JPH0240485A - Manufacture of nitrogen - Google Patents

Abstract

PURPOSE:To utilize the energy of waste gas effectively and reduce the power cost for nitrogen by a method wherein the waste gas is introduced into a high- temperature side expansion turbine to utilize the output of the high-temperature side expansion turbine as one part of the compressing power of material air. CONSTITUTION:A high-temperature side expansion turbine 16 is driven by the pressure of waste gas W and the output shaft of the turbine 16 is connected to the driving shaft of a compressor 1 through a power transmitting means 17 whereby power, generated in the turbine 16, is transmitted to the driving shaft of the compressor 1. The waste gas W having a pressure is introduced into a low-temperature side expansion turbine 10 to expand it and the pressure is retrieved by the turbine 16 to utilize it as one part of the compressing power of material air A. According to this method, a power necessary for the compressor 1 may be reduced. The temperature of the waste gas is risen in a pre-cooler 15 and is risen further by cooling the material air A in a preheater 2 while the waste gas drives the turbine 16 subsequently while becoming one part of the power for the compressor 1. Accordingly, a cost for the power may be reduced remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing nitrogen by compressing raw air and liquefying and separating it at low temperatures.

(Prior art) Fig. 3 is a system diagram showing a conventional general nitrogen production method, which is an autostatic method that co-produces a relatively small amount of liquefied nitrogen. This shows a method in which the temperature is directly generated without the use of heat.

It is compressed to 9.35 kg/ciA in compression chamber 1 and heated to high temperature (1
The 10,000 N/H raw air Δ, which has reached a temperature of 30°C, exchanges heat with the regeneration gas R described below in the preheater 2 to lower its temperature to 113°C, and then is cooled to 40°C in the aftercooler 3. Furthermore, the raw air A is cooled down to 5°C by the Freon cooler 4, and then the air is sucked by multiple units. i V55
a, and is purified by removing impurities such as water and carbon dioxide.

The purified raw material air A is introduced into the main heat exchanger 6, where it exchanges heat with the product nitrogen gas PN and exhaust gas W, which will be described later, and is cooled to near the liquefaction point. is introduced at the bottom of the The raw air is rectified in a rectification column 7 and separated into nitrogen gas GN at the top of the column and oxygen-enriched liquefied air LA at the bottom of the column.

Nitrogen gas GN is led out from the top of the rectification column 7, and a part of it (3800N-rr?/H) is transferred to the main heat exchanger 6 to exchange heat with the raw material air, and is heated to 5°C. After the temperature is recovered, the pressure is increased to 8.8 km and the product nitrogen gas PN is sent out. In addition, the remaining nitrogen gas GN is sent to the condenser evaporator 8.
It exchanges heat with the liquefied air LA introduced from the bottom of the tower into the condensing evaporator 8, and is condensed to become liquefied nitrogen LN. This liquefied nitrogen LN has a small fit (80Nm/H
) is collected as a product liquefied nitrogen PL, and most of the liquefied nitrogen LN is introduced into the upper part of the rectification column 7 as a reflux liquid from the rectification column 7.

On the other hand, the liquefied air LA at the bottom of the rectification column 7 is introduced into the condensing evaporator 8 after expanding through a valve, where it exchanges heat with the nitrogen gas GN, evaporates, and becomes an exhaust gas W (with a pressure of 4.7 kg/-). 6
1208 I/H). This exhaust gas W is partly Wa
(2300NTI+'/+1) is introduced into the main heat exchanger 6 and heated up by several tens of degrees, and then introduced into the expansion turbine 10, where it expands to a pressure of 1.28k (1/cm^) and generates cold. Part Wa of the exhaust gas is expanded to approximately the same pressure by the valve 11, and the remaining part Wb (3820NTI+'/
+1) and is introduced into the main heat exchanger 6, and the raw air A
Heat exchange is performed with the raw stone air △ to cool it.

The main heat exchanger 6 raises the temperature to room temperature (5℃) and the pressure is 1.2k.
The exhaust gas W derived from O/Cri^ is its − part Wc
(1500thn'/fl) is used as the regeneration gas R of the adsorbers 5a and 5b, and the remainder Wd (46
20NTI+'/+1) is released from valve 12 into the atmosphere. The regenerating gas R used to heat and regenerate one of the adsorbers 5b is heated by the high-temperature raw air A in the preheater 2, further heated by the heater 13, and then introduced into the adsorber 5b in the regeneration process. Furthermore, the regeneration gas R during cooling of the adsorber 5b is delivered from the valve 14 to the adsorber 5b1. :be introduced.

(Problem to be Solved by the Invention) However, in the above-mentioned method, most of the exhaust gas W having a pressure that is vaporized and led out in the condenser evaporator 8 is simply expanded in the valve 11 before entering the main heat exchanger 64. Because of this, exhaust gas W
The energy of nitrogen production equipment was being wasted, which worsened the unit consumption of nitrogen production equipment.

Furthermore, the exhaust gas W derived from the main heat exchanger 6 is 5°C
Although the temperature is relatively low, most of the energy is released into the atmosphere from the valve 12 without using its energy effectively.

Therefore, the present invention effectively utilizes the energy such as pressure and temperature of the above-mentioned initial gas to produce nitrogen-N? The purpose of this study is to describe a nitrogen production method that can reduce the unit consumption of J'>'24 equipment.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention introduces substantially all M of exhaust gas having a pressure vaporized in a condenser evaporator into a low temperature side expansion turbine, and has a pressure intermediate between the pressure of the exhaust gas and atmospheric pressure. , and is expanded to a pressure sufficient to obtain the refrigeration necessary for the operation of the equipment to generate refrigeration, which is then introduced into the main heat exchanger to exchange heat with the feed air to heat the culm, and this pressure is reduced. The heated gas is further heated by exchanging heat with the raw material air at room temperature or higher during the process from compression to production, and then introduced into the high-temperature side expansion turbine where it is expanded to atmospheric pressure and discharged. At the same time, the nitrogen production method is characterized in that the output of the high-temperature side expansion turbine is used as part of the power for compressing raw air, and a part of the pressured exhaust gas vaporized in the condenser evaporator is used in the low-temperature side expansion turbine. The exhaust gas is introduced into the air and expanded to atmospheric pressure to generate the refrigeration required for the operation of the equipment, and introduced into a heat exchanger to exchange heat with the raw material air before being discharged, while the remainder of the exhaust gas is not expanded. It is introduced into the main heat exchanger and heated by exchanging heat with the raw material air, and the heated exhaust gas having this pressure is heat exchanged with the raw material air at room temperature or higher during the process from compression to purification. Nitrogen is introduced into a high-temperature side expansion turbine to be expanded to atmospheric pressure and then outputted after the temperature has been raised, and the output of the high-temperature side expansion turbine is used as part of the power for compressing the raw material air. A manufacturing method is provided.

[For production]

With the above configuration, in addition to the conventional expansion turbine that operates in a low temperature range using the pressure of exhaust gas, a TS warm open side expansion turbine that operates in a temperature range from around room temperature to above room temperature is driven, and this output is transferred to the raw material air. By using the compressor as compression power, the power cost of the compressor can be reduced. In addition, all or most of the low-temperature exhaust gas is cooled by exchanging heat with raw air at room temperature or higher before being introduced into the purification process such as an adsorber, reducing the power cost of cooling equipment for the purification process. can be reduced.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on exemplary embodiments shown in the drawings.

First of all, FIG. 1 shows an embodiment of the nitrogen production apparatus to which the nitrogen production method according to claim 1 is applied, and the tree fruit downstream apparatus is similar to the system of the nitrogen production apparatus shown in the conventional example. This is an improved version in which a precooler 15 and a high temperature side expansion turbine 16 are added. Incidentally, the same elements as those in the conventional example shown in FIG. However, similarly to the conventional example, the expansion turbine used on the low temperature side is referred to as the low temperature side expansion turbine so as not to be confused with the above-mentioned high temperature side expansion turbine.

The above precooler 15 includes an aftercooler 3 and a fluorocarbon cooling 7J]
It exchanges heat between the low-temperature exhaust gas W and product nitrogen gas PN derived from the main heat exchanger 6 and the feed air A, and converts it into the feed air introduced into the Freon cooler 4. to cool down. The high-temperature side expansion turbine 16 provided at the final stage of the exhaust gas W exhaust system is driven by the pressure of the exhaust gas W to rotate, and its output shaft is connected to the drive shaft of the compressor 1 for the raw air A. , are connected by a power transmitter g217 such as coaxial or gear, and the power generated by the high temperature side expansion turbine 16 is transmitted to the drive shaft of the compressor 1. Roughly speaking, the precooler 15 and the high-temperature side expansion turbine 76 are configured to absorb almost the entire exhaust gas W generated in this nitrogen production device (the entire amount excluding the regeneration gas of the adsorbers 5a and 5b). has been done.

Next, a case will be described in which the apparatus of this embodiment is used to produce nitrogen gas at the same pressure and at the same level as the conventional apparatus shown in Sections 3 and 4 of Na.

First, it is compressed to 9.4 ka/dA by compressor 1, and the
The raw air A of 100008Tn'/11, which has reached a temperature of 30°C), is lowered in temperature to 95°C by exchanging heat with Oma's exhaust gas W in the preheater 2 compared to the conventional method, and then cooled to 40°C in the aftercooler 3. , is introduced into the precooler 15.

The raw air A is cooled to 22° C. by exchanging heat with the exhaust gas W and the product nitrogen gas PN in the precooler 15, and further cooled to 5° C. in the freon cooler 4, and then introduced into the adsorber 5a.

Then, as in the past, the feed air A purified by the adsorption Vfs 5a is introduced into the main heat exchanger 6, cooled, and introduced into the rectification column 7 at a pressure of 9.0 ko/cIi, where it is converted into nitrogen gas GN. and liquefied air LA.

Part of the nitrogen gas GN derived from the top of the refined dI column 7 (
3800117I+'/H) is introduced into the main heat exchanger 6 as product nitrogen gas PN, and the remaining nitrogen gas GN is introduced into the condensing evaporator 8 to become liquefied nitrogen 1-N. ) is collected as product liquefied nitrogen PL, and the remainder becomes the reflux liquid of the rectification column 7.

On the other hand, the liquefied air LA at the bottom of the rectification column 7 is evaporated in the condensing evaporator 8 to produce exhaust gas W (
6120N-+y+'/H). This slanderous gas W is
Almost the entire exhaust gas (6100 Nm''/II) is introduced into the main heat exchanger 6 and heated by several tens of degrees before being introduced into the low-temperature side expansion turbine 10. at a pressure intermediate between
a/ ai Expands to A. Then, at the valve 11, it merges with a portion of the exhaust gas expanded to the same pressure We (20N/H) and is introduced into the main heat exchanger 6.

The main heat exchanger 6 exchanges heat with the rough air A, and the pressure is 8.
The product nitrogen gas PN derived at 8 kQ/mA and a temperature of 5° C. and the lJ1 gas W derived at a pressure of 2.6 klJ/cIi^ and a temperature of 5° C. are introduced into the precooler 15,
Heat exchange is performed to the raw material air, and the raw material air A is cooled and humidified to 36° C. as described above. The product nitrogen gas PN, which is heated and eroded, is sent to the user at the same pressure.

On the other hand, the exhaust gas W led out from the precooler 15 exchanges heat with the high temperature raw material air A in the preheater 2 and is heated to 120°C. And that large number (46201hn”/H)
is introduced into the high temperature side expansion turbine 16, and the turbine 16
is rotated, the compressor I11 is driven via the power transmission means 17, and after being expanded to approximately atmospheric pressure (1°03k (J/ci^)), it is released into the atmosphere.
008m'/II) is used as the regeneration gas R of the adsorbers 5a and 5b in the same manner as in the past.

In this way, the exhaust gas W having a pressure is introduced into the low-temperature side expansion turbine 10, and the pressure is intermediate between the pressure of the exhaust gas W and the atmospheric pressure, and the pressure is sufficient to obtain the refrigeration necessary for operating the device. By recovering this pressure in the r4 hot side expansion turbine 16 and using it as part of the power to compress the raw material air, the product nitrogen gas PN with the same suspension as the conventional example shown in FIG. When obtaining the same pressure, the required power of the compressor 1 can be reduced from 1l100k to 990kw.

Furthermore, using the low temperature (5° C.) exhaust gas W and product nitrogen gas PN derived from the main heat exchanger 6 as a cooling source, the room temperature rough air Δ between the compression t11 and the adsorbers 5a and 5b for dressing is cooled. As a result, the power required for the Freon cooler 4 can be reduced from 48 kW to 21 kW. Therefore, including other required power, it is possible to reduce the fh power by approximately 11.5% during the rest period, and even if initial equipment costs such as the precooler 15 and the i:S hot water side expansion turbine 16 are required, By significantly reducing the power cost, the power consumption rate of the product nitrogen gas PN can be reduced. Furthermore, as is clear from the above embodiments, the method of the present invention can be put into practical use with only slight improvements to conventional equipment, and the equipment does not need to be enlarged. Furthermore, as in this embodiment, by introducing the product nitrogen gas PN into the precooler 15 together with the exhaust gas W, the cooling effect of the raw air A can be improved, but the product nitrogen gas PN is sent to the user at a low temperature. Even if only the exhaust gas W is introduced into the precooler 15, a sufficient effect can be obtained.

Next, FIG. 2 shows an embodiment of a nitrogen production apparatus to which the nitrogen production method according to claim 2 is applied, and this embodiment apparatus is similar to the embodiment apparatus shown in FIG. 1 above. Precooler 1
5 and a B hot water side expansion turbine 16 are added, and the exhaust gas W is divided into two systems. Incidentally, the same elements as those shown in FIGS. 1 and 3 are given the same reference numerals and detailed explanations will be omitted.

2 7751hn'/+1 derived from condenser evaporator 8
The exhaust gas W is a part of it (1100NT11'/II)
Wf is introduced into the low-temperature side expansion turbine 10 to obtain the cooling required for the device, and atmospheric pressure < (1, 2k (+/c
mA ) to generate cold and cool the feed air.
I will A part of this exhaust gas Wf is used as regeneration gas R for the suction W2S5a, 5b through the same route as in the conventional case. Excess gas Wg as regeneration gas R is discharged from valve 12.

On the other hand, the precooler 15 that cools the raw material air Δ introduced into the freon cooler 4 is supplied with the remaining part of the exhaust gas Wh (2.7 kCI
/mA, 1675 Nvn'/11) and product nitrogen gas PN are introduced to cool the raw material air. The exhaust gas wh heated to 36°C in the precooler 15 further cools the raw air A in the preheater 2 to reach a temperature of 105°C, and then is introduced into the high temperature side expansion turbine 16 to drive the turbine 16. It becomes part of the power of the compressor 1.

In the method of this embodiment as well, the power required for the compressor 1 and the fluorocarbon cooler 4 can be significantly reduced, as in the previous embodiment. In addition, the method of this example uses the product nitrogen gas P
This is a device with a low required pressure of N, and the pressure of the exhaust gas W exclusively from the condenser evaporator 8 is relatively low, and when the exhaust gas W is expanded in the low temperature side expansion turbine 10, the pressure of the expanded exhaust gas W is high. This is particularly effective when sufficient power is not available to drive the side expansion turbine 16.

The method of the present invention is not limited to the nitrogen production apparatus shown in the above embodiment, but can be applied to various nitrogen production apparatuses.

〔Effect of the invention〕

As explained above, the present invention effectively uses the energy such as the pressure and temperature of the exhaust gas discharged from the nitrogen production equipment for compressing and cooling the raw material air. The power cost and the power cost of the Freon cooler for cold W can be significantly reduced, and the unit of power source for product nitrogen gas can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of a nitrogen production device to which the present invention is applied, Fig. 2 is a system diagram showing another embodiment, and Fig. 3 is a system diagram showing a conventional nitrogen production method. .

Claims (1)

[Claims] 1. In a nitrogen production method in which raw air is compressed, purified, cooled, and liquefied and separated at a low temperature, substantially the entire amount of pressured exhaust gas separated in a rectification column and vaporized in a condensing evaporator is liquefied at a low temperature. refrigeration is produced by introducing it into a side expansion turbine and expanding it to a pressure intermediate between the pressure of the exhaust gas and atmospheric pressure, but sufficient to provide the refrigeration required for operation of the equipment, and then generating refrigeration. After introducing the exhaust gas into an exchanger and exchanging heat with the raw material air to raise the temperature, and exchanging heat with the raw material air at room temperature or higher during the compression to purification process, the exhaust gas having this pressure is further raised in temperature.
A method for producing nitrogen, which comprises introducing nitrogen into a high-temperature side expansion turbine, expanding it to atmospheric pressure, and discharging it, and using the output of the high-temperature side expansion turbine as part of the power for compressing raw material air. 2. In a nitrogen production method in which raw air is compressed, purified, and cooled to liquefy and separate at a low temperature, a part of the high-pressure exhaust gas separated in a rectifier and vaporized in a condensing evaporator is introduced into a low-temperature side expansion turbine. The air is expanded to atmospheric pressure to generate the refrigeration necessary for the operation of the equipment, which is introduced into a heat exchanger to exchange heat with the raw material air and then discharged, while the remaining part of the exhaust gas is subjected to main heat exchange without expansion. The exhaust gas having this pressure is introduced into the reactor and heated by exchanging heat with the raw material air, and the exhaust gas having this pressure is further heated by exchanging heat with the raw material air at room temperature or higher during the process from compression to purification, and then the high temperature side A method for producing nitrogen, which comprises introducing nitrogen into an expansion turbine, expanding it to atmospheric pressure, and discharging it, and using the output of the high-temperature side expansion turbine as part of the power for compressing raw air.