Abstract:
The present invention relates to an apparatus for recovering re-evaporated steam and condensate, and in particular, to an apparatus for mixing the steam re-evaporated from condensate that is discharged from a heating unit for heating an object to be treated, with high-temperature steam supplied from a boiler, and for resupplying the mixed steam to the heating unit. To this end, the apparatus comprises: a steam recovery unit for recovering the condensate discharged from a heating unit for heating an object to be treated, and the steam re-evaporated from the condensate, and then supplying the recovered re-evaporated steam to a steam-pressurizing unit and the recovered condensate to a boiler; and the steam-pressurizing unit for mixing the re-evaporated steam supplied from the steam recovery unit, with high-temperature steam supplied from the boiler and then supplying the mixed steam to the heating unit. Therefore, with a closed circuit, the apparatus can recover the whole quantity of the re-evaporated steam and condensate for use, prevent the release of steam into the air and utilize a latent heat contained in the condensate, thereby improving the efficiency of energy consumption.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation of pending International Patent Application PCT/KR2009/006259 filed on Oct. 28, 2009, which designates the United States and claims priority of Korean Patent Application No. 10-2008-0112781 filed on Nov. 13, 2008, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to an apparatus for recovering re-evaporated steam and condensate, and more particular, to an apparatus for mixing the steam re-evaporated from condensate that is discharged from a heating unit for heating an object to be treated, with high-temperature steam supplied from a boiler, and for resupplying the mixed steam to the heating unit. 
       BACKGROUND OF THE INVENTION 
       [0003]    In general, a steam heating system is constructed to be connected to a condensate recovery apparatus for supplying heated steam to a heating unit formed in a heat exchanger, and discharging condensate generated by heating. 
         [0004]      FIG. 1  is a block diagram illustrating the construction of a steam heating system according to the prior art. 
         [0005]    As shown in  FIG. 1 , the steam heating system includes a boiler  10  for producing high-temperature steam, first and second heating units  30  and  30 ′ for heating an object to be treated using the high-temperature steam produced and supplied from the boiler  10 , steam traps  40  and  40 ′ for discharging only the condensate supplied from the heating units  30  and  30 ′, a condensate tank  50  for collecting the condensate discharged from the steam traps  40  and  40 ′ and receiving makeup water from the outside, and a feed water pump  51  for allowing the condensate collected in the condensate tank  50  to be supplied to the boiler  10 . 
         [0006]    The condensate supplied to the boiler  10  by the feed water pump  51  is heated by a burner and is supplied to the first heating unit  30  and the second heating unit  30 ′ via a header  20  and check valves  31  and  31 ′ in the form of high-pressure superheated steam. 
         [0007]    The steam supplied to the first and second heating units  30  and  30 ′ is condensed while dropping in temperature through the heat exchange in the first and second heating units  30  and  30 ′ and then is changed into a wet saturated vapor state. 
         [0008]    At this time, the condensate produced when the steam is condensed in the first and second heating units  30  and  30 ′ is collected in the steam traps  40  and  40 ′ installed at a lower portion of the first and second heating units  30  and  30 ′. 
         [0009]    The steam traps  40  and  40 ′ generally employ a bucket or float type. When more than a predetermined amount of condensate is introduced into the steam traps  40  and  40 ′, the bucket or float is lifted up by buoyancy of the condensate to cause values  41  and  41 ′ of the steam traps to be opened so that only the condensate is discharged to the condensate tank  50 . 
         [0010]    The condensate discharged to the condensate tank  50  from the steam traps  40  and  40 ′ is partly evaporated to the air while dropping in pressure. Then, the residual condensate remaining in the condensate tank  50  is mixed with makeup water supplied from the outside and then is supplied to the boiler via the feed water pump  51 . 
         [0011]    The makeup water is generally supplied from a makeup water tank  60  and a makeup water supply pump  61 , which are installed separately, and a valve  62  may be installed on a supply line. 
         [0012]    Such a conventional, however, entails the following problems. 
         [0013]    The steam traps  40  and  40 ′ are installed to prevent the steam inside the heating units  30  and  30 ′ from being discharged, preferably, to prevent latent heat contained in the steam from escaping to the outside of the heating units  30  and  30 ′. However, among the condensate discharged to the condensate tank  50  from the steam traps  40  and  40 ′, a considerable amount of condensate is evaporated to the air, and thus the energy efficiency is extremely low. 
         [0014]    In addition, since the makeup water is required to be continuously supplied as much as steam lost to the air, a large quantity of water is consumed, and the condensate is fed to the boiler  10  in a state of dropping in temperature by being mixed with a large amount of room temperature makeup water. As a result, a large amount of fuel must be consumed to heat the low temperature condensate into high-temperature steam. 
         [0015]    Meanwhile, in order to improve such a problem involved in the use of the steam traps, a technology has been proposed in which the steam traps are removed from the lower portion of the first and second heating units  30  and  30 ′, a sealed type feed water tank is installed at a position lower than the first and second heating units  30  and  30 ′ to allow the condensate to be collected in the feed water tank by gravity, and the water in the sealed type feed water tank is forcibly supplied to the boiler via feed water pump. 
         [0016]    However, the steam heating system from which the team traps are removed encounters a problem in that the condensate can be moved by gravity but if the release of steam (part of steam released to the air) is not conducted, a difference pressure is not formed, resulting in slow heat circulation. 
         [0017]    Furthermore, a cavitation occurs when the feed water pump is actuated to feed the condensate collected in the feed water tank, thus leading to damage of the feed water pump. 
       SUMMARY OF THE INVENTION 
       [0018]    Accordingly, the present invention has been made in order to solve the above-mentioned problems associated with the prior art, and it is an object of the present invention to provide an apparatus for recovering re-evaporated steam and condensate for a boiler, in which the steam re-evaporated from condensate discharged from a heating unit for heating an object to be treated is mixed with high-temperature steam supplied from the boiler, and then the mixed steam is re-supplied to the heating unit. 
         [0019]    To achieve the above object, the present invention provides an apparatus for recovering re-evaporated steam and condensate, the apparatus including: a steam recovery unit for recovering condensate discharged from a heating unit for heating an object to be treated, and the steam re-evaporated from the condensate, and then supplying the recovered re-evaporated steam to a steam-pressurizing unit and the recovered condensate to a boiler; and the steam-pressurizing unit for mixing the re-evaporated steam supplied from the steam recovery unit, with high-temperature steam supplied from the boiler and then supplying the mixed steam to the heating unit. 
         [0020]    In addition, the steam recovery unit includes: an evaporation vessel connected with the heating unit for allowing the condensate produced through the heat exchange in the heating unit to be introduced thereinto and for recovering the steam re-evaporated from the condensate introduced into the evaporation vessel; and a feed water pump for allowing the condensate introduced into the evaporation vessel to be forcibly supplied to the boiler. 
         [0021]    Moreover, the steam recovery unit includes: a water level sensor installed at one side of the evaporation vessel  210  for detecting the water level of the condensate introduced into the evaporation vessel; and a water level control unit for analyzing the water level of the condensate detected from the water level sensor and outputting an operation control signal to the feed water pump based on a result of the analysis to control the operation of the feed water pump. 
         [0022]    Besides, the steam recovery unit further includes an overflow valve installed at one side of the evaporation vessel for preventing an overflow of the condensate due to the excessive introduction of the condensate into the evaporation vessel. 
         [0023]    In addition, the steam-pressurizing unit includes: a stream re-pressurization control valve for mixing the high-temperature steam supplied from the boiler with the re-evaporated steam supplied from the steam recovery unit, and supplying the mixed steam to the heating unit; a pressure sensor; disposed between stream re-pressurization control valve and the heating unit for detecting a pressure of the steam supplied to the heating unit; and a pressure control unit for outputting an operation control signal to the stream re-pressurization control valve based on the pressure detected from the pressure sensor and controlling the operation of the stream re-pressurization control valve. 
         [0024]    The apparatus for recovering re-evaporated steam and condensate according to the present invention as constructed above has an advantage in that a whole amount of re-evaporated steam and condensate is recovered for use in a state in which a closed circuit is constructed. 
         [0025]    In addition, the apparatus for recovering re-evaporated steam and condensate according to the present invention has an advantage in that the release of steam to the air is prevented, and a latent heat contained in the condensate is utilized, thereby improving the efficiency of energy consumption. 
         [0026]    Besides, the apparatus for recovering re-evaporated steam and condensate according to the present invention has an advantage in that the efficiency of energy consumption is improved, leading to a decrease in the amount of steam used and a remarkable reduction in the amount of fuel consumed to generate steam. 
         [0027]    Further, the apparatus for recovering re-evaporated steam and condensate according to the present invention has an advantage in that steam traps causing an obstacle to energy flow are removed to allow the flow rate of the steam to be continuously increased so that a heat transmittance can be increased and thus the heat exchange efficiency is maximized to enhance the heat transfer effect. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a block diagram illustrating the construction of a steam heating system according to the prior art. 
           [0029]      FIG. 2  is a block diagram illustrating the construction of a boiler system employing an apparatus for recovering re-evaporated steam and condensate according to the present invention. 
           [0030]      FIG. 3  is a block diagram illustrating the construction of an apparatus for recovering re-evaporated steam and condensate according to the present invention. 
           [0031]      FIG. 4  is a cross-sectional view illustrating the construction of a stream re-pressurization control valve of an apparatus for recovering re-evaporated steam and condensate according to the present invention. 
           [0032]      FIGS. 5 and 6  are waveform charts illustrating the amount of steam used per hour before and after installation of an apparatus for recovering re-evaporated steam and condensate according to the present invention. 
           [0033]      FIGS. 7 and 8  are waveform charts illustrating the amount of fuel consumed per hour before and after installation of an apparatus for recovering re-evaporated steam and condensate according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    Now, a preferred embodiment of the present invention will be described hereinafter in detail with reference to the accompanying drawings. 
         [0035]      FIG. 2  is a block diagram illustrating the construction of a boiler system employing an apparatus for recovering re-evaporated steam and condensate according to the present invention,  FIG. 3  is a block diagram illustrating the construction of an apparatus for recovering re-evaporated steam and condensate according to the present invention, and  FIG. 4  is a cross-sectional view illustrating the construction of a stream re-pressurization control valve of an apparatus for recovering re-evaporated steam and condensate according to the present invention. 
         [0036]    First, the description on the same elements as those in the prior art will be omitted to avoid redundancy, and the same elements as those in the prior art are denoted by the same reference numerals. 
         [0037]    As shown in  FIGS. 2 to 4 , a boiler system employing the apparatus for recovering re-evaporated steam and condensate according to the present invention includes a boiler  10  for producing high-temperature steam, a first heating unit  30  and a second heating unit  30 ′ for heating an object to be treated using the high-temperature steam produced and supplied from the boiler  10  via a header  20 , a steam-pressurizing unit  100  for supplying the steam used to heat the first and second heating unit  30  and  30 ′, a stream recovery unit  200  for recovering condensate discharged from first and second heating unit  30  and  30 ′, and the steam re-evaporated from the condensate, and an evaporated stream connecting tube  300  for allowing the re-evaporated steam recovered by the steam recovery unit  200  to be supplied to the steam-pressurizing unit ( 100 ). The apparatus for recovering re-evaporated steam and condensate is constructed of a closed circuit. 
         [0038]    The steam-pressurizing unit  100  is an element that mixes high-temperature steam supplied from the boiler  10  with the re-evaporated steam supplied from the steam recovery unit  200  and supplies the mixed steam to the first and second heating units  30  and  30 ′. The steam-pressurizing unit  100  includes a stream re-pressurization control valve  110 , a pressure sensor  130 , and a pressure control unit  140 . 
         [0039]    The stream re-pressurization control valve  110  mixes the high-temperature steam supplied from the boiler  10  with the re-evaporated steam supplied from the steam recovery unit  200  via the evaporated stream connecting tube  300 , and supplies the mixed steam to the first and second heating units  30  and  30 ′. 
         [0040]    The stream re-pressurization control valve  110  will be described hereinafter in more detail. 
         [0041]    The stream re-pressurization control valve  110  includes: a high temperature steam inlet port  111  for allowing the high-temperature steam supplied from the boiler  10  to be introduced into the stream re-pressurization control valve; a re-evaporated steam inlet port  112  for allowing the re-evaporated steam supplied from the steam recovery unit  200  to be introduced into the stream re-pressurization control valve; a steam discharge port  113  for allowing a mixture of the high-temperature steam and the re-evaporated steam to be discharged to the outside; an actuator  120  for controlling the ON/OFF operation of the stream re-pressurization control valve  110 ; an opening and closing rod  121  configured to be moved in response to the operation of the actuator  120 ; a first opening and closing part  122  installed at the opening and closing rod  121  of the actuator  120  for opening or closing a first through-hole  114  in response to the operation of the actuator  120 , the first through-hole allowing the high temperature steam inlet port  111  and the steam discharge port  113  to fluidically steam-communicate with each other therethrough; and a second opening and closing part  123  for opening or closing a second through-hole  115  allowing the re-evaporated steam inlet port  112  and the steam discharge port  113  to fluidically communicate with each other therethrough. 
         [0042]    Thus, when the high-temperature steam (arrow indicated by a solid line) is introduced into the stream re-pressurization control valve  110  through the high temperature steam inlet port  111  and is jetted to the steam discharge port( 113  through the first through-hole  114 , a pressure dropping phenomenon occurs at the second through-hole  115  of the re-evaporated steam inlet port  112 . As a result, ambient air is sucked in to generate vacuum pressure (negative pressure) so that the re-evaporated steam (arrow indicated by a doted line) is mixed with the introduced high-temperature steam ((arrow indicated by a solid line) and then is jetted to the heating units. 
         [0043]    The pressure sensor  130  is constructed to be installed between the stream re-pressurization control valve  110  and the first and second heating units  30  and  30 ′ so as to detect a pressure of the steam to be supplied to the first and second heating units  30  and  30 ′. Preferably, the pressure sensor  130  detects a pressure of the steam discharged from the steam discharge port  113  of the stream re-pressurization control valve  110  and supplied to the first and second heating units  30  and  30 ′, and applies a value of the detected pressure of the steam to the pressure control unit  140 . 
         [0044]    The pressure control unit  140  is constructed to output an operation control signal to the stream re-pressurization control valve  110  based on the pressure detected from the pressure sensor  130  and control the operation of the stream re-pressurization control valve. Preferably, the pressure control unit  140  analyzes the value of the steam pressure detected from the pressure sensor  130 , and outputs an operation control signal of the actuator  120  installed at the stream re-pressurization control valve  110  based on a result of the analysis so that the pressure of the steam supplied to the first and second heating units  30  and  30 ′ can be adjusted. 
         [0045]    In the meantime, although the pressure sensor  130  and the pressure control unit  140  have been described in this embodiment, it will obvious to a person of ordinary skill in the art that the design of the pressure sensor  130  can be modified into a temperature sensor for detecting a temperature of the steam and the design of the pressure control unit  140  can be modified into a temperature control means for outputting an operation control signal of the actuator  120 . 
         [0046]    The steam recovery unit  200  is constructed to recover condensate discharged from the first and second heating units  30  and  30 ′ and the steam re-evaporated from the condensate, and then supply the recovered condensate to the boiler and the recovered re-evaporated steam to the steam-pressurizing unit  100 . The steam recovery unit  200  includes an evaporation vessel  210 , a feed water pump  220 , a water level sensor  230 , a water level control unit  240 , and an overflow valve  250 . 
         [0047]    The evaporation vessel (Flash Vessel)  210  is connected with the first and second heating units  30  and  30 ′. When the condensate produced through the heat exchange in the first and second heating units  30  and  30 ′ is discharged from the first and second heating units  30  and  30 ′ by check valves  41  and  41 ′, it is introduced into the evaporation vessel. The steam recovery unit  200  recovers the steam re-evaporated and separated from the condensate recovered to the evaporation vessel  210  and supplies the recovered steam to the stream re-pressurization control valve  110 . 
         [0048]    That is, since the evaporation vessel  210  contains the condensate and the re-evaporated steam in a state in which they are separated from each other, it can selectively discharge the condensate and the re-evaporated steam. 
         [0049]    In addition, the evaporation vessel  210  may be installed at the same height as that of the first and second heating units  30  and  30 ′, and may be installed at a position lower than that of the first and second heating units  30  and  30 ′. The evaporation vessel  210  may be installed at a position higher than that of the first and second heating units  30  and  30 ′, but it is preferably installed at the position lower than that of the of the first and second heating units  30  and  30 ′ so that the condensate can be moved more easily through a free fall by gravity. 
         [0050]    The feed water pump  220  allows the condensate introduced into the evaporation vessel  210  to be forcibly supplied to the boiler  10 . 
         [0051]    The water level sensor  230  is installed at one side of the evaporation vessel  210  to detect the water level of the condensate introduced into the evaporation vessel  210 . 
         [0052]    The water level control unit  240  analyzes the water level of the condensate detected from the water level sensor  230  and outputs an operation control signal for controlling the operation of the feed water pump  220  to the feed water pump  220  based on a result of the analysis. 
         [0053]    The overflow valve  250  is constructed to be installed at one side of the evaporation vessel  210  to prevent an overflow of the condensate when an excessive amount of condensate is introduced into the evaporation vessel  210 . The overflow valve  250  is connected at one end thereof to the evaporation vessel  210  and is connected at the other end thereof to the makeup water tank  60  so that the condensate due to the overflow is discharged to the makeup water tank  60 . 
         [0054]    A non-explained reference numerals  31  and  31 ′ denote check valves, which perform an opening and closing operation of allowing the steam supplied from the steam-pressurizing unit  100  to be selectively introduced into the first heating unit  30  and the second heating unit  30 ′. 
         [0055]    In addition, a non-explained reference numeral  61  designates a feed pump for supplying water of the makeup water tank  60  to the boiler  10 , and a non-explained reference numeral  61  designates a valve. 
         [0056]    Next, the operation of the apparatus for recovering re-evaporated steam and condensate according to the present invention will be described hereinafter. 
         [0057]    At an initial operation stage, the high-temperature steam heated in the boiler  10  continues to be supplied to the stream re-pressurization control valve  110  of the steam-pressurizing unit  100  via the header  20  until the temperature of the first and second heating units  30  and  30 ′ reaches a predetermined temperature value set by a user. 
         [0058]    At the initial operation stage, since the temperature of the first and second heating units  30  and  30 ′ is low, a large amount of condensate is produced from the first and second heating units  30  and  30 ′ during the heat exchange, and the produced condensate is introduced into the evaporation vessel  210  via the check valves  41  and  41 ′. 
         [0059]    The water level control unit  240  detects the water level of the condensate in the evaporation vessel  210  through the water level sensor  230 . When the detected water level of the condensate reaches a predetermined water level value, the feed water pump  220  is operated to allow the condensate in the evaporation vessel  210  to be supplied to the boiler  10 . 
         [0060]    In addition, when an excessive amount of condensate is introduced into the evaporation vessel  210  to cause the overflow of the condensate to occur, the overflow valve  250 ) is operated to allow the condensate to be supplied to the makeup water tank  60 . 
         [0061]    In the meantime, when a predetermined period of time has elapsed after the initial operation stage, the condensate introduced into the evaporation vessel  210  is partly re-evaporated into steam. At this time, the re-evaporated steam is supplied to the re-evaporated steam inlet port  112  of the stream re-pressurization control valve  110  via the evaporated stream connecting tube  300 . 
         [0062]    The re-evaporated steam supplied to the re-evaporated steam inlet port  112  generates a vacuum pressure (negative pressure) around the second through-hole  115  formed between the re-evaporated steam inlet port  112  and the steam discharge port  113  while the high-temperature steam introduced into the steam re-pressurization control valve  110  through the high temperature steam inlet port  111  is discharged to the steam discharge port  113 . As a result, the re-evaporated steam supplied to the re-evaporated steam inlet port  112  is sucked into the first through-hole  114  so that it is supplied to the first and second heating units  30  and  30 ′ through the steam discharge port  113  together with the introduced high-temperature steam. 
         [0063]    That is, the re-evaporated steam that has been discarded is recovered for re-use so that the efficiency of energy consumption can be improved and the flow rate of the steam can be continuously increased owing to a difference pressure generated by the vacuum pressure on a closed circuit, thereby increasing the heat transmittance and simultaneously enhancing the heat exchange efficiency. 
         [0064]    When the first and second heating unit  30  and  30 ′ reach a predetermined temperature so that the pressure detected from the pressure sensor  130  reaches a predetermined pressure, the pressure control unit  140  outputs an operation control signal, i.e., an OFF signal to the actuator  120  to control the operation of the stream re-pressurization control valve  110  to be terminated. 
         [0065]    Thereafter, the pressure control unit  140  outputs an operation control signal, i.e., an ON signal to the actuator  120  to control the stream re-pressurization control valve  110  to be operated when the temperature of the first and second heating units  30  and  30 ′ drops to cause the pressure of the steam detected from the pressure sensor  130  to be low. 
         [0066]    Thus, while the high-temperature steam is supplied to the first and second heating units  30  and  30 ′ through the stream re-pressurization control valve  110 , the steam re-evaporated from the evaporation vessel  210  is sucked in due to the vacuum pressure (negative pressure) generated in the stream re-pressurization control valve  110  and is supplied to the first and second heating units  30  and  30 ′ so that the re-evaporated steam can be re-used. 
         [0067]      FIGS. 5 and 6 , and  FIGS. 7 and 8  are waveform charts illustrating the amount of steam used and fuel consumed per hour before and after installation of an apparatus for recovering re-evaporated steam and condensate according to the present invention, respectively. 
         [0068]    The amount of steam used per hour was approximately an average of 6,000 Kg/hr before the installation of an apparatus for recovering re-evaporated steam and condensate according to the present invention as shown in  FIG. 5  whereas the amount of steam used per hour was approximately an average of 4,000 Kg/hr after the installation of the apparatus as shown in  FIG. 6 . Thus, it can be seen that the amount of steam used per hour is decreased by about 2,000 Kg/hr after the installation of the apparatus. 
         [0069]    In addition, the amount of fuel consumed per hour was approximately an average of 660 l/hr before the installation of an apparatus for recovering re-evaporated steam and condensate according to the present invention as shown in  FIG. 7  whereas the amount of fuel consumed per hour was approximately an average of 430 l/hr after the installation of the apparatus as shown in  FIG. 8 . Thus, it can be seen that the amount of fuel consumed per hour is decreased by about 230 l/hr owing to the use of the re-evaporated steam after the installation of the apparatus. 
         [0070]    Therefore, the amount of steam supplied from the boiler  10  can be decreased as much as the amount of the re-evaporated steam produced from the evaporation vessel  210 . In addition, the amount of fuel consumed in the boiler  10  can also be saved as much as the reduced amount of the steam supplied from the boiler  10 . 
         [0071]    While the present invention has been described and illustrated with respect to the specific embodiments, it is to be understood that the present invention is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.