System for cooling recirculated off-gas in low density polyethylene production

Abstract

An improved heat exchanger system for cooling a recycle offgas in the production of high pressure low density polyethylene. A system for exchanging heat between a first material and a second material can include a shell for containing the first material therein, a plurality of tubes arranged within the shell for containing the second material therein, a tube sheet arranged at an end of the shell for restricting flow of the second material to the shell, and at least one collector conduit arranged outside of the shell for receiving at least one of the ends of the plurality of tubes, wherein at least one of the plurality of tubes extends through the tube sheet to the collector conduit. A cleaning tool can be arranged within the collector conduit for cleaning the tubes. A method for cooling a gas stream can include directing the gas stream to a heat exchanger system provided herein.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 979695, filed February 21, 2020, entitled “System for Cooling Recirculated Exhaust Gas in Low-Density Polyethylene Production,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments of the present invention generally relate to heat exchanger cooling systems. More particularly, these embodiments relate to improved heat exchanger systems for cooling exhaust gases recirculated to high-pressure low-density polyethylene reactors. Background Technology

[0004] In low-density polyethylene (LDPE) production, a high-pressure recirculation system cools unreacted waste gas (containing ethylene) from a high-pressure separator that is fluidly connected to the outlet of the high-pressure LDPE reactor. The cooled gas is then supplied to a secondary compressor and recirculated back to the LDPE reactor. This cooling operation is traditionally performed using one or more two-tube heat exchangers, in which unreacted waste gas flows through one tube and cooling water flows through another tube surrounding the first tube, or vice versa. Heat is transferred from the waste gas to the cooling water, thereby cooling the waste gas.

[0005] One challenge in using twin-tube heat exchangers in a recirculation system is that these exchangers experience a high pressure drop. Therefore, the secondary compressor needs to consume more power to increase the pressure of the unreacted exhaust gas being recirculated to the LDPE reactor. Another disadvantage of using twin-tube heat exchangers is that each heat exchanger is quite large, requiring more space than desired within the manufacturing facility.

[0006] One alternative design for a high-pressure recirculation system is to use a shell-and-tube heat exchanger instead of a two-tube heat exchanger. A shell-and-tube heat exchanger consists of an outer shell (i.e., a large pressure vessel) containing a bundle of tubes. Unreacted waste gas flows through the tubes, while cooling water flows through the shell. Compared to a two-tube heat exchanger, a shell-and-tube heat exchanger advantageously experiences a smaller pressure drop and occupies less space, as the tube bundle allows for more passes between the cooling water and the waste gas.

[0007] Despite these advantages, shell-and-tube heat exchangers have their own limitations. Because the tubes are housed within the heat exchanger's outer shell and terminate at the tube sheet, they are supported by welding to the tube sheet. These weld points are potential sources of leakage, potentially leading to gas leaks from the tubes to the shell. Therefore, unreacted gases containing ethylene may undesirably accumulate in the heat exchanger's shell, resulting in some ethylene not being recirculated. Consequently, the cost of LDPE production can increase due to gas leaks. This also creates safety risks in the cooling system.

[0008] Another problem associated with the use of conventional shell-and-tube heat exchangers is that the tubes can become clogged by any wax entrained in the unreacted gas. This wax can form when low molecular weight polyethylene becomes insoluble in the solution of unreacted gas due to decreasing temperature. Contaminated or clogged tubes can be difficult to clean because they are located inside the heat exchanger's outer shell. Furthermore, the tubes of conventional shell-and-tube heat exchangers are typically made of corrosion-resistant materials (such as carbon steel), and therefore can begin to leak due to corrosion failure.

[0009] Therefore, heat exchangers that are less prone to leakage and corrosion failure and thus have a longer lifespan are needed. Heat exchangers that are also easier to clean are also highly desirable. Summary of the Invention

[0010] An improved heat exchanger system and method are provided for cooling recirculated exhaust gas in high-pressure LDPE production. In one or more embodiments, the system for heat exchange between a first material and a second material can include: a housing for containing the first material therein; a plurality of tubes arranged within the housing for containing the second material therein; a tube sheet arranged at an end of the housing for restricting the flow of the second material to the housing; and at least one collector conduit arranged outside the housing for receiving at least one end of the plurality of tubes, wherein at least one of the plurality of tubes extends through the tube sheet to the collector conduit. A cleaning tool can be arranged within the collector conduit, the cleaning tool including a nozzle for spraying one of the tubes with a fluid at a pressure of up to 80 MPa during cleaning.

[0011] In one or more embodiments, the method for cooling an airflow can include directing the airflow to one or more heat exchangers for cooling the airflow, the one or more heat exchangers comprising: a housing for containing a cooling medium therein; a plurality of tubes disposed within the housing for containing the airflow therein; a tube sheet disposed at an end of the housing for restricting airflow to the housing; and at least one collector conduit disposed outside the housing for receiving at least one end of the plurality of tubes, wherein at least one of the plurality of tubes extends through the tube sheet to the collector conduit. Attached Figure Description

[0012] To gain a more detailed understanding of the above-described features of the present invention, a more specific description of the invention (briefly summarized above) can be obtained by referring to the embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings only show typical embodiments of the invention and should not be considered as limiting the scope of the invention, as the invention allows for other equivalent embodiments.

[0013] Figure 1A flowchart of an exemplary high-pressure low-density polyethylene (LDPE) production method according to one or more embodiments described herein is shown.

[0014] Figure 2 It shows that it can be used for Figure 1 A flowchart of an exemplary high-pressure recirculation system in an LDPE production method.

[0015] Figure 3A This document illustrates one or more embodiments of a method that can be used for... Figure 2 A partial side view of an exemplary shell-and-tube heat exchanger in a high-pressure recirculation system.

[0016] Figure 3B The following are illustrated according to one or more embodiments described herein: Figure 3A A detailed view of a portion of the heat exchanger.

[0017] Figure 4A The following are illustrated according to one or more embodiments described herein: Figure 3A A side view of the heat exchanger casing, in which the baffles are arranged inside the casing.

[0018] Figure 4B The following are illustrated according to one or more embodiments described herein: Figure 4A A cross-sectional view of the casing and deflector.

[0019] Figure 5 This document illustrates one or more embodiments of a cleaning method. Figure 3A A side view of an exemplary cleaning tool for the tubes of the heat exchanger shown.

[0020] Figure 5A The following are illustrated according to one or more embodiments described herein: Figure 5 A cross-sectional view of the cleaning tools.

[0021] Figure 6 A cross-sectional view of an exemplary collector catheter according to one or more embodiments described herein is shown, the collector catheter being capable of receiving Figure 3A The ends of the tubes of the heat exchanger, and capable of containing Figure 5 Cleaning tools. Detailed Implementation

[0022] It should be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, and / or functions of the present invention. Exemplary embodiments of components, arrangements, and constructions are described below to simplify this disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Furthermore, reference numerals and / or letters may be repeated in various exemplary embodiments and in the accompanying drawings provided herein. Such repetition is for simplicity and clarity and does not, in itself, indicate a relationship between the constructions and / or various exemplary embodiments described in the drawings. Moreover, the exemplary embodiments presented below can be combined in any combination, i.e., any element from one exemplary embodiment can be used in any other exemplary embodiment without departing from the scope of the invention.

[0023] Furthermore, certain terms are used in the following description and claims to refer to specific components. As those skilled in the art will understand, various entities can represent the same component by different names; therefore, the naming conventions used for the elements herein are not intended to limit the scope of the invention unless specifically defined herein. Moreover, the naming conventions used herein are not intended to distinguish between components with different names but the same function.

[0024] In the following description and claims, the terms “comprising” and “including” are used in an open-ended manner and should therefore be interpreted as “including but not limited to”. The phrase “consisting substantially of…” means that the described / claimed composition does not include any other component that substantially alters its properties by more than 5% and in no case any other component at a level greater than 3% by mass.

[0025] The term “or” will include both exclusive and inclusive cases, meaning that “A or B” will be synonymous with “at least one of A and B”, unless otherwise explicitly stated herein.

[0026] The indefinite articles “a” and “an” refer to the singular form (i.e., “one”) and the plural form (i.e., one or more) unless the context clearly indicates otherwise. For example, examples using “olefin” include examples in which one, two or more olefins are used, unless otherwise specified or the context clearly indicates that only one olefin is used.

[0027] The terms "wt%" refer to weight percentage, "volume%" refer to volume percentage, "molar%" refer to molar percentage, "ppm" refer to parts per million, and "ppm wt" and "wppm" are used interchangeably, referring to parts per million based on weight. All concentrations herein are based on the total amount of the composition described unless otherwise stated.

[0028] The term "α-olefin" refers to any straight-chain or branched compound containing carbon and hydrogen with at least one double bond between α and β carbon atoms. For the purposes of this specification and the appended claims, when a polymer or copolymer is referred to as including an α-olefin (e.g., poly-α-olefin), the α-olefin present in such polymer or copolymer is the polymeric form of the α-olefin.

[0029] The term "polymer" refers to any two or more identical or different repeating units / monomer units or units. The term "homopolymer" refers to a polymer having identical units. The term "copolymer" refers to a polymer having two or more units that are different from each other, including terpolymers, etc. The term "terpolymer" refers to a polymer having three units that are different from each other. The term "different" when it refers to units means that the units differ from each other by at least one atom or are isomerically different. Similarly, the definition of polymer used herein includes homopolymers, copolymers, etc. For example, when a copolymer is described as having a "propylene" content of 10% to 30% by weight, it should be understood that the repeating units / monomer units or (only) units in the copolymer are derived from propylene in the polymerization reaction, and the derived units are present in 10% to 30% by weight (based on the weight of the copolymer).

[0030] The term "fluid connectivity" means that fluid can flow from the first component to the second component directly or through at least a third component. The term "inlet" refers to the point where fluid enters the component, and the term "outlet" refers to the point where fluid leaves the component.

[0031] The naming of the elements and their groups used here is based on the periodic table adopted by the International Union of Pure and Applied Chemistry after 1988. An example of the periodic table is shown on the inside cover of Advanced Inorganic Chemistry, 6th edition, by F. Albert Cotton et al. (John Willie & Son Publishing, 1999).

[0032] Detailed descriptions are provided below. Each appended claim identifies a separate invention and, for infringement purposes, is considered to include equivalents of the various elements or limitations specified in the claims. Depending on the context, in some cases, all references to “invention” may refer only to certain specific embodiments. In other cases, it should be understood that references to “invention” will refer to the subject matter set forth in one or more claims, but not necessarily all of them. Each invention will be described in more detail below, including specific embodiments, versions, and examples; however, the invention is not limited to these embodiments, versions, or examples, which are included when the information in this disclosure is combined with publicly available information and techniques to enable those skilled in the art to practice and use the invention.

[0033] An improved shell-and-tube heat exchanger system is disclosed, comprising one or more heat exchangers containing multiple tubes arranged within a shell or container. The shell-and-tube heat exchanger system can be used as a cooling recirculation system, for example, in the production of high-pressure low-density polyethylene (LDPE). Unreacted gas from the LDPE reactor can flow through these tubes, and a cooling fluid can flow through the shell, resulting in heat exchange between the unreacted gas and the cooling fluid. A tube sheet can be arranged at the end of the shell to restrict the flow of unreacted gas from these tubes to the shell. One or more collection conduits can be positioned outside the shell of each heat exchanger to receive the ends of the tubes. At least a portion of the tubes uniquely extends through the tube sheet in the shell to the collection conduit outside the shell. Therefore, it is not necessary to support the tubes extending through the shell by connecting them to the shell. Since there is no potential source of leakage at the connection point, gas is unlikely to accumulate in the shell.

[0034] Preferably, the heat exchanger system of the present invention can include tubes made primarily of duplex stainless steel, which is highly corrosion-resistant, resulting in less gas leakage from the tubes to the casing. The heat exchanger system can also include a pair of longitudinal baffles arranged within the casing and on opposite sides of the casing. Such baffles can be positioned near the inlet of the casing, near the outlet of the casing, and / or at multiple locations along the length of the casing. They can guide the cooling fluid more towards the center of the casing and closer to the tubes, thereby providing better heat transfer.

[0035] The heat exchanger system can also include cleaning tools located inside each collection conduit for removing wax and any other contaminants accumulated inside the tubes. The cleaning tools can include nozzles for spraying wax using a fluid (e.g., water) pressurized enough to flush the wax into a drain tank, for example. Because the tubes extend outside the housing to the collection conduits, they are more easily accessible to workers in LDPE production facilities. Therefore, workers can easily determine when a tube leaving the housing is blocked by feeling if it is colder than usual. The cleaning tool can then be rotated to a position where the nozzle is aligned with the end of the blocked tube to allow fluid to flow through the nozzle. After cleaning, the cleaning tool can be rotated back to a position where fluid flow through the nozzle is no longer permitted.

[0036] LDPE production method

[0037] refer to Figure 1This diagram illustrates a flowchart of an example high-pressure LDPE production method using the heat exchanger system provided herein. As shown, feed stream 10 is first directed to primary compressor 12 to increase the pressure of feed stream 10. Feed stream 10 can include feedstocks typically used in the polymerization process for producing LDPE. For example, when producing polyethylene copolymers, feed stream 10 can include ethylene or ethylene mixed with at least one other comonomer. Alternatively, feed stream 10 can include ethylene, and at least one other comonomer can be directed to a compressed feed stream 14 exiting primary compressor 12.

[0038] Examples of suitable comonomers include: vinyl ethers, such as vinyl methyl ether and vinyl ether; α-olefins, such as propylene, 1-butene, 1-octene, and styrene; vinyl esters, such as vinyl acetate, vinyl butyrate, and vinyl neopentanoate; halogenated olefins, such as vinyl fluoride and vinylidene fluoride; acrylates, such as methyl acrylate, ethyl acrylate, and methacrylate; other acrylic or methacrylic acid compounds, such as acrylic acid, methacrylic acid, maleic acid, acrylonitrile, and acrylamide; and other compounds, such as allyl alcohol, vinyl silane, and other copolymerizable vinyl compounds. Two or more comonomers can be used when desired. α-olefin comonomers can be linear (e.g., linear C3-C20 α-olefins) or branched (e.g., α-olefins having one or more C1-C3 alkyl branches or aryl groups). Specific examples of α-olefins include: C3-C12 α-olefins, such as propylene; 1-butene; 3-methyl-1-butene; 3,3-dimethyl-1-butene; 1-pentene; 1-pentene having one or more methyl, ethyl, or propyl substituents; 1-hexene having one or more methyl, ethyl, or propyl substituents; 1-heptene having one or more methyl, ethyl, or propyl substituents; 1-octene having one or more methyl, ethyl, or propyl substituents; 1-nonene having one or more methyl, ethyl, or propyl substituents; 1-decene substituted with ethyl, methyl, or dimethyl; 1-dodecene; and styrene.

[0039] The compressed feed stream 14 exiting the primary compressor 12 can be directed to the secondary compressor 16 to further increase its pressure. The highly compressed feed stream 18 exiting the secondary compressor 16 can then be directed to the reactor 20, such as a tubular reactor or an autoclave reactor. LDPE polymers or copolymers can be produced within the reactor 20 using high-pressure and high-temperature polymerization methods. Various processing variables for achieving safe and economical operating conditions are known in the art. For example, when using a single autoclave reactor, polymerization processes can be carried out at pressures from approximately 131 MPa to approximately 210 MPa and temperatures from approximately 148°C to approximately 270°C. It should be understood that multiple reactors can be used alternatively.

[0040] The polymerization reaction can be enhanced by injecting at least one modifier or chain transfer agent. The modifier can be injected upstream of the primary compressor. Alternatively, it can be injected upstream of the secondary compressor or the reactor. Examples of suitable modifiers include isobutylene, propylene, n-butane, hexane, propane, 1-butene, and aldehydes such as acetaldehyde and propionaldehyde.

[0041] An effluent stream 22, containing LDPE polymer or copolymer and unreacted ethylene, comonomers, and / or modifiers, exits reactor 20. After experiencing a pressure drop in a valve, this effluent stream 22 can be directed to a high-pressure separator 24. The high-pressure separator 24 can separate the effluent stream 22 into a polymer-rich liquid phase 32 and an unreacted gas phase 26. The polymer-rich liquid phase 32 exiting the bottom of the high-pressure separator 24 can be directed to a low-pressure separator 34, where the pressure is further reduced. If necessary, the polymer-containing liquid stream 35 exiting the bottom of the low-pressure separator 34 can be sent to an extruder to pelletize the polymer. The unreacted gas stream 36 exiting the low-pressure separator 34 can be directed to a recirculation cleaning compressor 38, so that the pressure of stream 36 is increased to the pressure of feed stream 10. Then, the recirculated gas stream 46 exiting the cleaning compressor 38 can be directed to feed stream 10. A portion of the gas stream 46 exiting the cleaning compressor 38 can also be sent through stream 48 for purification.

[0042] Unreacted gas flow 26 exiting the high-pressure separator 24 can be directed to a cooling recirculation system 28, which can include the shell-and-tube heat exchanger system disclosed herein. The unreacted gas flow 26 can enter the cooling recirculation system 28 at a temperature, for example, from about 100°C to about 300°C, preferably from about 150°C to about 280°C, more preferably from about 200°C to about 260°C. The cooled unreacted gas flow 30 exits the recirculation system 28 at a temperature, for example, from about 15°C to about 80°C, preferably from about 15°C to about 50°C, more preferably from about 15°C to about 30°C. The pressure drop across the entire cooling recirculation system 28 can be as low as about 0.5 MPa to about 1.5 MPa, which is a significant improvement compared to conventional recirculation systems using two-tube heat exchangers.

[0043] The cooled unreacted gas stream 30 can be recirculated back into the compressed feed stream 14, allowing unreacted ethylene, comonomers, and / or modifiers to be redirected to the secondary compressor 16, which is in fluid communication with the LDPE reactor 20. Wax entrained in the unreacted gas passing through the cooling recirculation system 28 can be directed down through stream 40 to the sump tank 42. Any gas accumulating in the sump tank 42 can be redirected through stream 44 to gas stream 36 for recirculation.

[0044] heat exchanger system

[0045] The heat exchanger system disclosed here can be used as Figure 1 The cooling recirculation system 28. Figure 2 A flowchart of an exemplary heat exchanger system is shown. Airflow 100 (e.g., from...) Figure 1 The unreacted gas stream 26 can be initially supplied to one or more waste heat boilers 102 and 110 arranged in series to recover waste heat from the gas stream 100 and generate steam that can be used for other processing. Water 104 supplied to waste heat boiler 102 can be converted into medium-pressure steam 106 with a pressure of about 1 MPaG to about 2 MPaG. The outlet stream 108 leaving waste heat boiler 102 can be directed to the inlet of waste heat boiler 110. Water 112 supplied to boiler 110 can be converted into low-pressure steam 114 with a pressure of about 0.3 to about 0.5 MPaG.

[0046] The outlet flow 116 from the waste heat boiler 110 can lead to multiple sets of parallel shell-and-tube heat exchangers arranged in series. The first set can use hot water as the cooling medium, the second set can use cooling tower water as the cooling medium, and the third set can use chilled water as the cooling medium. This gradual cooling of unreacted gases results in more energy-efficient operation of the cooling cycle system. Figure 2 An embodiment of these parallel shell-and-tube heat exchanger assemblies is shown. More specifically, the outlet flow 116 from the waste heat boiler 110 can be split into a first flow 118 leading to shell-and-tube heat exchanger 120 and a second flow 119 leading to shell-and-tube heat exchanger 122. Coolest possible hot water (typically between approximately 40°C and approximately 60°C, for example, when economic considerations are taken into account) can enter heat exchangers 120 and 122 through flows 124 and 126, respectively, and exit heat exchangers 120 and 122 through flows 128 and 130, respectively. The outlet flow 132 exiting heat exchanger 120 and the outlet flow 134 exiting heat exchanger 122 can be combined into a gas flow 136, which can be further supplied to a gas-liquid separator 138 (also called a separator tank). The gas-liquid separator 138 can remove liquids, such as wax, entrained in the gas flow 136, which can be removed from the bottom of the gas-liquid separator through flow 140.

[0047] The outlet flow 142 exiting the gas-liquid separator 138 is then split into two additional flows 146 and 148 before being supplied to the shell-and-tube heat exchanger 144. Flow 146 is directed to the shell-and-tube heat exchanger 150, and flow 148 is directed to the shell-and-tube heat exchanger 152. Depending on the current weather conditions, the cooling tower water, as cold as possible, can enter heat exchangers 150, 144, and 152 through flows 154, 156, and 158, respectively, and exit heat exchangers 150, 144, and 152 through flows 160, 162, and 164, respectively. For example, the cooling tower water temperature can vary depending on the climate of the country where the LDPE production process is located and the season (hotter summers, colder winters). For example, the cooling tower water temperature can be between approximately 10°C and approximately 40°C. The outlet flow 166 exiting heat exchanger 150 and the outlet flow 168 exiting heat exchanger 152 can be directed to the gas flow 170 exiting heat exchanger 144. This gas flow 170 can then be supplied to the gas-liquid separator 172. The gas-liquid separator 172 can remove liquid, such as wax, entrained in the gas flow 170 through the flow 174.

[0048] The outlet flow 176 from the gas-liquid separator 172 is then split into two additional flows 180 and 182 before being directed to the shell-and-tube heat exchanger 178. Flow 180 is directed to the shell-and-tube heat exchanger 190, and flow 182 is directed to the shell-and-tube heat exchanger 192. Cold water, as cold as possible (typically between approximately 5°C and approximately 10°C), enters the heat exchangers 190, 178, and 192 through flows 194, 196, and 198, respectively, and exits the heat exchangers 190, 178, and 192 through flows 200, 202, and 204, respectively. The outlet flow 206 exiting the heat exchanger 190 and the outlet flow 208 exiting the heat exchanger 192 are directed to the gas flow 210 exiting the heat exchanger 178, which is then supplied to the gas-liquid separator 212. The gas-liquid separator 212 removes liquids, such as wax, entrained in the gas flow 210 through the flow 214. The outlet flow 216 from the gas-liquid separator can then be directed to a compressor, for example... Figure 1 The secondary compressor 16.

[0049] Figure 3A It shows that it can be used as Figure 2 A side view of a portion of an improved heat exchanger 300, showing one or more heat exchangers. The heat exchanger 300 may include a housing (rear view). Figure 4AThe heat exchanger 300 (represented in the figure) is a container through which a first material can flow through the outer shell. As shown, a bundle of tubes 304 can extend through the center of the heat exchanger 300, through which a second material can flow. Heat exchange is possible between the first and second materials. In one embodiment, the first material flowing through the outer shell 302 can be or may include water or other heat transfer fluids, and the second material flowing through the tubes 304 can be or may include unreacted gases from polyolefin production processes. It should be understood that the first and second materials can flow through the heat exchanger 300 in reverse order.

[0050] Tube 304 can be manufactured from any suitable material that is highly corrosion-resistant and can withstand the desired operating conditions within the heat exchanger 300. Particularly suitable materials are duplex stainless steels. Duplex stainless steels have a two-phase microstructure comprising ferritic and austenitic stainless steel grains. Another suitable material for tube 304 is austenitic stainless steel, such as SAE 316L grade stainless steel. Tube 304 can also comprise both duplex and austenitic stainless steels.

[0051] Still referencing Figure 3A The tube sheet 306 can be laterally disposed at one end of the housing 302 to restrict the flow of the second material from the tube 304 to the housing 302. The end of the tube 304 can extend through the tube sheet 306 to reach the inlet collection conduit 310a and the outlet collection conduit 310b. The inlet collection conduit 310a can be used to deliver the second material to the first or "inlet" end of each tube 304, and the outlet collection conduit 310b can be used to receive the second material from the second or "outlet" end of each tube 304, or vice versa.

[0052] The tubes 304 can be configured to have multiple parallel flows and passes as deemed necessary by those skilled in the art. For example, the heat exchanger 300 can include up to twenty tubes 304 arranged in parallel, each tube 304 constituting up to twelve passes to provide relatively high cooling capacity. As used herein, each “pass” is equal to a “tube length,” that is, the length of the tube between the tube sheet 306 and the opposite ends of the housing 302 of the heat exchanger 300. Thus, each tube 304 can be arranged such that material flowing through the tube 304 flows horizontally for one tube length (equivalent to one pass) in a first direction, and then horizontally for another tube length (equivalent to a second pass) in a second direction opposite to the first direction. This flow pattern can be repeated up to twelve passes before the material in each tube 304 leaves the heat exchanger 300. Since the heat exchanger 300 can include up to 20 tubes 304, the total number of tube lengths formed by the tubes 304 can be up to 240. It should be understood that the tubes 304 can be arranged in various other configurations known in the art.

[0053] Figure 3BAn enlarged detail of a portion 314 of the heat exchanger 300 is shown to more clearly illustrate a tube 304 extending through the tube sheet 306. Because the end of the tube 304 extends through the tube sheet 306, it is not necessary to weld the tube 304 to the tube sheet 306. Therefore, gas is unlikely to leak from the tube 304 and undesirably accumulate in the housing 302.

[0054] Figure 4A It shows Figure 3A The image shows a side view of the housing 302 of the heat exchanger 300, and also shows that the heat exchanger 300 may include one or more baffles 312, which are longitudinally positioned along the length of the housing 302. Figure 4B It is the outer casing 302 that passes through. Figure 4A The diagram shows a cross-sectional view along line 4B-4B. It illustrates that the flow deflector 312 can be positioned near opposite sides of the housing 302. The flow deflector 312 can be arranged to guide the flow in the housing 302 more towards the center and closer to the pipe 304. It should be understood that the flow deflector 312 can have other configurations depending on the direction of flow guidance through the housing 302.

[0055] Figure 5 It shows that it can be used for cleaning Figure 3A A side view of an exemplary cleaning tool 400 for the tubes of the heat exchanger 300 shown, and Figure 5A A cross-sectional view of the cleaning tool is shown (along...) Figure 5 (See line 5A-5A shown). Figure 5 As shown, cleaning tool 400 can be used to clean from Figure 3A The cleaning tool 400 removes contaminants such as wax from the tube 304. The cleaning tool 400 may include a housing 402 within which a nozzle 404 is located. An opening or conduit 406 may be positioned within the housing 402 to guide fluid, such as water, through the housing 402 to the nozzle 404. Figure 5 The thick arrows indicate the direction in which fluid (e.g., water) flows into and through tool 400. Alignment nose 408 can be positioned near nozzle 404 to hold nozzle 404 in place. Nozzle 404 can include piston 410 and spring 412 to regulate fluid flow.

[0056] It should be known that Figure 5A A cross-sectional view of the cleaning tool 400 is shown, with particular emphasis on one or more openings or holes 414 that can be drilled through the cleaning tool 400 to reduce its weight. The lighter the cleaning tool 400, the easier it is for the operator to maneuver and move it. Figure 6 As shown, the cleaning tool 400 can be positioned within the inlet collection conduit 310a and the outlet collection conduit 310b.

[0057] Workers can easily determine when a tube 304 is blocked by feeling the outside of the tube ends 308a and 308b leading to the collection conduits 310a and 310b. When one of the tube ends 308a or 308b is colder than usual, this indicates that the corresponding tube 304 is blocked.

[0058] The cleaning tool 400 can then be operated by rotating it to a position where the piston 410 is aligned with the tube 304 that needs cleaning. When the tool 400 is in this position, fluid (e.g., water) can be ejected from the nozzle 404 at pressures up to approximately 80 MPa. The force of the fluid washes away contaminants that have accumulated in the tube 304. To terminate the cleaning process, the cleaning tool 400 can be rotated back to its initial position, in which the nozzle is pressed against the inner wall of the collection conduit 310a or 310b by the spring 412, thereby restricting the flow of fluid from the nozzle 404.

[0059] The cleaning tool 400 can also be used to remove dirt from the pipe 304 in the same manner as described above.

[0060] Example List

[0061] This disclosure may also include any one or more of the following non-limiting embodiments:

[0062] 1. A system for heat exchange between a first material and a second material, comprising: a housing for containing the first material therein; a plurality of tubes arranged within the housing for containing the second material therein; a tube sheet arranged at an end of the housing for restricting flow of the second material to the housing; and at least one collector conduit arranged outside the housing for receiving at least one end of the plurality of tubes, wherein at least one of the plurality of tubes extends through the tube sheet to the collector conduit.

[0063] 2. The heat exchanger system according to Embodiment 1, wherein: at least one collector conduit includes an inlet collector conduit and an outlet collector conduit, at least one inlet end of the conduit is in fluid communication with the inlet collector conduit for receiving a second material from the inlet collector conduit, and at least one outlet end of the conduit is in fluid communication with the outlet collector conduit for conveying the second material to the outlet collector conduit.

[0064] 3. The heat exchanger system according to Embodiment 1 or 2, wherein: the plurality of tubes are substantially composed of duplex stainless steel, austenitic stainless steel or a combination thereof.

[0065] 4. The heat exchanger system according to embodiments 1 to 3 further includes: a pair of longitudinal guide vanes arranged inside the housing on opposite sides adjacent to the housing.

[0066] 5. The heat exchanger system according to Example 4, wherein: the pair of longitudinal guide vanes are arranged near the inlet of the shell, near the outlet of the shell, or at multiple locations along the length of the shell.

[0067] 6. The heat exchanger system according to embodiments 1 to 5 further includes: a cleaning tool disposed within at least one collector conduit, the cleaning tool including a nozzle for spraying fluid into one of the ends of a plurality of tubes during cleaning.

[0068] 7. The heat exchanger system according to Embodiment 6, wherein: the cleaning tool is rotatable to a first position, in which the nozzle is aligned with one of the ends of the plurality of tubes, and fluid is able to flow out from the nozzle.

[0069] 8. The heat exchanger system according to embodiment 6 or 7, wherein: the cleaning tool is rotatable to a second position in which the nozzle is not aligned with the end of one of the plurality of tubes and fluid does not flow out of the nozzle.

[0070] 9. The heat exchanger system according to Examples 1 to 8, wherein: the plurality of tubes includes up to twenty tubes arranged in parallel, each tube being arranged with up to twelve passes.

[0071] 10. A method for cooling an airflow includes: directing the airflow to one or more heat exchangers for cooling the airflow, the one or more heat exchangers comprising: a housing for containing a cooling medium therein; a plurality of tubes arranged within the housing for containing the airflow therein; a tube sheet arranged at an end of the housing for restricting airflow to the housing; and at least one collector conduit arranged outside the housing for receiving at least one end of the plurality of tubes, wherein at least one of the plurality of tubes extends through the tube sheet to the collector conduit.

[0072] 11. The method according to Example 10, wherein: the gas flow is directed from a separator in fluid communication with the outlet of the polyethylene production reactor to the one or more heat exchangers to form a cooled gas flow, the cooled gas flow being recirculated to a compressor in fluid communication with the inlet of the polyethylene production reactor.

[0073] 12. The method according to embodiment 10 or 11, wherein the gas flow is directed to one or more boilers arranged in series before being directed to one or more heat exchangers for generating steam.

[0074] 13. The method according to Examples 10 to 12, wherein: the plurality of tubes are substantially composed of duplex stainless steel, austenitic stainless steel or a combination thereof.

[0075] 14. The method according to embodiments 10 to 13, wherein: the one or more heat exchangers further include a pair of longitudinal guide vanes arranged inside the housing on opposite sides adjacent to the housing.

[0076] 15. The method according to Examples 10 to 14, wherein: the one or more heat exchangers further include a cleaning tool disposed within at least one collector conduit, the cleaning tool including a nozzle for spraying one of the ends of the plurality of conduits with fluid at a pressure up to about 80 MPa.

[0077] 16. The method according to embodiments 10 to 15, wherein: the plurality of tubes includes up to twenty tubes arranged in parallel, each tube being arranged with up to twelve passes.

[0078] 17. The method according to Examples 10 to 16 further includes: directing the airflow to a first group of one or more heat exchangers arranged in parallel for cooling the airflow with hot water at a temperature of about 40°C to about 60°C.

[0079] 18. The method according to Example 17 further includes: directing the gas flow leaving the first group of one or more heat exchangers to a first gas-liquid separator for removing liquid from the gas flow.

[0080] 19. The method according to Example 18 further includes: directing the gas flow leaving the first gas-liquid separator to a second group of one or more heat exchangers arranged in parallel for cooling the gas flow with cooling tower water at a temperature of about 10°C to about 40°C.

[0081] 20. The method according to Example 19 further includes: directing the gas flow leaving the second group of one or more heat exchangers to the second gas-liquid separator.

[0082] 21. The method according to embodiment 20 further includes: directing the gas flow exiting the second gas-liquid separator to a third group of one or more heat exchangers arranged in parallel for cooling the gas flow with cold water at a temperature of about 5°C to about 10°C.

[0083] 22. The method according to Example 21 further includes: directing the gas flow leaving the third group of one or more heat exchangers to the third gas-liquid separator.

[0084] 23. A method for cleaning the heat exchanger system of Example 6, comprising: rotating a cleaning tool to a first position such that a nozzle is aligned with at least one of the ends of a plurality of tubes to allow fluid to flow from the nozzle at a pressure of up to about 80 MPa.

[0085] 24. The method according to embodiment 23 or 6 further includes: rotating the cleaning tool to a second position such that the nozzle is not aligned with the end of one of the plurality of tubes and fluid is not allowed to flow out of the nozzle, thereby terminating the cleaning process.

[0086] Some embodiments and features have been expressed using a set of upper and lower numerical limits. It should be understood that a range includes any combination of two values, such as any lower value combined with any higher value, any two lower values ​​combined with / or any two higher values, unless otherwise stated. Certain lower, upper, and range limits appear in one or more of the following claims. All numerical values ​​are “approximate” or “about” indicating values, taking into account experimental errors and variations that a person skilled in the art would expect.

[0087] The various terms have been defined above. Where a term used in the claims is not defined above, it shall be given the broadest definition that has been given to a person skilled in the art, as reflected in at least one printed publication or authorized patent. Furthermore, all patents, test procedures, and other documents referenced in this application shall be incorporated herein in their entirety, provided that such disclosure is not contradictory to this application and is judicially permissible to include in this regard.

[0088] Although the foregoing relates to embodiments of the present invention, other embodiments of the present invention may be designed without departing from the basic scope of the present invention, the scope of which is determined by the following claims.

Claims

1. A heat exchanger system for exchanging heat between a first material and a second material, comprising: An outer casing for containing the first material; Multiple tubes are arranged inside the housing for containing a second material therein; Tube sheet, which is arranged at the end of the housing to restrict the flow of the second material into the housing; as well as At least one collector conduit is disposed outside the housing for receiving at least one end of the plurality of tubes, wherein at least one of the plurality of tubes extends through the tube sheet to the collector conduit; The heat exchanger system is characterized in that it further includes a cleaning tool rotatably arranged within the at least one collector conduit. The cleaning tool includes: a housing; a nozzle located within the housing for spraying fluid into one of the ends of the plurality of tubes during cleaning; and an opening positioned within the housing for guiding fluid through the housing to the nozzle. The nozzle includes a piston and a spring for regulating fluid flow, wherein fluid can be sprayed from the nozzle when the cleaning tool is rotated to a position where the piston is aligned with the tube to be cleaned, and fluid flow from the nozzle is restricted when the cleaning tool is rotated back to a position where the piston of the nozzle is pressed against the inner wall of the collector conduit by the spring.

2. The heat exchanger system according to claim 1, wherein: The at least one collector conduit includes an input collector conduit and an output collector conduit, at least one input end of the plurality of conduits is in fluid communication with the input collector conduit for receiving the second material from the input collector conduit, and at least one output end of the plurality of conduits is in fluid communication with the output collector conduit for conveying the second material to the output collector conduit.

3. The heat exchanger system according to claim 1 or claim 2, wherein: The multiple tubes are primarily composed of duplex stainless steel, austenitic stainless steel, or a combination thereof.

4. The heat exchanger system according to claim 1 or claim 2, further comprising: A pair of longitudinal guide vanes, the pair of longitudinal guide vanes being arranged inside the housing, adjacent to opposite sides of the housing.

5. The heat exchanger system according to claim 4, wherein: The longitudinal guide vanes are arranged near the inlet of the housing, near the outlet of the housing, or at multiple locations along the length of the housing.

6. The heat exchanger system according to claim 1, wherein: The cleaning tool can be rotated to a first position in which the nozzle is aligned with the end of one of the plurality of tubes, allowing fluid to flow out of the nozzle.

7. The heat exchanger system according to claim 6, wherein: The cleaning tool can be rotated to a second position in which the nozzle is not aligned with one of the ends of the plurality of tubes and fluid is not allowed to flow out of the nozzle.

8. The heat exchanger system according to claim 1 or claim 2, wherein: The plurality of tubes includes up to twenty tubes arranged in parallel, and each tube is arranged to have up to twelve passes.

9. A method for cooling an airflow, comprising: The airflow is directed to one or more heat exchangers for cooling the airflow, said one or more heat exchangers comprising: The outer casing, used to contain the cooling medium; Multiple tubes are arranged inside the housing to contain airflow therein; Tube sheet, disposed at the end of the housing, for restricting airflow toward the housing; and At least one collector conduit is disposed outside the housing for receiving at least one end of the plurality of tubes, wherein at least one of the plurality of tubes extends through the tube sheet to the collector conduit; The feature is that the one or more heat exchangers further include a cleaning tool rotatably arranged within the at least one collector conduit, the cleaning tool comprising: a housing; a nozzle located within the housing for spraying fluid into one of the ends of the plurality of tubes during cleaning; and an opening positioned within the housing for guiding fluid through the housing to the nozzle, the nozzle including a piston and a spring for regulating fluid flow, wherein fluid can be sprayed from the nozzle when the cleaning tool is rotated to a position where the piston is aligned with the tube to be cleaned, and fluid flow from the nozzle is restricted when the cleaning tool is rotated back to a position where the piston of the nozzle is pressed against the inner wall of the collector conduit by the spring.

10. The method according to claim 9, wherein: The airflow is directed from a separator in fluid communication with the outlet of the polyethylene production reactor to one or more heat exchangers to form a cooled airflow, which is then recirculated to a compressor in fluid communication with the inlet of the polyethylene production reactor.

11. The method of claim 10, wherein: The airflow is directed to one or more boilers arranged in series before being directed to the one or more heat exchangers, for generating steam.

12. The method according to claim 9 or claim 10, wherein: The multiple tubes are primarily composed of duplex stainless steel, austenitic stainless steel, or a combination thereof.

13. The method according to claim 9 or claim 10, wherein: The one or more heat exchangers further include a pair of longitudinal guide vanes arranged inside the housing on opposite sides adjacent to the housing.

14. The method according to claim 9 or claim 10, wherein: The nozzle of the cleaning tool sprays fluid at pressures up to 80 MPa into one of the ends of the plurality of tubes.

15. The method according to claim 9 or claim 10, wherein: The plurality of tubes includes up to twenty tubes arranged in parallel, each tube being arranged to have up to twelve passes.

16. The method according to claim 9 or claim 10, further comprising: The airflow is directed to one or more heat exchangers in the first group arranged in parallel, which are used to cool the airflow with hot water at a temperature of 40°C to 60°C.

17. The method of claim 16, further comprising: After the gas flow leaves one or more heat exchangers in the first group, the gas flow is directed to a first gas-liquid separator for removing liquid from the gas flow.

18. The method of claim 17, further comprising: After the gas stream leaves the first gas-liquid separator, the gas stream is directed to one or more heat exchangers in a second group arranged in parallel for cooling the gas stream with cooling tower water at a temperature of 10°C to 40°C.

19. The method of claim 18, further comprising: After the gas flow leaves one or more heat exchangers in the second group, the gas flow is directed to the second gas-liquid separator.

20. The method of claim 19, further comprising: After the gas flow leaves the second gas-liquid separator, the gas flow is directed to one or more heat exchangers in a third group arranged in parallel for cooling the gas flow with cold water at a temperature of 5°C to 10°C.

21. The method of claim 20, further comprising: After the gas flow leaves one or more heat exchangers in the third group, the gas flow is directed to the third gas-liquid separator.

22. A method for cleaning a heat exchanger system according to any one of claims 1-8, comprising: Rotate the cleaning tool to a first position such that the nozzle is aligned with one of the ends of the plurality of tubes to allow fluid to flow from the nozzle at pressures up to 80 MPa.

23. The method of claim 22, further comprising: The cleaning tool is rotated to a second position such that the nozzle is not aligned with one of the ends of the plurality of tubes and fluid is not allowed to flow out of the nozzle, thereby terminating the cleaning process.

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