Coal Washing Plant Research Articles

05/01406 Coal cleaning: A viable strategy for reducedcarbon emissions and improved environment in China?: Glomsrød, S. and Taoyuan, W. Energy Policy, 2005, 33, (4), 525–542

China is a dominant energy consumer in a global context and current energy forecasts emphasise that China's future energy consumption also will rely heavily on coal. The coal use is the major source of the greenhouse gas CO2 and particles causing serious health damage. This paper looks into the question if coal washing might work as low cost strategy for both CO2 and particle emission reductions. Coal washing removes dirt and rock from raw coal, resulting in a coal product with higher thermal energy and less air pollutants. Coal cleaning capacity has so far not been developed in line with the market potential. In this paper an emerging market for cleaned coal is studied within a CGE model for China. The macro approach catches the repercussions of coal cleaning through increased energy efficiency, lower coal transportation costs and crowding out effect of investments in coal washing plants. Coal cleaning stimulates economic growth and reduces particle emissions, but total energy use, coal use and CO2 emissions increase through a rebound effect supported by the vast reserve of underemployed labourers. A carbon tax on fossil fuel combustion has a limited effect on total emissions. The reason is a coal leakage to tax exempted processing industries.

Modes of Occurrence and Cleaning Potential of Trace Elements in Coals from the Northern Ordos Basin and Shanxi Province, China

Abstract Based on the analyses of 43 elements in 16 samples of the raw coal and feed coal collected from the northern Ordos basin and Shanxi Province, the modes of occurrence of these elements were studied using the method of cluster analysis and factor analysis, and the cleaning potential of the hazardous elements relatively enriched in the coals was discussed by analyzing six samples of the cleaned coal from the coal‐washing plants and coal cleaning simulation experiments. The results shows that the elements Br and Ba show a strong affinity to the organic matter, Cs, Cd, Pb, Zn and Hg partly to the organic matter, and the other trace elements are mainly associated with the mineral matter. Cs, Mo, P, Pb, Zn and S have positive correlations with the two principal factors, reflecting the complexity of their modes of occurrence. Some elements that were thought to show a faint relationship (Be with S and Sb with carbonates) in other rocks are found to have a strong interrelation in the coals. Clay minerals (mainly kaolinite) dominate in the coals, and Ta, Th, Ti, Sc, REE, Hf, U, Se, W, V, Nb, Mo, Al, P, Cr, Pb and Zn are distributed mostly in kaolinite, while K, Rb, Cs, and Na have much to do with illite. Conventional cleaning can reduce the concentrations of most hazardous elements in various degrees. The hazardous elements S, As, Sb, Se, Mo, Pb, Cd and Hg relatively enriched in some coals from the area studied have a relatively high potential of environmental risks. However, by physical coal cleaning processes, more than 60% of As and Hg were removed, showing a high degree of removal, more than 30% of Sb, as well as S, Pb and Cd partly associated with the inorganic matter were removed. Se and Mo showing a relatively low degree of removal could be further removed by deep crushing of the coal during physical cleaning processes, and the concentrations of S, Pb, Cd and Hg with a partial association with the organic matter could be decreased in such ways as the coal blending. Cluster analysis together with factor analysis is a rapid and effective way to deduce the mode of occurrence of an element from bulk samples, and the removability data of most hazardous elements are basically consistent with their modes of occurrence suggested, which indicates that the statistical analysis could predict the cleaning potential of hazardous elements during the physical coal cleaning.

Evaluation of the collective washing of coals from the Soma region with different characteristics

Coal basins may have different coal formations. Therefore, different coal characteristics can be seen even in the same coal seam. The characteristics of the coal and the type of the mineral matter in coal are very important factors for the design of coal washing plants. The Soma coal region in Turkey has different coal formations which necessitate a careful blending of the coals prior to the washing plant. At present, Soma coals are being washed in a conventional heavy media plant. However, coals from different productions zones are fed to the plant without any blending. The clean products are also not blended to gain a consistent quality before sale. In this study, five different types of coal from the Soma region were washed together in the same washing plant. First, these coals were submitted to float–sink tests. Data derived from these tests were used for the evaluation of the plant trials. A novel method was used for the evaluation of the coal's washability and its probable effects on the performance of the coal washing equipment. As a result, experiments and evaluations show that the coal formations in the Soma region have significant differences in their characteristics which can impair the performance of the coal washing plant. Thus, washing these coals in the same plant under the same conditions needs blending or a special feeding programme.

Coal cleaning: a viable strategy for reduced carbon emissions and improved environment in China?

China is a dominant energy consumer in global context and current energy forecasts emphasise that China's future energy consumption also will rely heavily on coal. The coal use is the major source of the greenhouse gas CO 2 and particles causing serious health damage. This paper looks into the question if coal washing might work as low cost strategy for both CO 2 and particle emission reductions. Coal washing removes dirt and rock from raw coal, resulting in a coal product with higher thermal energy and less air pollutants. Coal cleaning capacity has so far not been developed in line with the market potential. In this paper an emerging market for cleaned coal is studied within a CGE model for China. The macro approach catches the repercussions of coal cleaning through increased energy efficiency, lower coal transportation costs and crowding out effect of investments in coal washing plants. Coal cleaning stimulates economic growth and reduces particle emissions, but total energy use, coal use and CO 2 emissions increase through a rebound effect supported by the vast reserve of underemployed labourers. A carbon tax on fossil fuel combustion has a limited effect on total emissions. The reason is a coal leakage to tax exempted processing industries.

Practical Optimization Strategies for Coal-washing Plants

The MODSIM mineral processing plant simulator is used to find optimal combinations of target separation specific gravities for the separation units in a typical coal washing plant. The plant is set up to wash three size fractions separately in parallel streams. Two alternative flowsheets are examined: the first includes a dense-medium vessel, a dense-medium cyclone and a 2-stuge water-only cyclone, and the second includes a dense-medium vessel, a shaking table, a spiral separator and a bank of flotation cells. A simple graphical construction is used to find the optimal separation densities using data thai is generated by the simulator. Results are presented as optimal ash content - total yield curves for the combined clean coal products.

Process optimization in a supervision support system

We present details of the optimization task in a real-time (Thompson and Mertz 1993) knowledge-based (Moore et al. 1991, Larsson 1992) supervision support system in the coal washing domain. The Ash Control Model (AshMod) assists operators in maximizing clean coal yield while keeping ash (impurity) content within acceptable limits. AshMod assists the operator in plant situation assessment, fault diagnosis, and performance optimization. Situation assessment and fault diagnosis are mentioned briefly, since they have been described elsewhere in detail (Villanueva and Lamba 1997, 1998). We focus on the optimization task, which employs a hybrid artificial intelligence and operations research approach. The process is modelled through a set of extended states associated with the entire process and with individual components (circuits) within the plant. The scheduling optimizer continuously monitors the process, assesses the process state, and dynamically plans and performs integer and real optimization of a sequence of actions. The supervision support system captures domain knowledge through multiview models (Terspra et al. 1993) such as the goal tree success tree, plant schematic and fault cause network. AshMod performs deep reasoning through the use of knowledge models (Lind 1994) that capture purpose, function, structure, behaviour and heuristics. These knowledge models are mentioned briefly, since they have also been described elsewhere in detail (Villanueva and Lamba 1997, 1998). The supervision support system (Lamba 1995) is currently undergoing online validation at the B&C Coal Washing Plants operated by the Broken Hill Proprietary Limited (BHP 1998) at Port Kembla, Australia. The system is expected to be fully operational by the end of 1998.

Natural radionuclide contents in Spanish coals of different rank

The principal objective of this work was to determine the natural radionuclide contents of different rank coals from the Asturias and Galicia (important mining areas of Northwest Spain). It is known that there is a good correlation between ash content and the natural gamma radioactivity of these coals that may be used as the basis for natural gamma radiometric equipment for on-line determination of their ash content. For a more complete understanding of this correlation, an examination was made of which chemical components of the coal ash have the most significant influence on variations of the natural radionuclide content in coal. One hundred and twenty samples of the different products (run of mine (rom), washed coal, and wastes from coal-washing plants) were analysed for natural radionuclide content, in selected cases for chemical element content of their ashes, and coal wastes for mineral constituents. The radioactive analyses were performed by using a gamma spectrometer with an NaI(Tl) crystal. The elemental analyses were by X-ray fluorescence, and the mineral analyses were performed by X-ray diffraction. This study suggests that the highest values of natural radionuclide concentration are in coal wastes. The lignites from Galicia show lower concentration than the coals from Asturias.

Operator guidance system for coal washing

In this paper we present the analysis, design and implementation of the Ash Control Model (AshMod), a real-time knowledge-based operator guidance system (OGS) in the coal washing domain. The complexity of coal washing is such that a knowledge modelling methodology was needed for the development of this operator guidance system. The Knowledge Acquisition and Design Structuring (KADS) methodology guided us in the development of these knowledge models. We present an integration of the KADS methodology with the G2 real time implementation environment. AshMod assists the operator in monitoring the plant, performing fault diagnosis, and in plant optimisation. Furthermore, it assists the operator in maximising clean coal yield while keeping ash (impurity) content within acceptable limits. AshMod performs deep reasoning through the use of KADS-inspired knowledge models that capture purpose, function, structure, behaviour and heuristics. Knowledge validation and maintenance are facilitated through the use of graphical object-oriented knowledge models, implemented in G2. AshMod has been developed for the B and C coal washing plants operated by Broken Hill Proprietary Limited (BHP) at Port Kembla, Australia. 1,2 Owing to our focus on generality and reuse during the development of this operator guidance system, we expect that much of AshMod can be reused in future OGS developments in BHP-operated coal washeries, sinter plants, blast furnaces, coke ovens etc. AshMod is currently undergoing online testing at the coal washing plants.

98/00952 Flotation of hydrophobic flocculated coal for ash rejection: Li, R. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1995, 12, 870–874

In order to remove much more ash from the coal slurry of Tongshan coal washing plant and obtain high quality clean coal, the flotation of hydrophobic flocculated coal is studied to replace the conventional flotation.The main parameters of affecting this process such as the duration and intensity of the agitation, the amount and type of dispersant and nonpolar oil are investigated. The new process has been used to treat the coal slurry of 24.22% ash content, and the cleaned coal of 12.52% ash content with 86.58% weight recovery was obtained, compared to that of 17.78% ash content with 86.01% weight recovery by the conventional flotation. It is obvious that the flotation of hydrophobic flocculated coal is an efficient method to coal slurry beneficiation.

Operator guidance system for industrial plant supervision

In this paper we present monitoring, diagnosis and optimization in the Ash Control Model (AshMod), a knowledge-based operator guidance system (OGS) in the coal washing domain. AshMod assists the operator in monitoring the plant, performing fault diagnosis, and in plant optimization. It assists the operators in maximizing clean coal yield while keeping ash (impurity) content within acceptable limits. AshMod performs deep reasoning through the use of knowledge models that capture purpose, function, structure, behaviour and heuristics. Knowledge validation and maintenance is facilitated through the use of graphical object-oriented knowledge models. AshMod has been developed for the B&C coal washing plants operated by Broken Hill Proprietary Limited (BHP) at Port Kembla, Australia (The Broken Hill Proprietary Company Limited, Home Page, http://www bhp.com.au/; BHP, 1995) Owing to our focus on generality and reuse during the development of this OGS, we expect that much of AshMod can be reused in future OGS developments in BHP operated coal washeries, sinter plants, blast furnaces, coke ovens etc. AshMod is currently undergoing of line testing at the coal washing plants.

Coal Resources and Development of the Coal Industry in China

There are large coal resources of various types in China where it plays a dominant role in energy consumption. Since the foundation of the new China, the coal industry has developed rapidly. The annual output of coal produced increased from 32.43 Mt in 1949 to 1 billion tonnes in 1989. Now China is able to design, construct and equip large-scale coal mines as well as coal-washing plants. The coal industry has reached a level as advanced as that in other countries. Since coal is the main energy source in China rapid development of the industry will ensure that of the national economy. Hence, substantial funds should be invested in the coal industry. Attention should also be paid to coal transportation. Some railway lines should be renovated and some new ones built in order to increase the capacity for coal transport. In addition, research work should be conducted in mining and technology to raise productivity of the industry.

Surface Properties of Coal Fines in Water. I. Electrokinetics and Surfactant Adsorption”“

The adsorption of phenol, p-nitrophenol, the nonionic surfactant Triton X-100 (a commercial mixture of octylphenol poly ethoxylates) and the cationic surfactant dodecyltrimethylammonium bromide (DTAB) from aqueous solution on coal fines from a coal washing plant has been studied. Adsorbate solution concentrations range from 0-8 × 10-4 m. For the cationic and nonionic surfactants both adsorption isotherms and electrokinetic isotherms were determined. The adsorption of phenol, but not of Triton X-100 and DTAB, is found to increase with time for periods up to 300 h. For short contact times (< 30 h), the amount of Triton X-100 adsorbed is about three times higher than the amount of phenol adsorbed at the same solution concentration. The electrokinetic data show that the zeta potential of the coal is not affected by the adsorption of Triton X-100. On the other hand, adsorption of the cationic surfactant strongly influences the zeta potential. For negatively charged coal, i.e., at higher solution pH (iep of the...

“SEVONETT” Flotator, A Large Capacity Flotator

It is desired that the whole pulp stays in a flotator sufficiently long, not too long not too short, to satisfy the flotation time. The anther tried to develop a new flotator to contribute in this respect.After ascertaining that two principles of counter current flotation and mechanical agitation flotation may be combined in a cell by a test, he designed a new flotator named SEVONETT in memory of the Seventy One Birthdays of T.T., because the fundamental experiment with the basic form of the set of the rotor and the stator was completed just a day before his 71st birth day.In the cell of the SEVONETT flotator there are several units of the rotor and the stator, arranged vertically with a certain intervals. The pulp is fed at the center of the highest rotor, and draws out from the bottom. Air is blown into the pulp under each rotor. The rotor is devided into two parts by a horizontal plate. The pulp is rotated by the upper part, and the rotated pulp is scooped out radially by the vertical vanes of the stator which surrounds the rotor. The air blown into the pulp under the rotor is broken into many tiny bubbles. The air bubbles are carried out by the flow of the pulp into the annular space between the contour surface of the stators and the inner wall of the cell, and ascend against the pulp flowing down. Here the counter current flotation is realized.Several fundamental surveys and practical tests have shown that the SEVONETT flotator is competent for practical use.The speed of flotation in the SEVONETT flotator is high by virtue of the counter current priciple of flotation. The machine is economical with respect to its size, power and floor space requirement, and repairing.The type of the machine is a Vertical Multistage Mechanical Air Flotator.At present there are three 1.8m × 1.8m SEVONETTs at the Akabira Coal Washing Plant and one 1.2m × 1.3m SEVONETT at the Ponbetsu Coal Washing Plant, Hokkaido, Japan. The Akabira plant is going to have another four SEVONETTs in near future.

Treatment of phenolic effluents

AbstractThe following methods of disposal and treatment of phenolic liquors from coke oven plants are studied: direct use on froth flotation media in coal washing plant. The coal absorbs 60% of the phenols present, but only half the normal output can be used in this way. chemical oxidation of the phenols by ozone. This is satisfactory for dilute liquors (100 p.p.m. of phenols) but is too costly for spent ammoniacal liquors. biological oxidation. The activated sludge process is satisfactory but somewhat expensive. An enclosed percolating filter containing coke activated with soil organisms gave promising results. extraction of phenols. The use of light creosote oil in a rotating disc extractor gave promising results. For liquors rich in phenols, the procedure recommended is method (4) followed by methods (3) or (1) and then method (2) if desirable. Final effluents with 10–50 p.p.m. of phenols can be obtained.

Magnetizing roasting of iron ores

While on a visit to the Czechoslovak Republic, we had an opportunity to acquaint ourselves with the work of research institutes and industrial establishments engaged on ore beneficiat ion. The magnet iz ing-roas t ing benef ic ia t ion shop of the iron and steel works in the town of Trznets processes par t ia l ly oxidized largeinclus ion carbonate iron ores from 9 different mines. The average iron content in ore mixture is about 27~ the iron content in the form of carbonate consitutes 70-90% of the total iron, Nevertheless, during the roasting without the addit ion of solid reducing agent, these considerable variations in the composit ion of the ore do not affect the final result. According to the investigations of Czechoslovakscient is ts for a successful magnet iz ing-roas t ing of ores in which the hemat i te is the main i ron-containing constituent, it is necessary to add 2% (by weight of ore) of pulverized brown or ord inaryeoal to the ore. The ratio o f (CaO + MgO) to $iO2 in the ore is 0.5; the moisture content of the ore is 7%. The par t ic le size of the ore for roasting is below 25 ram; the <3ram fraction constitutes about 80%. The shop contains four roasting units (Fig.) each of which consists of a 47.5 x 2.4 m (181 m S working volume) roasting furnace and a 25.0 x 1.5 m (40 m s) cooler. The del ivery end of the furnace and the charging end of the cooler are located in a stationary chamber with a guiding trough on which the roasted ore from the furnace passes to the cooler. At the same t ime, the ore is sprayed with water so that the cooling process is speeded up and the steam produced establishes a positive pressure in the chamber, thus preventing the leakage of air into the chamber. The joint between the chamber furnace and the cooler is made tight with the use of spring rings. Air is not al lowed to enter the chamber because it would oxid ize the ore aM affect its magnet ic properties. The steam is drawn off into a separate tube which is connected to the del ivery end of the cooler; in this way, the ore is cooled in a steam atmosphere. The temperature ofroast ingis 800-850 ~ C; in the furnace itself, the ore cools down to 700 ~ C and in the cooler to 100" C. The temperature of waste gases is 250 ~ C. The furnace is fired by means of an end burner with a mixture of blast-furnace, coke-oven and natural gases of calor i f ic value approximate ly 3300 k c a l / m s. The use of gas of a lower calor i f ic value causes a rapid fal l in the throughput capac i ty of the furnace, and on the other hand, with a higher calor i f ic value of the gas the ore becomes overheated and the roasting process is upset. It is recommended to use gas of a higher calor i f ic value outside the furnace and allow on ly the combustion products into the furnace. At the meta l lu rg ica l combine in Rudniany, tai l ings of 5000 k c a l / k g calor i f ic value from coal washing plants are used as fuel for furnaces for the magnet iz ing roasting of the same ores, and now it is intended to change over to fuel oi l which was used previously. The t echnological results and heat consumption in the roasting process are the same for al l three types of fuel (gas, fuel oil and tailings)o The furnaces for the magnet iz ing roasting have forced draft, and the cool ing drums have natural draft. Each furnace is equipped with an exhaust fan of 24,000 mS/hr capaci ty . The cross sect ion of the tube for s team draw-off from the cooler is 2.2 t imes smal ler than the cross section of the cooler. With the above operat ing conditions the raw ore throughput of one unit constitutes 700-750 ton/24 hrs