Patent Publication Number: US-2007104626-A1

Title: Heat-transfer-medium heating and cooling apparatus

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a heat-transfer-medium heating and cooling apparatus, and, more particularly, to a heat-transfer-medium heating and cooling apparatus which performs temperature control of a low-temperature reactor which is used in a chemical reaction process or the like.  
      2. Description of the Related Art  
      A chemical reaction process, such as organic synthesis or crystallization, requires high-precision temperature control. The chemical reaction process therefore uses a double-structure container having an independent jacket which permits communication of a heat transfer medium with outside a reactor. As disclosed in Japanese Unexamined Patent Publication No. H11-37623, for example, the interior of the reactor is indirectly kept in a predetermined low temperature state by providing a heat transfer medium feeder for recirculating a heat transfer medium cooled down to a predetermined temperature to the jacket side of the reactor.  
      Such a heat transfer medium feeder generally has an expansion vessel provided in series to the heat-transfer-medium-suction side of the heat transfer medium pump to prevent bubbles from entering the heat transfer medium pump and absorb a change in volume originating from a change in temperature of heat transfer medium. To keep the suction pressure of the heat transfer medium pump constant, the expansion vessel is provided with pressure control means, such as a pressure control valve or a pressure reducing valve, which makes compressed gas enter the expansion vessel when the volume of the heat transfer medium decreases due to a reduction in temperature of heat transfer medium and drains the compressed gas from the expansion vessel when the volume of the heat transfer medium increases due to a rise in temperature of heat transfer medium.  
      In cleaning the reactor, it is necessary to perform an operation of cyclically supplying a high-temperature heat transfer medium to the jacket to heat a detergent in the reactor. This requires provision of some means for feeding the heat transfer medium in addition to the heat transfer medium feeder. The heat-transfer-medium feeding means, if configured to drain the heat transfer medium from inside the jacket and feed the heat transfer medium thereto, makes the device configuration including pipings complex, and needs to switch the heat transfer medium and the heat transfer medium to be supplied to the jacket from one to the other, thereby making the process complex.  
      As a solution to this problem, means for heating a heat transfer medium may be provided in the recirculation system of the heat transfer medium feeder, so that the heat transfer medium is heated to a predetermined temperature and recirculated to the jacket to heat the reactor. In the foregoing case where the expansion vessel is provided in series to the heat-transfer-medium-suction side of the pump, however, the heat transfer medium in the expansion vessel as well as the heat transfer medium in the pipings in the recirculation system and the jacket should be heated. This results in a huge energy cost required for heating and cooling. Because a large-scale system, in particular, uses a large expansion vessel, the response drops considerably, thus increasing the energy loss.  
      Further, an increase in volume which originates from a rise in temperature of heat transfer medium and vaporization of the heat transfer medium may cause expensive heat transfer medium vapor to be discharged outside when the pressure control means is actuated to discharge the gas in the expansion vessel.  
     SUMMARY OF THE INVENTION  
      Accordingly, it is an object of the invention to provide a heat-transfer-medium heating and cooling apparatus capable of reducing the energy cost and effecting efficient heating and cooling of a reactor by minimizing the amount of a heat transfer medium (coolant) to be heated and cooled, thereby avoiding complication and enlargement of the configuration of the apparatus.  
      To achieve the object, a heat-transfer-medium heating and cooling apparatus according to the present invention comprises a pump which pumps out a heat transfer medium; a cooling unit which cools the heat transfer medium discharged from the pump; a reactor whose temperature is controlled by the heat transfer medium output from the cooling unit; and a heating unit which heats the heat transfer medium output from the reactor, wherein a recirculation path for recirculating the heat transfer medium to the pump via the pump, the cooling unit, the reactor, and the heating unit, a reserve path being provided in a pump-suction-side path extending from the heating unit to the pump, and branching from the pump-suction-side path to connect to a liquid phase portion of an expansion vessel.  
      In the heat-transfer-medium heating and cooling apparatus according to the invention, the reserve path may branch upward from the pump-suction-side path, or the expansion vessel may have a condenser communicating with a gas phase portion of the expansion vessel, and having a cooling unit which cools a heat transfer medium vapor for liquification thereof, a path for returning the heat transfer medium liquefied by cooling in the cooling unit, and a gas relief valve which discharges a gas from the gas phase portion of the condenser according to a pressure in the condenser.  
      As the expansion vessel is so disposed as to branch from the recirculation path in the heat-transfer-medium heating and cooling apparatus of the invention, the heat transfer medium to be heated or cooled can be restricted to the heat transfer medium that recirculates in the recirculation path at the time of switching heating of the reactor to cooling, or vice versa, thus eliminating the need to heat or cool the heat transfer medium in the expansion vessel. This leads to a reduction in energy cost and an improved response and allows the reactor to be reliably heated or cooled to a predetermined temperature.  
      As the reserve path which connects to the expansion vessel is branched upward from the pump-suction-side path, bubbles present in the heat transfer medium flowing in the pump-suction-side path can be discharged to the expansion vessel efficiently, thus preventing the bubbles from entering the pump. Further, the provision of the condenser at the expansion vessel can prevent a heat transfer medium vapor in the expansion vessel from being discharged outside through the gas relief valve due to a pressure rise in the recirculation system.  
      What is more, because a heat transfer medium can be heated and cooled by a single closed cycle system, the apparatus configuration is prevented from becoming complex or larger, thereby leading to reductions in equipment cost and running cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The figure is a system diagram showing a heat-transfer-medium heating and cooling apparatus according to one embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      A heat-transfer-medium heating and cooling apparatus shown in the figure has a pump  11  which pumps out a heat transfer medium, a heat exchanger  12  or a cooling unit which cools down the heat transfer medium pumped out from the pump  11 , a reactor  13  whose temperature is controlled by the heat transfer medium output from the heat exchanger  12 , a heating unit  14  which heats the heat transfer medium output from the reactor  13 , and pipings which connect those components. The pipings form a recirculation path  15  of a closed cycle which recirculates a heat transfer medium to the pump  11  via the pump  11 , the heat exchanger  12 , the reactor  13  and the heating unit  14 .  
      The heat exchanger  12  cools the recirculating heat transfer medium to a predetermined temperature by indirectly exchanging heat with a low-temperature fluid, such as a low-temperature liquefied gas, which is supplied to the heat exchanger  12  from a low-temperature fluid inlet path  16  and discharged to a discharge gas path  17 . The heating unit  14  heats the recirculating heat transfer medium to a predetermined temperature with a heater  14   a.    
      The reactor  13  has a jacket  13   b  provided on the outer surface of a reaction container  13   a . The heat transfer medium flows through the jacket  13   b . The temperature of the heat transfer medium to be supplied to the jacket  13   b  is adjusted by controlling the opening/closing of a flow regulator  20  provided in the low-temperature fluid inlet path  16  and the performance of the heater  14   a  using a temperature indicator and controller (TIC)  19  provided in an inlet-side path  18  of the jacket  13   b.    
      A reserve path  23  which branches upward from a pump-suction-side path  21  and connects to a liquid phase portion  22   a  of an expansion vessel  22 , is provided in the pump-suction-side path  21  extending from the heating unit  14  to the pump  11 . The expansion vessel  22  is provided branching from the recirculation path  15  via the reserve path  23 , and, unlike the conventional type, is separated from the recirculation flow of the heat transfer medium, not in series to the recirculation flow from the viewpoint of flow. The expansion vessel  22  is configured so that the expansion vessel  22  and the recirculation path  15  exchange the heat transfer medium according to a change in the volume of the heat transfer medium flowing in the recirculation path  15 , and the recirculation path  15  is set in a liquid sealing state to inhibit a gas from entering the recirculation path  15  from the expansion vessel  22 .  
      A gas phase portion  22   b  of the expansion vessel  22  is connected with a gas inlet valve  24 , which is actuated according to the pressure in the expansion vessel  22 , and a condenser  25 . The condenser  25  is provided with a gas relief valve  26  which is actuated according to the pressure in the condenser  25 .  
      The condenser  25  has a cooling unit  27  for cooling a heat transfer medium vapor for liquification thereof, a mist separator  28  that separates the heat transfer medium liquefied by the cooling unit  27  and a gas which is not liquefied from each other, a heat transfer medium return path  29  for returning the heat transfer medium separated by the mist separator  28  to the expansion vessel  22 , and a float valve  30  which is opened and closed according to the amount of the heat transfer medium (the amount of the fluid) remaining in the mist separator  28  and a differential pressure.  
      The gas inlet valve  24  and the gas relief valve  26  are actuated according to a change in pressure originating from a change in the volume of the heat transfer medium recirculating in the recirculation path  15  which communicates with the valves  24  and  26  by means of pressure. When the heat transfer medium is heated to increase the volume, raising the pressure in the system, the gas relief valve  26  is actuated to release the gas in the system to the outside thereof, thereby keeping the pressure in the system to or lower a set upper limit pressure. When the heat transfer medium is cooled to decrease the volume, lowering the pressure in the system, the gas inlet valve  24  is opened to supply a gas which does not affect the heat transfer medium, e.g., a nitrogen gas, from outside the system as a compressed gas, thereby keeping the pressure in the system to or higher a set lower limit pressure.  
      At the time of discharging the gas from the gas relief valve  26 , the heat transfer medium vapor contained in the gas can be condensed for liquification by cooling the gas which is drained from the gas phase portion  22   b  of the expansion vessel  22  with the cooling unit  27  of the condenser  25 . This can prevent the heat transfer medium vapor as well as the gas to be released through the gas relief valve  26  from being discharged to the outside. When the amount of the heat transfer medium retaining in the mist separator  28  becomes a certain level or greater, the float valve  30  is opened to return the heat transfer medium to the expansion vessel  22  for recycle from the mist separator  28  via the heat transfer medium return path  29 .  
      In the thus configured heat-transfer-medium heating and cooling apparatus, with a predetermined cooling temperature set in the temperature indicator and controller  19  at the time of cooling the reactor  13 , the temperature indicator and controller  19  is actuated according to the temperature of the heat transfer medium flowing in the inlet-side path  18 , so that at the time of cooling, the cooling state of the heat transfer medium in the heat exchanger  12  is regulated by mainly controlling the degree of opening of the flow regulator  20 .  
      At the time of cooling, the heat transfer medium in the expansion vessel  22  flows into the recirculation path  15  due to a reduction in the volume of the heat transfer medium originating from a temperature drop, and the gas inlet valve  24  is opened or closed according to a pressure drop originating from a reduction in the amount of the heat transfer medium in the expansion vessel  22 , permitting supply of the compressed gas into the system to keep the pressure in the system at a predetermined pressure. At this time, the heat transfer medium which has a relatively high temperature flows into the recirculation path  15  from the expansion vessel  22 . As the flow amount of the heat transfer medium is a slight amount according to the amount of the volume of the heat transfer medium reduced by cooling, however, it does not cause a large change in the temperature of the heat transfer medium recirculating the recirculation path  15 .  
      Because the expansion vessel  22  is separated from the recirculation path  15 , it is unnecessary to cool the heat transfer medium in the expansion vessel  22 , making the amount of the heat transfer medium to be cooled smaller than the conventional apparatus in which all the heat transfer mediums are to be cooled. Therefore, the heat-transfer-medium heating and cooling apparatus of the invention can reduce the energy cost for cooling the heat transfer medium significantly as compared with the conventional apparatus, and is excellent in response characteristic.  
      With a predetermined heating temperature set in the temperature indicator and controller  19  at the time of heating the reactor  13 , the temperature indicator and controller  19  is actuated according to the temperature of the heat transfer medium flowing in the inlet-side path  18 , so that at the time of heating, the heating state of the heat transfer medium in the heating unit  14  is regulated by mainly controlling the performance of the heating unit  14 .  
      At the time of heating, an increase in the volume of the heat transfer medium originating from an increase in the temperature of the heat transfer medium causes a part of the heat transfer medium recirculating in the recirculation path  15  to flow-into the expansion vessel  22 , thus raising the pressure in the condenser  25 . The gas relief valve  26  is opened or closed according to the pressure rise to discharge the gas outside the system, thereby keeping the pressure in the system at a predetermined level. Bubbles of the heat transfer medium vapor generated by heating float in the heating unit  14  in the reserve path  23  branching upward from the pump-suction-side path  21 , thus preventing the pump  11  from sucking the bubbles. The bubbles of the heat transfer medium vapor floating in the expansion vessel  22  from the reserve path  23  flow into the liquid phase portion  22   a  of the expansion vessel  22 , and contacts a heat transfer medium lower in temperature than the heat transfer medium that recirculates in the recirculation path  15  for reliquification or is reliquefied at the cooling unit  27  of the condenser  25 .  
      Bubbles in the heat transfer medium can be efficiently floated toward the reserve path  23  to be separated by branching the reserve path  23  upward from the pump-suction-side path  21  in the vertical direction, and using thick pipes for the pump-suction-side path  21  and the reserve path  23  or bending the pump ( 11 ) side portion of the pump-suction-side path  21  downward.  
      Because the heat transfer medium to be heated is just the heat transfer medium that recirculates in the recirculation path  15  as mentioned above, it is possible to considerably reduce the energy cost required for heating the heat transfer medium and improve the response characteristic. In addition, while the heat transfer medium that is heated by the heating unit  14  according to an increase in the volume of the heat transfer medium flows into the expansion vessel  22 , the flow amount of the heat transfer medium is small and the heat transfer medium is not heated further. Accordingly, a heat transfer medium vapor is hardly generated in the expansion vessel  22 , so that even if the heat transfer medium vapor is evaporated, the vapor can be trapped by the condenser  25  for recycle, thereby minimizing the loss of the heat transfer medium.  
      The heating unit and the cooling unit in use, which are provided in the recirculation path  15 , can be selected adequately according to the conditions, such as the heating temperature, the cooling temperature and the process amount. Any heating source and any cooling source can be used. The cooling temperature in the cooling unit  27  can be set arbitrarily according to the boiling point of the heat transfer medium, the expected amount of vapor, and the vapor temperature. An ordinary cooling system, such as air cooling or water cooling, can be employed, and the cooling system can take any structure and shape. Further, the heat transfer medium in use can be selected adequately according to the cooling temperature and the heating temperature. For example, silicone oil or alcohols, hydrofluoroether can be used as the heat transfer medium.