Discovery of Significant Emission of Halogenated Polycyclic Aromatic Hydrocarbons From Secondary Zinc Smelting

Chlorinated and brominated polycyclic aromatic hydrocarbons (Cl/Br-PAHs) are persistent organic pollutants, and controlling their adverse effects requires the identification of their sources. However, current knowledge on the formations of Cl/Br-PAHs is far insufficient for source control, much less on their formation mechanisms. In this field study, we firstly discovered secondary zinc smelting as a significant source of Cl/Br-PAHs. The mean concentration of Cl/Br-PAHs emitted in stack gas from secondary zinc smelting was 9,553 ng/m3, exceeding concentrations from other metal smelting sources by one or two orders of magnitude. Cl/Br-PAHs with fewer rings were the dominant congeners in stack gas from secondary zinc smelting and secondary copper smelting. However, emissions from secondary aluminum smelting were dominated by congeners with more rings. The differences in congener profiles were attributable to the catalytic effects of metal compounds during smelting activities. Zinc oxide and copper oxide dominantly catalyzed dehydrogenation reactions, contributing to the formation of intermediate radicals and subsequent dimerization to Cl/Br-PAHs with fewer rings. Aluminum oxide induced alkylation reactions and accelerated ring growth, resulting in the formation of Cl-PAHs with more rings. The newly proposed mechanisms can successfully explain the emission characteristics of Cl/Br-PAHs during smelting activities and the higher concentrations of Cl/Br-PAHs from secondary zinc smelting, which should be useful in targeted source control.

Development of an Understanding of Reactive Mercury in Ambient Air: A Review

This review focuses on providing the history of measurement efforts to quantify and characterize the compounds of reactive mercury (RM), and the current status of measurement methods and knowledge. RM collectively represents gaseous oxidized mercury (GOM) and that bound to particles. The presence of RM was first recognized through measurement of coal-fired power plant emissions. Once discovered, researchers focused on developing methods for measuring RM in ambient air. First, tubular KCl-coated denuders were used for stack gas measurements, followed by mist chambers and annular denuders for ambient air measurements. For ~15 years, thermal desorption of an annular KCl denuder in the Tekran® speciation system was thought to be the gold standard for ambient GOM measurements. Research over the past ~10 years has shown that the KCl denuder does not collect GOM compounds with equal efficiency, and there are interferences with collection. Using a membrane-based system and an automated system—the Detector for Oxidized mercury System (DOHGS)—concentrations measured with the KCl denuder in the Tekran speciation system underestimate GOM concentrations by 1.3 to 13 times. Using nylon membranes it has been demonstrated that GOM/RM chemistry varies across space and time, and that this depends on the oxidant chemistry of the air. Future work should focus on development of better surfaces for collecting GOM/RM compounds, analytical methods to characterize GOM/RM chemistry, and high-resolution, calibrated measurement systems.

Optimization of SOFC stack gas distribution structure based on BP Neural network and CFD

The flow field distribution of solid oxide fuel cells significantly affects the performance of the stack. The flow uniformity can be improved and the power generation efficiency can be improved by optimizing the gas distribution structure of the stack. Based on the simplified 6kW stack model, the stack gas distribution structure with two-stage buffer cavity was designed, and the stack model was numerically simulated by ANSYS Fluent software. The BP neural network model, which can predict the uniformity of the outlet of the integrated stack, is established successfully. The parameters of the gas distribution structure are analyzed and optimized by using the orthogonal test and BP neural network. The results show that at the same time considering pile distribution structure under the condition of surface area and uniformity, when the first stage inlet buffer chamber depth is 40 mm, the channel width is 40 mm, the secondary inlet buffer chamber depth is 80 mm, can effectively reduce the electric pile distribution structure, surface area, to reduce heat loss, at the same time guarantee the integrated electric reactor outlet flow uniformity of more than 96%, greatly improves the efficiency of power generation.

Effect of Blending ratio on Co-Combustion of Coal and Biomass Through Emission Analysis

The environmental problems caused by industrial pollutants and global warming are on the rise. There is a need to develop a technology for reducing harmful pollutants. The co-combustion is getting serious attention by the scientists regarding its key facets to reduce the environmental pollutants. Its function is based on utilization of biomass with coal. In this work different types of biomass were used with coal samples to identify the suitable methodology. The biomass resource fulfills the requirement with reducing environmental pollutants and overcome energy crises. The ratios of biomass with coal samples were analyzed using stack gas analyzer. The banana tree waste (BTW) was found to be effective for reducing CO2 and CO emission. While, Cow dung manure (CDM) was found to be efficacious to decrease NOx. LC 80%+BTW 20% for SO2 and CDM for NO. To conclude, CDM and BTW decreases the emissions keeping blending ratio 80:20 with lignite coal to biomass in co-combustion respectively.

ANALISIS EMISI GAS BUANG HASIL PEMBAKARAN SOLAR DAN BIOSOLAR (B25) PADA FIRE TUBE BOILER

The use of biodiesel in boilers has great benefits because it reduces exhaust emissions. The purpose of this study is to test the quality of solar and biosolar raw materials as fuel from the boiler, analyze the concentration of pollutant gases (NOx, CO2, SO2) from the combustion of biosolar and diesel oil experimentally. The combustion system in the boiler tends to be simpler than compression ignition as is done with diesel engines. This research was conducted experimentally in a fire tube boiler, with a heat input rate of 60,000 kCal / hour and a pressure of 3 bar using biodiesel made from CPO (crude palm oil) as fuel. The mixture varies at 0, 5, 10, 15, 20 and 25% biodiesel in a mixture with biosolar diesel (B0, B5, B10, B15, B20 and B25). This research was carried out experimentally by testing the exhaust gas emissions generated from the stack gas stack which is expected to produce low exhaust emissions and are environmentally friendly. The results show that the use of biodiesel reduces gas emissions by increasing the value of biodiesel in the mixture. The results showed that the lowest gas emissions were around 4.142% (NOx); 12.50% (SO2) and 7.9% (CO2) contained in a mixture of 25% biodiesel in fuel (B25).