MINE POLLUTION CONTROL UNITThis invention relates to a mine pollution control unit.
When mines are working it is necessary to continually pump out seepage water to prevent them from flooding.
This is done with a system of pipes, pumps and power supplies installed in the underground workings of the mine. The pumps are designed for large volume removal of seepage water and are not concerned with particular pollutant or gas removal.
When a mine is closed, the pumping system is of too large a capacity. Pumping equipment is uneconomic to keep pumping or to be removed to another place.
As a result when a mine is closed the pumps are stopped, the mine floods with water and the pumps and the switch gear are destroyed.
The mine is then sealed to prevent any further access.
In a few cases the existing pipework has been coupled to a collective manifold at the surface, but this only collects general mine water rising by natural pressure and it does not handle gas or heavy pollutants.
Accumulated water in abandoned mines can contain pollutants can become pressurised, convey pollutants to surrounding strata. Gas may also form in the mine shaft or at pockets in the workings.
In the majority of cases abandoned mines are closed and sealed, with no further access or means of controlling the mine environment or its effects.
According to the present invention there is provided a mine pollution control unit able to control the mine environment after closure, by extraction of mine pollutant, mine water, balance the mine water pressure and extract gas.
Also monitor the mine environment.
It comprises a conductor set and sealed into a concrete base, such as a mine shaft plug.
The conductor goes from the surface to just below the concrete plug so that it can collect any gas that accumulates below the plug and in the ground surrounding the mine shaft. On the top of the conductor is a tree of valves which allows the control, installation, or removal of downhole equipment.
Within the conductor is run a casing which goes from the tree down to a sump constructed at a low point in the mine, such as the bottom of the mine shaft. Heavy pollutants can flow by natural gravity into the sump.
The sump is filled with high permeable fine material that prevents large particles entering the riser pipe.
The bottom of the casing within the sump has perforations and a screen.
Above the sump the casing has perforations that allow the entry of normal mine water.
Within the casing is installed a mine water pumping tubular, which goes from the tree down to an effective pumping depth and within which can be installed a submerged pump.
Also installed within the casing is a pollutant tube, from the tree down to a low point in the sump, so that heavy polluted water can be pumped to the surface for collection and treatment.
Within the casing or pollutant tube is a power supply tube to a pump unit for pumping the pollutant to the surface.
Also installed in the casing is an instrument tube which allows the running of instruments for data recording, monitoring and control signals.
An auxiliary access point may be used for additional jetting, injection of water or bacteria/chemical injection equipment.
The tree on the top of the conductor has stop valves for each of the systems also access chambers that allow the handling of downhole equipment even when the unit is under pressure.
Data handling, power and control of the mine pollution control unit is from a control panel.
Facilities may be shared by more than one mine.
Operation and maintenance of the mine pollution control unit can be from either fixed equipment on the surface, or from mobile equipment.
For convenience and economy, the mine pollution control unit can be installed prior to the mine closure. Although it is possible to install it after closure.
The natural separation of pollutant in the mine may be assisted by the injection of bacteria using the mine pollution control unit.
An auxiliary connection point at the tree flange may be used for insertion of downhole tubes and equipment for bacteria/chemical injection and circulation.
A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:FIG 1 is a diagrammatic view of the mine pollution control unit.
FIG 2 is a diagrammatic view showing typical operational and maintenance equipment.
Referring to the drawings a vertical conductor tube 1 is installed and sealed in a concrete base/plug 2 and of length to collect gas from the cavity 3 under the base/plug 2. Gas is extracted via stop valve 4 and gas pipe 5.
A casing 6 is run through the conductor tube 1 down to a sump 7 at a low point in the mine. The casing 6 has screened perforations 8 at the sump level to allow the entry of heavy pollutants. At a higher point it has unscreened perforations 9 to allow the entry of general mine water.
The top of the casing 6 is closed with a suspension unit 10 with slips 11, 12, which take the weight of the downhole tubulars.
The tree assembly 13 has a flange, body and valve positions and forms the transition between the downhole and surface equipment. The sump 7 collects heavy pollutant liquid. It is filled with high permeable material 14 to prevent large particles entering. A cover and screen 15 prevents loss of material 14 during recirculation.
A mine water pump tube 16 is run through the casing 4 down to a depth for effective pumping of general mine water with submerged pump 17.
A cage 18 allows extracted mine water to exit from the pump tube 16 through stop valve 19 and pipe 20.
A pollutant tube 21 is run through the casing from hanger slip 12 down to the sump 7. A suction screen 22 prevents large solids entering.
Jet nozzles 23 supplied with high pressure water from supply pipe 24 lift the heavy liquid pollutant and discharge it via pollutant tube 21, cage 25, stop valve 26 and pipe 27.
Closing valves 28, 29, 30 are large enough to allow cages, slips and tubulars to pass through. Formed blades in the valves close the riser tubes but allow them to accommodate equipment lines so that maintenance equipment 31 can be installed.
The pump 17 is suspended by cable from 32 and supplied with power by electric cable 33.
High pressure jet water is supplied by pipe 34 and valve 35.
Provision is made at the tree assembly 13 for an instrument access point 36 and an auxiliary access point 37 which may be used for an additional jet water system, injection of bacteria/chemicals or water injection.
At the surface gas is flared at 38 or stored at 39. Pollutant is treated at 40. General mine water is disposed at 41.
Electric power is supplied by generator or mains at 42 and used to power the submerged pump 17 via control unit 43, a gas extraction pump 44 and a high pressure water pump 45 for the supply ofjetting water.
Computer data is handled at 46, control of the system is from control panel.