Coal preparation in Poland - current situation and development prospects

Transcription

1 Coal preparation in Poland - current situation and development prospects Wieslaw S. Blaschke 1, Lidia Gawlik 2 1 Silesian University, Department of Mining and Geology Akademicka 2, Gliwice, Poland, viesbla@min-pan.krakow.pl, rg5@polsl.gliwice.pl 12 2 Polish Academy of Sciences, Mineral and Energy Economy Research Institute, Wybickiego 7, Krakow 65, P.O. Box 49, Poland, lidia.gawlik@min-pan.krakow.pl Introduction Coal mining industry in Poland is being constantly restructured since The aim of the restructuring processes is to reach economic effectiveness i.e. produce coal without losses. Till 1990 the capacity of the Polish mining industry was constantly developed and enlarged. This was connected with demand for coal in the block of socialistic countries. According to the settlements of the former Council for Mutual Economic Aid (CMEA), Poland was supposed to supply coal to former socialistic countries, so the production was constantly increased to the level of million tonnes per year. The level of about million tonnes was foreseen according to demand forecast of that time. In previous economic system, coal production costs were not an important issue. Also it was not necessary that the prices of coal cover costs of the coal production. In practice nearly all coal mines were unprofitable. The losses on coal productions were covered by budgetary subsidies. In that time in Poland operated 81 coal mines and 102 coal preparation plants that were strictly connected with coal mines. The change from centrally planned to market economy enforced the different way of coal mining industry management. Unprofitable coal mines were gradually closed down. In mines were operating and in 2004 only 41 coal mines exist, in which 43 coal preparation plants operate. There work also 8 independent coal mines in Poland, which were bought by their owners from closed coal mines. These coal preparation plants serve coal preparation services for coal mines or for coal users. 1

2 Coal reserves in Poland are abundant. They are the basis of the country s energy security. After the accession of Poland to the UE they may contribute to the increase of the energy security of the Europe. It may happen if costs of coal production in Polish coal mines will be lower that the prices of coal imported from the third countries to the UE. The structure of coal production Coal products that are sold on the domestic market are of quality adjusted to the users demands. It should be added here that the boilers in majority of Polish power plants heat and power plants and heat stations are designed for low quality coal. The boilers are gradually replaced to the new ones. Nevertheless still the majority of steam coal users prefers coal of relatively high ash content and low calorific value. Coking coal sold on the domestic market is of quality similar to the quality of internationally traded coal. Table 1 shows the number of coal preparation plants in different ranges of their capacities (in tonnes/ day). Table 1 Capacities of coal preparation plants in Poland Range of gross capacity, Number of coal preparation plants tonnes/day Steam coal Coking coal Total < Total Quality of hard coal Coal quality in seams is very good. In currently exploited seams coal quality is as follows [3]:! Calorific value 80.4% of reserves is of calorific value above 25 MJ/kg, 14.9% in the range of 22 25% and only 1,1% of seams is of calorific value below 20 MJ/kg. 2

3 ! Ash content 47.7% of reserves is located in seams of ash content lower than 10%, 37.2% in the range of 10 15% of ash content and only in 6% of reserves ash content is above 25%.! Sulphur content 33.4% of reserves is in seams of sulphur content lower than 0.6%, 36.8% of seams has sulphur content between 0.6% and 1.0% and only in 6.9% of seams sulphur content is above 2.0%. During the exploitation process quality of mined coal becomes much lower than quality inseam coal and as a result calorific value of coal directed to coal preparation plants is usually between 14.9 MJ/kg to 24.2 MJ/kg, and ash content in this coal is between 17% and 42%. High ash coal has to be and usually is washed. Sulphur content varies from 0.45% to 1.22% in saleable fines of steam coal and the average for the entire production equals to 0.83%. Ash content in saleable steam coal varies from 8.0% to 24.1% and the average is 19.1%. Calorific value varies from 29.7% to 19.8% and the average is 22.4%. In coarse coal ash content is seldom higher that 10%. Sulphur content is usually lower than 0.9 and calorific value is usually higher than 27 MJ/kg. Saleable products of coking coal are usually of better quality. Sulphur content varies from 0.51% 0.87% (average 0.67%), ash content 5.8% - 8.3% (average 6.8%) and calorific value varies from 28.2MJ/kg to 31.6 MJ/kg (average 29.5 MJ/kg). It has to be said that quality parameters of steam coal are in Poland usually given as received, while coking coal quality parameters are in dry basis. Table 2 shows the production and quality parameters of saleable coal in The structure of production and quality of saleable coal (2002 averages) Table 2 Production Quality parameters Item Calorific Ash Sulphur Million tonnes % value KJ/kg content % content % 1. Coking coal Steam coal Grain class + 20 mm Grain class 20 8 mm

4 2.3. Grain class 20(10)(8) 0 mm Washed fines Unwashed fines Fines mixtures Semi-products Total - hard coal Employment in coal preparation plants [6] Majority of coal preparation plants has been working for over a dozen or several dozens of years. The plant were designed and built neglecting economic criteria. Many buildings and long way of transportation are characteristic for the plants. Many of installed machines and equipment are out of date and done from low quality materials. Some of those machinery is currently gradually exchanged to the modern one produced in Polish factories or sometimes abroad. As the plants are so obsolete and worked out, the employment is very high. At the end of 2002 the total employment in Polish coal preparation plant was 12.2 thousands persons, out of which about 3 thousand were employed in repairs services. Technological schemes of Polish coal preparation plants In all 43 coal preparation plants there exist section for preparation middle and coarse grains (above 20 (10) mm). Production capacity of those sections is 79.0 ml tonnes of raw coal. In 30 coal preparation plants there exist sections for preparation fines of grain sizes from 20 (10) mm to 0,5 mm. Sections for slimes flotation work in 14 coal preparation plants. They treat coals of grain sizes from 1,0 (0,5) mm to 0 and can wash 8,4 ml tonnes of raw coal. Number of coal preparation units and their capacities are given in table 3, while in tables 4 capacities of coal preparation sections. 4

5 Item Number of coal preparation plants and units in Poland and their capacities Number of sections/ plants Gross capacity, tonnes/h. Table 3 Production capacity tonnes/day Ml (16 hours tonnes/year of work) Coal preparation plants (total) Out of which Sections of grain class washing Gravitational washing class + 20(10) mm Gravitational washing class 65 0 mm 1 Gravitational washing class 20(10) 0 mm Flotation class 1,0(0,5) 0 mm Table 4 Capacities of the sections according to applied washing equipment Technology of washing Capacity of the section tonne/hour % Dense media separators Jigs Hydrocyclones Dense media cyclones Spirals Parnaby Barells Total Technical and technological schemes of coal preparation plants differ depending on the type of washed coal (steam coal or coking coal), range of washing (all grain sizes or only some of them). It also depends on the time of construction and modernisation. A typical scheme of steam coal preparation of grain sizes +20 mm is given in figure 1. Figure 2 shows a typical scheme of washing and desulphurisation of steam coal fines of grain sizes 30(20) 0 mm and a typical scheme of coking coal washing is given in figure 3. 5

6 Figure 1. The technological scheme of steam coal preparation plant [1]. Raw coal (1) Oval throw screen Jaw crusher (2) (3) Straight-line vibrating screen Oval throw screen (4) Dense-medium separator (7) Straight-line vibrating screen (18) Refuse Stationary screen 1,0 mm (8) Vor siv conical sieve (5) Straight-line vibrating screen (9) to dense medium tank Straight-line vibrating screen (6) (10) Recuperator Recuperator (11) Oval throw screen (12) Nuts Cubes Classifying tank (14) Oval throw screen (13) Dorr thickener (15) Peas to sell or to crush (16) Vacuum disc filter Jaw crusher (17) Circular water Fines IIA 6

7 Figure 2. The technological scheme of the coal fines preparation and desulphurisation plant [2] mm Livella s screen (1) Jiq (2) Straight-line vibrating screen (3) Wastes Concentrate Vibrating centrifuge (4) HC D=500 (5) Concentrate Spirals (6) Spirals (7) HC D=100 (11) Bend sieve (8) Spirals (12) (9) (13) Spirals (10) Wastes (14) Flocculant HC D=100 Slimes from washing + 30 mm Flocculant Hyperbaric filter (15) Lamella tickeners (16) Dorr tickener (17) Concentrate Circural water (18) Tailings Filter presses 7

8 Figure 3. The technological scheme of the coking coal preparation plant [2] Raw coal Crusher φ 120 mm Wastes 20-0 mm Jig φ 20 mm Middlings 20-0 mm Vor-siv conical sieve Dense-medium sep. Crusher Sieve γ = 1.47 Sieve Wastes mm Concentrate 20-0 mm Centrifuge Classification sump From recuperation Flotation Concentrate 20-0 mm γ = 1.74 Vacuum filter Thickener γ = 1.1 Recuperator Middlings mm Dryer Flotation concentrate Filter presses Circural water Suspended matter To a classification sump Tailings Generally, steam coal preparation plants can be divided into the following groups: I. Two product washing of grain sizes (10) mm in dense media separators or water jigs. Grains below 20 (10) mm are sold as raw coal. II. Two product washing of grains (10) mm in dense media separators or water jigs. Two product washing of grain sizes 20 (10) 2 mm in water jigs or water cyclones. Grains below 0.5 mm are added to coal fines to prepare saleable mixture of steam coal. III. Two product washing of grain sizes (10) mm in dense media separators or water jigs. Two product washing of grains 20 (10) 2 mm in water jigs. Washing of grain sizes mm in spirals. Two product washing of grains mm in hydrocyclones. IV. Two product washing of grains (10) mm in dense media separators or water jigs. Washing of grain sizes mm or mm in dense media cyclones. Washing classes 3 (0.9) 0 (0.2) mm in hydrocyclones or spirals. V. Classes above 0.5 mm are washed in one of above-mentioned schemes. For the class below 0.5 mm flotation is used. VI. Three product washing is used in some coal preparation plants. Separated middlings are re-washed or sold as coal of lower quality. 8

9 The following two groups of technological schemes of coking coal preparation plant can be distinguished [3, 4]: I. Three - product washing of grain sizes mm in dense media separators. Two product washing of classes mm in water jigs or in dense media cyclones. Two product washing of crushed middlings (class 6 0.5) in water jigs or in dense media cyclones. Grains below 0.5 mm are floated. II. Selective crushing of raw coal to get grains 60 (50) mm. Three product washing of class 60(50) 0.5 mm in jigs. Crushing of middlings to below 6 mm and washing of class mm in water jigs or dense media cyclones. Flotation of grains below 0.5 mm. Coal preparation plants in Poland were always built as a part of coal mine. To decrease cost of transportation they were located nearby output shafts. Big tanks for raw coal were built to allow continuation of coal mining in case of failure in coal preparation plant. In case of break down in coal preparation plant raw coal was stored in those tanks. Machinery and equipment used in Polish coal preparation plants [3, 4, 5] Raw coal is put from output shaft of mine to the places of preliminary preparation before coal washing. Here there are places where wood, metal, rubber and other rubbish is removed. Too big lumps of coal are crushed. Then coal is put to the preliminary classification, where coal is divided into size classes appropriate to applied technology of washing. Here usually domestic screens (WK, PWK, PWP, PZ, PWE, ZDR, RT) or imported ones (Schenk, Siebtechnik, Don Valley, Livell, Allis) are applied. In Polish coal preparation plants 332 screens are applied, out of which 273 are of domestic construction and 59 from abroad. Washing of coal sizes above 20 (10) mm is done in Polish dense media separators type Disa (Disa 1, Disa 2S, Disa KU, Disa KR) or in water jigs - also produced in Poland like (OBZ, OZ, OZL, OS). It has to be mentioned that one separator Drew-Boy from the firm Denver works in one of plants. It washes coal sizes mm and is very effective. There are many types of machines for fine grains washing. Classes 20 (10) 0.5 (0.2) mm are usually washed in Polish jigs (OBM, OM, OS) and domestic hydrocyclones (HWO, HKZ). In many coal preparation plants foreign machines are installed: Allmineral and Batac jigs, Parnaby and AKW hydrocyclones, Krebs dense media cyclones, Reichert spirals. There are also some concentrators with natural dense media type Barrel. 9

10 Altogether 427 concentrators work in Poland, out of which 351 of Polish production and 76 from import. Flotation is used to wash coking coal. Also in two of steam coal preparation plants flotation is experimentally used. Polish steam coals are difficult to float. The basic flotation machines are mechanic flotation machines produced in Poland (IZ5, IZ12) and column flotation machines (FLOKOB 12, FLOKOB 24, FLOKOB 40). Also imported flotation machines are used type Allminerall (Allflot) and Denver. Many different solutions are used in coal preparation plants for de-watering, as the process is difficult. De-watering of coarse grains of concentrate takes place in vibrating screens produced in Poland (WP-2, PWP 1, PWE, PWL Z). Concentrates of grain sizes below 20 mm are dewatered in the set: screen de-watering sieve (OSO) vibration centrifuge (WOW) dewatering machine (Nael). In some plants Humbold centrifuges (HSG) work, as well as Wemco (H-900) or Humbold de-watering machines (Konturbex). Slimes (grains below 0.5 mm) are de-watered in the set: de-watering sieve hydraulic classifier radial thickener Dorra vacuum filter. Vacuum and disc filters are used (FTB, FTC, FTBO), domestic filter presses (PF-570, PF 1.2, PF 1.5) and hydrocyclones HKZ. As concerns imported machines, pressure filters Andritz (HBF-96) and belt filter presses (CPF- 2200, PL-2200) can be found. Sieve-sedimentary centrifuges and sedimentary centrifuges are not produced in Poland. They are imported from BIRD, Decanter, Humbold-Wedag and Wemco. Although they are expensive, they work very well in Polish conditions. Flotation tailings are de-watered in domestically produced filter presses ROW (type PF-570) of the production capacity 10 t/h and in imported presses from Andritz (type CPF-2200) of capacity 15 t/h. Filter presses EIMCO and CENDED 2000) are used. Drying of coal concentrates is applied only in coking coal preparation plants. 13 dries works in Poland, and they are equipped in domestically produced drier machines (type ROW I and ROW II) and also foreign driers type Denver and Hoelter. Because of environmental reasons the driers are to be closed. Decreasing of moisture will be achieved by use of vibration dewatering machines and sieve or sedimentary centrifuges in the technological scheme of the plant. 10

11 The work of coal preparation plants is centrally monitored and controlled from control room. In a part of plants the equipment for on-line monitoring of sulphur and moisture content are installed. Some of parts the plants are automated (heavy media, jigs, flotation). Development prospects of coal preparation in Poland Coal preparation process depends generally on: - Quality characteristic of coal in seams and the rate of contamination of coal during the exploitation process. - Quality and quantity demands of coal users. - Relation of prices for coal of different quality. The most important aspect of coal preparation is to produce products that are demanded on the market. This condition is generally met by Polish preparation plants. The current state of coal preparation in Poland is a result of the restructuring of coal mining industry. As coal preparation plants are technologically connected with coal mines, in case of mine closure also coal preparation plant is being closed. Only some of coal preparation plants which previously were a part of closed mine have been bought by private investors and now they offer services of coal preparation. In existing plants modernisation is needed. The plans for development includes opening the new or modernisation the old sections for preparation of coal fines (below 20 mm). In last few months the increase of coal prices on the international markets (both steam and coking coal) opens the new prospects for coal mining and especially coal preparation in Poland. Coal can be sold abroad at a very good price higher than before and higher than production costs. The problem of adjusting quality parameters of steam coal for the demand of foreign buyers stays open. Bibliography: 1. Blaschke Z.: Coal preparation in Poland. Present practice and perspectives. Proceedings of the American-Polish mining symposium. Mining in the New Millennium. Challenges and Opportunities. Las Vegas,

12 2. Blaschke Z.: Hard coal preparation in Poland. Journal of the Polish Mineral Engineering Society. Vol. II. No. 1(3), Blaschke W.: Influence of economic reforms in Poland on the role of coal preparation. Colloquium Coal Preparation. South African Coal Preparation Society. Witbank, Blaschke W., Gawlik L. : Coal preparation in Poland in the view of economic reform. Mineral Resources Management. Vol. 17, No. 4, Nycz R.: Current situation of coal preparation in Poland. Journal of the Polish Mineral Engineering Society. Vol. I. No. 2, 2000 (in Polish). 6..Nycz R., Majka-Myrcha B.: Status and prospects of hard coal washing in Poland. Journal of the Polish Mineral Engineering Society. Special Issue. No. 3(10),