A start-up system and method for synthesizing gas to olefin

Abstract

The present application relates to a kind of synthetic gas olefin starting system and starting method, synthetic gas olefin starting system includes fluidized bed reactor, also includes: water pipe, steam drum, control system, control system is linked with the control valve on each water pipe, for making steam and boiler water with cascade flow regulation mode control bed temperature after the domestication of synthetic gas olefin late stage.The present application is suitable for the starting stage of synthetic gas olefin technical device, mainly for the adjustment of reactor bed temperature;The present application uses the cascade process of steam and boiler water combination, utilizes the characteristics of steam temperature sensible heat small, heat absorption little, can realize the reasonable transition of heat removal means in the domestication stage, finally realizes gradually input water pipe;The present application can meet the requirement of bed temperature in domestication stage, avoid bed layer sudden drop, energy saving while can avoid the alternate condition of equipment, simultaneously, the present application can avoid catalyst bed layer when bed temperature rises too fast, fly temperature.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, specifically to a start-up system and method for syngas-to-olefins production. Background Technology

[0002] The method of converting syngas into liquid hydrocarbons through catalysis was invented in 1923 by German scientists Frans Fischer and Hans Tropsch, abbreviated as FT synthesis. This process involves the heterogeneous catalytic hydrogenation of CO over a metal catalyst, producing a mixture primarily composed of straight-chain alkanes and alkenes. Currently mature coal-to-olefins (CTO) technologies include four core technologies: coal gasification, syngas purification, methanol synthesis, and methanol-to-olefins (MTO). CTO first converts coal into syngas, then performs a syngas conversion process, followed by purification. The purified syngas is then used to produce crude methanol, which is subsequently distilled. The methanol product is ultimately supplied to the olefins plant to produce ethylene, propylene, and other products. Currently, the main problems with CTO are: long technical routes, numerous pieces of equipment, large investment in equipment, high raw material and energy consumption, and high water consumption.

[0003] While direct syngas-to-olefins (STO) avoids the synthesis and purification of intermediate products, resulting in a shorter process route and reduced investment and operating costs, the STO process has not yet achieved industrial-scale operation. Research remains primarily focused on catalyst development, with a significant lack of research on process flow development and product separation scheme design. Over the past few decades, Fischer-Tropsch synthesis catalysts have made substantial progress. Currently, commonly used catalysts are divided into two main categories based on their active components: iron-based catalysts and cobalt-based catalysts. Depending on the catalyst used and the target product, Fischer-Tropsch reactors are further classified into fixed-bed reactors, fluidized-bed reactors, and slurry-bed reactors. Fluidized-bed reactors are characterized by higher temperatures, higher conversion rates, no difficulties in liquid-solid separation, and products that are mostly low-carbon hydrocarbons. They also have lower construction and operating costs, and the low pressure drop saves on compression costs and facilitates the removal of heat released during the reaction. Furthermore, the low gas linear velocity reduces wear, making long-term operation possible. For example, Chinese invention patents CN 104226327 B and CN 104549447 B both disclose similar production methods, namely, using a CO and H2 mixture with a molar ratio of 0.5 to 3 as raw materials, and reacting the gases at a reaction temperature of 250 to 350°C, a reaction pressure of 0.5 to 2.5 MPa, and a volume hourly space velocity of 1000 to 4000 h⁻¹. -1 Under certain conditions, the reaction occurs when the catalyst is in contact with the reaction medium to produce hydrocarbons.

[0004] In the above scheme, the syngas to olefins catalyst adopts a novel Fischer-Tropsch catalyst with Fe, Co or Ni as the active component. The normal reaction temperature of the catalyst is ~330~380℃. Before use, the novel catalyst must be reduced with hydrogen and acclimated with syngas (CO+H2) or CO. During the acclimation period, the reactor bed temperature needs to be maintained at 280~365℃. If it is below 280℃, the acclimation reaction cannot be started. If it is above 365℃, the metal active component will start to undergo a large amount of Fischer-Tropsch reaction, rapidly releasing the heat of reaction, causing the bed temperature to soar.

[0005] To address these issues, existing technologies typically involve channeling boiler water into the reactor's water pipes, using the latent heat of vaporization of the water to remove the heat of reaction. However, because the latent heat of vaporization of boiler water is relatively large, while the heat released during the acclimation reaction is very small, the mismatch between heat absorption and release can easily lead to a sudden drop in bed temperature, causing the acclimation reaction to stop. If the temperature is raised to above 280°C using electric heating or heat tracing to restart the reaction, it is not only energy-intensive, but the repeated sudden temperature drops and rises can also cause frequent stress changes in the equipment, making it prone to damage. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a start-up system for syngas to olefins that can meet the requirements of bed temperature during the acclimatization stage, avoid sudden bed temperature drops, avoid catalyst bed overheating when the temperature rise is too high, and has low energy consumption and is friendly to equipment.

[0007] The second technical problem to be solved by the present invention is to provide a start-up method for the above-mentioned syngas-to-olefins start-up system, in view of the current state of the prior art.

[0008] The technical solution adopted by the present invention to solve at least one of the above-mentioned technical problems is as follows:

[0009] A start-up system for syngas-to-olefins includes a fluidized bed reactor and further includes:

[0010] The water pipes are multiple and located in the fluidized bed reactor. The inlet and outlet ends of each water pipe extend outside the fluidized bed reactor and are equipped with control valves for controlling the flow rate.

[0011] A steam drum is located beside the fluidized bed reactor, and the inlet and outlet of each water pipe are connected to the steam drum; the steam drum is also provided with an inlet for input of start-up steam;

[0012] The control system, linked with each control valve, is used to control the bed temperature in the later stages of syngas-to-olefins conversion by adjusting the flow rates of steam and boiler water in a stepped manner.

[0013] Preferably, at least two of the water pipes are used to introduce steam, and at least one is used to introduce boiler water.

[0014] Preferably, the control system is used to gradually increase the number of water pipes used to supply boiler water in the later stages of syngas-to-olefins acclimatization, based on the syngas load.

[0015] Preferably, the water pipe includes a steam pipe and a boiler water pipe. The first end of the steam pipe is a steam inlet connected to the top of the steam drum, and the second end is a steam outlet connected to the top of the steam drum. The first end of the boiler water pipe is a boiler water inlet connected to the bottom of the steam drum, and the second end is a steam outlet connected to the top of the steam drum.

[0016] Preferably, the second end of the boiler water pipe is connected to the output section of the steam pipe, and the connection point is located between the fluidized bed reactor and the steam drum. The second end of the boiler water pipe is linked to the control system through a control valve on the steam pipe.

[0017] Preferably, a pressure booster for pressurizing the boiler water is installed on the boiler water pipeline, and a control valve on the boiler water pipeline is located downstream of the pressure booster. Both the pressure booster and the control valve are linked to the control system.

[0018] A method for starting up syngas to olefins includes the following steps:

[0019] (1) The catalyst is reduced by passing H2 at 430-480℃, and the bed temperature rises rapidly. After the reduction stage, the acclimatization stage is carried out. At 280-365℃, the catalyst structure and morphology are gradually changed by reacting syngas with the catalyst surface to meet the requirements of syngas to olefins.

[0020] (2) As the acclimatization stage progresses, the activity of the catalyst gradually increases and the heat released by the reaction gradually increases. When the reaction temperature rises to 5℃~10℃ / min, steam at 250℃~340℃ is first introduced into the fluidized bed reactor through the steam pipe to remove the heat.

[0021] (3) As the catalyst activity is further enhanced, the olefin synthesis reaction is gradually started and the heat release continues to increase. When the reaction temperature rises to 10℃~20℃ / min, boiler water at 250℃~340℃ is introduced through the boiler water pipe. In the high-temperature reaction gas environment of 330℃~380℃ outside the water pipe, the boiler water is rapidly vaporized, carrying away many times more heat than steam at the same temperature.

[0022] (4) After the acclimatization stage ends, the normal reaction stage begins, with greater heat release and faster temperature rise. The control system gradually puts more boiler water pipes into use according to the increase in reaction load, so that the catalyst can maintain a stable reaction at 330-380℃.

[0023] (5) After the bed reaction temperature stabilizes, stop supplying steam to the steam pipeline.

[0024] Preferably, in step (4), depending on the heat release of the reaction and the size of the equipment, for every 10% to 20% increase in the reaction load, 1 to 10 more boiler water pipes are added to maintain the boiler water and steam system at a steady state of 230 to 270°C.

[0025] Compared with existing technologies, the advantages of this invention are as follows: This invention is applicable to the start-up stage of syngas-to-olefins technology plants, mainly used for regulating the reactor bed temperature; This invention adopts a stepped process combining steam and boiler water, utilizing the characteristics of low sensible heat rise and low heat absorption of steam, which can achieve a reasonable transition of heat transfer methods during the acclimation stage, and finally achieve gradual introduction of water pipes; This invention can not only meet the bed temperature requirements during the acclimation stage and avoid a sudden drop in bed temperature, saving energy, but also avoid alternating operating conditions of the equipment. At the same time, this invention can prevent the catalyst bed from overheating when the bed temperature rises too quickly. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] like Figure 1 As shown, the start-up system for syngas-to-olefins in this embodiment includes a fluidized bed reactor 1, and further includes:

[0029] The water pipes are multiple and are installed in the fluidized bed reactor 1. The inlet and outlet ends of each water pipe extend outside the fluidized bed reactor 1 and are equipped with a control valve 100 for controlling the flow rate.

[0030] Steam drum 2 is located beside fluidized bed reactor 1, and the inlet and outlet of each water pipe are connected to steam drum 2; steam drum 2 is also provided with an inlet for input of start-up steam;

[0031] The control system, linked with each control valve 100, is used to control the bed temperature in the later stage of syngas-to-olefins conversion by adjusting the steam and boiler water flow rates in a stepped manner.

[0032] In this embodiment, at least two water pipes are used for introducing steam, and at least one is used for introducing boiler water. The control system is used to gradually increase the number of water pipes used for introducing boiler water according to the syngas load during the later stages of syngas-to-olefins acclimatization.

[0033] The water pipes in this embodiment include a steam pipe 31 and a boiler water pipe 32. The first end of the steam pipe 31 is a steam inlet connected to the top of the steam drum 2, and the second end is a steam outlet connected to the top of the steam drum 2. The first end of the boiler water pipe 32 is a boiler water inlet connected to the bottom of the steam drum 2, and the second end is a steam outlet connected to the top of the steam drum 2.

[0034] In this embodiment, the second end of the boiler water pipe 32 is connected to the output section of the steam pipe 31, and the connection point is located between the fluidized bed reactor 1 and the steam drum 2. The second end of the boiler water pipe 32 is linked to the control system through the control valve 100 on the steam pipe 31.

[0035] A pressure booster 33 for pressurizing the boiler water is installed on the boiler water pipe 32. The control valve 100 on the boiler water pipe 32 is located downstream of the pressure booster 33. Both the pressure booster 33 and the control valve 100 are linked to the control system.

[0036] In this embodiment, the start-up method for syngas to olefins employs a stepped process combining steam and boiler water, gradually introducing water into the reactor to meet the bed temperature requirements during the acclimation phase. This avoids both a sudden drop in bed temperature and excessively high temperature rises that could cause catalyst bed overheating. The syngas to olefins process utilizes a fluidized bed and a novel Fischer-Tropsch catalyst. Heat from the reactor bed is dissipated through a steam drum directly connected to it. During startup, high-temperature steam is used to heat the boiler water to establish stable pressure and temperature.

[0037] 4) In the later stages of acclimatization, the catalyst has already acquired high activity and the heat release of the reaction increases. In order to prevent the Fischer-Tropsch reaction from starting in large quantities, certain heat removal measures are needed to maintain the temperature below 365℃.

[0038] Specifically, the following steps are included:

[0039] (1) The catalyst is reduced by passing H2 at 430-480℃, and the bed temperature rises rapidly. After the reduction stage, the reduced Fischer-Tropsch catalyst has metallic activity and will initiate the Fischer-Tropsch reaction in large quantities at 365℃. At 280℃-365℃, the catalyst surface is reacted with syngas, i.e., acclimation reaction, to gradually change the catalyst structure and morphology to meet the requirements of syngas to olefins.

[0040] (2) As the acclimatization stage progresses, the activity of the catalyst gradually increases and the heat released by the reaction gradually increases. In order to prevent the large-scale start of the Fischer-Tropsch reaction, heat removal measures are required to maintain the temperature below 365℃. When the reaction temperature rises by 5℃~10℃ / min, steam at 250~340℃ (preferably 300℃) is first introduced into the fluidized bed reactor through a steam pipe to remove the heat. The enthalpy of saturated steam at 300℃ is 2749kJ / kg, and the enthalpy of superheated steam at 350℃ is 2972kJ / kg. The heat removed, i.e. the enthalpy difference, is 223KJ / kg.

[0041] (3) As the catalyst activity further increases, the olefin synthesis reaction gradually starts and the heat release continues to increase. When the reaction temperature rises to 10℃~20℃ / min, boiler water at 250~340℃ (preferably 300℃, i.e. enthalpy value 1345kJ / kg) is introduced through the boiler water pipe. In the high-temperature reaction gas environment outside the water pipe, which exceeds 330℃~380℃, the boiler water rapidly vaporizes and produces 300℃ saturated steam with an enthalpy value of 2749kJ / kg, i.e. enthalpy difference 1404KJ / kg. It can be seen that the latent heat enthalpy difference of vaporization is ~7 times the sensible heat enthalpy difference of the heat carried away by the steam, and can carry away many times more heat than steam at the same temperature.

[0042] (4) After the acclimatization stage ends, the normal reaction stage begins, with greater heat release and faster temperature rise. The control system gradually puts more boiler water pipes into use according to the increase in reaction load. For every 10% to 20% increase in reaction load, 1 to 10 more boiler water pipes are put into use to maintain the boiler water and steam system at a steady state of 230℃ to 270℃ (preferably 250℃). The enthalpy of boiler water at 250℃ is 1085KJ / kg, which corresponds to the enthalpy of saturated steam of 2801KJ / kg, i.e., the enthalpy difference is 1716KJ / kg, so that the catalyst can maintain a stable reaction at 330 to 380℃.

[0043] (5) After the bed reaction temperature stabilizes, stop supplying steam for heat removal.

[0044] The following example illustrates the above method and process.

[0045] During startup, ultra-high pressure steam is used to heat the boiler water to establish a steam pressure of 8.5 MPaG and 300°C. The catalyst is first reduced by introducing H2 at 450°C. After reduction, the reaction bed is maintained at ~345°C, and syngas at ~30% load is introduced for the next stage of acclimation. During the acclimation stage, syngas is introduced into the reactor at 30% load, reacting with the catalyst surface at ~345°C to change the catalyst structure and morphology to meet the requirements of syngas-to-olefins production. The syngas temperature is heated to 345°C using electric heaters or other heating methods. In the later stages of start-up acclimation, when the reaction temperature rises by 8°C / min, 300°C steam is first introduced into the reactor's water pipes. Two steam pipes are connected to stabilize the reaction bed temperature at 345°C. The bed temperature is monitored; when the temperature rise reaches 15°C / min, a 300°C boiler water pipe is introduced to reduce the bed temperature to 345-350°C. After the acclimatization phase, the process enters the normal reaction stage. As the syngas load increases, the heat release becomes greater. The novel Fischer-Tropsch catalyst for syngas-to-olefins requires a stable reaction temperature of 330–380°C. This is achieved by adjusting the steam pressure through the steam drum to stabilize the bed temperature. During this stage, the syngas load is gradually increased, and more water pipes are added to maintain the boiler water and steam system at a steady state of 230–270°C. Through these steps, multiple water pipes are gradually connected to the boiler water and put into operation, stabilizing the reaction bed temperature at 330–380°C. Once the bed temperature stabilizes, at 100% load, the steam supply from the aforementioned steam pipes is stopped, ending the start-up phase and entering the normal reaction stage.

Claims

1. A method for starting up a synthesis gas to olefin system, the synthesis gas to olefin system comprising a fluidized bed reactor, characterized in that Also comprising: water pipes, multiple and arranged in the fluidized bed reactor, the inlet and outlet of each water pipe extending out of the fluidized bed reactor and provided with a control valve for controlling the flow rate; a steam drum arranged beside the fluidized bed reactor, the inlet and outlet of each water pipe being connected to the steam drum respectively; the steam drum is also provided with an inlet for inputting start-up steam; a control system associated with each control valve, for controlling the bed temperature in a step flow rate adjustment manner by steam and boiler water after the late domestication of the synthesis gas to olefins; comprising the following steps: (1) reducing the catalyst by passing H2 at 430-480℃, the bed temperature rises rapidly, after the reduction stage, the domestication stage is carried out, by reacting the synthesis gas with the catalyst surface at 280-365℃, gradually changing the catalyst structure and morphology to meet the needs of synthesis gas to olefins; (2) as the domestication stage proceeds, the activity of the catalyst gradually increases, the heat release of the reaction gradually increases, when the reaction temperature rises to 5-10℃ / min, first pass 250-340℃ steam into the fluidized bed reactor through the steam pipeline to take away the heat; (3) as the activity of the catalyst further increases, the olefin synthesis reaction is gradually started, the heat release continues to increase, when the reaction temperature rises to 10-20℃ / min, pass 250-340℃ boiler water through the boiler water pipeline, in the high temperature reaction gas environment of 330-380℃ outside the water pipe, the boiler water vaporizes rapidly; (4) the heat removal of the boiler water vaporization is 5-15 times that of the steam at the same temperature; (5) after the domestication stage ends, enter the normal reaction stage, the heat release is greater, the temperature rises faster, the control system gradually puts into use more boiler water pipelines according to the increase of the reaction load, so that the catalyst maintains stable reaction at 330-380℃; (6) after the bed reaction temperature stabilizes, stop feeding steam into the steam pipeline.

2. The method of claim 1, wherein: At least two of the water pipes are used for passing steam, and at least one is used for passing boiler water.

3. The method of claim 2, wherein: The control system is used for gradually increasing the number of water pipes for passing boiler water according to the synthesis gas load during the late domestication of the synthesis gas to olefins.

4. The method of claim 1 or 2 or 3, wherein: The water pipes include steam pipelines and boiler water pipelines, the first end of the steam pipeline is connected to the steam inlet on the top of the steam drum, and the second end is the steam outlet connected to the top of the steam drum, the first end of the boiler water pipeline is the boiler water inlet connected to the bottom of the steam drum, and the second end is the steam outlet connected to the top of the steam drum.

5. The method of claim 4, wherein: The second end of the boiler water pipeline is connected to the output section of the steam pipeline, and the connection is located between the fluidized bed reactor and the steam drum, the second end of the boiler water pipeline is connected to the control system through the control valve on the steam pipeline.

6. The method of claim 4, wherein: A pressurizer is arranged on the boiler water pipeline for pressurizing the boiler water, the control valve on the boiler water pipeline is located downstream of the pressurizer, and the pressurizer and the control valve are connected to the control system.

7. The method of claim 1 or 2 or 3, wherein: In step (5), according to the heat release of the reaction and the size of the equipment, the boiler water pipe is added by 1-10 pipes for every 10%-20% increase of the reaction load, so as to maintain the boiler water and steam system in a steady state of 230-270℃.

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