Opportunities of re-establishing underground mining in the...

DOI 10.2478/ntpe-2019-0057

2019

Volume 2 Issue 1

pp. 532-540

Opportunities of re-establishing underground mining in the borsod coal basin

in north-eastern Hungary

József Molnár, Ákos Debreczeni, Richárd Tompa Institution of Mining and Geotechnical Engineering,

University of Miskolc, Hungary

Date of submission to the Editor: 05/2019 Date of acceptance by the Editor: 08/2019

CADASTRE OF HUNGARIAN COAL RESERVES

Significant coal reserves remained in Hungary despite mine closures, and these

could be taken into account when considering future fuel and raw material

demand of the country. So Mining and Geological Survey of Hungary (MBFSZ)

contributed a new cadastre of Hungarian coal deposits of greater or less

reserves throughout the country which is available in electronic digital form

(https://map.mbfsz.gov.hu/coal_cadastre/). Geological information that can be

obtained using the database in question is of essential importance in mine

design. Coal basins of Hungary are showed by Figure 1.

Fig. 1 Coal basins of Hungary

Source: Mining and Geological Survey of Hungary – MBFSZ

DEMAND FOR NEW BROWN COAL SOURCES

A special research took place in the past years analyzing possibility of

establishing coal chemical industry in the Borsod region in question especially

Unauthentifiziert | Heruntergeladen 31.01.20 14:34 UTC

József MOLNÁR, Ákos DEBRECZENI, Richárd TOMPA 533

for methanol production. So reserves of brown coal were taken into

consideration such as near Kazincbarcika (Tardona), Edelény (Szendrő), and

Putnok (Dubicsány and Sajómercse II). Coal demand of chemical utilization

should be considered a lucky situation from mining point of view. On the one

hand such a plant needs coal of constant quantity and quality as raw material

and on the other hand opening a new mine of economic output requires one or

more major industrial consumers. Chemical industry which has similar

remarkable traditions in the region as mining can be the only major buyer as

utilization of coal for power generation is not preferred this time.

Although there are several brown coal deposits in the Borsod region, we focus

on the Dubicsány and Sajómercse II ones (Figure 2). Both coal deposits are

close the Sajó river at town of Putnok. Sajómercse II consists of the eastern

remains of the former Putnok underground coal mine south of Sajó furthermore

some 10 million tons of east of it. The Dubicsány deposit which is north of the

river is totally untouched as no production operations were in it in the past.

Main properties of mining point of view of both deposits are described in the

paper published by MBFSZ (Debreczeni et al. 2018). Institution of Mining and

Geotechnical Engineering was participant in preparing mining plans.

Fig. 2 Location of the Dubicsány and Sajómercse II coal deposits in the Borsod coal basin

Source: Mining and Geological Survey of Hungary – MBFSZ

The Dubicsány brown coal deposit

262 boreholes were sunk on the 23.58 km2 area of the Dubicsány brown coal

deposit. Both core sampling and geophysical analysis were done for the vast

majority of the holes. Two coal seams (IV and V) are available. Seam IV is thin,

not mineable and can be found only on a small part of the deposit. Seam V is

mineable and can be found over the whole area.

Thickness and mean calorific value of Seam V was determined for all boreholes

throughout the whole deposit. Valuating thickness and specific heat content

enabled more accurate determination of the borders of the parts of the mine (as


534 New Trends in Production Engineering – Volume 2, issue 1, 2019

shown fields North I, North II, South I and South II on Figure 3). Steadier seam

thickness and calorific value in a mine field is more advantageous from mining

engineering point of view.

Fig. 3 Average calorific value of the coal (MJ/kg) and borders of the parts

of the Dubicsány mine. Faults are highlighted by red lines Source: Molnár (editor-in-chief), 2018

Total thickness of layers between the two seams (mostly sand) is of 70-72 m at

average. Coal reserve of the Dubicsány deposit is concentrated in Seam V. Its

thickness is 5-6 m on the vast majority of the deposit except on the south-

western part and near the border of the seam. Thinner parts can be observed

only on the southwest area as the lower part of the seam is of rather poor quality.

Upper part of the seam is of higher sulfur content furthermore of higher calorific

value due to lower ash content. The lower layer of the seam is of lower sulfur

content and calorific value, this latter one as a result of higher ash content. Lower

calorific values can be observed for greater seam thickness.

According to recent technical standards and mining plans, upper part of the coal

seam is worth mine out using underground methods. Height of the coal face in

the longwalls is 2.5-3.5 m, depth of the seam is 120-230 m on the northern and

200-300 m at the southern part of the deposit, thickness, mineable reserve

estimates 49.9 million tons of 12.3 MJ/kg calorific value. The coal can be used

as raw material for the chemical industry. Development of a new mine was

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DUBICSÁNY BROWN COAL DEPOSITAVERAGE CALORIFIC VALUE OF THE

COAL (MJ/kg) AND BORDERS OF THE PARTS OF THE MINE (SEAM V)

1:20000

North I

North II

South I

South II



planned by Borsod Coal Mines company, so two inclined shafts were sunk and

more than 2000 m long drifts were made for exploration purposes beside drilling

boreholes in the 1980ies. These old drifts should be replaced by new

establishments.

The mine should be opened by two inclined shafts at the east side and a pair of

main drifts from east to west as it was planned in the 1980ies. Later a new

ventilation shaft or borehole will be necessary to enable proper ventilation.

Planned output of the mine amounts 1.54 million tons per year. Mine

construction takes 4.5 years. Output will be increased to the total output in 5

years plus time required by design and obtaining licenses. Mine is planned to

operate 37 years at the annual 1.54 million tons output level. Number of

employees is estimated 900 not including number of personnel of suppliers.

The main mine hazard to be expected is due to water contained in aggregates

of the roof layers. Dewatering is planned by wells drilled from the surface and

established in the hanging wall of the drifts. Quantity of water can be expected

12-14 m³/min during the mine construction and later 6-9 m³/min. Water can be

utilized in water supply of the region and/or industrial water in chemical industry

utilizing coal. Mining operation does not risk drinking water reserves.

Environmental impact of an underground mine is much less than of a surface

operation. Significant part of the inhabitants of the settlements of the region was

employed by coal mining so favorable reception of a new mine can be expected.

The Sajómercse II brown coal deposit

The Sajómercse II deposit of 13.6 km2 area consist of the remaining eastern

part of the former Putnok underground coal mine and the coal reserves east of

it. Geological exploration was based both on boreholes, using core sampling

and geophysical methods as well and summarizing experiences obtained in the

Putnok Mine.

The coal bearing strata contain 6 seams (low and high Borsod strips, seams I,

II, III and III/a). Total thickness of these strata estimates 110 m, average depth

is 270 m. The coal strips do not belong to the industrial reserve. Similarly Seam

III/a under Seam III does not worth for utilization too due to its low quality (8000

kJ/kg calorific value) and irregular spread. Properties of the three main seams

can be read in Table 1. The coal from these seams can be used as raw material

for the chemical industry.

Table 1 Properties of coal seams of the Sajómercse II brown coal deposit

seam

thickness [m]

height of coal faces of longwalls

[m]

coal reserve that can

be extracted by longwalls [million tons]

average calorific value of coal that can be extracted

by longwalls [kJ/kg]

Seam I 0.8-2.45 1.8-2.2 (average: 2.00) 5.289 12650

Seam II 0.7-5.65 2-2.5 (average: 2.25) 16.366 12000

Seam III 0.8-6.2 2.5-3.5 (average: 3.00) 15.974 13500

total 37.629 12728



Uniaxial strength of Seams I and II is of 12-24 MPa. A little bit lower strength (8-

18 MPa) can be observed in Seam III due to clay layers in it. Country rocks are

mostly low strength water-bearing layers consisting mostly of sand and clay.

Highest strength was observed in the covering rocks of Seam III which is

favorable for main drifts. Water hazard furthermore mud intrusion should be

expected in all seams from the hanging wall and the foot wall too. Dewatering

plans must take it into account.

Development of the Sajómercse II coal mine and extraction of the coal reserve

of Seam II are shown on Fig. 3. Development system consist of a pair of inclined

shafts on the northern side of the seams, a pair of main drifts in seam III as its

country rocks are of higher strength and finally a ventilation shaft or borehole on

the south.

Planned output of the mine amounts 1.0 million tons per year. Mine construction

takes 3 years. Output will be increased to the total output in 4 years plus time

required by design and obtaining licenses. Mine is planned to operate 37 years

at the output level. Number of employees is estimated 600 plus number of

personnel of suppliers.

The mine is endangered by water hazard. Dewatering is planned by wells drilled

from the surface and established in the hanging wall of the drifts. A detailed

hydrogeological exploration is needed before starting mining operations.

Quantity of water can be expected 6 m³/min according to experiences from

Putnok Mine. Water can be utilized in water supply of the region and/or industrial

water in chemical industry utilizing coal. Mining operation does not risk drinking

water reserves.

The mining area is close to the Lázbérc Protected Area, consequently a complex

sensitivity analysis is extremely important. Environmental impact of an

underground mine is much less than of a surface operation. Significant part of

the inhabitants of the settlements of the region was employed by coal mining so

favorable reception of a new mine can be expected.

Surface facilities and infrastructure of the two mines

Infrastructure required by a new mine is available in the region. There are

arterials and main railroad in the valley of Sajó, local roads from the arterial,

pipeline of potable water for the supply of the neighboring villages and electric

distribution centers.

Former mining facilities do not exist that can be available. So new industrial

roads power supply from two independent sources, water supply and sewage

and mine water drainage should be built. Furthermore new coal transportation

equipment is needed. This will be able to be designed when location and method

of the utilization will be known. Proper mine waste disposal site should be

established.

New buildings are required by the inclined shafts and the fan furthermore new

silos, maintenance facilities, a storage partly covered by shelter, transformers,

compressors, boiler, bath, dressing room, lamp house, dispatcher center, office,



parking place, internal road and railroad network, public utilities and guarding

facilities.

Carbon content of the coal

One of the most important properties of coal as raw material required by coal

chemistry is carbon content. The coal reserve of both deposits in question

furthermore of all seams throughout the whole basin are relatively young from

the Miocene epoch. Consequently its fix (non-organic) carbon content is

relatively low and its volatile content is relatively high.

A fairly strict relationship exists between the calorific value and fix carbon

content described by a linear regression function as it is shown by Figure 4. A

huge number of samples (5648) were analyzed and extremely good correlation

(a 0.9845 coefficient of determination and 0.814 MJ/kg-1 mean residual square

of estimation) was found.

0 10 20 30 40 50

Fix carbon content (%)

0

2

4

6

8

10

12

14

16

18

20

Calo

rific v

alu

e (

MJ/k

g)

Regression function:

F = 0.5154 C - 0.5655

Number of samples: 5648Coefficient of determination (R): 0.9845Mean residual square of estimation: 0.814 MJ/kg

Fig. 4 Calorific value vs. fix carbon content of the coal reserve of the Dubicsány

brown coal deposit in the Borsod coal basin in North-Eastern Hungary. Source: Molnár (editor), 2018

Remaining part of total carbon content of the coal is contained in its volatile part

consisting of compounds mostly carbon, hydrogen, nitrogen, oxygen and sulfur.

Similarly, confident analysis of 5783 samples was executed resulting linear



regression of 0.9781 coefficient of determination and 0.978 MJ/kg-1 of mean

residual square of estimation. Volatile content is measured approximately 5-

35% of the mass of each samples. Furthermore its combustable elements other

than carbon (hydrogen and sulfur) are of relatively smaller quantity and also

good linear relationship was found between these quantities and calorific value

of coal.

Consequently calorific value can be one of the parameters of the coal seam that

can be used for the design of the mining operations.

Unfortunately on the other hand sulfur content of the coal is relatively high than

should be taken into account in the selection of the appropriate chemical

technology.

3D modeling of Seam V` of the Dubicsány deposit to enable more accurate

estimations for mine design

A 3D model was and is still being developed to make mining plans more

accurate. This model consisted of the following elements.

• Based on the geological data of the deposit a three-dimensional (3D) model

was prepared for the numerical computations to determine the quantity and

the quality properties of the coal. A picture based on the block model

highlights the calorific value of the coal on the upper surface of Seam V

(Figure 5). Fine resolution of the model is demonstrated by the sizes of the

blocks that are obvious on the figure (Figure 6).

Fig. 5 3D block model of calorific value of Seam V of the Dubicsány deposit

Source: Drawn by Tompa R., 2018



Fig. 6 Ortographic view of a zoomed smaller part of the 3D block model of Seam V

of the Dubicsány deposit highlighting its fine resolution Source: Drawn by Tompa R., 2018

• Calorific value of the coal was determined as a function of different coal

quality parameters (moisture, ash, volatile, fix carbon, sulfur, hydrogen

content and higher calorific value). Univariate functions were obtained by

regression method. Numbers of points used for the estimations were very

high (5648-5989). Estimations proved to be accurate as coefficients of

determination were fairly high 0.7670 < R2 < 0.9948 and estimated errors of

calorific value were low of 0.335 MJkg-1 < D(F) < 2.248 MJkg-1.

• As coal quality changes (deteriorate) obviously from the covering layer of

Seam V downwards, it is an extremely important question to determine the

proper height of the coal face of the longwalls. This is important for the correct

selection of the longwall equipment thus enabling selective cutting. A

numerical analysis was done to find the distribution functions of the mass and

the heat content furthermore the mean calorific value of the coal as a function

of coal face height for the four parts of the mine. Future owners will be able

to use these result for proper decisions in mine valuation and mining

engineering design.

ACKNOWLEDGEMENTS

The described work/article was carried out as part of the „Sustainable Raw Material Management Thematic Network – RING 2017”, EFOP-3.6.2-16-2017-00010 project in the framework of the Széchenyi 2020 Program. The realization of this project is supported by the European Union, co-financed by the European Social Fund.

REFERENCES

Darling, P. editor (2011), SME Mining Engineering Handbook. Society of the Mining, Metallurgical and Mineral Exploration Inc. (SME, U.S.)

Debreczeni, Á., Havelda, T., Bombicz, J., Kaufmann, T., Verbőci, J., Bariczkayné Szeiler, Z. (2018), Kiemelt mélyművelésű szénbányászati projektek földtani bányászati adottságai. In Püspöki Z. (editor-in-chief), A hazai szénvagyon és



hasznosítási lehetőségei. Magyar Bányászati és Földtani Szolgálat, Budapest, pp. 85-146.

Molnár J. editor (2018), A dubicsányi barnakőszén előfordulás geometriai és minőségi adottságainak háromdimenziós modellezése, a gazdaságosan kitermelhető vagyon mennyiségének és minőségének újraértékelése. Kutatási jelentés. Miskolci Egyetem, Bányászai és Geotechnikai Intézet, Miskolc

Molnár, J., Tompa, R. (2016), Some questions of mine safety of small mines in Hungary. In 7th International Multidisciplinary Scientific Symposium – Universitaria SIMPRO 2016, 14-15 October,2016, Petrosany, pp. 445-450. Available at https://www.upet.ro/simpro/2016/downloads/Proceedings%20SIMPRO%202016.pdf. (Accessed: August 27th, 2018)

Molnár, J., Debreczeni, Á., Tompa, R. (2018), Challenges and Opportunities of Underground Coal Mining in North-Eastern Hungary. In Proc. 8th International Multidisciplinary Symposium „Challenges and opportunities for sustainable development through quality and innovation in engineering and research management”, UNIVERSITARIA SIMPRO 2018, pp347-352.. Available at https://www.upet.ro/simpro/2018/downloads/Proceedings%20SIMPRO%202018.pdf. (Accessed May 23, 2019)

Püspöki Z. editor-in-chief (2018), A hazai szénvagyon és hasznosítási lehetőségei. Magyar Bányászati és Földtani Szolgálat, Budapest.

Abstract. Numerous underground coal mines were in operation in the Borsod coal basin in north-eastern part of Hungary until the beginning of this century. The main area of utilization of the mined out coal beside power and heat generation was supplying households with fuel mostly for heating. In the beginning of the 1990ies the power plants in question were shut down for economic, environmental and technical reasons. Consequently all the mines were closed no later than 2004 and thousands of miners lost their jobs. A new perspective of coal mining can be enabled by other ways of utilization of coal, e.g. coal chemistry, etc. Safe and modern equipment and technology enabling high output, clean coal, furthermore high rate of yield are targeted. Opportunity of sustainable underground coal mining in the north-eastern part of Hungary is discussed in the paper. Analysis of the properties of coal deposits using three-dimensional (3D) modelling are used for considering opportunities of new mining operations. Models are being developed. Keywords: underground mining; sustainability; clean coal; coal


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