Cooling water flow regulating apparatus for coal gasification wells.

The present invention relates to a controller of the water flow of a cooling device of a gas discharge pipe, produced by gasification of an underground coal deposit, having near its base a chamber in which the liquid phase water is contacted with the vapor phase.

It finds its main application in the underground gasification, particularly in equipment for cooling the exhaust holes of the gas produced. The evacuation of gases produced by gasification of coal in situ deposits buried deep (1000 m or more) involves connecting these coal seams with the surface by means of a large number of discharge pipes, (hereinafter designated after a test). The evacuation of the gases produced, however, requires a perfect seal of underground gasifier, in particular on connection points of coal seams with the polls. To this end, the polls are sealed over a sufficient height in the land overlooking the field, using refractory cement. Nevertheless, surveys, through which the product gas having a temperature of 700 to 1000⁰C tend to expand and submit seals to significant constraints. In practice the tightness of seals can not be guaranteed if the temperature surveys (and therefore gas) exceeds 250 to 300 ° C.

For this purpose, it has already been proposed to install in each sample, preferably near the coal seam, a cooling apparatus which brings the gas produced at an allowable temperature of about 250 ° C.

And Belgian Patent No.847.383 discloses the cooling of the gas in a heat exchanger supplied with water from the surface, so as to produce steam which is then mixed with the gas stream. Some authors have proposed to spray water directly into the gas stream.

A common feature of these systems is the difficulty of adjusting the injected water flow. Or fine adjustment is necessary because too little water leads to overheating and destruction of the casing, and too much water causes disruption of the flow of gas or the invasion of the survey.

Water flow adjustment by the action exerted on the surface is difficult because of the precariousness of the available information on conditions downhole; it is another ineffective part because of the existence of a water column of about 1000m in height downstream of the regulatory body.

We are therefore forced to make an adjustment downhole, and resolve the difficulties inherent in this solution.

It is indeed not possible to implement known adjustment means, because of the following requirements: <ul><li>- The size of the latter must be reduced, because the underground gasification of surveys have smaller diameters generally between 200 and 250mm;</li><li>- Can not be used as mechanical adjustment means, due to high temperatures;</li><li>- The operation must remain reliable in harsh environments (high temperature, high pressure, acid gases);</li><li>- The dynamic behavior must be satisfactory; must especially avoid water hammer and tuning instabilities.</li></ul>

The present invention provides a flow controller that meets the conditions mentioned above.

It aims to overcome the drawbacks of known regulating devices and concerns a flow controller that can adjust downhole. It provides a solution to congestion technical problems, high temperature resistance, reliability and dynamic behavior.

It relates to a controller of the water flow of a cooling device of a gas discharge pipe, produced by gasification of an underground coal deposit, having near its base a chamber in which the liquid phase water is in contact with the vapor phase, essentially characterized in that the entry of water inside the cooling device of the gas discharge pipe produced by gasification of an underground coal deposit, is controlled by a piston movable in a substantially closed chamber; this piston comprising a water inlet duct, is subjected firstly to the water pressure from the surface and on the other hand to the force of a spring; the chamber further comprises an adjustable orifice, controlled by a needle, allowing the output of the water contained in the chamber.

According to an advantageous embodiment of the invention, all the side walls of the chamber, the spring and plunger are replaced by a solidarity expansion bellows of the water inlet control unit and solidarity of the adjustable orifice for the outlet of water from the bellows.

According to a preferred embodiment of the invention, the water inlet control unit consists of an elongate body forming the closure of the enclosure; this body is shaped externally so as to have alternating areas conical and cylindrical regions and moves axially in a cylindrical space whose walls comprise constrictions.

According to a particularly advantageous embodiment of the invention, the water inlet conduit passing through the elongated body is at least partially formed of a succession of restrictions and enlargements.

Other features and details of the invention will become apparent from the following detailed description, with non-limiting examples, with reference to the accompanying drawings.

In these drawings:<ul><li>- Figure 1 is a section through a general diagram of a sample provided with a cooling device and a flow controller;</li><li>- Figure 2 shows a diagram of the flow controller;</li><li>- Figure 3 is a sectional view of one embodiment of the flow regulator.</li></ul>

In these drawings, like reference numerals designate identical or similar elements.

Figure 1 shows a survey 1 connecting the surface 2 to a coal deposit 3. The refractory cement 4 surrounds the survey 1. The gas produced is shown by the arrows bearing reference number 5.

Inside the sample 1 is a water supply pipe 6 having at the bottom a heat exchanger 7 provided with a flow regulator 8.

2 shows the cooling device having an enclosure 11 in which the liquid phase 9 of the water is in equilibrium with the vapor phase 10.

The entry of water into the enclosure is controlled by a flow regulator 12 comprising a piston whose head acts as a closure of the orifice 13 located at the foot of the tube 6 supplying water under high pressure ( for example 100 bar) from the surface. The bottom of the cylinder 14 is pierced by a small hole 15 allowing the water contained in the cylinder to escape.

The opening or closing of this outlet 15 is controlled by a needle valve 16 whose position is fixed by the water level in the heat exchanger 7 for cooling the gas.

To this end, a float 17 is connected to the needle 16 by a set of levers 18. A spring 19 inserted into the cylinder 14 opposes the displacement of the piston 12 downwardly. The equilibrium position of the piston is obtained when the resultant of the forces acting on it is zero.

It is clear that when one hole 15 is closed, the water pressure in the chamber 14 moved up to the value of the pressure in the tube 4. When the needle 16 is lowered, it is established a flow rate " secondary "through the chamber 14 and the pressure in the latter will be determined by the relative pressure drops one hand in the intake duct 20 drilled through the piston 12, second in the hole 15 controlled by the needle 16.

This device is therefore a servo amplifying both the displacement and force of the regulating member 8 by making use of the potential energy available in the water upstream of the regulator. In one implementation formatting, the piston 12 is of the order of 10 times that of the needle 16 and the force applied to the shutter 13 of the order of 300 times that exerted on the needle 16.

As mentioned above, the movement of the needle 16 is controlled by a float 17 which follows the movement of the water level in the apparatus 7.

Under the conditions of operation set (20 to 30 bar), the density difference between the liquid and vapor phases is low and the buoyancy of the float 17 is modest; that is why this push has been amplified by a set of levers 18 interposed between the float 17 and the needle 16.

The operation of the entire control device 8 is summarized as follows. Assume that the water level descends in the heat exchanger 7; the float 17 accompanies the descent and transmits its movement to the needle 16 which descends in turn reduces the resistance and 15 to the exhaust of the secondary flow. Therefore the pressure drops in the chamber 14, the piston 12 drops and the main valve 21 opens, increasing the main rate to find a new balance. The process is reversed when the level rises in the heat exchanger 7.

Since the pressure in the chamber 14 is determined by the relative size of losses at the entrance and exit of the room, the leakage flow around the piston 12 to remain negligible in the input and output. Besides, if the leakage rate becomes important, it could cause additional pressure drop upstream such that the pressure in the chamber 14 can no longer reach a value sufficient to close the shutter 13. According to a form of implementation, we can replace the entire side walls of the chamber 14 - 12 piston - spring 19 by an expansion bellows connecting sealed to the shutter 13. in order to control the temperature in the polls 1 production , it is necessary to modulate the flow of water precisely in one- wide range, for example, between 10 to 100% of nominal flow. To this end the invention proposes a closure of an original geometry. Referring to Figure 3, there is shown an expansion of bellows 22 secured to a water intake control unit. This unit comprises an elongate body 23 and is constituted by a plurality of conical regions 33 alternating with cylindrical zones 25 and 26. This body 23 moves in a cylindrical space whose walls 27 have annular sections 28. The parts 29 and 30 ensure guiding of the body 23.

When the body 23 is close to its uppermost position, ie closing of the orifice 13, the cylindrical portions 25 are located opposite annular sections 28, the sections are closest and pass a minimum flow rate; a head 31 located shutter cancels this rate closed. When the body 23 descends, the tapered portions 24 are in opposite parts 28. Since the taper, one obtains a gradual and linear variation of the narrowed sections (and therefore flow rate) as the body descends.

When the body 23 is at its lowermost position, the cylindrical portions 35 are present in front of the annular sections 28. This position of the body 23 is outside the normal operating range; it allows the nominal flow to flow as a result of accidental overheating of the water upstream, relaxation causes partial vaporization.

The number of constrictions is adapted to the pressure drop to produce and therefore the depth of the gasification survey.

The water column moving above the regulatory body 8 has a mass and a significant inertia. The mass exceeds 1 tonne for a pipe 5cm in diameter and 1000m in length. Too rapid closing action of the controller 8 generates powerful hammer. To avoid this inconvenience, the running speed of the shutter body 21 is limited during the closing phase. In fact, during this phase, the secondary inflow is increased from the outflow of an additional flow required to inflate the bellows. By dimensioning leads 20 and bellows, we can choose at will the regulator's closing speed and thus the flow rate of change in order to minimize the necessary pressure in the upstream pipe during the closure.

To this end, the duct 20 is equipped with a succession of restrictions and enlargements 32 33. Each restriction, water acquires kinetic energy it loses in the following widened zone where the flow is strongly turbulent. The number of stages of the maze must be adapted to the importance of the upstream pressure and therefore the depth of the survey.

The described components should be assembled in a cylindrical volume. as narrow as possible, so they can be easily slipped inside the casing polls.

To reduce the overall width, the secondary labyrinth 32-33 is disposed above the main labyrinth 24-25-26-28.

It is clear that the invention is not limited to the example described above, but may be modified without departing from the spirit thereof. Thus we have described the case where the controller is for controlling the level of water in a heat exchanger for producing steam. Obviously we can use the controller with other cooling systems.

Also the direct control of needle movement can be obtained by the temperature of the gas downstream of the exchanger. In this case, the needle can be attached to a bracket supported by rods placed in the gas stream around the enclosure and made of a high coefficient of expansion material.

The needle can also be mounted on a membrane of a pressure capsule, as well when the pressure drops, the diaphragm is lowered and causes the opening of the regulator; and vice versa.

The advantages of the regulator realized according to the invention are obvious and can be summarized as follows:<ul><li>- Cylindrical geometry device suitable for high-depth surveys,</li><li>- Able to adjust the flow of water from 10 to 100% accurately, linearly depending on the deviation from the set point,</li><li>- Able to work under high pressure differences (100 bar and more)</li><li>- Operable with warm water (up to 250 ° C) becoming two-phase during expansion,</li><li>- Making use of the upstream pressure to actuate the valve according to a principle of the hydraulic servo,</li><li>- Adapted to sealingly close,</li><li>- Operable under the control of various physical values ​​(level, temperature, pressure),</li><li>- Able to avoid water hammer through the implementation of an automatic limitation of the closing speed.</li><li>- Using a throttle device to original geometry (labyrinth) for both the main flow for the secondary flow through the adjusting servomechanism</li><li>- Capable of operating with various liquids,</li><li>- Suitable for various uses (valve, pressure relief valve, etc ...).</li></ul>