Various Kinds Of Coal Research Articles

Czech and Slovak young brown coals in environmental applications

In recent time, various kinds of young brown (low-rank) coals are utilized increasingly not only as fuels, but also as valuable materials in advanced environmental applications. It should be noted in this context that significant deposits of the young brown coals can be found both in the Czech Republic as well as in Slovakia. For their effective applications e.g. in wastewater treatment or in soil remediation, the properties of the coals should be studied in more details and numerous physico-chemical characteristics should be measured. As a part of a common Czech-Slovak project, a series of various kinds of coals was collected, including North-Bohemian oxihumolites, lignite from South Moravia and several lignites from Slovakia (Baňa Zahorie). Basic properties were measured, such as acid-base titration curves, contents of main functional groups and sorption capability towards heavy metal cations (Cu2+, Zn2+, Co2+) and some organic pollutants. The contents of humic substances – main active constituents of the young coals – were also determined. Selected environmental applications of the brown coals will be mentioned further, e.g. for the removal of metal cations from waters or in phytoremediation of contaminated soils.

Development of a Heating Process of a Slag-Tapping Hole by Syngas Burning in a 150 t/d Entrained-Bed Coal Gasifier

Integrated coal gasification combined cycle systems are expected to raise the power generation efficiency of coal-fired power plants. In Japan, coal gasifiers are required to treat various kinds of coal imported from many countries because almost all of the coal is imported from abroad. In an entrained-bed coal gasifier, the slag-tapping hole must be heated adequately to discharge the molten slag. Thus, a heating technique has been developed to heat the hole from below, without using any auxiliary fuels. The technique is to burn the syngas, which descends through the hole at high temperature, by supplying oxygen from a pair of nozzles facing each other installed just below the hole. In this study, a design procedure to heat the hole by those nozzles was developed through thermal and flow simulations and actual gasification tests in a 150 t/d entrained-bed coal gasifier of pilot scale.

Гигиеническая характеристика и биологическое действие различных видов золы углей и мазута

Гигиеническая характеристика и биологическое действие различных видов золы углей и мазута

A novel model for cost performance evaluation of pulverized coal injected into blast furnace based on effective calorific value

The combustion process of pulverized coal injected into blast furnace involves a lot of physical and chemical reactions. Based on the combustion behaviors of pulverized coal, the conception of coal effective calorific value representing the actual thermal energy provided for blast furnace was proposed. A cost performance evaluation model of coal injection was built up for the optimal selection of various kinds of coal based on effective calorific value. The model contains two indicators: coal effective calorific value which has eight sub-indicators and coal injection cost which includes four sub-indicators. In addition, the calculation principle and application of cost performance evaluation model in a Chinese large-scale iron and steel company were comprehensively introduced. The evaluation results finally confirm that this novel model is of great significance to the optimal selection of blast furnace pulverized coal.

Analysis of hydrothermally-treated and weathered coals by X-ray photoelectron spectroscopy (XPS)

Analysis of hydrothermally-treated and weathered coals by X-ray photoelectron spectroscopy (XPS) was carried out, and the XPS C(1s) and N(1s) spectra obtained were curve-resolved into four peaks (C–C/C C/C–H, C–O, C O, and O–C O) and three peaks (pyridinic-N, pyrrolic-N, and quaternary-N), respectively. Upon hydrothermal treatment, the amount of carbon–oxygen forms decreased; while the ratio of pyridinic-N increased and quaternary-N decreased. On the other hand, some bituminous coals were subjected to natural weathering and laboratory oxidation, which gave opposite results compared to the hydrothermal treatment. The changes in the carbon–oxygen and organic nitrogen forms were discussed in terms of the effect of hydrothermal treatment and weathering (oxidation). Also, the XPS analysis of various kinds of coals (43 SS coals) was carried out, and the amounts of carbon–oxygen and organic nitrogen forms were discussed in terms of coal rank (carbon content).

Characteristics of Flue Gases and Ash in Oxygen-Blown Pulverized Coal Combustion

A new coal combustion technology for a large-scale power plant is required to be applicable to various kinds of coal. An oxygen-blown pulverized coal combustion experiment was investigated with a bench scale apparatus to understand such characteristics as the combustion efficiency, NOx concentration, conversion from fuel-N, the unburned fraction and composition of mineral matter in the collected ash. The experiment was conducted in a down-fired, cylindrical and vertical furnace. The primary oxygen is injected into the ejector to carry coal particles to the burner, and the swirled secondary one is fed through an annulus. The CO2 concentration in flue gas was much higher than that of air–coal combustion, and the value was eight out of ten. The results made a feasible condition for CO2 separation and sequestration. The NOx emission was ranged in concentrations from 1650 to 1800 ppm in the complete combustion region. The NOx concentration was much higher, however the NOx conversion ratio was about the same level as the case of air combustion. The decrease of low-boiling component such as Na, Mg, K and Ca was identified because the flame temperature of the oxygen-blown coal combustion was achieved about 3000 K. We suggested the vaporized calcium components in the fly ash have a potential of the furnace desulfurization and the effect of SOx attack to the heat exchanger was inhibited.

4304 純酸素吹き微粉炭バーナーの燃焼特性および流れ構造に関する基礎的研究(S62-1 高効率石炭火力発電(1),S62 高効率石炭火力発電)

An oxygen-blown pulverized coal burner for the utilization of various kinds of coal was newly proposed and developed. The combustion efficiency of 99.7% was achieved by the moderate swirl burner. The flame stabilization could not be realized by the strong swirl burner, and the contents of unburned carbon in ash were more than that of the moderate swirl burner experiment. The distribution of vorticity in the moderate swirling flow was equally proportioned even though the flow ratio was changed between 0.15 and 0.88. Additionally, the state of untidiness was observed near center part of the burner nozzle in the strong swirling flow. The close relationship between combustion efficiency and vorticity profiles was found by the flow analysis of PIV. The moderate swirl burner was suitable for designing the burner structure in the oxygen-brown pulverized coal combustion.

DESIGN AND FLOW ANALYSIS FOR AN OXYGEN-BLOWN PULVERIZED COAL BURNER

An oxygen-blown pulverized coal burner for utilization of various kinds of coal was newly proposed and developed. The combustion efficiency of 99.7% was achieved by the moderate swirl burner. The flame stabilization could not be realized by the strong swirl burner, and the content of unburned carbon in ash was more than that of the moderate swirl burner experiment. The distribution of vorticity in the moderate swirling flow was equally proportioned even though the flow ratio was changed between 0.15 and 0.88. Additionally, the state of untidiness was observed near the central part of the burner nozzle in the strong swirling flow. The close relationship between combustion efficiency and vorticity profiles was found by PIV analysis of the flow. The moderate swirl burner was suitable for designing the burner structure in oxygen-blown pulverized coal combustion.

Production of clean fuels by solvent skimming of coal at around 350 °C

The authors have recently presented a new coal extraction method by which various kinds of coals ranging from brown coals to bituminous coals could be extracted up to 80% of the parent coals in a flowing stream of tetralin or a coal derived oil, carbol oil, under 10 MPa at 350 °C. The extract obtained by this method was almost free from inorganic materials. In this study the effect of solvent recycling on the extraction behavior was examined to make the method practically applicable. The solvent recycling was found to be effective in enhancing the extraction yield and in decreasing further the inorganic fraction in the extract. The extract and residue obtained were characterized through various analyses. To examine how inorganic materials are removed by the extraction, the contents of inorganic elements, including harmful trace elements, in the extract were investigated. It was clarified that the presented method was effective in the removal of most of the inorganic elements including even harmful trace elements from coals, although the degree of removal was dependent on the kind of element.

99/02197 Operation results of the first commercial PFBC plant with high temperature ceramic filters: Suga, N. et al. Proc. Am. Power Conf., 1998, 60, (2), 608–613

Trial operation is now successfully underway at Tomato-Atsuma Unit No. 3 of Hokkaido Electric Power Co. (HEPCO) in Japan. This newly built 85 MWe unit is an innovative PFBC plant, which is the first commercial PFBC in Japan, and equipped with full capacity ceramic filters operated at 850 C. The high temperature ceramic filter effectively removes dusts in the hot gas and the dust loading at gas turbine inlet is much less than that of two-stage cyclones, minimizing the cost and time of gas turbine maintenance. The PFBC plant is composed of a pressurized fluidized-bed boiler, cyclones, ceramic filters, a gas turbine, a steam turbine, etc. and all of the equipment were manufactured and supplied by Mitsubishi Heavy Industries, Ltd. (MHI). Joint R and D program between HEPCO and MHI started 7 years ago, based on their own private funding and without any financial supports from public sectors, studying the optimum design of the first commercial PFBC aiming at environmental and economical advantages. And now fruitful results have been achieved. The commercial operation will start in March 1998 or earlier. Several troubles had been experienced during initial trial operation stage including pressure drop increase in ceramic filters. All these problemsmore » were solved one by one by the joint efforts of HEPCO and MHO. Load rejection tests, load swing tests, and automatic power control tests were successfully done in the spring of 1997. And tests with various kinds of coals are scheduled before the commercial operation.« less

On-Line Estimation of Coal's HGI by Neural Networks.

In a pulverized coal fired boiler, various kinds of coals are used as a fuel. It is important to estimate properties of fired coal at the on-line, in order to realize good operated performance just like oil or gas fired boiler. Hardgrove grindability index is one of the important properties. Neural network method is proposed to estimate the index. Experimental results show that our estimation model is effective on the pulverizer, and is superior to multiple regression analysis. Study on the appropriate network structures is also described.

A Novel Pulverized Coal Fired Burner

A novel pulverized coal fired burner, called “main burner with double primary air channels for pulverized coal”, is presented in this paper. Such a burner can burn various kinds of coals, including bituminous coal, low grade coal, lignite, semianthracite, anthracite, satisfying stability of combustion, controllability of the ignition location of pulverized coal, high efficiency, and low NO x , emission, thereby eliminating the unstable combustion caused by variation of coal quality and low load operation. It has not only solved the problem of low load operation and the combustion without oil assisting of Jiafu anthracite, which is the most difficult coal to burn in China, but also first successfully conducted the normal combustion in a tangentially pulverized anthracite fired furnace, as in a W-shaped flame furnace. According to the low load test on a tangentially pulverized coal fired furnace of 1025 t/h of anthracite combustion, its stability is superior to that of a W-shaped flame furnace with the same capacity, they will compete with each other in the future in China. This burner has been applied in the furnace of large scale, medium-and small-sized power stations in China, and even taken as finalized design for large tangentially low-volatile pulverized coal fired furnaces in Harbin Boiler Works, the biggest one in China. Also if used in W-shaped flame furnaces, it can further improve their combustion performance and reduce the steel consumption.

Iron/sulfur-catalyzed coal liquefaction in the presence of alcohol and carbon monoxide

The activities of several iron-based catalyst precursors towards the liquefaction of various kinds of coals, ranging from brown to bituminous, were examined in alcohol–carbon monoxide systems. Pentacarbonyliron (Fe(CO) 5) with or without sulfur, or synthetic pyrite were found to be excellent catalyst precursors. Primary alcohols (ethanol and 1-propanol)–CO acted as an effective hydrogen source, whereas branched alcohols were less effective. In the Fe(CO) 5/sulfur catalyzed liquefaction of Yallourn coal at 375°C for 120 min, a high conversion (99.5%) was achieved in the presence of ethanol and CO (7.0 MPa/cold). The two-staged reaction (375°C, 60 min+425°C, 60 min) further improved the oil yield to 59.1% with a slight decrease in the coal conversion. The uptake of alcohol into asphaltene and preasphaltene fractions was distinctly observed, especially for Illinois No. 6 coal. The infrared analyses of the asphaltene fractions from each coal showed absorption at around 1705 cm −1, characteristic for those obtained in the linear alcohol–CO systems. According to the characterization of the products by NMR and the preliminary study using a model compound, alkylation as well as the hydrogenolysis seem to contribute to the dissolution of coals.

Numerical Simulation of Pulverized Coal Combustion in a Furnace. Predictions of Emission Characteristics of NOx for Various Kinds of Coals and NOx Reduction due to Two-Stage Air Injection.

This paper discusses the predictions of both emission characteristics of NOx for various kinds of coals in single-stage combustion and NOx reduction due to two-stage combustion upon pulverized coal combustion using the authors' method of numerical simulation reported previously. The analyses have been compared with the experiments of single-stage combustion for various kinds of coals in the laboratory of the Central Research Institute of the Electric Power Industry and our results agree fairly well with their experimental data in the laboratory. The best conditions also can be predicted with sufficient accuracy on the position of injection port as well as the injection air flow rate for over fired air in two-stage combustion.

Coal Combustion in the Raceway and Tuyere of a Blast Furnace.

To achieve a pulverized coal rate of more than 200 kg/t, a technology is needed by which the combustion zone in front of tuyeres can be properly controlled in terms of the combustibility of pulverized coal. It is, especially, necessary to quantify the combustion behavior inside the tuyeres and raceway. Experiments were conducted on off-line models with and without coke to investigate the pyrolysis and combustion behavior of pulverized coal in order to analyze the influence of blast conditions and coal properties on their combustibility.(1) The final volatile yield of pulverized coal increases with the rise in blast temperature, and rise in O2 content accelerates the devolatilization rate.(2) With the progress of pyrolysis, the pulverized coal became spherical and a large number of pores formed in the particles. Thus the reactivity of char is estimated to be higher than that of coke.(3) Rising blast temperature is effective to improve the combustion efficiency of pulverized coal in the raceway, presumably a little effective to improve with the addition of steam. O2 enrichment at constant air ratio requires enhancement of the gas and particle mixture.(4) Q-factor that determined the final volatile yield can be shown by the blast temperature and C content in coal, and devolatilization rate parameters can also be learned by C content in coal. A practical equation representing the devolatilization rate inside tuyeres with various kinds of coal are presented.

自然発火および品質劣化をおこさない最大石炭貯蔵量のシミュレーション

The temperature increase curve due to the natural oxidation of a coal deposit was numerically simulated for a coal bed having a ‘spherical’ geometry. The maximum temperature occurred at the center of the bed when oxygen was fully supplied within the bed and near the surface when oxygen decreased due to the process of the reaction. The rate of temperature rise was significantly affected by the activation energy and frequency factor of the coal. Furthermore, the measurement of the moisture adsorbed on the oxidized coal samples showed that the loss in mass due to oxidation increased remarkably at temperatures above 120°C. In assuming the limiting temperature in coal storage to be 120°C, a maximum allowable amount of coal storage was estimated for various kinds of coal under the conditions of neither spontaneous combustion nor significant, loss in mass.

Ignition and combustion of coal particles at zero gravity

In the paper, the results of research on ignition and flame propagation between particles of various kinds of coal in conditions at zero gravity are presented. Direct and Schlieren photographs of the process were made. They illustrate the influence of the oxygen concentration in the air, the volatile contents in the coal and the distance between particles in the investigated process. The absence of free convection makes it possible to evaluate directly the influence of two heat transport mechanisms, i.e. the thermal conduction and radiation. There were also presented certain remarks resulting from the investigations of the ignition and burning of single coal particles which may be of use in modelling the coal-dust-air mixture combustion process.

石炭，石油中の硫黄，窒素分析における機器分析法の評価

Complying with the government's general policy of energy, Japanese electric power industries have been promoting plans to diversify energy sources. Accordingly, their consumption of coal, which was 7 million tons in 1975, was doubled in 1982. It is expected to go to increasing gradually hereafter.In spite of this current trend as referred above, the analyses of sulfur and nitrogen, which are necessary for quality control of various kinds of coal, are still being carried out based on the JIS (Japanese Industrial Standard) method for analyzing coal established in 1959. This method is inferior to the JIS Instrumental method for analyzing oil (modified in the late 1970's) in the analytical time and easiness of procedure. Therefore, the improvement of its inferiority is highly desirable.This paper describes the application of instrumental methods, which have been making a remarkable advance in recent years, to analyses of sulfur and nitrogen in coal, and reports the comparative evaluation of them with the conventional JIS method in terms of accuracy, precision and analytical time etc.As a result, the infrared sulfur analyzer (manufactured by LECO, U.S.A.) provided analytical values, which were obtained within three minutes, statistically equal to those by the Eschka Method (the JIS method). Permissible tolerance for repeatable measurements (n=2) was 0.01% for the sample contained below 0.5% of sulfur. In another instrumental method for analyzing nitrogen, combining a gas generator (manufactured by Sumitomo Co., Ltd.) with a gas chromatograph, the analytical values, which were obtained within five minutes, were statistically equal to those by the semi-micro Kjeldahl method (the JIS method). Permissible tolerance for repeatable measurements (n=2) was 0.04%. As noted above the short analytical time and easiness of procedure in the instrumental methods were verified. We also applied this instrumental method to oil for comparative study, and obtained analytical values almost equal to those obtained by the JIS instrumental method for analyzing oil.

Chemical Structure and Properties of Heat Treated Coal in the Early State of Carbonization (XII)

High vacuum pyrolysis was performed for Japanese original coals and heat treated coals. The molecular weight of resulting distillates was measured by vapour pressure and surface area of residual coal was determined by carbon dioxide according to the theory of Dubinin-Polanyi. The following results were obtained.1. For Yabari coal, the effect of the pyrolysis temperature was studied. The average molecular weight of distillates is about 400, which remains nearly constant at the temperatures of 350, 400, 450 and 500°C. At each temperature, distillates show an approximately same average empirical formula of C29H31O1·3. The results indicate that the substances of distillates are scarcely affected by the temperature of high vacuum pyrolysis. An interesting contrast to this result is shown in the yield of distillates which increases with increase in temperature.The surface area of residual coal increases with increasing temperature of pyrolysis above 400°C, and at 5007deg;C it reaches 167 m2/g, i. e., 50 % increase from the value of original coal.2. The effect of coal rank was examined with various kinds of coals, at the fixed heating temperature (500°C). The molecular weight of distillates increases with increase in coal rank as shown by Taiheiyo coal (329) and Bibai coal (346), reachs maximum (393) at Yabari coal and decreases on further increase in coal rank. However, Takamatsu coal shows an extremely low value (288). This relation bears clear resemblance to the previously reported relation between the yields of distillates and coal rank. When molecular weight of distillates were plotted against C% of distillates, almost all coals were found to lie on the straight line, including Takamatsu coal. This signifies that molecular weight of distillates increases with increasing C%.As for the surface area of residual coal, the youngest Tempoku coal shows the highest surface area (about 300 m2/g), and the surface area tends to decrease with increasing degree of coalification. The difference of the surface areas between original coal and residual coal is large for young coals, and it shows a decreasing tendency with increase in degree of coalification.3. The high vacuum pyrolysis of heat treated coals was performed under the idential condition (500°C) and the effect of heat treatment temperature was investigated. The molecular weight of distillates is generally unaffected when heat treatment temperature is below 400°C, but decrease rapidly at 450°C. This tendency can also be observed for the yields of distillates as reported previously, and combined results suggest that polymerization and decomposition might have been induced to an appreciable extent by the heat treatment at 450°C. The surface area of residual coal tends to increase with increase in heat treatment temperature above 500°C.

Chemical Structure and Properties of Heat Treated Coal in the Early State of Carbonization (VII)

Japanese original coals and heat treated coals were employed as samples for high vacuum pyrolysis and following results were obtained.1. The effect of temperature was studied for Yubari coal. The yields of the distillates and gaseous products increased with increasing temperature. The ultimate analysis of distill-ates shows that the carbon content is approximately equal to that of original coal, but the hydrogen content (about 8%) is 2% higher than that of the original coal.2. The effect of coal rank was examined with various kinds of coals, at the fixed heating temperature (500°C). The yields of distillates and gaseous products were found to be proportional to the hydrogen content and oxygen content of original coal, respectively. This suggests that each yield is influenced strongly by hydrogen or oxygen content. And in all kinds of coals, the hydrogen content of distillate is higher than that of original coal. The oxygen content of distillate is almost same with that of the residual coal, but is less than that of original coal.The hydrogen distribution to distillate increases almost linearly with increase in hy-drogen content of original coal, while the hydrogen distribution to residual coal and gaseous products remains constant, irrespective of thehydrogen content of original coal. The oxygen distribution to gaseous products changes under the influence of the oxygen content of original coal, but those to distillate and residual coal remains constent.3. The high vacuum pyrolysis of heat treated caol was performed under the identical condition (500°C) and the effect of heat treatment temperature was investigated. The yields of distillates and gaseous products generally decrease with increasing heat treatment temperature, though there are some exceptions. In heat treated coals, the yield of distillate also decrease curvilinearly with a decrease in hydrogen content of coal samples. However, on the contrary to original coals, the yields of gaseous products decrease rapidly with decreasing oxygen content in heat treated coals. When the atomic composition of distillate is expressed on the H/C-O*/C diagram, O*/C of distillate remains nearly constant apart from heat treatment temperature, and also agrees with O*/C of residual coal.