Analyzing the Formation of Gaseous Emissions during Aluminum Melting Process with Utilization of Oxygen-Enhanced Combustion

Oxygen-enhanced combustion (OEC) is a useful method for improving the efficiency of thermal plants and for decreasing greenhouse gas (GHG) emissions. Basic and modified burner designs utilizing OEC in the aluminum melting process in a rotary tilting furnace were studied. A combined approach comprising experimental measurement and simulation modeling was adopted aimed at assessing GHG emissions production. Reduction of up to 60% fuel consumption of the total natural gas used in the laboratory-scale furnace was achieved. The optimal oxygen concentration in the oxidizer regarding the amount of total GHG emissions produced per charge expressed as CO2 equivalent was 35% vol. Its further increase led only to marginal fuel savings, while the nitrogen oxide emissions increased rapidly. Using the modified burner along with OEC led to around 10% lower CO2 emissions and around 15% lower total GHG emissions, compared to using a standard air/fuel burner. CFD simulations revealed the reasons for these observations: improved mixing patterns and more uniform temperature field. Modified burner application, moreover, enables furnace productivity to be increased by shortening the charge melting time by up to 16%. The presented findings demonstrate the feasibility of the proposed burner modification and highlight its better energy and environmental performance indicators, while indicating the optimal oxygen enrichment level in terms of GHG emissions for the OEC technology applied to aluminum melting.

Silicon Metallurgy and Ecology Problems

Modern silicon production technology is associated with a risk of negative environmental impact due to the fact that in addition to the final product, other reaction products are formed, including dust, from the incomplete use of charge materials. Gases released during silicon smelting in ore-thermal furnaces are characterized by the content of a large amount of fine dust. Dust consists of 94–96% of silicon dioxide. As a result of the use of sulfur-containing raw materials in furnaces as sulfur reducing agents, sulfur compounds in the form of SO2 are present in the furnace gases entering for purification, and nitrogen oxides are also present. The developed silicon recovery smelting technology reduces the technological energy consumption and increases the furnace productivity in proportion to the amount of carbon replaced by silicon carbide. Replacing carbon with silicon carbide reduces the dust content and the amount of exhaust furnace gases, and changes their composition. Thus, reducing the amount of pollutants reduces their anthropogenic impact on the environment. Keywords: silicon, gas cleaning dust, gas capture system, microsilica

Efficiency of using alternative sources of heat in electric melting of metal

The paper considers ways to assess the efficiency of using alternative sources of heat when melting alloys in electric arc furnaces. The focus is on increasing furnace productivity and reducing production costs. The analysis of the use of various systems for intensifying melting in arc furnaces and their main indicators is carried out. An assessment of the efficiency of fuel use in electric arc furnaces has been carried out. The expected economic effect from the introduction of alternative energy sources in electric furnaces has been calculated. It is shown that the economic effect from the introduction of alternative energy sources on electric arc furnaces depends significantly on the increase in furnace productivity.

A Model to Control the Formation of Multi-Component Charge Portions on a Blast Furnace Conveyor

Introduction. Bell-less tops used in the charging area give significantly wider opportunities for regulating and distributing the charge material along the furnace top radius. Moreover, it becomes feasible to develop the methods for gas flow control and these methods shall differ from the conventional ones. One of such methods is introduction of multi-component portions of the charge with a technology based component ratio. Problem Statement. The bell-less top charging device is not designed for that type of portioning when the charge material mixing is accompanied with a simultaneous shift of one component with respect to other one for a certain set value, while charging. These portions can be formed with the use of computer-aided stock-conveying system, while discharging the material from weighing hoppers into the blast furnace conveyor. Purpose. This research aims at the development of the structure, the functioning algorithms and the mathematical model for the system to control the formation of multi-component mixed charge batches in order to increase the blast furnace productivity and to reduce the specific coke consumption. Materials and Methods. In this research, the methods of automatic control theory and artificial intellect for the synthesis of weight neuro-fuzzy controllers within the automatic control system of charge dosage have been used. The developed system designed to control multi-component charge portioning via PC has been tested by means of simulation modelling methods. Results. There has been developed an algorithm for operating the system for controlling the multi-component mixed charge preparation on the conveyor, given the arrangement of the specified components, their ratios in portions, total volumetric productivity of the conveyor, the variable geometry of the unloaded material, in the connection with the on-line information on the mixing process. The feasibility of the system has been verified by its simulation with the use of standard application tools. Conclusions. It has been established that the designed control system allows the formation of mixed portions of any composition defined by an operator at a given maximum output of the conveyor and prevents its overload in terms of mass or volume.

Technological suitability of semi-coke as a carbon reducer in production of manganese and silicon alloys

The article presents results of testing semi-coke as a carbon reducing agent in the production of manganese and silicon alloys. The fundamental possibility of using semi-coke in carbon part of the charge as a basic reducing agent for the production of ferrosilicon manganese is established. It is noted that the new reducing agent in its pure form works worse than in the mixture with coal. The greatest synergistic effect in the production of ferrosilicon manganese was achieved during the interaction of semi-coke with coal, while the following indicators were obtained: maximum furnace productivity of 43 t/day, maximum extraction coefficient of 87.9 %, and minimum specific dust formation of 49 kg/t of alloy. In the production of ferrosilicon the use of a new reducing agent did not give a significant positive effect, due to its low structural strength. It was revealed that the structure and type of the reducing agent affect the furnace performance: when using a reducing agent with a higher reactivity in the charge, it is possible to obtain higher furnace performance. In the production of ferrosilicon, a change in the specific dust generation is closely related to the level of daily production and specific energy consumption and can serve as an indicator of the furnace operation. The furnace performance, ceteris paribus, is determined by the amount of useful power input. With an excess of carbon in the charge an increase in useful power leads to a slight increase in the furnace performance, but at the same time, the energy consumption and specific dust formation significantly increase. It is shown, that the influence of technological factors on the technical and economic indicators of melting is determined by the degree of electrode seating in the furnace.

Еfficiency increase of powdered coal application at hot metal production and limestone calcination under unstable technology conditions

Operation of Ukraine ferrous metallurgy under conditions of dependence on import and instability of energy carriers supply, shortage of investments in modernization of production equipment, make the matter of cooperation between steel-works and research organization particularly actual. Basic results of cooperation between Z.I. Nekrasov Institute of Ferrous metallurgy, NAN of Ukraine and Dnepr steel-works in 2017–2019 on blast sfurnace operation pefection and technology of powdered coal injection into rotating limestone calcination furnaces. Results of the finding of the powdered coal optimal consumption shown, which ensure a high efficiency of the coke substitution, reaching of maximum possible blast furnace productivity as well as satisfactory utilization degree of the reducing gas ability. Results of implementation of a complex of measures presented, which ensure a rational distribution of the powdered coal by BF air tuyeres for making the heat conditions of the tuyere zone even by the blast furnace circle. Efficiency of application of technology of joint injection the powdered coal and natural gas was shown, which is achieved by improving the powdered coal combustion conditions in case of increase their mixing degree. Recommendations quoted for blast furnaces starting-up after their idling for a period exceeding the permissible one, without tapping the plug hot metal. The recommendations ensure an accident-free putting a blast furnace into operation followed by reaching planned parameters. Results of usage sensors information, measuring temperature of gas flow above the charge surface presented. The results allow to prove the correction of blast furnace charging mode by an expert module, generating correction impact to support control actions by technological personal. A complex of measures formed to prevent a disturbance of a blast furnace running in case of powdered coal injection in an amount exceeding 140 kg/t of hot metal and without application of special washover materials. The results of efficiency of the mastered technology, envisaging application manganese-bearing materials at a constant base, were shown. Results of diagnostics of workability of the facility for powdered coal injection into rotating limestone calcinating furnace presented, followed by elaboration recommendation on correction parameters of injection facility operation.

A Model to Control the Formation of Multi-Component Charge Portions on a Blast Furnace Conveyor

Introduction. Bell-less tops used in the charging area give significantly wider opportunities for regulating and distributing the charge material along the furnace top radius. Moreover, it becomes feasible to develop the methods for gas flow control and these methods shall differ from the conventional ones. One of such methods is introduction of multi-component portions of the charge with a technology based component ratio. Problem Statement. The bell-less top charging device is not designed for that type of portioning when the charge material mixing is accompanied with a simultaneous shift of one component with respect to other one for a certain set value, while charging. These portions can be formed with the use of computer-aided stock-conveying system, while discharging the material from weighing hoppers into the blast furnace conveyor. Purpose. This research aims at the development of the structure, the functioning algorithms and the mathematical model for the system to control the formation of multi-component mixed charge batches in order to increase the blast furnace productivity and to reduce the specific coke consumption. Materials and Methods. In this research, the methods of automatic control theory and artificial intellect for the synthesis of weight neuro-fuzzy controllers within the automatic control system of charge dosage have been used. The developed system designed to control multi-component charge portioning via PC has been tested by means of simulation modelling methods. Results. There has been developed an algorithm for operating the system for controlling the multi-component mixed charge preparation on the conveyor, given the arrangement of the specified components, their ratios in portions, total volumetric productivity of the conveyor, the variable geometry of the unloaded material, in the connection with the on-line information on the mixing process. The feasibility of the system has been verified by its simulation with the use of standard application tools. Conclusions. It has been established that the designed control system allows the formation of mixed portions of any composition defined by an operator at a given maximum output of the conveyor and prevents its overload in terms of mass or volume.