Ma Zengyi

Development of an evaporation crystallizer for desalination of alkaline organic wastewater before incineration

A wastewater evaporation-desalination pretreatment method was introduced to remove the Na+ and K+ salts in volatile organic compounds (VOCs) wastewater before it was fed into the incinerator. VOCs in the wastewater were volatilized in the evaporation system and then the vapor was combusted in an incinerator. Simulated phenol wastewater containing sodium chloride was evaporated and concentrated and sodium chloride was crystallized in different parameters. The experimental results showed that the higher initial concentration of sodium chloride increases the ratio of volatilization of VOCs, which was due to the effect of “salting out” (a decrease in the solubility of the nonelectrolyte, in the solution, or more rigorously, an increase in its activity coefficient, caused by the salt addition (Furter and Cook, 1967)). When evaporation speed was increased from 1.67 ml/min to 2.73 ml/min, the total removal coefficient of sodium chloride was about 99.88%–99.99%. This pretreatment procedure eliminates the slag phenomenon caused by Na+ and K+ salts during wastewater incineration, so the incinerator could operate continuously, and the wastewater evaporation could increase the heat value of wastewater, and the operation cost, would be reduced.

Combustion of electronic wastes using a drop tube furnace

High temperature combustion is a key during the pyrometallurgical recycling for electronic wastes. Former researches relating to thermal treatment concentrated on thermal decomposition during electronic wastes pyrolysis and oxidation, using e.g. thermogravimetric analysis (TGA) or lab-scale batch-feeding furnace. In the present research, a bench-scale incineration system was developed to study the combustion of electronic wastes and the emission characteristics. The system features a continuously-fed drop tube furnace. By using it, the combustion proceeds under comparable conditions and the emitted flue gas is steady & uniform, the thermodynamic equilibrium approach for conversions of inorganic halogen could be investigated. It also equips with a cooling & sampling unit for investigating the emission of post-combustion area. The effects of operating conditions on the completeness of combustion and the emission of inorganic Br for waste printed circuit boards were investigated systematically by using this furnace. Under the proposed conditions, the combustion is quiet complete and more than 99.89% organobrominated compounds contained in raw materials are destroyed and convert to HBr & Br2 in flue gas. The two forms of inorganic bromine seem reach thermodynamic equilibrium within 0.25 s. Further experiments could provide the datum for analyzing the combustion performance, the emission characteristics of organic pollutants and the mechanism of chlorinated dioxins (PCDD/Fs) & brominated dioxins (PBDD/Fs) formation by fly ash catalyzed de novo synthesis.

Rotational and Vibrational Temperatures of Atmospheric Double Arc Argon–Nitrogen Plasma

The spectroscopic technique is employed to study the emission of atmospheric argon–nitrogen plasma jet generated by an original dc double anode plasma torch. The molecular bands of the N2+ first negative system are observed at the torch exit and chosen to evaluate the rotational and vibrational temperatures in comparison with the simulated spectra. The excitation temperature (Texc≈9600 K) is determined from the Boltzmann plot method. The results show that the rotational, vibrational, electron and kinetic temperatures are in good agreement with one another, which indicates that the core region of atmospheric double arc argon–nitrogen plasma jet at the torch exit is close to the local thermodynamic equilibrium state under our experimental conditions.