Abstract:
Provided is an open cell-type apparatus for producing sodium hypochlorite based on electrolysis using soft water and salt. The apparatus includes: a sodium hypochlorite generator including a plurality of electrode plates supported by a support, a flow channel for air flow provided above the support and the electrode plates, and an air intake hole and an air exhaust hole which communicate with the flow channel; a cooling unit for lowering a temperature of the flow channel; and a controller for controlling operation of the cooling unit by detecting a temperature of the sodium hypochlorite generator. The apparatus constantly maintains an optimum temperature of the sodium hypochlorite generator in order to produce sodium hypochlorite of a high concentration with high efficiency.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an apparatus for producing sodium hypochlorite (NaOCl), and more particularly to an open cell-type apparatus for producing sodium hypochlorite which reduces hardness of cations deposited on a cathode and improves efficiency of electrolysis by maintaining a constant optimum temperature. 
         [0003]    2. Description of the Related Art 
         [0004]    Generally, as a disinfection method for water treatment plants, sewage treatment plants, swimming pools, large barns, contract foodservices, etc., a chemical disinfection method or an ozone disinfection method is used. However, in many cases, we are reluctant to use these methods because of some factors. For example, these methods are not economical by requiring use of costly chemicals and are not environment-friendly due to use of hazardous chemicals and generation of chemical residues. Especially, in the case of using ozone for disinfection, there is an issue related to hazardous ozone residues. Because of these problems, in restaurants or large contract foodservices for which through disinfection and hygiene management are required to be done, collective food poisoning accident occurs. 
         [0005]    For this reason, sodium hypochlorite (NaOCl), a chlorine-based disinfectant, which is a colorless transparent liquid with strong chlorine odor, has been preferably used. Typically, NaOCl was produced through electrolysis by supplying saline water to an electrolytic cell which is a saline water tank equipped with a series of electrodes therein. 
         [0006]    There are some known conventional technologies related to the production of sodium hypochlorite: Korean Patent No. 0592331, “electrolytic cell for preparing sodium hypochlorite”; and Korean Patent No. 0634889, “apparatus for producing sodium hypochlorite.” 
         [0007]    However, the conventional apparatuses for preparing sodium hypochlorite has the following problem: since heat is generated in the process of electrolyzing diluted saline water in an electrolytic cell, temperature of the sodium hypochlorite obtained rises to become higher than an optimum temperature of the diluted saline water in 30 minutes after starting of operation of the apparatus, and the concentration of effective chlorine decreases depending on an operation time of the apparatus. 
         [0008]    The information disclosed in the Background of the Invention section is only for the enhancement of understanding of the background of the invention, and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art. 
       RELATED ART DOCUMENT 
       [0009]    Patent Document 1: Korean Patent No. 0592331 
         [0010]    Patent Document 2: Korean Patent No. 0634889 
       SUMMARY OF THE INVENTION 
       [0011]    Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and the present invention is intended to propose an open cell-type apparatus for producing sodium hypochlorite of a high concentration which reduces hardness of cations deposited on a cathode and improves efficiency of electrolysis by constantly maintaining an optimum temperature. 
         [0012]    In accordance with one aspect of the present invention, there is provided an open cell-type apparatus for producing sodium hypochlorite based on electrolysis using soft water and salt, the apparatus including: a sodium hypochlorite generator including a plurality of electrode plates  25  supported by a support, a flow channel for air flow provided above the support and the electrode plates, and an air intake hole and an air exhaust hole which communicate with the flow channel; a cooling unit for lowering a temperature of the flow channel, the cooling unit being connected to the air intake hole; and a controller for controlling operation of the cooling unit by detecting a temperature of the sodium hypochlorite generator, in which the sodium hypochlorite generator includes a guide which is provided above an air intake pipe connected to the flow channel and guides air flow. 
         [0013]    Preferably, the open cell-type apparatus further includes a sodium hypochlorite collection tank equipped with a heat exchanger, the sodium hypochlorite collection tank being installed at a downstream of a sodium hypochlorite discharge pipe of the sodium hypochlorite generator, and controlling a temperature of the soft water. 
         [0014]    Preferably, the cooling unit may use a fan. 
         [0015]    Preferably, the cooling unit may use an air condenser interlocking with an air compressor. 
         [0016]    Preferably, the cooling unit may use an air cooler interlocking with an indoor unit. 
         [0017]    Preferably, the cooling unit may use an ice cooling fan. 
         [0018]    Preferably, the open cell-type apparatus may further include a backflow preventing unit for intercepting air flow, which is provided above an air intake pipe connected to the flow channel of the sodium hypochlorite generator, in which the backflow preventing unit is selectively provided with a baffle plate, a sheet, and an electric damper. 
         [0019]    Preferably, the controller may control the temperature of the soft water by causing a control board to receive temperature changes of the sodium hypochlorite generator and maintains the temperature of the flow channel within a preset range. 
         [0020]    According to the present invention, it is possible to prevent a rise in temperature during electrolysis, thereby suppressing generation of oxygen, maintaining a constant optimum temperature inside an electronic cell, and lowering hardness of cations deposited on a cathode in the electrolytic cell. These measures dramatically improve efficiency of electrolysis, enabling production of sodium hypochlorite of a high concentration. 
         [0021]    In addition, it is possible to maintain a high concentration of sodium hypochlorite produced at low temperature, without undergoing thermal decomposition. 
     
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
         [0022]    The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
           [0023]      FIG. 1  is a schematic view illustrating an overall arrangement of a manufacturing apparatus according to one embodiment of the present invention; 
           [0024]      FIG. 2  is a diagram illustrating the structure of a cooling means according to a first embodiment of the present invention; 
           [0025]      FIG. 3  is a diagram illustrating the structure of a cooling means according to a second embodiment of the present invention; 
           [0026]      FIG. 4  is a diagram illustrating the structure of a cooling means according to a third embodiment of the present invention; 
           [0027]      FIG. 5  is a diagram illustrating the structure of a cooling means according to a fourth embodiment of the present invention; and 
           [0028]      FIG. 6  is a diagram illustrating a backflow preventing unit according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. 
         [0030]    An apparatus for producing sodium hypochlorite according to the present invention uses electrolysis using soft water and sodium. When using a conventional manufacturing apparatus, due to heat generated during electrolysis, the temperature of sodium hypochlorite produced rises up to 40 to 50° C. which is 25 to 35° C. higher than the temperature of diluted saline water. This high temperature lowers an effective chlorine concentration, thus hindering sodium hypochlorite of a high concentration from being produced. Taking this circumstances into account, the present invention is intended to implement a technology of continuously producing sodium hypochlorite of a high concentration by performing electrolysis at temperature which is controlled in a manner adopted in a no-membrane open cell type apparatus. 
         [0031]    According to the present invention, a sodium hypochlorite generator  20  having an air intake hole  23  and an air exhaust hole  24  communicating with a flow channel  21   a  includes a plurality of electrode plates  25 . The sodium hypochlorite generator  20  is an electrolytic cell composed of a housing  21  and a series of electrode plates  25 , without a membrane (ion-exchange membrane), which are fixed by supports  35 . Terminals  26  are fixed at respective ends of the sodium hypochlorite generator  20  by flanges  31 , a sodium hypochlorite discharge pipes  42  is connected to a side surface of the housing  21 . A saline water supply pipe  15  is connected to a portion of the bottom of the housing  21 . In the housing  21 , the flow channel  21   a  is provided in an upper portion of an inside space of the housing in which the electrode plates  25  and the supports  35  are not provided. The air intake hole  23  and the air exhaust hole  24  are distanced from each other and are provided in an upper part of the housing  21  which is disposed above the fluid passage  21   a.    
         [0032]    Preferably, the sodium hypochlorite generator  20  is equipped with a guide  37  which guides air to an air intake pipe  33  connected to the flow channel  21 . The guide  37  may be made from the same material as the housing  21 , for example, acryl resin, and may be formed in an L-shape. The guide  37  is disposed in the housing  21 , in a position near the air intake hole  23 , and changes direction of air flow so that the air introduced in a vertical direction can flow in a horizontal direction. If the guide  37  is not provided, the air introduced through the intake pipe  33  may blow to the electrode plate  25 , thus impeding an electrolysis reaction. 
         [0033]    A sodium hypochlorite collection tank  40  having a heat exchanger  45  is installed at a downstream side of the sodium hypochlorite discharge pipe  42  of the sodium hypochlorite generator  20 , and preferably the temperature of the saline water is controlled using the heat exchanger  45 . 
         [0034]    In conventional apparatuses, a vacuum pressure is generated so that sodium hypochlorite and hydrogen can be simultaneously are suctioned through an upper part of a housing  21 . For this operation, a hydrogen gas discharger is installed in an upper storage tank, which renders the apparatus dangerous. 
         [0035]    However, according to the present invention, the sodium hypochlorite is discharged into the sodium hypochlorite collection tank  40 , which is disposed in a lower position than the housing  21 , via a discharge hole formed in the side surface of the housing  21 , without using an additional driving force. Soft water of a soft water storage tank  10  is sent to a sodium storage tank  14  through a first soft water supply pipe  11  and also to a saline water supply pipe  15  via the heat exchanger  45  of the sodium hypochlorite collection tank  40  through a second soft water supply pipe  12 . The heat generated from the sodium hypochlorite collection tank  40  is heat-exchanged with the soft water in the second soft water supply pipe  12  so that the soft water is maintained at an optimum temperature range. The optimum temperature for electrolysis of diluted saline water is 15 to 20° C., and more preferably 15° C. At this temperature, a best concentration of sodium hypochlorite can be obtained. 
         [0036]    According to the present invention, a cooling unit  50  to lower the temperature of the flow channel  21   a  is connected to the air intake hole  23  of the sodium hypochlorite generator  20 . In the process of operating and investigating the sodium hypochlorite generator  20 , the concentration of sodium hypochlorite is maintained in 7000 to 8000 ppm. However, through the investigation, in a specific season, the concentration rose up to 9000 to 10000 ppm and the high concentration was maintained for about 5 to 10 minutes. That is, the sodium hypochlorite produced at a high temperature experiences a decrease in concentration. Specifically, when the sodium hypochlorite produced at a high temperature is stored in a storage tank, it undergoes thermal decomposition due to the high temperature so that the concentration of the sodium hypochlorite remarkably decreases. 
         [0037]    As a result of performing various experiments in consideration of such a phenomenon, it is found that highest efficiency is obtained when inside temperature of the sodium hypochlorite generator  20  is maintained at 27 to 30° C. Table 1 shows that as for sodium hypochlorite produced at 50 to 60° C. by the sodium hypochlorite generator  20 , the concentration of chlorine in the sodium hypochlorite decreases by 14 to 16% due to decomposition at a high temperature in the sodium hypochlorite storage tank  17 . This phenomenon is conspicuous in summer during which natural cooling is impossible. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
             
               
                   
                 Temperature (° C.) 
               
             
          
           
               
                   
                 20 
                 24 
                 26 
                 27 
                 28 
                 29 
                 30 
                 32 
               
               
                   
               
               
                 Concentration 
                 8000 
                 8650 
                 8900 
                 9000 
                 9200 
                 9100 
                 9000 
                 8800 
               
               
                 (ppm) 
               
               
                   
               
             
          
           
               
                   
                 Temperature (° C.) 
               
             
          
           
               
                   
                 36 
                 38 
                 40 
                 46 
                 50 
                 54 
                 58 
                 60 
               
               
                   
               
               
                 Concentration 
                 8200 
                 8000 
                 7900 
                 7800 
                 7500 
                 7300 
                 7200 
                 7000 
               
               
                 (ppm) 
               
               
                   
               
             
          
         
       
     
         [0038]    According to the present invention, the air intake pipe  33  is connected to the air intake hole  23  of the sodium hypochlorite generator  20  so that air in the cooling unit  50  is supplied to above the flow channel  21   a . This enables the inside temperature of the housing  21  to be maintained in a range of 27 to 30° C. 
         [0039]    With reference to  FIG. 2 , according to a first embodiment, the cooling unit  50  uses a fan  52 . Preferably, the fan  52  maybe disposed inside a room, in a position near the sodium hypochlorite generator  20  for convenience in piping. However, if such an indoor installation is disadvantageous in terms of maintaining the temperature of the sodium hypochlorite generator  20 , the fan  52  may be disposed outside a room. Alternatively, both of an indoor fan and an outdoor fan may be installed and selectively used by a switching operation in response to temperature changes. 
         [0040]    With reference to  FIG. 3 , according to a second embodiment, the cooling unit  50  uses an air condenser  54  interlocking with an air compressor  56 . The air condenser  54  generates ultra speed revolution with compressed air output from the air compressor  56 . In this case, the air intake hole  23  and the guide  37  illustrated in  FIG. 2  may not be necessary so that the air condenser  54  may be directly connected to the flange  31 . 
         [0041]    With reference to  FIG. 4 , according to a third embodiment, the cooling unit  50  uses an air cooler  62  interlocking with an outdoor unit  64 . A coolant circulation path is formed between the air cooler  62  and the outdoor unit  64  like a general air conditioner. In a case where a room, in which the sodium hypochlorite generator  20  is installed, is equipped with an air conditioner, this air conditioner is used in combination with the above-described air cooler or with the fan  52 . 
         [0042]    With reference to  FIG. 5 , according to a fourth embodiment, the cooling unit  50  uses an ice cooling fan  66 . The ice cooling fan  66  has a structure of combining the fan  52  and ice or a coolant pack. In this case, the fan  52  may have a relatively small performance compared with the fan  52  according to the first embodiment. When the fourth embodiment is applied under conditions in which ice or coolant packs can be easily obtained, it is advantageous in terms of reduction in power for operating the cooling unit  500 . 
         [0043]    In addition, according to the present invention, a backflow preventing unit  70  for intercepting air flow may be further provided above the air intake hole  33  connected to the flow channel  21   a  of the sodium hypochlorite generator  20 . The backflow preventing unit  70  includes a baffle plate  71 , a sheet  72 , or an electric damper. The backflow preventing unit  70  prevents backflow of hydrogen gas or moisture contained in sodium hypochlorite into the air intake pipe  33  because the backflow of hydrogen gas or moisture causes the fan  52  or a motor of the cooling unit  50  to be damaged. The baffle plate  71  is a valve for closing or opening a channel of the air intake pipe  33 . The baffle plate  71  may be a semi-automatic type using a spring  73 , or a full automatic type using solenoid (not shown). The sheet  75  has a tubular shape and is made from a film-type material having chemical resistance and high flexibility. The sheet  75  expands t open the channel while the cooling unit  50  is operating, and contracts to close the channel when the operation of the cooling unit  50  is stopped. 
         [0044]    According to the present invention, a controller  80  for controlling operation of the cooling unit  50  by detecting a temperature of the sodium hypochlorite generator  20  may be further provided. The controller  80  controls the soft water storage tank  10 , the salt storage tank  14 , the sodium hypochlorite generator  20 , the sodium hypochlorite generator collection tank  40 , and the sodium hypochlorite generator storage tank  17  by using a control board  82 . In the case of operating a plurality of sodium hypochlorite generators  20 , a plurality of control boards  82  corresponding to the sodium hypochlorite generators  20 , respectively are connected to a central monitoring board  84  so that the plurality of sodium hypochlorite generators  20  are simultaneously controlled in remote. A rectifier  86  is connected to the terminal  26  of the sodium hypochlorite generator  20 . 
         [0045]    The controller  80  receives temperature changes of the sodium hypochlorite generator  20  via the control board  82  and thus controls the temperature of the soft water introduced and the temperature of the flow channel  21   a  within a preset temperature range. A temperature sensor  28  for detecting the temperature of the flow channel  21   a  is installed in the housing  21  of the sodium hypochlorite generator  20 . The control board  82  controls the temperature of the soft water introduced by adjusting an opening of a valve provided in the second soft water supply pipe  12 , and controls the temperature of the flow channel  21   a  of the sodium hypochlorite generator  20  by switching on and off the cooling unit  50 . 
         [0046]    In addition, a vent pipe  48  branches off from the sodium hypochlorite discharge pipe  42  connected between the sodium hypochlorite collection thank  40  and the sodium hypochlorite storage tank  17 . The vent pipe  48  is used to exhaust a trace amount of hydrogen gas contained in sodium hypochlorite transported from the sodium hypochlorite collection tank  40  to the sodium hypochlorite storage tank  17 . 
         [0047]    The control board  82  periodically receives not only a signal from the temperature sensor  28  of the sodium hypochlorite generator  20  but also a signal of temperature and pressure of main pipes including the first soft water supply pipe  11 , the second soft water supply pipe  12 , and the sodium hypochlorite discharge pipe  42 . In normal mode, when ambient temperature is excessively low like in winter, the control board  82  causes the soft water to be bypassed to the second soft water supply pipe  12  so that the soft water can be heated by the heat exchanger  45  in the sodium hypochlorite collection tank  40 . Conversely, when ambient temperature is excessively high like in summer, a portion of the soft water is bypassed so that the temperature of the soft water is lowered. When the temperature of the sodium hypochlorite generator  20  exceeds the preset range, 27 to 30° C., the cooling unit  50  starts operating to blow cold air into the flow channel  21   a  of the sodium hypochlorite generator  20 . The air introduced into the flow channel  21   a  guides hydrogen gas generated from the electrode plate  25  to an exhaust pipe  34  and causes only the sodium hypochlorite to be discharged into the sodium hypochlorite collection tank  40 . In this case, since the hydrogen gas is separated and exhausted through the exhaust pipe  34 , safety of the sodium hypochlorite generator is improved. When the temperature of the sodium hypochlorite generator  20  falls to the preset range, operation of the cooling unit  50  is stopped. This time, the operation of the backflow preventing unit  70  is manually stopped or automatically controlled using the electric damper. 
         [0048]    Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.