Abstract:
Provided is a combustion controller for a combustible gas of a pressurized water reactor nuclear power plant, and more particularly, to a combustion controller for a combustible gas installed in a rear end of a filtered vent system outside a containment vessel or an external chimney, configured to convert a combustible gas such as hydrogen, carbon monoxide, or the like, into steam, carbon dioxide, or the like, and simultaneously, operate by itself with no external power supply. Accordingly, the combustion controller for a combustible gas can perform stable combustion control with no probability of explosion of hydrogen through a recombining reaction of the combustible gas, prevent discharge of carbon monoxide, which is a toxic gas, and prevent backward flow of the flame through the quenching mesh.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0123981, filed on Oct. 17, 2013, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Field of the Invention The present invention relates to a combustion controller for a combustible gas of a pressurized water reactor nuclear power plant, and more particularly, to a combustion controller for a combustible gas installed in a rear end of a filtered vent system outside a containment vessel or an external chimney, configured to convert a combustible gas such as hydrogen, carbon monoxide, or the like, into steam, carbon dioxide, or the like, and simultaneously, operated by itself with no external power supply. 
         [0003]    2. Discussion of Related Art 
         [0004]    While a filtered vent system of a containment vessel installed at a nuclear power plant performs a function of discharging hydrogen, carbon monoxide and a non-condensable gas to the atmosphere, when hydrogen and a combustible gas are rapidly discharged to the atmosphere, combustion of the hydrogen occurs. In particular, when air is introduced from the outside, combusted flame may cause a backfire in a direction of filtered vent equipment. Accordingly, as the flame is generated, an exhaust tower or an exhaust chimney may be damaged, and of course, when the backfire occurs, the equipment may be seriously damaged according to circumstances. In particularly, when carbon monoxide is incompletely combusted to be directly discharged to the atmosphere, the carbon monoxide may be harmful to human bodies. 
         [0005]    Meanwhile, a passive apparatus for removing hydrogen is installed in the containment vessel. The passive apparatus is a passive autocatalytic recombiner PAR system. According to a scale of the containment vessel of the nuclear power plant, about 20 to 40 passive apparatuses are installed to remove hydrogen from the containment vessel through hydrogen catalyst combustion. 
         [0006]    The above-mentioned conventional PAR is a passive PAR disclosed in Korean Utility Model Publication No. 20-0464123, and includes a cover body having an inlet port formed at a lower end thereof and through which air including hydrogen gas is introduced, discharge ports formed at three surfaces of an upper end thereof and through which the introduced air is discharged, and a guide plate inclined from the three surfaces toward the remaining surface to guide the air flow to the discharge ports; a honeycomb type catalyst body mounted on a lower end of the cover body to react with the introduced hydrogen gas to remove hydrogen; and a catalyst body housing assembly, on which the catalyst body sits, configured to detachably mount the catalyst body on the lower end of the cover body, wherein a roof plate installed on the three surfaces, in which the discharge ports are formed, is provided on an upper end of the cover body to prevent liquid dropped from above from being introduced into the cover body through the discharge ports. 
         [0007]    However, even when an automatic catalyst coupler is installed in the containment vessel, a combustible gas such as hydrogen, carbon monoxide, and so on, in the containment vessel is discharged to the atmosphere through the filtered vent equipment while being incompletely oxidized when the combustible gas is exhausted to the outside of the containment vessel through the filtered vent equipment. Accordingly, even when the passive automatic catalyst recombiner disclosed in the related art is installed in the containment vessel, additional equipment is needed to remove a combustible gas such as hydrogen or carbon monoxide, which is unavoidably discharged to the outside. However, the PAR disclosed in Korean Utility Model Publication No. 20-0464123 is a structure that cannot be installed at the rear end of the filtered vent equipment outside the containment vessel or the external chimney. 
       CITATION LIST  
     Patent Literature 
       [0008]    (Patent Literature 1) Korean Utility Model Publication No. 20-0464123 
       SUMMARY OF THE INVENTION 
       [0009]    In order to solve the problems, the present invention is directed to a combustion controller for a combustible gas installed at a rear end of filtered vent equipment outside a containment vessel or a rear end of other exhaust equipment and capable of performing stable combustion control with no probability of explosion of hydrogen through a stable recombining reaction of air with a combustible gas, preventing discharge of toxic carbon monoxide, and preventing backfire of flame through a quenching mesh. In addition, the controller may be used in a discharge pipe of the combustible gas in equipment of a general industry. 
         [0010]    According to an aspect of the present invention, there is provided a combustion controller for a combustible gas which includes: a support frame having a combustible gas inlet port formed at a lower end thereof and a fluid inlet port formed at a side surface thereof; a quenching mesh disposed on the combustible gas inlet port or under an outlet port of the combustion controller for a combustible gas and fixed to the support frame; and at least one recombiner disposed on or under the quenching mesh and fixedly installed at the support frame. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The above and other objects, features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which: 
           [0012]      FIG. 1  is a view showing a combustion controller for a combustible gas according an embodiment of the present invention; 
           [0013]      FIG. 2  is a cross-sectional view showing a configuration of the combustion controller for a combustible gas of a pressurized water reactor of  FIG. 1 ; 
           [0014]      FIG. 3A  is a view showing a quenching mesh of a first embodiment of  FIG. 2 ; 
           [0015]      FIG. 3B  is a view showing a quenching mesh of a second embodiment of  FIG. 2 ; 
           [0016]      FIG. 4A  is a perspective view showing a recombiner of the first embodiment of  FIG. 2 ; 
           [0017]      FIG. 4B  is a perspective view showing a recombiner of the second embodiment of  FIG. 2 ; 
           [0018]      FIG. 5  is a view showing an installation state of a fan of the combustion controller for a combustible gas according to the present invention; and 
           [0019]      FIG. 6  is a cross-sectional view taken along line A-A of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0020]    Advantages and features of the present invention and a method of accomplishing these will be apparent from embodiments described below with reference to the accompanying drawings. 
         [0021]    However, the present invention is not limited to the embodiments described below but may be implemented in various modifications. The following embodiments are described in order to enable those of ordinary skill in the art to embody and practice the present invention. To clearly describe the present invention, parts not relating to the description are omitted from the drawings. 
         [0022]    Like reference numerals refer to like elements throughout the description of the drawings. 
         [0023]    Hereinafter, a combustion controller for a combustible gas according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings, but some elements not related to the spirit of the present invention will be omitted or simplified. However, the omitted elements are not necessary elements in the present invention but may be coupled and used in the present invention by those skilled in the art. 
         [0024]      FIG. 1  is a view showing an embodiment of a combustion controller for a combustible gas according to the present invention. 
         [0025]    As shown in  FIG. 1 , a containment vessel pressure regulation valve  510  to be opened when a pressure in a containment vessel  500  reaches a certain pressure or more is installed outside the containment vessel  500  to uniformly maintain a pressure in the containment vessel  500 . 
         [0026]    Since the containment vessel pressure regulation valve  510  is automatically opened when the pressure in the containment vessel  500  reaches a certain value or more regardless of a hydrogen concentration in the containment vessel  500 , a combustible gas and radioactive substances present in the containment vessel  500  are discharged to the containment vessel pressure regulation valve  510  with air to be introduced into filtered vent equipment  600 . Here, since the filtered vent equipment  600  performs a function of removing radioactive vapor and fission products included in the introduced air, when the radioactive vapor and the fission products included in the introduced air are removed, concentrations of hydrogen and carbon monoxide in the gas discharged from the filtered vent equipment  600  are increased to relatively high levels. Accordingly, since the combustible gas such as hydrogen, carbon monoxide, and so on, included in the gas discharged from the filtered vent equipment  600  should be removed so as not to be discharged to the outside, an automatic catalyst recombiner should be installed in a nuclear power plant chimney  700  through which the gas filtered in the filtered vent equipment  600  is discharged. 
         [0027]    While the combustion controller for a combustible gas according to the embodiment of the present invention shown in  FIG. 1  has been described as being installed in the nuclear power plant chimney  700 , the present invention is not limited thereto, it may be installed in the filtered vent equipment  600 . In this case, the combustion controller for a combustible gas may be installed in a flow path of a combustible gas or a storage tank of a combustible gas disposed in the filtered vent equipment  600 . 
         [0028]      FIG. 2  is a cross-sectional view showing a configuration of the combustion controller for a combustible gas of  FIG. 1 . 
         [0029]    As shown in  FIG. 2 , the combustion controller for a combustible gas according to the embodiment of the present invention includes a support frame having an outlet port  150  formed at an upper end thereof, and an external fluid inlet port  120  configured to be open at the bottom so as a combustible gas inlet port  100  to be formed at a lower end thereof through which a combustible gas is introduced, and formed at a sidewall of the support frame to introduce external air, a quenching mesh  200  disposed over the combustible gas inlet port  100  and coupled and fixed to one side of the support frame, and a recombiner  300  disposed over the quenching mesh  200  and coupled and fixed to one side of the support frame. 
         [0030]    While the quenching mesh  200  of the embodiment of the present invention shown in  FIG. 2  has been described as being disposed over the combustible gas inlet port  100 , the present invention is not limited thereto, it may be installed under the outlet port  150  of the combustion controller for a combustible gas. In this case, of course, the recombiner  300  is disposed under the quenching mesh  200 . 
         [0031]    Accordingly, the combustible gas discharged from the outlet port of the filtered vent equipment  600  is introduced into the nuclear power plant chimney  700  through the combustible gas inlet port  100 , and here, the external fluid inlet port  120  may have a structure in which the combustible gas can be easily introduced from the outside into the inside, rather than discharged from the inside to the outside. 
         [0032]    Meanwhile, the combustible gas introduced into the combustible gas inlet port  100  passes through the quenching mesh  200  to arrive at the recombiner  300  having a honeycomb structure, and the quenching mesh  200  is installed to prevent backfire of flame and propagation of the flame performs a stable recombining reaction. That is, a temperature of the flame is decreased due to heat transfer to the quenching mesh  200  while the flame propagates through the quenching mesh  200  to decrease intensity of the flame, and in a chemical aspect, the quenching mesh  200  changes an active radical that accelerates a chain branching reaction into a stable chemical species, and thus, reduces a chemical reaction rate to decrease the intensity of the flame. 
         [0033]    Accordingly, when a level of the heat transfer and a level of a radical termination reaction are intensified to a certain level or more, the flame may be extinguished, and hydrogen combustion can be controlled using flame intensity attenuation and flame extinguishing phenomena. 
         [0034]      FIGS. 3A and 3B  are views showing embodiments of the quenching mesh of  FIG. 2 . 
         [0035]    As shown in  FIGS. 3A and 3B , the quenching mesh  200  configured to prevent propagation of the flame is a fine metal net structure, which may be a stainless steel net structure, and the size and structure of the grid of the quenching mesh  200  can be different according to a type of the combustible gas. 
         [0036]    The combustible gas passing through the quenching mesh  200  is introduced into the recombiner  300  with the air introduced from the fluid inlet port  120 , and the combustible gas reacts with the oxygen included in the air. Here, as shown in the drawings, a shape of quenching mesh may be modified according to a shape of the recombiner. 
         [0037]      FIGS. 4A and 4B  are perspective views showing embodiments of the recombiner of  FIG. 2 . 
         [0038]    As shown in  FIGS. 4A and 4B , the recombiner  300  is a structure in which a catalyst is coated on a surface of the honeycomb structure, and a mixture of platinum or palladium and titanium dioxide or alumina may be used as the catalyst that can recombine the hydrogen and carbon monoxide. The recombiner  300  according to the present invention is not limited to the above-mentioned honeycomb structure and may be formed as a plate structure. 
         [0039]    A material of the catalyst is not particularly limited as long as the hydrogen gas reacts with the oxygen to be removed. For example, alumina is coated and then platinum is coated thereon to be used as the catalyst. The recombiner  300  shown in 
         [0040]      FIGS. 4A and 4B  are installed in a chimney  700  in a multi-stage such that all of the combustible gas is completely oxidized and then discharged to the outside. Here, the recombiner  300  may be formed in various shapes such as a circular or rectangular shape according to necessity as long as the recombiner  300  can be fixed in the chimney. 
         [0041]    Meanwhile, combustion may occur over the recombiner  300  when the concentrations of hydrogen and carbon monoxide are high. In this case, the flame may flow backward. In order to prevent the backward flow, the quenching mesh  200  is installed under the recombiner  300  as described above. 
         [0042]    The combustible gas passing through the quenching mesh  200  is introduced into the recombiner  300  with the air introduced through the fluid inlet port  120 , and the combustible gas reacts with the oxygen included in the air to be converted into steam, carbon dioxide, a non-condensable gas, and so on. Since such a reaction is generally an exothermic reaction and the gas is heated, the combustible gas can be discharged by the effect of buoyancy when the combustion controller for a combustible gas is installed in a gravity direction. That is, most of the gases are discharged over the combustion controller for a combustible gas by buoyancy, and a flow rate of the combustible gas discharged to the external atmosphere through the inlet port can be almost neglected. In addition, since the buoyancy of the combustible gas is generated by the heat generated upon recombining and the combustible gas is moved to above the recombiner  300  and discharged, the combustion controller for a combustible gas can be driven as passive equipment without separate power. 
         [0043]    As described above, since the combustible gas is converted into steam, carbon dioxide, a non-condensable gas, or the like, by recombining of the combustible gas and the air, safe combustion control with no probability of explosion of hydrogen can be performed. In addition, discharge of toxic carbon monoxide can be prevented, and backward flow of the flame can be prevented through the quenching mesh  200 . 
         [0044]      FIG. 5  is a view of another embodiment of the combustion controller for a combustible gas of the nuclear power plant according to the present invention, showing a state in which a separate fan is installed, and  FIG. 6  is a cross-sectional view taken along line A-A of  FIG. 5 . 
         [0045]    As shown in  FIG. 5 , the combustion controller for a combustible gas is installed in an annular section of the chimney  700 , and a fan  400  is installed at an upper portion of a center of the annular section such that the external air (the atmosphere) is forcibly introduced into a lower portion of the center of the annular section. The center of the annular section functions as an external air introduction passage  410 , and the air introduced at this time can pass through a fan fluid inlet port  420  to smoothly discharge the combustible gas introduced into the combustible gas inlet port  100  through the outlet port of the nuclear power plant chimney  700 . In this case, the recombiner  300  and the quenching mesh  200  are configured as an annular shape formed along a periphery of the external air introduction passage  410  as shown in  FIG. 6 . Here, the quenching mesh  200  may be selectively installed on or under the recombiner  300 . However, the combustion controller of a combustible gas having the annular shape according to the embodiment has the annular section, a lower portion of which is closed, such that any of the combustible gas introduced into the external air introduction passage  410  is prevented from being directly discharged to the atmosphere. 
         [0046]    Meanwhile,  FIG. 6  is a view of another embodiment of the recombiner  300  having an annular shape, showing a cross-sectional view taken along line A-A of  FIG. 5 . As shown in  FIG. 6 , the support frame  800  has an annular shape, the fan  400  is installed at the center of the annular section, and the recombiner  300  having an annular shape is installed in the support frame  800 . 
         [0047]    As can be seen from the foregoing, the combustion controller for a combustible gas according to the present invention is installed at the exhaust pipe or the exhaust chimney of the filtered vent equipment outside the containment vessel and capable of performing stable combustion control with no probability of explosion of hydrogen through a recombining reaction of the combustible gas, preventing discharge of carbon monoxide, which is a toxic gas, and preventing backward flow of the flame and propagation of the flame through the quenching mesh. 
         [0048]    It will be apparent to those skilled in the art that various modifications can be made to the above-described exemplary embodiments of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers all such modifications provided they come within the scope of the appended claims and their equivalents.