CONSTRUCTIVE DESIGN AND FEATURES OF THE PROCESSES IN THE ROASTING SHAFT FURNACES BY USING GASEOUS FUEL

The article analyzes shaft furnaces for lime production. According to the method of firing, shaft furnaces are of bulk type, semi-gas type, gaseous and liquid fuels. The disadvantages of the operation of the main modern kilns during lime burning have been established. The main aggregates for high-tonnage lime production are mine lime kilns, in which blast furnace coke or anthracite, or high-quality coals are used as fuel. Generally, lean fuels are used in industries where, together with the technological cycle, carbon dioxide is used, which are contained in flue gases with a concentration of 36−40%mass. The data on the operation of six furnaces on the territory of Ukraine at the enterprises showed that gas shaft furnaces of cylindrical and slotted type with a straight-lining profile were widely used. The parameters of such furnaces are productivity from 100 to 250 tons per day, shaft diameter from 3.2 to 5.4 m, and height 6−8 furnace diameters. Most often, they use heating systems with central and two rows of peripheral injection burners without protrusion. The most critical part of all furnaces is the distribution of gas flow rates over the cross-section of the furnace shaft and the depth of radial penetration of the gas flow into the material layer. Calculations of τ1 and τП were carried out in the following way: for τ1, the temperature range of the medium was chosen from 1300 to 250−300 °С, τox − the temperature range for the material was chosen from 1000 to 100 °С and the density of the product was taken into account at the degree of decomposition of limestone 98% (=1700 kg/m3). In the preheating zone, the limiting stage is the supply of heat from the gas to the lump material, and at the same time can be taken equal to ⁓400−450 kJ/(m2∙h∙К) and τ1 is estimated as 0.8÷1 hour. The total residence time of the material in the furnace (in the heating zone and in the firing zone) is estimated at 1.4÷1.5 hours. The average speed of material movement in the cylindrical part of the furnace is estimated as 0.004 m/s, which makes it possible to consider the filtering layer conditionally stationary. These characteristics affect the quality of limestone and the uniformity of limestone firing that was the basis for the design of roasting shaft kilns using gaseous fuel.

Characterization of dusts from secondary copper production

Various types of waste, including dusts, are produced in the pyrometallurgical production of copper from secondary raw materials. According to the European Waste Catalogue and Hazardous Waste List, dusts from secondary copper production are classified as hazardous waste. In secondary copper production 3.87 million tons of copper were produced worldwide in 2017. The dusts are produced in the following thermal operations: reduction of the melt in the shaft furnace (shaft furnace dust), converting (converter dust), and pyrometallurgical refining (refining dust). These dusts contain significant amounts of heavy metals (Zn, Pb, and Sn) in oxidic forms. The dusts are regarded as secondary raw materials, and it is necessary to look for ways of extracting these heavy metals. The aim of this work was to characterize the individual types of dust and determine their quantitative and qualitative composition. The content of heavy metals in copper shaft furnace dust is (52.16% Zn, 19.33% Pb), in copper converter dust (32.40% Zn, 14.46% Pb), and in refining dust (32.99% Zn).

Model-Based Analysis of Factors Affecting the Burden Layer Structure in the Blast Furnace Shaft

The distribution of burden layers in an ironmaking blast furnace strongly influences the conditions in the upper part of the process. The bed permeability largely depends on the distribution of ore and coke in the lumpy zone, which affects the radial gas flow distribution in the shaft. Along with the continuous advancement of technology, more information about the internal conditions of the blast furnace can be obtained through advanced measurement equipment, including 2D profiles and 3D surface maps of the top burden surface. However, the change of layer structure along with the burden descent cannot be directly measured. A mathematical model predicting the burden distribution and the internal layer structure during the descending process is established in this paper. The accuracy of the burden distribution model is verified by a comparison with experimental results. A sensitivity study was undertaken to clarify the role of some factors on the arising layer distribution, including the descent-rate distribution, the initial burden surface profile, and the charging direction through the charging matrix. The findings can be used as a theoretical basis to guide plant operations for optimizing the charging.

Thermodynamic Calculation of Hydrogen Chloride Generation in Blast Furnace Smelting Process

The generating pathways of hydrogen chloride in blast furnace smelting process may have two pathways: 1.sodium chloride and water react with phosphorus pentaoxide forming hydrogen chloride gas.2. Sodium chloride and water react with sulfur dioxide and nitrogen dioxide forming hydrogen chloride gas. Based on Thermodynamic calculation of hydrogen chloride generation in blast furnace smelting process, hydrogen chloride gas is generated in the upper part of blast furnace shaft ,the generating temperature main range from 300°C too 800°C.