JPH07165B2 - Refining method of hydrocarbon reformed gas - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for purifying alternative natural gas (SNG) that can be used as a substitute for natural gas, and more specifically, it is synthesized by steam reforming of hydrocarbons. Pressure fluctuation adsorption method (PSA method) from raw material gas consisting mainly of methane, hydrogen and carbon dioxide
And a method for producing a purified gas from which carbon dioxide has been removed.

[Conventional technology and its problems] Natural gas (LNG) has already become a major raw material for city gas in coastal large cities due to its stable supply, high calorific value, safety, etc. As a source, it is trying to expand demand.

However, in local cities, a situation in which the supply of LNG is temporarily stopped is considered in view of the small amount of storage and transportation commensurate with the relatively small demand. For this reason, it is necessary to provide an alternative energy supply device that can respond in an emergency.

LN is a requirement for alternative energy supply equipment.
It is required that a gas of almost the same quality as G can be supplied through the same pipe, that the start-up in an emergency can be performed quickly and that stability is high. To meet this demand, there is a process that combines a small SNG device by steam reforming of hydrocarbons such as butane and a carbon dioxide gas removal device as a gas generator.

The steam reforming of hydrocarbons such as butane is carried out in the next reaction step.

C ₄ H ₁₀ + 4H ₂ O → 4CO + 9H ₂ CO + H ₂ O CO ₂ + H ₂ CO + 3H ₂ CH ₄ + H ₂ O CO contained in the gas leaving the reforming furnace is converted to CO ₂ in the conversion furnace.

CO + H ₂ O CO ₂ + H ₂ As is clear from the above reaction formula, the gas composition varies depending on the reaction conditions, but each has 20 to 30% CO ₂ , and as it is, it has low calories and can be supplied to consumers. Therefore, a CO ₂ removal device is required.

Conventionally, a chemical absorption method or a physical absorption method has been used as a CO ₂ removal process, but these operations are usually performed at a high temperature or a high pressure, and there are drawbacks such as a long start-up time and an inability to deal with an emergency.

[Means for solving the problems] The present inventors have conducted extensive advances result of research and development of CO ₂ removal process by pressure swing adsorption method (hereinafter referred to as PSA adsorption method) As an alternative to conventional absorption method CO ₂ removal process The present invention is a stable CO ₂ removal method that can respond to emergencies, is easy to operate, and can be used as the pressure of purified gas without reducing the pressure of the raw material gas. .

That is, the gist of the present invention is to use three adsorption towers filled with an adsorbent that selectively adsorbs carbon dioxide, and to flow a raw material gas that is a hydrocarbon reforming gas containing carbon dioxide into these adsorption towers. A method for purifying a hydrocarbon reformed gas by adsorbing and removing carbon dioxide, comprising: (1) supplying a raw material gas in a pressurized state to a raw material end in order in a first adsorption tower. Then, while maintaining the inside of the tower at a constant pressure, the hydrocarbon reformed gas is led out from the product end as a purified gas, and a part of this purified gas is discharged from the hydrocarbon reformed gas from the third adsorption tower. Supplying to the product end of the second adsorption tower where pressure equalization is being performed by inflow, (2) supplying pressurized raw material gas to the raw material end, and maintaining a constant pressure inside the tower However, the hydrocarbon reformed gas was discharged as a purified gas from the end of the product. , A part of this purified gas is supplied to the product end of the second adsorption tower, which has been pressure-equalized by the inflow of the hydrocarbon reforming gas from the third adsorption tower, (3) The pressurized raw material gas is supplied to the raw material end, and the hydrocarbon reformed gas is discharged as a purified gas from the product end while maintaining a constant pressure in the tower. A part of the purified gas is supplied to the product end of the second adsorption tower to raise the pressure of the second adsorption tower, and at the same time, it is also supplied to the already exhausted third adsorption tower to form the third adsorption tower. Scavenging step, (4) Stop the flow of raw material gas, derive the hydrocarbon reformed gas from the product end, supply this hydrocarbon reformed gas to the already adsorbed third adsorption tower, and equalize the pressure. (5) Step of exhausting from the raw material end, (6) Derivation of hydrocarbon reformed gas as purified gas (7) A hydrocarbon reforming gas derived from the second adsorption tower in which the feed of the raw material gas is stopped, A step of inflowing a part of the purified gas from the third adsorption tower, which has derived the hydrocarbon reformed gas as a purified gas, from the end of the product to equalize the pressure, and (8) the hydrocarbon reformed gas A step of causing a part of the purified gas from the third adsorption tower, which is derived as a purified gas, to flow from the end of the product to increase the pressure, and during that period, the process cycle is performed in the second and third adsorption towers. The method for purifying a hydrocarbon reformed gas is characterized in that the phase is changed in each of the above.

[Specific Structure of the Invention] As the adsorbent used in the present invention, any of synthetic A type zeolite (molecular sieves 3A, 4A, 5A), synthetic X type zeolite (molecular sieve 13X), naturally occurring zeolite and molecular sieve carbon should be used. However, molecular sieve 4A is preferably used. The adsorption isotherm at 25 ° C of molecular sieve 4A is shown in Fig. 2.
As shown in Fig. 2, molecular sieve 4A adsorbs CO ₂ in an overwhelmingly large amount, but also CH ₄ at the same time. About 70% of the hydrocarbon reformed gas used in this method is CH ₄
Therefore, the adsorption amount of CH ₄ is considerably large when the partial pressure is taken into consideration.

By the way, the raw material gas is introduced from the raw material end of the adsorption tower, and the purified gas is taken out from the product end of the adsorption tower (1),
In the steps (2) and (3), it is considered that the CO ₂ adsorption front proceeds toward the end of the product while pushing up the CH ₄ adsorption front in front of it and replacing the adsorbed CH ₄ with it. This situation is shown in FIG. FIG. 3 (a) shows the state of no CO ₂ breakthrough, and FIG. 3 (b) shows the state of CO ₂ breakthrough. As is clear from Fig. 3, in order to suppress the CO ₂ contamination rate of the product gas, it is better to advance the step to the next adsorption tower in the state where the adsorption tower has not passed through CO ₂ , and conversely CH _In order to improve the recovery rate of ₄ , it is better to advance the step to the next adsorption tower in the state where the CO ₂ partially breaks through the adsorption tower. As described above, since the purified gas of the present invention is a heat source for city gas substitution, the incorporation of CO ₂ causes a reduction in calories, but a small amount (5% or less) is not a problem. Therefore, in the present invention, it is preferable to significantly increase CH ₄ recovery while allowing CO ₂ to pass through within an allowable range.

Another feature of the present invention will be explained by focusing on the second adsorption tower. In the step (1), a part of the purified gas in the first adsorption tower and the hydrocarbon reforming from the third adsorption tower are reformed. The gas equalizes the pressure in the second adsorption tower, and then a second portion of the purified gas from the first adsorption tower is supplied to the second adsorption tower in the step (2).
The pressure in the adsorption tower of the above is increased, and finally (3)
In the process of
The pressure of the second adsorption tower is increased to the same as the pressure of the raw material gas, and the pressure of the purified gas due to the subsequent adsorption in the second adsorption tower is the same as the raw material gas. It will be almost unchanged. That is, the pressure of the raw material gas can be used as it is as the pressure of the purified gas.

Also during the adsorption tower tower has finished the adsorption step and describing Figure 3 based on a large amount of CH ₄ together with the CH ₄ which has remained in the gap portion of the CH ₄ and adsorbent particles adsorbed on the adsorbent Exists. This is CH ₄ minutes transferred from the third adsorption tower to the second adsorption tower at the pressure equalization in the step (1). In the step (1), CH ₄ is partially transferred to the second adsorption tower by part of the purified gas from the first adsorption tower. Subsequently, in the steps (2) and (3), a part of the purified gas from the first adsorption tower is caused to flow into the product end of the second adsorption tower. In the pressurization process of the second adsorption tower, the CH ₄ adsorption front, which has a predominantly high partial pressure, has the effect of pushing down the CO ₂ adsorption front toward the end of the raw material, increasing the CH ₄ yield, and increasing the CH ₄ yield. It brings about an increase in the ingredients.

In the present invention, the lower part of the adsorption tower is filled with activated alumina having a volume of 1/10 or less of the volume of the adsorbent, and the adsorbent is filled thereover. The role of activated alumina is to allow moisture as a saturated steam pressure component contained in the steam reforming gas of hydrocarbon to be adsorbed on the activated alumina in the steps (1), (2) and (3), In the step (6), the moisture adsorbed on the activated alumina is desorbed to regenerate the activated alumina, whereby the so-called moisture PSA method using activated alumina is performed. This protects the adsorbent, which is sensitive to moisture.

The PSA method does not require any pressure energy except for the instrumentation air that operates the valve, and can be taken out as a purified gas pressure with almost no reduction in the pressure held by the raw material gas, which is extremely economical.

Further, in the exhaust gas and scavenging gas by desorption of the PSA method according to the present invention, some combustible gases such as H ₂ and CH ₄ are contained, and this gas is desirably used as a heat source for steam reforming. However, since the pressure of the desorbed and scavenged gas is discharged while holding the pressure required for the combustion burner, it can be stored and used in the hold tank.

In the steps (5) and (6), it is common to open to atmospheric pressure for exhausting and scavenging, but in the steps of exhausting and scavenging, suction is simultaneously performed using a decompression pump to obtain an adsorbent. It is also possible to promote the regeneration of. In this case, the pressure on the exhaust side of the decompression pump holds the pressure required for the heat source combustion burner for steam reforming.

Hereinafter, the method of the present invention will be specifically described with reference to FIG. 1. However, it should be understood that the operation shown below is an example and the present invention is not limited to this operation.

In FIG. 1, A, B and C are adsorption towers, 1 to 15 are opening / closing valves, and 16 to 2
1 is a control valve, 25 is a raw material gas, 26 is a purified gas, 27 is an exhaust gas, 31 to 37 are pipes, 41 is a purified gas hold tank, 42 is an exhaust gas hold tank, 51 is a decompression pump used when performing vacuum desorption, 61 is a CO ₂ concentration meter.

In operation, the hydrocarbon reformed gas is continuously refined while sequentially repeating the 9 steps described below. In addition, the operation time of each step can be arbitrarily controlled by a timer. In the following steps, steps 1 to
In step 3, the tower A is the adsorption step, in steps 4 to 6, the tower B is the adsorption step, and in steps 7 to 9, the tower C is the adsorption step.

Step 1 The on-off valves 1, 2, 10, 15 are opened and the raw material gas 25 is introduced into the adsorption tower A through the pipe 31 through the on-off valve 1. Purified gas flows from the product end of the adsorption tower through the on-off valve 2 and the pipe 32, and is stored in the purified gas hold tank 41 through the control valve 21. The outflow rate of the purified gas is controlled by the control valve 21. On the other hand, the gas from the adsorption tower C, which has already completed the adsorption step (steps 7 to 9), passes through the control valve 18, the on-off valve 15, the pipe 34, the on-off valve 10 and the control valve 17, and this is also due to a part of the purified gas. The inside of the tower is scavenged (washed) (step 9), and is supplied countercurrently to the regenerated adsorption tower B until the pressure between the adsorption towers B and C becomes almost equal (equal pressure). At this time, the gas moving speed is controlled by the control valves 18 and 17. With respect to the adsorption tower B, at the same time with the above-mentioned gas from the adsorption tower C, a part of the purified gas from the adsorption tower A is adjusted in speed by the control valve 20 through the pipe 32, and the pipes 36, 34 and the on-off valves 1
It is introduced into the adsorption tower B via the control valve 17.

Step 2 The on-off valve 14 is opened at the same time when the on-off valve 15 is closed. The adsorption tower A continues the same operation as in step 1. Adsorption tower B has open / close valve 15
However, the inflow of gas from the adsorption tower C is stopped by closing, but the internal pressure of the tower is increased while receiving a part of the purified gas from the adsorption tower A (pressurization). On the other hand, the adsorption tower C is an open / close valve.
By opening 14 to near atmospheric pressure (in the case of vacuum PSA method, it is sucked by decompression pump 51 and below atmospheric pressure)
The pressure is reduced and the adsorbed gas is desorbed and exhausted. On-off valve for exhaust gas
14, through the pipe 37 (in the case of the vacuum PSA method, sucked by the decompression pump 51) and stored in the exhaust gas hold tank 42.

Process 3 The on-off valve 13 is newly opened. The adsorption tower A continues the same operation as steps 1 and 2. The adsorption tower B continues the same operation as in step 2 and further increases in pressure, and reaches the same pressure as in adsorption tower A at the end of step 3. The adsorption tower C is scavenged (washed) inside the tower with a part of the purified gas from the adsorption tower A after the depressurization and desorption in step 2. That is, a part of the purified gas from the adsorption tower A is introduced into the adsorption tower C through the pipes 32 and 35, the control valve 19, the pipe 33, and the opening / closing valve 13, and the inside of the tower is washed countercurrently to open / close the valve 14 and the pipe 37. After passing through (in the case of the vacuum PSA method, sucked and exhausted by the decompression pump 51), it is stored in the exhaust gas hold tank. The scavenging (cleaning) gas speed is adjusted by selecting the opening degree of the control valve 19 so that the speed of the cleaning effect is the highest.

Step 4 The on-off valves 1,2,10,13,14 are closed and the on-off valves 6,7,15,5 are opened. The raw material gas 25 is introduced from the pipe 31 into the adsorption tower B through the on-off valve 6. Purified gas flows from the product end of the adsorption tower through the opening / closing valve 7 and the pipe 32, and is stored in the purified gas hold tank 41 through the control valve 21. The outflow rate of the purified gas is controlled by the control valve 21. On the other hand, from the adsorption tower A which has already completed the adsorption steps (1 to 3), the control valve 16, the opening / closing valve 5, the pipe 34, the opening / closing valve 15,
The gas, which has already been scavenged (cleaned) in the tower by a part of the purified gas (step 3), flows countercurrent to the regenerated adsorption tower C between the adsorption towers C and A. It is supplied until the pressure of is almost equal (equal pressure). At this time, the gas moving speed is controlled by the control valves 16 and 18. For the adsorption tower C, at the same time as the above gas from the adsorption tower A, a part of the purified gas from the adsorption tower B is adjusted in speed by the control valve 20 through the pipe 32, and the pipe 36, the on-off valve 15, the control valve 18 Is introduced into the adsorption tower C via.

Step 5 The opening / closing valve 4 is opened at the same time when the opening / closing valve 5 is closed. The adsorption tower B continues the same operation as in step 4. The adsorption tower C has an on-off valve 5
Although the inflow of gas from the adsorption tower A is stopped by closing, the internal pressure of the tower is raised (pressurization) while receiving a part of the purified gas from the adsorption tower B. On the other hand, the adsorption tower A is brought to near atmospheric pressure by opening the on-off valve 4 (in the case of the vacuum PSA method, it is sucked by the decompression pump 51 and is below atmospheric pressure).
The pressure is reduced and the adsorbed gas is desorbed and exhausted. The exhaust gas is stored in the exhaust gas hold tank 42 through the on-off valve 4 and the pipe 37 (in the case of the vacuum PSA method, it is sucked by the decompression pump 51).

Step 6 The on-off valve 3 is newly opened. The adsorption tower B continues the same operation as steps 4 and 5. The adsorption tower C continues the same operation as in step 5, and the pressure is further increased, and at the end of step 6, it reaches the same pressure as in the adsorption tower B. The adsorption tower A is scavenged (washed) inside the tower by a part of the purified gas from the adsorption tower B after the depressurization and desorption in step 5. That is, part of the purified gas from the adsorption tower B is pipe 3
2, 35, control valve 19, pipe 33, and on-off valve 3 are introduced into the adsorption tower A, and the inside of the tower is washed countercurrently and then through on-off valve 4 and pipe 37 (pressure reducing pump 51 in the case of the vacuum PSA method). (Suctioned and exhausted by) and stored in the exhaust gas hold tank. The scavenging (cleaning) gas speed is adjusted by selecting the opening degree of the control valve 19 so that the speed of the cleaning effect is the highest.

Step 7 The on-off valves 6,7,15,3,4 are closed and the on-off valves 11,12,5,10 are opened. The raw material gas 25 is introduced into the adsorption tower C from the pipe 31 through the on-off valve 11. Pipe 32 from the product end of the adsorption tower through the on-off valve 12.
Further purified gas flows out and is stored in the purified gas hold tank 41 through the control valve 21. The outflow rate of the purified gas is controlled by the control valve 21. On the other hand, the gas from the adsorption tower B, which has already completed the adsorption step (steps 4 to 6), passes through the control valve 17, the on-off valve 10, the pipe 34, the on-off valve 5 and the control valve 16, and this is also due to a part of the purified gas. The inside of the tower is scavenged (washed) (step 6) and is supplied countercurrently to the regenerated adsorption tower A until the pressure between the adsorption towers A and B becomes almost equal (equal pressure). At this time, the gas moving speed is controlled by the control valves 17 and 16. For the adsorption tower A, at the same time as the above-mentioned gas from the adsorption tower B, a part of the purified gas from the adsorption tower C is supplied from a pipe 32 to a control valve.
It is introduced into the adsorption tower A through the pipes 36 and 34, the on-off valve 5 and the control valve 16 after the speed is adjusted at 20.

Step 8 The on-off valve 9 is opened at the same time when the on-off valve 10 is closed. The adsorption tower C continues the same operation as in step 7. Adsorption tower A has open / close valve 10
However, the inflow of gas from the adsorption tower B is stopped by closing, but the tower internal pressure is increased (pressurization) while receiving part of the purified gas from the adsorption tower C. On the other hand, the adsorption tower B is brought to near atmospheric pressure by opening the on-off valve 9 (in the case of the vacuum PSA method, it is sucked by the decompression pump 51 to be below atmospheric pressure).
The pressure is reduced and the adsorbed gas is desorbed and exhausted. The exhaust gas is stored in the exhaust gas hold tank 42 through the on-off valve 9 and the pipe 37 (in the case of the vacuum PSA method, it is sucked by the decompression pump 51).

Step 9 The on-off valve 8 is newly opened. The adsorption tower C continues the same operation as steps 7 and 8. The adsorption tower A continues the same operation as in step 8 and further increases in pressure, and reaches the same pressure as in adsorption tower C at the end of step 9. After the decompression / desorption in step 8, the adsorption tower B is scavenged (washed) with a part of the purified gas from the adsorption tower C. That is, a part of the purified gas from the adsorption tower C is introduced into the adsorption tower B via the pipes 32 and 35, the control valve 19, the pipe 33, and the opening / closing valve 8, and the inside of the tower is washed countercurrently to open / close the valve 9 and the pipe. After passing through 37 (in the case of the vacuum PSA method, sucked and exhausted by the decompression pump 51), it is stored in the exhaust gas hold tank. The scavenging (cleaning) gas speed is adjusted by selecting the opening degree of the control valve 19 so that the speed of the cleaning effect is the highest.

As can be understood from the above description, the above-mentioned 9 steps have steps 1 to 3 as one unit, and in the relationship between columns,
This is repeated while changing the phase of each tower. This relationship is summarized in Table 1 for easy understanding.

The opening and closing of each on-off valve is automatically performed by a timer, a sequencer or the like. The time required for the cycle is 1 to 10 minutes, preferably 3 to 6 minutes per tower. Refined gas velocity CO ₂ concentration in the purified gas is sufficient to breakthrough less than 5% can be accomplished by adjusting the degree of opening of the control valve 21 manually, Other CO ₂ concentration meter in the path of the tube 32 Is provided, and when the CO ₂ concentration in the purified gas reaches the set value, the PSA method step can be performed.

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 A refining experiment was carried out using a butane steam reforming gas synthesized by a gas mixer. The three adsorption towers were made of stainless steel (inner diameter 28 mm × height 1.25 m), and the upper portion of each tower was filled with 427 g of molecular sieve 4A and the lower portion was filled with 95 g of activated alumina.

(B) Experimental conditions Operating temperature: 40 ° C Adsorption pressure: 6.0 kg / cm ² G Exhaust pressure: 1.0 kg / cm ² G Cycle time: 4.0 minutes / per tower Synthesis gas composition: H ₂ = 7.0%, CO ₂ 25.1 %, CH ₄ = 67.9%,
It also contains saturated steam at 40 ° C.

(B) Operating conditions As shown in FIG.

Step 1: As shown in (a).

Step 2: (b) As shown in the figure.

Step 3: (c) As shown in the figure.

Process 4, Process 5, Process 6: Figures (a) and (b), respectively
(C) In the figure, read as A → B, B → C, C → A.

Process 7, Process 8, Process 9: (a) diagram, (b) diagram, respectively
(C) In the figure, read as A → C, B → A, C → B.

(C) Experimental results The amount of raw material supply gas was 184.8 Nl / Hr, whereas the purified gas was 119.3 Nl / Hr
The CH ₄ recovery was 84.8%. Purified gas composition is H ₂ = 5.8
%, CO ₂ = 5.0%, CH ₄ = 89.2%, and dew point = -60 ° C.

Example 2 In Example 1, the concentration of CO ₂ gas in the purified gas was reduced by further narrowing the opening of the purified gas control valve.
The raw material synthesis gas composition and operating conditions are the same as in Example 1.

The experimental results showed that the purified gas was 95.3 Nl / Hr and the CH ₄ recovery rate was 77.5% with respect to the raw material supply gas amount of 170.3 Nl / Hr. The purified gas composition is H ₂ = 5.8%, CO ₂ = 0.1%, CH ₄ = 94.0%, dew point =-
It was 60 ° C.

[Example 3] A vacuum pump was connected to the exhaust side to reduce the exhaust pressure to 460 Torr.

(B) Experimental conditions The same as in Example 1.

(B) Operating conditions As shown in FIG.

Step 1: As shown in (a).

Step 2: (b) As shown in the figure.

Step 3: (c) As shown in the figure.

Process 4, Process 5, Process 6: Figures (a) and (b), respectively
(C) In the figure, read as A → B, B → C, C → A.

Process 7, Process 8, Process 9: (a) diagram, (b) diagram, respectively
(C) In the figure, read as A → C, B → A, C → B.

(C) Experimental results Purified gas 11 is 9.3 Nl / Hr as the raw material supply gas amount is 231.4 Nl / Hr
The H ₄ CH ₄ recovery was 91.8%. The purified gas composition is H
_{2 = 6.8%, CO 2 =} 5.0%, CH 4 = 88.2%, was dew point = -60 ° C..

[Advantages of the Invention] In removing carbon dioxide from a hydrocarbon reformed gas according to the present invention, (a) it is possible to easily respond in an emergency, (b) without damaging the pressure of the raw material gas, It can be purified without use.

[Brief description of drawings]

FIG. 1 is a system diagram for explaining the present invention, FIG. 2 is an adsorption equilibrium diagram of molecular sieves, FIG. 3 is an explanatory diagram showing a breakthrough state of an adsorption tower, and FIG. It is a schematic diagram which shows the operating conditions of Example 1, and FIG. 5 is a schematic diagram which shows the operating conditions of Example 3. A, B, C ... Adsorption tower, 1-15 ... Open / close valve 16-21 ... Control valve, 31-37 ... Pipe 51 ... Decompression pump, 61 ... CO ₂ concentration meter

Claims (2)

[Claims] 1. A three-piece adsorption tower filled with an adsorbent that selectively adsorbs carbon dioxide is used, and a raw material gas, which is a hydrocarbon reforming gas containing carbon dioxide, is passed through these adsorption towers. A method for purifying a hydrocarbon reformed gas by adsorbing and removing carbon dioxide, comprising: (1) supplying a raw material gas in a pressurized state to a raw material end in sequence in a first adsorption tower; While maintaining a constant pressure in the tower, the hydrocarbon reformed gas is discharged as a purified gas from the end of the product, and a part of this purified gas is introduced by the inflow of the hydrocarbon reformed gas from the third adsorption tower. Supplying to the product end of the second adsorption tower where pressure equalization is being performed, (2) supplying pressurized raw material gas to the raw material end and maintaining the inside of the tower at a constant pressure, The hydrocarbon reformed gas is derived from the end of the product as a purified gas, and this purified gas is discharged. A part of the above is supplied to the product end of the second adsorption tower where pressure equalization has already been performed by the hydrocarbon reforming gas inflow from the third adsorption tower to pressurize the second adsorption tower, (3) The pressurized raw material gas is supplied to the raw material end, and the hydrocarbon reformed gas is discharged as a purified gas from the product end while maintaining a constant pressure in the tower, and a part of this purified gas Is supplied to the product end of the second adsorption tower to pressurize the second adsorption tower and at the same time is also supplied to the already exhausted third adsorption tower to scavenge-clean the third adsorption tower, (4) A step of stopping the inflow of the raw material gas, deriving the hydrocarbon reformed gas from the product end, and supplying this hydrocarbon reformed gas to the already adsorbed third adsorption tower to equalize the pressure. (5) A step of exhausting from the end of the raw material, (6) Is it a second adsorption tower that delivers hydrocarbon reformed gas as a purified gas? A step of flowing a part of the purified gas from the end of the product to wash and scavenging the inside of the tower, (7) a hydrocarbon reformed gas derived from the second adsorption tower in which the flow of the raw material gas is stopped, and a hydrocarbon A step of causing a part of the purified gas from the third adsorption tower, which has derived the reformed gas as the purified gas, to flow from the end of the product to equalize the pressure, and (8) use the hydrocarbon reformed gas as the purified gas. A step of causing a part of the derived purified gas from the third adsorption tower to flow from the end of the product to raise the pressure, and further, during that time, the process cycle is performed in each of the second and third adsorption towers. A method for purifying a hydrocarbon reformed gas, which is performed by changing the phase. 2. The method according to claim 1, wherein the step (5) sucks and exhausts to a pressure below atmospheric pressure by a decompression pump, and the step (6) sucks and scavenges to a pressure below atmospheric pressure by a decompression pump. The method for purifying a hydrocarbon reformed gas according to claim 1.