How to start a Fischer-Tropsch plant

Abstract

A method for starting a Fischer-Tropsch plant, comprising: providing a Fischer-Tropsch plant including a fixed-bed Fischer-Tropsch unit downstream of a reverse water-gas shift unit; providing a feed stream containing hydrogen and carbon dioxide; passing the feed stream through a reverse water-gas shift unit to produce a synthesis gas in which carbon monoxide is concentrated; providing a first water supply source; using heat from the synthesis gas to generate a first steam from the first water supply source, thereby forming a cooled synthesis gas; and passing at least a portion of the first steam through a Fischer-Tropsch unit to raise the temperature of the Fischer-Tropsch unit to a first operating temperature of the Fischer-Tropsch unit.

Description

Technical Field

[0001] The present invention relates to a method for starting a Fischer-Tropsch plant and, after starting the Fischer-Tropsch plant, a method for operating the Fischer-Tropsch plant to produce hydrocarbon products.

Background Art

[0002] Examples of Fischer-Tropsch plants and their operation are described in International Publication Nos. 2021140227 (A1), 2018146276 (A1), 2017037175 (A1), 2015140100 (A1), 2015140099 (A1), 2015010939 (A1) and 2009128865 (A1).

[0003] The Fischer-Tropsch process is a set of chemical reactions that convert a mixture of carbon monoxide and hydrogen (also known as synthesis gas) into liquid hydrocarbons. These reactions occur in the presence of a metal catalyst, typically at a temperature of 150 to 300 °C and a pressure of 1 to several tens of atmospheres. The Fischer-Tropsch process ideally involves a series of chemical reactions that produce various hydrocarbons having the formula (C n H 2n+2 ). More useful reactions produce alkanes as follows: (2n + 1)H2 + nCO → C n H 2n+2 + nH2O (where n is typically 1 to 100 or more). The formation of methane (n = 1) is undesirable. Most of the alkanes produced tend to be straight-chain and are suitable for upgrading to produce middle distillate fuels such as diesel fuel and jet fuel. In addition to alkane formation, competing reactions result in small amounts of alkenes, as well as alcohols and other oxygenated hydrocarbons. The Fischer-Tropsch reaction is a highly exothermic reaction because the standard reaction enthalpy (ΔH) is -165 kJ / mol CO in total.

[0004] In a typical Fischer-Tropsch plant, the synthesis gas supplied to the Fischer-Tropsch unit is typically prepared by subjecting a feed gas containing hydrogen and carbon dioxide to a reverse water-gas shift reaction, converting some of the carbon dioxide and hydrogen into carbon monoxide and water.

[0005] In the startup of a typical Fischer-Tropsch plant, the temperature of the Fischer-Tropsch unit is raised to an operating temperature suitable for carrying out the Fischer-Tropsch reaction with desirable reaction rate, conversion rate, and / or selectivity. Raising the temperature typically involves passing steam through the Fischer-Tropsch unit. This increases the complexity of the plant and also increases costs in terms of the need for an external steam source.

[0006] The present invention aims to address at least some of the problems associated with the prior art, or to provide at least a commercially acceptable alternative solution to the prior art. [Overview of the project]

[0007] One aspect of this disclosure is a method for starting a Fischer-Tropsch plant, To provide a Fischer-Tropsch plant including a fixed-bed Fischer-Tropsch unit downstream of a reverse water-gas shift unit, To provide a supply stream containing hydrogen and carbon dioxide, The supply flow is passed through a reverse water-gas shift unit to produce synthesis gas with concentrated carbon monoxide, To provide a primary water supply source, The process involves using heat from the synthesis gas to generate a first steam from a first water source, thereby forming a cooled synthesis gas, The present invention relates to a method comprising passing at least a portion of a first steam through a Fischer-Tropsch unit to raise the temperature of the Fischer-Tropsch unit to a first operating temperature of the Fischer-Tropsch unit.

[0008] Another aspect of the present disclosure is a method for starting a Fischer-Tropsch plant and then operating the Fischer-Tropsch plant to produce hydrocarbon products, Starting the Fischer-Tropsch plant using the method defined above, The present invention relates to a method comprising operating a Fischer-Tropsch plant by supplying cooled synthesis gas to a Fischer-Tropsch unit after the Fischer-Tropsch plant has reached a first operating temperature, thereby producing hydrocarbon products. [Brief explanation of the drawing]

[0009] [Figure 1] This is a flowchart of one embodiment of the method according to the present invention. [Modes for carrying out the invention]

[0010] In a first embodiment, the present disclosure relates to a method for starting a Fischer-Tropsch plant, To provide a Fischer-Tropsch plant including a fixed-bed Fischer-Tropsch unit downstream of a reverse water-gas shift unit, To provide a supply stream containing hydrogen and carbon dioxide, The supply flow is passed through a reverse water-gas shift unit to produce synthesis gas with concentrated carbon monoxide, To provide a primary water supply source, The process involves using heat from the synthesis gas to generate a first steam from a first water source, thereby forming a cooled synthesis gas, The present invention relates to a method comprising passing at least a portion of a first steam through a Fischer-Tropsch unit to raise the temperature of the Fischer-Tropsch unit to a first operating temperature of the Fischer-Tropsch unit.

[0011] Each aspect or embodiment defined herein may be combined with any other aspect or embodiment unless expressly indicated otherwise. Specifically, any feature indicated as preferred or advantageous may be combined with any other feature indicated as preferred or advantageous.

[0012] An advantage of the present invention is that the method may allow the Fischer-Tropsch unit to reach operating temperature without the use of an external steam supply source. This reduces the complexity of the method and avoids the need for additional equipment to generate steam. By generating steam using heat from synthesis gas, the energy requirements of the method are reduced, thereby lowering costs and environmental impacts.

[0013] This method is a method for starting a Fischer-Tropsch plant. As used herein, the expression "starting a Fischer-Tropsch plant" may encompass a method of raising the Fischer-Tropsch unit to a temperature sufficient for carrying out the Fischer-Tropsch reaction.

[0014] This method includes providing a Fischer-Tropsch plant including a fixed-bed Fischer-Tropsch unit. Fischer-Tropsch units are well known in the art.

[0015] A fixed-bed Fischer-Tropsch unit is installed downstream of the reverse water-gas shift unit. Reverse water-gas shift units are well known in the art. Under the reverse water-gas shift reaction, carbon dioxide and hydrogen are converted as follows:

[0016] [ka]

[0017] In this method, a part of the carbon dioxide and a part of the hydrogen are converted into carbon monoxide and water. As can be understood, not all of the hydrogen is converted. This is because the synthesis gas needs to contain hydrogen, for example, for performing a subsequent Fischer-Tropsch reaction. The reverse water-gas shift unit preferably contains a catalyst containing nickel. Such a catalyst is particularly suitable for performing the reverse water-gas shift reaction at advantageous temperatures and pressures and with a high conversion rate. The reverse water-gas shift unit is preferably at a temperature of at least 700 °C. Such a temperature can make the conversion rate from carbon dioxide and hydrogen to carbon monoxide and water particularly high.

[0018] The fixed bed Fischer-Tropsch unit is provided downstream of the reverse water-gas shift unit. "Downstream" means that the fixed bed Fischer-Tropsch unit and the reverse water-gas shift unit are in fluid communication, and during normal operation of the Fischer-Tropsch plant, the gas flows through the reverse water-gas shift unit before flowing through the fixed bed Fischer-Tropsch unit.

[0019] This method includes providing a feed stream containing hydrogen and carbon dioxide. The feed stream can include chemical species other than hydrogen and carbon dioxide, such as water, carbon monoxide, methane, and ammonia, and solid chemical species such as dust and coke, for example. The components of the feed gas can vary depending on its production method and the starting materials used. The feed stream can be generated by gasification of a carbonaceous feedstock, such as municipal solid waste. Hydrogen can be generated by electrolysis of water. The energy for electrolysis can be from renewable resources, thereby making the method more environmentally friendly. Carbon dioxide can be a by-product of combustion. Carbon dioxide can be from flue gas. Carbon dioxide can be from a partial oxidation and / or gasification device. The feed stream can be subjected to one or more purification steps, for example, removing one or more of water, carbon monoxide, methane, ammonia, and solid chemical species, before being sent to the reverse water-gas shift unit. Suitable substrates are well-known in the art.

[0020] The method includes passing a feed stream through a reverse water gas shift unit to produce a syngas in which carbon monoxide is concentrated. As described above, not all of the hydrogen is converted. This is because the syngas needs to contain hydrogen, for example, to undergo a Fischer-Tropsch reaction later.

[0021] As used herein, the term "syngas" or "synthesis gas" may include a fuel gas mixture. In the method of the present invention, the syngas contains carbon monoxide (i.e., CO) and hydrogen (i.e., molecular hydrogen H2). The syngas may contain other chemical species such as, for example, water and / or unreacted carbon dioxide. "Carbon monoxide is concentrated" means that the syngas contains a greater amount of carbon monoxide than the feed stream. In other words, "producing a syngas in which carbon monoxide is concentrated by sending a feed stream through a reverse water gas shift unit" may include converting at least a part of carbon dioxide and hydrogen into carbon monoxide and water by sending a feed stream through a reverse water gas shift unit.

[0022] The method includes providing a first water source. The first water source may be from a Fischer-Tropsch plant such as process condensate and by-product water. In such a case, providing the water source may include subjecting the water source to one or more purification steps. Alternatively, the first water source may be an external water source such as boiler feed water.

[0023] This method involves using heat from the synthesis gas to generate a first steam from a first water source, thereby forming a cooled synthesis gas. The heat from the synthesis gas can also be transferred to the first water source, for example, using a heat exchanger. During the generation of the first steam, the synthesis gas and the first water source are typically not in direct contact with each other. The cooled synthesis gas is typically at a temperature suitable for supply to a Fischer-Tropsch unit. This method involves passing at least a portion of the first steam through the Fischer-Tropsch unit to raise the temperature of the Fischer-Tropsch unit to a first operating temperature. The first operating temperature can be a temperature sufficient for the Fischer-Tropsch reaction to take place. The Fischer-Tropsch unit can be raised from ambient temperature to the first operating temperature.

[0024] Generating steam from a first water source using heat from synthesis gas preferably involves passing the synthesis gas through a steam generating boiler connected to a first steam drum. This can be a particularly efficient method for generating steam. Steam generating boilers and steam drums are well known in the art.

[0025] The first operating temperature of the Fischer-Tropsch unit is preferably 100°C to 130°C. At these temperatures, the cooled synthesis gas supplied to the Fischer-Tropsch unit is not expected to undergo the Fischer-Tropsch reaction, in which case the Fischer-Tropsch unit can be further heated to a higher second operating temperature (as described later).

[0026] At least a portion of the first steam supplied to the Fischer-Tropsch unit is preferably supplied to the Fischer-Tropsch unit at a temperature of 200-310°C, preferably 240-290°C, and / or at a pressure of 16-99 bara, preferably 33-74 bara. Steam having such a temperature and / or pressure is known in the art as “high-grade” steam. Such temperatures and pressures may be particularly suitable for heating the Fischer-Tropsch unit to a first operating temperature. If the temperature is too low, the Fischer-Tropsch unit may take too long to reach the first operating temperature, or may not reach it at all. If the temperature is too high, the Fischer-Tropsch unit may reach an undesirable high temperature. If the pressure is too low, the efficiency of heating the Fischer-Tropsch unit to the first operating temperature may be low. If the pressure is too high, more complex or expensive equipment may be required.

[0027] The reverse water-gas shift unit preferably includes an autothermal reverse water-gas shift unit (where heat for the endothermic reverse water-gas shift reaction is provided by the combustion of fuel with oxygen), an electrically heated reverse water-gas shift unit, a plasma heated reverse water-gas shift unit, and / or a solid-oxide-electrolyser cell (SOEC). Such reverse water-gas shift units are well known in the art and are particularly suitable for converting a feed stream into synthesis gas. Furthermore, such reverse water-gas shift units are particularly suitable for generating heat for forming a first vapor.

[0028] The Fischer-Tropsch unit preferably comprises a catalyst containing cobalt, iron, and / or ruthenium, more preferably a cobalt-containing catalyst. Such catalysts are particularly effective in catalyzing the Fischer-Tropsch reaction and / or can advantageously allow the reaction to proceed at low temperatures and / or in high yields.

[0029] Preferably, the Fischer-Tropsch plant further includes a carbon dioxide recovery unit downstream of the reverse water-gas shift unit and upstream of the Fischer-Tropsch unit, and the method further includes passing at least a portion of the first steam through the carbon dioxide recovery unit to raise the temperature of the carbon dioxide recovery unit to a desired operating temperature. The carbon dioxide recovery unit can remove carbon dioxide from the cooled synthesis gas before it is sent to the Fischer-Tropsch unit. This allows for obtaining an optimal synthesis gas standard before supplying the cooled synthesis gas to the Fischer-Tropsch unit. By removing carbon dioxide from the cooled synthesis gas, the efficiency of the method and the subsequent Fischer-Tropsch reaction using the cooled synthesis gas can be increased. If carbon dioxide is not removed from the cooled synthesis gas, it can accumulate to more than 50 mol%, which may adversely affect the performance of the Fischer-Tropsch catalyst. By heating the carbon dioxide recovery unit using steam from the reverse water-gas shift unit, the carbon dioxide recovery unit can reach its operating temperature without using an external steam source. This reduces the complexity of the method. Since the first vapor is generated using heat from the synthesis gas, the energy requirements of this method are reduced, thereby lowering costs and environmental impacts. Carbon dioxide capture units are well known in the art. A carbon dioxide capture unit preferably uses a liquid chemical absorbent, more preferably an amine (e.g., an alkylamine selected from MEA, DEA, and MDEA), or one or more alkali metal carbonates, and / or a liquid physical absorbent, more preferably a liquid physical absorbent selected from one or more methanol, glycol, or glycol ethers. Such absorbents may be particularly suitable for removing carbon dioxide. The liquid chemical absorbent may also be part of a scrubber.

[0030] Preferably, the carbon dioxide recovery unit includes an amine carbon dioxide recovery unit comprising an absorption unit and a regeneration unit including a regeneration tower, wherein the desired operating temperature of the carbon dioxide recovery unit corresponds to the desired operating temperature at the bottom of the regeneration tower, and the desired operating temperature is 100°C to 180°C. Such amine carbon dioxide recovery units are well known in the art.

[0031] At least a portion of the first steam supplied to the carbon dioxide capture unit is supplied to the carbon dioxide capture unit at a temperature of preferably 170–230°C, more preferably 180–220°C, even more preferably 190–210°C, and / or at a pressure of 5–25 bara, more preferably 10–20 bara, and even more preferably 12–16 bara. Steam having such temperatures and / or pressures is known in the art as “lower” steam. Such temperatures and pressures are particularly suitable for heating the carbon dioxide capture unit to a desired operating temperature. If the temperature is too low, the carbon dioxide capture unit may take too long to reach the desired operating temperature, or may not reach it at all. If the temperature is too high, the carbon dioxide capture unit may reach undesirably high temperatures. If the pressure is too low, the efficiency of heating the carbon dioxide capture unit to the first operating temperature may be low. If the pressure is too high, the efficiency of heating the carbon dioxide capture unit to a first operating temperature may be low. If the pressure is too high, more complex equipment may be required and / or the safety of the method may be reduced.

[0032] Preferably, at least a portion of the first steam supplied to the carbon dioxide capture unit is pressure-reduced (e.g., using a pressure reducing valve) before being supplied to the carbon dioxide capture unit. This is because the vapor pressure conditions of the carbon dioxide capture unit may be lower than those of the Fischer-Tropsch unit. In other words, it may be preferable to supply "lower" steam to the carbon dioxide capture unit. Supplying "higher" steam to the carbon dioxide capture unit may cause the design temperature and pressure of the carbon dioxide capture unit to be exceeded.

[0033] Preferably, 30-50 mol% of the first steam is sent to the Fischer-Tropsch unit, and 50-70 mol% of the first steam is sent to the carbon dioxide recovery unit. This ensures that the Fischer-Tropsch unit and the carbon dioxide recovery unit reach their operating temperatures at an appropriate time during startup.

[0034] The feed stream is preferably delivered to the reverse water-gas shift unit at a temperature of 400°C to 1000°C, preferably 450°C to 900°C. Lower temperatures may mean that the reverse water-gas shift reaction occurs at an undesirably low rate and / or low selectivity, or not at all. Higher temperatures may increase the cost of the method, but the reaction rate and / or selectivity do not increase accordingly. To achieve such temperatures, the feed stream can be heated, for example, in an electric raw material heater.

[0035] Preferably, while raising the temperature of the Fischer-Tropsch unit to the first operating temperature, the cooled synthesis gas is not supplied to the Fischer-Tropsch unit at all. At temperatures below the operating temperature, the Fischer-Tropsch reaction may not occur, or may occur only at a slow rate and / or with low selectivity. In a further embodiment, the present disclosure relates to a method for starting a Fischer-Tropsch plant and then operating the Fischer-Tropsch plant to produce hydrocarbon products, Starting a Fischer-Tropsch plant using the method described in any of the prior claims, The present invention provides a method comprising: operating a Fischer-Tropsch plant by supplying cooled synthesis gas to a Fischer-Tropsch unit after the Fischer-Tropsch plant has reached a first operating temperature, thereby producing hydrocarbon products.

[0036] The advantages and preferred features of the first embodiment are the same in this embodiment.

[0037] The hydrocarbon product is preferably a liquid hydrocarbon product. As used herein, the term “liquid hydrocarbon” may encompass chemical species formed from carbon and hydrogen that are liquid at room temperature and room pressure. Hydrocarbons typically include alkanes, typically containing 1 to 100 or more carbon atoms per molecule. Liquid hydrocarbons preferably contain alkanes. Alkanes may be particularly desirable products. The hydrocarbon product can be subjected to one or more purification and / or modification and / or quality-enhancing steps. Suitable purification, modification, and quality-enhancing steps are well known in the art.

[0038] Sending cooled synthesis gas to a Fischer-Tropsch unit to produce hydrocarbon products typically involves contacting the cooled synthesis gas with a Fischer-Tropsch catalyst housed within the Fischer-Tropsch unit.

[0039] The molar ratio of hydrogen to carbon monoxide in the cooled synthesis gas is preferably 1.8 to 2.2, because this value is close to the stoichiometric ratio of approximately 2 in the Fischer-Tropsch reaction.

[0040] During the process of operating the Fischer-Tropsch plant, the process of supplying at least a portion of the first steam to the Fischer-Tropsch unit is preferably continued while the temperature of the Fischer-Tropsch unit rises to a second operating temperature higher than the first operating temperature, in which case the second operating temperature is at least 10°C higher than the first operating temperature, preferably at least 15°C higher than the first operating temperature, more preferably at least 20°C higher than the first operating temperature, and / or 135 to 250°C, preferably 150 to 240°C. Between the first and second operating temperatures, the Fischer-Tropsch unit can be heated just enough to carry out the Fischer-Tropsch reaction. However, such a Fischer-Tropsch reaction may not be optimized with respect to rate, yield, and / or selectivity. The exothermic nature of the Fischer-Tropsch reaction can raise the temperature of the Fischer-Tropsch unit, but by continuously heating the Fischer-Tropsch unit to a second operating temperature, the second operating temperature can be reached more quickly.

[0041] Preferably, after the Fischer-Tropsch unit has reached a second operating temperature, the process of supplying at least a portion of the first steam to the Fischer-Tropsch unit is stopped. At this point, an exothermic Fischer-Tropsch reaction may have occurred to a sufficient extent to heat the Fischer-Tropsch unit to the final desired operating temperature. At this point, the first steam can also be supplied to other "higher" steam users within the Fischer-Tropsch plant. The second operating temperature may be high enough to generate steam in the steam boiler connected to the Fischer-Tropsch unit. The final desired operating temperature is preferably 300°C or lower. Higher temperatures may increase the energy cost of the method without significantly increasing the level of liquid hydrocarbons produced.

[0042] Preferably, the volume of the first vapor supplied to the Fischer-Tropsch unit gradually decreases between the first and second operating temperatures. As used herein, the term “gradually decreases” may encompass multiple decreasing stages, e.g., at least two decreasing stages, or a continuous decrease with increasing temperature. As the temperature rises from the first operating temperature to the second operating temperature, the exothermic Fischer-Tropsch reaction increases, which means that the need for heating using the first vapor gradually decreases.

[0043] Preferably, the Fischer-Tropsch plant further comprises a carbon dioxide capture unit downstream of the reverse water-gas shift unit and upstream of the Fischer-Tropsch unit. Starting the Fischer-Tropsch plant includes sending at least a portion of the first steam to the carbon dioxide capture unit to raise the temperature of the carbon dioxide capture unit to a desired operating temperature, and operating the Fischer-Tropsch plant further includes sending the cooled synthesis gas to the carbon dioxide capture unit before sending the cooled synthesis gas to the Fischer-Tropsch unit to recover carbon dioxide from the cooled synthesis gas. The advantages and preferred features of the carbon dioxide capture unit are as described above.

[0044] Preferably, this method further includes recirculating the carbon dioxide recovered from the carbon dioxide capture unit into the supply stream. This avoids releasing carbon dioxide into the atmosphere and can increase the "carbon efficiency" of the method.

[0045] Operating the Fischer-Tropsch plant preferably further includes providing a second water source, generating a second steam from the second water source using heat from the Fischer-Tropsch unit, and sending at least a portion of the second steam to a carbon dioxide recovery unit to maintain its operating temperature. This avoids the need for an external steam source and the corresponding drawbacks mentioned above. Such second steam is typically "low-grade" and therefore suitable for sending to a carbon dioxide recovery unit.

[0046] Preferably, the Fischer-Tropsch unit comprises a tube side and a shell side, with a second water source provided on the shell side, and generating a second steam from the second water source using heat from the Fischer-Tropsch unit, which includes the use of a second steam drum connected to the shell side. "Tube side" means the inside of the tubes in the vessel where the Fischer-Tropsch reaction takes place. "Shell side" means the outside of the same tubes in the vessel, i.e., the space in the vessel between each tube and between each tube and the inner wall of the vessel. The Fischer-Tropsch unit can be cooled by providing a second water source on the shell side and generating steam from it. Since the Fischer-Tropsch reaction is an exothermic reaction, this ensures that the Fischer-Tropsch unit does not reach unnecessarily high operating temperatures.

[0047] Preferably, generating steam from a first water source using heat from the synthesis gas involves supplying the synthesis gas to a steam generating boiler connected to a first steam drum, the first steam drum generating steam at a higher pressure than the second steam drum. Typically, the first steam drum generates "higher" steam (because reverse water-gas shift units are usually operated at relatively high temperatures), while the second steam drum generates "lower" steam (because Fischer-Tropsch units are usually operated at relatively low temperatures).

[0048] The cooled synthesis gas supplied to the Fischer-Tropsch unit preferably contains less than 50 mol% carbon dioxide, more preferably less than 30 mol%, even more preferably less than 20 mol%, even more preferably less than 10 mol%, even more preferably less than 5 mol%, and even more preferably less than 1 mol%, based on the total number of moles of cooled synthesis gas supplied to the Fischer-Tropsch unit. As mentioned above, high concentrations of carbon dioxide may adversely affect the performance of the Fischer-Tropsch catalyst and reduce the efficiency of the method.

[0049] After the Fischer-Tropsch unit reaches a second operating temperature, it is preferable to stop the process of sending at least a portion of the first steam to the carbon dioxide recovery unit. At this point, the first steam can also be sent to other "higher" steam users within the Fischer-Tropsch plant. The second operating temperature may be sufficient to generate "lower" steam in the steam boiler connected to the Fischer-Tropsch unit, and by sending this to the carbon dioxide recovery unit, the temperature of the carbon dioxide recovery unit can be maintained during the operation of the Fischer-Tropsch plant.

[0050] Preferably, after the Fischer-Tropsch unit reaches a second operating temperature, at least a portion of the first steam is sent to one or both of the Fischer-Tropsch unit preheater and the refined bed preheater. This avoids the need for an external steam source to heat such preheaters and the corresponding drawbacks.

[0051] The present invention can be used to restart a temporarily stopped process, or to start up a Fischer-Tropsch unit when the Fischer-Tropsch catalyst requires activation.

[0052] The present invention will be described below in relation to the following non-limiting embodiments. [Examples]

[0053] An example of the method according to the present invention will be described with reference to Figure 1. The drawing is schematic, and it will be understood by those skilled in the art that further items of equipment such as reflux drums, compressors, pumps, vacuum pumps, towers, heat exchangers, temperature sensors, pressure sensors, pressure relief valves, control valves, flow controllers, level controllers, holding tanks, and storage tanks may be required in a commercial plant. Providing such equipment accessories does not constitute part of the present invention and follows conventional chemical engineering practices.

[0054] In Figure 1, a feed stream containing hydrogen and carbon dioxide is sent via line 1 to the inlet of the reverse water-gas shift unit 2, where synthesis gas 3 with concentrated carbon monoxide is produced. The high-temperature synthesis gas then passes through the synthesis gas boiler 4, generating high-grade steam 10 via a closely connected HP steam drum 9. The HP steam drum 9 is supplied with boiler feedwater 6, which circulates naturally back to the synthesis gas boiler 4 via a downpipe 7 and a riser pipe 8. During normal operation, the high-grade steam 10 is sent to high-grade steam users via line 11.

[0055] The cooled synthesis gas 5 is sent to the carbon dioxide recovery unit 22, where carbon dioxide is removed to obtain the appropriate synthesis gas specifications for the Fischer-Tropsch unit 15. The carbon dioxide 23 is recirculated to the reverse water-gas shift unit 2. The synthesis gas flow 14 enters the tubular side of the Fischer-Tropsch unit 15. The Fischer-Tropsch synthesis reaction is an exothermic reaction. The heat generated from the Fischer-Tropsch unit is used to raise the lower steam on the shell side of the Fischer-Tropsch unit 15 via the LP steam drum 18. The LP steam drum 18 is supplied with boiler feedwater 17, and the LP steam drum is connected to the Fischer-Tropsch unit 15 via a downpipe 24 and a riser pipe 25. During normal operation, the lower steam 19 is sent to lower steam users via line 20 and to the carbon dioxide recovery unit 22 via line 21. The lower steam is used to provide heat for the reboiling duty of the amine regeneration unit (not shown) in the carbon dioxide recovery unit 22.

[0056] During startup, the temperature of the Fischer-Tropsch unit 15 is raised by heating with higher steam from the HP steam drum 9 via line 26. The higher steam is added to the shell side of the Fischer-Tropsch unit 15, raising the temperature inside the unit and initiating the Fischer-Tropsch reaction. If the Fischer-Tropsch synthesis reaction does not occur, no lower steam is generated in the LP steam drum 18 to be supplied to the lower steam user and the carbon dioxide recovery unit 22. During startup, heat is supplied to the lower steam user by reducing the pressure of the higher steam through the pressure reducing valve 12 to the pressure of the lower steam user. This allows the carbon dioxide recovery unit 22 to start and achieve the appropriate synthesis gas specifications for the Fischer-Tropsch unit 15. Once the Fischer-Tropsch unit 15 reaches its operating temperature and has supplied sufficient lower steam to the lower steam user, the higher steam pressure reducing valve 12 is closed.

[0057] The detailed description above is provided for illustrative and illustrative purposes only and is not intended to limit the scope of the appended claims. Many modifications of the currently preferred embodiments shown herein will be obvious to those skilled in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. A method for starting the Fischer-Tropsch plant, To provide a Fischer-Tropsch plant including a fixed-bed Fischer-Tropsch unit downstream of a reverse water-gas shift unit, To provide a supply stream containing hydrogen and carbon dioxide, The supply flow is passed through the reverse water-gas shift unit to produce synthesis gas in which carbon monoxide is concentrated, To provide a first water supply source, Using the heat from the synthesis gas, a first steam is generated from the first water supply source, thereby forming a cooled synthesis gas. A method comprising passing at least a portion of the first steam through the Fischer-Tropsch unit to raise the temperature of the Fischer-Tropsch unit to a first operating temperature of the Fischer-Tropsch unit.

2. The method according to claim 1, wherein generating steam from the first water supply source using heat from the synthesis gas includes passing the synthesis gas through a steam generating boiler connected to a first steam drum.

3. The method according to claim 1 or claim 2, wherein the first operating temperature of the Fischer-Tropsch unit is 100°C to 130°C.

4. At least a portion of the first steam sent to the Fischer-Tropsch unit is sent to the Fischer-Tropsch unit. A temperature of 200°C to 310°C, preferably 240°C to 290°C, and / or The method according to any one of claims 1 to 3, wherein the material is delivered at a pressure of 16 to 99 bar, preferably 33 to 74 bar.

5. The method according to any one of claims 1 to 4, wherein the reverse water-gas shift unit includes an autothermal reverse water-gas shift unit, an electrically heated reverse water-gas shift unit, a plasma heated reverse water-gas shift unit, and / or a solid oxide electrolytic cell (SOEC).

6. The method according to any one of claims 1 to 5, wherein the Fischer-Tropsch unit includes a cobalt-containing catalyst.

7. The Fischer-Tropsch plant further includes a carbon dioxide capture unit downstream of the reverse water-gas shift unit and upstream of the Fischer-Tropsch unit. The method according to any one of claims 1 to 6, further comprising passing at least a portion of the first steam through the carbon dioxide recovery unit to raise the temperature of the carbon dioxide recovery unit to a desired operating temperature of the carbon dioxide recovery unit.

8. The carbon dioxide recovery unit includes an amine carbon dioxide recovery unit which includes an absorption unit and a regeneration unit which includes a regeneration tower. The desired operating temperature of the carbon dioxide recovery unit corresponds to the desired operating temperature of the bottom of the regeneration tower, and The method according to claim 7, wherein the desired operating temperature is 100°C to 180°C.

9. The method according to claim 7 or 8, wherein at least a portion of the first steam sent to the carbon dioxide recovery unit is depressurized before being sent to the carbon dioxide recovery unit.

10. The method according to any one of claims 7 to 9, wherein 30 to 50 mol% of the first steam is sent to the Fischer-Tropsch unit and 50 to 70 mol% of the first steam is sent to the carbon dioxide recovery unit.

11. The method according to any one of claims 1 to 10, wherein the supply flow is sent to the reverse water-gas shift unit at a temperature of 400°C to 1000°C, preferably 450°C to 900°C.

12. The method according to any one of claims 1 to 11, wherein the cooled synthesis gas is not supplied to the Fischer-Tropsch unit substantially at all while the temperature of the Fischer-Tropsch unit is raised to the first operating temperature.

13. A method for starting a Fischer-Tropsch plant and then operating the Fischer-Tropsch plant to produce hydrocarbon products, Starting the Fischer-Tropsch plant using the method described in any one of claims 1 to 12, A method comprising: operating the Fischer-Tropsch plant by supplying the cooled synthesis gas to the Fischer-Tropsch unit after the Fischer-Tropsch plant has reached the first operating temperature, thereby producing hydrocarbon products.

14. During the process of operating the Fischer-Tropsch plant, the process of supplying at least a portion of the first steam to the Fischer-Tropsch unit is continued until the temperature of the Fischer-Tropsch unit rises to a second operating temperature higher than the first operating temperature, and the second operating temperature is At least 10°C higher than the first operating temperature, preferably at least 15°C higher than the first operating temperature, more preferably at least 20°C higher than the first operating temperature, and / or The method according to claim 13, wherein the temperature is 135 to 250°C, preferably 150 to 240°C.

15. The method according to claim 14, wherein the step of supplying at least a portion of the first steam to the Fischer-Tropsch unit is stopped after the Fischer-Tropsch unit has reached the second operating temperature.

16. The method according to claim 15, wherein the volume of the first steam supplied to the Fischer-Tropsch unit gradually decreases between the first operating temperature and the second operating temperature.

17. The Fischer-Tropsch plant further includes a carbon dioxide capture unit downstream of the reverse water-gas shift unit and upstream of the Fischer-Tropsch unit. Starting the Fischer-Tropsch unit includes passing at least a portion of the first steam through the carbon dioxide recovery unit to raise the temperature of the carbon dioxide recovery unit to a desired operating temperature. The method according to any one of claims 13 to 16, further comprising operating the Fischer-Tropsch plant by passing the cooled synthesis gas through the carbon dioxide recovery unit to recover carbon dioxide from the cooled synthesis gas before sending the cooled synthesis gas to the Fischer-Tropsch unit.

18. The method according to claim 17, further comprising recirculating the carbon dioxide recovered from the carbon dioxide recovery unit to the supply flow.

19. Operating the aforementioned Fischer-Tropsch plant is To provide a second water supply source, The heat from the Fischer-Tropsch unit is used to generate a second steam from the second water supply source, The method according to any one of claims 13 to 18, further comprising sending at least a portion of the second steam to the carbon dioxide recovery unit to maintain the operating temperature of the carbon dioxide recovery unit.

20. The Fischer-Tropsch unit comprises a tubular side and a shell side, The second water supply source is provided on the shell side, The method according to claim 21, wherein generating the second steam from the second water supply source using heat from the Fischer-Tropsch unit includes using a second steam drum connected to the shell side.

21. Generating steam from the first water supply source using heat from the synthesis gas includes passing the synthesis gas through a steam generating boiler connected to the first steam drum. The method according to claim 20, wherein the first steam drum generates steam at a higher pressure than the second steam drum.

22. The method according to any one of claims 17 to 21, wherein the cooled synthesis gas sent to the Fischer-Tropsch unit contains less than 50 mol% carbon dioxide, preferably less than 30 mol% carbon dioxide, more preferably less than 20 mol% carbon dioxide, even more preferably less than 10 mol% carbon dioxide, even more preferably less than 5 mol% carbon dioxide, and even more preferably less than 1 mol% carbon dioxide, based on the total number of moles of cooled synthesis gas sent to the Fischer-Tropsch unit.

23. The method according to any one of claims 17 to 22, wherein the step of sending at least a portion of the first steam to the carbon dioxide recovery unit is stopped after the Fischer-Tropsch unit has reached the second operating temperature.

24. The method according to any one of claims 13 to 23, wherein, after the Fischer-Tropsch unit has reached the second operating temperature, at least a portion of the first steam is sent to one or both of the Fischer-Tropsch unit preheater and the refined bed preheater.

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