JPH0132434B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nitrogen separation device that separates nitrogen from air using a cryogenic separation method, and particularly relates to a nitrogen separation device suitable for recovering the pressure energy of excess product nitrogen as refrigeration. .

An example of a conventional nitrogen separator will be explained with reference to FIG.

In the nitrogen separation device shown in Figure 1, the pressure loss caused by the nitrogen separation device until nitrogen is separated from the raw air and extracted as product nitrogen is 1 Kg/cm ² G.
The pressure of the product nitrogen is often 5 to 8 kg/cm ² G. Therefore, the pressure of the product nitrogen is approximately 7 kg/
The case of cm ² G will be explained below as an example.

The raw air at room temperature that has been pressurized to approximately 8 kg/cm ² G is
A heat exchanger 1 is connected to the lower part of the single rectification column 10.
1, and while passing through the heat exchanger 11, the temperature rises from room temperature to approximately -170°C due to waste gas, which is the remaining gas after nitrogen has been separated from the product nitrogen and feed air. It cools down and some of it liquefies. The raw air in a gas-liquid mixed state flows through the raw air supply conduit 20 and is supplied to the lower part of the single rectification column 10. The single-type rectification column 10 is equipped with multiple stages of rectification plates 12 using a perforated plate system, etc., and the feed air in a gas state, which is part of the feed air supplied in a gas-liquid mixed state, passes through the rectification plates 12 and rises. As a result, the nitrogen content gradually increases, and at the top of the single rectification column 10, purified nitrogen has a nitrogen concentration of 99% or more. Approximately one-third of the purified nitrogen is extracted from the single rectification column 10 as product nitrogen through a product nitrogen extraction conduit 21 connected to the upper part of the single rectification column 10 and passing through the heat exchanger 11 . The remaining two-thirds of the purified nitrogen is liquefied by the condenser 13 installed at the top of the single rectification column 10, and most of it flows down the rectification pan 12 as a reflux liquid to separate nitrogen from the raw air. A part of the purified nitrogen used for purification and liquefied is transferred as product liquid nitrogen to the expansion turbine 1 through the product liquid nitrogen collection conduit 22 connected to the upper part of the single rectification column 10 and provided with a valve 30 in the middle.
4 will be extracted depending on the amount of cold generated. The reflux liquid that separates and refines nitrogen from the feed air and flows down to the bottom of the single rectifier 10 is liquefied and combined with the feed air supplied to the single rectifier 10 to become an oxygen-rich liquid and undergo single rectification. It remains at the bottom of column 10. This oxygen-rich liquid is extracted from an oxygen-rich liquid extraction conduit 23 which connects the bottom of the single rectification column 10 and the condenser 13 and is provided with an expansion valve 31 in the middle. The pressure is reduced to ~4 Kg/cm ² G and then supplied to the condenser 13. In the condenser 13, the oxygen-rich liquid liquefies 2/3 of the purified nitrogen, evaporates at the same time, and becomes waste gas.
The raw air is extracted from the waste gas extraction conduit 24 that connects the inlets of 4 and passes through the heat exchanger 11, and is cooled in the heat exchanger 11 and recovered to a temperature from about -180°C to about -150°C, after which it is sent to the expansion turbine. 14.
The waste gas undergoes adiabatic expansion in the expansion turbine 14, and its temperature drops to about -185° C., and the pressure energy of the waste gas is recovered as cold. The waste gas whose temperature has been lowered flows through a waste gas extraction conduit 25 that is connected to the outlet of the expansion turbine 14 and passes through the heat exchanger 11, and while passing through the heat exchanger 11, the raw air is cooled from about -185°C. After the temperature has recovered to room temperature, the waste gas is further circulated through the waste gas take-off conduit 25 and taken out of the nitrogen separator. On the other hand, the product nitrogen extracted from the single rectification column 10 flows through the product nitrogen extraction conduit 21 and passes through the heat exchanger 11, cooling the feed air and recovering the temperature to room temperature, after which the pressure is about 7 kg/
cm ² G, and is further distributed through the product nitrogen extraction conduit 21 to be separately sent to a user (not shown). In this case, in order to stabilize the operation of the single type rectification column 10, the amount of product nitrogen extracted from the single type rectification column 10 must be kept constant regardless of fluctuations in demand at the place of use. be. For this reason, the flow rate of the product nitrogen extracted from the single type rectification column 10 and flowing through the product nitrogen removal conduit 21 is measured by a flow rate detector 3 installed in the middle of the product nitrogen removal conduit 21 on the outlet side of the heat exchanger 11.
2 and sends the signal to the flow rate controller 33 connected to the flow rate detector 32. A flow rate regulator 33 is provided in the middle of the product nitrogen extraction conduit 21 on the stream side.
and the flow rate control valve 34 connected to the flow rate control valve 34, and the excess product nitrogen atmospheric release conduit 26 branched from the product nitrogen extraction conduit 21 between the flow rate detector 32 and the flow rate control valve 34 to release excess product nitrogen to the atmosphere. The valve opening degree of a flow rate control valve 35 provided in the flow rate control valve 35 and connected to the flow rate regulator 33 is adjusted by the flow rate regulator 33, respectively. In other words, if the amount demanded at the separate use site is smaller than the amount of product nitrogen extracted from the single rectifier 10, the excess product nitrogen with a pressure of approximately 7 kg/cm ² G will be transferred to the flow rate control valve 35. It is discharged to the atmosphere through the atmospheric discharge conduit 26.

In this type of nitrogen separation equipment, when the demand for product nitrogen decreases at a separate use site, the excess product nitrogen is simply released into the atmosphere, and the pressure energy contained in the excess product nitrogen cannot be recovered at all. Therefore, when the operating conditions of the rectification column are constant, there is a drawback that the amount of product liquid nitrogen collected cannot be further increased.

The present invention aims to eliminate the above-mentioned drawbacks, and is aimed at the inlet side of the heat exchanger of the product nitrogen extraction conduit through which the product nitrogen after being extracted from the rectification column and cooled by the heat exchanger flows through the product nitrogen. a flow rate detector is provided at the outlet side of the heat exchanger of the product nitrogen removal conduit, and a flow rate regulating valve is provided at the outlet side of the heat exchanger and at the downstream side of the flow rate detector, the product nitrogen The excess product nitrogen extraction conduit is branched from the extraction conduit, and the waste gas extracted from the rectification column, once temperature-recovered in the heat exchanger, and then adiabatically expanded in the expansion turbine flows through the waste gas extraction conduit. The surplus product nitrogen extraction conduit is connected to the inlet side of the vessel, and a flow rate control valve is provided in the surplus product nitrogen extraction conduit, and the amount of product nitrogen is adjusted according to the demand amount of the product nitrogen and the amount of the product nitrogen detected by the flow rate detector. By providing a flow rate regulator that adjusts the opening degree of each of the flow rate control valves, the pressure energy of excess product nitrogen is recovered as cold in the expansion turbine, and the amount of product liquid nitrogen to be collected is reduced to this cold. The purpose is to provide a nitrogen separator that can be further increased by a corresponding amount.

An embodiment of the present invention will be explained with reference to FIG.
In FIG. 2, the same devices, parts, etc. as in FIG. 1 are designated by the same reference numerals and their explanations will be omitted.

In FIG. 2, a flow rate detector 32' is installed on the inlet side of the heat exchanger 11 of the product nitrogen extraction conduit 21, which is provided with a flow rate regulating valve 34 connected to a flow rate regulator 33' on the outlet side of the heat exchanger 11. On the downstream side, a surplus product nitrogen extraction conduit 27 is branched from the product nitrogen extraction conduit 21 on the inlet side of the heat exchanger 11, and the surplus product nitrogen extraction conduit 27 is connected to the waste gas extraction conduit 24 on the inlet side of the heat exchanger 11. and surplus product nitrogen extraction conduit 27
A flow rate control valve 36 is provided in the middle of the flow rate control valve 36, and the flow rate control valve 36 and flow rate detector 32' are connected to the flow rate control valve 36.
3' respectively.

The flow rate of the product nitrogen extracted from the upper part of the single rectification column 10 and flowing through the product nitrogen extraction conduit 21 is detected by a flow rate detector 32'. Product nitrogen extraction conduit 2
For example, if the pressure of the raw air is about 8 Kg/cm ² G, the pressure is about 7
Kg/cm ² G when the demand for product nitrogen at a separate usage site (not shown) is less than the amount of product nitrogen extracted from the single rectifier 10, the flow rate control valve 34 is adjusted accordingly. The valve opening of flow controller 3
3' and at the same time, the flow rate control valve 36 is opened by a suitable amount by the flow rate regulator 33' in order to keep the amount of product nitrogen drawn out from the single rectification column 10 constant. After that, the excess product nitrogen flows through the excess product nitrogen extraction conduit 27 and the waste gas extraction conduit 24.
It joins with the circulating waste gas. Excess product nitrogen that has merged with the waste gas flows through the waste gas extraction conduit 24 and passes through the heat exchanger 11, while cooling the raw air and recovering the temperature to approximately -150°C, and then being supplied to the expansion turbine 14. Here, the temperature drops to approximately -185°C by adiabatic expansion, and the pressure energy possessed by the waste gas and excess product nitrogen is recovered as cold. The mixed gas of the waste gas exiting the expansion turbine 14 and surplus product nitrogen flows through the waste gas take-off conduit 25 and passes through the heat exchanger 11, while cooling the raw air and recovering the temperature to room temperature before taking out the waste gas. It further flows through the conduit 25 and is taken out of the nitrogen separator.

When the nitrogen separator is configured as in this example, surplus product nitrogen can be supplied to the expansion turbine without releasing it into the atmosphere due to a decrease in demand at other locations. The pressure energy possessed by can be recovered as cold.

According to the present invention, the pressure energy of excess product nitrogen can be recovered as refrigeration, so even if the operating conditions of the rectification column remain constant, the amount of product liquid nitrogen collected can be further increased by an amount equivalent to this refrigeration. effective.

[Brief explanation of drawings]

Fig. 1 is a diagram illustrating an example of a conventional nitrogen separation device, and is a system diagram of a conventional nitrogen separation device using a single rectification column, and Fig. 2 is a diagram illustrating an example of the present invention. , is a system diagram of a nitrogen separation apparatus according to the present invention using a single rectification column. 10...Single rectification column, 11...Heat exchanger, 13
... Condenser, 14 ... Expansion turbine, 20 ... Raw air supply conduit, 21 ... Product nitrogen extraction conduit,
22... Product liquid nitrogen collection conduit, 24... Waste gas extraction conduit, 25... Waste gas extraction conduit, 27...
... Surplus product nitrogen removal conduit, 32'...Flow rate detector, 33'...Flow rate regulator, 34, 36...Flow rate control valve.

Claims (1)

[Claims] 1. A heat exchanger that cools the pressurized raw material air;
a rectification column to which the raw material air cooled by the heat exchanger is supplied and which rectifies and separates nitrogen from the raw material air; In a nitrogen separation device having an expansion turbine that adiabatically expands temperature-recovered waste gas and recovers cold, the product nitrogen extracted from the rectification column and cooled by the heat exchanger flows through the product nitrogen. A flow rate regulator is provided on the inlet side of the heat exchanger in the product nitrogen removal conduit, a flow rate regulating valve is provided in the product nitrogen removal conduit on the outlet side of the heat exchanger, and , a surplus product nitrogen extraction conduit is branched from the product nitrogen extraction conduit on the downstream side of the flow rate detector, and the surplus product nitrogen extraction conduit is connected to the inlet side of the heat exchanger of the waste gas extraction conduit through which the waste gas flows. merge and connect,
A flow rate control valve is provided in the surplus product nitrogen extraction conduit,
A nitrogen separation apparatus characterized in that a flow rate regulator is provided that adjusts the opening degree of each of the flow rate control valves according to the demand amount of the product nitrogen and the amount of the product nitrogen detected by the flow rate detector.