JP2002355519A - Method of stably operating four tower-type pressure- swing adsorption equipment for hydrogen purification - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the flow rate of product gas, the purity of product hydrogen and the recovery rate of the product hydrogen corresponding to the temperature of the outside air environment in wintertime, summertime or the like in a four-tower-type pressure-swing adsorption equipment for hydrogen purification. SOLUTION: The method of stably operating the four tower-type pressure- swing adsorption equipment for hydrogen purification is characterized in that, by measuring and detecting the temperature of the product hydrogen gas, and then changing the cycle time according to the measured value, the flow amount of the product gas, the purity of the product hydrogen and the recovery rate of the product hydrogen can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for stably operating a four-column pressure swing adsorption apparatus for hydrogen purification.

[0002]

2. Description of the Related Art Hydrogen is a basic raw material used for adding hydrogen to unsaturated bonds, for oxyhydrogen flames, and for various other uses, and is also used as a fuel for fuel cells. Industrial methods for producing hydrogen include a steam reforming method and a partial combustion method for hydrocarbon gas. In the steam reforming method, a reformer is used, and a hydrocarbon gas is converted into a reformed gas by a catalytic reaction. The obtained reformed gas contains by-products such as CO and CO ₂ , surplus H ₂ O, and unreformed hydrocarbons, in addition to hydrogen as a main component. Therefore, if the reformed gas is used as it is in a fuel cell, for example, the cell performance will be impaired.

[0003] For example, among fuel cells, CO in hydrogen gas used in a phosphoric acid fuel cell (PAFC) is 1% (capacity%, the same applies hereinafter), and in a polymer electrolyte fuel cell (PEFC), 100 ppm (capacity ppm). Is the limit, and when these are exceeded, the battery performance is remarkably deteriorated. Therefore, it is necessary to purify the reformed gas before introducing it into the fuel cell and to remove those by-products. The hydrogen for adding hydrogen to the unsaturated bond or for the oxyhydrogen flame is usually used in a cylinder, and its purity is 5N (99.999%).
The above is required.

As one of the hydrogen purification methods for obtaining such high-purity hydrogen, a pressure swing adsorption method (PSA method: Pr
essure Swing Adsorption Method). In the PSA method, impurities in the reformed gas generated in the reformer and passed through the CO converter are adsorbed and separated into the adsorbent layer under pressure, and the adsorbed impurities are desorbed by reducing the pressure to around normal pressure.

[0005] Fig. 1 shows each adsorption tower A in a four-column pressure swing adsorption apparatus for hydrogen purification which is premised in the present invention.
FIG. 4 is a diagram showing an arrangement relationship of a pipe (line), each valve, an off-gas storage tank (off-gas tank), and the like. FIG.
Adsorption in 4-column pressure swing adsorption apparatus as shown in, equalization depressurization pressure equalization holding, vacuum, blowdown, purge, each step of the equalization repressurization, H ₂ boosted (boosted by hydrogen) are repeated, blown Off gas is generated in the down and purge steps.

FIG. 2 shows the four-column pressure for hydrogen purification shown in FIG.
Process flow of each adsorption tower in swing adsorption equipment and
It is a figure which shows the outline of an operation sequence. FIG. 2 also shows
This shows the pressure change in each adsorption tower as each process progresses.
ing. Reforming raw material gas such as city gas, that is, hydrocarbons
Steam reformer (combustion unit + reforming unit) to CO converter
Is supplied to the tower A, where H_Two
O, CO_Two, CO, CH _FourAdsorption of impurities such as
Uncharged hydrogen becomes purified hydrogen (product hydrogen).

Meanwhile, the tower B is purged from blowdown.
Is carried out. In the tower C, the pressure is reduced from
Is performed following the pressure reduction in the tower D._Two
A (hydrogen) pressurization step is performed. The supply of reformed gas is A
Before the impurities are saturated in the column and break through, D
Switched to a tower. At this point, the tower A
It is switched to the process of decompression holding and the following decompression,
Tower B is H _TwoSwitching to the step of boosting, C
The tower is switched from blowdown to purging,
The column is switched to the adsorption step. Hereafter, these processes
As shown in FIG.
Operated continuously.

During that time, off-gas generated in the blow-down step and the purge step is sent to the off-gas storage tank T. In these steps, off-gas during the blow-down step was generated in a step of desorbing impurities adsorbed under pressure to near normal pressure and desorbing them, and was stored in an off-gas storage tank via an off-gas conduit (off-gas line). Then, it is supplied to the burner of the reformer for hydrogen production.

[0009]

As described above, the four-column pressure swing adsorption apparatus for hydrogen purification employs adsorption, pressure equalization, pressure reduction, pressure equalization, pressure reduction, blowdown, purge, pressure equalization, H ₂
The operation is performed in a (hydrogen) pressurization cycle. However,
During operation of the four-column pressure swing adsorption apparatus for hydrogen purification, a difference in performance occurs depending on the external environmental temperature.
That is, the PSA operation temperature, that is, the temperature distribution of the adsorbent in the adsorption tower is affected by the outside air temperature (temperature difference), and not only adversely affects the purity of the product hydrogen, but also affects the recovery rate of the product hydrogen. .

As a method for avoiding the above problem, there is a flow control method. In the flow rate control method, since the outside air temperature has a great influence on the pressure increasing step, the pressure increases to a predetermined pressure within the time of the pressure increasing step according to the temperature of the raw material gas (the gas to be treated such as the reformed gas supplied to the adsorption tower). This is a method of adjusting the flow rate set value so that the pressure can be increased. But with this method,
Since only the pressurized flow rate fluctuates, the product hydrogen gas amount fluctuates greatly and the recovery rate is not stable. In addition, when the operating temperature is high, the adsorbing ability of the adsorbent is also reduced, so that the purity of the product hydrogen is reduced and its quality is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem in a four-column pressure swing adsorption apparatus for hydrogen purification, and the temperature of product hydrogen gas is adjusted in accordance with the outside air temperature in summer or winter. , The cycle time is changed based on the measured value. Accordingly, it is an object of the present invention to provide a stable operation method of a four-column pressure swing adsorption apparatus which stabilizes the product hydrogen gas flow rate, stabilizes the purity of the product hydrogen, and stabilizes the recovery rate. I do.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a hydrogen purification device for hydrogen purification.
A stable operation method of a tower-type pressure swing adsorption device that measures and detects the temperature of product hydrogen gas and changes the cycle time based on the measured value to stabilize the product gas flow rate and simultaneously A stable operation method for a four-column pressure swing adsorption apparatus, characterized by stabilizing the purity of hydrogen and the recovery rate.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a hydrogen purification 4
During the operation of the tower pressure swing adsorption device, the temperature of the product hydrogen is measured and detected, and the cycle time is changed based on the measured and detected value. This stabilizes the flow rate of the product hydrogen, stabilizes the purity of the product hydrogen, and stabilizes the recovery rate. In addition, it is possible to prevent a case in which the target apparatus performance does not reach the target performance due to a temperature difference in summer, winter, or day and night.

As a specific embodiment, when the temperature of the product hydrogen measured and detected is high, the cycle time is shortened. This is because, in the adsorption operation, when the temperature is high, the equilibrium adsorption amount is low, so that it is essential to reduce the processing capacity per unit adsorbent in order to keep the purity of the product hydrogen. In this case, a part of the product hydrogen used in the pressure increasing step is increased to a predetermined pressure at an actual flow rate. For this reason, the required amount of hydrogen in an ideal state decreases, and the recovery rate tends to improve. As the cycle time becomes shorter, the hydrogen recovery rate tends to decrease, but the above two effects are offset, and the product hydrogen purity and the recovery rate are stabilized.

Conversely, if the temperature of the product hydrogen measured and detected is low, the cycle time is lengthened. When the temperature of the product hydrogen is low, a part of the product hydrogen used in the pressurization step is pressurized to a predetermined pressure at an actual flow rate, so that the required amount of hydrogen in an ideal state increases and the recovery rate decreases. . Therefore, it is necessary to increase the cycle time and improve the recovery rate. On the other hand, when the temperature is low, the equilibrium adsorption amount increases, and the purity of the product hydrogen is maintained even when the cycle time is increased. Thus, the product hydrogen purity and the recovery rate are stabilized. According to the present invention, in the operation of the four-column pressure swing adsorption apparatus for hydrogen purification in this manner, stable operation can always be performed in accordance with the temperature difference in summer, winter, or day or night.

[0016]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to these Examples. In this embodiment, the apparatus shown in FIG. 3 was used. Activated carbon as a mixed bed in each of the adsorption towers A, B, C, D;
Zeolite was charged. As a gas to be supplied to the adsorption tower, city gas (desulfurized) is reformed with a steam reformer,
The reformed gas obtained from the reformer through the CO converter was used. The reformer includes a combustion section having a burner and a reforming section. Heat (ΔH) from the combustion section is supplied to the reforming section, and the raw material gas is converted into reformed gas by a catalytic reaction in the reforming section.

In FIG. 3, T is an off-gas storage tank, and F is a burner fuel gas conduit. If only off-gas is not enough as a burner fuel, city gas or the like is appropriately supplemented and supplemented. K is a burner combustion air conduit. TH is a temperature sensor set in the product hydrogen line. Note that FIG.
The description of the CO converter and the gas cooler following the middle reformer is omitted.

[0018] The reformed gas is mainly composed of hydrogen.
O, CH ₄ , CO ₂ , N _{2 and the} like are contained. These gases other than hydrogen are gases that are adsorbed and removed in the adsorption tower,
The temperature at which the reformed gas is introduced into the adsorption tower is about 20 to 40 ° C. Since the temperature of the reformed gas passed through the CO converter is higher than that, the reformed gas is cooled to such a temperature by a gas cooler and supplied to the adsorption tower.

Regarding the operation time of each step of the four-column pressure swing adsorption apparatus for hydrogen purification targeted in the present invention,
Step 1 is 5 to 60 seconds, preferably 20 to 30 seconds, Step 2 is 5 to 60 seconds, preferably 10 to 20 seconds, Step 3 is 110 to 300 seconds, preferably 120 to 190
Range of seconds. Therefore, the adsorption time in steps 1 to 3 is set in the range of 120 to 420 seconds, preferably 150 to 240 seconds.

In this embodiment, step 1 is 30 steps.
Second, step 2 was 20 seconds, and step 3 was 190 seconds. Therefore, the adsorption time in steps 1 to 3 is 240 seconds. Steps 4-6, 6-9 and 10-12
These are the same as steps 1 to 3, respectively. Step 1
3, step 4-6, step 7-9, step 10
12 is a subcycle, and steps 1 to 12
Is one cycle.

The operating pressure is 0.7 MPaG at the time of the adsorption step (the same until the end of the adsorption step), 0.6 MPaG at the time of uniform pressure reduction, pressure reduction hold and pressure reduction end, and 0.02 at the end of blowdown.
MpaG, 0.22 MPaG at the end of purge, and 0.68 MPa at the end of pressure increase. The adsorption pressure in the adsorption step is controlled by a control valve arranged in the purified hydrogen line, but is not shown. In the following operation, the valve V is open through steps 1 to 12. Blowdown (step) is abbreviated as blow (step) as appropriate.

In the operation of repeating the following steps 1 to 12, the temperature of the product hydrogen gas was measured by the temperature sensor TH as needed. In the comparative example, the above-mentioned adsorption time was always kept constant at 240 seconds. In the example, the product hydrogen gas temperature was set to 5 ° C., and the cycle time was changed by 0.6 seconds with respect to 1 ° C. between the reference temperature and the measured product hydrogen temperature (that is, 0.6 seconds / The cycle time was increased or decreased at a rate of ° C).

<Step 1> A tower = adsorption, B tower = blowing, C tower = equalizing pressure reducing, D tower = equalizing pressure increasing valves A1, A2 are opened, and the reformed gas is supplied to the A tower to perform the adsorption operation. Was carried out. In the meantime, the blowing step was performed in the tower B, the equalizing pressure reducing step was performed in the tower C, and the equalizing pressure increasing step was performed in the tower D. As for the other valves, the valves B5, C4, and D3 were opened, and the opening degrees of the valves W, X, Y, and Z were kept constant. Other valves are closed.

<Step 2> A tower = adsorption, B tower = blowing, C tower = reduced pressure, D tower = H ₂ boosting valve Same as step 1 except that the valve C4 and the valve X were closed. The raw gas was supplied to the tower A to perform the adsorption operation. During that time, a blowing step was performed in the tower B, a pressure reduction step was performed in the tower C, and a pressure equalizing step was performed in the tower D.

<Step 3> The reformed gas was continuously supplied in the same manner as in step 2 except that the tower A was adsorbed, the tower B was purged, the tower C was depressurized, and the tower D was H ₂ booster valves B4 and C4 were opened. The mixture was supplied to the tower A to perform an adsorption operation. Meanwhile, the purging step in the tower B, the depressurizing step in the tower C,
In the tower D, an H ₂ pressure increasing step was performed.

<Step 4> A tower = equalization pressure reduction, B tower = equalization pressure increase, C tower = blowing, D tower = adsorption valves D1 and D2 are opened, and reforming gas is supplied to D tower to perform adsorption operation. Was carried out. During that time, the equalizing pressure reducing step was performed in the tower A, the equalizing pressure increasing step was performed in the tower B, and the blowing step was performed in the tower C. With respect to the other valves, the valves A4, B3, and C5 were opened, and the opening degrees of the valves W, X, Y, and Z were kept constant. Other valves are closed.

<Step 5> Tower A = retained pressure, Tower B = H
₍₂₎ Pressurization, C tower = blow, D tower = adsorption In the same manner as in step 4 except that the valve A4 and the valve X were closed, the reforming gas was continuously supplied to the D tower to perform the adsorption operation. In the meantime, the tower A performed the reduced pressure holding step, the tower B performed the H ₂ pressure increasing step, and the tower C performed the blowing step.

<Step 6> A tower = depressurized, B tower = H ₂ increased, C tower = purge, D tower = adsorption Same as step 5 except that A4 and C4 were opened.
Subsequently, the reforming gas was supplied to the tower D to perform an adsorption operation.
In the meantime, the pressure reduction step is performed in the tower A, the H ₂ pressure increase step is performed in the tower B,
A purge step was performed in the tower.

<Step 7> A tower = blow, B tower = adsorption, C tower = equalizing pressure increase, D tower = equalizing pressure reducing valves B1 and B2 are opened, and reforming gas is supplied to B tower to perform adsorption operation. Was carried out. During that time, the blowing step was performed in the tower A, the equalizing pressure increasing step in the tower C, and the equalizing pressure reducing step in the tower D. With respect to the other valves, A5, C3, and D4 are opened, and valves W,
The opening degrees of the valve X, the valve Y, and the valve Z were made constant. Other valves are closed.

<Step 8> A tower = blow, B tower = adsorption, C tower = H ₂ pressurization, D tower = depressurization holding Same as step 7, except that valve D4 and valve X were closed. The raw gas was supplied to the tower B to perform the adsorption operation. In the meantime, the blowing process is performed in the tower A, and the blowing process is performed in the tower C.
_{(2) The} pressure raising step, and the reduced pressure holding step were performed in the tower D.

<Step 9> A tower = purge, B tower = adsorption, C tower = H ₂ pressure increase, D tower = pressure reduction Same as step 8 except that A4 and D4 were opened.
Subsequently, the reforming gas was supplied to the tower B to perform an adsorption operation.
Meanwhile, the tower A has a purge step, the tower C has a H ₂ pressure increasing step,
In the tower D, a pressure reduction step was performed.

<Step 10> Tower A = equalizing pressure increase, Tower B =
Equalization pressure reduction, C tower = adsorption, D tower = blow valves C1 and C2 were opened, and the reforming gas was supplied to the C tower to perform the adsorption operation. In the meantime, the equalizing pressure increasing step was performed in the tower A, the equalizing pressure reducing step was performed in the tower B, and the blowing step was performed in the tower D. With respect to the other valves, A3, B4, and D5 are opened, and valves W,
The opening degrees of the valve X, the valve Y, and the valve Z were made constant. Other valves are closed.

<Step 11> Tower A = H ₂ boost, Tower B =
Step 10 except that the pressure reduction was maintained, the tower C was adsorbed, and the tower D was blow valve B4 and valve X were closed.
In the same manner as described above, the reforming gas was continuously supplied to the column C to perform the adsorption operation. In the meantime, the tower A performed the H ₂ pressure increasing step, the tower B performed the reduced pressure holding step, and the tower D performed the blowing step.

<Step 12> Tower A = H ₂ boost, Tower B =
Depressurization, C tower = adsorption, D tower = purge Except that B4 and D4 were opened, the adsorption operation was performed by continuously supplying the reformed gas to the C tower in the same manner as in step 11. In the meantime, the H ₂ pressure increasing step was performed in the tower A, the pressure reducing step was performed in the tower B, and the purge step was performed in the tower D.

In both the comparative example and the example, the cycle consisting of steps 1 to 12 was repeatedly performed. That is, as comparative examples, steps 1-3, 4-6, 7-9,
Each of the adsorption times 10 to 12 was always performed at a constant value of 240 seconds. In addition, as an example, based on the product hydrogen gas temperature of 5 ° C., the measurement result of the product hydrogen temperature is compared with the reference temperature to determine the temperature difference, and the cycle time is increased and decreased at a rate of 0.6 seconds / ° C. did. Table 1 shows a representative example of the results.

[0036]

[Table 1]

As shown in Table 1, in the comparative example, the product hydrogen gas purity was reduced to 99.997% as a result of keeping the cycle time unchanged for 240 seconds even at the product hydrogen gas temperature of 30 ° C. In contrast, in the example, the cycle time was changed to 225 seconds at a product hydrogen gas temperature of 30 ° C., and as a result, the purity of the product hydrogen gas could be maintained at 99.999%. Although the hydrogen gas recovery rate slightly decreases, according to the present invention, 5N (99.9) required for hydrogenation of PEFC fuel or unsaturated bond or for oxyhydrogen flame is used.
Hydrogen having a purity of 99% or more can always be obtained.

[0038]

According to the present invention, it is possible to stabilize the product gas flow rate, stabilize the purity of product hydrogen, and recover product hydrogen in accordance with the outside air temperature during summer, winter, or day and night. The rate can be stabilized.

[Brief description of the drawings]

FIG. 1 is a diagram showing the arrangement of adsorption towers A to D, piping, valves, off-gas storage tanks, and the like in a four-column PSA apparatus for hydrogen purification.

FIG. 2 is a diagram schematically showing a process flow and an operation sequence of each adsorption tower in the four-column PSA apparatus for hydrogen purification shown in FIG.

FIG. 3 is a diagram showing the arrangement of the adsorption towers A to D, piping, valves, off-gas storage tanks, and the like in the four-column PSA apparatus for hydrogen purification used in Examples.

[Explanation of symbols]

 A to D adsorption tower T off-gas tank F burner fuel gas conduit K burner combustion air conduit TH product hydrogen gas temperature sensor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroki Furuta 1-5-20 Kaigan, Minato-ku, Tokyo Tokyo Gas Co., Ltd. (72) Inventor Tohru Takahashi 1-5-20 Kaigan, Minato-ku, Tokyo Tokyo Gas Inside (72) Inventor Kenichi Nakamura 3-7-1 Nishi Shinjuku, Shinjuku-ku, Tokyo Shinjuku Park Tower 10th floor Tokyo Gas Chemical Co., Ltd. Inside (72) Inventor Koji Aida 3-7-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo Shinjuku Park Tower 10F Tokyo Gas Chemical Co., Ltd. Person Kumiko Moriguchi 1-13-501, Arima 1-chome, Miyamae-ku, Kawasaki City, Kanagawa Prefecture (72) Inventor Hideki Miyajima 5-2-10 F-Terao, Tsurumi-ku, Yokohama City, Kanagawa Prefecture None (reference) 4D012 CA07 CB16 CD07 CE01 CE02 CF01 CF04 CG01 CH10 CJ01 CJ02 CJ05 CJ06

Claims (2)

[Claims] 1. A method for stably operating a four-column pressure swing adsorption apparatus for hydrogen purification, comprising measuring and detecting the temperature of product hydrogen gas, and changing the cycle time based on the measured value. A stable operation method for a four-tower pressure swing adsorption apparatus, characterized by stabilizing a flow rate, stabilizing the purity of product hydrogen, and stabilizing a recovery rate. 2. The method for stably operating the four-column pressure swing adsorption apparatus for hydrogen purification includes the steps of adsorbing, equalizing pressure reducing, equalizing pressure holding, reducing pressure, blowdown, purging, equalizing pressure increasing, hydrogen equalizing in each of the four towers. 2. The hydrogen purifying apparatus according to claim 1, wherein the step of increasing the pressure is in a repeated step.
Stable operation method of tower pressure swing adsorption device.