Debjani Nag

Use of organic binder in coke making

Abstract Phenol based resol type resin was used as a binder in coke making and the effects of the binder on coke strength studied. The results have indicated that addition of binder improves the coke hot strength (CSR) and coke cold strength (M40). The optimum quantity was determined as 0·3%. Petrographic analysis shows an agreement with the coke strength.

Prediction of Coke CSR from Ash Chemistry of Coal Blend

Coke reactivity index (CRI) and coke strength after reaction (CSR) are the most important parameters used to assess the blast-furnace coke quality. The present work describes the possibility of estimating CSR for coke from ash chemistry of coal blends. For development and validation of the regression model, data obtained from the Tata Steels coke oven battery numbers 8 and 9 were utilized. It was found that CSR is greatly influenced by coal ash chemistry.

Vitrinite Maceral Separation Using Column Flotation

ABSTRACT The separation of vitrinite is being primarily carried out through density-gradient concentration (DGC) method. However, this technology is limited to laboratory-scale operations, since gravity plays a trivial role in the separation of ultrafine particles. In the present investigation, processing of vitrinite macerals on a large scale was explored using column flotation. Two coal samples (medium coking and non-coking) of less than 500 µm size were processed at neutral pH in single-stage column operation. Column-flotation operating parameters such as air flow rate, collector, and frother dosage were optimized to obtain the maximum recovery of vitrinite maceral. Enrichment of vitrinite in flotation products was confirmed through petrography studies with respect to feed. The column-flotation results were compared against to theoretical value obtained from sink-and-float analysis. The extent of vitrinite enrichment using flotation column was further investigated through surface-characterization techniques such as contact angle, zeta potential, and Fourier transform-infrared spectroscopy. The column-flotation results showed that the maximum yield was 67% and 77.5% for Coals A and B and the corresponding recovery was 84% and 93%, respectively.

Characterization of Solvent Extract of an Indian Coal

This article describes characterization of a solvent-extracted Indian coal obtained from four different seams of the West Bokaro coal mines. The coal samples were extracted with the solvent N-methyl-2-pyrrolidone. Ethylenediamine was used as co-solvent. Extracts were analyzed for elemental, microscopical and swelling properties. Functional group analysis was conducted using the Fourier transform infrared spectroscopy (FTIR). A comparative study made with parent coal showed that extraction with organic solvent brings about a considerable increase in lower molecular weight organic components, lowers the ash content and improves the swelling property of coal. FTIR studies provided some information about the functional group present in the parent and extracted coals.

Use of phenolic resin in coke making at Tata Steel

Quality of coke is very much important for blast furnace productivity. Phenol-formaldehyde resin can be used as an additive in small quantity in the coal blend for improvement of coke quality. It enhances the fluidity of coal blend during co-pyrolysis with coal and hence improves the coke quality. After successful lab-scale study, this phenomenon has been demonstrated in top charge battery and heat-recovery oven of Tata Steel through plant trial. It was found that 0.3–0.4% addition of phenolic resin in the coal blend improves coke quality.

Enhancement of Coking Properties of Coal by Differential Screening

Coke plays a major role in blast-furnace operation. Quality of coke mainly depends upon the coal used in blend. As the reserve of good coking coal is diminishing, at this point of time, it is important to give emphasis on coal-preparation techniques. Keeping this in mind, this article presents a coal-preparation technique named “differential screening” based on a selective crushing principle. Different types of indigenous and imported coals are characterized and screened in different size fractions. These size fractions are again characterized and carbonization tests are designed based on their properties under stamp-charging condition. This research suggests that the use of a specific fraction of coal in the blend in order to achieve the higher coke strength after reaction (CSR).

Methodology to Improve the Mean Size of Coke for Stamp Charge Battery

Coke physical properties like mean size and distribution are very important for blast furnace operation. Coke properties mainly depend upon parent coal characteristics and carbonization conditions. Some additives were found to influence the coke properties. This article presents the influence of pyroxenite as an additive and effect on operating parameter on coke size.

Characterization and Utilization of Organo-Refined Extract in Metallurgical Coke Making

ABSTRACT High-ash Indian coals and washery discards were extracted using an organic solvent. Complete characterization study was carried out in order to measure its coking potential. The study revealed that swelling and thermoplastic properties of the extracts are better as compared to the parent coals. A new concept for studying the thermoplastic behavior of coal is introduced to access the coking potential of parent and extracted coal. A series of carbonization tests was performed considering organic extracts as one of the blend components. The carbonization study reflects that the addition of an optimum amount of extracts in the base-coal blends helped in improving the properties of metallurgical coke.

Microtextural analysis of coke from single and binary blend and its impact on coke quality

ABSTRACT Coke microtexture and microstructure is a function of feed coal composition and carbonisation process. If the process remains constant, the composition plays a vital role in developing the microtexture and microstructure which also reflects the coke quality. Knowledge of the influence of coal composition and characteristics on coke quality is a must for formulating a coal blend for coke making. To better understand how the coal transforms into coke requires the ability to correlate the microtextural and microstructural features to coal properties. Petrography is an important tool for comparing the feed coal and corresponding coke. In the present study, cokes manufactured from single coals and two-component blends under similar coking conditions were studied under the microscope to provide valuable information to coke makers. Not only the rank and quantification of macerals but also the association of macerals and minerals play an important role. Also the size and type of inertinite affect the coke quality. Micro-cracking, crack lengths and fissures identify the zone of weakness, whereas microtexture of cell walls suggests the strength-controlling parameters of coke. Pictorial concept followed in the present study is given below: GRAPHICAL ABSTRACT

Effect of Coarser Fraction on Coke Strength After Reaction (CSR) of Coke Plant Blend at Tata Steel

ABSTRACT Metallurgical coke plays three primary roles in blast furnaces. It acts as a source for supplying reducing gases for reduction of metal oxide; it acts as a support to the raw material burden while descending through blast furnace and lastly it acts as a porous medium through which reactive gases can pass through the blast furnace. These roles are significant in blast furnace operation. Coke strength after reaction (CSR), coke reactivity index (CRI) along with parameters like Micum indices (M40/M10) assess the suitability of coke for blast-furnace operation. With the installation of larger blast furnaces, the need of coke with high CSR is more than ever. There are already many established methods to improve coke CSR through blend design, process optimization, additives, etc. But these works somewhat overlook the effect of particle size on coke CSR. The current work presents the impact of coal granulometry on coke CSR. It was observed in laboratory-scale carbonization of a commercial blend that the elimination of the > 5 mm fraction from the blend improves coke CSR by 2 points.