Naohito Hayashi

Numerical and Experimental Investigation on Heat Propagation Through Composite Sinter Bed With Non-Uniform Voidage: Part I Mathematical Model and Its Experimental Verification

The mechanisms of heat transfer through the sinter beds of the MEBIOS process are discussed and their comprehensive mathematical model is proposed. The MEBIOS process, the concept of which has been proposed earlier by the authors, allows using both coarse and fine particles of iron ores in the same sinter bed. The study includes two parts. The first part describes the model content and the results of its experimental verification. The model accounts for coal combustion, limestone decomposition, moisture evaporation/condensation, and melting/solidifying of solid phases. The model predictions are in good agreement with the experimental data. Typical numerical results of the sintering process and the key parameters influencing the process efficiency are discussed in the second part of the study.

Study on Drying Organic Sludges by Thermal Jet Dryer—Part 2: Characteristics of Air-Particle Multiphase Flow in Thermal Jet Dryer

The authors are developing a thermal jet dryer (TJD) with a vertical disc-shaped drying tank for the purpose of reducing the volume of solid wastes with high water content, such as organic sludges. In order to obtain the characteristics of air-particle multiphase flow in a TJD, cold model experiments and computational fluid dynamics (CFD) simulations were conducted. The following results were obtained: (1) A combined eddy was generated in the tank, such as in a cyclone separator. (2) “Cascading” phenomena occurred in the particle discharging mechanism. (3) In the TJD, particles maintained consistent drying conditions throughout the drying process.

Development of dispersed-type sonophotocatalytic process using piezoelectric effect caused by ultrasonic resonance

Recently, degradation of persistent organic pollutants (POPs) with low biodegradability in the environment and in industrial and municipal wastewaters has gained importance. In this study, a dispersed-type sonophotocatalysis (SP) process, which is a combination of sonolysis and photocatalysis with dispersed light sources, has been proposed for the effective and energy-efficient degradation of POPs. In this method, the piezoelectric effect caused by ultrasonic resonance in a piezoelectric element is used for producing luminescence in a LED. A luminescent device composed of eight UV-LEDs and a piezoelectric element was designed for dispersion of UV light in water; this device was confirmed to show luminescence under ultrasonic irradiation. Sonophotocatalytic degradation experiments were carried out using several such devices, and the results were compared with those obtained in sonolysis, photocatalysis, and fixed-type SP. The comparison showed that the degradation rate constants in fixed-type and dispersed-type SP were larger than the sum of the rate constants obtained for sonolysis and photocatalysis; further, the synergetic effect caused by the combination of sonolysis and photocatalysis was 7.5% and 18% in fixed-type and dispersed-type SP, respectively.

Hexachlorobenzene removal from a model sediment by using ultrasonic irradiation

Persistent organic pollutants (POPs) are very difficult to degrade when present in the environment and finally accumulate in the human body. Therefore, it is essential to develop efficient technologies for removal of POPs from polluted sediments. In this study, the authors attempted to evaluate the potential of hexachlorobenzene (HCB; a POP) removal by using ultrasonic irradiation and its combination with other advanced chemical oxidation processes (AOPs) and surfactant addition. The average removal ratios for ultrasonic irradiation alone and ultrasonic in combination with UV light irradiation were almost identical at 40%, and the efficiency could be improved to about 49% by combination with photocatalysis or surfactant addition. The dual-frequency ultrasonic irradiation showed the highest HCB removal ratio.

Numerical and Experimental Investigation on Heat Propagation Through Composite Sinter Bed With Non-Uniform Voidage: Part II Prediction of Process Efficiency

The results of numerical simulation of the mosaic embedding iron ore sintering (MEBIOS) process according to the model presented in the first part of the study are introduced. The main objective of the second part is the elucidation of key factors influencing the process efficiency, particularly the sintering completeness, velocity of the heat wave propagation and maximum temperature achievable in the pellet during the wave propagation. Numerical results reveal that the mass fraction of coal, diameter of coal particles and air inlet velocity are of prime importance in determining efficiency of the MEBIOS sintering process.

11 – Mechanochemical plating and surface modification using ultrasonic vibration

Abstract: This chapter introduces the concept of a novel ultrasonic-assisted mechanochemical technique for coating metallic surfaces with other metal or ceramic materials and presents recent experimental results on its implementation in a number of material systems. In the first part the capability of the process to deposit micro-sized Ti particles on Al substrates is examined. Based on the results obtained, the process was modified to improve the degree of surface coverage. Then, it was applied to produce La-monazite coatings on stainless steel substrates. The last part of the chapter presents data on TiN nanocoatings deposited on Al, Ti and stainless steel substrates. On the whole, the results suggest that the proposed technique gives much better results when dealing with submicro and nanoparticles.

Effect of the Sonophotocatalytic Pretreatment on the Volume Reduction of Sewage Sludge and Enhanced Recovery of Methane and Phosphorus

In this study, the sonophotocatalytic process, i.e., combination of ultrasonic irradiation (US) and photocatalytic reaction, was proposed as a pretreatment process for the anaerobic digestion of organic sludge in order to drastically reduce the amount of sludge and promote the recovery of methane and phosphorus. Several series of experiments employing different techniques, i.e., sonophotocatalysis (SPC), US, photocatalysis (PC), and thermal treatment, were conducted by using a batch type apparatus. The results of the SPC treatment showed a decrease in sludge volume by about 50% and the synergetic effects of US and PC treatments which were clearly observed as increases in dissolved chemical oxygen demand of sludge filtrate and in phosphorus compounds dissolution from sludge particles. In the SPC process of sewage sludge, the photocatalytic reaction was enhanced by the sufficient disintegration of sludge flocks due to the US treatment. Any pretreatments applied promoted the anaerobic digestion process, however, there was little synergetic effect and the long time SPC treatment resulted in a decrease in the reaction rate.