Dryer regeneration system and method for gas raw material cracking

Abstract

The invention belongs to the field of ethylene and related technologies, and discloses a dryer regeneration system and method for gas raw material cracking. The system comprises a gas cracking raw material pipeline, a regeneration gas heat exchange unit, a distribution unit, a dryer user and a regeneration gas treatment unit. Methane / hydrogen tail gas or hydrogen-rich tail gas generated by conventional cracking is not used, circulating ethane generated by a cracking device and raw material ethane gas and raw material propane gas of the device are adopted as regeneration gas, the hydrogen-rich gas can be kept at high pressure and directly used as raw material gas of a PSA hydrogen concentration device, power consumption of a compressor of a PSA unit is reduced, and the energy consumption of the PSA unit is reduced. And the energy consumption of the whole device is reduced while more hydrogen products are produced as byproducts.

Description

Technical Field

[0001] This invention belongs to the field of ethylene and related technologies, and more specifically, relates to a dryer regeneration system and method for pyrolysis of gaseous feedstocks. Background Technology

[0002] Conventional feedstocks for ethylene plant cracking include liquid feedstocks such as naphtha and hydrotreated tail oil, and gaseous feedstocks such as ethane, propane, and saturated liquefied petroleum gas (LPG). Due to limitations in oil and gas resources, my country's ethylene plants have historically relied primarily on liquid feedstocks. However, with the continued rise in international oil prices, the profit margins for liquid feedstock cracking have been severely squeezed. Optimizing the quality of cracking feedstocks to increase ethylene product yield and reduce plant energy consumption is a crucial way for enterprises to improve economic efficiency and enhance market competitiveness.

[0003] The composition of pyrolysis products varies with the feedstock. Compared to liquid-phase feedstock pyrolysis, gas-phase feedstock pyrolysis, primarily composed of ethane, produces less methane. The dryer regeneration system of liquid feedstock pyrolysis units typically uses the unit's own methane / hydrogen tail gas (85% methane and 15% hydrogen) for regeneration. Because liquid-phase pyrolysis produces a large amount of methane / hydrogen, this tail gas is sufficient to meet the unit's regeneration gas requirements.

[0004] For ethane-based gaseous feedstock cracking, especially ethane cracking, the hydrogen yield is very high, approximately three times higher than that of other feedstock cracking, and the hydrogen content in the cracking products far exceeds that of methane. The amount of methane / hydrogen tail gas at the cold box outlet is very small, insufficient to meet the regeneration gas requirements. Such gaseous feedstock cracking units typically use low-pressure hydrogen-rich tail gas from the cold box outlet or a portion of the hydrogen-rich tail gas mixed with the methane / hydrogen tail gas as a regeneration gas source.

[0005] In a conventional ethane gaseous feedstock cracking and separation process, the cracked gas is pressurized in a cracked gas compressor and then cooled in stages. A large amount of C2 components and methane are condensed and used as feed to the demethanizer. The remaining uncondensed gas phase is separated into hydrogen-rich tail gas in a methane-hydrogen separator. Different separation processes use different pressure settings for hydrogen and methane separation; the pressure of the hydrogen-rich tail gas separated in the methane-hydrogen separator is generally between 1.0 MPaG and 3.0 MPaG. At this pressure, the temperature of the hydrogen-rich tail gas is low, requiring cooling to ambient temperature in a cold box before being sent to downstream systems. If used as regeneration gas, the pressure of this hydrogen-rich tail gas exiting the cold box needs to be set or reduced to below 1.0 MPaG to meet requirements.

[0006] The ambient temperature hydrogen-rich tail gas exiting the cold box is heated to a specified temperature and used as regeneration gas for the dryer. After regeneration, it is cooled and the moisture is separated, and the pressure is reduced to about 0.5 MPaG. It is then used as feed gas for the PSA hydrogen enrichment unit or as fuel gas for the unit. This pressure is suitable as fuel gas, but if it is sent to the PSA unit for further H2 purification, it needs to be pressurized again.

[0007] From an energy utilization perspective, if the cracked gas in an ethylene plant has already been pressurized for separation purposes, it is reasonable to directly produce low-pressure hydrogen-rich gas if the hydrogen is ultimately used as fuel gas; if the hydrogen needs to be purified to produce hydrogen products, it is more suitable to reduce the pressure and produce hydrogen-rich gas at a higher pressure as much as possible.

[0008] Therefore, for ethane-based gas cracking units using hydrogen as fuel, ethylene plants can produce low-pressure hydrogen-rich gas, which, after being used for dryer regeneration, can be directly fed into the fuel gas system. However, most refining and chemical enterprises in my country require the production of high-purity hydrogen products. In such cases, ethylene plants should ideally produce high-pressure hydrogen-rich gas, which should be directly sent to the PSA unit for purification. If it must be used as regeneration gas, it needs to be depressurized, and after being sent to the PSA, it needs to be pressurized again. For example, for a 1.5 million tons / year ethane cracking to ethylene plant, the compressor power would increase by at least 5000 kW, which is clearly detrimental to energy conservation.

[0009] In summary, for ethane-based gas-phase cracking units, especially those with high methane / hydrogen separation pressures and capable of producing high-pressure hydrogen-rich gas, there is an urgent need to find a new dryer regeneration device and method to replace the previous regeneration scheme of reducing the pressure of hydrogen-rich gas. This new method should meet the dryer regeneration requirements while increasing the unit's hydrogen production, saving energy and reducing consumption, and enhancing the unit's competitiveness. Summary of the Invention

[0010] The purpose of this invention is to address the shortcomings of existing technologies by proposing a dryer regeneration system and method for gaseous feedstock pyrolysis. This invention replaces the previous regeneration scheme that involved depressurizing hydrogen-rich gas, increasing hydrogen production while meeting dryer regeneration requirements, saving energy and reducing consumption, and enhancing the competitiveness of the equipment.

[0011] To achieve the above objectives, the present invention provides a dryer regeneration system for gaseous feedstock pyrolysis, the system comprising a gas pyrolysis feedstock pipeline, a regeneration gas heat exchange unit, a distribution unit, a dryer user, and a regeneration gas processing unit;

[0012] The regenerated gas heat exchange unit is used to heat part of the regenerated gas entering the dryer user and to recover and cool the heat of the regenerated gas discharged from the dryer user.

[0013] The distribution unit includes: a regeneration gas flow and temperature control subunit and a sequence control subunit;

[0014] The outlet of the gas cracking feedstock pipeline is divided into two paths, one of which is connected to the hot regenerated gas pipeline through the regenerated gas heat exchange unit, and the other is connected to the cold regenerated gas pipeline.

[0015] The hot regenerated gas pipeline and the cold regenerated gas pipeline merge into the regenerated gas inlet pipeline of the dryer user and are connected to the dryer user.

[0016] The regenerated gas flow and temperature control subunit is electrically connected to the hot regenerated gas pipeline and the cold regenerated gas pipeline, respectively, and is used to control the proportion of hot regenerated gas and cold regenerated gas entering the dryer user.

[0017] The dryer user is also provided with a regenerated gas outlet pipeline; the sequential control subunit is electrically connected to the regenerated gas inlet pipeline and the regenerated gas outlet pipeline of the dryer user respectively, and is used to control the inlet and outlet of the regenerated gas.

[0018] The regenerated gas outlet pipeline of the dryer user is connected to the regenerated gas treatment unit through the regenerated gas heat exchange unit.

[0019] In this invention, "electrical connection" refers to connection with control instruments on the pipeline via electrical signals.

[0020] According to the present invention, preferably, the regenerated gas heat exchange unit includes: a regenerated gas heater and a quench water cooler, and optionally further includes a regenerated gas inlet / outlet heat exchanger;

[0021] One of the outlets of the gas pyrolysis feedstock pipeline is connected to the hot regenerated gas pipeline through the regenerated gas heater; optionally, one of the outlets of the gas pyrolysis feedstock pipeline is connected to the hot regenerated gas pipeline in sequence through the cold source inlet and outlet of the regenerated gas inlet / outlet heat exchanger and the regenerated gas heater.

[0022] The regenerated gas outlet pipeline of the dryer user is connected to the regenerated gas treatment unit through the quench water cooler; optionally, the regenerated gas outlet pipeline of the dryer user is connected to the regenerated gas treatment unit in sequence through the heat source inlet and outlet of the regenerated gas inlet / outlet heat exchanger and the quench water cooler.

[0023] According to the present invention, preferably, the regenerated gas heater is a steam heater and / or an electric heater.

[0024] According to the present invention, preferably, the regeneration gas treatment unit includes: an impurity removal subsystem, and optionally further includes a separation buffer tank;

[0025] The impurity removal subsystem includes filters and / or coalescers.

[0026] According to the present invention, preferably, the regenerated gas outlet pipeline of the dryer user is connected in sequence to the filter, the coalescer, and the pyrolysis furnace through the regenerated gas heat exchange unit; optionally, the outlet of the coalescer is connected to the pyrolysis furnace through the separation buffer tank.

[0027] According to the present invention, preferably, the gas cracking feedstock pipeline is a circulating ethane cracking feedstock pipeline;

[0028] The system also includes an ethylene tower, a first vaporizer, a second vaporizer, and a cold box;

[0029] The cold box is equipped with a pyrolysis inlet, a pyrolysis outlet, a regeneration gas inlet, and a regeneration gas outlet;

[0030] The bottom of the ethylene tower is connected to an ethane discharge pipeline; the ethane discharge pipeline is divided into two lines, one of which is connected in sequence to the pressure regulating valve, the cold source inlet and outlet of the first vaporizer and the cracking inlet, and the other is connected to the cold source inlet and outlet of the second vaporizer and the regeneration gas inlet.

[0031] The cold box's pyrolysis outlet is connected to the pyrolysis furnace;

[0032] The regenerated gas outlet of the cold box is connected to the inlet of the gas pyrolysis feedstock pipeline.

[0033] According to the present invention, preferably, the gas cracking feedstock pipeline is a propane cracking feedstock pipeline;

[0034] The system also includes a liquid propane feed line, a propane vaporizer, a propane superheater, and a propane gas line;

[0035] The liquid propane feed line is sequentially connected to the propane vaporizer, propane superheater, and propane gas line; the outlet of the propane gas line is divided into two paths, one of which is connected to the cracking furnace through a pressure regulating valve, and the other is connected to the inlet of the gas cracking feedstock line.

[0036] In this invention, as a preferred embodiment, the gas feedstock cracking device is the device described in application number 201810812902.3, wherein the cracking furnace, ethylene tower and cold box are the cracking furnace, ethylene distillation tower and second cooling unit in the device described in application number 201810812902.3, and the dryer is the dryer installed after the alkali washing tower and / or the secondary cracked gas dryer included in the acetylene removal unit.

[0037] Another aspect of the present invention provides a method for regenerating a dryer for pyrolysis of gaseous feedstock, the method employing the above-described system and comprising the following steps:

[0038] S1: A portion of the regenerated gas feed is fed into the regenerated gas heat exchange unit for heating to obtain hot regenerated gas; the remaining portion of the regenerated gas feed is used as cold regenerated gas.

[0039] S2: The hot regenerated gas and cold regenerated gas are combined and sent to the dryer user through the sequence control subunit; and before the combination, the ratio of hot regenerated gas and cold regenerated gas entering the dryer user is controlled by the regenerated gas flow and temperature control subunit.

[0040] S3: After the dryer user performs regeneration, the regeneration gas discharged by the dryer user is sequentially sent to the regeneration gas heat exchange unit and the regeneration gas treatment unit for processing through the sequence control subunit.

[0041] According to the present invention, preferably, the regenerated gas feedstock is at least one of regenerated gas recycle ethane, regenerated gas feedstock ethane, and regenerated gas propane. In the present invention, the "regenerated gas feedstock ethane" refers to the ethane feedstock that enters the cracking furnace together with the first vaporized and depressurized ethane. As a preferred embodiment, the "regenerated gas feedstock ethane" refers to the ethane cracking feedstock referred to in the gas cracking ethane cracking described in application number 201810812902.3.

[0042] In this invention, the content of unsaturated hydrocarbons such as ethylene and propylene in the recycled ethane gas is ≤2 mol%, preferably ≤0.5 mol%; the water content of the recycled ethane gas is ≤1 ppmmol, and it does not contain sulfur, oxygen or other impurities; the water content of the recycled propane gas is ≤1 ppmmol, the content of methane and butane is ≤1 mol%, and it does not contain sulfur, oxygen, olefins or other impurities.

[0043] According to the present invention, preferably, the method for obtaining the regenerated gas circulating ethane includes: dividing the ethane discharged from the bottom of the ethylene tower into two streams; one stream exchanges heat with the cracked gas in the first vaporizer, and after recovering the cold energy in the cold box, to obtain the first vaporized depressurized ethane; the other stream exchanges heat with the top gas of the de-ethane tower in the second vaporizer, and after recovering the cold energy in the cold box, to obtain the second vaporized depressurized ethane.

[0044] The vaporization pressure of the second vaporizer is 0.1-0.2 MPa higher than that of the first vaporizer (in this invention, the ethane discharged from the bottom of the ethylene tower is under high pressure. When used as regeneration gas and feed gas for the cracking furnace, it needs to be depressurized (the lower the pressure after depressurization, the better for vaporization and recovery of cold energy); the vaporization pressure of the first vaporizer meets the pressure requirements for steam cracking in the cracking furnace; the vaporization pressure of the second vaporizer is 0.1-0.2 MPa higher than that of the first vaporizer to meet the pressure requirements for steam cracking in the cracking furnace after being used as a regeneration medium for the dryer. Moreover, the heat exchange temperature difference between the ethane discharged from the bottom of the ethylene tower and the top gas of the de-ethanizer is large. Increasing its vaporization pressure by 0.1-0.2 MPa can still ensure a sufficient heat exchange temperature difference).

[0045] The second vaporized and depressurized ethane is used as the regenerated gas recycled ethane gas;

[0046] The first vaporized and depressurized ethane is used as feed gas for the cracking furnace.

[0047] According to the present invention, preferably, the method for obtaining the regenerated propane gas includes sequentially feeding liquid propane into a propane vaporizer and a propane superheater for treatment to obtain vaporized propane gas.

[0048] The vaporization pressure of the propane vaporizer is 0.8-0.9 MPaG;

[0049] A portion of the vaporized propane gas is used as the regenerated propane gas, and the remainder of the vaporized propane gas is used as feed gas for the cracking furnace.

[0050] According to the present invention, preferably, a portion of the regenerated gas feed is fed into the regenerated gas heater of the regenerated gas heat exchange unit for processing to obtain the hot regenerated gas;

[0051] The regenerated gas is sequentially fed into a quench water cooler, a filter, a coalescer, and a separation buffer tank for cooling and impurity removal to obtain the pyrolysis furnace feed gas, which is then sent to the pyrolysis furnace.

[0052] In this invention, the regenerated gas discharge is processed by a filter and a coalescer to remove desiccant powder entrained during the regeneration process and hydrocarbons such as green oil that may be entrained. The purified regenerated gas then enters a separation buffer tank, where droplets are removed before it is used as feed gas for the pyrolysis furnace. Because the cooling temperature of the purified regenerated gas entering the separation buffer tank is increased, the amount of separable free water decreases; therefore, the size of the separation buffer tank is also appropriately reduced.

[0053] According to the present invention, preferably, a portion of the regenerated gas feed is fed into the regenerated gas inlet / outlet heat exchanger of the regenerated gas heat exchange unit to exchange heat with the regenerated gas outlet, thereby obtaining heated regenerated gas feed and cooled regenerated gas outlet;

[0054] The heated regenerated gas feed is fed into the regenerated gas heater of the regenerated gas heat exchange unit for processing to obtain the heated regenerated gas;

[0055] The cooled regenerated gas is sequentially fed into a quench water cooler, a filter, a coalescer, and a separation buffer tank for cooling and impurity removal to obtain the pyrolysis furnace feed gas, which is then sent to the pyrolysis furnace.

[0056] In this invention, the regenerated gas discharge adopts a scheme of regenerated gas inlet / outlet heat exchanger and quench water cooler connected in series, instead of using a circulating cooling water cooler. This not only recovers the waste heat of regeneration but also saves cooling water consumption, which is conducive to energy conservation and consumption reduction.

[0057] According to the present invention, preferably, the operating pressure of the dryer user is 0.7-1.1 MPaG.

[0058] According to the present invention, preferably, the operating pressure of the separation buffer tank is 0.6 MPaG-1.0 MPaG and the operating temperature is 90℃-150℃, so as to meet the requirements of sending it to the pyrolysis furnace for high-temperature steam pyrolysis.

[0059] According to the present invention, preferably, the gas feedstock pyrolysis unit where the pyrolysis furnace is located produces high-pressure hydrogen-rich tail gas, which is then directly used as the feedstock gas for the PSA hydrogen enrichment unit.

[0060] The beneficial effects of the technical solution of the present invention are as follows:

[0061] This invention does not use methane / hydrogen tail gas or low-pressure hydrogen-rich tail gas produced by conventional cracking units. Instead, it uses recycled ethane, cracking feedstock ethane gas, and cracking feedstock propane gas produced by the cracking unit, preferably recycled ethane, as regeneration gas. This allows the hydrogen-rich tail gas produced by the cracking unit to maintain a high pressure, directly serving as feedstock gas for the PSA hydrogen enrichment unit. This reduces PSA compressor power consumption, increases hydrogen recovery rate, produces more hydrogen byproducts, and reduces overall unit energy consumption.

[0062] On the other hand, the regenerated gas used in this invention is recycled ethane, ethane gas (crack feedstock), and propane gas (crack feedstock) produced by the pyrolysis unit. These gas sources themselves need to be heated and saturated with water or mixed with dilution steam before being sent to the pyrolysis furnace for pyrolysis. When used as regenerated gas, the higher temperature and water content do not affect its feeding into the pyrolysis furnace for pyrolysis. Therefore, it is not necessary to cool it to room temperature and fully separate the water, avoiding the equipment investment and energy waste required for cooling the regenerated gas and separating water in traditional regeneration schemes, and achieving the goal of energy saving and cost reduction.

[0063] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0064] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0065] Figure 1 A schematic diagram of a dryer regeneration system for gaseous feedstock pyrolysis provided in Embodiment 1 of the present invention is shown.

[0066] Figure 2 A schematic diagram of a dryer regeneration system for gaseous feedstock pyrolysis provided in Embodiment 2 of the present invention is shown.

[0067] The annotations in the attached figures are explained as follows:

[0068] 1. Gas pyrolysis feedstock pipeline; 2. Regeneration gas heat exchange unit; 3. Distribution unit; 4. Dryer user.

[0069] 5. Regenerated gas processing unit; 6. Hot regenerated gas pipeline; 7. Cold regenerated gas pipeline; 8. Regenerated gas inlet pipeline;

[0070] 9. Regenerated gas outlet pipeline, 10. Cracking furnace, 11. Ethylene tower, 12. First vaporizer, 13. Second vaporizer.

[0071] 14 Cold box, 15 First pressure regulating valve, 16 Second pressure regulating valve, 17 Liquid propane feed line, 18 Propane vaporizer, 19 Propane superheater, 20 Propane gas line;

[0072] 2-1 Regenerated gas heater, 2-2 Quenching water cooler, 2-3 Regenerated gas inlet / outlet heat exchanger;

[0073] 3-1 Regeneration gas flow and temperature control subunit; 3-2 Sequential control subunit;

[0074] 5-1 Filter, 5-2 Coalescer, 5-3 Separation buffer tank. Detailed Implementation

[0075] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0076] Example 1

[0077] This embodiment provides a dryer regeneration system for gaseous feedstock pyrolysis, such as... Figure 1 As shown, the system includes a gas pyrolysis feedstock pipeline 1, a regenerated gas heat exchange unit 2, a distribution unit 3, a dryer user 4, and a regenerated gas treatment unit 5;

[0078] The regenerated gas heat exchange unit 2 is used to heat part of the regenerated gas entering the dryer user 4 and cool the regenerated gas discharged from the dryer user 4; the regenerated gas heat exchange unit 2 includes: a regenerated gas heater 2-1, a quench water cooler 2-2, and a regenerated gas inlet / outlet heat exchanger 2-3; the regenerated gas heater 2-1 is a steam heater.

[0079] The regenerated gas treatment unit 5 includes: an impurity removal subsystem and a separation buffer tank 5-3; the impurity removal subsystem includes a filter 5-1 and a coalescer 5-2.

[0080] The distribution unit 3 includes: a regeneration gas flow and temperature control subunit 3-1 and a sequence control subunit 3-2;

[0081] The outlet of the gas cracking feedstock pipeline 1 is divided into two paths. One path is connected to the hot regenerated gas pipeline 6 through the cold source inlet and outlet of the regenerated gas inlet / outlet heat exchanger 2-3 and the regenerated gas heater 2-1 in sequence. The other path is connected to the cold regenerated gas pipeline 7.

[0082] The hot regenerated gas pipeline 6 and the cold regenerated gas pipeline 7 merge into the regenerated gas inlet pipeline 8 of the dryer user and are connected to the dryer user 4.

[0083] The regenerated gas flow and temperature control subunit 3-1 is electrically connected to the hot regenerated gas pipeline 6 and the cold regenerated gas pipeline 7 respectively, and is used to control the ratio of hot regenerated gas and cold regenerated gas entering the dryer user 4.

[0084] The dryer user 4 is also equipped with a regenerated gas outlet pipeline 9; the sequential control subunit 3-2 is electrically connected to the regenerated gas inlet pipeline 8 and the regenerated gas outlet pipeline 9 of the dryer user 4 respectively, and is used to control the inlet and outlet of the regenerated gas.

[0085] The regenerated gas outlet pipeline 9 of the dryer user 4 is connected in sequence to the heat source inlet and outlet of the regenerated gas inlet / outlet heat exchanger 2-3, the quench water cooler 2-2, the filter 5-1 and the coalescer 5-2; the outlet of the coalescer 5-2 is connected to the pyrolysis furnace 10 through the separation buffer tank 5-3.

[0086] The gas cracking feedstock line 1 is a circulating ethane cracking feedstock line;

[0087] The system also includes an ethylene tower 11, a first vaporizer 12, a second vaporizer 13, and a cold box 14;

[0088] The cold box 14 is equipped with a pyrolysis inlet, a pyrolysis outlet, a regeneration gas inlet, and a regeneration gas outlet.

[0089] The bottom of the ethylene tower 11 is connected to an ethane discharge pipeline; the ethane discharge pipeline is divided into two paths, one of which is connected in sequence to the cold source inlet and outlet of the first pressure regulating valve 15, the cold source inlet and outlet of the first vaporizer 12 and the cracking inlet, and the other path is connected to the cold source inlet and outlet of the second vaporizer 13 and the regeneration gas inlet.

[0090] The cold box 4 is connected to the pyrolysis outlet of the pyrolysis furnace 10;

[0091] The regeneration gas outlet of the cold box 4 is connected to the inlet of the gas cracking feedstock pipeline 1.

[0092] The cracking furnace 10, ethylene tower 11, and cold box 14 are the cracking furnace, ethylene tower, and cold box in the ethane feedstock cracking to ethylene production unit. The corresponding ethane feedstock cracking to ethylene production process adopts a pre-ethane removal and pre-hydrogenation separation process, utilizing cryogenic separation technology with high ethylene and hydrogen recovery rates. The methane / hydrogen tail gas produced by the process is very small, and the flow rate as dryer regeneration gas is too low to meet regeneration requirements. The process produces hydrogen-rich gas with a pressure of 2.8 MPaG. Using this 2.8 MPaG hydrogen-rich gas as dryer regeneration gas requires depressurization to below 0.7 MPaG. After regeneration, when sending it to the PSA unit for hydrogen purification, it needs to be pressurized to above 2.0 MPaG, with a pressurization power consumption of approximately 5300 kW, increasing annual electricity costs by approximately 45 million yuan.

[0093] Therefore, this embodiment also provides a method for regenerating a dryer in gaseous feedstock pyrolysis, the method employing the system described above. This allows the hydrogen-rich tail gas produced by the pyrolysis unit to maintain a high pressure, directly serving as the feed gas for the PSA hydrogen enrichment unit, reducing PSA compressor power consumption, increasing hydrogen recovery rate, producing more hydrogen byproducts, and reducing overall unit energy consumption.

[0094] The method includes the following steps:

[0095] S1: The regeneration gas feed is regeneration gas recycled ethane gas. The method for obtaining the regeneration gas recycled ethane gas includes: dividing the ethane discharged from the bottom of the ethylene tower 11 into two streams. One stream exchanges heat with the cracked gas in the first vaporizer 12 and recovers the cold energy in the cold box 14 to obtain the first vaporized depressurized ethane. The other stream exchanges heat with the top gas of the de-ethane tower in the second vaporizer 13 and recovers the cold energy in the cold box 14 to obtain the second vaporized depressurized ethane.

[0096] The vaporization pressure of the second vaporizer 12 is 0.85 MPaG, which is 0.15 MPaG higher than that of the first vaporizer 12.

[0097] The second vaporized and depressurized ethane is used as the regenerated gas recycled ethane gas;

[0098] The first vaporized and depressurized ethane is used as feed gas for the cracking furnace;

[0099] A portion of the regenerated gas feed is fed into the regenerated gas inlet / outlet heat exchanger 2-3 of the regenerated gas heat exchange unit to exchange heat with the regenerated gas outlet discharged from the dryer user 4, thereby obtaining heated regenerated gas feed; the heated regenerated gas feed is then fed into the regenerated gas heater 2-1 of the regenerated gas heat exchange unit for processing, thereby obtaining the hot regenerated gas.

[0100] The remaining portion of the regenerated gas feed is used as cold regenerated gas;

[0101] S2: The hot regenerated gas and the cold regenerated gas are combined and sent to the dryer user 4 through the sequence control subunit 3-2; and before the combination, the ratio of hot regenerated gas and cold regenerated gas entering the dryer user 4 is controlled by the regenerated gas flow and temperature control subunit 3-1.

[0102] S3: After the dryer user 4 is regenerated, the regenerated gas discharged from the dryer user 4 is sequentially sent to the regenerated gas inlet / outlet heat exchanger 2-3, quench water cooler 2-2, filter 5-1, coalescer 5-2 and separation buffer tank 5-3 through the sequential control subunit 3-2 for cooling and impurity removal, so as to obtain the cracking furnace feed gas and send it to the cracking furnace 10.

[0103] The operating pressure for the dryer user is 0.82 MPaG;

[0104] The operating pressure of the separation buffer tank is 0.70 MPaG, and the operating temperature is 90℃.

[0105] Example 2

[0106] This embodiment provides a dryer regeneration system for gaseous feedstock pyrolysis, such as... Figure 2 As shown, the only difference between this embodiment and Embodiment 1 is that:

[0107] The regenerated gas heater 2-1 is an electric heater;

[0108] The regenerated gas outlet pipeline 9 of the dryer user 4 is connected in sequence to the heat source inlet and outlet of the regenerated gas inlet / outlet heat exchanger 2-3, the quench water cooler 2-2, and the coalescer 5-2; the outlet of the coalescer 5-2 is connected to the pyrolysis furnace 10 through the separation buffer tank 5-3.

[0109] The gas cracking feedstock pipeline 1 is a propane cracking feedstock pipeline;

[0110] The system also includes a liquid propane feed line 17, a propane vaporizer 18, a propane superheater 19, and a propane gas line 20.

[0111] The liquid propane feed line 17 is sequentially connected to the propane vaporizer 18, the propane superheater 19, and the propane gas line 20; the outlet of the propane gas line 20 is divided into two paths, one of which is connected to the cracking furnace 10 through the second pressure regulating valve 16, and the other is connected to the inlet of the gas cracking feedstock line 1.

[0112] The regenerated gas feed is regenerated propane gas; the method for obtaining the regenerated propane gas includes sequentially feeding liquid propane to a propane vaporizer 18 and a propane superheater 19 for processing to obtain vaporized propane gas.

[0113] The vaporization pressure of the propane vaporizer 18 is 0.85 MPaG;

[0114] The cold source for the propane vaporizer 18 and the propane superheater 19 is quench water.

[0115] A portion of the vaporized propane gas is used as the regenerated propane gas, and the remainder of the vaporized propane gas is used as feed gas for the cracking furnace.

[0116] The purity of the liquid propane reaches 98 mol%, and the remaining components are 1 mol each of methane and butane. It contains no water, olefins, or other impurities, and the flow rate is sufficient for use as regeneration gas for the dryer.

[0117] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A dryer regeneration system for pyrolysis of gaseous feedstock, characterized in that, The system includes a gas pyrolysis feedstock pipeline, a regenerated gas heat exchange unit, a distribution unit, a dryer user, and a regenerated gas treatment unit; The regenerated gas heat exchange unit is used to heat part of the regenerated gas entering the dryer user and to recover and cool the heat of the regenerated gas discharged from the dryer user. The distribution unit includes: a regeneration gas flow and temperature control subunit and a sequence control subunit; The outlet of the gas cracking feedstock pipeline is divided into two paths, one of which is connected to the hot regenerated gas pipeline through the regenerated gas heat exchange unit, and the other is connected to the cold regenerated gas pipeline. The hot regenerated gas pipeline and the cold regenerated gas pipeline merge into the regenerated gas inlet pipeline of the dryer user and are connected to the dryer user. The regenerated gas flow and temperature control subunit is electrically connected to the hot regenerated gas pipeline and the cold regenerated gas pipeline, respectively, and is used to control the proportion of hot regenerated gas and cold regenerated gas entering the dryer user. The dryer user is also provided with a regenerated gas outlet pipeline; the sequential control subunit is electrically connected to the regenerated gas inlet pipeline and the regenerated gas outlet pipeline of the dryer user respectively, and is used to control the inlet and outlet of the regenerated gas. The regenerated gas outlet pipeline of the dryer user is connected to the regenerated gas treatment unit through the regenerated gas heat exchange unit.

2. The dryer regeneration system for gaseous feedstock pyrolysis according to claim 1, wherein, The regenerated gas heat exchange unit includes: a regenerated gas heater and a quench water cooler, and optionally also includes a regenerated gas inlet / outlet heat exchanger; One of the outlets of the gas pyrolysis feedstock pipeline is connected to the hot regenerated gas pipeline through the regenerated gas heater; optionally, one of the outlets of the gas pyrolysis feedstock pipeline is connected to the hot regenerated gas pipeline in sequence through the cold source inlet and outlet of the regenerated gas inlet / outlet heat exchanger and the regenerated gas heater. The regenerated gas outlet pipeline of the dryer user is connected to the regenerated gas treatment unit through the quench water cooler; optionally, the regenerated gas outlet pipeline of the dryer user is connected to the regenerated gas treatment unit in sequence through the heat source inlet and outlet of the regenerated gas inlet / outlet heat exchanger and the quench water cooler. Preferably, the regenerated gas heater is a steam heater and / or an electric heater.

3. The dryer regeneration system for gaseous feedstock pyrolysis according to claim 1, wherein, The regenerated gas treatment unit includes: an impurity removal subsystem, and optionally also includes a separation buffer tank; The impurity removal subsystem includes filters and / or coalescers; Preferably, the regenerated gas outlet pipeline of the dryer user is connected to the filter, coalescer, and pyrolysis furnace in sequence through the regenerated gas heat exchange unit; optionally, the outlet of the coalescer is connected to the pyrolysis furnace through the separation buffer tank.

4. The dryer regeneration system for gaseous feedstock pyrolysis according to claim 1, wherein, The gas cracking feedstock pipeline is a circulating ethane cracking feedstock pipeline; The system also includes an ethylene tower, a first vaporizer, a second vaporizer, and a cold box; The cold box is equipped with a pyrolysis inlet, a pyrolysis outlet, a regeneration gas inlet, and a regeneration gas outlet; The bottom of the ethylene tower is connected to an ethane discharge pipeline; the ethane discharge pipeline is divided into two lines, one of which is connected in sequence to the pressure regulating valve, the cold source inlet and outlet of the first vaporizer and the cracking inlet, and the other is connected to the cold source inlet and outlet of the second vaporizer and the regeneration gas inlet. The cold box's pyrolysis outlet is connected to the pyrolysis furnace; The regenerated gas outlet of the cold box is connected to the inlet of the gas pyrolysis feedstock pipeline.

5. The dryer regeneration system for gaseous feedstock pyrolysis according to claim 1, wherein, The gas cracking feedstock pipeline is a propane cracking feedstock pipeline; The system also includes a liquid propane feed line, a propane vaporizer, a propane superheater, and a propane gas line; The liquid propane feed line is sequentially connected to the propane vaporizer, propane superheater, and propane gas line; the outlet of the propane gas line is divided into two paths, one of which is connected to the cracking furnace through a pressure regulating valve, and the other is connected to the inlet of the gas cracking feedstock line.

6. A method for regenerating a dryer for pyrolysis of gaseous feedstock, characterized in that, The method employs the system described in any one of claims 1-5 and includes the following steps: S1: A portion of the regenerated gas feed is fed into the regenerated gas heat exchange unit for heating to obtain hot regenerated gas; the remaining portion of the regenerated gas feed is used as cold regenerated gas. S2: The hot regenerated gas and cold regenerated gas are combined and sent to the dryer user through the sequence control subunit; and before the combination, the ratio of hot regenerated gas and cold regenerated gas entering the dryer user is controlled by the regenerated gas flow and temperature control subunit. S3: After the dryer user performs regeneration, the regeneration gas discharged by the dryer user is sequentially sent to the regeneration gas heat exchange unit and the regeneration gas treatment unit for processing through the sequence control subunit.

7. The method for regenerating a dryer for pyrolysis of gaseous feedstock according to claim 6, wherein, The regenerated gas feed is at least one of regenerated gas recycled ethane, regenerated gas feedstock ethane, and regenerated gas propane. in, The method for obtaining the regenerated gas circulating ethane includes: dividing the ethane discharged from the bottom of the ethylene tower into two streams; one stream exchanges heat with the cracked gas in the first vaporizer, and after recovering the cold energy in the cold box, to obtain the first vaporized and depressurized ethane; the other stream exchanges heat with the top gas of the de-ethane tower in the second vaporizer, and after recovering the cold energy in the cold box, to obtain the second vaporized and depressurized ethane. The vaporization pressure of the second vaporizer is 0.1-0.2 MPaG higher than that of the first vaporizer; The second vaporized and depressurized ethane is used as the regenerated gas recycled ethane gas; The first vaporized and depressurized ethane is used as feed gas for the cracking furnace; The method for obtaining the regenerated propane gas includes sequentially feeding liquid propane into a propane vaporizer and a propane superheater for treatment to obtain vaporized propane gas. The vaporization pressure of the propane vaporizer is 0.8-0.9 MPaG; A portion of the vaporized propane gas is used as the regenerated propane gas, and the remainder of the vaporized propane gas is used as feed gas for the cracking furnace.

8. The method for regenerating a dryer for gaseous feedstock pyrolysis according to claim 6, wherein, A portion of the regenerated gas feed is fed into the regenerated gas inlet / outlet heat exchanger of the regenerated gas heat exchange unit to exchange heat with the regenerated gas outlet, thereby obtaining heated regenerated gas feed and cooled regenerated gas outlet; The heated regenerated gas feed is fed into the regenerated gas heater of the regenerated gas heat exchange unit for processing to obtain the heated regenerated gas; The cooled regenerated gas is sequentially fed into a quench water cooler, a filter, a coalescer, and a separation buffer tank for cooling and impurity removal to obtain the pyrolysis furnace feed gas, which is then sent to the pyrolysis furnace.

9. The method for regenerating a dryer for pyrolysis of gaseous feedstock according to claim 6, wherein, The operating pressure for the dryer user is 0.7-1.1 MPaG; The operating pressure of the separation buffer tank is 0.6-1.0 MPaG, and the operating temperature is 90℃-150℃.

10. The method for regenerating a dryer for pyrolysis of gaseous feedstock according to claim 6, wherein, The gas feedstock pyrolysis unit where the pyrolysis furnace is located produces high-pressure hydrogen-rich tail gas, which is then used directly as the feedstock gas for the PSA hydrogen enrichment unit.

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