Concept and procedures to minimize pollutants discharge from industries into the water environment are discussed in this paper, as well as the improvement of performance and energy conservation in wastewater treatments. The first priority should be the reduction or elimination of wastewater discharge from the production process before considering the treatments. Material balance in the production process can clarify the composition of wastewater, and thus the source of pollutants discharge. A flowchart to characterize the wastewater in terms of coagulation, biological and chemical degradation, and activated carbon adsorption of pollutants in the wastewater is introduced and discussed. Microbial quinone profile is successfully introduced to clarify the acclimatization of microbes to refractory chemicals such as dimethyl sulfoxide (DMSO). Various wastewater treatments are categorized for organic wastewater treatment on the basis of biodegradability of organic pollutants defined as BOD and the theoretical oxygen demand (ThOD) ratio and their molecular size. Major biological treatment processes are characterized from viewpoints of the power economy, which is defined as the mass of BOD removed per unit energy consumption, and the rate of BOD removal per unit floor area of each process. The effect of air diffuser arrangement on the energy consumption for oxygen supply is quantitatively evaluated and discussed because the aeration takes major part of the total energy consumption in the activated sludge process.

View full abstract

In enhanced biological phosphorus removal (EBPR) processes, activated sludge microorganisms accumulate large quantities of polyphosphate (polyP) intracellularly. We previously discovered that nearly all of the polyP could be released from activated sludge simply by heating it at 70°C for about 1 h. The addition of CaCl₂ precipitated the released polyP at room temperature without pH adjustment. In the present study, we examined the feasibility of this simple technique for recovering phosphorus (P) from municipal wastewater at pilot plant scale. The pilot plant tests demonstrated an average P recovery of about 40% over the one-year operating period.

View full abstract

The continuous production of hydrogen from rice winery wastewater in a continuously stirred tank reactor (CSTR) was investigated. The conversion efficiency of carbohydrate increased with the hydraulic retention time (HRT), but slightly decreased with the increase of the substrate concentration. The conversion of carbohydrate followed the Monod kinetics with a maximum rate of 1.34 g/(g-VSS·d) and a half-rate constant of 0.32 g/L. The overall production rates of volatile fatty acids (VFAs) and ethanol decreased with HRT, but increased with the substrate concentrations. The key acidogenic products were acetate, propionate, butyrate, and ethanol. Biogas produced under all test conditions was composed of hydrogen (37–52%) and carbon dioxide (46–60%). The specific hydrogen production rate increased with substrate concentration, but with the decrease of HRT. The hydrogen yield was in the range of 1.02–1.37 mol/mol-hexose. This CSTR has potential for the use in the hydrogen production from rice winery wastewater.

View full abstract

By using a Lab-scale Expanded Granular Sludge Bed (EGSB) reactor, the strategies of start-up and the changes of characteristics of granular sludge before and after start-up were investigated. In the first stage, the pentachlorophenol (PCP) concentration in wastewater was fixed at 5 mg/L, and the organic loading rate (OLR) gradually increased. The OLR increased to 5.4 kg COD/(m³-reactor d) after 25 days. Then began the second stage, OLR was stabilized as 5 kg COD/(m³-reactor d), while the PCP concentration was gradually increased. The PCP loading rate increased to 94.7 mg/(L-reactor d) in 63 days after the second stage start-up, the COD removal and PCP removal were 91.2% and 99.6% respectively. The EGSB reactor has the ability to bear PCP overloading to some extent. After the start-up was finished, the settlement velocity of granular sludge increased, the specific methanogenic activity of sludge and dechlorination rate of PCP were apparently increased. The results show that the two-stage start-up strategy is appropriate.

View full abstract

In a fluidized-bed porous carrier system, organic carbon and nitrogen in wastewater can be removed simultaneously. However, the excess sludge generated in the system has not been focused on. On the other hand, a membrane system can separate suspended solid from treated water and retain slowly growing microbes such as nitrifiers in the aeration tank. Porous carrier and membrane hybrid system with these respective advantages has been studied to enhance the nitrogen removal efficiency. In this study, the hybrid system was investigated to compare with a conventional carrier system in terms of the nitrogen removal rate from complex artificial wastewater (CAW) containing polypeptone as a nitrogen source. Moreover, the amounts of excess sludge generated in both systems were evaluated.
Longer sludge retention time of the hybrid system was expected to enhance the microbial autolysis and lead to the reduction of the excess sludge. Consequently, the amount of excess sludge generated in the hybrid system was reduced to about one-fourth of that in the carrier system for about two months. In addition, a lot of slowly growing protozoa preyed on the microorganisms, which might have contributed to the reduction of excess sludge. The removal rates of organic carbon and nitrogen in the hybrid system were higher than in the carrier system, due to the highly concentrated microorganisms in the hybrid system. A batch operation revealed that the nitrogenous compounds of polypeptone in CAW were rapidly removed by assimilation, while urea in the artificial wastewater was mainly removed by nitrification. Consequently, total nitrogen concentration in CAW containing polypeptone decreased faster than in artificial wastewater containing urea. These results show that nitrogenous compounds in CAW are easy to be removed. The hybrid system is an efficient system to enhance the nitrogen removal and has a capability to reduce the excess sludge.

View full abstract

Biological conversions of nitrogenous compounds closely resembling the chemistry of the anammox reaction were developed and maintained for approximately two years in fixed-bed, continuous-flow unit processes. Using a novel nonwoven matrix for biomass attachment, the anaerobic, autotrophic biofilm cultures were robust enough to survive occasional operational anomalies and to rebound quickly from temporary setbacks. Using a 2.7-l reactor with a hydraulic retention time of 7.5 hours, influent ammonium (NH₄⁺) and nitrite (NO₂^–) concentrations of approximately 250 mg N/l, each, were successfully treated with a total nitrogen (T-N) removal efficiency of 60%. T-N and NH₄⁺ volumetric removal rates of 40 and 20 mg N/l·h, respectively, were maintained for a one-year period of operation, which are in a suitable range for industrial applications. Using the nonwoven material of the 2.7-l reactor as a seed for a larger 14-l reactor, a fast transition to a stable, relatively high T-N mass removal rate of approximately 300 mg/h (NH₄-N removal, 150 mg/h) was possible. These results suggest that attached-growth processes such as employed here, with a nonwoven matrix, could serve well not only as a means of nitrogen abatement but also for mass cultivation of the slowly growing anaerobic ammonium-oxidizing cultures for use in development of new reactors.

View full abstract

Hydroxyalkanoates (HA) can be widely used as chiral building blocks for the synthesis of fine chemicals. In this study, HA monomers were produced directly using genetic engineering techniques. The recombinant E. coli HB101 harboring β-ketothiolase (PhbA) and acetoacetyl-CoA reductase (PhbB) of Ralstonia eutropha was found to be able to produce more than 1 g L^–1 of 3HB monomer extracellularly after 48 h of fermentation. Heterogenous expression of (R)-3-hydroxydecanol-ACP: CoA transacylase gene (phaG) isolated from Pseudomonas putida in E. coli HB101 led to 587 mg L^–1 extracellular production of 3-hydroxydecanoic acid (3HD) from fructose. The results demonstrated that HA can be produced by recombinant organisms directly without going through the PHA hydrolyzation process.

View full abstract

Dibenzothiophene (DBT) is the most excessive and refractory sulfur compound in fossil fuels. The methods for removing DBT, using bacteria, were twofold: the first one involved the destruction of the carbon skeleton; the second, the use of a sulfur-specific process of biodesulfurization, without cleaving the carbon ring. Because the second method does not degrade the value of the fuel, it is considered by most researchers to be the method of choice. Bacteria used for this study, were obtained from the soil collected from a field that contained waste water from a refinery. Using GC/MS, it was confirmed that the metabolic pathway used by this bacterium, involved a sulfur-specific process of biodesulfurization, named the ‘4S pathway’. This strain appears to have the ability to remove the organic sulfur from thiophenic compounds over a wide temperature range from 25 to 45°C. And the half time of the whole cells desulfurization activity was 32 days, three times more than Rhodococcus erythropolis IGTS8. With the excellent stability, it may have industrial application for biodesulfurization.

View full abstract

Rhodococcus sp. PN1 was isolated as a 4-nitrophenol (4-NP) degrading bacterium and can utilize 4-NP as a sole carbon, nitrogen, and energy source. This bacterium also degrades polynitrophenols such as 2,4-dinitrophenol and 2,4,6-trinitrophenol (picric acid). To elucidate the nitrophenol degradation pathways of strain PN1, a genomic library of strain PN1 was constructed using a Rhodococcus host-vector system and the genes encoding the pathways were screened from the library. Consequently, the gene clusters (nphRA1A2 and npdGIJ) encoding 4-NP hydroxylation and picric acid reduction were obtained from the library, respectively. The recombinant Rhodococcus strain containing the nphRA1A2 genes converted 4-NP into 4-nitrocatechol quantitatively, while that containing the npdGIJ genes transformed picric acid into its hydride Meisenheimer complex, quantitatively. Thus, it was found that strain PN1 has two quite different degradation mechanisms for nitrophenols, an oxygenation (4-NP hydroxylation) and a reduction (hydride transfer to the aromatic-ring of picric acid). Sequence analysis of the gene clusters suggested that the former encodes a member of the two component flavin diffusible monooxygenase family (NphA1 and NphA2), while the latter encodes an NADPH-dependent F₄₂₀ reductase (NpdG) and an F₄₂₀-dependent picric acid reductase (NpdI). Simultaneous degradation of 4-NP and picric acid by strain PN1 indicated that both degradation mechanisms can work simultaneously without significant inhibition. This capability of strain PN1 may contribute to the treatment of industrial wastewaters containing many kinds of nitrophenols

View full abstract

For extensive detection and monitoring of alkane-degrading bacteria, three combinations of PCR primer sets and gene probes were designed based on the homologous regions within a variety of alkane hydroxylase genes (alk genes) registered in the GenBank and examined their availability. PCR using the designed primers amplified DNA fragments with the expected sizes from all the tested bacterial strains used for primer design, and all of the amplified fragments gave positive results by Southern hybridization with the designed probes. The primers amplified DNA fragments with expected sizes from all the 76 wild-type newly isolated strains, while the probes gave positive results against the amplified fragments from 60 strains. Thus, the primer/probe system established in the present study can detect most of the alkane-degrading bacteria, and can be applied to evaluate alkane-degradation potential in the environments.
Applying the designed primers, behavior of microbial populations responsible for the degradation of n-alkanes, a major component of crude oil, was monitored in seawater microcosm during the crude oil degradation process to clarify the degradation mechanisms of n-alkanes. It revealed that the alkane-degrading bacteria altered according to the fates of n-alkanes with different carbon chain lengths, so that shorter alkanes were degraded first by alkane-degrading bacteria possessing alk genes of Group I (Group I alkane-degrading bacteria) and longer ones afterwards by Group II alkane-degrading bacteria.

View full abstract

We investigated the effect of inoculant on the emission of odorous compounds during isothermal thermophilic composting processes at 60°C. Of these compounds, ammonia and odorous sulfur compounds, hydrogen sulfide (H₂S), methylmercaptane (MMC), dimethylsulfide (DMS), and dimethyldisulfide (DMDS) were measured. We used three different inoculants, and found that composting with two of them, where vigorous organic matter decomposition occurred, generated a very high concentration of NH₃, as high as 4000 ppm, and also generated high concentrations of sulfur compounds, especially of MMC and DMDS. In contrast, very few odorous compounds were emitted during composting with the third inoculant; however, there was an extremely small degree of organic matter decomposition in this composting. These results indicate that it is not sufficient to merely compare odor emission when assessing the best operational conditions for composting with a small amount of odor emission. In other words, in assessing composting operations with regards to the effective reduction of odor emissions, it is important to simultaneously quantify the degree of organic matter decomposition that occurs.

View full abstract

We investigated the composting process of an aquatic plant for developing an effective method of their recycling. The changes in microflora were monitored by temperature gradient gel electrophoresis (TGGE) of the DNA fragments amplified by reverse transcription PCR from the 16S ribosomal RNA extracted from the compost. The decrease in the cellulose content of aquatic plant compost was found to be faster than that of other composts. During the phase when the specific activity of cellulase was high, the decrease in the cellulose content was rapid. In the TGGE analysis, a few bands were found that changed in intensity in relation to that of the specific activity of cellulase. The bacteria responsible for the bands were isolated and, based on the DNA sequences of the 16S rRNA, identified as Bacillus spp. For an effective composting process, we examined the use of the composted material as a seed. When the resultant compost was used as a seed for the next cycle of composting, the decrease in cellulose content during the second composting cycle occurred faster than that during the first cycle.

View full abstract

We investigated the effect of the polymer-drug interaction on the surface morphology of polymer microspheres and in vitro release properties. Polylactide microspheres enclosing the antitumor agent Irinotecan hydrochloride (CPT) were prepared by the solvent evaporation method of the O/O emulsion system in order to control the concentration of drugs in living organisms. The mean diameter of the polylactide microspheres was kept at approximately 50 μm while varying the content of CPT. The enclosing efficiencies in all runs were around 80%, independent of the CPT content. The surface morphology of polylactide microspheres was significantly affected by the content of the enclosing CPT. Furthermore, the degree of unevenness of the surface was increased with an increase in the CPT content in polylactide microspheres. DSC studies have suggested that the glass transition temperature of polylactide microspheres enclosing CPT shifted to lower temperatures with an increasing CPT content. It was assumed from DSC measurements that the morphological change of polylactide microspheres was induced by a polymer-drug interaction. In vitro release experiments suggested that the release rate in the early period increased with an increasing CPT content. From this study, it was pointed out that the drug, miscible with the matrix polymer, induced a change in surface morphology, providing a significant effect on release properties.

View full abstract

This paper focuses on the study of mesoporous zirconia and its composite mesoporous catalysis materials. On the basis of the synthesis of mesoporous zirconium oxide with an ordered pore structure through a surfactant templating technique, a new kind of composite mesoporous zirconia catalyst materials such as Pt-Ce/Meso-ZrO₂, and Pd-Y/Meso-ZrO₂, have been synthesized via a post-grafting method. XRD, TEM, EDS, and UV-Vis spectroscopy were adopted for the characterization of the synthesized materials. It was shown that cerium and yttrium could be successfully incorporated into the framework of mesoporous zirconia. The results of H₂-TPR experiment show that, after further loading with the noble metal Pt or Pd, our prepared samples show greater redox activation; the temperatures for catalytic reduction of these mesoporous composite catalysis materials could be greatly decreased. This new catalysis material may be expected to have potential applications in some practical fileds, including automobile waste gas treatment.

View full abstract

A preparation method is reported for the microencapsulation of SiO₂ by rapid expansion of supercritical solution with a nonsolvent. A suspension of SiO₂ in carbon dioxide containing a cosolvent and dissolved polymer is sprayed through a nozzle to atmospheric pressure. After rapid expansion, polymer microspheres were obtained. The microspheres do not tend to agglomerate, since the pure cosolvent is a nonsolvent for the polymer. The structure and morphology of microspheres were investigated by SEM and TEM. The obtained polymer microspheres are microcapsules of SiO₂ particles. The primary particle diameter and particle size distribution of microcapsules, could be controlled by changing the feed composition, pre-expansion pressure, temperature, and diameter of nozzle. The polymer feed composition is more effective than other factors on the control of particle size.

View full abstract

Nanometer-sized manganese oxides materials are one of the focuses for scientists in this field and novel properties may be found, due to quantum confinement effects. The most widely used cathode materials in primary alkaline batteries nsutite (γ-MnO₂) is often described as an intergrowth of pyrolusite and ramsdellite tunnel structures. Our research concerns the preparation, structures, and properties of nanometer-sized nsutite with the longest diameter sizes of about 30–40 nm from Mn(ClO₄)₂·6H₂O-(C₂H₅)₄NOH-CsMnO₄–H₂O basic systems, instead of traditional nsutite synthesized in the acidic environments. Flat perfect crystal surfaces of nanometer-sized nsutite characterized by FESEM show that there are pure and fewer cation vacancies defects on the surface of the frameworks, further proved by IR, TG, and BET methods. The CV experiment results showed that the currents at –240 mV, corresponding to the homogeneous reduction from Mn⁴⁺ to Mn³⁺, were twice of traditional samples from acidic environments, due to the small particle size, fewer cation vacancies, and larger numbers of Mn⁴⁺ ions on the surfaces.

View full abstract

Carboxyl-functionalized magnetic microspheres were prepared by in situ polymerization of styrene and methyacrylic acid at 85°C in the presence of nano-Fe₃O₄ in styrene, using lauroyl peroxide as an initiator. The effects of the surfactant, the weight ratio of magnetite to styrene, the amount of monomer and initiator on the polymerization reaction and microsphere properties were investigated in detail. Transmission electron microscopy showed the property of the surfactant on the surface of nano-Fe₃O₄ determined the magnetite content and the distribution of the magnetite in the microspheres. The optimum conditions of the reaction were optimized. The adsorption result of bovine-γIgG proves that the magnetic microspheres have a potential wide application in the biological field.

View full abstract

A polymerization method, currently proposed by the authors (Gu et al., 2002), for producing micron-sized polymer particles was examined. Soapfree emulsion polymerizations of styrene with an amphoteric initiator, 2,2′-azobis[N-(2-carboxyethyl)-2-2-methylpropionamidine] hydrate, were carried out in a range of initiator concentrations (4–10 mol/m³ H₂O) at a fixed pH of 8.3 adjusted with a buffer system of [NH₃]/[NH₄Cl]. Highly monodisperse polymer particles could be obtained with this method. The coefficients of the variation on particle size distribution were less than 2%, and the average particle sizes were in a range of 2.5–3 μm. To produce larger particles, applicability of a simple method to the present polymerization was also examined. The method employed was monomer addition during polymerization. This method enabled the production of polymer particles with an average size of 3.8 μm and a coefficient of the variation of 1.3%.

View full abstract

Biodegradable and controlled-release capsules composed of waste paper fibers as matrix and limonene droplets as core materials were prepared by utilizing the liquid-liquid dispersion. Encapsulation was performed due to coalescence between a droplets containing binder and fibers and those dissolving a gelling agent. In this experiment, methylcellulose as a binder and tannic acid as a gelling agent were used respectively. Paper fibers were treated hydrophobic prior to the encapsulation operation in order to improve waterproofing of capsules. It was investigated whether capsules could be prepared by this encapsulation process or not. Furthermore, it was investigated how the fiber concentration affected the morphology and release characteristics of capsules.
As a result, it was found that capsules were able to be prepared due to coalescence between two kinds of droplets and the capsule morphology was extremely changed with the fiber concentration. Moreover, it was found that the change in morphology considerably affected the release characteristics. Namely, in the case of the lower fiber concentration, monocore-type capsule containing limonene droplets were formed. However, as the fiber concentration increased, multicore-type capsules were formed.

View full abstract

The method for simulating the time-evolution of the particle size distribution of polymer particles generated in the O/W microemulsion polymerization of styrene initiated by a water-soluble initiator is proposed based on the following kinetic model: The radicals generated in the aqueous phase enter the micelles, propagate therein and transform them into new polymer particles with (1) negligible bimolecular termination in the aqueous phase, and with (2) negligible entry of the second radical into the preformed polymer particles, and hence, (3) propagation of growing radicals stops only by a chain transfer reaction to monomer, (4) growth of polymer particles stops only by the desorption of the radicals generated by chain transfer out of the particles, and (5) the radicals produced by chain transfer may desorb from the particle or initiate propagation in the same particle. The average diameter calculated from the simulated particle size distribution agrees well with that measured experimentally by dynamic light scattering. The simulated particle size distribution agrees with that measured experimentally with a transmission electron microscope.

View full abstract

Titanium diioxide, a large-band gap semiconductor and versatile photocatalyst, has been grafted into the pores of as-synthesized MCM-41 via a new precursor titanium glycolate. The products have been extensively characterized by FT-IR, powder XRD, nitrogen adsorption, TEM and HRTEM. It was found that titania was well dispersed into the silica walls via Si-O-Ti bonds and didn’t damage the hexagonal structure. Compared with other titanium alkoxides, such as titanium butoxide and titanium isopropoxide, titanium-grafted in MCM-41 via titanium glycolate is more satisfactory.

View full abstract

A thermal swing extraction system using a thermosensitive gel, poly-N-isopropylacrylamide (NIPA) crosslinked with 2,6-di(3-vinylbenzyl-1,2,4-triazol-5-yl)pyridine (BTP) was proposed. Extraction of Cd(II) in an aqueous nitrate solution and elution with acidic solutions (pH = 1 to 5) were tested by two thermosensitive gels prepared by the ultrasonic polymerization and the ordinary radical polymerization, called US-gel and FR-gel, respectively. Cd(II) was extracted in the gel shrunken at higher than LCST (lower critical solution temperature, 31°C) and released from the gel swollen at less than LCST. Such temperature-change of extractability for the US-gel was larger than that for the FR-gel. The US-gel, in which aggregates of BTP molecules are not formed, is suitable to the thermal-swing extraction system. The elution of Cd(II) into a weakly acidic solution (pH > 2) was promoted by the volume phase transition of gel from the shrinking state to the swelling one. Even in a very weakly acidic solution of pH 5, more than 50% of Cd(II) extracted was eluted by the volume phase transition of gel. These results suggest that the elution operation with the volume phase transition of gel is very effective for reducing a quantity of eluting agent.

View full abstract

A thermodynamic model for the ion-exchange reaction process from potassium tetratitanate (K₂Ti₄O₉, or expressed by K₂O·4TiO₂) fibers (Bao et al., 2002) was applied to the synthesis of derivatives of K₂Ti₄O₉ fiber through the hydration process, including H₂Ti₄O₉·1.2H₂O, TiO₂ fiber, K₂Ti₈O₁₇ fiber and K₂Ti₆O₁₃ fiber. A novel viewpoint was proposed that the Ti/K mole ratio (R) of the target products was taken as the controlling aim of the composition of hydrate intermediates in the hydration process. Based on this, the model was successfully used to predict the suitable conditions for the synthesis of phase-pure products. In the ion-exchange reaction process, the composition of hydrate intermediates was quantitatively controlled by the method of adjusting the pH value and K⁺ concentration with ion selective electrodes (ISEs).

View full abstract

Preparation and characterization of high solid acrylic based polyurethane/nano-silica coatings and acrylic latex/nano-silica coatings were investigated. For acrylic based polyurethane, nanocomposite polymer coatings with different nano-SiO₂ particles embedded were prepared via in situ polymerization or blending method. For acrylic latex, nanocomposite polymer coatings with nano-SiO₂ particles embedded were prepared by blending via high shear stirring or ball milling and in situ polymerization. The mechanical and optical properties of the nanocomposite polymer coatings were studied intensively using pendulum hardness tester, scanning probe microscope (SPM), instron testing machine, dynamic mechanical analyzer (DMA), transmission electron microscope (TEM), and ultraviolet-visible (UV-VIS) spectrophotometer. The coatings with micro-SiO₂ embedded were also investigated for comparison with the coatings containing nano-SiO₂. The results showed that the macro hardness, micro hardness, and scratch resistance were obviously improved via addition of nano-SiO₂. The tensile strength was also enhanced with the increasing content of nano-SiO₂. The UV absorbance in the wavelength of 290–400 nm increased as nano-SiO₂ content increased but did not change with micro-SiO₂ particles. Acrylic/nano-SiO₂ composite latex showed that different preparation method could cause different dispersion of nanoparticles in the polymer matrix.

View full abstract

Nano-sized SiO₂ particles were prepared via the sol-gel process, and evenly dispersed in the polyurethane resin. The tensile strength and 100% modulus of the polyurethane doped with SiO₂ were increased and the content of SiO₂ has an optimum value. Elongation at break had a downtrend at first and an ascending trend afterward with the increase of SiO₂. The addition of nano-sized SiO₂ not only increased the storage modulus but also improved the peak of tan δ of the polymer. Nano-sized SiO₂ hardly affected the low temperature-resistant properties, but improved the heat-resistant properties of the resin.

View full abstract

Biodegradable microcapsules entrapping an inorganic salt as a core material are prepared by the solvent evaporation method in the (W/O/W) emulsion system. The effects of the microcapsule preparation conditions on the microcapsule morphologies and the entrapment efficiency of an inorganic salt are investigated. The entrapment efficiency of inorganic salts into the microcapsules is improved by increasing the salt concentration, changing the type of salt in the outer aqueous phase, decreasing the concentration of the core material, and lowering the volume fraction of the dispersed droplets and changing the type of dispersion stabilizer. Especially, it is proven that a very high entrapment efficiency is obtained when gum arabic is used as the dispersion stabilizer.

View full abstract

Mono-core coating process using a draft-tube spouted-bed (DSB) with a converging nozzle and medium particles is proposed for fine and adhesive particles. In order to avoid the formation of agglomerates which tends to occur in the conventional fluidized bed coater, many attempts have been made in the past to establish improved fluidized bed coaters such as a spouted bed with a draft tube (DSB) and circulating fluidized bed coater. However, it has been found very difficult to perform coating on fine particles without forming agglomerates by these methods. In this study, the DSB with a converging nozzle and medium particles, in which the exfoliation effect and the disintegration force can be expected, is used for coating fine and adhesive particles with finer powder.
As a result, it was found that the mono-core coating of fine particles of an average diameter of about 26 μm could be achieved by using DSB with medium particles. However, it was shown difficult to control the amount of coating powder adhered to the seed particles was difficult because the exfoliation of coating powder occurred by the collision between medium particles and seed particles. Also, it was found that the coating efficiency of seed particles decreased with the increase of inlet gas velocity.

View full abstract