JPH10259991A - Heat exchanger for air separation device and air separation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the power efficiency of an entire device by arranging a fin that forms a channel with a large heat transfer area and/or a channel for increasing Reynolds number at a low-temperature side and a fin while conflicting with a low- temperature side at a high-temperature side in a heat exchanger. SOLUTION: In a coil gate fin-type heat exchanger being used for an air separation device, an entrance-side distributor D1 and an exit-side distributor D2 are arranged at both edge sides in a heat exchanger unit U of one unit constituting a main heat exchanger, at the same time, a corrugate fin F is divided into a low-temperature side and a high-temperature side, a fin F1 with a small corrugation pitch for increasing a heat exchange efficiency is arranged at the low-temperature side, and a fin F2 with a large corrugation pitch for reducing a pressure loss is arranged at the high- temperature side. More specifically, at the low-temperature side, a fin that forms a channel with a small channel section area, a channel with a large heat transfer area, or a channel indicating a high Reynolds number and has a relatively high heat exchange efficiency is arranged. On the other hand, at the hightemperature side, a fin that conflicts with that of the low-temperature side is arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger for an air separation device and an air separation device using the heat exchanger as a main heat exchanger, and more particularly to an improvement in heat exchange efficiency in a corrugated fin type heat exchanger. Also, the present invention relates to a technique capable of suppressing pressure loss as much as possible and improving the separation efficiency and operation stability of the air separation apparatus as a whole and reducing the running cost.

[0002]

2. Description of the Related Art Air separation apparatuses for separating air into nitrogen gas and oxygen gas are used in a wide range of fields such as steelmaking, chemicals, and electronics. Various studies have been conducted on such an air separation device with the aim of improving the separation efficiency, lowering the running cost, and improving the operation stability.

FIG. 6 is a flow chart showing a molecular sieve type air separation device developed under such a situation. The raw air is supplied by an air filter 1, a raw air compressor 2,
Air having a desired pressure, temperature, and humidity (hereinafter, sometimes referred to as compressed air) is passed through the cooler 3 and the like, and is guided to the molecular sieve adsorber 6. The molecular sieve adsorber 6 shown in the figure is a two-pair, one-switch system, and in the adsorber 6,
Moisture, carbon dioxide gas, hydrocarbon gas and the like in the compressed air are almost completely removed by the adsorption action of zeolite and the like. The compressed air led out of the adsorber 6 through the pipe 6a is led to the main heat exchanger 7 where it is cooled to near the liquefaction point by heat exchange with return gas to be described later. Is introduced to

[0004] The compressed air introduced into the lower column 8a is cooled and distilled while proceeding ascending in the lower column 8a. From the upper portion of the lower column 8a, a low-boiling nitrogen-rich liquid ( Liquid nitrogen 9 is taken out, while a high boiling point oxygen-rich liquid 10 is stored in the lower part (hereinafter sometimes referred to as a coarse distillation step). Upper nitrogen rich gas is supplied via line 13
To the main condenser 8b, where it is liquefied and
4 to return to the upper part of the lower tower 8a. The nitrogen-rich liquid in the upper part of the lower tower 8 a passes through the supercooler 12 through the pipe 15 and
led to the top of c.

On the other hand, the oxygen-rich liquid 10 is led to the middle stage of the upper tower 8c via the subcooler 12 by the pipe 25.
From the middle stage of the lower tower 8a, liquid nitrogen in the middle stage of the rough distillation process is led to the upper stage of the upper tower 8c via the supercooler 12 by the pipe line 11. As described above, the low-temperature liquid nitrogen and oxygen-rich liquid 10 introduced from the middle, upper, and top portions of the upper tower 8c and descending in the upper tower 8c undergo mass transfer with the gas rising in the upper tower 8c. The rectification proceeds by being performed.

By repeating these steps, high-purity nitrogen gas is collected at the top of the upper tower 8c, and high-purity liquid oxygen is stored at the lower part of the upper tower 8c. 17, and is returned to the main heat exchanger 7 as the return gas, and heat exchange is performed between the compressed air extracted from the molecular sieve adsorber 6 to utilize the cold. Commercialized as oxygen.

At this time, the molecular sieve adsorber 6
Is branched before being introduced into the main heat exchanger 7, and is compressed by the pressurizer 5 on the inlet side of the expansion turbine 5.
After being pressurized by a, it is introduced into the main heat exchanger 7, is cooled on the high temperature side of the main heat exchanger 7, is extracted from the middle thereof, is returned to the expansion turbine 5, and is adiabatically expanded. After being cooled, it is introduced into the middle stage of the upper tower 8c.
Further, from a position slightly below the upper part of the upper tower 8c, crude nitrogen gas (extracted gas) is extracted through the pipe line 20,
After utilizing the cold by heat exchange from the subcooler 12 through the main heat exchanger 7 as a return gas, the extracted gas after the heat exchange is passed through the regeneration gas heater 29 to the molecular sieve adsorber 6.
The gas is supplied to the molecular sieve adsorber 6 and is used for regeneration.
After being used for cooling the cooling water used for cooling the cooler 3. After the regenerative heating of the molecular sieve adsorber 6, the extracted gas is supplied to the molecular sieve adsorber 6 after the regenerative heating by switching the valves V ₁ and V ₂ to cool the same, thereby completing the preparation for switching to the adsorption step. . In addition, the extraction gas used for the regeneration of the molecular sieve adsorber 6 is sequentially released to the outside of the system.

In such an air separation device, the power of the air compressor immediately becomes the power performance of the device. However, the lower the outlet pressure of the air compressor, the lower the power of the air compressor. It is known that the performance of the air separation device as a whole is improved, and various studies are being made as a means for improving the performance in the direction of reducing the outlet pressure of the air compressor.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has as its object to focus on a main heat exchanger in an air separation device. By reducing pressure loss more effectively,
By providing a heat exchanger for an air separation device that can increase the power efficiency of the entire device, and by using the heat exchanger as a main heat exchanger, an air separation device with increased power efficiency can be provided. It is something to offer.

[0010]

Means for Solving the Problems A heat exchanger according to the present invention which can solve the above-mentioned problems is a corrugated fin type heat exchanger used for an air separation device. Fins forming a flow path having a large heat transfer area and / or a flow path for increasing the Reynolds number are arranged, and a flow path having a small heat transfer area and / or a flow path for decreasing the Reynolds number are formed on the high temperature side. Fins are arranged, or fins for forming a flow path having a small flow path cross-sectional area and / or a flow path for increasing the Reynolds number are disposed on the low temperature side of the heat exchanger, and the flow path is cut off on the high temperature side. The gist exists where fins forming a flow path having a large area and / or a flow path for reducing the Reynolds number are arranged.

The fins arranged on the low temperature side of the heat exchanger are preferably louver type fins or serrated fins from the viewpoint of increasing the heat exchange efficiency. The fins arranged on the high temperature side of the heat exchanger include: Plain type fins, herringbone type fins or perforate type fins are preferred from the viewpoint of enhancing the pressure loss reducing effect.

In the air separation apparatus according to the present invention, the heat exchanger is disposed for main heat exchange between product nitrogen, product oxygen and crude nitrogen gas and raw material air, so that the return gas can be cooled more efficiently. It is characterized by the fact that it is often used for cooling the raw material air, the pressure loss of the entire facility is reduced, and the power efficiency is increased.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, in an air separation device, the power of an air compressor immediately becomes the power performance of the device.
The lower the outlet pressure of the air compressor, the lower the power of the air compressor and the better the performance of the air separation device as a whole. The most effective means for lowering the outlet pressure of the air compressor is the low-pressure system in the air separation device, that is, the supercooler 12, the main heat exchanger 7, Molecular sieve adsorber 6
To reduce the pressure loss of the discharge line discharged to the atmosphere through the above process as much as possible.

The present inventors have confirmed that reducing the pressure of the discharge line by, for example, 0.1 kg / cm ² G reduces the outlet pressure of the air compressor by about 0.3 kg / cm ² G.
Leads to lowering. In this, a main condenser 8b is provided in an air separation device, in which heat exchange is performed between oxygen at the bottom of the rectification column and nitrogen at the top of the bottom column, where oxygen-nitrogen is exchanged. This is because the differential pressure in the low-pressure system is related to the differential pressure in the high-pressure system due to the boiling point under each pressure.

For example, the boiling point of oxygen at the top of the rectification column is
At about 1.4 kg / cm ² A and at -180 ° C., this oxygen evaporates with nitrogen at 5.4 kg / cm ² A at the bottom of the column at 178.2 ° C. (ie oxygen evaporates with nitrogen ,
Nitrogen condenses), but when the pressure of oxygen at the bottom of the rectification column drops by 0.1 kg / cm ² A to about 1.3 kg / cm ² A, the temperature becomes −180.7 ° C. 5.05 kg
Evaporate with nitrogen at -179 ° C at / cm ² A. That is, if the outlet pressure from the low-pressure system, that is, the upper tower, is reduced by 0.1 kg / cm ² A, the inlet pressure to the high-pressure system, that is, the lower tower, is reduced by 0.35 / cm ^{2.
kg / cm 2 A (5.4-5.05kg /} cm 2 A) will decrease it.

As is apparent from this, to improve the power performance of the air separation device, it is more preferable to suppress the pressure loss in the high pressure system (ie, the inlet line to the rectification column) than to reduce the pressure loss in the low pressure system (ie, the line). It is extremely effective to suppress the pressure loss in the line from the upper column of the rectification column.

The present invention focuses on the main heat exchanger, which is a major factor of pressure loss in the low pressure system, that is, in the line drawn from the upper tower of the rectification column, based on the above confirmation results. Research has been conducted with the aim of developing a heat exchanger that can reduce pressure loss as much as possible without reducing efficiency. In the main heat exchanger for the air separation device, heat is exchanged between the product nitrogen, product oxygen and crude nitrogen gas extracted in the cold state and the raw air, so that the raw air in the main heat exchanger is The inlet side (upper side in FIG. 6) has a relatively high temperature, and the outlet side (lower side in FIG. 6) of the raw material air has a low temperature close to a cold state. As a result, as described above, a fin having a higher heat exchange efficiency than the high temperature side (ie, a channel having a large heat transfer area or a channel having a high Reynolds number and a high turbulence forming ability) is provided on the low temperature side of the main heat exchanger as described above. Forming fins)
On the other hand, on the high-temperature side, fins having a smaller pressure loss than the low-temperature side (that is, fins having a large channel cross-sectional area or a channel having a low Reynolds number and a high laminar flow forming ability) are provided. I knew that the purpose would be achieved brilliantly if I placed it.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the structure and operation and effect of the heat exchanger according to the present invention will be specifically described with reference to the illustrated examples. However, the present invention is not limited to the following embodiments, and It is of course possible to implement the present invention with appropriate changes within a range that can be adapted to the purpose, and all of them are included in the technical scope of the present invention.

First, in a conventional main heat exchanger for an air separation device, corrugated fins are used in order to enlarge the effective heat transfer area. For example, as shown in FIG. Side Distributor D ₁
And the outlet distributor D ₂
The unit is a heat exchange unit U, and is configured by stacking a plurality of units. And, as the corrugated fin F of the heat exchange unit U, according to the required heat exchange efficiency and the allowable pressure loss, when high heat exchange efficiency is required, select a fin F having a small waveform pitch,
When pressure loss is important, a fin F having a large waveform pitch is used.

However, in the main heat exchanger for the air separation unit, heat is exchanged between the product nitrogen, product oxygen and crude nitrogen gas extracted in the cold state and the raw material air, so that the main heat exchanger is not used. The inlet side of the raw air (upper side in FIG. 6) has a relatively high temperature, and the outlet side of the raw air (lower side in FIG. 6) is cooled to near cold. And on the low temperature side,
Since cold recovery is performed by heat exchange at a low temperature, a fin having a high heat exchange efficiency (ie,
It is advantageous to use a fin that has a large heat transfer area or a fin that forms a high turbulence-forming ability by increasing the Reynolds number, while the temperature of the flowing gas rises toward the higher temperature side. Since the pressure loss increases due to the volume expansion, in order to suppress the pressure loss, a fin having a small pressure loss (that is, a channel having a large channel cross-sectional area or a channel having a small turbulence forming ability by suppressing the Reynolds number) is used. It is desirable to use a forming fin).

The present invention makes use of such knowledge by dividing a fin constituting one heat exchange unit into at least two of a high temperature side and a low temperature side, and disposing a fin having a high heat exchange efficiency on the low temperature side. By increasing the cold recovery rate and fins with low pressure loss on the high temperature side where the pressure loss increases due to the expansion of the flowing gas, the increase in the pressure loss due to the expansion of the flowing gas is suppressed. The pressure loss can be effectively suppressed while ensuring a low level of cold recovery.

FIG. 1 shows a main heat exchanger 1 of the present invention.
It is an explanatory view illustrating a heat exchange unit U of the unit, as well as placing the inlet side distributor D ₁ and the exit-side distributor D ₂ at both ends, divided into two corrugated fins F on the low temperature side and high temperature side, the low-temperature while on the side of placing the small fins F ₁ of the waveform pitch to increase the heat exchange efficiency, the fins F ₂ on the high temperature side is thereby reducing pressure loss by increasing the waveform pitch.

FIG. 2 shows another embodiment, in which the corrugated fin F is divided into three in the flow direction of the heat exchange fluid, and the fin F _{1 having} a small waveform pitch on the low temperature side and the fin F having a large waveform pitch on the high temperature side. _3.In the middle part, fins F2 each having a waveform pitch intermediate between the _two are arranged. The lower the temperature, the smaller the fin pitch and the higher the heat exchange efficiency. The structure is such that loss can be suppressed.

In this manner, the fin F is divided into three parts, or
By dividing the above, the heat exchange efficiency is increased by decreasing the fin pitch stepwise (or continuously) as the temperature becomes lower, and the fin pitch is increased stepwise as the pressure loss increases due to the volume expansion of the flowing gas. (Or continuous)
By increasing the pressure and suppressing the pressure loss, it is possible to obtain a heat exchanger having a low pressure loss and an excellent cold recovery rate.

In the examples shown in FIGS. 1 and 2, a corrugated fin using a plain type fin is shown as a typical example. However, the corrugated fin is not only a plain type but also a turbulent flow fin as shown in FIG. Louver-type fins (Fig. 3)
A) or a serrated fin (FIG. 3B), or a herringbone fin (FIG. 3C) or a perforated fin (FIG. 3C) having a laminar flow forming ability and easily obtaining a low pressure drop.
D) and the like are known. Of these, fins of the same type having different fin pitches are combined, or fins of different types are combined with each other in terms of the cross-sectional area of the flow path, the size of the heat transfer area, and the Reynolds number. Of course, it is also possible to use them in combination as appropriate according to the heat exchange efficiency and pressure loss that vary depending on the size (that is, the degree of turbulence forming ability). A fin having a relatively high heat exchange efficiency is arranged to form a flow passage, a flow passage having a large heat transfer area or a flow passage exhibiting a high Reynolds number. The object of the present invention can be similarly achieved by arranging fins having a low pressure loss that form a flow path having a small thermal area or a flow path exhibiting a low Reynolds number.

The overall structure of the heat exchange unit U used in the present invention is not limited to the examples shown in FIGS. 1 and 2, but can be arbitrarily changed as needed. As shown in the figure, arbitrary changes such as changing the introduction and discharge directions by the distributors D ₁ and D ₂ or extending the residence time of the fluid by changing the arrangement direction of the fins in the heat exchange unit as shown in FIG. 4B. Is also possible, and the assembly structure of the heat exchange unit U is also shown in FIGS.
It can be arbitrarily changed as shown in C, and all of them are included in the technical scope of the present invention.

Still another effective means for reducing the pressure loss in the heat exchanger is to improve the structure of a distributor provided in the main heat exchanger.
Hereinafter, this point will be described.

The ordinary distributor is provided for uniformly distributing the fluid entering from the inlet to the heat exchange section (HE) including the wide and fine pitch corrugated fins F in each unit. The distributor distributes and introduces fluid in the width direction of the heat exchange section by using a corrugated plate having a coarse pitch as shown in FIG. 7 or the like, or collects and discharges fluid from the width direction of the heat exchange section. It is configured to be able to.

However, in such a conventional heat exchanger, the flow direction of the fluid is changed at each of the heat exchange units, particularly at the outlet side distributor, and the flow path is narrower than the heat exchange section (HE). Since each fluid flows in a state, the occurrence of pressure loss is inevitable, and such a problem of pressure loss similarly occurs in the distributor portion of the heat exchanger as shown in FIGS. Come.

Therefore, further research was conducted to reduce the pressure loss generated at the distributor portion of such a corrugated fin type heat exchanger as much as possible. It has been confirmed that the pressure loss in the distributor portion can be more effectively reduced by using a structure in which a plurality of columns are assembled at appropriate intervals while leaving a passage space.

That is, the ordinary distributor provided in the corrugated fin type heat exchanger, as described above, converts the fluid entering from the inlet of the heat exchanger into the heat formed by the wide and fine pitch corrugated fins F in each unit. It is considered essential to evenly distribute the data to the exchange (HE). For example, as shown in FIG. 7 and the like, a structure in which a corrugated plate having a coarse pitch is sandwiched between plates and assembled is used. Causes large pressure loss.

However, according to the present inventors' various studies, it has been found that in the distributor, if a certain length is secured in the fluid flow direction, the gap between the plates can be maintained without disposing a corrugated plate inside. It was confirmed that the fluid was sufficiently distributed only by keeping the hollow state.
However, when assembling a heat exchanger with a large number of heat exchange units to which the distributor is attached, a large clamping force acts between the plates constituting the distributor, so that a pressure resistance sufficient to withstand the clamping force is applied. It is essential to ensure strength.

That is, it is considered effective to design the distributor focusing on the pressure resistance rather than the fluid distribution function, on the premise that a sufficient space for passing the fluid is secured. However, in a conventional distributor in which a corrugated plate is sandwiched between plates, the pressure resistance of the corrugated plate is not sufficient. A considerable pressure loss occurred in the corrugated plate.

However, considering the structure of the distributor with a particular focus on the improvement of the pressure resistance between the plates, which is necessary at the time of assembly, for example, as shown in FIG. It was found that it was sufficient to secure the pressure resistance sufficient to withstand the restraining force at the time of assembly by the support posts S. That is, the support S functions as a beam between the plates P disposed at both ends thereof, and can sufficiently support the restraining force applied in the vertical direction of the drawing. And since such a pillar has a superior pressure resistance compared with the conventional corrugated plate, it is possible to take a sufficiently large mounting interval, that is, it is possible to take a sufficiently large fluid passage space. As a result, the pressure loss at the distributor portion can be suppressed as much as possible.

The strut S used here is, in short, assembled at an appropriate interval between the plates P, P to provide pressure resistance. The strut S may have any shape and structure. In terms of securing the passage space for fluid, it is effective to assemble it as a rod-shaped support with a cross section of a round bar or a rectangular shape. However, in such a support, both ends of the support are brazed between the plates P and P. The joining operation becomes extremely complicated, which not only increases the production cost but also makes mass production difficult. Therefore, in consideration of manufacturing cost, productivity, and the like, it is advantageous to use a plate-shaped support S as shown in FIG. 8, for example, and to assemble it between the plates P, P by known means such as brazing. . At this time, as shown in FIG. 9, a method is employed in which one plate P and a plate-shaped support S are integrally formed by a drawing method or the like, and another plate P is joined to the other end of the support S. Then, the positioning and fixing of the column S can be performed very easily, so that such a structure can be said to be the most practical one in view of the easiness of manufacture.

However, in these examples, as described above, the columns are characterized by increasing the pressure resistance between the plates, so that the specific shapes and structures of the columns are not limited, and other shapes such as rods may be used. -Of course, it is also possible to use a structural support. When a plate-shaped support is used, the plate-shaped support is not only linear but also curved in the fluid flow direction as shown in FIG.
As shown in FIG. 1, an arbitrary shape, an arbitrary size, and an arbitrary number of holes W can be formed so that fluids can be diverted from each other through the holes W.

It is advantageous to reduce the pressure loss by setting the interval between the columns S as wide as possible as long as the required pressure-resistant strength can be ensured. However, the present inventors have confirmed that the effect of reducing the pressure loss is effective. In order to demonstrate
If the plate-like columns are assembled at intervals of about 3 to 15 times the fin pitch of the corrugated fins constituting the heat exchange section (for example, the symbol HE in FIG. 7) of the applied heat exchange unit, It has been found that the pressure loss can be sufficiently reduced. Thus, if the installation interval is excessively wide exceeding 15 times, the pressure resistance strength tends to be insufficient or the support must be excessively thick. On the other hand, if the support installation interval is less than 3 times, This is because the pressure resistance can be sufficiently increased, but it is difficult to obtain a satisfactory pressure loss reduction effect.

By the way, the corrugated fin type heat exchanger
The relationship between design pressure, pitch and plate thickness in the following equation
Can be t_p = P_t √ (P / 200σa) t_p : Separate sheet thickness, P_t : Pitch, P: Pressure
Force, σa: allowable stress of material (normal Al alloy is 2.3) Sheet thickness used for corrugated fin for heat exchanger
Is usually 1 mm and σa is 2.3.
Force 1.0kg / cm^Two Pitch P when G _t On
From the notation, P_t = T_p /√(P/200σa)=1.0/√(1.
0/200 · 2.3) = 21.4 mm.

On the other hand, in order to ensure the strength to withstand the load when the heat exchange unit is assembled by brazing, it must satisfy the buckling resistance (P _cr ) calculated by the following equation. During buckling strength ^{_{(P cr) = 4π 2 EI}} / l 2, I = tl 3/12 ( wherein, E: elastic modulus, I: sectional secondary moment, l:
Fin height t: Represents the fin plate thickness) Now, for two kinds of corrugated fins of the same material but of the same fin height and different plate thicknesses (therefore, E and l are the same), the respective buckling strengths P _Cr1 when determining the calculation formula P _Cr2, it becomes as the following equation, when the fin thickness is _{t 1: P Cr1 = [4π} 2 · E · (t 1 · l 3/1
2) / l ^3)] When the fin thickness is _{t 2: P Cr2 = [4π} 2 · E · (t 2 · l 3/1
Than 2) / l ^3)] the above _{equation, P Cr1 / P Cr2 = t} 1 / t 2 is derived. Further, under the condition that the same buckling strength is ensured, there is a substantially proportional relationship between the fin pitch (P) and the fin plate thickness (t), so that t ₁ / t ₂ = P _t1 / P _t2 Holds.

For example, 4.2 m generally used as a corrugated fin of a main heat exchanger for an air separator is used.
The thickness of the m-pitch fin is 0.4 mm, and the design fin pitch is 21.4 m when the thickness is 1 mm as described above.
m, these values are substituted into the above equation to determine the fin plate thickness for obtaining the buckling strength that can withstand the load at the time of assembling: 4.2 / 0.4 = 21.4 / t, That is, t ≒ 2 mm is derived. As a result, the fin thickness is 2 mm at the 21.4 pitch, but it is possible to secure a larger flow path area than that of the fin thickness of 0.4 mm at the 4.2 pitch.

On the other hand, the fin pitch of a normal corrugated fin used for a heat exchanger is Max: 4.2 m.
Since m and Min are 1.4 mm, considering these values, it is preferable to use the reinforcing column for securing the buckling strength against the load at the time of brazing by the reinforcing column provided in the distributor. When the mounting interval is determined, the minimum value is the Max / min ratio of the fin pitch, that is, 4.2 /
1.4 (= 3 times), and the maximum value is the ratio (ie, 21.4) of the corrugated fin pitch to the set fin pitch (ie, 21.4) with respect to the Min value (1.4).
/1.4=15 times), and the preferable minimum pitch interval of the reinforcing columns = 4.2 / 1.4.
= 3 times, preferred maximum pitch spacing of reinforcement columns = 21.4 / 1.
4 = 15 times. That is, by setting the mounting interval of the reinforcing columns in the distributor portion to be 3 to 15 times the fin pitch in the heat exchange section, sufficient buckling strength can be secured without alienating the fluid flow. Will be.

In the present invention, the pressure loss of the low-pressure line is reduced by devising the structure of the heat exchanger as described above, or by further improving the structure of the distributor constituting the heat exchanger. The feature is that the power of the machine is reduced, and such a feature can be effectively exerted on the conventional type air separation device as shown in FIG. 6, but the air separation device has the following features. It is possible to further enhance the pressure drop reduction or to obtain other effects by adding a special structure.

For example, FIG. 12 is a partial explanatory view showing another example of the air separation device provided with the main heat exchanger, and shows only the vicinity of the upper and lower columns of the rectification column. The portion may be considered to be the same as in the example of FIG.

In the example shown in FIG. 6, nitrogen gas roughly separated at the top of the lower column 8a is used to heat the liquid oxygen at the bottom of the upper column 8c of the rectification column, and the liquid oxygen is extracted from the upper side wall of the liquid level. The outputted oxygen-rich gas is taken out from the line 17 as product oxygen gas.

On the other hand, in this example, as shown in FIG.
Liquid air at the bottom of the upper rectification tower 8c is withdrawn as liquid from the line 30 and introduced into the evaporator 31. The evaporator 31
Is provided with a heat exchanger 32 for heating. In the heat exchanger 32 for heating, a part of the compressed air which is cooled by the main heat exchanger 7 and then supplied to the lower tower 8a of the rectification tower is branched. It is configured to be supplied as. Then, the liquid oxygen extracted from the upper rectification tower 8c is evaporated by heating it in the evaporator 31, and the cold is recovered from the line 33 in the main heat exchanger 7 in the same manner as described above, and then the product oxygen gas is produced. On the other hand, the compressed air that has been extracted and given cooling energy by the heating heat exchanger 32 is sent to the lower part of the lower tower 8a. Benefits brought by adopting this method include the following.

The pressure of the product oxygen gas can be increased. That is, as shown, when the evaporator 31 is provided below the liquid oxygen level L in the upper rectification tower 8c, the evaporator 31
Becomes lower than the liquid level L ₁ of the liquid oxygen is the liquid surface L in the pressure of the liquid oxygen supplied to the evaporator 31, the liquid in the liquid level L of the liquid oxygen in the upper column 8c evaporator 31 liquid head difference between the liquid level L ₁ of oxygen becomes higher by an amount corresponding to a (head difference) Hd. Although the boiling point rises by the pressure rise, the heating heat exchanger 32 in the evaporator 31 is compressed at a higher temperature than the crude nitrogen gas supplied to the main condenser 8b of the upper rectification tower 8c. Since the air is diverted and sent,
The liquid air in the evaporator 31 receives sufficient heat for evaporation and evaporates despite the pressure rise. Then, the pressure of the evaporating oxygen gas is withdrawn at a high pressure corresponding to the liquid head difference (head difference) Hd. In general, product oxygen gas is pressurized by a compressor to produce a product. However, since the product oxygen gas is pressurized through a compressor in the final stage of the extraction line, the pressure of the oxygen gas is increased in this portion. This can contribute to a reduction in power consumption of the equipment as a whole.

The purity of the product oxygen gas can be increased. That is, as shown in FIG. 6, when the oxygen gas is extracted from a position slightly higher than the liquid oxygen liquid level in the upper rectification tower 8c, the purity of the oxygen gas is determined based on the gas-liquid equilibrium in the upper tower 8c. It is impossible to increase the purity of the oxygen gas to more than 90%. For example, when the oxygen concentration of the liquid oxygen is 90%, the purity of the extracted oxygen gas must be about 87 to 88%. However, as in this example, a method is employed in which liquid oxygen at the bottom of the upper tower 8c is extracted in a liquid state to the evaporator 31 and then heated and evaporated. When the pressure and temperature in the evaporator 31 are properly controlled, It becomes possible to extract the oxygen gas maintaining the liquid oxygen purity at the bottom of 8c as the product gas. That is, the temperature and pressure conditions in the evaporator 31 are controlled, and a gas having a high nitrogen content that is first volatilized is released, so that the oxygen concentration in the gaseous phase becomes higher than that of the liquid oxygen (ie, sent from the upper column 8c). A gas-liquid equilibrium state (for example, a gas phase oxygen concentration of 90% and a liquid phase oxygen concentration of 92%) is obtained, and the liquid oxygen is introduced and the gas oxygen is extracted while maintaining this state. If it is performed continuously, it becomes possible to continuously obtain a 90% concentration oxygen gas as a product gas.

It is possible to reduce the pressure for introducing the compressed air into the lower tower 8a, that is, to reduce the power of the raw material air compressor.
That is, as described above, the fact that the purity of the product oxygen gas is increased by the operation with the evaporator 31 provided means that the purity of the liquid oxygen stored at the bottom of the upper rectification column 8c can be relatively reduced. In other words, the lower the purity of the liquid oxygen is, the lower its boiling point is, and it is possible to evaporate at a lower temperature. Accordingly, the nitrogen gas (gas sent from the top of the lower column 8a to the main condenser 8b) serving as a heating source for evaporating the liquid oxygen in the upper column 8c also has a lower pressure. Operating temperature will be lower). As a result, an operation in which the pressure of the lower tower 8a is set to a low level becomes possible, which can contribute to a reduction in the power of the raw material air compressor.

Although the above-described configuration has been described as a preferred configuration that can be additionally provided when the present invention is carried out, if the heat exchanger of the present invention configured as described above is used, Since the pressure loss can be kept as low as possible while guaranteeing a high level of heat exchange efficiency, if this is arranged as the main heat exchanger of the air separation unit, it will exhibit a stable and excellent cold recovery rate, Pressure loss due to the main heat exchanger in the low pressure side extraction line can be suppressed as much as possible, and power of the air compressor can be reduced.

The other equipment of the air separation apparatus in which the heat exchanger of the present invention is disposed, such as an air compressor, a cooler, a molecular sieve adsorber, an upper and lower tower of a rectification column, and their piping and connection. The structure and the like are not particularly limited, and it is possible to appropriately select and apply equipment, piping, connection methods, and the like applied to this type of air separation device. Rashig ring as well as rectification tower,
Of course, it can also be effectively used for a rectification column or the like in which a pole ring, a crowbar saddle, an intercross saddle, and other structural fillers are filled to reduce pressure loss.

[0051]

The present invention is configured as described above, and this heat exchanger can suppress a pressure loss as small as possible while guaranteeing a high level of heat exchange efficiency. Therefore, the air separation device using this heat exchanger as the main heat exchanger shows a stable and excellent cold recovery rate and reduces the pressure loss derived from the main heat exchanger in the low pressure side extraction line as much as possible. By reducing the power of the air compressor, it becomes possible to improve the separation efficiency and operation stability of the air separation device as a whole, and to reduce the running cost.

[Brief description of the drawings]

FIG. 1 is an explanatory view illustrating a heat exchange unit constituting a heat exchanger of the present invention.

FIG. 2 is an explanatory view illustrating another heat exchange unit constituting the heat exchanger of the present invention.

FIG. 3 is a partial perspective view showing another example of a corrugated fin used in the present invention.

FIG. 4 is a schematic plan view illustrating another heat exchange unit constituting the heat exchanger of the present invention.

FIG. 5 is a schematic drawing showing an example of assembling a heat exchange unit constituting the heat exchanger of the present invention.

FIG. 6 is an overall flow diagram illustrating an air separation device using the heat exchanger of the present invention.

FIG. 7 is an explanatory diagram showing a heat exchange unit of a conventional main heat exchanger used for an air separation device.

FIG. 8 is a schematic partial sectional view illustrating the structure of a distributor preferably provided in a heat exchange unit constituting the heat exchanger of the present invention.

FIG. 9 is a schematic partial sectional view illustrating another structure of a distributor preferably provided in a heat exchange unit constituting the heat exchanger of the present invention.

FIG. 10 is a partial cross-sectional view illustrating the structure of still another distributor preferably provided in the heat exchange unit that constitutes the heat exchanger of the present invention.

FIG. 11 is a partial cross-sectional view illustrating the structure of still another distributor preferably provided in the heat exchange unit that constitutes the heat exchanger of the present invention.

FIG. 12 is an explanatory diagram that extracts and shows characteristic portions of an air separation method and an apparatus preferably employed in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Air filter 2 Raw material air compressor 3 Cooler 4 Evaporative cooler 5 Expansion turbine 6 Molecular sieve adsorber 7 Main heat exchanger 8 Rectification tower 8a Lower tower 8b Main condenser 8c Upper tower 9 Nitrogen rich liquid 10 Oxygen rich liquid 29 Regeneration gas heater 31 Evaporator 32 Heat exchanger for heating F Corrugated fin D ₁ Inlet distributor D ₂ Distributor U Heat exchange unit P plate S Column W Hole

Claims (5)

[Claims] 1. A corrugated fin heat exchanger used in an air separation device, wherein a fin forming a flow path having a large heat transfer area and / or a flow path increasing a Reynolds number is provided on a low temperature side of the heat exchanger. Is placed, and on the hot side,
A heat exchanger for an air separation device, wherein fins forming a flow path having a small heat transfer area and / or a flow path for lowering the Reynolds number are arranged. 2. A corrugated fin type heat exchanger used for an air separation device, wherein a flow path having a small flow path cross-sectional area and / or a flow path having a high Reynolds number is formed on a low temperature side of the heat exchanger. A heat exchanger for an air separation device, wherein fins are arranged, and fins that form a flow path having a large flow path cross-sectional area and / or a flow path that reduces a Reynolds number are disposed on a high temperature side. 3. The heat exchanger for an air separation device according to claim 1, wherein the fin disposed on the low temperature side of the heat exchanger is a louver fin or a serrate fin. 4. The heat exchanger for an air separation device according to claim 1, wherein the fin disposed on the high temperature side of the heat exchanger is a plain fin, a herringbone fin, or a perforate fin. . 5. The air separator according to claim 1, wherein the heat exchanger is arranged for main heat exchange between product nitrogen, product oxygen and crude nitrogen gas and raw material air. apparatus.