Discharging system and method for fluidized bed reactor

Abstract

The invention relates to the technical field of petrochemical engineering, and provides a discharging 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; an exhaust line is connected between the discharge tank and the buffer tank; a conveying air pipe is connected between the discharging tank and the air conveying source; a powder conveying line is connected between the lower part of the discharging tank and a preset downstream device; a buffer exhaust pipeline is connected between the buffer tank and the gas compression cooling system; and each pipeline is provided with a control valve. According to the embodiment of the invention, the discharging efficiency can be improved, the fault probability is reduced, and the energy utilization rate can be improved while the material loss is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and in particular relates to a discharging system and method of a fluidized bed reactor. Background Art

[0002] Fluidized bed reactors are widely used in chemical, petroleum, metallurgy, nuclear industry and other fields. Taking the polyolefin industry as an example, the gas phase polyethylene process using fluidized bed reactors has many advantages such as simple process, flexible operation, no need for refined recovery of solvents, low equipment investment and production operation costs, and relatively clean and environmentally friendly. UCC (US5453471), BP (WO94 / 28032), Exxon (WO96 / 10591) and other companies have successively developed condensation and super condensation technologies, overcoming the difficulties in removing reaction heat from fluidized bed reactors and the limited amount of comonomer added, making the gas phase fluidized bed polyethylene process technology a commonly used polyethylene production process technology.

[0003] The gas phase fluidized bed polyethylene process generally includes several steps such as raw material refining, polymerization reaction, powder degassing, granulation, transportation, packaging, etc. In the polymerization reaction unit, refined ethylene, comonomer (1-butene-1 or 1-hexene or 1-octene), isopentane (induced condensing agent), hydrogen, nitrogen, etc. are added to the fluidized bed reactor, and polymerization reaction occurs under the action of catalyst and co-catalyst to produce polyethylene. The unreacted raw gas is discharged from the top of the fluidized bed reactor, and is recycled after being pressurized by the circulating gas compressor and cooled by the circulating gas cooler. The circulating gas fluidizes the polyethylene powder in the fluidized bed reactor and removes the reaction heat through the circulating gas cooler. When the polymerization reaction in the fluidized bed reactor reaches a certain extent, the bed material level and / or weight reaches the set value, the discharge system is turned on, and the polyethylene solid in the fluidized bed reactor is discharged from the discharge port on the side wall of the reactor, and then transported to the product degassing bin by nitrogen or exhaust gas recovery gas. The nitrogen introduced from the lower part of the degassing bin carries the hydrocarbon components in the resin powder and is blown out from the top of the degassing bin into the exhaust gas recovery system to recover liquid materials such as comonomers and induced condensing agents. The liquid materials are pumped back to the fluidized bed reactor, and the non-condensable gas is sent back to the discharge system as a conveying gas, or partially discharged to the flare due to pressure control requirements.

[0004] At present, most industrial fluidized bed polymerization reactors adopt the discharge method described in Chinese patent ZL200780037815.5, which consists of two or more discharge systems, which can discharge independently or in parallel. Each discharge system consists of a sedimentation container and a transfer container, a discharge pipeline and a control valve. The discharge port is mostly set at 0.2 to 0.5 meters above the distribution plate. During the discharge process, the polyethylene particles from the fluidized bed reactor entrain a large amount of raw gas that has just entered the fluidized bed reactor and has not yet participated in the polymerization reaction, as well as comonomers and condensing agents adsorbed and dissolved in the polyethylene particles, resulting in a series of problems such as loss of raw materials, increased load of subsequent degassing bins and exhaust gas recovery systems, and increased energy consumption. Specifically, because the pore volume inside and around the particles is filled with high-pressure gas mixtures, a large amount of gas or gas / liquid mixture is lost during the discharge process. Then, the lost gas must be replenished (consuming additional raw materials) or recycled for reuse. In particular, in the condensation process, as described in Chinese patents ZL201110290787.6 and ZL200780037815.5, the condensate content of the fluidized bed polymerization reactor is as high as 10wt%, and the condensate is generally introduced from the lower part of the fluidized bed reactor, and the condensate content of the material at the lower part of the bed is higher. Therefore, if the traditional discharging process is adopted, due to the excessively high condensate content of the material, during the process of discharging the material from the discharging pipeline near the distribution plate at the lower part of the fluidized bed, the material is easy to block the discharging pipeline and the discharging rate is slow. More importantly, the discharged material brings out more condensate, which not only causes a large amount of condensate loss in the reactor, but also increases the operating load of the degassing bin.

[0005] One solution is to use parallel alternating operation (cross discharge), and to transport gas between the settling containers and transfer containers of the two discharge systems through pressure balance to reduce material loss and energy consumption caused by discharge. However, even if parallel alternating operation is used, the operating pressure of the transfer tank is still high, and the material loss during the discharge process is still large.

[0006] Chinese patent ZL201410645418.8 moves the discharge port from the bottom of the fluidized bed reactor to the middle and upper part, avoiding the high liquid content area above the distribution plate, greatly reducing the amount of liquid entrainment during the discharge process; an ejector is set above the sedimentation container, and the gas in the sedimentation container is sucked through a pipeline connected to the sedimentation container to form a negative pressure inside the sedimentation container, so that the material in the fluidized bed reactor flows into the sedimentation container under the pressure difference. At the same time, the discharge port and pipeline near the distribution plate at the bottom of the fluidized bed reactor are retained for discharging agglomerates in the reactor in an emergency. Compared with the traditional discharge process, it can significantly reduce the loss of raw gas and energy loss.

[0007] Chinese patent ZL201510662171.5 solves the problem of liquid entrainment in discharge by setting up three layers of discharge ports, wherein the upper layer discharge port is located at 80% to 90% of the material surface height during normal operation of the gas phase fluidized bed reactor, the middle layer discharge port is located at 40% to 60%, and the lower layer discharge port is located 0.2 to 0.5 m above the distribution plate. Two-stage flash evaporation is used to replace the original cross-discharge mode. The polymer product discharged from the discharge port of the fluidized bed reactor enters the primary flash tank for flash evaporation, and enters the secondary flash tank for secondary flash evaporation under the action of gravity and pressure difference. The gas evaporated from the top of the primary and secondary flash tanks enters the circulating gas loop after filtration and pressurization, and part of the non-condensable gas is discharged to the recovery system. This method sets up three layers of discharge ports, each flash tank is equipped with two filters and two buffer tanks, and each set of discharge system is discharged at high frequency and pulsed to form a continuous and stable discharge flow. The process flow is relatively complex and the operation is difficult.

[0008] In summary, the prior art mostly adopts a discharge mode of two-stage containers operating in series, which has a relatively complicated process and low discharge efficiency. Summary of the invention

[0009] In view of this, the embodiments of the present disclosure provide a discharge system and method for a fluidized bed reactor to solve the technical problems in the prior art of using a discharge mode of two-stage containers in series operation, which has a relatively complicated process and low discharge efficiency.

[0010] In a first aspect of an embodiment of the present disclosure, a fluidized bed reactor discharge system is provided, comprising a discharge tank, a fluidized bed reactor, a buffer tank and a gas compression 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 provided with a control valve A for controlling the flow rate, and the gas balance line is provided with a control valve B for controlling the flow rate, wherein 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, and the exhaust line is provided with a control valve C for controlling the flow rate, and the exhaust line is used to transmit the exhaust gas of 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 provided with a control valve D for controlling the flow rate. The gas delivery pipe is used to introduce the gas input from the gas supply source into the discharge tank, and to transfer the solid in the discharge tank downward under the action of the gas pressure.

[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 provided with a control valve E for controlling 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 pipeline is connected between the buffer tank and the gas compression cooling system, and the buffer exhaust pipeline is used to transmit the uncondensed gas in the buffer tank to the gas compression cooling system.

[0016] In some embodiments, an air charging line is connected between the discharge tank and the gas compression cooling system. The air charging line is provided with a control valve F for controlling the flow rate. The air charging line is used to transfer the gas separated by the gas compression 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 then output to the fluidized bed reactor.

[0018] In some embodiments, the gas compression and cooling system outputs a processed first recycled gas, and the first recycled gas is output to a preset flare, a recovery system or the fluidized bed reactor.

[0019] In some embodiments, the gas compression cooling system outputs a processed first recovered liquid, and the first recovered liquid is output to a preset storage tank, a recovery system or the 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, an exhaust gas heat exchanger or at least two exhaust gas heat exchangers are provided between the discharge tank and the buffer tank;

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

[0023] When at least two exhaust gas heat exchangers are provided, the exhaust gas heat exchangers are divided into at least a primary heat exchanger and other levels of heat exchangers, wherein the cooling medium of the primary heat exchanger is cooling water, and the medium of the other levels of heat exchangers is one of refrigerated brine and liquid propylene.

[0024] In some embodiments, the fluidized bed reactor discharge system further comprises a circulating gas compressor and a circulating gas cooler, wherein:

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

[0026] In some embodiments, the first recycled gas is output to a pipeline between the recycle gas compressor and the recycle 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 also included, and the cryogenic recovery system is used to separate the first recycled gas to obtain a second recycled gas and a second recycled liquid.

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

[0030] In some embodiments, the second recycled gas is sent to the fluidized bed reactor after heat exchange with the exhaust gas from the discharge tank.

[0031] In some embodiments, the second recovered liquid is output to a preset storage tank, a recovery system, or the 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 also connected between the gas compression cooling system and the buffer tank, and the gas recovery pipeline is used to output part 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, it also includes a first gas purge pipeline connected to the discharge pipeline, and a second gas purge pipeline connected to the gas balance line, wherein the first purge pipeline is provided with a control valve G for controlling the flow, and the second purge pipeline is provided with a control valve H for controlling the flow, and the first / second gas purge pipelines are used to prevent pipeline blockage.

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

[0036] In some embodiments, 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 fluidized bed reactor, buffer tank, and gas compression cooling system are all mirror-imaged.

[0037] In some embodiments, a material level detection instrument, a temperature detection instrument and a pressure detection instrument are provided in the discharge tank.

[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 pipeline and transmit the pressurized gas to the cooler;

[0040] The cooler is used to cool the pressurized gas and transmit 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 a gas phase and the first recovered liquid in a liquid phase.

[0042] In some embodiments, the cryogenic recovery system includes at least one multi-stream heat exchanger, at least one gas-liquid separation tank, at least one gas expander and a 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 air inlet channel, wherein the gas cooling channel is used to transmit low-temperature gas to cool the multi-stream heat exchanger, the liquid cooling channel is used to transmit low-temperature liquid to cool the multi-stream heat exchanger, and the air inlet channel is used to transmit the first recycled gas, and the first recycled gas transmitted is cooled under the action of the cooling channel, and the cooled first recycled gas is transmitted to the gas-liquid separation tank;

[0044] The gas-liquid separation tank is used to separate the first recycled gas after cooling to obtain the first recycled gas in gas phase and the first recycled gas in liquid phase; transmit the first recycled gas in gas phase to the gas expander; and transmit the first recycled gas in liquid phase to the liquid pressure reducing valve;

[0045] The gas expander is used to expand and cool the first gas-phase recycled gas to obtain the low-pressure and low-temperature gas-phase first recycled gas, transmit the low-pressure and low-temperature gas-phase first recycled gas to the gas cooling channel of the multi-stream heat exchanger for cold recovery treatment to obtain the second recycled gas, and output the second recycled gas;

[0046] The liquid pressure reducing valve is used to perform throttling expansion treatment on the first liquid phase recovered gas transmitted in to obtain the cooled liquid phase first recovered gas, transmit the cooled liquid phase first recovered gas to the liquid cooling channel of the multi-stream heat exchanger for cold recovery treatment to obtain the second recovered liquid, and output the second recovered liquid.

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

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

[0049] Confirm that the 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 and the materials in the discharge tank reach equilibrium, control valves A and B are closed, and control valve C is opened to allow the discharge tank to exhaust gas into the buffer tank;

[0052] When the pressure in the discharge tank is reduced to a preset first pressure threshold, the control valve C is closed, and the control valves D and E are opened, and the solid in the discharge tank is discharged to a preset downstream device through the input gas;

[0053] When the solid in the discharge tank is discharged, the control valves D and E are closed, and the control valve F is opened, and the gas in the gas compression cooling system is used to inflate the discharge tank, so that the pressure in the discharge tank is increased;

[0054] When the pressure in 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 steps include:

[0056] Confirming that the pressure in the discharge tank is within a preset first pressure range;

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

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

[0059] The gas compression cooling system is turned on to allow the gas between the buffer tank and the gas compression cooling system to perform self-circulation.

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

[0061] In some embodiments, the first pressure threshold is no greater than 1 MPag, 0.5 MPag, 0.1 MPag or 0.01 MPag;

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

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

[0064] Preferably, the difference between the pressure in the fluidized bed reactor and the pressure in the discharge tank is not greater than 1.0 MPa.

[0065] According to a third aspect of the embodiments of the present disclosure, another method for discharging solids from a fluidized bed reactor is provided, comprising:

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

[0067] Open the control valves A and B, and close the control valves G and H, so that the fluidized bed reactor transfers materials to the discharge tank;

[0068] When the fluidized bed reactor reaches equilibrium with the materials in the discharge tank, the control valves A and B are closed, and the control valves G, H and C are opened to exhaust the gas from the discharge tank to the buffer tank;

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

[0070] When the solid in the discharge tank is discharged, the control valves D and E are closed, and the control valve F is opened, and the gas in the gas compression cooling system is used to inflate the discharge tank, so that the pressure in the discharge tank is increased;

[0071] When the pressure in 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 liquid separator is further provided between the exhaust gas heat exchanger and the gas compression cooling system. The exhaust gas liquid separator is used to perform a flash evaporation operation and gas-liquid separation on the cooling gas output by the exhaust gas heat exchanger, output the separated gas phase gas to the compression cooling system, and pressurize the separated liquid third recovered liquid and output it to the fluidized bed reactor.

[0073] Compared with the prior art, the embodiments of the present disclosure have at least the following beneficial effects: on the one hand, by combining the sedimentation container and the transfer container into one and providing a multifunctional discharge tank, the discharge process is greatly simplified, thereby improving the discharge efficiency and reducing the probability of failure. On the other hand, the exhaust gas from the discharge tank is pressurized by compression condensation and then all is returned to the fluidized bed reactor for recycling, thereby reducing material loss and improving energy utilization.

[0074] Beneficial Effects

[0075] Compared with the prior art, the embodiments of the present disclosure have at least the following beneficial effects: on the one hand, by combining the sedimentation container and the transfer container into one and providing a multifunctional discharge tank, the discharge process is greatly simplified, thereby improving the discharge efficiency and reducing the probability of failure. On the other hand, the exhaust gas from the discharge tank is pressurized by compression condensation and then all is returned to the fluidized bed reactor for recycling, thereby reducing material loss and improving energy utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0077] Figure 1 It is a schematic diagram of a first fluidized bed reactor discharge system provided in an embodiment of the present disclosure;

[0078] Figure 2 It is a schematic diagram of a second fluidized bed reactor discharge system provided in an embodiment of the present disclosure;

[0079] Figure 3 It is a schematic diagram of a third fluidized bed reactor discharge system provided in an embodiment of the present disclosure;

[0080] Figure 4 It is a schematic diagram of a fourth fluidized bed reactor discharge system provided in an embodiment of the present disclosure;

[0081] Figure 5 It is a schematic diagram of a fifth fluidized bed reactor discharge system provided in an embodiment of the present disclosure;

[0082] Figure 6 It is a schematic diagram of a sixth fluidized bed reactor discharge system provided in an embodiment of the present disclosure;

[0083] Figure 7 is a schematic diagram of a seventh fluidized bed reactor discharge system provided in an embodiment of the present disclosure;

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

[0085] Fig. 9 is a schematic diagram of a cryogenic recovery system in a fluidized bed reactor discharge system provided in an embodiment of the present disclosure;

[0086] Fig.10 is a schematic flow diagram of a method for discharging solids from a fluidized bed reactor provided in an embodiment of the present disclosure;

[0087] Fig.11 It is a schematic flow chart of another method for discharging solids from a fluidized bed reactor provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0088] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure.

[0089] It should also be noted that, for ease of description, only the parts related to the present disclosure are shown in the drawings. In the absence of conflict, the embodiments and features in the embodiments of the present disclosure can be combined with each other.

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

[0091] It should be noted that the modifications of "one" and "plurality" mentioned in the present disclosure are illustrative rather than restrictive, and those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

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

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

[0094] The following combination Figure 1-7 The discharge system of the fluidized bed reactor provided by the present invention is described in detail.

[0095] like Figure 1 In some of the embodiments shown, the embodiments of the present disclosure show a fluidized bed reactor discharge system, including a discharge tank, a fluidized bed reactor, a buffer tank and a gas compression cooling system, wherein:

[0096] A discharge pipeline and a gas balance line are connected between the discharge tank and the fluidized bed reactor, the discharge pipeline is provided with a control valve A for controlling the flow rate, and the gas balance line is provided with a control valve B for controlling the flow rate, wherein 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. When the fluidized bed reactor transfers material to the discharge tank, the material balance between the two is maintained through the gas balance line.

[0097] An exhaust line is connected between the discharge tank and the buffer tank. The exhaust line is provided with a control valve C for controlling flow. The exhaust line is used to transmit the exhaust gas of the discharge tank to the buffer tank.

[0098] An air delivery pipe is connected between the discharge tank and the gas supply source. The air delivery pipeline is provided with a control valve D for controlling the flow rate. The air delivery pipe is used to introduce the gas input from the gas supply source into the discharge tank, and transport the solid in the discharge tank downward under the action of air pressure.

[0099] A powder conveying line is connected between the lower part of the discharge tank and the preset downstream device. The powder conveying line is provided with a control valve E for controlling the flow rate. The powder conveying line is used to transfer the solids in the discharge tank downward to the downstream device. The downstream device may refer to a device for processing the solids in the discharge tank, which is a common setting in the art and is not subject to excessive restrictions.

[0100] A buffer exhaust pipeline is connected between the buffer tank and the gas compression cooling system, and the buffer exhaust pipeline is used to transmit the uncondensed gas in the buffer tank to the gas compression cooling system.

[0101] Compared with the prior art, the embodiments of the present disclosure have at least the following beneficial effects: on the one hand, by combining the sedimentation container and the transfer container into one and providing a multifunctional discharge tank, the discharge process is greatly simplified, thereby improving the discharge efficiency and reducing the probability of failure. On the other hand, the exhaust gas from the discharge tank is pressurized by compression condensation and then all is returned to the fluidized bed reactor for recycling, thereby reducing material loss and improving energy utilization.

[0102] like Figure 2 As shown, in some embodiments, an air charging line is connected between the discharge tank and the gas compression cooling system, and the air charging line is provided with a control valve F for controlling the flow rate. The air charging line is used to transfer the gas separated by the gas compression 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 preset storage tank or recovery system, or the condensate is pressurized and output to the fluidized bed reactor. The storage tank or recovery system may refer to a pre-set device for processing the condensate. It should also be noted that the condensate is pressurized and then output to the fluidized bed reactor is a more preferred treatment method.

[0104] In some embodiments, the gas compression cooling system outputs a processed first recycled gas, and the first recycled gas is output to a preset flare, a recovery system or the fluidized bed reactor. The first recycled gas may refer to the gas output after being processed by the gas compression cooling system. The flare may refer to a pre-set device for processing the first recycled gas. Outputting to a fluidized bed reactor is a more optimal treatment method.

[0105] In some embodiments, the gas compression cooling system outputs the first recovered liquid after treatment, and the first recovered liquid is output to a preset storage tank, a recovery system or the buffer tank, or the first recovered liquid is pressurized and output to the fluidized bed reactor. The first recovered liquid may refer to the liquid output after treatment by the gas compression cooling system. It is a more optimal treatment method to output the first recovered liquid to the fluidized bed reactor after pressurization.

[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. The gas filter is a common device in the art and will not be described in detail here.

[0107] like Figure 4Or as shown in Figure 5, in some embodiments, an exhaust gas heat exchanger or at least two exhaust gas heat exchangers are arranged between the discharge tank and the buffer tank; when one exhaust gas heat exchanger is arranged, the cooling medium of the exhaust gas heat exchanger is cooling water; when at least two exhaust gas heat exchangers are arranged, the exhaust gas heat exchanger is at least divided into a primary heat exchanger and other levels of heat exchangers, wherein the cooling medium of the primary heat exchanger is cooling water, and the medium of the other levels of heat exchangers is one of frozen brine and liquid propylene. Arranging 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 liquid separator is further provided between the exhaust gas heat exchanger and the gas compression cooling system, and the exhaust gas liquid separator is used to perform a flash evaporation operation on the cooling gas output by the exhaust gas heat exchanger and to perform gas-liquid separation, and to output the separated gas phase gas to the compression cooling system, and to pressurize the separated liquid third recovered liquid and output it to the fluidized bed reactor.

[0109] It should be pointed out that when an exhaust gas heat exchanger and an exhaust liquid separator are set up, there is no need to set up a cryogenic recovery system. Conversely, when a cryogenic recovery system is set up, there is no need to set up an exhaust gas heat exchanger and an exhaust liquid separator. Of course, the exhaust gas heat exchanger and the exhaust liquid separator are not contradictory to the cryogenic recovery system and can coexist; however, the exhaust liquid separator and the cryogenic recovery system have some overlapping functions, so based on the consideration of reducing system complexity, it is not recommended to set up the two at the same time.

[0110] In some embodiments, the fluidized bed reactor discharge system further comprises a circulating gas compressor and a circulating gas cooler, wherein the top outlet of the fluidized bed reactor is connected to the air inlet of the circulating gas compressor, the air outlet of the circulating gas compressor is connected to the air inlet of the circulating gas cooler, and the air 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 recycled gas is output to a pipeline between the recycle gas compressor and the recycle gas cooler.

[0112] like Figure 4 As shown, in some embodiments, 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.

[0113] like Figure 6As shown, in some embodiments, a cryogenic recovery system is further included, and the cryogenic recovery system is used to separate 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 after being processed by the cryogenic recovery system. The second recovered liquid may refer to the liquid output after being processed by the cryogenic recovery system.

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

[0115] In some embodiments, the second recycled gas is heat exchanged with the exhaust gas from the discharge tank and then sent to the fluidized bed reactor. It should be noted that the second recycled gas and the exhaust gas from the discharge tank can be mixed through a pipeline or through a device or passage provided on the equipment body, and no further restrictions are made here.

[0116] In some embodiments, the second recovered liquid is output to a preset storage tank, a recovery system, or the buffer tank; or, the second recovered liquid is pressurized and then output to the fluidized bed reactor. It is a more optimal treatment method for the second recovered liquid to be pressurized and then output to the fluidized bed reactor.

[0117] In some embodiments, a gas recovery pipeline is further connected between the gas compression cooling system and the buffer tank, and the gas recovery pipeline is used to output part of the gas obtained after being processed by the gas compression cooling system to the buffer tank, so as to form a gas cycle between the buffer tank and the gas compression cooling system. In order to ensure the long-term continuous and stable operation of the system, a gas recovery pipeline is set to form a gas cycle, which can ensure a minimum reflux flow rate and prevent the gas compression cooling system from stopping operation due to lack of gas source, thereby greatly improving the stability of the fluidized bed reactor discharge system in the present disclosure during operation.

[0118] like Figure 3 As shown, in some embodiments, it also includes a first gas purge pipeline connected to the discharge pipeline, and a second gas purge pipeline connected to the gas balance line, wherein the first purge pipeline is provided with a control valve G for controlling the flow, and the second purge pipeline is provided with a control valve H for controlling the flow, and the first / second gas purge pipeline is used to prevent pipeline blockage. Since when valves A and B are closed, the material of the fluidized bed reactor will be transmitted into the pipeline, resulting in blockage of the pipeline line between the fluidized bed reactor and valves A / B, it is necessary to set the first / second gas purge pipeline to blow in gas to prevent blockage.

[0119] In some embodiments, the connection port between the first gas purge pipeline and the discharge pipeline is located between the fluidized bed reactor and control valve A; the connection port between the second gas purge pipeline 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 arranged in parallel with the discharge tank, and the parallel discharge tank has the same structure as the discharge tank, and the connection mode, connecting pipes, and control valves between the fluidized bed reactor, the buffer tank, and the gas compression cooling system are all mirror-imaged. The parallel discharge tank may refer to a discharge tank with the same structure as the discharge tank (i.e., the same structure and the same interface). The mirror image setting may refer to the connection mode between the parallel discharge tank and each other component being the same as the discharge tank, such as Figure 7 The parallel discharge tanks have the same setting mode, connection relationship, connecting pipes, control valves (A', B', C', D', E', F', G', H'), etc. as the discharge tanks. There is no need to set a gas balance line between multiple discharge tanks, which greatly simplifies the discharge process, reduces the use of control valves, and reduces the probability of failure. In addition, two or more sets of discharge tank discharge systems can be operated independently without affecting each other. They can be operated simultaneously or alternately. They are flexible to operate and have strong adaptability, which can meet the diverse needs of high-load production. Especially when emergency discharge is required under accident conditions, when they can be operated simultaneously, the discharge speed can be increased.

[0121] In some embodiments, the discharge tank is provided with a material level detection instrument, a temperature detection instrument and a pressure detection instrument, which 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, 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 transmit 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 a gas phase and the first recovered liquid in a liquid phase. It should be pointed out 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 adopt a two-stage compression arrangement, that is, it includes two-stage gas compressors, two coolers, and two gas-liquid separators. The liquid from the gas-liquid separator between the two-stage gas compressors is sent to a buffer tank or is pressurized by a pump and sent to a 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 is not less than 0.1 MPa and not less than 0.2 MPa.

[0125] like Fig. 9 As shown, in some embodiments, the cryogenic recovery system includes at least one multi-stream heat exchanger, at least one gas-liquid separation tank, at least one gas expander and a 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 air inlet channel, wherein the gas cooling channel is used to transmit low-temperature gas to cool the multi-stream heat exchanger, the liquid cooling channel is used to transmit low-temperature liquid to cool the multi-stream heat exchanger, and the air inlet channel is used to transmit the first recycled gas, and the first recycled gas transmitted is cooled under the action of the cooling channel, and the cooled first recycled gas is transmitted to the gas-liquid separation tank;

[0127] The gas-liquid separation tank is used to separate the first recycled gas after cooling to obtain the first recycled gas in gas phase and the first recycled gas in liquid phase; transmit the first recycled gas in gas phase to the gas expander; and transmit the first recycled gas in liquid phase to the liquid pressure reducing valve;

[0128] The gas expander is used to expand and cool the first gas-phase recycled gas to obtain the low-pressure and low-temperature gas-phase first recycled gas, transmit the low-pressure and low-temperature gas-phase first recycled gas to the gas cooling channel of the multi-stream heat exchanger for cold recovery treatment to obtain the second recycled gas, and output the second recycled gas;

[0129] The liquid pressure reducing valve is used to perform throttling expansion treatment on the first liquid phase recovered gas transmitted in to obtain the cooled liquid phase first recovered gas, transmit the cooled liquid phase first recovered gas to the liquid cooling channel of the multi-stream heat exchanger for cold recovery treatment to obtain the second recovered liquid, and output the second recovered liquid.

[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 the multi-stream heat exchanger, and after its temperature is reduced to -90 to -130°C, it enters the gas-liquid separator; the gas phase at the top of the gas-liquid separator enters the multi-stream heat exchanger for heat exchange, and then enters the gas expander (such as a turbine expander) for expansion and refrigeration to obtain a low-pressure and low-temperature gas, and then enters the multi-stream heat exchanger to further recover the cold, and then is 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 after entering the multi-stream heat exchanger to recover the cold, it is sent out as the second recovered liquid.

[0131] The exhaust gas from the discharge tank is pressurized by compression condensation and / or cryogenic separation technology and then all of it is sent back to the fluidized bed reactor for recycling. At the same time, the process flow is optimized by a system integration method to reduce material loss and improve energy utilization. More importantly, a large amount of clean liquid can be obtained and sent back to the fluidized bed reactor to improve product quality. In addition, the present disclosure also helps to improve the regulatory effect of the new process technology proposed in Chinese patents ZL201410748891.9, ZL201610404207.4, ZL202010801584.8, etc. on product quality.

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

[0133] like Fig.10 As shown, the embodiment of the present disclosure also provides a method 100 for discharging solids from a fluidized bed reactor, the method being applied to the aforementioned (such as Figure 2 ) shown in the fluidized bed reactor discharge system, the method comprising:

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

[0135] Step 102, opening 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 materials in the discharge tank reach equilibrium, control valves A and B are closed, and control valve C is opened to allow the discharge tank to exhaust gas into the buffer tank.

[0137] Step 104, when the pressure in the discharge tank is reduced to a preset first pressure threshold, the control valve C is closed, the control valves D and E are opened, and the solids in the discharge tank are discharged to a preset downstream device through the input gas. The first pressure threshold may refer to a preset limit value for limiting the pressure in the discharge tank.

[0138] Step 105, when the solid in the discharge tank is discharged, close the control valves D and E, open the control valve F, and inflate the discharge tank with the gas in the gas compression cooling system to increase the pressure in the discharge tank.

[0139] Step 106: When the pressure in 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 for limiting the pressure in the discharge tank.

[0140] In some embodiments, before opening the control valves A and B, the steps include: confirming that the pressure in the discharge tank is within a preset first pressure range; confirming that the difference between the pressure in the fluidized bed reactor and the pressure in the discharge tank is within a preset second pressure range. The first / second pressure range may refer to a preset limit range for limiting the pressure in the discharge tank and the difference between the pressure in the fluidized bed reactor and the pressure in the discharge tank.

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

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

[0143] In some embodiments, the first pressure threshold is no more than 1MPag, 0.5MPag, 0.1MPag or 0.01MPag; preferably, the first pressure threshold is no more than 0.01MPag. By setting the discharge tank to operate under a slightly positive or negative pressure of less than 0.01MPag after exhaust, the low-molecular compounds adsorbed in the polymer can be flashed out to the greatest extent, while reducing the amount of gas entering the post-system to a lower level, and then pressurized and sent back to the fluidized bed reactor. On the one hand, the circulation path of this part of low-molecular compounds in the system is reduced, the introduction of impurities is avoided, and the raw material consumption is reduced; on the other hand, the devolatilization and recovery load of the post-system is reduced, which helps to improve product quality.

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

[0145] like Fig.11 As shown, the embodiment of the present disclosure also provides a method 200 for discharging solids from a fluidized bed reactor, the method being applied to the aforementioned (such as Figure 3 ) shown in the fluidized bed reactor discharge system, the method comprising:

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

[0147] Step 202, opening the control valves A and B, and closing the control valves G and H, so that the fluidized bed reactor transfers materials to the discharge tank.

[0148] Step 203, when the fluidized bed reactor and the materials in the discharge tank reach equilibrium, the control valves A and B are closed, and the control valves G, H and C are opened to allow the discharge tank to exhaust gas to the buffer tank.

[0149] Step 204, when the pressure in the discharge tank is reduced to a preset first pressure threshold, the control valve C is closed, and the control valves D and E are opened to deliver gas to the discharge tank so that the solids in the discharge tank are discharged to a preset downstream device.

[0150] Step 205, when the solid in the discharge tank is discharged, close the control valves D and E, open the control valve F, and inflate the discharge tank with the gas in the gas compression cooling system to increase the pressure in the discharge tank.

[0151] Step 206: When the pressure in the discharge tank rises to a 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, 204-206 and the technical effects brought about can be referred to Figure 2 The corresponding steps 101, 104-206 in the embodiments are not described here in detail. The difference between step 200 and step 100 is that a first gas purge pipeline and a second gas purge pipeline are added, and the detailed description thereof is as mentioned above.

[0153] The present disclosure is further explained below by some comparative examples:

[0154] Taking a gas phase fluidized bed process device with an annual output of 120,000 tons of linear low-density polyethylene (LLDPE) as an example, the conventional single-peak LLDPE film product is produced, and the discharge is about 25 times per hour, the fluidized bed inlet temperature is about 49°C, and the discharge temperature is about 60-65°C. The discharge system is arranged on the single gas phase fluidized bed reaction system, and the single gas phase fluidized bed reaction system includes a circulating gas loop composed of a gas phase fluidized bed reactor, a circulating gas compressor, and a circulating gas cooler connected in sequence, and also includes a catalyst feeding system and various raw material feeding systems. From the lower part of the fluidized bed reactor to the upper part of the reactor, the concentration of the raw material gas decreases in sequence, a part of the raw material gas undergoes polymerization reaction in the lower part of the reactor, and the unreacted and fully polymerized particles continue to undergo polymerization reaction in the upper part of the gas phase fluidized bed reactor with the rising raw material gas flow, and part of the raw material gas that has not reacted is discharged from the top of the fluidized bed reactor and recycled together with the raw material gas to form a circulating gas loop, and the discharge port is arranged on the gas phase fluidized bed reactor. As described in Chinese patent ZL200780037815.5, the discharge system includes a sedimentation container and a transfer container, the feed port of the sedimentation container is connected to the discharge port of the single gas phase fluidized bed reactor, the bottom of the sedimentation container is connected to the feed port of the transfer container, the bottom of the transfer container is connected to the downstream degassing bin, and the top of the sedimentation container and the transfer container are both connected to the single gas phase fluidized bed reactor. The traditional fluidized bed reactor is a discharge port at a position 0.3m above the fluidized bed distribution plate at the bottom of the fluidized bed. When the polymerization reaction proceeds to a certain extent, the discharge system begins to discharge. However, since the fluidized bed reactor is bottom-fed, a lot of materials will be entrained without participating in the reaction during the process of discharging the powder from the bottom. The working pressure of the gas phase fluidized bed reactor is about 2.0-2.4MPag, the operating pressure of the sedimentation container is about 1.1-1.2MPag, and the operating pressure of the transfer container is about 0.5-0.6MPag. The gas content entrained in each discharge is about 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 device with an annual output of 120,000 tons of linear low-density polyethylene (LLDPE) as an example, to produce conventional LLDPE film products, the bed temperature of the upper part of the fluidized bed reactor is about 88°C, the pressure is about 2.35MPag, the condensate is introduced into the lower part of the fluidized bed reactor, the condensate content is about 5wt%, the discharge is about 25 times per hour, the fluidized bed inlet temperature is about 49°C, and the discharge temperature is about 60-65°C. The discharge system is arranged on the side wall of the gas-phase fluidized bed reactor, and the gas-phase fluidized bed reaction system includes a circulating gas loop composed of a gas-phase fluidized bed reactor, a circulating gas compressor, and a circulating gas cooler connected in sequence, and also includes a catalyst feeding system and various raw material feeding systems. The concentration of the raw gas decreases from the lower part to the upper part of the fluidized bed reactor. A part of the raw gas undergoes polymerization reaction in the lower part of the reactor, and the unreacted and completely polymerized particles continue to undergo polymerization reaction in the upper part of the gas phase fluidized bed reactor along with the rising raw gas flow. Some of the unreacted raw gas is discharged from the top of the fluidized bed reactor and recycled together with the raw gas to form a circulating gas loop. The discharge port is set on the gas phase fluidized bed reactor.

[0157] like Figure 5As shown, a discharge system of a fluidized bed reactor comprises: 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 cooling system, a pipeline connecting the buffer tank and the gas compression cooling system; a delivery gas pipeline connecting the discharge tank, and a control valve D installed on the delivery gas pipeline; a gas supply line connecting the discharge tank and the lower The powder conveying line of the swimming device and the control valve E installed on the powder conveying line; the charging line connecting the gas compression cooling system and the discharge tank and the control valve F installed on the charging line; the first gas purge pipeline connected to the discharge pipeline and the control valve G arranged on the first purge pipeline, the second gas purge pipeline connected to the gas balance line and the control valve H arranged on the second purge pipeline, the inlet of the first gas purge pipeline is located between the fluidized bed reactor and the control valve A; the inlet of the second gas purge pipeline is located between the fluidized bed reactor and the control valve B. The top outlet of the fluidized bed reactor is connected to the circulating gas compressor, the circulating gas compressor is connected to the circulating gas cooler, and the circulating gas cooler is connected to the bottom of the fluidized bed reactor. A gas filter is provided on the top of the discharge tank, the exhaust line is connected to the gas filter, and the charging line is also connected to the gas filter. An exhaust gas heat exchanger is arranged between the discharge tank and the buffer tank. The gas compression cooling system adopts a two-stage compression process, which consists of a two-stage gas compressor, two coolers, and two gas-liquid separators. The liquid from the gas-liquid separator between the two-stage gas compressor is sent to the buffer tank. The outlet pressure of the gas compressor is higher than the operating pressure of the fluidized bed reactor, and the set value is 3.0 MPag.

[0158] The discharge tank is operated intermittently, and the buffer tank and the gas compression cooling system are operated continuously. Before performing the discharge operation, the gas compression cooling system is first turned on to allow the gas to self-circulate between the buffer tank and the gas compression cooling system. The steps of discharging solids from the fluidized bed reactor include:

[0159] Step 1: Confirm that the 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 requirements, 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 reaches the set value, open control valves A and B, close control valves G and H, and discharge 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 rate of each component in the discharge flow is: LLDPE powder 15000kg / h, discharge gas 1293kg / h. The main components of the discharge gas are ethylene, hydrogen, nitrogen, comonomers butene and hexene, refrigerant isopentane, etc., among which ethylene, butene and hexene are unreacted monomers, and there is no liquid in the discharge flow. When the powder is no longer transferred from the fluidized bed reactor to the discharge tank, a balance is formed between the two, and the discharge is completed. At this time, the pressure of the discharge tank is about 2.35MPag. The solid material discharged in the discharge tank in one discharge process accounts for 70%-90% of the volume. The discharge time is generally less than 60s.

[0161] Step 3: After the discharge is completed, close the control valves A and B, open the control valves G, H and C, exhaust gas from the discharge tank to the buffer tank, and reduce the pressure of the discharge tank to the specified value P3. The set value of P3 is 0.15MPag. The exhaust gas from the discharge tank is cooled to 40°C after heat exchange with cooling water in the exhaust gas heat exchanger, and then enters the exhaust gas separator to reduce the pressure to 0.2MPag and perform gas-liquid separation. The liquid is pressurized by the 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 head of the fluidized bed reactor. The gas enters the buffer tank to reduce the pressure to 0.15MPag. The uncondensed gas is discharged from the top of the buffer tank and is sucked into the first-stage compressor to increase the pressure to 0.8MPag. After being cooled to 40°C by the first-stage cooler, it enters the first-stage gas-liquid separation tank. The liquid from the primary gas-liquid separator tank is directly sent to the buffer tank, and the condensate from the buffer tank is pumped and sent back to the fluidized bed reactor. The return port is located in the pipeline between the circulating gas cooler and the bottom head of the fluidized bed reactor. The gas from the primary gas-liquid separator tank enters the secondary compressor and is pressurized to 3.0MPag. After being cooled to 40°C by the secondary cooler, it enters the secondary gas-liquid separator tank. A part of the gas at the top of the secondary gas-liquid separator tank returns to the buffer tank to form a gas cycle to ensure the continuous and stable operation of the compressor. The circulation flow rate is not less than 700kg / hr; the other part is controlled by the pressure of the secondary gas-liquid separator tank and sent to the fluidized bed reactor as the first recovered gas from the gas compression cooling system. Its return port is located in the pipeline between the circulating gas compressor and the circulating gas cooler. The liquid from the bottom of the secondary gas-liquid separator tank is the first recovered liquid of the gas compression cooling system and is pumped back to the fluidized bed reactor. Its return port is located at the side wall about 3 meters above the distribution plate of the fluidized bed reactor.

[0162] Step 4: After the exhaust is completed, close the control valve C, open the control valves D and E, and use the conveying gas to transport the solids in the discharge tank to the downstream device; nitrogen is used as the conveying gas.

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

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

[0165] After adopting the above operation steps, the gas content in each discharge is about 0.05-0.06 kg / kg PE (the main components are ethylene, hydrogen, nitrogen, comonomer 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, and no exhaust gas heat exchanger and exhaust gas liquid separator are set in the middle. A deep cold recovery system is set after the gas compression cooling system. The first recovered gas from the gas compression cooling system enters the multi-stream heat exchanger, and after its temperature is reduced to -110°C, it enters the gas-liquid separator; the gas phase at the top of the gas-liquid separator enters the multi-stream heat exchanger for heat exchange, enters the turbine expander for expansion and refrigeration, and obtains low-pressure and low-temperature gas, and then enters the multi-stream heat exchanger for further recovery of cold, and is sent to the buffer tank as the second recovered gas; the liquid phase at the bottom of the gas-liquid separator is throttled and expanded by the pressure reducing valve to reduce its temperature, and after entering the multi-stream heat exchanger to recover cold, it is also sent to the buffer tank as the second recovered liquid, so that the buffer tank temperature is reduced to about 15°C. By optimizing the process flow by using the system integration method, the energy utilization rate is improved while reducing material loss. In addition, the set value of the discharge tank pressure P3 is 0.12MPag. After adopting the above operation steps, the gas content in each discharge is about 0.045-0.050 kg / kg PE (the main components are ethylene, hydrogen, nitrogen, comonomers and refrigerant, etc.).

[0168] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to 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 words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

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 cooling system, wherein: A discharge pipeline and a gas balance line are connected between the discharge tank and the fluidized bed reactor, the discharge pipeline is provided with a control valve A for controlling the flow rate, and the gas balance line is provided with a control valve B for controlling the flow rate, wherein 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 balance of the material between the discharge tank and the fluidized bed reactor; An exhaust line is connected between the discharge tank and the buffer tank, and the exhaust line is provided with a control valve C for controlling the flow rate, and the exhaust line is used to transmit the exhaust gas of the discharge tank to the buffer tank; A gas delivery pipe is connected between the discharge tank and the gas supply source. The gas delivery pipeline is provided with a control valve D for controlling the flow rate. The gas delivery pipe is used to introduce the gas input from the gas supply source into the discharge tank, and to transfer the solid in the discharge tank downward under the action of the gas pressure. A powder conveying line is connected between the lower part of the discharge tank and the preset downstream device. The powder conveying line is provided with a control valve E for controlling 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 pipeline is connected between the buffer tank and the gas compression cooling system, and the buffer exhaust pipeline is used to transmit the uncondensed gas in the buffer tank to the gas compression cooling system.

2. The fluidized bed reactor discharge system according to claim 1, characterized in that: An air charging line is connected between the discharge tank and the gas compression cooling system. The air charging line is provided with a control valve F for controlling the flow rate. The air charging line is used to transfer the gas separated by the gas compression cooling system to the discharge tank.

3. The fluidized bed reactor discharge system according to claim 1, characterized in that: The buffer tank discharges the 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 then output to the fluidized bed reactor.

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

5. The fluidized bed reactor discharge system according to claim 1, characterized in that: The gas compression cooling system outputs the processed first recovered liquid, which is output to a preset storage tank, a recovery system or the buffer tank, or the first recovered liquid is pressurized and output to the fluidized bed reactor.

6. The fluidized bed reactor discharge system according to claim 2, characterized in that: 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.

7. The fluidized bed reactor discharge system according to claim 1, characterized in that: An exhaust gas heat exchanger or at least two exhaust gas heat exchangers are arranged between the discharge tank and the buffer tank; When an 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 divided into at least a primary heat exchanger and other levels of heat exchangers, wherein the cooling medium of the primary heat exchanger is cooling water, and the medium of the other levels of heat exchangers is one of refrigerated brine and liquid propylene.

8. The fluidized bed reactor discharge system according to claim 1, characterized in that: It also includes a circulating gas compressor and a circulating gas cooler, wherein: The top outlet of the fluidized bed reactor is connected to the air inlet of the circulating gas compressor, the air outlet of the circulating gas compressor is connected to the air inlet of the circulating gas cooler, and the air outlet of the circulating gas cooler is connected to the bottom of the fluidized bed reactor.

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

10. The fluidized bed reactor discharge system according to claim 8, 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.

11. The fluidized bed reactor discharge system according to claim 1, 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.

12. The fluidized bed reactor discharge system according to claim 11, characterized in that: The second recycled gas is output to a predetermined flare, a recovery system, or the fluidized bed reactor.

13. The fluidized bed reactor discharge system according to claim 12, characterized in that: The second recovered gas is sent to the fluidized bed reactor after heat exchange with the exhaust gas from the discharge tank.

14. The fluidized bed reactor discharge system according to claim 11, characterized in that: The second recovered liquid is output to a preset storage tank, a recovery system, or the buffer tank; or, The second recovered liquid is pressurized and then output to the fluidized bed reactor.

15. The fluidized bed reactor discharge system according to claim 1, characterized in that: 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 part 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.

16. The fluidized bed reactor discharge system according to claim 2, characterized in that: It also includes a first gas purge pipeline connected to the discharge pipeline, and a second gas purge pipeline connected to the gas balance line, wherein the first purge pipeline is provided with a control valve G for controlling the flow, and the second purge pipeline is provided with a control valve H for controlling the flow, and the first / second gas purge pipelines are used to prevent pipeline blockage.

17. The fluidized bed reactor discharge system according to claim 16, characterized in that: The connecting port between the first gas purge pipeline and the discharge pipeline is located between the fluidized bed reactor and control valve A; the connecting port between the second gas purge pipeline and the gas balance line is located between the fluidized bed reactor and control valve B.

18. The fluidized bed reactor discharge system according to claims 1 to 17, 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 fluidized bed reactor, the buffer tank, and the gas compression cooling system are all mirror-imaged.

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

20. The fluidized bed reactor discharge system according to any one of claims 1 to 17, characterized in that: The gas compression cooling system comprises 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 pipeline and transmit the pressurized gas to the cooler; The cooler is used to cool the pressurized gas and transmit 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 a gas phase and the first recovered liquid in a liquid phase.

21. The fluidized bed reactor discharge system according to any one of claims 11 to 17, characterized in that: The cryogenic recovery system includes at least one multi-stream heat exchanger, at least one gas-liquid separation tank, at least one gas expander and a liquid pressure reducing valve, wherein: The multi-stream heat exchanger includes at least one gas cooling channel, at least one liquid cooling channel and at least one air inlet channel, wherein the gas cooling channel is used to transmit low-temperature gas to cool the multi-stream heat exchanger, the liquid cooling channel is used to transmit low-temperature liquid to cool the multi-stream heat exchanger, and the air inlet channel is used to transmit the first recycled gas, and the first recycled gas transmitted is cooled under the action of the cooling channel, and the cooled first recycled gas is transmitted to the gas-liquid separation tank; The gas-liquid separation tank is used to separate the first recycled gas after cooling to obtain the first recycled gas in gas phase and the first recycled gas in liquid phase; transmit the first recycled gas in gas phase to the gas expander; and transmit the first recycled gas in liquid phase to the liquid pressure reducing valve; The gas expander is used to expand and cool the first gas-phase recycled gas to obtain the low-pressure and low-temperature gas-phase first recycled gas, transmit the low-pressure and low-temperature gas-phase first recycled gas to the gas cooling channel of the multi-stream heat exchanger for cold recovery treatment to obtain the second recycled gas, and output the second recycled gas; The liquid pressure reducing valve is used to perform throttling expansion treatment on the first liquid phase recovered gas transmitted in to obtain the cooled liquid phase first recovered gas, transmit the cooled liquid phase first recovered gas to the liquid cooling channel of the multi-stream heat exchanger for cold recovery treatment to obtain the second recovered liquid, and output the second recovered liquid.

22. The fluidized bed reactor discharge system according to any one of claims 1 to 17, characterized in that: Under normal working conditions, the discharge tank operates periodically according to a preset duration, and the buffer tank and the gas compression cooling system operate continuously.

23. The fluidized bed reactor discharge system according to claim 7, characterized in that: An exhaust gas liquid separator is also provided between the exhaust gas heat exchanger and the gas compression cooling system. The exhaust gas liquid separator is used to perform a flash evaporation operation on the cooling gas output by the exhaust gas heat exchanger and to separate the gas and liquid, output the separated gas phase to the compression cooling system, and pressurize the separated liquid third recovered liquid and output it to the fluidized bed reactor.

24. A method for discharging solids from a fluidized bed reactor, characterized in that: The method is applied to the fluidized bed reactor discharge system according to claim 2, and the method comprises: Confirm that the 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 and the materials in the discharge tank reach equilibrium, control valves A and B are closed, and control valve C is opened to allow the discharge tank to exhaust gas into the buffer tank; When the pressure in the discharge tank is reduced to a preset first pressure threshold, the control valve C is closed, and the control valves D and E are opened, and the solid in the discharge tank is discharged to a preset downstream device through the input gas; When the solid in the discharge tank is discharged, the control valves D and E are closed, and the control valve F is opened, and the gas in the gas compression cooling system is used to inflate the discharge tank, so that the pressure in the discharge tank is increased; When the pressure in the discharge tank rises to a preset second pressure threshold, the control valve F is closed and the discharge process ends.

25. The method according to claim 24, characterized in that Before opening the control valves A and B, the method includes: Confirming that the pressure in the discharge tank is within a preset first pressure range; It is confirmed that the difference between the pressure in the fluidized bed reactor and the pressure in the discharge tank is within a preset second pressure range.

26. The method according to claim 24, characterized in that Before confirming that the control valves A, B, C, D, E, and F are all in a closed state, the steps include: The gas compression cooling system is turned on to allow the gas between the buffer tank and the gas compression cooling system to perform self-circulation.

27. The method for discharging solids from a fluidized bed reactor according to claim 24, characterized in that: The second pressure threshold is not less than 0.6 MPag.

28. The method according to claim 24, characterized in that The first pressure threshold is not greater than 1 MPag, 0.5 MPag, 0.1 MPag or 0.01 MPag; Preferably, the first pressure threshold is not greater than 0.01 MPag.

29. The method according to claim 25, characterized in that The difference between the pressure in the fluidized bed reactor and the pressure in the discharge tank is not greater than 1.5 MPa, 1.2 MPa or 1.0 MPa; Preferably, the difference between the pressure in the fluidized bed reactor and the pressure in the discharge tank is not greater than 1.0 MPa.

30. A method for discharging solids from a fluidized bed reactor, characterized in that: The method is applied to the fluidized bed reactor discharge system according to claim 17, and the method comprises: Confirm that the control valves A, B, C, D, E, and F are all in the closed state; Open the control valves A and B, and close the control valves G and H, so that the fluidized bed reactor transfers materials to the discharge tank; When the fluidized bed reactor reaches equilibrium with the materials in the discharge tank, the control valves A and B are closed, and the control valves G, H and C are opened to exhaust the gas from the discharge tank to the buffer tank; When the pressure in the discharge tank is reduced to a preset first pressure threshold, the control valve C is closed, and the control valves D and E are opened to deliver gas to the discharge tank so that the solids in the discharge tank are discharged to a preset downstream device; When the solid in the discharge tank is discharged, the control valves D and E are closed, and the control valve F is opened, and the gas in the gas compression cooling system is used to inflate the discharge tank, so that the pressure in the discharge tank is increased; When the pressure in 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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