A catalyst loading method for a fixed-bed Fischer-Tropsch synthesis reactor

Abstract

The application discloses a catalyst loading method of a fixed-bed Fischer-Tropsch synthesis reactor with a tube column, which comprises the following steps: (1) cleaning the reaction tube column and loading a blocking spring at the bottom of the reaction tube column; (2) connecting the bottom end of the reaction tube column with the outlet pipe of a pump, injecting light oil with a distillation range of 100-230 DEG C into the reaction tube column to a certain height through the pump, stopping the pump and maintaining the oil level at the height through a pressure control valve arranged on a cross line connecting the pump outlet and the pump inlet; (3) loading catalyst into the reaction tube column from the top opening of the reaction tube column, and maintaining the oil level height in step (2) through the pressure control valve; and (4) after the catalyst loading is completed, discharging the light oil from the reaction tube column and recovering the light oil. The application avoids the loss caused by the breakage of the catalyst, ensures the uniform loading of the catalyst in the reaction tube column, the consistency of the bulk density, is favorable for reducing the axial temperature difference and improving the performance of the catalyst.

Description

Technical Field

[0001] This invention relates to the field of Fischer-Tropsch synthesis, and particularly to a catalyst loading method for a tubular fixed-bed Fischer-Tropsch synthesis reactor. Background Technology

[0002] Fischer-Tropsch synthesis is a strongly exothermic reaction, and a tubular reactor is a preferred reactor type. Currently, the diameter of the tubular reactors used in Fischer-Tropsch synthesis is generally in the range of 26mm-42mm, and the length can reach 10-12m, with a single reactor containing tens of thousands of tubes. Catalyst loading is a key factor affecting the stable operation of the tubular reactor. Improper catalyst loading not only affects mass and heat transfer but also causes localized overheating, and in severe cases, catalyst runaway and deactivation. Therefore, how to ensure more uniform catalyst loading in the tubular reactor is an urgent problem to be solved.

[0003] CN105126709B discloses a catalyst loading device and method for a tubular fixed-bed reactor. The loading device consists of three parts: a conveying device, a dispensing device, and a feeding device. Through automatic dispensing and vibratory loading, it reduces the labor intensity of on-site workers and improves work efficiency and loading accuracy. This invention ensures the consistency of catalyst loading between different reaction tubes, but it does not consider how to avoid bridging during the loading process, nor how to avoid catalyst powdering and breakage caused by physical impact during the falling process.

[0004] CN1607032A discloses a method for loading a catalyst. This method involves inserting a chain-like material into the reaction tube during the catalyst loading process, with the lower end of the chain-like material positioned higher than the upper end of the catalyst layer. This method can largely avoid the "bridging" phenomenon during catalyst loading, and the resistance of the chain-like material can reduce catalyst pulverization and breakage caused by physical impact during catalyst falling in a fixed-bed tubular reactor. However, since the reaction tubes are typically 10-15m high, collisions between the catalyst and the chain-like material during the falling process can still cause catalyst breakage. This inevitably leads to a higher catalyst packing density at the bottom of the reaction tube compared to the top, resulting in higher heat release in the lower bed and an axial temperature difference. Furthermore, the need to continuously pull up the chain-like material during catalyst loading inevitably leads to prolonged loading time and increased labor intensity for workers.

[0005] CN102989376B and CN102989375B disclose a catalyst loading method for a tubular reaction reactor. This method improves the uniformity of catalyst loading and reduces the difficulty of catalyst loading by controlling the catalyst loading rate. However, it does not consider how to avoid catalyst pulverization and breakage caused by physical impact during the falling process; nor does it consider the problem of inconsistent packing density between the upper and lower parts of the catalyst bed.

[0006] The inventions mentioned above all involve catalyst loading technology for tubular reactors. The catalyst loading uniformity is mainly improved by automatic dispensing, insertion of chain materials, and control of loading rate. However, the above methods only partially alleviate or solve the problem of catalyst loading uniformity. Problems such as easy catalyst breakage, inconsistent packing density between upper and lower catalyst beds, and large axial temperature difference still exist. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide a catalyst loading method for a tubular fixed-bed Fischer-Tropsch synthesis reactor, so as to avoid the loss caused by catalyst packing damage, facilitate the uniform loading of catalyst in the reaction tubes, and improve the catalytic reaction effect.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A catalyst loading method for a tubular fixed-bed Fischer-Tropsch synthesis reactor, the catalyst loading method comprising:

[0010] (1) Clean the reaction tubes thoroughly and install a sealing spring at the bottom of the reaction tubes;

[0011] (2) Then connect the bottom end of the reaction tube to the outlet pipe of the pump, and inject a certain height of light oil with a distillation range of 100-230℃ into the reaction tube through the pump. Then stop the pump and maintain the oil level at this height through the pressure control valve set on the cross line connecting the pump outlet and the pump inlet.

[0012] (3) The catalyst is loaded into the reaction tube from the top opening of the reaction tube so that the catalyst settles in the reaction tube and forms a catalyst bed. At the same time, the oil level in step (2) is maintained by the pressure control valve to prevent the oil level from rising and overflowing during the addition of the catalyst to the reaction tube.

[0013] (4) After the catalyst is loaded, drain the light oil from the reaction tube and recover it.

[0014] In some embodiments, when cleaning the reaction tube in step (1), the reaction tube can be cleaned by a high-pressure water gun or steel brush to make the inner wall of the reaction tube smooth and free of dirt; then, a sealing spring is installed at the bottom of the reaction tube. The distance from the top of the sealing spring to the bottom of the reaction tube is represented by L and can be 5-40cm, preferably 10-30cm, such as 15, 20 or 25cm.

[0015] Those skilled in the art will understand that the distance (L) between the sealing spring and its bottom end in each reaction tube should be kept consistent to ensure consistent catalyst loading. In some embodiments, the deviation of the distance L between the top and bottom ends of the sealing spring in different reaction tubes should be controlled within ±3cm (i.e., the difference between the L value in any reaction tube and the L value in any other reaction tube is within ±3cm), preferably within ±1cm, such as ±0.5cm or 0.

[0016] In step (2) of this invention, light oil is injected into the reaction tube from the bottom using a pump, and the oil level is maintained by a pressure control valve installed across the line. Those skilled in the art will understand that the pressure control valve can open when the pressure exceeds a set value and close when the pressure falls below the set value, so that when the oil level in the reaction tube rises due to the addition of the catalyst, light oil can be promptly discharged from the bottom of the reaction tube to maintain the oil level.

[0017] Preferably, the light oil used is selected from light hydrocarbons produced by Fischer-Tropsch synthesis with a distillation range of 100℃ to 230℃, such as 100-200℃ or 140-230℃. Using Fischer-Tropsch synthesis oil can avoid the poisoning of the catalyst by sulfur in the oil. Selecting a distillation range of 100℃ to 230℃ for the light oil prevents volatilization during catalyst loading, thus avoiding safety hazards, and also prevents hydrogenolysis during catalyst reduction, which could lead to catalyst carbon buildup, and promotes subsequent Fischer-Tropsch synthesis. Preferably, the light oil can be a light white oil with the grades W-20, W-30, W-40, or W-60.

[0018] In some embodiments, the distance between the light oil injected in step (2) and the upper end of the reaction tube is in the range of 100cm-150cm. This is to prevent the catalyst from being damaged during the fall due to the excessive distance between the oil level and the upper end of the tube, and to prevent the oil droplets from splashing during the catalyst loading process due to the insufficient distance between the oil level and the upper end of the tube.

[0019] In a preferred embodiment, the pump outlet is provided with a pump outlet valve, which is connected to the bottom of the reaction tube via an oil inlet pipeline and to the pump inlet via a crossover line; the oil inlet pipeline is provided with an oil inlet valve, and the crossover line is provided with a pressure gauge and the pressure control valve in sequence along the material flow direction.

[0020] Preferably, when the pump starts, first ensure that the pump is in self-circulation state by means of a cross-line, then gradually adjust the cross-line pressure control valve to input light oil into the reaction tube. After the oil level rises to the predetermined height H, record the corresponding oil pressure P, then stop the pump and maintain the oil level at this height H by means of a pressure control valve.

[0021] In this invention, the pump can be a centrifugal pump, gear pump, screw pump, plunger pump, diaphragm pump, etc., and the pump head needs to be higher than the length of the reaction tubes; centrifugal pumps and diaphragm pumps are preferred. The pressure control valve can be a needle valve, regulating valve, back pressure valve, etc., with back pressure valves being preferred.

[0022] In some implementations, the pump inlet of the connecting line is further connected to a light oil storage tank, thereby providing the light oil used for injection and recovering the light oil when the catalyst is added, improving the injection and recovery efficiency of the light oil.

[0023] In step (3) of the present invention, the catalyst is loaded into the reaction tube from the top opening of the reaction tube so that the catalyst settles in the reaction tube and forms a catalyst bed. Considering that the settling of the catalyst in light oil is different from that of conventional catalyst loading, in order to prevent phenomena such as "bridging", "channeling" and "deviation" in the catalyst loading in light oil, in a preferred embodiment, the ratio of the diameter of the reaction tube to the equivalent diameter of the catalyst should be 15:1-30:1, for example 25:1, preferably 15:1-20:1.

[0024] Preferably, in order to ensure catalyst strength while reducing catalyst methane selectivity, the catalyst cross-sectional diameter should not exceed 2 mm, and the catalyst cross-sectional diameter is preferably 1.4 mm to 1.8 mm.

[0025] In a preferred embodiment, to ensure the catalyst loading effect, the catalyst loading rate (i.e., the rate at which the height of the formed catalyst bed rises) should not exceed 10 cm / s, such as 4-6 cm / s or 8-10 cm / s, to prevent catalyst bridging. In this invention, to avoid the problem of overflow caused by the oil level rising during catalyst loading, the oil pressure (P) in step (2) is maintained constant by a pressure control valve, allowing excess light oil to return through the pressure control valve.

[0026] Those skilled in the art will understand that, to prevent catalyst leakage, it is well known in the art that, before loading the catalyst in step (3), the catalyst may be added sequentially to the reaction tubes, for example, by means of methods such as adding... Porcelain balls and The ceramic balls should be filled to a uniform height, for example, 15-25cm, such as 20cm.

[0027] In a preferred embodiment, in step (4), after the catalyst is loaded, the oil pressure is released to atmospheric pressure through the pressure control valve, so that the light oil exits from the reaction tube. Then, the catalyst bed is purged from top to bottom with an inert gas, preferably nitrogen, to remove the light oil adsorbed on the catalyst. At the same time, since the catalyst is added to the light oil, the catalyst dust is easier to separate from the catalyst. With the subsequent purging, the catalyst dust removal effect is significantly better.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] (1) In this invention, the injection and discharge of light oil are carried out through the bottom of the reaction tube, which requires simple equipment, is easy to operate, and saves light oil; moreover, the activity of the catalyst is significantly improved and the C5+ space yield is also improved after adding light oil compared with not adding it.

[0030] (2) By adding light oil to the reaction tubes, the falling rate of the catalyst is slowed down, reducing the probability of catalyst breakage. At the same time, by controlling the ratio of the reactor inner diameter to the equivalent diameter of the catalyst and the catalyst loading rate, the consistency of the pressure drop and packing density of the catalyst beds in multiple tubes is improved, which helps to reduce the axial temperature difference, thereby improving the catalyst activity and space-time yield and reducing methane selectivity. Under the premise of ensuring good loading effect, the catalyst loading efficiency is high. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a loading apparatus for implementing the loading method of the present invention;

[0032] Explanation of reference numerals in the attached figures:

[0033] 3-Reaction tube; 4-Oil level; 5-Blocking spring; 6-Oil inlet line; 7-Oil inlet valve; 8-Pump outlet valve; 9-Pump; 11-Crossover line; 12-Pressure control valve; 13-Pressure gauge. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0035] Figure 1A schematic diagram of a filling device for implementing the filling method of the present invention is shown, wherein the pump outlet is provided with a pump outlet valve 8, the pump outlet valve 8 is connected to the bottom end of the reaction tube 3 through an oil inlet pipeline 6 and connected to the pump inlet through a cross line 11; an oil inlet valve 7 is provided on the oil inlet pipeline 6, and a pressure gauge 13 and a pressure control valve 12 are sequentially provided on the cross line 11 along the material flow direction.

[0036] After cleaning the reaction tube 3 and installing the sealing spring 5 at a distance L from the bottom end, the pump 9 can be started to prepare to inject light oil into the reaction tube. When the pump 9 is started, the cross-line 11 is used to ensure that the pump 9 is in a self-circulation state. Then, the cross-line pressure control valve 12 is gradually adjusted to input the light oil into the reaction tube 3. After the oil level 4 rises to the predetermined height H, the corresponding oil pressure P is recorded. Then the pump is stopped and the oil level 4 is maintained at this height H by the pressure control valve 12.

[0037] The catalyst is loaded into the reaction tube 3 through the top opening so that it settles and forms a catalyst bed. At the same time, the oil level 4 is maintained by the pressure control valve. After the catalyst is loaded, the oil pressure is released to atmospheric pressure by the pressure control valve 12 so that the light oil exits from the reaction tube. Then, the catalyst bed is purged from top to bottom with an inert gas, preferably nitrogen, to remove the light oil adsorbed on the catalyst.

[0038] The present invention will be further described below with reference to the embodiments.

[0039] Example 1

[0040] The tubular fixed-bed reactor has 113 reaction tubes, each 6m long and 25mm in inner diameter. It employs... Figure 1 The catalyst is loaded using the shown loading device. A sealing spring is installed 15 cm from the bottom of the reaction tube. Using W-20 (distillation range 120-160℃) light white oil as the light oil feedstock, the oil is slowly injected into the tube using a centrifugal pump and a pressure control valve (back pressure valve selected). The oil level is 5 m high, and the oil pressure is 35 kPa. The pump is then stopped. The catalyst is then added sequentially into the tube. Porcelain balls and Ceramic balls, each 20 cm high, were used to prevent catalyst leakage. 2.3 kg of clover-type catalyst (preparation details can be found in Example 2 of CN201810200988.4; the catalyst is 4-8 mm long, has a cross-sectional diameter of 1.7 mm, and an equivalent diameter of 1.5 mm) was weighed and added to the reaction tubes in three batches at a rate of 4-6 cm / s. After loading, the oil pressure was reduced to zero using a back pressure valve, and the tubes were purged with N2 from the top to remove dust and remove light white oil from the catalyst. After purging, the bed pressure drop and bulk density of the 113 tubes were measured and the data were recorded. Statistical and experimental results are shown in Tables 1, 2, and 3.

[0041] Example 2

[0042] The difference from Example 1 is that the light oil used is W-30 (distillation range 135-170℃), the catalyst cross-sectional diameter is 1.8mm, the equivalent diameter is 1.6mm, and the catalyst loading rate is 8-10cm / s.

[0043] The statistical and experimental results are shown in Tables 1, 2 and 3.

[0044] Example 3

[0045] The difference from Example 1 is that the light oil used is W-60 (distillation range 185-225℃), the catalyst cross-sectional diameter is 1.6mm, the equivalent diameter is 1.4mm, and the catalyst loading rate is 3-5cm / s.

[0046] The statistical and experimental results are shown in Tables 1, 2 and 3.

[0047] Comparative Example 1

[0048] The tubular fixed-bed reactor has 113 reaction tubes, each 6m long and 25mm in inner diameter. Sealing springs are installed 15cm from the bottom of each tube. Additives are then sequentially added to the tubes. Porcelain balls and Ceramic balls, each 20cm high, were used to prevent catalyst leakage. 2.3kg of clover-shaped catalyst (4-8mm long, 1.7mm in diameter, equivalent diameter 1.5mm) was weighed and added to the reactor tubes in three batches via free fall at a rate of 4-6cm / s. After loading, dust was removed from the catalyst by purging the tubes from the top with N2. After purging, the bed pressure drop and bulk density of the 113 tubes were measured and the data were recorded. During the purging process, a large amount of catalyst dust was found, resulting in a large pressure drop deviation. The bulk density of the catalyst at the bottom was significantly higher than that at the top, leading to a large axial temperature difference in the tubular reactor.

[0049] Comparative Example 2

[0050] In Example 1, the W-20 light white oil was replaced with a heavy diesel oil fraction at 300-400°C, and everything else remained the same as in Example 1. Although the catalyst packing density in the upper, middle, and lower parts was relatively uniform, it was found that the heavy diesel oil fraction was difficult to desorb from the catalyst due to its high viscosity. This not only affected the accuracy of the pressure drop measurement data, but more seriously, the residual heavy diesel oil fraction underwent a chemical reaction (hydrogenolysis reaction) during reduction, generating carbon deposits, which reduced the number of active sites on the catalyst and decreased its performance.

[0051] Comparative Example 3

[0052] In the examples, the cross-sectional diameter of the clover catalyst was increased to 3 mm, with an equivalent diameter of 2.7 mm, while other aspects remained the same as in the examples. It was found that the larger particle size of the catalyst led to enhanced internal diffusion, making it easier for H2 to enter the catalyst particles compared to CO. This resulted in a higher hydrogen-to-carbon ratio inside the catalyst particles, leading to increased methane production and a decrease in the target product C5+.

[0053] Comparative Example 4

[0054] The catalyst addition rate of 4-6 cm / s in the previous example was replaced with arbitrary addition, while everything else remained the same as in the previous example. During implementation, it was found that the catalyst was prone to bridging, especially in tubes containing internal thermocouples. This resulted in multiple rework steps, which was very time-consuming.

[0055] As can be seen from Tables 1 and 2, when the catalyst is loaded using the method of the present invention, the pressure drop deviation of multiple reaction tubes is small, the amount of rework is small, and the packing density of the upper, middle and lower parts of the catalyst bed is more uniform. As can be seen from the results in Table 3, after using the catalyst loading method of the present invention, the axial temperature difference of the catalyst bed is low, which means that the catalyst utilization rate is improved. Therefore, the CO conversion rate and the space-time yield of the target product C5+ are high.

[0056] Table 1. Statistics on pressure drop of 113 reaction tubes

[0057]

[0058]

[0059] Table 2. Bed packing density

[0060]

[0061] The catalysts loaded in the examples and comparative examples were reduced under the same conditions, at 215°C, 3MPa, and for 800 hours. -1 The Fischer-Tropsch reaction was carried out under the condition of H2 / CO=2. The axial temperature difference and experimental results are shown in Table 3.

[0062] Table 3. Axial temperature difference and experimental results of the reaction tubes.

[0063]

[0064] As can be seen from Tables 1, 2 and 3, compared with the comparative example, when the catalyst was loaded using the example, the catalyst loading uniformity was better, the pressure drop of the catalyst bed in different tubes could be controlled within ±5%, the catalyst packing density was more consistent, and the axial temperature difference was lower when the catalyst carried out the Fischer-Tropsch reaction; and the catalyst activity was significantly improved, the methane selectivity was reduced, and the C5+ space-time yield was increased.

[0065] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A catalyst loading method for a tubular fixed-bed Fischer-Tropsch synthesis reactor, the catalyst loading method comprising: (1) Clean the reaction tubes thoroughly and install a sealing spring at the bottom of the reaction tubes; (2) Then connect the bottom end of the reaction tube to the outlet pipe of the pump, and inject a certain height of light oil with a distillation range of 100-230℃ into the reaction tube through the pump. Then stop the pump and maintain the oil level at this height through the pressure control valve set on the cross line connecting the pump outlet and the pump inlet. (3) The catalyst is loaded into the reaction tube from the top opening of the reaction tube so that the catalyst settles in the reaction tube and forms a catalyst bed. At the same time, the oil level in step (2) is maintained by the pressure control valve to prevent the oil level from rising and overflowing during the addition of the catalyst to the reaction tube. (4) After the catalyst is loaded, drain and recover the light oil from the reaction tubes; In step (3), the ratio of the diameter of the reaction tube to the equivalent diameter of the catalyst is 15:1-30:1, and the diameter of the catalyst cross section is 1.4-1.8 mm; the catalyst is added uniformly to the reaction tube at a rate of ≤10 cm / s.

2. The catalyst loading method according to claim 1, characterized in that, In step (4), after the catalyst is loaded, the oil pressure is released to atmospheric pressure through the pressure control valve so that the light oil exits from the reaction tube. Then, the catalyst bed is purged from top to bottom with inert gas to remove the light oil and catalyst dust adsorbed on the catalyst.

3. The catalyst loading method according to claim 1, characterized in that, In step (1), the distance from the top of the sealing spring to the bottom of the reaction tube is denoted by L and is 5-40cm.

4. The catalyst loading method according to claim 3, characterized in that, The deviation between the distance L from the top to the bottom of the sealing spring in different reaction tubes is within ±3cm.

5. The catalyst loading method according to claim 4, characterized in that, In step (1), the distance from the top of the sealing spring to the bottom of the reaction tube is represented by L and is 10-30cm; the deviation of the distance L from the top of the sealing spring to its bottom in different reaction tubes is within ±1cm.

6. The catalyst loading method according to claim 5, characterized in that, In step (2), the distance between the injected light oil and the upper end of the reaction tube is in the range of 100cm-150cm.

7. The catalyst loading method according to any one of claims 1-6, characterized in that, The light oil used is selected from light hydrocarbons with a distillation range of 100℃-230℃ produced by Fischer-Tropsch synthesis.

8. The catalyst loading method according to claim 7, characterized in that, The light oil used is selected from light white oils with the grades W-20, W-30, W-40 or W-60.

9. The catalyst loading method according to any one of claims 1-6 and 8, characterized in that, The pump outlet is equipped with a pump outlet valve, which is connected to the bottom of the reaction tube via an oil inlet pipeline and to the pump inlet via a crossover line; the oil inlet pipeline is equipped with an oil inlet valve, and the crossover line is equipped with a pressure gauge and the pressure control valve in sequence along the material flow direction.

10. The catalyst loading method according to claim 9, characterized in that, When the pump starts, first ensure that the pump is in self-circulation state by crossing the line, then gradually adjust the pressure control valve of the crossing line to input light oil into the reaction tube. After the oil level rises to the predetermined height H, record the corresponding oil pressure P, then stop the pump and maintain the oil level at this height H by the pressure control valve.

11. The catalyst loading method according to claim 10, characterized in that, The pump is a centrifugal pump or a diaphragm pump, and the pressure control valve is a back pressure valve.

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