JPH0699015A - Pressure swing adsorption method - Google Patents

Abstract

PURPOSE:To obtain an operating method of a pressure swing adsorber for recovering a specified component from a starting gaseous material, such as waste gas of a fermentation process, a tobacco process, etc., where there is much variation in the specified component, such as CO2. CONSTITUTION:Based on the optimum time cycle for the component concentration and flow rate condition suitable for the recovery of specified components, the time ratio between an adsorptive process and a washing process is changed. The recovery of the specified components by an adsorbent in adsorbers 5A, 5B depends on the concentration and gas flow rate of the specified components, such as CO2 and CO in a gaseous starting material. On the other hand, the whole process cycle of the pressure rise, adsorption, washing and desorption in a pressure swing adsorber is fixed. Therefore, the time ratio between the adsorptive process and washing process is changed in the time cycle, permitting the operation under conditions where adsorptivity of the adsorber is made maximum use of.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to the production of CO ₂ from a raw material gas whose concentration concentration varies with the operation, such as CO ₂ contained in exhaust gas from fermentation processes, tobacco processes, etc.
_{The present} invention relates to a method of operating a pressure swing adsorption device that recovers specific components such as ₂ .

[0002]

2. Description of the Related Art For example, by arranging a plurality of adsorption towers and operating the pressure rising step, the adsorption step, the washing step, and the desorption step alternately in each of the adsorption towers, CO and CO ₂ from combustion exhaust gas from a boiler or the like is operated. The method of recovering a specific gas such as
JP-A-63-77515, JP-A-1-20301
As described in JP-A-8, it is known as a pressure swing adsorption method (PSA method).

This pressure swing adsorption method is a relatively small-scale facility, and is a target of recovery of C in exhaust gas (raw material gas).
It has a feature that it can be continuously recovered even when the content of a specific gas such as O or CO ₂ is small.

Further, the concentration of a specific gas in a raw material gas to which the conventional pressure swing adsorption method is applied, for example, a combustion exhaust gas of a boiler or the like does not change much with the operation, and therefore, the required recovery gas is The adsorbent is selected and the time cycle time is set to a constant value according to the product concentration.

However, in order to secure the CO ₂ purity of the product to be adsorbed / collected, the above-mentioned conventional pressure swing adsorption method is adjusted to the contained CO ₂ concentration condition in which the exhaust gas fluctuation range accompanying the operation of the exhaust gas generation equipment is the lowest. However, as shown in FIG. 5, for example, as shown in FIG. 5, when CO _{2 is} adsorbed and recovered from a raw material gas such as a gas discharged from a fermentation process or a tobacco process, which has a large fluctuation in CO ₂ concentration,
₂ Only when the concentration is 99% or more, CO _{2 is used} as the source gas.
Currently, it is collected by liquefaction equipment.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to recover a specific component economically at a high recovery rate, even in the case of a raw material gas in which the content of the specific component to be recovered varies greatly. It is to provide a pressure swing adsorption method that can be performed.

[0007]

SUMMARY OF THE INVENTION The present invention is a pressure swing adsorption method for recovering a specific component from a source gas in which the concentration of the specific recovery component in the source gas fluctuates greatly. It is characterized in that the time cycle of the pressure swing adsorption device is changed and followed according to the concentration and the raw material gas flow rate.

[0008]

The recovery of the specific component by the adsorbent in the adsorption tower depends on the concentration of the specific component such as CO ₂ and CO in the raw material gas and the gas flow rate to and from the adsorption tower. On the other hand, in the conventional pressure swing adsorption device, the time cycle of all steps of pressurization, adsorption, cleaning and desorption is fixed. The present invention changes the ratio of the times of the adsorption process and the cleaning process in this time cycle, that is, when the concentration of the gas component to be adsorbed and recovered in the raw material gas is low, the ratio of the cleaning process is increased. On the contrary, when the concentration of the gas component to be adsorbed / collected is high, by increasing the ratio of the adsorption step, it becomes possible to operate under the condition that the adsorption capacity of the adsorption device can be maximized.

[0009]

EXAMPLE The present invention shows that the concentration of CO _{2 in} the source gas is as shown in FIG.
An example will be described in which CO ₂ is recovered using the equipment shown in FIG. 1 with beer fermentation exhaust gas that fluctuates from 30 to 99% in 3 days as a raw material gas.

In the figure, the exhaust gas from the beer fermentation equipment is passed through a cooling tower 1, a dehumidifier 2 and a raw gas holder 3 and then a blower 4 to an adsorption tower according to the CO ₂ content concentration in the raw material gas. Adjust the incoming flow rate,
Each of the two adsorption towers 5A and 5B charged with 1.4 kg of activated carbon was fed into each of the two adsorption towers 5A and 5B for adsorption / recovery.

The operation steps in the adsorption towers 5A and 5B are as shown in FIG.
While passing through the washing step, the other adsorption tower is in the desorption step, each time cycle is set to about 160 seconds, and according to the CO ₂ content concentration in the raw material gas, as shown in FIG. The flow rate conditions were set, and the time ratio between the adsorption and cleaning processes was changed so that the required flow rates for the adsorption and cleaning processes could flow.

FIG. 3 shows the concentration of CO ₂ contained in the feed gas when the purity of product CO ₂ is 98.5% under the ultimate vacuum of 50 to 55 Torr.
The flow rate of CO ₂ supplied to the adsorption tower is shown.

In the figure, a curve a shows the amount of CO ₂ supplied per washing step shown in FIG. 2, and a curve b shows the amount of CO ₂ supplied per adsorption step shown in FIG.

In the case of the curve a, when the CO ₂ content concentration in the raw material gas is 30%, the CO ₂ gas flow rate is approximately 22 liters / step, and when it is 95%, the CO ₂ gas flow rate is approximately 7 liters / step. It decreased to step.

In the case of curve b, CO ₂ in the raw material gas
When the content concentration is 30%, the gas flow rate of CO ₂ is about 9
The gas flow rate of CO ₂ was increased to about 22 liters / step at 95%.

As is clear from the above data, the CO ₂ concentration of the raw material gas changes by changing the time ratio of the gas amount in the adsorption process and the cleaning process, and by appropriately flowing it, the efficiency can be ensured while ensuring product purity. CO ₂ can be recovered.

FIG. 4 shows the relationship between the CO ₂ concentration in the raw material gas and the recovery rate when the purity of the product CO ₂ is intended to be 98.5% under the ultimate vacuum of 50 to 55 Torr. In comparison with the case of the B curve showing the case of the conventional method in which the conventional time cycle is not adjusted, the present invention shown in the A curve in which the supply amount is adjusted to the concentration of CO ₂ and the time cycle is adjusted In the case of, the recovery rate is significantly increased.

[0018]

The present invention has the following effects.

(1) Even when the concentration fluctuations of specific components such as CO and CO ₂ in the raw material gas are remarkable, the pressure swing adsorption device can be used under a high recovery rate, and recovery can be performed at low cost. Becomes

[Brief description of drawings]

FIG. 1 shows an equipment flowchart of a pressure swing adsorption system to which the present invention is applied.

FIG. 2 is an explanatory diagram of time cycle setting in the pressure swing adsorption system of the present invention.

FIG. 3 shows the relationship between the concentration of CO ₂ contained in the raw material gas and the flow rate of the supply gas.

FIG. 4 is a diagram showing the effect of the CO ₂ recovery rate according to the present invention in comparison with that according to the conventional method.

[Fig. 5] Days from start of fermentation of beer fermentation exhaust gas and C
The relationship with the O ₂ concentration is shown.

[Explanation of symbols]

1 Cooling tower 2 Dehumidifier 3 Raw gas holder 4 Blower 5A, 5B Adsorption tower

Claims (1)

[Claims] 1. A pressure swing adsorption method for recovering a specific component from a raw material gas in which the concentration of the specific recovered component in the raw material gas greatly fluctuates, the method according to the concentration of the specific recovered component flowing into the adsorption tower and the flow rate of the raw material gas. A pressure swing adsorption method in which the time cycle of the pressure swing adsorption device is changed and followed.