ADSORPTION COMPRESSOR

The object of the invention is a method for producing pressurized gas, the method comprising: directing the gas to be pressurized to one or more closable gas spaces 5 of compressor means, pressurizing the gas directed to the gas space, releasing and/or transferring the pressurized gas for further processing.

Further, the object of the invention is an arrangement for producing pressurized gas, which arrangement comprises: compressor means with one or more closable 10 gas spaces, into which the gas to be pressurized can be directed, means for pres surizing the gas directed to the gas space, means for releasing and/or transferring the pressurized gas for further processing.

In industry, pressurized gas, such as compressed air, is required for several func- 15 tions and its production requires a lot of energy. According to estimates, in several European countries approximately 7 to 12% of electricity consumed by industry goes into producing compressed air. Compressed air is typically produced with com pressors, wherein the energy required for the compression effort is obtained using electric actuators powered by mains electricity. One application of a compressor is a 20 piston compressor, wherein a piston moving back and forth in a space compresses air fed or sucked into the space, which air is released after the compression for fur ther processing.

Hydrogen compressors based on metal hydrides for pressurizing hydrogen, e.g. for 25 transportation or storage, are also previously known. Therein, the alloys used as the reactor have a property of binding hydrogen and when heated, a property of releas ing hydrogen, which is utilized in the storage and consumption of hydrogen. They are thus intended for storage or transportation of hydrogen for later use, and are not intended for producing compressed air or for pressurizing other gases or fluids. 30 They are also heavy.

Further, adsorption-based means and methods e.g. for storing and enriching mole cules contained in air are known, e.g. from the publication US 3164454 A. Their purpose is not, however, to utilize waste heat from an external system for produc- 35 ing compressed air or any other gas in such a manner that the energy contained in the pressurized gas could be utilized in the new and inventive way according to the present invention.

The reference US 2012118004 A1 discloses a pressurizing arrangement for gaseous fuel, wherein the gas to be pressurized is cooled with gas circulated in a closed cir cuit via desorption. The purpose of the desorption is not to pressurize the gas to be cooled, rather the desorbed gas is first cooled, and then circulated at reduced pres sure and in a cooled state in order to cool the gaseous fuel circulating in a separate process. Thus, this solution does not produce pressurized gas for further processing. Further, the references WO 2016 179439 A1 (D2) and EP 1139006 A1 disclose con tainers for gaseous fuels whose pressurization is adjusted with an adsorption mate rial for purposes of use.

The compression effort required by conventional compressors is high and reducing the effort requires better equipment. There is also a growing need for equipment with higher efficiency with regard to the compression effort for producing pressur ized fluid or gas, such as compressed air, in a cost-effective manner.

The purpose of the present invention is to provide a novel method and arrangement for producing pressurized gas in such a manner that some of the mechanical energy previously required for the compression is replaced with waste heat or renewable energy obtained from an external system, which can be converted in a new and in ventive way for pressurizing gas to be utilized in further processing. The above-mentioned purpose of the invention is achieved with the method accord ing to the present invention in such a way that the gas space of the compressor means is fitted with an adsorption material, whereby in order to pressurize the above-mentioned gas: molecules of the gas directed to the gas space are adsorbed to the adsorption material, after which the adsorption material is heated to create a desorbing effect on the molecules of the adsorbed gas by means of heating means arranged in connection with the gas space and/or adsorption material, which heat ing means are arranged to utilize waste heat or renewable energy from an external system, and that the gas pressurized as a result of the desorption is released and/or transferred from the gas space via an internal primary circuit (6b) into an external high-pressure space, a pressure accumulator, an external system and/or a closed primary circuit of the compressor in order to utilize the waste heat or renewable en ergy stored in the pressurized gas.

Further, the purpose of the present invention is achieved with the arrangement ac cording to the invention, characterized in that the gas space of the compressor means is fitted with an adsorption material, to which molecules of the above-men tioned gas directed to the gas space can be adsorbed, and that the means for pres surizing the gas comprise heating means for heating the adsorption material in or der to create a desorbing effect on the molecules of the adsorbed gas, which means have been arranged in connection with the gas space and/or adsorption material and arranged to utilize waste heat or renewable energy from an external system, and transfer means for releasing and/or transferring the gas pressurized as a result of the desorption within the closed gas space via an internal primary circuit to an external high pressure space, a pressure accumulator, an external system and/or a closed primary circuit of the compressor in order to utilize the waste heat or renew able energy stored in the pressurized gas.

The advantage achieved with the method and apparatus according to the invention is that a greater proportion of the compression effort of the gas to be pressurized in the gas space of the compressor is performed at a lower temperature and pressure. The mechanical compression effort required is reduced and it is significantly lower than in conventional compressors, as a part of the effort is replaced with the heat transfer of the desorption step, wherein the heat transfer obtains its energy from waste heat or renewable energy from an external system. Further, the compressor means of the invention do not comprise conventional moving means for providing the change in volume required in forming the pressure. By way of heating the ad sorption material with waste heat or renewable energy, the pressurization of the gas space can be carried out in a timed manner, which allows for momentary level ing of consumption peaks. Thereby, no pressure loss resulting from the heat loss of the prior art solutions is created, particularly in long-term pressurization. In addi tion, the waste heat or renewable energy stored in the pressurized gas can be fur ther utilized, whereby the compression effort required by the arrangement of the in vention is significantly better than that of conventional compressor equipment and compression methods. Preferred embodiments of the invention, e.g. for further utilization of the waste heat and renewable energy, are presented in the accompanying dependent claims.

Next, the invention is described in more detail with reference to the accompanying drawings, in which:

Figure 1 shows an arrangement according to a preferred embodiment of the in vention, Figure 2 shows an arrangement according to another preferred embodiment of the invention with compressors connected in parallel,

Figure 3 shows an arrangement according to a third preferred embodiment of the invention with a primary and a secondary circuit,

Figure 4 shows the arrangement according to the embodiment shown in figure

3 with compressors connected in series,

Figure 5 shows an arrangement according to a fourth preferred embodiment of the invention with an internal primary circuit,

Figure 6 shows an arrangement according to a fourth preferred embodiment with a plate heat exchanger, Figure 7 shows an arrangement according to a fifth preferred embodiment with a pressure transmitting system in connection with the primary and the secondary circuit, and

Figure 8 shows another preferred embodiment of the pressure transmitting sys tem according to the invention.

Figure 1 shows a diagrammatic view of the compressor means according to a pre ferred embodiment of the invention, indicated by reference number 1. Although the compressor means of the invention do not correspond to conventional compressors with regard to their structure and function, the compressor means are hereinafter referred to with the term compressor. The compressor is a static compressor. The compressor 1 herein comprises a gas space 3 defined by a cylindrical frame 2. The gas to be pressurized, which in this embodiment is air, is fed into the gas space 3, for which purpose a connection 5a, for example a feed channel 5a, fitted with a non-return valve 5 or the like, has been arranged in connection with the compres sor. The gas to be pressurized can be gas that has already been pre-pressurized in a compressor corresponding to the compressor 1 or in another manner (e.g. in a second compressor 11 described hereinafter).

According to the invention, the gas space 3 has been fitted with an adsorption ma terial, indicated by reference number 7. The adsorption material 7 has been posi tioned in the gas space 3 in such a way that air fed into it flows through it or in con nection with it. Thus, oxygen and nitrogen, and possibly carbon dioxide, contained in the air fed into the gas space 3 are adsorbed to the adsorption material, in other words, they leave the gas phase to such extent. Other gases can also be used in place of air, in which case the adsorbable material can consist of other molecules. The adsorption material can be e.g. zeolite, perovskite, graphene, iron oxides, acti vated carbon, silica gel, MOF and/or a geopolymer. Other adsorbing materials are also known and they are being continuously developed and discovered, thus the above mentioned are only examples of materials for the adsorption element. The adsorption material 7 is preferably a porous, and further, a nanoporous element in creasing the adsorption area of the element, or it has been formed in some other way into an article with such structure and dimensions that its adsorption area is optimized to be as large as possible. The nanoporous structure enables the adsorp tion phenomenon to function in the intended manner in general. This type of a po rous structure is achieved or can be achieved, for example, by 3D printing. Provid ing a nanoporous structure is known per se, and is thus not described in more detail herein. Preferably oxygen and nitrogen, and possibly other molecules in air, are ad sorbed to the adsorption material when the adsorption material is as cool as possi ble.

In the embodiment shown in figure 1, the air (or other gas) to be pressurized is fed into the gas space 3 preferably when the adsorption material has cooled down suffi ciently after previous pressurization cycles or is otherwise cool enough. The cooling can take place passively over time at low pressure or by additional active cooling. The air or other gas to be pressurized can be gas that is already pre-pressurized or gas at an atmospheric pressure. In a preferred embodiment of the invention, in ac tive cooling the arrangement comprises cooling means indicated by reference num ber 8'. The cooling means 8' can be e.g. a heat exchanger arranged in the gas space 3 or in connection therewith, through which circulation of water or circulation of another fluid providing the cooling has been arranged. Active cooling of the ad sorption material 7 takes place particularly in the step where air is taken into the gas space 3 though the non-return valve 5 and the feed channel 5a and/or before it. Thereby, the adsorption material is able to adsorb more nitrogen and oxygen (or gas molecules in case of another gas) than without active cooling. In this case, the pressure within the gas space 3 does not increase like in conventional compressors, nor is the temperature allowed to increase. Thus, the molecules bound to the ad sorption material further allow for more air (gas) to be pressurized to be fed so that the pressure of the gas phase increases to a similar level as in conventional com- pressors. Thereby, gas can be fed until a desired pressure level is reached, after which heating takes place and the pressure level is maintained. Alternatively, gas can be fed in such an amount that the pressure level is lower than the desired pres sure level, but the pressure can be increased to a desired level by heating, and then maintained.

The air contained in the gas space 3 is pressurized by heating the adsorption mate rial 7 in order to create a desorbing effect. For this purpose, according to the inven tion, heating means have been arranged in connection with the gas space and/or adsorption material 7. The heating means can be a heat exchanger functioning as cooling means 8, through which circulation of water or circulation of another fluid providing the heating has been arranged by way of means 9a and 9b for circulating the fluid. The heating means are herein indicated by reference number 8. The heat ing means can also be heating means separate from the cooling means 8'. The heating means 8 have been arranged to utilize waste heat or renewable energy from an external system 10. The waste heat from an external system 10 can be en ergy obtained from an exhaust gas of an external motor, waste heat from an exter nal process or waste heat from cooling fluid or energy obtained from waste heat from a conventional compressor performing the pre- or post-pressurization, which is circulated through the heat exchanger in order to heat the adsorption material so as to create a desorbing effect. The renewable energy can be e.g. solar energy or geothermal energy. The oxygen and nitrogen and other gases adsorbed to the ad sorption material during desorption are released back into the gas phase of gas space 3, whereby the pressure of the air fed into the closed gas space 3 in the gas space 3 increases. It is also possible for the fluid circulation providing the cooling and/or heating to be formed by way of means 9a and 9b for circulating the fluid, such as flow paths, to be open in such a way that the fluid (e.g. water) is fed di rectly into the gas space 3 and removed from the gas space.

In this way, pressurized gas, in this example, air (compressed), can be transferred for further processing by opening the flow path 6a with a controlled valve 6. The control of the valve 6 is preferably electrical control, whereby the function of the valve 6 can be timed in a desired manner. Opening the valve 6 can occur after the desorption has come to an end. Alternatively, opening the valve 6 can occur during desorption, whereby, for example, the pressure in the gas space 3 can be main- tained at a level that is sufficiently high, but not too high, and at an even level, for a longer period of time. In this way, the temperatures prevailing in the gas space can also be affected as heat loss resulting from the temperature increase caused by ex cessive increase in pressure is avoided. Thereby, the high temperatures caused by the compression effort of the prior art, resulting in heat loss, are also avoided.

In further processing, the air pressurized as a result of the desorption is transferred to an external high-pressure space, a pressure accumulator, an external system and/or the closed primary circuit of the compressor. The advantage of this embodi ment is also the fact that the compressor itself functions as a pressure accumulator or a pressure vessel from which the pressurized air can be fed directly to an exter nal system.

A single compressor 1 (compressor means) may function in a somewhat discontinu ous mode or give out a "pulsating" yield of compressed air. For this purpose, it is preferred to connect two or more compressors in parallel, as is shown in figure 2. In figure 2, there are four compressors, each with their own set of valves, through which pressurized air is directed to a common channel. The function of each com pressor has been phased in relation to one another by way of controlling the valves and heat exchangers in such a way that at least the pressure fed to an external sys- tern is as even as possible. This embodiment can also be applied to other static compressors, such as diaphragm compressors and screw compressors. It can also be envisaged that the method applying the arrangement presented hereinbefore and hereinafter can also be applied on fluids instead of gas. In figure 3, a preferred embodiment of the invention is shown, wherein the gas (air) to be pressurized has been arranged to circulate in a primary circuit, i.e. in a so- called adsorption circuit 6b. Therein, the adsorption circuit 6b eventually directs the gas through e.g. a non-return valve out of the process or where necessary, to be reused in one or more preceding steps of the pressurization process. The non-return valve can be a controllable non-return valve. Thus, the gas pressurized in the com pressor 1 is first directed to a high-pressure space 120a, formed herein by a space on the piston rod side of the piston unit 120. Therein, a moving piston 121 has been arranged in connection with the high-pressure space 120a, moving to the left by means of pressurized gas, such as air, fed from the gas space 3, in figure 3. The piston 121 separates the primary circuit 6b (and the high-pressure space 120a) from the secondary circuit 122 on its other side and particularly from the piston unit space 120b comprised as a part of the secondary circuit 122. Gas, for example air or another fluid, separate from the primary circuit, fed into the space 120b via the secondary circuit 122 is pressurized as the piston 121 moves (moves to the left in figure 3) as a result of the pressurized gas fed into the high-pressure space 120a. The gas in the space may already be pre-pressurized using means not shown herein arranged in connection with the secondary circuit before the above-mentioned pres surization achieved with the primary circuit. Thus, the fluid pressurized and/or under pressurization in the secondary circuit can be transferred for further use e.g. to an external system 40. For example, the fluid pressurized in the space 120b can be fed into a turbine, whereby the hydraulic energy can be further converted to electric en ergy for appropriate use.

In a preferred embodiment presented in connection with figure 3, the fluid pressur- ized in the secondary circuit can be used in connection with the pressurization pro cess in the compressor 1. For this purpose, the gas, such as air, to be fed into the compressor is fed via a conventional auxiliary compressor 11 to a gas space 3. The auxiliary compressor 11 is preferably used by means of a drive, such as an electric motor 13, wherein an auxiliary motor 14 has been arranged in connection there- with. The auxiliary motor 14 can be a hydraulic or pneumatic motor to which the pressurized fluid (gas or liquid) of the secondary circuit 122 can be directed via transfer means 15 in order to provide additional moment to the drive, such as the motor 13. The transfer means 15 are herein presented by way of reference and they may also include the above-mentioned turbine, wherein the energy of the fluid of the secondary circuit 122 fed into the transfer means 15 can be converted to electric energy and directed directly to the electric motor 13. The auxiliary compres sor may in such an arrangement also be positioned in another location, for example after the compressor 1 to assist in the pressurization of the gas pressurized in the space 3, or the pressurized fluid may be directed to an altogether separate auxiliary compressor not shown herein fitted correspondingly with a drive and an auxiliary motor. Preferably, an additional heat exchanger 12 has been arranged in connection with the auxiliary compressor 11, with which heat exchanger the waste heat gener ated by the auxiliary compressor can be recovered and utilized, for example, by feeding it to the means (9a, 9b) for circulating the fluid substance and thus further to the heating means. It can also be envisioned that the pressurized gas of the pri mary circuit 6b exiting though the non-return valve can be utilized in the auxiliary motor 14. Other means can also be used for changing the state (pressure) of the secondary circuit instead of the piston 121 (piston unit). These types of means can consist of, for example, a flexible film.

Figure 4 shows a preferred embodiment of the invention, wherein at least one addi tional compressor 1' has been connected in series in connection with the compres sor 1 for pressurizing the gas to be pressurized gradually before its release and/or transfer into an external high-pressure space, a pressure accumulator, an external system 40, 120 and/or the primary circuit of the compressor 1, 100, 200 shown in figure 5. Thus, the pressurization is achieved in compressors arranged one after an other. This arrangement is advantageous particularly when high pressures are re quired, particularly when pressurizing gas or another fluid moving through the sec ondary circuit. This arrangement, wherein at least one additional compressor 1' has been connected in series in connection with the compressor 1, can also be applied to the embodiment shown in figure 1.

Figure 5 shows a preferred embodiment of the above-mentioned internal primary circuit that can be used to make the above process even more effective. Therein, the arrangement comprises a piston unit 100 acting as a compressor, wherein the space 103' defined by its frame 102, the gas space 103 has been arranged in a manner presented in more detail hereinafter. This type of a structure forms a so- called static compression compressor. At a first end of the piston rod of the movable piston 112, which end is located in the gas space 103, a piston member 111 has been arranged. An adsorption material 107 has been arranged in connection with the piston member 111 in such a way that it moves along with the piston member 111. Heating means 108 have been arranged in connection with the frame 102 of the piston unit 100. They have been arranged in the space defined by the frame 102 in such a way that they are in a connection that heats the adsorption material 10. In this case, the shapes between the heating means 108 and the adsorption material 107 have been chosen to be such that they are able to move in relation to each other when the piston member 111 moves. Meanwhile, the piston member 111 (adsorption material 107) and the heating means define a gas space 103, wherein the gas, such as air, to be pressurized, fed into the space 103' can be fed or directed via, for example, a connecting channel fitted with a valve 114. It is also possible to return the air fed into the gas space back into the space 103' via another controllable valve 115 and another connecting channel. The heating means 108 have been arranged to utilize waste heat or renewable energy from an external sys tem 10 in essentially the same way as in the embodiment presented in figure 1.

Feed means 109a have been arranged from the external system 10 to the frame 102 of the piston unit 100, by means of which the waste heat or renewable energy from the external system 10 is taken to the heating means 108. In this case, re moval means 109b have also been arranged in the frame 102, by means of which the medium circulated in the gas space 103 carrying the waste heat or renewable energy is removed or directed to be reused. The heating means can also be another type of means. For example, the heating means may consist of a massive heat ex changer.

At the other end for the piston rod, means for moving the piston rod have been ar ranged. The arrangement is herein presented in a schematic view, wherein the cir cuit moving the piston includes a hydraulic or pneumatic actuator 130, by means of which a force moving the piston rod is applied to the second end 112 of the piston rod. The second end 112 has been arranged to move within the space 113 of the frame 102 of the piston, which space is separate from the space 103' into which the air to be pressurized is fed. This arrangement for moving the piston rod may also be another type of arrangement, for example a crank mechanism or an electric linear motor.

The function of the piston unit 100 can be described based on the above-presented structure in the following manner. When the piston is in the position shown in figure 1 (down), the air to be pressurized can be fed via the valve 105 to a space 103' in side the frame 102, and thereon further to the gas space 103. In the gas space 103, the oxygen and nitrogen contained in the air (or the gas molecules in general) are adsorbed to the adsorption material 107 in connection with the gas space 103. In this step, the adsorption material and air fed into the gas space 103 may also ac tively be cooled by means of, for example, cooling means 108' arranged in connec tion with the heating means or separate cooling means that can appropriately be positioned in another location than in connection with the heating means. As an ex ample of such an arrangement, mention can me made of cooling means not shown positioned at the piston rod through which cooling means, for example cold water, can be brough to into connection with the adsorption material.

After this or at the end of this step, the heating means 108 heat the adsorption ma terial 107 as well as the surrounding gas while the piston member 111 moves along with the movement of the piston rod towards the upper position and onward to the upper position. The circulation of the heating medium can also be formed as an open circulation such as in the first embodiment. Desorption begins a result of the heating, whereby the oxygen and nitrogen adsorbed in the adsorption material 107 are released into the gas space 103. Thereby, the pressure and heat in the gas space 103 increase as the compression movement of the piston member 111 assists in it. It should be mentioned that the compression movement of the piston member 111 can also take place before the desorption and/or after desorption. As the de sorption progresses, the pressure eventually increases sufficiently for the valve 106 of the flow path 106a between the gas space 103 and the separate compressor part 120 opens up and the pressurized air is allowed into the high-pressure space 120a, as shown in figure 3, or into a similar compressor part. The pressurization is further enhanced if the piston member 111 moves during desorption. The compression movement of the piston member thereby creates additional pressurization. By tim ing the heating and cooling as well as the function of the piston member, synchronization of the pressurization can also be achieved, whereby, for example, a desired formation of pressure over time can be provided.

Figure 5 shows a preferred embodiment wherein the gas (air) to be pressurized cir culates in a closed primary circuit, i.e. in a so-called adsorption circuit 106b, indi cated with a dashed line in figure 5. Therein, the adsorption circuit 106b directs the gas to be pressurized back into the space 103' repeatedly for re-pressurization. Therein, a moving piston 121 has been arranged in the high-pressure space 120a, moving by means of the pressurized gas, such as air, fed from the piston unit 100. This has already been presented in the embodiment according to figure 3. In this case, an additional heat exchanger can be provided in connection with the flow path 106a. The purpose of the additional heat exchanger is to further heat the gas al ready pressurized in the flow path 106a and thereby further increase the pressure of the gas in the compressor part 120. The separate gas, such as air or another fluid, fed into the space 120b via the secondary circuit 122 is pressurized as the pis ton 121 moves (moves to the left in figure 3) as a result of the pressurized gas be ing fed into the high-pressure space 120a. This fluid pressurized in the secondary circuit can be transferred for further use as already described above.

The advantage of this embodiment is that instead of air, other gases that are more effectively adsorbed can be circulated in the closed adsorption circuit. This type of gas can be, for example, carbon dioxide, nitrogen, argon. Additionally, a closed sys tem keeps cleaner, as the fluid pressurized in the secondary circuit is not mixed with the gas of the adsorption circuit. Further, this arrangement allows for each primary circuit arranged sequentially or in series (see figure 4) and one or more secondary circuits to have different pressure levels in relation to each other. This can be imple mented, for example, by different ratios of the areas of the piston member 111 of the piston unit 100 and the movable piston 121 arranged in the high-pressure space 120. One such application is presented hereinafter in connection with figure 7. Dif ferent valve controls also enable forming different pressure levels.

This embodiment can be applied in connection with other types of static compres sion compressors as well as kinetic compressors, such as radial or axial compres sors. Figure 6 shows another preferred embodiment of the invention, wherein the adsorp tion material has been positioned in a compressor arrangement whose structure corresponds to that of a plate heat exchanger. Therein, elongated gas spaces 203 positioned alternately between the plates 220 and combined heating means and cooling means 208, 208' form the compressor. In figure 3, they are shown sepa rately from each other, but they may be in direct or indirect contact with each other, where applicable. In figure 3, the air (or another gas) to be pressurized is brought via a valve 205 to branching gas spaces 203. The gas spaces 203 are fitted with an adsorption material 207, in which the adsorption (and desorption) takes place. Heating and cooling the adsorption material 207 is carried out with heating means 208 and cooling means 208' in connection with the external system 10. The timing of their function and their effect on the function of the compressor (adsorp tion/desorption activities) has already been presented in connection with the exem plary embodiments according to figures 1 to 5. As the pressure increases in the gas spaces 203, the valve 206 opens up and the pressurized air is allowed into the ex ternal system or to other further processing. The embodiment presented in figures 3 to 5 with a primary circuit and a secondary circuit can also be applied to this ar rangement. Instead of or in addition to a plate heat exchanger, a corresponding embodiment can be implemented using a structure based on a pipe heat exchanger and/or a brush heat exchanger.

Some preferred embodiments of the pressure formation according to the invention have been presented above. Owing particularly to its cyclical nature, the pressure of the fluid pressurized in the secondary circuit utilized in further processing in relation to the pressure formed in the adsorption circuit may in some applications be in dis advantageous ratios in relation to one another in different phases of the cycle, par ticularly when the pressure of the fluid of the secondary circuit is desired to be as even as possible and/or different pressure levels compared to the adsorption circuit are required in general. In this case, pressures produced by a system that may briefly produce very high pressures may not be optimally utilized. In other words, adjusting the forces of these two circuits with regard to one another may be prob lematic, due to the compression ratios of the fluids compared to one another, for example. Therefore, an exemplary embodiment for adjusting these pressure ratios in principle is shown in figure 7. In figure 7, an arrangement corresponding to the one shown in figure 3 is shown with the exception of the feeding of pressurized gas fed from the pressure space 3. Therein, the gas pressurized after the pressure space 3 can be fed into a pressure transmitting system carrying out the above-mentioned function. The pressure trans mitting system herein comprises two piston units 130 and 131 connected in parallel, in which the cross-sectional areas of the piston rods thereof differ from one an other. In this case, also the ratios of the areas of the pistons on the primary side and on the secondary side differ from one another. There can be more than two piston units, and the pressurized gas can be fed to the opposite side of the piston rod in at least one piston unit, unlike in figure 7. The feeding of the pressurized fluid from the pressure space 3 is directed to the desired piston unit 130 or 131, to their high-pressure space 130a, 131a, via the corresponding valves 16 and 26. The valves may be controlled independently of each other. This arrangement allows for the pressure changing in the primary circuit to be adjusted to a preferably even level desired in the secondary circuit 122 for utilization e.g. in an external system 40. This type of an arrangement forms a stepwise adjustment, which is more accu rate the more piston units the pressure transmitting system comprises.

Figure 8 shows a general principle view of a continuous pressure transmitting sys tem between the primary and secondary circuit according to a preferred embodi ment, which may be applied in many ways. Likewise, the arrangement presented herein corresponds to the one shown in figure 3 with the exception of feeding pres surized gas fed from the pressure space 3. In this embodiment, the principle is, in ter alia, to provide continuous adjustment of the pressures of the primary circuit and the secondary circuit by means of a non-linear mechanism and/or a structure with inertia (mass). In the example according to figure 8, the utilization of inertia is implemented by storing or binding the high pressure momentarily produced by e.g. the primary circuit (or too high a pressure fed into the system) into the inertia of a structure 145 with a moving (rotating) mass (accelerating the mass) and transmit ting (or releasing) the kinetic energy of the mass further to the secondary circuit 122 at the stage where its movement begins to slow down. Thus, the pressure of the fluid substance formed in the secondary circuit can be kept at a level that is as even as possible while utilizing the pressure formed in the primary circuit as well as possible. The acceleration of the structure 145 with a mass is accomplished as the first piston unit 140 in connection with the primary circuit 6b affects the structure 145 with a rotating mass from a certain first point PI or area. Another piston unit 150 is in connection with the structure 145 with a rotating mass from a second point P2, wherein its space 151 is in connection with the secondary circuit 122. Thereby, in this embodiment the secondary circuit 122 utilizes the inertia of the moving parts, but instead of it or in addition to it, this pressure transmitting system may also utilize the non-linear transmission ratio, keeping the pressure (forces) of the secondary circuit and the pressure (forces) of the primary circuit in a static balance in relation to one another, even though the primary pressure (or corre sponding forces) vary. The transmission ratio can be made variable where neces sary. The transmission ratios and inertias are affected by, for example, the locations of the points PI and P2 in relation to one another (the radial location in relation to one another) from the mass 145, the rotation angle of the structure 145 with a ro tating mass and the weight of the structure with a mass. Thus, the pressures of the primary and the secondary circuit need not be equal in relation to one another, but a higher or lower pressure level can be achieved for the secondary circuit 122 using this arrangement.

As an example of another type of continuous pressure transmission (instead of iner tia), mention can be made of a weight (mass) that can be lifted and lowered, lo cated between the primary circuit and the secondary circuit (not shown in the fig ures) via a mechanical connection. To provide a desired transmission ratio, the weight can be arranged to move along a predetermined track, e.g. guided by a sup porting surface. Another exemplary solution is to arrange one or more pressure ac cumulators between the primary and secondary circuit, whereby control of the pres sure (and the transmission ratio) between the primary circuit, secondary circuit and the pressure accumulator can be formed in a desired manner. Instead of a pressure accumulator, a so-called electric accumulator can be used, wherein means, such as an induction brake, have been arranged in the mechanical connection between the primary circuit and the secondary circuit, which means resist the movement of the mechanical connection where necessary, storing the excess energy as electric charge in a battery or a capacitor. This energy can at a chosen point in time be con verted to a force assisting the movement of the connection, thereby providing con tinuous pressure transmission. These are examples of arrangements wherein the purpose is to receive force and effort by the process at the beginning of the desorption step, when the primary pressure is at its highest (possibly higher than that required by the secondary cir cuit) and to provide additional force and effort for pressurizing the secondary circuit when the pressure in the primary circuit starts to decrease.