Lu Shengyong

Inhibition of de novo synthesis of PCDD/Fs by SO2 in a model system

The effect of sulfur dioxide (SO(2)) on de novo synthesis of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/F) and biphenyls (PCB) was investigated in model systems containing carbon, activated by cupric chloride (CuCl(2)). Five types of carbons (activated carbon, three types of carbon blacks, and graphite) were used to test the universal character of our results. The influence of SO(2) on speciation and behavior of copper compounds, catalytic oxidation of carbons, and formation of organic chlorine (extractable organic chlorine and non-extractable organic chlorine) was also studied to investigate the inhibition mechanism of SO(2) on de novo synthesis. It was found that SO(2) can sulfate CuCl(2), but does not react with CuO and CuCl(2).CuO in a 10% O(2)/N(2) atmosphere at 300 degrees C. The suppression by SO(2) of organic chlorine (C-Cl) formation also confirmed these findings. It was also found that catalytic oxidation of carbons was strongly suppressed by SO(2). A dramatic decrease in PCDD/Fs formation was observed for all five carbons, while adding SO(2); at the same time the average chlorination level also decreased. However, the inhibiting effect on PCB was less apparent compared with that on PCDD/F. On the basis of the experimental results, the conversion of both cupric and cuprous chloride into the non-reactive sulfate was proposed as inhibition mechanism.

Simulation of ball motion and energy transfer in a planetary ball mill

A kinetic model is proposed for simulating the trajectory of a single milling ball in a planetary ball mill, and a model is also proposed for simulating the local energy transfer during the ball milling process under no-slip conditions. Based on the kinematics of ball motion, the collision frequency and power are described, and the normal impact forces and effective power are derived from analyses of collision geometry. The Hertzian impact theory is applied to formulate these models after having established some relationships among the geometric, dynamic, and thermophysical parameters. Simulation is carried out based on two models, and the effects of the rotation velocity of the planetary disk Ω and the vial-to-disk speed ratio ω/Ω on other kinetic parameters is investigated. As a result, the optimal ratio ω/Ω to obtain high impact energy in the standard operating condition at Ω = 800 rpm is estimated, and is equal to 1.15.

PCDD/FS emission in a 150T/D MSW and coal co-firing fluidized bed incinerator

Incineration as a method of reducing Municipal Solid Waste (MSW) volume and recovery of energy has been developed gradually in China. More attention is paid on polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, (PCDD/Fs) formed in MSW incineration process. This paper presents results of the analysis of PCDD/Fs in the residues of a fluidized bed incinerator co-firing MSW and coal in the Yuhang Thermal Power Plant. The effects of operation conditions and the wet scrubber system on PCDD/Fs formation were also analyzed. PCDD/Fs emitting from the smoke stack was 0.92 I-TEQ ng/Nm3. After the wet scrubber emission of dioxins increased and the shifting of homologue profiles in flue gas was also observed, PCDFs were not detected in the incinerator residues. From this, we can see that in the MSW incineration process, the formation mechanism of PCDFs was different from that of PCDDs. The results will benefit further research on the optimal operation of incinerator and control of PCDD/Fs emission from the MSW incinerator.

Evolution of PCDD/F-signatures during mechanochemical degradation in municipal solid waste incineration filter ash

Mechanochemical degradation (MCD) is employed for the dechlorination of polychlorinated dibenzo-p-dioxins (PCDD) and -furans (PCDF) in filter ashes from municipal solid waste incinerators, respectively with the assist of six additive systems. The evolution of PCDD/F-signatures in all eleven samples are systematically monitored and studied at the level of individual congeners, and special attention is paid to CP-route congeners, 2,3,7,8-substitution, 1,9-substitution, and 4,6-PCDF. The PCDD/F-isomers distribution follows an analogous pattern, indicating the similar acting mechanism for all additives: additives transfer electrons to attack the CCl bond and then expulse chlorine. MC dechlorination is not favored for the chlorine on β-position (2,3,7,8-position). The oxygen with stronger electronegativity in PCDD/Fs negatively influences CCl bond to accept donated electrons, hindering the removal of chlorine on 1,9-position for PCDD, and chlroine on 4,6-position for PCDF. Finally, two fair dechlorination pathways for PCDD and PCDF are respectively proposed based on the detailed analysis of CP-route congeners. The evolution of PCDD-signatures is clear, yet obscure for PCDF-signatures, which still requires further investigations.

Long-Term Monitoring of Dioxin and Furan Level in Soil Around Medical Waste Incinerator

The annual generation of solid waste is quite huge in China. For instance, approx. 157 million tons of municipal solid waste (MSW) and 2.04 billion tons of industrial solid waste (14.29 million tons of hazardous waste) were produced in 2009 (National Bureau of Statistics of China, 2010). These wastes would contaminate green land, drinking water and even air, ultimately threatening human health, so they must be treated in scientific methods. Waste treatment is a big challenge for every country. At present, the conventional disposal system according the hierarchy of methodologies includes recycle, compost, combustion and landfill. Combustion has noticeable advantages in volume and weight reduction, disinfection and short time cost, can also realize energy recovery by using waste to energy plants. Thermal treatment (pyrolysis and incineration) is the widely applied technology for waste treatment, for instance, accounting for 18.2% of MSW treatment in China and 11.9% in USA (2009). There are over 300 central incinerators for hazardous solid waste (HSW) in China (National Development and Reform Commission of China, 2003) and 93 municipal solid waste incinerators (National Bureau of Statistics of China, 2010). The present Chinese regulations prohibit the co-combustion of HSW and MSW (Ministry of Environment Protection, 2001). However, waste incineration is still a controversial issue among social and scientific communities due to its secondary pollution, especially after the observation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in incinerators (Olie et al., 1977). Waste incineration is thought a major source of PCDD/Fs in the environment. UNEP (UNEP Chemical, 2005) published the standardized toolkit for identification and quantification of dioxin and furan, including the emission factor of PCDD/Fs from combustion and incineration. Research (Gao et al., 2009; Ni et al., 2009) shows the emission factor of PCDD/Fs from medical waste incinerators (MWI) is nearly 63.3 μg I-TEQ/ton refuse into the atmosphere and 1.73 μg I-TEQ/ton from municipal solid waste incinerators (MSWI) in China, respectively. There are 135 dioxins and 175 furans, each with a different number and position of the chlorine atoms. 17 congeners of PCDD/Fs with 2,3,7,8 positions substituted by chorine are very toxic, which can induce a variety of adverse health problems, such as sarcomas, lymphomas and stomach cancer (Mitrou et al., 2001). These toxic pollutants can be formed by de novo synthesis and from precursor compounds (McKay, 2002), be emitted into the air through the stack, and transported to the ambient air,

Experimental study on low temperature thermal treatment of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in fly ash

The effects of temperature and time on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) distribution in fly ash of a municipal solid waste incinerator (MSWI) were studied in a tubular oven under nitrogen atmosphere. The PCDD/Fs in the gas phase and solid phase were detected by high-resolution gas chromatography coupled with low resolution mass spectrometry (HRGC/LRMS) separately. The experimental results showed that the major congener was octa-chlorinated dibenzo-p-dioxin (OCDD) in the gas phase and the low chlorinated congeners were the major products in the solid phase. There were high levels of OCDD in the gas phase in several experimental conditions although the PCDD/Fs in the solid phase could be decomposed. The optimum condition for PCDD/Fs decomposition in fly ash was a heating time of 60 min at 400 °C under nitrogen atmosphere.