The present invention relates to a valve for a device for degassing liquid mixtures. To increasing numbers of energy wells, such as for geothermal heating and energy stores as well as indirectly cooled technical systems such as freezer stores, ice rinks etc., compounds are added having a low boiling point, with the purpose of preventing freezing in the pipes. Examples of such additives are ammonium hydroxide, where the ammonia in 12.5% ammonium hydroxide has a boiling point of 39°C, and ethylic alcohol which has a boiling point of 78.5°C, both at atmospheric pressure.

It is common that plastic piping is used for transporting the liquid in the systems. Plastic pipes are not diffusion tight, but gases such as oxygen, nitrogen and carbon dioxide, and also other gases, can diffuse in from the environment to the liquid in the systems.

Also when using metal pipes, leakage in occurs via joints in the system.

Gas can also leak in from a gas-filled equipment connected to the liquid systems. Such equipment may be cooling machines.

A major problem with heating- and cooling systems comprising a heat carrying liquid is corrosion inside the systems. Moreover, compounds, primarily oxygen, nitrogen, carbon dioxide, result in that the energy efficiency deteriorates since these compounds may accumulate on heat exchangers, and there act as an insulator, and also aggregate in pumps, which deteriorates the efficiency of such pumps. Apart from oxygen, nitrogen and carbon dioxide, there may be other compounds that it is desired to remove, such as hydrogen sulphide or sulphur dioxide or gaseous cooling media. In such systems, there are different types of corrosion, such as general corrosion, galvanic corrosion, erosion corrosion, crevice corrosion, microbiologically induced corrosion and local group corrosion. The water quality is of great importance for the corrosion process. Primarily, the corrosion depends, inter alia, upon the amount of dissolved compounds, gases dissolved in the liquid, the pH value, the temperature, etc. One parameter which is very important is the

concentration of dissolved oxygen in the liquid, since oxygen is necessary for an oxidation process.

For closed water systems, which today are the most common ones, gases precipitating from the liquid, such as air, will occur as bubbles at high points in the system.

The ability of water to dissolve air depends upon temperature, pressure and salinity. Water dissolves more gas at higher pressures and lower temperatures.

The consumed oxygen during oxidation within the system is replaced by oxygen from the environment leaking into the system so as to achieve equilibrium with respect to oxygen in the system.

Therefore, systems need to be degassed in order to lower the oxygen rates in the system.

Moreover, nitrogen and carbon dioxide need to be removed from the systems, because of the negative effects of these compounds on heat exchangers and pumps.

In order to remove harmful gases, such as oxygen, nitrogen and carbon dioxide, the liquid mixture can be subjected to an underpressure, whereupon the gases are removed. Such a lowering of the boiling point, however, results in that the additives for a lowering of the freezing point are driven out from the liquid mixture before the said harmful compounds. I n the Swedish patent no 1551369-0, an invention is described that solves this problem.

One problem with a system according to the said patent is that the pressure reduction valve setting must be changed manually when the pressure in the closed system changes. The reason for a pressure change may be a change of the temperature of the liquid flowing in the closed system, leakage of liquid from the system or that the system has been

manipulated.

I n order for the desired underpressure in the separated part, where degassing is to take place, to be maintained at a desired level, so that desired compounds and elements this way are separated, the pressure reducing valve must therefore be reset after a pressure change in the closed system.

The present invention solves this problem.

The present invention relates to a pressure reduction valve for a device for degassing certain compounds in liquid mixtures having low boiling points in closed liquid systems, wherein a subpart of the liquid is separated for degassing and wherein degassed liquid is restored to the closed system, wherein the pressure reduction valve is arranged to be located on a conduit in which the said subpart is arranged to flow, and is characterised in that the pressure reduction valve comprises a house with an inlet and an outlet for the separated liquid, in that the pressure reduction valve comprises a piston which is movable in the said house, which piston is arranged to, to a larger or smaller extent, throttle the supply of the liquid separated to the pressure reduction valve, in that a pump is connected downstream of the pressure reduction valve, in that a compression spring is arranged to act between one end wall of the piston and the house, in that a channel is arranged through the piston, which channel connects the inlet/outlet of the pressure reduction valve to the side of the piston facing towards the said spring, and in that the piston is sealed in relation to the inside of the house. Below, the invention is described in detail, party in connection to exemplifying embodiments illustrated in the enclosed drawings, wherein

-Figure 1 illustrates a method for degassing compounds and elements from a liquid mixture -Figure 2 shows a cross-section of a pressure reduction valve according to a first

embodiment

-Figure 3 shows a cross-section of a pressure reduction valve according to a second embodiment.

In Figure 1, a method is illustrated for degassing certain compounds in liquid mixtures having low boiling points and in closed cooling systems. The conduit 1 belongs to a liquid system for cooling.

A subpart of the liquid is separated from the system 1 using a conduit 2 for degassing, and wherein degassed liquid is restored to the closed liquid system using a conduit 9.

According to the said patent, a subpart is separated from the closed system, where a pressure reduction valve 3 is caused to lower the pressure of the separated liquid to a predetermined underpressure. The flow direction of the liquid is shown using the arrow at the conduit 2. The pressure-reduced liquid is caused to be taken to a degassing tank 4, where degassing of the liquid is caused to occur. The pressure in the degassing tank is caused to be sufficiently low in order for certain compounds to leave the liquid in gas phase. The pressure of a main part of the separated liquid is increased using a first pump 5, restoring this part of the liquid to the system via a conduit 9. After the degassing tank 4, a second pump 6 is arranged to increase the pressure of a smaller part of the liquid separated from the conduit 1 and the gas in the degassing tank 4 to a sufficiently high pressure so that certain compounds condense and thereby dissolve in the liquid, while other compounds stay in gas phase. The second pump 6 is caused to pump the liquid and gas to a deairing tank 7 comprising a float deairing valve 8, through which separated gases flow to the environment. The float deairing valve is of suitable known type.

The remaining part of the liquid in the degassing tank 4 is caused to be pumped directly from the degassing tank 4 back to the closed system 1, using the first pump 5.

Of course, the said underpressure and the pressure in the deairing tank 7 depend upon which gases to depart in gas phase and thereby be separated, and which are desired to remain in the liquid mixture.

The present invention relates to a pressure reduction valve for a device of the type shown in Figure 1, for degassing certain compounds in liquid mixtures having low boiling points, in closed systems. The present pressure reduction valve can be used as the pressure reduction valve 3 in Figure 1.

Thus, the present pressure reduction valve is primarily intended for a device in which a subpart of the liquid is separated for degassing, and wherein degassed liquid is restored to the closed system, wherein the pressure reduction valve is arranged to be located on a conduit in which the said subpart is intended to flow.

According to the invention, the pressure reduction valve comprises a house 31; 32 having an inlet 11; 21 and an outlet 16;26 for the separated liquid.

The pressure reduction valve comprises a piston 12; 22, which is movably arranged in the house 31; 32, and which piston is arranged to, to a larger or smaller extent, throttle the supply of the liquid separated by the pressure reduction valve.

A pump is connected downstream of the pressure reduction valve. A compression spring 14; 24 is arranged to act between one end wall 17; 27 of the piston 12; 22 and the house 31; 32. Furthermore, a channel 13; 23 is arranged through the piston, which channel connects the inlet 11; 21 of the pressure reduction valve to the side of the piston 12; 22 facing towards the said spring 14; 24. The piston is sealed to the inside of the house using o-rings 20; 30 or any other suitable sealing. This channel 13; 23 results in that the pressure on the surface of the piston facing towards the spring is the same as the pressure at the outlet 16; 26 of the pressure reduction valve.

According to a preferred embodiment, the spring force of the said spring 14; 24 is settable by said end wall 17; 27 being displaceable relative to the said house 31; 32. According to a preferred embodiment, the said end wall is displaceable relative to the house by it being threaded in the house.

According to a first embodiment of the invention, the said piston 12 has a channel 33 running perpendicularly to the direction of motion of the piston, where the channel 33 in a first position of the piston debouches at the inlet 11 and outlet 16 of the pressure reduction valve, respectively, and wherein the piston 12 in a second position which is separated from the first position covers a part of the inlet and/or outlet. According to a second embodiment of the invention, a needle 32 projects out from the said piston 22, a pointed end of which is arranged to cooperate with a seat at the inlet 21 of the pressure reduction valve, so as to form a needle valve, and wherein at a displacement of the piston 22 relative to the house the needle valve throttles the inlet 21 to a larger or smaller extent. The needle 32 is sealed to the house using an o-ring 30 or corresponding , arranged between the side of the piston 22 facing away from the spring and the outlet 26 of the pressure reduction valve.

A channel 19, 29 runs through the house 31, 32 to the environment on the side of the piston 12; 22 facing away from said spring. This channel results in that the side of the piston facing away from the spring has atmospheric pressure. According to a preferred embodiment, a mechanical control means 18; 28 runs through the wall of the hose in the channel 19; 29, which control means is arranged to mechanically influence the piston so that the pressure reduction valve can release more liquid from the inlet to the outlet, when the control means is affected manually.

The control means in the said first embodiment may be a pin 18 arranged to abut against and press the piston 12 in a direction towards the spring. The control means in said second embodiment may be an L-shaped 28 detail, arranged to abut against and press the piston 22 in a direction towards the spring.

As an example, the system pressure, that is the pressure upstream of the pressure reduction valve, may for instance be 0.5 to 6 bars. In this context, the pressure downstream of the pressure reduction valve may for instance be -0.95 to -0.6 bars. The system pressure and the lower pressure created by the pressure reduction valve are determined by what compounds and elements to leave the system in gas phase.

The function of the pressure reduction valve with respect to the embodiment in Figure 2 is the following. At startup, the control means 18 is depressed so that the piston 12 allows liquid to flow through the outlet 16, whereby an underpressure is created in the pressure reduction valve. If the system pressure sinks, the underpressure in the channel 13 increases in proportion to the pressure change, due to that the said pump has the same flow, and pulls the piston 12 to the left i Figure 2, whereby the throttle in the valve decreases. This results I that the pressure increases on the surface of the piston facing towards the spring 15, because of the channel 13, whereby the piston 12 moves to the right in Figure 2 and the throttling in the valve increases.

If the system pressure increases, for instance due to a temperature increase in the liquid mixture, the piston moves to the right in Figure 2, whereby the throttling increases proportionally to the pressure change because the said pump has the same flow. This results in that the pressure on the surface of the piston 12 facing towards the spring 14 decreases as a result of an increased underpressure in the channel 13, whereby the piston moves to the left in Figure 2 and the throttling in the valve decreases.

By adapting the spring constant of the spring 15, the pressure reduction valve compensates changes in the system pressure, so that the underpressure which is created in the pressure reduction valve is substantially constant. Hence, the present invention solves the initially mentioned problem.

The function of the pressure reduction valve regarding the embodiment in Figure 3 is the following. At startup, the control means 28 is depressed so that the piston 22 and therefore also the needle valve 32 allows liquid to flow in through the pressure reduction valve. The said pump sucks the liquid through the outlet 26, whereby an underpressure is created in the pressure reduction valve. If the system pressure decreases, the underpressure increases in proportion to the pressure change, because the said pump has the same flow, and pulls the piston 22 to the left in Figure 3, whereby the throttling in the valve decreases. This results in that the pressure increases at the same time as the pressure against the surface of the piston facing towards the spring 25 increases because of the channel 23, whereby the piston 22 moves to the left in figure 3 and the throttling of the valve increases.

If the system pressure increases, for instance as a result of a temperature rise in the liquid mixture, the piston 22 moves to the left in Figure 3, because the underpressure changes in proportion to the pressure change, since the said pump has the same flow. This results in that the pressure on the surface of the piston 22 facing towards the spring 24 increases due to the channel 23, whereby the piston moves to the right in Figure 3, whereby the throttling in the valve increases. By adapting the spring constant of the spring 25 and its original force towards the end wall 17; 27, the pressure reduction valve can compensate for changes in the system pressure so that the underpressure being created in the pressure reduction valve is substantially constant.

Above, a number of embodiments have been described. It is apparent to the skilled person that the detailed design of the pressure reduction valve can be varied without departing from its function.

Therefore, the present invention is not to be considered limited to the above described embodiments, but may be varied within the scope of the enclosed claims.