Tom 22 2006 Zeszyt 4
WIES£AW S. BLASCHKE*, LIDIA GAWLIK**, STANIS£AW A. BLASCHKE***
Coal preparation technology in Poland
K e y w o r d s
Coal preparation plant, steam coal, coking coal, mining wastes recovery
A b s t r a c t
The paper presents, in the synthetic way, the basic types of coal preparation plants that work is Poland. The technological scheme of coking coal preparation plants is described as well as two typical schemes of steam coal preparation plants. Some attention is paid to operating in coal preparation plants sections of preparation and desulphurization of coal fines. The technologies of coal recovery from flotation tailing ponds and recovery of mining wastes are also mentioned.
Introduction
Hard coal is a basic energy resource in Poland. Its production goes on in two coal basins: Uppers Silesian Coal Basin and Lublin Coal Basin. Coal in deposits is of very good quality, but during exploitation some waste rock from roof and floor are won together with coal and get into run of mine coal.
The main user of coal in Poland is power industry. About 95% of electricity is produced from coal (61% from hard coal and 34% from brown coal). Steam hard coal exploited in mines where ash content is lower than 25% is not washed and is directed straight to be burned
* Prof. D.Sc. Eng., ** Ph.D. Eng., *** M.Sc. Eng., Mineral and Energy Economy Research Institute of the Polish Academy of Sciences, Krakow, Poland.
in boilers adjusted for usage of such coal. The other steam coal is directed to coal preparation plants, where the grains of gangue are removed (Blaschke W., Gawlik 1999; Blaschke W., Gawlik 1993).
For electricity and heat production about 45 million tonnes of steam coal a year is used. The second huge hard coal user is coke engineering, where about 11 million tonnes of coking coal is used. Traditionally all coking coal is washed.
About 18—20 million tonnes of coal a year is exported. The exported coal is the washed one. In the eighties there worked 105 preparation plants in Poland. After the system changes in the Polish economy (started in 1989) many of coal mines were gradually closed (Blaschke W. 2001; Blaschke W., Gawlik 2001; Blaschke Z. 2000). Together with coal mines many of coal preparation plants were also closed. Now there exist 48 coal preparation plants that belong to 8 companies (some of them are coal mining companies, the others are independent coal preparation companies).
1. Technologies of coking coal preparation
Coking coal (type hard) is exploited in 4 mines equipped with coal preparation plants. Coal washing is conducted in three sections that differ in size of grains in feed. Grain sizes above 20 mm are washed in dense media. Grain sizes 20—0.5 mm are washed in jigs. Grain sizes below 0.5 mm are floated. Schematic diagram of the process is shown in Figure 1 (Kowalczyk, Strzelec 2004). Raw coal preparation station Preliminary classification Dense media separation > 20 mm Jigging < 20 mm Enrichment by flotation < 0.5 mm
Coal loading Rejects loading
Fig. 1. Schematic diagram of the coking coal preparation process Rys. 1. Uproszczony schemat procesu wzbogacania wêgla koksowego
2. Technologies of steam coal preparation
Steam coal is exploited in 32 coal mines. In some of the mines there exist two coal preparation plants. There are few different schemes of preparation that depend on the quality of the feed and especially the content of waste rock (Bieñko 2004; Blaschke Z. 2001; Gawliñski 2004; Kurczabiñski, £ój 2004; Nycz, ZieleŸny 2004).
The first scheme is shown in Figure 2, where the schematic diagram of the coal preparation process is given. The grain sizes +200 mm are separated from raw coal and are directed to the Bradford crushers, where the waste rock +65 mm is separated. Remaining feed is classified. Depending on the ash content it is possible to achieve unwashed 10(6)—0 mm class of coal , that is a saleable product and/or entire 65—0 mm class is washed on jigs. The concentrates from jig are separated into 65—20 mm and 20—0 mm grain sizes and these
C o m m er ci al p ro d u ct : F in es 1 0–0 m m O II co m m e rc ia l p roduct 65 – 2 5 m m C o m m er c ial pr o d uc t: W ash ed sl im es 0 ,5 – 0 m m C o m m er c ial pr o d uc t: R a w fi n es 6 (10) – 0 m m C o m m er ci al p ro d u ct : F in es 2 0–0 m m C o m m er c ial pr o d uc t: R aw sl ime s 0 ,5 – 0 m m Washing in coarse jigs OS Dewatering
Water - slurry circuit
Dewatering Raw coal preparation station Dewatering Grinding Classification R ej ec ts 6 5– 0m m Re je ct s + 6 5 m m R ej ec ts 1 0– 0m m R e ject s 0 ,5 – 0 m m Classification Pre-classification Washing -fine coal jigs
Dewatering 250 – 0 mm 1000 t/h
Flotation
Fig. 2. Scheme of steam coal preparation process (variant I) Rys. 2. Schemat procesu wzbogacania wêgla energetycznego (wariant I)
became saleable products. Middlings from the jig are crushed to below 10 mm sizes and are washed in fines jig. The products are dewatered. Grain sizes of coal below 0.5 mm are recovered from the water in the flotation process.
The other variant of coal washing scheme is shown in Figure 3. The class 200—20 mm, separated from the feed, is washed in three-product dense media separator. The solid medium is magnetite. The concentrate is separated into two grain sizes 200—30 mm and 30—20 mm, which are saleable products. The middlings are crushed and added to 20—0 mm class extracted from the feed. The grains below 1.5 mm are extracted from that mixture. These are not washed but are added to the concentrate from two-product jigs, where the class 20—1.5 mm is washed. The product separated from the washeries water is treated as tailings. It frequently is used in fluidized bed boilers.
Container of circulating water Raw coal preparation station Dewatering 200 – 0 mm
Primary sizingÆ 20 mm (3–products) densemedium separator
Crushing of products
Æ 20 mm Dense medium circuitand regeneration 200 – 20 mm Sizing at string screensÆ1.5 mm (2 products) jig washer Dewatering of product Final sizing Æ 30 mm Classification of waste water Vacuum filtration of fines Effluent clarification Dewatering at filter presses 20 – 0 mm 20 – 1.5 mm 1 .5– 0m m S te am coa l m ix 20 –0 m m C le ane d coa l 30– 20 m m D is ca rds 20 –0 m m D isc ar d s 200– 0 m m C le ane d co al 2 0 0–30 m m
Fig. 3. Scheme of steam coal preparation process (variant II) Rys. 3. Schemat procesu wzbogacania wêgla energetycznego (wariant II)
3. Technologies of preparation and desulphurization of fines
Coal exploited in Eastern part of the Upper Silesian Coal Basin is characterized by high sulphur content. For the preparation of coal fines the following scheme is applied. Raw coal is separated into classes 200—30 mm and 30—0 mm. Large size is directed for washing as it is given in Figure 3. From the class 30—0 the class 30—2 mm is separated and washed in tree-product jigs. The middlings are crushed and turned back for the washing. From the 2—0 mm class the slimes below 0.1 mm are separated. The class 2—0.1 is washed on spirals. Middlings are washed in different set of spirals. The technological scheme of the process is shown in the Figure 4 (Poznañski 2004).
30–0 mm
Loading onto transport means
Coal dewatering Dewatering
of reject Coal dewatering Dewateringof reject
Washing, A Jig Crushing of middlings Washing, spiral washers Middlings Washing, spiral washers Classification, Liwell screens Classification, Hydrocyclones 500mm Û Dewatering of slimes Treatment of post-washery waters 2–0,1 mm 30–2 mm 0,1–0 mm 2–0 mm
Fine Coal Preparation and Desulphurisation Plant
Classification 200–30 mm 30–0 mm Loading of fine coal Loading of reject
Coal Preparation Plant
Fig. 4. Technological scheme of preparation and desulphurization of steam coal fines Rys. 4. Technologiczny schemat wzbogacania i odsiarczania mia³ów wêgla energetycznego
4. The technology of coal recovery from flotation tailing ponds
For many years the flotation tailings of coking coal were stored and treated as wastes. They were put into ponds. The research show that the material gathered there is the coal that can be a good product for energy production. One plant for recovery the coal from the ponds have been built. The exploited wastes are divided into +3.0 mm and 3—0.3 mm classes. Large grains are used, without preparation, for land reclamation. Small grains are floated. Two stages flotation are done. Concentrates are sold to power plants. The process is economically viable. The schematic diagram of the preparation of flotation tailing wastes is shown in Figure 5 (Dziwok, Grzesik 2004).
5. The technology of post mining wastes washing
In former years the post mining wastes as well as large sized wastes from steam coal washing were stored together in heaps. As a result of inaccurate washing processes (the Chancea washeries with sand were used) many coal grains got into wastes. Polish – Hungarian enterprise “Haldex” deals with the recovery of that coal. They operated six coal preparation plants in the former years. The enterprise have already washed 144 million tonnes of the wastes. The technological scheme of the preparation plants is shown in Figure 6 (Kucharzyk 2004). The process goes on in hydrocyclones with dense media. The medium is water and stone. All received products are saleable.
Sludge points Receiving station of post-flotation wastes Initial dehydration +20 +3.0 3.0 – 0.3 Classification Æ 3.0 mm andÆ0.3 mm Resolving of feed Flotation – 1 degreest Vacuumed dehydration Drying Clearing of post-flotation water Dehydration of loam leavings Flotation – 2 degreend Vacuumed dehydration Recultivation Loading of commercial coal
Fig. 5. Scheme of coal recovery from flotation tailings pond Rys. 5. Schemat odzysku wêgla z osadników odpadów flotacyjnych
In recent years the preparation processes in classical preparation plant working in coal mines have been improved, so less coal grains goes into wastes. For that reason the process of new heaps recovery is not economically justified. Now only two Haldex preparation plants still work on mining heaps. The other serve services of coal preparation for those mines where there is lack of fines preparation sections.
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Flushing with water, dewatering, classification Ground sedimentation ponds Washing hydrocyclones Dewatering, classification Disliming 45 – 0 mm Adjustment of density
and d.m. level in mixer 200 – 0 mm Clean water Concentrate Slime Reject Po st w as h er y wa te rs 2 0–0 m m 3– 0m m 4 5–3 m m 45 – 2 0 m m B ro k en st on e Ce ra m ic sc h is t P eas Fi ne s II a
Fig. 6. Scheme of coal recovery from mining wastes Rys. 6. Schemat odzysku wêgla z odpadów wêglowych
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WIES³AW S. BLASCHKE, LIDIA GAWLIK, STANIS³AW A. BLASCHKE
TECHNOLOGIE PRZERÓBKI WÊGLA W POLSCE
S ³ o w a k l u c z o w e
Zak³ad przeróbki wêgla, wêgiel energetyczny, wêgiel koksowy, odzysk wêgla z odpadów
S t r e s z c z e n i e
W artykule w sposób syntetyczny omówiono podstawowe typy zak³adów przeróbki wêgla jakie funkcjonuj¹ w Polsce. Opisano schemat technologiczny zak³adów przeróbki wêgla koksowego oraz dwa typowe schematy zak³adów przeróbki wêgla energetycznego. Zwrócono uwagê na dzia³aj¹ce w zak³adach przeróbczych sekcje wzbogacania i odsiarczania mia³ów wêglowych. Wspomniano równie¿ o odzysku wêgla z osadników odpadów flotacyjnych oraz odzysku wêgla z odpadów wêglowych.
