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EP-4740741-A1 - DEVICE AND CORRESPONDING METHOD FOR REFRIGERATING FLUIDS BY HEAT EXCHANGE WITH LIQUEFIED CRYOGENIC GAS IN A TWO-PHASE FLOW

EP4740741A1EP 4740741 A1EP4740741 A1EP 4740741A1EP-4740741-A1

Abstract

The present invention relates to a device (100) for refrigerating fluids by heat exchange with liquefied cryogenic gases in a two-phase flow comprising a heat exchanger (20) configured to receive at least one fluid to be refrigerated (24), a first supply line (A) activatable to supply a first gaseous (1) to said heat exchanger (20) and a second supply line (B) activatable to supply a liquefied cryogenic gas (11) to said heat exchanger (20).

Inventors

  • FRATI, MAURIZIO

Assignees

  • Societa' Italiana Acetilene & Derivati S.I.A.D. S.p.A. in breve S.I.A.D. S.p.A.

Dates

Publication Date
20260513
Application Date
20251107

Claims (13)

  1. Device (100) for refrigerating fluids comprising: - a heat exchanger (20) configured to receive at least one fluid to be refrigerated (24); - a first supply line (A) to be activated to supply a gaseous (1) to said heat exchanger (20); - a second supply line (B) to be activated to supply a liquefied cryogenic gas (11) to said heat exchanger (20); said first supply line (A) and said second supply line (B) comprising a first conduit (2) and a second conduit (12), respectively, hydraulically connected to each other and to a third conduit (2a) at a connection point (16) upstream of said heat exchanger (20), said third conduit (2a) ending in at least one injector (8) apt to inject said liquefied cryogenic gas (11) and/or said gaseous (1) into said heat exchanger (20), wherein said first supply line (A) is to be activated when said at least one injector (8) is immersed in said fluid to be refrigerated (24) and said second supply line (B) is not activated, in order to flush at least said injector (8) and said third conduit (2a) to prevent clogging by said fluid to be refrigerated (24).
  2. Device (100) according to claim 1, wherein, at said connection point (16), said gaseous (1) and said liquefied cryogenic gas (11) mix to form a two-phase refrigerant fluid.
  3. Device (100) according to claim 1 or 2, wherein said first supply line (A) comprises a first flow control device (4) installed on said first conduit (2) and configured to regulate the flow of said gaseous (1) within said first conduit (2), and wherein said second supply line (B) comprises a second flow control device (14) installed on said second conduit (12) and configured to regulate the flow of said liquefied cryogenic gas (11) within said second conduit (12).
  4. Device (100) according to claim 1 or 2, wherein said first flow control device (4) comprises a shut-off valve (4a), configured to enable or interrupt the flow of said gaseous (1), and a three-way valve (40), configured to selectively direct the flow of said gaseous (1) into a first secondary conduit (41) or into a second secondary conduit (42), each equipped with respective manual flow regulators (43, 44) apt to enable the delivery of said flow of said gaseous (1) exiting said first flow control device (4) at mutually different flow rates, and wherein said second flow control device (14) comprises a shut-off valve (14a), configured to enable or interrupt the flow of said liquefied cryogenic gas (11), and a three-way valve (50), configured to selectively direct the flow of said liquefied cryogenic gas (11) into a first secondary conduit (51) or into a second secondary conduit (52), each equipped with respective manual flow regulators (53, 54) apt to enable the delivery of said flow of said liquefied cryogenic gas (11) exiting said second flow control device (14) at mutually different flow rates.
  5. Device (100) according to one or more of the preceding claims, wherein said second conduit (12) comprises, at said connection point (16), an atomizing nozzle apt to disperse in form of microparticles said liquefied cryogenic gas (11) into said gaseous (1) to obtain said two-phase refrigerant fluid so that the liquid phase is dispersed in the gaseous phase.
  6. Device (100) according to one or more of the preceding claims, wherein said liquefied cryogenic gas (11) comprises nitrogen or other liquefied refrigerant gases normally used for industrial refrigerating applications.
  7. Device (100) according to one or more of the preceding claims, wherein said gaseous (1) comprises said liquefied cryogenic gas (11) in the gaseous state, or another liquefied cryogenic gas, or mixtures of gases chemically compatible with said fluid to be refrigerated (24) and free of components solidifiable under the operating conditions of said device (100).
  8. Device (100) according to one or more of the preceding claims, comprising a central control unit (17) and pressure sensors (6, 6a) in data communication with said central control unit (17), said pressure sensors (6, 6a) being apt to detect the pressure value of the fluids present in the conduits (2, 12, 2a) in proximity to said connection point (16).
  9. Device (100) according to the preceding claim, further comprising: - a first flow sensor (5) in data communication with said central control unit (17), installed in said first supply line (A) and apt to measure the flow rate of said gaseous (1) along said first conduit (2); - a second flow sensor (15) in data communication with said central control unit (17), installed in said second supply line (B) and apt to measure the flow rate of said liquefied cryogenic gas (11) along said second conduit (12); and - a temperature sensor (22) in data communication with said central control unit (17), installed in said heat exchanger (20) and apt to measure the temperature of said fluid to be refrigerated (24).
  10. Device (100) according to one or more of the preceding claims, wherein said heat exchanger (20) comprises a level sensor (23) in data communication with said central control unit (17) apt to measure the level of said fluid to be refrigerated (24) within said heat exchanger (20), so as to determine when said fluid to be refrigerated (24) submerges said at least one injector (8), and/or whether said fluid to be refrigerated is at a suitable level within said heat exchanger (20) to perform heat exchange, allowing the sending of said two-phase refrigerant fluid into said heat exchanger (20).
  11. Device (100) according to one or more of the preceding claims, comprising a plurality of injectors (8), distributed within said heat exchanger (20) or along the side walls of said heat exchanger (20), said third conduit (2a) branching into a plurality of secondary conduits (7), each leading to a respective injector (8) of said plurality of injectors (8).
  12. Method for refrigerating a fluid to be refrigerated (24) contained in a heat exchanger (20), comprising the steps of: - activating a first supply line (A) to supply a gaseous (1) towards said heat exchanger (20) along a first conduit (2); - activating a second supply line (B) to supply a liquefied cryogenic gas (11) towards said heat exchanger (20) along a second conduit (12); - introducing, through a third conduit (2a) in fluid communication with said first conduit (2) and with said second conduit (12) in correspondence to a connection point (16) and ending with at least one injector (8), said gaseous (1) and said liquefied cryogenic gas (11) into said heat exchanger (20) to refrigerate said fluid to be refrigerated (24); - activating said first supply line (A) when said at least one injector (8) is immersed in said fluid to be refrigerated (24) and said second supply line (B) is not activated, in order to flush at least said injector (8) and said third conduit (2a) to prevent clogging by said fluid to be refrigerated (24).
  13. Method according to claim 11, comprising at least one of: (i) a step of measuring the pressure value of the fluid present in the conduits (2, 12, 2a) in proximity of said connection point (16) by means of pressure sensors (6, 6a), as well as the level value of said fluid to be refrigerated (24) within said heat exchanger (20) by means of said level sensor (23), said pressure sensors (6, 6a) and said level sensor (23) being in data communication with a central control unit (17), and of activating, through said central control unit (17), a first flow control device (4) installed on said first supply line (A); (ii) a step of measuring the flow rate of said gaseous (1) along said first conduit (2) by means of a first flow sensor (5) in data communication with said central control unit (17), measuring the flow rate of said liquefied cryogenic gas (11) along said second conduit (12) by means of a second flow sensor (15) in data communication with said central control unit (17), measuring the temperature of said fluid to be refrigerated (24) by means of a temperature sensor (25) at the inlet of said heat exchanger (20), measuring the flow of said fluid to be refrigerated (24) through a flow sensor (26) at the inlet of said heat exchanger (20), the temperature of refrigerated fluid (27) through the temperature sensor (28) at the outlet of said heat exchanger (20), measuring the level of said fluid to be refrigerated (24) through said level sensor (23) within said heat exchanger (20), measuring the internal pressure of said heat exchanger (20) through a pressure sensor (21), said temperature sensors (25, 27), said flow sensor (26) and said level sensor (23) being in data communication with said central control unit (17), and activating, by means of said central control unit (17), a first flow control device (4) installed on said first supply line (A) and/or a second flow control device (14) installed on said second supply line (B).

Description

FIELD OF INVENTION The present invention relates to a device, and a corresponding method, for exchanging heat between fluids by direct contact, wherein one of the fluids is a two-phase refrigerant fluid composed of a liquid phase, consisting of a liquefied cryogenic gas, and a gaseous phase, consisting of the same gas or of a different gas, hereinafter also referred to simply as gas phase. During the heat exchange process, such two-phase refrigerant fluid acts to absorb heat from another fluid in the liquid state, eventually containing also solid parts, which, upon contact with the two-phase refrigerant fluid, releases heat and is thus refrigerated, possibly even undergoing partial freezing. As a result of this heat transfer, the liquid phase of the two-phase refrigerant fluid transitions to the gaseous state. For simplicity, hereinafter, in the case is not specified, the two-phase refrigerant fluid consisting of the liquid phase, due to the liquefied cryogenic gas and to the gaseous phase will also be referred to as cold fluid. As fluids that release heat during the heat exchange are considered, by way of example and not limitation, liquids or two-phase fluids consisting of a liquid phase containing solid or semisolid parts and similar materials, hereinafter referred to as hot fluid, fluid to be refrigerated or refrigerated fluid, depending on whether they must undergo, are undergoing or have undergone the refrigerating process, i.e., the heat exchange. In particular, but without limiting the invention, the hot fluids include food products such as sauces, condiments, fruit juices, vegetable broths containing pieces of the same, pastes obtained from the pressing of vegetables, grape must, i.e., the fluid obtained from the crushing of grapes. STATE OF THE ART Various techniques are known and currently used for direct heat exchange between fluids employing liquefied cryogenic gases as refrigerating fluids, i.e., for absorbing heat during the heat exchange process with another fluid. In known systems, the heat exchange process is achieved by injecting the liquefied cryogenic gas into the volume of the fluid to be refrigerated. The direct contact between the cold and hot fluids for heat exchange usually occurs in suitable containment devices, also known as exchangers, which may be insulated and/or operated under pressure. It is known that heat exchange becomes difficult when the hot fluid, during the cooling process, exhibits high viscosity and/or low turbulence. These aspects may lead to localized freezing and cause malfunctions of the apparatus in the zones where heat exchange occurs. A cryogenic gas is understood to mean a gas that must be maintained at extremely low temperatures, generally below -150°C, to remain in a liquid form. Typical examples of cryogenic gases include liquid nitrogen, liquid oxygen, liquid hydrogen and liquid helium. For the purposes of the process of the heat exchange of the present invention, liquid carbon dioxide is also considered equivalent to a cryogenic gas. The main liquefied cryogenic gases of industrial interest are carbon dioxide (CO2) and nitrogen, in the follows also in indicated as CO2 and N2, respectively. In case the liquefied cryogenic gas is N2, the management of heat exchange is more complex, than, for example, with CO2, due to the higher thermal gradient, respect to the case of CO2, relative to the hot fluids to be cooled in normal usage. This gradient causes a high exchange velocity, thus making temperature and management control more difficult. For an evaluation of the thermal gradient of N2, it has to be considered that, since nitrogen has a very low boiling temperature (approximately -196°C at atmospheric pressure, and about - 170°C at 10 bar), nitrogen causes an immediate and significant temperature drop, in the regions near the injection point into the hot fluid, as a consequence of the intense localized heat exchange. This may lead to solidification of part of the hot fluid mass close to the injection zone resulting in malfunctions of the exchanger and, in many cases, alteration of the chemical/physical and commercial characteristics and valuation of the product. As example, as considering as hot fluid grape must, fluid in which the semisolid component consists of crushed grapes and the liquid component consists of juice released from the crushed of them. A heat exchange with sudden, high and localized heat exchange may cause freezing of the grape skins and of must portions, producing obstructions and malfunctions in the exchanger. Moreover, the grape skins exposed to such intense heat exchange can experience excessive cooling, degrading properties important for the final product quality, such as wine. Such rapid and localized heat exchange can be prevented by generating sufficient turbulence in the hot fluid, so that at the initial contact of the fluids, i.e., near the injection point, the heat is dispersed, exchange in a volume of the fluid to be refrigera