Coke Reactivity Index Research Articles

98/03557 Oxidative semicoking of coal in fluidized bed

Coke Strength after Reaction (CSR) and the concomitant Coke Reactivity Index (CRI) are useful parameters for assessing the behavior of coke in blast furnace. To measure CSR and CRI of the resultant coke from a particular metallurgical coal or blend, a pilot scale oven test for producing appropriate industrial grade coke for measurements is unavoidable. If the quantity of coal sample available is not sufficient for pilot scale oven test, CSR measurement of the resultant coke is normally not possible. CanmetENERGY has developed a procedure for producing coke to allow CSR measurement involving relatively small amounts of coal sample (∼15 kg). The procedure involves producing semi-coke using the Sole Heated Oven in accordance with ASTM standard D2014-97 (2004). In the Sole Heated Oven test the coal sample is heated only from the bottom (the sole) up to 950 °C with the top of the oven charge rising to 500 °C over a period of 6–7 h. The resulting semi-coke is quenched (either wet or dry) and subsequently reheated to 1100 °C under nitrogen for 1 h. CSR and CRI are measured using the coke produced using this procedure. To demonstrate the validity of CSR and CRI measured using this approach, identical coal blends were carbonized concurrently using the CanmetENERGY pilot scale moveable wall oven (460 mm wide, 350 kg capacity) and the procedures mentioned above. CSR and CRI of the cokes produced by these two approaches were compared. Statistical analysis and coke textual analysis were performed to demonstrate the relevance of this novel approach on CSR determination.

98/03555 Method of estimation and characteristics for coke heat quantities of coking coal

Coke Strength after Reaction (CSR) and the concomitant Coke Reactivity Index (CRI) are useful parameters for assessing the behavior of coke in blast furnace. To measure CSR and CRI of the resultant coke from a particular metallurgical coal or blend, a pilot scale oven test for producing appropriate industrial grade coke for measurements is unavoidable. If the quantity of coal sample available is not sufficient for pilot scale oven test, CSR measurement of the resultant coke is normally not possible. CanmetENERGY has developed a procedure for producing coke to allow CSR measurement involving relatively small amounts of coal sample (∼15 kg). The procedure involves producing semi-coke using the Sole Heated Oven in accordance with ASTM standard D2014-97 (2004). In the Sole Heated Oven test the coal sample is heated only from the bottom (the sole) up to 950 °C with the top of the oven charge rising to 500 °C over a period of 6–7 h. The resulting semi-coke is quenched (either wet or dry) and subsequently reheated to 1100 °C under nitrogen for 1 h. CSR and CRI are measured using the coke produced using this procedure. To demonstrate the validity of CSR and CRI measured using this approach, identical coal blends were carbonized concurrently using the CanmetENERGY pilot scale moveable wall oven (460 mm wide, 350 kg capacity) and the procedures mentioned above. CSR and CRI of the cokes produced by these two approaches were compared. Statistical analysis and coke textual analysis were performed to demonstrate the relevance of this novel approach on CSR determination.

97/04405 Enhancement of mechanical dewatering of fine clean coal by surface active additives: Singh, B. P. et al. Solid Liquid Separate Miner. Metall. Ind., Sel. Pap. Natl. Semin., 1996, 130–139. Edited by Bhima R. R. and Ansari, M. I., Indian Institute of Mineral Engineers, Bhubaoeswar Chapter, Bhubaneswar, India

Solvent refined coal (SRC) prepared from high-ash Indian non/weakly coking coals, as reported earlier (S.B. Choudhury, B.B. Brahamachari, S.R. Dwivedi, A.K. Roy, P.K. Dasgupta, M. Chakraborty, R. Hague, Solvent refined coal from high-ash non-coking coals/washery middlings for use in metallurgical coke making: part I, Fuel Processing Tech., USA, June '96, pp. 203–213), when blended in small doses (8–12%) with substandard coking blends and carbonised, yields coke with increased anisotropy as well as hot and cold strengths. This is reflected by positive improvement in the values of the Micum indices (M40 and M10), coke reactivity index (CRI) and the coke strength after reaction with CO2 (CSR) and also the optical texture of the resultant coke as reported in this paper. The authors confirmed, by pilot scale carbonisation tests (250 kg/batch) that SRC produced by the technology developed (S.B. Choudhury, B.B. Brahamachari, S.R. Dwivedi, A.K. Roy, P.K. Dasgupta, M. Chakraborty, R. Hague, Solvent refined coal from high-ash non-coking coals/washery middlings for use in metallurgical coke making: part I, Fuel Processing Tech., USA, June '96, pp. 203–213) can help in substituting high-fluid low ash prime coking coals (PCC) to the extent of 30% (by weight). The use of SRC can thus accommodate additional quantum of medium coking coals (MCC) in the coking blends of the major Indian steel plants. The large reserves of indigenous medium coking coals, especially low volatile medium coking coals (LVMC) after beneficiation can also be used in the blends for making blast furnace grade coke thereby conserving scarce prime coking coals.

Solvent refined coal from high-ash non/weakly coking coals for use in metallurgical coke making. Part II: utilization as a coking additive

Solvent refined coal (SRC) prepared from high-ash Indian non/weakly coking coals, as reported earlier (S.B. Choudhury, B.B. Brahamachari, S.R. Dwivedi, A.K. Roy, P.K. Dasgupta, M. Chakraborty, R. Hague, Solvent refined coal from high-ash non-coking coals/washery middlings for use in metallurgical coke making: part I, Fuel Processing Tech., USA, June '96, pp. 203–213), when blended in small doses (8–12%) with substandard coking blends and carbonised, yields coke with increased anisotropy as well as hot and cold strengths. This is reflected by positive improvement in the values of the Micum indices (M 40 and M 10), coke reactivity index (CRI) and the coke strength after reaction with CO 2 (CSR) and also the optical texture of the resultant coke as reported in this paper. The authors confirmed, by pilot scale carbonisation tests (250 kg/batch) that SRC produced by the technology developed (S.B. Choudhury, B.B. Brahamachari, S.R. Dwivedi, A.K. Roy, P.K. Dasgupta, M. Chakraborty, R. Hague, Solvent refined coal from high-ash non-coking coals/washery middlings for use in metallurgical coke making: part I, Fuel Processing Tech., USA, June '96, pp. 203–213) can help in substituting high-fluid low ash prime coking coals (PCC) to the extent of 30% (by weight). The use of SRC can thus accommodate additional quantum of medium coking coals (MCC) in the coking blends of the major Indian steel plants. The large reserves of indigenous medium coking coals, especially low volatile medium coking coals (LVMC) after beneficiation can also be used in the blends for making blast furnace grade coke thereby conserving scarce prime coking coals.

95/01200 Manufacture of binder-free pellets of low-rank coal

A two-stage study was undertaken to establish what effect, if any, perchloroethylene has on coal coking properties. Stage 1 was a kinetic study in which the Gieseler fluidity of samples of a high fluidity coal was measured over a 64-week period. Two of the samples were left untreated, with one stored in air and one immersed in water. The third sample was also stored in air, but was soaked in perchloroethylene for 2 h and then air dried immediately prior to fluidity testing. In Stage 2, seven different coking coals were studied, covering three different Australian coal measures and a wide range of coking rank. For each coal, a 40 kg clean coal composite was formed using laboratory water-based methods, a Reflux Classier for the 0.038–0.25 mm and 0.25–2.0 mm size fractions and a Mintek jig for the 2.0–16 and 16–50 mm size fractions. This 40 kg composite was then subdivided into four sub-samples. Samples A and B were coked immediately, whereas Samples C and D were stored in open trays at ambient conditions for a month before coking. Samples B and D were soaked in perchloroethylene for 2 h and then air dried prior to coke testing, whereas Samples A and C were left untreated. Coal properties were measured prior to coking, and after coking the NSC Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) were measured.In Stage 1 it was found that storage under water was able to maintain the sample fluidity better than refrigerated storage. The combined Stage 1 and 2 results showed that perchloroethylene had a detrimental effect on the coking properties of many coals. Hence coking tests on clean coal composites formed using heavy organic liquids may often under predict a coal’s true coking properties. This could lead to many coal deposits being undervalued. Perchloroethylene had the largest detrimental effect on the fluidity, CRI and CSR of coals that started with relatively poor properties. Perchloroethylene had a negligible effect on coals with relatively good initial coking properties. There was no clear correlation with vitrinite reflectance. The three most seriously affected coals all had relatively high inertinite content. It is speculated that the higher porosity of inertinite might allow greater access and retention of perchloroethylene in the coal particles.The laboratory water-based methods were able to produce clean coal composites that matched the proximate, petrographic and coal swelling number properties of the coal preparation plant product. The dilatometer and fluidity results were lower than those of the coal preparation plant, but this can be explained by the up to three month delay between mining of the original sample and the coking of the composite. These delays were an unavoidable part of the research nature of this project and had nothing to do with the water based methods deployed. If these water-based methods of preparing clean-coal composites were to become standardized, then there is no reason why a well equipped coal testing facility could not receive a refrigerated bore core and produce a clean coal composite within the period of a week.

Coke reactivity: Effect of Fe 2O 3 and K 2CO 3 addition to the coal charge before carbonization

Six individual coals and one blended metallurgical coal were used in this investigation, and two additives, Fe 2O 3 (up to 1%) and K 2CO 3 (0.5%), were added to each coal before carbonization. Results showed that the additives strongly increase CRI (coke reactivity index) and decrease CSR (coke strength after reaction) of each coke, but there are no significant changes in coke microstructure.

Estimation of Coke Properties using Petrographic Analysis of Semi-coke

The authors have tried to estimate coke properties by means of petro-graphic analysis on semi-cokes obtained from Gieseler plastometer.In this study, a series of 14 coals ranging from 0.79 to 1.67 in reflectance of vitrinite was used.Gieseler plastometer tests were carried out on these coals, and produced semi-cokes were examined by polarized microscopy to determine the properties of the different types of optical anisotropy.The authors found that the properties of carbonized coke have been correlated highly with the petrographic analysis of semi-cokes.This means that coke properties such as drum strength (DI) coke strength after reac-tion (CSR) and coke reactivity index (CRI) can be estimated from the petrographic analysis of semi-cokes.This method could be applied to the blending theory of coals.