Theoretical consideration in establishing the parameters of longwall panel

Transcription

1 GOSPODARKA SUROWCAMI MINERALNYMI Tom Zeszyt 4/2 MAREK JASZCZUK*, JAN KANIA* Theoretical consideration in establishing the parameters of longwall panel Introduction So far the level of mining production concentration was assessed on the basis of analysis of coal mine production in Poland or on the basis of tendencies in the world mining industry. New perspective as regards the problem of high mining production concentration, considered as a daily production for which the balance between the cost of coal winning and the revenue from coal selling is reached, including geological-and-mining, technical-and-organizational and economical-and-financial conditions referring to a given longwall face, was suggested in the paper. To facilitate the analysis of the economic efficiency of coal extraction from the longwall face a model enabling the designation of daily coal output was devised, securing the achievement of the assumed profit or the balance between the costs of coal production and incomes from sales for a specific longwall. The proposed procedure involves the following stages: designation of the daily coal output in relation to the economic, mining and geological conditions, designation of the daily coal output in relation to the production potential of mining machinery and organizational factors for a specific longwall, determination of the conditions of efficient extraction on the grounds of the comparison between the two coal output quantities mentioned above. * Silesian University of Technology, Faculty of Mining and Geology, Institute of Mining Mechanization, Gliwice.

2 96 If, on the grounds of the potential of the longwall system, it is impossible to designate such coal output that secures the economic efficiency, the analysis should focus on the option of reducing the costs of coal production. Such conclusion stems from the fact that after the possibilities of the longwall field are explored (resources) in consideration of a given production potential of the mining equipment at the coal company s disposal, this is the only way to improve efficiency. 1. The economic model The economic model involves the required daily output treated as an explainable variable and the coal field reserves and extraction time as explanatory variables. Other impact factors were expressed as model parameters. The selection of coal reserves and extraction time as the explanatory variables predominantly resulted from the assumed method of designating the daily coal output in consideration of the simultaneous change in the coal reserves and the extraction time. Due to the use of time factor in the analysis, two main criteria were taken into account during the cost division: relationship between costs component and production scale, relationship between costs component and duration of longwall panel mining. The inclusion of the time factor has led to the derivation of three costs categories [3]: absolutely fixed costs K BS, which are the costs of the preparation of the longwall field for mining, these costs may change rapidly, due to different technologies of driving roads and the adoption of different organization and the technical means used in moving the longwall equipment for further longwall cut-through; relatively fixed costs K WS, entailing the costs of the functioning of the spatial underground structure of the coal mine. The extraction time of the coal field depends on the achieved daily coal output and the reserves of the longwall field. Its variability may result from the intensity of mining, associated, for example, with seasonal demand for coal, or, with the occurrence of other factors limiting coal output; variable costs K Z which are proportional to the changes in coal output and to the scope of the activity of the coal mine. On the bases of the above mentioned costs categories, the devised economic model [3] makes it possible to determine the required daily coal output in relation to the reserves of the longwall field and its extraction time for the assumed profit level or for the assumed balance between the costs of coal production and the incomes from coal sales. The model takes into account the total costs of coal production, including all stages of the production process: the preparatory operations, longwall moves, extraction, closing down of the longwall. The model fulfilling the assumptions of the accepted methodology was based on economic modeling used in testing critical functional zones of longwall faces or coal mines [1, 4].

3 The economic calculations based on the designed model make it possible to select the optimal solution for the assumption of a specific level of profit. The analysis was carried out in view of operational profit. In consideration of the assumed profit level, the longwall panel resources may be determined as follows: 97 Z0 ( KBS kws t) Zp C ( Z k ) z 0 z [t] (1) or, the extraction time for the longwall panel with the assumed resources Z p. Zp[ C ( Z0 k )] Z0 K t Z k z z BS 0 ws [d] (2) Whereas, to designate the quantity of the daily output of coal that will secure the assumed profit level for given longwall panel resources, the following formula is employed: Z0 kws Q Z0 K ( Cz Z0 kz ) Zp BS [t/d] (3) where: Zp coal reserves of the longwall field [t], Z 0 assumed profit level, K BS absolutely fixed costs [PLN], k WS relatively fixed costs related to the time unit [PLN/day], t extraction time [day], C Z sale price for one ton of produced coal [PLN/t], k Z elementary variable costs, variable costs related to a ton of produced coal [PLN/t], Q daily coal output [t/day]. In Figure 1 the line of the costs balance R K (red line) and the line of coal winning costs balance in consideration of the assumed profit R kz (green line) or loss R ks (blue line) are shown. The break-even points for coal winning costs are indicated on each line. The graphs of the function of costs balance show that the assumed value of profit (points Z k1 Z k5 ) or loss (points S k1 S k5 ) exert a significant impact on the quantity of the daily output of coal, if the resources of the longwall panel are small, but, if the resources are large, such impact is definitely less significant. If the extraction time is maintained as constant, the achievement of the assumed profit level requires a substantially higher daily output of coal (point Z k2 and R kz ) in comparison

4 98 Fig. 1. Graph of the function of coal winning costs for the assumed profit or loss level Rys. 1. Wykres funkcji kosztów wydobycia wêgla dla zak³adanego poziomu zysku lub strat with the break-even point for costs and profits (point R k2 on line R k ). Moreover, in such case it is necessary to increase the resources of the longwall panel. 2. The daily coal output conditioned by the technical potential of machinery The analysis focused on the possibilities of achieving a high concentration of extraction under the mining and geological conditions of a specific longwall also requires a model that would enable the designation of the coal output in view of the technical potential of the longwall system. Assuming that the coal output is primarily conditioned by the technical parameters of the shearer loader, a model of the production process in the longwall may be utilized, as it considers: the theoretical capacity of the shearer loader, the degree of its utilization under given mining conditions, the parameters of the longwall face, actual worktime of mining machinery on a face, the cutting sequence. Considering a different course of the production process in the longwall, related to a specific nature of the two basic cutting sequences, the daily coal output from the longwall may be calculated as [2]:

5 W Q T (4) Q t T t where: Q t theoretical capacity of the shearer loader, T available work time of mining machinery on a face, T index of work time availability, t operational efficiency index. The theoretical capacity of the shearer loader under given mining conditions is derived from the following equation, in consideration of the technical parameters of the shearer loader (v max,z) and other parameters associated with the natural conditions and a given extraction system (H, ): 99 where: H longwall height, z nominal width of web, v max maximal haulage speed, coal density. Qt Hzvmax (5) The technological efficiency ratio is derived from the following equations: unidirectional cutting sequence: t kq L ( vu Llk ) 1 p z v ( 1 ) m (6) bidirectional cutting sequence t zp vp 2kQ L 1 zz v z v z ( Llk ) 1 v 1 v p ( 1 p z ) p v z (7) where: k Q index of theoretical capacity utilization of the shearer, L longwall length, L k length of shearer loader,

6 100 p z index of technological operations contribution, v u,v m haulage speed of the shearer in a course of cutting and return trip, v z,v p haulage speed of the shearer in downstream and upstream cutting trips, z z,z p width of the web of the shearer in downstream and upstream cutting trips. The index of theoretical capacity utilization of the shearer relates to the real average efficiency of the shearer, resulting from the effective width of web (z e ) and form the value of mean haulage speed achieved in the course of cutting under given operational conditions (v), to the theoretical capacity of the shearer. It reflects the utilization of potential technical possibilities of the shearer in the longwall face and is calculated for unidirectional sequences only in a cutting trip, whereas for bidirectional ones both in downstream and upstream cutting trips, from the following equation: k Q ze z v v max (8) Due to a specific nature of both cutting sequences and different state of the external load of the shearer, resulting, first and foremost, from the process of loading, the shearer achieves different haulage speeds for downstream and upstream trips. This factor is considered in the designation of the technological efficiency ratio by the quotient of the mean values of haulage speed achieved for both cutting directions (v z /v p,v p /v z for the bidirectional cutting sequence and v u /v m for the unidirectional sequence). All the above mentioned parameters (Q t,k Q,v z /v p or v u /v m ) represent the technical factors in the model. Another important aspect considered in the model is the effective production time of the shearer (the theoretical capacity utilization), which is both an organizational and a technical factor. The effective production time is the resultant of: available work time of mining machinery on a face (T) and the degree of this time utilization ( T ). The available work time of mining machinery on a face stems from the accepted form of production organization (number of shifts, number of production shifts), the requirements connected with the operational conditions prevailing in the longwall and the distance between the longwall and the shaft. Its full utilization may be limited by unplanned downtime caused by mining, technical or organizational reasons. The value of the technological efficiency index makes it possible to determine which part of the potential daily coal output, derived from the theoretical capacity of the shearer under specific mining conditions and from the real production time of the shearer during 24 hours (T T ), is the daily output that may be obtained for the applied cutting sequence. On the grounds of the values of this index, it is possible to trace the influence of particular factors associated with the utilization of the theoretical capacity of the shearer loader, the duration of the sumping operations and the length of the longwall, on the possibility of achieving a high concentration of extraction for the applied cutting sequence.

7 Procedure of designating high concentration of coal production The proposed model enables the designation of the required daily output of coal for the assumed profit level, on the basis of forecasting particular coal winning costs components. The coal output is a determinant of high concentration of production and may be used for analyzing the efficiency of working faces during extraction works, or after the completion of the longwall strip, for deriving information on the impact of particular technological and organizational factors on the classified costs categories. The algorithm of the procedure for given longwall resources and the equipment at the disposal of a coal mine is shown in Figure 2. The first stage entails the preparation of input data on: geological and mining conditions, technical equipment, economic and organizational aspects. The data on the geological and mining conditions should comprise the information on the mining technology used in the longwall, and the longwall panel parameters, as they are essential for determining the production potential of the longwall and longwall panel reserves, and for forecasting dislocations in coal seams deposition. The minimal range of information should include: the characteristics of the mining technology (longwall layout and working sequence, roof control: with caving or backfilling, advancing or retreating longwall), the geometrical parameters of the longwall panel (height, width, length, inclination), coal density, coal cutability in a given seam, occurrence of interlayers (cutability, density), forecasted natural hazards (methane, rock mass tremors), occurrence of faults (height of throw of fault, azimuth, location), washing away of the coal seam. The data on the technical equipment should entail all mining machinery used in the course of: preparatory works, longwall s support functions connected with moves of machinery and longwall shut down, extraction works. The characteristics of the mining equipment should include the specifications of the technical parameters that are essential for forecasting: the advance of headings and longwall raise, the course of the processes of disassembly, moving and assembly of machinery, the production potential of the longwall face. The economic and organizational data referring to the preparation of the longwall panel and the ensuing extraction works should include the information concerning: the given longwall face, the production level on which it is located in relation to the outlay of the mine.

8 102 Fig. 2. Procedure of daily coal output determination for given reserves of longwall field and given longwall machinery Rys. 2. Procedura okreœlania dziennego uzysku wêgla dla danych rezerw pola przodka œcianowego i danych maszyn przodka œcianowego

9 103 To estimate the costs associated with longwall faces, the following information is required: number of longwalls mined in particular months, number of months during which extraction works were carried out in the analyzed longwall panel, number of longwalls mined on a given production level in particular months, length of transport routes on a given production level, length of transport routes in the coal mine, reserves of the analyzed longwall panel, total reserves of the longwall panels mined on a given production level, total coal output won from the analyzed longwall panel in the calendar year, total coal output of the mine in the calendar year, annual capital costs of coal production related to the coal mine. The organizational aspect, involving the planning of the coal mine operation, includes the following issues: number of longwalls in the coal mine and on a given production level in the analyzed time frames, preparation of the longwall panel, system of the organization of works in roadways and longwall faces, location of the longwall panels, and, in additional, the analyses of the seasonality of coal sales. Depending on the technical equipment at the disposal of the mine, the range of preparatory operations, the length of transport routes, the system of moving longwall machinery, the system of work organization and the mining and geological conditions, the analysis should be conducted for all possible options of the longwall panel preparation in view of designating absolutely (permanently) fixed costs K BS and the duration of the above mentioned operations. In the next step, on the grounds of the data on particular costs components, the values of the parameters characterizing relatively fixed costs K WS and unitary variable costs K Z should be derived, as well as the forecasted coal sale price C Z for the analyzed time frame. To designate the production potential of the working face, a theoretical model of the course of coal production process was applied [2]. The parameter that describes the assumed technical solution of the coal shearer is the maximal haulage speed. If the factors that reduce the daily output of coal are considered, for example the seasonal nature of coal sales, or the occurrence of geological disturbances in the longwall panel, the time when the demand for coal on the market is slack should be determined and the coal output estimated for such time. On the bases of the influence factors expressed as parameters, the simulation of their impact may be conducted on the grounds of the proposed economic model. At first, the break-even point for costs and profits should be designated for given longwall panel reserves,

10 104 to check if it is possible to meet the condition of effective coal production. Such condition is fulfilled, when the production potential of the longwall is bigger than the daily output of coal designated for the break-even point of the costs balance. Then, for the assumed profit level, the concentration of coal production is designated, together with the corresponding range of extraction time of the longwall panel. After determining, for each pair of parameters Q i, t i,the technical and organizational parameters of mining the longwall, including: the option of longwall panel preparation, cutting sequence, technological efficiency index, time availability of machines, the required degree of machine utilization, the best option is selected from the point of view of planning the operation of the coal mine and minimizing the failure to reach the assumed technical objective. If the condition of effective mining is not met, the sensitivity analysis of the model should be made in view of particular influence factors, to determine an essential strategy of cost-cutting in coal winning process. While considering the periods during which the demand for coal is slack, the break even point for costs and profits in the cost balance is designated for given resources of the longwall panel and the parameters that describe such period: its duration and the quantity by which the daily output should be reduced. If the condition of effective mining is met; however, for the designated daily output of coal in reference to other periods (when the market is not slack), the range of the actual daily coal production concentration is designated. Next, the procedure adopted for the period in which the daily output is not reduced is followed. If the above mentioned condition is not met, there are two possibilities: the first one identical to the one described above, involves the determination of an essential strategy of cutting the total coal production costs from a given longwall. If this is impossible, the total coal production costs should be derived for the following cases: extraction of the longwall without any limitations, extraction with limitations in consideration of slack demand for coal. In the next step, on the bases of the foregoing, the forecasted, corrected profit or loss level is determined. Conclusions The technical and organizational conditions exert both direct and indirect impacts on the option of achieving the required daily output. The direct impact involves the production potential of the longwall face and the degree of its utilization, whereas the indirect one involves shaping the values of relatively fixed costs depending on the extraction time of the longwall panel with specific coal reserves. The economic conditions determine the required daily output providing, in consideration of specific coal reserves, the balance of the costs. The sine qua non prerequisite of achieving at least the balance between the costs is such degree of the utilization of the production potential that could provide the daily coal output determined by the economic conditions.

11 105 REFERENCES [1] J a b ³ o ñ s k a - F i r e k B., 1999 Kierunki strategii dzia³ania kopalñ w œwietle badañ modelowych. Zeszyty Naukowe Politechniki Œl¹skiej, seria Górnictwo 2000, Gliwice. [2] Jaszczuk M.,1999 Wp³ywstanuobci¹ enia kombajnu œcianowego du ej mocy na mo liwoœæ uzyskania wysokiej koncentracji wydobycia. Zeszyty Naukowe Politechniki Œl¹skiej, seria Górnictwo nr 1406, Gliwice. [3] Jaszczuk M., Kania J., 2007 Warunki skutecznego i efektywnego wybierania pok³adów wêgla systemem œcianowym. Prace Naukowe-Monografie, CMG KOMAG, Gliwice. [4] M a g d a R., 1999 Modelowanie i optymalizacja elementów kopalñ. Biblioteka Szko³y Eksploatacji Podziemnej, Kraków. TEORETYCZNE ROZWA ANIA O USTALANIU PARAMETRÓW PRZODKA ŒCIANOWEGO S³owa kluczowe Przodek œcianowy, koszty produkcji wêgla, czynniki krytyczne, efektywnoœæ ekonomiczna, dzienny uzysk wêgla, techniczny potencja³ systemów przodka œcianowego Streszczenie Proponowana metoda jest oparta na innym podejœciu do przodka œcianowego, z uwzglêdnieniem analizy kosztów etapu prac przygotowawczych przed rozpoczêciem wydobycia. Ujêcie czynnika czasu doprowadzi³o do wyodrêbnienia trzech kategorii kosztów: koszty absolutnie sta³e K BS, koszty wzglêdnie sta³e K WS, koszty zmienne K Z. THEORETICAL CONSIDERATION IN ESTABLISHING THE PARAMETERS OF LONGWALL PANEL Key words Longwall face, coal production costs, crucial factors, economic efficiency, daily coal output, technical potential of longwall systems Abstract The proposed method is based on a different approach to a longwall face, including the analysis of the costs of the preparatory works stage previous to extraction works. The inclusion of the time factor has led to the derivation of three costs categories: absolutely fixed costs K BS, relatively fixed costs K WS, variable costs K Z. On the grounds of the above mentioned three costs categories an economic model was designed, enabling the designation of daily coal output depending on the reserves of a given longwall panel and its extraction time, for the assumed profit level, or for the assumed balance between the costs of coal production and the incomes from coal sales. The model incorporates the total costs of coal production, including all stages of the production process: preparation works of the longwall panel, longwall moves, extraction works, longwall shut down. The grounds for the model, in accordance with the assumed methodology, were provided by economic modeling used in diagnosing critical functional zones of longwall faces or coalmines. The analysis of the possibilities of obtaining high concentration of extraction under definite mining and geological conditions of a given longwall face requires a model that should make it possible to designate the coal output in view of the technical potential of the longwall system. If it is assumed that the coal output is mainly conditioned by the technical parameters of the shearer loader, the model of the production process in the longwall

12 106 may be utilized, as it includes: theoretical capacity of the shearer loader, the degree of its utilization under given mining conditions, parameters of the longwall face, actual worktime of mining machinery on a face, cutting sequence. Thus, the analysis entails the technical, organizational and technological aspects. Considering a different course of the production process in the longwall, related to a specific nature of the two basic cutting sequences, the daily coal output from the longwall is function of: theoretical capacity of the shearer loader, available work time of mining machinery on a face, work time availability, operational efficiency index. The theoretical capacity of the shearer loader under given mining conditions is derived in consideration of the technical parameters of the shearer loader and other parameters associated with the natural conditions and a given extraction system. A suggested method for determination of required daily production, which is an indicator of mining production concentration in the aspect of balancing the total cost of coal winning and the revenue from coal selling, can be used for: determination of minimal daily production, which will ensure effective mining, in conditions of a given longwall (given height, length and panel) and with a use of technical equipment available in the mine, determination of longwall panel parameters and determination of mining duration for technical equipment available in the mine, selection of technical equipment which will enable effective mining in conditions of a given longwall, for assumed total costs of coal winning.