Reactivity of chars from New Zealand coals

Equipment for measuring the reactivity of chars from highly reactive coals, based on recent Norwegian developments, has been assembled. Measuring techniques are described, and the results of measurement with a range of New Zealand coals are presented. The measured reactivities are compared with results obtained by using the German standard method for reactivity, and the comparison confirms the advantages of the Norwegian method for use with coals of high reactivity. By overseas standards, New Zealand's subbituminous coals have phenomenally high reactivities.     

New chemical structural features of coal. A comparison of several coals

Structural features of several coals of different ranks are compared using an adaptation of the transalkylation reaction. In the present application of this method, trifluoromethanesulphonic acid is used as catalyst and toluene is used in excess as acceptor and solvent. The process can be visualized as a disproportionation reaction in which intermolecular alkyl transfers occur. Under the influence of the acid catalyst, aryl-alkyl bonds in coal are cleaved and alkyl-aryl bonds are formed with the excess toluene solvent. Thus, a large number of substituted toluene derivatives are formed by transfer of groups from coal. Concentrations of ≈ 20 substituent groups and connecting groups are estimated and compared for a range of coals and numerous other compounds are present in small amounts. These compounds are tabulated for two coals and the possible significance and origin of some of them are discussed. The mechanism of the transalkylation reaction as it applies to coal and the reactions of a limited number of relevant model systems are also discussed.     

Fusion temperatures of PFA from New Zealand sub-bituminous coals

The ash fusion temperatures of 20 analysed samples of pulverized fuel ash obtained from the Meremere coal-burning power station have been determined. It is shown that the fusion temperatures can be related to the acid-soluble calcium and iron oxide contents, and that it is possible to predict the softening and hemisphere temperatures of ash cubes with a precision of ca. 10 to 20 °C in either oxidizing or reducing atmospheres. Removal of the magnetic iron fraction from the PFA reduced both the softening and hemisphere temperatures by ca. 10 to 15 °C in an oxidizing atmosphere, and in a reducing atmosphere it increased the softening temperature by ca. 10 °C and the hemisphere temperature by ca. 30 °C.     

Chemical characterization of solid coals through magic-angle 13C nuclear magnetic resonance

Recently developed ¹³C n.m.r. techniques for high resolution in solids are applied to native coals. The quantity and distribution of hydroxyl groups in the samples are determined by combining chemical modification through acetylation with the n.m.r. measurements. Spectral subtraction isolates the reaction product resonances. Spectroscopic separation of protonated and non-protonated carbons through pulse programming techniques is also demonstrated. Finally, the susceptibility of the aliphatic carbons in coals to low-temperature oxidation is shown clearly by subtraction of spectra of the oxidized and unoxidized materials.     

Studies related to the structure and reactivity of coals 17. The chemical structure of asphaltenes and residues from reactions of Victorian brown coals

The chemical structures of the asphaltenes and residues from reactions of a range of brown coals with widely varying atomic H/C ratios have been examined by chemical and spectroscopic methods, and have been shown to be remarkably consistent. Asphaltenes and residues from brown coals with high atomic H/C ratios show a small but significant increase in incorporation of aliphatic, guest material although the main bulk of material is derived from the host component of the coal (i.e. ligno-cellulosic or tannin derived material).     

Studies related to the structure and reactivity of coals : 16. The chemical structure of the oil products from reactions of Victorian brown coals

A suite of Victorian brown coals and the guest and host components of the coals obtained by 320 °C extraction have been reacted to obtain oils for analysis by n.m.r. and g.c.-m.s. techniques. Batch autoclave experiments without solvent, but with 10 MPa initial hydrogen pressure in the presence of stannic oxide, were undertaken at 405 °C. Oils derived from the macromolecular host material were highly polar materials and contained mainly phenols, and one- and two-ring aromatic hydrocarbons. They were of similar composition for all Victorian low-sulphur brown coals. In contrast, oils derived from the guest material were mainly a mixture of n-alkanes and terpenoid-derived cyclic hydrocarbons, and the ratio of these two types of compounds varied with the coal.     

Studies related to the structure and reactivity of coals : 18. The chemical structures of products from reactions of a suite of higher rank Australian coals

The structure of the oils, asphaltenes and residues obtained by the thermal reactions of a suite of Australian higher rank coals under hydrogen or nitrogen have been studied by chemical and spectroscopic methods. The host-guest model that has been used to describe the structure of Australian brown coals cannot be applied directly to the higher rank coals. Evidence is provided that suggests that a modified version of the model may be of use in describing the structure of some subbituminous coals. The methodology has proved to be useful in the understanding of structural features of coals which are often not rank dependent, e.g. Callide coal (ABL2), a subbituminous coal, has been shown to have characteristics of both very high and also low rank coals.     

Aryl-alkyl groups in coals

A method has been developed for detecting ethyl, propyl, and isopropyl substituents on aryl rings in coals. This method complements an earlier method for determining aryl-methyl groups. Examination of five coals showed that 0.1-0.3% of the carbon was in aryl-ethyl groups. Aryl-propyl, aryl-isopropyl, and larger aryl-alkyl groups were not detected. Aryl-methyl is the dominant aryl-alkyl group in coals and generally accounts for ≈1% of the carbon.     

Prediction of ash fusion temperature from ash composition for some New Zealand coals

Three improved techniques are presented for predicting the fusibility temperatures of coal ash from ash composition for particular coalfields. The first uses ternary equilibrium phase diagrams where the vertices are percent base, percent fluxing acidic oxides and percent non-fluxing acidic oxides. For reducing conditions FeO is a base, but for oxidizing conditions Fe₂O₃ is a non-fluxing acid. Plots of ash fusibility results on these diagrams show the range of behaviour of a particular coal and where low temperatures occur. They can be used to predict behaviour of fresh samples. The second method uses multiple regression equations above and below the minimum in the ash fusion temperature-percent base plot (usually 38% base), using as predictors, percent base (B), B², and acid flux and base flux factors F_A, F_B (or their logarithms). The third technique, the most accurate, uses stepwise regression, again on split observations above and below the minimum in the ash fusion temperature-percent base plot. With 40 parameters it is possible to identify the significant ash fusion parameters present for each ash fusion measurement in each coalfield. Two sets of observations which included measurements of borate (B₂O₃) showed that it caused a significant but negligible reduction in ash fusion temperature.     

Abnormalities in the chemical properties of tertiary coals of Upper Assam and Arunachal Pradesh

Certain abnormalities in the chemical properties of the oligocene coals of Upper Assam and Arunachal Pradesh, which could be attributed to the marine environment and peculiar depositional conditions are discussed. It has been observed that: marine depositional conditions were responsible for the perhydrous nature of the coals which increases with the intensity of marine environment; and graphs of carbon versus oxygen are useful for the identification of a seam and/or field. It has also been suggested that oxygen was replaced by organic sulphur thereby lowering the oxygen content of these coals. This aided the development of their agglutinating properties.     

Pyrolysis—gas chromatography of Australian coals. 2. Bituminous coals

Pyrolysis—gas chromatography (Py—g.c.) was used to characterize quantitatively a series of high- to low-volatile bituminous Permian Australian coals. The levels of n-alkanes, n-alkenes and triterpenoids released by pyrolysis all decrease as a function of increasing rank and thus, the coal samples can be classified into three distinct groups. Carbon Preference Indices (CPI's) for alkanes and alkene/alkane ratios also decrease as a function of rank. The triterpenoids have exclusively the hopane skeleton. The hopane isomeric distributions exemplify the geological maturity of bituminous coals relative to brown coal (lignite). A significant correlation has been established between the level of n-alkanes and n-alkenes released under Py-g.c. conditions and the predicted oil yield by pyrolysis of these coals. Further development and application of the techniqueshould enable much to be learnt relating to the quality and yield of flash pyrolysis tars as well as the original coal macromolecular structure.     

Deno oxidation. Isolation of high-molecular-weight aliphatic material from coals and further model compound studies/

Long-chain aliphatic materials present in coals are not completely oxidized using the procedure described by Deno (Fuel 1978, 57, 455). They are adsorbed on the filter cake during the work-up procedure and can be isolated by extracting the filter cake. The amounts present are similar to those observed by Hayatsu et al. (Fuel in press). Also-phenol is not completely oxidized under these conditions, but gives products with m/e as high as 310. Products from the oxidation of phenol include ethane and propane tricarboxylic acids and benzene tri- and tetracarboxylic acids.     

Reaction of coals in hot acidic phenol at constant acid concentration

Previous work showed that the efficient ‘depolymerization’ of bituminous coals in hot phenol containing p-toluenesulphonic acid failed to occur and that the acid was destroyed during the reaction. Four coals varying in rank from lignite to low volatile bituminous were treated with refluxing phenol containing p-toluenesulphonic acid with the acid concentration held constant. The amount of colloidal material, of pyridine-soluble material, of benzene—ethanol solubles, and the number average molecular weight of the pyridine extractables were measured as a function of time. Although the reaction proceeds better with the lower rank coals, a large portion of the products is colloidal material. Treatment of coals with hot acidic phenol does not lead to their complete depolymerization. Treatment of Bruceton coal with refluxing phenol saturated with BF₃ also failed to give complete depolymerization. The formation of colloidal suspensions during investigations employing spectral and other physical measurements may lead to results that are susceptible to misinterpretation.     

新型煤化工技术和经济竞争力分析

对煤化工及新型煤化工产业的分类和主要技术进行了归纳,分析和对比了新型煤化工各产业的竞争力,为计划投资新型煤化工项目建设的企业提供一定的借鉴。     

Structure in cokes from coals of different rank

A range of bituminous coals has been carbonized to 1273 K. Polished surfaces of the solid products, carbons or cokes, are examined for optical texture by optical microscopy. Fracture surfaces of the carbons are examined by scanning electron microscopy (SEM). The carbon from the lowest rank coal (NCB Code No. 702) is isotropic and fracture surfaces are featureless. Carbons from coals of ranks 602, 502 are optically isotropic but fracture surfaces are granular (size 0.1–0.2 μm), indicating small growth units of mesophase. In the carbon/coke from a 401 coal, the anisotropic optical texture and grain size are both ≈0.5–10 μm diameter. Coke from a coking coal (301a, 301b) has a layered structure extending in units of at least 20 μm diameter with sub-structures ~ 1.5 μm within the layers, indicating perhaps that the bedding anisotropy of these coals is not totally lost in the fluid phase of carbonization. The carbons from the higher rank coals have the bedding anisotropy of the parent coal. The combined techniques of optical microscopy and SEM (both before and after etching of the fracture surfaces of coke in chromic acid solution) reveal useful detail of structure in carbons/cokes and of the mechanism of carbonization of coking coals.     

Prediction of macerals contents of Indian coals from proximate and ultimate analyses using artificial neural networks

Coal, a prime source of energy needs in-depth study of its various parameters, such as proximate analysis, ultimate analysis, and its biological constituents (macerals). These properties manage the rank and calorific value of various coal varieties. Determination of the macerals in coal requires sophisticated microscopic instrumentation and expertise, unlike the other two properties mentioned above. In the present paper, an attempt has been made to predict the concentration of macerals of Indian coals using artificial neural network (ANN) by incorporating the proximate and ultimate analysis of coal. To investigate the appropriateness of this approach, the predictions by ANN are also compared with conventional multi-variate regression analysis (MVRA). For the prediction of macerals concentration, data sets have been taken from different coalfields of India for training and testing of the network. Network is trained by 149 datasets with 700 epochs, and tested and validated by 18 datasets. It was found that coefficient of determination between measured and predicted macerals by ANN was quite higher as well as mean absolute percentage error was very marginal as compared to MVRA prediction.     

Integrated instrumental analysis of soft brown coals

A method for the simultaneous determination of calorific value Q^r, ash yieldA^r and total water content W^r_t of soft brown coals is described. The method involves instrumental analysis of brown coal samples using neutron thermalization and gamma back-scattering techniques. Over 80 coal samples (1.1 kg) were analysed, having Q^rvalues up to 15.5 MJ kg^?1,A^r ranging from 3.6 to 76.1 wt% and W^r_t ranging from 11.4 to 61.7 wt%. A comparison of the results from the instrumental method with those of standard laboratory analyses is given, followed by a discussion of the accuracy of the method and of possible ways for improving it.     

Determination of organic oxygen content of coals

Fast neutron activation analysis has been used to determine organic oxygen (O_org) content of coals by subtracting the oxygen content of the mineral matter from the total oxygen content of the coals. Mineral matter was isolated by low temperature ashing in an oxygen plasma. Optimum ashing conditions produce minimal changes in chemical composition of mineral matter; these changes were taken into account when calculating the O_org content. The O_org contents of whole coals are substantially different — in some cases by as much as 47% — from the ASTM oxygen contents and those calculated on a dry, mineral matter free basis from the ultimate analysis data. Excellent agreement between the FNAA O_org contents of the whole and demineralized coals lends support to the reliability of this experimental approach.     

Zirconium and hafnium in Bulgarian coals

A study of the geochemical behaviour of zirconium (Zr) and afnium (Hf) in several Bulgarian coal deposits has shown that the content of these elements varies considerably, the highest concentrations being found in fragments of coalified woods included in sandstones. Zr and Hf content of the lithotypes of the coals is lower than that of the corresponding whole coal samples. The Zr/Hf ratio for xylain and vitrain is always lower than that for whole coal samples. Zr and Hf are mainly associated with the inorganic matter of the coals and Zr_org and Hf_org dominate only in the low ash coals of some deposits. It is assumed that Zr_org and Hf_org were leached from the terrigenous minerals supplied to the peat swamp and fixed by the organic matter. These processes result in a slight separation of both elements.     

单种煤性质对其焦炭性质的影响

通过测定11种单种煤和所炼坩埚焦的性质，得出单种煤挥发分与平均最大反射率在合适的范围内，所炼坩埚焦的反应性最小，结构强度最大。