Workers’ Health Risk Factors in the Production of Iron Ore Pellets

Introduction. The labor of workers of the main occupations in the mining industry is characterized by a combined effect of occupational risk factors, which can be further aggravated by adverse environmental conditions. Objective: to study working conditions of employees in the mining industry. Materials and methods. We conducted a hygienic assessment of the technological process of manufacturing oxidized fluxed and non-fluxed pellets during the extraction of iron ore by surface mining and its further processing into high-quality raw materials for ferrous metallurgy, and a study of harmful physical and chemical factors of the working environment. Results. We established that a sinter machine operator (Class 3.3 hazard working conditions in the summer time), an operator of the agglomeration and firing furnace (Сlass 3.4), and a bunker operator in the shop for fired pellets (Сlass 3.3) work in hot occupational environment. The average value of the intensity of thermal radiation over the irradiation period (1.35 hours) for agglomeration and firing furnace operators was 356.2 W/m2 or 2–2.5 times higher than the maximum permissible level. Increased noise levels (Class 3.2) were measured at the workplaces of conveyor, sinter and furnace operators (14.8 % and 9.25 %). At individual workplaces of sintering machine operators, we registered elevated dust concentrations (Class 3.1), noise levels (Classes 3.1 and 3.2), sulfur dioxide concentrations (Class 3.1), and the sum of irritant chemicals (Classes 3.1 and 3.2 by excess of the maximum permissible concentration (MPC)) were recorded. At workplaces and in the service area of the furnaces at agglomeration and roasting, the maximum permissible level was exceeded for dust (Class 3.1), noise (Classes 3.1 and 3.2), sulfur dioxide (Class 3.1), and the sum of irritant chemicals (Classes 3.1 and 3.2). Conclusions: The hygienic analysis of the technological process of manufacturing iron ore pellets at the pelletizing plant indicates the presence of sources and conditions forming adverse occupational factors posing health risks for workers. In order to address occupational health and safety issues, it is necessary to introduce comprehensive measures to prevent health disorders in the working population.

Analysis of Contact Reaction Phenomenon between Aluminum–Silver and p+ Diffused Layer for n-Type c-Si Solar Cell Applications

In this study, the contact mechanism between Ag–Al and Si and the change in contact resistance (Rc) were analyzed by varying the firing profile. The front electrode of an n-type c-Si solar cell was formed through a screen-printing process using Ag–Al paste. Rc was measured by varying the belt speed and peak temperature of the fast-firing furnace. Rc value of 6.98 mΩ-cm−2 was obtained for an optimal fast-firing profile with 865 °C peak temperature and 110 inches per min belt speed. The contact phenomenon and the influence of impurities between the front-electrode–Si interface and firing conditions were analyzed through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The EDS analysis revealed that the peak firing temperature at 865 °C exhibited a low atomic weight percentage of Al (0.72 and 0.36%) because Al was involved in the formation of alloy of Si with the front electrode. Based on the optimal results, a solar cell with a conversion efficiency of 19.46% was obtained.

Combustion Characteristics and NOx Emission through a Swirling Burner with Adjustable Flaring Angle

A swirling burner with a variable inner secondary air (ISA) flaring angle β is proposed and a laboratory scale opposed-firing furnace is built. Temperature distribution and NOx emission are designedly measured. The combustion characteristics affected by variable β are experimentally evaluated from ignition and burnout data. Meanwhile, NOx reduction by the variable β is analyzed through emissions measurements. Different inner/outer primary coal-air concentration ratios γ, thermal loads and coal types are considered in this study. Results indicate that β variation provides a new approach to promote ignition and burnout, as well as NOx emission reduction under conditions of fuel rich/lean combustion and load variation. The recommended β of a swirling burner under different conditions is not always constant. The optimal βopt of the swirling burner under all conditions for different burning performance are summarized in the form of curves, which could provide reference for exquisite combustion adjustment.