JPH11316079A - Operating method for nitrogen generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operating method for a nitrogen generator capable of preferably meeting various kinds of operating conditions requested by a user. SOLUTION: A nitrogen generator comprises a rectifying tower 5 for applying a low temperature separation to feed air to produce liquid nitrogen and gas nitrogen, a feed air inlet valve 8 for adjusting the quantity of the feed air supplied to the rectifying tower 5 and a microcomputer 17 in which various data D1 to D15 for operating the device is stored. To the microcomputer 17, the extract data D16 and D17 of liquid nitrogen and gas nitrogen are inputted. The feed air inlet valve 8 is controlled depending on the calculated result based on the extract data D16 and D17 and the various kinds of data D1 to D15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for operating a nitrogen generator by a cryogenic separation method.

[0002]

2. Description of the Related Art In this type of nitrogen generating apparatus, the conditions of each part of the apparatus and the set product gas nitrogen generation amount and product liquid nitrogen generation amount are input to a microcomputer to calculate a necessary raw material air amount. The method of automatically operating by outputting as the set value of the raw material air amount controller,
For example, it is known as seen in JP-A-62-123279.

This automatic operation method is operated in a purity priority mode in which the purity of product nitrogen is almost constant, and the amount of liquefied raw material air during the simultaneous production of product gas nitrogen and product liquid nitrogen is the same as the amount of product liquefied nitrogen. Was treated as a quantity.

[0004]

As described above, the conventional automatic operation method operates only in the purity priority mode,
In addition, since the change in the liquefaction rate of the raw material air during the simultaneous production of product gas nitrogen and liquid nitrogen was not taken into account, there was a problem that it was not possible to suitably cope with various operating conditions required by the user.

Accordingly, it is an object of the present invention to provide a method for operating a nitrogen generator which can suitably cope with various operating conditions required by a user.

[0006]

In order to achieve the above-mentioned object, the present invention provides a method of supplying raw material air cooled by an expansion turbine driven by waste gas from a rectification tower to the rectification tower, A nitrogen generator that generates product gas nitrogen and product liquid nitrogen by a cold separation method. The amount of raw material air required by using the conditions of each part of the device and the set product gas nitrogen generation amount and product liquid nitrogen generation amount And operating the nitrogen generator to output the set value as a set value of the raw material air regulator, wherein one of the following methods (a) to (g) is performed. .

(A) In the purity priority mode in which the purity of the product nitrogen is substantially constant, the amount of the raw material air is automatically corrected in accordance with the liquefaction rate of the raw material air which changes depending on the amount of the product gas nitrogen to be collected and the amount of the product liquid nitrogen. I do.

(B) Calculating the raw material air amount according to the liquid nitrogen collection amount priority mode characteristic mainly based on the product liquid nitrogen collection amount depending on the amount of cold applied to the raw material air.

(C) Calculating the raw material air amount according to the purity priority mode characteristic and the liquid nitrogen collection priority mode characteristic.

(D) It is determined whether one point given by the set product gas nitrogen generation amount and the product liquid nitrogen generation amount belongs to one of the two mode characteristics, and the raw material is determined according to the determined mode characteristic. Calculate the air volume.

(E) The pressure of the liquid air supplied to the nitrogen condenser provided in the rectification column is automatically controlled according to the set liquid air pressure so that the product nitrogen pressure becomes substantially constant.

(F) At least two of the product gas nitrogen generation amount and the product liquid nitrogen generation amount obtained during the initial operation of the apparatus.
From the point data, an operation characteristic line, for example, an operation characteristic line at the time of rated operation, at the time of reduction operation or at the time of increase operation is obtained, and one point on the characteristic line of the purity priority mode and one point of the characteristic line of the liquid nitrogen collection priority mode, An operation characteristic line composed of a purity priority mode characteristic line and a liquid nitrogen collection priority mode characteristic line is obtained from data of at least three points, that is, one point which is a branch point of both mode characteristic lines, and the raw material air amount is determined according to the operation characteristic line. Calculate,
Alternatively, a mode division characteristic line that divides both mode regions is obtained from two points, which are branch points of both mode characteristic lines in the two operation characteristic lines, and the product gas nitrogen generation amount set above is determined using the mode division characteristic line. It is determined in which of the two modes the point given by the product liquid nitrogen generation amount is, and the amount of the raw material air is calculated according to the mode characteristics of the determined area.

(G) detecting any one of the product nitrogen purity, the cooling amount, and the product nitrogen pressure, and when the detected value is out of any of the corresponding product nitrogen purity range, the cooling amount range, and the product nitrogen pressure range, Product nitrogen purity and refrigeration volume so that any of the detected product nitrogen purity, refrigeration amount, and product nitrogen pressure fall within the applicable product nitrogen purity range, refrigeration range, and product nitrogen pressure range. Automatically corrects the raw material air amount and the liquid nitrogen pressure set for the product nitrogen pressure.

Since the present invention is constructed as described above, it operates as follows. That is, according to the above configuration (a), the purity of the product nitrogen is always a constant value, so that it is possible to prevent waste of power consumption due to an excessive amount of the raw material air and deterioration of the purity of the product nitrogen due to a shortage of the raw material air. .

According to the configuration (b), the amount of product gas nitrogen is adjusted according to the required amount of product liquid nitrogen, and the amount is supplied to an expansion turbine to increase the amount of refrigeration, thereby obtaining product liquid nitrogen. The amount can be increased.

Further, with the configuration (c), the operation can be performed with each mode characteristic suitable for the product gas nitrogen amount and the product liquid nitrogen amount to be collected.

According to the configuration (d), operation with incorrect mode characteristics can be prevented.

[0018] Further, according to the above configuration (e), the operation can be performed in a state where the product nitrogen pressure is substantially constant irrespective of a change in the pressure of the liquid air supplied to the nitrogen condenser.

Further, according to the configuration (f), the product gas nitrogen generation amount and the product liquid nitrogen generation amount at the time of design are corrected with the actual product gas nitrogen generation amount and product liquid nitrogen generation amount data obtained during the initial operation. , Suitable operation can be performed.

Further, according to the configuration (g), even if the product nitrogen purity, the cooling amount, and the product nitrogen pressure change due to external conditions during operation, aging, etc., the command values corresponding to these are feedback-controlled. Correction is made automatically, and a suitable operation can always be performed.

Accordingly, it is possible to perform a suitable operation corresponding to various operation conditions required by the user.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
7 will be described.

FIG. 2 is a system diagram showing an example of a nitrogen generator to which the present invention is applied.

In this figure, 1 is a raw material air compressor, 2
Is an adsorption tower, 3 is an expansion turbine, 4 is an air heat exchanger, 5 is a rectification tower, 5a and 5b are rectification plates and a liquid air reservoir, 6
Is a nitrogen condenser, 7 is a liquid nitrogen tank, 8 is a raw air inlet valve, 9 is a turbine inlet valve, 10 is a bypass valve, 11 is a pressure reducing valve, 12 is a purity meter, 13 is a pressure gauge, 14 is a liquid level gauge, 1
Reference numeral 5 denotes a bypass valve opening detector, of which a part of the expansion turbine 3 and the air heat exchanger 4, the rectification tower 5, the nitrogen condenser 6, the turbine inlet valve 9, the bypass valve 10, and the pressure reducing valve 1
1. The liquid level gauge 14 and the bypass valve opening detector 15 are housed in a cool tank 16. Reference numeral 17 denotes a microcomputer, and reference numerals 18 and 19 denote input interfaces and input / output interfaces.

In the nitrogen generator having such a configuration,
The raw material air, which has been pressurized to 7 to 9 kg / cm ² G by the raw material air compressor 1, enters the adsorption tower 2 and liquefies and solidifies during cooling, causing carbon dioxide gas and moisture which cause clogging of the air heat exchanger 4 and the like. After it is removed, it enters the cooling tank 16. The raw material air entering the cold storage tank 16 is heat-exchanged with the product nitrogen gas from the rectification tower 5 and the waste gas from the expansion turbine 3 by the air heat exchanger 4, and cooled to about -165 to -175 ° C. The part enters the rectification column 5 in a liquefied state. Here, the gaseous raw material air rises in the rectification tower 5, and comes into gas-liquid contact with the descending liquid on the rectification plate 5a provided in the rectification tower 5 to become nitrogen-rich. Then, product nitrogen having a nitrogen purity equal to or lower than a specified value is collected from the upper portion of the rectification column 5. The product nitrogen collected in a gaseous state enters the air heat exchanger 4, where the temperature is restored to room temperature, and then supplied to the place of use. The product nitrogen collected in a liquid state is stored in a liquid nitrogen tank 7. On the other hand, the oxygen-rich liquid air which becomes a descending liquid in the rectification tower 5 and falls below the rectification tower 5 is taken out from the rectification tower 5 and decompressed to 3 to 4 kg / cm ² G by the pressure reducing valve 11 to about 7 ° C. The temperature is lowered, and is supplied to the liquid air reservoir 5b installed above the rectification tower 5. This liquid air is heat-exchanged with a part of the product nitrogen gas in the nitrogen condenser 6, becomes gaseous, enters the air heat exchanger 4, and has a temperature of −140 to −15.
After the temperature is recovered to about 0 ° C, it enters the expansion turbine 3 and
The amount of heat consumed in the cold storage tank 16, that is, the amount of cold corresponding to the cooling loss, the generation of liquid nitrogen, and the like is generated by the adiabatic expansion. The gas discharged from the expansion turbine 3 enters the air heat exchanger 4 and exchanges heat with the raw material air to recover the temperature to room temperature. Then, the gas is used as a regeneration gas for the adsorption tower 2, that is, as a gas for removing carbon dioxide gas, moisture and the like. It is released into the atmosphere after being used.

FIG. 1 is an operation characteristic diagram showing the relationship between the amount of gas nitrogen generated by the nitrogen generator and the amount of liquid nitrogen.
QAMAX and QAR are characteristic lines when the raw material air amount is rated, increased, and decreased. (A), which are indicated by oblique lines,
(B) and (C) are a region where the maximum collection amount of gas nitrogen exceeds GNMAX, a region where the maximum collection amount of liquid nitrogen exceeds LNMAX, and a region where the minimum collection amount of gas nitrogen GNMIN is not reached.

First, the characteristic line QAG when the raw material air amount is rated
Will be described. This characteristic line QAF corresponds to the first point (G
NB1, LNB1) and a second point (GNB2, LNB2)
F (GAST1) connecting the second point (GNB2,
LNB2) and a straight line f (GAST2) connecting the third point (GNB3, LNB3). The first point (GNB
1, LNB1 (= 0)) is an operation for collecting only nitrogen gas when the liquid nitrogen tank 7 is full, for example, and it is not necessary to collect liquid nitrogen. The squeezing and the amount of cold have been reduced. The gas nitrogen amount GND1 at this first point is determined to a value such that the nitrogen purity becomes a specified value. That is, it is the nitrogen purity priority mode. The amount of gas that can be supplied to the expansion turbine 3 is the amount obtained by subtracting the amount of product gas nitrogen and the amount of product liquid nitrogen from the amount of raw material air supplied to the cool tank 16, that is, the amount of waste gas. , You only need to use some of them.

When it becomes necessary to collect not only gaseous nitrogen but also liquid nitrogen, the amount of waste gas supplied to the expansion turbine 3 is increased as compared with the case of collecting only gaseous nitrogen. At this time, it is necessary to consider the liquefaction rate of the raw material air as described later, but in order to set the purity priority mode in which the nitrogen purity is almost constant, the sum of the gas nitrogen amount and the liquid nitrogen amount is substantially constant. Thus, the waste gas is supplied to the expansion turbine 3. However, the amount of gas that can be supplied to the expansion turbine 3 is the amount obtained by subtracting the amount of product gas nitrogen and the amount of product liquid nitrogen from the amount of raw material air supplied to the cool tank 16 as described above, that is, the amount of waste gas. Only a large amount of the waste gas can be supplied to the expansion turbine 3 as a large amount. In the purity priority mode, the gas nitrogen amount and the liquid nitrogen amount obtained when the exhaust gas amount is supplied to the expansion turbine 3 are the second points, GNB2 and LNB2. And
When the amount of liquid nitrogen is to be increased, the purity priority mode is stopped, the amount of gas nitrogen is reduced, the amount of waste gas is increased, and the load on the expansion turbine 3, that is, the amount of liquid nitrogen, is increased. Set to collection priority mode. At this time, the amounts of gas nitrogen and liquid nitrogen are the third points of GNB3 and LNB.
3.

To summarize the above, the first point (GNB1,
A straight line f (GAST1) connecting the second point (GNB2, LNB2) and the second point (GNB2, LNB2) is a purity priority mode characteristic line that makes nitrogen purity substantially constant, and a second point (GNB2, LNB2) and a third point (GNB3, LNB2). LNB3) connecting straight line f (GAST
2) is a liquid nitrogen sampling priority mode characteristic line depending on the amount of cooling of the expansion turbine, and the branch point between these characteristic lines is the second characteristic line.
(GNB2, LNB2).

Purity priority mode characteristic line f (GAMAX1)
And a liquid nitrogen collection priority mode characteristic line f (GAMAX2), and an operation characteristic line QAMAX at the time of increase, and a purity priority mode characteristic line f (GARE1) and a liquid nitrogen collection priority mode characteristic line f (GARE2). The characteristic line QAR can be drawn in the same manner as the rated operation characteristic line QAF described above. In addition, a branch point of both operation characteristic lines, for example, a second point (GNB2, LNB2) and a fourth point (GNB2)
4, LNB4), a mode segmentation characteristic line f (SP) for segmenting both mode regions can be obtained.

Next, the liquefaction rate of the raw air will be described. As described above, the straight line f connecting the first point and the second point
(GAST1) Above is the purity priority mode. Nitrogen purity is determined by the descending liquid L ₂ and the rising gas V
(L ₂ / V). When feed air into the rectification column is supplied, as described above, some of which become liquefied and the liquid air L _1. This liquefaction amount is the expansion turbine 3
, That is, the amount of cooling, the amount of liquid nitrogen collected in the purity priority mode increases, the amount of cooling of the expansion turbine 3 also increases, and the amount of liquefaction also increases. The increase in the liquefied amount is alpha, when a constant amount of added liquid nitrogen content gas nitrogen content, the ratio of rising gas V and the descending liquid L ₂ is _{(L 2 -α) / (V} -α) , And is smaller than the ratio (L ₂ / V) when the liquefaction rate is not considered, so that the nitrogen purity is deteriorated. Therefore, in the purity priority mode, gas nitrogen that collects not only gas nitrogen but also liquid nitrogen,
When co-producing liquid nitrogen, it is necessary to reduce the nitrogen recovery rate in consideration of changes in the amount of liquefied raw material air. That is, (GNB2 + LNB2) at the second point is smaller than (GNB1 + LNB1) at the first point.

FIGS. 3 to 6 are flowcharts showing one example of the operation process of the present invention.

First, in process 1, each of the input data D ₁ to
D ₁₇ is input to the microcomputer 17 via the input interface 18. Among the input data, D ₁ to
D ₁₅ is such as configuration data The data and programs during that obtained during the initial operation of such test runs, is intended to be entered during the initial setup, the normal, as the user by entering only D _16, D ₁₇ It looks good.

The respective input data will be described.
D ₁ is the maximum value QAMAX feed air quantity, the maximum amount that Suikome the plant side, which is a value determined from such as the ability of the feed air compressor 1. D ₂ is the minimum value QAMIN the feed air amount at the time of steady operation of the feed air compressor 1, which is a value determined from the weight loss limit of plant or feed air compressor 1. D ₃
Is a miscellaneous air volume QBG, a measuring device before entering the cold storage tank 16,
This is the total value of the amount of air supplied to the adsorption tower 2, the expansion turbine 3, and the like. D ₄ is the minimum value GNMIN gas nitrogen content to determine the area (C) of FIG. 1 is a value set to prevent become like flooding too reducing gas nitrogen collection amount. D ₅ is the largest collection amount LNMAX liquid nitrogen quantity to determine the region (B) of FIG. 1 is a value determined from the ability of the expansion turbine 3. D ₆ to D ₉ and D ₁₀ to D ₁₃ is the value of each gas nitrogen content and the liquid nitrogen amount in the first to fourth points of FIG. D ₁₄ is at the rated, i.e. the first to third point on the operation characteristic line QAF in FIG 1 (GNB1~GNB3, L
Is the value of the feed air amount in NB1～LNB3), also D ₁₅ is a weight loss upon, that is, the value of the feed air volume in the fourth point (GNB4, LNB4) is a branch point of the operating characteristic curve QAR in FIG . D ₁₆ and D ₁₇ are the values of the amount of gas nitrogen and the amount of liquid nitrogen GNINP and LNIN to be collected.
P is data input by the user during driving as described above.

When these data D _{1 to} D ₁₇ are input to the microcomputer 16, as a process 2, the waste gas concentration CB 1 at the time of collecting only the gas nitrogen at the first point (GNB 1, LNB 1) is determined as follows. It is calculated by equation (1).

CB1 = {(QAF−QBG) × 0.2095 {(QAF−QBG) − (GNB1 + LNB1)} (1) In process 3, using this waste gas concentration CB1, the following (2) According to the equation, when the amount is increased, that is, the operation characteristic line QAMAX
GNMAX is calculated as the maximum amount of gaseous nitrogen collected in the step (a).

GNMAX = {(QAMAX−QBG) × (CB1−0.2095)} CB1 (2) Then, in process 4, the data D ₁₆ ,
D ₁₇ , the value of the amount of gas nitrogen to be collected GNI
It is determined whether or not the value of NP and the value of liquid nitrogen LNINP are inside the regions (A) to (C) in FIG. 1. If not, the values GNINP and LNIN are not included.
Automatically correct GINNP to GNMAX or GNMIN and LNINP to LNMAX so that P is inside.

Next, in process 5, the data D ₁₆ , D
_It is further determined which of ₁₇ is the purity priority mode area (above the broken line) or the liquid nitrogen collection priority mode area (below the broken line) in FIG. That is, the gas nitrogen amount GNSP at the intersection of the purity priority mode characteristic line f (GAMAX1) and the mode classification characteristic line f (SP) of the operation characteristic line QAMAX when the raw material air amount is increased is expressed as f (GAMAX1) = f
As (SP), calculated is the data D ₁₆ GNINP
Is greater than or equal to this GNSP.
Whether NP is above f (SP), that is, f (S
P) Obtain the gas nitrogen amount corresponding to LNINP above, and
Check if INP is greater than this gas nitrogen amount,
If it is larger than NSP or larger than the gas nitrogen amount on f (SP), it is determined that the gas is in the purity priority mode area, and the flow proceeds to the calculation in the purity priority mode. It is determined that there is, and the processing shifts to the calculation in the liquid nitrogen collection priority mode.

Process 6 is a process for re-determining LNINP. When it is determined in process 5 that LNINP is in the purity priority mode area, LNINP is changed to the characteristic line f (GAMAX).
1), that is, LNINP is smaller than the amount of liquid nitrogen corresponding to GNINP on f (GAMAX1). If it is determined that LNINP is in the liquid nitrogen collection priority mode area, LNINP is changed to the characteristic line f. (GA
MAX2), that is, f (GAMAX)
2) From the amount of liquid nitrogen corresponding to GINNP above, LNIN
Check that P is small. If it is outside of both characteristic lines, LNINP is automatically corrected to be the liquid nitrogen amount corresponding to GNINP on both characteristic lines.

In the next process 7, the optimum raw material air amount QA is calculated for each of the two modes. At this time, in the purity priority mode, as described above, the correction coefficient ε due to the change in the liquefied amount of the raw air is calculated by the following equation (3), and the optimum raw air quantity QA is calculated using the coefficient ε as shown in the following (4). It is calculated by the formula.

Ε = ｛(GNB1 + LNB1) −GNB2｝ ÷ LNB2 (3) QA = (GNINP + ε × LNINP) × ｛CB1 ÷ (CB1-0.2095)｝ + QBG (4) Also, liquid nitrogen collection priority In the mode, GNB2 to GN
B4 and LNB2～LNB4, i.e. calculated by the coefficient k ₁ to k ₃ using the second to fourth gas nitrogen content of points and liquid nitrogen level in FIG. 1 from the following (5) (7), these coefficients Using k _{1 to} k ₃ , the optimum raw material air amount QA is calculated by the following equation (8).

[0042] _{QAF = k 1 × GNB2 + k} 2 × LNB2 + k 3 ...... (5) QAF = k 1 × GNB3 + k 3 × LNB3 + k 3 ...... (6) QAF = k 1 × GNB4 + k 3 × LNB4 + k 3 ...... (7) QA = k ₁ × GNINP + k ₂ × LNINP + k ₃ (8) Then, the calculated optimum raw material air amount QA and data D ₂
Is determined, and when QA is smaller, QAMIN is defined as QA.

The gas nitrogen amount GNIN thus set
The optimum raw material air amount QA is determined according to P and the liquid nitrogen amount LNINP. However, when the raw material air amount is out of a predetermined allowable range due to aging, external conditions, etc. It is necessary to correct the raw material air amount so as to fall within a predetermined allowable range.

Process 8 is a feedback control process for performing such a correction. Taken into the microcomputer 17 nitrogen purity A ₀ detected by the purity meter 12 through the input-output interface 19, an upper limit A _H and the lower limit value A _L of the preset nitrogen purity range this
When A ₀ exceeds A _H , that is, when the purity is deteriorated, the raw air amount Q is calculated using a predetermined correction coefficient β.
When A is increased and A ₀ becomes lower than A _L , that is, when the purity becomes too good, the raw material air amount QA is reduced using the correction coefficient β, and the nitrogen purity A ₀ is set to the set nitrogen purity. Be within the range. Further, the change in the amount of cold can be detected as a change in the liquid level of the liquid air in the liquid air reservoir 5b of the rectification tower 5 or a change in the opening of the bypass valve 10. That is, if the amount of cold is insufficient, the liquid level of the liquid air drops. If the amount of cooling is excessive, the liquid level of the liquid air tends to rise.
In order to suppress this, the opening of the bypass valve 10 increases. Therefore, the bypass valve opening OS ₀ detected by the bypass valve opening detector 15 and the liquid level L ₀ detected by the liquid level gauge 14 are set to the preset upper limit value OS _H of the bypass valve opening and the liquid level. Compare with the lower limit of the level L _{L
When 0} exceeds OS _H, that is, when cold amount is excessive decreases the feed air amount QA using a predetermined correction coefficient gamma, also when L ₀ is lower than L _L, i.e. insufficient cold quantity Is corrected, the raw material air amount Q is calculated using the correction coefficient γ.
Increasing the A, so that the bypass valve opening OS ₀ is smaller than the upper limit value OS _H of the bypass valve opening degree is set, also larger than the lower limit value L _L of the liquid surface level set liquid surface level L ₀ That is, the amount of cold is set to fall within the set amount of cold.

By such feedback control, the optimum raw material air amount Q calculated based on the gas nitrogen amount GNINP and the liquid nitrogen amount LNINP initially set in both the purity priority mode and the liquid nitrogen collection priority mode.
A shows the input / output interface 1
It is output as a set value for the raw material air inlet valve 8 via 9.

Next, the control of the pressure of the liquid air in the liquid air reservoir 5b supplied to the nitrogen condenser 6 will be described with reference to the flowchart of FIG.

In the liquid nitrogen collection priority mode, the oxygen concentration of the waste gas approaches the oxygen concentration in the air (20.95%) in order to reduce the gas nitrogen amount as described above.
% When collecting only gas nitrogen, since the oxygen concentration of the waste gas is around 35%, the liquid air reservoir 5b
When the liquid air pressure is constant, the liquefaction point changes due to the difference in oxygen concentration, and the pressure of the raw air and the pressure of gas nitrogen change. Therefore, when the oxygen concentration of the waste gas changes, the liquid air pressure is changed to change the pressure of the raw air,
It is necessary to keep the gas nitrogen pressure constant.

Therefore, at the time of initial operation such as test operation, FIG.
The first point (GNB1, LNB1) and the third point (GNB1,
3, LNB3) optimal liquid air pressure PB1, PB
Investigate B3, and in process 1
D₁₈, D₁₉Each data D ₁~ D₁₇Input
Microcomputer 17 via the interface 18
, And in the next process 2, the first point (GNB1, LNB
NB1) and third point (GNB3, LNB3) and setting
Waste gas at the specified points (GNINP, LNINP)
The oxygen concentrations CB1, CB3 and CBINP of
It is calculated by the equations (9) to (11).

CB1 = {(QAF−QBG) × 0.2095} (QAF−QBG) − (GNB1 + LNB1)} (9) CB3 = {(QAF−QBG) × 0.2095} ( QAF-QBG)-(GNB3 + LNB3)｝ (10) CBINP = {(QAF-QBG) × 0.2095} (QA-QBG)-(GNINP + LNINP)｝ (11) In process 3, Each of these values C obtained in process 2
Points set using B1, CB3 and CBINP (GN
INP, LNINP)
INP is calculated by the following equation (12).

PBINP = {(CBINP-CB3) ÷ (CB1-CB3)} × (PB1-PB3) + PB3 (12) In this manner, the pressure of the raw material air and the pressure of the gas nitrogen are optimal to be constant. Although the liquid air pressure PBINP is determined, since the pressure of gas nitrogen changes due to aging, external conditions, and the like, when these pressures deviate from a predetermined allowable range, these pressures fall within a predetermined allowable range. It is necessary to correct the liquid air pressure to fall within.

Process 4 is a feedback control process for performing such a correction. The gas nitrogen pressure P ₀ detected by the pressure gauge 13 is input / output interface 1
Taken into the microcomputer 17 via the 9, which is compared with the upper limit value P _H and the lower limit value P _L of a preset gas nitrogen pressure range, when the P ₀ exceeds P _H, i.e. gas nitrogen pressure high If it is too long, the liquid air pressure PBINP is lowered using the correction coefficient δ, and if P ₀ becomes lower than P _L , that is, if the gas nitrogen pressure is too low, the liquid air pressure BPIMP is corrected using the correction coefficient δ. Then, the liquid air pressure PBINP is corrected so that the gas nitrogen pressure P ₀ falls within the set gas nitrogen pressure range.

By such feedback control, the initially set gas nitrogen amount GNIMP and liquid nitrogen amount L
Optimal liquid air pressure PBIN calculated by NINP
P is input / output interface 1 after modification
9 is output as a set value for the bypass valve 10.

The equations (1) to (12), the upper limit, the lower limit, and the correction coefficients are stored in the microcomputer 17 in advance.

Although not specifically illustrated, the raw air amount QA and the liquid air pressure PBI set as command values are set.
The deviation between the NP and the actual amount of the raw material air or the liquid air pressure detected by a flow meter, a pressure gauge, or the like is obtained, and the microcomputer 17 controls the raw material air inlet valve 8 or the bypass valve 10 so that the deviation becomes zero. Can be feedback controlled.

[0055]

As described above, according to the present invention,
Regardless of the change in the liquefaction rate of the raw air, the purity of the product nitrogen is almost constant at all times, so that it is possible to prevent waste of power consumption due to an excessive amount of the raw air and deterioration of the purity of the product nitrogen due to shortage of the raw air. By operating in the liquid nitrogen collection priority mode characteristic, it is possible to increase the amount of product liquid nitrogen to be collected, and to operate in each mode characteristic suitable for the product gas nitrogen amount and the product liquid nitrogen amount to be collected. It is possible to determine whether the mode belongs to either of the two mode characteristics.Therefore, it is possible to prevent the operation with the wrong mode characteristic and to change the pressure of the liquid air supplied to the nitrogen condenser so that the product nitrogen pressure is almost constant. The product gas nitrogen generation amount and the product liquid nitrogen generation amount at the time of design can be adjusted to the actual product gas nitrogen generation amount obtained during the initial operation. Correct operation can be performed by correcting the product liquid nitrogen generation data, and even if the product nitrogen purity, cooling amount and product nitrogen pressure change due to external conditions during operation, aging, etc. The corresponding command value is automatically corrected by feedback control, so that a suitable operation can always be performed. As a result, it is possible to perform a suitable operation corresponding to various operating conditions required by the user.

[Brief description of the drawings]

FIG. 1 is an operation characteristic diagram of the present invention showing a relationship between a gas nitrogen amount and a liquid nitrogen amount.

FIG. 2 is a system diagram showing an example of a nitrogen generator to which the present invention is applied.

FIG. 3 is a flowchart illustrating an example of an operation process of the present invention.

FIG. 4 is a flowchart showing an example of an operation process of the present invention.

FIG. 5 is a flowchart illustrating an example of an operation process according to the present invention.

FIG. 6 is a flowchart illustrating an example of an operation process of the present invention.

FIG. 7 is a flowchart illustrating an example of a liquid air pressure control process according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Raw material air compressor 3 Expansion turbine 4 Air heat exchanger 5 Rectification tower 6 Nitrogen condenser QAF Rated operation characteristic line QAMAX Increased operation characteristic line QAR Decreased operation characteristic line f (GAST1), f (GAMAX1), f (GARE1)
Purity priority mode characteristic line f (GAST2), f (GAMAX2), f (GARE2)
Liquid nitrogen sampling priority mode characteristic line f (SP) mode classification characteristic line

Claims (1)

[Claims] 1. A rectification column for producing liquid nitrogen and gaseous nitrogen by cryogenically separating raw air, an adjusting means for adjusting the amount of the raw air supplied to the rectification column, and an apparatus for operating the apparatus. A microcomputer in which various data are stored, wherein the microcomputer receives the collected data of the liquid nitrogen and the gas nitrogen, and calculates a calculation result based on the collected data and the various data. A method for operating the nitrogen generator, wherein the adjusting means is controlled in accordance with the following.