Production of isotropic coke in industrial trials

2007

A series of coking coals covering a wide range of coalification, thermoplastic properties and geographical origin were carbonized at two different scales. All the coals used are available in the international market and they are used by the cokemaking industry in blend preparation. The cokes were produced in two movable wall ovens of 15 and 300 kg capacity available at INCAR-CSIC facilities. The quality of the cokes was assessed by means of reactivity towards carbon dioxide and mechanical strength before and after the reaction with CO2. The results obtained are very promising and a good correlation between the quality parameters of the cokes produced in the two ovens was found. The use of a semi-pilot oven against big-capacity ovens in the optimization of complex coking blends allows to obtain valuable results by using small amount of coal (15 kg vs. 300-400 kg) with the advantages that it is quicker, more flexible and of lower cost.

2009

XIII 1 Background .

ISIJ International, 2019

2017

Metallurgical coke is an important raw material for iron making in a blast furnace. Two significant criteria for selecting high quality coke are Coke Reactivity Index (CRI) and Coke Strength after Reaction with carbon dioxide (CSR). CSR and CRI tests are expensive, labor-intensive and timeconsuming. Meanwhile, CSR has linear inverse relation with CRI. Hence, research for coke quality can be focused on coke reactivity with CO2, which depicts the CRI. Part of this study aims at analyzing coke gasification with carbon dioxide of industrially manufactured coke. Thermogravimetric analysis of cokes was conducted by heating the cokes to a certain temperature and soaking in CO2. Using non-isothermal methods, the kinetic parameters, such as activation energy and pre-exponential constant, were calculated during the heating period in CO2. Conversions during the soaking period were also obtained from TGA and were correlated with CRI of the cokes. Another part of study was concentrated on production of cokes in laboratory. Different bituminous, coking coals and a sub-bituminous coal were used for coal carbonization, which was conducted in a horizontal tube furnace by heating samples in an inert atmosphere at different heating rates. Samples were also produced by addition of two binders, asphaltene and ash free coal, in bituminous and sub-bituminous coal and the effect of the binders on the carbonization products were studied. In this study, the CO2 reactivity of the cokes was detected by using Thermo-Gravimetric Analysis (TGA); the samples were heated to 1100˚C in an inert atmosphere and soaked at 1100 ˚C in CO2 for two hours. Total porosity of the cokes was determined by using image stitching of thin sections in digital microscopy at 250X magnification, followed by image processing in MATLAB. Raman spectroscopy was carried out to observe the spectra radiated from the coke samples, which gave two distinct peaks, indicative of graphitic carbon and disoriented carbon; extent of graphitization was calculated using the area under the peaks.

Energy & Fuels, 2014

Nuclear-grade graphite samples, anisotropic commercial graphite, graphitized co-cokes, and anthracites were characterized using X-ray diffraction, Raman spectroscopy, and temperature-programmed oxidation. Through evaluation of relationships between structural parameters, it was observed there is better likelihood to obtain isotropic or near-isotropic graphite from co-cokes than anthracites. The addition of coal to petroleum feed, i.e., vacuum resid or decant oil, reduces the concentration of large isochromatic units in a co-coke structure, thus leading to a graphitic structure that lacks anisotropic character upon graphitization of the co-coke. The structural characteristics of graphitized anthracites showed more similarities to anisotropic commercial graphite, in comparison to graphitized co-cokes. It was also found that coking a vacuum resid/coal blend offers better potential for producing an isotropic or near-isotropic graphite than the coking of a decant oil/coal blend. Increasing the co-coking temperature from 465 to 500°C appeared to favor obtaining isotropic or near-isotropic graphite upon graphitization.

ISIJ International, 2019

In the present study, we prepare several types of specimens from non-caking coal-including specimens in which noncovalent bonds between O-functional groups in coal are cleaved by pyridine and HPC-derived thermoplastic components are introduced into the pores produced by swelling, as well as specimens consisting of physical blends with HPC-and examine the influence of heating conditions and types of caking agents on the production of high-strength coke using a SUS tube. We also investigate the influence of heating conditions and types of caking agents on the strength of coke from pelleted specimens and determine the optimal conditions for producing high-strength coke from non-caking coal. HPC with a wide range of thermoplastic properties is more effective as caking agents than additives containing only low-molecular-weight or high-molecular-weight components. In addition, the strength of the produced coke depends on the amount of the additive, and optimal values of the additive amount are present. It was found that the following heating schedule is effective for producing high-strength coke from noncaking coal with added caking agents: First, high-speed heating (20°C/min) to an intermediate temperature in the range 400-600°C, recognized as the thermoplastic temperature range for typical caking coal; then, low-speed heating (3°C/min) to the temperature range of 900-1 000°C. Moreover, we demonstrate that, by increasing the rate of heating in the thermoplastic temperature range, it is possible to reduce the amount of caking agent added.

Fuel, 2019

Eight cokes made from coals/blend with different properties (vitrinite mean maximum reflectance = 0.90-1.66, logarithm Gieseler maximum fluidity = 4.16-1.30) were subjected to gasification and annealing simulating the conditions within an ironmaking blast furnace (BF). The specific methodology utilised included gasification of coke with BF gas-temperature profile from 900 to 1400°C (corresponding from the thermal reserve zone to the cohesive zone) and annealing of coke up to 2000°C (corresponding to the raceway region). The coke microstrength and macrostrength were determined using ultra-micro indentation and tensile test to understand the effect of coal precursor properties on the strength of the resulting coke and the changes when processed under the simulated BF conditions. Under the high temperatures in the simulated BF processes, the cokes from different coals showed significant differences in their properties, even though most of them had similar Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) values. Coke microtextures experienced significant reflectance loss and structure change upon simulated BF gasification and annealing conditions. The decreases in mean maximum reflectance and bireflectance were more severe for the coke produced from the high rank coal. The cokes made from coals with higher rank and lower Gieseler maximum fluidity exhibited greater change in their microstructure upon high temperatures. As a result, microstrength of cokes produced from these coals decreased more than that of coke made from the parent coals with a lower rank and higher Gieseler maximum fluidity; this tendency was more significant in the Reactive Maceral Derived Components (RMDC) than Inert Maceral Derived Components (IMDC) microtextural type. Degradation of macrostrength of cokes produced from coals with higher rank and lower maximum fluidity was also more severe due to the greater decrease in their microstrength.

Vacuum, 1989

In this study we have accomplished the textural characterization of two series of cokes obtained on an industrial scale with and without preheating stages, in order to interpret the origins of the changes in their properties of technological interest (reactivity and mechanical strength). The real and apparent densities, the volume distribution of pores and microphotographs of the materials ha ve been obtained. The higher mechanical strength of "preheated" cokes appears to be due to a lower number of holes (i.e. pores of larger size) that are present, as observed using scanning electron microscopy. The restrained decrease in the volatile material blend produces a decrease in the reactivity of the obtained "preheated" cokes as well as "wet" ones. The highest reactivity of "preheated" cokes can be explained on the basis of the slightly higher porosity.

ISIJ International

In continuation of the present authors' studies on production of high strength coke from lignite by sequential binderless hot briquetting and carbonization, this study has been carried out aiming at proposing methods to produce high strength coke from non-/slightly caking coals of subbituminous to bituminous rank. This paper firstly demonstrates preparation of cokes with cold tensile strengths above 10 MPa from two single non-caking coals (particle size; < 106 μm) by applying briquetting at temperature and mechanical pressure of over 200°C and 100 MPa, respectively. Such strength of coke is obtained over a wide range of heating rate, 3-30°C/min, during carbonization with final temperature of 1 000°C. Then, a simple pretreatment, fine pulverization of coal to particle sizes smaller than 10 or 5 μm, is examined. This pretreatment enables to prepare coke with tensile strength even over 25 MPa, by decreasing porosity of resulting coke and more extensively the size of macropores simultaneously. The coke strength changes with carbonization temperature having a particular feature; significant development of strength at 600-1 000°C, i.e., after completion of tar evolution, in which macropores and non-porous (dense) part of coke shrink in volume, inducing bonding and coalescence of particles and thereby arising the strength.

2013

The use of petroleum coke as an additive in coal blends has been tested and established successfully to produce metallurgical coke of acceptable quality at JSW. The performance of coke produced from coking coal blends containing petroleum coke was successfully tested in Blast furnaces. The amount of petroleum coke that may be incorporated in the blend without impairing the coke quality considerably depends mainly on the particle size and the rheological properties of the coal blend. The addition of petroleum coke produces a decrease in Maximum Fluidity (MF) in the blend due to the liberation of low molecular weight substances during heating within the plastic range and hydrogen containing species available to generate fluidity in co carbonization system. The use of low volatile petroleum coke as an additive resulted in better yield and reduction of coke ash.The ability of petroleum coke to interact with coal during plastic stage to impart good bonding between components and maintain...