Catalytic graphitization of cokes by indigeneous mineral matter

Indigeneous mineral matter in coals acts catalytically towards graphitization during heat treatment of coals to 2273 K. Nineteen coals of a wide range of rank were demineralized by acid extraction. Original and demineralized coals were carbonized in the range 1073–2273 K, and the resulting cokes examined by optical microscopy, X-ray diffraction and phase-contrast high resolution electron microscopy. Optical microscopy indicated the extent of formation of anisotropic carbon in the resultant cokes. The (002) X-ray diffraction profiles indicated three types of catalytic effect, for which electron microscopy demonstrated different crystallite structures and interrelations. The importance of catalytic graphitization in metallurgical cokes in relation to their strength and reactivity is discussed.     

石墨化温度对针状焦热膨胀系数的影响

测定了三种不同类型针状焦(石油针状焦,煤沥青针状焦以及加氢煤沥青针状焦)的热膨胀系数,同时测定了不同石墨化温度下针状焦的CET值,指出了在2500℃～3000℃石墨化温度范围内,不同种类的针状焦CET值都呈现出线性增长,并且指出了由于加氢煤沥青针状焦具有特殊的结构而导致其石墨化以后具有最小的CET值。     

Puffing inhibitors for coal tar based needle coke

The efficiency of various puffing inhibitors has been studied systematically using carbon samples prepared from coal tar based needle coke. Puffing was reduced by the addition of nickel and cobalt oxides. The bulk density of moulded blocks subjected to graphitization was increased also by the addition of these oxides, because of their catalytic ability for carbonization. No sulfide was observed during the graphitization process, implying that puffing inhibition is not necessarily due to the reaction of metals with sulfur compounds in cokes. The interlayer spacing of needle cokes mixed with effective puffing inhibitors was considerably decreased during graphitization. The action of puffing inhibitors seems to change the timing between the gas evolution and the softening of carbon bodies.     

Mild coal extraction for the production of anode coke from Blue Gem coal

The quality and availability of petroleum coke used in the manufacture of carbon anodes for aluminum production is a growing concern to the industry. Coke quality and yields have progressively declined as changes in refinery practice and the move towards processing an increasing proportion of heavier sour crudes have affected coke properties, resulting in an increase in the metal impurities and sulfur content of the coke. An alternative supply of anode coke is required to supplement or eventually replace calcined petroleum coke. The significant domestic reserves of coal could represent a viable carbon resource for anode production, provided defined coke specifications can be met and at a cost that is economically viable.The principal objective of this study was to examine the feasibility of producing anode grade coke by the UKCAER process for the mild solvent extraction of coal. Blue Gem coal from Eastern Kentucky was dissolved in a high boiling point solvent, the mineral matter and unreacted products removed by filtration, and the clean coal liquid converted to coke. The performance of the coal in solvent extraction was compared to a very reactive coal from Western Kentucky. A simple solvent-extraction screening test was established to assess potential candidate materials and process variables without the need for prolonged and complex routines. The coals were assessed in more detail to determine the optimum process conditions by conducting larger scale extraction tests to yield sufficient material for conversion to coke. The green cokes were calcined and the products characterized. The composition and structure of the calcined cokes were compared to typical petroleum coke and assessed for their use in the fabrication of carbon anodes.     

Multi-factors affecting coke solution loss reaction

The coke reactivity index (CRI) of several industrial cokes and their multi-level properties were tested. The multi-level properties included specific surface, apparent porosity, microtexture, graphite crystalline structure, and mineral matter. The factors affecting coke solution loss reaction were evaluated following the literature reports.     

Effect of coal blending ratio on CO<Subscript>2</Subscript> coke gasification

Coke gasification is largely influenced by the raw coal, catalyst, and blending ratios, pore structure, and specific surface area of the raw coal. In this study, several properties of cokes related to their reactivity were measured using coke reactivity test apparatus (CRTA), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Brunauer-Emmet-Teller (BET) surface area analysis, and energy dispersive X-ray spectroscopy (EDS) to investigate the characteristics of coke gasification. The results indicated that the reactivity of coke in the temperature range from 950 to 1,050 °C was affected by the type of coke and its specific surface area rather than the general properties of the coke, although the overall reactivities at the other temperatures were uniform. EDS analysis showed that the catalyst acted on the reactivity of cokes at low temperatures, whereas the BET analysis indicated that the reactivity at high temperature was influenced by the specific surface area.     

Comparative study of reactivity to CO2 of cokes used in stone wool production

The reactivity towards CO₂ of seven types of commercial coke used in stone wool production has been measured in a thermo gravimetric analyser (TGA). The cokes originated from Western and Eastern Europe and from China. For three of the cokes, the porosity, density and surface area were determined. The directly measured porosities of the cokes was slightly low, indicating that there are pores that are not connected with the outer surface. This is supported by the measured densities and microphotos.The measurements showed that the Chinese cokes were the least reactive while the European cokes made on American coal were the most reactive. The reactivity of the one Eastern European coke in the measurements had an intermediate reactivity.Simulations with a cupola model show that 25% more coke is needed for stone wool production if the coke is changed to a type with half the reactivity towards O₂ and CO₂.The TGA method proved to be a good method for ranking the coke with respect to reactivity with CO₂.     

Reactivity of heat-treated coals in air at 500 °C

Twenty one US coals, of widely ranging rank, have been carbonized under controlled conditions to 1000 °C, and the reactivity in air at 500 °C of the resulting chars or cokes has been measured by a gravimetric method. The reactivities lie within a well-defined band when plotted against rank of the parent coal. The lower-rank coal chars are more reactive than those prepared from high-rank coals. In extreme cases, the reactivity found for a Montana lignite char is some 100 times as great as that obtained for a char produced from a Pennsylvania low-volatile coal. Variation of reactivity with heat-treatment temperature (600 to 1000 °C) has been studied for three coals. As heat-treatment temperature increases, there is a decrease in reactivity. Some results are reported on the effects which mineral matter and pore structure have on the reactivity parameter. Chars containing high concentrations of magnesium and calcium impurities are most reactive. The amount of macro and transitional porosity in a char has a marked influence on reactivity.     

Graphitization behavior of hydrogenated ethylene tar pitch

The graphitization behavior of cokes prepared from ethylene tar pitch (ETP) hydrogenated at temperatures from 473 to 673 K has been studied by magnetoresistance measurements at liquid nitrogen temperature and by scanning electron microscopy. Graphitization heat treatment of the cokes was carried out at 3273 K. Hydrogenation temperatures of 473 and 523 K resulted in graphitized cokes with random layer plane textures and low degrees of graphitization. Hydrogenation at higher temperatures was effective in promoting development of flow-type textures during graphitization. The coke from ETP hydrogenated at 673 K showed the highest graphitizability, preferred orientation and flow-type texture developed by heat treatment.     

Bonding of solid additives in cokes from coals: a microscopy study

Cortonwood Silkstone (NCB class 401) and Betteshanger (NCB class 301 a/204) coals were co-carbonized with solid additives such as anthracite, coke breeze, green and calcined petroleum cokes. The resultant carbonization products (cokes) were examined by optical microscopy and SEM was used to investigate polished surfaces etched by chromic acid and fracture surfaces. For both coals only the anthracite and green petroleum coke become bonded to the coal cokes. This probably results from softening and interaction of interfaces of the anthracite and green coke with the fluid coal via a mechanism of hydrogenating solvolysis during the carbonization process. The coke breeze and calcined petroleum cokes were interlocked into the matrix of coal coke.     

Study of the relation between the phosphorus content of coal and coke

Established methods for the determination of phosphorus in coal and coke were compared and found to give results in satisfactory agreement. The method for the determination of phosphorus described in BS 1016, ‘Methods for the analysis and testing of coal and coke’, Part 9, 1977 was used to study the relation between the phosphorus content of coals and their corresponding cokes. The cokes were prepared on laboratory, test oven and industrial scales, by the carbonization of various bituminous coals within the range of volatile matter yield of 16–40 wt%. The determined values of the phosphorus contents of these cokes and their parent coals indicated that the phosphorus present in the coal is completely retained in cokes carbonized to temperatures between 900 and 1050 °C. On the basis of these experimental results it is suggested that the phosphorus content of coke can generally be calculated from a knowledge of the phosphorus content of the coal and the coke yield with an accuracy which is sufficient for normal requirements.     

Steam gasification of oil coke catalyzed by alkali metal hydridotetracarbonylferrates: Effects of alkali metal cations

A gravimetric study of the catalytic activity of alkali metal hydridotetracarbonylferrates on steam gasification of oil coke at 800°C revealed the following order with respect to the cation: Na > Li > K > Rb > Cs. This order was not consistent with that of the catalytic activity of alkali metal carbonates. The most reactive rubidium and potassium carbonates at a higher loading level exhibited poor binary effect when they were used with iron in the form of alkali metal ferrate. This offered important information for interpreting the mechanism of steam gasification of coal using the Fe-Na binary catalyst. The reactivity of the oil coke was slightly enhanced by preoxidation. The sodium ferrate gave a remarkable difference in the catalytic reactivity of gasification between the original and pre-oxidized cokes. The increase in oxygen content rather than that in surface area may play an important role in the pre-oxidized coke impregnated with the catalyst.     

单种煤结焦性能评价与焦炭质量预测

根据11种单种煤的性质,在实验室20kg小焦炉上进行了11种单种煤和8种配煤方案的炼焦实验,并对焦炭进行了筛分组成、冷态强度、焦炭热性质等分析,初步建立了焦炭质量预测模型。实验结果表明:单一的煤质指标与焦炭强度的关系不是很明显,选用煤质多因素指标进行焦炭质量预测,其预测效果较好;单一的煤质指标(Vd、R0max、Ad)与焦炭反应性之间有较好的关系,且焦炭的反应性随反应温度的升高而增大。     

利用神木不粘性块煤炼制炭质还原剂

本文介绍利用神木不粘结性块煤炼制优质铁合金专用焦，通过对块焦的筛分组成分析、工业分析和灰分分析，焦炭的反应性能、比电阻、强度、石墨化程度研究，证明该煤炼制的块焦具有比电阻高，灰分、硫、磷、铝和高温下石墨化程度低的优点。该焦可代替冶金焦冶炼铁合金。     

Influence of coal forced oxidation on technological properties of cokes produced at laboratory scale

The effect of coal oxidation in air at 140 °C on the technological properties of cokes obtained at laboratory scale from two medium volatile bituminous coals has been studied. The proximate and ultimate analyses do not show important changes with coal oxidation time. However oxidation clearly has a strong effect on the plastic properties of the coals in view of the fact that the Gieseler fluidity eventually disappears. From this point variations in plastic properties can still be detected by FSI. Other changes, such as a shortening of the length of the saturated fragments of the aliphatic chains, a decrease in the aliphatic hydrogen content and an increase in the oxygen-containing groups are detected by PA-FTIR. It was also found that the main coke quality indices (mechanical strength and reactivity to CO₂) of both coke series are impaired with coal oxidation. A close relationship between reactivity to CO₂ and the micropore specific surface area of the cokes has been corroborated.     

添加炭素物料改善焦炭性能的研究

通过向炼焦配煤中添加石油焦、人造石墨和天然石墨并炼焦处理，研究了添加炭素物料对焦炭性能的影响，结果发现，添加少量炭素物料有效地提高了焦炭强度并降低了焦炭的反应性。     

Influence of coal forced oxidation on technological properties of cokes produced at laboratory scale

The effect of coal oxidation in air at 140 °C on the technological properties of cokes obtained at laboratory scale from two medium volatile bituminous coals has been studied. The proximate and ultimate analyses do not show important changes with coal oxidation time. However oxidation clearly has a strong effect on the plastic properties of the coals in view of the fact that the Gieseler fluidity eventually disappears. From this point variations in plastic properties can still be detected by FSI. Other changes, such as a shortening of the length of the saturated fragments of the aliphatic chains, a decrease in the aliphatic hydrogen content and an increase in the oxygen-containing groups are detected by PA-FTIR. It was also found that the main coke quality indices (mechanical strength and reactivity to CO₂) of both coke series are impaired with coal oxidation. A close relationship between reactivity to CO₂ and the micropore specific surface area of the cokes has been corroborated.     

Enhancements in nickel-catalyzed hydrogasification of carbon by surface treatments

A pitch coke was given 4 types of pretreatment to modify the surface state; air oxidation, heatingquenching, steam treatment and hydrogen treatment. The treated cokes were impregnated with nickel and gasified in an atmospheric hydrogen flow. The catalytic reactivity of the pitch coke was enhanced by these pretreatments. Several properties of pretreated cokes were compared and it seemed that highly hydrophilic or acidic surfaces of carbon were unfavorable to metal-catalyzed hydrogasification. The reactivity enhancement was ascribed to an increase in the hydrogen adsorption capacity of nickel on the pretreated coke. The oxygen-containing surface groups are presumed to inhibit the spillover of atomic hydrogen from nickel to carbon. The effect of 1 type of pretreatment. heating-quenching, seems to relate to the expansion in pore volume.     

A semi-industrial scale study of petroleum coke as an additive in cokemaking

The addition of petroleum coke to a typical industrial coal blend used in the production of metallurgical coke was studied. Cokes were produced at semi-industrial scale at the INCAR coking plant, using petroleum coke of different particle size distribution as an additive. Special attention was paid to changes caused in the textural properties (porosity, pore size distribution, fissures at the interface between metallurgical coke and petroleum coke) which have been found to be responsible for variations in the metallurgical coke quality parameters (e.g., mechanical strength and reactivity towards CO₂). Variation in porosity was found to depend on particle size and the proportion of the additive. The decrease in the microporosity (i.e., pore radius<3.7 nm) of the metallurgical cokes observed when petroleum coke is added to the coal blend, is postulated to be one of the main factors responsible for the decrease in the reactivity of these cokes. The variation of the mechanical strength indices can be explained by the changes in porosity and the quality of the interfaces between petroleum coke and metallurgical coke.     

炼焦机理和焦炭质量预测的研究进展

综述了煤的热塑性、炼焦机理和焦炭质量预测的研究进展。煤的化学结构如煤中镜质组的烷基侧链和移动氢的含量决定了煤的热塑性,核磁共振、质子磁共振热分析、拉曼光谱和电子顺磁共振谱等从分子水平解释煤的热塑性、配合煤的相互作用和炼焦机理。塑性成焦机理认为,良好的氢传递和分子重排是炼焦中获得优质焦炭的重要条件,塑性成分在焦炭光学组织形成中非常关键,改变加热速率可使煤的光学组织形成机理改变。碱度指数（modified basicity index,MBI）、复合焦势（composite coking potential,CCP）和组合煤指数（combined coal index,CCI）等参数可精确地预测焦炭反应后强度和焦炭反应性。矿物质对焦炭强度的影响是研究热点,控制焦炭的裂纹和尺寸是未来焦炭质量的要求。