BR102019020293B1 - SAFETY BUFFRED MULTIFLUID HEAT EXCHANGER AND SAFETY BUFFRED MULTIFLUID THERMAL EXCHANGE PROCESS - Google Patents

Abstract

The present invention patent application refers to a buffered multifluid heat exchanger (1) and a buffered multifluid heat exchange process, belonging to the technical sector of heat exchange equipment and processes; said heat exchanger (1) comprising: lower pipe or tubular bundles (2) through which hot process fluid Q to be cooled circulates; by piping or tubular bundle (3) through which cold process fluid F circulates to be heated upper, parallel and spaced in relation to the lower piping (2); per vessel (4) containing pipes (2) and (3), equipped with inlet nozzles (2)? and outlet (2) of the pipe (2), inlet nozzles (3)? and outlet (3) of the pipe (3); and by a portion of buffer fluid T that fills part of the vessel (4) and that covers the lower pipe (2) through which the hot process fluid Q to be cooled circulates.

Description

INTRODUCTION

[001] This descriptive report refers to a patent application for a buffered multifluid heat exchanger and a buffered multifluid heat exchange process, belonging to the technical sector of heat exchange equipment and processes, which were developed to provide greater security, greater simplicity and lower cost compared to usual equipment and processes.

STATE OF THE TECHNIQUE

[002] In the chemical process industry, the need to heat or cool fluids in heat exchangers/exchangers is very common. This equipment consists of vessels where two or more fluids come into indirect contact, transferring heat from the hot fluid to the cold fluid.

[003] In several situations, this equipment can process chemically incompatible fluids, which, when in contact, can produce exothermic chemical reactions, explosions, formation of by-products, unwanted products or even the loss of products being heated or cooled.

[004] Typical examples of this type of situation are the cooling of sulfuric or phosphoric acid with water, substances that when in direct contact react intensely generating heat and an extremely corrosive diluted solution. The cooling of soluble hydrocarbons together can, if they are mixed, lead to the production of mixtures that are difficult to separate, with loss of products and other similar situations.

[005] In some situations it is not desired for the cold fluid to reach high temperatures to avoid its thermal decomposition. A typical example of this system are amine and glycol reboilers in the petrochemical industry.

[006] It is common in the industry, to avoid such problems, for the cooling process to be carried out in systems with multiple heat exchangers, in order to prevent the fluids from coming into contact with each other in the event of failure. , minimizing the damage caused in the event of failure or in order to prevent the cold fluid from being subjected to high temperatures that could cause its decomposition.

[007] This is the typical case of so-called “trim coolers” used, for example, in the sulfuric acid industry for heating boiler water, (fig. 15). This arrangement allows that, in the event of a heat exchanger failure, the process fluids, sulfuric acid and deionized boiler water, do not come into direct contact, generating contamination of the boiler water.

[008] Another system that attempts to avoid this contact is presented in the patent application, in PCT BR 2016 050287, from the same applicant, in which the process fluids, to be heated and cooled, circulate in respective circuits and a fluid inert to the fluids process is circulated in an intermediate circuit provided for thermal exchange and so that, in the event of failure or leakage, there is no contamination of the process fluids (fig. 16) and that, unlike conventional systems, the unit can be maintained in operation or stopped under normal conditions.

[009] Still, for example, in the sulfuric acid industry, hot sulfuric acid at temperatures above 180°C is cooled in water boilers; The contact of these fluids under operating conditions resulted in important exothermic reactions, with major damage to equipment, industrial assets and operator safety.

[010] In the petroleum processing industry, the surface temperatures of reboilers must be maintained below 165°C to prevent the degradation of amines.

OBJECTIVES OF THE INVENTION

[011] Thus, the objective of the present patent is to provide a new modeling of a thermal exchange device (heat exchanger), which allows eliminating the need for systems with multiple heat exchangers (“trim coolers”), said present heat exchanger using an intermediate fluid, called “buffer fluid”.

[012] Another objective of the invention is to provide a heat exchanger that provides safe thermal exchange between two or more incompatible process fluids, using buffer fluid endowed with appropriate physicochemical characteristics in relation to the process fluids, allowing increased operational safety.

[013] Another objective is to provide a heat exchanger that allows minimizing the decomposition of the cold fluid, using buffer fluid with appropriate physicochemical characteristics in relation to process fluids, ensuring an established film temperature for the cold fluid. .

[014] Another objective is to provide a heat exchanger with relatively simple construction and manufacturing.

[015] Another objective is to provide a heat exchanger with low manufacturing, acquisition, operation and maintenance costs.

[016] Another objective is to provide a thermal exchange process carried out by the heat exchanger.

[017] Another objective is to provide a thermal exchange process that presents lower cost, greater safety and greater operational simplicity than those that use one or more heat exchangers using incompatible fluids.

BRIEF DESCRIPTION OF THE INVENTION

[018] Therefore, taking into account the problems of the prior art referred to above and with the aim of overcoming them and aiming to meet the related objectives, the heat exchanger was developed, the object of the present patent, which has as a distinguishing characteristic the fact of using three or more fluids, with two or more fluids being process fluids for heating/cooling and one fluid being a “buffer fluid” that transports heat between the two or more process fluids; Said buffer fluid is selected or formulated based on its chemical compatibility characteristics with other fluids, boiling temperature, viscosity, density and chemical compatibility with the materials of the process equipment under operating conditions.

[019] In a system with, for example, three fluids: a hot process fluid that will be cooled, a cold process fluid that will be heated and the buffer fluid, the safety buffered multifluid heat exchanger, object of this patent, is essentially comprised of: a pressure vessel; by two bundles of tubes through which cold fluid and hot fluid flow internally, parallel and located inside the vessel; by a space internal to the vessel, in which the bundles of tubes are arranged and by a portion of buffer fluid that partially fills the internal space and which covers the bundle of tubes through which the heated process fluid flows, in order to carry out a thermal exchange process comprised, substantially, by the steps of: thermal exchange of the hot process fluid with the buffer fluid; evaporation of the buffer fluid; thermal exchange between the buffer fluid vapor and the cold process fluid; condensation of the buffer fluid; thermal exchange between the condensed buffer fluid and the hot process fluid and beginning of a new cycle.

[020] This construction of the heat exchanger and constitution of the process carried out by it overcome the prior art problems alluded to above. This way of constructing the heat exchanger and the thermal exchange process carried out by it eliminates the need for systems with multiple heat exchangers (“trim coolers”), used, for example, in the sulfuric acid industry for heating hot water. boiler, as it allows that, in the event of a heat exchanger failure, the process fluids, sulfuric acid and deionized boiler water, do not come into direct contact, generating contamination of the boiler water, and at the same time said to be present heat exchanger and process have a relatively simpler construction, thus meeting the objective of the invention.

[021] This heat exchanger construction and process constitution also prevent the cold fluid from being subjected to high temperatures that could promote its decomposition, since, regardless of the temperature of the hot fluid, the cold fluid will only be subjected to the temperature boiling point of the buffer fluid, which will be selected to guarantee this performance.

[022] The present heat and process exchanger are an alternative to the system described in PCT BR 2016 050287, from the same applicant, as it simplifies its construction, in which the process fluids, to be heated and cooled, circulate in respective exchangers of heat and a fluid inert to the process fluids circulates in a third intermediate heat exchanger, providing thermal exchange, since this entire construction is simplified by the present heat exchanger formed by a bundle of tubes for the heated process fluid, a bundle of tubes for the process fluid to be cooled and simply a portion of buffer fluid that performs thermal exchange between the process fluids, thus meeting another objective of the invention.

[023] In addition to the above advantages, the present heat exchanger and the process carried out by it present lower manufacturing, acquisition, operation and maintenance costs compared to the usual ones mentioned above, thus meeting other objectives of the invention.

LIST OF DRAWINGS

[024] The attached drawings refer to the safety buffered multifluid heat exchanger and safety buffered multifluid heat exchange process, objects of the present patent, in which:

[025] fig. 1 shows a schematic of the safety buffered multifluid heat exchanger 1;

[026] fig. 2 shows the same previous figure and the operating indication of heat exchanger 1;

[027] figs. 3 to 6 show various versions of a device 7 to reduce the loss of efficiency in the contact region between the vapor and condensate of the buffer fluid “T;

[028] figs. 7 to 9 show various construction possibilities for piping 2 for hot fluid “Q” to be cooled and piping 3 for cold fluid “F” to be heated that are part of heat exchanger 1;

[029] figs. 10 to 13 show variations regarding the quantities of process fluids that can be expected in heat exchanger 1;

[030] fig. 14 shows a schematic of the thermal exchange process carried out by heat exchanger 1 of the previous figures;

[031] fig. 15 shows a schematic of the prior art “trim coolers” process; It is

[032] fig. 16 shows a schematic of one of the possibilities of the equipment covered by PCT BR 2016 050287 from the same applicant, from the state of the art.

DETAILED DESCRIPTION BASED ON DRAWINGS

[033] As illustrated in the figures listed above and as provided for in the invention, the buffered multifluid heat exchanger 1, object of the present patent invention, is intended for thermal exchange between hot process fluids to be cooled and cold process fluid to be heated, particularly when these fluids are chemically incompatible and which, when in contact, can generate exothermic chemical reactions, explosions, formation of undesirable by-products or the loss of the products being heated and cooled or, in the case where I am interesting or necessary, if it guarantees a maximum film temperature for the cold fluid, in order to preserve its quality or other characteristics.

[034] Thus, said present buffered multifluid heat exchanger 1 is formed (fig. 1): by lower pipe 2 through which a hot process fluid “Q” to be cooled circulates; by piping 3 through which a cold process fluid “F” circulates to be heated upper, parallel and spaced in relation to the lower piping 2; by a vessel 4 that contains said pipes 2 and 3, equipped with inlet nozzles 2' and outlet 2” communicating with the respective ends of the pipe 2 through which a hot process fluid “Q” to be cooled circulates, from inlet nozzles 3' and outlet 3” communicating with the respective ends of the piping 3 through which a cold process fluid “F” to be heated circulates; said nozzles 2', 2”, 3',3” connected to pipes connected to equipment 100, 101 (fig. 2) that use the cooled process fluid “R”, coming from the heated process fluid “Q”, and the heated process fluid “A”, coming from cold process fluid “F”; Said buffered multifluid heat exchanger 1 is also formed by a portion of buffer fluid “T” that fills part of the vessel 4 and covers the lower pipe 2 through which a hot process fluid “Q” circulates to be cooled.

[035] In detail, pipes 2 and 3 can be made up of smooth tubular bundles, fins with longitudinal fins, circumferential fins, helical fins, twisted tubes or any other type of tube or device appropriate and suitable to promote and maximize exchange between the hot fluids “Q” and cold “F”, circulating in pipes 2 and 3 respectively, and the buffer fluid “T”.

[036] The equipment is equipped with nozzles and inlet 2', 3' and outlet 2”, 3” for hot process fluids “Q” and cold “F”, nozzles for feeding 5 and draining 6 of buffer fluid “T” , nozzles for instruments, pressure relief valves and others (not illustrated) in accordance with good industrial practices and technical standards in different countries.

[037] Buffer fluid “T” is selected based on its chemical compatibility and boiling temperature in relation to process fluids “Q” and “F” and its physicochemical characteristics.

[038] The operating principle of the buffered multifluid heat exchanger 1 is extremely simple and benefits from the high heat transfer coefficients obtained in boiling and condensation processes, when compared to the heat transfer coefficients obtained in systems of convection.

[039] Thus, (fig. 2) the hot fluid “Q” is admitted through its inlet nozzle 2' and passes through the tubular bundle 2; As this occurs, this fluid transfers heat to the buffer fluid “T”, which occupies part of the chamber formed by vessel 4 of the heat exchanger 1. The buffer fluid “T”, which was chosen based on its chemical compatibility and temperature boiling temperature relative to the process fluids “Q” and “F” and their physical-chemical characteristics, boils and forms vapor from the buffer fluid “VT”, removing heat from the hot fluid “Q”, which is thus cooled and constitutes in the cooled fluid “R”, which leaves the tubular bundle 2 through the outlet nozzles 2” and is fed into equipment 100 that makes use of the cooled fluid “R”, at the end of which the fluid returns to being hot process fluid “ Q”, which is fed back, through the inlet nozzles 2', into the buffered multifluid heat exchanger 1 and the cycle restarts.

[040] The same substantially occurs in relation to the cold fluid “F”. Thus, the cold fluid “F” is admitted through its inlet nozzles 3' and passes through the tubular bundle 3; As this occurs, this fluid receives heat from the “VT” buffer fluid vapor, which condenses, forming condensate of the “CT” buffer fluid, that is, the “T” buffer fluid returns to the liquid phase, during which occurs heat transfer to the cold fluid “F”, which is thus heated and constitutes the heated fluid “A”, which leaves the tubular bundle 3 through the outlet nozzle 3” and is fed into the equipment 101 that makes use of the heated fluid “A”, at the end of which the fluid returns to cold process fluid “F”, which is fed back, through the inlet nozzle 3', into the buffered multifluid heat exchanger 1 and the cycle restarts.

[041] The vapors “VT” produced by the boiling of the buffer fluid “T” in contact with the pipe 2, in which the hot fluid “Q” circulates, rise and find the tubular bundle 3 where the cold fluid “F” is transported.

[042] Upon encountering this tubular bundle 3, where the cold fluid “F” passes, the vapor of buffer fluid “VT” is condensed forming the condensate of buffer fluid “CT”, (buffer fluid “T” in liquid phase) which returns to the buffer fluid body “T” where it is evaporated again by the hot process fluid “Q”. The process continues indefinitely.

[043] During this operation, the “VT” buffer fluid vapors that rise from boiling in the hot fluid beam 2 come into contact with the condensate of the “CT” buffer fluid coming from the cold fluid beam 3 (upper).

[044] In this movement, some thermal exchange that may occur between the vapors and droplets of buffer fluid “T”, although small, since vapors and liquid are at the same temperature and, therefore, the driving force for heat transfer is harmed. To eliminate or minimize this effect, a device 7 can be provided to reduce the loss of efficiency in the contact region between the vapor and condensate of the “T” buffer fluid. In one possible embodiment, this device 7 may be constituted by the upper tubular bundles 3, through which the cold fluid “F” to be heated flows, be inclined (fig. 3), or be provided with baffles 8 (fig. 4) to accelerate and direct condensate drainage and routing.

[045] In another possible embodiment, this device 7 to reduce the loss of efficiency in the contact region between the vapor and condensate of the “T” buffer fluid may consist of gas-liquid separating devices such as fins, Chevron-type separators 9 (fig.5) or chicane fins 10 (fig. 6), or others installed in the region between the lower 2 and upper 3 tubular bundles, in which hot “Q” and cold “F” fluids circulate, respectively.

[046] Within the basic construction, described above, the buffered multifluid heat exchanger 1, object of the present patent, may present modifications related to materials, dimensions, construction details and/or functional configuration, without leaving the scope of the requested protection .

[047] Within this, the tubular bundles 2 and 3 can be of different natures, such as conventional longitudinal horizontal bundles as illustrated in figure 1, U-Bundle type bundles (fig. 7) or mixtures thereof installed horizontally or vertical (figs. 8, 9).

[048] An important change in relation to conventional exchangers is that in the present buffered multifluid heat exchanger 1 with “T” buffer fluid, there is no characterization of competing flow arrangements, counter currents, cross flow, and others. The buffer fluid “T” inside the equipment is at its boiling temperature in the process condition, so that the entire fluid along the entire length of the tubular bundles 2, 3 “sees” the buffer fluid at the same time. temperature, therefore, the location of the inlet nozzles 2', 3' and outlet 2”, 3” of the equipment and the tubular bundles 2, 3 is indifferent.

[049] Another important advantage that can be exploited with a buffered multifluid heat exchanger 1 with buffer fluid “T” is that the boiling of this fluid limits the temperature at which the hot fluid “Q” or cold fluid “F” are subject to contact indirect; that is, the tubes or plates transporting the cold fluid “F” will never “see” a temperature higher than the boiling temperature of the buffer fluid “T”, in the same way, the tubes or plates transporting the hot fluid “Q” , they will also never “see” temperatures below that of the buffer fluid “T” and evaporation. This feature allows this buffered multifluid heat exchanger 1 to process sensitive fluids or those that may suffer decomposition or deterioration due to exposure to high or low temperatures.

[050] The exchanger can use more than two process fluids; for example, you can have two heating fluids “Q” and one cooling fluid “F” (fig. 10), or two cooling fluids “F” and one heating fluid (fig. 11), or two of each (fig. 12) or, in theory, as long as the mechanical construction of the equipment is viable, as many fluids as desired (fig. 13).

[051] The proposed devices were originally developed to reduce the volume of inert fluid/buffer in indirect sulfuric acid cooling systems such as the one presented in the Safehr® patent application: PCT BR 2016 050287, since the proposed arrangement eliminates completely the need for accessory equipment and devices, notably pump, piping, expansion tanks, control instruments, and others.

[052] However, the technology described can be used in any system in which it is necessary to heat and cool fluids and where, for any reason, there is no interest in these fluids coming into contact in the event of failure or if one wants to limit and film temperature of one of the fluids.

[053] The buffered multifluid heat exchanger 1, as described above, carries out a multifluid heat exchange process, buffered for safety, essentially comprising:

[054] - Provide a lower pipe 2 through which a hot process fluid “Q” to be cooled flows;

[055] - Provide an upper pipe 3 through which a cold process fluid “F” to be heated flows, parallel and which keeps a space in relation to the lower pipe 2;

[056] Provide an airtight vessel 4 inside the body of which the tubes (2), (3) are housed and connected to inlet nozzles 2', 3' and outlet nozzles 2", 3", respectively;

[057] Provide a portion of buffer fluid “T”, heat transfer fluid, inert in relation to the hot “Q” and cold “F” fluids, which partially fills the vessel 4 and covers the lower piping 2, through which circulates hot fluid “Q” to be cooled;

[058] Provide the steps (figs. 2, 14):

[059] Circulation of the hot fluid “Q” to be cooled in the lower pipe 2 and the circulation of the cold fluid “F” to be heated in the upper pipe 3;

[060] Thermal exchange of the buffer fluid “T” with the hot fluid “Q” to be cooled that flows in the lower pipe 2 and vaporization of the buffer fluid “T”, forming cooled fluid “R” and buffer fluid vapor “VT” ;

[061] Upward movement of the buffer fluid vapor “VT” until it reaches and contacts the upper pipe 3 through which the cold fluid “F” to be heated flows;

[062] Thermal exchange between the buffer fluid vapor “VT” and the cold fluid “F” to be heated that flows in the upper pipe 3 and condensation of the buffer fluid vapor “VT”, forming heated fluid “A” and condensate of “CT” buffer fluid;

[063] Downward movement of the “CT” buffer fluid condensate until it joins the “T” buffer fluid body in the liquid phase and restarts the cycle.

[064] Step to reduce loss of efficiency in the contact region between the steam “VT”, in upward movement, and the condensate “CT”, in downward movement, of the buffer fluid “T”, carried out in the space between the pipes 2 through which hot process fluid “Q” circulates and pipes 3 through which cold process fluid “F” circulates.

Claims (8)

1) “SAFETY BUFFERED MULTIFLUID HEAT EXCHANGER”, comprising piping (2) through which hot process fluid “Q” circulates to be cooled, by piping (3) through which cold process fluid “F” circulates to be heated , CHARACTERIZED by lower piping (2) through which hot process fluid “Q” to be cooled circulates; by piping (3) through which cold process fluid “F” to be heated circulates, parallel and spaced in relation to the lower piping (2); by vessel (4) that contains the pipes (2) and (3), equipped with opposing inlet (2)' and outlet (2) nozzles communicating with the respective ends of the pipe (2), opposing inlet nozzles (3 )' and outlet (3)” communicating with the respective ends of the pipe (3); said nozzles (2)', (2)”, (3)', (3)” connected to pipes connected to equipment (100), (101) that use the cooled process fluid “R”, coming from the fluid of heated process fluid “Q” and the heated process fluid “A”, coming from the cold process fluid “F”; Said buffered multifluid heat exchanger (1) is also formed by a portion of buffer fluid “T” that fills part of the vessel (4) and covers the lower piping (2) through which the hot process fluid “Q” to be circulated. cold. 2) - “SAFETY BUFFERED MULTIFLUID HEAT EXCHANGER”, according to claim 1, characterized in that the pipes (2) and (3) may be constituted by smooth tubular bundles, finned with longitudinal fins, circumferential fins, helical fins, tubes suitable twists to promote and maximize thermal exchange between the hot “Q” and cold “F” fluids, circulating in the pipes (2) and (3) respectively, and the buffer fluid “T”. 3) - “SAFETY BUFFERED MULTIFLUID HEAT EXCHANGER”, according to claim 1, characterized in that the buffer fluid “T” is selected based on its chemical compatibility with the process fluids “Q” and “F” and their physicochemical characteristics. 4) - “SAFETY BUFFERED MULTIFLUID HEAT EXCHANGER”, according to claim 1, characterized by a device (7) to reduce the loss of efficiency in the region of contact between the vapor and condensate of the buffer fluid “T, comprised by the beams upper tubulars (3), through which the cold fluid “F” to be heated flows, be inclined or equipped with baffles (8) or said device (7) to reduce the loss of efficiency in the contact region between the steam and condensate of buffer fluid “T” can be made up of gas-liquid separating devices such as fins, Chevron-type separators (9) or baffle fins (10), installed in the region between the lower (2) and upper (3) tubular bundles, in the which circulate hot “Q” and cold “F” fluids, respectively. 5) - “SAFETY BUFFERED MULTIFLUID HEAT EXCHANGER”, according to claim 1 or 2, characterized in that the pipes (2) and (3) are tubular bundles (2) and (3) horizontal longitudinal, transversal, bundles of the type U (U-BUNDLE) or mixtures thereof installed horizontally or vertically. 6) - “SAFETY BUFFERED MULTIFLUID HEAT EXCHANGER”, according to claim 1, characterized by using more than two process fluids, such as: two heating fluids “Q” and one cooling fluid “F” or two cooling fluids “F” is one for heating or two of each or as many fluids as desired and that the mechanical construction of the equipment can accommodate. 7) - “SAFETY BUFFERED MULTIFLUID THERMAL EXCHANGE PROCESS”, carried out by the heat exchanger (1) of claims 1 to 6, characterized by: - Providing a lower pipe (2) through which a hot process fluid flows “ Q” to be cooled; - Provide an upper piping (3) through which a cold process fluid “F” to be heated flows, parallel and keeping a space in relation to the lower piping (2); - Provide an airtight vessel (4) inside the body of which the tubes (2), (3) are housed and connected to the inlet (2'), (3') and outlet (2”), (3) nozzles. ”), respectively; - Provide a portion of buffer fluid “T”, a heat transfer fluid, inert in relation to the hot “Q” and cold “F” fluids, which partially fills the vessel (4) and covers the lower piping (2), through which circulates hot fluid “Q” to be cooled; - Provide the steps for: - Circulation of the hot fluid “Q” to be cooled in the lower pipe (2) and the circulation of the cold fluid “F” to be heated in the upper pipe (3); - Thermal exchange of the buffer fluid “T” with the hot fluid “Q” to be cooled that flows in the lower pipe (2) and vaporization of the buffer fluid “T”, forming cooled fluid “R” and vapor of buffer fluid “T” ; - Upward movement of the buffer fluid vapor “VT” until it reaches and contacts the upper pipe (3) through which the cold fluid “F” to be heated flows; - Thermal exchange between the vapor of buffer fluid “VT” and the cold fluid “F” to be heated that flows in the upper pipe (3) and condensation of the vapor of buffer fluid “VT”, forming heated fluid “A” and condensate of “CT” buffer fluid; - Downward movement of the “CT” buffer fluid condensate until it joins the “T” buffer fluid body in the liquid phase and restarts the cycle. 8) - “SAFETY BUFFERED MULTIFLUID THERMAL EXCHANGE PROCESS”, according to claim 7, characterized by a step of reducing efficiency loss in the contact region between the upwardly moving “VT” steam and the condensate “CT”, in downward movement, of buffer fluid “T”, carried out in the space between the pipes (2) through which hot process fluid “Q” circulates and pipes (3) through which cold process fluid “F” circulates, carried out through the upper piping (3) longitudinal, transversal, flat or inclined and/or equipped with baffles (8) or by gas-liquid separating devices such as fins, Chevron type separators (9) or baffle fins (10), installed in the region between the lower (2) and upper (3) tubular bundles, in which hot “Q” and cold “F” fluids circulate, respectively.