A rapid start-up method for an ethane cracking and ethylene production hydrogenation device

Abstract

The present application relates to a kind of quick start method of hydrogenation device of ethane cracking for ethylene matching, comprising the following steps: after the airtightness check of hydrogenation device is qualified, using inert gas is replaced, then the hydrogenation device is passed into ethane and is punched, and it is punched to 1.0~5.0Mpa.This start method can avoid the device temperature of start process, effectively shorten the start time, improve start efficiency.

Description

Technical Field

[0001] This invention relates to a start-up method for an alkyne gas-phase hydrogenation and alkyne removal unit, specifically to a rapid start-up method for an ethane cracking to ethylene supporting hydrogenation unit. Background Technology

[0002] The ethylene industry is the leading sector of the petrochemical industry, and ethylene production is a crucial indicator of a country's petrochemical industry level. Currently, there are three main feedstocks for ethylene production both domestically and internationally: petroleum, coal, and ethane. The petroleum route utilizes naphtha cracking, which not only has a heavy feedstock structure and high production costs but also a high dependence on petroleum resources. China's ethylene production primarily uses naphtha as feedstock, resulting in higher costs than ethylene production in North America and the Middle East, which uses inexpensive ethane. Compared to naphtha, ethane cracking yields lower amounts of methane, propylene, and butadiene, but higher ethylene yield. Among all traditional cracking feedstocks, ethane cracking yields the highest ethylene and lowest methane, meaning that the energy consumption of the separation unit is relatively low. Methane, typically used as fuel, has the lowest economic value. Therefore, ethane is the highest-quality cracking feedstock for ethylene production, offering advantages such as high ethylene yield, short process flow, lower equipment investment, and less pollution.

[0003] Steam cracking is the most widely used method for producing ethylene. The main reaction is relatively simple (as shown in equations (1)-(8)). Ethane undergoes dehydrogenation at 750–850 °C and 150–350 kPa to produce ethylene, with hydrogen as a byproduct. Other major products during the reaction include methane, acetylene, propylene, propane, butadiene, and other hydrocarbons. The residence time of the reactants in the cracking furnace is approximately 0.1–0.5 s. Injecting steam into the reactor can reduce the partial pressure of hydrocarbons, thereby reducing the coking rate at high temperatures.

[0004] C2H6→C2H4+H2 (1)

[0005] 2C2H6→C3H8+CH4 (2)

[0006] C3H8→C3H6+H2 (3)

[0007] C3H8→C2H4+CH4 (4)

[0008] C3H6→C2H2+CH4 (5)

[0009] C2H2 + C2H4 → C4H6 (6)

[0010] 2C2H6→C2H4+2CH4 (7)

[0011] C2H6 + C2H4 → C3H6 + CH4 (8)

[0012] Because ethane cracking products contain a small amount of acetylene impurities, selective hydrogenation is required to remove the acetylene to below 1 ppm before it can be used as a raw material for the production of polymer-grade ethylene.

[0013] The hydrogenation process and feedstock composition of the ethane cracking to ethylene hydrogenation unit differ significantly from those of traditional pre- / post-C2 hydrogenation units (see Table 1). In the ethane cracking to ethylene hydrogenation process, the feedstock entering the hydrogenation reactor contains not only C2 fractions but also some C3 fractions. While removing acetylene, some propyne and propadiene also need to be removed. The feedstock has a high H2 content, 20–30 times that of the post-hydrogenation process, and the CO content fluctuates greatly (range 0.02%–0.10 vol%), making start-up difficult, time-consuming, and prone to temperature runaway. Simultaneously, CO can compete with acetylene and ethylene in the feedstock for adsorption, occupying active sites and thus inhibiting catalyst activity. In the ethane cracking to ethylene hydrogenation process, the minimum CO content is 0.01%, lower than in other hydrogenation processes, and the large fluctuations in CO content further hinder stable operation of the unit. Especially during the initial startup phase, the feedstock cracked gas enters the reactor bed. Before the reactor pressure reaches the set pressure, the feedstock gas cannot flow, and alkynes and dienes are statically adsorbed by the catalyst, generating a large amount of adsorption heat. When this heat accumulates to a certain level, it will drive the hydrogenation reaction of alkynes and dienes, further generating reaction heat. If the catalyst reaction temperature is low and the activity is high, the large amount of adsorption and reaction heat will cause the bed temperature to rise rapidly, easily leading to overheating. Overheating not only wastes materials and causes economic losses, but also prolongs the start-up time. Furthermore, overheating can cause catalyst coking, covering active sites, reducing catalyst activity, accelerating catalyst deactivation, and severely affecting the long-term stability of the catalyst.

[0014] Table 1. Composition of feedstocks for different hydrogenation processes

[0015]

[0016] CN200980154641.X discloses a method for selectively hydrogenating acetylene to ethylene, comprising: contacting a feed stream containing ethylene and acetylene with a catalyst under reaction conditions, thereby producing an output feed stream with reduced acetylene content, wherein the feed stream contains 1-8000 ppm carbon monoxide (CO). Specifically, the process feed stream containing ethylene, ethane, and acetylene is compressed, and the temperature is adjusted to cool the compressed gas before it enters a hydrogenation reactor. A layered spherical catalyst is used to selectively hydrogenate the acetylene fraction in the feed, wherein the CO content in the feed is 1-8000 ppm, and the reaction conditions include a pressure of 100 kPa-14.0 MPa and a selective hydrogenation reaction temperature of 10-300 °C. In this process, when a large amount of carbon monoxide is present, the monoxide acts as a reversible inhibitor at the active catalyst site. The acetylene removal method disclosed in this invention does not describe the start-up pressurization and heating processes, nor does it solve the problem of overheating during the start-up of the hydrogenation unit.

[0017] CN201510684013.X discloses a selective hydrogenation method for alkynes and / or dienes in C2 and C3 fractions. The method involves mixing a cracked gas stream from the top of a pre-propane or pre-ethane stripper with a hydrogen-rich gas stream containing carbon monoxide to obtain a stable hydrogen-rich gas stream with a carbon monoxide content of 0.15–0.3 mol%. The carbon monoxide concentration fluctuates within ±20%. This mixed hydrogen-rich cracked gas stream is compressed to 2–4 MPa, subjected to heat exchange, and then reacted with a palladium-supported selective hydrogenation catalyst in a fixed-bed hydrogenation reactor. This hydrogenation method, specifically designed for pre-propane stripper hydrogenation processes in C2 fractions, effectively avoids reactor runaway temperatures and alkyne leaks caused by significant fluctuations in carbon monoxide in the cracked gas from the preceding system. Under high space velocity conditions, it effectively improves catalyst activity and selectivity while saving on the amount of active catalyst components required.

[0018] Wu Hao et al. (Chemical Industry Progress, 2002, 21(9):673-675) analyzed the influence of CO concentration on the hydrogenation reaction in the pre-hydrogenation process of C2, discussed the factors of CO formation, and proposed effective measures to reduce CO formation and control CO concentration fluctuations: strengthen sulfur injection operation, reduce the feeding temperature of the cracking furnace, and prevent methanol from entering the cracking furnace, etc., to ensure stable operation of the unit. Huang Wenjiao et al. (Industrial Catalysis, 2016, 24(8):58-63) adopted the cylinder gas injection method to prevent overheating during the start-up process of the unit, ensuring that the CO concentration in the cracked gas is greater than 2000×10. -6 .

[0019] Liang Yulong et al. (Petrochemical Technology, 2018, 47(2):192-196) effectively suppressed the initial activity of the C2 pre-hydrogenation catalyst by passivating it. During the start-up of the low-space-velocity C2 pre-hydrogenation unit, the reactor was directly pressurized to 3.6 MPa with cracked gas. After pressurization, the reactor was heated to the inlet temperature of 64°C at a rate of 10°C every 30 minutes. The outlet product was qualified and there was no "temperature runaway". In this technology, the initial activity of the catalyst is reduced by passivation, and there is no temperature runaway during the start-up process. However, this start-up method is only suitable for specific passivated catalysts and is not suitable for the stable start-up of all C2 pre-hydrogenation units.

[0020] The isothermal C2 hydrogenation reactor start-up process reported by Xue Xinchao, Zeng Feipeng, et al. (Ethylene Industry, 2016, 28(3):39-43) involved first pressurizing the system with nitrogen to 1.0 MPa during the first start-up process, and then adjusting the CO concentration in the material to 1800 mL / m³. 3 The reactor temperature rises, the unit overheats, and the system shuts down. During the second restart, nitrogen purging is performed, the inlet temperature is set to 15℃, and the inlet CO is adjusted to 5000 mL / m³. 3 The temperature gradually increased, and the start-up process took 7.5 hours. During the first start-up in this report, the unit experienced a temperature spike, and during the second start-up, the CO concentration was high, and the heating process took a long time.

[0021] In her doctoral dissertation at Lanzhou University, "Development and Application Research of C2 Pre-hydrogenation Catalysts," Che Chunxia recommends a startup method for a C2 pre-hydrogenation unit. The startup process requires pre-pressurizing the reactor with gas cylinders to a CO content of 5000 μL / L, followed by nitrogen pressurization to a bed pressure of 0.6 MPa, which is maintained for 4–6 hours. The reactor inlet feed valve and pipeline bypass feed valve are then opened, and the bypass pressurization is performed to 3.6 MPa. The flow rate is then adjusted to a higher level to begin reactor preheating and temperature rise. This technology requires a high CO content in the reactor during startup and involves a long pressurization time using N2. Furthermore, the N2 pre-pressurization introduces impurities and fails to address the issue of reducing the pressurization speed during the start-up process to prevent rapid accumulation of adsorbed heat and subsequent temperature runaway.

[0022] The above-mentioned prior art discloses the start-up process of acetylene selective hydrogenation units, which are all for the C2 pre-propane dehydrogenation process and the C2 pre-ethane dehydrogenation process. By controlling the stability and content of CO in the feedstock, the unit temperature runaway caused by CO fluctuations during the start-up process can be effectively avoided.

[0023] However, the acetylene hydrogenation process is carried out under certain pressure conditions. Before reaching the reaction pressure conditions, it is necessary to carry out stamping. During the stamping process, the raw material gas cannot flow, and a large amount of adsorption heat generated by the static adsorption of alkynes and alkenes on the catalyst cannot be diffused in time. When the heat accumulates to a certain extent, the alkynes and dienes will undergo hydrogenation reactions, further generating reaction heat and causing the temperature of the device to soar. None of the above existing studies can solve the problem that the stamping process will bring the risk of temperature runaway during the start-up process of the device. Especially in the hydrogenation device supporting the ethane cracking to produce ethylene, compared with other C2 hydrogenation devices, the CO content in the hydrogenation raw material is low, with the lowest CO being 0.01%, and CO can compete with acetylene and ethylene in the material for adsorption, occupying the active sites, thus playing a role in inhibiting the activity of the catalyst. In the hydrogenation raw material supporting the ethane cracking to produce ethylene, the lower CO content is more unfavorable for the stable start-up of the device during the start-up process.

[0024] In addition, in these disclosed start-up methods, the required CO concentration for start-up is higher than the CO content in the normal hydrogenation raw material gas. After the start-up heating process is completed, it is necessary to adjust and reduce it to the concentration range of CO in the normal hydrogenation raw material gas, which prolongs the start-up time. At the same time, as a catalyst activity inhibitor, when the content of CO decreases, more adsorption sites of the catalyst will be "released", which increases the risk of temperature runaway of the device.

[0025] Therefore, it is very crucial to develop a stable and efficient start-up method for the acetylene selective hydrogenation device, especially for the start-up method of the hydrogenation device supporting the ethane cracking to produce ethylene. Summary of the Invention

[0026] Based on the above, the main object of the present invention is to provide a rapid start-up method for the hydrogenation device supporting the ethane cracking to produce ethylene, which can avoid the temperature runaway of the device during the start-up process, effectively shorten the start-up time, and improve the start-up efficiency.

[0027] For this purpose, the present invention provides a rapid start-up method for the hydrogenation device supporting the ethane cracking to produce ethylene, including the following steps: After the airtightness of the hydrogenation device is checked and qualified, it is replaced with an inert gas, and then ethane is introduced into the hydrogenation device for stamping until 1.0 - 5.0 Mpa.

[0028] In the rapid start-up method for the hydrogenation device supporting the ethane cracking to produce ethylene according to the present invention, the inert gas is, for example but not limited to, nitrogen.

[0029] In the rapid start-up method for the hydrogenation device supporting the ethane cracking to produce ethylene according to the present invention, preferably, ethane is introduced into the hydrogenation device for stamping until 1.5 - 2.5 Mpa.

[0030] The rapid start-up method for an ethane cracking to ethylene-supporting hydrogenation unit according to the present invention preferably includes the following steps: after pressing, the hydrogenation feedstock for ethane cracking to ethylene-supporting production that meets the start-up requirements is introduced into the hydrogenation unit; the hydrogenation unit is continued to be heated until the inlet and outlet temperature difference of the hydrogenation reactor of the hydrogenation unit is 2-30°C, and the temperature in the hydrogenation reactor rises from top to bottom and forms multiple temperature gradients, the temperature gradient being 1-12°C; the bed heating is completed when the acetylene at the final outlet of the hydrogenation unit is qualified.

[0031] Specifically, the hydrogenation feedstock for ethane cracking to ethylene production that meets the start-up requirements refers to the ethane cracking furnace being put into normal and stable operation, and the cracking products being separated by a de-ethane de-ethanizer, with the top effluent from the de-ethanizer serving as the hydrogenation feedstock, and its composition meeting the start-up requirements.

[0032] The temperature gradient mentioned in this invention refers to the temperature difference between two adjacent temperature measuring points when multiple temperature measuring points are set from top to bottom in the hydrogenation reactor of the hydrogenation device.

[0033] The rapid start-up method for the ethane cracking to ethylene hydrogenation unit according to the present invention preferably involves pressurizing the hydrogenation unit to a reaction pressure of 1.0–5.0 MPa for 0.5–3 min using the hydrogenation feedstock.

[0034] The rapid start-up method for an ethane cracking to ethylene hydrogenation unit according to the present invention preferably comprises, based on the volume of the hydrogenation feedstock, at least: CO 0.01%–0.5%, hydrogen 20–55%, acetylene 0.1–1.0%, ethylene 30–75%, and ethane; more preferably, the hydrogenation feedstock comprises at least: CO 0.02%–0.04%, hydrogen 25–35%, acetylene 0.15–0.5%, ethylene 35–70%, and ethane. In the hydrogenation feedstock of the present invention, ethane is a balance gas, and its content is not particularly limited; the ethane content can be adjusted according to the content of other components in the hydrogenation feedstock.

[0035] The rapid start-up method for an ethane cracking to ethylene hydrogenation unit according to the present invention preferably includes a hydrogenation unit that is a single-stage or multi-stage hydrogenation reactor. When the hydrogenation unit is a multi-stage hydrogenation reactor, the hydrogenation reactors are connected in series or in parallel.

[0036] The rapid start-up method for the ethane cracking to ethylene hydrogenation unit described in this invention, when the hydrogenation unit is a two-stage hydrogenation reactor connected in series: the inlet temperature of the first-stage hydrogenation reactor is adjusted to 60-70°C, the inlet-outlet temperature difference is 5-25°C, and the temperature gradient is 2-10°C; the inlet temperature of the second-stage hydrogenation reactor is adjusted to 65-80°C, the inlet-outlet temperature difference is 3-20°C, and the temperature gradient is 1-6°C.

[0037] The rapid start-up method for an ethane cracking to ethylene hydrogenation unit according to the present invention, when the hydrogenation unit is a three-stage hydrogenation reactor connected in series: the inlet temperature of the first stage hydrogenation reactor is adjusted to 50-65°C, the inlet-outlet temperature difference is 5-25°C, and the temperature gradient is 2-10°C; the inlet temperature of the second stage hydrogenation reactor is adjusted to 55-70°C, the inlet-outlet temperature difference is 3-25°C, and the temperature gradient is 2-10°C; the inlet temperature of the third stage hydrogenation reactor is adjusted to 60-80°C, the inlet-outlet temperature difference is 3-20°C, and the temperature gradient is 1-6°C.

[0038] The rapid start-up method for the hydrogenation unit supporting ethane cracking to ethylene production according to the present invention preferably includes a hydrogenation reactor that is an adiabatic bed or an isothermal bed, and more preferably an adiabatic bed.

[0039] The rapid start-up method for an ethane cracking to ethylene hydrogenation unit according to the present invention allows for the use of any pressing method, such as ethane pipeline gas pressing, as long as the pressure required by the present invention is met. The pressing time is not limited. Preferably, the ethane pressing time is 15–240 minutes.

[0040] The rapid start-up method for an ethane cracking to ethylene hydrogenation unit according to the present invention preferably includes the following step between the inert gas purging and the ethane purging: CO is introduced into the hydrogenation unit to achieve a CO volume concentration of 1000–10000 ppm. Pre-injecting CO into the hydrogenation reactor suppresses initial catalyst activity, and combined with ethane purging, reduces the purging time of the cracked gas and dilutes the concentration of alkynes and dienes in the hydrogenation feedstock, further reducing the risk of unit overheating.

[0041] The rapid start-up method for an ethane cracking to ethylene hydrogenation unit described in this invention is applicable to all acetylene selective hydrogenation units, especially units using an ethane cracking to ethylene hydrogenation process. It selectively hydrogenates the acetylene contained in the overhead effluent of the ethane cracking unit, completely converting it into ethylene, while the ethylene is not lost.

[0042] The rapid start-up method for an ethane cracking to ethylene hydrogenation unit described in this invention uses a selective hydrogenation catalyst, including but not limited to supported catalysts. For example, the support can be alumina, silica, etc., and the active component can be noble metals such as Pd, Pt, and Au, or non-noble metals such as Ni and Fe. Preferably, a selective hydrogenation catalyst with Pd as the main active component is used. However, this invention is not particularly limited to this; the selective hydrogenation catalyst used in the hydrogenation process can be adjusted according to the actual requirements of the hydrogenation process.

[0043] The rapid start-up method for an ethane cracking to ethylene hydrogenation unit described in this invention uses pre-hydrogenation process conditions commonly used in this technical field, such as those disclosed in CN104098426A: reactor inlet temperature 35℃~180℃, reaction pressure 2.0~4.0MPa, and gas hourly space velocity 4000~25000h⁻¹. -1 The preferred process conditions of this invention are: reactor inlet temperature 30℃~180℃, reaction pressure 1.0~5.0MPa, and reaction volume hourly space velocity 2000~20000h⁻¹. -1 More preferred conditions are: inlet temperature 50℃~120℃, reaction pressure 1.5~2.5MPa, and volumetric hourly space velocity 6000~15000h⁻¹. -1 .

[0044] The rapid start-up method for the ethane cracking to ethylene hydrogenation unit described in this invention preferably includes, during the reactor heating process, fine-tuning the inlet temperature of each reactor according to the required load distribution of each reactor after the temperature of each reaction bed has basically stabilized.

[0045] The beneficial effects of this invention are as follows:

[0046] The start-up method for an ethane cracking to ethylene hydrogenation unit disclosed in this invention employs the injection of ethane as the cracking feedstock. Compared to the traditional method of slowly pressurizing the hydrogenation unit using cracked gas as the feedstock, this invention directly pressurizes the unit from a slightly positive pressure to a reaction pressure of 1.0–5.0 MPa using ethane. This method features faster pressurization and shorter pressurization time. Simultaneously, this method avoids the problem of alkynes and dienes being statically adsorbed by the catalyst due to the stagnant feedstock gas, generating significant adsorption heat. This heat accumulation, when sufficient, drives the hydrogenation reaction of alkynes and dienes, preventing further heat generation and potential overheating issues. Furthermore, the presence of a large amount of ethane dilutes the concentration of alkynes and dienes in the hydrogenation feedstock, effectively reducing the risk of overheating during the heating process and shortening the time from hydrogenation start-up to product qualification. The use of ethane pressurization in this invention also avoids impurities introduced by nitrogen pressurization, shortening product qualification time and reducing material loss.

[0047] Furthermore, when CO is introduced during nitrogen replacement and ethane pressurization, the initial catalyst activity can be suppressed. Combined with ethane pressurization of the reactor, the pressurization time of the cracked gas is reduced and the concentration of alkynes and dienes in the hydrogenation feedstock is diluted, further reducing the risk of overheating of the unit. Attached Figure Description

[0048] Figure 1 This is a process flow diagram for single-stage isothermal hydrogenation and acetylene removal in light hydrocarbon cracking.

[0049] In the attached figures, the following labels are used:

[0050] 1-Ethane cracking gas, 2-Hydrogenation feedstock, 3-Hydrogenation product; 4-Ethane cracking tower, 5-Hydrogenation unit, 6-Demethanizer tower. Detailed Implementation

[0051] The following provides a detailed description of the embodiments of the present invention: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods in the following embodiments without specific conditions are generally performed under conventional conditions. Unless otherwise specified, all percentages in the following embodiments and comparative examples are by weight.

[0052] Raw material source and specifications

[0053] Hydrogenation feedstock: C2 fractions produced by steam thermal cracking of low-carbon alkane feedstocks are generally treated with selective hydrogenation to remove acetylene. The catalysts used for acetylene removal are typically palladium-based selective hydrogenation catalysts. The catalysts used in domestic ethane cracking to ethylene hydrogenation units mainly include Shell's 7741B-T and 7741B-R catalysts, Südschau's Olemax-252 and Olemax-253 catalysts, PetroChina's PEC-21 catalyst, and Sinopec's BC-H-21B catalyst.

[0054] Detection methods

[0055] The content of each component in the hydrogenation feedstock and the outlet gas of each hydrogenation reactor was analyzed using gas chromatography under the following operating conditions:

[0056] a) Detector: Hydrogen flame detector;

[0057] b) Chromatographic column: a stainless steel column with a length of 3.0m and an inner diameter of 3mm;

[0058] c) Inlet temperature: 70℃;

[0059] d) Column temperature: 110℃;

[0060] e) Detector temperature: 150℃.

[0061] Calculation formula

[0062]

[0063] Figure 1 This is a process flow diagram for a single-stage isothermal hydrogenation and acetylene removal process in light hydrocarbon cracking. (See also...) Figure 1As shown, ethane cracking gas 1 passes through ethane cracking tower 4, and the resulting hydrogenation feedstock 2 enters hydrogenation unit 5 for selective hydrogenation. The resulting hydrogenated product 3 is then separated in demethanizer tower 6. The hydrogenation unit 5 of this invention is a rapid start-up method for an ethane cracking-supported ethylene selective hydrogenation unit. This method includes the following steps:

[0064] (1) After the air tightness of the hydrogenation unit 5 for ethane cracking to ethylene is qualified, an inert gas such as nitrogen is used for replacement. Then ethane is introduced into the hydrogenation unit 5 and pressurized to 1.0-5.0 MPa.

[0065] (2) Introduce ethane cracking to ethylene hydrogenation feedstock that meets the start-up requirements into hydrogenation unit 5.

[0066] Example 1

[0067] The hydrogenation unit is a 500ml C2 hydrogenation side-stream unit, employing a three-stage series adiabatic bed process for selective hydrogenation removal of acetylene. The hydrogenation catalyst is Shell's 7741B-T, which uses alumina as a support and approximately 0.03% Pd as the active component. The composition of the hydrogenation feedstock is shown in Table 2.

[0068] (1) After the airtightness of the hydrogenation unit is qualified, the inert gas nitrogen replacement is qualified.

[0069] (2) CO is injected into the first, second and third stage hydrogenation reactors of the hydrogenation unit. The catalyst loading amount of each hydrogenation reactor is 350 ml. CO is injected into the steel cylinder (10 L / cylinder, pressure 6 MPa). The CO content is about 1500 ppm. The CO injection time is 1.5 h.

[0070] (3) Ethane pressurization: Pressurize the hydrogenation reactor to 1.0 MPa for 10 min.

[0071] (4) Open all the feed valves and continue to press the reactor bed through the bypass hydrogenation feedstock. The pressing time is 1 minute and the pressure is 2.3 MPa. The inlet temperature of the hydrogenation reactor is preheated to 30°C by the cracked gas. The bed temperature rises by 2°C after the pressing is completed.

[0072] (5) The reactant gas is heated until a positive temperature difference appears in the first-stage hydrogenation reactor, meaning the temperature in the first-stage hydrogenation reactor gradually increases from top to bottom. Four temperature measuring points are set up from the inlet to the outlet of the first-stage hydrogenation reactor. Once a 3°C temperature gradient is formed between two adjacent measuring points (i.e., the inlet-outlet temperature difference of the first-stage hydrogenation reactor is 9°C), samples are taken for analysis. The conversion rate of the first-stage hydrogenation reactor is tested at 52%, and the heating of the first-stage hydrogenation reactor is completed. Heating of the second-stage hydrogenation reactor then begins until a positive temperature difference appears in the second-stage hydrogenation reactor, meaning the temperature in the second-stage hydrogenation reactor gradually increases from top to bottom. Four temperature measuring points are set up from the inlet to the outlet of the second-stage hydrogenation reactor. Six temperature measuring points are used. Heating of the second-stage hydrogenation reactor ends when a 2°C temperature gradient is formed between two adjacent measuring points (i.e., a 10°C temperature difference between the inlet and outlet of the reactor) and the acetylene concentration at the reactor outlet is below 85 ppm. Heating of the third-stage hydrogenation reactor then begins until a positive temperature difference is observed, meaning the temperature gradually increases from top to bottom. Four temperature measuring points are used in the third-stage reactor from inlet to outlet. Heating of the third-stage hydrogenation reactor ends when a 2°C temperature gradient is formed between two adjacent measuring points (i.e., a 6°C temperature difference between the inlet and outlet of the reactor) and the acetylene concentration at the reactor outlet is below 1 ppm.

[0073] (6) After the reaction bed temperature stabilized, the inlet temperature of each hydrogenation reactor was fine-tuned according to the required load distribution of each hydrogenation reactor to ensure that the acetylene outlet of the third-stage hydrogenation reactor was below 1 ppm and the total ethylene selectivity of the first, second, and third-stage hydrogenation reactors was ≥60%. From the start of the pressurization to the qualified acetylene outlet of the third-stage hydrogenation reactor, the total start-up time was 4.6 hours, and the start-up was completed. The reaction pressure was 2.3 MPa and the reaction volume hourly space velocity was 7500 h⁻¹. -1 The inlet reaction temperatures of the first, second, and third stage hydrogenation reactors are 50.7℃, 58.9℃, and 62.5℃, respectively.

[0074] Table 2 Composition of Hydrogenation Feedstock

[0075]

[0076] Example 2

[0077] The hydrogenation unit is a 500ml C2 hydrogenation side-stream unit, employing a three-stage series adiabatic bed process for selective hydrogenation removal of acetylene. The hydrogenation catalyst is Shell's 7741B-T, which uses alumina as a support and approximately 0.03% Pd as the active component. The composition of the hydrogenation feedstock is shown in Table 3.

[0078] (1) After the airtightness of the hydrogenation unit is qualified, the inert gas nitrogen replacement is qualified.

[0079] (2) Ethane pressurization: The hydrogenation reactor is pressurized to 4.8 MPa for 20 min.

[0080] (3) Open all the feed valves and continue to press the reactor bed through the bypass hydrogenation feedstock. The pressing time is 1 minute and the pressure is 5.0 MPa. The inlet temperature of the hydrogenation reactor is preheated to 30°C by the cracked gas. The bed temperature rises by 2°C after the pressing is completed.

[0081] (4) The reactant gas is heated until a positive temperature difference appears in the first-stage hydrogenation reactor, meaning the temperature in the first-stage hydrogenation reactor gradually increases from top to bottom. Three temperature measuring points are set up from the inlet to the outlet of the first-stage hydrogenation reactor. Once a temperature gradient of 8°C is formed between two adjacent measuring points (i.e., the inlet-outlet temperature difference of the first-stage hydrogenation reactor is 16°C), samples are taken for analysis. The conversion rate of the first-stage hydrogenation reactor is tested to be 55%, and the heating of the first-stage hydrogenation reactor is completed. Heating of the second-stage hydrogenation reactor then begins until a positive temperature difference appears in the second-stage hydrogenation reactor, meaning the temperature in the second-stage hydrogenation reactor gradually increases from top to bottom. Three temperature measuring points are set up from the inlet to the outlet of the second-stage hydrogenation reactor. There are three temperature measuring points. Heating of the second-stage hydrogenation reactor ends when a 5°C temperature gradient is formed between two adjacent measuring points (i.e., the inlet-outlet temperature difference is 10°C) and the acetylene concentration at the outlet of the second-stage hydrogenation reactor is below 100 ppm. Heating of the third-stage hydrogenation reactor then begins until a positive temperature difference appears, meaning the temperature gradually increases from top to bottom. Three temperature measuring points are set up from the inlet to the outlet of the third-stage hydrogenation reactor. Heating of the third-stage hydrogenation reactor ends when a 3°C temperature gradient is formed between two adjacent measuring points (i.e., the inlet-outlet temperature difference is 6°C) and the acetylene concentration at the outlet of the third-stage hydrogenation reactor is below 1 ppm.

[0082] (5) After the reaction bed temperature stabilized, the inlet temperature of each hydrogenation reactor was fine-tuned according to the required load distribution of each hydrogenation reactor to ensure that the acetylene outlet of the third-stage hydrogenation reactor was below 1 ppm and the total ethylene selectivity of the first, second, and third-stage hydrogenation reactors was ≥60%. From the start of the pressurization to the qualified acetylene outlet of the third-stage hydrogenation reactor, the total start-up time was 4.6 hours, and the start-up was completed. The reaction pressure was 5.0 MPa and the reaction volume hourly space velocity was 14000 h⁻¹. -1 The inlet reaction temperatures of the first, second, and third stage hydrogenation reactors are 52.4℃, 63.9℃, and 64.2℃, respectively.

[0083] Table 3 Composition of Hydrogenation Feedstock

[0084]

[0085] Example 3

[0086] The 500ml C2 hydrogenation side-stream unit employs a three-stage series adiabatic bed process for selective hydrogenation removal of acetylene. The hydrogenation catalyst used is PEC-21 from PetroChina, which uses alumina as a support and is loaded with approximately 0.03% Pd as the active component. The composition of the hydrogenation feedstock is shown in Table 4.

[0087] (1) After the airtightness of the hydrogenation unit is qualified, the inert gas nitrogen replacement is qualified.

[0088] (2) CO is injected into the first, second and third stage hydrogenation reactors of the hydrogenation unit. The catalyst loading amount of each hydrogenation reactor is 400ml. CO is injected into the steel cylinder (10L / cylinder, pressure 6MPa). The CO content is about 1800ppm. The CO injection time is 1.0h.

[0089] (3) Ethane pressurization: The hydrogenation reactor is pressurized to 1.8 MPa for 15 min.

[0090] (4) Open all the feed valves and introduce hydrogenation feedstock through the bypass reactor bed at a pressure of 2.0 MPa. The inlet temperature of the hydrogenation reactor is preheated to 28°C by the cracked gas. After the pressurization is completed, the bed temperature rises by 2°C.

[0091] (5) Heat the reactant gas until a positive temperature difference appears in the first-stage hydrogenation reactor, meaning the temperature in the first-stage hydrogenation reactor gradually increases from top to bottom. Three temperature measuring points are set up from the inlet to the outlet in the first-stage hydrogenation reactor. Heating of the first-stage hydrogenation reactor ends when a temperature gradient of 6°C is formed between two adjacent measuring points, i.e., the inlet-outlet temperature difference of the first-stage hydrogenation reactor is 12°C. Then, heating of the second-stage hydrogenation reactor begins until a positive temperature difference appears in the second-stage hydrogenation reactor, meaning the temperature in the second-stage hydrogenation reactor gradually increases from top to bottom. Three temperature measuring points are set up from the inlet to the outlet in the second-stage hydrogenation reactor. Heating of the second-stage hydrogenation reactor ends when a temperature gradient of 6°C is formed between two adjacent measuring points, i.e., the inlet-outlet temperature difference of the first-stage hydrogenation reactor is 12°C. A temperature gradient of 10°C is formed at the temperature points, meaning the inlet and outlet temperature difference of the second-stage hydrogenation reactor is 20°C. The acetylene concentration at the outlet of the second-stage hydrogenation reactor is below 100 ppm, and heating of the second-stage hydrogenation reactor is completed. Heating of the third-stage hydrogenation reactor then begins until a positive temperature difference is achieved, meaning the temperature in the third-stage hydrogenation reactor gradually increases from top to bottom. Three temperature measuring points are set up from the inlet to the outlet of the third-stage hydrogenation reactor. Heating of the third-stage hydrogenation reactor is completed when a temperature gradient of 4°C is formed between two adjacent measuring points, meaning the inlet and outlet temperature difference of the third-stage hydrogenation reactor is 8°C. The acetylene concentration at the outlet of the third-stage hydrogenation reactor is below 1 ppm.

[0092] (6) After the reaction bed temperature stabilizes, the inlet temperature of each hydrogenation reactor is fine-tuned according to the required load distribution, ensuring that the acetylene outlet of the third-stage hydrogenation reactor is below 1 ppm, and the total ethylene selectivity of the first, second, and third-stage hydrogenation reactors is ≥60%. From the start of the pressurization to the qualified acetylene outlet of the third-stage hydrogenation reactor, the total start-up time is 3.5 hours, and the start-up is complete. The reaction pressure is 2.0 MPa, and the reaction volume hourly space velocity is 8000 h⁻¹. -1 The inlet reaction temperatures of the first, second, and third stage hydrogenation reactors are 50.5℃, 57.9℃, and 65.7℃, respectively.

[0093] Table 4 Composition of Hydrogenation Feedstock

[0094]

[0095] Example 4

[0096] The 500ml C2 hydrogenation side-stream unit employs a two-stage series adiabatic bed process for selective hydrogenation removal of acetylene. The hydrogenation catalyst used is Olemax-252 from Südschau, Germany. The Olemax-252 hydrogenation catalyst uses alumina as a support and is loaded with approximately 0.04% Pd as the active component. The composition of the hydrogenation feedstock is shown in Table 5.

[0097] (1) After the airtightness of the hydrogenation unit is qualified, the inert gas nitrogen replacement is qualified.

[0098] (2) CO is injected into the first and second stage hydrogenation reactors of the hydrogenation unit. The catalyst loading amount of each hydrogenation reactor is 450 ml. CO is injected into the steel cylinder (10 L / cylinder, pressure 6 MPa). The CO content is about 1600 ppm. The CO injection time is 1.0 h.

[0099] (3) Ethane pressurization: The hydrogenation reactor is pressurized to 2.3 MPa for 22 min.

[0100] (4) Open all the feed valves and introduce hydrogenation feedstock through the bypass reactor bed at a pressure of 2.5 MPa. The inlet temperature of the hydrogenation reactor is preheated to 28°C by the cracked gas. After the pressurization is completed, the bed temperature rises by 2°C.

[0101] (5) Heat the reaction feed gas until a positive temperature difference appears in the first stage hydrogenation reactor, that is, the temperature in the first stage hydrogenation reactor gradually increases from top to bottom. There are 4 temperature measuring points from the inlet to the outlet in the first stage hydrogenation reactor. When a temperature gradient of 5°C is formed between two adjacent temperature measuring points, that is, the inlet and outlet temperature difference of the first stage hydrogenation reactor is 15°C, take a sample for analysis. The conversion rate of the first stage hydrogenation reactor is tested to be 80%, and the heating of the first stage hydrogenation reactor is ended. Start heating the second stage hydrogenation reactor until a positive temperature difference appears in the second stage hydrogenation reactor, that is, the temperature in the second stage hydrogenation reactor gradually increases from top to bottom. There are 5 temperature measuring points from the inlet to the outlet in the second stage hydrogenation reactor. When a temperature gradient of 5°C is formed between two adjacent temperature measuring points, that is, the inlet and outlet temperature difference of the second stage hydrogenation reactor is 20°C, and the acetylene at the outlet of the second stage hydrogenation reactor is less than 1 ppm, the heating of the second stage hydrogenation reactor is ended.

[0102] (6) After the reaction bed temperature stabilizes, the inlet temperature of each hydrogenation reactor is fine-tuned according to the required load distribution, ensuring that the acetylene outlet of the second-stage hydrogenation reactor is below 1 ppm and the total ethylene selectivity of the first and second-stage hydrogenation reactors is ≥60%. From the start of the pressurization to the qualified acetylene outlet of the second-stage hydrogenation reactor, the total start-up time is 3.8 hours, and the start-up is complete. The reaction pressure is 2.5 MPa and the reaction volume hourly space velocity is 9000 h⁻¹. -1 The inlet reaction temperatures of the first and second stage hydrogenation reactors are 65.5℃ and 72.9℃, respectively.

[0103] Table 5 Composition of Hydrogenation Feedstock

[0104]

[0105] Example 5

[0106] The 500ml C2 hydrogenation side-stream unit employs a single-stage adiabatic bed process for selective hydrogenation removal of acetylene. The hydrogenation catalyst used is PEC-21 from PetroChina, which uses alumina as a support and is loaded with approximately 0.03% Pd as the active component. The composition of the hydrogenation feedstock is shown in Table 6.

[0107] (1) After the airtightness of the hydrogenation unit is qualified, the inert gas nitrogen replacement is qualified.

[0108] (2) Inject CO into the hydrogenation reactor of the hydrogenation unit. The catalyst loading amount is 500 ml. Inject CO into a steel cylinder (10 L / cylinder, pressure 6 MPa). The CO content is about 2000 ppm. The CO injection time is 40 min.

[0109] (3) Ethane pressurization: The hydrogenation reactor is pressurized to 3.0 MPa for 25 min.

[0110] (4) Open all the feed valves and introduce hydrogenation feedstock through the bypass reactor bed at a pressure of 3.2 MPa. The inlet temperature of the hydrogenation reactor is preheated to 32°C by the cracked gas. After the pressurization is completed, the bed temperature rises by 2°C.

[0111] (5) Heat the reaction feed gas until a positive temperature difference appears in the hydrogenation reactor, that is, the temperature in the hydrogenation reactor gradually increases from top to bottom. Five temperature measuring points are set in the hydrogenation reactor from the inlet to the outlet. When a temperature gradient of 6°C is formed between two adjacent temperature measuring points, that is, the temperature difference between the inlet and outlet of the hydrogenation reactor is 24°C, take a sample for analysis until the acetylene at the outlet of the hydrogenation reactor is less than 1 ppm, and the heating ends.

[0112] From the start of the pressurization process to the acetylene discharge from the hydrogenation reactor reaching acceptable levels, the total start-up time was 3.0 hours, and the start-up was completed. The reaction pressure was 3.2 MPa, and the reaction volume hourly space velocity was 10,000 h⁻¹. -1 The inlet reaction temperature of the hydrogenation reactor is 83.4℃.

[0113] Table 6 Composition of Hydrogenation Feedstock

[0114]

[0115] Comparative Example 1

[0116] The hydrogenation unit is a 500ml C2 hydrogenation side-stream unit, which uses a three-stage series adiabatic bed process for selective hydrogenation removal of acetylene. The hydrogenation catalyst is Shell's 7741B-T, which uses alumina as a support and approximately 0.03% Pd as the active component. The composition of the hydrogenation feedstock is shown in Table 2.

[0117] (1) After the airtightness of the hydrogenation unit is qualified, the inert gas nitrogen replacement is qualified.

[0118] (2) CO is injected into the first, second and third stage hydrogenation reactors of the hydrogenation unit. The catalyst loading amount of each hydrogenation reactor is 350 ml. CO is injected into the steel cylinder (10 L / cylinder, pressure 6 MPa). The CO content is about 1500 ppm. The CO injection time is 1.5 h.

[0119] (3) Open the feed valve and use the hydrogenation feedstock to pressurize the reactor bed through the bypass to pressurize the reactor to 2.3 MPa for 15 min. The inlet temperature of the hydrogenation reactor is preheated to 30°C by the cracked gas. The bed temperature rises by 2°C after the pressing is completed.

[0120] (4) When the reaction feed gas is heated, the inlet temperature rises when the temperature of the first stage hydrogenation reactor is 45.5℃. Heating is stopped, but the inlet temperature continues to rise rapidly. The device overheats and the inlet temperature of the first stage hydrogenation reactor reaches a maximum of 180℃. The reactor is depressurized in a chain reaction. Due to the overheating during the pressurization process, the device fails to start up.

[0121] Comparative Example 2

[0122] The hydrogenation unit is a 500ml C2 hydrogenation side-stream unit, which uses a three-stage series adiabatic bed process for selective hydrogenation removal of acetylene. The hydrogenation catalyst is Shell's 7741B-T, which uses alumina as a support and approximately 0.03% Pd as the active component. The composition of the hydrogenation feedstock is shown in Table 3.

[0123] (1) After the airtightness of the hydrogenation unit is qualified, the inert gas nitrogen replacement is qualified.

[0124] (2) The feed valve was fully opened, and the hydrogenation reactor bed was continuously pressurized by the bypass hydrogenation feedstock. The pressing time was 23 minutes and the pressure was 5.0 MPa. The inlet temperature of the hydrogenation reactor continued to rise, the unit overheated, and the unit failed to start up.

[0125] Comparative Example 3

[0126] The 500ml C2 hydrogenation side-stream unit employs a two-stage series adiabatic bed process for selective hydrogenation removal of acetylene. The hydrogenation catalyst used is Olemax-252 from Südschau, Germany. The Olemax-252 hydrogenation catalyst uses alumina as a support and is loaded with approximately 0.04% Pd as the active component. The composition of the hydrogenation feedstock is shown in Table 5.

[0127] (1) After the airtightness of the hydrogenation unit is qualified, the inert gas nitrogen replacement is qualified.

[0128] (2) CO is injected into the first and second stage hydrogenation reactors of the hydrogenation unit. The catalyst loading amount of each hydrogenation reactor is 450 ml. CO is injected into the steel cylinder (10 L / cylinder, pressure 6 MPa). The CO content is about 1600 ppm. The CO injection time is 1.0 h.

[0129] (3) Ethane pressurization: Pressurize the hydrogenation reactor to 0.5 MPa for 10 min.

[0130] (4) Open all the feed valves and introduce hydrogenation feedstock through the bypass reactor bed at a pressure of 2.5 MPa. The inlet temperature of the hydrogenation reactor is preheated to 28°C by the cracked gas. After the pressurization is completed, the bed temperature rises by 2°C.

[0131] (5) The reaction feed gas is heated. A temperature difference of 7°C appears in the bed of the first hydrogenation reactor, but the inlet temperature shows an upward trend. Heating is stopped, and the inlet temperature is allowed to drop and stabilize for 15 minutes. Heating is then continued until the temperature in the first hydrogenation reactor gradually increases from top to bottom. Four temperature measuring points are set from the inlet to the outlet in the first hydrogenation reactor. When a temperature gradient of 56°C is formed between two adjacent temperature measuring points, that is, the inlet and outlet temperature difference of the first hydrogenation reactor is 15°C, samples are taken for analysis. The conversion rate of the first hydrogenation reactor is tested to be 80%, and the heating of the first hydrogenation reactor is ended. The second hydrogenation reactor is then heated until a positive temperature difference appears in the second hydrogenation reactor, that is, the temperature in the second hydrogenation reactor gradually increases from top to bottom. Five temperature measuring points are set from the inlet to the outlet in the second hydrogenation reactor. When a temperature gradient of 5°C is formed between two adjacent temperature measuring points, that is, the inlet and outlet temperature difference of the second hydrogenation reactor is 20°C, and the acetylene at the outlet of the second hydrogenation reactor is less than 1 ppm, the heating of the second hydrogenation reactor is ended.

[0132] (6) After the reaction bed temperature stabilized, the inlet temperature of each hydrogenation reactor was fine-tuned according to the required load distribution, ensuring that the acetylene outlet of the second-stage hydrogenation reactor was below 1 ppm and the total ethylene selectivity of the first and second-stage hydrogenation reactors was ≥60%. From the start of the pressurization to the qualified acetylene outlet of the second-stage hydrogenation reactor, the total start-up time was 10.8 hours, and the start-up was completed. The reaction pressure was 2.5 MPa and the reaction volume hourly space velocity was 9000 h⁻¹. -1 The inlet reaction temperatures of the first and second stage hydrogenation reactors are 65.5℃ and 72.9℃, respectively.

[0133] The results from Comparative Examples 1 and 2 show that in Comparative Examples 1 and 2, the reactor bed temperature rose rapidly due to the lack of ethane pressurization, causing overheating and ultimately resulting in start-up failure. The results from Comparative Examples 3 and 4 show that in Comparative Example 3, insufficient pressurization pressure led to overheating during the reaction, and the total start-up time was nearly three times that of the present invention.

[0134] The start-up method for an ethane cracking to ethylene hydrogenation unit disclosed in this invention employs the injection of ethane as the cracking feedstock. Compared to the traditional method of slowly pressurizing the hydrogenation unit using cracked gas as the feedstock, this invention directly pressurizes the unit from a slightly positive pressure to a reaction pressure of 1.0–5.0 MPa using ethane. This method features faster pressurization and shorter pressurization time. Simultaneously, this method avoids the problem of alkynes and dienes being statically adsorbed by the catalyst due to the stagnant feedstock gas, generating significant adsorption heat. This heat accumulation, when sufficient, drives the hydrogenation reaction of alkynes and dienes, preventing further heat generation and potential overheating issues. Furthermore, the presence of a large amount of ethane dilutes the concentration of alkynes and dienes in the hydrogenation feedstock, effectively reducing the risk of overheating during the heating process and shortening the time from hydrogenation start-up to product qualification. The use of ethane pressurization in this invention also avoids impurities introduced by nitrogen pressurization, shortening product qualification time and reducing material loss.

[0135] Furthermore, when CO is introduced during nitrogen replacement and ethane pressurization, the initial catalyst activity can be suppressed. Combined with ethane pressurization of the reactor, the pressurization time of the cracked gas is reduced and the concentration of alkynes and dienes in the hydrogenation feedstock is diluted, further reducing the risk of overheating of the unit.

[0136] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the present invention.

Claims

1. A rapid start-up method for an ethane cracking to ethylene production unit with a hydrogenation arm, characterized in that, Includes the following steps: After the airtightness of the hydrogenation unit is checked and found to be qualified, it is purged with inert gas, and then ethane is introduced into the hydrogenation unit for pressurization to 1.0-5.0 MPa. The process also includes the following steps: after stamping, the hydrogenation feedstock for ethane cracking to ethylene production that meets the start-up requirements is introduced into the hydrogenation unit, and the hydrogenation unit is continued to be heated until the inlet and outlet temperature difference of the hydrogenation reactor of the hydrogenation unit is 2~30℃, the temperature in the hydrogenation reactor rises from top to bottom and forms multiple temperature gradients, the temperature gradient is 1~12℃, and the bed heating is completed when the acetylene at the end outlet of the hydrogenation unit is qualified. The hydrogenation feedstock is pressurized in the hydrogenation device to a reaction pressure of 1.0–5.0 MPa for 0.5–3 min. Based on the volume of the hydrogenation feedstock, the hydrogenation feedstock includes at least: 0.01% to 0.5% CO, 20% to 55% hydrogen, 0.1% to 1.0% acetylene, 30% to 75% ethylene, and ethane; Between the inert gas replacement and the introduction of ethane for tamping, the following step is also included: CO is introduced into the hydrogenation device to make the volume content of CO in the hydrogenation device reach 1000 to 10000 ppm.

2. The rapid start-up method according to claim 1, characterized in that, The inert gas is nitrogen.

3. The rapid start-up method according to claim 1, characterized in that, Ethane is introduced into the hydrogenation unit and pressurized to 1.5–2.5 MPa.

4. The rapid start-up method according to claim 1, characterized in that, Based on the volume of the hydrogenation feedstock, the hydrogenation feedstock includes at least: 0.02% to 0.04% CO, 25% to 35% hydrogen, 0.15% to 0.5% acetylene, 35% to 70% ethylene, and ethane.

5. The rapid start-up method according to claim 1, characterized in that, The hydrogenation device is a single-stage or multi-stage hydrogenation reactor. When the hydrogenation device is a multi-stage hydrogenation reactor, the hydrogenation reactors are connected in series or in parallel.

6. The rapid start-up method according to claim 5, characterized in that, The hydrogenation device is a two-stage hydrogenation reactor, with each stage connected in series. The inlet temperature of the first stage hydrogenation reactor is adjusted to 60-70°C, the inlet-outlet temperature difference is 5-25°C, and the temperature gradient is 2-10°C. The inlet temperature of the second stage hydrogenation reactor is adjusted to 65-80°C, the inlet-outlet temperature difference is 3-20°C, and the temperature gradient is 1-6°C.

7. The rapid start-up method according to claim 5, characterized in that, The hydrogenation device is a three-stage hydrogenation reactor connected in series. The inlet temperature of the first stage hydrogenation reactor is adjusted to 50~65℃, the inlet-outlet temperature difference is 5~25℃, and the temperature gradient is 2~10℃. The inlet temperature of the second stage hydrogenation reactor is adjusted to 55~70℃, the inlet-outlet temperature difference is 3~25℃, and the temperature gradient is 2~10℃. The inlet temperature of the third stage hydrogenation reactor is adjusted to 60~80℃, the inlet-outlet temperature difference is 3~20℃, and the temperature gradient is 1~6℃.

8. The rapid start-up method according to claim 5, characterized in that, The hydrogenation reactor is an adiabatic bed or an isothermal bed.

9. The rapid start-up method according to claim 8, characterized in that, The hydrogenation reactor is an adiabatic bed.

10. The rapid start-up method according to claim 1, characterized in that, The ethane is pressurized for 15 to 240 minutes.

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