Title of Invention

METHOD OF GENERATING NITROGEN AND APPARATUS FOR USE IN THE SAME

Abstract There is provided a method of generating nitrogen which includes cryogenically separating compressed air introduced into a high-pressure column 11, storing liquid air 13 in a bottom portion of the high-pressure column 11 and taking nitrogen in gaseous form from an upper portion of the high-pressure column 11, introducing the liquid air 13 stored in the bottom portion of the high-pressure column 11 into a low-pressure column 12, cryogenically separating the liquid air 13 introduced into the low-pressure column 12 and storing oxygen-enriched liquid air 22 in a bottom portion of the low-pressure column 12 and taking nitrogen in gaseous form from an upper portion of the low-pressure column 12 as a product gas. Liquid air 13 taken through an extraction pipe 20 is introduced into a portion of a rectification part 12a of the low-pressure column 12 in which the number of theoretical plates from a column bottom side is set within the range of one to ten.
Full Text DESCRIPTION
METHOD OF GENERATING NITROGEN AND
APPARATUS FOR USE IN THE SAME
Technical Field
The present invention relates to a method of
generating nitrogen and an apparatus for use in the same.
Background Art
An example of coolant injection type nitrogen
generating apparatuses currently in use is of a single
rectification type, as shown in Fig. 3. This nitrogen
generating apparatus performs the steps of: compressing
air as a raw material in an air compressor 31; passing
the compressed air through a drain separator 32 and a
CFC cooler 33 into adsorption columns 34 to remove carbon
dioxide and water from the compressed air; introducing
the compressed air passed through the adsorption columns
34 through a supply pipe 35 into a main heat exchanger
36 to heat-exchange the compressed air with a refrigerant
therein, thereby cooling the compressed air down to an
ultra low temperature; introducing the compressed air
cooled down to the ultra low temperature through an inlet
pipe 37 into a rectification column 38 to cryogenically


liquefy and separate the compressed air therein, thereby
producing a product nitrogen gas; introducing the product
nitrogen gas through a product nitrogen gas extraction
pipe 39 into the above-mentioned main heat exchanger 36
to raise the temperature of the product nitrogen gas up
to near room temperature; and feeding the product nitrogen
gas into a main pipe 40. The above-mentioned
rectification column 38 will be described in further
detail. The rectification column 38 further cools the
compressed air, cooled down to the ultra low temperature
by the main heat exchanger 36, to liquefy part of the
compressed air into liquid air 41, thereby storing the
liquid air 41 in a bottom portion thereof, while storing
only nitrogen in gaseous form in an upper portion thereof.
The rectification column 38 includes a dephlegmator 42
incorporating a condenser 42a at its column top. Part
of the nitrogen gas stored in the upper portion of the
rectification column 38 is fed through a first reflux
pipe 43a into the above-mentioned condenser 42a. The
pressure in the above-mentioned dephlegmator 42 is lower
than that in the rectification column 38. The stored
liquid air (containing 50 to 70% N2; and 30 to 50% O2)
41 accumulated in the bottom portion of the rectification
column 38 is fed through a feed pipe 44 with an expansion
valve 44a into the dephlegmator 42, and is gasified to


cool the internal temperature down to a temperature not
greater than the boiling point of liquid nitrogen. This
cooling liquefies the nitrogen gas fed into the condenser
42a, and the liquid nitrogen passes through a second reflux
pipe 43b to flow down and be supplied to the upper portion
of the rectification column 38. Liquid nitrogen is
injected and supplied as a coolant from a liquid nitrogen
tank (not shown) through an inlet pipe 45 into the upper
portion of the rectification column 38. The liquid
nitrogen flows down within the rectification column 38
to countercurrently contact and cool the compressed air
raising from the bottom portion of the rectification
column 38, thereby liquefying part of the compressed air.
In this course, a high boiling point component in the
compressed air is liquefied and stored in the bottom
portion of the rectification column 38, and the nitrogen
gas which is a low boiling point component is stored in
the upper portion of the rectification column 38 (the
boiling point of oxygen: approximately -183°C; and the
boiling point of nitrogen: approximately -196°C). In
Fig. 3, the reference numeral 46 designates a waste gas
outlet pipe for feeding gasified liquid air (waste gas)
within the dephlegmator 42 into the heat exchanger 36
to decrease the temperature of the compressed air passing
therethrough, 47 designates a first release pipe for

releasing the gasified liquid air passed through the heat
exchanger 36 into the atmosphere, 48 designates a second
release pipe for releasing a He gas in gaseous form (having
a boiling point lower than that of the nitrogen gas)
contained in the nitrogen gas into the atmosphere, and
4 9 designates a cold box for vacuum insulating the interior
thereof.
Patent document 1: Japanese Patent Application
Laid-Open No. 11-101576 (1999)
Disclosure of the Invention
Problems to be Solved by Invention
Improvements have been made heretofore in the
nitrogen generating apparatuses employing the single
rectification scheme as described above for reducing the
amount of raw material air in order to reduce gas
production costs. However, the current A/N (the amount
of raw material air/the amount of produced nitrogen) ratio
approximately equal to 2.1 is already close to the limit,
and it is difficult to further reduce the amount of raw
material air to accomplish reductions in power
consumption, the amount of coolant and costs of
facilities.
In view of the foregoing, it is an object of the
present invention to provide a method of generating


nitrogen which is capable of significantly reducing the
amount of raw material air to accomplish the reductions
in power consumption, the amount of coolant and costs
of facilities, and an apparatus for use in the same.
Means for Solving Problems
To accomplish the above object, a first aspect of
the present invention is intended for a method of
generating nitrogen which comprises: compressing air
taken from outside by using an air compression means;
cooling the compressed air down to a low temperature in
a main heat exchanger and then introducing the compressed
air into a high-pressure column; cryogenicallyseparating
the compressed air introduced into the high-pressure
column by using a difference in boiling point between
components in the compressed air; storing liquid air in
a bottom portion of the high-pressure column and taking
nitrogen in gaseous form for use as a reflux liquid from
an upper portion of the high-pressure column; introducing
the liquid air stored in the bottom portion of the
high-pressure column through a liquid air extraction
passage into a low-pressure column; cryogenically
separating the liquid air introduced into the
low-pressure column by using a difference in boiling point
between components in the liquid air; storing


oxygen-enriched liquid air in a bottom portion of the
low-pressure column and taking nitrogen in gaseous form
from an upper portion of the low-pressure column to
introduce the nitrogen as a product gas into a product
gas extraction passage; introducing the nitrogen in
gaseous form extracted for use as the reflux liquid from
the upper portion of the high-pressure column into a
condenser to liquefy the nitrogen; refluxing part of the
liquid nitrogen as the reflux liquid to the high-pressure
column and feeding the remainder of the liquid nitrogen
to the upper portion of the low-pressure column; and
introducing liquid nitrogen or liquid oxygen from outside
a system into the low-pressure column as a coolant for
supplementing heat loss in the heat exchanger or heat
entering from outside, wherein the liquid air taken
through the liquid air extraction passage is introduced
into a portion of a rectification part of the low-pressure
column in which the number of theoretical plates from
a column bottom side is set within the range of one to
ten. A second aspect of the present invention is intended
for an apparatus for generating nitrogen which comprises :
an air compression means for compressing air taken from
outside; a main heat exchanger for cooling the compressed
air compressed by the air compression means down to a
low temperature; a high-pressure column for cryogenically

separating the compressed air cooled down to the low
temperature through the main heat exchanger by using a
difference in boiling point between components in the
compressed air to store liquid air in a bottom portion
of the high-pressure column and to take nitrogen in gaseous
form for use as a reflux liquid from an upper portion
of the high-pressure column; a low-pressure column
receiving the liquid air taken from the bottom portion
of the high-pressure column through a liquid air
extraction passage and for cryogenically separating the
liquid air by using a difference in boiling point between
components in the liquid air to store oxygen-enriched
liquid air in a bottom portion of the low-pressure column
and to take nitrogen in gaseous form from an upper portion
of the low-pressure column; a product gas extraction
passage for receiving the nitrogen taken in gaseous form
from the upper portion of the low-pressure column as a
product gas; a condenser receiving the nitrogen in gaseous
form extracted for use as the reflux liquid from the upper
portion of the high-pressure column and for liquefying
the nitrogen; a reflux passage for refluxing part of the
liquid nitrogen taken from the condenser as the reflux
liquid to the high-pressure column; a feed passage for
feeding the remainder of the liquid nitrogen taken from
the condenser to the upper portion of the low-pressure


column; and an inlet passage for introducing liquid
nitrogen or liquid oxygen from outside a system into the
low-pressure column as a coolant for supplementing heat
loss in the heat exchanger or heat entering from outside,
wherein the liquid air taken through the liquid air
extraction passage is introduced into a portion of a
rectification part of the low-pressure column in which
the number of theoretical plates from a column bottom
side is set within the range of one to ten.
Effects of the Invention
In the course of studies for obtaining a nitrogen
generating method which is capable of significantly
reducing the amount of raw material air to accomplish
significant reductions in power consumption, the amount
of coolant and costs of facilities, and an apparatus for
use in the same, the present inventors have focused
attention on the fact that the process of feeding the
liquid air stored in the bottom portion of the
high-pressure column into the low-pressure column to
cryogenically separate the liquid air again enables the
low-pressure column to extract the nitrogen component
in the above-mentioned liquid air, thereby achieving an
improvement in the yield of the high purity nitrogen gas,
when the following steps are executed: compressing air


taken from outside by using the air compression means,
cooling the compressed air down to a low temperature in
the main heat exchanger and then introducing the
compressed air into the high-pressure column,
cryogenically separating the compressed air introduced
into the high-pressure column by using a difference in
boiling point between components in the compressed air,
storing liquid air in the bottom portion of the
high-pressure column and taking nitrogen in gaseous form
for use as a reflux liquid from the upper portion of the
high-pressure column, introducing the liquid air stored
in the bottom portion of the high-pressure column through
the liquid air extraction passage into the low-pressure
column, cryogenically separating the liquid air
introduced into the low-pressure column by using a
difference in boiling point between components in the
liquid air, storing oxygen-enriched liquid air in the
bottom portion of the low-pressure column and taking
nitrogen in gaseous form from the upper portion of the
low-pressure column to introduce the nitrogen as a product
gas to a product gas extraction passage, introducing the
nitrogen in gaseous form extracted for use as the reflux
liquid from the upper portion of the high-pressure column
into the condenser to liquefy the nitrogen, refluxing
part of the liquid nitrogen as the reflux liquid to the


high-pressure column and feeding the remainder of the
liquid nitrogen to the upper portion of the low-pressure
column, and introducing liquid nitrogen or liquid oxygen
from outside a system into the low-pressure column as
a coolant for supplementing heat loss in the heat exchanger
or heat entering from outside. Thus, the present
inventors have made a series of studies. As a result,
the present inventors have attained the present invention
by finding the fact that the introduction of the liquid
air taken through the liquid air extraction passage into
a portion of the rectification part of the low-pressure
column in which the number of theoretical plates from
a column bottom side is set within the range of one to
ten provides a significant improvement in the yield of
the high purity nitrogen gas to significantly reduce the
amount of raw material air, thereby accomplishing the
significant reductions in power consumption, the amount
of coolant and costs of facilities (thatis, accomplishing
the significant reductions in power consumption and the
costs of facilities by reducing the size of the facilities
related to raw material air, and accomplishing the
significant reduction in the amount of coolant by
significantly reducing the amount of coolant [the amount
of injection of the liquid nitrogen] which supplements
the heat loss in the main heat exchanger and by utilizing


the cooling energy of the liquid nitrogen injected into
the low-pressure column even in a low-pressure region).
In the present invention, an example of a rectification
means for use in the rectification part of the low-pressure
column may include a structure known as rectification
trays or packings (a structured packing, a random packing
and the like).
In the present invention, when an inlet of the inlet
passage is provided in a lower portion of the rectification
part of the low-pressure column, liquid nitrogen or liquid
oxygen may be introduced as a coolant into a lower space
of the rectification part of the above-mentioned
low-pressure column.
In the present invention, when an exhaust gas
outlet for introducing an exhaust gas in a lower portion
of the low-pressure column to outside is provided in a
lower portion of the rectification part of the
low-pressure column, the gas stored in the lower portion
of the above-mentioned low-pressure column and containing
less high purity nitrogen gas can be introduced as the
exhaust gas to the outside. This further improves the
yield of the high purity nitrogen gas extracted from the
upper portion of the above-mentioned low-pressure column .
Brief Description of Accompanying Drawings



Fig. 1 is a diagram showing a preferred embodiment
of a nitrogen generating apparatus according to the
present invention.
Fig. 2 is a diagram showing another preferred
embodiment of the nitrogen generating apparatus according
to the present invention.
Fig. 3 is a diagram showing a conventional
apparatus.
Description of Reference Numerals and Characters
11 high-pressure column
12 low-pressure column
12a rectification part
13 liquid air
16 condenser
20 extraction pipe
22 oxygen-enriched liquid air
Best Mode for Carrying Out the Invention
Next, a preferred embodiment according to the
present invention will now be described in detail, with
reference to the drawings.
Fig. 1 shows a preferred embodiment of a nitrogen
generating apparatus according to the present invention.
In Fig. 1, the reference numeral 1 designates a raw


material air compression apparatus which includes a raw
material air compressor 2 for compressing air taken from
outside (to a pressure of approximately 0.47 MPaG), a
heat exchanger 3 for heat-exchanging an exhaust gas taken
out of a low-pressure column 12 to be described later
and the compressed air which is compressed in the raw
material air compressor 2 to heat the exhaust gas up to
an increased temperature and to cool the compressed air
down to a decreased temperature, and a drain separator
4 . The reference numeral 5 designates a cooler for
cooling down the compressed air passed through the
above-mentioned raw material air compression apparatus
1 by using cooling water, and 6 and 7 designate air
pretreatment apparatuses including a pair of adsorption
columns for adsorptively removing moisture and carbon
dioxide from the compressed air passed through the
above-mentioned cooler 5. The reference numeral 8
designates a main heat exchanger of a plate-fin type.
The compressed air passed through the above-mentioned
adsorption columns 6 and 7 through a compressed air supply
pipe 9 is fed into the main heat exchanger 8. The main
heat exchanger 8 cools the compressed air down to an ultra
low temperature (approximately -175 °C ) by the heat
exchange action with a high purity nitrogen gas and an
exhaust gas to be described later.


The reference numeral 10 designates a
rectification column of a double rectification type which
includes a high-pressure column 11 (driven at a pressure
of approximately 0.45 MPaG) , and the low-pressure column
12 (driven at a pressure of approximately 0.04 MPaG)
provided over the high-pressure column 11. In the
above-mentioned high-pressure column 11, the compressed
air cooled by the main heat exchanger 8 and fed into a
lower portion of the high-pressure column 11 is further
cooled down and cryogenically separated by the use of
a difference in boiling point between components in the
compressed air, whereby a high boiling point component
(oxygen) in the compressed air is liquefied and stored
as liquid air 13 (having an oxygen concentration of
approximately 35% by volume) in a bottom portion of the
high-pressure column 11 whereas nitrogen as a low boiling
point component is taken in gaseous form from a top portion
of the high-pressure column 11.
The reference numeral 15 designates a first reflux
pipe for feeding the high purity nitrogen gas taken from
the top portion of the above-mentioned high-pressure
column 11 into a condenser 16 to be described below. The
high purity nitrogen gas fed by the first reflux pipe
15 into the condenser 16 is liquefied by the condenser
16. Part of the high purity liquid nitrogen is refluxed


as a reflux liquid through a second reflux pipe 17 to
the top portion of the above-mentioned high-pressure
column 11, whereas the remainder of the high purity liquid
nitrogen is introduced through a supply pipe 18 into a
super-cooler 19, is cooled down by the heat exchange with
the high purity nitrogen gas, and is then supplied to
the top portion of the above-mentioned low-pressure
column 12.
The reference numeral 20 designates an extraction
pipe (liquid air extraction passage) with an expansion
valve 20a for feeding the liquid air 13 stored in the
bottom portion of the above-mentioned high-pressure
column 11 to rectification tray parts (rectification
parts) 12a of the low-pressure column 12. In this
preferred embodiment, the above-mentioned liquid air 13
is fed to between the lowest rectification tray and the
tenth lowest rectification tray (both not shown) in the
rectification parts 12a of the low-pressure column 12.
The reference numeral 21 designates a liquid nitrogen
inlet pipe for feeding liquid nitrogen from a liquid
nitrogen tank (not shown) (supplied with liquid nitrogen
from the outside of the apparatus) into a lower portion
of the rectification tray parts 12a of the low-pressure
column 12. In the low-pressure column 12, the liquid
air 13 in a gas-liquid mixed state fed through the


extraction pipe 20 is further cooled down and
cryogenically separated by the use of a difference in
boiling point between components in the liquid air 13,
whereby a high boiling point component (oxygen) in the
liquid air 13 is liquefied and stored as oxygen-enriched
liquid air 22 (having an oxygen concentration of
approximately 90% by volume) in a bottom portion of the
low-pressure column 12 whereas nitrogen as a low boiling
point component is taken in gaseous form from a top portion
of the low-pressure column 12, as in the high-pressure
column 11. The high purity nitrogen gas taken from the
top portion of the low-pressure column 12 (having a
nitrogen concentration of approximately 100% by volume,
which is approximately equal to the nitrogen
concentration of the high purity nitrogen gas taken from
the top portion of the high-pressure column 11) is obtained
by feeding the liquid air 13 stored in the bottom portion
of the high-pressure column 11 into the low-pressure
column 12 and cryogenically separating the liquid air
13 again. The amount of nitrogen gas thus obtained is
much greater than the amount of nitrogen gas obtained
from a nitrogen generating apparatus of a single
rectification type.
The condenser 16 is immersed in the oxygen-enriched
liquid air 22 stored in the bottom portion of the


above-mentioned low-pressure column 12. As described
above, the condenser 16 liquefies the high purity nitrogen
gas taken from the top portion of the above-mentioned
high-pressure column 11, and evaporates the
oxygen-enriched liquid air 22 around the condenser 16
by heating to generate an ascending gas within the
low-pressure column 12. The ascending gas, the high
purity liquid nitrogen flowing down from the top portion
of the low-pressure column 12 and the liquid air 13
supplied to the rectification parts 12a of the
low-pressure column 12 are rectified by coming into
contact with each other, whereby the oxygen-enriched
liquid air 22 is stored in the bottom portion whereas
the high purity nitrogen gas is taken from the top portion,
as discussed above.
The reference numeral 23 designates an extraction
pipe for extracting the high purity nitrogen gas from
the top portion of the above-mentioned low-pressure
column 12. The high purity nitrogen gas is heated up
to room temperature by passing the high purity nitrogen
gas through the super-cooler 19 and the main heat exchanger
8. After a nitrogen compressor 24a in a nitrogen
compression apparatus 24 compresses the high purity
nitrogen gas to a predetermined pressure, the compressed
high purity nitrogen gas is introduced into a product


nitrogen gas extraction pipe (product gas extraction
passage) 25, and is supplied as a product nitrogen gas
to a customer site. The reference numeral 26 designates
an exhaust gas extraction pipe extending from the lower
portion of the rectification parts 12a of the
above-mentioned low-pressure column 12 (that is, a
portion below a liquid air inlet at which the liquid air
from the extraction pipe 2 0 enters the rectification parts
12a) . The exhaust gas extraction pipe 26 serves to
extract an exhaust gas (having an oxygen concentration
of approximately 80% by volume) generated by the
evaporation of the oxygen-enriched liquid air 22 in the
bottom portion of the above-mentioned low-pressure column
12. This exhaust gas is introduced by the exhaust gas
extraction pipe 26 into the main heat exchanger 8 and
is heated therein up to room temperature. After the
heated exhaust gas is further heated in the heat exchanger
3, the heated exhaust gas is used as a regenerating gas
for the adsorption columns 6 and 7, and is released to
the atmosphere. In Fig. 1, the reference character 24b
designates a cooler in the nitrogen compression apparatus
24.
The reference numeral 28 designates a backup system
line in which backup liquid nitrogen evaporators 28b
evaporate liquid nitrogen within a backup liquid nitrogen


tank 28a to feed the nitrogen gas into the product nitrogen
gas extraction pipe 25, thereby avoiding the interruption
of the supply of nitrogen gas when the present apparatus
fails or there arises a shortage of the product nitrogen
gas. In Fig. 1, the reference numeral 29 designates a
cold box for vacuum insulating the interior thereof.
This nitrogen generating apparatus produces a
product nitrogen gas in a manner to be described below.
First, the raw material air compressor 2 takes air from
outside thereinto to compress the air. The compressed
air is passed through the heat exchanger 3, the drain
separator 4 and the cooler 5 so that moisture is removed
from the compressed air and the compressed air is cooled
down. Thereafter, the compressed air is fed into the
adsorption column 6 (7) so that moisture and carbon dioxide
are adsorptively removed from the compressed air. Next,
the compressed air from which moisture and carbon dioxide
are adsorptively removed is fed through the compressed
air supply pipe 9 into the main heat exchanger 8, and
is cooled down to an ultra low temperature in the main
heat exchanger 8. The cooled compressed air is
introduced into the lower portion of the high-pressure
column 11. Next, the introduced compressed air is cooled
down by bringing the compressed air into countercurrent
contact with the reflux liquid passed through the


condenser 16 back to the top portion of the high-pressure
column 11. Part of the cooled air is liquefied and stored
as the liquid air 13 in the bottom portion of the
high-pressure column 11. The liquidair 13 is fedthrough
the extraction pipe 20 with the expansion valve 20a into
the low-pressure column 12 to cool down the condenser
16. This cooling liquefies the high purity nitrogen gas
fed from the top portion of the high-pressure column 11
into the condenser 16. Part of this high purity liquid
nitrogen becomes the reflux liquid which in turn passes
through the second reflux pipe 17 back to the top portion
of the high-pressure column 11, whereas the remainder
of the high purity liquid nitrogen passes through the
supply pipe 18, is cooled down by the super-cooler 19,
and is supplied to the top portion of the above-mentioned
low-pressure column 12. In the course of cooling by
contacting the introduced compressed air and the reflux
liquid within the high-pressure column 11 as described
above, oxygen serving as the high boiling point component
in the compressed air is liquefied and flows down and
the nitrogen remains in gaseous form in the top portion
of the high-pressure column 11 and is fed through the
first reflux pipe 15 into the condenser 16 because of
the difference in boiling point between nitrogen and
oxygen.


On the other hand, the liquid nitrogen serving as
a cooling source is fed from the liquid nitrogen tank
through the liquid nitrogen inlet pipe 21 into the
low-pressure column 12 . The ascending gas generated from
the oxygen-enriched liquid air 22 within the low-pressure
column 12 is cooled by bringing the ascending gas into
countercurrent contact with the high purity liquid
nitrogen supplied from the condenser 16 to the top portion
of the low-pressure column 12 and the liquid air 13
introduced into the low-pressure column 12. In the
course of this cooling, oxygen serving as the high boiling
point component in the compressed air is liquefied, flows
down and is stored as the oxygen-enriched liquid air 22
in the bottom portion of the low-pressure column 12 to
cool down the condenser 16, and the nitrogen in gaseous
form is taken from the top portion of the high-pressure
column 11 through the extraction pipe 23 into the
super-cooler 19 and the main heat exchanger 8, heated
up to near room temperature and is fed out as the product
nitrogen gas because of the difference in boiling point
between nitrogen and oxygen. The exhaust gas in the
bottomport ion of the above-mentioned low-pressure column
12 is taken out by the exhaust gas extraction pipe 26,
is used as the regenerating gas for the adsorption columns
6 and 7, and is released to the atmosphere.


As described above, this preferred embodiment uses
the rectification column 10 of the double rectification
type to feed the liquid air 13 stored in the bottom portion
of the high-pressure column 11 into the low-pressure
column 12, thereby cryogenically separating the liquid
air 13 again. Thus, the yield of the high purity nitrogen
gas is significantly improved (improved up to an A/N ratio
approximately equal to 1. 4) . This significantly reduces
the amount of raw material air to reduce the size of the
facilities related to the raw material air (the raw
material air compressor 2, the pair of adsorption columns
6 and 7, their incidental piping facilities and the like) ,
thereby reducing power consumption and costs of
facilities. Additionally, this preferred embodiment
significantly reduces the amount of coolant (the amount
of injection of the liquid nitrogen) which supplements
the heat loss in the main heat exchanger 8, and utilizes
the cooling energy of the liquid nitrogen injected into
the low-pressure column 12 even in a low-pressure region
to further reduce the amount of injection of the liquid
nitrogen. Further, this preferred embodiment reduces
the size of the cold box 29 to decrease the heat leak
from the cold box 29, thereby accomplishing the further
reduction in the amount of injectionofthe liquid nitrogen.
In this preferred embodiment, the amount of injection


of the liquid nitrogen can be reduced to approximately
0.5% of the amount of product nitrogen.
Fig. 2 shows a second preferred embodiment of the
nitrogen generating apparatus according to the present
invention. The second preferred embodiment is adapted
to feed liquid nitrogen as a cooling source from the liquid
nitrogen tank to the top portion of the low-pressure column
12 in the first preferred embodiment described above.
Other parts of the second preferred embodiment are similar
to those of the first preferred embodiment, and like
reference numerals and characters are used to designate
similar parts . The second preferred embodiment produces
functions and effects similar to those of the first
preferred embodiment described above.
The first and second preferred embodiments
described above use the rectification tray parts as the
rectification parts 12a of the above-mentioned
high-pressure column 11 (that is, the rectification is
carried out by rectification trays). The present
invention, however, is not limited to this. The
rectification may be carried out by using various packings
such as a structured packing, a random packing and the
like. In this case, the liquid air 13 to be stored in
the bottom portion of the above-mentioned high-pressure
column 11 is introduced into a portion of the packing


having a height corresponding to the first to tenth
theoretical plates in the rectification parts 12a which
accommodate the packing. The liquid nitrogen is
introduced into the lower portion of the rectification
parts 12a of the low-pressure column 12 or the upper
portion of the rectification parts 12a such as the top
portion in the first and second preferred embodiments
described above, but may be introduced into any portion
(including the rectification parts 12a) of the
low-pressure column 12 or into any portion of the
high-pressure column 11. The liquid nitrogen is
introduced into the low-pressure column 12 as the cooling
source in the first and second preferred embodiments
described above. However, liquid air may be introduced
in place of the liquid nitrogen.
Industrial Applicability
The present invention significantly improves the
yield of the high purity nitrogen gas to significantly
reduce the amount of raw material air, thereby
accomplishing significant reductions in power
consumption, the amount of coolant and the costs of
facilities.


WE CLAIM:
1. A method of generating nitrogen comprising: compressing air taken from
outside by using an air compression means; after introducing the
compressed air into an adsorption column to adsorptively remove
moisture and carbon dioxide, cooling the compressed air down to a low
temperature in a main heat exchanger and then introducing the
compressed air into a high-pressure column; cryogenically separating the
compressed air introduced into the high-pressure column by using a
difference in boiling point between components in the compressed air;
storing liquid air in a bottom portion of the high-pressure column and
taking nitrogen in gaseous form for use as a reflux liquid from an upper
portion of the high-pressure column; introducing the liquid air stored in the
bottom portion of the high-pressure column through a liquid air extraction
passage into a low-pressure column; cryogenically separating the liquid air
introduced into the low-pressure column by using a difference in boiling
point between components in the liquid air; storing oxygen-enriched liquid
air in a bottom portion of the low-pressure column and taking nitrogen in
gaseous form from an upper portion of the low-pressure column to
introduce the nitrogen as a product gas into a product gas extraction


passage; introducing the nitrogen in gaseous form extracted for use as the
reflux liquid from the upper portion of the high-pressure column into a
condenser to liquefy the nitrogen; refluxing part of the liquid nitrogen as the
reflux liquid to the high-pressure column and feeding the remainder of the
liquid nitrogen to the upper portion of the low-pressure column; and
introducing liquid nitrogen or liquid oxygen from outside a system into the low-
pressure column as a coolant for supplementing heat loss in the heat
exchanger or heat entering from outside,
wherein the liquid air in a bottom portion of the high-pressure column taken
through the liquid air extraction passage is introduced into a portion of a
rectification part of the low-pressure column in which the number of
theoretical plates from a column bottom side is set within the range of one to
ten; oxygen-enriched air in gaseous form is taken from an exhaust gas outlet
provided at only one part below the rectification part of the low-pressure
column and above the condenser; the oxygen-enriched air is introduced into
the main heat exchanger to cool the compressed air and then introduced into
the heat exchanger of the air compression means and the adsorption column;
and after being used as a cold source for the air compression means and as
a regenerating gas for the adsorption column, the oxygen-enriched air is
released to the atmosphere.


2. An apparatus for generating nitrogen comprising: an air compression
means for compressing air taken from outside; an adsorption column for
adsorptively removing moisture and carbon dioxide from the compressed
air compressed by the air compression means; a main heat exchanger for
cooling the compressed air passed through the adsorption column to a low
temperature; a high-pressure column for cryogenically separating the
compressed air cooled down to the low temperature through the main heat
exchanger by using a difference in boiling point between components in
the compressed air to store liquid air in a bottom portion of the high-
pressure column and to take nitrogen in gaseous form for use as a reflux
liquid from an upper portion of the high-pressure column; a low-pressure
column receiving the liquid air taken from the bottom portion of the high-
pressure column through a liquid air extraction passage and for
cryogenically separating the liquid air by using a difference in boiling point
between components in the liquid air to store oxygen-enriched liquid air in
a bottom portion of the low-pressure column and to take nitrogen in
gaseous form from an upper portion of the low-pressure column; a product
gas extraction passage for receiving the nitrogen taken in gaseous form
from the upper portion of the low-pressure column as a product gas; a
condenser receiving the nitrogen in gaseous form extracted for use as the


reflux liquid from the upper portion of the high-pressure column and for
liquefying the nitrogen; a reflux passage for refluxing part of the liquid nitrogen
taken from the condenser as the reflux liquid to the high-pressure column; a
feed passage for feeding the remainder of the liquid nitrogen taken from the
condenser to the upper portion of the low-pressure column; and an inlet
passage for introducing liquid nitrogen or liquid oxygen from outside a system
into the low-pressure column as a coolant for supplementing heat loss in the
heat exchanger or heat entering from outside,
wherein the liquid air in a bottom portion of the high-pressure column taken
through the liquid air extraction passage is introduced into a portion of a
rectification part of the low-pressure column in which the number of
theroretical plates from a column bottom side is set within the range of one to
ten; oxygen-enriched air in gaseous form is taken from an exhaust gas outlet
provided at only one part below the rectification part of the low-pressure
column and above the condenser; the oxygen-enriched air is introduced into
the main heat exchanger to cool the compressed air and then introduced into
the heat exchanger of the air compression means and the adsorption column;
and after being used as a cold source for the air compression means and as
a regenerating gas for the adsorption column, the oxygen-enriched air is
released to the atmosphere.

3. The apparatus as claimed in claim 2, wherein an inlet of the inlet passage
is provided at the bottom of the rectification part of the low-pressure
column.


There is provided a method of generating nitrogen
which includes cryogenically separating compressed air
introduced into a high-pressure column 11, storing liquid
air 13 in a bottom portion of the high-pressure column
11 and taking nitrogen in gaseous form from an upper
portion of the high-pressure column 11, introducing the
liquid air 13 stored in the bottom portion of the
high-pressure column 11 into a low-pressure column 12,
cryogenically separating the liquid air 13 introduced
into the low-pressure column 12 and storing
oxygen-enriched liquid air 22 in a bottom portion of the
low-pressure column 12 and taking nitrogen in gaseous
form from an upper portion of the low-pressure column
12 as a product gas. Liquid air 13 taken through an
extraction pipe 20 is introduced into a portion of a
rectification part 12a of the low-pressure column 12 in
which the number of theoretical plates from a column bottom
side is set within the range of one to ten.

Documents:

00261-kolnp-2008-abstract.pdf

00261-kolnp-2008-claims.pdf

00261-kolnp-2008-correspondence others.pdf

00261-kolnp-2008-description complete.pdf

00261-kolnp-2008-drawings.pdf

00261-kolnp-2008-form 1.pdf

00261-kolnp-2008-form 2.pdf

00261-kolnp-2008-form 3.pdf

00261-kolnp-2008-form 5.pdf

00261-kolnp-2008-international publication.pdf

00261-kolnp-2008-pct request form.pdf

261-KOLNP-2008-ABSTRACT 1.1.pdf

261-KOLNP-2008-CANCELLED PAGES.pdf

261-KOLNP-2008-CLAIMS 1.1.pdf

261-KOLNP-2008-CORRESPONDENCE 1.1.pdf

261-KOLNP-2008-CORRESPONDENCE OTHERS 1.1.pdf

261-kolnp-2008-correspondence.pdf

261-KOLNP-2008-DESCRIPTION (COMPLETE) 1.1.pdf

261-KOLNP-2008-DRAWINGS 1.1.pdf

261-kolnp-2008-examination report.pdf

261-KOLNP-2008-FORM 1 1.1.pdf

261-kolnp-2008-form 18.1.pdf

261-kolnp-2008-form 18.pdf

261-KOLNP-2008-FORM 2 1.1.pdf

261-KOLNP-2008-FORM 3 1.1.pdf

261-KOLNP-2008-FORM 3-1.1.pdf

261-kolnp-2008-form 3.pdf

261-kolnp-2008-form 5.pdf

261-KOLNP-2008-FORM-27.pdf

261-kolnp-2008-granted-abstract.pdf

261-kolnp-2008-granted-claims.pdf

261-kolnp-2008-granted-description (complete).pdf

261-kolnp-2008-granted-drawings.pdf

261-kolnp-2008-granted-form 1.pdf

261-kolnp-2008-granted-form 2.pdf

261-kolnp-2008-granted-specification.pdf

261-KOLNP-2008-INTERNATIONAL PRELIMINARY REPORT.pdf

261-KOLNP-2008-INTERNATIONAL SEARCH AUTHORITY REPORT.pdf

261-KOLNP-2008-OTHERS.pdf

261-kolnp-2008-others1.1.pdf

261-KOLNP-2008-PA.pdf

261-kolnp-2008-pa1.1.pdf

261-KOLNP-2008-PETITION UNDER RULE 137 1.1.pdf

261-KOLNP-2008-PETITION UNDER RULE 137.pdf

261-KOLNP-2008-REPLY TO EXAMINATION REPORT.pdf

261-kolnp-2008-reply to examination report1.1.pdf

261-KOLNP-2008-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

261-kolnp-2008-translated copy of priority document1.1.pdf

abstract-00261-kolnp-2008.jpg


Patent Number 248137
Indian Patent Application Number 261/KOLNP/2008
PG Journal Number 25/2011
Publication Date 24-Jun-2011
Grant Date 21-Jun-2011
Date of Filing 18-Jan-2008
Name of Patentee AIR WATER INC.
Applicant Address 2, KITA 3-JO NISHI 1-CHOME, CHUO-KU, SAPPORO-SHI HOKKAIDO
Inventors:
# Inventor's Name Inventor's Address
1 AKIRA YOSHINO C/O AIR WATER INC. HEADQUARTER, 1-20-16, HIGASHISHINSAIBASHI, CHUO-KU, OSAKA-SHI, OSAKA 542-0083
2 RYOSUKE MATSUBAYASHI C/O AIR WATER INC., SAKAI OFFICE, 2-6-40, CHIKKO-SHINMACHI, SAKAI-SHI, OSAKA 592-8331
3 JUNYA SUENAGA C/O AIR WATER INC., SAKAI OFFICE, 2-6-40, CHIKKO-SHINMACHI, SAKAI-SHI, OSAKA 592-8331
4 SHINYA OKUMURA C/O AIR WATER INC., SAKAI OFFICE, 2-6-40, CHIKKO-SHINMACHI, SAKAI-SHI, OSAKA 592-8331
5 KOJI TANAKA 2-10-8, KONGO, OSAKASAYAMA-SHI, OSAKA 589-0006
PCT International Classification Number F25J 3/04,C01B 21/04
PCT International Application Number PCT/JP2006/312103
PCT International Filing date 2006-06-16
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2005-183898 2005-06-23 Japan