JPS635132B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a purging inert gas used for purging heatable, toxic, and other hazardous gases in a reactor in a chemical plant, for example. [Background art and its problems] Generally, when inspecting, repairing, cleaning, etc. tanks, equipment, piping, etc. such as reactors in chemical plants and other various plants, the designated space of those reactors, etc. flammable gas, toxic gas,
If other dangerous gases remain, there is a risk of fire, explosion, poisoning, etc., so they must be completely purged. Conventionally, as a means of purging the hazardous gas, the hazardous gas has been replaced with nitrogen gas, which is safe and has no danger of fire, explosion, toxicity, or the like. However, if the inside of the reactor etc. is filled with nitrogen gas, the amount of oxygen will decrease accordingly, and if a worker enters the inside of the reactor etc. in this state for inspection or other work, there is a risk of oxygen deficiency. There is. Therefore, it is necessary to further replace the nitrogen gas with air, but since nitrogen gas is colorless and odorless, it is difficult to identify its presence, and in order to confirm whether the nitrogen gas has been completely replaced with air, it is necessary to It is necessary to detect the oxygen concentration using a detector, etc. However, in actual work, frequent detection is troublesome, so the number of oxygen detections tends to be reduced or only the bottom of the reactor is detected, so there is always a risk of oxygen deficiency. For this reason, even if a device were to enter a reactor or the like with insufficient oxygen detection, it was desired to be able to immediately identify that nitrogen gas remained for purging. [Object of the Invention] An object of the present invention is to provide an inert gas for purging in various plants that allows workers to easily identify the residual inert gas such as nitrogen gas used for purging. . [Means and effects for solving the problem] The present invention provides a method for purging hazardous gas in a predetermined space such as a reactor by adding a substance that can identify the presence of the gas to the inert gas. The purpose is to achieve the above-mentioned object by making it possible for the operator to easily recognize the residual inert gas for purging through the sensual effects of the operator's sense of smell. [Example] Hereinafter, an example in which the present invention is applied to a reactor of a petrochemical plant will be described based on the drawings. A raw material supply pipe 1 is provided on one side of the lower part of the reactor 10.
2 is connected to the raw material supply pipe 12, and a safety valve branch pipe 1 is connected to the raw material supply pipe 12 from the side close to the reactor 10.
4. A bypass pipe 16 and a purge branch pipe 18 are branched, respectively. Branch piping 14 for the safety valve
A safety valve 20 is provided, a bypass pipe 22 is provided to bypass the safety valve 20, and a bypass valve 24 is provided in the middle of the bypass pipe 22. Further, a bypass valve 26 is also provided in the middle of the bypass pipe 16, and these bypass pipes 16 and the safety valve branch pipe 1
4 is connected to a flare system piping 30 via a connecting pipe 28, and a flare (not shown) for burning dangerous gas such as combustible gas is connected to this flare system piping 30. A first valve 32 and a second valve 32 are installed in the middle of the purge branch pipe 18 from the side closer to the raw material supply pipe 12.
valves 34 are provided, and these first and second valves 3
Purge branch pipe 18 on the tip side of 2, 34
A purge gas supply pipe 36 and an air supply pipe 38 are respectively connected to the purge gas supply pipe 36 and the air supply pipe 38. Further, a first intermediate discharge pipe 42 having a discharge valve 40 in the middle is connected to an intermediate position between the first valve 32 and the second valve 34 of the purge branch pipe 18, and the purge gas supply pipe A second intermediate discharge pipe 46 having a discharge valve 44 in the middle is connected to the connecting portion between the air supply pipe 36 and the air supply pipe 38 . The purge gas supply pipe 36 is provided with an on-off valve 48 and a flow rate regulating valve 50 in the middle thereof, and is connected to a nitrogen gas cylinder 54 as an inert gas supply source via a cylinder mouth on-off valve 52 . Further, a blending pipe 56 is provided to bypass the flow rate regulating valve 50 of the purge gas supply pipe 36, and a blending ratio regulating valve 58 and a compound storage container 60 are provided in the middle of this blending pipe 56. In this compound storage container 60, substances such as odorants, stimulants, or colorants are stored in nitrogen gas as substances that can identify the presence of the gas.
It is said to be a substance whose existence can be easily identified by humans through sensual senses such as smell and sight. Examples of these substances include hydrogen sulfide, methyl mercaptan, ethyl mercaptan, sulfur dioxide gas, cresol, phenol, aldehyde, ammonia, styrene, butene, benzene, and the like. In addition, the amount of the substance that can identify the presence of nitrogen gas for purging should be 5 to 50% so that even if the substance is flammable, toxic, etc., it is not dangerous to humans.
100 ppm, and furthermore, the substance has properties such as odor and color that are different from the gas to be purged in the reactor 10 etc. For example, ammonia is used in a styrene tank. , a gas that allows humans to identify that the gas to be purged and the gas to be purged are different is used. An on-off valve 62 is connected to the air supply pipe 38 connected to the purge branch pipe 18, and an air supply source 64 is also connected thereto. A compressor or the like may be directly connected to the air supply source 64, or a compressor or the like may be connected via an accumulator tank when a large volume of air is to be supplied in a short time. At the top of the reactor 10, there is a tower top discharge pipe 66,
A vent pipe 68 and an extraction pipe 70 for transferring the product in the reactor 10 to the next process are connected to each other. A discharge valve 72 is provided in the middle of the tower top discharge pipe 66, and the tip of the tower top discharge pipe 66 is connected to the flare system pipe 30 to direct the gas to be purged in the reactor 10 to the tower. Flare system piping 30 directly via top discharge piping 66
It is also now possible to discharge it to Further, a vent valve 74 is provided in the middle of the vent pipe 68, and the tip of the vent pipe 68 is open to the atmosphere. At the bottom of the reactor 10, a tower bottom pipe 76 is provided which is connected to a slop tank (not shown), etc., and a drain pipe 78 is also provided.
A drain valve 82 is provided in the middle of each tube. A tower top manhole 84 is provided at the upper side of the reactor 10, and a tower bottom manhole 86 is provided at the lower part, and these manholes 84,
Workers can enter the reactor 10 from 86 to perform work. Next, the purge operation in this example will be explained. This purge operation consists of three steps detailed below: liquid/gas removal operation, dangerous gas purge operation using nitrogen gas, and nitrogen gas purge operation using air. This is done by performing the steps in this order. Liquid/gas venting operation This is an operation for extracting liquid/gas fractions from the reactor system, which is a predetermined space consisting of the reactor 10 and piping connected to this reactor 10, to the outside of the system. opens the bottom valve 80 and opens the bottom pipe 76.
Extract to slop tank via. On the other hand, the dangerous gas in the system opens the bypass valve 24 and the bypass valve 26, and passes through the raw material supply piping 12, the safety valve branch piping 14, the bypass piping 22, the bypass piping 16, and the connecting piping 28 to the flare system piping 30.
and incinerated with a flare (not shown).
Furthermore, the discharge valve 72 of the tower top discharge pipe 66 provided at the top of the reactor 10 is also opened as necessary to discharge the gas directly from the tower top to the flare system pipe 30. The gas in the system is discharged to the flare system piping 30 until the residual pressure in the system becomes zero. When the residual pressure in the reactor system becomes approximately zero due to the hazardous gas purge operation using nitrogen gas, the bypass valve 24 and the bypass valve 26 are closed.
On the other hand, the first valve 32 and the second valve 34 of the purge branch pipe 18 are opened, the on-off valve 48 and the flow rate adjustment valve 50 of the purge gas supply pipe 36 are opened, and the cylinder mouth on-off valve 52 is opened.
is opened and nitrogen gas for purging is introduced into the system from the nitrogen gas cylinder 54. At this time, the mixing pipe 5
6, the mixing ratio adjustment valve 58 is replaced with the flow rate adjustment valve 5.
By adjusting the amount together with 0 to an appropriate amount, the odorant, etc. stored in the compound storage container 60 is blended into the nitrogen gas at the predetermined amount described above, and reacted via the raw material supply pipe 12. Supplied into the container 10. When supplying this nitrogen gas for purging, a nitrogen gas line having a purge gas cylinder, a compound storage container, etc. may also be provided in the tower bottom piping 76, and nitrogen gas may also be supplied from this tower bottom piping 76. good. The nitrogen gas can be supplied to the reactor 10 by purging it into the flare system using a so-called one-through method while keeping the exhaust valve 72 at the top of the tower open, or by closing the exhaust valve 72 and purging it to a constant pressure using a so-called batch method. The pressure within the reactor 10 may be increased and then the exhaust valve 72 may be opened to release the pressure to the flare system. This purging with nitrogen gas is carried out from the vent pipe 68 or drain pipe 78 in the downstream direction through the vent valve 7 provided respectively.
4 or open the drain valve 82 to sample the gas in the system at appropriate intervals, check the concentration of hazardous gas, and continue purging until the hazardous gas is gone. When the hazardous gas becomes zero in this way, the first and second purge branch pipes 18
valves 32, 34 and purge gas supply piping 36
Each valve 48, 50, 52, 58 in the system is closed to stop purging nitrogen gas into the flare system. Nitrogen gas purge operation using air After opening the vent valve 74 of the vent pipe 68 and venting the nitrogen gas in the reactor system to the atmosphere until the residual pressure becomes zero, the first valve 32 and the first valve of the purge branch pipe 18 are opened. The second valve 34 and the on-off valve 62 of the air supply pipe 38 are opened, compressed air is supplied from the air supply source 64, and nitrogen gas still remaining in the system is forcibly discharged to the atmosphere. This purge of nitrogen gas with compressed air is carried out by the vent piping 68.
This is done in a so-called one-through method with the vent valve 74 open. After that, the manholes 84 and 86 at the top and bottom of the tower are opened, and a ventilation fan (not shown) is attached to the bottom manhole 86 in the downstream part to introduce atmospheric air into the reactor 10, and the top manhole in the upstream part is introduced into the reactor 10. From 84, the residual gas in the system is purged. In this way, while purging the residual gas in the reactor 10 with air, oxygen detection is performed as appropriate, and purging is continued until the oxygen content reaches 20% or more. If the oxygen in the reactor 10 is detected to be 20% or more, the working environment in the reactor 10 is determined to be acceptable, and internal work such as cleaning inside the reactor 10 is started. In this case, since the specific gravity of nitrogen gas is lighter than air, there is a risk that nitrogen gas will remain in the upper part of the reactor 10, and even if the oxygen content is 20% or more at the bottom of the column, it may be 10% at the top of the column. Therefore, caution is required. If such oxygen detection is carried out accurately and frequently to confirm that the oxygen content is 20% or more, and then work is started inside the reactor 10, there will be no accident, but if oxygen is not detected, Oxygen deficiency accidents may occur if the user enters the top of the tower only to detect oxygen at the bottom, or only infrequently, or when oxygen is detected only at the bottom of the tower. However, since the nitrogen gas of this example contains 5 to 100 ppm of the above-mentioned odorant as described above, it is possible to immediately check whether nitrogen gas remains in the reactor 10 and prevent the occurrence of the above-mentioned accident. There is an effect that can be avoided. In carrying out the present invention, the inert gas is not limited to the nitrogen gas mentioned above, but may also be argon gas or other inert gases, but nitrogen gas is advantageous in terms of cost. In addition, the method of blending an odorant or the like with an inert gas is not limited to the structure in which the blending pipe 56 and the compound storage container 60 are provided as in the above embodiment. It may also be injected directly into the supply line. [Experimental Example] In order to clarify the effects of the present invention, purging nitrogen gases having the compositions shown in Table 1 below were adjusted to purge specified columns and tanks.

【table】

[Table] As a result, all five workers were able to recognize the presence of the purge nitrogen gas, and the work progressed safely. [Effects of the Invention] According to the present invention, there is an effect that in various plants, workers can easily recognize that inert gas used for purging remains.

[Brief explanation of the drawing]

The figure is a system diagram showing an embodiment in which the inert gas for purging according to the present invention is applied to a reactor of a chemical plant. 10...Reactor, 18...Purge branch piping, 30
...Flare system piping, 36...Purge gas supply piping, 3
8... Air supply piping, 50... Flow rate adjustment valve, 54... Nitrogen gas cylinder as an inert gas supply source, 56...
Mixing piping, 58...Blending ratio adjustment valve, 60...Blend storage container, 64...Air supply source, 68...Vent piping, 76...Bottom piping, 78...Drain piping.

Claims (1)

[Scope of Claims] 1. An inert gas for purging, characterized in that an inert gas for purging dangerous gas in a predetermined space is blended with a substance that can identify the presence of the gas. 2. The inert gas for purging according to claim 1, wherein the inert gas is nitrogen gas. 3. The inert gas for purging according to claim 1 or 2, characterized in that the amount of the substance that can identify the presence of the gas is 5 to 100 ppm.