Thermoplastic Properties Of Coal Research Articles

Construction of vitrinite molecular structures based on 13C NMR and FT-IR analysis: Fundamental insight into coal thermoplastic properties

Attempts were made to construct the molecular structures of vitrinite samples from four bituminous with different ranks and to investigate the correlation of molecular structures to thermoplastic properties of vitrinite by using a number of advanced analytical techniques combined with theoretical methods. The Gieseler plastometry and caking index showed that the Ewirgol vitrinite had a high fluidity (MF = 17675 ppm), wide plastic range (ΔT = 105.1 °C) and good caking properties (G = 99.32). Various analytical technique, e.g. Solid-state 13C nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis and Raman spectroscopy, provided comprehensive structural information for establishing molecular models of vitrinite samples with Density Functional Theory. These molecular models showed that the Ewirgol vitrinite had more cyclic aliphatic structures that contribute significantly to the fluidity development and caking properties. These cyclic aliphatic structures could be precursors of the aromatic rings in liquid molecules during coking and provide transferable hydrogens that saturate the free radicals in the thermoplastic range. The cyclic aliphatic structures may facilitate the formation of such molecular structures with an appropriate molecule size that maintains the mobile phase in the thermoplastic range to develop fluidity.

The influence of process water chemistry on coal thermoplastic properties

Process water re-use is a common practice in Australian coal preparation plants. It is an effective solution to on-site water scarcity and minimizes environmental impact. This paper investigates the effect of inorganic mineral salts in the process water on the thermoplastic properties of metallurgical coals after a short period of mild oxidation. Two different metallurgical coals were treated with the process water received from a coal preparation plant and exposed to air at ambient temperature. The thermoplastic properties of the samples treated with salt solutions were measured using Gieseler plastometry. The results suggested that the fluidity of coal decreased as the concentration of inorganic salts increased. When different salt solutions were used, the degree of fluidity reduction was found to be similar at the same concentration. Examination of the coal surface with SEM-EDS analysis showed the existence of both sodium and chlorine on the surface of process water treated coal while the surface analysis by X-ray photoelectron spectroscopy (XPS) indicated a relatively insignificant chemical reaction between the inorganic ions present in the water and the coal surface after rinsing the samples. Salts appeared to precipitate on non-maceral matter and act as an inert (non-plastic) additive.

Importance of Biomass and Binder Selection for Coking Briquette Preparation. Their Effect on Coal Thermoplastic Properties

Blends consisting of a high volatile bituminous coal, biomass, and binder that were used in the preparation of briquettes were analyzed in order to select the best components from the viewpoint of ...

Thermoplastic Properties of Coal and Coal Extract

The aim of this study is to find a simple, effective, and non-destructive way to estimate the fluidity of coal. Three kinds of metallurgical coals were blended in a specific ratio for fluidity measurement by a Gieseler plastometer and coke strength by the Roga test. One of the metallurgical coals was extracted with four kinds of solvents. The solvent-extracted extracts further underwent heat treatment at different temperatures and were then added to the blended coal to examine the change of fluidity and coke strength. Both the heat-treated and untreated coal extracts were further investigated by elemental analysis, thermogravimetric analysis, solid-state 13C nuclear magnetic resonance, and X-ray diffractometry, and it was found that the heat treatment will increase the degree of graphitization. The aromatic carbon content was found to correlate significantly with the fluidity of coal, and the relationship among the ratio of aromatic carbon/aliphatic carbon, aromaticity, and fluidity was studied in this work. Finally, X-ray diffractometry is suggested to be a non-destructive method to estimate the fluidity of coal.

Recycling tyre wastes as additives in industrial coal blends for cokemaking

Two industrial coal blends (B1 and B2) used in cokemaking were selected for this study. Two wastes from scrap tyres (TC, F) were added to these coal blends at different ratios (98:2 and 95:5). The investigation was focused on assessing the influence of the additives on thermoplastic properties of coal by means of the Gieseler fluidity test and thermogravimetric analysis. In addition, the blends were carbonized in a 17kg electrically heated movable wall oven in order to examine the quality of the resultant cokes. Quality of the cokes produced was evaluated by measuring their cold mechanical strength, reactivity and post-reaction strength. It was found that ash composition of the additives contribute to a deterioration in coke quality. Moreover, F causes a greater decrease in coke strength after reaction with CO2 due to the diminution of bulk density in the coking process and to the higher basicity index. Trace elements were also studied in relation to waste addition.

Effect of the addition of waste sawdust on thermoplastic properties of a coal

Three different sawdusts obtained as wastes from the furniture and flooring industry were selected to study their influence on coal thermoplastic properties. A bituminous coal with a high volatile matter content was chosen as base coal. To investigate the effect of reducing the oxygen content of the sawdusts upon the coal’s properties, the sawdusts were heat treated to 250°C. Blends of the coal with the three as-received and then heat-treated sawdusts were tested. In order to gain a better insight into the subject, the sawdusts were pyrolyzed at 400°C to determine the effect of the resulting char and bio-oil upon the plastic properties of the base coal. The Gieseler curves corresponding to the coal–sawdust blends were calculated from the curves corresponding to the coal-char and coal-bio-oil blends. The errors obtained were in all six cases lower than the repeatability allowed by the ASTM standard for the Gieseler test. Considering that the effect of the additives is the sum of both chemical and physical effects, it was possible to evaluate the contribution of each of these to the reduction of coal fluidity. In all cases it was found that the physical effects were more important. The textural properties of the chars obtained at 400°C from the biomass were found to be important for determining the influence of biomass on the coal fluidity.

Relevance of the composition of municipal plastic wastes for metallurgical coke production

This study is concerned with the effects of the composition of mixed plastic wastes on the thermoplastic properties of coal, the generation of coking pressure and the quality of the resulting cokes in a movable wall oven at semipilot scale. The mixed plastic wastes were selected to cover a wide spectrum in the relative proportions of high- and low-density polyethylenes (HDPE and LDPE), polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET). From the results it was deduced that the reduction in Gieseler fluidity in the coal blend is linked to the total amount of polyolefins in the waste. It was also found that these thermoplastics increase the pressure exerted against the wall in the course of the coking process and that coke quality is maintained or even improved. However, when the level of aromatic polymers such PS and PET are increased at the expense of polyolefins, the coking pressure decreases. Thus, the amount of aromatic polymers such as PS and PET in the waste is critical, not only for controlling Gieseler fluidity and coking pressure, but also for avoiding deterioration in coke quality (reactivity towards CO2CRI and mechanical strength of the partially-gasified coke CSR). An amount of polyolefins in the waste lower than 65wt.% for a secure coking pressure is established.

Importance of the textural characteristics of inert additives in the reduction of coal thermoplastic properties

Seven carbonaceous materials of different origin were chosen in order to study the influence of their porous structure on the modification of the thermoplastic properties of a bituminous coal. The materials included were: two non-coking coals, a petroleum coke, coke fines, two residues from tyre recycling and a bituminous residue. The materials were heat-treated to 900 °C to prevent any chemical interaction between the volatiles evolved during co-carbonization. The thermoplastic properties of blends that contained 10 wt.% of additive were measured by means of the Gieseler test. Microporosity was measured by CO 2 adsorption at 273 K, whereas meso and macroporosity were determined by means of mercury porosimetry. The results of the porous structure assessment are discussed in relation to the modification of coal plasticity.

Influence of coal thermoplastic properties on coking pressure generation: Part 2 – A study of binary coal blends and specific additives

A number of coal blends and pitch/coal blends were evaluated using rheometry, thermogravimetric analysis and microscopy to confirm and further elucidate the coking pressure mechanism previously proposed by Duffy et al. (2007) [1]. We confirm that blending a low rank, high fluidity, low coking pressure coal, with a high rank, low fluidity, high coking pressure coal can significantly reduce the coking pressure associated with the latter. Interestingly, blending does not necessarily result in a fluidity that is midway between that of the two coals; sometimes the fluidity of the blend is less than that of the low fluidity coal, especially when the coals are significantly different in rank. This occurs because the increase in complex viscosity ( η*) through resolidification of the low rank, high fluidity coal counteracts the reduction in η* resulting from softening of the high rank, low fluidity coal. It has also been confirmed that the η* of the resultant blend can be estimated from the η* of each component coal using a logarithmic additivity rule commonly employed for polymer blends. Polarised light microscopy has indicated that the degree of mixing between coals of different rank is minimal, with fusion restricted to the particle surface. It is therefore inappropriate to think of such a coal blend in the same way as a single coal, since each component coal behaves relatively independently. This limited fusion is important for understanding the coking pressure mechanism for blends. It is proposed here that the lower rank coal, which softens at lower temperature, is able to expand into the interparticle voids between the high rank coal that is yet to soften, and these voids can create channels for volatiles to traverse. Then, and importantly, when the high rank coal begins to expand, the pore structure developed in the resolidified structures of the low rank coal can facilitate removal of volatiles, while the resolidified material may also act as a suitable sorbent for volatile matter. This is considered to be the primary mechanism by which coal blending is able to alleviate coking pressure, and applies to addition of inert material also. Addition of a coal tar pitch was found to increase fluidity but also to extend the thermoplastic range to lower temperatures. This caused an increase in the swelling range, which was accompanied by a long plateau in η*, a feature which has previously been observed for certain high fluidity, high pressure coals. Elasticity and η* at the onset of expansion were also higher for both the pitch impregnated coals and the high pressure blends, which supports previous findings for singly charged high pressure coals, and confirms the potential use of such criteria for identifying potentially dangerous coals/blends.

Influence of additives of various origins on thermoplastic properties of coal

Two coking coals of different rank were chosen in order to assess the influence of various additives on their thermoplastic properties. Six additives of different origin and characteristics were selected: two non-coking coals, together with a commercial coal tar pitch, a residue from the bottom of the benzol distillation tower and two residues from the tyre recycling industry. The effect of the additives on coal thermoplastic properties was assessed by means of the Gieseler test. The additives were pyrolyzed to a final temperature of 550°C and the tar characterized by means of Fourier transform infrared spectroscopy (FTIR) and gas chromatography (GC). The influence of the additives on coal thermoplasticity is related to the volatile matter content of the additive, its evolution profile with temperature and the composition of the tar obtained during the pyrolysis of the additives.

PET recycling for the modification of precursors in carbon materials manufacture

The possibility of using a mixture of PET waste from mineral water bottles and a high rank bituminous coal as precursor for the production of carbon materials was studied. Taking into account the fact that a 10 wt% addition of PET waste totally changes the thermoplastic properties of coal, blends of coal and PET of up to 50 wt% were subjected to thermogravimetric analysis and carbonization at 800 °C. The chars produced were evaluated by optical microscopy and surface area measurements. The presence of PET waste promotes the formation of isotropic carbon and increases the microporosity of the chars obtained from the blends. For comparison purposes, the coal was oxidized at 200 °C for 24 h to avoid the fluid stage of the coal and afterwards carbonised in the same conditions. The causes of the effect of PET waste on the texture of the chars obtained from the blends are discussed.

Suppressed vitrinite reflectance in the Ferron coalbed gas fairway, central Utah: possible influence of overpressure

Chemical and thermoplastic properties of coals in the Ferron coalbed methane fairway indicate that coals in the north are of higher rank than coals in the south. Measured vitrinite reflectance does not accurately show this variation of coal rank. Although vitrinite reflectance in the southern and central part of the fairway is consistent with other measures of coal rank, suppressed vitrinite reflectance is observed in the north where methane contents are relatively high. This coincidence of suppressed reflectance and relatively high coalbed methane yields may be significant. We speculate that the suppressed reflectance values result from a burial history where overpressure developed during the early stages of coalification and persisted until recent uplift and cooling; such instances may be diagnostic of prospective coalbed methane targets elsewhere.

98/00145 Studies on generation of excessive coking pressure. 1. Semicoke contraction versus thermoplastic properties of coals

98/00145 Studies on generation of excessive coking pressure. 1. Semicoke contraction versus thermoplastic properties of coals

Studies on Generation of Excessive Coking Pressure. 1. Semicoke Contraction versus Thermoplastic Properties of Coals

There are two views on the mechanism of generation by some coals of excessive coking pressure and on laboratory testing methods for coking coals. According to one of them, the excessive pressure is generated in a coal thermoplastic layer if its viscosity is too high. Another view is that some properties of a semicoke layer are responsible for generating high pressure. The two layers, i.e., semicoke and plastic layers, follow each other when they move from coke oven wall to the oven center plane during the coking process. The aim of our work was to seek an answer to whether thermoplastic properties of coals and volume contraction (or expansion) observed for their semicoke layers are interrelated. The following characteristics were measured for a set of 42 coals: (i) Gieseler thermoplastic properties determined in two independent laboratories using two different standard methods and (ii) contraction values of carbonized coals by the Koppers-INCAR test. In general, rather diffused or no relationships were found between the contraction on one hand and the thermoplastic properties on the other. It is concluded that the above two views might be synthesized on the condition that causative links could be found between more specific characteristics of thermal decomposition during coal plastic state and contraction of semicoke layer. This issue is a subject of part 2 of the paper.

97/01700 Characterization of petroleum coke as an additive in metallurgical coke making. Modification of thermoplastic properties of coal

97/01700 Characterization of petroleum coke as an additive in metallurgical coke making. Modification of thermoplastic properties of coal

Some aspects of the role of coal thermoplasticity and coke structure in coal gasification: 3. The effect of rank, pitch and sodium carbonate on Brabender plastometry parameters

The thermoplastic properties of coal are a significant factor in determining gasification behaviour in most gasification processes. This investigation has involved the use of constant shear rate (Brabender) plastometry to study the plastic properties of a wide range of coals varying from 101 to 902 in the NCB Classification. The results obtained show more complex behaviour during the carbonization process than reported previously and are compared with ASTM Gieseler plastometry and BS dilatometry results. Some coals have two peaks in the caking region of the plastometry curve. This has been attributed to an initial peak corresponding to softening of the coal followed by caking due to active decomposition. The phenomenon was observed for coals with ranks 301a to 602, the temperature difference between the peaks being largest for the prime coking coals. It has been shown that this technique produces much additional information about the initial phase of the carbonization process. The effect of pitch and sodium carbonate addition on the plastometry parameters has also been studied. The results show that small amounts of these additives can radically change the plastometry curves. Pitch increases the plastic range whereas sodium carbonate reduces it. The addition of sodium carbonate tends to modify the plastometry curves so that they are similar to coals of lower rank whereas pitch addition, in general, tends to increase fluidity and, in the case of low-rank coals, produces plastometry curves similar but not identical to higher-rank coals.

Thermoplastic properties of coals at elevated pressures: 3. Effects of low-temperature preoxidation and subsequent heat-treatment on behaviour in H 2 and He

The thermoplastic properties of a mildly preoxidized Lower Kittanning seam low volatile coal have been examined at elevated pressures of H 2 and He utilizing a high-pressure microdilatometer. It was observed that the maximum swelling parameter ( V s , vol%) of the preoxidized coal was significantly restored at elevated pressures of He. The thermoplastic properties of the preoxidized coal were even further restored at high pressures of H 2. The results indicate that carbonization of this coal at elevated H 2 pressures reduces the effect of preoxidation by removing some of the oxygen introduced during preoxidation and replacing it with reactive donatable hydrogen. It was shown that subsequent heat-treatment of the preoxidized coal at a relatively mild condition (in vacuum at 403 K) results in dramatic reductions in the thermoplastic behaviour of coal when subsequently carbonized at elevated pressures of H 2 or He.

Thermoplastic properties of coal at elevated pressures: 2. Low-temperature preoxidation of a Pittsburgh Seam coal

The thermoplastic properties of a preoxidized Pittsburgh Seam HVAb coal (air-treated at 383 K to different levels of weight gain) were examined using a high-pressure microdilatometer over a range (0.1–2.9 MPa) of pressures. The results suggest that the thermoplastic properties of the coal, depending on the extent of preoxidation, can be significantly different at elevated pressures from those at atmospheric pressure. The maximum swelling parameters of this preoxidized coal are always lower than those of untreated coal at pressures < 1.0 MPa. However, > 2.0 MPa, the maximum swelling parameters of the mildly oxidized samples are, in general, greater than those of untreated coal.