Supriya Ghosh

Maximisation of non-coking coals in coke production from non-recovery coke ovens

Abstract The blast furnace has been, and is likely to remain, the dominant technology for ironmaking. Coke is fed to blast furnace as a fuel and its quality plays a significant role in controlling the performance of the furnace. The quality of coke depends on the quality of coal or its blend, coking parameters and precarbonisation techniques, if any. With decreasing availability and increasing cost of good quality hard coking coal, coke makers face a tough challenge for production of metallurgical coke at competitive rates. Coke quality has been enhanced in recent times by introduction of precarbonisation techniques, such as compaction of the blend into cakes, so as to improve its bulk density. JSW Steel has adopted the newly developed vibrocompaction precarbonisation technique, along with non-recovery ovens, having a capacity to produce 1˙2 Mtpa of coke. Optimisation of coal blend and bulk density of cake produced from vibrocompaction has helped JSW use inferior coals up to 35% in the coal blend, without adversely affecting the coke quality. The present paper discusses the optimisation of bulk density and coal blend, and use of non-coking coals in the coal blend to obtain the desired coke with properties: coke strength after reaction (CSR) exceeding 64%, coke reactivity index (CRI) <25% and Micum index (–10 mm) (M10) <6%.

Optimisation of coal blend and bulk density for coke ovens by vibrocompacting technique non-recovery ovens

Abstract The quality of coke produced in a coke oven depends on the coal blend characteristics and carbonisation conditions. Scarcity of good quality coking coal made it necessary to look for techniques capable of producing superior coke from inferior coals. Precarbonisation techniques improve the bulk density of the coal charge and produce good quality coke from inferior coals. The stamp charging technique, the most effective among them requires finer crushing of coal and higher moisture as binder, both requiring additional energy. JSW Steel has adopted vibrocompaction along with non-recovery ovens for its 1·2 Mtpa coke production. This is a highly ecofriendly coke making process producing excellent quality coke from inferior coals. It increases the bulk density of cake, similar to stamp charging, using compaction in place of stamping. A cake density of 1·10 t m−3 has been achieved using the vibrocompacting technique with optimum moisture and crushing fineness. Coal blend containing up to 35% soft coal and coking coal having 32% volatile matter have been successfully used to produce a coke with coke strength after reaction >65%, coke reactivity index <25% and M10 <6%. The paper discusses the experience of operating vibrocompaction non-recovery coke ovens.

Phonon Coupling with Excitons and Free Carriers in Formadinium Lead Bromide Perovskite Nano-Crystals

Organometal halide perovskites in the form of nanocrystals (NCs) have attracted enormous attention due to their unique optoelectronic and photoluminescence (PL) properties. Here, we examine the phase composition and the temperature dependence of emission line width broadening in formamidinium lead bromide (FAPbBr3) perovskite nanocrystals (NCs) for light-emitting applications and identify different charge-carrier scattering mechanisms. Our results show most of the emission is from the orthorhombic phase. The PL line width broadening at high temperature is dominated by the Fröhlich interaction between the free charge carriers and the optical phonons. At low temperatures, the peak of the PL spectrum exhibits a continuous red shift indicating an increase of excitons contribution at lower temperatures, and concurrently the line width also narrows down due to the inhibition of the optical phonons. From the temperature-dependent measurements, the coupling strength of both the charge phonon interaction and the exciton phonon interaction have been determined. The obtained results indicate that the charge phonon coupling strengths are higher compared to the exciton phonon coupling.