Physical,chemical and electrical analysis of dust generated from cement plants for dust removal with an electrostatic precipitator

The physical, chemical and electrical characteristics of cement dust generated from a cement plant have been investigated by using a dust analyzer and a high voltage conductivity cell based on JIS B 9915. Major constituents of raw material cement dust generated from the first grinding process are CaO (41.77%), SiO₂ (11.72%), Al₂O₃ (3.45%), and Fe₂O₃ (1.47%), while the cement clinker dust generated from the second grinding process consists of mainly CaO (48.09-65.50%), SiO₂ (14.02-21.56%), Al₂O₃ (2.86-3.76%), and Fe₂O₃ (1.77-2.66%). Size distribution of the raw material cement dust is bi-modal in shape and the mass median diameter (MMD) is 3.68 μm, whereas the cement clinker dust also displays bi-modal distribution and the MMD of the cement clinker dust is in the range of 7.89-58.78 μm. The resistivity of raw material cement dust is so high as 10¹⁴ ohm·cm at 300 °C, that cement dust would not precipitate well by the electrostatic precipitator.     

Optimization fluidization characteristics conditions of nickel oxide for hydrogen reduction by fluidized bed reactor

We evaluated the optimal conditions for fluidization of nickel oxide (NiO) and its reduction into high-purity Ni during hydrogen reduction in a laboratory-scale fluidized bed reactor. A comparative study was performed through structural shape analysis using scanning electron microscopy (SEM); variance in pressure drop, minimum fluidization velocity, terminal velocity, reduction rate, and mass loss were assessed at temperatures ranging from 400 to 600 °C and at 20, 40, and 60 min in reaction time. We estimated the sample weight with most active fluidization to be 200 g based on the bed diameter of the fluidized bed reactor and height of the stocked material. The optimal conditions for NiO hydrogen reduction were found to be height of sample H to the internal fluidized bed reactor diameter D was H/D=1, reaction temperature of 550 °C, reaction time of 60 min, superficial gas velocity of 0.011 m/s, and pressure drop of 77 Pa during fluidization. We determined the best operating conditions for the NiO hydrogen reduction process based on these findings.     

The evaluation of excess biomass growth in sewers

A few sections of the sewers in Watertown were experiencing clogging due to an excess biomass growth. It was suspected that the wastewaters discharged from Fisher-Barton's two facilities were causing excess biomass growth. Madison raw sewage had a slightly lower biomass growth than the mixture of industrial wastewater and domestic sewage samples. From microscopic examination of biomass, the main cause of excess biomass growth is thought to be toilet tissue. Biomass is attached to toilet tissue, decomposing it gradually and generating extracellular polymeric substances (EPS). Then, suspended particulates including graphite and precipitates are attached to the biomass and filamentous organisms, especiallySphaerotilus natans, leading to the increase in the biomass volume. We found that the filamentous bacteria were present in biofilm by FISH. A significant amount of graphite was embedded to biomass grown in sewer. Since the major cause of excess biomass appeared to be toilet tissue, it would not be economical to employ a filtration system for complete graphite separation. Instead, it is recommended that the manufacturing process where graphite is used be assessed and a best management practice is in place. Key words: Excess Biomass Growth, FISH, Sewer, Evaluation, Wastewater     

Effect of Compositional Variation on the Microstructural Evolution and the Castability of Al–Mg–Si Ternary Alloys

This study examined the microstructural evolution and castability of Al–Mg–Si ternary alloys with varying Si contents. Al–6Mg–xSi alloys (where x = 0, 1, 3, 5, and 7; all compositions in mass pct) were examined, with Al–6 mass pct Mg as a base alloy. The results showed that in the ternary alloys with Si ≤ 3 pct, the solidification process ended with the formation of eutectic α-Al–Mg₂Si phases generated by a univariant reaction. However, in the case of ternary alloys with Si > 3 pct, solidification was completed with the formation of α-Al–Mg₂Si–Si ternary eutectic phases generated by a three-phase invariant reaction. In addition to the eutectic Mg₂Si phases, the primary Mg₂Si phases formed in each of the ternary alloys, and the size of both sets of phases increased with increasing Si content. The two-phase eutectic α-Al–Mg₂Si nucleated from the primary Mg₂Si phases. The inoculated Al–6Mg–1Si alloy had the smallest grain size. Moreover, the grain-refining efficacy of the Al–5Ti–B master alloy in the ternary alloys decreased with increasing Si content in the alloys. Despite the poisoning effect of Si on the potency of TiB₂ compounds in the inoculated Al–6Mg–1Si alloy, the grain size of the alloy was slightly smaller than that of the Al–6Mg binary alloy. This resulted from the increasing growth restriction factor (induced by Si addition) of the Al–6Mg–1Si alloy. In terms of the castability, the examined alloys showed different levels of susceptibility to hot tearing. Among the alloys, the ternary Al–6Mg–5Si alloy exhibited the highest susceptibility to hot tearing, whereas the Al–6Mg–7Si exhibited the lowest. The severity of hot tearing initiated by the unraveling of the bifilm was determined by the freezing range, grain size, and the amount of eutectic phases at the end of the solidification process.

     

Two-dimensional correlation analysis of spectroelectrochemical data for p-benzoquinone reduction in acetonitrile

Two-dimensional (2D) spectral correlation analysis has been employed to interpret the complex spectroelectrochemical data obtained from an electrochemical system undergoing following reactions after electron transfer. The system used was electrochemical reduction of p-benzoquinone (p-BQ) in acetonitrile, which produces anion radicals and dianions at its first and second reduction potentials. The dianions undergo a fast comproporationation reaction with neutral p-BQ molecules to produce anion radicals back, complicating the spectral analysis. Upon application of 2D correlation analysis in conjunction with the self-modeling curve resolution technique, we were able not only to resolve the spectra and determine the sequence of spectral emergence but also to extract the individual spectra. The techniques offer a very powerful tool for interpreting highly convoluted spectra obtained from a system where a series of chemical reactions occur following the electron transfer at the electrode/electrolyte interface.     

Effect of thixoextrusion parameters on mechanical properties of 7003 Aluminum wrought alloy

The processing of high strength Al wrought alloys does lead either to restrictions for geometrical complexity or to high production costs due to low productivity and multiple-step processes.Thixoextrusion process to overcome these difficulties has been under investigation.In the present study, the effect of thixoextrusion parameters was investigated on mechanical properties of 7003 Al wrought alloy.The maximum extrusion pressure of the thixoextrusion process is three times lower than that of the hot extrusion process.The elongated grains which have the axisymmetry with extrusion direction are generally observed during hot extrusion process, while the microstructures of the thixoextruded are isotropic.The tensile and yield strengthes of the thixoextruded bar are lower than those of the hot extruded bar, while the elongation value of the thixoextruded bar is higher than that of the hot extruded bar.     

The preparation of V2O5/TiO2 catalyst supported on the ceramic filter candle for selective reduction of NO

In order to prepare the catalytic filters based on V₂O₅/TiO₂ for the removal of NO_x and participate simultaneously from the flue gas stream, the experimental study was carried out. The effective method to support TiO₂ layer in the pore of the commercial ceramic filter element was developed. TiO₂ layer was supported on the filter element by three methods; impregnation with Ti solution, sol-gel dip coating and sol-gel centrifugal coating. As the model test to check the catalytic activity, NO reduction in the oxidizing stream was investigated. The catalytic filter prepared by applying the centrifugal force showed the best NO conversion more than 90% when the face velocity was 0.02 m/sec. This was a very promising result for the application of catalytic filter for the flue gas control at high temperature. The supporting methods by the impregnation and dip coating were not recommended because the TiO₂ layer was concentrated in the exterior layer of the filter element. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8–10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University     

Comparison of different methods to quantify fat classes in bakery products

The definition of fat differs in different countries; thus whether fat is listed on food labels depends on the country. Some countries list crude fat content in the ‘Fat’ section on the food label, whereas other countries list total fat. In this study, three methods were used for determining fat classes and content in bakery products: the Folch method, the automated Soxhlet method, and the AOAC 996.06 method. The results using these methods were compared. Fat (crude) extracted by the Folch and Soxhlet methods was gravimetrically determined and assessed by fat class using capillary gas chromatography (GC). In most samples, fat (total) content determined by the AOAC 996.06 method was lower than the fat (crude) content determined by the Folch or automated Soxhlet methods. Furthermore, monounsaturated fat or saturated fat content determined by the AOAC 996.06 method was lowest. Almost no difference was observed between fat (crude) content determined by the Folch method and that determined by the automated Soxhlet method for nearly all samples. In three samples (wheat biscuits, butter cookies-1, and chocolate chip cookies), monounsaturated fat, saturated fat, and trans fat content obtained by the automated Soxhlet method was higher than that obtained by the Folch method. The polyunsaturated fat content obtained by the automated Soxhlet method was not higher than that obtained by the Folch method in any sample.     

A study on the characteristics of improvement in filtration performance by dust precharging

A hybrid dust-collector combining electrostatic charging with fabric filtration was developed and its performance characteristics were evaluated. Charged particles build porous dendritic structure on the filter surface by electrostatic attraction, increasing the collection efficiency of dust particles and reducing the pressure drop through the deposited dust layer and filter media. The cleaning performance of the dust layer is improved because the dendritic structured dust layer may be removed more easily by pulse jet cleaning flow. The results of the experiment showed a reduction of fine particle emission by 37% and 13% energy saving by precharging dust particles before filtration.