Characterization and abatement of SOx, NOx and PCDD/Fs in iron ore sinter machine wind legs

It was observed that SOx and NOx, in large concentrations, are getting released from certain wind boxes below the sinter machine. The particulates released from specific wind legs were characterized using Quantitative Evaluation of Materials by Scanning Electron Microscopy (QEMSCAN). Particulates with spherical, cubical, needle and bar-like morphologies containing K, Na, Cl were found. Nitrogen-based solids were found in clutter-like morphology. Some particles had a mixture of the above, SOx and NOx. A method of dissolving SOx, NOx and breaking them down into harmless substances was explored in this research. The deposits in the wind legs were dissolved in demineralized water and solutions of sodium bicarbonate, urea, and di-sodium borate deca-hydrate (borax) to estimate the absorbance of K, Na, Cl, Ca, Mg, S, and N based compounds present. Demineralized water and sodium bicarbonate were found to be the most effective sorbents of SOx and NOx. The filtrates were examined under QEMSCAN and found that SOx and NOx are not present. Based on the above finding, a solution of sodium bicarbonate and water 0.01% v/v was sprayed into a wind box and found that SOx and NOx have got reduced by about 55%. To maximize the capture of SOx and NOx, the solution was optimized at 0.02% v/v. With this novel technique, capital intensive Desulphurization (De-SOx) and Denitrification (De-NOx) installation can be avoided. Additionally, an economical solution to the Polychlorinated dibenzo para-dioxins and polychlorinated dibenzofurans (PCDD/Fs) emission was explored in this research. Various physicochemical mechanisms of forming harmful substances are described in this paper.

Technological parameters determining the sintering process intensity

The sintering intensity is an important factor determining techno-economic efficiency of sinter production which provides the blast-furnace process with the main type of agglomerated iron ore raw materials. The charge sintering rate depends on technological parameters of the sintering process. Therefore, a systematic study of sintering technological parameters, which determine its intensity, is of practical and scientific interest. Indicators of the sintering process intensity are considered that assess it from both the mechanical and heat engineering positions. It is shown that in its purest form the sintering process intensity is characterized by the vertical agglomeration rate and combustion intensity of the sintering charge carbon. Two other indexes − the specific productivity for suitable sinter and intensity of heat output in the combustion zone – are less representative for the comparative estimation of sintering intensity, since their values depend on sintered mass strength and thermal effect of carbon combustion respectively. These factors go beyond the essence of the sintering intensity concept. Since content of fines of 5 – 0 mm at different sinter plants is not equal, representative performance comparison of sintering process is possible only taking into account the total amount of fines generated throughout the agglomerate transport path from sinter machine to blast furnace or the results of testing the agglomerate strength in a drum. A comprehensive systematic classification of techniques has been developed to intensify the sintering process based on the material-component principle using four levels of separation – objects, directions, paths and methods in which each subsequent level concretizes and develops the previous one. Its value is universality, which makes it possible to apply a systematization and separation system for almost all already known and future methods of sintering process intensification.

MODELING OF PHOSPHORUS PRODUCTION PROCESSES AND DEVELOPING A MANAGEMENT STRUCTURE BASED ON GREY SYSTEMS

The agglomeration process is one of the complex, multidimensional technological processes; it takes place under conditions of a large number of disturbing influences. As a result, the amount of return during sintering reaches 40-50%. The work is devoted to the development of a mathematical model capable of predicting and controlling the sintering point based on real-time data. As the main parameters for the construction of predictive models, data measured in real time were used – the temperature in the vacuum chambers and the gas velocity determined through the measured pressure (rarefaction) in the vacuum chambers. This paper describes the methodology and basic algorithms for modeling agglomeration processes, starting from the ingress of the charge into the sinter machine and ending with the production of a suitable agglomerate. The obtained curves of the developed mathematical model of temperature in vacuum chambers served as the basis for testing the forecast model based on the use of the theory of gray systems and the optimization algorithm of the "swarm of particles". Based on the developed mathematical model, a system for predicting the sintering point is constructed, which is the basis for determining the quality of the agglomerate, which will reduce the return volume during sintering. The general structure of the sinter control system based on a dynamic predictive model is also proposed. The practical significance of the developed predictive model based on the theory of gray systems is as follows: - forecast of the sintering point value of the agglomerate and synthesis of the control action based on the forecast; - the algorithm for constructing a mathematical model of the forecast can be used for any process that has the character of a "gray exponential law".

Analysis of the Effect of Ventilation Bars on the Packing Structure of Sinter Bed by DEM Simulation

The effect of ventilation bars on the porosity of a sinter bed charged on a sinter machine was investigated. The behavior of the sinter feed was calculated by discrete element method (DEM) simulation. By taking into account the adhesion force, the sinter feed in the wet state was represented and the simulation parameters were determined to reproduce the experimental values of the angle of repose. The porosity of the sinter bed was calculated, and the mechanism of the formation of the packing structure and the cause of the distribution of porosity in each region were clarified. As a result, it is shown that in the case of shear flow, the higher the powder pressure during flow, the higher the porosity.

Temperature Distribution Estimation in a Dwight–Lloyd Sinter Machine Based on the Combustion Rate of Charcoal Quasi-Particles

The coke combustion rate in an iron ore sintering process is one of the most important determining factors of quality and productivity. Biomass carbon material is considered to be a coke substitute with a lower CO2 emission in the sintering process. The purpose of this study was to investigate the combustion rate of a biomass carbon material and to use a sintering simulation model to calculate its temperature profile. The samples were prepared using alumina powder and woody biomass powder. To simplify the experimental conditions, alumina powder, which cannot be reduced, was prepared as a substitute of iron ore. Combustion experiments were carried out in the open at 1073 K~1523 K. The results show that the combustion rates of the biomass carbon material were higher than that of coke. The results were analyzed using an unreacted core model with one reaction interface. The kinetic analysis found that the kc of charcoal was higher than that of coke. It is believed that the larger surface area of charcoal may affect its combustion rate. The analysis of the sintering simulation results shows that the high temperature range of charcoal was smaller than that of coke because of charcoal’s low fixed carbon content and density.

Automatic System Design Humification of Sinter Burden in Aglomeration Shop JSC «Ural Steel»

The authors propose a comprehensive solution to decrease in humidity control sinter charge sinter shop JSC Ural Steel. The main task of sinter production is the maximum productivity of the sinter machine with a sat-isfactory agglomerate quality. One of the key parameters affecting the sinter belt performance is the moisture content of the humidity sinter. Changes in the granulometric and chemical composition and physical and me-chanical properties of the components of the charge necessitate the search for new values of the optimum hu-midity of the charge. A system for automatic control of sintering machine productivity has been developed. Au-tomatic control is based on the principle of operation of a stepping type extreme regulation system with memo-rizing the extremum (maximum) of the output parameter. The simulation of the pump electric drive is implement-ed based on the developed automatic control loop for the moisture content of the sinter charge. Implementation of the proposed system for automatic wetting of the sinter charge will increase the productivity of the sinter machine by 1,4 % while reducing the water consumption by 1,7 %.

Improvement of Agglomeration Technology by a Sinter Mix Preheating

A series of industrial experiments was carried out on the sinter machine No. 1 of the sinter department of JSC "Ural Steel". The dynamics of the sinter mix temperature during the technological stages of its preparation from pelleting to loading on pallets was studied, depending on a water temperature change during pelletizing. It was defined that for the winter working of the sinter department of JSC "Ural Steel" the water temperature increases, which supplied the pelletizer to moistening, for every 10 ° C, facilitates an increase in the temperature of the sinter mix on the pallets by 1.5-2.0 °C. Therefore, for stable sinter mix production with a temperature of more than 55 ° C, it is necessary to use water supplied to the pelletizer for moistening, with a temperature of at least 85°C. To implement the proposed technology, it is necessary to equip the sinter machines with water-heating recuperative heater, installed above the sintering machine behind the ignition hood and using heat, radiated from the surface of the sinter.

Displacement of the Ingnition Furnace in the Iron Ore Sintering with Re-Circulation of Waste Gases

In search of new technologies for the iron ore sintering process, the re-circulation of waste gases in the process can provide some advantages in relation to the conventional process. For such study, a sintering multi-phase model was used for the assessment of the re-circulation of waste gases in the process. Five cases of re-circulation of waste gases in the sintering process were analyzed, always aiming at a stable operation in the process. The results of the simulation indicate an enlargement of the combustion front with the re-circulation of the waste gases and the possibility of existing a reduction of the solid fuel consumption. As a result, there was an increase of the calcium-silicate fraction, providing a sinter reducibility improvement, apart from the reduction of the emission of CO2 and PCDD/Fs in the sinter machine.