Published : Proceedings of The First International Mine Environment and
Ventilation Symposium. Indian School of Mines Dhambad 11-12 December
2000, ISBN 81-204-1458-6.
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EXPERIENCE OF THE USE OF NITROGEN
AND FOAM TECHNOLOGY IN THE CZECH COAL MINES
Dr. A.Adamus, MinE
Associate Professor, Institute of Safety Engineering,
VSB - Technical University Ostrava, 17. Listopadu Street,
708 33 Ostrava-Poruba, Czech Republic,
It was on the 8th of August 1949, when nitrogen inertization of an underground fire
was first used at the Doubrava Mine in the Czech part of the Upper Silesian Coal field.
Since then many countries have used nitrogen for fighting, suppression and prevention
of underground fires. This paper reviews experience of the use of nitrogen in the Czech
Republic. Special attention is paid to the first use of nitrogen in the Czech Republic,
being probably the first instance of the use of pure nitrogen for fighting a mine fire. The
present day use of nitrogen, its sources, consumption and technological equipment,
include isofoam technology is reviewed.
USE OF NITROGEN AT THE DOUBRAVA MINE, 1949
In the Czech Republic, the first time nitrogen was used for fighting a mine fire in the
Ostrava-Karvina Coal basin after a methane explosion at the Doubrava mine (Hajek 1969,
Adamus 1995). The methane explosion occurred at a longwall face in the Hubert seam on
February 12th, 1949. The explosion was followed by a fire, which was further complicated by
other methane and coal dust explosions that occurred during sealing off the next day. It was
necessary to seal all four of the mine shafts at the surface, two downcast and two upcast. The
shafts ware sealed with airtight plugs covered with clay and a layer of sand. The Czech
patent for fighting fires with nitrogen, registered in the Czech Republic by Mr. Wild from the
"Moravia nitrogen plant Ostrava-Marianske hory", was used at the Doubrava mine on the
direction of Mr. Artur Kanczucky, the mine director, who chose this method for returning the
mine to production. A cryogenic nitrogen generator Linde, from the "Moravia nitrogen plant
Ostrava-Marinske hory", was sited in the compressor hall of the Doubrava mine. The nitrogen
plant was driven by 2.5 - 3.0 MPa of air pressure. Nitrogen gas was intermittently injected
into the mine from August 8th, 1949 to September 12th, 1950, the mine was then re-opened.
The total quantity of nitrogen used during this time was 5.057 million m3 at a concentration
of 99.5 % of N2. Daily averages reached 16000-17000 m3 of nitrogen gas (10-11 m3 min-1)
with an output temperature + 9 0C. The nitrogen gas was delivered to the shaft by a pipeline,
with a diameter of 100 mm, and by drill rods with diameters of 100 mm down the shaft to a
level of 540 m.
NITROGEN INERTIZATION - TODAY EXPERIENCE
The knowledge obtained through the use of nitrogen at the Doubrava mine was used with
success by mines rescue teams in the Ostrava-Karvina Basin (OKB). Three pressure bottle
trailers containing 630 m3 each were manufactured and delivered to the Central Mines Rescue
Station at the OKB in 1957. The pressure bottle trailers of 945 m3 capacity were bought later.
Nitrogen gas transported by pressure trailers was used for suppression of heating and
inertization of balancing chambers (permeate chambers). Two types of Russian liquid
nitrogen mobile tankers, type STK, of 2.5 m3 and 5.0 m3 capacity (0.25 MPa) were bought in
1979.
Two types of transportable liquid nitrogen containers of 500 and 1000 litre were made by
FEROX Decin, Czech Republic, and were bought in 1980. Since 1986 15 m 3 liquid nitrogen
mobile tankers of the type TN 15 /FEROX Decin/ have been used. Liquid nitrogen technology
has been used in the prevention of spontaneous combustion of coal since 1979, by the use of
nitrogen flushing. For fighting mine fires, the Central Mine Rescue Station of Ostrava in OKB
bought a jet turbine, type GIG 4 made in Ukraine, which produces 340 m3 min-1 of inert
exhaust gases.
A mobile evaporator type MOD 200, which produces 200 m3 min-1 of nitrogen gas, was
manufactured for the Central Mines Rescue Station in Most in 1984. The evaporator is
supplied with liquefied nitrogen by a mobile tanker TN 15. The same mobile evaporator was
manufactured for the Central Mines Rescue Station in Kladno in 1989.
Progress in the use of nitrogen inertization continued in 1988 by the building of
evaporation stations, three at the mines in OKB, in the North Bohemia Coal Basin three
stations and in the Kladno Coal Basin two stations. They were equipped with a 15-20 m3
liquid nitrogen storage tank and 15-20 m3 min-1 nitrogen air evaporators. The purpose of
these stations has been, above all, to supply the mines with nitrogen gas for the control of
spontaneous combustion. For the same reason in 1989 equipment based on molecular sieves,
PSA system, type CMS 600 made in Germany and manufactured by the INGA company,
which produces 10 m3 min-1 of 98 % concentrated nitrogen gas was acquired. Later, another
PSA nitrogen generator, type CMS 900, which produces 15 m3 min-1 of nitrogen gas, was
bought. Both molecular sieves are working in the OKB at present.
The consumption of nitrogen has been steadily rising in the OKB, for this reason a central
nitrogen pipeline connecting the OKB mines and the steelworks Nova Hut Ostrava, utilising
the nitrogen produced as a by-product of the production of oxygen, was constructed. The
central nitrogen pipeline of the OKB was opened in April of 1993 and it is the main source of
nitrogen in the OKB today.
The reduction in the Czech coal industry output (- 53 % sinc e 1985 to 1999) has not
reduced the consumption of nitrogen. Along with the closure of some mines have also closed
some evaporation stations, but the general consumption of nitrogen is still rising due to the
existence of the central nitrogen plant in the Ostrava-Karvina Basin. The total consumption of
nitrogen in the Czech mines in the years 1949-1999 reached 424 mil. m3 (58.3 mil. in 1999).
The North-Bohemia Brown Coal Basin uses the most liquid nitrogen. The consumption of
nitrogen in the years of 1981-1963 was 5.84 mil m3 of nitrogen gas. From it was used 63 %
for prevention and 37 % for suppression of fires. This basin consumed 52,000 m3 of nitrogen
in 1998 (recalculated to gaseous nitrogen). The Kladno Coal Basin uses liquid nitrogen.
There was used 1.926 mil. m3 of nitrogen gas (60 % for prevention and 40 % for suppression
of mine fires and coal storage) in the years of 1984-1994. In 1994 their consumption of
nitrogen was 109,500 m3 (recalculated to gaseous). There have been nitrogen used only
occasionally during last five years.
The highest nitrogen consumption is in the Ostrava-Karvina Coal Basin. The central
nitrogen pipeline produces nitrogen with a concentration of 99 %. In December 1997 were
installed two polymer membrane units of the Generon type by Messer at the start of the
pipeline which supports the prevention mode of the pipeline by adding 2000 m3h-1 of the
nitrogen. Output during prevention mode is up to 7000 m3h-1 of nitrogen gas continuously, for
the control of spontaneous combustion. When in the suppression mode, the pipeline provides
300 m3min-1 of nitrogen gas for a period up to10 hours with a maximum input pressure of
1,6MPa. The total length of the pipeline on the surface is 45 km. The distance between the
nitrogen source and the first mine Dukla is 13.5 km to the west. This main branch has a
diameter of 300 mm, the branches between the mines have a diameter of 150-250 mm, and
the main subsurface branches have a diameter of 150 mm. The Central Mine Rescue Station
in Ostrava has 2000m flexible hoses, of the type NITROGEN, made in Germany by
PARSCH, with a diameter of 150 mm and working pressure of 1.5 MPa. The nitrogen is
usually used in Ostrava-Karvina Basin for the control of spontaneous combustion. Nitrogen is
released through unrecoverable branches, which are situated in the waste 30-50 m behind a
face, with about an 8-15 m3 min-1 nitrogen infusion flow rate. The recommended nitrogen
infusion flow rate for the control of waste spontaneous combustion in the Ostrava-Karvina
Basin is 10-15 m3 min-1. An optimisation of a nitrogen inertization of wastes has been solved
at the VSB-Technical university Ostrava, Institute of safety engineering, and results have
been published in (Adamus, 1997). The specific consumption of the nitrogen gas in OKB
reached 5,073 m3 t-1 in 1999, recalculated under total output of OKB, include mines, which do
not use nitrogen.
THE APPLICATION OF THE FOAM TECHNOLOGY
The objective gob inertization with gaseous nitrogen in to obtain threshold oxygen
concentration in the spontaneous combustion process in a critical zone of a longwall face gob.
The resent research shows (Adamus 1997) that a threshold oxygen concentration for sponcom of coal in the Ostrava-Karvina Coal Basin is 6 %. The incubation period of spon-com is
usually 6 weeks in Ostrava-Karvina Coal Basin .It is recommended to reduce the oxygen
concentration in a gob to 11 %. It is very difficult to obtain this value of the oxygen
concentration in a critical zone of a gob just by means of the gaseous nitrogen in longwall
faces with high output. Therefore, further steps to reduce a gob permeability have been
adapted.
One of the methods to increase aerodynamic resistance of a gob is foam application for
gob foaming to prevent air leakage through a gob. Applied technology of gob foaming by
means of nitrogen detergent foam that had been injected to a gob (Voracek 1994)was used in
Ostrava-Karvina Coal Basin as early as in 1992. The effect of detergent foam in gob is usually
inhibition and due to relatively short lifetime of the detergent foam, the products (twokomponent isofoam) manufactured by EKOCHEM, S.A. Katowice (Poland) are used to
reduce ventilation of gobs in some cases. The whole range products manufactured by this
company was being gradually approved for the application in mines in the Czech Republic in
1994 - 1997 including: regular Krylamina foam, extra-light foam, Ekofoam, DU Krylamina
glue, DU/S Krylamina glue, lumping set to be used with the EKOCHEM “Hydrox-Adal”
products and component transportation containers. The application of a two-component
Krylamina foam was approved by the Mining Authorihy and Hygienic Department of the
Czech Republic as well as by the mines in the Ostrava-Karvina Coal Basin and mines in the
Mostecka Coal Company S.A. in the Northern Czech Brown Coal Basin.
The regular Krylamina and extra-light Krylamina type foam are a two-component
materials made of water solution of acrylic-urea resins with modified additive of 1,1 - 1,2
g.cm-3, pH 7,5 - 9,5 and transparent yellow-beige catalyst of 1,1 - 1,03 g.cm-3, pH 2,5 - water
solution of the orthophosphoric acid with foam agents and modifiers. They feature very low
emission of free formaldehyde, good anti-electric properties, increased strength and sufficient
elasticity. Krylamine foams are produced on the application spot by means of compressed air
foaming or foaming equipment. A foaming gun produces regular light foam - mixing ratio
4:3, 20-40-fold foaming or extra-light foam - mixing ratio 1:1, 30-50-fold foaming. Produced
foam is flexible. The foam might be applied to fill selected spaces, it becomes flexible after 5
minutes, it reaches full insulating properties after 24 hours. When the environment humidity is
higher than 70% it does not change its volume. The lifetime of the extra-light foam is limited
- after three weeks the properties of foam deteriorate. The “regular” foam is ageing-resistant,
the minimum period when it does not change its capacity is 12 month and is elastic. Average
measuring density of dry foam is 3-5 kg.m-3.
The “Hydrox-Adal” pumping set includes :

two-circuit compressed air force pump of the design that makes it possible to change the
ratio of forced media capacity in specific circuits,

force route for separate resin and catalyst forcing for a pump to a mixing spot,

mixer with infection head,

foaming gun.
The pump capacity is 14l/min. Foam production components are transported in 30-liter
containers. Pumping set is mobile, two operators are sufficient to operate it.
“Extra-light” foam is used to seal longwall gobs to increase aerodynamic resistance of a
gob and prevent endogenous fires of coal. It can be used for cavity filling where is a threat of
explosive gas accumulation. Regular foam is used to fill the cavities above longwall face
support, narrow working sealing, pack strip fillings, ceiling sealing, insulating and air
stoppings. Foams allow fast and easy application and efficient sealing. Walls of the cavities to
be filled can be both dry or wet.
“Krylamine” INJECTION IN THE LONGWALL NO. 139702 IN THE Lazy OKD, a.s.
IN Orlova COAL MINE
The seam no. 512 of Karvina layers of the 5,5 m thickness was extracted by Panda
shearer (CdF), Gerlach conveyor and Dynatrac chainless vehicle in December 1995 in the
longwall face no.139702. There was an incident of spontaneous combustion of coal and the
longwall face was sealed with fire stops. The longwall face was opened and extraction
restarted on 12 April 1996, but due to the symptoms of endogenous fire it was sealed again on
22 April 1996 after the progress of 22 meters. While the symptoms of endogenou fire
appeared, the longwall face was inertized with gaseous nitrogen. 1,2 mil m3 of gaseous
nitrogen was used for inertization up to 30 May 1996.
The longwall face was opened again on 15 June 1996 with immediate extraction.
Accumulation of CO was noticed in the upcast in the afternoon on 18 June 1996. It was
possible to determine that the situation got stabilized due to tremendous effort that was caused
by a complicated case of spontaneous ignition on 20 June 1996. The Krylamina foam together
with gaseous nitrogen inertization played major role in fighting endogenous fire that appeared
in the longwall face no. 139702 in the Lazy Coal Mine in the Ostrva-Karvina Coal Basin that
was extracted. Krylamina foam was used to seal longwall face gobs at the caving line in both
roads in a full profile continuously together with gaseous nitrogen inertization at the volume
flow of 20 m3.min -1. The Krylamina foam helped to reduce a gob permeability and obtain
higher efficiency of gaseous nitrogen inertization.
CONCLUSIONS
The existing experience in nitrogen application in mines in the Czech Republic are in fact
identical with the existing experience published in the literature (Both 1981, Garg 1978,1987,
Harris 1981, Casadamint 1986). Nitrogen can be successfully applied to prevent and inhibit
fires. We cannot conclude however, that application of this technology may eradicate fires
completely. Therefore, it is reasonable to use together with nitrogen inertization other
prevention and inhibition methods. One of the possibilities to increase the efficiency of
nitrogen inertization is the application of filling foam materials for gob foaming. The twocomponent Krylamina foam is used for this purpose in the Ostrava.Karvina Coal basin.
THE AUTHOR PROPOSITION
The author proposes a discussion on the theoretical and practical details of the experience
of the use of nitrogen in mines and the historical verification of the usage of Nitrogen.
Proposals of technical co-operation or of the holding of a conference or any ideas, information
or suggestions can be sent to the e-mail addresses: alois.adamusor@vsb.cz .
Literature
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Czech Coalmines. Proceedings of the 7th US Mine Ventilation Symposium, Lexington, June
1995, pp 237-241.
Adamus, A., Vlcek, J. (1997), The Optimisation of the Nitrogen Infusion Technology.
Proceedings of the 6th International Mine Ventilation Congress, Pittsburgh, May 1997.
Adamus, A., Veznikova, H. (1997) The Influence of the Nitrogen Inertization to a Kinetic of
the Spontaneous Combustion of Coal. Research report of the project no. GACR 105/95/1111,
VSB-TU Ostrava, January 1997.
Both,W.(1981), Fighting Mine Fires with Nitrogen in the German Coal Industry. The Mining
Engineer, May,1981, pp 797-804.
Casadamont, M.B. (1986), L´utilisation de l´azote dans les travaux du fond. Publications
Techniques des Charbonnages de France, No. 3, 1986, pp 1-15.
Garg, P.C., Bhowmick, P.C. (1978), Use of Nitrogen Flushing to Spontaneous Heating –
proposals for a Trial in an India Mine, Journal of Mineral, Metal and Fuels, September 1978,
pp 315-322.
Garg, P.C. (1987), Development of Nitrogen Infusion Technology for Fighting and Inhibition
of Fires. Journal of Mineral, Metal and Fuels, August 1987, pp 368-377,394.
Hajek, L.(1969), Twenty years after Doubrava. Zachranar nr. 2 - 10, 1969
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