JPH09141039A - Gasoline vapor adsorption, separation and recovery method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method of safety and effectively separating and recovering gasoline vapor in a gasoline tank and to provide the device therefor. SOLUTION: Gasoline vapor containing gasoline is introduced from the bottom part of an adsorber 1 to adsorb gasoline from the gasoline vapor by an adsorbent with which the adsorber 1 is packed and to discharge air from the top of the adsorber 1, and also, the adsorbed gasoline by the adsorbent is recovered. In this case, as the adsorbent, silica gel subjected to hydrophobic treatment is used. When gasoline vapor is introduced into the adsorber 1, water droplets are sprayed to the vapor to keep the inside of the adsorber 1 at such suitable relative humidity that the adsorbent is not dried. While kept in this state, the temperature in the adsorber 1 during adsorption is heat-exchanged in the axial direction and also the differential potential of the adsorbent caused in the adsorber is neutralized, and the gasoline adsorbed by the adsorbent is sucked by a vacuum pump 20, and is cooled and recovered, thereby regenerating the absorbent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasoline vapor adsorption / separation method and apparatus for separating and recovering gasoline vapor in a gasoline tank.

[0002]

2. Description of the Related Art Gasoline vapor in a gasoline tank is
In general, unlike the composition of gasoline itself, it is a gas mixture consisting of low boiling point components, the main components of which are butane and pentane, and some hexane. This gas mixture has low volatility and is a hydrocarbon with a boiling point of 60 ° C and a molecular weight of 70 or less. Volatile gasoline in a large tank exists in the air in a state close to saturation of 40% concentration, and is a liquid in the tank. When gasoline is injected, it is exhausted to the outside together with the internal gas, but the amount of the above-mentioned gasoline vapor is enormous, and if this is released into the atmosphere as it is, the atmospheric environment will deteriorate and cause pollution. It is not preferable in terms of resource saving.

Therefore, in petroleum refining plants, in order to recover gasoline vapor, it is generally performed to wash with kerosene, but kerosene that has absorbed gasoline requires a step of separating again in a distillation column. This equipment can be used for the first time in an oil refining plant and cannot be realized in a normal urban area.

A method has also been developed in which, instead of the above kerosene, a cleaning solution using lean oil is used for cleaning. This method basically aims at downsizing of the oil plant, but since the absorption liquid that saturated and absorbed gasoline in the absorption tower must be separated and recovered by a separate regenerator by vacuum, the entire equipment Is inevitably large in size, and since this method is a wet process, various mists are entrained, so there are many operational problems, and the concentration of the outlet is determined by the performance of the vacuum pump. There is also a problem in that the vacuum device requires a large amount of money for recovery.

Further, attempts have been made to recover gasoline vapor by a membrane separation method. However, this method requires a great amount of power because the pressure of the introduced gas must be increased, and the exhaust gas concentration is also reduced. In order to reduce the amount, it is necessary to use a multi-stage method, so that the apparatus is expensive, and the chemical deterioration phenomenon of the membrane material cannot be ignored. Therefore, it is almost impossible to reduce the emission concentration to 8% or less.

On the other hand, it has been considered to recover gasoline vapor by using a conventional solvent recovery device using activated carbon as an adsorbent, but when activated carbon adsorbs gasoline at a high concentration, the activated carbon generates heat of 100 ° C. or more due to heat of adsorption. May occur, and spontaneous ignition may occur due to the presence of air, or static electricity may be generated due to friction between the gas flow and activated carbon, causing a gas explosion with the sparks. If you try to dilute the concentration to recover the gasoline, the size of the device becomes large and it becomes impractical.

Further, since the VPSA method (vacuum pressure swing adsorption) utilizing the adsorption method switches the operation in a short time, the temperature does not rise to a high temperature, so there is no danger of spontaneous ignition, it is safe, and the regeneration is low. Since it is a dry type that adopts the vacuum page, it is possible to provide an inexpensive separation device.
When the method is applied to the recovery of gasoline vapor, the recovered gasoline is diluted by a large amount of purge air, and the gasoline is recovered only as a gas.

However, since the release of gasoline vapor to the atmosphere leads to air pollution and waste of resources, as described above, recovery of gasoline from gasoline vapor from the viewpoint of improving the atmospheric environment and saving resources. Is a very important issue.

[0009]

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, the present invention provides a method and apparatus for safely and efficiently separating and recovering gasoline vapor in a gasoline tank. It is what

[0010]

The structure of the gasoline vapor adsorption separation / recovery method of the present invention, which has been made for the purpose of solving the above-mentioned problems, has a structure in which gasoline vapor containing gasoline is introduced from the bottom of an adsorption tower, When adsorbing gasoline from gasoline vapor by the adsorbent filled inside and exhausting air from the tower top and collecting the gasoline adsorbed by the adsorbent, silica gel subjected to hydrophobic treatment is used as the adsorbent, and gasoline vapor is used. When the adsorbent is introduced into the adsorption tower, water vapor is sprayed on the vapor to keep the adsorbent inside the tower at an appropriate relative humidity so that the adsorbent does not dry, while the temperature inside the tower is heat-exchanged in the axial direction and generated in the tower. It is characterized in that the potential difference of the adsorbent is neutralized, and the gasoline adsorbed by the adsorbent is sucked by a vacuum pump at the time of regeneration of the adsorbent, cooled, and recovered. Further, the apparatus is constructed such that gasoline vapor containing gasoline is introduced from the bottom of the column, and the column is filled with an adsorbent made of silica gel subjected to a hydrophobic treatment, and the gasoline is adsorbed by the adsorbent. Adsorption of gasoline from steam and discharge of air from the top of the tower consists of multiple conductive metal plates or multiple metal cylinders inside the adsorption tower. In addition, the heat exchange member for neutralizing the potential difference generated in the tower is installed and grounded, and water droplets are sprayed on the gasoline vapor to the gasoline vapor introduction part of the adsorption tower to prevent the adsorbent from drying inside the tower during adsorption. A steam generator for appropriately maintaining relative humidity is additionally provided, while the gasoline adsorbed by the adsorbent during regeneration of the adsorbent is sucked by a vacuum pump and cooled by a cooler to be collected. Than it is.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION That is, the present invention is based on the above-mentioned VSPA.
Utilizing the advantages of the law, high-concentration (20%) gasoline vapor gasoline is separated and collected by the adsorption method without danger of ignition, etc., and the concentration of gasoline in the outlet air is remarkable, for example, up to about 0.1%. In order to make it possible to lower the temperature, first of all, it is necessary to select a suitable adsorbent.

Therefore, in the present invention, nonflammable silica gel is used as the adsorbent without using flammable activated carbon. Originally, hygroscopic silica gel is also suitable for adsorbing gasoline, but at the same time it will dry the gas, and if the adsorbent particles flow and rub in a dry atmosphere,
There is an unavoidable risk of ignition and explosion due to static electricity generated between particles and the discharge phenomenon. Thus, the silica gel used in the present invention eliminates or reduces its hygroscopic properties,
It is necessary to prevent the particles from being charged by electric conduction by allowing the passing gas or gasoline vapor to have an appropriate moisture and humidity.

[0013]

Next, an embodiment of the present invention will be described with reference to the drawings.
Fig. 1 is a chart showing the isotherms of the pentane adsorption amount when treating gasoline vapor using silica gels that have been subjected to four types of hydrophobization treatment, and Fig. 2 is the VPSA of the adsorbent of Fig. 1.
FIG. 3 is a longitudinal sectional view of an example of an adsorption tower used in the apparatus of the present invention, FIG. 4 is a horizontal sectional view of FIG. 3, FIG. 5 is another example of the apparatus of the present invention, and two towers including a regeneration system are shown. It is a systematic diagram of an adsorption device.

In general, silica gel selectively adsorbs moisture by the -OH group on the surface, but when a silane coupling agent or the like is diluted with a solvent and immersed, it easily hydrolyzes in the adsorption pores and dehydrates intermolecularly. It is known that it becomes a gel-like substance, becomes a film of Si-O-Si, and the inside of the pores is changed to hydrophobic. The silica gel material suitable for the present invention is preferably one having pores having a pore size of 40 to 100 Å which has been subjected to the above-mentioned hydrophobic treatment. That is,
It is important to select an adsorbent that has excellent adsorption-desorption characteristics. Actually, when an adsorption-desorption operation experiment was performed using silica gel whose pores were hydrophobized, the degree of hydrophobization depended on the pore size and was closely related to the adsorption-desorption characteristics of gasoline. It turned out to be.

The following four different pore sizes that have been hydrophobized
Using the seed silica gel, the experiment of removing and recovering gasoline from gasoline vapor by VSPA operation was conducted. (1) Surface area 600 m ² / g, average pore diameter 30 Å (hydrophobic component attachment amount 1.6%) (2) Surface area 450 m ² / g, average pore diameter 60 Å (hydrophobic component attachment amount 6.8%) (3) Surface area 300 m ² / g, average pore diameter 100Å (hydrophobic component adhesion amount 3.0%) (4) Surface area 450m ² / g, average pore diameter 60Å (hydrophobic component adhesion amount 2.4%) As a result, pentane adsorption amount There is a difference in performance depending on the size, and the amount of hydrophobic component added is large and the pore size is 60.
It was found that silica gel as large as ~ 100Å excels in adsorption performance. That is, the shape of each isotherm of silica gel is
As shown in the chart in Fig. 1, (2), (3) and (4) are concave or almost linear with excellent desorption, whereas (1) with a small pore size of 30 Å has hydrophobic components attached. Because the amount is small,
It was found that the adsorption performance was poor, and the shape of the isotherm was convex. Moreover, 150g of silica gel of (4) is put in a 1 liter cylindrical plastic container (inner diameter 90mm, height 165mm), covered, and attached to a shaker (Yamato Scientific SA-31) to make it horizontally wide.
After shaking for 5 minutes at a shaking rate of 280 / min at 40 mm, the lid is opened promptly, and an electrostatic potential measuring device (Kasuga Denki KSD-0103) is used.
When the electrostatic charge was measured by using a sensor, the sensor was placed 150 mm from the bottom of the container and perpendicular to the center of the diameter direction, and the electric potential was -0.1 kV, and it was found that charging was difficult.

The VPSA performance of the above four kinds of adsorbents is as shown in the chart of FIG. 2, and there is a significant difference in the required amount of purge gas depending on the adsorbents.
The adsorbents have been found to be most suitable for the present invention.
The purge coefficient is (actual air purge amount / supply gas) / {vacuum pressure / adsorption pressure.
(mmHg)}.

By adopting the above-mentioned hydrophobic adsorbent, it becomes possible to keep the humidity between the particles of the adsorption tower at a humidity of 60% or more which is not charged. However, the concentration of gasoline in the adsorption tower is essentially 20% by volume or more near the inlet, and even if mixed with air, it exceeds the explosive concentration range (1.5 to 6%), so there is no danger, but the gas inside the adsorption tower is not dangerous. As the engine progresses, the gasoline concentration decreases until it reaches the explosion limit. At this time,
If there is a potential difference between the wall of the adsorption tower and the fluid, sparks may occur due to the discharge phenomenon.To prevent this, it is also necessary to ground all over the tower. Is. As described above, the adsorbent (4) does not need to be grounded because it is difficult to be charged as described above, but grounding further enhances safety.

On the other hand, it is known that when adsorption and vacuum desorption are repeated, a large adsorption tower causes a temperature gradient in the axial direction, the upper part of the tower has a relatively high temperature and the bottom part has a low temperature. This is because the heat of adsorption is lost along with the outflow of gas from the top of the column, and the normal vacuum desorption operation becomes impossible due to the decrease in the temperature of the adsorption layer, and the amount of purge air is inevitably increased. Increased,
The yield of recovered gasoline is reduced. Generally, it is most effective for the gasoline yield by the adsorption method to heat the bottom of the tower and cool the top of the tower. Therefore, as described above, the top of the tower becomes relatively hot and the bottom of the tower becomes cold. The phenomenon must prevent this.

For that purpose, heat may be exchanged in the axial direction inside the tower, and it is preferably achieved by installing a plurality of cylindrical heat exchange members which are heat conductors and good electric conductors. When this heat exchange member is installed, if it is grounded, it is sufficient to take measures against static electricity without taking measures against static electricity, and the safety is enhanced.

3 and 4 show the construction of the adsorption tower used in the present invention. In each drawing, 1 is an adsorption tower filled with an adsorbent 2 inside, 3 is an upper lid of the adsorption tower 1, 4 Is an air inlet provided in the adsorption tower 1, 5 is an inlet for introducing a raw material gas, that is, gasoline vapor into the adsorption tower 1, 6,
Reference numeral 7 denotes a heat exchange member which is arranged in the adsorption tower 1 and is composed of concentric metal heat transfer tubes for heating the inside of the tower 1 to a uniform temperature.
Is an outlet for pressurized air provided in the adsorption tower 1, 9 is also a regeneration purge gas introduction part, and the metal heat transfer cylinders 6 and 7 are installation members 10
Grounded. The heat exchange members 6 and 7 are wire nets or plates made of copper or aluminum that can also serve as good electric conductors with heat conductors, and may be installed in the tower in a spiral shape other than a cylindrical shape. The surface area of the adsorbent 2 is 45
The silica gel of (4) above, which has been subjected to the hydrophobic treatment with 0 m ² / g and a pore size of 60 Å, is used.

The adsorption device shown in FIG. 5 is a two-column vacuum adsorption device comprising the adsorption towers 1, 1'of FIG.
11, 11 ', 12, 12' are opening / closing valves provided in pipes connecting the gas introduction pipe 13 and the gas introduction ports 5, 5'of the adsorption towers 1, 1 ', 14, 14', 1
5 and 15 'are check valves provided in the pipe connecting the exhaust gas outflow pipe 16 and the upper part of the adsorption towers 1 and 1', 17 are steam generators, 18 and 18 'are inside the adsorption towers 1 and 1' Humidity detector, 19 is a purge gas feeding unit, 20 is a vacuum pump, 21 is a pipe for collecting gasoline, 22
Is a cooler provided in the pipe 21 so that the cooling water 23 is flown into the cooler, and the device is constituted by the above, and its operation is as follows.

In the above apparatus, when the raw material gas containing gasoline is fed from the raw material gas introduction pipe 13, the humidity of the gas is adjusted to 60 to 80% by the steam generator 15, and the on-off valve 11
After being introduced into the adsorption tower 1 through the raw material gas introduction port 5 and adsorbing and removing the gasoline component through the layer of the adsorbent 2, clean air is discharged from the exhaust gas outflow pipe 16 through the check valve 14. Is discharged as. During this time, the humidity of the layer of the adsorbent 2 is automatically adjusted to 70% by the steam generator 17 and the humidity detector 18.

On the other hand, in the adsorption tower 1 ', the air from the purge gas feeding section 19 is introduced into the tower from the top through the check valve 15' and the adsorbent 2 is adsorbed at a high concentration. The gasoline is desorbed, and the desorbed gasoline is compressed under atmospheric pressure and introduced into the cooler 22 through the pipe 21, and most of it is liquefied by cooling by the cooling water 23 flowing in the cooler 22 and becomes liquid gasoline. Be recovered. The unrecovered gasoline vapor is processed in the adsorption tower 1 through the pipe 21 and the switching valve 8.

The apparatus of the present invention performs the above operation for each adsorption tower 1, 1 '.
The gasoline is continuously recovered by alternately performing the above, but actually, 25 L / min of gasoline vapor containing 60% humidity and 20% by volume of gasoline mixed in the air of about 1 atm. Is introduced into the adsorption tower at 5 minutes, and the operation of adsorbing and removing gasoline is carried out for 5 minutes.
When desorption regeneration was performed by setting to
There was no change at 60% and the gasoline concentration was only 0.1%. This means that most of the gasoline components in the gasoline vapor have been adsorbed and removed. Regeneration of the adsorbent was performed under the conditions of an air purge rate of 0.12 L / min, a tower temperature of 35 ° C, and a cooling water temperature of 20 ° C flowing through the cooler, and the recovered liquid gasoline had a yield of 99.9%. It was On the other hand, the saturated air with no gasoline recovered was returned to the inlet of the adsorption tower and sent to the adsorption process again, but the amount of gas did not affect the amount of adsorption.

[0025]

The present invention is as described above, and since the vacuum regeneration adsorption method is used and the silica gel subjected to the hydrophobic treatment in the pores suitable for removing and recovering gasoline in the air is used as the adsorbent, Humidity of 60% or more is maintained for moisture without adsorbing and removing it, and only gasoline in the air is adsorbed and removed, while in the regeneration process, vacuum desorption is performed with a minimum amount of purge air. Since the gasoline can be collected with a high yield, the structure of the device can be simplified. Therefore, if the device of the present invention is installed at a gas station in an urban area, the atmospheric environment can be improved and resources can be saved.

[Brief description of the drawings]

FIG. 1 is a chart showing isotherms of pentane adsorption amounts when treating gasoline vapor with four kinds of adsorbents.

FIG. 2 is a chart showing the VPSA performance of the adsorbent of FIG.

FIG. 3 is a vertical sectional view of an example of an adsorption tower used in the present invention.

FIG. 4 is a transverse sectional view of FIG. 3;

FIG. 5 is a system diagram of a two-column type adsorption device including a regeneration system as an example of the device of the present invention.

[Explanation of symbols]

 1,1 'Adsorption tower 2 Adsorbent 3 Adsorption tower lid 4 Air inlet 5 Raw material gas inlet 6,7 Heat exchange member 8 Pressurized air outlet 9 Regeneration purge gas inlet 10 Adsorption tower installation member (grounding) (Also serves as a member) 11, 11 ', 12, 12' Switching valve 13 Gas inlet pipe 14, 14 ', 15, 15' Check valve 16 Exhaust gas outlet pipe 17 Steam generator 18, 18 'Humidity detector 19 Page gas Feeding unit 20 Vacuum pump 21 Pipe for collecting gasoline 22 Cooler 23 Pipe 24 Cooling water

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[Procedure amendment]

[Submission date] January 22, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

Further, attempts have been made to recover gasoline vapor by a membrane separation method, but this method requires a large amount of power because the pressure of the recovered gas must be lowered, and the exhaust gas concentration is also reduced. In order to reduce the amount, it is necessary to use a multi-stage method, so that the apparatus is expensive, and the chemical deterioration phenomenon of the membrane material cannot be ignored. Therefore, it is almost impossible to reduce the emission concentration to 8% or less.

Claims (2)

[Claims] 1. A gasoline vapor containing gasoline is introduced from the bottom of the adsorption tower, and the adsorbent filled in the adsorption tower adsorbs gasoline from the gasoline vapor and discharges air from the top of the tower while adsorbing the adsorbent. When recovering the gasoline, a silica gel subjected to a hydrophobic treatment is used as the adsorbent, and when the gasoline vapor is introduced into the adsorption tower, water vapor is sprayed onto the vapor to prevent the adsorbent from drying inside the tower. While adsorbing, the temperature inside the column is heat-exchanged during adsorption and the potential difference of the adsorbent generated in the column is neutralized, and the gasoline adsorbed by the adsorbent is vacuumed during regeneration of the adsorbent. A method for adsorbing, separating and collecting gasoline vapor, which comprises sucking with a pump, cooling and collecting. 2. A gasoline vapor containing gasoline is introduced from the bottom of the tower, an adsorbent made of silica gel subjected to a hydrophobic treatment is filled in the tower, and the adsorbent adsorbs gasoline from the gasoline vapor. Inside the adsorption tower, which is designed to exhaust air from the top, consists of multiple conductive metal plates or metal multi-cylinders, etc. to heat-exchange the temperature in the tower in the axial direction during adsorption and to generate a potential difference inside the tower. Generates water vapor that keeps the adsorbent inside the tower at a proper relative humidity so that water droplets are sprayed on the gasoline vapor introduction part of the adsorption tower to prevent the adsorbent from drying during adsorption. A gasoline vapor adsorption / separation / recovery device characterized in that while the adsorbent is attached, the gasoline adsorbed by the adsorbent is sucked by a vacuum pump and cooled by a cooler to be recovered when the adsorbent is regenerated. Place.