JP2006266532A - Air separating device and its operating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air separating device and its operation method capable of eliminating impurities accumulated in a falling liquid film type condenser of a main condenser while continuously operating the air separating device. <P>SOLUTION: In this air separating device applying the falling liquid film type condenser composed of a plurality of heat exchange cores 14, 15 in the main condenser 11, the heat exchange cores 14, 15 are respectively provided with valves 17a, 17b for stopping introduction of a nitrogen gas, on passages 14a, 15a introducing the nitrogen gas as warm fluid to the heat exchangers 14, 15. A weight reducing operation is performed in the air separating device, the introduction of nitrogen gas as warm fluid to the heat exchange cores as cleaned objects among the plurality of heat exchange cores is stopped, the introduction of liquefied oxygen as cold fluid to the heat exchange cores is continued, and components of high boiling point accumulated on a liquefied oxygen-side heat transfer face of the heat exchange cores is cleaned and eliminated by the liquefied oxygen. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air separation device and a method for operating the same, and more particularly, to an air separation device including means for cleaning high boiling point components accumulated on a heat transfer surface of a falling liquid film type condenser used in a main condenser and its It relates to the driving method.

  As an apparatus for industrially producing oxygen and nitrogen, an air separation apparatus to which a cryogenic separation method produced by low-temperature distillation using a double rectification column using air as a raw material is generally used. The typical air separation apparatus consists of a medium pressure column with an operating pressure of about 6 bar and a low pressure column of about 1.4 bar, the medium pressure column and the low pressure column being thermally coupled. Has been. That is, the main condenser is installed to liquefy the nitrogen gas at the top of the intermediate pressure tower and vaporize the liquid oxygen at the bottom of the low pressure tower. As the main condenser, an infiltrating plate fin heat exchanger is often used. In the main condenser of this system, since there is a liquid oxygen liquid head, there is a part where the temperature difference becomes small in the middle part of the main condenser.

  A falling liquid film type condenser (DFR) improved with respect to this infiltration type main condenser has been put into practical use (for example, see Patent Document 1). Since the main condenser itself is not infiltrated with liquefied oxygen, the temperature difference in the main condenser is substantially constant, and this falling liquid film type condenser can be operated even with a small temperature difference. For this reason, the operation pressure of the intermediate pressure tower is lower than the conventional one, and the basic unit of product power can be greatly improved.

  In the air separation device, trace amounts of high-boiling impurities such as dinitrogen monoxide and carbon dioxide may be mixed in the raw air, and these impurities are concentrated in the main condenser at the lower part of the low-pressure column. In the conventional infiltration type main condenser, the liquefied oxygen side heat transfer surface is always infiltrated with liquefied oxygen, but in the falling liquid film type condenser, part of the oxygen heat transfer surface is completely dried, There is a concern that high-boiling impurities accumulate.

  In particular, dinitrogen monoxide present at about 0.3 ppm in the atmosphere is characterized by a high solidification point of −102 ° C. and low volatility. Therefore, when liquefied oxygen containing a small amount of dinitrogen monoxide is vaporized, it is a substance that is likely to be concentrated in the liquid phase and solidified on the heat transfer surface. For this reason, in an air separation apparatus that employs a falling liquid film type condenser as the main condenser, it is necessary to periodically treat the main condenser so as not to accumulate dinitrogen monoxide or the like.

As a method of removing clogged substances (high boiling point impurities) accumulated in the main condenser while continuously operating the air separator, the air separator having a plurality of infiltration type main condensers is a target for removing clogged substances. It has been proposed to block nitrogen gas and liquefied oxygen introduced into the condenser, introduce oxygen at room temperature from the outside into the main condenser, and sublimate and remove the clogging substances accumulated in the main condenser (for example, , See Patent Document 2).
JP 2000-111247 A JP 2001-221567 A

  In the method described in Patent Document 2, it takes time and energy to warm the condenser operating at a low temperature to room temperature, and when the operation of the condenser is resumed after processing, Time and cooling to cool the main condenser at room temperature to the operating temperature are required. That is, energy (heat and cold) is required each time impurities are removed. Further, each time the condenser is washed, oxygen gas having product purity is required, which has an influence on the yield.

  Therefore, the present invention provides an air separation apparatus that uses a falling liquid film type condenser as a main condenser, and can remove impurities accumulated in the falling liquid film type condenser while continuously operating the air separation apparatus. It aims at providing a device and its operating method.

  In order to achieve the above object, the air separation device of the present invention is a hot fluid in each heat exchanger core in the air separation device using a falling liquid film type condenser comprising a plurality of heat exchange cores in the main condenser. Each path for introducing nitrogen gas is provided with a valve for stopping the introduction of the nitrogen gas.

  In addition, the operation method of the air separation device according to the present invention is a method of operating an air separation device using a falling liquid film type condenser having a plurality of heat exchange cores as a main condenser, and performs a reduction operation of the air separation device. Stopping the introduction of nitrogen gas, which is a warm fluid, into the heat exchange core to be cleaned in the plurality of heat exchange cores, and continuing the introduction of liquefied oxygen, which is a cold fluid, into the heat exchanger core, The high boiling point component accumulated on the liquefied oxygen side heat transfer surface of the heat exchange core is washed away with liquefied oxygen.

  According to the present invention, the air separator can be continuously operated. Further, there is no need to use wasted energy as in the prior art, and the yield of the product is not affected.

  FIG. 1 is a system diagram showing an embodiment of a main condenser to which the present invention is applied. The main condenser 11 heat-exchanges the nitrogen gas at the top of the intermediate pressure tower 12 and the liquefied oxygen at the bottom of the low pressure tower 13 to liquefy the nitrogen gas and vaporize the liquefied oxygen. It is installed in the lower space of the tower 13.

  The main condenser 11 shown in this embodiment includes two heat exchanger cores 14 and 15, and the nitrogen gas of the intermediate pressure tower 12 is introduced into the upper part of the condensation passage in each of the heat exchanger cores 14 and 15. The nitrogen gas passages 14a and 15a to be discharged, the liquefied nitrogen passages 14b and 15b for extracting the liquefied nitrogen from the lower portion of the condensation passage and returning to the intermediate pressure tower 12, and the liquefied oxygen accumulated at the bottom of the low pressure tower 13 is pumped by the pump 16. The liquefied oxygen passages 14c and 15c for supplying the upper part of the evaporation passage are provided.

  The liquefied oxygen that has not evaporated in the evaporation passage flows down from the lower end of the evaporation passage to the bottom of the low-pressure column 13. The nitrogen gas paths 14a and 15a are provided with valves 17a and 17b for stopping the introduction of nitrogen gas into the heat exchanger cores 14 and 15, respectively.

  During normal operation, the valves 17a and 17b are both open, and the nitrogen gas extracted from the intermediate pressure tower 12 to the path 18 is branched into the nitrogen gas paths 14a and 15a, so that both the heat exchanger cores 14 and Each of the 15 condensation passages is introduced as a warm fluid. The liquefied oxygen extracted from the low-pressure tower 13 to the path 19 is pumped by the pump 16 and branches from the path 20 to the liquefied oxygen paths 14c and 15c to the evaporation passages of both the heat exchanger cores 14 and 15, respectively. Introduced as a cold fluid.

  The nitrogen gas flowing into the condensation passages of the heat exchanger cores 14 and 15 exchanges heat with liquefied oxygen flowing down the evaporation passages, condenses and liquefies into liquefied nitrogen, and is extracted into the liquefied nitrogen passages 14b and 15b. It is introduced from the path 21 to the top of the intermediate pressure tower 12 as a reflux liquid. The oxygen gas flowing into the evaporation passages of the heat exchanger cores 14 and 15 exchanges heat with the nitrogen gas flowing through the condensation passage while flowing down the liquefied oxygen side heat transfer surface, and part of the oxygen gas is evaporated. It becomes oxygen gas, rises in the evaporation passage, and directly rises in the low pressure column 13.

  When the high-boiling components accumulated on the liquefied oxygen side heat transfer surface of one heat exchanger core 14 are washed and removed, first, the air separation device is operated to reduce the amount of raw air introduced into the intermediate pressure tower 12. At the same time, the valve 17a of the nitrogen gas path 14a is closed to stop the introduction of the nitrogen gas into the heat exchanger core 14.

  As a result, since the warm fluid is not supplied to the condensation passage of the heat exchanger core 14, the liquefied oxygen flowing through the evaporation passage of the heat exchanger core 14 is not heated by the warm fluid, and is thus liquefied without being vaporized. The high boiling point component that has flowed down the oxygen side heat transfer surface and accumulated on the liquefied oxygen side heat transfer surface of the heat exchanger core 14 is taken into the liquid and flows down to the bottom of the low pressure column 13. Therefore, the high boiling point component accumulated on the liquefied oxygen side heat transfer surface of the heat exchanger core 14 is removed by the liquefied oxygen, and the liquefied oxygen side heat transfer surface is cleaned.

  After washing the liquefied oxygen side heat transfer surface of the heat exchanger core 14, the valve 17a is opened to restart the operation in the heat exchanger core 14, and the valve 17b of the nitrogen gas path 15a is closed to close the heat exchanger core 15 By stopping the introduction of nitrogen gas to the liquefied oxygen side heat transfer surface, the high-boiling components accumulated on the liquefied oxygen side heat transfer surface of the heat exchanger core 15 are removed by liquefied oxygen in the same manner as described above. be able to.

  By periodically performing such a washing operation, it is possible to avoid the accumulation of a large amount of high-boiling components on the liquefied oxygen side heat transfer surface, and it is possible to continuously operate the air separation device in a stable state over a long period of time. .

  FIG. 2 is a system diagram showing an embodiment in which the present invention is applied to an air separation apparatus equipped with a double rectification column. Note that the main condenser portion is shown enlarged in view of the drawing.

  This air separation device is compressed to a predetermined pressure by a raw material air compressor 31 and cooled by an after cooler 32, and then purified by removing impurities in the air such as moisture and carbon dioxide by an adsorber 33 used for switching. Is done. This purified air is cooled to the vicinity of the dew point by heat exchange with the product gas or the like in the main heat exchanger 34 to become low-temperature air. This low-temperature air is introduced into the lower part of the intermediate pressure tower 36 through the path 35, and is separated into nitrogen gas at the top of the tower and oxygen-enriched liquefied air at the bottom of the tower by distillation operation in the intermediate pressure tower 36.

  The oxygen-enriched liquefied air extracted from the bottom of the intermediate pressure column 36 to the path 37 is introduced into the middle stage of the low pressure column 40 through the supercooler 38 and the pressure reducing valve 39, and is distilled by this low pressure column 40. Then, it is separated into nitrogen gas at the top of the column and liquefied oxygen at the bottom of the column.

  A part of, for example, about 10% of the nitrogen gas extracted from the top of the intermediate pressure tower 36 into the path 41 branches to the path 42, and heat exchange with the purified air in the heat exchanger 34 leads to an intermediate temperature. After the temperature rises, cold is generated by adiabatic expansion in the expansion turbine 43. The low-temperature, low-pressure nitrogen gas that has flowed out of the expansion turbine 43 into the path 44 is again heated to near room temperature through the main heat exchanger 34 and then taken out of the system from the path 45.

  The nitrogen gas branched from the path 41 to the path 46 is introduced into the main condenser 51 as a warm fluid. The main condenser 51 includes four heat exchanger cores 53, 54, 55, 56 having the same performance in a container 52, and each of the heat exchanger cores 53, 54, 55, 56 includes Similarly, the nitrogen gas passages 53a, 54a, 55a, 56a for introducing nitrogen gas into the upper portion of the condensation passage, the liquefied nitrogen passages 53b, 54b, 55b, 56b for extracting liquefied nitrogen from the lower portion of the condensation passage, and the liquefied oxygen are evaporated. Liquefied oxygen passages 53c, 54c, 55c, and 56c are provided in the upper part of the passage, and nitrogen gas to the heat exchanger cores 53, 54, 55, and 56 is provided in the nitrogen gas passages 53a, 54a, 55a, and 56a. Valves 57a, 57b, 57c, and 57d for stopping the introduction of each are provided.

  Further, a liquefied oxygen extraction path 58 for extracting liquefied oxygen that has flowed down to the bottom of the container without being vaporized by the heat exchanger cores 53, 54, 55, 56 is provided at the bottom of the container 52. An oxygen gas extraction path 59 for extracting oxygen gas vaporized by the heat exchanger cores 53, 54, 55, and 56 is provided.

  During normal operation, the valves 57a, 57b, 57c, and 57d are all open, and the nitrogen gas in the path 46 branches into the nitrogen gas paths 53a, 54a, 55a, and 56a, respectively, and all the heat exchanger cores 53 are provided. , 54, 55, 56 are introduced into the condensation passages. The liquefied nitrogen flowing through each condensation passage is condensed and liquefied to liquefied nitrogen by exchanging heat with liquefied oxygen, which is a cold fluid flowing through the adjacent evaporation passage.

  The liquefied nitrogen is extracted into the liquefied nitrogen passages 53b, 54b, 55b, and 56b, and merges with the liquefied nitrogen passage 60. A part of the liquefied nitrogen flowing through the liquefied nitrogen passage 60 is branched into the intermediate pressure tower passage 61 and introduced as a reflux liquid to the top of the intermediate pressure tower 36. The liquefied nitrogen branched from the liquefied nitrogen path 60 to the low pressure column path 62 is introduced as a reflux liquid to the top of the low pressure column 40 through the supercooler 38 and the pressure reducing valve 63.

  On the other hand, part of the liquefied oxygen extracted from the bottom of the low-pressure column 40 to the liquefied oxygen pump 64 is branched into the path 65 and circulated to the bottom of the low-pressure column 40, and the remainder passes through the path 66 to the main condenser. 51 is introduced as a cold fluid. This liquefied oxygen is a warm fluid that branches into the liquefied oxygen paths 53c, 54c, 55c, and 56c, is introduced into the evaporation paths of all the heat exchanger cores 53, 54, 55, and 56, and flows through the adjacent condensation passages. Heat exchange with liquefied nitrogen is performed, and a part thereof is evaporated and becomes oxygen gas, which rises from the evaporation path to the upper portion of the container 52.

  Further, the liquefied oxygen that has not evaporated flows down from the evaporation path to the bottom of the container 52. The liquefied oxygen extracted from the container 52 to the liquefied oxygen extraction path 58 and the oxygen gas extracted to the oxygen gas extraction path 59 merge into the path 67 and are then introduced into the lower portion of the low-pressure column 40, where oxygen gas Becomes the rising gas of the low-pressure column 40.

  Nitrogen gas is extracted from the top of the low-pressure column 40 to the path 68, passes through the supercooler 38 and the main heat exchanger 34, and is extracted from the path 69 to the outside of the system. Further, from the lower part of the low-pressure column 40, oxygen gas is extracted into the path 70, passes through the main heat exchanger 34, and is extracted out of the system from the path 71.

  When cleaning one of the heat exchanger cores 53, 54, 55, 56, for example, the heat exchanger core 53, the valve 57 a of the nitrogen gas path 53 a for introducing nitrogen gas into the heat exchanger core 53 is closed. Then, the introduction of nitrogen gas into the heat exchanger core 53 is stopped. In this state, by continuing the introduction of liquefied oxygen from the liquefied oxygen path 53c, the liquefied oxygen side heat transfer surface in the evaporation passage of the heat exchanger core 53 is washed, and the high boiling point component accumulated on the liquefied oxygen side heat transfer surface Is removed.

  Here, when the total of the nitrogen liquefaction capacities of the four heat exchanger cores 53, 54, 55, and 56 corresponds to 90% of the amount of raw material air (10% flows to the expansion turbine), heat exchange is performed. The nitrogen liquefaction capacity when washing one of the heat exchanger cores 53, 54, 55, 56, for example, the heat exchanger core 53 is the sum of the three heat exchanger cores 54, 55, 56, and the amount of raw material air 68% (= 90% × 3/4). Therefore, when cleaning one heat exchanger core, it is necessary to perform a reduction operation in which the amount of raw material air is reduced by 22% (= 90% -68%).

  Such a cleaning operation is periodically performed on each of the heat exchanger cores 53, 54, 55, 56, so that each liquefied oxygen side heat transfer surface of the falling liquid film type condenser constituting the main condenser 51 is obtained. It is possible to wash away high-boiling components such as dinitrogen monoxide accumulated in the substrate. Thereby, since the liquefied oxygen side heat transfer surface can be cleaned while continuously operating the air separator, the continuous operation time of the air separator can be extended.

It is a systematic diagram which shows one example of the main condenser to which this invention is applied. It is a systematic diagram which shows the example of 1 form which applied this invention to the air separation apparatus provided with the double rectification tower.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Main condenser, 12 ... Medium pressure tower, 13 ... Low pressure tower, 14, 15 ... Heat exchanger core, 14a, 15a ... Nitrogen gas path, 14b, 15b ... Liquefied nitrogen path, 14c, 15c ... Liquefied oxygen path, DESCRIPTION OF SYMBOLS 16 ... Pump liquefied oxygen, 17a, 17b ... Valve, 31 ... Raw material air compressor, 32 ... After cooler, 33 ... Adsorber, 34 ... Main heat exchanger, 36 ... Medium pressure tower, 38 ... Supercooler, 39 ... pressure reducing valve, 40 ... low pressure column, 43 ... expansion turbine, 51 ... main condenser, 52 ... vessel, 53, 54, 55, 56 ... heat exchanger core, 53a, 54a, 55a, 56a ... nitrogen gas path, 53b , 54b, 55b, 56b ... liquefied nitrogen path, 53c, 54c, 55c, 56c ... liquefied oxygen path, 57a, 57b, 57c, 57d ... valve, 58 ... liquefied oxygen extraction path, 59 ... oxygen gas extraction path, 60 ... liquefied nitrogen pathway, 1 ... medium pressure column path, 62 ... pressure column path, 63 ... pressure reducing valve, 64 ... liquid oxygen pump

Claims (2)

  In an air separation apparatus using a falling film membrane condenser composed of a plurality of heat exchange cores in the main condenser, introduction of the nitrogen gas into each path for introducing nitrogen gas as a warm fluid into each heat exchanger core An air separating device provided with a valve for stopping the operation.   In the operation method of the air separation apparatus using the falling liquid film type condenser composed of a plurality of heat exchange cores in the main condenser, the air separation apparatus is operated in a reduced amount and becomes a washing target in the plurality of heat exchange cores. The introduction of nitrogen gas, which is a warm fluid, into the heat exchange core is stopped, the introduction of liquefied oxygen, which is a cold fluid, into the heat exchanger core is continued, and the liquefied oxygen side heat transfer of the heat exchange core is performed by the liquefied oxygen A method for operating an air separation device, wherein high-boiling components accumulated on a surface are washed away.

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