System for storing and using pressure energy freed in a controlled sequence of explosions

Field of application of the invention

The present invention refers to the sector of industrial plants for transforming chemical bond energy into mechanical and/or electrical energy, and more precisely to a system for storing and using pressure energy freed in a controlled sequence of explosions. State of the art Nowadays, in spite of the increasing exploitation of nuclear energy and of renewable sources, world energy requirements are still largely satisfied by fossil fuels, such as gas, oil and coal suitably treated. It is well known that, the chemical bond energy present in these fuels is extracted in the form of heat during its reaction with oxygen, the oxidizing agent par excellence in the atmosphere, discarding drosses, oxides and volatile substances. The heat produced during combustion is exploited in different ways to produce electric energy, the form easiest to transport and highly versatile in use. For example, in gas turbines the combustion products become mixed with compressed environmental air and act directly on the blades of a turbine connected to an alternator. In steam turbines the heat given off from combustion is used to transform water into supersaturated steam; its subsequent expansion in contact with the blades of the turbine whose shaft is spliced to the rotor of an alternator produces the mechanical work for

generation of electric energy. These conversion processes have the following disadvantages: a) efficiency usually lower than 55%; b) release of large quantities of carbon dioxide, and other more or less polluting gases into the atmosphere; c) dependency on stocks of these fuels which are becoming drastically reduced at the current rate of exploitation. Summary of the invention

The aim of the present invention is to solve the above mentioned drawbacks and indicate a different way of exploiting the chemical bond energy. In order to achieve such objects, the subject of the present invention is a system for conversion of the chemical bond energy contained in non-combustible exploding materials, including:

- an explosion chamber for said exploding materials occluded by a first massive mobile element, hereinafter called the "hammer";

- a chamber for the compression of an inert gas, said chamber including a second mobile element, hereinafter called the "dancer", less massive than the hammer, at least one end of which is hermetic with the wall of the compression chamber, and a second end placed so as to be hit by the hammer projected by the thrust produced by each explosion triggered in said exploding materials; - a first tank communicating with said compression chamber through a first one-way valve for entry into the first tank of gas compressed at high pressure in the compression chamber consequent upon the stroke made by the dancer following its impact with the hammer;

- means for conveying gas at high pressure in the first tank to a mechanical actuator;

- means for allowing the gas leaving the actuator to re-enter the compression chamber, as described in claim 1.

The term "triggered" hereinafter signifies the automatic or manual action needed to start the explosion. Exploding materials can be chosen from among those commonly known, whether simple ones (such as TNT, C4, T4, etc.) or composite (such as

black powder, dynamite, blasting gelatine, etc.). Triggering the exploding materials is also a commonly known method, chosen according to the type of explosive.

In a preferred form of realizing the invention, the explosion chamber adjoins the chamber in which the hammer is housed.

The working fluid consists of an inert gas, such as molecular Nitrogen or noble gases, or a mixture of non-flammable gases.

In another preferred form of realizing the invention, the explosion chamber is situated inside the body of the hammer through an opening in its base. In another preferred form of realizing the invention, the chamber housing the hammer and the compression chamber housing the dancer communicate through a duct, narrower than both chambers, while the hammer has an extension longer than the duct. The hammer, the dancer and the first one-way valve are preferably made of special steels.

A qualifying aspect of the invention consists in the possibility of reaching a high rate of compression using a dancer able to efficiently transfer the quantity of motion received in its impact with the hammer, to the gas. In other words, the lesser mass of the dancer compared with that of the hammer (for example, ten or more times less), enables the dancer to acquire a considerable initial speed favouring compression. Dancer speed is gradually reduced by the compression of the gas till zero is reached, when running steadily, before impact with the one-way valve, opened by the overpressure so generated, which will reach its highest value when the dancer completes its stroke. For example, choosing a ratio of 1 to 10 between dancer mass and that of the hammer, an inverse ratio between the respective strokes must be considered, and consequently an alteration in the length of their respective housing chambers. The withdrawal of small quantities of gas at very high pressure from the first tank by means of pressure reducers, and subsequent expansion when in contact with a mechanical actuator, such as a turbine, generates a large amount of useful work at a very high rate of efficiency.

Further characteristics of the present invention deemed innovative are described in the dependent claims.

According to one aspect of the invention, means for letting gas into the compression chamber include at least one cylinder with piston activated by a lever, in turn actuated by the hammer. Said means also include a second and a third tank, wherein:

- a duct fitted with a second one-way valve conveys gas at low pressure from the second tank to the cylinder;

- a duct fitted with a third one-way valve conveys pre-compressed gas from the cylinder to the third tank in communication with the compression chamber.

According to another aspect of the invention, means for extracting compressed gas from the first tank include a fourth and more capacious tank connected in series to the first tank in order to level pressure fluctuations when the hammer makes impact with the dancer.

According to another aspect of the invention, the system includes means for absorbing the recoil caused by the explosion which generates the hammer thrust; said means comprise a third massive mobile element which obstructs a damping chamber into which gas at high pressure, obtained in progression, is put in.

According to another aspect of the invention, the system includes means for recovering and treating hot solid and gaseous refluents produced by the explosion, said means having ducts whose opening is obstructed by the hammer when idle, and opened during the translation caused by the explosion.

According to another aspect of the invention, said means for recovery and treatment include those for cogeneration.

According to another aspect of the invention, means for absorbing the recoil are put in contact with heat exchangers for further use, for example cogeneration.

According to another aspect of the invention, means of cogeneration communicate with chambers for depuration of fumes.

According to another aspect of the invention, the hammer comprises an axial hole for introduction of small supplementary propellants by telescopic positioning. These propellants explode in sequence prior to impact with the dancer in order to increase the pulse received from the hammer. According to another aspect of the invention, exploding materials comprise separate propellants triggered in sequence.

According to another aspect of the invention, the first one-way valve is mushroom shaped, with one head inside the first tank, a shank passing through the walls of the compression chamber and of the first tank, and a base extending inside the compression chamber, the shank being longer than the overall thickness of the walls through which it passes. According to another aspect of the invention, both ends of the dancer comprise damping material. Realization of the system is simplified by the cylindrical symmetry of all the components most closely involved in transmission of impact and gas compression. Direction of the axis of symmetry has no a precise orientation in space, nevertheless the best is a vertical direction since it favours return of the hammer and dancer after the impact thanks to their own weight, in addition to the effect of pressure so generated. The invention can also be realized according to differing scale factors, depending on what the user actually needs. By way of an example, it would be possible to employ the system of the invention to produce electric energy in plants producing several hundred of Megawatt (even Gigawatt). In this case vertical disposition of a massive reinforced concrete infrastructure is preferable, with its base firmly sunk underground. The exploding material must be chosen from among the most powerful types as a ten-ton hammer must be sufficiently accelerated. In this case, starting from an initial pressure of 200 atm (20.265 MPa), the inert gas can be compressed to 2,000 atm (202.65 MPa) and ultimate pressure can exceed 9,000 atm (911.92 MPa). Limited to the example here described, and due to the very high pressure inside the tank that feeds the actuator, very strict precautionary measures will be necessary, such as the burying of the tank far from a built-

up area or in the seabed. The materials employed to build the walls of the - compression chamber and the tanks must also be adequate for the purpose, such as materials composed of titanium fibres differently interweaved and impregnated with polymeric resins, so as to form superimposed layers of considerable thicknesses (of the order of decimetres).

As far as concerns normal operation, the propagation of seismic waves and the noise generated by the explosions must be kept within parameters of environmental security used in designing industrial plants for transformation of energy; this will be possible if ordinary antiseismic systems and antipropagation techniques are employed.

A further subject of the present invention is a method for controlling the system already subject of the present invention, as described in the claims on method. The method includes the following steps cyclically repeated: - measurement of gas pressure upstream of a mechanical actuator;

- comparison of the measurement so taken with the numeric value of a pre-established lower threshold of pressure, and triggering of at least one explosion of defined power if the measurement taken is below threshold.

According to a variant of realization, several explosions are operated in rapid sequence during the hammer translation. Advantages of the invention

With the present invention levels of efficiency (intended as a ratio between useful work and the chemical bond energy contained in the base material) higher than those obtainable by current methods using fossil fuels, can be reached.

Non-combustible exploding materials to be employed as a source of energy are realizable at low production costs from substances commonly available in nature, so avoiding dependence on fossil fuels subject to depletion and increasingly costly. Carbon dioxide emissions form an insignificant fraction of the total compared with that produced by burning fossil fuels.

Solid" and gaseous refluents of the exploded materials contain microscopic ^" particles completely treated by ordinary means, thus avoiding emissions harmful to the environment.

Using stoichiometric methods a precise calculation can be made of the useful work obtainable from an explosion, contrary to what happens using traditional fossil fuels where variable factors related to heat absorption by liquid and gaseous interfaces must be taken into account. A further advantage consists in the fact that the heat given off during the explosion and the pressure associated with the recoil are exploitable as secondary sources of energy (cogeneration).

Paradoxically, the danger associated with exploding materials is less than that with fuels currently used for generating electric energy. While an accidental spark can sometimes provoke undesired and even violent explosions in fuels, explosives, on the contrary, need adequate and complex triggering to explode, so the explosive reaction can only occur purposely under pre-arranged optimum conditions of security and never accidentally. Brief description of the figures

Further purposes and advantages of the present invention will become clearer from the following detailed description of an example of realization of the same and from the attached drawings furnished only by way of explanation and not limitation, wherein:

- figure 1 shows a perspective view of the system subject of the present invention, complete with final user;

- figure 2 shows a schematization of the system of figure 1 where the main elements are seen in partial section along a longitudinal plane;

- figure 2a shows the lower part of the schematization visible in figure 2, in greater detail;

- figure 2b shows the upper part of the schematization visible in figure 2, in greater detail; - figure 3 shows a partial view of a section along a longitudinal plane perpendicular to the view in figure 2.

Detailed description of some preferred forms of realization of the invention With reference to figure 1, a base Ia which sustains a tall infrastructure Ib, converging towards a dome-shaped summit Ic containing a first tank for inert gas at high pressure. The system also comprises other tanks for the same gas at different pressure levels. The figure also shows: a second tank 2 containing gas at a low starting pressure, a third tank 3 containing precompressed gas, a fourth tank 4 containing gas at the ultimate high pressure and, finally, a fifth tank 5 containing gas at working pressure. Inside a power unit 7 a duct 6 from tank 5 conveys gas at working pressure to a turbine type actuator 7a, with its shaft spliced to the shaft of an electric alternator 7b whose armature is connected to a transformer 7c. Exhausted working gas from the actuator 7a reaches tank 3 through a duct 8. Transformer 7c feeds conductors 9 which depart from a pylon 10 directed towards substations (not shown). Uppermost in the infrastructure Ib is an opening 11 from which a flue 12 emerges. Tank 2 receives gas at low pressure through a compressor 13 of a type available in the market, along with its duct 14. Two delivery ducts 15 and 16 enable tank 2 to communicate with means of compression inside the infrastructure Ib. Two return ducts, 17 and 18, connect said means of compression with tank 3. This latter also communicates with a compression chamber inside the infrastructure Ib through a duct 19. Tank 4 communicates with tank 5 through a pressure reducer 20. A duct 21 leads off from the first tank with gas at high pressure situated in the summit Ic of the infrastructure Ib, to fill tank 4. Duct 21 is divided into two branches, 22 and 23, branch 22 ending in tank 4 and branch 23 in a damping chamber inside the base Ia. The damping chamber is also reached by duct 16a coming from tank 2.

The schematization in figure 2 shows the cylindrical symmetry of the sectioned whole, consisting of the base Ia surmounted by infrastructure Ib and summit Ic, in relation to vertical axis A-A. The base Ia is partially buried and comprises a damping chamber 24 inside which a recoil device 25 is visible. Infrastructure Ib comprises: an explosion chamber 26; a massive

element 27, "hereinafter called "hammer", ending in an extension 28; a chamber 29 housing the hammer 27, and a guiding duct 30 for extension 28. Duct 30 originates from a hole in the upper wall of chamber 29 housing the hammer 27 and ends in a compression chamber 31, housing a long mobile element 32, hereinafter called "dancer". Compression chamber 31 is surmounted by a tank 33 structured to contain gas at high pressure. The walls of chamber 31 and of tank 33 present a hole 34 through which passes the shank 35 of a one-way valve 36. AU these elements are cylindrically symmetrical with axis A-A. Visible inside the infrastructure Ib, right and left of hammer 27, are two cylinder-piston groups 37 and 38 activated by their respective levers 39 and 40 with one end resting on hammer 27. Infrastructure Ib comprises, inside the two side walls of the housing chamber 29, two chambers 41 and 42 for recovery and treatment of refluents and for cogeneration, above which can be seen two chambers 43 and 44 for the depuration and treatment of fumes. Chambers 43 and 44 also communicate with the external environment through two respective openings 11 and 45 for discharge of the treated residues into the atmosphere. The figure also shows a tank 2 for the inlet of gas at low pressure and a tank 3 for the recovery of precompressed gas. Both tanks 2 and 3 communicate with the two above mentioned means of compression represented by the cylinder-piston groups 37 and 38 for delivery 15 and 16 and compressed discharge 17 and 18.

Figure 2a gives a more detailed view of the lower part of the structure shown in figure 2. In particular, it can be noted that the recoil device 25 has a lateral cavity 46 including a projection 47 on the lateral wall of the damping chamber 24. Projection 47 is shorter than cavity 46. Elements 46 and 47 together control the stroke which limits translation of the recoil device 25 inside the damping chamber 24. The damping chamber is endowed with a cooling system (not shown in the figures) for recovery of the heat from the explosion, exploitable as secondary source of energy. The recoil device 25 delimits the lower end of the explosion chamber 26; this chamber 26 communicates with the environment outside the infrastructure

Ib through' ducts 48 and 49 for introduction of exploding materials. The diameter of the explosion chamber 26 is less than of the damping chamber 24 and of the chamber 29 housing the hammer 27. This provides a free space delimited uppermost by a base of the hammer 27 and below by a base of the recoil device 25. When idle, overall length of the hammer 27 and its extension 28 is greater than the height of the housing chamber 29 so that the head 50 of the extension 28 enters the guiding duct 30, ensuring that the hammer-prolongation group translates along axis A-A. Extension 28 is longer than the guiding duct 30, so ensuring contact between the head 50 and the base 51 of the dancer 32 when the hammer 27 completes its stroke. Each lever 39, 40 consists of two practically orthogonal arms 52 and 53, 54 and 55 pivoted at the conjunction point 56, 57 fixed to the infrastructure Ib. The longer lever arms 53 and 55 rest on the upper face of the hammer 27 at two rolling supports 56a and 57a placed at its summit. At one end of each shorter arm 52 and 54 is a rectilinear groove 58, 59 inside which a pivot 60, 61, orthogonally inserted in the shank of the corresponding piston 62, 63 can freely slide. Supports 56a and 57a extend over the body of the hammer

27 and have corresponding seats in the wall of the housing chamber 29. Two ducts 15 and 16 depart from the inflow tank 2 to engage along the wall of the cylinders 64 and 65 in an approximately central position, open when the pistons are completely retracted and closed when the pistons reach the end of their stroke. Along ducts 15 and 16 two one-way valves 66 and 67 are installed to prevent compressed gas flowing back into tank 2. From ducts 15 and 16 two ducts, respectively 15a and 16a, rebranch and reach the damping chamber 24 for initial inflow of the gas through two one-way valves 15b and 16b installed to prevent the reflux of compressed gas inside tank 2. Two further ducts 17 and 18 depart from the ends of cylinders 64 and 65 terminating inside the recovery tank 3. Ducts 17 and 18 carry two one-way valves 68 and 69 to prevent the reflux of gas in cylinders 64 and 65.

The hammer 27 presents an axial hole 28a which passes through extension

28 of the hammer 27 for introduction of small supplementary propellants.

Telescopic means, not shown in the figures, are used to introduce these supplementary propellants into extension 28 of the hammer 27 these being placed in the slightly rounded head 50.

For the sake of clarity, the following components are not shown in the figures: trigger devices for the exploding material, a forced ventilation system in the explosion chamber 26 for ejection of solid and gaseous residuals, a cooling and fire extinguisher apparatus.

Figure 2b shows in greater detail, the upper part of the structure in figure 2. In particular, it will be noted that the dancer 32 is formed of two truncated cones 32a and 32b joined by their shorter ends to a cylindrical rod 32c in correspondence of the minor bases. The longer bases of truncated cones 32a and 32b also respectively form the lower 51 and upper 70 ends of the dancer 32. These ends are slightly concave and include damping material. The upper end 70 facing valve 36 is hermetic with the walls of the compression chamber 31. The one-way valve 36 is mushroom shaped so as to include a cap 71, inside tank 33, the shank 35 passing through hole 34 in the wall of tank 33 and in the wall of compression chamber 31, with a rounded cylindrical foot that penetrates inside compression chamber 31. The shank 35 is slightly longer than the thickness of the walls through which it passes, so that the valve 36 opens due solely to pressure by the gas against the foot 72. The upper wall of compression chamber 31 is a slightly concave to receive the foot 72. Gas compressed by dancer 32 flows into tank 33 through channels 73 realized in the walls crossed through by the hole 34. These channels are concentric to the axis of shank 35, their upper ends lying within the area covered by cap 71 and their lower ends remaining external to the area covered by the foot 72. In the non-limitative example, channels 73 are curved with convexity facing the shank 35 and have an internal helicoidal profile (not shown in the figures). Constructively, the one-way valve 36 is placed in its seat during realization of tank 33 and of chamber 31 and can be divided into two parts rigidly joined, for example by screwing. Two one-way valves 74 and 75 are respectively installed on the branch ducts 22 and 23, to prevent reflux of gas into tank 33. On duct 19 which

connects recovery tank- 3 with compression chamber 31 a one-way valve 76 is installed to prevent reflux of gas into compression chamber 31 when the dancer 32 is operative. Duct 19 ends in the upper part of the compression chamber 31 near the foot 72 of the one-way valve 36; this favours the return of the dancer 32 on completion of compression due to pressure from the gas from tank 3.

Though not visible in the figure, in contact with the walls of the compression chamber 31 heat exchangers are present to recover heat developed during compression and exploitable as a secondary source of energy (cogeneration).

Figure 3 shows further details of the structure of figure 2. In particular, it will be noted that chambers 41 and 42 for recovery and treatment of refluents and for cogeneration communicate with the housing chamber 29 through ducts 77 and 78 whose opening is occluded by the hammer 27 when idle. The points where ducts 77 and 78 enter the housing chamber 29 are at such a distance from the base that when the hammer 27 rises access to these ducts is left free to allow discharge of refluents generated during the explosion. Chambers 41 and 42 contain a cooling system (not shown in the figure) for recovery of heat exploitable as a secondary source of energy. Chambers 41 and 42 also communicate with chambers 43 and 44 through ducts 79, 80 for treatment of the fumes. The chambers for fume treatment are fitted with doors 81 and 82 giving access to these chambers for installation, maintenance and manoeuvre of the filtering, treatment, cooling and depuration systems of refluents from the explosion (not shown in the figures).

During operation, a distinction must be made between steady phase and the start-up phase during which the final pressure in the tank 4 is gradually reached, guided by explosions of increasing intensity. In both phases the working fluid consists of inert gas, such as molecular Nitrogen or a noble gas, or a mixture of non-flammable gases. At the beginning of the start-up phase, compression chamber 31, damping chamber 24, cylinders 64 and 65 and tanks 2, 3, 33, 4 and 5 contain gas at low pressure. At this point,

propellants of low potential are introduced into explosion chamber 26, which is duly closed and the explosion triggered. The trigger device initiates a reaction of decomposition of the exploding material (chemical reaction causing the explosion) with immediate generation of a large amount of gasses at a very high temperature and pressure. As a consequence of the instantaneous overpressure in the explosion chamber 26, the hammer 27 is violently projected towards the upper wall of the housing chamber 29. The head 50 of the extension 28 of the hammer 27 passes through the guiding duct 30 entering compression chamber 31 where it violently hits the base 51 of the dancer 32. As a consequence of this violent impact, a quantity of motion is transferred from the hammer 27 to the dancer 32, which is projected upwards, compressing the gas contained inside the compression chamber 31. This compression causes the one-way valve 36 to rise gradually with consequent flow of gas into tank 33. Without constituting any limitation on the invention, it is advisable to choose a ratio between the hammer and dancer masses from 1 to 10, and an inverse ratio for the length of their respective translations in the respective chambers. Initially, in this starting phase of the process, since there is as yet no high pressure either in compression chamber 31 or, consequently, in tank 33, the upper end 70 of dancer 32 can hit foot 72 of one-way valve 36, so opening it. Initial care is therefore needed to favour formation of pressure in tank 33, such as employment of propellants of limited potential. The initial sensitivity of the one-way valve 36 is lessened due to the helicoidal profile of channels 73 which slows down the flow of gas towards tank 33. Once the gas has entered tank 33 in this way it cannot leave through channels 73 below since its pressure is sufficient to press down the head 71 of valve 39 in order to occlude their openings. The ascent of hammer 27 determines rotation of levers 39 and 40 around the fulcrum 56 and 57 as due to the thrust on the longer arms 53 and 55. Consequent activation of pistons 62 and 63 by the shorter arms 52 and 54 compresses the gas contained in cylinders 64 and 65. Thus compressed, the gas flows into recovery tank 3, and from there to compression chamber 31, replacing the volume of gas let into tank 33. From

tank 33 the compressed gas flows to tank 4 and to damping chamber 24. On reaching the end of their stroke, hammer 27 and dancer 32 fall back into their initial positions due to their own weight, so permitting pistons 62 and 63 to recover their initial position due to the combined effect of the weight of the longer arms 53 and 55 and of the gas at low pressure coming from tank 2 and let into cylinders 64 and 65. During the explosion, the recoil device 25 is projected downwards into the damping chamber 24, compressing the gas there contained, which becoming overheated damps the stroke of the recoil device 25. The steps above described are repeated at intervals for explosions of increasing intensity, till the desired pressure is reached in the tank 4, monitored by a manometer (not shown). In this way the start-up phase gradually ends and the steady phase begins, during which calculated amounts of gas at high pressure can be continuously taken from tank 4 to have it expanded in the mechanical actuator 7a, so creating mechanical work. For a better use of the available actuators, the gas should be partially expanded to reach a pressure compatible with the working pressure of the selected actuator, while ensuring that pressure of the exhausted gas downstream of the actuator is higher than that of the gas in tank 3, so favouring recovery of the exhausted gas within the working fluid's hermetic circuit.

The steady pressure in tank 4 is determined by the difference between the pulse increases due to action by dancer 32 and the decreases due to continuous withdrawal of gas by the actuator. In order to maintain pressure in the tank 4 at a constant average level (and so zero said difference), the sum of said increases must be equal in time to the decrease due to expansion inside the actuator 7a subjected to continuous work. This aim is achieved by programming a suitable system to control the process so that the following steps be cyclically repeated: - measurement of gas pressure inside tank 4 (or equivalently in tank 5, pressure reduction produced by reducer 20 remaining constant);

- comparison between the measurement taken and a pre-established lower threshold of pressure;

- triggering of at least one explosion whenever the measurement taken is below threshold. A criterion to establish the value of said lower threshold of pressure consists in choosing it so that the difference between upstream and downstream pressure at the actuator 7a be such that actuator efficiency can still be considered optimum. The choice of typology and the amount of exploding material to employ in a single explosion obviously depends on the energy the system is required to produce. This imposes appropriate dimensioning of the useful volume for the compressing chamber 31 and for the pressure of the gas filling it, when the group consisting of the hammer 27 and the dancer 32 are idle. Said dimensioning can be decided by any competent technician. As previously said, the hammer 27 and the dancer 32 preferably translate along a vertical axis, with the base Ia well sunk underground. In theory the direction of translation could be differently inclined, for example horizontal. In this case, it is advisable that end 51 of dancer 32 should also be hermetic so as to create pressure inside the guiding duct 30 during the return of dancer 32, so favouring the return of hammer 27.

On the basis of the description here given for a preferred example of realization, it is obvious that some changes can be made by a technician of the sector without thereby departing form the field of the invention, as it will appear from the following claims.