Coke Strength After Reaction Research Articles

Design, development and installation of a system for addition of oil–water emulsion on coal blend at coke oven, Durgapur steel plant

A selective crushing unit was installed at the Durgapur Steel Plant (DSP) of the Steel Authority of India Ltd (SAIL) in March 1997 for better coal preparation and improvement in coke quality with respect to M10, coke reactivity index (CRI) and coke strength after reaction (CSR). However, the selective crushing performance deteriorated especially during the monsoon period, because of poor fluidisation of coal due to a high moisture level in the coal charge. In the selective crushing unit at DSP, coal is fed from silos to primary crusher units through two conveyors, namely C14-A and C14-B. The system is designed for a maximum moisture level of 8·5% in the coal charge. During the monsoon period, the moisture level of the coal increases beyond 8·5%, leading to problems such as jamming of chutes and classifiers. Sometimes the classifiers are bypassed in order to supply coal to service bunkers continuously. This causes deterioration of coal crushing and in turn coke quality. Addition of an oil-water emulsion to the coal blend reduces the angle of repose and improves the bulk density of coal charge improving its flowability. It also allows more coal to be charged per oven leading to an increase in oven throughput. The Research and Development Centre for Iron and Steel (RDCIS), SAIL has designed and installed a system for oil-water emulsion spraying over coal blend for the first time in DSP. The system has been commissioned and is in continuous operation. Trials were conducted with varying proportions of oil and water mixture in the emulsion. High speed diesel oil and water were varied in the ratio of 1:5 to 1:6 so that the oil addition to the coal blend was around 0·02 to 0·03% of the coal charge. Spraying of oil-water emulsion has also given rise to benefits in respect of crushing levels (through 3 mm) and coke quality (M10) improvement etc.

Determination of metallurgical coke reactivity at INCAR: NSC and ECE-INCAR reactivity tests

Certain aspects of the Nippon Steel Corp. (NSC) based test for measuring metallurgical coke reactivity were studied at the Spanish National Coal Institute (INCAR). It was found that some highly reactive cokes do not follow the correlation between the coke reactivity index (CRI) and the coke strength after reaction (CSR) observed in most metallurgical cokes. It was proved that the temperature of the furnace at the beginning of the NSC test is irrelevant to the subsequent determination of CRI and CSR. By starting the test with a hot furnace, the total operation time and energy consumption can be reduced. In addition, a good correlation was found between the NSC test and a simpler and more economical test: the ECE-INCAR reactivity test.

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.

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.

Coke Strength after CO2 Reaction for Coke Used Blast Furnace

In order to standardize the testing method for coke strength after reaction (CSR) which is used widely for evaluation of coke quality at high temperatures, studies have been carried out on a few points involved in the method. The findings are outlined as follows:1) Sample temperature greatly affects CSR values. Temperature control at three points (at the center of a sample, and at top and bottom of the oven-wall) is preferable.2) The volume of samples required for the first-stage lot is 10kg. The appropriate crushing of the lot is achieved by a jaw-crusher and grains of larger than 21mm are crushed furthermore.3) A 19-21mm fraction of the sample thus crushed will closely represent the whole sample.4) The CSR testing method is accurate to the extent that standard deviations of CRI and CSR are 0.79 and 1.10 respectively.5) Reaction temperature, reaction time and CO2 volume, have affects on CSR values by 2-3%/10°C, 0.3%/min. and 0.1-0.2%10.1l, respectively.

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.