JP2008039343A - Absorbent reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absorbent liquid reproducing method eliminating copper content in absorbent liquid without causing elution of unnecessary metal ion while suppressing a cost increase. <P>SOLUTION: Lithium hydroxide is added into the absorbent of an absorption refrigerator or an absorption heat pump containing a lithium bromide water solution as a main component (ST14), and an insoluble substance containing the copper content produced in consequence is eliminated (ST15). Since an additive is lithium hydroxide containing the same kind of metal component as the metal component of lithium bromide which is the main component of the absorbent, metal content not required in a process of removing copper content is not mixed into the absorbent, and since lithium hydroxide is used to produce the insoluble substance, the cost increase can be suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an absorption liquid regeneration method, and more particularly to an absorption liquid regeneration method for removing copper in the absorption liquid.

  Many absorption refrigerators and absorption heat pumps (hereinafter referred to as “absorption refrigerators”) use an aqueous lithium bromide solution as an absorbent and water as a refrigerant. In general, absorption refrigerators and the like are mainly made of steel, and copper or a copper alloy is used for the heat exchanger. Conventionally, the heat exchanger part is corroded by lithium bromide aqueous solution (absorbing liquid), copper is eluted in the absorbing liquid, and the copper in the absorbing liquid is deposited on the steel. Was accelerating corrosion.

Against this background, examples of techniques for removing copper from the absorbing solution to prevent the progress of corrosion of steel materials include the following. As an example, a copper ion removing device that removes copper ions by applying voltage to an insoluble electrode is installed in an absorption refrigerator or the like, or a metal (for example, aluminum) whose oxidation-reduction potential is significantly lower than copper is installed in the absorbing solution. Then, there is one that deposits and removes copper ions in the absorbing solution (see, for example, Patent Document 1). Another example is the substitution deposition and adsorption of copper ions and iron ions by passing and contacting a lithium bromide solution containing copper ions and iron ions, which are oxidizing agents, in fine particles of activated carbon or ion exchange resin. By doing this, there is a method of reducing the copper ions and iron ions in the absorption liquid to prevent corrosion of the equipment material in the absorption refrigerator or the like (for example, see Patent Document 2).
Japanese Patent Publication No. 7-94932 (page 2) Japanese Patent Laid-Open No. 7-208825 (paragraph 0009, etc.)

  However, a device using a copper ion removing device that applies a voltage to an insoluble electrode and electrolytically removes copper ions requires an electrode potential control device and the like, resulting in high costs. Further, when a metal having a remarkably lower oxidation-reduction potential than copper is installed in the absorbing solution, unnecessary metal ions are eluted as the absorbing solution. Moreover, when using activated carbon, the removal efficiency of copper content is low, and the method of using an ion exchange resin requires the cost of the ion exchange resin and the cost for regenerating the ion exchange resin.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an absorbent regenerating method for removing copper from the absorbent without causing unnecessary metal ions to elute into the absorbent while suppressing an increase in cost. .

  In order to achieve the above-mentioned object, an absorption liquid regeneration method according to the invention described in claim 1 is applied to an absorption liquid of an absorption refrigerator or an absorption heat pump mainly composed of an aqueous lithium bromide solution as shown in FIG. A step (ST14) of adding lithium hydroxide; and a step (ST15) of removing insoluble substances containing copper produced by the addition of lithium hydroxide.

  If comprised in this way, since the process of adding lithium hydroxide to an absorption liquid is provided, the copper content in an absorption liquid can be deposited as an insoluble substance. In addition, since the additive is lithium hydroxide containing the same metal component as the metal component of lithium bromide, which is the main component of the absorbent, unnecessary metal is not mixed into the absorbent in the process of removing copper. . In addition, since lithium hydroxide is used to generate the insoluble material, an increase in cost can be suppressed.

The absorbent regenerating method according to claim 2 is the absorbent regenerating method according to claim 1, wherein the amount of lithium hydroxide added is an alkali of the absorbent after the insoluble material is removed. The amount is such that the degree is 200 mol / m ³ or more. Here, “alkalinity” refers to the property of having an excess of hydroxide ions in an aqueous solution, and in this specification refers to the amount of hydroxide ions per unit volume.

  If comprised in this way, most copper content in an absorption liquid can be deposited as an insoluble substance, and the removal rate of a copper content can be improved.

  Moreover, the absorption liquid reproduction | regeneration method based on invention of Claim 3 is a process of adding the said lithium hydroxide in the absorption liquid reproduction | regeneration method of Claim 1 or Claim 2, as shown, for example in FIG. Prior to ST14), the absorption liquid is extracted from the absorption refrigerator or absorption heat pump (ST11); the absorption liquid after the insoluble material is removed is injected into the absorption refrigerator or absorption heat pump (ST17); Is provided.

  With this configuration, since the insoluble substance is generated and removed after the absorption liquid is extracted from the absorption refrigerator or the absorption heat pump, the work for removing the insoluble substance can be easily performed, and the removal rate of the insoluble substance can be improved. it can.

  Moreover, the absorption liquid reproduction | regeneration method based on invention of Claim 4 is the absorption liquid reproduction | regeneration method of any one of Claims 1 thru | or 3, for example, as shown in FIG. A step (ST16) of adjusting the alkalinity of the absorbing solution by adding hydrogen bromide to the absorbing solution after the removal is provided.

  With this configuration, the alkalinity of the absorption liquid can be set to an appropriate value for the operation of an absorption refrigerator, etc., and hydrogen bromide reacts with lithium hydroxide to form the main component of the absorption liquid. And water are produced, so that the absorbing solution regenerated by the added hydrogen bromide is not adversely affected.

  According to the present invention, since lithium hydroxide is added to the absorption liquid, the copper content in the absorption liquid can be precipitated as an insoluble substance. In addition, since the additive is lithium hydroxide containing the same metal component as the metal component of lithium bromide, which is the main component of the absorbent, unnecessary metal is not mixed into the absorbent in the process of removing copper. . In addition, since lithium hydroxide is used to generate the insoluble material, an increase in cost can be suppressed.

  Embodiments of the present invention will be described below. In the present invention, the aqueous solution of lithium bromide containing the copper content to be removed is used as an absorption liquid for absorption refrigerators and absorption heat pumps (hereinafter referred to as “absorption refrigerators”). This absorption refrigerator or the like uses water as a refrigerant and an aqueous lithium bromide solution as an absorption liquid. The absorption refrigerator cools the fluid to be cooled by removing the latent heat when the refrigerant absorbed by the absorption liquid becomes water vapor from the fluid to be cooled. The absorption heat pump heats the fluid to be heated by giving the fluid to be heated the absorption heat generated when the refrigerant vapor is absorbed by the absorption liquid. The copper content in the absorbing solution is typically dissolved in a lithium bromide aqueous solution.

  First, with reference to FIG. 1, the absorbing liquid regeneration method according to the first embodiment of the present invention will be described. First, a LiBr (lithium bromide) aqueous solution containing copper to be removed is extracted from an absorption refrigerator or the like and placed in a container such as a drum can (ST11). At this time, when a foreign substance such as a metal oxide such as iron is floating in the LiBr aqueous solution, it is preferable to remove the foreign substance using a relatively coarse filter (a filter capable of removing the foreign substance).

  When the LiBr aqueous solution (absorbing liquid) is transferred to the container, a plurality of a predetermined amount of LiBr aqueous solution are sampled from the container (ST12). The amount of LiOH (lithium hydroxide) added to the LiBr aqueous solution in the container is determined using the plurality of samples (ST13). The addition amount of LiOH is determined as follows. LiOH having different addition amounts is added to a plurality of samples. Typically, a predetermined amount of LiOH is added to each sample. After filtering each sample, the alkalinity of each sample is measured. From the relationship between the alkalinity obtained in advance and the copper removal rate (for example, see FIG. 3 described later) To determine the amount of LiOH added.

  The reason why alkalinity was used as a standard for determining LiOH required for intended copper removal is that alkalinity can be typically measured by a titration method using phenolphthalein as an indicator. This is because according to the titration method, by adding an indicator to the LiBr aqueous solution extracted from an absorption refrigerator or the like, it is possible to obtain LiOH required for copper removal intended on the spot. Note that the amount of copper contained in the LiBr aqueous solution may be directly measured using an ICP analyzer or the like. When using an ICP analyzer or the like to measure the copper content, the copper content to be removed using the sample before the step (ST11) of extracting the LiBr aqueous solution from the absorption refrigerator and placing it in a container such as a drum can LiOH may be obtained by adding LiOH to the LiBr aqueous solution containing, and measuring the copper content of the LiBr aqueous solution after removing insoluble substances in advance. When using an ICP analyzer, it takes time and cost to transport the sample to the location where the ICP analyzer is located. However, the titration method can determine the LiOH required for the intended removal of copper on the spot. Therefore, it is preferable. If there is a method that can easily measure the copper content in addition to measuring the alkalinity, add a predetermined amount of LiOH to the above-mentioned plurality of samples and remove the copper content from each sample. The amount of copper after the measurement may be measured, and LiOH required for removing the copper content may be determined from the amount of LiOH added to the sample that is equal to or less than a predetermined value.

  Once the amount of LiOH added to the LiBr aqueous solution in the container is determined, the predetermined amount of LiOH determined in the previous step (ST13) is then added to the LiBr aqueous solution in the container and stirred (ST14). Then, a blue insoluble substance is deposited. Blue insoluble material typically precipitates when stirring is stopped. Next, this insoluble substance is removed (ST15). Insoluble material is typically removed by passing the aqueous LiBr solution in the container through a filter. As the filter, it is preferable to use a filter having a relatively fine mesh because an insoluble material can be removed with a high probability.

  Since the LiBr aqueous solution from which this insoluble material has been removed usually has a high alkalinity for use in an absorption refrigerator or the like, the alkalinity is adjusted by adding HBr (hydrogen bromide), and within the control standard value ( The alkalinity is within a range suitable for operation in an absorption refrigerator or the like (ST16). When HBr is used to adjust the alkalinity, HBr reacts with LiOH to produce water and LiBr, which is the main component of the absorbing solution, which is preferable because it is not necessary to remove the added HBr. When the alkalinity is adjusted, the adjusted LiBr aqueous solution is poured into an absorption refrigerator or the like (ST17) and used as an absorption liquid for the absorption refrigerator or the like. In this way, the copper content contained in the absorbent is removed and the absorbent is regenerated.

  Next, an absorbent regenerator 10 according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a system diagram of the absorbent regenerator 10. In FIG. 2, an alternate long and two short dashes line represents an absorption refrigerator 91 in which an absorption liquid that removes copper in the absorption liquid regenerating apparatus 10 is used, and a pipe 92 that connects the absorption refrigerator 91 and the absorption liquid regenerating apparatus 10. . The absorbent regenerator 10 includes a container 14 into which an absorbent AS (LiBr aqueous solution) extracted from the absorption refrigerator 91 is placed, and a pipe 11 that guides the absorbent AS from the absorption refrigerator 91 to the container 14. The pipe 11 includes a pump 12 for extracting the absorbing liquid AS from the absorption refrigerator 91, and a filter case 13 in which a filter 13f for removing foreign matter such as metal oxide is contained in the absorbing liquid AS. It is installed. The filter 13f is a relatively coarse filter (for example, a nominal aperture of 5 μm: 3M liquid filter back 100 series model 125 (trade name) manufactured by Sumitomo 3M Limited, or a nominal aperture of 2.5 mm: the same model 124). Used.

  Further, the absorbent regenerator 10 includes a pipe 15 that extracts the absorbent AS in the container 14 for stirring and filtering. The pipe 15 is provided with a pump 21 that extracts the absorbent AS from the container 14. The pipe 15 is connected to the three-way valve 22. In addition to the pipe 15, a pipe 16 and a pipe 17 are connected to the three-way valve 22. The pipe 16 is provided with a filter case 23 in which a filter 23f for removing insoluble substances generated by adding LiOH to the absorbent AS is accommodated. As the filter 23f, a filter having a relatively fine mesh (for example, a nominal aperture of 1 μm: 3M liquid filter back 500 series model 522 (trade name) manufactured by Sumitomo 3M Limited) is used. The pipe 16 is connected to the three-way valve 24 on the side opposite to that connected to the three-way valve 22.

  In addition to the pipe 16, a pipe 18 and a pipe 19 are connected to the three-way valve 24. The pipe 18 is disposed so as to return the absorbing liquid AS to the container 14. A pipe 17 is connected to the pipe 18. On the other hand, at the end of the pipe 19, a container 20 for containing the absorbent AS after removing insoluble substances is disposed.

  The absorbent regenerator 10 configured as described above operates as follows. Before operating the absorbent regenerator 10, the pipe 92 is connected to the pipe 11. The other end of the pipe 92 is connected to an absorption liquid inlet for maintenance of the absorption refrigerator 91. After the pipe 92 is connected, the inside of the absorption refrigerator 91 is pressurized with an inert gas such as nitrogen gas, and then the valve for the absorption liquid inlet for maintenance of the absorption refrigerator 91 is opened. Then, the pump 12 is started, the absorption liquid AS is extracted from the absorption refrigerator 91, and the extracted absorption liquid AS is put into the container 14. At this time, the absorbent AS flows into the container 14 through the filter 13f. By passing through the filter 13f, foreign substances such as metal oxide in the absorbing liquid AS are removed. When the extraction of the absorption liquid AS in the absorption refrigerator 91 is completed, the valve of the absorption liquid inlet for maintenance of the absorption refrigerator 91 is closed and the pump 12 is stopped. Note that the filter 13f and the filter case 13 do not have to be provided when no foreign matter is present in the absorbent AS. Further, when the absorbing liquid AS can be extracted only by pressurization with an inert gas in the absorption refrigerator 91, the pump 12 may not be provided.

When the absorption liquid AS is put in the container 14, a predetermined amount of LiOH is added to the absorption liquid AS in the container 14. The predetermined amount of LiOH is such an amount that the alkalinity of the absorbent AS after removing the produced insoluble substance described later becomes 200 mol / m ³ or more, and is typically obtained by taking a plurality of samples. When LiOH is added, the pump 21 is started, the three-way valve 22 is switched so that the absorbing liquid AS flows from the pipe 15 to the pipe 17, and the absorbing liquid AS returns to the container 14 through the pipe 18 (the pipe 16 and the pipe). The three-way valve 24 is switched (so that it does not flow into 19). In this way, the absorbing liquid AS is circulated from the container 14 back to the container 14 through the pipes 15, 17, 18, and the absorbing liquid AS to which LiOH has been added is stirred. Stirring is performed for about 10 to 30 minutes. By stirring, the absorption liquid AS and LiOH react reliably, and the copper content in the absorption liquid AS is deposited as a blue insoluble substance.

  After the stirring, the three-way valves 22 and 24 are switched so that the absorbing liquid AS flows from the container 14 through the pipe 15, the pipe 16, and the pipe 18 and returns to the container 14 again. If it makes such a flow, absorption liquid AS will pass filter 23f, and the insoluble substance deposited by this will be caught by filter 23f. The absorption liquid AS is filtered for about 60 minutes. After the filtration is completed, the three-way valve 24 is switched so that the absorbent AS flows from the pipe 16 to the pipe 19. Thereby, the absorbing liquid AS in the container 14 is transferred to the container 20.

  The absorption liquid AS transferred to the container 20 is suitable for use in the absorption refrigerator 91 while most of the copper content (typically about 95% of the copper content in the absorption liquid AS) is removed. It is higher than alkalinity. Therefore, the alkalinity is adjusted by adding HBr to the absorbent AS in the container 20. The addition of HBr is typically done manually. When the adjustment of the alkalinity is completed, the absorption liquid AS in the container 20 is reinjected into the absorption refrigerator 91.

  The absorption refrigerator 91 has been described above as an example, but the same applies to an absorption heat pump. In addition, an absorption cold / hot water generator that can generate cold water and hot water can be regarded as one form of an absorption refrigerator, and is included in the concept of an absorption refrigerator in this specification.

  In the above description, the container 14 into which the absorption liquid AS extracted from the absorption refrigerator 91 and the container 20 into which the filtered absorption liquid AS is to be provided are distinguished from each other. However, the filtered absorption liquid AS is returned to the container 14. The container 20 may be omitted. In this way, the absorbent regenerator 10 can be made compact. However, if the container 20 is provided separately from the container 14, the absorption liquid AS before and after filtration can be reliably separated, so that the filtered absorption liquid AS and the absorption liquid AS that could not be filtered are not mixed.

  In the above description, the absorbent regenerator 10 has been described as having the three-way valves 22 and 24. However, instead of the three-way valve 22, two-way valves may be provided in the pipes 16 and 17, respectively. Instead, a two-way valve may be provided for each of the pipes 18 and 19.

  In addition, as an example of the implementation timing of the present invention, the copper content in the absorption liquid (LiBr aqueous solution) is periodically measured with an ICP analyzer or the like during periodic inspection of the absorption refrigerator, etc., and the concentration of the copper content is predetermined. When the concentration becomes higher than the concentration, the copper content in the absorbing solution may be removed by the absorbing solution regeneration method according to the present invention. If it does in this way, corrosion of an absorption refrigerator etc. can be prevented continuously.

Hereinafter, examples in which tests were performed using a beaker will be described. Five LiBr aqueous samples containing 26.0 mg / L of copper were prepared. The alkalinity of this sample was 23 mol / m ³ (same for all five). LiOH was added to these samples in different amounts. After the addition, the mixture was stirred and allowed to stand for about 60 minutes. Thereafter, the mixture was filtered through 5 types C filter paper (JISP3801) to remove the precipitate of blue insoluble material generated by the addition of LiOH. Thereafter, the alkalinity and copper content of the sample after filtration were measured with an ICP emission spectrometer. About each sample, the alkalinity after filtration, the copper content after filtration, and the copper content removal rate are collectively shown in FIG.

  As shown in FIG. 3, there is a correlation between the alkalinity of the LiBr aqueous solution after filtration and the copper content removal rate. In other words, the copper removal rate has a correlation with the amount of LiOH added. Using this correlation, it is possible to determine the amount of LiOH added in the absorption liquid regeneration method according to the first embodiment of the present invention (see step ST13 in FIG. 1), without using an ICP analyzer or the like. The amount of LiOH added can be determined.

It is a flowchart explaining the absorption liquid reproduction | regeneration method which concerns on the 1st Embodiment of this invention. It is a systematic diagram of the absorption liquid reproduction | regeneration apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the correlation of the alkalinity of the solution after filtration, the copper content in a solution, and a copper content removal rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Absorption liquid reproduction | regeneration apparatus 12, 21 Pump 14, 20 Container 22, 24 Three-way valve 23f Filter 91 Absorption refrigerator

Claims (4)

Adding lithium hydroxide to an absorption solution of an absorption refrigerator or absorption heat pump mainly composed of an aqueous lithium bromide solution;
Removing insoluble substances containing copper produced by the addition of lithium hydroxide;
Absorption liquid regeneration method. The amount of lithium hydroxide added is such that the alkalinity of the absorbent after removal of the insoluble material is 200 mol / m ³ or more;
The method for regenerating an absorbent according to claim 1. Extracting the absorbent from the absorption refrigerator or absorption heat pump prior to adding the lithium hydroxide;
Injecting the absorption liquid after removing the insoluble substance into the absorption refrigerator or absorption heat pump;
The method for regenerating an absorbent according to claim 1 or 2. Adding hydrogen bromide to the absorbent after removing the insoluble material to adjust the alkalinity of the absorbent;
The absorption liquid reproduction | regeneration method of any one of Claim 1 thru | or 3.

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