JPS6144230B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a closed circulation type absorption refrigerating machine, and more particularly to an absorption refrigerating machine equipped with a liquefaction removal device that can efficiently remove hydrogen gas generated within the refrigerating machine. [Background of the Invention] Generally, a closed circulation type absorption refrigerator uses water as a refrigerant and a concentrated lithium bromide aqueous solution as an absorption liquid. The highest temperature part of the refrigeration cycle in an absorption chiller is the high-temperature regenerator that concentrates the absorption liquid, and the maximum temperature in a dual-effect chiller can reach approximately 160°C. The concentration of lithium bromide in the absorption liquid at this time is approximately
The concentration is as high as 65%. Therefore, the lithium bromide aqueous solution, which is originally highly corrosive, becomes high temperature and highly concentrated, further increasing its corrosivity, and therefore an inhibitor is generally added for the purpose of preventing corrosion of refrigerator materials. There are various types of inhibitors, but they all have advantages and disadvantages, and none can completely prevent corrosion. Therefore, hydrogen generated due to corrosion of carbon steel, which is the main constituent material of the refrigerator, accumulates inside the refrigerator. However, since the absorption refrigerator has a completely hermetic structure and operates at several mmHg to several tens of mmHg internally, the generated hydrogen increases the internal pressure and reduces the refrigeration effect. For this reason, in the past, refrigerator operators periodically used exhaust pumps such as vacuum pumps to
Accumulated hydrogen was forcibly discharged from the aircraft.
However, recently there has been a trend towards further downsizing of absorption chillers, and although maintenance-free and unmanned operation has become a major industrial advantage for such small machines, the removal of hydrogen gas inside the machine has become a major obstacle. It's summery. Furthermore, absorption chillers are generally installed in closed rooms with poor ventilation, such as basements within buildings. Therefore, it is not preferable to discharge a large amount of explosive and flammable hydrogen gas at once.
Conventional absorption refrigerators are equipped with a bleed tank and vacuum pump to store non-condensable gases, but none have a device that detoxifies non-condensable gases such as hydrogen and automatically maintains internal pressure. . [Object of the Invention] An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and to provide a closed circulation type absorption refrigerating machine that continuously liquefies and removes hydrogen gas inside the machine. [Summary of the invention] In order to achieve such an object, the present invention has the following features:
It oxidizes and liquefies hydrogen gas generated in a closed container, and is particularly equipped with a device that liquefies and removes it using a metal oxide whose free energy change during reaction with the hydrogen gas is negative. [Example] Hereinafter, details of the present invention will be explained using examples shown in the drawings. Generally, closed circulation absorption refrigerators use water as a refrigerant and a concentrated aqueous solution of lithium bromide as a hygroscopic absorbent. As shown in the principle system diagram in Fig. 1, this refrigerator consists of a regenerator 1, a condenser 2, an evaporator 3, an absorber 4, pumps 6 that circulate absorption liquid and refrigerant between these, and It consists of an exchanger (not shown), and each part operates as follows. (A) Evaporator 3 Chilled water flows through the tubes of the evaporator tube bundle of evaporator 3, and refrigerant is spread outside the tubes, drawing heat from the cold water using the latent heat of evaporation. (B) Absorber 4 Lithium bromide aqueous solution has a significantly lower evaporation pressure than water at the same temperature, and can absorb water vapor generated at considerably lower temperatures. In the absorber 4, the refrigerant evaporated in the evaporator 3 is absorbed by a lithium bromide aqueous solution (absorption liquid) sprinkled on the outer surface of the tube bundle of the absorber, and the absorption heat generated at this time is cooled by cooling water passing through the tubes. . (C) Regenerators 1a, 1b The concentration of the dilute solution that has absorbed the refrigerant in the absorber 4 decreases, and its absorption capacity becomes weaker. Therefore, the solution circulation pump 6
A part of the refrigerant is sent to the high-temperature regenerator 1a, heated by high-temperature steam, etc., and the refrigerant vapor is evaporated and separated.
The solution is concentrated and the concentrated solution is returned to the absorber 4. Furthermore, a part of the dilute solution discharged from the absorber 4 is sent to the low-temperature regenerator 1b by the solution circulation pump 6, where it is heated and concentrated by the refrigerant vapor generated in the high-temperature regenerator 1a.
The concentrated solution returns to absorber 4. (D) Condenser 2 The refrigerant vapor separated in the regenerator 1 is cooled by cooling water flowing through the pipes in the condenser 2, condenses into liquid, and returns to the evaporator 3. (E) Heat exchanger A low-temperature dilute solution heading from the absorber 4 to the regenerator 1 is preheated by a high-temperature concentrated solution heading from the regenerator 1 to the absorber 4, thereby reducing the amount of heating by the regenerator. (F) Pump 6 Pump 6 circulates concentrated solution, dilute solution, and refrigerant. The absorber 4, the regenerator 1, and the pump 6 have the same function as the compressor of a compression refrigerator. The absorption liquid circulates between the regenerator 1 and the absorber 4 via a heat exchanger during refrigerator operation. Generally, the higher the concentration of the absorption liquid, the higher the refrigeration efficiency, so in order to concentrate the absorption liquid,
Regenerator 1 needs to be maintained at a higher temperature. On the other hand, in the refrigerator, in the high-temperature regenerator 1a and the low-temperature regenerator 1b, when concentrating the lithium bromide solution, non-condensable gases such as H ₂ generated by corrosion and NOx generated by the reduction of the inhibitor NO ₃ - are generated together with water vapor. do. This non-condensable gas is led to and stored in a bleed tank 7 maintained at a high vacuum. This bleed tank 7 normally has a capacity of about 50 ml, and is periodically operated by an operator to discharge non-condensable gas to the outside of the machine using a bleed pump 8. The present invention provides such a closed-circulation absorption refrigerator, in which hydrogen gas generated by corrosion of constituent materials is oxidized and removed in the high-temperature and low-temperature regenerators of the refrigerator. A reactor filled with metal oxide, especially copper oxide, is installed between the tank and the tank. The reactor is then heated with waste heat from a high-temperature regenerator, and hydrogen generated within the reactor is passed through to form water vapor, which is then cooled and removed by liquefaction. The best way to make hydrogen harmless and reduce its volume is to liquefy it as water. Oxidation methods for this purpose include methods using catalysts, methods using oxidizing agents, and methods using reduction reactions of metal oxides. Among these, methods using catalysts are generally expensive and additionally require an oxidizing agent. The use of oxidizing agents is undesirable because it promotes corrosion of the constituent materials. Furthermore, oxidizing agents are generally expensive and difficult to regenerate. On the other hand, methods using metal oxides are generally cheaper and easier to regenerate, although it depends on the type. More specifically, any metal oxide whose free energy change during the reaction of reducing the metal oxide with hydrogen is negative can be used in principle. Among them, copper oxide is advantageous. Copper oxide has a negative free energy change when reacting with hydrogen even at room temperature, and in principle the reaction can proceed even at room temperature. However, in practice, it is preferable to raise the reaction temperature to quickly liquefy the generated hydrogen. The inventors obtained through experiments
Figure 2 shows the relationship between hydrogen removal rate and temperature when CuO is used. It can be seen that the hydrogen removal rate increases as the reaction temperature increases, and hydrogen is removed as H ₂ O at temperatures above about 250°C. However, in a closed circulation absorption chiller, combustion waste gas of several hundred degrees Celsius is discharged from the boiler of the high-temperature regenerator, so the advantage of using this waste heat is that the reaction temperature can be raised without the need for new energy. There is. In the reaction of oxidizing hydrogen with copper oxide, the larger the surface area of the copper oxide used, the more advantageous it is, and this is greatly affected by the filling amount, but if the filling amount or packing density is too large, the pressure between the inside of the refrigerator and the bleed tank will increase. Since the difference is not that large, it will be difficult to quickly extract hydrogen from the aircraft. Therefore, in this case, the important issue is whether the copper oxide used will react effectively not only on the surface but also on the inside to become metallic copper. Figure 3 shows the results of investigating the reactivity of copper oxide. A quartz tube with an inner diameter of 1 cm was filled with 19 g of copper oxide in the form of a wire with a diameter of 0.05 cm and a length of 0.5 cm.
It was heated to 290°C, hydrogen gas was flowed at a flow rate of 3 ml/min, and the hydrogen concentration was analyzed using a gas chromatograph. As is clear from the figure, the hydrogen removal rate is
It is 100% up to 30 hours, but drops rapidly after 30 hours. From the following reaction equation, 19g of CuO
This agrees with the theoretically calculated results assuming that 100% reaction occurs, and it can be seen that copper oxide reacts 100%. CuO+H ₂ →Cu+H ₂ O As a hydrogen liquefaction removal device, the present invention uses a reactor filled with copper oxide and an attached cooling device to convert hydrogen into gaseous H ₂ O, and then cools it to liquid form.
It is removed as H ₂ O. In the present invention, the copper oxide filled in the reactor is preferably small in the form of linear or granular shapes in order to maximize its surface area. Further, in the present invention, copper oxide is used because a high reaction rate can be obtained at a relatively low temperature, but other materials such as iron oxide, nickel oxide, cobalt oxide, lead oxide, etc. can be used. Furthermore, as for the heating temperature, from the results shown in Figure 2, the reaction can proceed if it is 100℃ or higher, but in practical terms, it is more than 100℃ or higher.
300°C is appropriate; temperatures over 300°C are not a good idea from the point of view of energy conservation. The water vapor generated by the reaction with copper oxide is liquefied and removed by a cooler attached after the reactor. As a result, no gas flows into the bleed tank, and the pressure is always kept lower than that inside the machine, allowing the pressure inside the refrigerator to be maintained and stable operation to be possible. The water vapor cooler may use cooling water that circulates inside the refrigerator. When storing condensate in a cooler, assuming that the operating time of the refrigerator is approximately 1000 hours/year and assuming maintenance free for 5 years, an extremely small size of about 1.5 is sufficient for a normal refrigerator. Next, examples of the present invention will be described. Example 1 A gas-fired dual-effect absorption refrigerator with a refrigeration capacity of 250 tons was used, and a liquefaction removal device was installed in the middle of the bleed piping from the high-temperature and low-temperature regenerators to the bleed tank. The liquefaction removal device consists of a reactor in which 100 g of linear CuO with a diameter of 0.05 cm and a length of 0.5 cm is filled in a stainless steel container with a vent hole of 3 cm in inner diameter and 20 cm in length.
A cooler with attached copper pipes for passing 25°C cooling water was used. The refrigerator was operated at full load and its waste heat was used to maintain the reactor at 250°C.
As a result of gas chromatography analysis of gas sampled from the bleed tank using a vacuum pump, no hydrogen gas was detected even after 100 hours. Additionally, no increase in pressure inside the aircraft was observed. Example 2 The temperature of the reactor was maintained at 200° C. in the same manner as in Example 1, and gas analysis of the bleed tank was conducted. As a result, no hydrogen was detected even after 100 hours, and there was no pressure increase inside the refrigerator. Example 3 Metal copper was collected after the reaction from the reactors used in Examples 1 and 2, heated to 400°C in air for 5 hours, and then filled into a reactor with a diameter of 2 cm and a length of 20 cm. and the reaction temperature was maintained at 300°C. As a result of gas analysis in the extraction tank after 50 hours of operation using the same method as in Example 1, no hydrogen was detected. Example 4 As shown in Fig. 4, the reactor consists of an inner tube 9 made of stainless steel with a diameter of 30 mm and an outer tube 10 with a diameter of 150 mm provided with heat exchange fins 8, an exhaust gas inlet pipe 11 of a high temperature regenerator, and a gas discharge tube. Diameter filled into pipe 12 and inner cylinder 9
It consists of linear CuO13 with a length of 0.5 mm and a length of 5 mm. Such a reactor was arranged in the extraction piping of a gas-fired dual-effect absorption refrigerator having a refrigeration capacity of 125 tons as shown in the system diagram in FIG. Hydrogen gas generated in the high-temperature and low-temperature regenerators is introduced into the reactor 16 through a bleed pipe 14 and a valve 15. The CuO pellets 13 in the reactor 16 are heated to about 300° C. by exhaust gas at about 500° C. from the high temperature regenerator supplied through the heating gas inlet pipe 18. At this time, the heating efficiency of CuO is increased by the heat exchange fins 8. In the reactor 16, hydrogen gas reacts with CuO to become water vapor, and the reacted CuO is reduced to metal Cu. The generated water vapor passes through a valve 20 and is cooled into a drain by a cooler 22 having a flexible pipe 21 through which cooling water is passed. There is a hydrogen detector 2 in the bleed tank 23.
4 is set, and an alarm 25 is configured to notify when hydrogen gas flows into the bleed tank 23. A 125 refrigeration ton dual effect absorption chiller was operated at full load for 50 hours, but no alarm was generated to notify the inflow of hydrogen into the bleed tank 23. Further, gas sampled from the bleed tank 23 by the vacuum pump 26 was analyzed using a gas chromatograph, but no hydrogen was detected. Thereafter, after 500 hours of continued operation, the alarm 25 was activated and the inflow of hydrogen into the bleed tank 23 was detected. So valves 15 and 20
was closed, valves 26 and 27 were opened to allow hydrogen gas to flow through the reactor 16, and a small amount of hydrogen in the bleed tank 23 was discharged by the vacuum pump 26. As a result, the alarm 25 stopped operating again, and the refrigerator continued to operate smoothly from then on. Moreover, the reduced metal Cu in the reactor 16 could be regenerated into CuO again by opening the air introduction valves 28 and 29 and introducing air. [Effects of the Invention] As described above, according to the present invention, it is clear that the hydrogen gas conventionally generated in a refrigerator can be efficiently and continuously liquefied and removed with a simple operation. This has the great effect of preventing a pressure rise inside the machine and maintaining high refrigeration performance without maintenance.
Further, according to the present invention, there is no danger of releasing dangerous hydrogen gas into a small room all at once, and hydrogen gas, which has a high risk of explosion, can be easily rendered harmless. Furthermore, it is clear that hydrogen can be continuously liquefied and removed while at the same time the reaction product can be regenerated without much effort, and that, together with exhaust gas utilization, this method has great effects both economically and in terms of resource conservation.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the principle of a closed circulation absorption refrigerator, Figure 2 is a diagram showing the relationship between hydrogen removal rate and reaction temperature, Figure 3 is a diagram showing the relationship between hydrogen removal rate and time, and Figure 4 is a diagram showing the relationship between hydrogen removal rate and time. The figure is a sectional view of an embodiment of a reactor for liquefaction removal used in the present invention, and FIG. 5 is a system diagram of an embodiment of a closed circulation type absorption refrigerator of the present invention. 1... Regenerator, 2... Condenser, 3... Evaporator,
4...Absorber, 7...Bleed tank, 16...Reactor, 22...Cooler, 23...Bleed tank, 24
...Hydrogen detector.

Claims (1)

[Scope of Claims] 1. A device for cooling a cooling medium by repeatedly concentrating and diluting an aqueous solution of a hygroscopic substance in a closed container, the container being filled with a metal oxide, and containing a metal oxide. a reactor that oxidizes and evaporates hydrogen gas generated in the container through the hydrogen gas; and a cooler that cools and liquefies the vapor from the reactor, and is configured to liquefy and remove the hydrogen gas. A closed circulation absorption refrigerator characterized by being equipped with a liquefaction removal device. 2. The closed circulation absorption refrigerating machine according to claim 1, wherein the liquefaction removal device is disposed between the high-temperature and low-temperature regenerators and the bleed tank. 3. The closed circulation absorption refrigerator according to claim 1, wherein the reactor of the liquefaction removal device is heated with exhaust gas from a high-temperature regenerator. 4 The metal oxide filled in the reactor is:
A closed circulation absorption refrigerator according to claim 1, characterized in that the material is copper oxide. 5 The metal oxide filled in the reactor is:
The closed circulation absorption refrigerator according to claim 1, characterized in that the material is any one of iron oxide, nickel oxide, cobalt oxide, and lead oxide. 6. Claim 1, characterized in that the liquefaction removal device is equipped with two or more reactors in parallel so that the reacted metal copper can be regenerated while liquefying and removing hydrogen generated in the refrigerator. Closed circulation type absorption refrigerator.