JPS6135842A - Replacement of catalyst - Google Patents

Abstract

PURPOSE:To prevent the oxidation of a catalyst over a long period of time, by a method wherein the catalyst in the tower tank of a hydro-desulfurization reaction tower is wetted with mineral oil while an air impermeable plate material is laid on the surface of a catalyst except a catalyst withdrawal position and the catalyst is withdrawn from the position receiving no laying of said plate. CONSTITUTION:A system is substituted with inert gas and the pressure in the system is lowered so as to almost reach atmospheric pressure and the partition valves 6, 9 respectively provided to the outlet piping 5 and tower bottom piping 8 arranged to the upstream and downstream sides of the reactor 7 are closed by blind plates to perform the separation of the reactor 7 from both upstream and downstream sides. Subsequenly, the manhole provided to the tower top of the reactor 7 to purge the gas in the reactor 7 for a while and, thereafter, a worker enters the manhole to lay an air impermeable plate material 30 on the upper surface of a catalyst bed 27. A working hole 31 is formed to the center of the air impermeable plate material 30 and the operator can successively take out the catalyst in the catalyst bed 2 from the hole 31.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for replacing catalysts such as so-called spent catalysts whose activity has deteriorated in various columns and tanks in chemical plants, such as hydrodesulfurization reactors. .

[Background technology and its problems] Generally, various catalysts are used in columns and tanks in chemical plants, but these catalysts suffer from a decrease in activity due to poisoning due to the accumulation of carbides, metals, etc., and a decrease in mechanical strength. It must be replaced due to fracture due to deterioration, equipment repair or inspection, etc.

This catalyst replacement work needs to shorten the plant operation period as much as possible, so it is necessary to shorten the construction period.In addition, the catalyst in use is often in a reducing atmosphere, and this is necessary for catalyst replacement. If exposed to the atmosphere, there is a risk of heat generation and ignition due to oxidation of carbides, sulfur, etc. that adhered to the catalyst during use, and SO! Appropriate replacement work must be carried out while preventing the effects on the human body due to the generation of catalyst particles, as well as the effects on the human body due to catalyst dust.

Conventionally, when removing 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 remove the catalyst. Since the regeneration is carried out by combustion inside the reactor, it takes a long time to regenerate, which is not only cost-effective, but also has drawbacks such as the expense of dealing with pollution caused by sow and the like generated 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 moistened with light oil etc. by a shutdown operation and the catalyst is removed. A method is used to extract it without oxidizing it. However, in the former method, it is technically difficult to completely shut off air during the catalyst removal process, and the catalyst gradually depletes over time due to air leakage from the worker's airline mask. Oxidation heat generation may cause the temperature inside the reactor to rise significantly during catalyst extraction work, the production of gases such as SOx, and furthermore, the working environment may be extremely deteriorated due to dust, etc., and there may be a risk of fire. This is not a good method for replacing the catalyst.Also, the latter method of moistening with light oil, etc. is effective for a working period of about -weeks, but is not necessarily effective for longer periods of time, and especially if the This method is also not perfect, as in large reactors the extraction process takes quite a long time, lasting over a week.

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.

[Fifth 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 has the following features:
After the catalyst is moistened with mineral oil such as diesel oil by the operation shutdown operation, a non-porous board is laid on the surface of the catalyst except for the catalyst removal position, and the catalyst is removed from the position where the non-porous board is not laid. The purpose of this invention is to perform extraction, thereby almost completely covering the surface of the catalyst to prevent oxidation of the catalyst, and to enable work in an air atmosphere to achieve the above object. Mineral oils used include diesel oil, kerosene,
It includes a wide range of oils, including heavy oils rich in aromatics and low in asphaltene content. The mineral oil used for this primary wetting has a distillation property of 90% and a distillation temperature of 350%.
℃ or less is preferable, but since the cleaning oil is used under high temperature and high pressure in the present invention, this point is not so important. Also, as the non-porous board material, urethane mat, urethane sheet, vinyl sheet, soft rubber A sheet or the like may be used, and in short, any plate material that is flexible or pliable and non-breathable may be used.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows an example of a chemical plant to which the present invention is applied, and in this figure, an on-off valve 2 and a pump 3 are provided in the middle of a supply pipe l that supplies raw material oil such as heavy oil.
A heating furnace 4 is provided on the discharge side of the pump 3 to heat the pump to a predetermined temperature. 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 separate the front and rear edges. Reactor 7 for use etc.
It is connected to the. 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. 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 bottom liquid extraction pipe 19, and the discharge side of this pump 20 is branched into two parts, one of which is a bottom liquid next process supply pipe 22 having an on-off valve 21 in the middle. , the other is a bottom liquid circulation pipe 24 which also has an on-off valve 23 in the middle, and the tip of this bottom liquid circulation pipe 24 is
It is connected between the on-off valve 2 of the supply pipe 1 and the pump 3.

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

In addition, the code|symbol 27 in the figure is the catalyst layer accommodated in the reactor 7,
Reference numeral 28 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 coating liquid supply pipe is closed. The on-off valve 25 of 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 sampled as appropriate to confirm that the switch has been completely switched to mineral oil such as light oil, and the entire system is operated for recycling.
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 withdraw the bottom liquid. The liquid extracted from the 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 stopping the supply of mineral oil, 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. Additionally, the heating furnace 4 is shut down and the temperature of the reactor 7 is lowered to near room temperature. After this, open the on-off valve 12 of the flare piping 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 close to atmospheric pressure. Lower it. When the pressure becomes close to atmospheric pressure, the outlet piping 5 before and after the reactor 7
Then, blind plates are inserted into the gate valves 6 and 9 provided in the tower bottom pipe 8, respectively, to cut off the front and rear edges of the reactor 7.

Next, the manhole at the top of the reactor 7 was opened, and after purging the gas in the reactor 7 for a while, a worker entered through the manhole under an air atmosphere, and as shown in Figure 2,
A non-porous plate material 30 is laid on the upper surface of the catalyst layer 27 of the reactor 7. This impermeable plate material 30 is made of a urethane mat, a urethane sheet, a vinyl sheet, a soft rubber sheet, etc., and has a working hole 31 formed in its center, through which a worker can clean the catalyst inside the catalyst layer 27. will be sequentially transported outside.

In addition, if the temperature inside the reactor 7 rises during this carrying out operation, the non-porous plate 30 should be removed and any of the above operations, starting from the supply of mineral oil such as light oil, should be carried out. Repeat this process, and after completing the series of operations, remove the non-porous plate material 30 again.
, and carry out the catalyst again.

According to this embodiment as described above, the catalyst is moistened with mineral oil such as light oil, the interior of the catalyst is filled with this mineral oil, and then a non-porous layer is formed on the surface of the catalyst layer 27 made of the wetted catalyst. Since the plate material 30 is laid to block air, oxidation of the catalyst is prevented, and no heat is generated during the work of carrying out or replacing the catalyst. In addition, since the wetting operation and plate laying operation of this catalyst can be performed in a relatively short time, the efficiency of each operation is high and it is extremely economical.Especially in medium and small vessels, the oxidation prevention function can be fully demonstrated.・Since the amount of mineral oil such as light oil and the non-porous plate material 30 used to wet the catalyst is relatively small and the price is low, this method is more effective than the conventional method using 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, and it is safe and secure. Hygienic. 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 in carrying out the present invention, the non-breathable plate material 30 is
As in the previous embodiment, it is made of one piece and has a hole 3 in the center.
The non-porous plate material is not limited to the structure having one 1, but the non-porous plate material is divided into many pieces, and the divided non-porous plate material is spread over the catalyst layer 27 without any gaps, and in this state, the predetermined portion of the non-porous plate material is 1
Peel off the divided piece to make a working hole, and after extracting some of the catalyst from this hole, lay down the peeled divided piece again to fill the hole, and instead peel off the divided piece adjacent to this divided piece to perform the catalyst removal work. This method may be used to remove the catalyst one by one by repeating this operation. However, this method has the disadvantage that the air blocking effect is inferior to that of the previous example because a small gap is created between each divided piece. be.

FIG. 3 shows another embodiment that improves the example in which the non-air permeable plate material is divided.
is divided into a plurality of concentric circles, and these concentric circles are divided into many parts in the radial direction, thereby forming a large number of divided pieces 40A. This non-breathable board material 4 divided into many parts
On the top surface of 0, there is a cover member unit 41 made of a plurality of non-breathable plates made of vinyl sheets or the like.
will be laid down. This cover member unit 41 is made up of, for example, four cover members 41A, 41B, 41c, and 4LD, and each of these cover members 41A, to 410 has holes 42A for removing the catalyst at different positions, respectively. 42B
, 42C, and 42D are formed. That is, the lowermost cover member 41A in the figure has a hole 42A having a diameter slightly larger than that of the divided piece 40A at the center of the impermeable plate 40, and has a hole 42A with a diameter slightly larger than that of the divided piece 40A. The second cover member 41B corresponds to one of the fan-shaped divided pieces 4OA formed between the outer periphery of the central divided piece 4OA and a concentric circle one space outward from this, and also corresponds to this divided piece 4OA. Similarly, the third cover member 4IC from the bottom has a fan-shaped hole 42B with a slightly larger size.
Between the third concentric circle, the cover member 41 at the top position corresponds to one of the sector-shaped division pieces 40A formed between the third concentric circle from the center and the outer periphery, and the cover member 41 corresponds to one of the fan-shaped division pieces 40A formed between the third concentric circle from the center and the outer periphery, and the cover member 41 has a sector shape with slightly larger dimensions. It has a hole 42C or 42D.

To extract the catalyst using these cover members 41A to 410, first, place the lowermost cover member 41A on the non-ventilated member 40, and insert the non-porous member through the center hole 42A. Peel off the center division piece 40A of 40 and take out the catalyst in the center.

After a predetermined amount of catalyst has been extracted, the central divided piece 40A is returned to close the lid, the cover member 41A is removed, and the second cover member 41B from the bottom is installed. At this time, the divided piece 40 at the position corresponding to the hole 42B of the cover member 41B
After peeling off A and taking out the catalyst in the same way, remove the divided piece 4O again.
A is returned, and then the cover member 41B is rotated in the circumferential direction by one piece of the divided piece 40A, and the divided piece 40A at the position corresponding to the hole 42B is peeled off again to extract the catalyst. Divided piece 40A forming the second circumference from the inside
After that, the third and uppermost cover members 41C and 410 are operated in the same manner as the second cover member 41B to remove the catalyst from the entire catalyst layer.

According to the embodiment shown in FIG. 3, most of the non-ventilated plate material 40 divided into a large number of parts is covered with the cover member unit 41, so that the non-porous plate material 40 is separated from the dividing line of the non-porous plate material 40. It is possible to effectively prevent air from entering the catalyst side, and more effectively prevent oxidation of the catalyst.

Further, the present invention is limited to a plant including a reactor for hydrodesulfurization as shown in the above embodiment; it is also applicable to catalyst replacement operations in other types of plants.

[Effects of the Invention] As described above, according to the present invention, there is an effect that 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 implementing the method of the present invention, Fig. 2 is a sectional view showing the main parts of an example of implementing the method of the present invention, and Fig. 3 is another example. FIG. 2 is an exploded perspective view of main parts. 1... Supply piping, 4... Heating furnace, 5... Outlet piping. 6.9... Gate valve, 7... Reactor, 8... Tower bottom piping, ll... Separator, 17... Distillation column, 19...
Tower bottom liquid extraction piping, 24... Tower bottom circulation piping, 26...
Coating liquid supply pipe, 27...Catalyst layer, 30.40...
Non-breathable plate material, 31...hole, 4OA...divided piece, 4
1... Cover member unit, 41A to 410... Cover member, 42A to 42D... Hole.

Claims (1)

[Claims] (1) After moistening the catalyst in the columns and tanks of a chemical plant with mineral oil, a non-porous board is laid on the surface of the catalyst moistened with mineral oil, except for the catalyst extraction position, and A catalyst replacement method characterized by pulling out the catalyst from a position where no plate material is laid.