JPH04295586A - Air separation method and device - 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]

0001

[Industrial Application Field] The present invention relates to an air separation device.
In particular, it relates to the control of a rectification column for recovering argon.

0002

2. Description of the Related Art An example of a conventional air separation device will be explained with reference to FIG.

FIG. 2 is a system diagram of an oxygen, argon and nitrogen extraction plant using the cryogenic air separation method. After moisture and carbon dioxide have been removed by a pretreatment process not shown in the figure, the feed air of about 5 kg/cm2G, which has been cooled to about -170° C., is supplied to the lower column 1 of the rectification column. The lower column of the rectification column 1
The air that has entered rises in the lower column 1 of the rectification column, exchanges heat with liquid oxygen to be described later in the main condenser 2, and is condensed to become the reflux liquid in the lower column 1 of the rectification column. This reflux liquid is subjected to gas-liquid contact with the above-mentioned rising air to undergo rectification and separation, and is separated into high-purity liquid nitrogen at the upper part of the lower column 1 of the rectifying column and into oxygen-rich liquid air at the lower part.

In the liquid air supercooler 6 and liquid nitrogen supercooler 7, the liquid air and high-purity liquid nitrogen separated in the lower column 1 of the rectification column are separated into the product nitrogen and It is supercooled to below the saturation temperature by heat exchange with the waste gas, and is supplied to the upper column 3 of the rectification column as a reflux liquid. The supplied reflux liquid descends in the upper column 3 of the rectification column and is supplied to the liquid distillation section of the main condenser 2. In the upper column 3 of the rectification column, the descending liquid exchanges heat with the rising air in the lower column 1 of the rectification column in the main condenser 2, and is evaporated to become rising gas in the rectification column 3. This rising gas is subjected to gas-liquid contact with the above-mentioned descending liquid to undergo rectification and separation, and the product is separated into nitrogen product in the upper part of the upper column 3 of the rectification column, waste gas in the middle part, and product oxygen in the lower part.

On the other hand, a part of the supercooled liquid air is supplied to the crude argon column condenser 5, where it is evaporated by heat exchange with the rising gas in the crude argon column 4, which will be described later, and is passed on to the rectification column in a gaseous state. It is fed to tower 3. A part of the argon-rich gas is extracted as feed gas from the middle of the upper column 3 of the rectification column, becomes the rising gas of the crude argon column 4, and is condensed by heat exchange with liquid air in the upper crude argon column condenser 5. ,
It descends as a reflux liquid from the crude argon column 4 and returns to the upper column 3 of the rectification column. In the crude argon column 4, the ascending gas and the descending liquid are brought into contact with each other, and the argon is rectified to a purity of about 98% in the upper part, and then supplied to the next step as crude argon gas.

The purity of product oxygen and crude argon varies greatly due to the rectification separation of oxygen and argon in the crude argon column 4. Further, the reflux ratio of the crude argon column 4 changes depending on the amount of liquid air supplied to the crude argon column condenser 5. Therefore, it is important for stable operation of the device to keep the supply amount of liquid air constant. However, due to the characteristics of the air separation equipment, instantaneous fluctuations applied to the rectification column due to external and internal factors are unavoidable, and in particular, when performing automatic control, problems arise in the stable supply of liquid air regarding crude argon column 4 control. was there.

[0007] An example of a related device of this type is JP-A-62-206373.

[0008]

[Problems to be Solved by the Invention] In order to operate the conventional equipment stably with a high product recovery rate, it is necessary to stabilize the operating conditions of the rectification column, but the above-mentioned conventional technology takes into consideration optimal control of the rectification column. As a result, the operation of the equipment was left to the experience and skills of veteran operators, and progress in achieving high product yields, automation, and labor-saving equipment was delayed.

An object of the present invention is to provide an air separation method and apparatus that eliminate the above-mentioned drawbacks and enable high product yield, automation, and labor saving.

0010

[Means for Solving the Problems] The above object is achieved by independently extracting liquid air lines from the lower column of the rectification column for reflux to the upper column of the rectification column and for supplying the crude argon column condenser. .

[0011]

[Operation] Since a fixed amount of liquid air is always held in the lower liquid air fraction of the lower column of the rectification column, the line of liquid air for reflux to the upper column of the rectification column and for supplying to the crude argon column condenser is purified. By providing the distillation column independently from the lower column extraction, this liquid distillate is used as a buffer, and instantaneous fluctuations occur in either the reflux amount to the fractionation column upper column or the crude argon column condenser supply amount. Also, since there is no influence on the other, the operational control of the rectification column can be stabilized.

0012

[Embodiment] An embodiment of the present invention will be explained below with reference to FIG. Note that the same parts as those in the prior art are indicated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, for example, when shifting to a reduction operation, the amount of feed air supplied to the lower column 1 of the rectification column is also reduced, so that the mass balance of the lower column 1 of the rectification column is such that the amount of air supplied to the upper column 3 of the rectification column is reduced. It is necessary to reduce the amount of refluxed liquid air. but,
In this case, the feed gas amount and reflux amount of the crude argon column 4 increase or decrease depending on the amount of liquid air supplied to the crude argon column condenser 5 to determine the reflux ratio, so it is necessary to control the amount of liquid air supplied independently.

Since liquid air is held in the lower liquid air fraction of the lower column 1 of the rectification column, the liquid air line for reflux to the upper column 3 of the rectification column and for supplying the crude argon column condenser 5 is connected to the rectification column. By providing the lower column independently from the extraction of the lower column 1,
This liquid distillate can be used as a buffer. Therefore, there is no mutual interference between the reflux amount to the upper column 3 of the rectification column and the amount supplied to the crude argon column condenser 5, and even if one changes, it has no effect on the other, which is an important factor in product recovery rate and purity. It is possible to eliminate fluctuations in the internal conditions of the upper column 3 of the rectification column and the crude argon column 4.

[0015]

According to the present invention, the apparatus can be optimally controlled by stabilizing the operating conditions of the rectification column, so that it is possible to achieve high product yields, automation, and labor savings.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing one embodiment of the present invention.

FIG. 2 is a system diagram showing control in the prior art.

[Explanation of symbols]

1... Lower rectification column, 2... Main condenser, 3... Upper rectification column, 4...
Crude argon column, 5... Crude argon column condenser, 6... Liquid air supercooler, 7... Liquid nitrogen supercooler, 8... Liquid level controller, 9... Flow rate controller, 10... Differential pressure controller.

Claims (2)

[Claims] Claim 1: In an air separation method for separating oxygen, argon, and nitrogen from air by a cryogenic air separation method, liquid air extracted from a lower column of a rectification column is supercooled, and the entire amount of the supercooled liquid air is separated from argon. An air separation method characterized in that it is fed to a column condenser feed. Claim 2: In an air separation device for separating oxygen, argon, and nitrogen from air using a cryogenic air separation device, a liquid air pipe line for refluxing to an upper column of a rectification column and for supplying to a condenser of a crude argon column. An air separation method characterized by comprising pipe lines for independently extracting liquid air from the lower column of the rectification column, and a heat exchanger provided in the middle of the liquid air pipes for supercooling the liquid air. Device.