Method for removing alkali liquor during shutdown of direct coal liquefaction device

Abstract

The invention discloses a method for removing alkali liquor during shutdown of a direct coal liquefaction device. A system comprises a tank area alkali liquor tank, a coal liquefaction device alkali liquor buffer tank, a reaction heating furnace, a first reactor, a second reactor, a high-temperature and high-pressure separator, an alkali liquor discharge buffer tank, a foam cyclone separator and a defoamer. By adopting an innovative idea, the alkali liquor is discharged to the alkali liquor discharge buffer tank of the coal liquefaction device for buffering, degassing and defoaming, and then is pressurized and conveyed to the alkali liquor tank of the tank area for storage through the alkali liquor conveying pump of the coal liquefaction device, so that the aim of continuous shutdown and massive alkali liquor removal of the direct coal liquefaction device is fulfilled, the shutdown time is saved for enterprises, and the production efficiency is improved. And certain economic benefits are brought.

Description

Technical Field

[0001] The invention belongs to the field of direct coal liquefaction, in particular to a method for withdrawing alkali liquid during shutdown of a direct coal liquefaction device. Background Art

[0002] my country has realized the industrial application of coal direct liquefaction technology. Since the coal was put into operation, the coal direct liquefaction device has achieved a stable, long-term, high-quality operation level after years of scientific research and technical transformation. Due to the engineering development of the second-generation coal direct liquefaction technology, the second-generation coal direct liquefaction technology process route has made corresponding adjustments to the early coal direct liquefaction project, canceling the internal circulation pumps at the bottom of the two reactors, canceling the internal circulation cups and center tubes inside the reactor, and adding a large circulation pump at the bottom of the high-temperature and high-pressure separator. The circulating material is extracted from the bottom of the high-temperature and high-pressure separator and returned to the inlet of the first reactor, forming a large circulation reaction system including the reactor-high-temperature and high-pressure separator, eliminating the vapor-liquid interface in the reactor, extending the operation cycle, and improving the economic benefits of the device.

[0003] At present, during the shutdown and alkali-removal operation of the coal liquefaction unit, since the storage tanks in the tank area are non-pressure tanks, when the reactor alkali liquid passes through the coal slurry heating furnace outlet and a large amount of alkali-removal liquid is removed, it drops to the low point of the reactor when needed to shut down the process to prevent the pressure from flowing to the tank area. The alkali-removal liquid is discharged to the tank area through the reactor instead. The alkali-removal speed is slow. At the same time, when the alkali liquid is withdrawn to the bottom of the reactor, it is easy to cross-gas, causing overpressure in the tank area storage tanks, affecting the shutdown node of the coal liquefaction unit.

[0004] Therefore, for the second-generation process technology of direct coal liquefaction, it is necessary to explore a method of optimizing the oil and alkali drainage process using the existing process to ensure that the shutdown requirements of the device meet the oil and alkali drainage requirements and meet the needs of the coal liquefaction device during shutdown. Summary of the invention

[0005] The object of the present invention is to provide a system and method for de-alkali liquid during shutdown of a coal direct liquefaction device, so as to solve the problem of de-alkali liquid during shutdown of a coal direct liquefaction device in the second generation coal direct liquefaction process technology.

[0006] In order to achieve one aspect of the above-mentioned invention object, the system for shutting down and withdrawing alkali liquid from a coal direct liquefaction device provided by the present invention adopts the following technical scheme:

[0007] A system for de-alkali liquid during shutdown of a coal direct liquefaction device, the system comprising an alkali liquid tank in a tank area, an alkali liquid buffer tank of a coal liquefaction device, a reaction heating furnace, a first reactor, a second reactor, a high temperature and high pressure separator, an alkali liquid discharge buffer tank, a foam cyclone separator and a defoamer; wherein:

[0008] The alkali liquid tank in the tank area is connected to the alkali liquid buffer tank of the coal liquefaction device through an alkali liquid delivery pump in the tank area, so as to deliver the alkali liquid in the tank area into the alkali liquid buffer tank of the coal liquefaction device;

[0009] The alkali liquid buffer tank of the coal liquefaction device is connected to the reaction heating furnace through the alkali liquid pressure pump of the coal liquefaction device, and the reaction heating furnace is connected in series with the first reactor, the second reactor and the high-temperature and high-pressure separator in sequence, so that the alkali liquid from the alkali liquid buffer tank of the coal liquefaction device is sequentially sent to the reaction heating furnace, the first reactor, the second reactor and the high-temperature and high-pressure separator for alkali washing;

[0010] The feed port of the foam cyclone separator is connected to the reaction heating furnace, the first reactor, the second reactor and the high-temperature and high-pressure separator respectively, so as to receive the alkali solution discharged from the reaction heating furnace and the first reactor, the second reactor and the high-temperature and high-pressure separator and perform foam separation;

[0011] The alkali solution discharge buffer tank is connected to the bottom outlet of the foam cyclone separator to receive the separated alkali solution;

[0012] The defoamer is used to eliminate the foam from the top outlet of the foam cyclone separator, and send the defoamed material back to the alkali solution discharge buffer tank;

[0013] The bottom of the alkali liquid discharge buffer tank is connected to the alkali liquid tank in the tank area through an alkali liquid delivery pump of a coal liquefaction device, so as to deliver the alkali liquid in the alkali liquid discharge buffer tank back to the alkali liquid tank in the tank area.

[0014] In order to achieve one aspect of the above-mentioned invention object, the system for shutting down and withdrawing alkali liquid from a coal direct liquefaction device provided by the present invention adopts the following technical scheme:

[0015] A method for shutting down a coal direct liquefaction device and removing alkali liquid, the method comprising the following steps:

[0016] S1) delivering the alkali liquid in the tank area to the alkali liquid buffer tank of the coal liquefaction device through the alkali liquid delivery pump in the tank area, and delivering it to the reaction heating furnace, the first reactor, the second reactor and the high temperature and high pressure separator in sequence through the alkali liquid pressure pump of the coal liquefaction device for alkali washing;

[0017] S2) After the alkali washing is completed, the alkali liquid delivery pump in the tank area and the alkali liquid pressure pump of the coal liquefaction device are stopped to stop the alkali liquid delivery;

[0018] S3) discharging the alkali solution in the reaction heating furnace, the first reactor, the second reactor and the high temperature and high pressure separator into the alkali solution discharge buffer tank after the foam is separated by the foam cyclone separator; at the same time, using a defoamer to eliminate the foam separated from the foam cyclone separator and sending the defoamed material to the alkali solution discharge buffer tank;

[0019] S4) After the alkali liquid is discharged, the alkali liquid in the alkali liquid discharge buffer tank is pressurized by the alkali liquid delivery pump of the coal liquefaction device and then sent to the alkali liquid tank in the tank area for storage.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] The present invention aims at the fact that the alkali liquid tank in the tank area is a non-pressure tank. The alkali liquid tank in the tank area is easily over-pressurized by using nitrogen to pressurize the alkali liquid. In addition, since the alkali liquid for alkali washing contains a surfactant, foam is easily generated in the alkali liquid tank in the tank area, resulting in a further slowdown in the speed of alkali liquid withdrawal at the end stage, affecting the shutdown node of the coal liquefaction device. The present invention adopts an innovative idea to discharge the alkali liquid into the alkali liquid discharge buffer tank of the coal liquefaction device for buffering, degassing and defoaming, and then pressurized by the alkali liquid delivery pump of the coal liquefaction device to the alkali liquid tank in the tank area for storage.

[0022] The invention achieves the purpose of a method for continuous shutdown of a coal direct liquefaction device and large-scale alkali liquid withdrawal, saves shutdown time for the enterprise, and brings certain economic benefits.

[0023] The present invention innovatively solves the problem that the alkali liquid tank in the tank area is a non-pressure tank and the alkali liquid is easily over-pressurized by using nitrogen to pressurize and transport the alkali liquid.

[0024] The present invention provides buffering, degassing and defoaming of alkali solution after alkali washing is completed, so as to prevent bubbling of alkali solution tank in tank area, which leads to further slowing down of alkali solution withdrawal speed in the final stage and affects the shutdown node of coal liquefaction device. The present invention has low investment cost, high economic benefit, small safety risk and simple operation.

[0025] The present invention has made a lot of improvements and innovations in design, production, commissioning and other aspects, and put forward a series of control indicators to ensure that the alkali solution is buffered, degassed and defoamed, and avoid the problem of overpressure of the alkali solution tank in the tank area. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic flow chart of an embodiment of a system for shutting down and withdrawing alkali liquid in a direct coal liquefaction device according to the present invention;

[0027] Attached Figure 1 Description of the mark:

[0028] 101. Alkali liquid tank in tank area; 102. Alkali liquid buffer tank in coal liquefaction unit; 103. Reaction heating furnace; 104. First reactor; 105. Second reactor; 106. High temperature and high pressure separator; 107. Alkali liquid discharge buffer tank; 108. Foam cyclone separator; 109. Defoamer;

[0029] 201, alkali liquid delivery pump in the tank area; 204, alkali liquid booster pump in the coal liquefaction unit; 202, feed pump in the coal liquefaction unit; 203, alkali liquid delivery pump in the coal liquefaction unit; 301, liquid level control valve of alkali liquid buffer tank in the coal liquefaction unit; 302, outlet flow control valve of alkali liquid booster pump in the coal liquefaction unit; 303, outlet flow control valve of alkali liquid delivery pump in the coal liquefaction unit; 304, vent control valve of alkali liquid discharge buffer tank; 305, nitrogen control valve of alkali liquid discharge buffer tank;

[0030] 401. Alkali liquid inlet valve of alkali liquid tank in tank area; 402. Alkali liquid tank extraction valve in tank area; 403. Alkali liquid water pump inlet valve in tank area; 404. Alkali liquid water pump outlet valve in tank area; 405. Alkali liquid buffer tank extraction valve of coal liquefaction unit; 406. Alkali liquid booster pump inlet valve of coal liquefaction unit; 407. Alkali liquid booster pump outlet valve of coal liquefaction unit; 408. Inlet valve of feed pump of coal liquefaction unit; 409. Feed pump outlet valve of coal liquefaction unit; 410. The outlet valve of the alkali liquid delivery pump of the coal liquefaction unit; 416, the inlet valve of the alkali liquid delivery pump of the coal liquefaction unit; 411, the extraction valve of the alkali liquid discharge buffer tank; 412, the valve for discharging alkali liquid at the outlet of the reaction heating furnace; 413, the valve for discharging alkali liquid from the first reactor; 414, the valve for discharging alkali liquid from the second reactor; 415, the valve for discharging alkali liquid from the high-temperature and high-pressure separator; 417, the nitrogen valve at the outlet of the feed pump of the coal liquefaction unit; 418, the valve for the alkali liquid to enter the defoamer;

[0031] 501. Inlet filter of alkali liquid delivery pump in tank area; 502. Inlet filter of alkali liquid booster pump in coal liquefaction unit; 503. Inlet filter of feed pump in coal liquefaction unit; 504. Inlet filter of alkali liquid delivery pump in coal liquefaction unit; 601. Outlet check valve of alkali liquid delivery pump in tank area; 602. Outlet check valve of alkali liquid booster pump in coal liquefaction unit; 603. Outlet check valve of feed pump in coal liquefaction unit; 604. Outlet check valve of alkali liquid delivery pump in coal liquefaction unit;

[0032] Figure 2 It is a schematic diagram of a foam cyclone separator;

[0033] Attached Figure 2 Description of the markings: 118, feed inlet of the foam cyclone separator; 128, top outlet of the foam cyclone separator; 138, bottom outlet of the foam cyclone separator;

[0034] Figure 3 It is a structural schematic diagram of a defoamer;

[0035] Attached Figure 3 Marking instructions: 119, foam inlet, 129,. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0037] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0038] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0039] like Figure 1 As shown, the system for shutting down and withdrawing alkali liquid from a coal direct liquefaction device of the present invention comprises an alkali liquid tank 101 in the tank area, an alkali liquid buffer tank 102 of the coal liquefaction device, a reaction heating furnace 103, a first reactor 104, a second reactor 105, a high-temperature and high-pressure separator 106, an alkali liquid discharge buffer tank 107, a foam cyclone separator 108 and a defoamer 109.

[0040] The alkali liquid tank 101 in the tank area is used to store alkali liquid, and is connected to the alkali liquid buffer tank 102 of the coal liquefaction device via an alkali liquid delivery pump 201 in the tank area, so as to deliver the alkali liquid in the tank area into the alkali liquid buffer tank 102 of the coal liquefaction device.

[0041] The alkali liquid buffer tank 102 of the coal liquefaction device is connected to the reaction heating furnace 103 through the alkali liquid pressure pump 204 of the coal liquefaction device, and the reaction heating furnace 103 is connected in series with the first reactor 104, the second reactor 105 and the high temperature and high pressure separator 106 in sequence, so that the alkali liquid from the alkali liquid buffer tank of the coal liquefaction device is sequentially sent to the reaction heating furnace, the first reactor, the second reactor and the high temperature and high pressure separator for alkali washing; the specific connection is well known in the art, for example, the outlet of the reaction heating furnace is connected to the feed port at the bottom of the first reactor, the outlet at the top of the first reactor is connected to the feed port at the bottom of the second reactor, and the outlet at the top of the second reactor is connected to the feed port of the high temperature and high pressure separator. Among them, it is well known in the art that when the direct coal liquefaction reaction is carried out, the reaction heating furnace is used to heat the oil-coal slurry to reach a predetermined temperature so as to enter the first reactor and the second reactor for direct coal liquefaction reaction, and the coal liquefaction reaction product is separated from the second reactor by the high temperature and high pressure separator, and the specific connection can be referred to CN 108998068 A.

[0042] The feed port of the foam cyclone separator 108 is respectively connected to the reaction heating furnace 103, the first reactor 104, the second reactor 105 and the high temperature and high pressure separator 106, so as to receive the alkali solution discharged from the reaction heating furnace and the first reactor, the second reactor and the high temperature and high pressure separator and perform foam separation; the specific connection is well known in the art, for example, the feed port 118 of the foam cyclone separator is respectively connected to the outlet of the reaction heating furnace and the bottom of the first reactor, the second reactor and the high temperature and high pressure separator through a pipeline, so as to receive the alkali solution. Of course, in order to facilitate the control of the discharge of the alkali solution, valves can also be set on each pipeline accordingly, which is well known in the art.

[0043] like Figure 2 As shown, the foam cyclone separator 108 may be a cyclone separator well known in the art, and the light foam is separated from the top by cyclone and the alkali solution is discharged from the bottom. The specific structure is well known in the art and will not be described in detail here.

[0044] The defoamer 109 is used to eliminate the foam from the top outlet of the foam cyclone separator 108 and return the defoamed material to the alkali solution discharge buffer tank 107, wherein the defoamer can be a defoaming device commonly used in the art.

[0045] In one embodiment, Figure 3As shown, the defoamer 109 includes a foam inlet 119, a spray liquid inlet pipe 129 and a shell, the upper end of the shell is closed and the lower end is open to serve as the bottom outlet 179 of the defoamer, and the shell is sequentially connected to a first cylindrical section 139, a reduced diameter section 149, a second cylindrical section 159 and an expanded diameter section 169 from top to bottom, the foam inlet 119 is arranged on the side wall of the first cylindrical section 139, the spray liquid inlet pipe 129 passes through the first cylindrical section 139 from top to bottom and extends into the second cylindrical section 159 so as to feed the spray liquid, and the end of the spray liquid inlet pipe is a reduced diameter end 189, for example, reduced to 1 / 3 to 2 / 3 of the original diameter, such as 1 / 2, that is, the end diameter of the reduced diameter end 189 can be 1 / 3 to 2 / 3 of the diameter of the tubular part of the spray liquid inlet pipe 129. During operation, the spray liquid, such as alkali liquid, enters the spray liquid inlet pipe and then sprays out from the reduced diameter end, the induced foam enters from the foam inlet and is mixed and defoamed in the second cylindrical section and the expanded diameter section, and then is discharged from the bottom outlet of the defoamer and enters the alkali liquid discharge buffer tank. Among them, the reduced diameter refers to the reduction of the diameter from top to bottom, and the expanded diameter refers to the expansion of the diameter from top to bottom; the length and inclination angle of the reduced diameter section and the expanded diameter section (i.e., the angle between its side wall and the axial direction) can be adjusted according to actual conditions, such as the length of the reduced diameter section can be 1 / 3 to 2 / 3 of the first cylindrical section, such as 1 / 2, and its inclination angle can be 30°-60°, such as 45°, and the length of the expanded diameter section can be 2 / 3 to 4 / 3 of the first cylindrical section, such as 1. The lengths of the two are equal, and their inclination angles can be 10°-20°, such as 15°. The defoamer used in the present invention has a simple structure and good defoaming effect using alkali liquid.

[0046] The alkali liquid discharge buffer tank 107 is connected to the bottom outlet of the foam cyclone separator 108 so as to receive the separated alkali liquid; and the bottom of the alkali liquid discharge buffer tank 107 is connected to the alkali liquid tank in the tank area through the alkali liquid delivery pump 203 of the coal liquefaction device, so that after the alkali liquid discharge is completed, the alkali liquid in the alkali liquid discharge buffer tank 107 can be sent back to the alkali liquid tank 101 in the tank area.

[0047] In one embodiment, the top of the alkali liquid discharge buffer tank 107 is respectively provided with a first alkali liquid inlet and a second alkali liquid inlet, wherein the first alkali liquid inlet is connected 138 to the bottom outlet of the foam cyclone separator so as to receive the separated alkali liquid; the foam inlet 119 of the defoamer 109 is connected to the top outlet 128 of the foam cyclone separator, the bottom outlet of the defoamer is connected to the second alkali liquid inlet thereunder, and the second alkali liquid inlet extends into the alkali liquid discharge buffer tank so as to send the material from the defoamer below the liquid surface for better defoaming; an alkali liquid outlet is provided at the bottom of the alkali liquid discharge buffer tank, and is respectively connected to the spray liquid inlet pipe 129 of the defoamer 109 and the tank area alkali liquid tank 101 through the coal liquefaction device alkali liquid delivery pump 203 so as to deliver alkali liquid to the defoamer and the tank area alkali liquid tank; and an exhaust pipe is also provided at the top of the alkali liquid discharge buffer tank, and a nitrogen pipe can also be provided here to send nitrogen, which is conducive to controlling and regulating the pressure in the alkali liquid discharge buffer tank.

[0048] The method for shutting down and removing alkali liquid from a coal direct liquefaction device using the above system includes the following steps S1-S4:

[0049] S1) delivering the alkali liquid in the tank area to the alkali liquid buffer tank of the coal liquefaction device through the alkali liquid delivery pump in the tank area, and delivering it to the reaction heating furnace, the first reactor, the second reactor and the high temperature and high pressure separator in sequence through the alkali liquid pressure pump of the coal liquefaction device for alkali washing;

[0050] Specifically, in step S1, the alkali liquid in the tank area can be first transported to the alkali liquid buffer tank of the coal liquefaction device through the alkali liquid delivery pump in the tank area; then the alkali liquid in the alkali liquid buffer tank of the coal liquefaction device is transported to the reaction heating furnace through the alkali liquid pressure pump of the coal liquefaction device for heating, and then sent to the first reactor, the second reactor and the high temperature and high pressure separator for alkali washing. In some embodiments, the alkali liquid temperature in the tank area is 60-70°C; the outlet pressure of the alkali liquid delivery pump in the tank area is 1.0-1.5MPa, which is more conducive to sending back to the tank area and defoaming.

[0051] S2) After the alkali washing is completed, the alkali liquid delivery pump in the tank area and the alkali liquid pressure pump of the coal liquefaction device are stopped to stop the alkali liquid delivery;

[0052] Specifically, in step S2, after the alkali washing is completed, the alkali liquid delivery pump in the tank area can be stopped from delivering alkali liquid to the alkali liquid buffer tank of the coal liquefaction device; and then after all the alkali liquid in the alkali liquid buffer tank of the coal liquefaction device is discharged, the alkali liquid booster pump of the coal liquefaction device is stopped. In some embodiments, the temperature of the alkali liquid buffer tank of the coal liquefaction device is 50-60°C; and the outlet pressure of the alkali liquid booster pump of the coal liquefaction device is 2.0-2.5MPa.

[0053] S3) discharging the alkali solution in the reaction heating furnace, the first reactor, the second reactor and the high temperature and high pressure separator into the alkali solution discharge buffer tank after the foam is separated by the foam cyclone separator; at the same time, using a defoamer to eliminate the foam separated from the foam cyclone separator and sending the defoamed material to the alkali solution discharge buffer tank;

[0054] Specifically, in step S3, when the alkali liquid is discharged, the alkali liquid in the reaction heating furnace, the first reactor, the second reactor and the high temperature and high pressure separator can be discharged to the alkali liquid discharge buffer tank after the foam is separated by the foam cyclone separator; at the same time, the foam separated from the foam cyclone separator is eliminated by a defoamer and the defoamed material is sent to the alkali liquid discharge buffer tank. In some embodiments, the temperature of the alkali liquid discharge buffer tank of the coal liquefaction device is 50-60°C; the pressure of the alkali liquid discharge buffer tank of the coal liquefaction device is 0.1-0.15MPa.

[0055] S4) After the alkali liquid is discharged, the alkali liquid in the alkali liquid discharge buffer tank is pressurized by the alkali liquid delivery pump of the coal liquefaction device and then sent to the alkali liquid tank in the tank area for storage.

[0056] In some embodiments, the pressure after pressurization by the alkali solution delivery pump of the coal liquefaction device is 1.0-1.5 MPa.

[0057] The present invention is further described below with reference to embodiments:

[0058] Example 1

[0059] like Figure 1-3 As shown, when preparing for alkali washing, first open the relevant valves, and transport the alkali liquid in the alkali liquid tank in the tank area to the alkali liquid buffer tank 102 of the coal liquefaction unit through the alkali liquid delivery pump 201 in the tank area (the alkali liquid temperature in the tank area is 60-70°C; the outlet pressure of the alkali liquid delivery pump in the tank area is 1.0-1.5MPa); then the alkali liquid in the alkali liquid buffer tank of the coal liquefaction unit is transported to the reaction heating furnace (heating can be performed to control the temperature if necessary) through the alkali liquid booster pump 204 in the coal liquefaction unit (the alkali liquid buffer tank temperature of the coal liquefaction unit is 50-60°C; the outlet pressure of the alkali liquid booster pump of the coal liquefaction unit is 2.0-2.5MPa), and then sequentially sent to the first reactor, the second reactor and the high temperature and high pressure separator for alkali washing.

[0060] When the alkali washing is completed, the valve 412 for discharging alkali liquid at the outlet of the reaction heating furnace, the valve 413 for discharging alkali liquid at the first reactor, the valve 414 for discharging alkali liquid at the second reactor, and the valve 415 for discharging alkali liquid at the high temperature and high pressure separator are opened to discharge the alkali liquid (temperature: 50-60°C, pressure: 0.5-1.0MPa) to the foam cyclone separator 108 for foam separation, and the separated alkali liquid enters the alkali liquid discharge buffer tank 107 for buffering, degassing, and defoaming. The foam and the alkali liquid as the spray liquid enter the defoamer 109 for defoaming and then enter the alkali liquid discharge buffer tank 107 (temperature: 50-60°C, pressure: 0.1-0.15MPa), wherein part of the alkali liquid in the alkali liquid discharge buffer tank 107 enters the defoamer 109 as a spray liquid via the alkali liquid delivery pump of the coal liquefaction device. The pressure of the alkali liquid discharge buffer tank 107 can be controlled by the alkali liquid discharge buffer tank nitrogen control valve 305 and the alkali liquid discharge buffer tank venting control valve 304.

[0061] When the alkali liquid is returned, the opening and closing of relevant valves are adjusted. After being filtered through the inlet filter 504 of the coal liquefaction unit alkali liquid delivery pump, the alkali liquid is pressurized through the coal liquefaction unit alkali liquid delivery pump 203 (the outlet temperature of the coal liquefaction unit alkali liquid delivery pump: 50-60°C, pressure: 1.0-1.5MPa), and the flow rate is controlled by the outlet flow control valve 303 of the coal liquefaction unit alkali liquid delivery pump, and the alkali liquid enters the tank area alkali liquid tank 101 through the opened alkali liquid inlet tank area alkali liquid tank valve 401 for storage.

Claims

1. A system for de-alkali liquid during shutdown of a coal direct liquefaction device, the system comprising an alkali liquid tank in a tank area, an alkali liquid buffer tank of a coal liquefaction device, a reaction heating furnace, a first reactor, a second reactor, a high temperature and high pressure separator, an alkali liquid discharge buffer tank, a foam cyclone separator and a defoamer; wherein: The alkali liquid tank in the tank area is connected to the alkali liquid buffer tank of the coal liquefaction device through an alkali liquid delivery pump in the tank area, so as to deliver the alkali liquid in the tank area into the alkali liquid buffer tank of the coal liquefaction device; The alkali liquid buffer tank of the coal liquefaction device is connected to the reaction heating furnace through the alkali liquid pressure pump of the coal liquefaction device, and the reaction heating furnace is connected in series with the first reactor, the second reactor and the high-temperature and high-pressure separator in sequence, so that the alkali liquid from the alkali liquid buffer tank of the coal liquefaction device is sequentially sent to the reaction heating furnace, the first reactor, the second reactor and the high-temperature and high-pressure separator for alkali washing; The feed port of the foam cyclone separator is connected to the reaction heating furnace, the first reactor, the second reactor and the high-temperature and high-pressure separator respectively, so as to receive the alkali solution discharged from the reaction heating furnace and the first reactor, the second reactor and the high-temperature and high-pressure separator and perform foam separation; The alkali solution discharge buffer tank is connected to the bottom outlet of the foam cyclone separator to receive the separated alkali solution; The defoamer is used to eliminate the foam from the top outlet of the foam cyclone separator, and send the defoamed material back to the alkali solution discharge buffer tank; The bottom of the alkali liquid discharge buffer tank is connected to the alkali liquid tank in the tank area through an alkali liquid delivery pump of a coal liquefaction device, so that the alkali liquid in the alkali liquid discharge buffer tank is sent back to the alkali liquid tank in the tank area.

2. The system according to claim 1, characterized in that The defoamer comprises a foam inlet, a spray liquid inlet pipe and a shell, the upper end of the shell is closed and the lower end is open to serve as the bottom outlet of the defoamer, and the shell comprises, from top to bottom, a first cylindrical section, a reduced diameter section, a second cylindrical section and an expanded diameter section which are interconnected, the foam inlet is arranged on the side wall of the first cylindrical section, the spray liquid inlet pipe passes through the first cylindrical section from top to bottom and extends into the second cylindrical section, and the end of the spray liquid inlet pipe is a reduced diameter end.

3. The system according to claim 2, characterized in that The top of the alkali solution discharge buffer tank is respectively provided with a first alkali solution inlet and a second alkali solution inlet, wherein the first alkali solution inlet is connected to the bottom outlet of the foam cyclone separator to receive the separated alkali solution; The foam inlet of the defoamer is connected to the top outlet of the foam cyclone separator, the bottom outlet of the defoamer is connected to the second alkali solution inlet below it, and the second alkali solution inlet extends into the alkali solution discharge buffer tank so as to send the material from the defoamer below the liquid surface; An alkali liquid outlet is provided at the bottom of the alkali liquid discharge buffer tank, and is respectively connected to the spray liquid inlet pipe of the defoamer and the alkali liquid tank in the tank area through an alkali liquid delivery pump of the coal liquefaction device, so as to deliver alkali liquid to the defoamer and the alkali liquid tank in the tank area; and an exhaust pipe is also provided at the top of the alkali liquid discharge buffer tank.

4. A method for shutting down a coal direct liquefaction device and removing alkali liquid, the method comprising the following steps: S1) delivering the alkali liquid in the tank area to the alkali liquid buffer tank of the coal liquefaction device through the alkali liquid delivery pump in the tank area, and delivering it to the reaction heating furnace, the first reactor, the second reactor and the high temperature and high pressure separator in sequence through the alkali liquid pressure pump of the coal liquefaction device for alkali washing; S2) After the alkali washing is completed, the alkali liquid delivery pump in the tank area and the alkali liquid pressure pump of the coal liquefaction device are stopped to stop the alkali liquid delivery; S3) discharging the alkali solution in the reaction heating furnace, the first reactor, the second reactor and the high temperature and high pressure separator into the alkali solution discharge buffer tank after the foam is separated by the foam cyclone separator; at the same time, using a defoamer to eliminate the foam separated from the foam cyclone separator and sending the defoamed material to the alkali solution discharge buffer tank; S4) After the alkali liquid is discharged, the alkali liquid in the alkali liquid discharge buffer tank is pressurized by the alkali liquid delivery pump of the coal liquefaction device and then sent to the alkali liquid tank in the tank area for storage.

5. The method according to claim 4, characterized in that In step S1, the alkali liquid in the tank area is first transported to the alkali liquid buffer tank of the coal liquefaction device through the alkali liquid transport pump in the tank area; then the alkali liquid in the alkali liquid buffer tank of the coal liquefaction device is transported to the reaction heating furnace through the alkali liquid booster pump of the coal liquefaction device for heating, and then sent to the first reactor, the second reactor and the high-temperature and high-pressure separator for alkali washing.

6. The method according to claim 5, characterized in that The alkali solution temperature in the tank area is 60-70°C; the outlet pressure of the alkali solution delivery pump in the tank area is 1.0-1.5MPa.

7. The method according to claim 5 or 6, characterized in that: In step S2, after the alkali washing is completed, the alkali liquid delivery pump in the tank area is stopped from delivering alkali liquid to the alkali liquid buffer tank of the coal liquefaction device; and then after all the alkali liquid in the alkali liquid buffer tank of the coal liquefaction device is output, the alkali liquid booster pump of the coal liquefaction device is stopped.

8. The method according to claim 7, characterized in that The temperature of the alkali liquid buffer tank of the coal liquefaction device is 50-60°C; the outlet pressure of the alkali liquid booster pump of the coal liquefaction device is 2.0-2.5MPa.

9. The method according to claim 7 or 8, characterized in that: In step S3, when the alkali liquid is discharged, the alkali liquid in the reaction heating furnace, the first reactor, the second reactor and the high-temperature and high-pressure separator is discharged into the alkali liquid discharge buffer tank after the foam is separated by the foam cyclone separator; at the same time, the defoamer is used to eliminate the foam separated from the foam cyclone separator and the defoamed material is sent to the alkali liquid discharge buffer tank.

10. The method according to claim 9, characterized in that The temperature of the alkali liquid discharge buffer tank of the coal liquefaction device is 50-60°C; the pressure of the alkali liquid discharge buffer tank of the coal liquefaction device is 0.1-0.15MPa; The pressure after pressurization by the alkali solution delivery pump of the coal liquefaction device is 1.0-1.5MPa.

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