Chapter 113
The chosen needs of Polish restructured coal mines concerning the ventilation and struggling against gas,
dust and air-conditioning dangers
K. Matuszewski |
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Rudzka Coal Company, Poland |
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ABSTRACT
In this paper the selected needs of Polish coal mines with regard to their ventilation, minimisation of gas, dust and air-shortage dangers are presented. As far as ventilation is concerned: the need to broaden the use of the synchronic inverter cascades for speed regulation of main fans and the delivery of ventilation air duct to ensure a delivery of 11*17 m³/s (650*1000 m³/min) has been shown. As far as gas dangers are concerned there exists a need for the dissemination of dispatcher's help systems, training a safety personnel in use of so called synoptic display table, a supply of 0,83*1,67 m³/s (50*100 m³/min) of nitrogen in gaseous state for fire prevention as well as the use of modern mineral and chemical means have been mentioned. In order to help to reduce the dust danger the projected need for a modern generation of dry or wet dust collectors enabling a reduction in dustiness to NDS standards and equipping all longwalls with cutting machines with permanent and working installations of internal sprinklers have been postulated. In the case of air conditioning, the need to install 300 kW movable coolers with 300 kW single gear fans for the supply of 10 m³/s (600 m³/min) and an overall air pressure increase from 1600 to 2000 Pa has been presented. In the most dangerous coal mines attention has been drawn to the need for the installation and application of stationery coolers operating intermittently.
Introduction
Since the beginning of the `90s, the restructuring of the Polish coal industry has been carried out, which has experienced great difficulties with the adaptation to a free-market economy. During the `90s there was a drop in the demand for coal in Poland from 116 m tons per year in 1990 to about 80 m tons at the end of the '90 s. At present the government program of restructuring the coal industry (introduced 30.06.1998 for the years 1998-2002), with the significant support of state budget funding is being realized. The main emphasis of the program has been devoted to the restructuring of employment on the basis of a social package and the closing down of the mines. PLN 4,3251 billion will be given in 1998-2002 for the limiting of employment, which accounts for about 50% of production costs ranging at PLN 1,4874 billion for the closing down of mines considered to be permanently unprofitable.
Because of the loss of cash flow by the enterprises producing coal in recent years investments have been limited. As an example in 1998-1999: PLN 925,7 mln was given in investments, which was only 73% of the government's planned programme. The biggest needs of Polish coal mines concern the purchase of modern equipment for production purposes (coal-cutters, longwall conveyors, transportation equipment and haulage systems), as well as the making of blind headings. The mechanized sections have to be renovated and modernized. The mining headings occupy the dominant position in for investment capital. The funding needed for ventilation and the fight against ventilation dangers (methane, fire, climatic and dust etc.) making about 6% of total production costs are essential from the point of view of working safety.
It has been planned that at the beginning of 2001 in productive coal groups, 39 mines will be grouped and the total number of mines will be 42. In the next years further restructuring of the Polish coal industry will be carried out and should be expected that the number of coal mines will be further reduced because of their consistent unprofitability, their amalgamation and the working out of coal beds. The forthcoming changes of the Polish coal industry make aeorology face new challenges, which should be given attention .
In the following paper the selected needs of Polish coal mines, will be presented:
ventilation,
gas dangers,
dust dangers,
air-conditioning.
The chosen needs of restructuring coal mines with regard to ventilation
The growing concentration of production creates new requirements for ventilation staff associated with mines and with technical and scientific units. Below, the chosen needs for Polish restructured coal mines have been presented concerning:
main fans,
auxiliary ventilation,
measurement and monitoring of mine ventilation.
Main fans
The number of longwalls in the mining industry is falling systematically, connected principally with the growing concentration of production as well as with the decreasing number of mines. In connection with this, the mines' need for the amount of air delivered to the headings is declining. Because of the restructuring being carried out, the model of mines is becoming simplified (closing down shafts, regions, levels). The reduced need of the mines for supplied air, despite the building of new levels creates the need to modify or replace the main fan stations supplying the ventilation networks. In most mines adjustment of the main fan operating point according to changing network resistance is being achieved uneconomically, due to throttling on dampers in ventilation channels. When the analyses of the mine's need for the air in the long term indicate that it will gradually decrease, the use of synchronic inverter cascades to regulate the speed of fans has to be considered in some cases. Positive outcomes for such a solution are known from now abandoned "Siemianowice" mine. In order to ensure the rational and economic use of air in the ventilation system, an essential role is played by the ventilation dams on the railroads and roof and floor rails. The new regulations lay down strict requirements upon the mines for the provision of ventilation dams on railroads and ropeways. According to § 249 of the regulation … the doors of ventilation dams installed on the way of railroads or car roads have to be opened automatically or mechanically. The above mentioned regulation… in § 250 forbids the construction of dams on the roadways or rope transport routes unless they are mechanical or self-opening and closing automatically, without the need of manual assistance.
Despite of the use by the mines, by way of rail transport, of many technical solutions, there is the need for simple and cheap ventilation dams. On the rail roof roads as SKL as well as diesel locomotives it is worthwhile to introduce the solution of automatic dams - of such a type as KROK. For the roadways with rail-tracks there is the need for simple and cheap ventilation dams.
Auxiliary ventilation
As mining operations gradually become progressively deeper there is the need to supply an increasing amount of air to the newly drilled headings and blind headings of larger diameters. Simultaneously, according to § 259 of the regulations … the speed of air ventilation flow in a blind heading aerated by air duct should attain a velocity of at least 0,3 m/s in coalfields of the second, third and fourth category of methane danger. The above conditions create a situation such that in the drilled blind headings in methane-rich coalfields, especially at great depths, there is an urgent need to design and produce lute fans meeting the following requirements:
ensuring an airflow from 10 to 17 m³/s,
of a size allowing introduction down shafts and transport by rail,
limitations of noise to a level below 85 dB [A].
At the moment there are fans of the series 1000 type being produced and installed into the system of flow: they are too large in size. (fan WLE-1004 A (single geared, rotor guided type) or they have too low output (below 11,0 m³/s) and do not have a level of noise below 85 dB (A) (the two-gear backward fans WLE - 1004 B and WLE-1005 B). A step forward seems is seemed to be the preparation for production by POWEN of a two-gear fan; WLE-1005 B/1 which would ensure the economical exploitation in a wide range of situations (for short blind headings and during days when work is not being carried out). The fan WLE-1005 B/1, being of large size, a moderate output of 10,8 or 5,4 m³/s and a power demand of 40/10 kW for first and second gear has not been approved for use hitherto.
It should be remembered that lute fans are approved for use in the Polish coal underground mining industry. Lute fans produced by. the Korfmann company, eg. Fan WS 9-500/80 of low noise emission, of lower electrical energy demand and higher nominal efficiency than fans actually produced by POWEN may constitute competition for local producers within Poland.
Measurement and monitoring of mine ventilation
The measurement of the ventilation in the mine is divided into two categories: periodical measurements made using portable equipment and permanent measuring installations at fixed points or monitoring stations covering the entire mine. To be able to ascertain the condition of the ventilation of the mine it is necessary to know the following parameters;
air flow rates,
air pressures,
temperatures,
levels of gases in the mine atmosphere.
In ventilation measurement the best known is gasometric but anemometric as well as thermo-measurement and baro-measurement are less well known. At the check-points where gas- and fire safety supervisors are located for the control of air supply, as well as the condition of ventilation equipment underground, anemometers, manometers (for the control of the airtight integrity of the dams), the air inflow gauge (for the control of opening and closing the dams ) and flow gauges for the control of the operation of the lute fans are installed.
In 1995 in the "Miechowice" mine system of early fire detecting SAP-1 was introduced within the restructuring programme, additional equipment enabling permanent measurement, registration and monitoring of fan working parameters. In the above mentioned solution of the main fan stations the following are measured: static pressure in the exhaust shaft and in the channel before and after the dampers, the average airflow speed in the channel (the fan's output), active instantaneous power demand of the fan motor (energy outlay) and the temperature of the bearings.
In the future, in some mines, the monitoring system for the ventilation net of the mines will have to be reconstructed to meet the needs of safety and to improve efficiency in terms of energy savings.
SELECTED needs of Polish restructured coal mines IN RESPECT OF gas HAZARDS
In Polish coal mines the basic and significant gas hazards arise from the presence of methane and the risk of fire. These constitute selected needs and their significance in the restructured Polish coal industry is discussed here with respect to:
gas monitoring,
fire prevention.
Gas monitoring
Gas monitoring consists of the periodic measurement of gases within the mine using portable equipment, and by the use of constant monitoring installations (stationary equipment). As a result of an mining accident which occurred in 1998 at the "Niwka-Modrzejów" mine, Polish rescue regulations now oblige the rescue staff to possess [9]”
oxygen meters for continuous measurement which indicate and signal the level of oxygen,
meters which allow continuous measurement of gas content, in particular CO, CO2 and CH4,
equipment to meter humidity and temperature.
It should be pointed out that the above mentioned needs are connected. For the measurement of gas concentration the ATX 620, made by the Industrial Scientific Corporation from the USA is commonly used.
It seems advisable that ventilation staff should be additionally equipped with small, easy and cheap meters for monitoring oxygen and carbon monoxide concentrations.
The most modern gasometric systems in Poland eg. methano-fire SMP, enabling the continuous measurement of methane levels, of carbon monoxide and other parameters seem to meet all the basic requirements concerning work safety. However it would be reasonable to increase the measurement range of carbon monoxide, using meters of the ACO type. It would be especially helpful for the control of the gas concentration at the first stage of carrying out fire prevention actions before installing chromatographs. In the presence of natural dangers it would be worthwhile to consider the broadening of the functioning of the SMP systems by implementing in the most dangerous mines a system of help by a controller (the action manager) and safeguarding the mine operatives by using the display synoptic table. This table will enable the display of danger zones in case of fire or sudden inflows of methane after the underground rockbursts, together with information about escape-routes and parameters of mine's atmosphere in the blind headings. The controller managing the action at its first stage and then the action manager should have the possibility to display on the synoptic table:
the indicated danger zone,
the location of the gauges together with the pointing out the state of mining atmosphere and the air in these region,
instructions directing the staff,
location of phones.
Fire prevention
Fire prevention measures cover several approaches. Below are described the points concerning the inertial nitrogen method and the use of new mineral and chemical components.
Gaseous nitrogen in Polish mines has been used on a large scale since 1983 in the "Sośnica" mine based on movable equipment for turning liquid nitrogen into gas, using APA-1 equipment with the capacity to produce a flow of 0,56 m³/s (33,4 m³/min). In 1998 the Central Mining Rescue Station in Bytom became the owner of modern membrane equipment type - HPLC for extracting nitrogen from atmospheric air. The membrane aggregate type-HPLC 7208 for extracting from atmospheric air enables the production of 0,17 m³/s (10 m³/min) of nitrogen content above 97% [2]. Despite positive experiences of the use of above mentioned aggregate in several Polish mines, with regard to too low a rate of extraction of nitrogen being achieved, there is an urgent need of to ensure that Polish mines can be provided with a supply of gaseous nitrogen at a rate of 0,83-1,67 m³/s (50-100 m³/min/).
In fire prevention , as well as methane containment and climatic conditioning, mineral and chemical components have been used for many years. From the mineral components in Polish mines up to the '90 s there have been used cement, gypsum and anhydrite. In the `90s new joint-filling foams and gels appeared on the market. Foams (eg.durafoam) have lower joint-filling efficiency parameters and durability than gels, but have many times greater foam making ability (from 4 to 12) than mixtures (about 2). From gels used at present the most commonly used is strataseal or Pozament. Chemical means can be divided into foams and glues. Chemical foams can be divided into two main groups:
urea (urea, urea-formaldehyde)
phenol (phenolo-formaldehyde, phenolo-sulphone)
The chemical glues are used mainly to strengthen the rock mass and can be divided into:
polyurethane,
urea.
New mineral and chemical components being used in fire prevention as well as methane and climatic are used for:
isolation of the gangway,
filling up the empty spaces behind the roof-supports,
isolation of coal beds with blind headings,
consolidation of rock mass,
isolation of headings not being exploited,
filling up the gaps,
building up the bridges and isolating dams.
In the next years there will be a need to use a wide range of mineral and chemical means, with the usage of equipment producing and supplying the means selected in accordance with modern technology.
The selected needs of Polish restructured coal mines concerning dust dangers
The problem of protection against dust dangers from the aspect of its harmfulness for health is one of the most neglected domains of working hygiene and health protection and is connected with enormous financial needs which should be recognised in order to attain complex prevention. The border-line approved values of dust concentration in the headings or rooms has been stipulated in the Regulation of the Minister of Economy from 1st December 1997 [7] are higher than those given by NDS, which creates a need for the authorities to modify the permissible levels of dust to accord within the levels quoted by NDS.
In accordance with the curent mining regulations the blind headings drilled with cutters should be carried out with the use of dust extraction equipment. The blind headings drilled by cutters aired by combined ventilation should have, in the pre-heading zone, an additional ventilation lute equipped with dust extraction equipment. The blind headings drilled by cutters aired by extractive-type (suction) ventilation, should have stationary dust extraction equipment.
In the future, in order to have a dust level equal to or lower than the NDS figures the heading should be equipped with suitable dust collectors. At the moment the requirements are met by the use of wet dust extractor type AU or 800/1000 of "Halemba" mine construction. When preserving a high technical standard, it seems that the wet dust collectors being used will not be able to meet the requirements of safety regulations as outlined above, and there is an urgent need of to construct a new generation of dry or wet dust collectors and to maintain a very high-standard regime in fighting the dust in order not to exceed the NDS maximum limits in drilled headings.
Furthermore in headings drilled by cutters aired on basis of suction ventilation, air curtains have to be used, allowing the cutter operator to work from a position where there is fresh air inflow and making it impossible for dust-laden air to get to the heading.
The reduction of dust hazards during the exploitation of the coal bed involves a number of undertakings, as the dustiness which measured in ventilation headings does not come only from the operation of the cutter at the face, but is also caused by other operations such as moving the mechanical roof support or the crushing of coal in the haulage systems, which in the Polish coal industry in general are situated in the path of flow of fresh air. Despite these other factors, it seems that the basic source of dustiness at the faces in Polish coal mines is the result of the cutting process. Unfortunately, Polish mining regulations do not oblige the mines to use the system of so-called internal sprinkling, however in leading coal-producing countries various, sometimes different solutions to combat of struggle against dust concentrations are used. In order for the sprinkling system on the cutter to work properly, the following conditions have to be met:
it has to have clean water, which means filters must be used in Polish mines,
there has to be water pressure of a minimum of 6 MPa on the cutters by means of a pump installed in the gateway or on the cutter,
high durability and efficiency of seals in the head and arm of the cutter.
To effectively combat the dangers of dust at coal-faces should be paid to the condition of the cutting heads, or knives (it is essential that they are self- sharpening). To decrease the dustiness of the heading complex, and wide-ranging projects are required: large financial outlays are necessary. Of fundamental importance is the efficient operation on the cutters by the internal sprinklers.
The selected needs of Polish coal mines concerning air-conditioning
The climatic conditions in Polish coal mines are getting worse and worse from year to year, which is connected with the mining process and the growing concentration of production. Since 1986 a progressive increase in the number of headings with temperatures exceeding 28°C has been observed. Since 1986 the number of such headings has increased from 59 to 224 in 1999, despite the decreasing number of coal mines. In order to improve the climatic conditions one has to use all classic means for improvement and to decrease the amount of air supplied to the headings. In a situation when, despite using classic means of improving climatic climate conditions, improvement cannot be achieved to reduce the temperature below 33°C (according to readings from a dry-bulb thermometer). Therefore it is necessary to use cooling equipment. The cooling equipment can be divided into:
portable cooling equipment,,
fixed cooling installations (section) equipment,
core cooling equipment.
Movable cooling equipment
In Polish coal-mines in the `80s cooling equipment of the GUC-250p type on intermediary production produced under licence by WUCh in Dębica has been used. In `90s, there appeared directly acting cooling equipment type LKM2-290 produced by Wende-Malter and type DV-290 of GFW, and a system of slightly inferior quality: cooling equipment type GUC-330B. For the systems already in use in Polish mines, cooling equipment of types LKM2-290, DV-290 and GUC-330B local one-gear fan is needed of models series one-thousand, ensuring an airflow of about 10 m³/s and total pressure increase from 1600 to 2000 Pa for overcoming the pressure drop in the air cooler. The fan would replace that used in such situations such as fan type WLE-1003B or WLE-1005B.
For the improvement of climatic conditions in the faces the GFW solution based on the aggregate cooling water type KM-250 is appropriate, placed in the blind heading, from which the hoses supplying the cooled water are linked to air coolers type - SPK22 suspended from sections of mechanical roof support. It should not be anticipated that a refrigeration system is applicable because of its usual use in faces up to 1,2 m, which are rarely exploited and because of the complexity of the installation.
Stationary (section) cooling equipment
Because of the difficult climatic conditions in Polish coal mines several portable cooling systems are in use. In a few mines there is the need to instal stationary (section) cooling equipment for intermittent operation. In German mines, in difficult climatic conditions, de-centralised water equipment is being used of a power level of 600 to
3000 kW. The standard equipment offered by GFW is the equipment KM-2000 with cooling power above 1800 kW. The cooling equipment of KM-2000 type, apart from its own equipment incorporates pre-heading coolers (evaporators) and joined together by pipes with cold water coolers evaporating water. The stationary cooling equipment with internal water circulation is used for air-conditioning of 1-2 class ventilation regions. The cooling water flowing at a rate of 0,077 m³/s (110 m³/h) is supplied to 6-8 underground coolers usually of cooling power of 250 or 350 kW. It seems that in future years, in several coal mines, eg. Zofiówka, Sośnica, Bielszowice, Halemba, there will be a need to instal stationary (section) cooling equipment of a power of about 2000 kW.
Central cooling equipment.
Central air-conditioning has been run in 2000 at "Pniówek" mine, because of the difficult climatic conditions which can be expected to occur in this mine. In the conditions of Polish coal mines, typically because of the very difficult financial situation, it seems, that in the first place it should be implemented in mines of (according to forecasts) the worst climatic conditions to support the supplement the stationary cooling equipment of 1000-3000 kW, which in the future could be conjoined with the equipment for central air-conditioning.
Conclusions
On the basis of the considerations put forward, the present needs of Polish restructured coal mines seem to be as follows:
Within the ventilation systems
with regard to having a reduced need for fresh air, connected with the growing concentration of production in faces it should be to broaden the use of synchronic invertor cascades for the regulation of fan speeds in the main fan stations or to use other methods to co-ordinate the fans' output to the main ventilation network,
on the main tracked roadways and handling levels floor handling, simple and cheap ventilation dams similar to KROK should be used for roof transport,
for drilled blind headings there is urgent need of constructing and producing air duct fans of the type of series 1000 of not excessive size and quiet in operation, yet producing an current of air from 11 to 17 m³/s.
To reduce gas dangers
increase the purchases of portable measuring instruments for the concentration of gas equipped with alarms that are triggered should the approved concentration be exceeded,
broaden the system of help for the controller (fire action manager) and facilitate the rescue of miners and rescuing the staff by use of synoptic table display in mines in which there are high-level natural dangers,
ensure the possibility of supplying 50-100 m³/min of nitrogen in gaseous state for fire prevention,
broaden the use of modern mineral and chemical means in fire prevention as well as the equipment for their manufacture, making and supply using modern technological methods.
To minimise danger from dust:
construct dry or wet dust collectors of the new generation enabling in the future dustiness only to exist at or below the values laid down by NDS,
broaden the use of air curtains on the heading cutters in drilled blind headings aired by extractive ventilation,
equip all faces with cutters having permanent and operational installations of internal sprinklers.
with regard to air-conditioning:
re-equip the movable cooling equipment that is being used, of power of about 300 kW with single-gear fans ensuring an airflow of 10 m ³/s and total pressure increase from 1600 to 2000 Pa,
implement the stationary (section) cooling equipment with intermittent activity in mines in which the greatest climatic danger is present.
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Matuszewski K.: Skuteczny sposób kontroli i zagrożenia pożarowego i metanowego w kopalni. Mechanizacja i Automatyzacja górnictwa 1998, nr 11
Matuszewski K., Trenczek S.: Stosowanie nowych środków mineralnych i chemicznych w profilaktyce górniczej. Bezpieczeństwo pracy i ochrona środowiska w górnictwie 1999, nr 11
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The chosen needs of Polish restructured coal mines concerning