JPS62142984A - Method of separating gas - 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 [Field of Application of the Invention] The present invention relates to a gas separation method for separating a product gas from a source gas and collecting the product gas.

[Stock of invention]

Gas separation techniques are well known in which raw material gas is cooled and supplied to a gas separation unit such as I-seedling separation or adsorption separation to collect product gas. In particular, by liquefying and rectifying air using air as a raw material gas, nitrogen (Nz) and oxygen (
02), Air separation devices that separate argon (Ar), etc. are in operation in various fields.

In this type of gas separation device, it is necessary to pressurize or depressurize the raw material gas (air, etc.) depending on the operating conditions, and therefore it is necessary to install equipment such as a compressor or an expansion turbine. This type of equipment is often operated continuously for a long period of time (and power sources such as electric power associated with this operation are
The biggest challenge is how to reduce operating costs.

In the past, many technologies have been developed to address this issue, but one of them is to connect the expander and compressor (directly or through gears, etc.) in order to efficiently generate cold in the air separation equipment. It is known to utilize an expansion turbine with a compressor (coupled with a compressor). A typical example of this technology is disclosed in Japanese Patent Laid-Open No. 60-23771.

This technology raises the temperature by passing gaseous air or gaseous nitrogen from the lower column of the double rectification column, which has passed through the reheat circuit of the main heat exchanger, through a circulation heat exchanger installed separately from the main heat exchanger. After that, the pressure is increased by applying it to the load blower (compressor) of the expansion turbine, and this pressurized air is cooled by passing it through the above-mentioned circulation heat exchanger, and then introduced into the expansion turbine to generate the refrigeration necessary for the equipment. be. According to this technique, it is possible to generate the necessary refrigeration for the device and to effectively reduce the flow rate of the expansion turbine, so that the basic unit of product gas (02) can be reduced.

By the way, in the above method, the liquefied gas or gas extracted from the lower column of the double rectification column is supplied to the circulation heat exchanger, and a part of the gas is supplied to the circulation heat exchanger via the reheat circuit of the main heat exchanger. Since the configuration is such that the temperature is recovered by supplying heat to the water, a circulation heat exchanger must be installed as a matter of course, which complicates the equipment and increases equipment costs. Also, the gas that is supplied to the compressor of the expansion turbine with a compressor for pressurization.

Since it is sent to the compressor through a complicated route, there is a large pressure loss and energy loss along the way, making it impossible to obtain the desired effect. In addition, the liquefied gas or gas extracted from the lower column of the rectifying column has a temperature of about -170°, and even if a part of it is supplied to the reheat circuit of the main heat exchanger and combined with the heated gas, it will not be circulated. There is a large difference in the temperature of the return gas from the heat exchanger, and the cooling loss is large. [Object of the Invention] An object of the present invention is to provide a gas separation method that has a simple configuration and can perform gas separation efficiently. That's true.

[Summary of the invention]

The present invention provides a gas separation method in which a raw material gas is cooled through a heat exchanger, the cooled raw material gas is supplied to a gas separation section, and a product gas is separated and collected therein. After the gas is brought back to room temperature in a heat exchanger, it is supplied to a compressor connected to an expansion turbine to increase the pressure.The product gas after the pressure increase is cooled in a heat exchanger and then supplied to the expansion turbine for insulation. It is characterized by expanding the product gas and recovering the temperature of the adiabatically expanded product gas using a heat exchanger before collecting it.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail based on specific examples.

FIG. 1 is a diagram showing an embodiment of the present invention. In this embodiment, air is used as the raw material gas, and nitrogen is extracted from this air as the product gas. In this figure, l is a heat exchanger that cools the feed air to a temperature suitable for rectification separation. 2 is a rectification column that rectifies raw air and separates nitrogen.

3 is a condenser, which liquefies the rising gas rising inside the rectification column 2 using oxygen-rich liquid air from the lower part of the rectification column 2. 4 is an expansion turbine with a compressor.

Note that the compressor in this example is the blower of the expansion turbine.
It is. 5 to 7 are valves, and 8 is a flow rate controller. 9
and 10 are valves.

The operation in this embodiment is as follows.

First, air taken in from the atmosphere is pressurized to about 3 Kp/dG by a compressor (not shown), and moisture and acid gas are removed by a pressure swing type adsorption tower (not shown).
Conduit 11 leads to heat exchanger 1 . In the heat exchanger 1, the feed air is cooled to about -172°C by heat exchange with the low-temperature return gas. This cooling air is supplied to the rectification column 2 through a conduit. In the rectification column 2, rectification is repeated, with high-latitude nitrogen being separated at the top of the column and oxygen-rich liquid air being separated at the bottom of the column. This liquid air is led from the bottom of the tower through conduit 13 to condenser 3, during which it is pressurized to about 0.3 Kq/cl G, and serves as a cold source for liquefying nitrogen in the condenser. The liquid air subjected to nitrogen condensation is led as a gas to the heat exchanger 1 through the conduit 14, where its temperature is recovered by heat exchange with the raw air, and taken out from the apparatus through the conduit 15 at approximately atmospheric pressure. It is then released into the atmosphere or used as regeneration gas in adsorption towers.

On the other hand, the high-purity nitrogen gas that has been rectified and separated in the upper part of the rectification column 2 is taken out from the pipe 16, and a part of it is led to the condenser 3 where it is liquefied, becomes liquid nitrogen, and passes through the pipe 17. Rectification tower 2
It becomes a descending liquid.

When collecting liquid nitrogen, conduit 18. Sample via valve 10. Of the high-purity nitrogen gas extracted from the conduit 16, the remaining nitrogen gas that was supplied to the condenser 3 passes through the conduit 19 and is led to the heat exchanger 1, where it exchanges heat with the raw air and cools down to room temperature. will be recovered.

This high-purity nitrogen gas of about 2.3 Kg/di G, now at room temperature, is supplied to the blower of the expansion turbine 4 through conduit 4, where it is pressurized to about 3.6 Kq/al G.

The pressurized high-purity nitrogen gas passes through conduit 4, is cooled down to room temperature by an aftercooler (9), and is again supplied to heat exchanger 1 through conduit n, where it is further cooled (approximately -150
℃) 8. In addition, when collecting high-pressure, high-purity nitrogen (
In this example, approximately 3.6 Kg/cIIG of nitrogen gas is collected via conduit and valve 9. This results in approximately 3.
OK4/CI! Even if the pressure of the raw material air is about 3.6 to 1-G, it is possible to obtain a product nitrogen gas of about 3.6-/-G. This means that the raw air can be kept at a low pressure, which greatly contributes to reducing operating costs.

Now, high-purity nitrogen cooled to about -150° C. by the heat exchanger 1 passes through the conduit S, and is led to the expansion turbine 4 via the conduit δ and the valve 5. In the expansion turbine 4, the nitrogen gas is adiabatically expanded to approximately 0.49/cdG, thereby generating refrigeration. ``The high-purity nitrogen gas expanded by the expansion turbine 4 passes through a conduit 28 to the heat exchanger! guided by. Then, heat is exchanged with the raw air in the heat exchanger l, and the temperature is restored to room temperature, approximately 0.3 K9/C.
Product nitrogen gas having a pressure of 111 G is collected from conduit 4.

Next, a method for adjusting the balance of cold energy in the device will be explained. Cold energy balance is achieved by expansion turbine 4
It is adjusted by the valve 5 provided at the 0 inlet.

The amount of liquid nitrogen liquefied in the condenser 3 can be increased or decreased by using surplus cold energy when the valve 5 is fully opened and the expansion turbine 4 is fully loaded, and liquid phosphorus can be extracted as a product gas. If liquid nitrogen is not to be collected or if the amount of liquid nitrogen to be collected is small, the valve 5 is throttled and the expansion turbine 4 is closed.
Reduce the amount of nitrogen gas supplied. At this time, the amount of sampled product nitrogen gas can be stabilized by detecting the flow rate with the flow rate controller 8 and controlling the valve 6 so that the detected value approaches the set scheduled amount of sampled amount. Furthermore, when the end-use demand for nitrogen gas suddenly decreases, by closing the valve 7 and releasing the nitrogen gas to the atmosphere, it is possible to prevent a sudden change in the outlet pressure of the expansion turbine 4.

According to the embodiment described above, it is possible to operate with a low pressure of the raw air, and it is expected that the compressor for increasing the pressure of the raw air can be downsized and the operating energy can be saved. Furthermore, since the refrigeration energy can be significantly increased, liquid nitrogen can be collected without installing equipment such as a liquefaction circuit.

It also becomes possible to collect high-pressure nitrogen gas, eliminating the need for equipment such as a compressor.

In the above-described embodiments, air is used as the raw material gas, and high-purity nitrogen is extracted from the air, but the present invention is not limited thereto. The raw material gas may be any mixed gas containing the gas composition to be separated and collected. Further, the type of gas to be separated and collected is not limited to nitrogen, but may be any useful gas such as oxygen or argon, and of course, these gases may be collected simultaneously. Further, in the embodiment shown in FIG. 1, a rectification gas separation apparatus using a rectification column between the gas separation sections is used, but the present invention is not limited to this. Depending on the type of gas to be separated and collected or the purity of the gas,
You can choose the appropriate one. For example, when simultaneously collecting oxygen and nitrogen, a known double rectification column may be used, and when also collecting argon, a crude argon column may be installed. Naturally, a gas separation device using low-temperature adsorption using an adsorbent may also be used. Of course, an appropriate combination of a rectification gas separation device using a rectification column and a low-temperature adsorption type gas separation device may be used.

〔Effect of the invention〕

According to the present invention, gas separation can be performed efficiently with a simple configuration. As a result, the plant becomes smaller,
This greatly contributes to reducing operating costs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention. l... Heat exchanger, 2... Rectification column, 3...
... Condenser, 4 ... Expansion turbine with compressor, 5 - 7 ... Valve, 8 ... Flow rate controller,
9, 10... Valve, 11-29... Conduit, Seki... After cooler, Father... Gas separation section\no, / 11 Figure

Claims (1)

[Claims] 1. In a gas separation method in which a raw material gas is cooled through a heat exchanger, the cooled raw material gas is supplied to a gas separation unit to separate a product gas, and the product gas is collected, the product gas is heat exchanged. After the temperature is recovered by a heat exchanger, the product gas is supplied to a compressor connected to an expansion turbine to increase the pressure, and the product gas after the pressure increase is cooled by a heat exchanger, and then supplied to the expansion turbine for adiabatic expansion. A gas separation method characterized by recovering the temperature of the product gas in a heat exchanger and collecting it.