JPS5845482A - Pre-treatment method for air separator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention The present invention relates to an air separation device for obtaining pure oxygen, pure nitrogen, etc. from air, and in particular, a pretreatment method for an air separation device that efficiently removes moisture and carbon dioxide from the air. Regarding.

Since air separation equipment is operated at low temperatures, it is necessary to remove water and carbon dioxide, which are condensed and solidified components.

Conventionally, these removal methods have been referred to as temperature difference adsorption methods. ) has been adopted. (
Special Publication Showa 47-35185. Tokuko Sho 55-4113, etc.)
. In this method, the desorption temperature is raised by about 200° C. relative to the adsorption temperature, and the adsorbent is regenerated by the temperature difference. Generally, the adsorption capacity of an adsorbent varies widely depending on the temperature, and water and carbon dioxide can be sufficiently removed by the TSA method. However, there is a drawback that a large amount of heat is required to heat the adsorbent, which increases the manufacturing cost of the product. As a method to compensate for the above drawbacks, pressure difference adsorption method (Pressure Swing Adsorpt
A pretreatment device employing ion+ (hereinafter referred to as PSA method) was proposed in Japanese Patent Laid-Open No. 103778/1983. This method utilizes the fact that the adsorption capacity of the adsorbent changes depending on the partial pressure of the adsorbed component, and the pressure is lower than the adsorption pressure.

The adsorbent is regenerated by burning waste nitrogen at the bottom, and no heat is used to regenerate the adsorbent, reducing product costs. FIG. 1 shows a system diagram of an air separation device to which a PSA method pretreatment device is applied.

The air introduced from the pipe 7 is pressurized by the compressor 1, passes through the cooler 2 and the pipe 8, and is sent to the PSA pre-method processing equipment 3 where moisture and carbon dioxide are adsorbed and removed. It is supplied to the rectification column 5 via the exchanger 4 and piping 10. The supplied air is separated into pure oxygen, pure nitrogen, high pressure waste nitrogen, and low pressure waste nitrogen using the difference in boiling points. The high-pressure waste nitrogen is sent to a double expansion turbine (hereinafter referred to as a turbine) 6 via a pipe 13, a heat exchanger 4, and a pipe 14, where it is adiabatically expanded, and then passed through a pipe 15 to a pipe 11. It joins with the low-pressure waste nitrogen flowing through the pipe 12, the heat exchanger 4, the pipe 16, and the pipe 17 as waste nitrogen to the PSA pre-method processing equipment 3, and after regenerating the adsorbent, is discharged from the pipe 18. Ru. Pure oxygen is recovered as a product via piping 21, heat exchanger 4, and piping 23, and pure nitrogen is recovered as a product via piping 22, heat exchanger 4, and piping 24. Here, the turbine 6 requires brake gas to control the rotation speed, and the piping 1
A part of the waste air flowing through the turbine 6 is sent to the turbine 6 as brake gas via a pipe 19, and is discharged to the atmosphere from a pipe 20. Therefore, there was a drawback that the flow rate of waste nitrogen supplied to the PSA method pretreatment device decreased, and the regeneration efficiency of the adsorbent decreased.

An object of the present invention is to provide a pretreatment means for an air separation device that improves the regeneration efficiency of adsorbent through effective use of turbine brake gas and efficiently removes moisture and carbon dioxide from the air.

In the system diagram of the air separation device shown in Figure 1, piping 1
The flow rate of waste nitrogen flowing through the turbine 9 is adjusted so that the gas temperature when discharged from the turbine 6 to the pipe 20 is usually 100° C. or less, and is discharged to the atmosphere via the pipe 20. On the other hand, the temperature of waste nitrogen flowing through the pipe 17 depends on heat exchange with the air in the heat exchanger 4, and is usually lower than the air temperature.

The conditions for using the adsorbent are preferably such that the adsorption temperature is low and the desorption temperature is high. Therefore, the PSA pre-legal legal processing device 3
If the temperature of the waste nitrogen produced can be raised, the adsorbent regeneration efficiency will be further improved.

Therefore, an attempt was made to reuse waste nitrogen used as turbine brake gas for adsorbent regeneration. by this,
Since the flow rate of waste nitrogen used for regenerating the adsorbent increases and the desorption temperature increases, the regeneration efficiency of the adsorbent improves, making it possible to more efficiently remove moisture and carbon dioxide from the air. In addition, it became possible to use a sufficient flow rate of waste nitrogen as turbine brake gas, lowering the operating temperature of the turbine and improving safety. In addition,
What is important in implementing the present invention is to suppress pressure fluctuations in waste nitrogen used as turbine brake gas. In other words, when pressure fluctuations occur when switching between multiple adsorption towers used in the pre-PSA process, the rotational speed of the turbine changes, which causes pressure and temperature changes in the air separation equipment, reducing the separation efficiency of the rectification tower. do. Therefore, when switching between adsorption towers, it is necessary to release waste nitrogen from a bypass pipe that has a resistance equivalent to the pressure loss of the adsorption tower, or to suppress pressure fluctuations by wrapping a pressure regulator such as a safety valve around the turbine outlet pipe. It would be effective to provide a means to do so.

An embodiment of the present invention will be described below with reference to FIG. Air introduced from piping 7 is pressurized by compressor 1, and then passed through cooler 2.
, piping 8, PSA pre-legal treatment equipment 3 pipes 9, heat exchanger 4
, and is supplied to the rectification column 5 via piping 10. The supplied air is separated into pure oxygen, pure nitrogen, high pressure waste nitrogen, and low pressure waste nitrogen using the difference in boiling points. Pure oxygen is recovered as a product via piping 21, heat exchanger 4, and piping 23, and pure nitrogen is recovered as a product via piping 22, heat exchanger 4, and piping 24. High pressure waste nitrogen is pipe 13, heat exchanger 4, pipe 14
After being sent to the turbine 6 via the pipe 15 and adiabatically expanded, it joins with the low-pressure waste nitrogen flowing through the pipe 11 via the pipe 15, and after passing through the heat exchanger 4 and the pipe 16 as waste nitrogen, the pipe 19 and is branched off as a flow to piping 25. Piping 1
The waste nitrogen branched into the pipe 9 passes through the turbine 6 and the pipe 20, and then branches into the pipe 26 and the pipe 27. The waste nitrogen branched into the pipe 26 is discharged into the atmosphere. The waste nitrogen branched into the pipe 27 joins with the waste nitrogen flowing through the pipe 25, is sent to the PSA pre-processing equipment via the pipe 17, and after regenerating the adsorbent is released into the atmosphere via the pipe 18. be done.

The pressure, temperature and flow rate of the air flowing through the pipe 9 are 5.5 kg/Cm2G, 30°C and 300O, respectively.
Nm3/h, and the pressure, temperature, and flow rate of waste nitrogen flowing through the pipe 25 are each 0.2 kg/C1n2G.

28℃ and 11l 100N/h, the pressure, temperature and flow rate of waste nitrogen flowing through the pipe 19 are each 0.2kg/cm2
G, under the conditions of 28°C and 280 Nm3/h, pipe 2
The operation was carried out by changing the waste nitrogen flow rate of No. 7 to O and 200 Nm3/h. When the waste nitrogen flow rate is ONm3/h, the temperature and flow rate of the waste nitrogen flowing through the pipe 17 are 11
At 1100 N/h and 28° C., the moisture and carbon dioxide concentrations in the flowing air of pipe 9f were less than IpJ)m and 4 ppm, respectively. In contrast, the piping according to the invention 2
When the waste nitrogen flow rate in pipe 17 is 200 Nm3/h, the temperature and flow rate of waste nitrogen flowing through pipe 17 are respectively 3
At 3°C and 130 ONm3/h, both the nuclear power and carbon dioxide concentrations in the air flowing through the pipe 9 were below 11) pm.

According to the present invention, waste nitrogen as turbine brake gas, which has conventionally been released into the atmosphere, can be effectively used for regenerating the adsorbent, resulting in the following effects.

(1) It has the effect of improving the performance of removing moisture and carbon dioxide from the air. (2) Since it is possible to increase the desorption temperature,
Further improvement of the above removal performance is achieved.

(3) The flow rate of waste nitrogen that can be used as turbine brake gas can be greatly increased compared to the conventional method, and the turbine temperature can be lowered to extend the life of the equipment.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an air separation apparatus employing a PSA method pretreatment apparatus, and FIG. 2 is a system diagram of an air separation apparatus employing a PSA method pretreatment apparatus as an embodiment of the present invention.

Claims (1)

[Claims] 1. Before the PSA method, 710-pressure air is brought into contact with an adsorbent to remove moisture and carbon dioxide from the air, and the adsorbent that has adsorbed moisture and carbon dioxide is regenerated by purging waste nitrogen under pressure around atmospheric pressure. A pretreatment method for an air separation device, characterized in that waste nitrogen used as brake gas for a dual expansion turbine is reused for purging of a PSA method pretreatment device in an air separation device employing a treatment device.