JPH0112536B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to various towers and tanks in chemical plants,
For example, the present invention relates to a method for replacing a catalyst such as a so-called waste catalyst whose activity has deteriorated in a hydrodesulfurization reactor.

[Background technology and its problems] Generally, various catalysts are used in columns and tanks in chemical plants.
Replacement is necessary due to a decrease in activity due to poisoning due to accumulation of metals, etc., fracture due to decrease in mechanical strength, and repair or inspection of equipment.

This catalyst replacement work needs to shorten the construction period because it is necessary to shorten the plant operation period as much as possible, and the catalyst in use is often in a reducing atmosphere, which is exposed to the atmosphere for catalyst replacement. If opened, there is a risk of heat generation and ignition due to the oxidation of carbides, sulfur, etc. that adhered to the catalyst during use, and there is a danger that the ignition will cause SOx to be generated, which will affect the human body, and furthermore, the human body will be affected by the catalyst dust. Appropriate replacement work must be carried out while preventing any effects on the equipment.

Conventionally, when extracting a catalyst from a relatively small reactor, the method used was to regenerate it with steam or air, completely burn it inside the reactor, and then extract the catalyst. Since regeneration is performed by combustion, it not only takes a long time to regenerate and increases costs, but also has drawbacks such as the cost of dealing with pollution caused by the generation of SOx and the like during regeneration. In addition, in large reactors, as a method to prevent ignition due to oxidation of the catalyst, nitrogen gas is supplied into the reactor and the catalyst is extracted under this nitrogen gas atmosphere, or the catalyst is shut down by an operation shutdown operation. The method used is to moisten the catalyst with light oil or the like and extract it without oxidizing the catalyst. However, in the former method, it is technically difficult to completely shut off air during the catalyst extraction process, and
Due to air leakage from the worker's airline mask, the catalyst gradually oxidizes and generates heat over time, causing the temperature inside the reactor to rise significantly during the catalyst removal process, generating gases such as SOx, and This is not necessarily a good method for replacing the catalyst, as it creates an extremely poor working environment due to dust, and sometimes there is a risk of fire. In addition, the latter method of moistening with light oil etc. is effective for a working period of about one week, but it is not necessarily effective for longer working periods, especially for a fairly large reactor for more than one week. This method is also not perfect, as the extraction process takes quite a long time.

Therefore, there is a need for a catalyst replacement method that does not generate heat due to oxidation of the catalyst even during long-term operation.

[Object of the Invention] An object of the present invention is to provide a safe and economical catalyst replacement method that can effectively prevent oxidation of a catalyst over a long period of time.

[Means and effects for solving the problems] The present invention first wets the catalyst with mineral oil such as diesel oil by a shutdown operation, and then secondarily coats the surface of the catalyst with a foam layer. However, this aims to achieve the above object by completely coating the surface of the catalyst to prevent oxidation of the catalyst and making it possible to work in an air atmosphere.

The mineral oil used in the present invention includes a wide range of mineral oils such as light oil, kerosene, and heavy oil rich in aromatic elements with a low content of asphaltenes. The mineral oil used for this primary wetting is preferably a light oil with a distillation property of 90% and a distillation temperature of 350°C or less,
Since the cleaning oil is used under high temperature and pressure in the present invention, this point is not so important. In addition, animal protein, whale oil, etc. are used as the stock solution for forming the foam layer.

[Example] Hereinafter, an example of the present invention will be described based on the drawings.

An on-off valve 2 and a pump 3 are provided in the middle of a supply pipe 1 that supplies raw material oil such as heavy oil, and a heating furnace 4 is provided on the discharge side of this pump 3 to enable heating to a predetermined temperature. ing. A gate valve 6 is provided in the middle of the outlet pipe 5 from the heating furnace 4, and a plate can be inserted to cut off the front and rear edges. The reactor 7 is connected to the reactor 7, etc. In the middle of the bottom pipe 8 of this reactor 7, a gate valve 9 into which a blind plate similar to that described above can be inserted is provided, and a cooler 10 is also provided, the tip of which is connected to the top of the separator 11. ing. This separator 11
A flare pipe 13 having an on-off valve 12 in the middle is connected to the top of the separator 11, and a gas circulation pipe 14 is connected to the gas phase portion of the separator 11. A blower 15 is provided in the middle of the gas circulation pipe 14, and the tip of the gas circulation pipe 14 is connected to the supply pipe 1 between the pump 3 and the heating furnace 4. Hydrogen gas normally flows through this gas circulation pipe 14 during plant operation.

The liquid withdrawal pipe 16 of the separator 11 is connected to the center of a distillation column 17, and the distillation column 17 is provided with a column top pipe 18 and a bottom liquid withdrawal pipe 19. A pump 20 is provided in the middle of this column bottom liquid extraction pipe 19, and this pump 20
The discharge side is branched into two, one being a tower bottom liquid next process supply pipe 22 having an on-off valve 21 in the middle,
The other end is a bottom liquid circulation pipe 24 which similarly has an on-off valve 23 in the middle, and the tip of this bottom liquid circulation pipe 24 is connected between the on-off valve 2 of the supply pipe 1 and the pump 3.

A coating liquid supply pipe 26 having an on-off valve 25 in the middle is connected to the supply pipe 1 upstream from the connection part of the tower bottom liquid circulation pipe 24 and downstream from the on-off valve 2. Mineral oil such as diesel oil is now supplied through the

One end of a stock solution supply pipe 27 is connected to the top of the reactor 7, a foaming device 28 is provided in the middle of the stock solution supply pipe 27, and the other end is connected to a stock solution storage tank 29. The foaming device 28 is provided with an air suction pipe 30, and the air from the air suction pipe 30 and the stock solution storage tank 2 are
The stock solution 31 for forming a foam layer in 9 is combined in a foaming device 28 and foamed. As the foaming device 28, one having a general structure used for extinguishing petroleum storage tanks is used. Further, as the stock solution 31 stored in the stock solution storage tank 29, animal protein, whale oil, etc. are used.

Note that the reference numeral 31 in the figure is a drain pipe provided at the bottom of the reactor 7.

Next, a method for replacing the catalyst in the plant of this example will be explained with reference to FIG. 2 as well.

Before starting the operation shutdown operation, the heating temperature of the heating furnace 4 is lowered, and the temperature of the reactor 7 is gradually lowered to about 200°C. Next, the on-off valve 2 of the supply pipe 1 is closed, and the on-off valve 25 of the coating liquid supply pipe 26 is opened to switch from raw oil to mineral oil such as light oil. After switching to mineral oil, the oil in the reactor 7 is appropriately sampled to confirm that the switch has been completely switched to mineral oil such as light oil, and the entire system is operated for recycling. That is, the on-off valve 21 of the bottom liquid next process supply pipe 22 connected to the bottom liquid withdrawal pipe 19 of the distillation column 17 is closed, and the on-off valve 23 of the bottom liquid circulation pipe 24 is opened to remove the bottom liquid. The liquid extracted from the extraction pipe 19 is returned to the supply pipe 1 via the bottom liquid circulation pipe 24, and this recycling operation is continued for 1 to 60 hours.

At the same time as the recycling operation is completed, the on-off valve 25 of the coating liquid supply pipe 26 is closed, and the supply of mineral oil such as light oil is stopped. After the supply of mineral oil is stopped, a so-called oil purge is performed to remove excess mineral oil present in the heating furnace 4, outlet piping 5, reactor 7, and tower bottom piping 8 using recycled hydrogen gas flowing through the gas circulation piping 14. , and the heating furnace 4 is shut down to lower the temperature of the reactor 7 to near room temperature. After that, open the on-off valve 12 of the flare pipe 13 to discharge the hydrogen gas in the system, replace the system with inert gas (usually nitrogen gas), and bring the pressure in the system to near atmospheric pressure. Lower it. When the pressure becomes close to atmospheric pressure, blind plates are introduced into the gate valves 6 and 9 provided in the outlet pipe 5 and the bottom pipe 8 of the reactor 7, respectively, to cut off the front and rear edges of the reactor 7.

Then, as also shown in FIG.
The manhole at the top of the tower was opened and the foaming device 28
is driven to inject the stock solution 31 in the stock solution storage tank 29 into the reactor 7 through the stock solution supply pipe 27 in a foamed state. When a foam layer 34 of a predetermined thickness is formed on the upper surface of the catalyst layer 33 of the reactor 7 by injection of the foamed stock solution 31, the injection operation is completed. After this, a worker enters through the manhole of the reactor 7 under an air atmosphere and carries out the catalyst inside the reactor 7 to the outside. During this unloading process, the foam layer 3
When the thickness of 4 becomes thinner, foam the stock solution 31 as appropriate.
Additional supply will be made.

If the temperature inside the reactor 7 rises during the unloading operation, repeat the above operations starting from supplying mineral oil such as light oil, and after completing the series of operations, restart the catalyst again. will be carried out.

According to the present implementation as described above, the catalyst is first wetted with mineral oil such as light oil, the interior of the catalyst is filled with this mineral oil, and then the catalyst layer 33 made of the catalyst filled with this mineral oil is wetted. Since the foam layer 34 is formed on the surface and the surface of the catalyst layer 33 is secondarily shielded from the air, oxidation of the catalyst is completely prevented and no heat is generated during the work of carrying out and replacing the catalyst. Further, since the wetting and foam coating operations of the catalyst can be carried out in a relatively short time, the work efficiency is high and it is extremely economical. Furthermore, since the amount of mineral oil such as light oil that wets the catalyst and the stock solution 31 for forming the foam layer 34 is relatively small and the price is low, it is advantageous from this point of view compared to the conventional method that uses a large amount of nitrogen gas. It is also economical. In addition, since the catalyst does not burn, there is no pollution caused by the combustion of the catalyst, and since the catalyst is removed in a wet state, there is no generation of dust, making it safe and sanitary. be. Furthermore, since the work is carried out in an air atmosphere, accidents such as oxygen deficiency do not occur, and from this point of view as well, a safe work environment can be ensured.

Note that the present invention is not limited to a plant including a reactor for hydrodesulfurization as shown in the above embodiment, but can also be applied to catalyst replacement work in other types of plants.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a catalyst replacement method that does not generate heat or the like when replacing the catalyst and can be carried out safely.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an example of a chemical plant that implements the method of the present invention, and FIG. 2 is a sectional view showing the operating state of the main parts thereof. 1... Supply piping, 4... Heating furnace, 5... Outlet piping, 6, 9... Gate valve, 7... Reactor, 8... Bottom piping, 11... Separator, 17... Distillation column , 19
... Tower bottom liquid extraction piping, 24 ... Tower bottom circulation piping, 2
6... Coating liquid supply piping, 28... Foaming device, 29
...Standard solution storage tank, 31...Standard solution for foam layer formation,
33... Catalyst layer, 34... Foam layer.

Claims (1)

[Claims] 1 After first moistening the catalyst in the columns and vessels of a chemical plant with mineral oil, the catalyst is transferred to the columns and vessels with the surface of the catalyst moistened with this mineral oil being secondarily coated with a foam layer. A method for replacing a catalyst, characterized by removing it from a catalyst.