Geothermal cooling of a coolant used in a heat exchange device

Abstract

A method and apparatus for cooling coolant used in heat exchange equipment in a plant are disclosed. The method is carried out in a plant having the apparatus disclosed herein. The method and apparatus utilize a geothermal cooling loop to cool at least a portion of a total amount of coolant circulating in a coolant loop used to cool surfaces of heat exchange equipment in the plant.

Description

Technical Field

[0001] This disclosure generally relates to cooling warm coolant received from heat exchange equipment in a plant. Background Technology

[0002] Petrochemical processes may involve cooling reactors and process streams. For example, polymerization reactions are typically exothermic, and coolants can be used to remove heat from the surfaces of the polymerization reactor to control the polymerization temperature within the reactor. Coolants can flow through jackets on the surfaces of the polymerization reactor to remove heat from the reactor, and warm coolants can flow out of the jackets and then be cooled, thus serving as a detour for continuous cooling of the reactor. To cool process streams within a plant, heat exchangers can be used to remove heat from the process streams with coolants.

[0003] The warm coolant generated when the coolant absorbs heat from the surface of a heat exchanger (e.g., the surface of an exothermic polymerization reactor) can be cooled using a coolant heat exchanger for recycling back into the heat exchanger. For example, a coolant heat exchanger can be a shell-and-tube heat exchanger or a plate-and-frame heat exchanger. A utility cooling medium, such as cooling tower water or seawater, flows through the coolant heat exchanger, removing heat from the coolant through the heat transfer surface area of ​​the coolant heat exchanger. The utility cooling medium can be supplied by a tower water system, and the size of the tower water system (the volume of water required in the system) depends on the cooling load of the heat exchanger. The coolant heat exchanger is responsible for cooling the heat exchanger because it cools the coolant that has heated up through contact with the surface of the heat exchanger. In addition to drift in such cooling systems, the heat absorbed by the coolant and transferred to the utility cooling medium also produces water vapor emissions (water lost through evaporation) in tower water systems. In tower water systems that supply a common cooling medium to heat exchangers used for cooling process streams, the heat exchangers may experience hydrocarbon leakage into the common cooling medium due to, for example, the pressure difference between the higher-pressure process stream on one side of the heat exchanger and the lower-pressure common cooling medium on the other side.

[0004] It is necessary to reduce the amount of common cooling medium evaporating from the tower water system and reduce hydrocarbon emissions from the process flow heat exchangers. Summary of the Invention

[0005] A method for cooling a coolant used in a heat exchange device in a factory, the method comprising: introducing a first warm coolant having a first temperature into an inlet of a cooling system including a geothermal cooling circuit; and cooling the first warm coolant in the cooling system to form a cooled coolant having a second temperature, wherein the second temperature is lower than the first temperature, wherein the inlet of the cooling system is fluidly connected to a coolant outlet of the heat exchange device in the factory, and wherein the outlet of the cooling system is fluidly connected to a coolant inlet of the heat exchange device in the factory.

[0006] A cooling device for cooling a coolant in heat exchange equipment in a factory includes a geothermal cooling circuit comprising an underground conduit buried at a depth below the surface within the factory boundary, such that the ambient temperature at that depth is consistently within the range of approximately 40°F (4°C) to approximately 80°F (27°C). The geothermal cooling circuit is configured to receive warm or intermediate coolant to form a cooled coolant with a temperature ranging from approximately 60°F (15.5°C) to approximately 100°F (37.8°C). An inlet fluid connection of the geothermal cooling circuit is made to the coolant outlet of the heat exchange equipment in the factory, and an outlet fluid connection of the geothermal cooling circuit is made to the coolant inlet of the heat exchange equipment in the factory.

[0007] Other technical features will be apparent to those skilled in the art from the following figures, description and claims. Attached Figure Description

[0008] For a more complete understanding of this disclosure, reference is now made to the following description in conjunction with the accompanying drawings, wherein:

[0009] Figure 1 It is a schematic floor plan of the factory, which includes a device for cooling the coolant used in the heat exchange equipment.

[0010] Figure 2 This is a schematic floor plan of the factory, which uses another device for cooling the coolant used in heat exchange equipment.

[0011] Figure 3A A schematic plan view of the conduit arrangement in the geothermal cooling circuit is shown.

[0012] Figure 3B A cross-sectional side view of another conduit arrangement in a geothermal cooling circuit is shown.

[0013] Figure 4 It shows Figure 1 and Figure 2 The diagram shows the implementation plan of the factory, which is a polyethylene production plant.

[0014] Figure 5 It uses a coolant jacket as a heat exchange device. Figure 4 A schematic diagram of a loop slurry reactor.

[0015] Figure 6 It uses one or more heat exchangers as heat exchange equipment. Figure 4 A schematic diagram of INRU.

[0016] Figure 7 It uses a condenser as a heat exchange device. Figure 4A schematic diagram of a redistillation column. Detailed Implementation

[0017] Illustrative aspects of the subject matter claimed herein will now be disclosed. For clarity, not all features of actual implementations are described in this specification. It will be understood that during the development of any such practical aspect, numerous decisions must be made regarding the implementation to achieve the developer's specific objectives, such as complying with system- and business-related constraints that may vary from implementation to implementation. Furthermore, it will be understood that such development work, however complex and time-consuming, is routine for those skilled in the art who will benefit from this disclosure.

[0018] As used herein, the term "flow" refers to a composition of the components of the various flows disclosed herein. The term "flow" may also refer to and mean related equipment used to move the composition from one location to another, such as conduits, lines, and pipes (e.g., flow from one equipment unit to another).

[0019] As used herein, the term "conduit" refers to a tubular structure through which fluid can flow and has a rated wall thickness for fluid pressure. For example, a conduit can be embodied as a pipe or tube. Alternatively, a conduit can refer to a section of pipe or tube, or a series or string of pipes or tubes.

[0020] As used herein, the term "coolant" refers to a liquid fluid that can be used for heat exchange purposes, such as cooling the surfaces of equipment. Equipment surfaces that can be coolants can be the outer surfaces of reactor equipment or the heat exchange surfaces in a heat exchanger. Suitable coolants as used herein include, for example, water obtained as steam condensate from a process in a plant, or water obtained from another water source.

[0021] This document discloses a method for cooling a coolant used in heat exchange equipment in a factory. The method can be carried out in a factory having an embodiment of the cooling apparatus disclosed herein. The method and apparatus utilize a geothermal cooling loop to cool at least a portion of the total amount of coolant circulating in a coolant loop used to cool the surfaces of the heat exchange equipment in the factory. The perimeter of the factory can be used to house the geothermal cooling loop, and the arrangement disclosed herein allows for sufficient duct length for proper cooling. The disclosed method and apparatus can be used to cool the coolant in heat exchange equipment without using a common cooling medium supplied from a cooling tower. Since no common cooling medium is needed to cool the coolant, evaporation of the common cooling medium and leakage of hydrocarbons into the common cooling medium are reduced. Instead, the geothermal cooling loop uses the earth as a radiator to cool the warm coolant supplied from the heat exchange equipment in the factory. In some aspects, the geothermal cooling loop can be used in combination with mechanical cooling devices, such as air finned coolers.

[0022] For large-scale polyethylene production plants, approximately half of the utilities in a tower water system are used to cool the loop slurry reactor. It is believed that replacing the tower water system with the reactor coolant using the disclosed methods and apparatus can reduce the amount of utilities required in the plant by up to 50%. Reducing the amount of utilities required in the plant lowers the capital costs of the tower water system (including the size and number of pumps and tanks used in the tower water system), thereby reducing the power consumption and maintenance costs of the tower water system. Reducing the amount of utilities required in the plant also reduces the likelihood and occurrence of problems associated with the use of utilities, including scaling in the tower water system, evaporation of utilities in the tower water system, and hydrocarbon emissions.

[0023] Furthermore, the cooling efficiency of a tower water system varies with air temperature and humidity; therefore, the common cooling medium used in a tower water system depends on changes in air temperature and humidity caused by weather events and seasonal conditions. Because the disclosed methods and apparatus can be used to cool the coolant in heat exchange equipment without the use of a common cooling medium, the cooling efficiency is less dependent on air temperature and humidity, as the temperature of geothermal cooling can be maintained within a small temperature range (e.g., annual variation less than 10°F (5.6°C)) unaffected by atmospheric air temperature and humidity.

[0024] Figure 1 This is a schematic plan view of plant 100, which has a device 110 for cooling the coolant used in heat exchange equipment 111. Figure 2 This is a schematic floor plan of plant 100, which uses a different device 210 for cooling the coolant used in heat exchange equipment 111. The following description applies to... Figure 1 and Figure 2 Factory 100 in the middle, except for the places where differences are discussed.

[0025] Plant 100 may be a refining or petrochemical plant, for example configured to convert hydrocarbon feedstocks into products through chemical and engineering techniques such as reaction, separation, heating, cooling, or combinations thereof. Plant 100 may include processing equipment such as reactors (e.g., one or more polymerization reactors), heat exchangers (e.g., shell-and-tube, plate and frame), separators (e.g., flash tanks, purge vessels, vapor-liquid separators, distillation columns, pressure swing absorption units, stripping columns, absorption columns, or combinations thereof), valves, pumps, compressors, blowers, control equipment (e.g., logic controllers, communication networks), sensors (e.g., transducers, thermocouples, gas analyzers), safety equipment, and combinations thereof.

[0026] Plant 100 may include heat exchange equipment 111, which uses a coolant to remove heat from a reactor or from a process stream. Non-limiting examples of heat exchange equipment 111 may include a cooling jacket on a polymerization reactor, one or more heat exchangers in an isobutane and nitrogen recovery unit (INRU), a condenser in a redistillation column in a monomer / diluent recovery system, or combinations thereof. Plant 100 may include other equipment and processes, but are not shown for clarity of this disclosure.

[0027] Heat exchange device 111 can provide warm or hot coolant in flow 120 via outlet 112 of heat exchange device 111. Flow 120 (e.g., via pipe connectors such as tee connectors) is fluidly connected to Figure 1 Device 110 and Figure 2 Device 210. Devices 110 and 210 are configured to divide the warm coolant received from stream 120 into three parts: a first warm coolant in stream 131, a second warm coolant in stream 132, and a third warm coolant in stream 133. The flow of the warm coolant in stream 131 is parallel to the flow of the warm coolant in stream 132 and the flow of the warm coolant in stream 133; and the flow of the warm coolant in stream 132 is parallel to the flow of the warm coolant in stream 133.

[0028] exist Figure 1 In device 110, flow 131 is fluidly connected to inlet 141 of cooling system 140A. Cooling system 140A of device 110 includes a geothermal cooling circuit 142, which includes a series of conduits connected end-to-end. The geothermal cooling circuit 142, shown in dashed lines, indicates that the conduits are below the surface (e.g., buried underground). Outlet 143 of geothermal cooling circuit 142 is outlet 143 of cooling system 140A. Regarding... Figure 1 In the device 110, the inlet 141 of the cooling system 140A is also the inlet of the geothermal cooling circuit 142, and the outlet 143 of the cooling system 140A is also the outlet of the geothermal cooling circuit 142. The inlet 141 and outlet 143 of the geothermal cooling circuit 142 can be located on or above the surface of the pad site of the plant 100. In various aspects, the geothermal cooling circuit 142 in the cooling system 140A can have a temperature of about 1 to about 2 Btu / °F-ft. 2 The heat transfer coefficient.

[0029] exist Figure 2In device 210, flow 131 is fluidly connected to inlet 145 of cooling system 140B. Cooling system 140B of device 210 includes a mechanical cooling device 146 fluidly connected to inlet 141 of geothermal cooling circuit 142. Mechanical cooling device 146 can be any heat exchanger that does not use cooling fluid to remove heat from the warm coolant passing through mechanical cooling device 160 in cooling system 140B of device 210. In various aspects, mechanical cooling device 146 is an air-finned heat exchanger; in alternative aspects, mechanical cooling device 146 may be embodied as two or more air-finned heat exchangers arranged in series, in parallel, or both. Warm coolant from flow 131 flows into inlet 145 of the air-finned heat exchanger, where heat is transferred from the warm coolant to the contact surfaces in the air-finned heat exchanger. The fins of the air-finned heat exchanger transfer heat to the air in the atmosphere. In various aspects, a fan can be used to blow air across the fins of the air-finned heat exchanger. In various aspects, the mechanical cooling device 146 in the cooling system 140B (e.g., embodied as one or more air finned coolers) may have approximately 12 Btu / °F-ft. 2 The heat transfer coefficient, and the geothermal cooling loop 142 in the cooling system 140B can have a heat transfer coefficient of about 1 to about 2 Btu / °F-ft. 2 The heat transfer coefficient.

[0030] exist Figure 2 In device 210, mechanical cooling device 146 is shown as fluidly connected to geothermal cooling circuit 142 upstream of geothermal cooling circuit 142. Mechanical cooling device 146 has an inlet 145 fluidly connected to flow 131 and an outlet 148 fluidly connected to flow 147. Flow 147 fluidly connects to the inlet 141 of geothermal cooling circuit 142. The outlet 143 of geothermal cooling circuit 142 is the outlet 143 of cooling system 140B. The inlet 141 and outlet 143 of geothermal cooling circuit 142 may be at or above the surface of the pad site of plant 100. Including mechanical cooling device 146 upstream of geothermal cooling circuit 142 provides coolant cooling that 1) does not utilize a tower water system and 2) when the warm coolant in flow 144 is cooled to the same outlet temperature as... Figure 1 Compared to the length of the geothermal cooling circuit 142 in device 110, it can be reduced Figure 2 The length of the geothermal cooling circuit 142 in device 210. (The last part is incomplete and likely refers to a different concept.) Figure 1 similar, Figure 2 The geothermal cooling circuit 142, shown in dashed lines, also indicates that the conduit is below the surface (e.g., buried underground). Regarding Figure 2 In the device 210, the inlet 145 of the cooling system 140B is the inlet of the mechanical cooling device 146, and the outlet 143 of the cooling system 140A is the outlet of the geothermal cooling circuit 142.

[0031] In both devices 110 and 210, the geothermal cooling circuit 142 extends around plant 100. Various aspects of this disclosure envision the geothermal cooling circuit 142 having a temperature suitable for cooling the warm coolant to the geothermal temperature at the depth of the buried conduit (e.g., a temperature in the range of about 40°F (4°C) to about 80°F (27°C); alternatively, a temperature in the range of about 45°F (7.2°C) to about 75°F (23.9°C); alternatively, a temperature in the range of about 50°F (10°C) to about 70°F (21.1°C); alternatively, a temperature in the range of about 50°F (10°C) to about 70°F (21.1°C); alternatively, a temperature in the range of about 50°F (10°C) to about 70°F (21.1°C). Temperatures ranging from approximately °F (10°C) to approximately 60°F (15.6°C), combined with depths ranging from approximately 8 ft (2.4 m) to approximately 40 ft (12.2 m); alternatively, depths ranging from approximately 10 ft (3 m) to approximately 40 ft (12.2 m); alternatively, depths ranging from approximately 10 ft (3 m) to approximately 30 ft (9.2 m); alternatively, depths ranging from approximately 20 ft (6.0 m) to approximately 30 ft (9.2 m).

[0032] exist Figure 1 and Figure 2 In this design, the geothermal cooling circuit 142 is shown to have a length equivalent to one loop around the perimeter of the plant 100; however, it is conceivable that the geothermal cooling circuit 142 may loop around the perimeter of the plant 100 two or more times. In some aspects, the number of loops around the plant 100 may also include fractional loops, such as 1.25, 1.5, 1.75, 2.25, 2.5, 2.75, or more loops. In various aspects, the perimeter may be within the boundary of the plant 100.

[0033] In devices 110 and 210, outlet 143 of cooling systems 140A and 140B is fluidly connected to flow 144.

[0034] Flow 132 is a bypass line through which a portion of the warm coolant flows without being cooled (e.g., via cooling system 140A) or heated (e.g., via heater 134). The coolant in flow 132 may be heated or cooled by the ambient conditions at plant 100; however, apart from any heating or cooling effect provided by the ambient conditions, there is no equipment in flow 132 to heat or cool the coolant in flow 132.

[0035] Stream 133 is connected to heater 134. Heater 134 is configured to heat the warm coolant received from stream 133 to produce heated coolant in stream 135. Heater 134 may be embodied as any device capable of heating the coolant in stream 133, such as a shell-and-tube heat exchanger, mixer, distributor, or ejector. In various aspects, heater 134 may be embodied as a shell-and-tube heat exchanger, and a heating medium (e.g., steam) may be supplied to heater 134 via stream 136. The heating medium may be on the shell side or tube side of heater 134, and heater 134 may not be configured to mix the heating medium with the coolant. For example, heat may be transferred from the steam, causing water vapor to condense and be removed from heater 134 in stream 137 as steam condensate. The condensate may be recycled or sent to a drain (sewage). In various aspects, heater 134 may be embodied as an ejector, such as a pick heater, and steam used as the heating medium may be supplied to the ejector via stream 136. The supplied steam can be mixed with the coolant received from stream 133 in the ejector to heat the coolant via direct steam injection. In this respect, stream 137 may be omitted. In one configuration, a four-inch steam ejector can add 300 psig of steam directly to the coolant via an 18-inch pipe elbow.

[0036] Flows 132 and 144 are configured to combine to form flow 151. Flows 135 and 151 are configured to combine to form combined coolant flow 150. Combined coolant flow 150 is fluidly connected to inlet 113 of heat exchange device 111. Although flow 132 is... Figure 1 and Figure 2 The flow 120 is shown as being between flow 131 and flow 133, but this disclosure contemplates that apparatus 110 and apparatus 210 can be configured to divide flow 120 into flows 131, 132, and 133. Alternatively, flows 132 and 135 are contemplated to be combined to form flow 151, and flow 151 is combined with flow 144 to form flow 150. Alternatively, flows 144, 132, and 135 can all be combined to form flow 150, and in such respects, apparatus 110 and apparatus 210 do not include flow 151.

[0037] The flow rate of coolant in devices 110 and 210 can be controlled by coolant flow controllers 165 and 166. Coolant flow controller 165 can receive a setpoint signal 168 from a heat exchanger controller 167 connected to heat exchanger 111. For example, in an aspect where heat exchanger 111 includes a cooling jacket for a polymerization reactor, heat exchanger controller 167 may include a reactor controller configured to control the temperature of the polymerization reactor. Alternatively or additionally, in an aspect where heat exchanger 111 includes a heat exchanger for an INRU, heat exchanger controller 167 may include a process flow temperature controller for the heat exchanger output in the INRU. Alternatively or additionally, heat exchanger controller 167 may include a process flow temperature controller for a condenser in a distillation column. For example, the temperature setpoint of controller 167 may be input by an operator.

[0038] Coolant flow controller 165 is configured to actuate control valves 161, 163, and 164. Coolant flow controller 165 may be electrically or pneumatically connected (indicated by dashed lines) to control valve 161 in flow 144 to control the flow rate of cooled coolant flowing out of cooling system 140A, connected to control valve 163 to control the flow rate of heated coolant flowing out of heater 134, and connected to control valve 164 to control the flow rate of a heating fluid (e.g., steam) in flow 136 that provides heat in heater 134. Coolant flow controller 165 may be configured to sense or detect conditions of the combined coolant in flow 150, such as coolant temperature, pressure, or flow rate, via a sensor coupled to the flow rate of the combined coolant in flow 150.

[0039] The coolant flow controller 165 can control the return coolant temperature in the flow 150 at a setpoint coolant temperature. The coolant flow controller 165 can detect or sense the condition in the coolant of the flow 150, compare the detected condition with the coolant temperature setpoint (e.g., provided by signal 168 from reactor controller 167), and send one or more output signals 169 to adjust the valve opening position of one or more of valves 161, 163, and 164 (e.g., the adjustment of each valve is based on the difference between the detected coolant temperature and the coolant temperature setpoint).

[0040] Coolant flow controller 166 is configured to actuate control valve 162 located in a coolant bypass line (in flow 132). Coolant flow controller 166 may be electrically or pneumatically connected (shown as dashed lines) to control valve 162 in flow 132 to control the flow rate of warm coolant in the bypass line (i.e., flow 132). Coolant flow controller 166 may be configured to sense or detect the condition of the combined coolant in flow 150 (also referred to as the return coolant flow) via a sensor coupled to the flow rate of warm coolant in flow 120, such as the temperature, pressure, or flow rate of the warm coolant.

[0041] The coolant flow controller 166 can control the flow rate of warm coolant in the flow 132. The coolant flow controller 166 can detect or sense the condition of the coolant in the flow 132, compare the detected condition with a coolant condition setpoint, and send one or more output signals 170 to adjust the valve opening position of the valve 162 (e.g., the adjustment is based on the difference between the detected coolant condition and the setpoint).

[0042] Figure 3A A schematic plan view of the arrangement of the conduits 301 in the geothermal cooling circuit 142 is shown, and Figure 3B A cross-sectional side view of another arrangement of the conduit 301 in the geothermal cooling circuit 142 buried beneath the surface 300 is shown. (Including...) Figure 3A and Figure 3B This is to illustrate two arrangements of the conduit 301 in the geothermal cooling circuit 142. Figure 3A and Figure 3B The geothermal cooling circuit 142 consists of a series of conduits 301 (e.g., pipes or pipe segments) connected end to end.

[0043] exist Figure 3A In the diagram, when the factory 100 is viewed in plan view, the conduit 301 forms a spiral flow path around the factory 100. The conduit 301 can be placed in an outward spiral configuration such that the outer section 303 of the conduit 301 in the spiral is farther from the periphery 302 of the factory 100 than the inner section 304 of the conduit 301 in the spiral.

[0044] Figure 3B As shown, one segment 305 of catheter 301 can be buried beneath another segment 306 of catheter 301. Various aspects of this disclosure envision catheter 301 having… Figure 3A Configuration and Figure 3B Combinations of configurations (e.g., a spiral arrangement with vertical separation of the catheter but no lateral separation of the catheter, or a spiral arrangement having both vertical and horizontal separation of the catheter).

[0045] Figure 3A and Figure 3BThe conduit 301 can be buried at a depth ranging from depth D1 to depth D2. Depth D1 can be in the range of approximately 8 ft (2.4 m) to approximately 30 ft (9.2 m) below the surface 300; alternatively, in the range of approximately 8 ft (2.4 m) to approximately 30 ft (9.2 m) below the surface 300; alternatively, in the range of approximately 8 ft (2.4 m) to approximately 20 ft (6.0 m) below the surface 300; alternatively, in the range of approximately 8 ft (2.4 m) to approximately 12 ft (3.6 m) below the surface 300. Depth D2 can be located in the range of approximately 12 ft (3.6 m) to approximately 40 ft (12.2 m) below the surface 300; alternatively, in the range of approximately 20 ft (6.0 m) to approximately 40 ft (12.2 m) below the surface 300; alternatively, in the range of approximately 20 ft (6.0 m) to approximately 30 ft (9.2 m) below the surface 300; alternatively, in the range of approximately 12 ft (3.6 m) to approximately 30 ft (9.2 m) below the surface 300; alternatively, in the range of approximately 12 ft (3.6 m) to approximately 20 ft (6.0 m) below the surface 300. At depths ranging from 10 ft to 40 ft (3.0 m to 12.2 m), the ground temperature is relatively constant throughout the year, ranging from approximately 40°F (10°C) to approximately 80°F (15.6°C). At depths ranging from 20 ft to 30 ft (6.0 m to 9.2 m), the ground temperature remains relatively constant throughout the year, ranging from approximately 50°F (10°C) to approximately 60°F (15.6°C).

[0046] In all respects, the tubing size of conduit 301 may be in the range of 1.25 inches to 6 inches of nominal tubing size (nominal diameter (DN) of 32 mm to 150 mm); alternatively, in the range of 1.25 inches to 4 inches (DN of 32 mm to 100 mm); alternatively, in the range of 1.5 inches to 3 inches (DN of 40 mm to 80 mm); alternatively, 1.5 inches (DN of 40 mm); alternatively, 2 inches (DN of 50 mm); alternatively, 3 inches (DN of 80 mm); alternatively, 4 inches (DN of 100 mm); alternatively, 5 inches (DN of 125 mm); alternatively, 6 inches (DN of 150 mm). In all respects, the length of each conduit 301 may be in the range of approximately 1 ft (0.3048 m) to approximately 20 ft (6.096 m).

[0047] In the case of conduit 301 with a nominal pipe size of 2 inches (50 mm DN), the length of the conduit for the geothermal cooling circuit 142 can range from approximately 11 km to approximately 30 km. More specifically, Figure 1 The conduit in the geothermal cooling circuit 142 of the device 110 may have a total length ranging from about 15 km to about 30 km. Figure 2The conduit in the geothermal cooling circuit 142 of device 210 can have a total length ranging from approximately 11 km to approximately 13 km. Figure 1 Compared to the geothermal cooling circuit 142 in device 110, Figure 2 The shorter length of the geothermal cooling circuit 142 in device 210 can be attributed to Figure 2 The cooling system 140B includes a mechanical cooling device 146. Figure 1 The cooling system 140A in the middle does not include the mechanical cooling device 146).

[0048] The conduit 301 can be joined end-to-end by a connector, polymer welding (melting the ends together), adhesive, or a combination thereof. In various aspects, connectors (such as elbow connectors) can be used to change the orientation of the conduit 301 around the plant 100; alternatively, the conduit 301 can be flexible, and any of the conduits 301 can be bent to change the orientation of the geothermal cooling circuit 142.

[0049] The conduit 301 in the geothermal cooling circuit 142 may be made of a polymeric material (e.g., polyethylene). The thermal conductivity of polyethylene may be from about 0.3 W / mK to about 0.5 W / mK. Polyethylene has a higher thermal conductivity than other polymers (e.g., polyvinyl chloride = about 0.1 W / mK to 0.25 W / mK, polypropylene = about 0.1 W / mK to 0.2 W / mK), and a lower thermal conductivity than metals (e.g., copper = about 400 W / mK, aluminum = 250 W / mK). Using a conduit 301 made of a polymeric material (e.g., polyethylene) avoids corrosion that can occur when metal conduits are buried underground and in continuous contact with coolant on the inner surface and subsurface components on the outer surface. Furthermore, the geothermal cooling circuit 142 may be located around the plant 100 and may accommodate a length of end-to-end connected polyethylene conduit 301 (pipe or pipe segment) suitable for cooling the coolant to the Earth's temperature at the depth of the polyethylene conduit 301.

[0050] In all respects, the conduit of the geothermal cooling circuit 142 may be an underground conduit buried at a certain depth below the surface, such that the geothermal temperature at that depth is always in the range of about 40°F (4°C) to about 80°F (27°C); alternatively, in the range of about 45°F (7.2°C) to about 75°F (23.9°C); alternatively, in the range of about 50°F (10°C) to about 70°F (21.1°C); alternatively, in the range of about 50°F (10°C) to about 60°F (15.6°C).

[0051] An example of polyethylene conduit is DRISCOPLEX pipe, which is commercially available from Performance Pipe, a subsidiary of Chevron Phillips Chemical Company LP.

[0052] heat exchange equipment

[0053] The heat exchange device 111 disclosed herein may include any device in plant 100, configured to contact a coolant with a heat exchange surface to remove heat from the heat exchange surface. The heat exchange surface typically separates the coolant from a heat source, which may be a process flow or reaction medium within a reactor.

[0054] Figure 4 It shows Figure 1 and Figure 2 The schematic diagram of the implementation scheme of factory 100 is a polyethylene production plant. Figure 4 The various components within can be fluidly connected via one or more conduits (e.g., pipes, tubes, flow lines, etc.) suitable for conveying a specific flow. In various aspects, Figure 4 The factory 100 can have a battery limit of approximately 450m × 250m; alternatively, approximately 400m × 200m.

[0055] The reagent stream (also known as the feed stream) flows into the loop slurry reactor. Polymerization of the reagent (e.g., monomers and optionally comonomers) produces polymers in the form of solid particles. The polymerization product stream containing the polymer flows from the loop slurry reactor to the flash chamber. The flash chamber is configured to separate the polymerization product stream into a gas stream and a polymer stream.

[0056] The gas stream can flow from the flash chamber to the monomer / diluent recovery unit, which includes a redistillation column and a lightistillation column. The redistillation column can also be referred to as the first distillation column or the heavy product column. The redistillation understream and redistillation sidestream can flow from the redistillation column. The intermediate hydrocarbon (HC) stream can flow from the redistillation column to the lightistillation column. The lightistillation column can also be referred to as the second distillation column or the light product column. The light hydrocarbon stream, the lightistillation sidestream, and the lightistillation understream containing olefin-free isobutane can flow from the lightistillation column. For example, olefin-free isobutane can be recycled to a loop slurry reactor.

[0057] The polymer stream can flow from the flash chamber to the purge container. The purge gas stream can flow to the purge container. The purge polymer stream containing the polymer can flow out of the purge container. The waste purge gas stream can flow from the purge container to the isobutane and nitrogen recovery unit (INRU).

[0058] Isobutane and nitrogen can be recovered from the INRU. Isobutane recovered from the INRU can be recycled to the redistillation column and / or equipment within the INRU, such as a compressor within the INRU. Nitrogen recovered from the INRU can be recycled to the purge vessel and / or equipment within the INRU, such as a compressor within the INRU.

[0059] In various aspects of a polyethylene production plant, the heat exchange equipment 111 discussed herein can be used with... Figure 4 Loop slurry reactor Figure 4 INRU, Figure 4 This is associated with a redistillation column or a combination thereof. For example, heat exchange device 111 may be one or more cooling jackets wound around the outer surface of a loop slurry reactor. The outer surface of the polymerization reactor may be the heat exchange surface that the coolant contacts as it flows through the cooling jacket. In another or alternative aspect, heat exchange device 111 may include an INRU heat exchanger in the isobutane and nitrogen removal unit (INRU) of plant 100. The shell-and-tube or plate-and-frame configuration of the INRU heat exchanger provides the heat exchange surface that the coolant contacts as it flows through the INRU heat exchanger. In another or alternative aspect, heat exchange device 111 may include a condenser of a redistillation column in a monomer / diluent recovery unit. The shell-and-tube or plate-and-frame configuration of the condenser provides the heat exchange surface that the coolant contacts as it flows through the condenser.

[0060] Figure 5 This is a schematic diagram of a loop slurry reactor 500 that uses a coolant jacket 501 as a heat exchange device. In other words, Figure 1 The heat exchange device 111 in the middle can be embodied as including Figure 5 Cooling jacket 501 of the loop slurry reactor 500.

[0061] Warm coolant from stream 120 can be received from coolant outlet 512 of loop slurry reactor 500. The warm coolant can be cooled by flowing through apparatus 110 or 210 as described herein to produce the combined coolant in stream 150. At coolant inlet 513 of loop slurry reactor 500, warm coolant can be received from... Figure 1 Device 110 or Figure 2 Device 210 receives the combined coolant in flow 150. Cooling jacket 501 receives cooled coolant via coolant supply line 502 of loop slurry reactor 500. Coolant flows through coolant supply line 502, through cooling jacket 501, and into warm coolant line 503 of loop slurry reactor 500. Warm coolant in line 503 flows to coolant outlet 512 of loop slurry reactor 500 and via flow 120 to device 110 or 210 (…). Figure 1 or Figure 2 ).

[0062] Although Figure 5 A loop slurry reactor 500 is depicted, but heat exchange equipment 111 may include a cooling jacket for an additional loop slurry reactor, which is configured similarly or substantially the same as the loop slurry reactor 500 in terms of cooling jacket 501, coolant supply line 502, and warm coolant line 503. In these respects, the coolant supply line of the additional reactor may be fluidly connected to a coolant inlet 513, and the warm coolant line of the additional reactor may be fluidly connected to a coolant outlet 512.

[0063] The loop slurry reactor 500 has eight legs 504; however, more or fewer legs may be used in the loop slurry reactor 500. Each leg 504 has a cooling jacket 501 wrapped around its outer surface. Polymerization of one or more olefins (e.g., monomers such as ethylene or propylene, optionally with comonomers such as butene, hexene, or octene) in an inert diluent (e.g., isobutane or other alkanes) occurs within the loop slurry reactor 500. Polymerization may be carried out in the presence of a polymerization catalyst such as Ziegler Natta or a metallocene catalyst. As the polymerization proceeds, reaction conditions can be controlled to promote the desired degree of polymerization and reaction rate while maintaining a temperature below the temperature at which the polymer product will enter the solution. As mentioned, due to the exothermic nature of the polymerization reaction, a cooling jacket 501 (around a portion of the support leg 504) is provided through which coolant can circulate as needed to remove excess heat (heat of reaction) from the reactor 500, thereby maintaining the reactor temperature within the desired range, for example, from about 150°F to about 250°F (65°C to 121°C).

[0064] Cooling system 140A in device 110 (see Figure 1 ) and the cooling system 140B in device 210 (see Figure 2 The coolant is configured to provide cooling in the flow 150 within the temperature range disclosed herein. It can be controlled as described herein. Figure 1 and Figure 2 Valves 161, 162, 163 and 164 are used to control the temperature of the coolant being cooled in flow 150, thereby facilitating the maintenance of the temperature of the loop slurry reactor 500 within a desired range, for example, the reactor temperature is in the range of about 150°F to about 250°F (65°C to 121°C).

[0065] Figure 6 It uses one or more heat exchangers 601 and 602 as heat exchange devices. Figure 4 A schematic diagram of the INRU 600. That is to say, Figure 1 The heat exchange device 111 in the middle can be embodied as including Figure 6Heat exchangers 601 and 602.

[0066] Warm coolant in stream 120 can be received from coolant outlet 612 of INRU 600. The warm coolant can be cooled by flowing through apparatus 110 or 210 as described herein to produce the combined coolant in stream 150. At coolant inlet 613 of INRU 600, warm coolant can be received from... Figure 1 Device 110 or Figure 2 Device 210 receives the combined coolant in flow 150. Heat exchangers 601 and 602 receive cooled coolant via coolant supply line 603. Coolant flows through coolant supply line 603, through heat exchangers 601 and 602, and into warm coolant line 604. The warm coolant in line 604 flows to coolant outlet 612 of INRU 600 and then via flow 120 to device 110 or 210. Figure 1 or Figure 2 ).

[0067] INRU 600 may include Figure 6 The equipment marked in the middle includes heat exchangers 601 and 602. This equipment can be used as follows: Figure 6 The fluid connection is shown. The INRU 600 is configured to draw fluid from a purge container (such as...). Figure 4 The purge vessel (also known as a degassing vessel) receives purge gas containing hydrocarbons and nitrogen and separates the components from the purge gas for recovery. Figure 6 The stream contains a high-purity nitrogen stream and a high-purity isobutane stream.

[0068] Heat exchanger 601 can be embodied in any suitable heat exchanger (e.g., shell and tube or plate and frame type) that utilizes the coolant disclosed herein to reduce the temperature of the compressed gas stream, causing the hydrocarbons in the compressed gas stream to condense and produce a warm coolant. For example, in heat exchanger 601, a combination of coolant received from stream 150 and coolant supply line 603 can remove heat from the compressed gas stream, such that the compressed gas stream with a temperature in the range of 100°F to 350°F (37.7°C to 176.7°C) produces a first cooled gas stream with a temperature in the range of 50°F to 150°F (10°C to 65.6°C).

[0069] Heat exchanger 602 can be embodied in any suitable heat exchanger (e.g., shell and tube or plate and frame type) that utilizes the coolant disclosed herein to lower the temperature of the stagnant stream, causing the hydrocarbons in the stagnant stream to condense and produce a warm coolant. For example, in heat exchanger 602, a combination of coolant received from stream 150 and coolant supply line 603 can remove heat from the stagnant stream, such that the stagnant stream with a temperature in the range of 70°F to 170°F (21.1°C to 76.7°C) produces a second cooling gas stream with a temperature in the range of -20°F to 110°F (-28.8°C to 43.4°C).

[0070] Figure 7 This is a schematic diagram of a redistillation column 700, which uses the condenser 710 on the overhead stream 722 as a heat exchange device. In other words, Figure 1 The heat exchange device 111 in the middle can be embodied as including Figure 7 The condenser 710.

[0071] Warm coolant in stream 120 can be received from coolant outlet 712 of condenser 710. The warm coolant can be cooled by flowing through apparatus 110 or 210 as described herein to produce cooled coolant in stream 150. At coolant inlet 713 of condenser 710, coolant can be received from... Figure 1 Device 110 or Figure 2 The device 210 receives the cooled coolant from the stream 150. The coolant flows through the condenser 710 and absorbs heat from the overhead stream 722, causing at least a portion of the overhead stream 722 to condense to form... Figure 4 The intermediate hydrocarbon (HC) stream flows through the condenser. The warm coolant flows to the coolant outlet 712 of the condenser 710 and then via stream 120 to device 110 or 210 (in...). Figure 1 or Figure 2 middle).

[0072] In the operation of redistillation column 720, the gas stream 721 received from the flash tank can be separated in redistillation column 720 into overhead stream 722, bottom stream 723, and optional side stream 724. At least a portion of the gas in overhead stream 722 can be condensed in condenser 710 to form Figure 4 The intermediate hydrocarbon (HC) stream is present. Undistilled components in redistillation column 720 may exit redistillation column 720 in bottom stream 723. Side stream 724 may optionally exit redistillation column 720.

[0073] The overhead stream 722 may contain C4 and lighter hydrocarbons (e.g., butane, isobutane, propane, ethane, methane, or combinations thereof) and any light gas (e.g., nitrogen). For example, based on the total weight of the intermediate hydrocarbon stream, C4 and lighter hydrocarbons and gases may be present in the overhead stream 722 in an amount of about 80% to about 100%, alternatively about 90% to about 99.99999%, alternatively about 99% to about 99.9999%. Alternatively, based on the total weight of the intermediate hydrocarbon stream, C5 and heavier hydrocarbons may be present in the overhead stream 722 in an amount of about 0% to about 20%, alternatively about 10% to about 0.000001%, alternatively about 1.0% to about 0.0001%.

[0074] The bottom stream 723 may include heavy alkanes (e.g., heptane, other large alkanes, or both) with a carbon number greater than that of the olefins used in polymerization. Based on the total weight of the bottom stream 723, hydrocarbons other than heavy alkanes may be present in the bottom stream 723 in an amount of less than about 15%, alternatively less than about 10%, and alternatively less than about 5%.

[0075] Side stream 724 may contain comonomers, such as 1-butene or 1-hexene. For example, based on the total weight of redistilled side stream 320, the comonomer may be present in side stream 724 in an amount of about 20% to about 98%, alternatively about 40% to about 95%, and alternatively about 50% to about 95%. In various aspects of comonomer recovery in side stream 724, the comonomer may be recycled to the polymerization reactor, for example... Figure 5 500 ring-tube slurry reactor.

[0076] The redistillation column 720 may include a reboiler in the bottom stream 723, which is configured to reboil at least a portion of the bottom stream 723 and return it to the redistillation column 720 in the form of vapor.

[0077] Redistillation column 720 can operate at suitable temperatures and pressures, for example, it can be adapted to achieve... Figure 4 The separation of components in a gas stream. For example, a redistillation column 720 can be operated such that the temperature at the top and bottom of column 720 is in the range of about 15°C to about 233°C. Redistillation column 720 can be operated at pressures in the range of about 14.7 psig (101.3 kPag) to about 527.9 psig (3.64 MPag). Redistillation column 720 may include any number of trays or packing to provide the separation described herein.

[0078] method

[0079] The following will refer to Figures 1 to 7 The components in the document describe the methods.

[0080] exist Figure 1The first method performed in the apparatus 110 may include a first method of cooling a coolant used in a heat exchange device 111 in the plant 100. The first method includes introducing a first warm coolant having a first temperature in a flow 131 into an inlet 141 of a cooling system 140A including a geothermal cooling circuit 142. The first method may also include cooling the first warm coolant in the geothermal cooling circuit 142 of the cooling system 140A to form cooled coolant in a flow 144 having a second temperature, wherein the second temperature is lower than the first temperature. In the first method, the inlet 141 of the cooling system 140A may be fluidly connected to a coolant outlet 112 of the heat exchange device 111 in the plant 100, and the outlet 143 of the cooling system 140A may be fluidly connected to a coolant inlet 113 of the heat exchange device 111 in the plant 100. The first method may also include receiving the first warm coolant at the inlet 141 of the cooling system 140A via a warm coolant flow 120 connected to the coolant outlet 112 of the heat exchange device 111 in the plant 100.

[0081] In each respect, the first temperature can be in the range of about 130°F (54.4°C) to about 190°F (87.8°C), and the second temperature can be in the range of about 60°F (15.5°C) to about 100°F (37.8°C). In another respect, the second temperature can be in the range of about 65°F (18.3°C) to about 70°F (21.1°C).

[0082] The first method may further include dividing the warm coolant stream 120 into a first warm coolant stream 131, a second warm coolant stream 132, and a third warm coolant stream 133. The first method may further include flowing the second warm coolant through stream 132 (e.g., a bypass line) and flowing the third warm coolant through heater 134 to form a heated coolant stream 135. The first method may further include combining the cooled coolant generated by the cooling system 140A, the second warm coolant stream 132, and the heated coolant stream 135 to form a combined coolant stream 150. The first method may also include directing the combined coolant stream 150 to the coolant inlet 113 of the heat exchange device 111.

[0083] The first method may further include controlling the flow rates of the cooling coolant in flow 144, the second warm coolant in flow 132, the heated coolant in flow 135, or a combination thereof, such that the temperature of the combined coolant flow 150 is in the range of about 60°F (15.5°C) to about 100°F (37.8°C).

[0084] exist Figure 2The method performed in apparatus 210 may include a second method for cooling a coolant used in heat exchange equipment 111 in plant 100. The second method includes introducing a first warm coolant in a stream 131 having a first temperature into an inlet 145 of a cooling system 140B comprising a mechanical cooling device 146 and a geothermal cooling circuit 142. In various aspects, this introduction step includes introducing the first warm coolant in stream 131 having a first temperature into the inlet 145 of the mechanical cooling device 146. The second method may also include cooling the first warm coolant in the mechanical cooling device 146 to form an intermediate coolant in a stream 147 having a third temperature. The second method may also include introducing the intermediate coolant in stream 147 having a third temperature into an inlet 141 of the geothermal cooling circuit 142 and cooling the intermediate coolant in the geothermal cooling circuit 142 of the cooling system 140B to form a cooled coolant in a stream 144 having a second temperature, wherein the second temperature is lower than the first temperature. In the second method, the inlet 145 of the cooling system 140B is fluidly connected to the coolant outlet 112 of the heat exchange device 111 in the plant 100, and the outlet 143 of the cooling system 140B is fluidly connected to the coolant inlet 113 of the heat exchange device 111 in the plant 100. The second method may also include receiving a first warm coolant at the inlet 145 of the cooling system 140B via a warm coolant flow 120 connected to the coolant outlet 112 of the heat exchange device 111 in the plant 100.

[0085] In each respect, the first temperature can range from about 130°F (54.4°C) to about 190°F (87.8°C), and the second temperature can range from about 60°F (15.5°C) to about 100°F (37.8°C). In another respect, the second temperature can range from about 65°F (18.3°C) to about 70°F (21.1°C). In yet another respect, the third temperature is lower than the first temperature and higher than the second temperature.

[0086] The second method may further include dividing the warm coolant stream 120 into a first warm coolant stream 131, a second warm coolant stream 132, and a third warm coolant stream 133. The second method may further include flowing the second warm coolant through stream 132 (e.g., a bypass line) and flowing the third warm coolant through heater 134 to form a heated coolant stream 135. The second method may further include combining the cooled coolant generated by cooling system 140B, the second warm coolant in stream 132, and the heated coolant in stream 135 to form a combined coolant stream 150. The second method may also include directing the combined coolant stream 150 to the coolant inlet 113 of heat exchange device 111.

[0087] The second method may further include controlling the flow rates of the cooling coolant in flow 144, the second warm coolant in flow 132, the heated coolant in flow 135, or a combination thereof, such that the temperature of the combined coolant flow 150 is in the range of about 60°F (15.5°C) to about 100°F (37.8°C).

[0088] Additional notes

[0089] Methods and apparatus for cooling coolants used in heat exchange equipment in plants have been described. This application also relates to the subject matter described in the following numbered paragraphs (referred to as "paragraphs" or "paras"):

[0090] Paragraph 1. A method for cooling a coolant used in a heat exchange device in a factory, the method comprising: introducing a first warm coolant having a first temperature into an inlet of a cooling system including a geothermal cooling circuit; and cooling the first warm coolant in the cooling system to form a cooled coolant having a second temperature, wherein the second temperature is lower than the first temperature, wherein the inlet of the cooling system is fluidly connected to a coolant outlet of the heat exchange device in the factory, and wherein the outlet of the cooling system is fluidly connected to a coolant inlet of the heat exchange device in the factory.

[0091] Paragraph 2. The method as described in paragraph 1 further includes: receiving the first warm coolant at the inlet of the cooling system via a warm coolant stream connected to the coolant outlet of the heat exchange device in the plant.

[0092] Paragraph 3. The method as described in paragraph 1 or 2, wherein the first temperature is in the range of about 130°F (54.4°C) to about 190°F (87.8°C), and the second temperature is in the range of about 60°F (15.5°C) to about 100°F (37.8°C).

[0093] Paragraph 4. The method as described in any one of paragraphs 1 to 3, wherein the second temperature is in the range of about 65°F (18.3°C) to about 70°F (21.1°C).

[0094] Paragraph 5. The method of any one of paragraphs 1 to 4, wherein the cooling system further comprises a mechanical cooling device having an outlet having a fluid connection with an inlet of the geothermal cooling circuit, the method further comprising: introducing a first warm coolant having a first temperature into the inlet of the mechanical cooling device; cooling the first warm coolant in the mechanical cooling device to form an intermediate coolant having a third temperature; introducing the intermediate coolant having the third temperature into the inlet of the geothermal cooling circuit; and cooling the intermediate coolant in the geothermal cooling circuit to form the cooled coolant having a second temperature.

[0095] Paragraph 6. The method as described in paragraph 5, wherein the third temperature is lower than the first temperature and higher than the second temperature.

[0096] Paragraph 7. The method as described in paragraph 5 or 6, wherein the mechanical cooling device includes an air finned cooler.

[0097] Paragraph 8. The method as described in any one of paragraphs 1 to 7, wherein the heat exchange device is configured to cool the process stream in a loop polymerization reactor, an isobutane and nitrogen removal unit (INRU), or the overhead stream of a redistillation column.

[0098] Paragraph 9. The method of any one of paragraphs 1 to 8, wherein the geothermal cooling circuit comprises an underground conduit buried at a depth below the surface such that the ambient temperature at the depth is always in the range of about 40°F (4°C) to about 80°F (27°C).

[0099] Paragraph 10. The method of any one of paragraphs 1 to 9, wherein the geothermal cooling circuit comprises at least two conduits arranged to have a length such that heat transfer through the conduits to the earth produces a coolant having the second temperature.

[0100] Paragraph 11. The method of any one of paragraphs 1 to 10, wherein the underground conduit has a nominal pipe size in the range of about 1.25 inches to about 6 inches.

[0101] Paragraph 12. The method as described in any one of paragraphs 9 to 11, wherein the underground conduit comprises one or more sections of polyethylene pipe.

[0102] Paragraph 13. The method as described in any one of paragraphs 9 to 12, wherein at least a portion of the underground conduit is buried along the perimeter of the plant.

[0103] Paragraph 14. The method as described in any one of paragraphs 1 to 13 further comprises: dividing the warm coolant flow into a first warm coolant, a second warm coolant, and a third warm coolant; flowing the second warm coolant through a bypass line; flowing the third warm coolant through a heater to form a heated coolant; combining the cooled coolant, the second warm coolant, and the heated coolant to form a combined coolant flow; and directing the combined coolant flow to the coolant inlet of the heat exchange device.

[0104] Paragraph 15. The method of any one of paragraphs 1 to 14 further comprises: controlling the flow rate of the cooling coolant, the second warm coolant, the heated coolant, or a combination thereof, such that the temperature of the combined coolant flow is in the range of about 60°F (15.5°C) to about 100°F (37.8°C).

[0105] Paragraph 16. A cooling device for cooling a coolant in a heat exchange device in a plant, the cooling device comprising: a geothermal cooling circuit including an underground conduit buried at a depth below the surface within the plant boundary, such that the ambient temperature at said depth is always in the range of about 40°F (4°C) to about 80°F (27°C), wherein the geothermal cooling circuit is configured to receive a warm or intermediate coolant to form a cooled coolant with a temperature in the range of about 60°F (15.5°C) to about 100°F (37.8°C), wherein the inlet of the geothermal cooling circuit is fluidly connected to the coolant outlet of the heat exchange device in the plant, and wherein the outlet of the geothermal cooling circuit is fluidly connected to the coolant inlet of the heat exchange device in the plant.

[0106] Paragraph 17. The cooling device as described in paragraph 16 further includes: an air finned cooler having an outlet fluidly connected to the inlet of the geothermal cooling circuit, wherein the inlet of the air finned cooler is fluidly connected to the coolant outlet of the heat exchange equipment in the plant, wherein the air finned cooler is configured to receive the warm coolant and form the intermediate coolant, wherein the geothermal cooling circuit is configured to receive the intermediate coolant.

[0107] Paragraph 18. A cooling device as described in paragraphs 16 or 17, wherein the underground conduit comprises one or more sections of polyethylene pipe having a nominal pipe size in the range of 1.25 inches to 6 inches.

[0108] Paragraph 19. The cooling device as described in any one of paragraphs 16 to 18, wherein at least a portion of the underground conduit is buried along the perimeter of the plant.

[0109] Paragraph 20. A cooling device as described in any one of paragraphs 16 to 19, wherein the heat exchange device is configured to cool the process stream in a loop polymerization reactor, an isobutane and nitrogen removal unit (INRU), or the overhead stream of a redistillation column.

[0110] While this disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions, and modifications may be made herein without departing from the spirit and scope of this disclosure as defined by the appended claims. Furthermore, the scope of this application is not intended to be limited to the specific embodiments of the methods, machines, manufactures, compositions of matter, means, processes, and steps described in the specification. As will readily be understood by one of ordinary skill in the art from this disclosure, methods, machines, manufactures, compositions of matter, means, processes, or steps existing or to be developed thereafter can be utilized to perform substantially the same function or achieve substantially the same results as the corresponding embodiments described herein. Therefore, the appended claims are intended to include such methods, machines, manufactures, compositions of matter, means, processes, or steps within their scope.

Claims

1. A method for cooling a coolant used in a heat exchange device in a polyethylene production plant, the method comprising: The warm coolant flow is divided into a first warm coolant, a second warm coolant, and a third warm coolant; The second warm coolant flows through the bypass line; The third warm coolant is passed through the heater to form a heated coolant; a first warm coolant having a first temperature is introduced into the inlet of a cooling system including a geothermal cooling circuit, wherein the geothermal cooling circuit includes a series of underground conduits buried at a certain depth within the boundary of the polyethylene production plant, such that the ambient temperature at the depth is always in the range of 40℉ (4℃) to 80℉ (27℃). The first warm coolant is cooled in the cooling system to form a cooled coolant having a second temperature, wherein the second temperature is lower than the first temperature; The cooled coolant, the second warm coolant, and the heated coolant are combined to form a combined coolant stream; and The combined coolant flow is directed to the coolant inlet of the heat exchange equipment; The inlet fluid of the cooling system is connected to the coolant outlet of the heat exchange equipment in the polyethylene production plant. The outlet fluid of the cooling system is connected to the coolant inlet of the heat exchange equipment in the polyethylene production plant.

2. The method of claim 1, further comprising: The first warm coolant is received at the inlet of the cooling system via a warm coolant stream from the coolant outlet of the heat exchange equipment connected to the polyethylene production plant.

3. The method of claim 2, wherein the first temperature is in the range of 130℉ (54.4℃) to 190℉ (87.8℃) and the second temperature is in the range of 60℉ (15.5℃) to 100℉ (37.8℃), wherein the second temperature is in the range of 65℉ (18.3℃) to 70℉ (21.1℃).

4. The method of claim 1, wherein the cooling system further comprises a mechanical cooling device having an outlet fluidly connected to the inlet of the geothermal cooling circuit, the method further comprising: The first warm coolant having the first temperature is introduced into the inlet of the mechanical cooling device; The first warm coolant is cooled in the mechanical cooling device to form an intermediate coolant with a third temperature; The intermediate coolant having the third temperature is introduced into the inlet of the geothermal cooling circuit; and The intermediate coolant is cooled in the geothermal cooling circuit to form the cooled coolant having the second temperature.

5. The method of claim 4, wherein the third temperature is lower than the first temperature and higher than the second temperature.

6. The method of claim 4, wherein the mechanical cooling device comprises an air finned cooler.

7. The method of claim 1, wherein the heat exchange device is configured to cool i) the process stream in the isobutane and nitrogen removal unit or the overhead stream of the redistillation column, and ii) the loop polymerization reactor.

8. The method of claim 1, wherein the series of underground conduits Having a certain length, the coolant generates the cooling effect at the second temperature through the heat transfer to the earth via the series of underground conduits.

9. The method of claim 1, wherein the series of underground conduits has a nominal pipe size in the range of 1.25 inches to 6 inches, wherein the series of underground conduits comprises polyethylene pipe.

10. The method of claim 1, wherein at least a portion of the series of underground conduits is buried along the perimeter of the polyethylene production plant.

11. The method of claim 1, wherein the series of underground conduits has a spiral arrangement, wherein the spiral arrangement has a first section of conduit and a second section of conduit, wherein the first section of conduit and the second section of conduit are i) horizontally separated, ii) vertically separated, or iii) both horizontally separated and vertically separated.

12. The method of claim 1, wherein the depth is in the range of 8 ft (2.4 m) to 40 ft (12.2 m) below the ground surface.

13. A cooling device for cooling a coolant in a heat exchange device in a polyethylene production plant, the cooling device comprising: A geothermal cooling circuit comprising a series of underground conduits buried at a depth within the boundary of the polyethylene production plant, such that the ambient temperature at that depth is always within the range of 40℉ (4℃) to 80℉ (27℃), wherein the geothermal cooling circuit is configured to receive a first warm coolant or an intermediate coolant to form a first cooling coolant with a temperature in the range of 60℉ (15.5℃) to 100℉ (37.8℃), and The inlet fluid of the geothermal cooling circuit is connected to the coolant outlet of the heat exchange equipment in the polyethylene production plant. The outlet fluid of the geothermal cooling circuit is connected to the coolant inlet of the heat exchange equipment in the polyethylene production plant, and The cooling device is configured as follows: The warm coolant flow is divided into the first warm coolant, the second warm coolant, and the third warm coolant; The second warm coolant flows through the bypass line; The third warm coolant is passed through the heater to form a heated coolant; The cooled coolant, the second warm coolant, and the heated coolant are combined to form a combined coolant stream; and The combined coolant flow is directed to the coolant inlet of the heat exchange device.

14. The cooling device of claim 13, wherein the depth is in the range of 8 ft (2.4 m) to 40 ft (12.2 m) below the ground surface.

15. The cooling device of claim 13, further comprising: An air finned cooler having an outlet fluidly connected to the inlet of the geothermal cooling circuit, wherein the inlet of the air finned cooler is fluidly connected to the coolant outlet of the heat exchange equipment in the polyethylene production plant, wherein the air finned cooler is configured to receive the warm coolant and form the intermediate coolant, wherein the geothermal cooling circuit is configured to receive the intermediate coolant.

16. The cooling device of claim 13, wherein the series of underground conduits comprises polyethylene conduits with nominal pipe sizes ranging from 1.25 inches to 6 inches.

17. The cooling device of claim 13, wherein at least a portion of the series of underground conduits is buried along the perimeter of the polyethylene production plant.

18. The cooling apparatus of claim 13, wherein the heat exchange device is configured to cool i) the process stream in the isobutane and nitrogen removal unit or the overhead stream of the redistillation column, and ii) the loop polymerization reactor.

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