Patent Description:
Exhaust gas discharged from a boiler of a power generation facility contains pollutants such as nitrogen oxides (NOx), dust, and sulfur oxides (SOx). Therefore, boiler facilities are equipped with environmental facilities such as a denitration facility for removing nitrogen oxides, an electrostatic precipitator for removing dust, and a desulfurization facility for removing sulfur oxides, in the rear of the combustion chamber.

Recently, as environmental regulations have been strengthened, catalysts have been added to the denitration facility. In the electrostatic precipitator, a bag filter is additionally installed to enhance the collection efficiency by a hybrid method. In addition, in the desulfurization facility, the desulfurization efficiency has been increased by increasing the amount of limestone or increasing the volume of the reactor.

However, since the pressure loss of the boiler increases due to the addition of such environmental facilities, it is necessary to increase the capacity of the boiler blower or lower the load of the boiler. Moreover, since environmental facilities are degraded due to aging, the number of cases where the boiler is operated by lowering the load is increasing in order to comply with environmental regulations.

Recently, as the quality of coal has been lowered, the amount of air supplied to the boiler has been increased to increase the combustion efficiency of coal in the boiler. However, in this case, the amount of exhaust gas is increased, and it is difficult for environmental facilities to cope with the increased amount of exhaust gas. Therefore, there is a case where the load of the boiler is lowered to reduce the amount of exhaust gas.

On the other hand, there is a case where the power generation facility is operated with higher output than the design capacity of the boiler due to power shortage. In this case, damage to the environmental facilities is accelerated, and the boiler may suddenly stop due to damage to main equipment of the environmental facilities. Therefore, it is required to reduce the burden on the environmental facilities by suppressing an increase in the amount of exhaust gas of the boiler.

<CIT> describes a method of controlling operation of an oxygen combustion boiler, wherein the oxygen ratio of the air is controlled according to the load of the boiler. <CIT> describes a method of controlling exhaust gas in an oxygen combustion boiler, wherein the amount of oxygen is controlled in accordance to the amount of the NOx and unburned combustibles in the exhaust gas.

The present invention provides a boiler facility and its operation method capable of reducing the amount of exhaust gas of a boiler without causing a decrease in output of the boiler, thereby capable of optimally operating environmental facilities by reducing burden on environmental facilities.

A boiler facility according to an embodiment of the present invention is described in claim <NUM> and includes a boiler, a fuel pipe, an air duct, an oxygen supplier, and a control unit. The boiler includes a combustion chamber in which a burner is installed, and the fuel pipe supplies fuel to the burner. The air duct supplies air sucked by a blower to the boiler. The oxygen supplier includes an oxygen pipe connected to the air duct and a flow rate controller provided in the oxygen pipe, and increases an oxygen ratio in the air to be supplied to the boiler. The control unit sets an air amount that is smaller than a reference air amount for burning the fuel and an oxygen amount to be added to the air, and controls the blower and the flow rate controller according to the set air amount and the set oxygen amount. The set oxygen amount is any one of the amount of oxygen to be supplied to the boiler in which a total amount of exhaust gas discharged from the combustion chamber becomes equal to the amount of reference exhaust gas that is discharged when the reference air amount is supplied, and the amount of oxygen to be supplied to the boiler in which an output of the boiler becomes equal to an output that is generated when the reference air amount is supplied.

A heat exchanger is installed in an exhaust gas duct at the rear end of the combustion chamber, and the air duct is connected to the boiler via the heat exchanger. The heat exchanger recovers waste heat from the exhaust gas and heats the air in the air duct. The oxygen pipe is connected to the front of the heat exchanger in the air duct.

A method of operating a boiler facility according to an embodiment of the present invention is described in claim <NUM> and includes two steps. In one step, a control unit sets a supply air amount to be supplied to the boiler in which the boiler discharges an exhaust gas amount that is smaller than a reference exhaust gas amount, and controls an output of a blower installed in an air duct to supply the set supply air amount to the boiler. In another step, the control unit sets an oxygen amount to be supplied to the boiler in which a total amount of exhaust gas becomes equal to the reference exhaust gas amount, and controls a flow rate controller provided in an oxygen pipe to further supply the set oxygen amount to the air duct.

A heat exchanger is installed in an exhaust gas duct at the rear end of a combustion chamber, and the air duct is connected to the boiler via the heat exchanger. The heat exchanger recovers the waste heat from the exhaust gas and heats the air to be supplied to the boiler. The oxygen pipe is connected to the front end of the heat exchanger in the air duct, and the oxygen-added air is heated in the heat exchanger.

A method of operating a boiler facility according to another embodiment of the present invention is described in claim <NUM> and includes two steps. In one step, a control unit sets a supply air amount to be supplied to the boiler in which the boiler discharges an exhaust gas amount that is smaller than a reference exhaust gas amount, and controls an output of a blower installed in an air duct to supply the set supply air amount to the boiler. In another step, the control unit sets an oxygen amount to be supplied to the boiler in which an output of the boiler becomes equal to an output generated when a reference air amount is supplied, and controls a flow rate controller provided in an oxygen pipe to further supply the set oxygen amount to the air duct.

According to one embodiment, the output of the boiler can be improved without increasing the amount of exhaust gas in the combustion chamber. In this case, power supply and demand can be smoothly performed without burdening environmental facilities. According to another embodiment, the amount of exhaust gas in the combustion chamber can be reduced while keeping the output of the boiler the same. In this case, the denitration efficiency of the denitration facility can be improved, deterioration of the performance of the catalyst can be suppressed, clogging of the gas re-heater can be prevented, and the desulfurization facility can be stably operated.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains.

<FIG> is a configuration diagram of a boiler facility according to a first embodiment of the present invention.

Referring to <FIG>, a boiler facility <NUM> of the first embodiment includes a boiler <NUM> having a combustion chamber <NUM> in which a burner <NUM> is installed, and environmental facilities installed in the rear of the combustion chamber <NUM> to treat the exhaust gas of the combustion chamber <NUM>. The fuel is supplied to the burner <NUM> through a fuel pipe <NUM>, and air sucked by a blower <NUM> is supplied to the burner <NUM> and the combustion chamber <NUM> through an air duct <NUM>.

The fuel of the boiler <NUM> may be a fossil fuel such as pulverized coal or heavy oil. When the fuel is pulverized coal, a pulverized coal burner may be used. The pulverized coal burner injects the pulverized coal and air into the combustion chamber <NUM>, and the pulverized coal injected into the combustion chamber <NUM> is space-burnt in a floating state. The pulverized coal burner may be a low NOx burner with low NOx combustion.

The boiler <NUM> generates steam using the thermal energy of the combustion chamber <NUM>, and the steam is supplied to a steam turbine (not shown). The exhaust gas discharged from the combustion chamber <NUM> contains pollutants, and the pollutants are reduced while the exhaust gases pass through the environmental facilities.

The environmental facilities may include a denitration facility <NUM> for removing nitrogen oxides (NOx), an electrostatic precipitator <NUM> for removing dust, and a desulfurization facility <NUM> for removing sulfur oxides (SOx). The exhaust gas from which pollutants have been removed through the denitration facility <NUM>, the electrostatic precipitator <NUM>, and the desulfurization facility <NUM> is discharged to the atmosphere through a chimney.

The denitration facility <NUM> may be configured as a selective catalytic reduction device. The selective catalytic reduction unit injects a reducing agent (ammonia, urea, etc.) into the exhaust gas to convert the nitrogen oxides to water and nitrogen on the catalyst. The reaction formula of the denitration facility <NUM> is as follows.

4NO + 4NH<NUM> + O<NUM> → 4N<NUM> + <NUM><NUM>O.

The electrostatic precipitator <NUM> is suitable for large-scale exhaust gas treatment, and a bag filter (not shown) may be additionally provided to enhance the dust collection efficiency in a hybrid manner. As the amount of exhaust gas passing through the denitration facility <NUM> increases, the denitration efficiency decreases and the catalyst wear phenomenon becomes worse. The efficiency of the electrostatic precipitator <NUM> also decreases as the exhaust gas amount increases.

A heat exchanger <NUM> is installed in the exhaust gas duct between the denitration facility <NUM> and the electrostatic precipitator <NUM>, and the air duct <NUM> is connected to the boiler <NUM> via the heat exchanger <NUM>. The heat exchanger <NUM> recovers waste heat from the exhaust gas to heat the air to be supplied to the boiler <NUM>, thereby enhancing the combustion efficiency of the boiler <NUM>. The heat exchanger <NUM> may be referred to as an air pre-heater.

The exhaust gas of the combustion chamber <NUM> contains a large amount of sulfur oxides due to combustion of sulfur in the fossil fuel. The desulfurization facility <NUM> can remove sulfur oxides by a wet process using limestone, and the reaction formula is as follows.

CaCO<NUM> + SO<NUM> + ½H<NUM>O → CaSO<NUM>·½H<NUM>O + CO<NUM>.

In the desulfurization facility <NUM>, the sulfur dioxide of the exhaust gas is neutralized by reaction with limestone and converted into gypsum, and the gypsum is recycled for industrial use. A circular mist eliminator <NUM> may be installed at the top of a reactor <NUM> of the desulfurization facility <NUM>. The mist eliminator <NUM> prevents the gypsum slurry inside the reactor <NUM> from flowing out of the reactor <NUM>.

If more exhaust gas than the design permissible amount of the mist eliminator <NUM> passes through the mist eliminator <NUM>, the flow rate of the exhaust gas will exceed the designed critical flow rate of the mist eliminator <NUM>, and a large amount of gypsum slurry may flow over a gas re-heater (or gas gas heater, GGH) <NUM> side installed at the rear of the reactor <NUM>. In this case, the gas re-heater <NUM> is clogged by the gypsum slurry, and the clogging of the gas re-heater <NUM> leads to an increase in the pressure of the exhaust gas duct.

Further, since the function of the mist eliminator <NUM> is deteriorated as the use time is increased, the gypsum slurry is adhered on the circular edge and interferes with the passage of the exhaust gas. In this case, since the exhaust gas is concentrated at the central portion of the mist eliminator <NUM>, the flow rate of the central portion of the mist eliminator <NUM> is increased, and the gypsum slurry may flow over the gas re-heater <NUM> side. At this time, if the amount of exhaust gas is reduced, it is possible to prevent the gypsum slurry from overflowing.

As described above, as the amount of exhaust gas of the boiler <NUM> increases, the efficiency of the denitration facility <NUM> and the electrostatic precipitator <NUM> becomes lower and an abnormality may occur in the desulfurization facility <NUM>. When such a problem occurs, conventionally, a method of reducing the amount of exhaust gas by lowering the load of the boiler <NUM> has been dealt with. However, in this case, the output of the power generation facility is lowered.

The boiler facility <NUM> of the first embodiment includes an oxygen supplier <NUM> and a control unit <NUM>. The oxygen supplier <NUM> may include an oxygen storage portion <NUM>, an oxygen pipe <NUM> connecting the oxygen storage portion <NUM> and the air duct <NUM>, and a flow rate controller <NUM> installed in the oxygen pipe <NUM>. The oxygen supplier <NUM> can easily produce oxygen using liquid oxygen or an oxygen separation membrane.

The oxygen pipe <NUM> is connected to the front of the heat exchanger <NUM> among all air ducts <NUM>. In this case, the oxygen-added air is heated in the heat exchanger <NUM> and then supplied to the boiler <NUM>.

The control unit <NUM> controls the blower <NUM> and the flow rate controller <NUM>. Specifically, the control unit <NUM> sets an air amount that is smaller than a reference air amount for combustion of the fuel, and lowers the output of the blower <NUM> so that the set air amount is supplied to the boiler <NUM>. At the same time, the control unit <NUM> sets an oxygen amount required for combustion, and controls the flow rate controller <NUM> to supply the set oxygen amount to the air duct <NUM>. That is, the control unit <NUM> increases the oxygen ratio in the air instead of reducing the amount of air to be supplied to the boiler <NUM>.

The reference air amount for combustion of the fuel is defined as the sum of a theoretical air amount for the combustion of the fuel and an excess air amount. The theoretical air amount is theoretically calculated according to the composition of the fuel to completely burn the fuel. However, if only the theoretical air amount is supplied, it is actually incomplete combustion. Therefore, in actual combustion, the excess air amount is added to the theoretical air amount to supply more air than the theoretical air amount.

The set air amount of the control unit <NUM> may be equal to or slightly larger than the theoretical air amount. That is, the control unit <NUM> may set the air amount to be supplied to the boiler <NUM> by subtracting the excess air amount from the reference air amount or reducing the excess air amount.

Even when the air amount supplied to the boiler <NUM> is reduced, since an appropriate amount of oxygen is supplied by the oxygen supplier <NUM>, the combustion of the fuel is not hindered, and the amount of the exhaust gas discharged from the combustion chamber <NUM> is not increased. Further, since the flow rate of the exhaust gas is reduced in the denitration facility <NUM> or the desulfurization facility <NUM>, the denitration efficiency or the desulfurization efficiency can be increased. In addition, a wear phenomenon of the denitration catalyst and clogging of the heat exchanger <NUM> and gas re-heater <NUM> can be effectively prevented.

The boiler facility <NUM> of the first embodiment can increase the output of the boiler <NUM> while maintaining the same amount of exhaust gas as that of supplying the reference air amount to the boiler <NUM>. Alternatively, the boiler facility <NUM> of the first embodiment can reduce the amount of exhaust gas while maintaining the same output of the boiler <NUM> as when supplying the reference air amount to the boiler <NUM>. The amount of exhaust gas discharged from the combustion chamber <NUM> is approximately <NUM> times the supply air amount.

<FIG> is a configuration diagram of a boiler facility according to an example.

Referring to <FIG>, in the boiler facility <NUM> of a not-claimed example, the oxygen pipe <NUM> may be connected to the rear end of the heat exchanger <NUM> among all the air ducts <NUM>. That is, the oxygen pipe <NUM> may be connected to the air duct <NUM> between the heat exchanger <NUM> and the boiler <NUM>. In this case, only the air sucked by the blower <NUM> is heated while passing through the heat exchanger <NUM>, and oxygen is directly supplied to the boiler <NUM>. The boiler facility <NUM> of the not-claimed example has the same configuration as that of the first embodiment except for the position of the oxygen supplier <NUM>.

Next, a method of operating the boiler facility (<NUM>, <NUM>) according to the first embodiment and the not-claimed example will be described.

If the power supply and demand is difficult due to the cooling load in summer or the heating load in winter, the power generation facility can be operated to achieve higher output than rated power generation capacity. However, if there is no design margin in the boiler <NUM> and environmental facilities, damage or malfunction may occur in these facilities. In this case, the boiler facilities <NUM> and <NUM> are operated by increasing the output of the boiler <NUM> while maintaining the same amount of exhaust gas as that of supplying the reference air amount to the boiler <NUM>.

For example, the amount of exhaust gas generated when the reference air amount is input in a <NUM> MW coal-fired power plant is normally <NUM>,<NUM>,<NUM><NUM>/h (referred to as "reference exhaust gas amount" for convenience). When the output of the boiler <NUM> is increased by <NUM> %, the amount of exhaust gas also increases by approximately <NUM> %, so that an enormous load is imposed on the environmental facilities installed rear of the combustion chamber <NUM>.

In this case, the control unit <NUM> may set the air amount that discharges the exhaust gas amount (e.g., <NUM>,<NUM>,<NUM><NUM>/h) to be smaller than the reference exhaust gas amount, and lowers the output of the blower <NUM> so that the set air amount may be supplied to the boiler <NUM>. At the same time, the control unit <NUM> may set the oxygen amount (e.g., <NUM>,<NUM>/h) in which the total amount of exhaust gas becomes equal to the reference exhaust gas amount, and controls the flow rate controller <NUM> so that the set oxygen amount may be further supplied to the air duct <NUM>.

The total amount of exhaust gas from the combustion chamber <NUM> is then <NUM>,<NUM>,<NUM><NUM>/h, which can improve the boiler <NUM> output by approximately <NUM> % while maintaining the design standards of the boiler <NUM>. The oxygen ratio of the air increases from <NUM> % to <NUM> %. Since the exhaust gas amount is approximately <NUM> times the supply air amount, the control unit <NUM> may set the supply air amount corresponding to the target exhaust amount by using this relationship.

As another example, the control unit <NUM> may set the air amount that discharges the exhaust gas amount (e.g., <NUM>,<NUM>,<NUM><NUM>/h) to be smaller than the reference exhaust gas amount, and lowers the output of the blower <NUM> so that the set air amount is supplied to the boiler <NUM>. At the same time, the control unit <NUM> may set the oxygen amount (e.g., <NUM>,<NUM>/h) in which the total amount of exhaust gas becomes equal to the reference exhaust gas amount, and may control the flow rate controller <NUM> so that the set oxygen amount is further supplied to the air duct <NUM>.

The total amount of exhaust gas from the combustion chamber <NUM> is then <NUM>,<NUM>,<NUM><NUM>/h, which can improve the boiler <NUM> output by approximately <NUM> % while maintaining the design standards of the boiler <NUM>. The oxygen ratio of the air increase from <NUM> % to <NUM> %. It is known that when the oxygen ratio in the air is increased to <NUM> %, the energy saving efficiency is about <NUM> % or more, so the output of the boiler <NUM> is expected to actually increase by more than <NUM> %.

According to the above-described method, the output of the boiler <NUM> can be increased without increasing the amount of exhaust gas. Therefore, it is possible to smoothen the supply and demand of electric power without burdening environmental facilities.

Next, as the operating time of the environmental facilities installed rear of the combustion chamber <NUM> increases, the performance of the catalyst may deteriorate due to deterioration or poisoning of the catalyst. In this case, the catalyst should be replaced or regenerated, but it is difficult to replace and regenerate the catalyst during operation. In addition, in order to comply with environmental regulations, it is most often operated by reducing the load of the boiler <NUM>.

However, in this case, the output of the boiler <NUM> is inevitably lowered, and the catalyst of the denitration facility <NUM> tends to be poisoned more quickly due to the low temperature of the exhaust gas, so that the stable operation of the denitration facility <NUM> becomes difficult in the long term. In this case, the boiler facilities <NUM> and <NUM> are operated in such a manner that the amount of exhaust gas is reduced while maintaining the same output of the boiler <NUM> as in the case of supplying the reference air amount to the boiler <NUM>.

For example, in a <NUM> MW coal-fired power plant, the control unit <NUM> may set the air amount that discharges about <NUM>,<NUM>,<NUM><NUM>/h, which is <NUM> % lower than the reference exhaust gas amount, and lowers the output of the blower <NUM> so that the set air amount may be supplied to the boiler <NUM>. At this time, the control unit <NUM> may set the oxygen amount (e.g., <NUM>,<NUM>/h) in which the output of the boiler <NUM> becomes equal to the output that is generated when the reference air amount is input, and controls the flow rate controller <NUM> to further supply the set oxygen amount to the air duct <NUM>.

The actual amount of exhaust gas is then <NUM>,<NUM>,<NUM><NUM>/h, which is approximately <NUM> % of the reference exhaust gas amount. The total amount of exhaust gas is reduced by approximately <NUM> %, and the output of the boiler <NUM> can be kept the same.

When the amount of exhaust gas is reduced by about <NUM> % in the general denitration facility <NUM>, the denitration efficiency is increased by about <NUM> %. As the supply air amount decreases, the amount of nitrogen oxides also decreases, so that the concentration of nitrogen oxides at the entrance of the denitration facility <NUM> is lowered. Further, since the exhaust gas amount decreases, the temperature of the exhaust gas discharged from the combustion chamber <NUM> rises. Therefore, since the inlet temperature of the denitration facility <NUM> rises, deterioration of the performance of the catalyst can be suppressed.

On the other hand, when the heat exchanger <NUM> installed rear of the denitration facility <NUM> is clogged by ammonium sulfate or the like, the pressure loss increases and the operation of the boiler <NUM> becomes difficult. However, when the amount of exhaust gas passing through these facilities is reduced by the above-described method, the denitration facility <NUM> can be operated without lowering the output of the boiler <NUM>.

In addition, since the mist eliminator <NUM> is provided at the upper part of the reactor <NUM> of the desulfurization facility <NUM>, the gypsum slurry from the reactor <NUM> is prevented from flowing to the gas re-heater <NUM> side. However, when partial clogging of the mist eliminator <NUM> occurs due to deterioration of the mist eliminator <NUM> or defects of the cleaning device, the flow rate of the exhaust gas may locally exceed the critical flow rate of the mist eliminator <NUM>. In this case, since the gypsum slurry flows over the gas re-heater <NUM> side, clogging of the gas re-heater <NUM> can occur.

Claim 1:
A boiler facility (<NUM>) comprising:
a boiler (<NUM>) having a combustion chamber (<NUM>) in which a burner (<NUM>) is installed;
a fuel pipe (<NUM>) for supplying fuel to the burner;
an air duct (<NUM>) for supplying air sucked by a blower (<NUM>) to the boiler;
an oxygen supplier (<NUM>) including an oxygen pipe (<NUM>) connected to the air duct and a flow rate controller (<NUM>) provided in the oxygen pipe, to increase an oxygen ratio in the air supplied to the boiler; and
a control unit (<NUM>) for setting an air amount that is smaller than a reference air amount for burning the fuel and an oxygen amount to be added to the air, and for controlling the blower and the flow rate controller according to the set air amount and the set oxygen amount, wherein
the set oxygen amount is any one of the amount of oxygen to be supplied to the boiler in which a total amount of exhaust gas discharged from the combustion chamber becomes equal to the amount of reference exhaust gas that is discharged when the reference air amount is supplied, and the amount of oxygen to be supplied to the boiler in which an output of the boiler becomes equal to an output that is generated when the reference air amount is supplied,
wherein
a heat exchanger (<NUM>) is installed in an exhaust gas duct at the rear of the combustion chamber (<NUM>), the air duct (<NUM>) is connected to the boiler (<NUM>) via the heat exchanger (<NUM>), and
the heat exchanger (<NUM>) is configured to recover waste heat from the exhaust gas and heat the air in the air duct (<NUM>), and wherein
the oxygen pipe (<NUM>) is connected to the front of the heat exchanger (<NUM>) in the air duct (<NUM>).