Bulk Density Of Charge Research Articles

I600 from the CSR test as a measure of pilot oven coke strength

ABSTRACTIn this study, I600 test results were compared with conventional drum indices. The I600 test is equivalent to the CSR I-drum test without pre-reaction of coke with CO2. The aim of this study was to determine to what extent the results of the I600 test could provide a useful indicator of the results of the commonly used coke strength indices. It was found that I600 correlated best with indices which had most similar particle size and drum revolutions. Further, significant improvement of relationship between CSR and CRI was obtained by incorporating the I600 index into the regression. Moreover, it was found that charge bulk density not only affected the values for the conventional drum indices, but it also affected the relationship between them and I600. Thus, charge bulk density must be included in regression aiming to compare drum indices especially those comparing results from tests with different number of drum revolutions.

INFLUENCE OF THE TWO-STAGE SINTERING MODE ON STRUCTURE FORMATION AND PROPERTIES OF POWDERED ALL-PRESSED BIMETALLIC IRON-BASED MATERIALS

The paper justifies the urgency and efficiency of obtaining bimetallic iron-based materials by two-step isothermal sintering to enable forming the structure of the product bases at the first stage and activating diffusion processes in the wear-resistant layer only at the second stage to eliminate any high-porosity areas and brittle inclusions at interlayer boundaries typical for powder materials doped with carbides, nitrides and borides. The analysis of equation solutions for diffusion in two-component heterogeneous powder systems made it possible to propose an option for determining the time and temperature of homogenizing sintering of bimetallic materials taking into account grain-size distribution of powders, concentration and partial diffusion coefficients of components, charge bulk density, initial and final porosity of the products. Experiments proved that bimetallic materials containing 15– 20 wt.% of chromium carbide, 20–25 wt.% of ferrochromium and iron as the rest component in the wear-resistant layer charge have the best combination of hardness, wear resistance and radial compression strength after sintering in a chamber furnace in protective medium at 1150–1180 °C with a holding time of 1,5–2,0 hours at the first stage, and in an induction furnace at 1350– 1370 °C for 25–35 s with a heating rate of 450–470 °C/s at the second stage. Structure formation peculiarities of the interlayer boundaries and wear-resistant layer during two-step sintering of all-pressed bimetallic materials are shown. It is found that for high-temperature sintering by high-frequency (8 or 16 kHz) heating at the second stage, the depth of chromium diffusion from the wear-resistant layer to the matrix is 120–130 μm, and Cr concentration in various points of interlayer and interparticle boundaries varies between 1 and 30 wt.% thus allowing formation of a transition layer with a structure consisting of a ferritic-austenitic matrix with martensitic colonies and dispersed particles of (Cr,Fe)23C6, (Cr,Fe)7C3 and (Cr,Fe)3C2 ferrochromium carbides uniformly distributed over the volume.

Nanostructure of cokes

Twenty eight cokes made from Australian coals and prepared under a range of experimental conditions were examined using Small Angle Neutron Scattering (SANS) and Ultra Small Angle Neutron Scattering (USANS) to determine the size distribution of all of their pores and also pores inaccessible to deuterated toluene (closed pores) in the size range 1 to 1000 nm radius. The main findings were that in all cokes, even those made from relatively inertinite-rich coals, nearly all pores of <5 nm radius were closed and >70% of the pores of 1000 nm in radius or larger were open. At intermediate pore sizes, the fraction of open pores was highly variable, with cokes made from inertinite-rich coals having more open pores. For all cokes made from coals sourced in Queensland, Australia, the number of open pores increased linearly with increasing inertinite content of the original coal and was not strongly affected by rank over the range investigated (0.9–1.3% mean maximum vitrinite reflectance). In contrast, all of the cokes made from the coals from the Illawarra region, New South Wales, Australia, had less than half the number of total or open pores than the other cokes. The number of pores of <5 nm radius decreased with increasing rank of the starting coal and was not strongly affected by the starting maceral composition or region of origin. The ratio of number of pores in cokes made from inertinite-rich concentrates to those made from the corresponding vitrinite concentrate from the same coal varied with pore size and was greatest at around 100 nm pore radius. The number of pores in cokes at all sizes below 1000 nm was largely unaffected by the bulk density of the charge, oven size or method of quenching. The insensitivity of numbers of nanometre-sized pores in coke to coke preparation conditions can explain why increasing the bulk density of a coal charge may increase coke strength but will have much less effect on coke reactivity to carbon dioxide.

Effect of surfactants on aluminosilcate refractory properties

Results are provided for a study of the effect of surface-active substances (SAS) based on polyethylene-naphthalene sulfonic acids (SP-1, Thermoplast-1, Thermoplast-3, Thermoplast-4, Thermoplast-5, 3 MB) on the production properties of refractory charges and physicoceramic properties of objects based on ordinary and high-alumina chamottes, and also electromelted corundum. It is established that on introducing the test SAS there is an increase in charge bulk density, which in turn promotes a reduction in molding pressure, increases raw material density and improves mechanical properties both after drying and for finished objects.