Effect of agglomerate properties on agglomerate stability in fluidized beds

Fluidized bed agglomeration is used to stabilize particulate mixtures and reduce dust emissions. This technology is applied to a variety of production processes for the pharmaceutical, chemical, fertilizer and food industries. In most of these applications, agglomerate stability is an essential criterion. Agglomerates and granules that do not conform to size and shape specifications may create problems in downstream processes, such as tableting, thus compromising process efficiency and product quality. When an agglomerate is formed in a fluidized bed, it can grow by incorporating other bed particles, split into smaller fragments, or be eroded by fluidized bed solids. The objective of the present study is to determine the critical agglomerate liquid content at which the rates of agglomerate growth and shrinkage are balanced when artificial agglomerates made from glass beads and water are introduced into a fluidized bed. This study examined the effects of agglomerate size, agglomerate density, liquid viscosity, binder concentration, and fluidizing gas velocity on the critical initial liquid content. This study found that small agglomerates and low density agglomerates displayed higher critical initial moisture contents. When the viscosity was increased by using sugar solutions, agglomerates were very stable and had very low critical initial moisture contents. The study also found that as the superficial gas velocity increased, the agglomerates started to fragment, rather than erode.     

Laboratory scale study on rheological behavior,morphological and structural properties of crosslinked polyacrylamide composite hydrogels embedded with date seed powder

Incorporation of biofillers in polymeric hydrogels has continued to receive great attention in recent times because of their excellent properties. In this study, polyacrylamide (PAM) and polyethyleneimine (PEI) were used to develop novel composite hydrogels filled with date seed powder (DSP) via chemical crosslinking technique. Pristine PAM/PEI hydrogel and PAM/PEI‐DSP hydrogels at various DSP loadings were fabricated and subjected to gelation at 40°C for 24 h. The impact of various DSP loadings on the hydrogel samples developed was investigated using hybrid rheometer, SEM, XRD, and FTIR instruments, respectively. Rheological measurements confirmed the viscoelastic responses of the neat PAM/PEI hydrogel and the PAM/PEI‐DSP hydrogels reinforced with various DSP contents (0.8, 2.4, and 4 wt %). The dynamic strain, dynamic frequency and time sweep tests demonstrated that PAM/PEI‐DSP hydrogels were slightly more elastic than the virgin PAM/PEI hydrogel. The SEM characterization revealed the surface micrographs of the neat PAM/PEI hydrogel and the PAM/PEI‐DSP hydrogels at different DSP loadings to be smooth, homogeneous, and dense. Besides, the SEM micrographs supported the incorporation of DSP in the PAM/PEI‐DSP hydrogel samples. XRD analysis showed that the structures of neat PAM/PEI hydrogel and PAM/PEI‐DSP hydrogels filled with various DSP contents were predominantly amorphous while FTIR results confirmed the functional groups and evidence of crosslinking in the neat PAM/PEI hydrogel and the PAM/PEI‐DSP hydrogels embedded with different DSP contents. It is believed that these new hydrogels have huge development potentials and promising future in wastewater treatment and removal of heavy metal ions in aqueous solutions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42110.     

Effect of particle agglomeration on heavy metals adsorption by Al- and Ca-based sorbents during fluidized bed incineration

Al- and Ca-based materials can serve as metal sorbents or agglomeration inhibitors in fluidized beds. Although particle agglomeration could affect the adsorption efficiency of metal sorbents, Al- and Ca-based materials have been found to inhibit the particle agglomeration phenomenon during the incineration process. Accordingly, this study emphasizes the effect of particle agglomeration on heavy metal adsorption by Al- and Ca-based sorbents in a fluidized bed. The results show that Al- and Ca-based sorbents inhibit the tendency of particle agglomeration caused by Na. Thus, high concentrations of heavy metals exist mainly in fine particles compared to those present in the large particles when Na is added to the system. However, the addition of Na apparently increased the adsorption efficiency and followed the sequence of Cr > Cd > Pb with an increase in the operating temperature. A comparison of sorbents and Na additive for the relative enrichment factor showed that Na plays an important role in capturing Cr with Al- and Ca-based sorbents. Also, both sorbent adsorption and Na agglomeration are the dominant mechanisms for capturing Cd. The results of adding Na and an Al-based sorbent presented positive effects for Pb adsorption; however, a negative effect was observed with the addition of Na and a Ca-based sorbent at low temperatures.     

Effect of homogenization parameters on selected physical properties of lemon aroma powder

The aim of this study was to examine the relationship between homogenization parameters of lemon aroma emulsion and selected physical properties of obtained powders. Emulsion was prepared in a high shear homogenizer (10 min, 24,000 rpm) or a two-stage pressure homogenizer (30_10 or 60_20 MPa). A 30% emulsion of maltodextrin and Arabic gum in the ratio 7:1 by mass in water and aroma was prepared. The addition of lemon aroma was 2, 6 and 10% (w/w). It was found that in emulsions an increase of aroma addition caused an increase in diameter from 2.4 to 4 μm for Ultra Turrax high shear homogenization and did not change the diameter size for pressure homogenization. For pressure homogenization similar viscosity values were observed. A different effect was observed for high shear homogenization (31–40 mPa s). Increase in aroma addition caused an increase in viscosity. Moreover, a similar diameter of the aroma phase after reconstitution of emulsion from powder (0.7–1.3 μm) was observed. In powders with an increasing amount of aroma, regardless of homogenization method, an increase in porosity, spread of particle size and total colour differences and also a decrease in loose bulk density, solubility and lightness were observed. The lowest apparent density of powders was found for an emulsion containing 6% aroma. The shape of powder particles did not differ from themselves.     

Effect of alkali concentrations and operating conditions on agglomeration/defluidization behavior during fluidized bed air gasification

Biomass gasification plays an important role in finding a solution to the energy crisis, and the fluidized bed (FB) is recognized as an important technique for using biomass. However, this process significantly tends toward bed material agglomeration. Accordingly, the aim of this study is to emphasize the effects of operating conditions and different Na concentrations on agglomeration behavior during FB air gasification. Defluidization time decreases as Na concentration increases from 0.8 to 3%. Defluidization time decreases as temperature and the amount of bed materials increase. In addition, no significant change in the trend for this process occurs as the equivalence ratio increases. Adding CaO and Al₂O₃ can significantly prolong this process, and the inhibition level follows the sequence: Al₂O₃ > CaO. The same observations are noted during both incineration and air gasification in the FB at various operating conditions.     

Effect of trisodium citrate on morphological,structural, and optical properties of fluorine-doped ZnO structures

In this work, we present the effect of trisodium citrate (TSC) addition via a hydrothermal method on the morphological, compositional, structural, and optical changes of fluorine-doped zinc oxide (FZO) on silicon substrates. Field emission scanning electron microscopy revealed vertically aligned nanorods for FZO and pebble and block-like microstructures of different sizes upon TSC addition. X-ray diffraction analysis revealed a hexagonal structure for all the samples. Upon addition of TSC, the sample growth along the c-axis was inhibited strongly and the growth along the a-axis was developed. The crystallite size increased from 28.73 nm to 30.38 nm upon addition of TSC. The oxygen deficiency and, the presence of zinc, oxygen, fluorine, and sodium in the studied samples were confirmed by energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy (XPS). Ultraviolet (UV)-visible analysis revealed the optical energy band gap increment from 3.204 eV to 3.241 eV with TSC addition. Photoluminescence (PL) analysis revealed a significant improvement in the intensity ratio of the near band emission to deep level emission from 5.44 to 12.59 upon TSC addition, indicating crystal quality improvement. Both UV–visible and PL analyses showed that the studied samples were blue-shifted upon TSC addition. The different morphologies with promising properties could be employed in different applications, eliminating the complexity and reducing cost in the fabrication of hybrid structures, and nano/microcomposites.     

Effect of solid circulation rate on coating efficiency and agglomeration in circulating fluidized bed type coater

Circulating fluidized bed was proposed to be used as a coater, and coating experiments of glass beads with silica powder were performed in a circulating fluidized bed. Glass beads and silica powder were chosen as model particles, because their shape was almost spherical. The respective effects of gas flow rates supplied from a distributor and from an air nozzle for solid circulation, feed rate of powder suspension and particle content in the bed on coating efficiency and agglomeration are mainly discussed. Coating efficiency in circulating fluidized bed coater was correlated well with solid circulation time rather than with gas flow rates or solid circulation rate, while the agglomeration among core particles was mainly governed by solid circulation rate.     

不同固化体系对环氧粉末涂料性能的影响

通过非等温示差扫描量热分析(DSC),热重分析(TGA)及物理力学性能测试研究了分别以双氰胺、二氨基二苯基砜、线形酚醛树脂为固化剂,2-甲基咪唑为固化促进剂的环氧树脂体系的固化行为,热稳定性及其粉末涂料性能,并利用外推法求出不同固化体系的理论固化温度。结果表明:双氰胺/2-甲基咪唑体系的综合性能最好,其理论固化温度为142℃,热失重起始分解温度为410℃,冲击强度为50 cm,60°光泽为83,表面电阻为1.33×1012Ω。     

Effect of carbonation of fresh egg white prior to spray drying on physical and functional properties of powder

The effect of carbonation on physical and functional properties of egg white powder during spray drying and storage under vacuum, air, and CO₂ gas was investigated. Carbonation (2,000?mg/kg) of fresh egg white before spray drying was found to improve the foaming properties of the fresh egg white powder. However, the carbonation caused accelerated changes in color, solubility, and foaming properties of the powder during storage. In addition, the results showed greater changes in the color and decreased solubility in the powder samples stored in impermeable hermetically sealed bags under CO₂ and vacuum conditions than in normal air.     

Effect of precursor concentration on structural,morphological and opto-electric properties of ZnO thin films prepared by spray pyrolysis

Sprayed ZnO films were grown on glass substrate at 400 °C using zinc chloride as precursor with different molar concentrations varying from 0.05 to 0.2 M. X-ray diffraction patterns reveal that ZnO films are polycrystalline with hexagonal wurtzite structure with preferred orientation in (002) plane. Optical measurements show that transmittance reaches a maximum value of 95% in the visible region for ZnO films prepared from precursor with 0.05 M concentration. The films obtained from the precursor with 0.1 M concentration have the highest electrical conductivity and photocurrent values.     

Evaluation of physical,rheological, microbial,and organoleptic properties of meat powder produced by Refractance Window drying

Meat spoils very rapidly and its microbial load exceeds the permitted limit very soon even if it is kept in a refrigerator. The main goal of this study was to dry meat by a Refractance Window drier successfully, for the first time, and to evaluate its compositional, physical, rheological behavior, microbiological, and organoleptic properties. Meat powder produced by RW drying had good physical properties including maximum absolute density of 0.81?g?cm^?3, porosity of 0.67, rehydration ratio of 2.8, L* value of 64, and minimum a*/b* value of 0.57. Herschel–Bulkley and Bingham models could predict rheological indices of meat powder solutions with high R² rates of 0.955–0.995. Sensory evaluation indicated that although meat powder obtained from 3?mm slices was more favorable for panelists, the consistency of 2?mm meat powders was more agreeable, which could be attributed to better functional properties of more dried samples. 100°C and 2?mm treatment could decrease aerobic bacterial count from 6.1 to 3.7 log CFU/g and Enterobacteriaceae population from 3.1 log CFU/g to nil successfully. In summary, our comparison indicated that meat powder produced by Refractance Window drying technique can lead to better dried products than dried meats having been prepared with other novel techniques recently.     

Effects of different compatibilizers on the rheological,thermomechanical, and morphological properties of HDPE/LLDPE blend‐based nanocomposites

The influence of two different compatibilizers and their combination (maleic anhydride grafted high density polyethylene, HDPE‐g‐MA; maleic anhydride grafted linear low density polyethylene, LLDPE‐g‐MA; and 50/50 wt % mixture of these compatibilizers) on the rheological, thermomechanical, and morphological properties of HDPE/LLDPE/organoclay blend‐based nanocomposites was evaluated. Nanocomposites were obtained by melt‐intercalation in a torque rheometer in two steps. Masterbatches (compatibilizer/nanoclay 2:1) were obtained and subsequently diluted in the HDPE/LLDPE matrix producing nanocomposites with 2.5 wt % of nanoclay. Wide angle X‐ray diffraction (WAXD), steady‐state rheological properties, and transmission electron microscopy (TEM) were used to determine the influence of different compatibilizer systems on intercalation and/or exfoliation process which occurs preferentially in the amorphous phase, and thermomechanical properties. The LLDPE‐g‐MA with a high melt index (and consequently low viscosity and crystallinity) was an effective compatibilizer for this system. Furthermore, the compatibilized nanocomposites with LLDPE‐g‐MA or mixture of HDPE‐g‐MA and LLDPE‐g‐MA exhibited better nanoclay's dispersion and distribution with stronger interactions between the matrix and the nanoclay. These results indicated that the addition of maleic anhydride grafted polyethylene facilitates both, the exfoliation and/or intercalation of the clays and its adhesion to HDPE/LLDPE blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1726–1735, 2013     

石粉-矿渣粉复掺混凝土性能的研究

研究了石粉与矿渣粉复掺对混凝土拌合物工作性能和抗压强度的影响,并对其孔结构和水化产物进行了分析。结果表明,石粉的掺入,改变了混凝土水化产物,提高了其致密性;适当的复掺比例可以在有效保持混凝土抗压强度的基础上,明显改善其工作性能和孔结构;复掺料等量替代40%的水泥时,石粉和矿渣复掺的最佳比例约为2/3。     

Effect of chemical structure and shear force on the morphology and properties of jet printed black micropatterns using imide epoxy binders

Epoxy and epoxy acrylates with phthalimide groups on the main chain or pendent side chain were synthesized and used as binders for solvent‐free UV‐curable inks. Effects of chemical structures on the solubilities of binders in monomers, together with the influences of shear force and ink compositions on the morphology and nanoindentation properties of the microstripes were studied. PIK1 inks containing BAPSBD epoxy with phthalimide groups on the main chain showed shear‐thinning behaviors and pigment aggregation problems. Variations of the shear stress at different positions of the dispenser led to PIK1 microstripes with rough central regions and smoother edges. AMPDP acrylate with pendent phthalimide side chain afforded not only good solubility in monomers but also good thermal and mechanical properties after curing. Stripes prepared by the PIK2 ink containing AMPDP exhibited straight edge and smooth surface. Considering the solubility and compatibility in inks, together with properties of cured stripe, binders with pendent phthalimide groups are better candidate as UV‐curable ink compositions than those with main chain phthalimide groups. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of shear rate on structural,mechanical, and barrier properties of chitosan/montmorillonite nanocomposite film

The dispersion of MMT‐Na⁺ (montmorillonite) layers in a chitosan polymer matrix, using the homogenization, was performed. The effect of shear rate was characterized on the mechanical, barrier, and structural properties of nanocomposites. Elongation at break (EAB) was unaffected by shear rate, which decreased after homogenization, increased above 13,000 rpm, however, tensile strength (TS) dramatically increased up to 59 MPa at 16,000 rpm. Water vapor permeability (WVP) and oxygen permeability (OP) of the homogenized nanocomposite decreased more than that of untreated nanocomposite and OP was not significantly changed above 16,000 rpm of shear rate. XRD result and TEM images indicated that three types of tactoids, exfoliation, and intercalation were generated and the largest distance of 18.87 Å between MMT‐Na⁺ layers was produced at 16,000 rpm. The results indicate that homogenization was a beneficial method for effectively dispersing MMT‐Na⁺ layers in a chitosan polymer matrix and that a shear rate of 16,000 rpm was the effective condition. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of calcination temperature on structural and morphological properties of bismuth ferrite nanoparticles

Bismuth Ferrite (BiFeO3) is one such materials which has shown very promising multiferroic and excellent optical properties. In this paper, we report effect of annealing temperature on the structural, morphological and optical properties of BiFeO₃ nanoparticles synthesised through sol-gel auto-combustion method. Nanoparticles prepared were calcined at three different temperatures, 400 °C, 500 °C and 600 °C, and named as BFO1, BFO2 and BFO3, respectively. X-ray diffraction confirmed the rhombohedral structure with R3c space group as a primary phase. However, a secondary phase Bi₂Fe₄O₉ was also observed which decreases with increasing temperature. The crystallite sizes were found to increase with increasing temperature with BFO2 as anomaly. Field emission scanning electron microscopy (FESEM) shows clear grain formation for all the samples. TEM micrographs and SAED patterns show crystalline grains with rhombohedral structure. All the functional groups observed in the Fourier infrared spectroscopy (FTIR) measurement are indexed. The FTIR spectra shows presence of two prominent vibrational modes in the wave number range 447 and 560 cm^-1 corresponding to the stretching of Fe-O bonds. Raman analysis shows presence of a peak at ~527 cm^-1 for (BFO3) which was absent in other two samples. Also, the intensity of the A₁-1 mode was found stronger than that of A₁-2 mode in all the samples which confirmed the stability of the structure, except for BFO1.     

Effect of pigmentation on the surface chemistry and surface free energy of paper coating binders

The effect of the addition of clay and TiO₂ pigments on the surface energy and surface chemistry of films made from polymers used in paper coating formulations was evaluated. The polymers were carboxymethyl cellulose, polyvinyl alcohol and a protein-based polymer - all water-soluble - and two styrene-butadiene latexes of different carboxylation levels. The morphology of the surfaces was characterized by SEM examination, gloss measurement and stylus profilometry. Chemical composition was determined by EDS and XPS techniques. Surface energy and its Lifshitz-van der Waals and acid-base components were obtained from contact angle measurements using the van Oss et al. approach. Even though the addition of pigment increasingly upset the planar surface of the films, their surface chemistry and surface energy were only slightly affected over the pigmentation range studied (up to 40% by volume) and were dominated by the characteristics of the binder polymer.     

Effect of fillers on morphological properties and wear characteristics of XNBR/NR blends

The blends of carboxylated acrylonitrile butadiene rubber (XNBR) and natural rubber (NR) were prepared using a blending technique in the presence of different types of carbon black. The effect of filler on morphological and wear characteristics was studied. ISAF N234 carbon black showed a significant effect on curing, mechanical, and thermal studies. The DIN abrader results showed high abrasion resistant properties of 80 wt % NR and 20 wt % XNBR with ISAF N234. The rubber compound containing 40 wt % of NR and 60 wt % of XNBR with ISAF N234 is found to be the toughest rubber against all types of rock. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120:710–718, 2011     

Effect of mixed solvent on structural,morphological, and optoelectrical properties of spin-coated TiO2 thin films

Nanocrystalline TiO₂ anatase thin films have been synthesized from alkoxide solution via sol–gel spin coating method. The effects of different solvents of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and tert-butanol as well as those of mixed solvents on crystal structure, thermal behavior, morphology, and optoelectrical properties were investigated. It was found that not only the occurrence of rutile with anatase phase was solvent dependent, but also the morphology and optoelectrical properties of the films were strongly affected by solvent type. However, using two different types of alcohols as a single solvent brings the advantages of both solvents. Also, some unique properties in mixed solvent samples could be achieved. The viscosity, gel time, boiling point, possible complexes, dipole moment, and chain length of the solvent affect the packing density, lattice distortion, interfaces, thickness, optical band gap, refractive index, and extinction coefficient.     

Effect of calcination temperature on the microstructure,composition and properties of nanometer agglomerated 8YSZ powders for plasma spray-physical vapor deposition (PS-PVD) and coatings thereof

Homemade nano-agglomerated powders 8YSZ powders for PS-PVD were prepared by the spray drying, then calcination processes at four different temperatures (500 °C, 700 °C, 900 °C and 1100 °C) were carried out on the spray-dried powders. Checked by laser particle sizer, scanning electron microscope (SEM) and X-ray diffraction (XRD), the physical properties, microstructure and phase constitutions of the calcined powders were investigated. The results show that the size of powders calcined at 500 °C is increased relative to the spray-dried powder, whereas the powders calcined at 700 °C, 900 °C and 1100 °C possess smaller size. The binding force of the primary particles tend to rise with the increase of calcination temperature. When the temperature was up to 900 °C and above, it was found that the sintering neck indicating with strong binding was formed between the primary particles. In parallel, the powders underwent an m-ZrO₂ to t-ZrO₂ transition as the calcination temperature rose. It is also found that the PS-PVD prepared coatings which were obtained by using the above powders undergo a transformation from a feather-like to a dense laminate structure as the calcination temperature rises. It is noteworthy that the coating obtained by the powders calcined at 700 °C have a special three-layer composite structure of near dense surface layer, columnar intermediate layer and dense sub-layer. The composite structural coating has excellent adhesion and thermal shock resistance, with a bonding strength of 81MPa and no major spalling when water quenched 100 cycles at 1100 °C.