Patent Publication Number: US-2022234003-A1

Title: Environmental equipment and power generation system using same

Description:
TECHNICAL FIELD 
     The disclosure relates to environmental equipment and a power generation system including the same, and more particularly to environmental equipment for reducing discharge of pollutants and a power generation system including the same. 
     BACKGROUND ART 
     Numerous thermoelectric power plants generally operate based on coal or petroleum. In particular, with recently tightened regulations on environmental pollution, environmental equipment capable of reducing discharge of pollutants has been increasingly researched, developed and spread. 
     The related art of such environmental equipment has already been disclosed in Korean Patent Publication No. 2017-0142377 (titled “POLLUTANT REMOVAL APPARATUS AND COMBINED CYCLE POWER GENERATION SYSTEM” and published on Dec. 28, 2017). This related art is characterized in the pollutant removal apparatus that reduces pollutants generated from the thermoelectric power plants. 
     However, acceptable pollutant-discharge standards are tightened, and thus high-efficiency technology of using a denitrifying catalyst is required to reduce nitrogen oxide, i.e., a precursor of fine dust, which has come up as an environmental issue, into a few PPM levels. Therefore, the conventional environmental equipment includes a denitrifier based on selective catalytic reduction (SCR), which is placed after a flue gas desulfurizer (FGD). The denitrifier based on the SCR needs to use a burner for heating exhaust gas in order to raise the temperature of the exhaust gas. Therefore, the conventional environmental equipment has a problem in that operating costs are excessively increased. 
     DISCLOSURE 
     Technical Problem 
     An aspect of the disclosure is to provide environmental equipment, of which operating costs are significantly reduced, and a power generation system including the same. 
     Technical Solution 
     To achieve the aspect of the disclosure, there is provided a power generation system including: a boiler; an electric generator which produces electricity based on steam generated in the boiler; a first denitrifier which receives exhaust gas from the boiler and denitrifies the exhaust gas by spraying a reductant to the exhaust gas; a low low-temperature electric precipitator which collects dust from the exhaust gas provided from the first denitrifier; a second denitrifier which secondarily denitrifies the exhaust gas by spraying the reductant to the exhaust gas provided from the low low-temperature electric precipitator and provides the exhaust gas toward a chimney; a first heat exchanger which is provided between the first denitrifier and the low low-temperature electric precipitator and cools the exhaust gas provided to the low low-temperature electric precipitator; and a second heat exchanger which is connected to the first heat exchanger between the low low-temperature electric precipitator and the second denitrifier and heats the exhaust gas provided to the second denitrifier. 
     The second denitrifier may secondarily denitrify the exhaust gas based on a low temperature selective catalytic reduction (SCR). 
     The first heat exchanger may cool the exhaust gas, to be provided to the low low-temperature electric precipitator, to have a temperature of 80˜100 degrees, and the second heat exchanger may heat the exhaust gas, to be provided to the second denitrifier, to have a temperature of 150˜200 degrees. 
     The power generation system may further include: a third heat exchanger which is provided between the second denitrifier and the chimney and cools the exhaust gas to be provided to the chimney; and a fourth heat exchanger which is connected to the third heat exchanger and heats air to be provided to the boiler and used for combustion. 
     The power generation system may further include a catalyst regenerator which is connected to at least one of the first denitrifier and the second denitrifier and supplies a catalyst regeneration material toward a catalyst in the denitrifier. 
     The catalyst regenerator may spray dry ice toward the catalyst. 
     The catalyst regenerator may alternately spray dry ice and hot steam toward the catalyst. p The catalyst regenerator may include: a sprayer which is provided outside the denitrifier and supplies the catalyst regeneration material from the outside, and a spraying nozzle which is extended from the sprayer to an inside of the denitrifier and moves up and down inside the denitrifier by a motive power source to spray the catalyst regeneration material toward the catalyst. 
     The catalyst regenerator may spray the catalyst regeneration material to the catalyst when the catalyst is poisoned. 
     Meanwhile, environmental equipment connected to a boiler of a power generation system according to the disclosure may include: an electric generator which produces electricity based on steam generated in the boiler; a first denitrifier which receives exhaust gas from the boiler and denitrifies the exhaust gas by spraying a reductant to the exhaust gas; a low low-temperature electric precipitator which collects dust from the exhaust gas provided from the first denitrifier; a second denitrifier which secondarily denitrifies the exhaust gas by spraying the reductant to the exhaust gas provided from the low low-temperature electric precipitator and provides the exhaust gas toward a chimney; a first heat exchanger which is provided between the first denitrifier and the low low-temperature electric precipitator and cools the exhaust gas provided to the low low-temperature electric precipitator; and a second heat exchanger which is connected to the first heat exchanger between the low low-temperature electric precipitator and the second denitrifier and heats the exhaust gas provided to the second denitrifier. 
     The second denitrifier may secondarily denitrify the exhaust gas based on a low temperature SCR. 
     The first heat exchanger may cool the exhaust gas, to be provided to the low low-temperature electric precipitator, to have a temperature of 80˜100 degrees, and the second heat exchanger may heat the exhaust gas, to be provided to the second denitrifier, to have a temperature of 150˜200 degrees. 
     The power generation system may further include: a third heat exchanger which is provided between the second denitrifier and the chimney and cools the exhaust gas to be provided to the chimney; and a fourth heat exchanger which is connected to the third heat exchanger and heats air to be provided to the boiler and used for combustion. 
     The power generation system may further include a catalyst regenerator which is connected to at least one of the first denitrifier and the second denitrifier and supplies a catalyst regeneration material toward a catalyst in the denitrifier. 
     The catalyst regenerator may spray dry ice toward the catalyst. 
     The catalyst regenerator may alternately spray dry ice and hot steam toward the catalyst. 
     The catalyst regenerator may include: a sprayer which is provided outside the denitrifier and supplies the catalyst regeneration material from the outside, and a spraying nozzle which is extended from the sprayer to an inside of the denitrifier and moves up and down inside the denitrifier by a motive power source to spray the catalyst regeneration material toward the catalyst. 
     The catalyst regenerator may spray the catalyst regeneration material to the catalyst when the catalyst is poisoned. 
     Meanwhile, a power generation system according to the disclosure includes: a boiler; an electric generator which produces electricity based on steam generated in the boiler; a low low-temperature electric precipitator which receives exhaust gas from the boiler and collects dust from the exhaust gas; a denitrifier which denitrifies the exhaust gas by spraying the reductant to the exhaust gas provided from the low low-temperature electric precipitator and provides the exhaust gas toward a chimney; a first heat exchanger which is provided between the electric generator and the low low-temperature electric precipitator and cools the exhaust gas provided to the low low-temperature electric precipitator; and a second heat exchanger which is connected to the first heat exchanger between the low low-temperature electric precipitator and the denitrifier and heats the exhaust gas provided to the denitrifier. 
     Meanwhile, environmental equipment connected to a boiler of a power generation system according to the disclosure includes: an electric generator which produces electricity based on steam generated in the boiler; a low low-temperature electric precipitator which receives exhaust gas from the boiler and collects dust from the exhaust gas; a denitrifier which denitrifies the exhaust gas by spraying the reductant to the exhaust gas provided from the low low-temperature electric precipitator and provides the exhaust gas toward a chimney; a first heat exchanger which is provided between the electric generator and the low low-temperature electric precipitator and cools the exhaust gas provided to the low low-temperature electric precipitator; and a second heat exchanger which is connected to the first heat exchanger between the low low-temperature electric precipitator and the denitrifier and heats the exhaust gas provided to the denitrifier. 
     Advantageous Effects 
     Environmental equipment according to the disclosure and a power generation system including the same, in which exhaust gas is heated based on waste heat of the exhaust gas without a burner, have effects on reducing operating costs and facilitating easy installation and operation of the system. 
     The technical effects of the disclosure are not limited to the foregoing effects, and other technical effects will become apparent to those skilled in the art through the following descriptions. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a conceptual view schematically illustrating a power generation system according to an embodiment of the disclosure, 
         FIG. 2  is a conceptual view illustrating automatic catalyst-regeneration equipment in the power generation system according to an embodiment of the disclosure, and 
         FIG. 3  is a flowchart showing operations of environmental equipment according to an embodiment of the disclosure. 
     
    
    
     MODE FOR CARRYING OUT DISCLOSURE 
     Below, embodiments of the disclosure will be described with reference to the accompanying drawings. However, the embodiments are not limited to embodiments set forth herein, but may be variously given to complete the disclosure and help a person having ordinary knowledge in the art to fully understand the scope of the disclosure. The shapes, etc. of elements in the accompanying drawings may be exaggerated for clearer description, and like numerals refer to like elements throughout the accompanying drawings. 
       FIG. 1  is a conceptual view schematically illustrating a power generation system according to an embodiment of the disclosure, and  FIG. 2  is a conceptual view illustrating automatic catalyst-regeneration equipment in the power generation system according to an embodiment of the disclosure. 
     As shown in  FIGS. 1 and 2 , a power generation system  1000  according to an embodiment of the disclosure includes a boiler  100 , environmental equipment  200 , and a chimney  300 . 
     First, the boiler  100  includes a combustion space in which a burner is installed. In the boiler  100 , fuel is supplied to the burner, and air flows into the combustion space. Thus, the boiler  100  generates steam with thermal energy in the combustion space. In this case, the fuel supplied to the boiler  100  may include fossil fuel such as pulverized coal or heavy oil. 
     For example, when pulverized coal is used as fossil fuel, the burner is provided as a pulverized-coal burner to spray air and pulverized coal into the combustion space. In this case, the pulverized-coal burner may include a low NOx burner to which a low NOx (nitrogen oxide) combustion process is applied. However, the low NOx burner is merely to describe an embodiment of the disclosure, and various kinds of burners may be used. Further, power generation equipment (not shown) is connected to the boiler and produces electricity based on steam provided by the boiler  100 . 
     Meanwhile, the environmental equipment  200  may include a first denitrifier  210 , a first rotary air-preheater  220 , an electric precipitator  230 , a desulfurizer  240 , a second denitrifier  250 , and a catalyst regenerator  260 . In this case, the environmental equipment  200  is connected to the boiler  100  and forms a course to discharge exhaust gas, from which pollutants are removed, to the atmosphere through the chimney  300 . 
     First, the first denitrifier  210  is placed between the boiler  100  and the first rotary air-preheater  220  and receives exhaust gas from the boiler  100 . In this case, the first denitrifier  210  may receive the exhaust gas which is primarily denitrified by a selective non-catalytic reduction (SNCR) device or NOx burner installed in the boiler  100 . Thus, the first denitrifier  210  secondarily denitrifies the exhaust gas received from the boiler  100 . 
     Here, the first denitrifier  210  may include selective catalytic reduction (SCR) device. Thus, the first denitrifier  210  sprays ammonia, urea or the like reductant to the exhaust gas, thereby converting nitrogen oxide into nonpolluting water and nitrogen on the catalyst. 
     Meanwhile, the first rotary air-preheater (or gas air heater, GAH) is placed between the first denitrifier  210  and the electric precipitator  230 . Thus, the first rotary air-preheater  220  recovers waste heat from the exhaust gas provided by the denitrifier. Further, the first rotary air-preheater  220  previously heats air flowing into the combustion space, thereby improving a combustion efficiency of the boiler  100 . In other words, the first rotary air-preheater  220  heats air supplied into the boiler  100  and used for combustion with remaining heat previously used for the combustion. 
     Further, the electric precipitator  230  is provided as a low low-temperature electric precipitator between the first rotary air-preheater  220  and the desulfurizer  240  and collects dust from the exhaust gas provided by the first rotary air-preheater  220 . Here, the electric precipitator  230  may be provided as a dust collector based on electrostatic separation. Thus, dust in the exhaust gas is charged by a metal wire of a cathode, and the charged dust is adhered to an anode shaped like a plate or tube. 
     The electric precipitator  230  is suitable for large-scale exhaust gas treatment and may additionally include a bag filter to improve a dust-collection efficiency by a hybrid manner. However, this is merely for describing an embodiment of the disclosure, and does not limit the kinds of dust collectors. 
     Meanwhile, the desulfurizer  240  is provided between the electric precipitator  230  and the second denitrifier  250  and desulfurizes the exhaust gas provided by the electric precipitator  230 . Here, the desulfurizer  240  may internally include a cyclone for gas/liquid contact enhancement to improve a desulfurization efficiency. Further, the desulfurizer  240  may be enlarged as compared with a conventional one and additionally include a plurality of gypsum sludge spraying nozzles or the like to keep a desulfurization efficiency of 98% or higher. Further, the desulfurizer  240  may include a mist eliminator in an inside upper portion thereof to prevent gypsum slurry from spilling out. Thus, sulfur dioxide of the exhaust gas is neutralized by reaction with limestone in the desulfurizer  240  and changed into gypsum. In this case, the gypsum may be recycled for industrial use. 
     Meanwhile, the second denitrifier  250  is provided between the desulfurizer  240  and the chimney  300  and receives the exhaust gas from the desulfurizer  240 . In this case, the second denitrifier  250  may include a low-temperature SCR device. Thus, the second denitrifier  250  denitrifies the exhaust gas provided by the desulfurizer  240  so that the denitrified exhaust gas can be discharged to the atmosphere through the chimney  300 . 
     Meanwhile, a first heat exchanger  11  is provided between the first rotary air-preheater  220  and the electric precipitator  230 . The first heat exchanger  11  is connected to a second heat exchanger  12  provided between the desulfurizer  240  and the second denitrifier  250 . Here, the first heat exchanger  11  and the second heat exchanger  12  may be embodied by tube-type gas gas heaters (GGH). The first heat exchanger  11  cools the exhaust gas, and the second heat exchanger  12  heats the exhaust gas. Further, a third heat exchanger  13  is provided between the second denitrifier  250  and the chimney  300 . The third heat exchanger  13  is connected to a fourth heat exchanger  14  provided on a course where air for combustion flows into the first rotary air-preheater  220 . Here, the third heat exchanger  13  may be provided as an air preheater that recovers waste heat from the exhaust gas, and thus air to be supplied to the boiler  100  and used for combustion is heated by the fourth heat exchanger  14 . The third heat exchanger  13  and the fourth heat exchanger  14  may be embodied by rotary or tubular heat exchangers. 
     Further, the catalyst regenerator  260  may be connected to at least one of the first denitrifier  210  and the second denitrifier  250 . The catalyst regenerator  260  sprays catalyst regeneration materials to catalysts  211  and  251  when the catalysts  211  and  251  are poisoned during the operations of the denitrifiers, thereby preventing the life of the catalysts  211  and  251  from being shortened. In this case, the catalyst regenerator  260  may spray the catalyst regeneration materials including dry ice to the catalysts. 
     The catalyst regenerator  260  may include a catalyst-regeneration material feeder  261 , a sprayer  262 , and a spraying nozzle  263 . The catalyst-regeneration material feeder  261  may be placed outside the denitrifier and feed the catalyst regeneration material such as dry ice pellet into the sprayer  262 . Further, the sprayer  262  sprays the catalyst regeneration material to the catalysts  211  and  251 . To this end, the sprayer  262  is connected to the spraying nozzle  263  neighboring on the catalysts  211  and  251  outside the denitrifiers and supplies the catalyst regeneration material to the spraying nozzle  263 . Here, the spraying nozzle  263  includes a single spraying hole or a plurality of spraying holes to uniformly spray the catalyst regeneration material to the entire surfaces of the catalysts  211  and  251 . The spraying nozzle  263  may be connected to a motor, an actuator or the like motive power source, and move up and down inside the denitrifier. 
     Thus, the catalyst regenerator  260  has an advantage of preventing the catalyst from being poisoned and shortened in life. 
     The catalyst regenerator  260  in an embodiment of the disclosure is connected to at least one of the first denitrifier  210  and the second denitrifier  250 . However, the catalyst regenerator  260  may be installed only in the second denitrifier  250 , and may be installed in both the first denitrifier  210  and the second denitrifier  250  when coal quality is bad. 
     In an embodiment of the disclosure, the catalyst regenerator  260  sprays dry ice. However, this is merely for describing an embodiment of the disclosure, and the catalyst regenerator may alternately spray dry ice and hot steam. 
     Further, the environmental equipment  200  according to an embodiment of the disclosure includes the first denitrifier  210  and the second denitrifier  250 . However, this is merely for describing an embodiment of the disclosure, and the environmental equipment  200  may include only the second denitrifier  250  without the first denitrifier  210  as necessary. 
     Below, operations of the environmental equipment according to an embodiment of the disclosure will be described in detail. Here, repetitive descriptions to the foregoing elements will be avoided, and like numerals refer to like elements. 
       FIG. 3  is a flowchart showing operations of environmental equipment according to an embodiment of the disclosure. 
     As shown in  FIG. 3 , the environmental equipment  200  according to an embodiment of the disclosure removes pollutants from exhaust gas provided by the boiler  100  and discharges the exhaust gas to the atmosphere through the chimney  300 . 
     First, the exhaust gas discharged from the boiler  100  is primarily denitrified in the first denitrifier  210  (S 100 ). In this case, the first denitrifier  210  sprays a reductant to the exhaust gas so that nitrogen oxide can be converted into water and nitrogen. 
     Further, the exhaust gas discharged from the first denitrifier  210  is provided to the first rotary air-preheater  220 . In this case, the exhaust gas provided to the first rotary air-preheater  220  has a temperature of about 360 degrees. Here, the first rotary air-preheater  220  recovers waste heat from the exhaust gas and heats air, which will be provided to the boiler  100  and used for combustion, with the waste heat. 
     Then, the exhaust gas is supplied from the first rotary air-preheater  220  to the electric precipitator  230  via the first heat exchanger  11 . In this case, the exhaust gas having a temperature of about 180˜250 degrees is provided to the first heat exchanger  11 , and the first heat exchanger  11  recovers heat from the exhaust gas so that the exhaust gas having a temperature of about 90 degrees, for example, 80˜100 degrees can be provided to the electric precipitator  230 . 
     Then, the electric precipitator  230  collects dust from the exhaust gas (S 200 ). The exhaust gas, from which dust has been removed, is provided to the desulfurizer  240 . In this case, the exhaust gas provided to the desulfurizer  240  may be maintained at a temperature of about  90 . 
     Further, the desulfurizer  240  desulfurizes the exhaust gas (S 300 ). Thus, sulfur dioxide of the exhaust gas is neutralized by reaction with limestone and changed into gypsum, and the desulfurizer  240  supplies the desulfurized exhaust gas to the second denitrifier  250 . In this case, the exhaust gas passed through the desulfurizer  240  may have a temperature of about 50 degrees. 
     Meanwhile, the second heat exchanger  12  placed between the desulfurizer  240  and the second denitrifier  250  heats the exhaust gas provided by the desulfurizer  240  so that the exhaust gas having a temperature of about 150˜200 degrees can be provided to the second denitrifier  250 . Here, the second heat exchanger  12  does not need a burner because the waste heat of the exhaust gas is recycled to heat the exhaust gas. Thus, the environmental equipment  200  excludes or does not employ the burner, thereby reducing fuel costs by more than 10 billion won per year in the case of a 500 MW-class coal-fired power station. 
     Meanwhile, the second denitrifier  250  secondarily denitrifies the exhaust gas (S 400 ). Here, the second denitrifier  250  secondarily denitrifies the exhaust gas based on low-temperature SCR, so that the secondarily denitrified exhaust gas can be provided toward the chimney  300 . Here, the exhaust gas may have a temperature of about 150˜200 degrees. 
     Meanwhile, the third heat exchanger  13  recovers waste heat from the exhaust gas provided toward the chimney, and thus the exhaust gas having a temperature of about 60˜85 degrees is discharged through the chimney  300 . In this case, the fourth heat exchanger  14  additionally raises the temperature of air, which will be provided to the first rotary air-preheater  220  and used for combustion, by 25 degrees or higher, based on the waste heat recovered in the third heat exchanger  13 . Thus, the environmental equipment  200  improves the efficiency of the boiler by about 1% or more, and has an effect on reducing costs by 3.3 billion won per year in the case of the 500 MW-class coal-fired power station. 
     Accordingly, the environmental equipment according to the disclosure and the power generation system including the same have effect on reducing operating costs and facilitating easy installation and operation of the system because the exhaust gas is heated based on the waste heat of the exhaust gas without the burner. 
     The embodiments of the disclosure described above and illustrated in the accompanying drawings should not be construed as limiting the technical idea of the disclosure. The scope of the disclosure is limited only by matters disclosed in the appended claims, and various improvements and changes can be made by a person having ordinary knowledge in the art without departing from the technical idea of the disclosure. Therefore, such improvements and changes fall within the scope of the disclosure as long as they are apparent to those skilled in the art.