Masahiro Hirasawa

Novel process for recycling metallic elements from mixtures of metal oxide wastes and waste polyvinyl chloride

A new pyrometallurgical process that involves recycling steel-making dusts and waste PVC simultaneously is proposed. In this work, firstly, a thermodynamic analysis of the proposed reaction process for steel-making dusts + PVC system is performed using the Facility for the Analysis of Chemical Thermodynamics (F*A*C*T) computational system. It is found that the simultaneous chlorination and reduction of ZnO and Fe 2 O 3 in the dusts by PVC and the separation of Zn from Fe under controlled chlorine and oxygen potentials are thermodynamically possible. To testify the results of the thermochemical consideration, thermogravimetry-mass spectrometry (TG-MS) analysis of the reactions in the ZnO/ Fe 2 O 3 /PVC system is carried out at temperatures up to 950°C. A batch-type reactor experiment is also made to investigate the possibility of the separation of Zn from Fe in ZnO/Fe 2 O 3 mixture by the reactions between the oxides and PVC. The results of the TG-MS and batch type reactor experiments show that recovering zinc and metallic iron from mixtures of ZnO, Fe 2 O 3 and PVC and effective Zn/Fe separation can be achieved.

Enhancement of gas phase heat transfer by acoustic field application

This study discusses a possibility for enhancement of heat transfer between solids and ambient gas by application of powerful acoustic fields. Experiments are carried out by using preheated Pt wires (length 0.1-0.15 m, diameter 50 and 100 micro m) positioned at the velocity antinode of a standing wave (frequency range 216-1031 Hz) or in the path of a travelling wave (frequency range 6.9-17.2 kHz). A number of experiments were conducted under conditions of gas flowing across the wire surface. Effects of sound frequency, sound strength, gas flow velocity and wire preheating temperature on the Nusselt number are examined with and without sound application. The gas phase heat transfer rate is enhanced with acoustic field strength. Higher temperatures result in a vigorous radiation from the wire surface and attenuate the effect of sound. The larger the gas flow velocity, the smaller is the effect of sound wave on heat transfer enhancement.

A two-stage reduction process for silicon production

A new Two-Stage Reduction Process is proposed for the production of high purity silicon. The porous SiC separates molten SiO 2 from an evacuated chamber. In the first stage, the molten SiO 2 reacts with SiC to produce gaseous SiO. In the second stage, SiO is sucked through the porous SiC wall and is reduced to Si. The fundamental potential of this process is examined by experiments and theoretical considerations. The conditions for the formation of Si are investigated. The Si formation rate and the rate controlling steps of this process are discussed on the basis of the kinetic theory.

Thermal Decomposition of Printed Circuit Board in the Presence of Zinc Oxide under Inert and Oxidative Atmosphere: Emission Behavior of Inorganic Brominated Compounds

Thermal degradation of a FR-4 type printed circuit board, PCB, containing brominated flame retardant has been studied both in inert and oxidative atmosphere for the emission control of harmful brominated compounds. The presence of oxygen in atmosphere resulted in the reduction of the yield of hydrogen bromide, one of the major brominated compounds in thermal treatment, and in the enhancement of the formation of bromine and hypobromous acid. The intentional addition of zinc oxide to the PCB powder sample gave rise to the fixation of Br as zinc bromide. It also resulted in the promotion of the release of brominated compounds in comparison to the case of pure PCB. Thus, the addition of the oxide can be a benefit with respect to the bromine fixation and the kinetics of thermal treatment of PCB as well as metal recovery.

Formation of Carbonaceous Materials by Ultrasonic Atomization of Aqueous Ethanol Solution and Pyrolysis Treatment

The ultrasonic atomization of aqueous ethanol solution and the consequent pyrolysis treatment has been employed in order to explore a new technique for preparation of carbonaceous compounds. The deposition of fibrous carbon on titanium catalyst has been observed after 5 hours of treatment at pyrolysis temperature of 973–1173 K. The yield in carbon has increased in comparison to the control experiment without ultrasonic atomization. A TEM analysis has shown that the fibre has the diameter of 30 nm and the fibre growth occurs from the catalyst particles.

Synergetic Effect of Ultrasound Irradiation in the COD Removal and Degradation of L-Ascorbic Acid in Aqueous Solution by Aerobic Treatment

The ultrasound irradiation and simultaneous oxygen bubbling into the L-ascorbic acid aqueous solution has been studied in order to establish a cost-effective oxidation process for wastewater treatment. The application of ultrasound considerably increases the decomposition rate, while the relative chemical oxygen demand (COD) value is essentially unchanged. The influence of various process parameters, such as temperature and oxygen flow rate, has been studied. Moreover, we have carried out preliminary experiments on the influence of the addition of metal oxide particles, i.e. SiO2 and TiO2. The effects of particles on the degradation of AH2 and the COD compounds are discussed.

Effect of gas injection on the behavior of slag foaming with smelting reduction of iron oxide by graphite

The effect of gas injection on slag foaming with smelting reduction of iron oxide from molten CaO-Li 2 O-SiO 2 -Al 2 O 3 slag systems is investigated under argon atmosphere at 1573K. Two slag compositions with basicity (=(N CaO +N Li2O )/N SiO2 ; N: molar fraction) 1.0 and 2.0 are chosen. The initial iron oxide concentration is changed from 3 to 10 mass%. A graphite tube, which is 40mm in length and 10mm in outer diameter, is employed as a reductant. The rotation speed of the graphite tube is from 1.67 to 15 s -1 . Injection gas (Ar or CO) flow rate is varied between 0.33×10 -6 and 6.67×10 -6 Nm 3 /s. The slag foaming is evaluated by gas holdup, e. It is found that slag foaming behavior is affected by gas injection in the case of the slag with a composition of 38.4%CaO-20.5%Li 2 O-41.1%Si02, in which the reaction is controlled by mass transfer. Gas holdup at first increases and then decreases slightly with the increase in gas injection flow rate. This result is discussed on the basis of the reaction kinetics and physical behavior of bubbles. Reaction rate constant increases with the increase in gas injection flow rate. On the other hand, bubble coalescence is also enhanced by gas injection. The net effect of gas injection on slag foaming is the result of two opposing effects of (1) enhancement of gas evolution accompanied by increased rate of the reaction and (2) bubble coalescence in the foamed slag. But in the case of the slag with a composition of 57.9%SiO 2 -28.1%Li 2 O-14.0%Al 2 O 3 , in which chemical reaction is the rate controlling step, no foaming phenomenon is observed even under the condition that gas is injected. The present experimental results of slag foaming can be fitted using a drift-flux model.