7TH EUROPEAN COKE AND IRONMAKING CONGRESS - ECIC 2016

The area of the surface of a coke that is accessible to gas is one important predictor of its reactivity. During burnout the surface area of the coke increases, and the rate of this increase differs between cokes. This increase has been attributed to the presence of fine closed pores in cokes that open up on burnout. Although it is certain that such closed pores exist, much is unknown about their nature. For instance, the size distribution of these closed pores and how it varies between cokes has not been previously measured. Small angle neutron scattering (SANS) is a technique that is especially useful for determining the total pore size distributions on the nanoscale size – from 1nm to 1 μm. SANS can also be used to distinguish between pores that are accessible to fluids from those that are not. In this study, six samples of cokes prepared from Australian coals (two cokes prepared in research coke ovens, and inertinite- and vitrinite-rich fractions of two coals coked in a 70 g oven), have been examined using SANS and Ultra Small Angle Neutron Scattering (USANS) to determine their relative pore size distributions and the fraction of pores that are closed as a function of pore size over the size range 1nm to 1 μm. New findings include: - Nearly all fine (<5nm radius) pores in cokes are closed. For the cokes investigated, the fraction of closed pores increased with decreasing pore size from < 25% at about 1 μm, 50% at 250 nm radius, rising to over 90% closed for pores of less than 5 nm radius. - For cokes made from maceral concentrates, the number of pores in the cokes made from inertinite concentrates was far greater than those from the corresponding vitrinite concentrates, especially around 50 nm. However the number of pores of <5nm radius was present to an equal extent in both cokes. The fact that in some cokes even comparatively large pores are closed suggests that some pore closure occurs during the coking process after the volatiles have been released.