Effect of natural gas composition on reverberatory furnace thermal efficiency for nickel alloys

The purpose of the article is to develop and substantiate the principles of an energy model of an industrial reverberatory furnace taking into account chemical composition and properties of natural gas as well as to calculate the furnace thermal efficiency in order to estimate its industrial performance. To conduct the research mathematical calculations are performed based on the data of chemical and physical analysis of flue gases and chimney temperature using standard graphs of excess air and enthalpy values of flue gas components. The measurement of the amount of waste pollutants is carried out using MRU Delta 65-3 gas analyzers, which identify the total amount of gases (O2, CO, NO, H2S) They determine the temperature, pressure (vacuum), calculate the content of CO2 and installation efficiency as well. Aspen Hysys program is used to verify the mathematical model. The data on the properties of natural gas are obtained including the data on chemical composition, molecular weight, calorific value, excess air during combustion. The data on flue gases are also obtained, which include the data on the burnt gas components, molecular weights, enthalpy, calorific value, flue gases ratio at the temperatures from 94°C to 316°C. The chemical reactions of combustion given with the number of moles required and formed for each reaction are used to calculate the thermal efficiency of a reverberatory furnace for nickel alloys. The calculated data are confirmed by Aspen Hysys software. Based on the studies conducted, it is found that the variable having the greatest influence on the thermal efficiency is the low calorific value, since it depends on the composition of the natural gas. The proposed methods for calculating the thermal efficiency using a computer program are effective if an operator wants to evaluate the furnace operation efficiency on site.

Silver-Containing Concentrate Processing

The goal of the research was to melt the silver-containing concentrate from the Dukatsk deposit (Magadansk region) in a reverberatory furnace. Preparatory research has established that internal collector smelting is an effective way to recover precious metals from the flotation concentrate of the Dukatsk deposit. This method is based on the property of lead and copper in the concentrate in an amount comparable to that of silver, to collect precious metals in a metal or matte phase in the process of segregation smelting. Recovery of silver in a high-grade alloy in one technological operation corresponds to the planned performance (silver recovery into an alloy of 93.0%) in processing flotation concentrates at non-ferrous industry plants.

A SYSTEM APPROACH TO CARCINOGENIC RISK ASSESSMENT AND MANAGEMENT FOR METALLURGICAL WORKERS EMPLOYED IN VARIOUS BLISTER COPPER PRODUCTION PROCESSES

The paper presents results of the application of the system approach to carcinogenic risk assessment and management based on the identification carcinogens, prediction carcinogenic effects and rationale for targeted preventive and curative measures. Evidence from metallurgical shops where various blister copper production processes are used regardless of the existing smelting technologies shows the risk of cancer to be Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeingeptable even when the working conditions are classified as permissible (class 2) in terms of chemical factors. The highest carcinogenic risk values are observed for occupations with workplaces characterized by a significant release of dust, arsenic being the main risk contributor. In cases of the blast furnace and reverberatory furnace smelting, carcinogenic risks for workers with a 25-year length of employment exceed the permissible level by 17.6 and 28.8 times, respectively, and in the case of bath smelting, carcinogenic risks exceed the permissible level by 5.1 times. The maximum length of employment for bath smelting shop workers amounts to 5.14 years, being by 1.42 and 0.89 years higher than that for the blast furnace and reverberatory furnace smelting shop workers, respectively. The observed cancer mortality rates exceed significantly the expected mortality rates for the tumor of all sites in cases of combined and respiratory cancers. The highest cancer mortality rates were recorded for batch loaders (60%) and smelter (40%) with the highest predicted carcinogenic risk values. Cancer-specific marker levels higher normal ones were detected in 73% of workers from the increased individual carcinogenic risk group. The proposed system approach to carcinogenic risk assessment and management will make it possible to try out components of the risk-based approach in the supervisory activities at industrial facilities with exposure to carcinogens, to establish the acceptable risk levels depending on the length of employment, identify the priority carcinogens; it will also allow indicating a rationale for additional testing for occupational carcinogenesis predictors as part of routine medical examination procedures and to develop preventive measures against key risk factors.