C.S. Canga

Gas chromatographic study for the evaluation of the suitability of bituminous waste material as an additive for coke production

Abstract Waste materials derived from coking plants can be used in situ as bituminous additives in cokemaking. The effectiveness of such materials in the plastic coal range was compared with a coal-tar and four derived pitches of different applications. The volatile matter released from 400 up to 500°C by the additives (VM400–500), which was evaluated by thermogravimetric analysis, was clearly related to the extent of the modification of the Gieseler maximum fluidity of coking coal/additive blends. The decrease in the amount of volatile fraction in the CS 2 extracts of the additives and the increase in the abundance of polycyclic aromatic hydrocarbons (PAHs) of relatively high molecular mass were evaluated by capillary gas chromatography with flame ionization detection (GC–FID) analysis. From regression analysis, it can be deduced that there is a relationship between the compositional parameters deduced from GC–FID analysis and the volatile matter released in the plastic range of a coking coal (VM400–500). Both composition and VM400–500 of the additive, were found to be responsible for the enhancement in fluidity caused by the presence of the additive in the co-carbonization system. GC–FID analysis may be a good method to assess the effectiveness of a bituminous additive in the coal plastic stage and to acquire a better understanding of the components involved in this critical stage of the carbonization process. The changes induced in the plastic range by the additive modify the development of coke anisotropy and the bonding between coke matrix and inert material and, consequently, are responsible for the improvement in the coke properties.

Hydrogen donor and acceptor abilities of pitches from coal and petroleum evaluated by gas chromatography

Abstract Among the characteristics of coal-tar and petroleum pitches, the thermal reactivity of their constituents is one of the most important because it determines the development of mesophase and, consequently, the structure of graphitizable carbons (cokes). At the early stages of the carbonization process the hydrogen transfer reactions and the availability of donatable hydrogen are crucial to give high fluidity/low viscosity systems. In such conditions, aromatic molecular systems have enough mobility to stack parallel to each other resulting in a more ordered coke structure. A chemical procedure for estimating the reactivity of a pitch to supply and consume hydrogen from the reaction system is the co-carbonization with anthracene and 9,10-dihydroanthracene (DHA) as hydrogen acceptor and donor agents, respectively. A series of pitches including impregnation and binder coal-tar pitches, petroleum pitches and pitch-like residues from the by-products coking plants was studied. Carbon disulphide extracts from the co-carbonization systems (pitch+anthracene and pitch+DHA) were analyzed by capillary gas chromatography. Results indicate that pitches with the highest hydrogen donor ability favour the formation of 1,2,3,4-tetrahydroanthracene in the reaction system. The relation between the amount of volatile matter released in the temperature range of 400–500°C and the hydrogen donor and acceptor ability of the pitches can be considered as important factors in the development of coke structure.

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

Abstract 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 CO 2 ). 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

Modifications of coking coal and metallurgical coke properties induced by coal weathering

Chemical changes in the structure of organic matter of coking coals during storage modify their thermoplastic properties and behaviour during carbonization. As a result, the anisotropic carbon structure of the metallurgical cokes produced and their physical properties are altered. In this work, the weathering behaviour of 10 bituminous coals of different geographic origin, rank and thermoplastic properties, used as components in the preparation of industrial coking blends for coke manufacture, was studied by means of Gieseler plastometry and Fourier transform infrared (FTIR) spectroscopy. These coking coals were stored in piles at the Instituto Nacional del Carbon (INCAR) open stockyard for a period of time of up to 7 months. Special attention was paid to the relationship between the relative amount and type of aliphatic hydrogen (semi-quantitatively evaluated by FTIR), and thermoplastic properties. Depending on the nature of the coking coal, a different response to natural weathering can be expected. Thus, the results showed that there is a direct link between a decrease in methylene groups and a loss of fluidity in the weathered coals, resulting in a decrease in anisotropic carbon of the resultant cokes with weathering time. In addition, the rate of anisotropic carbon loss induced by weathering could be associated with the rank parameters of the initial coals.

Application of a laboratory test to resolve the problem of coking a dangerous coal

Abstract A laboratory test developed to measure expansion and contraction was used to resolve the problem of coking a dangerous Spanish coal. The indications of this test were used to determine the minimum amounts of three different high volatile coals that it was necessary to add, to reduce the risk of coking this dangerous coal. Laboratory results were backed by tests carried out on a semi-industrial scale, without losing sight of certain safety limits.

Coke oven gas control by one-line gas chromatography

SummaryA gas chromatograph will thermal conductivity detector (TCD) connected on line via a cleaning train to the semi-industrial scale Coke Oven Text Plant of the Spanish National Coal Institute (INCAR), has been used to control the evolution of the permanent gases during the coking process.The undesirable presence of oxygen in the coke oven gas can be detected with this system that will be applied to determine the end of the coking process by quantitative analysis of the gas evolved.

Influence of wet and preheated coal charging on the nature of quinoline insolubles of coal tars and their derived pitches

Differences between primary quinoline insoluble (QI) material of coal tars and their derived pitches caused by preheating carbonization have been studied using microscopic techniques, Coulter Laser particle size analysis and solid-state 13C NMR. The selected tars were produced from the same coal using wet and preheated charging at the INCAR experimental coking test plant, which operates on a semi-industrial scale. Specific operational conditions were successfully applied not only to reduce the ash content and the QI and toluene insoluble (TI) contents in the tars produced by the preheating process, but also to modify the nature of the QI particles. In addition, structural changes in the insoluble materials formed during the pitch production from the tar have been monitored.

Wet and preheated carbonization of a Spanish high volatile coal and blends with a Spanish prime coking coal

Abstract A Spanish high volatile coal (Modesta coal) and blends of this coal with 25, 50 and 75 wt.% of a Spanish prime coking coal (Figaredo coal) were coked at semi-industrial scale, either wet or by previous preheating. As the prime coking coal (Figaredo coal) is a dangerously swelling coal, the maximum amount to be added was established using the ASTM sole heated oven test. The high volatile coal increased coke strength considerably by preheating in comparison to wet charging. Blends adding 25 and 50 wt.% of Figaredo coal improved coke strength by preheating, although to a lower degree. However, as a result of the 75 wt.% addition of Figaredo coal, coke strength was impaired. Coke strength was measured by MICUM and IRSID tests and the cokes were also studied by image analysis, optical and scanning electron microscopy.

Microscopic examination of coals and carryover from wet and preheated carbonization

Abstract A blend of two Spanish coals was carbonized on a semi-industrial scale using wet and preheated charging. The wet and preheated coal blends were characterized by optical microscopy, and structural changes due to the preheating process i.e. development of porosity, fissuring, etc., were observed. Preheater fines and material carried over in the charging gases from the wet and preheated coal blend were characterized by proximate analysis and optical microscopy. Carryover material was characterized optically according to the ICCP char classification system. Preheating not only produced an increase in the amount of carryover but also modified its structural features. Preheating also resulted in an increase of anisotropic material in the carryover particles.