Molasses and air blown coal tar pitch binders for the production of metallurgical quality formed coke from anthracite fines or coke breeze

The effect of the type and the amount of hardeners, such as ammonium nitrate, ammonium carbonate and nitric acid on the molasses bonded briquettes prepared from anthracite fines or coke breeze were investigated. Amongst the hardener studied the best results were obtained with 2.5% ammonium nitrate hardener. The briquettes produced with this hardener were highly water resistant but not waterproof and their tensile strengths were not adequate to be used as a substitute for the metallurgical coke. Therefore, the briquettes were prepared with molasses containing 2.5% ammonium nitrate hardener and air blown coal tar pitch blended binder. When the blended binder was used for the production of anthracite fines or coke breeze briquettes, after curing at 200 °C for 2 h, they became waterproof and their tensile strengths were found to be sufficient to be used as a substitute for coke oven coke. The briquettes after curing could be directly charged into the blast furnace without carbonizing them at high carbonization temperatures. Since molasses and coal tar pitch, are relatively cheap and readily available materials, the process investigated could be economical way of producing high quality formed coke.     

Phenolic resin binder for the production of metallurgical quality briquettes from coke breeze: Part I

Phenol based novalac, resol and the blend of both resins were used as binders in briquette production from coke breeze. The effects of the amount of catalyst on the tensile strength of the cured briquette were studied. The results obtained have indicated that the highest tensile strength could not be attained unless the blend of novalac and resol was used as binder. The most suitable blend was the binder prepared from the hydrochloric acid catalyzed novalac of F/P = 0.5 and the N/P = 0.3 catalyzed resol of F/P = 2.0. When this blend was used as a binder the tensile strength of the cured briquettes did not drop even if they were carbonized at 470 °C and 570 °C. Their strengths at these carbonization temperatures were 67 MPa and 72 MPa respectively, and the rise in the temperature resulted in some increase in their strength. These results show the fact that as the formed coke briquettes descends from the top of the blast furnace, the rise in temperature will not deteriorate their strength; it will probably improve their properties. Therefore, only curing at 200 °C for 2 h will be sufficient for the briquettes to be used as substitute for metallurgical coke in the blast furnace.     

Influence of oxidative stabilization on the electrochemical behaviour of coal tar pitch derived carbons in lithium batteries

A commercial coal tar pitch was thermally treated at 430 °C for 4 h and then submitted to hot filtration in order to separate the isotropic phase from the mesophase developed during the treatment. Each phase was then oxidatively stabilized in order to preserve its structure during carbonization and then carbonized at temperatures ranging from 700 to 1000 °C. The effect of the microstructure, particle morphology and chemical composition of the carbons and also the influence of their carbonization temperature on the electrochemical behaviour as electrode materials in lithium cells were studied.Galvanostatic cycling of lithium test cells using the carbon materials as positive electrodes showed the improvement of the electrochemical performance in both isotropic and anisotropic phases by stabilization with air previous to carbonization. More subtle differences between isotropic and anisotropic samples were evidenced and interpreted in terms of their textural properties. Moreover, the electrochemical impedance spectroscopy (EIS) has been demonstrated to be an interesting technique to elucidate the changes occurred in the electrode interfaces when these coal tar pitch based carbons are cycled.     

Influence of properties of bituminous binders on the strength of formed coke

The role of different chemical characteristics (coking value, quinoline insolubles, elemental composition, β-resin, toluene solubles) of various coal tar- and petroleum-based bituminous binders, such as heavy fraction of HTC tar, processed LTC tar, pitch and asphalt as also the mixed binder in controllling the strength of formed coke made from char prepared from non-coking Chirimiri coal and coke breeze (prapared after carbonising Jharia coal), respectively, has been studied in some detail. The objective was to investigate as to whether and how the properties of these bituminous binders govern the strength of formed coke. It is found that these properties of the binders do play significantly important role in controlling the strength of formed coke both during curing and carbonisation. These parameters of the binders are found to be closely related with their atomic C/H ratios. Notwithstanding the varying composition of the binders of different origin-be they coal tar or petroleum based, the atomic C/H ratio seems to be the most important characteristics of the bituminous binders, upon which the strength of formed coke depends predominantly. This also holds true when mixed binders were used. The results show that at a C/H ratio of about 1, the strength of the briquettes either on curing or on carbonising remains almost similar and that strong cured briquettes can be produced by using a bituminous binder with a C/H ratio less than 1, whilst for obtaining strong carbonised briquettes, binders with C/H ratio greater than 1 are preferable.     

型煤型焦技术研究新进展

根据国内型煤型焦生产情况认为,应注重研究焦油、沥青类粘结剂的改性机理。为了避免型煤在炭化时软化变形和粘连,型煤预处理是非常重要的过程,预处理工艺及如何实现工业上预处理和炭化一体化是值得研究的课题。酚醛树脂作为粘结剂,固化后残炭多,强度大,而且只经低温预处理即可达到高炉用焦的要求,值得国内借鉴,今后的研究要立足如何降低酚醛树脂的成本。     

Effect of densification parameters on the low-energy tribological behavior of carbon/carbon composites

The low-energy tribological behavior was investigated in carbon/carbon composites fabricated by processing with different densification parameters. In the densification process, different impregnating precursors and carbonization temperatures were used to investigate the influence on physical and mechanical properties, microstructure and tribological behavior. Experimental results indicate that the density and hardness of resin-based specimens are higher than those of pitch-based specimens after four densification cycles. When increasing carbonization temperature in the specimens based on coal tar pitch, the open porosity increases whereas both the bulk density and the hardness decrease. When comparing the tribological properties of the specimens with different impregnating precursors, coal tar pitch specimens show lower and more stable friction coefficients and exhibit lower weight losses. This is because the pitch matrix is transferred to the preferred orientation structure carbon after carbonization. The different carbonization temperatures do influence the tribological properties; specimens carbonized at 700 °C exhibit the lowest weight loss and the most stable friction coefficient.     

Coal carbonization with addition of hydrochloric acid as a way of improving coke quality

The possibility to expand the base of raw materials for carbonization using more lower grade and noncoking coals has been examined. Plastometric indices of the parent coals (C=79.0-87.2 wt% daf): x, shrinkage of coal and y, thickness of the thermoplastic layer were determined. It was established that the addition of 1 M HCl to coal increases the thickness of the thermoplastic layer (y) of gaseous (C=82.7 wt% daf) and rich (C=87.2 wt% daf) coals by 15-20% and the strength of the solid carbonized residue from 64 up to 84% and from 92 up to 94 %, respectively. A comparative evaluation of gaseous (C=82.2-82.7 wt% daf) coal according the degree of its restorativity is given. The strength of the coke is obtained from untreated gaseous coal and with HCl additive in the temperature region of carbonization of 450-800 °C. It is established that the greatest increase of coke strength takes place in the temperature region of 550-750 °C. Data of X-ray diffraction show that structural changes take place at coal carbonization.     

On the chemistry of the oxidative stabilization and carbonization of carbonaceous mesophase

Two mesophase samples, one derived from a coal-tar pitch (M-A) and the other from a naphthalene-based pitch (M-B), were stabilized with air in a temperature range of 200-300 °C and then carbonized to 1000 °C. Elemental analysis and FTIR spectroscopy were used to monitor the changes produced by oxygen in the chemical composition of the mesophase samples at different stages of stabilization (from 200 to 300 °C) and after carbonization of the stabilized samples (from 300 to 1000 °C). The results show that oxidative stabilization is a dehydrogenative process, where the hydrogen removed is predominantly aliphatic and the oxygen uptake is mainly in the form of C-O-C and CO groups. The more aliphatic character of M-B accelerates the stabilization process with respect to M-A. M-B shows a higher weight gain and also a greater variety of oxygen-containing functional groups. As a result, the plasticity of M-B is more affected by changes in the stabilization temperature than that of M-A. Thus, the stabilization process is easier to control in the case of M-A. On carbonization, oxygen and hydrogen are removed from the stabilized samples and the carbons generated exhibit an increase in interlayer spacing and a decrease in crystallite size as the carbonization temperature increases.     

型煤与焦粉型焦粘合剂的研究及应用

探讨了型煤粘合剂的粘结机理 ,介绍了几种主要粘合剂的分类 ,重点论述了WIN -1型民用与锅炉型煤粘合剂、WIN - 2超微粉造气型煤粘合剂及WIN - 3焦粉型焦粘合剂的研究和应用情况 ,利用这些粘合剂生产的锅炉型煤、造气型煤、焦粉型焦等产品均达到了应用要求     

Needle coke formation derived from co-carbonization of ethylene tar pitch and polystyrene

Ethylene tar pitch was co-carbonized with waste polystyrene to prepare needle coke. The modified properties of mesophase, which were greatly improved due to increasing naphthenic and other alkyl content, availed the formation of needle coke with high quality. The coefficient of thermal expansion value was decreased from 3.2 × 10⁻⁶/°C to 0.3 × 10⁻⁶/°C and the optical texture of the coke was changed from coarse mosaic texture to flow domain of high uniaxial orientation after adding waste polystyrene into ethylene tar pitch. The low viscosity of the mesophase pitches favored the development of mesophase and highly uniaxial arrangement. The increase in alkyl group content greatly improved characteristics of the needle coke.     

Effect of oxidation pre-treatment at 220 to 270 °C on the carbonization and activation behavior of phenolic resin fiber

The effect of oxidation pre-treatment of a phenolic resin fiber was examined from two aspects: one is to examine if the pre-treatment can be a means to increase the yield of carbon fiber and activated carbon fiber (ACF), and the other is to study the effect of the pre-treatment on the carbonization and activation behavior. A phenolic resin fiber was oxidized in air at 220 to 270 °C and it was subsequently carbonized at 900 °C and activated by steam at 900 °C. The oxidation was found to affect significantly the subsequent carbonization process in the way that the yield of the carbonized fiber increased with the severity of the oxidation. On the other hand, the oxidation was found not to affect the chemical and physical properties of the carbonized fiber. The ACF produced from the oxidized fiber had almost same pore structure as the ACF produced from the non-treated fiber when compared at a same activation level. The maximum yield of ACF produced from the oxidized fiber was 1.13 times larger than the yield of ACF produced from the non-treated fiber. Thus we could increase the production yield of ACF significantly without losing its high adsorption performance.     

A graphite foam reinforced by graphite particles

Graphite foam was obtained after carbonization and graphitization of a pitch foam formed by the pyrolysis of coal tar based mesophase pitch mixed with graphite particles in a high pressure and temperature chamber. The graphite foam possessed high mechanical strength and exceptional thermal conductivity after adding the graphite particles. Experimental results showed that the thermal conductivity of modified graphite foam reached 110 W/m K, and its compressive strength increased from 3.7 MPa to 12.5 MPa with the addition of 5 wt% graphite particles. Through the microscopic observation, it was also found that fewer micro-cracks were formed in the cell wall of the modified foam as compared with pure graphite foam. The graphitization degree of modified foam reached 84.9% and the ligament of graphite foam exhibited high alignment after carbonization at 1200 °C for 3 h and graphitization at 3000 °C for 10 min.     

Investigation of resole, novalac and coal tar pitch blended binder for the production of metallurgical quality formed coke briquettes from coke breeze and anthracite

In order to reduce the cost and also enlarge the solid carbon source suitable for the formed coke production further investigations were conducted to produce formed coke using anthracite which can provide a new and relatively economic abundant raw material suitable for this purpose. The results indicated that, anthracite can also be used for the production of metallurgical quality formed coke, but the tensile strength of the anthracite formed coke were found to be comparatively lower than that of the coke breeze formed coke, 64.6 MPa, 73.2 MPa, respectively, when carbonized at 950 °C for 1 h, due to the decomposition of the volatiles that causes fissures, cracks and new pores. To produce anthracite briquettes of higher tensile strength, either anthracite of lower volatile matter should be used or it should be blended with coke breeze.     

Effect of carbonization rate on the properties of a PAN/phenolic-based carbon/carbon composite

The effect of carbonization rate in a wide range (1, 100 and 1000 °C/min) on the properties of a PAN/phenolic-based carbon/carbon (C/C) composite was studied. The results indicated that the composite processed at a higher carbonization rate had a higher porosity level, more large pores and a more graphitic structure than that processed at a lower carbonization rate. After second graphitization the bending properties of composites carbonized at 1 °C/min and 1000 °C/min were comparable. The composite carbonized at 1000 °C/min had the highest fracture energy. The composite carbonized at 100 °C/min showed the worst mechanical performance among three. The large increase in carbonization rate can be beneficial to the industry from an economic point of view.     

Rheological behavior and thermal properties of pitch/poly(vinyl chloride) blends

The effect of adding poly(vinyl chloride) (PVC) and coke filler on the rheological behavior and thermal properties of a coal tar pitch was investigated with a view to developing an appropriate viscoelastic binder for the injection molding of graphite components. Dynamic mechanical analysis revealed that the pitch formed compatible blends with PVC featuring a single glass transition temperature (Tg) intermediate to the two parent Tg’s. Adding PVC to the pitch increased melt viscosity substantially and resulted in strong shear thinning behavior at high PVC addition levels. Adding coke powder as filler increased the melt viscosity even further and enhanced shear thinning trends. Pyrolysis conducted in a nitrogen atmosphere revealed interactions between the PVC and pitch degradation pathways: the blends underwent significant thermal decomposition at lower temperatures but showed enhanced carbon yields at high temperatures. Pyrolytic carbon yield at 1000 °C was further improved by a heat treatment (temperature scanned to 400 °C) in air or oxygen. However, carbon yield decreased with addition of PVC. In addition, the degree of ordering attained following a 1 h heat treatment at 2400 °C also decreased with increasing PVC content.     

Preparation of highly crystalline carbon nanofibers from pitch/polymer blend

High crystalline carbon nanofibers were prepared by using polymer blend technique. Naphthalene-based mesophase pitch (AR pitch) was dispersed finely in polymethylpentene matrix, spun by using a melt-blown spinning machine, stabilized at 160 °C in an oxygen atmosphere and carbonized at 900 °C in a nitrogen atmosphere. Bundles of the carbon nanofibers with ca. 100 nm in diameter were obtained after removal of polymethylpentene at the carbonization process. No impurity carbon was observed. The carbon nanofibers consisted of fine carbon crystallites with preferred orientation along the fiber axis. After heating to 3000 °C, the carbon crystallites grew drastically to have an interlayer spacing of 0.3367 nm and a crystallite thickness of 56.9 nm, respectively, with remarkable improvement of the preferred orientation of the crystallites. Advantages and disadvantages of the present method were discussed briefly.     

Analysis of the carbonization and formation of coal tar pitch mesophase under dynamic conditions

Thermokinetic analysis of three pitch samples was carried out: coal tar pitch obtained from light coke oven tar (P), mesophase pitch after 10.5 h (MP1), and mesophase pitch after 12 h (MP2) thermopreparation at 410 °C. The process was realized in a continuous system with a 10 kg mass being charged to the reactor. It was demonstrated using Kissinger’s law that the temperature criterion, the first-order thermokinetics and the calculated Arrhenius law parameters fulfill the isokinetic effect when the classical routes of thermokinetic analysis of the samples prepared under dynamic conditions (at three heating rates) are used, which makes the qualitative interpretation of differences between these samples difficult. An alternative solution was proposed using the relative rate of thermal decomposition. The temperature ranges of the chemical reactions leading to the formation of mesophase structures, as well as the temperature ranges of the coking processes of the Fixed Carbon phase, were determined.     

Phenolic resin binder for the production of metallurgical quality briquettes from coke breeze: Part II the effect of the type of the basic catalyst used in the resol production on the tensile strength of the formed coke briquettes

In order to develop a new and cost effective formed coke production process which does not require higher temperature carbonization stage, coke breeze was briquetted with resol binders and the change in the tensile strength of the briquettes with the amount and the type of the alkaline metal hydroxides, alkaline earth metal oxides, their carbonates and amine catalysts were studied. It was recognized that carbonates of alkaline or alkaline earth metals have a modifying effect on the properties of resol binders which results in briquettes of higher tensile strength than the resol produced with hydroxide or oxides of these metals. The average tensile strength of the briquettes was found to be much higher with the sodium carbonates catalyzed resol used as binder comparing with sodium hydroxide catalyzed resoles. The former was 45.40 MPa while the latter was 33.72 MPa. Although triethanolamine catalyzed resol, resulted in the briquettes of the highest tensile strength (53.43 MPa), among the catalyst studied in this work, due to flammability caused by triethanolamine, it was found unsuitable for this purpose.     

Influence of the coke filler on the carcinogenicity of pitch–coke mixtures on carbonization

The emissions of benzo[a]pyrene at different temperatures and its concentration in the exhaust gases are measured in laboratory experiments on the carbonization (at temperatures up to 850°C) of coalpitch and petroleum-pitch binders and their mixtures with roasted petroleum and pitch coke. These pitch–coke mixtures are similar in composition to the anode mass used in aluminum production. The experiments confirm that the total benzo[a]pyrene emissions are much greater in the carbonization of petroleum pitch produced by cracking (T _so = 100°C) than for electrode pitch (T _so = 89°C) and other coal pitch. In most experiments, the benzo[a]pyrene emissions in the carbonization of pitch–coke mixtures is markedly less than for individual binder pitches. It is found that the benzo[a]pyrene emissions in the carbonization of a mixture based on pitch coke are much less than for a mixture based on petroleum coke in the high-temperature region that presents the greatest environmental hazard.     

Microstructure of carbon/carbon composites reinforced with pitch-based ribbon-shape carbon fibers

Carbon/carbon composites were prepared with ribbon-shape pitch-based carbon fibers serving as reinforcement and thermosetting PFA resin and thermoplastic pitch as matrix precursors. The composites were heat treated to 1000, 1600 and 2700 °C. Microstructural transformations taking place in the reinforcement, carbon matrix, and the interface were studied using polarized optical and scanning electron microscopy. The fiber/matrix bond and ordering of the carbon matrix in heat-treated composites was found to vary depending on the heat treatment temperature of the fibers. Stabilized fiber cleaved during carbonization of resin-derived composites. In contrast, fibers retain their shape during carbonization of pitch matrix composites. Optical activity was observed in composites made with carbonized fibers; the extent decreases with increased heat treatment of the fibers. Studies at various heat treatment temperatures indicate that ribbon-shape fibers developed ordered structure at 1600 °C when co-carbonized with thermosetting resin or thermoplastic pitches.