Fluidized bed reactor discharge system and method

Abstract

The present disclosure relates to the field of petroleum chemical technology, and provides a discharge system and method of a fluidized bed reactor. The system comprises a discharge tank, a fluidized bed reactor, a buffer tank and a gas compression cooling system; a discharge pipeline and a gas balance line are connected between the discharge tank and the fluidized bed reactor; a gas discharge line is connected between the discharge tank and the buffer tank; a conveying gas pipeline is connected between the discharge tank and a gas source; a powder conveying line is connected between the lower part of the discharge tank and a preset downstream device; a buffer gas discharge pipeline is connected between the buffer tank and the gas compression cooling system; and control valves are arranged in each pipeline. The embodiment of the present disclosure can improve the discharge efficiency, reduce the failure probability, and improve the energy utilization rate while reducing the material loss.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, and particularly relates to the discharge system and method of a fluidized bed reactor. Background Technology

[0002] Fluidized bed reactors are widely used in chemical, petroleum, metallurgical, and nuclear industries. Taking the polyolefin industry as an example, the gas-phase polyethylene process using a fluidized bed reactor has many advantages, including a simple process, flexible operation, no need for solvent refining and recovery, lower equipment investment and operating costs, and relative cleanliness and environmental friendliness. Companies such as UCC (US5453471), BP (WO94 / 28032), and Exxon (WO96 / 10591) have successively developed condensation and ultracondensation technologies, overcoming problems such as the difficulty in removing the heat of reaction and the limitation on the amount of comonomer added in fluidized bed reactors. This has made the gas-phase fluidized bed polyethylene process technology the most widely used polyethylene production technology today.

[0003] The gas-phase fluidized bed polyethylene process generally includes several steps such as raw material refining, polymerization reaction, powder degassing, granulation, conveying, and packaging. In the polymerization unit, refined ethylene, comonomers (1-butene-1, 1-hexene, or 1-octene), isopentane (inducing condenser), hydrogen, and nitrogen are added to the fluidized bed reactor. Under the action of a catalyst and co-catalyst, a polymerization reaction occurs to produce polyethylene. Unreacted raw material gases are discharged from the top of the fluidized bed reactor, pressurized by a circulating gas compressor, and cooled by a circulating gas cooler before being recycled. The circulating gas keeps the polyethylene powder in the fluidized bed reactor in a fluidized state and removes the heat of reaction through the circulating gas cooler. When the polymerization reaction in the fluidized bed reactor reaches a certain stage, and the bed level and / or weight reach a set value, the discharge system is activated, discharging the solid polyethylene from the side wall of the reactor. The solid polyethylene is then transported to the product degassing chamber by nitrogen or exhaust gas recovery gas. Nitrogen gas introduced from the bottom of the degassing chamber carries hydrocarbon components from the resin powder and is blown out from the top of the degassing chamber into the exhaust gas recovery system. Liquid materials such as copolymer monomers and induced condensers are recovered and pumped back to the fluidized bed reactor. Non-condensable gases are sent back to the discharge system as transport gases, or partially discharged to the flare as required by pressure control.

[0004] Currently, most industrial fluidized bed polymerization reactors employ the discharge method described in Chinese patent ZL200780037815.5, which consists of two or more discharge systems. These systems can discharge independently or in parallel, alternating between systems. Each discharge system comprises a settling container, a transfer container, discharge pipelines, and control valves. The discharge port is typically located 0.2–0.5 meters above the distribution plate. During discharge, the polyethylene particles from the fluidized bed reactor carry a large amount of raw material gas that has just entered the reactor and has not yet participated in the polymerization reaction, as well as comonomers and condensers adsorbed and dissolved in the polyethylene particles. This results in a series of problems, including raw material loss, increased load on the subsequent degassing chamber and exhaust gas recovery system, and increased energy consumption. Specifically, because the pore volume within and around the particles is filled with a high-pressure gas mixture, a large amount of gas or gas / liquid mixture is lost during discharge. The lost gas must then be replenished (consuming additional raw materials) or recovered and recycled. Especially in the condensation process, as described in Chinese patents ZL201110290787.6 and ZL200780037815.5, the condensate content in fluidized bed polymerization reactors can reach as high as 10 wt%. Since the condensate is typically introduced from the bottom of the fluidized bed reactor, the condensate content in the lower part of the bed is even higher. Therefore, if a traditional discharge process is used, the high condensate content of the material easily clogs the discharge pipe near the distribution plate at the bottom of the fluidized bed, resulting in a slow discharge rate. More importantly, the discharged material carries away a significant amount of condensate, causing substantial losses of condensate in the reactor and increasing the operating load on the degassing chamber.

[0005] One solution is to use parallel alternating operation (cross-discharge), where gas is transferred between the settling containers and transfer containers of the two discharge systems through pressure balancing, reducing material loss and increased energy consumption during discharge. However, even with parallel alternating operation, the operating pressure of the transfer tank remains high, and material loss during the discharge process is still significant.

[0006] Chinese patent ZL201410645418.8 moves the discharge port from the bottom to the upper middle part of the fluidized bed reactor, avoiding the high liquid content zone above the distribution plate, thus significantly reducing liquid entrainment during the discharge process. An ejector is installed above the settling container, and a pipeline connected to the settling container draws gas from it, creating a negative pressure inside. This pressure difference forces the material in the fluidized bed reactor into the settling container. Simultaneously, the discharge port and pipeline near the distribution plate at the bottom of the fluidized bed reactor are retained for emergency discharge of agglomerates. Compared to traditional discharge processes, this significantly reduces feed gas loss and energy loss.

[0007] Chinese patent ZL201510662171.5 addresses the issue of liquid entrainment during discharge by employing a three-layer discharge system. The upper discharge port is located at 80%–90% of the material level during normal operation of the gas-phase fluidized bed reactor; the middle discharge port is located at 40%–60%; and the lower discharge port is located 0.2–0.5 m above the distribution plate. A two-stage flash evaporation process replaces the original cross-discharge mode. The polymerization product discharged from the fluidized bed reactor's discharge port enters the first-stage flash tank for flash evaporation, and then enters the second-stage flash tank for secondary flash evaporation under gravity and pressure difference. The gas distilled from the tops of the first and second-stage flash tanks is filtered and pressurized before entering the circulating gas loop, with some non-condensable gases discharged to the recovery system. This method, with its three-layer discharge system and each flash tank equipped with two filters and two buffer tanks, utilizes high-frequency, pulsed discharge from each system to create a continuous and stable discharge stream. However, the process is complex and difficult to operate.

[0008] In summary, existing technologies mostly adopt a two-stage container series operation discharge mode, which is relatively cumbersome and has low discharge efficiency. Summary of the Invention

[0009] In view of this, the present disclosure provides a discharge system and method for a fluidized bed reactor to solve the technical problem that the discharge mode using a two-stage container series operation in the prior art has a relatively cumbersome process and low discharge efficiency.

[0010] A first aspect of this disclosure provides a fluidized bed reactor discharge system, including a discharge tank, a fluidized bed reactor, a buffer tank, and a gas compression and cooling system, wherein...

[0011] A discharge pipeline and a gas balance line are connected between the discharge tank and the fluidized bed reactor. The discharge pipeline is equipped with a control valve A to control the flow rate, and the gas balance line is equipped with a control valve B to control the flow rate. The discharge pipeline is used to transport the material in the fluidized bed reactor to the discharge tank, and the gas balance line is used to maintain the material balance between the discharge tank and the fluidized bed reactor.

[0012] An exhaust line is connected between the discharge tank and the buffer tank. The exhaust line is equipped with a control valve C to control the flow rate. The exhaust line is used to transmit the exhaust gas from the discharge tank to the buffer tank.

[0013] A gas delivery pipe is connected between the discharge tank and the gas supply source. The gas delivery pipe is equipped with a control valve D to control the flow rate. The gas delivery pipe is used to introduce the gas input from the gas supply source into the discharge tank, and under the action of gas pressure, the solid in the discharge tank is transported downward.

[0014] A powder conveying line is connected between the lower part of the discharge tank and the preset downstream device. The powder conveying line is equipped with a control valve E to control the flow rate. The powder conveying line is used to transfer the solid in the discharge tank downward to the downstream device.

[0015] A buffer exhaust pipe is connected between the buffer tank and the gas compression and cooling system. The buffer exhaust pipe is used to transfer uncondensed gas in the buffer tank to the gas compression and cooling system.

[0016] In some embodiments, an inflation line is connected between the discharge tank and the gas compression and cooling system. The inflation line is equipped with a control valve F to control the flow rate. The inflation line is used to transmit the gas separated by the gas compression and cooling system to the discharge tank.

[0017] In some embodiments, the buffer tank discharges condensate through the powder conveying line, and the condensate is output to a preset storage tank or recovery system; or, the condensate is pressurized and output to the fluidized bed reactor.

[0018] In some embodiments, the gas compression cooling system outputs a first recovered gas after processing, which is then output to a preset flare, recovery system, or fluidized bed reactor.

[0019] In some embodiments, the gas compression cooling system outputs a first recovered liquid after processing, which is then output to a preset storage tank, recovery system, or buffer tank; or, the first recovered liquid is pressurized and output to the fluidized bed reactor.

[0020] In some embodiments, a gas filter is provided on the top of the discharge tank, and the exhaust line and the inflation line are connected to the discharge tank through the gas filter.

[0021] In some embodiments, a discharge gas heat exchanger or at least two discharge gas heat exchangers are provided between the discharge tank and the buffer tank;

[0022] When an exhaust gas heat exchanger is installed, the cooling medium of the exhaust gas heat exchanger is cooling water;

[0023] When at least two exhaust gas heat exchangers are installed, the exhaust gas heat exchangers are at least divided into a primary heat exchanger and other stages of heat exchangers, wherein the cooling medium of the primary heat exchanger is cooling water, and the medium of the other stages of heat exchangers is either chilled brine or liquid propylene.

[0024] In some embodiments, the fluidized bed reactor discharge system further includes a recirculating gas compressor and a recirculating gas cooler, wherein...

[0025] The top outlet of the fluidized bed reactor is connected to the inlet of the circulating gas compressor, the outlet of the circulating gas compressor is connected to the inlet of the circulating gas cooler, and the outlet of the circulating gas cooler is connected to the bottom of the fluidized bed reactor.

[0026] In some embodiments, the first recovered gas is output to a pipeline between the recirculating gas compressor and the recirculating gas cooler.

[0027] In some embodiments, the first recovered liquid is output to a pipeline between the circulating gas compressor and the circulating gas cooler, and / or a pipeline between the circulating gas cooler and the fluidized bed reactor, and / or the fluidized bed reactor.

[0028] In some embodiments, a cryogenic recovery system is further included, which is used to separate the first recovered gas to obtain a second recovered gas and a second recovered liquid.

[0029] In some embodiments, the second recovered gas is output to a preset flare, recovery system, or fluidized bed reactor.

[0030] In some embodiments, the second recovered gas exchanges heat with the exhaust gas from the discharge tank before being sent to the fluidized bed reactor.

[0031] In some embodiments, the second recovered liquid is discharged to a preset storage tank, recovery system, or buffer tank; or,

[0032] The second recovered liquid is pressurized and then output to the fluidized bed reactor.

[0033] In some embodiments, a gas recovery pipeline is further connected between the gas compression cooling system and the buffer tank. The gas recovery pipeline is used to output a portion of the gas obtained after processing by the gas compression cooling system to the buffer tank, so as to form a gas circulation between the buffer tank and the gas compression cooling system.

[0034] In some embodiments, the system further includes a first gas purging line connected to a discharge line and a second gas purging line connected to a gas balance line. The first purging line is provided with a control valve G for controlling the flow rate, and the second purging line is provided with a control valve H for controlling the flow rate. The first / second gas purging lines are used to prevent pipe blockage.

[0035] In some embodiments, the connection between the first gas purging line and the discharge line is located between the fluidized bed reactor and control valve A; the connection between the second gas purging line and the gas balance line is located between the fluidized bed reactor and control valve B.

[0036] In some embodiments, at least one parallel discharge tank is also included, which has the same structure as the discharge tank and whose connection method, connecting pipes, and control valves with the fluidized bed reactor, buffer tank, and gas compression cooling system are mirror images of each other.

[0037] In some embodiments, the discharge tank is equipped with a material level detection instrument, a temperature detection instrument, and a pressure detection instrument.

[0038] In some embodiments, the gas compression cooling system includes a gas compressor, a cooler, and a gas-liquid separator, wherein,

[0039] The gas compressor is used to pressurize the gas transmitted from the buffer exhaust pipe and transmit the pressurized gas to the cooler.

[0040] The cooler is used to cool the pressurized gas and then transfer the cooled gas to the gas-liquid separator.

[0041] The gas-liquid separator is used to separate the cooled gas to obtain the first recovered gas in the gas phase and the first recovered liquid in the liquid phase.

[0042] In some embodiments, the cryogenic recovery system includes at least one multi-flow heat exchanger, at least one gas-liquid separator, at least one gas expander, and one liquid pressure reducing valve, wherein...

[0043] The multi-stream heat exchanger includes at least one gas cooling channel, at least one liquid cooling channel, and at least one inlet channel. The gas cooling channel is used to transfer low-temperature gas to the multi-stream heat exchanger for cooling. The liquid cooling channel is used to transfer low-temperature liquid to the multi-stream heat exchanger for cooling. The inlet channel is used to transfer the first recovered gas and, under the action of the cooling channel, cools the first recovered gas, and then transfers the cooled first recovered gas to the gas-liquid separator.

[0044] The gas-liquid separator is used to separate the cooled first recovered gas to obtain a gaseous first recovered gas and a liquid first recovered gas; the gaseous first recovered gas is transferred to the gas expander; and the liquid first recovered gas is transferred to the liquid pressure reducing valve.

[0045] The gas expander is used to expand and cool the first recovered gas in the gas phase to obtain a low-pressure and low-temperature first recovered gas in the gas phase. The low-pressure and low-temperature first recovered gas in the gas phase is then transferred to the gas cooling channel of the multi-flow heat exchanger for cold energy recovery treatment to obtain the second recovered gas, and the second recovered gas is output.

[0046] The liquid pressure reducing valve is used to throttle and expand the incoming liquid phase first recovery gas to obtain a cooled liquid phase first recovery gas. The cooled liquid phase first recovery gas is then transmitted to the liquid cooling channel of the multi-stream heat exchanger for cold energy recovery to obtain the second recovery liquid, which is then output.

[0047] In some embodiments, under normal operating conditions, the discharge tank operates periodically according to a preset duration, while the buffer tank and the gas compression cooling system operate continuously.

[0048] A second aspect of this disclosure provides a method for discharging solids from a fluidized bed reactor, the method being applied to the fluidized bed reactor discharge system as described in claim 2, the method comprising:

[0049] Confirm that control valves A, B, C, D, E, and F are all in the closed state;

[0050] Open the control valves A and B to transfer the material in the fluidized bed reactor to the discharge tank;

[0051] When the fluidized bed reactor reaches equilibrium with the material in the discharge tank, control valves A and B are closed and control valve C is opened to allow the discharge tank to vent gas to the buffer tank.

[0052] When the pressure inside the discharge tank decreases to a preset first pressure threshold, control valve C is closed and control valves D and E are opened, and the solids inside the discharge tank are discharged to a preset downstream device by the input gas.

[0053] After the solids in the discharge tank are discharged, control valves D and E are closed, and control valve F is opened. The gas in the gas compression cooling system is used to pressurize the discharge tank, thereby increasing the pressure inside the discharge tank.

[0054] When the pressure inside the discharge tank rises to a preset second pressure threshold, the control valve F is closed, and the discharge process ends.

[0055] In some embodiments, before opening the control valves A and B, the following steps are included:

[0056] Confirm that the pressure inside the discharge tank is within a preset first pressure range;

[0057] Confirm that the pressure difference between the fluidized bed reactor and the discharge tank is within a preset second pressure range.

[0058] In some embodiments, before confirming that control valves A, B, C, D, E, and F are all in the closed state, the following steps are included:

[0059] Turn on the gas compression cooling system to enable gas self-circulation between the buffer tank and the gas compression cooling system.

[0060] In some embodiments, the second pressure threshold is not less than 0.6 MPa.

[0061] In some embodiments, the first pressure threshold is not greater than 1 MPa, 0.5 MPa, 0.1 MPa, or 0.01 MPa;

[0062] Preferably, the first pressure threshold is not greater than 0.01 MPa.

[0063] In some embodiments, the pressure difference between the fluidized bed reactor and the discharge tank is no greater than 1.5 MPa, 1.2 MPa, or 1.0 MPa;

[0064] Preferably, the pressure difference between the fluidized bed reactor and the discharge tank is no greater than 1.0 MPa.

[0065] A third aspect of this disclosure provides another method for discharging solids from a fluidized bed reactor, comprising: the method comprising:

[0066] Confirm that control valves A, B, C, D, E, and F are all in the closed state;

[0067] Open control valves A and B, and close control valves G and H to allow the fluidized bed reactor to transfer material to the discharge tank;

[0068] When the fluidized bed reactor and the material in the discharge tank reach equilibrium, control valves A and B are closed, and control valves G, H and C are opened to allow the discharge tank to vent gas to the buffer tank.

[0069] When the pressure inside the discharge tank decreases to a preset first pressure threshold, control valve C is closed and control valves D and E are opened to supply gas to the discharge tank so that the solids inside are discharged to a preset downstream device.

[0070] After the solids in the discharge tank are discharged, control valves D and E are closed, and control valve F is opened. The gas in the gas compression cooling system is used to pressurize the discharge tank, thereby increasing the pressure inside the discharge tank.

[0071] When the pressure inside the discharge tank rises to a preset second pressure threshold, the control valve F is closed, and the discharge process ends.

[0072] In some embodiments, an exhaust gas separator is further provided between the exhaust gas heat exchanger and the gas compression and cooling system. The exhaust gas separator is used to perform flash evaporation and gas-liquid separation on the cooled gas output from the exhaust gas heat exchanger, output the separated gas phase to the compression and cooling system, and pressurize the separated liquid phase third recovery liquid before outputting it to the fluidized bed reactor.

[0073] The beneficial effects of this disclosed embodiment compared to the prior art include at least the following: Firstly, by combining the settling container and the transfer container into one, and by setting up a multi-functional discharge tank, the discharge process is greatly simplified, thereby improving discharge efficiency and reducing the probability of failure. Secondly, by using compression condensation to pressurize the exhaust gas from the discharge tank and then sending it back to the fluidized bed reactor for recycling, material loss is reduced while energy utilization is improved.

[0074] Beneficial effects

[0075] The beneficial effects of this disclosed embodiment compared to the prior art include at least the following: Firstly, by combining the settling container and the transfer container into one, and by setting up a multi-functional discharge tank, the discharge process is greatly simplified, thereby improving discharge efficiency and reducing the probability of failure. Secondly, by using compression condensation to pressurize the exhaust gas from the discharge tank and then sending it back to the fluidized bed reactor for recycling, material loss is reduced while energy utilization is improved. Attached Figure Description

[0076] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0077] Figure 1 This is a schematic diagram of the first fluidized bed reactor discharge system provided in the embodiments of this disclosure;

[0078] Figure 2 This is a schematic diagram of the second type of fluidized bed reactor discharge system provided in the embodiments of this disclosure;

[0079] Figure 3 This is a schematic diagram of the third type of fluidized bed reactor discharge system provided in the embodiments of this disclosure;

[0080] Figure 4 This is a schematic diagram of the fourth type of fluidized bed reactor discharge system provided in the embodiments of this disclosure;

[0081] Figure 5 This is a schematic diagram of the fifth fluidized bed reactor discharge system provided in the embodiments of this disclosure;

[0082] Figure 6 This is a schematic diagram of the sixth fluidized bed reactor discharge system provided in the embodiments of this disclosure;

[0083] Figure 7 This is a schematic diagram of the seventh fluidized bed reactor discharge system provided in the embodiments of this disclosure;

[0084] Figure 8 This is a schematic diagram of the gas compression and cooling system in the fluidized bed reactor discharge system provided in this embodiment of the disclosure;

[0085] Figure 9 This is a schematic diagram of the cryogenic recovery system in the fluidized bed reactor discharge system provided in the embodiments of this disclosure;

[0086] Figure 10 This is a schematic flow diagram of a method for discharging solids from a fluidized bed reactor according to an embodiment of this disclosure;

[0087] Figure 11 This is a schematic flow diagram of another method for discharging solids from a fluidized bed reactor, provided in an embodiment of this disclosure. Detailed Implementation

[0088] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0089] It should also be noted that, for ease of description, only the parts relevant to this disclosure are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other.

[0090] It should be noted that the concepts of "first" and "second" mentioned in this disclosure are used only to distinguish different systems, devices, modules or units, and are not used to limit the order of functions performed by these systems, devices, modules or units or their interdependencies.

[0091] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0092] The names of messages or information exchanged between multiple devices in the embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of such messages or information.

[0093] The technical solution provided by this invention is applicable to the discharge of gas-solid fluidized bed reactors and gas-liquid-solid fluidized bed reactors, and is especially applicable to the discharge of gas-phase fluidized bed polymerization reactors for the production of polyethylene and polypropylene.

[0094] The following combination Figure 1-7 The fluidized bed reactor discharge system provided by this invention will be described in detail.

[0095] like Figure 1 In some embodiments shown, this disclosure illustrates a fluidized bed reactor discharge system, including a discharge tank, a fluidized bed reactor, a buffer tank, and a gas compression and cooling system, wherein...

[0096] A discharge pipeline and a gas balance line connect the discharge tank and the fluidized bed reactor. The discharge pipeline is equipped with a control valve A to control the flow rate, and the gas balance line is equipped with a control valve B to control the flow rate. The discharge pipeline is used to transport material from the fluidized bed reactor to the discharge tank, and the gas balance line is used to maintain material balance between the discharge tank and the fluidized bed reactor. When the fluidized bed reactor transfers material to the discharge tank, the gas balance line maintains the material balance between the two.

[0097] An exhaust line is connected between the discharge tank and the buffer tank. The exhaust line is equipped with a control valve C to control the flow rate. The exhaust line is used to transmit the exhaust gas from the discharge tank to the buffer tank.

[0098] A gas delivery pipe is connected between the discharge tank and the gas supply source. The gas delivery pipe is equipped with a control valve D to control the flow rate. The gas delivery pipe is used to introduce the gas input from the gas supply source into the discharge tank, and under the action of air pressure, the solids in the discharge tank are transported downward.

[0099] A powder conveying line is connected between the lower part of the discharge tank and a pre-designated downstream device. The powder conveying line is equipped with a control valve E to control the flow rate. The powder conveying line is used to transfer the solids in the discharge tank downwards to the downstream device. The downstream device can refer to a device for processing the solids in the discharge tank. This device is a common feature in the field and is not subject to much restriction.

[0100] A buffer exhaust pipe is connected between the buffer tank and the gas compression and cooling system. The buffer exhaust pipe is used to transfer uncondensed gas in the buffer tank to the gas compression and cooling system.

[0101] The beneficial effects of this disclosed embodiment compared to the prior art include at least the following: Firstly, by combining the settling container and the transfer container into one, and by setting up a multi-functional discharge tank, the discharge process is greatly simplified, thereby improving discharge efficiency and reducing the probability of failure. Secondly, by using compression condensation to pressurize the exhaust gas from the discharge tank and then sending it back to the fluidized bed reactor for recycling, material loss is reduced while energy utilization is improved.

[0102] like Figure 2 As shown, in some embodiments, an inflation line is connected between the discharge tank and the gas compression and cooling system. The inflation line is equipped with a control valve F to control the flow rate. The inflation line is used to transfer the gas separated by the gas compression and cooling system to the discharge tank.

[0103] In some embodiments, the buffer tank discharges condensate through the powder conveying line, and the condensate is output to a pre-set storage tank or recovery system; alternatively, the condensate is pressurized and output to the fluidized bed reactor. The storage tank or recovery system may refer to pre-installed equipment for treating the condensate. It should also be noted that pressurizing the condensate and outputting it to the fluidized bed reactor is a more preferred treatment method.

[0104] In some embodiments, the gas compression and cooling system outputs a first recovered gas after processing, which is then output to a pre-designated flare, recovery system, or fluidized bed reactor. The first recovered gas may refer to the gas output after processing by the gas compression and cooling system. The flare may refer to a pre-installed device for processing the first recovered gas. Outputting to a fluidized bed reactor is a preferred processing method.

[0105] In some embodiments, the gas compression cooling system outputs a first recovered liquid after processing. This first recovered liquid is then output to a preset storage tank, recovery system, or buffer tank; alternatively, the first recovered liquid is pressurized and output to the fluidized bed reactor. The first recovered liquid can refer to the liquid output after processing by the gas compression cooling system. Pressurizing the first recovered liquid and outputting it to the fluidized bed reactor is a preferred processing method.

[0106] In some embodiments, a gas filter is provided on the top of the discharge tank, and the exhaust line and the inflation line are connected to the discharge tank through the gas filter. Gas filters are common devices in the art and will not be described in detail here.

[0107] like Figure 4As shown in Figure 5, in some embodiments, one or at least two exhaust gas heat exchangers are provided between the discharge tank and the buffer tank; when one exhaust gas heat exchanger is provided, the cooling medium of the exhaust gas heat exchanger is cooling water; when at least two exhaust gas heat exchangers are provided, the exhaust gas heat exchangers are at least divided into a primary heat exchanger and other stages of heat exchangers, wherein the cooling medium of the primary heat exchanger is cooling water, and the medium of the other stages of heat exchangers is one of chilled brine or liquid propylene. Providing multiple stages of exhaust gas heat exchangers can cool the exhaust gas to a lower temperature, so that the exhaust gas separator can obtain more liquid.

[0108] like Figure 5 As shown, in some embodiments, an exhaust gas separator is also provided between the exhaust gas heat exchanger and the gas compression cooling system. The exhaust gas separator is used to perform flash evaporation and gas-liquid separation on the cooled gas output from the exhaust gas heat exchanger, output the separated gas phase to the compression cooling system, and pressurize the separated liquid third recovery liquid before outputting it to the fluidized bed reactor.

[0109] It should be noted that when an exhaust gas heat exchanger and an exhaust liquid distributor are installed, a cryogenic recovery system is not required. Conversely, when a cryogenic recovery system is installed, an exhaust gas heat exchanger and an exhaust liquid distributor are not required. Of course, the exhaust gas heat exchanger and exhaust liquid distributor are not contradictory to the cryogenic recovery system and can coexist; however, the functions of the exhaust liquid distributor and the cryogenic recovery system partially overlap. Therefore, to reduce system complexity, it is not recommended to install both simultaneously.

[0110] In some embodiments, the fluidized bed reactor discharge system further includes a circulating gas compressor and a circulating gas cooler, wherein the top outlet of the fluidized bed reactor is connected to the inlet of the circulating gas compressor, the outlet of the circulating gas compressor is connected to the inlet of the circulating gas cooler, and the outlet of the circulating gas cooler is connected to the bottom of the fluidized bed reactor. The gas-phase fluidized bed reactor, the circulating gas compressor, and the circulating gas cooler work together to form a circulating gas loop.

[0111] In some embodiments, the first recovered gas is output to a pipeline between the recirculating gas compressor and the recirculating gas cooler.

[0112] like Figure 4 As shown, in some embodiments, the first recovered liquid is output to a pipeline between the circulating gas compressor and the circulating gas cooler, and / or a pipeline between the circulating gas cooler and the fluidized bed reactor, and / or the fluidized bed reactor.

[0113] like Figure 6As shown, in some embodiments, a cryogenic recovery system is further included, which separates the first recovered gas to obtain a second recovered gas and a second recovered liquid. The second recovered gas may refer to the gas output from the cryogenic recovery system after processing. The second recovered liquid may refer to the liquid output from the cryogenic recovery system after processing.

[0114] In some embodiments, the second recovered gas is output to a preset flare, recovery system, or fluidized bed reactor.

[0115] In some embodiments, the second recovered gas is heat-exchanged with the exhaust gas from the discharge tank before being sent to the fluidized bed reactor. It should be noted that the second recovered gas and the exhaust gas from the discharge tank can be mixed through pipelines or through devices or passages provided on the equipment body, without further restrictions.

[0116] In some embodiments, the second recovered liquid is discharged to a preset storage tank, recovery system, or buffer tank; or, the second recovered liquid is pressurized and discharged to the fluidized bed reactor. Discharging the second recovered liquid to the fluidized bed reactor after pressurization is a preferred treatment method.

[0117] In some embodiments, a gas recovery pipeline is further connected between the gas compression cooling system and the buffer tank. The gas recovery pipeline is used to output a portion of the gas obtained after processing by the gas compression cooling system to the buffer tank, thereby forming a gas cycle between the buffer tank and the gas compression cooling system. To ensure the system's long-term continuous and stable operation, the gas recovery pipeline forms a gas cycle, guaranteeing a minimum return flow rate and preventing the gas compression cooling system from stopping due to a lack of gas supply. This significantly improves the operational stability of the fluidized bed reactor discharge system in this disclosure.

[0118] like Figure 3 As shown, in some embodiments, a first gas purging line connected to the discharge line and a second gas purging line connected to the gas balance line are also included. The first purging line is equipped with a control valve G to control the flow rate, and the second purging line is equipped with a control valve H to control the flow rate. The first / second gas purging lines are used to prevent pipeline blockage. Because when valves A and B are closed, the material from the fluidized bed reactor will be transferred into the pipeline, causing blockage in the pipeline between the fluidized bed reactor and valves A / B, it is necessary to install the first / second gas purging lines to purge gas and prevent blockage.

[0119] In some embodiments, the connection between the first gas purging line and the discharge line is located between the fluidized bed reactor and control valve A; the connection between the second gas purging line and the gas balance line is located between the fluidized bed reactor and control valve B.

[0120] Please refer to Figure 7 In some embodiments, at least one parallel discharge tank is also included, arranged in parallel with the discharge tank. The parallel discharge tank has the same structure as the discharge tank, and its connection methods, connecting pipes, and control valves with the fluidized bed reactor, buffer tank, and gas compression cooling system are mirror images of each other. A parallel discharge tank can refer to a discharge tank with the same structure as the discharge tank (i.e., the same construction and the same interfaces). A mirror image arrangement can mean that the connection methods between the parallel discharge tank and other components are the same as those of the discharge tank, such as... Figure 7 The parallel discharge tanks share the same setup, connection relationships, connecting pipes, and control valves (A', B', C', D', E', F', G', H') as the discharge tanks. Multiple discharge tanks do not require gas balance lines, significantly simplifying the discharge process, reducing the use of control valves, and lowering the probability of failure. Furthermore, two or more discharge tank systems can operate independently without mutual interference, allowing for simultaneous or alternating operation. This flexibility and adaptability meet the diverse needs of high-load production. Especially in emergency situations requiring simultaneous discharge, the ability to increase discharge speed can be significantly enhanced.

[0121] In some embodiments, the discharge tank is equipped with a level detection instrument, a temperature detection instrument, and a pressure detection instrument. These instruments are commonly used in the art and will not be described in detail here.

[0122] like Figure 8 As shown, in some embodiments, the gas compression cooling system includes a gas compressor, a cooler, and a gas-liquid separator. The gas compressor pressurizes the gas supplied through the buffer exhaust pipe and transmits the pressurized gas to the cooler. The cooler cools the pressurized gas and transmits the cooled gas to the gas-liquid separator. The gas-liquid separator separates the cooled gas to obtain the first recovered gas in a gaseous phase and the first recovered liquid in a liquid phase. It should be noted that the gas compressor can be a screw compressor or a centrifugal compressor, and the pressure generated by the gas compressor is higher than the pressure generated by the fluidized bed reactor.

[0123] Preferably, the gas compression cooling system can employ a two-stage compression configuration, comprising two gas compressors, two coolers, and two gas-liquid separators. Liquid from the gas-liquid separator between the two gas compressors is sent to a buffer tank or, after being pressurized by a pump, to the fluidized bed reactor. The pressure difference between the outlet pressure of the gas compressor and the operating pressure of the fluidized bed reactor is not less than 0.1 MPa.

[0124] Furthermore, the pressure difference between the outlet pressure of the gas compressor and the operating pressure of the fluidized bed reactor shall not be less than 0.1 MPa and not less than 0.2 MPa.

[0125] like Figure 9 As shown, in some embodiments, the cryogenic recovery system includes at least one multi-flow heat exchanger, at least one gas-liquid separator, at least one gas expander, and one liquid pressure reducing valve, wherein...

[0126] The multi-stream heat exchanger includes at least one gas cooling channel, at least one liquid cooling channel, and at least one inlet channel. The gas cooling channel is used to transfer low-temperature gas to the multi-stream heat exchanger for cooling. The liquid cooling channel is used to transfer low-temperature liquid to the multi-stream heat exchanger for cooling. The inlet channel is used to transfer the first recovered gas and, under the action of the cooling channel, cools the first recovered gas, and then transfers the cooled first recovered gas to the gas-liquid separator.

[0127] The gas-liquid separator is used to separate the cooled first recovered gas to obtain a gaseous first recovered gas and a liquid first recovered gas; the gaseous first recovered gas is transferred to the gas expander; and the liquid first recovered gas is transferred to the liquid pressure reducing valve.

[0128] The gas expander is used to expand and cool the first recovered gas in the gas phase to obtain a low-pressure and low-temperature first recovered gas in the gas phase. The low-pressure and low-temperature first recovered gas in the gas phase is then transferred to the gas cooling channel of the multi-flow heat exchanger for cold energy recovery treatment to obtain the second recovered gas, and the second recovered gas is output.

[0129] The liquid pressure reducing valve is used to throttle and expand the incoming liquid phase first recovery gas to obtain a cooled liquid phase first recovery gas. The cooled liquid phase first recovery gas is then transmitted to the liquid cooling channel of the multi-stream heat exchanger for cold energy recovery to obtain the second recovery liquid, which is then output.

[0130] As a specific example, a typical process flow of a cryogenic recovery system may include: the first recovered gas from the gas compression cooling system enters a multi-flow heat exchanger, where its temperature is reduced to -90 to -130°C, and then enters a gas-liquid separator; the gas phase at the top of the gas-liquid separator enters the multi-flow heat exchanger for heat exchange, and then enters a gas expander (such as a turbine expander) for expansion and cooling to obtain low-pressure, low-temperature gas, which then enters the multi-flow heat exchanger for further recovery of cold energy before being sent out as the second recovered gas; the liquid phase at the bottom of the gas-liquid separator is throttled and expanded by a pressure reducing valve to reduce its temperature, and then enters the multi-flow heat exchanger for recovery of cold energy before being sent out as the second recovered liquid.

[0131] The exhaust gas from the discharge tank is pressurized using compression condensation and / or cryogenic separation technologies and then completely recycled back to the fluidized bed reactor. Simultaneously, the process flow is optimized using system integration methods, reducing material loss while improving energy utilization. More importantly, a large amount of clean liquid can be returned to the fluidized bed reactor, improving product quality. Furthermore, this disclosure also helps to enhance the product quality control effects of the new process technologies proposed in Chinese patents ZL201410748891.9, ZL201610404207.4, and ZL202010801584.8.

[0132] In some embodiments, under normal operating conditions, the discharge tank operates periodically for a preset duration, while the buffer tank and gas compression cooling system operate continuously. The preset duration can range from 1 minute to 100 minutes, or even longer, depending on the specific operating conditions of the system, and is not specifically limited here.

[0133] like Figure 10 As shown, this disclosure also provides a method 100 for discharging solids from a fluidized bed reactor, the method being applied to the aforementioned (e.g.) Figure 2 The fluidized bed reactor discharge system shown in the figure, the method includes:

[0134] Step 101: Confirm that control valves A, B, C, D, E, and F are all in the closed state.

[0135] Step 102: Open the control valves A and B to transfer the material in the fluidized bed reactor to the discharge tank.

[0136] Step 103: When the fluidized bed reactor and the material in the discharge tank reach equilibrium, close control valves A and B, and open control valve C to allow the discharge tank to vent gas to the buffer tank.

[0137] Step 104: When the pressure inside the discharge tank decreases to a preset first pressure threshold, control valve C is closed, and control valves D and E are opened. The solids inside the discharge tank are discharged to a preset downstream device by the input gas. The first pressure threshold may refer to a preset limit value used to restrict the pressure inside the discharge tank.

[0138] Step 105: After the solids in the discharge tank are discharged, close control valves D and E, open control valve F, and pressurize the discharge tank with gas from the gas compression cooling system to increase the pressure inside the discharge tank.

[0139] Step 106: When the pressure inside the discharge tank rises to a preset second pressure threshold, the control valve F is closed, and the discharge process ends. The second pressure threshold may refer to a preset limit value used to restrict the pressure inside the discharge tank.

[0140] In some embodiments, before opening the control valves A and B, the process includes: confirming that the pressure in the discharge tank is within a preset first pressure range; and confirming that the pressure difference between the fluidized bed reactor and the discharge tank is within a preset second pressure range. The first and second pressure ranges may refer to preset limits respectively used to limit the pressure in the discharge tank and the pressure difference between the fluidized bed reactor and the discharge tank.

[0141] In some embodiments, before confirming that the control valves A, B, C, D, E, and F are all in the closed state, the process includes: turning on the gas compression cooling system to enable the gas between the buffer tank and the gas compression cooling system to perform self-circulation.

[0142] In some embodiments, the second pressure threshold is not less than 0.6 MPa.

[0143] In some embodiments, the first pressure threshold is no greater than 1 MPa, 0.5 MPa, 0.1 MPa, or 0.01 MPa; preferably, the first pressure threshold is no greater than 0.01 MPa. By operating under a slightly positive or negative pressure (less than 0.01 MPa) after the discharge tank is vented, the low-molecular-weight compounds adsorbed in the polymer can be flashed out to the maximum extent, while the amount of gas entering the downstream system is reduced to a low level, and then pressurized and sent back to the fluidized bed reactor. On the one hand, this reduces the path of these low-molecular-weight compounds circulating in the system, avoids the introduction of impurities, and reduces raw material consumption; on the other hand, it reduces the devolatilization and recovery load of the downstream system, which helps to improve product quality.

[0144] In some embodiments, the pressure difference between the fluidized bed reactor and the discharge tank is no greater than 1.5 MPa, 1.2 MPa, or 1.0 MPa; preferably, the pressure difference between the fluidized bed reactor and the discharge tank is no greater than 1.0 MPa.

[0145] like Figure 11 As shown, this disclosure also provides a method 200 for discharging solids from a fluidized bed reactor, the method being applied to the aforementioned (e.g.) Figure 3 The fluidized bed reactor discharge system shown in the figure, the method includes:

[0146] Step 201: Confirm that control valves A, B, C, D, E, and F are all in the closed state.

[0147] Step 202: Open control valves A and B, and close control valves G and H to allow the fluidized bed reactor to transfer material to the discharge tank.

[0148] Step 203: When the fluidized bed reactor and the material in the discharge tank reach equilibrium, close the control valves A and B, and open the control valves G, H and C to allow the discharge tank to vent gas to the buffer tank.

[0149] Step 204: When the pressure inside the discharge tank decreases to a preset first pressure threshold, control valve C is closed and control valves D and E are opened to supply gas to the discharge tank so that the solids inside are discharged to a preset downstream device.

[0150] Step 205: After the solids in the discharge tank are discharged, close control valves D and E, open control valve F, and pressurize the discharge tank with gas from the gas compression cooling system to increase the pressure inside the discharge tank.

[0151] Step 206: When the pressure inside the discharge tank rises to the preset second pressure threshold, the control valve F is closed, and the discharge process ends.

[0152] In some embodiments, the specific implementation of steps 201 and 204-206 and the resulting technical effects can be found in [reference]. Figure 2 Steps 101 and 104-206 in the corresponding embodiments will not be repeated here. The difference between step 200 and step 100 is the addition of a first gas purge line and a second gas purge line, which are described in detail above.

[0153] The present disclosure is further explained below through some comparative embodiments:

[0154] Taking a gas-phase fluidized bed process unit with an annual production capacity of 120,000 tons of linear low-density polyethylene (LLDPE) as an example, the production of conventional single-peak LLDPE film products involves approximately 25 discharges per hour, with a fluidized bed inlet temperature of approximately 49°C and a discharge temperature of approximately 60–65°C. The discharge system is located on a single-phase fluidized bed reaction system, which includes a circulating gas loop consisting of a gas-phase fluidized bed reactor, a circulating gas compressor, and a circulating gas cooler connected in sequence. It also includes a catalyst feeding system and various raw material feeding systems. From the bottom to the top of the fluidized bed reactor, the concentration of the raw material gas decreases sequentially. A portion of the raw material gas undergoes polymerization in the bottom of the reactor, while unreacted and incompletely polymerized particles continue to polymerize in the upper part of the gas-phase fluidized bed reactor with the rising raw material gas flow. Some unreacted raw material gas is discharged from the top of the fluidized bed reactor and recycled along with the raw material gas, forming a circulating gas loop. The discharge port is located on the gas-phase fluidized bed reactor. As described in Chinese Patent ZL200780037815.5, the discharge system includes a settling container and a transfer container. The inlet of the settling container is connected to the discharge port of the single-phase fluidized bed reactor, the bottom of the settling container is connected to the inlet of the transfer container, and the bottom of the transfer container is connected to the downstream degassing chamber. The tops of both the settling container and the transfer container are connected to the single-phase fluidized bed reactor. Traditional fluidized bed reactors use a discharge port 0.3m above the fluidized bed distribution plate at the bottom of the fluidized bed. The discharge system begins discharging after the polymerization reaction has progressed to a certain stage. However, because the fluidized bed reactor has a bottom feed, a significant amount of unreacted material is carried away during the bottom discharge process. The operating pressure of the gas-phase fluidized bed reactor is approximately 2.0-2.4 MPa, the operating pressure of the settling container is approximately 1.1-1.2 MPa, and the operating pressure of the transfer container is approximately 0.5-0.6 MPa. The gas content carried in each discharge is approximately 0.08–0.09 kg / kg PE (the main components are ethylene, hydrogen, nitrogen, comonomers, and refrigerant isopentane, etc.).

[0155] Comparative Example 1

[0156] Taking a gas-phase fluidized bed process unit with an annual production capacity of 120,000 tons of linear low-density polyethylene (LLDPE) as an example, for the production of conventional LLDPE film products, the upper bed temperature of the fluidized bed reactor is approximately 88°C, the pressure is approximately 2.35 MPa, and condensate is introduced into the lower part of the fluidized bed reactor with a condensate content of approximately 5 wt%. The reactor discharges approximately 25 times per hour, the fluidized bed inlet temperature is approximately 49°C, and the discharge temperature is approximately 60–65°C. The discharge system is located on the side wall of the gas-phase fluidized bed reactor. The gas-phase fluidized bed reaction system includes a circulating gas loop consisting of a gas-phase fluidized bed reactor, a circulating gas compressor, and a circulating gas cooler connected in sequence, as well as a catalyst feeding system and various raw material feeding systems. From the bottom to the top of the fluidized bed reactor, the concentration of the feed gas decreases sequentially. A portion of the feed gas undergoes polymerization in the bottom of the reactor, while unreacted and fully polymerized particles continue to polymerize in the top of the gas-phase fluidized bed reactor along with the rising feed gas stream. Some unreacted feed gas is discharged from the top of the fluidized bed reactor and recycled together with the feed gas to form a circulating gas loop. The discharge port is located on the gas-phase fluidized bed reactor.

[0157] like Figure 5As shown, a discharge system for a fluidized bed reactor includes: a discharge tank, a discharge pipeline connecting the fluidized bed reactor and the discharge tank, and a discharge valve A installed on the discharge pipeline; a gas balance line connecting the discharge tank and the fluidized bed reactor, and a control valve B installed on the gas balance line; a buffer tank, an exhaust line connecting the discharge tank and the buffer tank, and a control valve C installed on the exhaust line; a gas compression and cooling system, a pipeline connecting the buffer tank and the gas compression and cooling system; a gas delivery pipeline connecting the discharge tank, and a control valve D installed on the gas delivery pipeline; and a connection between the discharge tank and the lower... The fluidized bed reactor includes a powder conveying line and a control valve E installed on the powder conveying line; an inflation line connecting the gas compression cooling system and the discharge tank, and a control valve F installed on the inflation line; a first gas purging line connected to the discharge line, and a control valve G installed on the first purging line; a second gas purging line connected to the gas balance line, and a control valve H installed on the second purging line; the inlet of the first gas purging line is located between the fluidized bed reactor and control valve A; the inlet of the second gas purging line is located between the fluidized bed reactor and control valve B. The top outlet of the fluidized bed reactor is connected to a circulating gas compressor, the circulating gas compressor is connected to a circulating gas cooler, and the circulating gas cooler is connected to the bottom of the fluidized bed reactor. A gas filter is installed at the top of the discharge tank, and the exhaust line is connected to the gas filter, as is the inflation line. An exhaust gas heat exchanger is installed between the discharge tank and the buffer tank. The gas compression cooling system adopts a two-stage compression process, consisting of two-stage gas compressors, two coolers, and two gas-liquid separators. Liquid from the gas-liquid separator between the two-stage gas compressors is sent to a buffer tank. The outlet pressure of the gas compressor is higher than the operating pressure of the fluidized bed reactor, with a set value of 3.0 MPa.

[0158] The discharge tank operates intermittently, while the buffer tank and gas compression cooling system operate continuously. Before performing the discharge operation, the gas compression cooling system is activated to allow gas to circulate between the buffer tank and the gas compression cooling system. The steps for discharging solids from the fluidized bed reactor include:

[0159] Step 1: Confirm that control valves A, B, C, D, E, and F on the pipeline connected to the discharge tank are all closed; confirm that the discharge tank pressure P2 meets the design specifications, and the difference between the fluidized bed reactor pressure P1 and the discharge tank pressure P2 is not greater than 1.2 MPa, which is taken as 1.2 MPa in this embodiment.

[0160] Step 2: When the material level and / or bed weight reach the set value, open control valves A and B, and close control valves G and H to discharge material from the fluidized bed reactor to the discharge tank. Under the action of pressure difference and gravity, the product is discharged from the discharge pipeline. The average flow rates of each component in the discharge stream are: LLDPE powder 15000 kg / h, discharge gas 1293 kg / h. The main components of the discharge gas are ethylene, hydrogen, nitrogen, comonomers butene and hexene, and refrigerant isopentane, etc. Among them, ethylene, butene, and hexene are unreacted monomers, and there is no liquid in the discharge stream. When the powder no longer transfers from the fluidized bed reactor to the discharge tank, an equilibrium is reached between the two, and the discharge is completed. At this time, the pressure in the discharge tank is approximately 2.35 MPa. 70%-90% of the solid material in the discharge tank is discharged in one discharge process. The discharge time is generally less than 60 seconds.

[0161] Step 3: After discharge is completed, close control valves A and B, and open control valves G, H, and C to vent gas from the discharge tank to the buffer tank, reducing the pressure in the discharge tank to the specified value P3, which is set at 0.15 MPa. The exhaust gas from the discharge tank exchanges heat with cooling water in the exhaust gas heat exchanger, reducing its temperature to 40°C. It then enters the exhaust gas separator, where the pressure is reduced to 0.2 MPa and gas-liquid separation is performed. The liquid is pressurized by a pump and sent back to the fluidized bed reactor. The return port is located in the pipeline between the circulating gas cooler and the bottom end cap of the fluidized bed reactor. The gas enters the buffer tank, where the pressure is reduced to 0.15 MPa. The uncondensed gas is discharged from the top of the buffer tank and drawn into the first-stage compressor, where it is pressurized to 0.8 MPa. After being cooled to 40°C by the first-stage cooler, it enters the first-stage gas-liquid separator. Liquid from the primary gas-liquid separator is directly sent to the buffer tank. Condensate from the buffer tank is pressurized by a pump and returned to the fluidized bed reactor. The return port is located in the pipeline between the circulating gas cooler and the bottom end cap of the fluidized bed reactor. Gas from the primary gas-liquid separator is pressurized to 3.0 MPa by the secondary compressor, cooled to 40°C by the secondary cooler, and then enters the secondary gas-liquid separator. Part of the gas from the top of the secondary gas-liquid separator returns to the buffer tank, forming a gas cycle to ensure continuous and stable operation of the compressor, with a circulation flow rate of not less than 700 kg / hr. The other part, controlled by the pressure of the secondary gas-liquid separator, is sent to the fluidized bed reactor as the first recovered gas from the gas compression and cooling system. Its return port is located in the pipeline between the circulating gas compressor and the circulating gas cooler. Liquid from the bottom of the secondary gas-liquid separator, as the first recovered liquid from the gas compression and cooling system, is pressurized by a pump and returned to the fluidized bed reactor. Its return port is located approximately 3 meters above the distribution plate on the side wall of the fluidized bed reactor.

[0162] Step 4: After venting is complete, close control valve C and open control valves D and E to send the solids in the discharge tank to the downstream device using conveying gas; nitrogen is selected as the conveying gas.

[0163] Step 5: After feeding is completed, close control valves D and E, open control valve F, and use gas from the gas compressor cooling system to fill the discharge tank. At the same time, backflush the filter above the discharge tank to increase the pressure of the discharge tank to the specified value P2, which is 1.15 MPa in this embodiment.

[0164] Step 6: After pressurization is complete, close control valve F, and the discharge tank returns to its initial state. This completes one discharge process, and the tank awaits the next discharge.

[0165] After adopting the above operating steps, the gas content in each discharge is approximately 0.05–0.06 kg / kg PE (the main components are ethylene, hydrogen, nitrogen, comonomers, and refrigerant isopentane, etc.).

[0166] Comparative Example 2

[0167] The difference from Comparative Example 1 is that the pressure from the discharge tank directly enters the buffer tank, without an intermediate discharge gas heat exchanger and discharge gas separator. A cryogenic recovery system is installed after the gas compression and cooling system. The first recovered gas from the gas compression and cooling system enters a multi-stream heat exchanger, where its temperature drops to -110°C, and then enters a gas-liquid separator. The gas phase at the top of the gas-liquid separator enters the multi-stream heat exchanger for heat exchange, then enters a turbine expander for expansion and cooling, resulting in low-pressure, low-temperature gas. This gas then enters the multi-stream heat exchanger for further recovery of cold energy and is sent to the buffer tank as the second recovered gas. The liquid phase at the bottom of the gas-liquid separator undergoes throttling and expansion through a pressure reducing valve to lower its temperature. After entering the multi-stream heat exchanger for further recovery of cold energy, it is also sent to the buffer tank as the second recovered liquid, reducing the temperature of the buffer tank to approximately 15°C. By optimizing the process flow using a system integration approach, material loss is reduced while energy utilization is improved. Furthermore, the discharge tank pressure P3 is set at 0.12 MPa. After adopting the above operating steps, the gas content in each discharge is approximately 0.045–0.050 kg / kg PE (the main components are ethylene, hydrogen, nitrogen, comonomers, and refrigerants, etc.).

[0168] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A fluidized bed reactor discharge system, characterized in that, It includes a discharge tank, a fluidized bed reactor, a buffer tank, and a gas compression and cooling system, among which, A discharge pipeline and a gas balance line are connected between the discharge tank and the fluidized bed reactor. The discharge pipeline is equipped with a control valve A to control the flow rate, and the gas balance line is equipped with a control valve B to control the flow rate. The discharge pipeline is used to transport the material in the fluidized bed reactor to the discharge tank, and the gas balance line is used to maintain the material balance between the discharge tank and the fluidized bed reactor. An exhaust line is connected between the discharge tank and the buffer tank. The exhaust line is equipped with a control valve C to control the flow rate. The exhaust line is used to transmit the exhaust gas from the discharge tank to the buffer tank. A gas delivery pipeline is connected between the discharge tank and the gas supply source. The gas delivery pipeline is equipped with a control valve D to control the flow rate. The gas delivery pipeline is used to introduce the gas input from the gas supply source into the discharge tank, and under the action of gas pressure, the solid in the discharge tank is transported downward. A powder conveying line is connected between the lower part of the discharge tank and the preset downstream device. The powder conveying line is equipped with a control valve E to control the flow rate. The powder conveying line is used to transfer the solid in the discharge tank downward to the downstream device. A buffer exhaust pipe is connected between the buffer tank and the gas compression and cooling system. The buffer exhaust pipe is used to transfer the uncondensed gas in the buffer tank to the gas compression and cooling system. An inflation line is connected between the discharge tank and the gas compression and cooling system. The inflation line is equipped with a control valve F to control the flow rate. The inflation line is used to transfer the gas separated by the gas compression and cooling system to the discharge tank. A gas recovery pipeline is also connected between the gas compression cooling system and the buffer tank. The gas recovery pipeline is used to output a portion of the gas obtained after processing by the gas compression cooling system to the buffer tank, so that a gas cycle is formed between the buffer tank and the gas compression cooling system.

2. The fluidized bed reactor discharge system according to claim 1, characterized in that, The buffer tank discharges condensate through the powder conveying line. The condensate is output to a preset storage tank or recovery system, or the condensate is pressurized and output to the fluidized bed reactor.

3. The fluidized bed reactor discharge system according to claim 1, characterized in that, The gas compression and cooling system outputs the processed first recovered gas, which is then output to a preset flare, recovery system, or fluidized bed reactor.

4. The fluidized bed reactor discharge system according to claim 3, characterized in that, The gas compression cooling system outputs the processed first recovered liquid, which is then output to a preset storage tank, recovery system, or buffer tank. Alternatively, the first recovered liquid is pressurized and output to the fluidized bed reactor.

5. The fluidized bed reactor discharge system according to claim 2, characterized in that, The top of the discharge tank is equipped with a gas filter, and the exhaust line and the inflation line are connected to the discharge tank through the gas filter.

6. The fluidized bed reactor discharge system according to claim 1, characterized in that, One or at least two exhaust gas heat exchangers are provided between the discharge tank and the buffer tank. When an exhaust gas heat exchanger is installed, the cooling medium of the exhaust gas heat exchanger is cooling water; When at least two exhaust gas heat exchangers are installed, the exhaust gas heat exchangers are at least divided into a primary heat exchanger and other stages of heat exchangers, wherein the cooling medium of the primary heat exchanger is cooling water, and the medium of the other stages of heat exchangers is either chilled brine or liquid propylene.

7. The fluidized bed reactor discharge system according to claim 4, characterized in that, It also includes a recirculating gas compressor and a recirculating gas cooler, wherein, The top outlet of the fluidized bed reactor is connected to the inlet of the circulating gas compressor, the outlet of the circulating gas compressor is connected to the inlet of the circulating gas cooler, and the outlet of the circulating gas cooler is connected to the bottom of the fluidized bed reactor.

8. The fluidized bed reactor discharge system according to claim 7, characterized in that, The first recovered gas is output to the pipeline between the circulating gas compressor and the circulating gas cooler.

9. The fluidized bed reactor discharge system according to claim 7, characterized in that, The first recovered liquid is output to the pipeline between the circulating gas compressor and the circulating gas cooler, and / or the pipeline between the circulating gas cooler and the fluidized bed reactor, and / or the fluidized bed reactor.

10. The fluidized bed reactor discharge system according to claim 3, characterized in that, It also includes a cryogenic recovery system, which is used to separate the first recovered gas to obtain a second recovered gas and a second recovered liquid.

11. The fluidized bed reactor discharge system according to claim 10, characterized in that, The second recovered gas is output to a preset flare, recovery system, or fluidized bed reactor.

12. The fluidized bed reactor discharge system according to claim 11, characterized in that, The second recovered gas exchanges heat with the exhaust gas from the discharge tank before being sent to the fluidized bed reactor.

13. The fluidized bed reactor discharge system according to claim 10, characterized in that, The second recovered liquid is discharged to a pre-set storage tank, recovery system, or buffer tank; or, The second recovered liquid is pressurized and then output to the fluidized bed reactor.

14. The fluidized bed reactor discharge system according to claim 1, characterized in that, It also includes a first gas purging line connected to the discharge line and a second gas purging line connected to the gas balance line. The first gas purging line is equipped with a control valve G for controlling the flow rate, and the second gas purging line is equipped with a control valve H for controlling the flow rate. The first and second gas purging lines are used to prevent pipeline blockage.

15. The fluidized bed reactor discharge system according to claim 14, characterized in that, The connection between the first gas purging line and the discharge line is located between the fluidized bed reactor and control valve A; the connection between the second gas purging line and the gas balance line is located between the fluidized bed reactor and control valve B.

16. The fluidized bed reactor discharge system according to any one of claims 1 to 15, characterized in that, It also includes at least one parallel discharge tank arranged in parallel with the discharge tank. The parallel discharge tank has the same structure as the discharge tank, and the connection method, connecting pipes, and control valves between the parallel discharge tank and the fluidized bed reactor, buffer tank, and gas compression cooling system are mirror images of each other.

17. The fluidized bed reactor discharge system according to any one of claims 1 to 15, characterized in that, The discharge tank is equipped with a material level detection instrument, a temperature detection instrument, and a pressure detection instrument.

18. The fluidized bed reactor discharge system according to claim 4, characterized in that, The gas compression cooling system includes a gas compressor, a cooler, and a gas-liquid separator, wherein... The gas compressor is used to pressurize the gas transmitted from the buffer exhaust pipe and transmit the pressurized gas to the cooler. The cooler is used to cool the pressurized gas and then transfer the cooled gas to the gas-liquid separator. The gas-liquid separator is used to separate the cooled gas to obtain the first recovered gas in the gas phase and the first recovered liquid in the liquid phase.

19. The fluidized bed reactor discharge system according to any one of claims 10 to 13, characterized in that, The cryogenic recovery system includes at least one multi-flow heat exchanger, at least one gas-liquid separator, at least one gas expander, and one liquid pressure reducing valve. The multi-stream heat exchanger includes at least one gas cooling channel, at least one liquid cooling channel, and at least one inlet channel. The gas cooling channel is used to transfer low-temperature gas to the multi-stream heat exchanger for cooling. The liquid cooling channel is used to transfer low-temperature liquid to the multi-stream heat exchanger for cooling. The inlet channel is used to transfer the first recovered gas and, under the action of the cooling channel, cools the first recovered gas, and then transfers the cooled first recovered gas to the gas-liquid separator. The gas-liquid separator is used to separate the cooled first recovered gas to obtain a gaseous first recovered gas and a liquid first recovered gas; the gaseous first recovered gas is transferred to the gas expander; and the liquid first recovered gas is transferred to the liquid pressure reducing valve. The gas expander is used to expand and cool the first recovered gas in the gas phase to obtain a low-pressure and low-temperature first recovered gas in the gas phase. The low-pressure and low-temperature first recovered gas in the gas phase is then transferred to the gas cooling channel of the multi-flow heat exchanger for cold energy recovery treatment to obtain the second recovered gas, and the second recovered gas is output. The liquid pressure reducing valve is used to throttle and expand the incoming liquid phase first recovery gas to obtain a cooled liquid phase first recovery gas. The cooled liquid phase first recovery gas is then transmitted to the liquid cooling channel of the multi-stream heat exchanger for cold energy recovery to obtain the second recovery liquid, which is then output.

20. The fluidized bed reactor discharge system according to any one of claims 1 to 15, characterized in that, Under normal operating conditions, the discharge tank operates periodically according to a preset time period, while the buffer tank and the gas compression and cooling system operate continuously.

21. The fluidized bed reactor discharge system according to claim 6, characterized in that, An exhaust gas separator is also provided between the exhaust gas heat exchanger and the gas compression and cooling system. The exhaust gas separator is used to perform flash evaporation and gas-liquid separation on the cooled gas output from the exhaust gas heat exchanger. The separated gas phase is output to the compression and cooling system, and the separated liquid phase is pressurized and output to the fluidized bed reactor.

22. A method for discharging solids from a fluidized bed reactor, characterized in that, The method is applied to the fluidized bed reactor discharge system as described in claim 1, and the method includes: Confirm that control valves A, B, C, D, E, and F are all in the closed state; Open the control valves A and B to transfer the material in the fluidized bed reactor to the discharge tank; When the fluidized bed reactor reaches equilibrium with the material in the discharge tank, control valves A and B are closed and control valve C is opened to allow the discharge tank to vent gas to the buffer tank. When the pressure inside the discharge tank decreases to a preset first pressure threshold, control valve C is closed and control valves D and E are opened, and the solids inside the discharge tank are discharged to a preset downstream device through the input gas. After the solids in the discharge tank are discharged, control valves D and E are closed and control valve F is opened. Gas from the gas compression and cooling system is used to inflate the discharge tank through the inflation line, increasing the pressure inside the discharge tank. The gas is then transported to the buffer tank through the gas recovery pipeline, so that a gas cycle is formed between the buffer tank and the gas compression and cooling system. When the pressure inside the discharge tank rises to a preset second pressure threshold, the control valve F is closed, and the discharge process ends.

23. The method according to claim 22, characterized in that, Before opening the control valves A and B, the following steps are included: Confirm that the pressure inside the discharge tank is within a preset first pressure range; Confirm that the pressure difference between the fluidized bed reactor and the discharge tank is within a preset second pressure range.

24. The method according to claim 22, characterized in that, Before confirming that control valves A, B, C, D, E, and F are all in the closed state, the following steps are included: Turn on the gas compression cooling system to enable gas self-circulation between the buffer tank and the gas compression cooling system.

25. The method according to claim 22, characterized in that, The second pressure threshold is not less than 0.6 MPa.

26. The method according to claim 22, characterized in that, The first pressure threshold is not greater than 1 MPa, 0.5 MPa, 0.1 MPa or 0.01 MPa; the first pressure threshold is not greater than 0.01 MPa.

27. The method according to claim 23, characterized in that, The pressure difference between the fluidized bed reactor and the discharge tank shall not exceed 1.5 MPa, 1.2 MPa, or 1.0 MPa; the pressure difference between the fluidized bed reactor and the discharge tank shall not exceed 1.0 MPa.

28. A method for discharging solids from a fluidized bed reactor, characterized in that, The method is applied to the fluidized bed reactor discharge system as described in claim 17, and the method includes: Confirm that control valves A, B, C, D, E, and F are all in the closed state; Open control valves A and B, and close control valves G and H to allow the fluidized bed reactor to transfer material to the discharge tank; When the fluidized bed reactor and the material in the discharge tank reach equilibrium, control valves A and B are closed, and control valves G, H and C are opened to allow the discharge tank to vent gas to the buffer tank. When the pressure inside the discharge tank decreases to a preset first pressure threshold, control valve C is closed and control valves D and E are opened to supply gas to the discharge tank so that the solids inside are discharged to a preset downstream device. After the solids in the discharge tank are discharged, control valves D and E are closed and control valve F is opened. Gas from the gas compression and cooling system is used to inflate the discharge tank through the inflation line, increasing the pressure inside the discharge tank. The gas is then transported to the buffer tank through the gas recovery pipeline, so that a gas cycle is formed between the buffer tank and the gas compression and cooling system. When the pressure inside the discharge tank rises to a preset second pressure threshold, the control valve F is closed, and the discharge process ends.

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