High-strength Coke Research Articles

Mixer to Disintegrate Coal Quasi-particles for Manufacturing High Strength Coke

Mixer to Disintegrate Coal Quasi-particles for Manufacturing High Strength Coke

Production of High-Strength Coke from Formed Coal Containing Low-Quality Coal by Pressurized Carbonization

Production of High-Strength Coke from Formed Coal Containing Low-Quality Coal by Pressurized Carbonization

Production of High-Strength Coke by Pressurization Carbonization of Modified-Biomass Blended Coal

Production of High-Strength Coke by Pressurization Carbonization of Modified-Biomass Blended Coal

The fracture characteristics and enhancement mechanism of crushing strength for the coke with hot pressing

High-strength coke is essential to the ironmaking and steelmaking industries. The crushing strength of coke could be improved effectively when the hot pressing technique is carried out with proper parameters. The fracture characteristics and enhancement mechanism of crushing strength for the coke with hot pressing were investigated by experiment and finite element method with the brittle cracking model. Results show that the crushing strength of coke is improved greatly when the hot pressing is conducted at 420 ℃∼440 ℃ for the 1/3 coking coal. Coke's crushing strength is mainly affected by porosity and pores' spatial distribution. For the high porosity, the coke has thin pore walls and the cracks could easily penetrate the entire coke. Therefore, the high porosity contributes to the decrease of crushing strength. If the pore distribution is uneven, the cracks expand rapidly in the pores aggregation region and the coke has lower crushing strength. In the initial and middle thermoplastic stages, conducting the hot pressing technique with low stress could enhance the crushing strength of coke. The coke porosity is high when the coal is pressed with high stress at the early thermoplastic stage. The high pressing stress may result in uneven pores distribution if the hot pressing technique is conducted at the middle thermoplastic stage. Therefore, the high pressing stress would impede the enhancement of crushing strength when the coal is pressed at the early and middle thermoplastic stages. When the hot pressing technique is conducted with high stress at the later thermoplastic stage, the coke would have low porosity, even pore distribution, low reactivity and high crushing strength.

Staged Pyrolytic Conversion of Acid-Loaded Woody Biomass for Production of High-Strength Coke and Valorization of Volatiles

Staged Pyrolytic Conversion of Acid-Loaded Woody Biomass for Production of High-Strength Coke and Valorization of Volatiles

Strength and Gasification Reactivity of Coke Prepared by Blending a Ca/C Composite and Coal

In this study, a calcium/carbon composite (Ca/C) was prepared from porous CaO by the water vapor swelling method; its pores were filled with tar-derived carbonaceous material to produce high-strength and highly reactive coke. The properties of coke prepared by blending the Ca/C composite and caking-coal were then investigated. The mesopores in the swelling Ca disappeared and the crushing strength was developed by filling tar-derived carbonaceous material into the porous Ca. Thus, a Ca/C composite could be produced by the abovementioned method, wherein the tar-derived carbonaceous material and Ca species were in close proximity. When the Ca/C composite was blended into the caking-coal, the strength of the coke obtained increased by up to 50% of Ca/C blending, which made it possible to produce high-strength coke. On examining the C structure of the prepared coke by X-ray diffraction, that of the original coke was found to be almost unchanged by adding the Ca/C composite. Conversely, the Ca/C blended-coke showed higher CO2 gasification reactivity than the original coke prepared from caking-coal. Based on the CO2 gasification reactivity test of the demineralized coke, it was clear that an increase in the gasification reactivity of the Ca/C blended-coke depended upon the catalytic effect of Ca. Thus, this method helped produce high-strength and highly reactive coke.

Preparation of High Strength Coke from Indonesian Lignite by Deeply Pulverized

Coke production from lignite was studied as a continuation of research showing the effectiveness of a sequence of hot briquettes and carbonization on preparations high strength coke from Indonesian lignite. The hot briquetting and carbonization cokes from three Indonesian lignites with a deeply pulverized. Ball milling carried out for 10 hours and 20 hours to obtain a small particle size. Raw lignite hot briquettes at mechanical pressure and temperature of 128 MPa and 200 °C, respectively, allowed cokes to be produced with a tensile strength (TS) of 7-11 MPa. Pretreatment, 10 hour and 20 hour ball milling, respectively increasing TS from the resulting coke to 15-23 and 19-36 MPa. Moreover, it is proved in this study that the structure on the coke fracture has a smooth texture and solid with less pore. There is a strong correlation between TS and coke density of individual lignites.

Production of High-Strength Coke from Low-Quality Coals Chemically Modified with Thermoplastic Components

Production of High-Strength Coke from Low-Quality Coals Chemically Modified with Thermoplastic Components

Production of high-strength and low-gasification reactivity coke from low-grade carbonaceous materials by vapor deposition of tar

Carbon/carbon composites were prepared from pyrolyzed-chars of lignite or low-strength coke (drum index of DI1506 = 52) and a coke-oven-gas tar through a gaseous-tar vapor deposition method to investigate the possibility of producing high-strength coke from low-grade coal or coke. The optimum vapor deposition temperature was examined under tar pyrolysis temperature of 700 °C and holding time of 30 min. The highest strength of prepared composite was observed at a vapor deposition temperature of 300 °C. The pore volume of the composite prepared at the vapor deposition temperature of 300 °C was the smallest among other samples prepared at that of 400–700 °C. The strength was improved by filling the carbonaceous materials derived from tar into the pores. The tar utilization coefficient was extremely low at 1.0 wt% or less. When same treatment was carried out for coke with different DI and pyrolyzed-cahr of lignite under the optimum conditions, it became clear that the composite prepared from any coke or pyrolyzed-char of lignite is comparable in strength to high-strength coke (DI1506 = 87). It was thus found that the present method can prepare high-strength coke from low-grade carbonaceous materials. The gasification rate of the composite prepared from low-strength coke was 0.5 times smaller than that of the original sample.

Structure Analysis of High Strength Coke Using X-ray CT

Structure Analysis of High Strength Coke Using X-ray CT

Production of High-Strength Coke from Low-Quality Coals Chemically Modified with Thermoplastic Components

Production of High-Strength Coke from Low-Quality Coals Chemically Modified with Thermoplastic Components

Preparation of pelletized coke by co-carbonization of caking coal and pyrolyzed char modified with tar produced during pyrolysis of woody biomass

To further the utilization of biomass for cokemaking at ironmaking facilities and to reduce CO2 emissions, carbon/carbon composite (CC) from tar and char is produced from the pyrolysis of a woody biomass with quartz-made fixed-bed reactor at 10 °C/min to 200–500 °C. Then, the optimum conditions for preparing high-strength coke by blending caking coal and CC is investigated. The specific surface areas of char and tar yields via sawdust pyrolysis are maximized at 550 °C. When the mixture of pyrolyzed char and tar produced in large quantities during the same process is co-pyrolyzed, the pore observed in prepared char completely disappears due to filling of carbonaceous materials derived from tar-pyrolysis into char pores, and char yield is improved. When the strength of the coke prepared from the mixture and pelletization of caking coal and prepared CC is investigated, the indirect tensile strength of the prepared coke tends to decrease with an increase in temperature of CC preparation. And, it was found that the optimum CC preparation temperature is 250 °C (CC250) for high-strength coke preparation. Although increasing the blending ratio of CC250 to caking-coal decreases the strength of the coke, the extent of decreasing strength is smaller than that of slightly-caking coal or pyrolyzed char blended to caking coal. The filling of carbonaceous materials derived from tar-pyrolysis into pores of sawdust char during CC preparation influences the coke strength, such that the value is greater than that of physical mixture of sawdust char and carbonaceous materials from tar prepared with individually (carbonaceous materials derived from tar not loaded into pore in char).

Influence of tarry material deposition on low-strength cokes or pyrolyzed chars of low rank coals on the strength

In this fundamental laboratory scale investigation, carbon/carbon (C/C) composites were prepared from a mixture of pyrolyzed-chars of low-rank coals (lignite and sub-bituminous coals) or low-strength cokes (drum index: DI1506 = 52 and 73) and coke-oven gas (COG) tar to investigate the possibility of producing high-strength coke for blast furnace use from low-grade coals or cokes. In addition, the optimum conditions for composite preparation and the influence of the tarry material on the strength of the prepared C/C composite was examined. The C/C composites were prepared as follows: the tar was first added over particles of coke or char at room temperature, subsequently, the mixture was pyrolyzed at a predetermined temperature (500–900 °C) in an inert atmosphere. The indirect tensile strength of the C/C composite prepared at a pyrolysis temperature of 500 °C increased with increasing weight ratio of tar to cokes (3.5–4.5 MPa) or chars (2.0–3.0 MPa) up to a ratio of 2.0; at this point, the indirect tensile strength reached approximately 6.0 MPa. The indirect tensile strength of the C/C composites prepared with the weight ratio of tar to cokes/chars of 2.0 also increased with increasing pyrolysis temperature, reaching approximately 7.0–7.5 MPa at 800–900 °C, which was comparable to the ca. 7.0 MPa strength of the high-grade cokes (DI1506 = 87) used in commercial blast furnaces. Based on pore size distribution measurements using the mercury intrusion porosimetry, N2 adsorption, and polarized optical microscope methods, it was likely that the increase in the indirect tensile strength of the prepared C/C composite occurred because of the vapor infiltration of tar-derived carbonaceous materials into the micro-, meso- and macro-pores in the low-grade cokes and pyrolyzed chars during the pyrolysis of the mixtures.

Effects of iron compounds on pyrolysis behavior of coals and metallurgical properties of resultant cokes

The utilization of highly reactive and high-strength coke can enhance the efficiency of blast furnace by promoting indirect reduction of iron oxides. Iron compounds, as the main constituent in iron-bearing minerals, have aroused wide interest in preparation of highly reactive iron coke. However, the effects of iron compounds on pyrolysis behavior of coal and metallurgical properties of resultant cokes are still unclear. Thus, three iron compounds, i. e., Fe3O4, Fe2O3 and FeC2O4 · 2H2O, were adopted to investigate their effects on coal pyrolysis behavior and metallurgical properties of the resultant cokes. The results show that iron compounds have slight effects on the thermal behavior of coal blend originated from thermogravimetric and differential thermogravimetric curves. The apparent activation energy varies with different iron compounds ranging from 94. 85 to 110. 11 kJ/mol in the primary pyrolysis process, while lower apparent activation energy is required for the secondary pyrolysis process. Iron compounds have an adverse influence on the mechanical properties and carbon structure of cokes. Strong correlations exist among coke reactivity, coke strength after reaction, and the content of metallic iron in cokes or the values of crystallite stacking height, which reflect the dependency of thermal property on metallic iron content and carbon structure of cokes.

Characteristic Properties of Lignite To Be Converted to High-Strength Coke by Hot Briquetting and Carbonization

A sequence of hot briquetting and carbonization (HBC) is a promising technology for the production of coke with a high mechanical strength from lignite, but factors affecting the coke strength have not yet been fully understood. The HBC cokes prepared from 12 lignites in this study showed diverse tensile strength (e.g., from 0.2 to 31.2 MPa in the preparation at 200 °C and 112 MPa for hot briquetting and 1000 °C for carbonization), and the coke strengths could not be explained by differences in commonly used structural properties of the parent lignites, such as elemental composition and contents of volatile matter/fixed carbon and ash. In this study, two methods were proposed for correlating the coke strength with the lignite properties, which employed the chemical structure analyzed by solid-state 13C nuclear magnetic resonance or the volumetric shrinkage during carbonization. A stronger coke was obtained from lignite that contained more aliphatic carbons (less aromatic carbons) or shrank more considerab...

Influence of binder (coal tar and pitch) addition on coal caking property and coke strength

In order to increase the usage of semi-soft coking coal, various technologies have been developed and commercialized. Among these, an additive for improving coal caking property (hereinafter referred to as a binder) is promising. Here the mechanism of binders for improving coal caking property and the influence of binder addition to coal with different particle size on caking property and coke strength were investigated. The thermogravimetric analysis and dilatometry tests have suggested that as for coal-derived binder, the gas generating from the binder interacts with coal before coal starts to soften and that coal is reformed in-situ during heating by the interaction, which leads to enhancement of caking property. On the other hand, as for petroleum-derived binder, the experiments have implied that the reason why the petroleum-derived binder enhances coal caking properties is that the gas generating as a result of pyrolysis of the petroleum-derived binder “in” the plastic coal helps the plastic coal to swell and become more fluid. Moreover, dilatation differs greatly with coal types and particle size fractions. When the specific dilatation volume of fine coal is equal to that of coarse coal, the coke structure becomes more homogeneous, which leads to high strength coke structure. There is a possibility that under the binder addition ratio being constant, coke with maximum DI can be obtained by adding binders to fine coal and coarse coal separately so that the specific dilatation volume of fine coal becomes equal to that of coarse coal.

浸透現象に着目した石炭の軟化溶融特性の新評価方法

A novel measurement method for coal thermoplasticity was developed, where permeation distance of thermally plastic coal into glass beads layer placed on the coal sample was measured. The characteristic of this method is simulating the condition in a coke oven, especially void structure around the plastic layer by using glass beads and coking pressure by applying a load. In a standard condition, the coal sample is heated to 550 °C, and coal sample softens and permeates into the glass beads layer, then the permeation distance is measured after cooling the sample. The maximum permeation distance measured is roughly correlated with Gieseler fluidity, however large deviation is observed especially for high fluidity coals. Moreover, the deterioration of coke strength is observed in case that long permeation distance coal is used in a coal blend for cokemaking. This new measurement method clearly shows the difference in coking property of high fluidity coal as well as solving the problems in Gieseler plastometer method for evaluating high fluidity coals. By employing the permeation distance method, contribution to the production of high strength coke and effective usage of caking coal will be expected.

Producing high-quality coke from blends of domestic and imported coal at PAO Zaporozhkoks

The evolution of quality requirements on blast-furnace coke indicates the need to use low-sulfur imported coal of the required quality. The best performance characteristics of European blast furnaces are noted. At such furnaces, with the injection of pulverized coal, the consumption of low-reactivity blast-furnace coke is 280.9–355.8 kg/t of hot metal. On the basis of the requirements imposed on coal used in the production of low-reactivity, low-sulfur, high-strength coke, an industrial coking method has been developed and tested at PAO Zaporozhkoks on the basis of Ukrainian, Russian, and United States coal of the required quality. The coke produced is tested in blast furnace 5 at PAO Zaporozhstal’. The results show that coke of improved quality may be obtained from batch containing 50% Ukrainian coal, 30% Russian coal, and 15% United States coal at PAO Zaporozhkoks. Thus, in the first 11 months of 2013, the quality of the blast-furnace coke produced was as follows: moisture content 3.6%; ash content 11.0%; sulfur content 0.78%; M 10 = 6.3%; content of the >80 mm class 4.1%; content of the <25 mm class 3.1%; CRI = 31.8%; CSR = 51.9%.

Examination of Coking Behavior of Coking Coal and Binder through Characterization Utilizing High Temperature Solvent Fractionation

Steel industries need to increase the use of low-grade coals in coke making due to the recent rapid increase in coking coal price. To do so, it is necessary to effectively use binders, and it is desired to develop a theory on how to mix coals and binders effectively. In this work the coal fractionation method proposed by the authors was applied to characterize coals and binders. Three different-rank coals and two binders (HPC developed by Kobe Steel and ASP) that were heat-treated at 400°C in advance were separated into several fractions having different molecular weight by sequential solvent extractions at different temperatures up to 350°C. The chemical and physical properties of each fraction were found to be almost independent of the coal and binder types. Then, it was clarified that the thermoplastic behaviors of the mixture of coals and binders can be explained by focusing on the relative abundance of the fractions in the mixture. It is therefore possible to determine an appropriate mixing ratio of coals and binders to realize the thermoplastic behavior required to obtain high-strength coke. This approach can be expected as a new mixing theory which is applicable even to low-grade coals and newly-developed binders.

Preparation of High-Strength Coke by Carbonization of Hot-Briquetted Victorian Brown Coal

Cokes with tensile strengths of 6–37 MPa were prepared by binderless briquetting and subsequent carbonization up to 900 °C of pulverized Victorian brown coal that had little fluidity and very low reflectance. Application of mechanical pressures of 64–128 MPa at temperatures of 130–200 °C caused softening of the coal because of mobilization of both low- and high-molecular-mass components, deformation of the coal matrix, and then coalescence/bonding of particles. The resulting coke had a density as high as 1.1–1.3 g/cm3 and tensile strength of 28–37 MPa, which was 5–6 times that of conventional metallurgical coke.