Patent Description:
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 <CIT>). This related art is characterized in the pollutant removal apparatus that reduces pollutants generated from the thermoelectric power plants.

<CIT> deals with providing a method for removing gaseous mercury in flue gas that make it possible to remove mercury in flue gas extremely satisfactorily while handling is made easy and cost increases are kept under control. In order to accomplish this object, this document adopts the method of removing gaseous mercury in flue gas, in which, after water-insoluble mercury in the flue gas is converted into water-soluble mercury by placing the flue gas in contact with a solid catalyst formed by a metal oxide, wet-type absorption is performed on the water-soluble mercury.

<CIT> describes a process of thermally treating flue gases which come from a boiler system and are conducted through two series-connected flue gas aftertreating plants, wherein the second flue gas aftertreating plant is an NOx - removing plant and is operated at a higher flue gas temperature than the first flue gas aftertreating plant, and of thermally treating combustion air to be supplied to the boiler system. This process is characterized in that heat of the flue gases is used to reheat the flue gases and to preheat air.

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.

An aspect of the invention is to provide environmental equipment, of which operating costs are significantly reduced, and a power generation system including the same.

To achieve the aspect of the invention, 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 <NUM>-<NUM> degrees, and the second heat exchanger may heat the exhaust gas, to be provided to the second denitrifier, to have a temperature of <NUM>-<NUM> 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, the environmental equipment for connecting to a boiler of a power generation system according to the invention includes: 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 environmental equipment 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 environmental equipment 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.

An environmental equipment according to the invention 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 invention are not limited to the foregoing effects, and other technical effects will become apparent to those skilled in the art through the following descriptions.

Below, embodiments of the invention 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 invention and help a person having ordinary knowledge in the art to fully understand the scope of the invention.

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> is a conceptual view schematically illustrating a power generation system according to an embodiment of the invention, and <FIG> is a conceptual view illustrating automatic catalyst-regeneration equipment in the power generation system according to an embodiment of the invention.

As shown in <FIG> and <FIG>, a power generation system <NUM> according to an embodiment of the invention includes a boiler <NUM>, environmental equipment <NUM>, and a chimney <NUM>.

First, the boiler <NUM> includes a combustion space in which a burner is installed. In the boiler <NUM>, fuel is supplied to the burner, and air flows into the combustion space. Thus, the boiler <NUM> generates steam with thermal energy in the combustion space. In this case, the fuel supplied to the boiler <NUM> 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 invention, 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 <NUM>.

Meanwhile, the environmental equipment <NUM> may include a first denitrifier <NUM>, a first rotary air-preheater <NUM>, an electric precipitator <NUM>, a desulfurizer <NUM>, a second denitrifier <NUM>, and a catalyst regenerator <NUM>. In this case, the environmental equipment <NUM> is connected to the boiler <NUM> and forms a course to discharge exhaust gas, from which pollutants are removed, to the atmosphere through the chimney <NUM>.

First, the first denitrifier <NUM> is placed between the boiler <NUM> and the first rotary air-preheater <NUM> and receives exhaust gas from the boiler <NUM>. In this case, the first denitrifier <NUM> may receive the exhaust gas which is primarily denitrified by a selective non-catalytic reduction (SNCR) device or NOx burner installed in the boiler <NUM>. Thus, the first denitrifier <NUM> secondarily denitrifies the exhaust gas received from the boiler <NUM>.

Here, the first denitrifier <NUM> may include selective catalytic reduction (SCR) device. Thus, the first denitrifier <NUM> 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 <NUM> and the electric precipitator <NUM>. Thus, the first rotary air-preheater <NUM> recovers waste heat from the exhaust gas provided by the denitrifier. Further, the first rotary air-preheater <NUM> previously heats air flowing into the combustion space, thereby improving a combustion efficiency of the boiler <NUM>. In other words, the first rotary air-preheater <NUM> heats air supplied into the boiler <NUM> and used for combustion with remaining heat previously used for the combustion.

Further, the electric precipitator <NUM> is provided as a low low-temperature electric precipitator between the first rotary air-preheater <NUM> and the desulfurizer <NUM> and collects dust from the exhaust gas provided by the first rotary air-preheater <NUM>. Here, the electric precipitator <NUM> 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 <NUM> 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 <NUM> is provided between the electric precipitator <NUM> and the second denitrifier <NUM> and desulfurizes the exhaust gas provided by the electric precipitator <NUM>. Here, the desulfurizer <NUM> may internally include a cyclone for gas/liquid contact enhancement to improve a desulfurization efficiency. Further, the desulfurizer <NUM> 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 <NUM>% or higher. Further, the desulfurizer <NUM> 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 <NUM> and changed into gypsum. In this case, the gypsum may be recycled for industrial use.

Meanwhile, the second denitrifier <NUM> is provided between the desulfurizer <NUM> and the chimney <NUM> and receives the exhaust gas from the desulfurizer <NUM>. In this case, the second denitrifier <NUM> may include a low-temperature SCR device. Thus, the second denitrifier <NUM> denitrifies the exhaust gas provided by the desulfurizer <NUM> so that the denitrified exhaust gas can be discharged to the atmosphere through the chimney <NUM>.

Meanwhile, a first heat exchanger <NUM> is provided between the first rotary air-preheater <NUM> and the electric precipitator <NUM>. The first heat exchanger <NUM> is connected to a second heat exchanger <NUM> provided between the desulfurizer <NUM> and the second denitrifier <NUM>. Here, the first heat exchanger <NUM> and the second heat exchanger <NUM> may be embodied by tube-type gas gas heaters (GGH). The first heat exchanger <NUM> cools the exhaust gas, and the second heat exchanger <NUM> heats the exhaust gas. Further, a third heat exchanger <NUM> is provided between the second denitrifier <NUM> and the chimney <NUM>. The third heat exchanger <NUM> is connected to a fourth heat exchanger <NUM> provided on a course where air for combustion flows into the first rotary air-preheater <NUM>. Here, the third heat exchanger <NUM> may be provided as an air preheater that recovers waste heat from the exhaust gas, and thus air to be supplied to the boiler <NUM> and used for combustion is heated by the fourth heat exchanger <NUM>. The third heat exchanger <NUM> and the fourth heat exchanger <NUM> may be embodied by rotary or tubular heat exchangers.

Further, the catalyst regenerator <NUM> may be connected to at least one of the first denitrifier <NUM> and the second denitrifier <NUM>. The catalyst regenerator <NUM> sprays catalyst regeneration materials to catalysts <NUM> and <NUM> when the catalysts <NUM> and <NUM> are poisoned during the operations of the denitrifiers, thereby preventing the life of the catalysts <NUM> and <NUM> from being shortened. In this case, the catalyst regenerator <NUM> may spray the catalyst regeneration materials including dry ice to the catalysts.

The catalyst regenerator <NUM> may include a catalyst-regeneration material feeder <NUM>, a sprayer <NUM>, and a spraying nozzle <NUM>. The catalyst-regeneration material feeder <NUM> may be placed outside the denitrifier and feed the catalyst regeneration material such as dry ice pellet into the sprayer <NUM>. Further, the sprayer <NUM> sprays the catalyst regeneration material to the catalysts <NUM> and <NUM>. To this end, the sprayer <NUM> is connected to the spraying nozzle <NUM> neighboring on the catalysts <NUM> and <NUM> outside the denitrifiers and supplies the catalyst regeneration material to the spraying nozzle <NUM>. Here, the spraying nozzle <NUM> 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 <NUM> and <NUM>. The spraying nozzle <NUM> 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 <NUM> has an advantage of preventing the catalyst from being poisoned and shortened in life.

The catalyst regenerator <NUM> in an embodiment of the invention is connected to at least one of the first denitrifier <NUM> and the second denitrifier <NUM>. However, the catalyst regenerator <NUM> may be installed only in the second denitrifier <NUM>, and may be installed in both the first denitrifier <NUM> and the second denitrifier <NUM> when coal quality is bad.

In an embodiment of the invention, the catalyst regenerator <NUM> sprays dry ice. However, this is merely for describing an embodiment of the invention, and the catalyst regenerator may alternately spray dry ice and hot steam.

Further, the environmental equipment <NUM> according to an embodiment of the invention includes the first denitrifier <NUM> and the second denitrifier <NUM>. However, this is merely for describing an embodiment of the invention, and the environmental equipment <NUM> may include only the second denitrifier <NUM> without the first denitrifier <NUM> as necessary.

Below, operations of the environmental equipment according to an embodiment of the invention will be described in detail. Here, repetitive descriptions to the foregoing elements will be avoided, and like numerals refer to like elements.

<FIG> is a flowchart showing operations of environmental equipment according to an embodiment of the invention.

As shown in <FIG>, the environmental equipment <NUM> according to an embodiment of the invention removes pollutants from exhaust gas provided by the boiler <NUM> and discharges the exhaust gas to the atmosphere through the chimney <NUM>.

First, the exhaust gas discharged from the boiler <NUM> is primarily denitrified in the first denitrifier <NUM> (S100). In this case, the first denitrifier <NUM> 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 <NUM> is provided to the first rotary air-preheater <NUM>. In this case, the exhaust gas provided to the first rotary air-preheater <NUM> has a temperature of about <NUM> degrees. Here, the first rotary air-preheater <NUM> recovers waste heat from the exhaust gas and heats air, which will be provided to the boiler <NUM> and used for combustion, with the waste heat.

Then, the exhaust gas is supplied from the first rotary air-preheater <NUM> to the electric precipitator <NUM> via the first heat exchanger <NUM>. In this case, the exhaust gas having a temperature of about <NUM>-<NUM> degrees is provided to the first heat exchanger <NUM>, and the first heat exchanger <NUM> recovers heat from the exhaust gas so that the exhaust gas having a temperature of about <NUM> degrees, for example, <NUM> - <NUM> degrees can be provided to the electric precipitator <NUM>.

Then, the electric precipitator <NUM> collects dust from the exhaust gas (S200). The exhaust gas, from which dust has been removed, is provided to the desulfurizer <NUM>. In this case, the exhaust gas provided to the desulfurizer <NUM> may be maintained at a temperature of about <NUM>.

Further, the desulfurizer <NUM> desulfurizes the exhaust gas (S300). Thus, sulfur dioxide of the exhaust gas is neutralized by reaction with limestone and changed into gypsum, and the desulfurizer <NUM> supplies the desulfurized exhaust gas to the second denitrifier <NUM>. In this case, the exhaust gas passed through the desulfurizer <NUM> may have a temperature of about <NUM> degrees.

Meanwhile, the second heat exchanger <NUM> placed between the desulfurizer <NUM> and the second denitrifier <NUM> heats the exhaust gas provided by the desulfurizer <NUM> so that the exhaust gas having a temperature of about <NUM>-<NUM> degrees can be provided to the second denitrifier <NUM>. Here, the second heat exchanger <NUM> does not need a burner because the waste heat of the exhaust gas is recycled to heat the exhaust gas. Thus, the environmental equipment <NUM> excludes or does not employ the burner, thereby reducing fuel costs by more than <NUM> billion won per year in the case of a 500MW-class coal-fired power station.

Meanwhile, the second denitrifier <NUM> secondarily denitrifies the exhaust gas (S400). Here, the second denitrifier <NUM> secondarily denitrifies the exhaust gas based on low-temperature SCR, so that the secondarily denitrified exhaust gas can be provided toward the chimney <NUM>. Here, the exhaust gas may have a temperature of about <NUM>-<NUM> degrees.

Meanwhile, the third heat exchanger <NUM> recovers waste heat from the exhaust gas provided toward the chimney, and thus the exhaust gas having a temperature of about <NUM>-<NUM> degrees is discharged through the chimney <NUM>. In this case, the fourth heat exchanger <NUM> additionally raises the temperature of air, which will be provided to the first rotary air-preheater <NUM> and used for combustion, by <NUM> degrees or higher, based on the waste heat recovered in the third heat exchanger <NUM>. Thus, the environmental equipment <NUM> improves the efficiency of the boiler by about <NUM> % or more, and has an effect on reducing costs by <NUM> billion won per year in the case of the 500MW-class coal-fired power station.

Accordingly, the environmental equipment according to the invention 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 invention described above and illustrated in the accompanying drawings should not be construed as limiting the technical idea of the invention. The scope of the invention 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 invention.

Claim 1:
A power generation system (<NUM>) comprising:
a boiler (<NUM>)
an electric generator which produces electricity based on steam generated in the boiler (<NUM>);
a first denitrifier (<NUM>) which receives exhaust gas from the boiler (<NUM>) and denitrifies the exhaust gas by spraying a reductant to the exhaust gas;
a low low-temperature electric precipitator (<NUM>) which collects dust from the exhaust gas provided from the first denitrifier (<NUM>);
a second denitrifier (<NUM>) which secondarily denitrifies the exhaust gas by spraying the reductant to the exhaust gas provided from the low low-temperature electric precipitator (<NUM>) and provides the exhaust gas toward a chimney (<NUM>);
a first heat exchanger (<NUM>) which is provided between the first denitrifier (<NUM>) and the low low-temperature electric precipitator (<NUM>) and cools the exhaust gas provided to the low low-temperature electric precipitator (<NUM>); and
a second heat exchanger (<NUM>) which is connected to the first heat exchanger (<NUM>) between the low low-temperature electric precipitator (<NUM>) and the second denitrifier (<NUM>) and heats the exhaust gas provided to the second denitrifier (<NUM>).