Pyrolysis gas quenching tank

Abstract

The utility model discloses a pyrolysis gas quenching tank. The circular tank body is sealed with the upper cover, and the bottom of the tank body is a lower opening for collecting heavy oil. The inner tank is sleeved with the outer tank, a water cavity is formed between the outer tank and the inner tank, and cooling water is introduced into the water cavity. An arc-shaped gas inlet pipe at the upper part of the tank body is internally tangent to the inner tank to ensure that pyrolysis gas tangentially enters the inner tank. And an inlet at the lower end of the air outlet pipe is arranged at the lower part of the inner tank. Atomizing nozzles are evenly distributed on the lower portion of the upper cover in the circumferential direction and communicated with a high-pressure water pipe. Insulating layers cover the upper cover and the lower opening. High-temperature pyrolysis gas enters the inner tank to be quenched, and coked heavy oil is subjected to centrifugal force separation.

Description

Technical Field

[0001] The utility model is applied to ethylene cracking and relates to cracking gas rapid cooling, in particular to a cracking gas rapid cooling tank. Background Art

[0002] After high-temperature thermal cracking of hydrocarbons, the resulting cracked gas, including components such as ethylene, propylene, butene, butadiene, alkynes, and aromatics, enters a quench boiler for rapid cooling to prevent a decrease in olefin yield and an increase in heavy tar production while also recovering heat. However, as the cracked gas condenses on the walls of the quench boiler's heat exchange tubes, hydrocarbons adhere to them. At high temperatures, they readily condense to form coke, leading to severe coking within the quench boiler, reducing heat exchange efficiency and, in severe cases, clogging the tubes and even causing equipment failure. To ensure safety, production must be shut down for coke removal, severely impacting the safe operation and economic benefits of the equipment.

[0003] CN113293027A discloses a quench oil tower, a quench oil production device, and a quench oil production system. The quench oil tower comprises a tower body and a cyclone separation structure. The tower body includes a cavity and a cracked gas pipeline connection port connected to the cavity. The cyclone separation structure is disposed within the cavity to separate the cracked gas entering the cavity into gas, solid, and liquid. This solves the technical problem that conventional steam cracking units are prone to long operating cycles and energy waste due to the presence of small amounts of coke powder and asphalt in the cracked gas during coal-to-naphtha production.

[0004] CN111704521B discloses a system and method for rapidly cooling olefin reaction products. The system comprises a reactor, an oil-gas pre-quenching tower, and a main fractionating tower. The reactor's discharge line serves as the feed line for the oil-gas pre-quenching tower; the oil-gas pre-quenching tower's discharge line serves as the first feed line for the fractionating tower, and the oil-gas pre-quenching tower's bottom discharge line serves as the second feed line for the main fractionating tower. The main fractionating tower's bottom discharge line returns to the oil-gas pre-quenching tower. The invention's inventiveness lies in its use of the oil-gas pre-quenching tower to rapidly cool the process gas, thereby reducing the occurrence of coking reactions during subsequent process gas processing and the frequent equipment shutdowns caused by coking.

[0005] CN209161963U provides a quench oil tower comprising a vertical cylinder with a lower end cap disposed at the bottom of the cylinder, connected to a bottom oil outlet pipe. An upper end cap is disposed at the top of the cylinder, with a gas outlet provided. The cylinder comprises an upper rectifying section and a lower rectifying section. The lower region of the lower rectifying section is provided with a gas feed inlet and a two-phase feed inlet. Multiple layers of first trays are arranged within the central cavity. A first spray pipe is disposed within the upper cavity, the inlet of which is connected to a quench oil return port. Multiple layers of second trays are disposed within the lower cavity of the upper rectifying section. This quench oil tower effectively separates heavy fuel oil from light fuel oil, is less susceptible to coking, and has a long operating cycle.

[0006] CN212451305U provides a device for preventing coking in oil-gas quenchers, comprising a steam drum, a quencher, and a steam mixing ejector. The drum boiler water outlet is connected to the quencher boiler water inlet, which in turn is connected to the steam mixing ejector boiler water inlet, which in turn is connected to the drum boiler water inlet. The heating steam inlet delivers heating steam to the steam mixing ejector to increase the boiler water temperature. This device can increase the boiler water and quencher tube bundle wall temperature, preventing condensation and coking in the quencher during initial operation. Utility Model Content

[0007] The technical problem solved by the utility model is to provide a cracking gas quenching tank to quench the high-temperature cracking gas and avoid the subsequent device from coking and causing shutdown.

[0008] The technical solution adopted by the present invention is as follows: the circular tank body of the cracking gas quenching tank is sealed with the upper cover, and the bottom of the tank body is the lower opening; the tank body includes an outer tank and an inner tank, the inner tank is inserted into the outer tank, and a water cavity is formed between the two tanks. A water inlet is designed at the lower part or bottom of the water cavity, and a water outlet is designed at the upper part or top. At the upper part of the tank body, an arc-shaped air inlet pipe is inscribed in the inner tank to ensure that the cracking gas enters the inner tank tangentially to generate centrifugal force. The upper cover fixes the air outlet pipe, and the inlet at the lower end of the air outlet pipe is connected to the cover body, and the cover body is arranged at the lower part of the inner tank. Below the upper cover, atomizing nozzles are evenly distributed around the circumference, and the atomizing nozzles are connected to the high-pressure water pipe above the upper cover.

[0009] Furthermore, in order to ensure safe production and the temperature of heavy oil, the upper cover and the lower opening are insulated with an insulation layer.

[0010] Furthermore, in order to reduce the thermal stress of the inner tank, the inner tank is cylindrical or spherical.

[0011] Furthermore, in order to enhance the measured cooling water temperature difference data, the water outlet is designed at the location where the air intake pipe enters tangentially.

[0012] Furthermore, to ensure smooth water flow in the water cavity, the cross-sectional area of ​​the water outlet must not be less than twice the cross-sectional area of ​​the water inlet.

[0013] The beneficial effects of this utility model are as follows: the high-temperature cracked gas enters the inner tank tangentially, is rapidly cooled to 280-380°C through atomization, and the coked heavy oil is separated by centrifugal force, while the light oil gas enters the distillation tower or heat exchanger, avoiding shutdown of subsequent equipment due to coking. Auxiliary water cooling can recover and reuse heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the main structure of Example 1;

[0015] Figure 2 yes Figure 1 Schematic diagram from top view;

[0016] Figure 3 yes Figure 1 AA cross-sectional view of ;

[0017] Figure 4 This is a schematic diagram of the main structure of Example 2;

[0018] Figure 5 This is a schematic diagram of the main structure of Example 3;

[0019] In the figure: 1-outer tank, 2-water cavity, 3-inner tank, 4-lower port, 5-water inlet, 6-cover, 7-insulation layer, 8-high-pressure water pipe, 9-atomizing nozzle, 10-air outlet pipe, 11-upper cover, 12-water outlet, 13-air inlet pipe. Implementation Method

[0020] The accompanying drawings are schematic diagrams of the structures of the present invention. Structures not described in detail represent prior art. In the following structural descriptions, it should be understood that terms such as "up and down," "front and back," "left and right," "vertical and horizontal," "top and bottom," and "inside and outside" refer to relative positions or positional relationships based on the accompanying drawings. These terms are intended solely to simplify the description of the structures and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, in the descriptions of this application, "plurality" means two or more, unless otherwise specified.

[0021] Attachment Figure 1 and attached Figure 3 The solid arrows in the figure indicate the direction of gas flow. Figure 1 The dashed arrows in the figure indicate the cooling water flow direction. Example

[0022] The structure of the cracking gas quenching tank in this embodiment is shown in the attached figure. Figure 1-3As shown, the circular tank body is sealed with the upper cover 11, and the bottom of the tank body is a lower opening 4. The tank body includes an outer tank 1 and an inner tank 3, and the inner tank 3 is set in the outer tank 1. There is a water cavity 2 between the inner and outer tanks. The water cavity 2 is designed with a water inlet 5 at the bottom and a water outlet 12 at the top.

[0023] At the upper part of the tank body, the air inlet pipe 13 for the cracked gas is connected. The air inlet pipe 13 is arc-shaped and cuts into the inner tank 3. Figure 3 As shown, the cracking gas enters the inner tank 3 tangentially.

[0024] The top cover 11 of the tank body is fixedly installed with an air outlet pipe 10, the inlet of the air outlet pipe 10 is set at the lower part of the inner tank 3 and connected to the cover 6. Below the top cover of the inner tank 3, atomizing nozzles 9 are evenly distributed around the circumference, and the atomizing nozzles 9 are connected to the high-pressure water pipe 8 above the tank body cover, as shown in the attached figure. Figure 1 and attached Figure 2 shown.

[0025] The upper cover 11 and the bottom of the tank body are insulated with an insulation layer 7. The insulation layer of the upper cover 11 is to prevent scalding accidents and ensure safe production. The insulation layer at the bottom opening is to ensure the temperature of the downstream heavy oil and prevent a large temperature drop, which will increase viscosity and deteriorate fluidity.

[0026] When the present invention is in use, high-temperature cracked gas enters the inner tank 3 tangentially from the inlet pipe 13. Simultaneously, the atomizing nozzle 9 sprays atomized water or atomized quench oil to cool the high-temperature cracked gas at 600-800°C to 280-380°C. Low-carbon cracked gas and water vapor with a melting point below 280°C are collected from the hood and flow through the outlet pipe 10 into the downstream device, such as a distillation tower or a heat exchanger. Heavy oil with a melting point above 280°C and solids and liquids in the cracked gas, i.e., substances prone to coking, condense together and, under the centrifugal force of the rotating gas within the inner tank, move toward the center of the inner tank. Finally, they flow down the vertical outlet pipe 10 in the center of the inner tank, obliquely fall through the hood 6 into the lower port 4, and then gather and flow out through the lower port 4 as water-free heavy oil. The mixed gas discharged from the gas outlet pipe 10 is cooled by a fractionating tower or a heat exchanger to form an oil-water mixture which is fed into the high-pressure water pipe 8 as quenching oil and sprayed out by the atomizing nozzle 9 to cool the cracked gas again.

[0027] This utility model utilizes the inventive concept of CN111704521B to pre-cool the coke components in the cracked gas in a quench tank. This allows the heavy oil, which is prone to coking, to be separated from the light oil in the quench tank, thus preventing coking in subsequent equipment. The utility model uses one standby unit, controlled by valves, with one unit for quenching production and the other for cleaning coke, allowing subsequent equipment to achieve continuous production.

[0028] The smaller the particle size of the cooling water or quench oil sprayed from the atomizing nozzle 9, the more conducive it is to instantaneous heat absorption and vaporization, resulting in a better quenching effect. The cooling water or quench oil pressure and flow rate are designed to keep the cracked gas temperature between 280°C and 380°C, ensuring that the heavy oil collected at the lower outlet is moisture-free. The inner tank is cooled by the cooling water within the water cavity, which keeps the inner tank temperature relatively low and provides auxiliary cooling. After the high-temperature cracked gas enters the inner tank, heavy oil condenses on the inner wall and flows down to the lower outlet. When the outlet pipe temperature exceeds 400°C, or the temperature difference between the water inlet and outlet falls below 23°C, the quench tank can be replaced and the coke inside the tank cleaned. The water outlet should ideally be located where the cracked gas enters tangentially, in the high-temperature zone of the inner tank, to increase the measured water temperature difference. Example

[0029] In order to reduce the deformation of the inner tank due to temperature stress, the cylindrical tank body in Example 1 is changed to a spherical shape in this embodiment, as shown in the attached figure. Figure 4 As shown, the curved tank body can expand and contract freely, reducing thermal stress caused by thermal expansion and contraction of the inner tank, thereby increasing the tank's service life. The increased inner tank volume relieves the gas pressure generated by the quenching atomization steam, facilitating the rapid tangential entry of the cracked gas. The increased inner tank surface area helps enhance auxiliary water cooling. Example

[0030] In order to avoid the formation of dead corners in the water cavity 2, the formation of water vapor, and the resulting thermal resistance, the positions of the water inlet 5 and the water outlet 12 can be modified. The water inlet is located at the bottom of the water cavity, and the water outlet is located at the top of the water cavity. Figure 5 It should be noted that the cross-sectional area of ​​the water outlet 12 should not be less than twice the cross-sectional area of ​​the water inlet 5 .

[0031] This simple structure, installed near the cracking furnace, rapidly cools the cracked gas, condensing the heavy oil that forms the coking reaction into a liquid, thus avoiding shutdowns in subsequent distillation towers or heat exchangers due to coking. One unit is in use, with one unit as a backup, enabling continuous production. Auxiliary cooling of the water chamber cooling water helps reduce the amount of spray cooling water, 1) reducing atomizing steam generation and lowering internal tank steam pressure; 2) lowering oil-water separation pressure; and 3) enabling significant heat recovery.

[0032] Although the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, such as changing the curved air intake pipe to a straight air intake pipe. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cracking gas quenching tank, wherein the circular tank body is sealed with an upper cover (11), and the bottom of the tank body is a lower opening (4); the characteristics are: The tank body comprises an outer tank (1) and an inner tank (3) mounted inside the outer tank (1), with a water cavity (2) between the two tanks; The lower part or bottom of the water chamber (2) is designed with a water inlet (5), and the upper part or top is designed with a water outlet (12); At the upper part of the tank body, the arc-shaped air intake pipe (13) is internally cut with the inner tank (3); The upper cover (11) fixes the air outlet pipe (10), the inlet of the air outlet pipe (10) is connected to the cover body (6), and the cover body (6) is arranged at the lower part of the inner tank (3); Atomizing nozzles (9) are evenly distributed around the circumference below the upper cover (11), and the atomizing nozzles (9) are connected to the high-pressure water pipes (8) above the upper cover (11).

2. A cracking gas quenching tank according to claim 1, characterized in that: The upper cover (11) and the lower opening (4) are insulated by a heat-insulating layer.

3. The cracking gas quenching tank according to claim 1, characterized in that: The inner tank (3) is cylindrical or spherical.

4. The cracking gas quenching tank according to claim 1, characterized in that: The water outlet (12) is designed at the location where the air inlet pipe (13) enters tangentially.

5. The cracking gas quenching tank according to claim 1, characterized in that: The cross-sectional area of ​​the water outlet (12) is not less than twice the cross-sectional area of ​​the water inlet (5).

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