Method and system for regenerating desulfurization adsorption bed of ethylene unit

Abstract

The invention relates to a method and a system for regenerating a desulfurization adsorption bed of an ethylene unit, the method is characterized in that preheated vaporized ethane preheated by a cold box is divided into two streams, one stream is used as regenerated gas to perform regeneration treatment on the desulfurization adsorption bed and returns to a cracking furnace of the ethylene unit to participate in cracking reaction after being cooled; the other part is used as diluted temperature-adjusted ethane to return to the cracking furnace of the ethylene device to participate in cracking reaction, water is not introduced into the circulating ethane in the whole process, and wet hydrogen sulfide is not formed, so that an alkali washing system additionally arranged for treating the wet hydrogen sulfide can be reduced, the occupied area and equipment investment of the system are reduced, and the competitiveness of the ethylene device is further improved. Moreover, according to the system disclosed by the invention, the methane hydrogen generated by the ethylene device is directly used as a fuel to return to the combustor of the cracking furnace after heat exchange, and sulfides are not introduced, so that the problem that the sulfides in the discharged flue gas after combustion of the methane hydrogen exceed the limit can be avoided, and the environment-friendly up-to-standard emission of the flue gas is realized.

Description

Technical Field

[0001] This disclosure relates to the petrochemical field, and more specifically, to a method and system for regenerating a desulfurization adsorption bed in an ethylene plant. Background Technology

[0002] An ethylene production unit employs a separation process prior to propane removal and hydrogenation. In this unit, due to a change in feedstock, high-sulfur crude oil was used as the cracking feedstock, resulting in a sulfur content in the cracked gas far exceeding the design value. The C2 hydrogenation system in the ethylene unit is used to remove acetylene components from C3 and lower grade cracked gases. Hydrogen from the cracked gas is used to hydrogenate the acetylene under the action of a catalyst to ensure the product specifications of the polymer-grade ethylene. The C2 hydrogenation catalyst has certain requirements regarding impurity content, requiring the total sulfur content to not exceed 1 ppmw. Therefore, to avoid poisoning of the C2 hydrogenation catalyst and to ensure the qualification of the polymer-grade ethylene / propylene product, a desulfurization adsorption bed must be added before the C2 hydrogenation system to remove organic and inorganic sulfur from the C3 and lower grade cracked gases. When the adsorbent in the desulfurization adsorption bed reaches saturation, desulfurization can no longer be achieved. At this point, high-temperature gas is required to regenerate the desulfurization adsorption bed.

[0003] Existing desulfurization adsorption beds often use methane hydrogen produced by the ethylene plant as regeneration gas during regeneration. However, using methane hydrogen produced by the ethylene plant increases the number of equipment, investment, and floor space required. Furthermore, the sulfide content in the flue gas from the cracking furnace exceeds limits, and the presence of a wet hydrogen sulfide environment poses certain safety risks to the ethylene plant. Summary of the Invention The purpose of this disclosure is to provide a method and system for regenerating a desulfurization adsorption bed in an ethylene plant, in order to solve the problems of large footprint and investment, excessive sulfides in exhaust gas, and the impact of wet hydrogen sulfide on the ethylene plant in the prior art.

[0004] To achieve the above objectives, the first aspect of this disclosure provides a method for regenerating a desulfurization adsorption bed in an ethylene plant. The method includes: sequentially vaporizing and preheating circulating ethane produced by the ethylene plant to obtain preheated vaporized ethane; dividing the preheated vaporized ethane into first preheated vaporized ethane and second preheated vaporized ethane; heating the first preheated vaporized ethane and using it as regeneration gas in the desulfurization adsorption bed for regeneration treatment; cooling the obtained regenerated ethane in a circulating ethane cooler and returning it, along with the second preheated vaporized ethane, to the cracking furnace of the ethylene plant; and cooling the methane hydrogen produced by the ethylene plant and returning it to the burner of the cracking furnace.

[0005] Optionally, the ethylene content in the recycled ethane is less than 0.5 mol%.

[0006] Optionally, the flow rate ratio of the first preheated vaporized ethane to the preheated vaporized ethane is (0.2~0.5):1.

[0007] Optionally, the method further includes adjusting the pressure drop of the pressure reducing valve before the circulating ethane is vaporized, so as to increase the pressure of the circulating ethane by P. 压降 The P 压降 The value is 80~150 kPaG.

[0008] Optionally, the method further includes vaporizing the circulating ethane in a circulating ethane vaporizer to obtain vaporized ethane at a temperature of -38 to -34°C; and preheating the vaporized ethane in a cold box to obtain preheated vaporized ethane at a temperature of 25 to 35°C.

[0009] Optionally, the method further includes cooling the regenerated ethane in a circulating ethane cooler to obtain raw material ethane at a temperature of 35-40°C; heating the second preheated vaporized ethane in a circulating ethane superheater to obtain diluted temperature-regulating ethane at a temperature of 35-40°C; and mixing the raw material ethane with the diluted temperature-regulating ethane before feeding it into the cracking furnace.

[0010] Optionally, the ethylene unit further includes a drying unit; the method further includes, before the methane hydrogen is returned to the burner of the cracking furnace, allowing the cooled methane hydrogen to enter the drying unit for regeneration treatment, and allowing the resulting methane hydrogen to enter the burner of the cracking furnace as fuel.

[0011] The second aspect of this disclosure provides a system for regenerating a desulfurization adsorption bed in an ethylene plant using the method described in the first aspect. The system includes a circulating ethane vaporizer, a cold box, a desulfurization adsorption bed, and a circulating ethane cooler. The circulating ethane vaporizer includes a circulating ethane inlet, a vaporized ethane outlet, a cracked gas inlet, and a heat-exchange cracked gas outlet; The cold box includes a vaporized ethane inlet, a preheated vaporized ethane outlet, a methane hydrogen inlet, and a methane hydrogen outlet; the preheated vaporized ethane outlet pipeline includes a regeneration gas branch line and a dilution and temperature control branch line. The desulfurization adsorption bed includes a regenerated gas inlet and a regenerated ethane outlet; The circulating ethane cooler includes a regenerated ethane inlet and a cooled ethane outlet; The circulating ethane inlet of the circulating ethane vaporizer is connected to the circulating ethane outlet of the ethylene unit; the vaporized ethane outlet of the circulating ethane vaporizer is connected to the vaporized ethane inlet of the cold box; the preheated vaporized ethane outlet of the cold box is connected to the regeneration gas inlet of the desulfurization adsorption bed via the regeneration gas branch line; the regeneration ethane outlet of the desulfurization adsorption bed is connected to the regeneration ethane inlet of the circulating ethane cooler; the preheated vaporized ethane outlet of the cold box is connected to the cracking furnace inlet of the ethylene unit via the dilution and temperature control branch line; the cooled ethane outlet of the circulating ethane cooler is connected to the cracking furnace inlet of the ethylene unit; the methane hydrogen inlet of the cold box is connected to the methane hydrogen outlet of the ethylene unit; the methane hydrogen outlet of the cold box is connected to the burner inlet of the cracking furnace.

[0012] Optionally, a circulating ethane superheater is provided in the dilution and temperature control branch line for heating the preheated vaporized ethane flowing through the dilution and temperature control branch line.

[0013] Optionally, the ethylene unit further includes a drying unit; the drying unit includes a regenerated gas inlet and a water-containing regenerated gas outlet; the methane hydrogen outlet of the cold box is connected to the regenerated gas inlet of the drying unit; and the water-containing regenerated gas outlet of the drying unit is connected to the burner inlet of the cracking furnace.

[0014] Through the above technical solution, this disclosure divides the preheated vaporized ethane, preheated in a cold box, into two streams. One stream serves as regeneration gas to regenerate the desulfurization adsorption bed and, after cooling, returns to the pyrolysis furnace of the ethylene unit to participate in the pyrolysis reaction. The other stream serves as diluted and temperature-controlled ethane, also returning to the pyrolysis furnace of the ethylene unit to participate in the pyrolysis reaction. Since no moisture is introduced into the circulating ethane throughout the process, wet hydrogen sulfide is not formed. This reduces the need for an additional alkaline scrubbing system to handle wet hydrogen sulfide, thereby reducing the system's footprint and equipment investment, and ultimately enhancing the competitiveness of the ethylene unit. Furthermore, the system of this disclosure allows the methane hydrogen produced by the ethylene unit to be directly returned to the burner of the pyrolysis furnace as fuel after heat exchange, without introducing sulfides. This avoids the problem of excessive sulfides in the exhaust gas after the combustion of methane hydrogen, achieving environmentally compliant emissions.

[0015] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of a system for regenerating a desulfurization adsorption bed in an ethylene plant.

[0017] Figure 2This is a schematic diagram of the system used for the regeneration of the desulfurization adsorption bed in an ethylene plant, as shown in Comparative Example 1 of this disclosure.

[0018] Explanation of reference numerals in the attached figures 1. Pressure reducing valve; 2. Circulating ethane vaporizer; 3. Cold box; 4. Desulfurization adsorption bed; 5. Circulating ethane superheater; 6. Circulating ethane cooler; 7. Electric heater; 8. C2 hydrogenation unit; 9. Drying unit; 10. Methane hydrogen regenerator cooler; a. Circulating ethane; b. Vaporized ethane; c. Methane; d. Hydrogen; e. Tail gas; f. Preheated vaporized ethane; g. Regenerated gas; h. Regenerated ethane; i. Diluted and temperature-controlled ethane; m. Raw material ethane; j. Cracking furnace feed; k. Cracking furnace burner feed; l. Cracking gas. Detailed Implementation

[0019] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0020] In this disclosure, unless otherwise stated, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise expressly and specifically defined.

[0021] The first aspect of this disclosure provides a method for regenerating a desulfurization adsorption bed in an ethylene plant. The method includes: sequentially vaporizing and preheating circulating ethane produced by the ethylene plant to obtain preheated vaporized ethane; dividing the preheated vaporized ethane into first preheated vaporized ethane and second preheated vaporized ethane; heating the first preheated vaporized ethane and using it as regeneration gas in the desulfurization adsorption bed for regeneration treatment; cooling the obtained regenerated ethane in a circulating ethane cooler and returning it, along with the second preheated vaporized ethane, to the cracking furnace of the ethylene plant; and cooling the methane hydrogen produced by the ethylene plant and returning it to the burner of the cracking furnace.

[0022] Through the above technical solution, this disclosure divides the preheated vaporized ethane, preheated in a cold box, into two streams. One stream serves as regeneration gas to regenerate the desulfurization adsorption bed and, after cooling, returns to the pyrolysis furnace of the ethylene unit to participate in the pyrolysis reaction. The other stream serves as diluted and temperature-controlled ethane, also returning to the pyrolysis furnace of the ethylene unit to participate in the pyrolysis reaction. Since no moisture is introduced into the circulating ethane throughout the process, wet hydrogen sulfide is not formed. This reduces the need for an additional alkaline scrubbing system to handle wet hydrogen sulfide, thereby reducing the system's footprint and equipment investment, and ultimately enhancing the competitiveness of the ethylene unit. Furthermore, the system of this disclosure allows the methane hydrogen produced by the ethylene unit to be directly returned to the burner of the pyrolysis furnace as fuel after heat exchange, without introducing sulfides. This avoids the problem of excessive sulfides in the exhaust gas after the combustion of methane hydrogen, achieving environmentally compliant emissions.

[0023] In one embodiment, the ethylene unit includes a desulfurization adsorption bed and a C2 hydrogenation unit, with the adsorption bed positioned upstream of the C2 hydrogenation unit. In this embodiment, the C2 hydrogenation unit removes acetylene components from C3 and lower-grade cracked gases. Hydrogen from the cracked gas is used to hydrogenate the acetylene under the action of a catalyst to ensure the product specifications of the polymerization-grade ethylene. Since the C2 hydrogenation catalyst has certain requirements regarding impurity content, requiring the total sulfur content to not exceed 1 ppmw, a desulfurization adsorption bed must be added before the C2 hydrogenation system to remove organic and inorganic sulfur from the C3 and lower-grade cracked gases, in order to avoid catalyst poisoning and ensure the qualification of the polymerization-grade ethylene / propylene product.

[0024] In a preferred embodiment, in order to ensure good removal of sulfur from the cracked gas, there are three desulfurization adsorption beds, two of which are in normal use and one is on standby, and they are regenerated every 72 hours.

[0025] In one embodiment, the ethylene unit further includes a pyrolysis gas phase dryer, a pyrolysis gas liquid phase dryer, and a hydrogen dryer to remove moisture from the corresponding materials. These dryers are configured with one in operation and one on standby. When these dryers reach saturation in terms of moisture adsorption, the standby unit will be switched on.

[0026] In one embodiment, the cracked gas generated by the ethylene unit is desulfurized by a desulfurization adsorption bed and then enters the C2 hydrogenation unit for hydrogenation treatment. After hydrogenation, the cracked gas is cooled by passing through a cold box and a circulating ethane vaporizer before entering the subsequent cryogenic unit.

[0027] In one embodiment, the recycled ethane used in this disclosure is recycled ethane produced by an ethylene plant, wherein the ethylene content in the recycled ethane is less than 0.5 mol%, preferably less than 0.25 mol%. In this embodiment, the recycled ethane contains a small amount of ethylene. When the ethylene content is high, during the regeneration process of the recycled ethane at high temperatures, the ethylene may polymerize or coke on the catalyst surface, affecting the service life of the desulfurization catalyst.

[0028] In one embodiment, the circulating ethane vaporizer used in this disclosure is a conventional choice in the art, and this application does not make any special requirements. For example, the circulating ethane vaporizer can be a heat exchanger.

[0029] In one embodiment, the method further includes introducing the recycled ethane into a recycled ethane vaporizer to exchange heat with the cracked gas, thereby vaporizing a portion of the recycled ethane into gaseous ethane, resulting in vaporized ethane and cooled cracked gas. In this embodiment, the recycled ethane recovers heat from the cracked gas, thereby lowering the temperature of the cracked gas from -15°C to -20°C to -25°C to -30°C, and raising the temperature of the recycled ethane to -38°C to -33°C.

[0030] In one embodiment, the vaporized ethane is preheated in a cold box to obtain preheated vaporized ethane at a temperature of 25~35°C.

[0031] In one embodiment, the method further includes adjusting the pressure drop of the pressure reducing valve before the circulating ethane vaporizes, so as to increase the pressure of the circulating ethane by P. 压降 The P 压降 The pressure increase of circulating ethane is 80~150 kPaG. 压降 It needs to be set according to the pressure drop of the desulfurization adsorption bed.

[0032] In this embodiment, since the desulfurization adsorption bed has a certain pressure drop, and the cracking furnace also has a certain pressure requirement for the circulating ethane, the vaporization pressure of the circulating ethane needs to be adjusted according to the actual pressure drop. This will also cause changes in the vaporization temperature of the circulating ethane, affecting the heat transfer temperature difference and heat exchange area of ​​the circulating ethane vaporizer. Calculations based on actual conditions show that the total pressure drop of the desulfurization adsorption bed, regeneration gas pipeline, valves, etc., is approximately 90-120 kPa. Circulating ethane from the bottom of the ethylene distillation column is pumped to the circulating ethane vaporizer system. The pressure upstream of the pressure reducing valve is approximately 900-1000 kPaG. Simulation calculations for the circulating ethane vaporizer show that its vaporization pressure is increased, raising the pressure downstream of the pressure reducing valve from the current 700-750 kPaG to 800-850 kPaG. The heat load of the circulating ethane vaporizer increases by approximately 0.1-0.3 MW, and the heat exchanger temperature decreases by approximately 1-2°C. Increasing the pressure of the circulating ethane by 80-150 kPaG allows for complete vaporization in the vaporizer, although the vaporization temperature increases by approximately 3-4°C. Simultaneously, the temperature of the cracked gas on the other side of the vaporizer increases by about 0.01-0.1°C, having minimal impact on the cracked gas temperature on the process side. This means it will not cause fluctuations or affect subsequent cryogenic processes. Although the heat exchange temperature of the circulating ethane vaporizer decreases, calculations show that the heat exchange area is sufficient. Furthermore, the temperature of the circulating ethane after reheating in the cold box remains at 25-35°C, consistent with the original design value.

[0033] In one embodiment, the cold box used in this disclosure is a conventional choice in the art, and this application does not make any special requirements. For example, the cold box is a heat exchanger.

[0034] In a preferred embodiment, the heat source of the cold box can be one or more of methane, hydrogen, recycled ethane and cracked gas produced by the ethylene plant, or it can be an external heat source, such as hot water.

[0035] In one embodiment, the flow rate ratio of the first preheated vaporized ethane to the preheated vaporized ethane is (0.2~0.5):1. In this embodiment, the circulating ethane in the device comes from the bottom of the ethylene distillation column, with a total flow rate of approximately 32,000 kg / h. When the cracked gas desulfurization adsorption bed is regenerated using circulating ethane, the consumption is approximately 10,000 kg / h. Therefore, the flow rate of circulating ethane can fully meet the regeneration gas consumption requirements of the cracked gas desulfurization adsorption bed.

[0036] In one embodiment, the regenerated gas is heated to the regeneration temperature by a heating device and then fed into a desulfurization adsorption bed for regeneration treatment to obtain the regenerated ethane. The regeneration temperature is 280-300°C.

[0037] In one embodiment, the heating device used in this disclosure is a conventional choice in the art, and this application does not make any special requirements. For example, the heating device can be an electric heater or a heat exchanger.

[0038] In one embodiment, the method further includes cooling the regenerated ethane using a circulating ethane cooler to obtain raw material ethane at a temperature of 35-40°C; and heating the second preheated vaporized ethane using a circulating ethane superheater to obtain diluted temperature-regulating ethane at a temperature of 35-40°C.

[0039] In one embodiment, the total sulfur content in the regenerated ethane is 0.05~0.06% by weight.

[0040] In this embodiment, the regenerated ethane contains sulfur-containing compounds such as hydrogen sulfide, carbonyl sulfide, and carbon disulfide. It then enters the cracking furnace for cracking, where all the sulfur components are converted into hydrogen sulfide. This hydrogen sulfide then follows the cracked gas into the separation unit at the furnace outlet, where it is absorbed in the alkaline scrubbing tower. Although the hydrogen sulfide content in the cracked gas increases, the increase is very limited, only 5.0~6.0 kg / h. The alkaline scrubbing tower in the ethylene unit's separation unit can fully handle this increase in hydrogen sulfide without causing additional impact on the existing alkaline scrubbing tower and alkali circulation system. This reduces or even eliminates the amount of sulfur injected into the ethane cracking furnace to prevent coking, thus saving investment and operating costs.

[0041] In one embodiment, both the circulating ethane cooler and the circulating ethane superheater are heat exchangers, wherein the heat exchange medium of the circulating ethane cooler is quench water, and the heat exchange medium of the circulating ethane superheater is cooling water.

[0042] In a preferred embodiment, the raw material ethane is mixed with the diluted temperature-regulating ethane before being fed into the cracking furnace of the ethylene plant. In this embodiment, the diluted temperature-regulating ethane not only regulates the temperature of the regenerated ethane but also adjusts the sulfur content in the feed to the cracking furnace of the ethylene plant, further avoiding additional impact on the existing alkali washing tower and alkali circulation system.

[0043] In one implementation, such as Figure 1 As shown, the method for regenerating the desulfurization adsorption bed in an ethylene plant includes: The pressure drop of the circulating ethane produced by the ethylene unit, with an ethylene content of less than 0.5 mol%, is regulated by a pressure reducing valve to increase the pressure of the circulating ethane by P. 压降 The P 压降The pressure is 80~150 kPaG; the pressurized circulating ethane is introduced into a circulating ethane vaporizer to exchange heat with the cracked gas, resulting in vaporized ethane at a temperature of -38 to -34°C and cracked gas at a temperature of -28.05 to -28.12°C; the vaporized ethane is introduced into a cold box to exchange heat with methane and / or hydrogen produced by the ethylene unit, resulting in preheated vaporized ethane at a temperature of 25~35°C; The first preheated vaporized ethane is heated to 280-300°C and then used as regeneration gas before entering the desulfurization adsorption bed for regeneration treatment to obtain regenerated ethane. The regenerated ethane is then fed into a circulating ethane cooler to exchange heat with cooling water, resulting in raw material ethane at a temperature of 35-40°C. The second preheated vaporized ethane is then fed into a cycloane superheater to exchange heat with quench water, resulting in diluted temperature-regulating ethane at a temperature of 35-40°C. The flow ratio of the regeneration gas to the preheated vaporized ethane is (0.2-0.5):1. The raw material ethane is mixed with the diluted and temperature-controlled ethane and then fed into the cracking furnace of the ethylene unit; The methane and / or hydrogen produced by the ethylene unit are introduced into a cold box to exchange heat with the cracked gas and vaporized ethane to obtain cooled methane hydrogen; the cooled methane hydrogen is then introduced into each dryer of the ethylene unit for dryer regeneration treatment, and the obtained methane hydrogen is then introduced into the burner of the cracking furnace for combustion to obtain exhaust gas.

[0044] like Figure 1 As shown, a second aspect of this disclosure provides a system for regenerating a desulfurization adsorption bed in an ethylene plant using the method described in the first aspect. The system includes a circulating ethane vaporizer, a cold box, a desulfurization adsorption bed, and a circulating ethane cooler. The circulating ethane vaporizer includes a circulating ethane inlet, a vaporized ethane outlet, a cracked gas inlet, and a heat-exchange cracked gas outlet. The cold box includes a vaporized ethane inlet, a preheated vaporized ethane outlet, a methane hydrogen inlet, and a methane hydrogen outlet. The preheated vaporized ethane outlet pipeline includes a regeneration gas branch line and a dilution and temperature-regulating branch line. The desulfurization adsorption bed includes a regeneration gas inlet and a regenerated ethane outlet. The circulating ethane cooler includes a regenerated ethane inlet and a cooled ethane outlet. The circulating ethane inlet of the circulating ethane vaporizer is used for... The circulating ethane outlet of the ethylene unit is connected; the vaporized ethane outlet of the circulating ethane vaporizer is connected to the vaporized ethane inlet of the cold box; the preheated vaporized ethane outlet of the cold box is connected to the regeneration gas inlet of the desulfurization adsorption bed via the regeneration gas branch line; the regenerated ethane outlet of the desulfurization adsorption bed is connected to the regenerated ethane inlet of the circulating ethane cooler; the preheated vaporized ethane outlet of the cold box is connected to the cracking furnace inlet of the ethylene unit via the dilution and temperature control branch line; the cooled ethane outlet of the circulating ethane cooler is connected to the cracking furnace inlet of the ethylene unit; the methane hydrogen inlet of the cold box is used to connect to the methane hydrogen outlet of the ethylene unit; the methane hydrogen outlet of the cold box is connected to the burner inlet of the cracking furnace.

[0045] In one embodiment, a circulating ethane superheater is provided in the dilution and temperature control branch line for heating the preheated vaporized ethane flowing through the dilution and temperature control branch line.

[0046] In one embodiment, the ethylene unit further includes a drying unit; the drying unit includes a regeneration gas inlet and a water-containing regeneration gas outlet; the methane hydrogen outlet of the cold box is connected to the regeneration gas inlet of the drying unit; and the water-containing regeneration gas outlet of the drying unit is connected to the burner inlet of the cracking furnace.

[0047] In one embodiment, the system further includes a heating device disposed on a pipeline between the preheated vaporized ethane outlet of the cold box and the preheated vaporized ethane inlet of the desulfurization adsorption bed, for heating the preheated vaporized ethane entering the desulfurization adsorption bed.

[0048] In a preferred embodiment, the preheated vaporized ethane outlet pipeline of the cold box is divided into a regeneration gas pipeline and a dilution and temperature control pipeline; the regeneration gas pipeline is divided into a temperature control branch and a temperature rise branch; the heating device is installed on the temperature rise branch to raise a portion of the preheated vaporized ethane to at least the regeneration temperature; the outlet pipeline of the heating device and the temperature control branch are merged into a single pipeline connected to the preheated vaporized ethane inlet of the desulfurization adsorption bed to regulate the temperature of the stream entering the desulfurization adsorption bed.

[0049] In one embodiment, the desulfurization adsorption beds used in this disclosure consist of three beds: two in normal use and one on standby. The desulfurization adsorption beds are connected in parallel, and can be switched off promptly if any one of the adsorption beds malfunctions.

[0050] In one embodiment, the heat exchange area of ​​the circulating ethane vaporizer is 571~600 m². 2 .

[0051] In one embodiment, depending on the actual operating conditions, one or more of the following are independently provided on the pyrolysis gas inlet pipeline, pyrolysis gas outlet pipeline, regenerated gas inlet pipeline, and regenerated gas outlet pipeline of the desulfurization adsorption bed: a sequential control valve, a regulating valve, a flow detection device, and a temperature detection device.

[0052] In one embodiment, the system further includes a control unit electrically connected to each sequential control valve, each regulating valve, each flow detection device, and each temperature detection device, for receiving signals from each flow detection device and each temperature detection device, and for automatically adjusting the opening degree of each sequential control valve and each regulating valve based on the signals.

[0053] In a preferred embodiment, the control unit further includes a safety interlock unit, which introduces sequential control logic into the safety interlock system to prevent valve malfunction, i.e., the sequential control valve on the cracked gas side will not open simultaneously with the sequential control valve on the circulating ethane side, causing cracked gas to enter the circulating ethane and resulting in overpressure in the circulating ethane system.

[0054] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0055] Example 1 use Figure 1 The system shown is used for the regeneration of the desulfurization adsorption bed in an ethylene plant, including the following methods: The pressure drop of the circulating ethane produced by the ethylene unit, with an ethylene content of less than 0.5 mol%, is regulated by a pressure reducing valve to increase the pressure of the circulating ethane by P. 压降 The P 压降 The pressure is 100 kPaG; the pressurized circulating ethane is introduced into the circulating ethane vaporizer to exchange heat with the cracked gas, resulting in vaporized ethane at a temperature of -34.6℃ and cracked gas at a temperature of -28.05℃; the vaporized ethane is introduced into the cold box to exchange heat with methane and / or hydrogen produced by the ethylene unit, resulting in preheated vaporized ethane at a temperature of 30℃; The first preheated vaporized ethane is heated to 280-300°C and then used as regeneration gas before entering the desulfurization adsorption bed for regeneration treatment to obtain regenerated ethane. The regenerated ethane is then fed into a circulating ethane cooler to exchange heat with cooling water, resulting in raw material ethane at 40°C. The second preheated vaporized ethane is then fed into a cycloane superheater to exchange heat with quench water, resulting in diluted temperature-regulating ethane at 40°C. The flow ratio of the regeneration gas to the preheated vaporized ethane is 0.3125:1. The raw material ethane is mixed with the diluted and temperature-controlled ethane and then fed into the cracking furnace of the ethylene unit; The methane and / or hydrogen produced by the ethylene unit are introduced into a cold box to exchange heat with the cracked gas and vaporized ethane to obtain cooled methane hydrogen; the cooled methane hydrogen is then introduced into each dryer of the ethylene unit for dryer regeneration treatment, and the obtained methane hydrogen is then introduced into the burner of the cracking furnace for combustion to obtain exhaust gas.

[0056] Comparative Example 1 use Figure 2 The system shown is used for the regeneration of the desulfurization adsorption bed in an ethylene plant, including the following methods: The methane, hydrogen, and tail gas produced by the ethylene unit are treated in a cold box to obtain preheated methane hydrogen. Part of the preheated methane hydrogen is then sent to the drying unit of the ethylene unit for regeneration treatment in the dryer to obtain water-containing methane hydrogen. Another part of the preheated methane hydrogen is heated to the regeneration temperature by a heating device and then sent to the desulfurization adsorption bed for regeneration treatment to obtain sulfur-containing methane hydrogen. The sulfur-containing methane hydrogen and water-containing methane hydrogen are then mixed and returned to the burner of the cracking furnace of the ethylene unit for combustion to obtain exhaust gas. The circulating ethane is sequentially pressure-regulated by a pressure-reducing valve, vaporized by a circulating ethane vaporizer, heated in a cold box, and heated by a circulating ethane superheater before returning to the cracking furnace of the ethylene unit.

[0057] A comparison of Example 1 and Comparative Example 1 shows that, using the method of this disclosure, no moisture is introduced into the circulating ethane throughout the process, thus preventing the formation of wet hydrogen sulfide. This reduces the need for an additional alkaline scrubbing system to handle wet hydrogen sulfide, thereby reducing system footprint and equipment investment, and ultimately enhancing the competitiveness of the ethylene plant. Furthermore, the system of this disclosure allows the methane hydrogen produced by the ethylene plant to be directly returned to the burner of the ethylene plant's cracking furnace as fuel after heat exchange, without introducing sulfides. This avoids the problem of excessive sulfides in the exhaust gas after methane hydrogen combustion, achieving environmentally compliant emissions.

[0058] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0059] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0060] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for regenerating a desulfurization adsorption bed in an ethylene plant, characterized in that, The method includes: The recycled ethane produced by the ethylene unit is sequentially vaporized and preheated to obtain preheated vaporized ethane; The preheated vaporized ethane is divided into first preheated vaporized ethane and second preheated vaporized ethane. The first preheated vaporized ethane is heated and then used as regeneration gas to enter the desulfurization adsorption bed for regeneration treatment. The resulting regenerated ethane is cooled by a circulating ethane cooler and then returned to the cracking furnace of the ethylene unit along with the second preheated vaporized ethane. The methane hydrogen produced by the ethylene unit is cooled and then returned to the burner of the cracking furnace.

2. The method according to claim 1, characterized in that, The ethylene content in the recycled ethane is below 0.5 mol%.

3. The method according to claim 1, characterized in that, The flow rate ratio of the first preheated vaporized ethane to the preheated vaporized ethane is (0.2~0.5):

1.

4. The method according to claim 1, characterized in that, The method further includes adjusting the pressure drop of the pressure reducing valve before the circulating ethane is vaporized, so as to increase the pressure of the circulating ethane by P. 压降 ; The P 压降 The value is 80~150 kPaG.

5. The method according to claim 1, characterized in that, The method further includes vaporizing the recycled ethane in a recycled ethane vaporizer to obtain vaporized ethane at a temperature of -38 to -34°C; The vaporized ethane is preheated in a cold box to obtain preheated vaporized ethane at a temperature of 25~35℃.

6. The method according to claim 1, characterized in that, The method further includes cooling the regenerated ethane using a circulating ethane cooler to obtain raw material ethane at a temperature of 35-40°C; The second preheated vaporized ethane is heated by a circulating ethane superheater to obtain diluted temperature-regulating ethane at a temperature of 35~40℃; The raw material ethane is mixed with the diluted and temperature-controlled ethane and then fed into the cracking furnace.

7. The method according to claim 1, characterized in that, The ethylene plant also includes a drying unit; The method further includes, before the methane hydrogen is returned to the burner of the cracking furnace, allowing the cooled methane hydrogen to enter a drying unit for regeneration treatment, and then using the resulting methane hydrogen as fuel in the burner of the cracking furnace.

8. A system for regenerating a desulfurization adsorption bed in an ethylene plant using the method described in any one of claims 1 to 7, characterized in that, The system includes a circulating ethane vaporizer, a cold box, a desulfurization adsorption bed, and a circulating ethane cooler; The circulating ethane vaporizer includes a circulating ethane inlet, a vaporized ethane outlet, a cracked gas inlet, and a heat-exchange cracked gas outlet; The cold box includes a vaporized ethane inlet, a preheated vaporized ethane outlet, a methane hydrogen inlet, and a methane hydrogen outlet; the preheated vaporized ethane outlet pipeline includes a regeneration gas branch line and a dilution and temperature control branch line. The desulfurization adsorption bed includes a regenerated gas inlet and a regenerated ethane outlet; The circulating ethane cooler includes a regenerated ethane inlet and a cooled ethane outlet; The circulating ethane inlet of the circulating ethane vaporizer is connected to the circulating ethane outlet of the ethylene unit; the vaporized ethane outlet of the circulating ethane vaporizer is connected to the vaporized ethane inlet of the cold box; the preheated vaporized ethane outlet of the cold box is connected to the regeneration gas inlet of the desulfurization adsorption bed via the regeneration gas branch line; the regeneration ethane outlet of the desulfurization adsorption bed is connected to the regeneration ethane inlet of the circulating ethane cooler; the preheated vaporized ethane outlet of the cold box is connected to the cracking furnace inlet of the ethylene unit via the dilution and temperature control branch line; the cooled ethane outlet of the circulating ethane cooler is connected to the cracking furnace inlet of the ethylene unit. The methane hydrogen inlet of the cold box is connected to the methane hydrogen outlet of the ethylene unit; the methane hydrogen outlet of the cold box is connected to the burner inlet of the cracking furnace.

9. The system according to claim 8, characterized in that, A circulating ethane superheater is provided in the dilution and temperature control branch line for heating the preheated vaporized ethane flowing through the dilution and temperature control branch line.

10. The system according to claim 8, characterized in that, The ethylene plant also includes a drying unit; The drying device includes a regenerated gas inlet and a water-containing regenerated gas outlet; The methane hydrogen outlet of the cold box is connected to the regeneration gas inlet of the drying device; the water-containing regeneration gas outlet of the drying device is connected to the burner inlet of the pyrolysis furnace.

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