GB2107840A - Integrated mine water system - Google Patents

Abstract

This invention relates to an integrated mine water system for use in a coal mine. The system comprises a water chilling unit 10 located on the mine surface, a pump 11 for circulating the chilled water to an insulated pipe train 12 which leads the chilled water to air conditioning units 13 underground in the mine, a return pipe train 14 for leading water from the air- conditioning units 13 to the surface, and connection points 15 in the insulated pipe train 12 for supply of service water underground in the mine. <IMAGE>

Description

SPECIFICATION Integrated mine water system This invention relates to an integrated mine water system particularly, but not exclusively, for use in a coal mine.

Service water is extensively used in coal mines, for instance in dust suppression sprays, for fire fighting, for cooling of eiectric motors and mining machinery and as the hydraulic fluid in hydraulic tools and mining machinery. The service water is supplied at ambient temperature and low pressure from a service water main extending throughout the mine workings. It is common practice to cool water used for dust suppression and cooling use thereby to inhibit the occurrence of heatings or fires in the seam by reducing the temperature of the coal, dust and ambient air. To this end chilling units are located underground and service water is chilled therein before being fed to dust suppression sprays, mining machines and working faces.

Much mining in Britain is carried out at depths of over 2,000 ft. As the depth of working increases, the ambient air temperature at the face also increases. Moreover, even in relatively shallow workings, the machinery and miners generate a large amount of heat, raising the ambient air temperature of the working. To combat this it is customary to provide air conditioning in the mine. This is generally achieved by air conditioning units located near the face. Air is blown over cooling coils in which is circulating a heat exchange fluid. The fluid is heated up as it cools the air and is therefore returned to a chilling unit for recooling. Generally the chillings unit is on the surface, although an intermediate chilling unit may be provided in the mine. An example of such a mine air conditioning system is shown in British Patent No. 1 582 1 54.

In many cases the fluid is brine or water, as these are readily available at the mine.

It is therefore customary for there to be at least three pipe trains in the roadways and shafts of a mine to chilling units located in face areas and, in some cases, at the pit bottom. All these take valuable space and need to be maintained in situ and extended as the mine workings extend. After exhaustion of reserves in a working, these have to be removed. Installation, maintenance and removal costs are therefore high.

It is an aim of the present invention to provide an integrated water system for use in a mining operation which at least in part overcomes the disadvantages of presently used systems.

Therefore according to the present invention, an integrated mine water system comprises a water chilling unit for location on the mine surface, a pump for circulating the chilled water to an insulated pipe train which leads the chilled water to at least one air conditioning unit underground in the mine, a return pipe train for leading water from the or each air conditioning unit to the surface and at least one connection point in the insulated pipe train for supplying service water underground in the mine.

The chilled water will be supplied under pressure principally because of the hydrostatic head between the surface and the point of use. At the or each connection point for supplying service water underground, there must be sufficient pressure to ensure adequate flow of service water to machinery underground. Generally a pressure of about 500 p.s.i. is required. It will therefore be necessary to use high pressure piping and connectors in the insulated pipe train.

The pump, which may be located on the surface or underground, functions to supply sufficient pressure to overcome pipework resistance and ensure an adequate flow of chilled water around the pipe trains. The capacity of the pump will be determined with regard to the length of the pipe trains and the water flow requirements for the or each air conditioning unit and for the or each connection point. It is necessary to be able to provide an adequate flow for fire fighting from any one of the connection points.

In a mine water supply as presently used, chilled service water, for dust suppression or cooling purposes apart from air conditioning, is obtained by use of high pressure water to water heat exchanqers. As there is no bleed off in such a system for service water, the pump in the chilled water circuit must operate a high pressure to produce the required water flow. However, in the system of the present invention, the pump operates a low pressure, thereby reducing running costs.

The water is preferably chilled to between 3 and 50C so that it does not freeze in the pipes. If necessary the water may contain a freezing point depressant, such as a glycol, so that the lower temperatures may be employed. This may be advantageous in very deep mines, but will have the disadvantage that it will necessitate addition of the freezing point depressant continuously to the water system. It may also be possible to use common salt at the freezing point depressant.

However, this may cause problems of corrosion in other apparatus using the water and should therefore be used only if unavoidable. The pressure at which the chilled water is supplied to the or each air conditioning unit will be adjusted to suit the particular type of unit used. Generally the water pressure will be in the range from 0 to 500 p.s.i. Preferably, the pressure at the or each connection point for service water will be about 500 p.s.i.

Normally, there will be two air conditioning units per face being worked in the mine, with one unit located at each end of the face. There may also be air conditioning units at the pit bottom and in the main roadways in the mine. The capacity of the water chilling unit and the pipe trains will need to be designed to be able to meet the demands of these units and of any other machinery connected to the or each connection point.

The return pipe train may not need to be insulated but should also be constructed from pressure-resistant piping and connectors.

Preferably the returned water is passed to the chilling unit for recooling and recycling within the system. As some water will be taken out of the system it will also be necessary to provide a topup water supply for maintaining the capacity of the system.

In a normal coal mine there are at least two shafts, usually called the upcast and downcast shafts. Preferably the chilled water train will be located in the downcast shaft. This is advantageous because the downcast shaft is used to take fresh air into the mine and the upcast shaft is used to take stale air and other gases out of the mine; Thus, the chilled water will not be heated by the stale air in the mine.

Preferably, there are a number of connection points each located at or near a face end or roadway junction. If the connection point is for use in supplying service water for fire fighting it may require a pressure-reducing valve so that the water does not rupture the hoses or injure miners in the area. Similarly, if the water is to be used in an irrigated dust filter or any mining machinery a pressure reducing valve may be needed. However, it is an advantage of the present invention that in many cases the need for a pressurising means is eliminated. For instance service water used for motor cooling and dust suppression sprays on mining machines generally operate at a pressure of about 500 p.s.i., and so the chilled water can be used directly. Moreover, there is no need to cool the water before it is sprayed.Also some mining machines such as roadheaders or hydraulic mining machines use high pressure jets of water to win mineral or rock. The jets are generally produced in two stages involving pressurisation of normal mains water and intensification of the pressure in proprietary equipment. The use of the pressurised chilled water will eliminate the need for the initial pressurising means.

Another advantage of the present invention is that all water used in the mine is chilled. This increases the amount of cooling in the mine and therefore contributes to the improvement of the mine environment by reducing the temperature in many locations. It also contributes to the prevention of heatings or fires within the mine.

A large part of the heat generated within the mine will be transferred either directly or indirectly, via the air conditioning units, to the water and therefore will be removed from the mine in the return pipe train. The water will be at a temperature of about 300C. The remaining heat is removed from the mine by the mine ventilation system as hot air.

Preferably the heat from the mine is used to provide heat for surface installations, for instance pit baths, district heating systems, or office and workshop heating. This may be achieved by use of heat exchangers in conjunction with the chilling unit. A novel method of achieving this is shown in our co-pending patent application No.

(Case 4404).

Advantageously, the water chilling unit includes means for using the cooling effect of surface ambient air temperatures to cool the water in the return pipe train. This may be, for instance, a cooling tower. The use of such means will reduce the cooling capacity requirement of the chilling unit and will increase the cooling capacity of the whole system. In winter or at night cold ambient air temperatures may considerably reduce the energy consumption of the chilling unit giving rise to large financial savings. A further "free" cooling effect will be provided by use of mains water to top up the system as this will be supplied at from 8 to 120C.

Although the present invention is described below with reference to a coal mine, its application is not limited to this field and it will find use in other mining operations, for instance gold or uranium mining.

The present invention will now be described by way of example only with reference to the accompanying drawing, which shows a schematic layout of a coal mine including a system according to the invention.

Referring now to the drawing, there is shown part of a mine for extracting coal from a panel 1. A face 2 in the panel 1 is being worked by mining machine 3. The face 2 is serviced by an in-bye and out-bye roadway 4 and 5 respectively which connect to a branch roadway 6, which in turn connects to main roadway 7. The main roadway 7 runs between a downcast shaft 8 and an upcast shaft 9. Ventilation is provided in the mine by blowing fresh air down the downcast shaft 8, or exhausting air up the upcast shaft 9. Using arrangements of ventilation doors and air bridges (not shown) the fresh air is directed around the mine so that it does not cross its own path and is exhausted from the mine through the upcast shaft 9.

The drawing shows only one face, although generally at least two faces are worked or being prepared in a mine. Similar arrangements for each face are provided, although variations in equipment are made for each face to suit its particular conditions.

The mine includes an integrated water system according to the present invention which comprises a water chilling unit 10 and a pump 11 located on the surface. The pump 11 supplies chilled water at a temperature of about 40C and a pressure sufficient to circulate the required amount of water to an insulated pipe train 12. The insulated pipe train comprises high pressure piping and connectors and is indicated in the drawing by hatched lines. It is connected to air conditioning units 1 3 located at each end of the face 2.

The units comprise a series of coils through which chilled water at a pressure of up to 1 500 p.s.i. is fed and are each able to remove about 1 50 kW of heat from the air stream. Air is blown over the coils by a fan and thereby cooled. The chilled water is heated as it cools the hot air, and is fed into a return pipe run 14 indicated by unhatched lines. The water emerges from the air conditioning units at a temperature of about 300 C. The return pipe run 14 removes water from the mine and returns it to the water chilling unit 10 for cooling and recycling.

The insulated pipe train 12 includes connection points 1 5 for air conditioning units and also for supplying water for purposes other than air conditioning. The connection point 1 5 at the end of roadway 5 is connected directly to the water sprays (not shown) in the mining machine 3.

Since the water is supplied at a pressure of up to 1 500 p.s.i. it can be used directly as the spray water without needing to be cooled or pressurised.

Other connection points 1 5 for instance those at roadway junctions, may include pressure reduction valves so that the water may be supplied to hoses for fire fighting. The connection points may also be used to supply water to hydraulically operated machinery, such as arch croppers, hacksaws, drills, etc., or be used in irrigated dust filters at face ends, or for cooling electric motors or other mining machines.

Since the chilled water will be removed from the system by use of the connection points, there will be less water recycled than is originally supplied. The capacity of the system is topped up using water supply 16. The chilling unit 10 is designed to remove up to about 8,000 kW of heat and this may be utilised in a heating system generally indicated as 17. This may be a water heating system for use in pit baths or district heating or a central heating system for use in pit buildings.

The present invention has the advantages that it reduces the amount of piping to be installed underground from three to two pipe trains by eliminating the need for a separate service water main. It also reduces the need for water chilling units and pressurising units underground and reduces the running costs of the chilled water circulating pump. Very little maintenance has to be carried out underground and there is an increase in the amount of cooling of the mine environment. All of the water used in the mine provides useful air conditioning and the use of water to water heat exchangers is not required.

The economic efficiency of the mine's operation is increased further by the use of the expelled heat from the chilling unit in other systems and by exploiting the 'free' cooling effect of surface ambient air temperatures and mains water supply, Thus the present invention provides an improved system of supplying water to a mine, which results in the more economical operation of the mine.

Claims (9)

Claims

1. An integrated mine water system comprising a water chilling unit for location on the mine surface, a pump for circulating the chilled water to an insulated pipe train which leads the chilled water to at least one air conditioning unit underground in the mine, a return pipe train for leading water from the or each air conditioning unit to the surface, and at least one connection point in the insulated pipe train for supplying service water underground in the mine.

2. A system according to claim 1, wherein the water is chilled to a temperature between 3 and 50C.

3. A system according to either one of claims 1 and 2, wherein the water contains a freezing point depressant.

4. A system according to any one of the preceding claims, wherein there are a plurality of air conditioning units underground.

5. A system according to any one of the preceding claims, wherein there are a plurality of connection points.

6. A system according to any one of the preceding claims, and including a pressurereducing valve at each connection point.

7. A system according to any one of the preceding claims, wherein heat extracted from water in the return pipe train by the chilling unit is used to provide heat for surface installations.

8. A system according to any one of the preceding claims, and including means for using the cooling effect of surface ambient air temperature to cool water in the return pipe train.

9. A system according to claim 8, wherein the means is a cooling tower.

1 0. An integrated mine water system substantially as hereinbefore described with reference to the accompanying drawing.