, fine mud texture, low calorific value, and susceptibility to serious sliming. After oxidization, the O element content increased, whereas that of C and H elements decreased. Therefore, many oxygen-containing functional groups formed on coal slimes surface, such as C–O–C, C=O, and O=C–O, which imparted strong hydrophilicity, thereby reducing the flotation effects. Thus, with the aim to improve the flotation effects, we investigated the influence of flotation conditions, such as impeller speed, pulp concentration and air flow rate, on flotation effects. Based on our experiments, optimal flotation conditions were determined as follows: impeller speed, 1800 r/min; pulp concentration, 60 g/L; and air flow rate, 0.25 m3/(m2·min).

This paper presents the influence of different methods of sewage sludge conditioning on the effectiveness of dewatering. In the laboratory research, three conditioning methods were tested: (1) with the use of biomass ash, (2) chemical conditioning by means of polyelectrolyte and (3) dual conditioning with the application of biomass ash in conjunction with polyelectrolyte. The specific resistance to filtration, the moisture content and characteristics of filtrates were measured. The influence of sludge conditioning on capillary suction time and the initial pH was also examined. The obtained results showed that MC and SRF decreased after sludge conditioning. Among all tested methods, the dual conditioning influenced the sludge dewaterability to the highest extent. Due to their effectiveness, physical and dual conditioning methods might be a promising alternative for the application of polyelectrolytes. The reduction of polyelectrolyte consumption has also economic benefits, which was confirmed in a previous economic analysis.

This paper presents the results of experimental studies on desulfurization of high sulfur Indian coal by oil agglomeration using linseed oil. During experimental studies, various operating parameters like effect of pH, particle size, pulp density, agglomeration time, agitation rate and linseed oil dose were studied to find their impact on clean coal properties like sulfur reduction ratio (S/So), ash reduction ratio (A/Ao) and gross calorific value (GCV) ratio (GCV/GCVo). Experimental results showed that raw coal with 5.52% sulfur, 13.47% ash and GCV of 7038 kcal/kg can be beneficiated to produce clean coal with 2.18% sulfur along with 5.32% ash and 7769 kcal/kg GCV. Physico-chemical characterizations of raw and clean coal samples were carried out by using Field Emission Scanning Electron Microscope (FESEM), Fourier Transformation Infrared (FTIR) and Petrographic analysis to appraise the product quality. Microscopic analysis using FESEM confirmed the formation of agglomerates and reduction of mineral matters from coal structure. Petrographic analysis further confirms the increases in vitrinite, inertinite and liptinite from 68.62 to 73.61%, 12.45 to 14.07% and 3.25 to 4.27% respectively in the clean coal along with reduction of pyritic sulfur (from 9.37 to 3.87%) and mineral matter (from 6.31 to 4.18%). FTIR results infers the reduction of sulfur, oxygen rich hydrocarbons and minerals along with increase of carbon, hydrogen rich hydrocarbons in the clean coal.

Strong water binding ability of extracellular polymeric substances (EPS) and high compressibility of sludge during compression dewatering have greatly hindered the improvement of sludge dewaterability. In this paper, a novel combined conditioning method was proposed to enhance the sludge dewaterability. The sludge was firstly disintegrated by NaCl, then the sludge particles were re-flocculated by cationic polyacrylamide (CPAM), meanwhile the sludge filter cake was modified with rice husk (RH) as filter aid. The results showed that combined NaCl-CPAM-RH conditioning greatly improved the sludge dewaterability compared with that of raw sludge. The optimal NaCl pretreatment lasted 120 min with a dosage of 0.25 mol/L, the optimal CPAM and RH dosage was 30 mg/L and 50 wt%, respectively, which led to a moisture content of sludge cake of 65.44%. The changes of sludge liquid and solid phase conditioned by NaCl-CPAM-RH were analyzed. The NaCl pretreatment disintegrated the sludge floc structure with the release of protein and polysaccharide from EPS and Ca2+ and Mg2+ from sludge flocs to liquid, accompanying with the release of water trapped in sludge matrix. The addition of CPAM and RH reconstructed the sludge flocs with a big mean diameter d(0.5) of 126.84 μm, and the sludge filter cake showed a porous and rigid structure with a porosity increment of 138.62% and a compressibility reduction of 39.62% compared to that of raw sludge.

An experimental-scale electrostatic precipitator (ESP) was built to investigate the influence of temperature and gas media on collection efficiency and energy consumption. High temperature was harmful to the performance of the ESP and had a considerable influence on large particles. The maximum collection efficiency was lower and energy consumption was higher under coal pyrolysis gas media than under air. Two improvement methods, namely, gas media conditioning and positive polarity power supply, were studied in this work. Both methods can improve the performance of high-temperature ESP under coal pyrolysis gas media. The improvement in collection efficiency under the effect of gas conditioning decreased and that under the effect of a positive power supply increased with the increase in temperature. Gas conditioning and positive power supply increased the maximum collection efficiencies of the ESP at 600 °C under coal pyrolysis gas media by 3.0% and 11.8%, respectively.

In this research, ground walnut shells were used in order to improve the sewage sludge treatment. The influence of walnut shells on capillary suction time (CST); the sludge moisture content (MC), bound water (BW), the specific resistance to filtration (SRF) as well as the total bacteria number was investigated. The results have shown that the addition of ground walnut shells into sewage sludge affected the reduction of total bacteria count and the improvement of sewage sludge dewaterability. The addition of ground walnut shells in the amount of approximately 200% of sewage sludge dry mass (DS) decreased the MC by 66%, CST by 68% and SRF by 64%. The total bacteria number was reduced by approximately 88% after physical conditioning with the use of walnut shells in a dosage of 200% DS. It was proved that walnut shells might be considered as a material assisting the sewage sludge treatment.

As a by-product of the coal washing process, the methods involving the resource utilization of coal slime are very few because of its strong agglomeration and large water content. In this work, we propose a new way to dispose of coal slime, which involves preparing semi-coke water slurry (SCWS) with coal slime. When using sodium humate as dispersant at a dosage of 0.8 wt%, the solid concentration of ordinary SCWS reached a maximum (63.8 wt%) , and the concentration improved to 65.3 wt% after adding 15 wt% coal slime, and the calorific value of the slurry (18.07 MJ/kg) that can meet the Chinese standard (GB/T 18855–2002). The role of coal slime in improving the ability of SCWS is to optimize the particle size distribution as a small size material; additionally, it can improve the hydrophilicity of particulates through oxygen-containing groups and minerals, which increased the performance of SCWS.

In India, groundnut is mainly used for oil extraction or consumed in roasted form prompting a need for diversification to further increase its value and utility. In the present study, spray drying of groundnut milk was carried out using three variables of spray dryer i.e., inlet air temperature (180–220 °C), atomization air pressure (2–3 bar), feed pump speed (24–36 rpm) using Box-Behnken design of Response Surface methodology. The moisture content of powder decreased with an increase in inlet air temperature and atomization air pressure. The bulk density increased with increase in atomization air pressure. Maximum dispersibility (98.48%) was observed at an atomization air pressure of 2.57 bar. The insolubility index of the powder increased and lightness value (L*) decreased with an increase in inlet air temperature. The optimized conditions for spray drying of groundnut milk were inlet air temperature: 186 °C, atomizing air pressure: 2.5 bar and feed pump speed: 27 rpm.

International audience; Large mineral fillers have long been used in papermaking for many reasons. The finish of the writing and printing paper depends on using the fillers as internal or surface treatments. During this study, Tamarisk sp. and Prunus amygdalus pulp-filled papers with raw phosphogypsum (PG) and calcined PG (CPG) at different percentages were studied. First, the prepared minerals (treated and untreated ones) were characterized by different analytical methods such as SEM and EDS. Subsequently, different handsheets with a basis weight 60 g−2 were prepared on a Rapid Khöten sheet former following the standard method. The added amounts of PG and CPG fillers were included from 0% to 15% based on the pulp. The effects of incorporation as well as the quality fillers into physical and optical properties were assessed. It can be deduced that the incorporation of CPG at 800 °C improved filler retention by as high as 92%, and the optical properties of the filled paper was strikingly enhanced, while the strength properties were practically negatively influenced. It was clear that calcinationstepsreduce the fiber–filler–fiber bond. Thus, results are in accordance with the SEM observation, which confirmed the obtained physical properties.

Among the various species of microalgae, Spirulina platensis has recently attracted attention from food and pharmaceutical industries due to its high contents of protein and bioactive compounds. Due to its high moisture content, a major challenge in the use of this microalga is its perishability. In this work, we investigated the use of a non-conventional rotary dryer (with an inert bed) for drying microalga Spirulina platensis. We quantified the effects of air temperature, feed rate, rotation speed, and filling degree of the inert particles on process performance. We then performed an optimization study using the Differential Evolution algorithm to identify the operating conditions that maximize process yield. We also performed a DEM simulation to gain a better understanding of the fluid dynamics. The results prove that this non-conventional system offers an interesting alternative for expanding use of this biomass, when performed under appropriate operating conditions.

The flotation beneficiation of phosphate ore is increasingly facing challenges, especially for finely disseminated sedimentary ores rich in carbonates. This study aims to optimize and assess the impact of key hydrodynamic parameters including pulp density, air flowrate and impeller speed on flotation and metallurgical responses (i.e. grade, recovery, flotation rate constant and selectivity index (SI)). We carried out locked cycle flotation tests using the best conditions from the rougher flotation test to generate an experimental simulation of a continuous circuit. The mineralogical and chemical properties were characterized by mineral liberation analysis (MLA) and inductively coupled plasma optical emission spectroscopy (ICP-OES) techniques, respectively. A modified-McGill bubble size viewer was used for measuring bubble sizes and evaluating the interaction between hydrodynamic factors and bubble diameters. Finally, the design of experiment (DOE) method was applied to determine the relative intensity of the studied factors. It was found that under optimal conditions with the targets of high recovery and maximum SI, the final apatite concentrate achieved a recovery of 86.3% at a grade of 35.5%, while the MgO content was 1.2% and 84.3% of dolomite was removed from a feed ore containing about 25% P2O5, 4.6% MgO, and 41% CaO. Furthermore, another locked cycle flotation test showed that a 0.82% MgO content in the final apatite concentrate can be achieved with an apatite recovery of 75.6% at a P2O5 grade of 36.76% , and a ratio CaO/P2O5 = 1.33. The obtained concentrate in this investigation under the optimum conditions is the highest in both apatite recovery and grade with low MgO content reported in the literature.

Numerous fine coal processing technologies like froth flotation, enhanced gravity separation exist today, but their insularity have led to the adoption of oil agglomeration as a retrieval technique. In the present study, coal fines were recovered by the oil agglomerating process with the agglomerating oil as a waste vegetable oil - waste mustard oil. The effect of pulp density, oil dosage and agglomeration time were analysed on the responses – organic matter recovery (% OMR) and ash rejection (% AR). The responses were optimized using three–level Box Behnken experimental design in conjunction with the Response Surface Methodology. The resulting conditions were 99.69% for % OMR and 62.56% for % AR, showcasing that waste mustard oil has good agglomerating properties, despite of the heat treatment undergone by it during frying. Optimization studies were also performed by minimizing the oil dosage to countervail the poor economics of the oil agglomeration process. The observed conditions were investigated as 79.21% for % OMR and 65.41% for % AR obtained at an oil dosage of 8.39%. The comparative examination of these results with the contemporary studies of different oil types proved that waste mustard oil is a much better bridging liquid than the currently available oils.

The flotation performance of lignite is poor even if a high dosage of the collector is used. In this work, the lignite in the Huolinhe Coalfield of Inner Mongolia was used, and its physicochemical properties were determined by proximate analysis, particle size analysis and Fourier transform infrared spectroscopy. The flotation performances of lignite using six collectors were investigated. Moreover, the flotation responses of lignite with combined collector and two emulsified collectors were compared. It was found that the polar groups in the collector structure were helpful to improve the flotation of lignite through reducing the induction time to 15 ms, only 1/12 of that of the traditional collector (190 ms for diesel). The induction time was in the order of diesel> kerosene> emulsified kerosene> emulsified diesel> C1 (one of the nameless collectors), consistent with the flotation performance. C1 and emulsified collectors significantly improved the flotation performance of lignite by promoting the floating of coarse coal (−500 + 250 μm).

Saline water is widely used in coal preparation plants and problems are seen in these plants that a large amount of coal froth accumulates on top of thickeners in settling, the first step of dewatering process. However, the influence of saline water on settling in dewatering of coal froth products was rarely investigated. In this study, settling of coal slurry and coal froth in three different types of saline water was investigated. It turned out that saline water accelerated the settling velocity of particles that detached from froth, while increasing the amount of froth floating on top of water. The two effects both presented in settling of coal slurry and coal froth, however, the accelerated settling velocity of detached particles by salinity was more pronounced in settling of coal slurry, and the increased amount of froth by salinity was more pronounced in settling of coal froth. The mechanisms underpinning the two effects were investigated through Scanning Electron Microscopy (SEM) and oscillatory rheology. For particles detached from froth, saline water enhanced the particle attraction in coagula, so the coagula size increased and therefore the settling speed of particles also increased with water salinity. For coal froth, the balance of forces on particles determined the state of particles. Capillary attraction and buoyancy force counteracted gravity force to hold particles in froth. The capillary attraction increased with water salinity, so did the amount of froth floating on top of water.

Feijoa (Acca sellowiana B.) is a fruit harvested in South America that is characterized by its nutritional value, high pectin content and high trading potential. In this study, freeze concentration was combined with spray drying to produce feijoa powder. Freeze concentration technology is proposed as a step prior to spray drying to increase the solid concentration and to avoid the feijoa gelation process. The drying parameters were optimized by studying the inlet air temperature (180, 195 and 210 °C), maltodextrin concentration (7, 16 and 25%) and atomizer system (two-fluid nozzle or rotary disk) on a pilot scale spray dryer. The process yield, moisture content, water activity, hygroscopicity, solubility, and colour preservation were determined. The freeze concentration technique allowed the solid content to increase without causing gelation and with low differences in colour. Statistical analysis showed that the maltodextrin concentration significantly affected all the response variables after spray drying. In addition, the temperature affected the solute yield and particle size. The optimum spray drying conditions to obtain feijoa pulp powder were 22.64% maltodextrin concentration, 180 °C inlet air temperature and nozzle as the atomizer system. At these optimum conditions, feijoa pulp powder with a 26.6% process yield, 6.5% (wb) moisture content, 20.7% hygroscopicity, 0.16 water activity, 92.8% solubility and ΔE of 27.71 were obtained. The combination of freeze concentration and spray drying allowed the production of fruit pulp powders from sensitive or gelled fruit pulps.

The purpose of this study is a comparative analysis of droplet burnout rates of coal-water slurries with typical composition (based on coal dust) and new compositions of waste-derived slurries (based on coal flotation waste and used petroleum oil). The main variable parameters included the temperature in the combustion chamber (700–900°С), the initial droplet diameter (0.8–2.2 mm), the particle size (40–250 μm) and the component composition of slurry. We tested the effect of these parameters on three main characteristics: ignition delay time, burnout time, and burnout rate). The dominant impact of petroleum oil on ignition delay times and burnout rates of fuel slurry droplets was found. These parameters can change 2- or 3-fold with the addition of as little as 15–25% of used turbine oil. It was established that the ultra-grinding of coal dust is impractical to increase the burnout rate of a slurry droplet. The burnout rates of fuel slurries based on coal dust and coal processing waste are almost identical under adequate conditions. Also, the burnout rates of a coal-water slurry containing petrochemicals, in contrast to those of coal-water slurry, grow nonlinearly as the droplet size increases. In the conditions under study, the investigated characteristics may change several times. This result shows ample opportunities for adjusting combustion systems to the required conditions and a wide range of slurry compositions.