ITMI20090039A1 - PROCEDURE AND SYSTEM FOR THE GENERATION OF USING ENERGY LIQUID AND OR GASEOUS HEAT SOURCES ON BOARD OF NAVAL UNITS - Google Patents

Description

PROCEDURE AND SYSTEM FOR THE GENERATION OF ENERGY USING LIQUID AND / OR GASEOUS HEAT SOURCES ON BOARD NAVAL UNITS.

DESCRIPTION

The present invention relates to a process and a system for the generation of energy using liquid and / or gaseous heat sources on board naval units.

As for naval applications, in the period between the years 1970-1980, the United States Navy studied the application of Rankine cycles by coupling them directly to the propulsion system to increase its power. The system was not fully applied due to difficulties mainly due to the use of high pressure circuits in naval units. With a view to increasing the autonomy of naval units, it is convenient to use ORC (Organic Rankine Cycle) cycles using organic fluids which do not present the risk of condensation in the turbine. In the patent "METHGD AND APPARATUS FOR DECREASING MARINE VESSEL POWER PLANT EXHAUST TEMPERATURE" ~ US7121906B2 (Oct. 17, 2006) and in the patent application "RANKINE CYCLE DEVICE HAVING MULTIPLE TURBO-GENERATORS" -US 2006/0112692 Al (Jun. 1, 2006) describes methods and equipment for reducing the thermal profile emitted by the fumes of naval units and the production of electricity on board. The methods described in these patents use organic refrigerant fluids within a Rankine cycle for the production of electricity by using the sensible heat contained in the fumes of the ship, claiming the evaporation of the refrigerant in evaporators in direct contact with the combustion exhausts. . The claimed solution is limited by the lack of systems to prevent the possible entrainment of condensed phases from the evaporator to the turbocharger blades, with possible erosion of the latter, or of steam from the condenser to the pumping circuit, with possible disengagement and / or damage to the pumps. Surprisingly, the present invention provides a system suitable for the generation of mechanical and / or electrical energy by means of ORC circuits both for the propulsion of naval units and for its use on board. The inventive process responds to the growing demand in the naval field to have technical solutions that allow better autonomy, flexibility, reduction of the environmental impact, less expensive maintenance, fully integrating with the auxiliaries and with both electrical and mechanical on-board propulsion systems. The invention allows to advantageously exploit the thermal waste on board with temperatures between 50 and 800 ° C and more preferably between 70 3 570 ° C. The heat necessary for the evaporation of the organic working fluid inside the ORC systems is displaced from the hot sources to the cold ones, and from these ORC systems to the external environment, thanks to direct or indirect transport systems that use organic heat transfer fluids or inorganic. The solution has the advantage of not being limited to the use of refrigerants but can use, as appropriate, integrally or in a stage of the system, also other organic fluids as long as they have thermal and thermochemical stability at the working conditions.

The process, claimed in the present application, for the generation of energy on board naval units uses liquid and / or gaseous heat sources coming from the engine apparatus and / or from the on-board auxiliaries themselves and comprises the following stages: a) heat exchange indirectly between said gaseous heat sources, and / or direct or indirect exchange with said liquid sources by means of organic or inorganic heat transfer fluids (e.g. water, molten salts, low-melting molten metals or their alloys), and one or more subsystems able to generate energy through thermodynamic cycles where organic Rankine fluids (ORC) circulate; b) consequent vaporization in one or more vaporizers of the organic fluid in said ORC subsystems, its expansion in at least one turboexpander; c) heat exchange, in at least one recuperator, between said expanded organic vapor and the same organic fluid previously liquefied in at least one condenser placed downstream in the cycle. e) relaunching the organic condensate leaving said condensers at the preselected pressure by means of one or more pumping subsystems and closing the thermodynamic cycle; d) dissipation of the condensation heat of the organic fluid circulating in said ORC systems by means of cold sources placed inboard and / or outboard; f) conversion of the mechanical energy produced by the turboexpanders of the ORC systems into electrical energy by means of electrical generators.

In addition to the process, a system for the generation of energy on board naval units is also claimed, using liquid and / or gaseous heat sources between temperatures between 50 and 800 ° C and more preferably between 70 and 570 ° C coming from the engine system. and / or by on-board auxiliaries including;

one or more equipment for transporting heat to the ORC subsystem (s) from inboard hot springs; - one or more subsystems where organic fluids circulate capable of generating energy through Rankine thermodynamic cycles (ORC),

one or more heat transfer equipment from the ORC subsystem (s) to cold sources placed inboard and / or outboard;

one or more apparatuses suitable for inhibiting the entrainment of liquid phases to the blades of the turboexpanders and / or for inhibiting vapor phases to the pumping devices of the organic fluid circuit in the ORC subsystems;

- one or more devices for monitoring / regulation of the operating parameters of the ORC sections, of the heat transport sections from the hot sources to the organic cycle and from the latter to cold sources internal and / or external to the naval unit

one or more electric generators equipped with devices for coupling with the ORC turboexpanders;

- one or more devices for interconnection, transformation, regulation and / or power factor correction of the electricity produced by the system;

- one or more control sections for the distribution of the electricity produced between the electrical loads of the naval unit.

The apparatuses claimed in the inventive system can comprise, advantageously for the ORC section, the use of systems suitable for inhibiting the entrainment of liquid phases to the blades of the turboexpander or of gaseous phases to the pumping circuit of the ORC system by means of traps for the steam and / or liquid abatement systems inside or outside the evaporator of the organic fluid, such as for example septa, networks or apparatus with centrifugal effect. The system contemplates the possibility of using at least one electrical generator, including at least one subsystem for connection to the electrical network of the vessel. In order to minimize maintenance and eliminate wear, the turbogenerator can be with active magnetic bearings, and can, for example, consist of a single body, comprising a cantilevered impeller and a high frequency generator placed between the structures of the two magnetic bearings, each consisting of an axial / radial system. The rotor shaft of the generator is held suspended in levitation by the bearings without having contact surfaces. In addition to the power supply transformers, the system can also include a control unit for the ORC systems for the start-up, running and shutdown phases, which a distribution unit for the electrical energy generated by the ORC system dividing it between electric motors of propulsion that among the most varied electrical loads. In the case of using electric motors for propulsion, they are equipped with cooling systems and static or dynamic devices for regulating the number of revolutions that allow accurate regulation throughout the entire speed range, both forward and reverse. . It is also possible to provide coupling / decoupling systems between electric motors and the axles of the propulsion system.

Brief description of the figures

In continuation of what has been previously described, two possible exemplary and non-limiting schemes are reported illustrating further aspects and methods of the invention. It is evident that further variations, modifications and different application methods of the present system can be implemented by persons skilled in the state of the art without departing from the spirit of the inventive system or from the claims thereon. Figure 1 illustrates a conceptual block diagram in which the main phases and sections present in the inventive system are highlighted. Figure 2 shows a typical and simplified scheme of the system.

Detailed description of the inventive system

The block diagram of figure 1 shows the section relating to the engine and on-board auxiliaries generating heat [1]. This section may include, for example, one or more internal combustion engines and / or one or more gas turbines connected to the propulsion axes of the vessel [3] thanks to appropriate coupling / decoupling systems [2], Alternatively to what is illustrated , the aforementioned internal combustion engines and / or gas turbines can only supply mechanical energy to alternators in order to produce energy for propulsion by means of electric motors. The section of the engine and auxiliary equipment may include one or more boilers and / or auxiliary diesel engines necessary for the operation of the vessel or for the heating of fluids and goods or finally any combination of on-board equipment generating thermal energy and / or mechanics. The aforementioned section therefore includes both sources having a higher energy capacity and thermal level, and heat sources having a lower thermal level but equally usable by means of the present inventive system. The thermal waste is supplied indirectly to the energy generation section [5], using an appropriate organic or inorganic heat transfer medium flowing in one or more primary transport circuits [4]. The power generation section can contain one or more cycles equipped with one or more working fluids. The fluid, after having transferred heat to the cold source of the generator, is recirculated to the hot source. It may be convenient to have one or more secondary heat transport circuits indicated generically in block [6] in the case of simultaneous withdrawal from sources with a high thermal level together with withdrawal from sources at a lower temperature. The possible lower enthalpy level sources include the aforementioned lubrication and cooling circuits of internal combustion engines or gas turbines, which can transfer, in whole or in part, the thermal energy to the working fluid of the cycle. Rankine, thanks to heat exchangers arranged in series or parallel in these circuits. In this case the secondary heat transport system from the hot to the cold sources of the organic cycle may not need an independent circuit but be integrated with the aforementioned engine lubrication and cooling systems. Section [7] includes the on-board refrigeration equipment and communicates directly with the external environment, from which it takes the cooling fluid suitable for dissipating the rejection heat. The sections of the motor and auxiliary equipment, the block for ORC generation, the heat transport units are interconnected to this section. The turboexpander, present in the section operating the organic cycle, can be connected to an electric generator [8J. Any electricity produced by the cycle, previously transformed [9] to the appropriate voltage and possibly re-phased, is sent by means of the electrical interconnection and control power station [10] of the generation system to the ship's electrical network. The electrical energy injected, in whole or in part, is taken from the grid in order to drive one or more electric motors [11] coupled to the propulsion axis. Alternatively, the generated energy can be directly connected, after transformation to the appropriate voltage, to the electric propulsion system. In both cases, however, there is always a system for regulating the number of revolutions of the electric motor [12]. Alternatively to what is described in the block diagram indicated, the mechanical energy produced by the turbogenerator of the Rankìne cycle can be used without being transformed into electrical energy, by connecting the shaft of the expansion turbine by means of servomechanical systems for coupling / decoupling with the propulsion axis and also to the regulation of the number of revolutions. In particular applications of the system, the previously indicated diagram can be limited only to the primary heat transport circuit, without including the secondary withdrawal circuit from sources at a lower temperature, or use only sources with a lower thermal level without adopting an extraction circuit from sources with higher temperature level.

The simplified diagram of Figure 2 illustrates a generic possible application of the inventive system. The fuel stream [1] and the combustion air [2] feed the propulsion system [3], which may or may not include additional auxiliary energy generating equipment. A stream, or several streams, of high temperature exhaust fumes come out of the propulsion / auxiliary system. The exhausted ones release sensible heat, to the current of the heat transport circuit, by means of one or more exchangers / boilers [4]. The boiler can be composed, for example, of single spiral tubes, or of a removable tube bundle with a floating plate, in order to compensate for the expansion of the tubes with respect to the shell of the exchanger. The extractability of the bundle allows easy cleaning of the shell side and of the pipes. Inside the pipes a relatively high velocity of the heat transfer fluid must be ensured (higher than 0.6 m / s and preferably higher than 1 m / s}, in order to avoid stagnation of the same, and localized overheating, 1 such as in the case of use of organic fluid could alter its properties, causing a reduction in the life span. The temperature of the combustion fumes can, if necessary, be controlled by means of turbo-blowers / turbo-aspirators designed to mix the current at high temperature with air or exhaust or their mixtures at a lower temperature. The primary heat transport system is preferably composed of at least two pumps [5], of which at least one is in stand-by, while the second ensures the circulation of the fluid and provides for the transfer of heat from the source to the circuit of the ORC turbogenerator The circuit is equipped with an expansion tank [6] for the heat transfer fluid and one or more supply tanks [1] for the fluid. In a possible variant of the scheme, the heat transfer fluid circuit can be conveniently integrated with one or more auxiliary boilers, in order to improve the flexibility and efficiency of the system. A three-way valve [8] can be usefully installed on the heat transport circuit to divert the heat transfer fluid to a heat dissipation circuit [9] during the start-up and shutdown phases of the generation system and / or the engine system and auxiliaries on board. During these operations, the previously cooled current is introduced into the primary heat transport circuit, by-passing the OCR system. Once these operations have been completed, the aforementioned three-way valve is re-switched so as to feed the heat exchanger [10] of the circuit operating the Rankine cycle. The previously mentioned heat dissipation system is preferably integrated with the cooling system of the vessel, and uses refrigerating fluids from the external environment such as water or air [11], which, once heated, are released beyond outside the vessel [12]. The heat transfer fluid circulating from the sources at higher temperatures releases sensible heat to the working fluid of the organic cycle, with the aim of vaporising it. The working fluid is fed to the turboexpander during normal plant operation by means of the line [13] when the by-pass line [14] is intercepted. The by-pass line can be opened, totally or partially during the start or stop operations of the system. Upstream of the turbo-expansion apparatus there is preferably a device suitable for inhibiting the entrainment of liquid phases to the blades of the expander. The vapor of the organic fluid activates the turboexpander [15], which can be directly coupled to the electric generator [16] through an elastic joint generating electrical energy, or be connected to the propulsion axis of the vessel through a convenient system of coupling / uncoupling. The steam discharged from the expander flows through the regenerator [17], where it preheats the organic fluid, releasing sensible heat and thus improving the efficiency of the cycle. The use of a regenerator allows both a decrease in the heat released in the condensation and a decrease in the heat introduced into the cycle during the heating phase of the liquid, since this working fluid is evaporated starting from a higher temperature than to the output from the capacitor. The steam is then sent into the condenser [18] where it is cooled and liquefied by the passage of the refrigeration fluid coming from the heat dissipation circuit. The liquefied organic fluid is then fed, through a pumping system [19], to the regenerator and then to the evaporator, thus closing the cycle. Upstream of the pumping system there is preferably an apparatus suitable for preventing the passage of steam to the pumps. In a variant of the inventive system, the condenser of the organic fluid is not cooled directly by the refrigeration system of the vessel, but transfers heat to a second organic cycle, which generates a further amount of energy and transfers heat to the connected heat dissipation system. with the external environment. The exhausted combustion products, after having transferred heat to the primary heat transport system, are sent to the exhaust [20], using, if necessary, a suitable turbo-blower / turbo-aspirator. In a variant of the system, the exhausted ones can further exchange heat with respect to that transferred to the ORC system, in one or more exchangers / economizers, in order to heat suitable currents, increasing energy efficiency. If gas temperatures are reached such as to allow the formation of acid condensates, it is necessary to use high-quality materials in the discharge pipes and in the recovery boilers. The electric generator is connected to a transformer [21], which is in turn connected to the electrical network of the vessel and to the connection and control center of the electrical equipment [22] on board. The propulsion electric motor [25] is then connected to the mains by means of a transformer [23] and includes a speed control system [24]. Finally, the electric motor is combined with the propulsive axis thanks to an appropriate coupling / decoupling device [26].

Example 1:

A naval propulsion system includes a gas turbine characterized, under standardized ISO conditions (dry bulb temperature equal to 15 <a> C, 60% relative humidity, pressure 1013 mbar), by the following parameters:

Flue gas flow [kg / s] 67.8 Exhaust gas temperature [° C] 530 Natural gas flow [kg / h] 5000 Heating power. Infer. natural gas [kj / kg] 44196 Inlet thermal power [kW] 61432.4 Electric power [kW] 22080 Electric efficiency [%] 36 The fumes at the exhaust of this unit enter a boiler where they release 17.7 MW of heat to a heat transfer fluid cooling down to at about 300 ° C. The fluid (1370 t / h} acquires sensible heat by heating from 250 ° C to 270 ° C and is sent to an exchanger, where it transfers heat to a liquid stream of isopentane at 150 ° C under pressure, raising its temperature up to 240 ° C and making it vaporize to be used in an energy production system using an organic Rankine cycle. The heat transfer fluid which has cooled down to about 250 ° C is re-launched, by means of a pumping system, to the fumes cauldron. The isopentane vapors produced (147 t / h) are expanded (expansion ratio about 10.6} in a turbine with high isentropic efficiency (83%), producing about 4100 kW at the shaft. The expanded steam enters an exchanger-regenerator at 186 ° C, where it preheats the liquid stream of the working fluid up to 150 ° C, cooling down to 85 ° C. The steam stream enters a condenser, where it transfers latent heat to the refrigeration circuit of the vessel, condensing and cooling down to 40 ° C. In order to inn to raise the efficiency of the cycle the organic fluid passes into an exchanger where it receives a further amount of heat (3.4 MW} at low enthalpy (86 ° C) coming from the cooling system of the vessel, from the jackets and from the lubrication of the diesel alternators on board and increasing its temperature up to 70 ° C, while the refrigeration fluid cools down to 80 ° C. The Rankine cycle closes thanks to the relaunch of the organic fluid, through the pumping system, to the previously mentioned exchanger-regenerator. The shaft of the organic fluid expansion turbine is coupled to an electrical generator through an elastic coupling. The tearing of the medium voltage switchboard of the vessel takes place after transformation to 6.6 kV. 3990 kWe are produced (alternator efficiency equal to 0.974, having neglected heat losses by radiation from the system). A portion of the available electrical power is used for the electrical loads of the Ranking cycle and the heat transport circuit from the gas turbine fumes {280 kWe approximately). The remainder is available for on-board services or marine propulsion in the case of CODLAG (COmbined Diesel-eLectric And Gas) or CODAG systems using electric propulsion transformers and synchronous electric motors equipped with variable frequency static actuators for regulating the number of turns. Finally, the fumes from the turbogas at 300 °, before being sent to the turbo-aspirator of the exhaust pipe, can transfer a further amount of heat (8.5 MW) to service fluids, cooling down to 180 ° C, in order to further raise the thermal efficiency of the vessel.

Example 2:

The exhausted combustion products 400 ° C (45.4 kg / s) pass into a boiler where they release 7.1 thermal MW to a heat transfer fluid, cooling down to about 26Q ° C. The circulating fluid (231 t / h) passes from 200 ° C to 250 ° C and is placed in an evaporator exchanger belonging to a Rankine cycle, where it transfers heat to a pressurized liquid stream of octamethylcyclotetrasiloxane at 132 ° C, causing it to vaporize and raise it the temperature up to 240 ° C. The heat transfer fluid, which has cooled down to about 200 ° C, is re-launched by means of a pumping system, to the furai calderina. The vapors of the organic fluid produced (131 t / h) are expanded from 20 atm up to 0.6 atm in a turboexpander with magnetic bearings with isentropic efficiency equal to 80%, producing about 1220 kW at the shaft. The expanded vapor enters an exchanger-regenerator at 148 ° C, where it preheats the liquid stream of the working fluid up to 132 ° C, cooling down to 100 ° C. The steam current enters an exchanger where it condenses and cools down to 89 ° C, The phase transition heat (6 MW ca) is transferred in the condenser to a water cooling circuit, which heats up to 40 ° C up to at 80 ° C and can be used for on-board services. The Rankine cycle closes thanks to the relaunch of the organic fluid, through the pumping system, to the previously mentioned exchanger-regenerator. A portion of the energy produced is used for the electrical loads of the Ranking cycle and the heat transport circuit from the fumes of the gas turbine {130 kWe}. The remainder is available for on-board services or ship propulsion by means of synchronous electric motors with LCI (Load commutaded inverter) drive,

Claims (7)

Claims 1. A process for the generation of energy on board naval units using liquid and / or gaseous heat sources with temperatures between 50 and 800 ° C coming from the engine and / or auxiliaries on board comprising the following stages: a) heat exchange with one or more subsystems generating energy through thermodynamic cycles where Rankine organic fluids (ORC) circulate, being said indirect exchange with said gaseous sources or direct / indirect with said liquid sources; b) consequent vaporization in a vaporizer (s) of the organic fluid circulating in said ORC subsystems, its expansion in a turboexpander (s); c) heat exchange, in a recuperator (s), between the vaporized and expanded organic fluid and the same liquefied organic fluid in a condenser (s) located downstream of said turboexpander and of said recuperator; e) increasing the pressure of the organic condensate leaving said condenser (s) to the preselected value by means of one or more pumping subsistries and closing the thermodynamic cycle; d) dissipation of the condensation heat of the organic fluid circulating in said ORC systems by means of cold sources placed inboard and / or outboard; f) conversion of the mechanical energy produced by the turboexpander (s) of the ORC systems into electrical energy by means of an electrical generator (s). 2. A system for the generation of energy on board naval units using liquid and / or gaseous heat sources between 50 and 800 ° C from the engine and / or on-board auxiliaries comprising: one or more equipment for transporting heat to the ORC subsystem (s) from inboard hot springs; - one or more subsystems where organic fluids circulate capable of generating energy through Rankine thermodynamic cycles (ORC), one or more heat transfer equipment from the ORC subsystem (s) to cold sources placed inboard and / or outboard; one or more apparatuses able to inhibit the entrainment of liquid phases to the blades of the turboexpanders and / or to inhibit the vapor phases of the pumping devices of the organic fluid circuit in the ORC subsystems; - one or more devices for monitoring / regulation of the operating parameters of the ORC sections, of the heat transport sections from the hot sources to the organic cycle and from the latter to cold sources internal and / or external to the naval unit one or more electric generators equipped with devices for coupling with the turboexpander (s) ORC; - one or more devices for interconnection, transformation, regulation and / or power factor correction of the electricity produced by the system; one or more control sections for the distribution of the electrical energy produced between the electrical loads of the naval unit. 3. System as per claim 2 in which there are: one or more electric motors for the propulsion of the naval unit using shares of the energy produced by the ORC system; one or more static regulators of the number of revolutions of the electric propulsion system. 4. System according to claim 2 wherein the turboexpander (s) of the ORC subsystem (s) uses active magnetic bearings in order to minimize maintenance and eliminate wear of the mechanical parts. 5. System as per claim 2 in which the ORC subsystem (s) exchanges further shares of heat, by means of one or more additional heat exchangers, with inboard thermal sources in order to increase the thermal efficiency of the cycle and / or the vessel . 6. System as per claim 2 in which the heat transport circuit (s) from the hot sources uses a removable tube bundle heat exchanger (s) in order to facilitate the cleaning operations and with a floating head to compensate for the expansion of the tubes. 7. System as per claim 2 where the temperature of the hot springs, when made up of combustion gases, is controlled by means of one or more turbo-blowers / turbo-aspirators suitable for mixing the stream at high temperature with air or exhaust or their mixtures at a lower temperature .