JPS5948647B2 - Mixed gas adsorption separation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adsorbing and separating a mixed gas using a pressure swing method, which converts pressure energy possessed by a raw material gas into mechanical energy to reduce power and obtain cooling. This cooling allows the adsorption operation to be performed at low temperatures.

Many embodiments of the pressure swing method have been proposed because heating and cooling means for the adsorbent can be omitted during adsorption and regeneration, but there are many problems that need to be solved for practical application.

For example, when producing oxygen by adsorbing and separating nitrogen using air as a raw material, there is a drawback that the power required to compress the raw material gas to the adsorption pressure is large because there is a large amount of nitrogen as a component to be adsorbed.

Furthermore, when separating gas mixtures by conventional adsorption, it is known that so-called low-temperature adsorption, which operates at low temperatures, is advantageous because it increases the adsorption capacity of the adsorbent, and has the advantage that the equipment can be made smaller. In addition, for example, when air is used as a raw material to separate oxygen and nitrogen, moisture in the raw air,
It was also well known that easily condensable components such as carbon dioxide significantly reduce the adsorption capacity and therefore need to be removed.

However, as a means of obtaining cold to solve these problems, conventionally known cryocoolers have been used to achieve low-temperature adsorption.
Alternatively, attempts were made to remove easily condensable components, but
This has a high power unit consumption and requires a separate heat source, so the current situation is that the use of separation of mixed gases by low-temperature adsorption has not been carried out effectively.

The present invention was made to eliminate the above-mentioned drawbacks, and uses the gas pressure of non-adsorbed gas in the pressure swing method to drive an adiabatic expansion engine, convert pressure energy into mechanical energy, and recover power. , the adsorption operation is performed at low temperature by cooling the low temperature gas whose temperature has been lowered by driving the adiabatic expansion engine, and the cooling source is used as a cold source for condensation removal when there is an easily condensable component in the raw material gas. It is something.

Hereinafter, an example in which oxygen is produced by adsorbing and separating nitrogen using air as a raw material will be described with reference to the drawings.

The raw air drawn into the compressor 2 from the pipe 1 is compressed to a pressure of approximately 6 ata, then cooled by the water cooler 3, and then sent via the valve 4 to the regenerative heat exchanger 5, such as a regenerator, which is composed of a plurality of regenerators. be introduced.

The regenerators 5 are used by switching over each cycle for a certain period of time, and if the regenerator 5a is currently used and the regenerator 5b is in the regenerative cooling period, raw air is introduced into the cooler 5a through the valve 4a. Ru.

(Hereinafter, valves and equipment with the same numbers will be used interchangeably.

) The raw air introduced into the regenerator 5a is cooled by exchanging heat with the regenerator material cooled in the previous cycle as described later, and
After removing the water and carbon dioxide contained therein, the water is discharged through the valve 6a.

Next, it is introduced from the pipe 7 through the valve 8 into the adsorbers 9, which are provided in plurality and are used in a selective manner.

The adsorbent 9 is filled with an adsorbent such as molecular sheep that selectively adsorbs nitrogen, and adsorption and regeneration are alternately repeated at regular intervals.

Now, when the adsorber 9a is in the adsorber and 9b is in the regeneration period, raw air is supplied to the adsorber 9a through the valve 8a,
Nitrogen is selectively adsorbed in an appropriate amount flowing through the valve 10a, and unadsorbed oxygen is taken out via the valve 10a.

This oxygen is then introduced into the expansion turbine 12 through the pipe 11, and the turbine 12 is driven once to obtain power, which is recovered by driving the generator 13.

Oxygen gas, whose temperature has been lowered due to expansion while recovering power in the expansion turbine 12, is partially branched, flows through a pipe 14b, and is passed through a valve 15b to a flexible pipe 16b provided in the regenerator 5b in the regeneration period. flows to cool the inside of the vessel 5b.

After cooling the inside of the regenerator 5b and raising the temperature to almost room temperature, the oxygen gas is led out through the valve 17b and then supplied to the consumer through the pipe 18.

Next, the adsorber 9b in the regeneration period first reduces the pressure of the nitrogen adsorbed in the previous cycle through the valve 19bI, and then
, and is introduced into the regenerator 5b via the valve 21b.

In the regenerator 5b, raw air flows in the previous cycle, and after cooling and leading out the inside of the regenerator 5b while entraining moisture and carbon dioxide separated and removed from the air, the valve 22b and the pipe 2
It is released after 3.

When this pressure reduction operation is completed, a portion of the low-temperature oxygen gas that has exited the expansion turbine 12 is made to flow back into the adsorber 9b via the pipe 24 and valve 25b to scavenge the remaining nitrogen, and this oxygen is replaced by the reduced pressure nitrogen gas. It is discharged from the pipe 23 through the same path as the flow.

The method of the present invention is carried out as described above. In the above embodiment in which oxygen is obtained as a product by selectively adsorbing nitrogen from air, the product oxygen concentration is 80% and the yield is 5.
The pressure, temperature, enthalpy, and flow rate at the main parts in the case of 0% are as shown in the following table.

(In the following table, A to ■ respectively represent the positions shown in the drawings.

From the table above, if the efficiency of the expansion turbine is 80%, the recovered power is 3.9 Kcal/Nm3 of raw air.

Therefore, on a scale where the processing air amount is 10,100 N/hr, it is 170
The intrusive heat in a device operated at ℃ is approximately 2.5 Kcal
/Nm3, so this is also 1.4 Kc
The power of a l / Nrn3 can be recovered,
The theoretical power (isenthalpic compression) when compressing air at 20°C/ata to 6 ata is 56.7 Kcal
/Nm3, resulting in a power recovery rate of 25%.

If this increases to a device scale with a processing air amount of 1000 Nm3/hr, the intrusive heat will be approximately 1.2 Kcal/N.
m3, and the power recovery rate is 4.8%.

In addition, in order to obtain a product oxygen gas with a concentration of 50%, the outflow oxygen is 0.44 Nm 3/hr and the power generated by the expansion turbine is 6.3 Kea 17 Nm" since the raw air is processed. When the air flow rate is 1100 N''/hr, the intrusive heat is covered.''2. 6.7% of the air compression power can be recovered.

Furthermore, when the amount of air to be processed is 1100 ON3/hr, 90% of the power can be recovered.

In the above embodiment, nitrogen was adsorbed on the adsorbent and oxygen was used as a non-adsorbed gas, but it goes without saying that the present invention can also be applied to adsorption and separation of specific components of mixed gases in general.

As explained above, in the present invention Q, the mixed gas pressurized to the adsorption pressure is guided to the adsorber to adsorb and separate the adsorbed components, and the non-adsorbed component gas is led to the adiabatic expansion engine. Since the cooling generated when the non-adsorbed component gas expands adiabatically is used, there is no need for separate power for the necessary cooling, and pressure energy can be converted into mechanical energy and power can be recovered. The basic unit can be significantly reduced.

In addition, since the mixed gas is cooled by the above-mentioned refrigeration, the adsorption operation can be performed at a low temperature, and the mixed gas can be efficiently adsorbed and separated. Since it can be reliably removed from the mixed gas, it has the effect of effectively performing adsorption operations.

[Brief explanation of drawings]

The drawings are process diagrams showing one embodiment of the present invention. 2... Compressor, 5 a + 5 b...
・Regenerator, 9a. 9b... Adsorption device, 12... Expansion turbine, 13... Generator.

Claims (1)

[Claims] 1. When adsorbing and separating a mixed gas by the pressure swing method, the pressurized mixed gas is passed through a regenerative heat exchanger to cool it, and after condensing and removing easily condensable components in the gas, it is guided to an adsorber for selective separation. The adsorbed component gas is adsorbed and separated, and the non-adsorbed component gas is sent to an adiabatic expansion engine to drive it, thereby converting pressure energy into mechanical energy and recovering power. The low-temperature non-adsorbed component gas whose temperature has been lowered is passed through a regenerative heat exchanger to recover and extract the cold, while a portion is used for desorption and regeneration of the adsorber in the regeneration period, as well as for regeneration of the adsorber. After expanding the adsorbed pressurized component gas in the vessel during depressurization, it is passed through a regenerative heat exchanger in the regeneration period to cool the inside of the vessel and remove condensed components, allowing adsorption at low temperatures. 1. A method for adsorption separation of mixed gases, characterized by carrying out an operation.