A plant for generating mechanical energy from a carrier fluid under cryogenic conditions.

Abstract

A plant (1) for generating mechanical energy from a carrier fluid under cryogenic conditions, the plant (1) comprising a cryogenic tank (10) configured to store the carrier fluid under cryogenic conditions, and a volumetric tank (20). The plant (1) further comprises a supply circuit (30) arranged as a connection between the cryogenic tank (10) and the volumetric tank (20), the supply circuit (30) comprising a pump (31) configured to increase the pressure of the carrier fluid, and a main heat exchanger (32) arranged downstream of the pump (31) and configured to facilitate heat exchange between a heat source and the carrier fluid in order to increase the temperature of the carrier fluid and evaporate it. The plant (1) provides an engine body (40) configured to generate mechanical energy, the engine body (40) including at least one working chamber (41) having an inlet port (42) arranged in fluid communication with a volumetric tank (20) and an outlet port (43) connected to a discharge circuit (60) for spent carrier fluid, and a recirculation circuit (70) designed to send a portion of the spent carrier fluid to the volumetric tank (20).

Description

Technical Field

[0001] The present invention relates to a plant and a method for generating mechanical energy from a carrier fluid under cryogenic conditions.

[0002] The term "cryogenic conditions" is intended to mean a carrier fluid in a low-temperature state, particularly a carrier fluid in a low-pressure state substantially equal to atmospheric pressure at a temperature lower than the critical point temperature of the carrier fluid.

[0003] Furthermore, the term "carrier fluid" is intended to mean fluids belonging to the family of cryogenic liquids such as, for example, nitrogen, oxygen, ammonia, etc., and common fluids having a critical temperature far below room temperature such as, for example, methane.

[0004] The present invention is used in various applications including, for example, power generation, propulsion (land, rail, ship), transportation of industrial machinery or high-efficiency regasification of fluids under cryogenic conditions (for example, methane after transportation in a methane tanker).

Background Art

[0005] Engines driven by compressed air are known. A historical example is represented by the locomotives on the Naples-Portici railway line, the compressed air engines of which were driven by compressed air taken in by a dispenser that measures the amount of compressed air stored in a pressurized tank and required by the engine cycle in order to obtain mechanical energy from the compressed air.

[0006] A serious problem with this system was that it could only be supplied at a relatively low pressure of up to 12 bar due to safety issues. Due to the low pressure, the amount that could be put into the tank for filling the compressed air was limited, resulting in limited autonomy of operation.

[0007] Furthermore, the progressive extraction of compressed air from the tank itself led to a decrease in air pressure and a reduction in function until the engine stopped.

[0008] A further problem was related to the high consumption of air drawn from the tank. In fact, the direct use of compressed air taken in as a carrier gas did not allow for any savings.

[0009] Another problem was the cost of supplying compressed air provided by the compressor, which, as is well known, was inefficient and involved very high supply costs.

[0010] Furthermore, even if this solution increased air pressure to increase the power obtained from the engine, other problems associated with the use of compressed air still remained.

[0011] The first problem is that the expansion of air and the associated drop in temperature can cause water condensation and carbon dioxide generation, which can interrupt engine operation at certain levels. The second problem is related to the low temperatures reached by exhaust gases at the engine exhaust port, which can lead to safety issues and / or environmental damage. For these reasons, air is never compressed beyond 10-12 bar.

[0012] Therefore, the success of compressed air engines is limited to applications such as coal mines, where the use of fuel and / or electric motors is not recommended for safety reasons. Essentially, this system of compressed air engines is a system of compressed air engines with high compressed air consumption. [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] In this regard, the fundamental technical problem of the present invention is to propose a plant and method for generating mechanical energy from a carrier fluid under cryogenic conditions, which will solve the aforementioned shortcomings of the prior art.

[0014] In particular, an object of the present invention is to provide a plant and method for efficiently and continuously generating mechanical energy from a carrier fluid under cryogenic conditions.

[0015] A further object of the present invention is to provide a plant and method for generating mechanical energy from a carrier fluid under cryogenic conditions, which is free from condensation and / or "ice" problems during discharge of the plant itself.

[0016] A further object of the present invention is to provide a plant and method for generating mechanical energy from a carrier fluid under cryogenic conditions, which tends to operate with very little carrier fluid consumption.

[0017] A further object of the present invention is to provide a plant and method for generating mechanical energy from a carrier fluid under cryogenic conditions, which does not affect the environment. [Means for solving the problem]

[0018] The specified technical problems and objectives are substantially realized by a plant for generating mechanical energy from a carrier fluid under cryogenic conditions, comprising a cryogenic tank configured to store the carrier fluid under the cryogenic conditions, and a capacity tank. The plant further comprises a supply circuit arranged as a connection between the cryogenic tank and the capacity tank, comprising a pump configured to increase the pressure of the carrier fluid, and a main heat exchanger located downstream of the pump, comprising a main heat exchanger configured to increase the temperature of the carrier fluid and to facilitate heat exchange between a heat source and the carrier fluid in order to evaporate the carrier fluid. The plant provides an engine body configured to generate mechanical energy, comprising an engine body comprising at least one working chamber having an inlet port arranged in fluid communication with the capacity tank and an outlet port connected to a discharge circuit for spent carrier fluid, and a recirculation circuit designed to send a portion of the spent carrier fluid to the capacity tank.

[0019] Furthermore, the specified technical problem and objective is a method for generating mechanical energy from a carrier fluid under cryogenic conditions, - A preliminary step of preparing a cryogenic tank to contain a fluid at an extremely low temperature (Tcryo) and pressure level (Pcryo), - Preliminary step of preparing the capacity tank, - A preliminary step of preparing the engine body designed to produce expansion and compression phases, - A preliminary step of supplying mass M2 of pressure level Prec and supply temperature Trec to a capacity tank. This is substantially achieved by methods including

[0020] The method is, - A circulation step in which the pressure of the carrier fluid is increased from the Pcryo level to the Pproc level, wherein Pproc is higher than Pcryo and Prec. - A circulation step in which the temperature of the carrier fluid is raised from Tcryo to a first process temperature Tproc1, wherein Tproc1 is higher than Tcryo. - A circulation step in which the temperature of the carrier fluid is raised from Tproc1 to a second process temperature Tproc2, wherein Tproc2 is higher than Tproc1. - A circulation step in which a mass M1 of carrier fluid with temperature Tproc2 and pressure level Pproc is supplied to a capacity tank. - A circulation step in which masses M1 and M2 of carrier fluids are mixed to obtain mass M1+M2 with supply temperature Tfeed and pressure level Pfeed. - A circulation step in which the mass M1 + M2 of carrier fluid with pressure level Pfeed and supply temperature Tfeed is supplied from the capacity tank to the engine body. - A circulation step that generates mechanical energy by expanding the mass M1+M2 of the carrier fluid within the engine body in order to lower the pressure from level Pfeed to level Pex (below Pfeed) and lower the temperature from Tfeed to Tex (below Tfeed). - A circulation step of discharging the mass M1 of the fluid towards the external environment, - A circulation step of compressing the mass M2 of the fluid to increase the pressure from level Pex to level Prec and increase the temperature from Tex to Trec, and supplying the mass M2 at the pressure level Prec and the supply temperature Trec to the capacitive tank is also included.

[0021] A further feature of the present invention will become clearer from the indicative and thus non-limiting description of a preferred but non-exclusive embodiment of such a device, as shown in the accompanying drawings.

Brief Description of the Drawings

[0022] [Figure 1] A preferred embodiment of a plant for generating mechanical energy according to the present invention is schematically shown. [Figure 2A-2C] Diagrams of each component of the plant of FIG. 1 are shown. [Figure 3A-3F] Diagrams of each component of the components of FIGS. 2A to 2C in different operating configurations are shown. [Figure 4] A Mollier diagram of the open operating cycle of the plant of FIG. 1 is shown.

Mode for Carrying Out the Invention

[0023] Regarding the attached drawings, the reference numeral "1" as a whole indicates a plant for generating mechanical energy from a carrier fluid under cryogenic conditions.

[0024] The term "cryogenic conditions" is intended to mean a carrier fluid in a low-temperature state, particularly a carrier fluid in a low-pressure state substantially equal to atmospheric pressure at a temperature lower than the critical point temperature of the carrier fluid.

[0025] Furthermore, the term "carrier fluid" is intended to mean a fluid belonging to the family of cryogenic liquids such as, for example, nitrogen, oxygen, ammonia, etc., and a general fluid having a critical temperature far below room temperature such as, for example, methane.

[0026] Basically, as shown in Figure 1, Plant 1 includes a cryogenic tank 10, a capacity tank 20, a supply circuit 30 connecting the cryogenic tank 10 to the capacity tank 20 and including a pump 31 and a main heat exchanger 32, an engine body 40, a discharge circuit 60, and a recirculation circuit 70.

[0027] The cryogenic tank 10 is configured to store the carrier fluid under the cryogenic conditions described above.

[0028] Under normal operating conditions, almost all of the carrier fluid in the cryogenic tank 10 is in a liquid state. However, as will be shown below, a relatively small proportion of the carrier fluid stored in the cryogenic tank 10 may be supplied in a gaseous state, or, if necessary, the carrier fluid may be converted to a solid state.

[0029] Advantageously, the carrier fluid is stored in the cryogenic tank 10 at a pressure approximately equal to the ambient pressure, thus resolving the problems associated with pressurized tanks.

[0030] Regarding dimensions and shape, the size of the cryogenic tank 10 can be determined "ad hoc" depending on the plant's use and space and autonomy requirements.

[0031] Advantageously, since almost all of the carrier fluid is stored in a virtually liquid state, it is possible to store large quantities.

[0032] In fact, for the same volume, a carrier fluid in liquid form has hundreds of times more mass than the same carrier fluid in gaseous form.

[0033] According to one aspect of the present invention, the cryogenic tank 10 may include a suction vacuum pump 11 configured to extract a portion of a gaseous carrier fluid from the cryogenic tank 10 in order to obtain a pressure lower than atmospheric pressure within the cryogenic tank 10.

[0034] In particular, the vacuum pump 11 can be operably positioned in the upper part of the cryogenic tank 10 to extract from the gaseous portion of the carrier fluid that is above the liquid portion of the carrier fluid.

[0035] The preferred use of the vacuum pump 11 allows for the determination of, for example, the triple point thermodynamic state of the carrier fluid in order to create the pressure and temperature conditions within the cryogenic tank 10.

[0036] More preferably, the vacuum pump 11 may be used to reach a pressure and temperature in the cryogenic tank 10 that is lower than the pressure and temperature that determine the triple point thermodynamic state.

[0037] This feature can be advantageously used, in non-limiting examples, in marine applications where it is necessary to at least partially solidify the carrier fluid stored in the cryogenic tank 10 in order to limit or further eliminate resonance phenomena and prevent the ship from capsizing.

[0038] This state is adjustable.

[0039] The supply circuit 30, which connects the cryogenic tank 10 to the capacity tank 20, is operably positioned downstream of the cryogenic tank 10.

[0040] Generally, the supply circuit 30 is configured to modify the thermodynamic conditions of the carrier fluid in order to make it available for energy-efficient use.

[0041] The supply circuit 30 includes a pump 31 configured to increase the pressure of the carrier fluid, and a main heat exchanger 32 operably positioned downstream of the pump 31, which is configured to promote heat exchange between the heat source and the carrier fluid in order to increase the temperature of the carrier fluid and evaporate the carrier fluid, preferably to completely evaporate the carrier fluid.

[0042] The pump 31 may be operably positioned within the cryogenic tank 10, or operably positioned in fluid communication with the cryogenic tank 10 via a conduit.

[0043] In particular, the pump 31 is operably positioned to draw a liquid carrier fluid from the cryogenic tank 10.

[0044] A check valve 33 may also be provided between the cryogenic tank 10 and the pump 31.

[0045] Advantageously, the check valve 33 allows for the intermittent use of the pump 31 without causing a "backflow" toward the cryogenic tank 10, and therefore without the pressure in the cryogenic tank 10 rising due to the carrier fluid returning from the supply circuit 30 to the cryogenic tank 10. This allows for an optimal solution to the size and insulation of the cryogenic tank 10.

[0046] Advantageously, by acting on a substantially incompressible liquid, the pump 31 requires only negligible operating energy costs overall compared to the mechanical energy generated by the plant 1.

[0047] In a further embodiment, the pump 31 can be controlled and adjusted according to the speed of the engine body 40.

[0048] Functionally, as will be described in detail below, the pump 31 causes an increase in the pressure of the carrier fluid to obtain a high-pressure carrier fluid in a liquid state.

[0049] Preferably, the carrier fluid is typically brought to a supercritical pressure.

[0050] This transformation is shown on the Mollier diagram by segment AB in Figure 4.

[0051] The check valve 34 may be placed between the pump 31 and the main heat exchanger 32.

[0052] The check valve 34 may be configured to relieve the load on the pump 31 caused by the backflow, which may be a gaseous carrier fluid returning from the heat exchanger 32, and the effects of the pump 31 on the carrier fluid flowing through the supply circuit 30.

[0053] The main heat exchanger 32 is configured to heat the high-pressure liquid carrier fluid to accelerate its state change.

[0054] In particular, the main heat exchanger 32 is configured to facilitate the state change of the carrier fluid from a liquid state to a gaseous state, preferably a supercritical gas phase.

[0055] In particular, the main heat exchanger 32 raises the temperature reached by the carrier fluid above its critical temperature.

[0056] Furthermore, the main heat exchanger 32 is configured to maintain the carrier fluid pressure at approximately a constant value relative to the value obtained following the operation of the pump 31.

[0057] In this specification, the term “heat source” is intended to mean any heat source having a temperature higher than the carrier fluid at the outlet of pump 31, preferably higher than the critical temperature of the carrier fluid.

[0058] This heat source can have any properties, as long as it is suitable for the purpose.

[0059] According to exemplary and therefore non-limiting embodiments, air or seawater can be used, as in the case of known methane regasification applications.

[0060] According to further embodiments, the main heat exchanger 32 can be associated with, for example, a solar collector plant that acts as a heat source, in order to obtain thermal energy at virtually zero cost.

[0061] According to further embodiments, plant 1 may include an auxiliary plant, not shown in the figure, which is associated with or can be associated with a main heat exchanger 32, in order to generate mechanical energy, which transfers its own waste heat to the main heat exchanger 32, acting as a cold heat source.

[0062] Preferably, this auxiliary plant for generating mechanical energy includes a Stirling engine.

[0063] In particular, the Stirling engine is positioned between the heat source and the main heat exchanger 32.

[0064] In particular, the Stirling engine uses heat from a heat source to supply energy to the Stirling engine's expansion chamber, while using the main heat exchanger 32 to extract energy from the Stirling engine's compression chamber. In other words, the carrier fluid acts as a cooling source, extracting heat from the Stirling engine.

[0065] In the case of a Stirling engine, it may be particularly advantageous to provide a heat source with a temperature higher than that of the atmosphere and / or seawater. For example, the heat source may include a low-enthalpy plant for heat recovery from a solar collector or other generation cycle.

[0066] Structurally, the main heat exchanger 32 can be made according to any known type of configuration, as long as it is suitable for the purpose.

[0067] Functionally, heating of the carrier fluid within the main heat exchanger 32 occurs in basically two steps.

[0068] In the first step, the high-pressure liquid carrier fluid receives heat from the heat source via the main heat exchanger and undergoes a phase change, changing from a liquid to a gaseous state.

[0069] This change in state allows the high-pressure gaseous carrier fluid to produce a "hydraulic press" effect.

[0070] In fact, the volume of a carrier fluid in a liquid state is less than a fraction of the volume occupied by the same mass of a carrier fluid in a gaseous state.

[0071] Therefore, in the second heating step, this amplification effect is used to further increase the temperature of the high-pressure gaseous carrier fluid.

[0072] This transformation is shown on the Mollier diagram by segment BC in Figure 4.

[0073] Therefore, functionally, the supply circuit 30 converts the low-pressure liquid carrier fluid from the cryogenic tank 10 into a high-pressure gaseous carrier fluid.

[0074] In summary, the carrier fluid stored in the cryogenic tank 10 is under cryogenic conditions, that is, it is at a cryogenic temperature, higher than the melting point of the carrier fluid, and at a pressure approximately equal to atmospheric pressure.

[0075] In other words, carrier fluids under cryogenic conditions are not in a state where they can be used advantageously and directly generate mechanical work.

[0076] By using the supply circuit 30, the pressure of the carrier fluid is increased by the pump 31, and its temperature is changed by the main heat exchanger 32. Furthermore, the main heat exchanger 32 facilitates the change of state of the carrier fluid from liquid to gas.

[0077] Thus, the carrier fluid at the outlet of the supply plant is in a "original liquid" state (i.e., a high-pressure gas state). This state is indicated by reference numeral "C" in Figure 4.

[0078] The capacity tank 20 is movably positioned downstream of the main heat exchanger 32 and is in fluid communication with the main heat exchanger 32.

[0079] As shown in Figure 1, the supply circuit 30 may further include a measuring tank 73, a valve 72 configured to shut off the supply circuit 30, and a valve 73 positioned between the measuring tank 73 and the capacity tank 20.

[0080] The capacity tank 20 is configured to collect a predetermined amount of "original liquid" carrier fluid from the supply circuit 30 and mix it with the amount of recirculated carrier fluid recovered from the engine body 40 by the recirculation circuit 70, in order to supply it favorably to the engine body 40.

[0081] In other words, the capacity tank 20 is preferably sized to mix the "original liquid" carrier fluid and the recirculated carrier fluid in order to obtain a predetermined amount of the carrier fluid defined as the "supply carrier fluid".

[0082] Furthermore, the capacity tank 20 is of a suitable size for measuring the supply carrier fluid that the engine body 40 should supply.

[0083] This carrier fluid, defined as the "supply carrier fluid," has a pressure and temperature state that is the average of the pressure and temperature states of the "source liquid" carrier fluid and the recirculated carrier fluid. This "supply" state is indicated by reference number "E" in Figure 4.

[0084] The characteristics of the recirculation circuit 70 and the ratio of the "original liquid" carrier fluid to the recirculated carrier fluid are described in detail below.

[0085] The "recirculation" state is instead indicated by reference number "D" in Figure 4.

[0086] The engine body 40 is configured to generate mechanical energy and includes at least one working chamber 41 having a capacity tank 20 from which a supply carrier fluid is supplied, an inlet port 42 arranged in fluid communication with the capacity tank 20, and an outlet port 43 connected to a discharge circuit 60 for used carrier fluid, indicated by reference numeral "G" in Figure 4.

[0087] The expansion of the "original liquid" carrier fluid is indicated by reference number "EG" in Figure 4.

[0088] The working chamber 41 is configured by at least one movable wall 44 to convert the expansion and / or movement of the supply carrier fluid into mechanical work.

[0089] Preferably, the movable wall 44 is configured to move between the top dead center and the bottom dead center. Alternatively, the movable wall 44 may be configured to rotate around an axis.

[0090] The term "spent carrier fluid" is intended to refer to the carrier fluid in this post-conversion state, which has low enthalpy and temperature and pressure conditions suitable for release into the environment.

[0091] The engine body 40 can be manufactured in any type, as long as it is suitable for the required purpose.

[0092] According to a preferred embodiment, the engine body 40 is of the reciprocating type.

[0093] In particular, in a manner known by itself, the engine body 40 includes at least one cylinder 45 defining an operating chamber 41 having an inlet port 42 associated with a supply valve 46 and an outlet port 43 associated with a discharge valve 47. The cylinder 45 houses a piston 48 that is slidably constrained within the cylinder 45 and integral with its respective movable wall 44, and a connecting rod 49 constrained to the piston 48. Finally, the connecting rod 49 is constrained to a drive shaft 50.

[0094] Functionally, the engine body 40 is configured such that the conversion operation of the engine body 40 to the supply carrier fluid can be substantially divided into two separate operating steps.

[0095] In the first operating step, the supply valve 46 is opened, and high-pressure supply carrier fluid from the capacity tank 20 is sent to the working chamber 41 of the engine body 40, which causes the first movement of the movable wall 44, and therefore the first movement of the drive shaft 50.

[0096] Since this is a mechanical mass transfer phenomenon, the pressure, temperature, and enthalpy of the supply carrier fluid can be considered to be approximately constant during this first operating step.

[0097] In other words, mechanical energy is generated as a result of the transfer of the mass of the supply carrier fluid to the working chamber 41.

[0098] Furthermore, in the first operating step, the supply carrier fluid maintains its pressure and enthalpy at approximately constant levels without undergoing thermodynamic transformation.

[0099] After the first operating step is completed, the second operating step is initiated. This second operating step consists of a transformation similar to a polytropic transformation, which exchanges the mechanical work with the movable wall 44 of the operating chamber 41.

[0100] In particular, during the second operating step, a portion of the enthalpy of the supply carrier fluid is converted into mechanical energy.

[0101] In particular, the temperature and pressure of the supplied carrier fluid decrease, and the carrier fluid can be considered used carrier fluid.

[0102] In the second operating step, the transfer of the mass of the supply carrier fluid from the capacity tank 20 to the working chamber 41 is completed, so the mass of the carrier fluid in the working chamber can be considered constant.

[0103] The mechanical energy obtained in this second expansion step is negligible compared to the mechanical energy obtained in the first transfer step.

[0104] In the following description, the travel cycle of the engine body 40 is described as a function of the angle assumed by the drive shaft 50 during its rotation, which occurs in a clockwise direction.

[0105] In particular, the position of the drive shaft 50 when the movable wall 44 is at top dead center is assumed to be at an angle of 0 degrees.

[0106] In particular, during the first operating step, the drive shaft 50 moves from 12 degrees to 50 degrees, while during the second operating step, the drive shaft 50 moves from 50 degrees to 180 degrees.

[0107] In further embodiments not shown in the attached diagrams, the engine body 40 may be of the fluid engine type.

[0108] In this embodiment, the first operation step and the second operation step occur substantially simultaneously.

[0109] Once the operation step is complete, the spent carrier fluid is at least partially sent to the discharge circuit 60. The discharge circuit 60 is designed to discharge the carrier fluid into the environment under the conditions indicated by reference numeral "F" in the Mollier diagram of Figure 4. The discharge circuit 60 may include a collection tank 61 for the spent carrier fluid and a discharge duct designed to discharge the spent carrier fluid at least partially from Plant 1.

[0110] The discharge circuit 60 may further include a discharge valve 62.

[0111] According to a further aspect of the present invention, plant 1 may include a system 80 for stopping the operation of the engine body 40, which is configured to stop the operation of the plant.

[0112] Preferably, the shutdown system 80 can be associated with the pump 31 so as to block the extraction of carrier fluid from the cryogenic tank 10 and thus its supply to the plant 1.

[0113] The stop system 80 can also be operated through the valve 74 connected to the stop system 80.

[0114] According to one aspect of the present invention, the plant 1 may include a replenishment circuit 90 associated with the discharge circuit, configured to replenish the cryogenic tank 10 with a portion of the spent fluid passing through the discharge circuit 60, particularly a portion of the spent fluid passing through the collection tank 61.

[0115] Alternatively, plant 1 may include a replenishment circuit 90, which is associated with the supply circuit and configured to replenish the cryogenic tank 10 with a portion of the gaseous carrier fluid that has exited the main heat exchanger 32.

[0116] Advantageously, the replenishment circuit 90 prevents the pressure drop in the cryogenic tank 10 from excessively decreasing due to the extraction of the liquid carrier fluid by the pump 31, thereby avoiding problems such as solidification of the carrier fluid.

[0117] In fact, the gaseous carrier fluid introduced into the cryogenic tank 10 by the replenishment circuit 90, after subtracting the liquid carrier fluid extracted by the pump 31, maintains a nearly constant pressure in the cryogenic tank 10.

[0118] Advantageously, the replenishment circuit 90 also allows the pump to draw from the cryogenic tank 10 an amount that balances the pressure drop caused by the instantaneous consumption of liquid carrier fluid required, for example, for the operation of plant 1.

[0119] In other words, when the pump 31 withdraws the carrier fluid from the cryogenic tank 10, the operating pressure of the cryogenic tank 10 is restored by replacing the volume of the liquid carrier fluid withdrawn by the pump 31 with the volume of the reintegrated gaseous spent carrier fluid.

[0120] Pilot-operated valves for flow blocking and adjustment can be operably positioned in the discharge circuit 60 and the replenishment circuit 90 for flow adjustment.

[0121] According to a particular aspect of the present invention, the recirculation circuit 70 is designed to send a portion of the spent carrier fluid drawn from the working chamber 41 of the engine body 40 to the capacity tank 20.

[0122] Advantageously, the use of the recirculation circuit 70 allows the spent carrier fluid discharged into the atmosphere from the discharge circuit 60 to be in environmentally safe and suitable temperature and pressure conditions. In other words, the spent carrier fluid is discharged at a pressure and temperature that does not harm plant 1 and the environment.

[0123] In fact, the recirculation circuit 70 is configured to draw a portion of the used carrier fluid from the working chamber 41, increase its temperature and pressure, and, after polytropic compression as shown in the Mollier diagram at reference number "GD" in Figure 4, introduce it into the capacity tank 20. In the capacity tank 20, the recirculated carrier fluid mixes with the "original liquid" carrier fluid from the supply circuit 30, thereby increasing its pressure and temperature. This state of the carrier fluid is shown in the Mollier diagram at reference number "D" in Figure 4.

[0124] In fact, the temperature of the recirculated carrier fluid is higher than the temperature of the "original liquid" carrier fluid from the supply circuit 30 after polytropic compression.

[0125] In contrast, the pressure of the recirculated carrier fluid is lower than the pressure of the "original liquid" carrier fluid from the supply circuit 30.

[0126] The mixing of the recirculated carrier fluid with the "original liquid" carrier fluid from the supply circuit 30 occurs in a predetermined controlled manner that defines the supply carrier fluid.

[0127] In other words, the amounts of recirculated carrier fluid and carrier fluid from the supply circuit 30 must satisfy a predetermined mutual ratio as described below.

[0128] According to a preferred embodiment, this mass ratio between the recirculated carrier fluid and the "original liquid" carrier fluid is 23 to 1.

[0129] Polytrope compression can be performed, depending on the embodiment of Plant 1, using a suitable compressor or, advantageously, the engine body 40, by utilizing the return stroke of the piston 48 from bottom dead center to top dead center.

[0130] Since the two embodiments of Plant 1 have substantially the same characteristics as the cryogenic tank 10 and the supply circuit 30, the technical characteristics of the engine body 40 and the recirculation circuit 70 will be described in detail below with particular attention to them.

[0131] The first embodiment is schematically shown in Figures 1, 2A-2C and 3A-3F.

[0132] In this embodiment, the engine body is of the reciprocating motion type as shown in Figures 2A to 2C.

[0133] In this embodiment, the engine body 40 is - Accepting the supply carrier fluid, - To induce an expansion phase in the supplied carrier fluid, - Converting the displacement and / or expansion of the supplied carrier fluid into mechanical energy, - To induce a compression phase of the spent carrier fluid and It was configured to perform the following actions.

[0134] In other words, the engine body 40 is configured to perform first and second operating steps and a polytrope compression step with respect to the supply carrier fluid.

[0135] Furthermore, in this embodiment, the engine body 40 is integrated with the recirculation circuit 70 and the energy dissipation and mixing tank 20.

[0136] In other words, the capacity tank 20 and the recirculation circuit 70 are formed within the engine body 40 and are defined by the operation and movement of their components. The recirculation circuit 70 and / or the capacity tank 20 may be integrated with the engine body 40.

[0137] In detail, the engine body 40 has a supply chamber 51 and a discharge chamber 52, which are formed within the cylinder and are located between the operating chamber 41 and the inlet port 42 and between the operating chamber 41 and the outlet port 43, respectively.

[0138] The supply valve 46 and the discharge valve 47 are associated with the supply chamber 51 and the discharge chamber 52, respectively.

[0139] In particular, each of the valves 46 and 47 is a poppet valve and includes lower planar elements 46a and 47a configured to close the bottoms of the respective chambers 51 and 52 in order to define airtight separation from the working chamber 41, and stems 46b and 47b integrated with the lower planar elements 46a and 47a.

[0140] Each of the valves 46 and 47 is slidably constrained in their respective chambers 51 and 52 to define translational movement along a linear trajectory.

[0141] The inlet port 42 is formed in the engine body 40 at the upper part of the engine body 40 and is oriented substantially transversely to the longitudinal axis of the supply chamber 51.

[0142] Similarly, the outlet port 43 is formed in the engine body 40 at the upper part of the engine body 40 and is substantially transverse to the longitudinal axis of the discharge chamber 52.

[0143] The supply valve 46, according to a particular structural embodiment, has a cavity 46c formed within the stem 46b that defines a first storage volume "V1". The stem 46b also preferably has a through hole 46d formed in the short direction of the stem 46b that leads to the cavity 46c.

[0144] The valve also has a closing element 46e for closing the cavity 46c.

[0145] Preferably, the closing element 46e is threaded, and the size of the first storage volume "V1" can be adjusted depending on how tightly it is tightened within the cavity 46c.

[0146] The supply chamber 51, together with the supply valve 46, defines a second storage volume "V2". In other words, this second storage volume "V2" is defined as the volume of the supply chamber 51 minus the size of the supply valve 46 and the first storage volume "V1".

[0147] In this embodiment, the first storage volume "V1" and the second storage volume "V2" defined in this way define the capacity tank 20.

[0148] According to a further aspect of the present invention, the dimensional ratio of the first storage volume "V1" to the second storage volume "V2" is 1 to 23.

[0149] The supply valve 46 is movable within the supply chamber 51 so that it can take on one of four different operating configurations.

[0150] In particular, the supply valve 46 can take a closed configuration, also defined as the first configuration shown in Figure 2c, in which the through-hole 46d faces the inlet port 42 of the engine body 40, and the lower planar element 46a closes the supply chamber 51 at its bottom. Furthermore, in this closed configuration, the stem 46b is substantially attached to the wall of the engine body 40 and closes the supply chamber 51 at its top.

[0151] When the supply valve 46 is lowered, it can take on a second configuration in which the through-hole 46d does not face the inlet port 42, the inlet port 42 is closed by the stem 46b, and the lower planar element 46a closes the supply chamber 51 at the bottom. In this configuration, the stem 46b still closes the supply chamber 51 at the top so that the first storage volume "V1" does not come into fluid communication with the second storage volume "V2".

[0152] The supply valve 46 can be lowered further to take on a third configuration, in which the through-hole 46d does not face the inlet port 42, the inlet port 42 is closed by the stem 46b, and the lower planar element 46a closes the supply chamber 51 at the bottom. In this configuration, the first storage volume "V1" is in fluid communication with the second storage volume "V2".

[0153] Finally, the supply valve 46 can also be in an open configuration, which is also defined as a fourth configuration, in which case the stem 46b closes the inlet port 42 and the first storage volume "V1" and the second storage volume "V2" are in fluid communication with the operating chamber 41.

[0154] On the other hand, the discharge valve 47 can have two operating configurations.

[0155] In particular, the discharge valve 47 can be configured in a closed state where the discharge valve 47 closes the supply chamber 52 and the outlet port 43 at its bottom, or in an open state where the outlet port 43 is in fluid communication with the operating chamber 41.

[0156] Advantageously, according to further structural embodiments as shown in the attached figures, in the open configuration, since the supply valve 46 or the discharge valve 47 may enter the operating chamber 41 at least partially, a plurality of recesses are formed on the movable wall 44, and the recesses are formed at least partially complementary to the supply valve 46 and the discharge valve 47 so as not to come into contact with the supply valve 46 and the discharge valve 47.

[0157] The movement cycle of the engine body 40 in the above embodiment is described in detail below.

[0158] In the following description, the travel cycle of the engine body 40 is described as a function of the angle assumed by the drive shaft 50 during its rotation, which occurs in a clockwise direction.

[0159] In particular, the position of the drive shaft 50 when the movable wall 44 is at top dead center is assumed to be at an angle of 0 degrees.

[0160] In particular, Figure 3A shows the first step in which the supply valve 46 is in a closed configuration or a first configuration and the discharge valve 47 is in a closed configuration.

[0161] In this step, the recirculated carrier fluid is located in the second storage volume "V2".

[0162] The first storage volume "V1" is filled with the "original liquid" carrier fluid supplied from the supply circuit 30 through the inlet port 42.

[0163] Preferably, according to the preferred use of Plant 1, the mass ratio of the "original liquid" carrier fluid to the recirculated carrier fluid is 1 to 23. Advantageously, this allows for very low consumption.

[0164] The movable wall 44 is close to the top dead center.

[0165] During this step, the drive shaft 50 moves from an angle of 356 degrees to an angle of 6 degrees.

[0166] Figure 3B shows the next step in the transfer cycle, with the discharge valve 47 in a closed configuration. During this step, the supply valve 46 is first switched to a second configuration to close the inlet port 42, and then switched to a third configuration so that the first storage volume "V1" is in fluid communication with the second storage volume "V2". In this configuration, the recirculated carrier fluid can be mixed with the "original liquid" carrier fluid from the supply circuit 30, thereby obtaining the supply carrier fluid.

[0167] This step corresponds to the first operation step of the engine body 40 described above.

[0168] During this step, the movable wall 44 remains substantially near top dead center, and the drive shaft 50 moves from an angle of 6 degrees to an angle of 12 degrees.

[0169] Figure 3C shows a step in which the supply valve 46 is switched to an open configuration or a fourth configuration, while the discharge valve 47 is in a closed configuration.

[0170] During this step, the first storage volume "V1" and the second storage volume "V2" are in fluid communication with the operating chamber 41 so that the supply carrier fluid can move into the operating chamber 41. This step corresponds to the second operating step of the engine body 40 described above. The movable wall 44 is moved downward by the thrust of the supply carrier fluid. During this step, the drive shaft 50 moves from an angle of 12 degrees to an angle of 170 degrees.

[0171] Figure 3D shows the steps of the transfer cycle with the supply valve 46 and discharge valve 47 in an open configuration.

[0172] During this step, a large amount of used carrier fluid, corresponding to the amount of carrier fluid arriving from the supply circuit 30, is sent from the operating chamber 41 to the discharge circuit 60. The movable wall 44 is near the bottom dead center.

[0173] During this step, the drive shaft 50 moves from an angle of 170 degrees to an angle of 180 degrees.

[0174] Figure 3E shows the steps of the transfer cycle in which the supply valve 46 is in an open configuration or a first configuration, while the discharge valve 47 is switched to a closed configuration. During this step, the spent carrier fluid is adiabatically compressed by the movable wall 44.

[0175] During this step, the drive shaft 50 moves to a 180-degree angle.

[0176] During this step, the working chamber 41 further accommodates the amount of carrier fluid corresponding to the recirculated carrier fluid.

[0177] Finally, Figure 3F shows the steps of the transfer cycle, where the recirculated carrier fluid is in the capacity tank 20 after polytrope compression.

[0178] During this step, the drive shaft 50 moves from an angle of 180 degrees to an angle of 356 degrees.

[0179] Advantageously, this embodiment has several advantages that make its use very effective.

[0180] The first advantage relates to the simplicity of the engine body 40's structure. In fact, the engine body 40 is substantially configured as a typical diesel engine. Advantageously, in other words, any existing diesel or Otto engine can be converted into the engine body 40.

[0181] In particular, the engine body 40 of the present invention can be obtained by modifying an existing diesel or Otto engine. In this case, the modification is limited to the control of the cylinder head and valves, which can be done mechanically or electronically.

[0182] The second advantage relates to the compactness of Plant 1. In fact, the recirculation circuit 70 and the capacity tank 20 are formed within the engine body 40.

[0183] Herein, further embodiments of Plant 1, not shown in the attached diagrams, are described.

[0184] In this embodiment, the recirculation circuit 70 is associated with the collection tank 61 of the discharge circuit 60 and includes a compressor that is connected to and moved by the engine body 60.

[0185] Basically, a compressor is configured to perform three distinct functions in particular: - A portion of the spent carrier fluid, calculated for recirculation in volumetric and according to the desired plant discharge temperature, is extracted from the collection tank 61 by a pilot-operated valve for flow blocking and adjustment. - Compressing the carrier fluid, - To send the compressed used carrier fluid to the capacity tank 20. Here, pressure and temperature can be measured using suitable measuring instruments.

[0186] Furthermore, a check valve can be placed between the compressor and the capacity tank 20, so that the carrier fluid contained in the capacity tank 20 does not return to the compressor.

[0187] According to one aspect of the present invention, the operation of the plant can be entrusted to the rotation of the drive shaft 50 or to a control unit.

[0188] The present invention also relates to a method for generating mechanical energy from a carrier fluid under cryogenic conditions, which can preferably be carried out by the aforementioned plant 1.

[0189] The method includes a preliminary step of preparing a cryogenic tank 10 to contain a carrier fluid at an extremely low temperature Tcryo and pressure level Pcryo. This state of the carrier fluid is indicated by reference numeral "A" in the Mollier diagram of Figure 4.

[0190] The method also includes a preliminary step of preparing a capacity tank 20 and an engine body 40 designed to produce an expansion phase and a compression phase.

[0191] The method further includes a preliminary step of supplying a mass M2 of carrier fluid at recirculation temperature Trec and pressure level Prec to a capacity tank 20. This mass M2 of the carrier fluid in the aforementioned recirculation state is indicated by reference number "D" in the Molyet diagram of Figure 4.

[0192] At this point, the method includes a circular step.

[0193] In particular, the method includes the step of increasing the pressure of the carrier fluid from the Pcryo level to the Pproc level, where Pproc is greater than both Pcryo and Prec. This state is indicated by reference numeral "B" in the Mollier diagram of Figure 4.

[0194] Preferably, the step of increasing the pressure of the carrier fluid from the Pcryo level to the Pproc level is performed by the pump 31.

[0195] Next, the method includes the steps of raising the temperature of the carrier fluid from Tcryo to a first process temperature Tproc1, where Tproc1 is greater than Tcryo, and raising the temperature of the carrier fluid from Tproc1 to a second process temperature Tproc2, where Tproc2 is greater than Tproc1.

[0196] This state is indicated by reference number "C" in the Mollier diagram of Figure 4.

[0197] These steps are preferably performed by the main heat exchanger 32.

[0198] Furthermore, in these steps, the carrier fluid is converted from a liquid to a gas, thereby obtaining the carrier fluid in the aforementioned "original liquid" state.

[0199] The method then includes the step of supplying a mass M1 of working fluid with temperature Tproc2 and pressure level Pproc to a capacity tank 20.

[0200] Preferably, the carrier fluid mass M2 comes from the recirculation circuit 70, while the carrier fluid mass M1 comes from the supply circuit 30.

[0201] At this point, the method includes the step of mixing the masses M1 and M2 of the carrier fluid, which are the "source liquid" and the recirculated fluid, respectively, to obtain the mass M1 + M2 of the carrier fluid at the supply temperature Tfeed and pressure level Pfeed.

[0202] The pressure Prec of the recirculating carrier fluid is assumed to be lower than the pressure Pfeed of the supply carrier fluid. Furthermore, the temperature Trec of the recirculating carrier fluid is higher than the temperature Tfeed of the supply carrier fluid.

[0203] This mass M1+M2 represents the aforementioned supply carrier fluid state. This state is indicated by reference number "E" in the Mollier diagram in Figure 4.

[0204] Once the mass M1+M2 of the carrier fluid is obtained, it is supplied from the capacity tank 20 to the engine body 40 at a pressure level Pfeed and a supply temperature Tfeed.

[0205] The method then includes the step of expanding the mass M1+M2 of the carrier fluid in the engine body 40 in order to reduce the pressure from level Pfeed to level Pex below Pproc and to reduce the temperature from Tfeed to Tex below Tfeed, thereby generating mechanical energy.

[0206] This step is indicated by the reference number "EG" in the Mollier diagram in Figure 4.

[0207] The final state of carrier fluid expansion is indicated by reference number "G" in the Mollier diagram in Figure 4.

[0208] Finally, the method includes the step of discharging the mass M1 of the fluid toward the external environment.

[0209] This step is preferably performed in the discharge circuit 60. The discharge state is indicated by reference number "F" in the Mollier diagram of Figure 4.

[0210] The method further includes the step of increasing the pressure from level Pex to level Prec and increasing the temperature from Tex to Trec, and compressing the mass M2 of the fluid to supply a mass M2 at pressure level Prec and supply temperature Trec to the capacity tank 20. This step is indicated by reference number "GD" in the Mollier diagram of Figure 4.

[0211] Preferably, the steps of increasing the pressure from level Pex to level Prec and increasing the temperature from Tex to Trec, and compressing the mass M2 of the fluid to supply a mass M2 at pressure level Prec and supply temperature Trec to the capacity tank 20 are performed by the recirculation circuit 70.

[0212] According to one embodiment of the method, the carrier fluid used is nitrogen. In this embodiment, the pressure and temperature values ​​are as follows: - The pressure level Patm is approximately equal to atmospheric pressure, and - The pressure level Pproc has a value in the range of approximately 300 bar to approximately 400 bar. - The pressure level Pfeed has a value in the range of approximately 250 bar to approximately 300 bar. - The pressure level Pex has a value in the range of approximately 2 bar to approximately 4 bar. - The temperature Tcryo is approximately -205°C. - The temperature Tproc1 is approximately -80°C. - The temperature Tproc2 is approximately +70°C. - The temperature Trec is approximately +680°C. - The temperature Tfeed is approximately +480°C, and - The temperature range (Tex) is approximately -20°C to +20°C.

[0213] According to a further embodiment of the method, the carrier fluid is methane. In this embodiment, the pressure and temperature values ​​are as follows: - The pressure level Patm is approximately equal to atmospheric pressure, and - The pressure level Pproc has a value in the range of approximately 200 bar to approximately 220 bar. - The pressure level Pfeed has a value in the range of approximately 150 bar to approximately 200 bar. - The pressure level Pex has a value in the range of approximately 2 bar to approximately 4 bar. - The temperature Tcryo is in the range of approximately -130°C to approximately -90°C. - The temperature Tproc1 is in the range of approximately -40°C to approximately -30°C. - The temperature Trec is approximately +360°C. - The temperature Tfeed is in the range of approximately +280°C to approximately +300°C, and - The temperature range (Tex) is approximately -20°C to +20°C.

[0214] Advantageously, the present invention solves the shortcomings encountered in the prior art.

[0215] In particular, the objective achieved is to provide a plant and method for generating mechanical energy from a carrier fluid under cryogenic conditions, which is free from condensation and / or "ice" problems during discharge of the plant itself.

[0216] This result is achieved by the presence of the recirculation circuit 70, which allows the temperature of the spent carrier fluid at the outlet of plant 1 to be sufficient to prevent condensation and / or ice formation.

[0217] A further objective achieved is to provide a plant and method for generating mechanical energy from a carrier fluid under cryogenic conditions, and to provide a plant and method that can operate with very little carrier fluid consumption.

[0218] This result is achieved by the recirculation circuit 70, which enables very low consumption of carrier fluid.

[0219] A further objective achieved is to provide a plant and method for generating mechanical energy from a carrier fluid under cryogenic conditions, and to provide a plant and method that does not affect the environment.

[0220] This result is achieved by the possibility of operation without combustion.

Claims

1. A plant (1) for generating mechanical energy from a carrier fluid under cryogenic conditions, - A cryogenic tank (10) configured to store the carrier fluid under the aforementioned cryogenic conditions, - Capacity tank (20), - A supply circuit (30) connecting the cryogenic tank (10) to the capacity tank (20), comprising a pump (31) configured to increase the pressure of the carrier fluid, and a main heat exchanger (32) located downstream of the pump (31), configured to promote heat exchange between a heat source and the carrier fluid in order to raise the temperature of the carrier fluid and evaporate the carrier fluid. - An engine body (40) configured to generate the aforementioned mechanical energy, comprising at least one working chamber (41) having an inlet port (42) arranged in fluid communication with the capacity tank (20) and an outlet port (43) connected to a discharge circuit (60) for used carrier fluid. The plant (1) includes a recirculation circuit (70) designed to send a portion of the used carrier fluid to the capacity tank (20).

2. The engine body (40) is - Accepting the aforementioned carrier fluid, - To induce the expansion phase of the carrier fluid, - Converting the displacement and / or expansion of the carrier fluid into mechanical energy, - To induce a compression phase of the used carrier fluid and The plant (1) according to claim 1, configured to perform the following.

3. The plant (1) according to claim 1 or 2, wherein the recirculation circuit (70) and / or the capacity tank (20) are formed within the engine body (40).

4. The plant (1) according to any one of claims 1 to 3, wherein the engine body (40) is of the reciprocating type.

5. The plant (1) according to any one of claims 1 to 4, comprising a replenishment circuit (90) connected to the discharge circuit (60) and / or the supply circuit (30) and configured to send a portion of the gaseous carrier fluid to the cryogenic tank (10).

6. Plant (1) according to any one of claims 1 to 5, comprising an auxiliary plant for generating mechanical energy, the auxiliary plant preferably comprising an engine, and more preferably comprising a Stirling engine connected to or connectable to the main heat exchanger (32), the Stirling engine being operably positioned between the heat source and the main heat exchanger (32) to transfer heat to the carrier fluid by the main heat exchanger (32).

7. The plant according to any one of claims 1 to 6, wherein the engine body includes a supply valve (46) connected to the inlet port (42) and slidably inserted into a supply chamber (51), the supply chamber facing the operating chamber (41) at its top, and the supply valve (46) includes a lower planar element (46a) configured to close the bottom of the supply chamber (51) in a closed configuration of the supply valve (46) to isolate the supply chamber (51) from the operating chamber (41), and a stem (46b) having a through hole (46d) configured to close the supply chamber (51) at its top in the closed configuration of the supply valve (46), wherein in the closed configuration, the through hole (46d) faces the inlet port (42) to allow the inlet port (42) to communicate with a cavity (46c) formed in the stem (46b).

8. A method for generating mechanical energy from a carrier fluid under cryogenic conditions, - A preliminary step of preparing a cryogenic tank (10) to contain a fluid at an extremely low temperature Tcryo and pressure level Pcryo, - Preliminary step of preparing the capacity tank (20), - A preliminary step of preparing the engine body (40) designed to house the expansion and compression phases, - A preliminary step of supplying the mass M2 of pressure level Prec and supply temperature Trec to the capacity tank (20). Includes, - A circulation step in which the pressure of the carrier fluid is increased from the Pcryo level to the Pproc level, wherein Pproc is greater than Pcryo and Prec. - A circulation step in which the temperature of the carrier fluid is raised from Tcryo to a first process temperature Tproc1, wherein Tproc1 is higher than Tcryo. - A circulation step of raising the temperature of the carrier fluid from Tproc1 to a second process temperature Tproc2, wherein Tproc2 is higher than Tproc1, - A circulation step of supplying the mass M1 of the working fluid with the temperature Tproc2 and pressure level Pproc to the capacity tank (20), - A circulation step in which the masses M1 and M2 of the carrier fluid are mixed to obtain a mass M1 + M2 with a supply temperature Tfeed and a pressure level Pfeed, - A circulation step in which the mass M1 + M2 of the carrier fluid having the pressure level Pfeed and supply temperature Tfeed is supplied from the capacity tank (20) to the engine body (40), - A circulation step in which the mass M1 + M2 of the carrier fluid in the engine body (40) is expanded to generate mechanical energy in order to lower the pressure from level Pfeed to level Pex below Pfeed, and to lower the temperature from Tfeed to Tex below Tfeed, - A circulation step in which the mass M1 of the fluid is discharged toward the external environment. - A circulation step in which the mass M2 of the fluid is compressed to increase the pressure from level Pex to level Prec and the temperature from Tex to Trec, and the mass M2 at the pressure level Prec and supply temperature Trec is supplied to the capacity tank (20). Methods that include this.

9. The method according to claim 8, wherein the carrier fluid is nitrogen.

10. Regarding pressure levels, - The pressure level Patm is approximately equal to atmospheric pressure, and - The pressure level Pproc has a value in the range of approximately 300 bar to approximately 400 bar. - The pressure level Pfeed has a value in the range of approximately 250 bar to approximately 300 bar. - The pressure level Pex has a value in the range of approximately 2 bar to approximately 4 bar. Regarding temperature levels, - The temperature Tcryo is approximately -205°C. - The temperature Tproc1 is approximately -80°C. - The temperature Tproc2 is approximately +70°C. - The temperature Trec is approximately +680°C. - The temperature Tfeed is approximately +480°C, and - The method according to claim 9, wherein the temperature Tex is in the range of about -20°C to about +20°C.

11. The method according to claim 8, wherein the carrier fluid is methane.

12. Regarding pressure levels, - The pressure level Patm is approximately equal to atmospheric pressure, and - The pressure level Pproc has a value in the range of approximately 200 bar to approximately 220 bar. - The pressure level Pfeed has a value in the range of approximately 150 bar to approximately 200 bar. - The pressure level Pex has a value in the range of approximately 2 bar to approximately 4 bar. Regarding temperature levels, - The temperature Tcryo is in the range of approximately -130°C to approximately -90°C. - The temperature Tproc1 is in the range of approximately -40°C to approximately -30°C. - The temperature Trec is approximately +360°C. - The temperature Tfeed is in the range of approximately +280°C to approximately +300°C, and - The method according to claim 11, wherein the temperature Tex is in the range of about -20°C to about +20°C.

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