JP2007187352A - Starting method of boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for starting a boiler without reduction in generation efficiency of another boiler unit. <P>SOLUTION: When it is ensured that the exhaust gas temperature of a boiler is an acid-dew point or higher at the time of starting of the boiler such as midnight shutdown starting (DSS) operation or weekly shutdown starting (WSS) of thermal power generation, a forcing blower 12 is operated to start the boiler without supply of auxiliary steam from a steam drum 31 of another furnace 2B to a vapor air preheater 25, and when the pressure of a vapor drum 21 of its own furnace 2A rises to a predetermined value, supply of auxiliary steam AS from the steam drum 21 of the own furnace 2A to the steam air preheater 25 is started. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a boiler startup method, and more particularly to a boiler startup method suitable for thermal power generation midnight stop startup (DSS) operation and weekend stop startup (WSS) operation.

  Recently, the difference between the maximum and minimum load of electric power is increasing, and thermal power plants are also required to adjust the load accordingly. In other words, there are few cases where a boiler for thermal power generation always operates the boiler load at the full load, and the boiler load is operated by raising or lowering the load to 75% load, 50% load or 25% load. Doing so-called midnight stop start (hereinafter referred to simply as DSS) and weekend stop start (hereinafter referred to simply as WSS) operation and carrying an intermediate load. Operations that improve power generation efficiency are being carried out.

  The DSS operation is a case where the boiler unit is stopped at midnight and started the next morning in order to cope with the difference in power demand between daytime and nighttime, and the stop time is about 6 to 12 hours, which is called hot start. Moreover, since WSS operation is operationally less demanded on the weekend, the boiler unit is stopped on the weekend and started to respond to the increase in power demand at the beginning of the week. The stop time is about 12 to 36 hours. . When starting up in about 24 hours, it is called a warm start.

During normal operation, as shown in FIG. 5, steam from the steam drum 21 of the furnace (own can) 2 </ b> A belonging to its own boiler unit passes through the auxiliary steam supply valve 22, the auxiliary steam header 23, and the SAH temperature adjustment valve 24. The steam type air preheater (SAH) 25 is led to heat the steam type air preheater 25 on the upstream side of the air preheater 10, and the air from the forced air blower 12 is heated here. Air that has been sent to the air preheater 10 and heated to a predetermined temperature through the air preheater 10 is sent to the furnace (self-can) 2A. Therefore, the steam drum 31 of the furnace (other can) 2B of another boiler unit is disconnected from the auxiliary steam supply system by closing the auxiliary steam supply valve 32. The exhaust gas from the furnace 2A is discharged from the chimney 13 through the air preheater 10 from the flue 9.
When the boiler unit is normally stopped based on the DSS and WSS based on the power supply command due to such demand and supply requirements, the boiler is extinguished and the ventilator is stopped, and the boiler unit can be started from such a state. Necessary. FIG. 6 shows a stopped state. In the figure, the shaded device indicates that it is stopped.

  In the conventional boiler starting method, as shown in FIG. 7, the auxiliary steam header 23 and the SAH temperature are opened from the steam drum 31 of the other furnace (other can) 2B by opening the auxiliary steam supply valve 32 when the boiler is started. Auxiliary steam was supplied to the steam air preheater 25 via the regulating valve 24, the steam air preheater 25 was operated, and the boiler was started. That is, while operating the steam type air preheater 25, the forced air blower 12 is started, air heated through the air preheater 10 is sent to the furnace (own can) 2A, and the pressure of the steam drum 21 is a predetermined value. For example, when the pressure reaches 4 MPa, the auxiliary steam supply valve 32 of the other can is closed and the auxiliary steam supply valve 22 of the own can is opened as shown in FIG. 8, thereby switching the supply source of the auxiliary steam from the other can to the own can. Thereafter, the steam air preheater 25 was operated with its own auxiliary steam. An outline of this control is shown in FIG.

  As described above, in the conventional boiler unit starting method, auxiliary steam is supplied from the steam drum 31 of the other can, so that the generator output of the other can is suppressed and the amount of generated steam is kept within the limit value.

However, in the conventional boiler starting method, auxiliary steam is supplied from the steam drum of another boiler unit and the steam air preheater is operated when the boiler is started, so the generator output of the other boiler unit is The power generation efficiency of other boiler units is reduced.
Therefore, an object of the present invention is to solve the above-described problems and provide a method for starting a boiler without reducing the power generation efficiency of another boiler unit.

In order to achieve the above object, the present invention does not supply auxiliary steam from other cans when the boiler exhaust gas temperature can be secured above the acid dew point during midnight stop start (DSS) operation or weekend stop start (WSS) operation. That is, the boiler is started without operating the steam air preheater (SAH). The present invention is specifically configured as follows.
In the boiler start-up method according to the present invention, when it is ensured that the exhaust gas temperature of the boiler is higher than the acid dew point when the boiler is started, auxiliary steam from the steam drum of another furnace is supplied to the steam-type air preheater. The boiler is started by operating the forced draft fan without supply, and when the pressure of the steam drum of its furnace rises to a predetermined value, auxiliary steam from the steam drum of its furnace is supplied to the steam air preheater. The supply is started.
The present invention can be applied to either a boiler start-up in a DSS operation of thermal power generation or a boiler start-up in a WSS operation.

The boiler start-up method of the present invention detects the inlet temperature of the air preheater, and when the exhaust gas temperature of the boiler can be confirmed to be the inlet temperature at which the acid dew point (sulfuric acid condensation temperature) or higher is confirmed, It is preferable to start the boiler by operating the ventilator.
The time when the pressure of the steam drum of the own furnace has increased to a predetermined value is the time when the pressure has increased to, for example, 4 MPa, and at this time, supply of auxiliary steam from the steam drum of the own furnace to the steam air preheater is started. Is possible.
The boiler startup method of the present invention is preferably applied to a pulverized coal fired boiler or an oil fired boiler.

  According to the present invention, when a boiler for thermal power generation DSS operation or WSS operation is started, auxiliary steam from the steam drum of another boiler unit is not supplied to the steam air preheater, that is, the steam air preheater is operated. Since a boiler is started in the state which does not carry out, a boiler can be started, without reducing the electric power generation efficiency of another boiler unit.

Hereinafter, the present invention will be described based on the illustrated embodiments.
FIG. 1 shows an example of a pulverized coal fired boiler facility used for thermal power generation. 1 is a pulverized coal fired boiler, 2A is a furnace of the pulverized coal fired boiler 1, and 3 is formed downstream of the furnace 2A. Rear heat transfer section 4 is a burner for pulverized coal combustion disposed in the furnace 2A, 5 is a wind box for the burner 4, 6 is a mill for pulverizing and drying the coal and supplying it to the burner 4 as pulverized coal , 7 is a primary air line for supplying primary air for conveying pulverized coal to the mill 6, 8 is a secondary air line for supplying secondary air for combustion to the wind box 5, and 9 is discharged from the pulverized coal fired boiler 1. A flue (exhaust line) through which exhaust gas flows through 10 is an air preheater (AH) that exchanges heat between the exhaust gas and primary air and secondary air, 11 is a primary ventilator (PAF) that pumps primary air, and 12 is two A forced draft fan that pumps the next air ( DF), 13 is a chimney that is connected to the flue 9.

  The furnace 2A includes a economizer 15 that heats feed water obtained from a condenser through a feed pump 14, and a number of evaporator tubes that further heat the feed water heated by the economizer 15 to generate saturated steam. (Evaporator) 16, a steam drum 21 that collects saturated steam generated in the evaporator pipe 16, a primary superheater a and a secondary superheater that superheats saturated steam from the steam drum 21 to generate superheated steam b. In the furnace 2A, an evaporation pipe 16, a secondary superheater b, a primary superheater a, a reheater d, and a economizer 15 are sequentially arranged from the upstream side to the downstream side. The steam drum 21 is installed in the upper part of the furnace, and the steam drum 21 is provided with a brackish water separator that separates the steam and water contained in the water from the evaporation pipe 16.

The flow of the combustion gas will be described. The gas burned in the furnace 2A first passes through the evaporator tube 16, the secondary superheater b, the primary superheater a, the reheater d, and the economizer 15, and part of the gas is in the furnace. Is used for heat transfer adjustment, and the rest is discharged from the chimney 13 through the air preheater 10 from the flue 9.
The evaporation pipe 16 and the economizer 15 are heated by the hot air flowing in the furnace 2A, and the feed water heated by the economizer 15 is sent to the evaporator pipe 16 via the steam drum 21 and further heated. Saturated steam generated in the evaporation pipe 16 is sent via the steam drum 21 to the primary superheater a disposed in the furnace 2A. The saturated steam is superheated by the primary superheater a and the secondary superheater b, and superheated steam (main steam) is generated.
The high pressure turbine (main steam turbine) c is rotated by the superheated steam generated in the superheaters a and b, and is discharged from the high pressure turbine c and heated by the resuperheater d. Steam turbine) e is rotated, and primary generator f is driven to generate power.

On the other hand, an auxiliary steam supply system (22, 23, 24) is connected to the saturated steam supply pipe L1 extending from the steam drum 21 to the primary superheater a. That is, the inlet of the auxiliary steam header 23 is connected to the pipe L3 via the auxiliary steam supply valve 22, and the pipe L2 from the steam drum 31 of the other furnace 2B is connected to the pipe L3 via the auxiliary steam supply valve 32. Is connected. A steam air preheater 25 is connected to the outlet of the auxiliary steam header 23 through a pipe L4 via a SAH temperature control valve 24. The steam air preheater 25 is provided between the forced air blower 12 and the air preheater 10.
Here, to supplement the explanation of the functions of the air system equipment, the forced air blower (FDF) 12 forcibly pushes the combustion air into the furnace 2A and pressurizes the furnace pressure to 2.4 to 5.88 kPa. It works to make it burn. Providing this push-in ventilator 12 makes the boiler 1 an airtight structure and prevents outside air from leaking. Therefore, it is easy to manage the combustion air, and the boiler 1 can be operated efficiently with a minimum amount of air.

The air preheater (AH) 10 uses the preheating of the combustion gas to preheat the air necessary for burning the fuel in the boiler before it is sent from the forced air blower 12 to the furnace 2A to improve combustibility and It is installed to improve boiler efficiency such as reduction of exhaust gas loss.
The steam air preheater (SAH) 25 is provided between the forced air blower 12 and the air preheater 10 and preheats the air from the forced air ventilator 12 to a predetermined temperature. When the boiler load decreases or the inlet temperature of the air preheater 10 decreases, the low temperature side metal temperature of the air preheater 10 decreases and low temperature corrosion due to sulfuric acid gas occurs. In order to prevent this, the steam-type air preheater 25 is heated so that the low temperature side metal temperature of the air preheater 10 does not fall below the dew point of sulfuric acid gas.

That is, auxiliary steam is supplied to the steam air preheater 25, but when the temperature of the condensate supplied from the condenser to the boiler becomes low during the start-up operation, the condensate is saturated at the steam drum 21 of the boiler. As a result, the exhaust gas is deprived of heat. For this reason, when the exhaust gas flows through the rear heat transfer section 3 of the boiler, the temperature is remarkably lowered, and the heat exchanger tube of the air preheater 10 disposed on the downstream side is made to be below the acid dew point (condensation temperature of sulfuric acid). The tube is dew point eroded. In order to prevent this, the inlet temperature of the air preheater 10 is heated by the steam air preheater 25.
In FIG. 1, reference numeral 30 denotes a control device for controlling the air, feed water, and temperature (main steam temperature) system of the boiler unit including the auxiliary steam supply system (22, 23, 24), and is mainly composed of a computer. Yes. Reference numeral 31 denotes an acid dew point detection means that detects the inlet temperature of the air preheater 10 and monitors that the low temperature side metal temperature of the air preheater 10 does not become lower than the dew point of sulfuric acid gas.

<During normal operation>
During normal operation of the boiler 1, primary air is supplied to the mill 6 through the air preheater (AH) 10 by the operation of the primary ventilator 11, and pulverized coal pulverized and dried by the mill 6 is supplied to the burner 4. . Moreover, secondary air is supplied to the wind box 5 through the steam type air preheater (SAH) 25 and the air preheater (AH) 10 by the operation of the forced air blower 12, and the pulverized coal is burned in the furnace 2A.
Due to the heat of the generated combustion gas, the evaporator pipe 16, the superheaters a and b, the reheater d, the economizer 15 and the like are heated to generate steam, and the intermediate pressure turbines c and e are driven to generate power. On the other hand, the exhaust gas flows through the flue 9 and is introduced into the air preheater 10, where the primary air and the secondary air are heated and heat recovery is performed.

<When operation is stopped>
When the operation of the boiler unit is stopped based on DSS, WSS, the auxiliary steam supply valves 22, 32 and the regulating valve 24 are closed, the boiler is extinguished, and the primary ventilator 11, the push ventilator 12, the steam type air preheater. 25, the air preheater 10 is stopped (see FIG. 6). The hatched device in the figure indicates that it is stopped.

<When the boiler starts>
As shown in FIG. 3, the boiler startup method of the present embodiment starts the boiler 1 while keeping the auxiliary steam supply valves 22 and 32 and the regulating valve 24 closed. That is, the boiler is ignited using light oil as the starting fuel, and the forced air blower 12 is started in a state where the steam air preheater 25 is stopped, and the air heated through the air preheater 10 is supplied to the furnace (self Can) Feed into 2A.
After the generators are paralleled, the fuel is switched from the starting diesel oil to the main fuel pulverized coal. That is, the primary ventilator 11 is operated, the primary air is supplied to the mill 6 through the air preheater 10, and the dried pulverized coal is supplied to the burner 4 to be burned in the furnace 2A. Further, as shown in FIG. 4, the auxiliary steam supply valve 22 of the own can and the SAH temperature adjustment valve 24 are opened, and supply of the auxiliary steam AS to the steam air preheater 25 is started from the own drum steam drum 21 through the auxiliary steam header 23. Thereafter, the steam air preheater 25 is operated with the auxiliary steam AS from the self-propelled steam drum 21, and the boiler is operated.

  As shown in FIG. 2 (a), the boiler start-up method of the present embodiment is characterized in that auxiliary steam from the steam drum 31 of another furnace (other can) 2B is supplied to the steam air preheater 25 when the boiler is started. Without operating the steam air preheater (SAH) 25, without operating the steam air preheater (SAH) 25, the boiler is started by operating the forced air blower (FDF) 12, and then the steam drum of its own furnace 2A When the saturated steam pressure of 21 rises to a predetermined value, for example, 4 MPa, auxiliary steam is started to be supplied from the steam drum 21 of its own furnace 2A to the steam air preheater 25. In the conventional boiler starting method (FIG. 2B), the auxiliary steam is supplied from the steam drum 31 of another furnace (other can) 2B to the steam air preheater 25 through the pipes L2, L3, and L4. In contrast, the steam air preheater 25 is operated to start the boiler.

  Another feature of the boiler starting method according to the present embodiment is that the boiler is started when it is ensured that the exhaust gas temperature of the boiler is equal to or higher than the acid dew point. The reason for this is that, during start-up operation, if the temperature of the feed water supplied to the boiler is lowered, the heat of the exhaust gas is deprived more, so the exhaust gas is cooled down and the air preheater 10 disposed downstream thereof This is because the heat exchanger tube is brought to an acid dew point (condensation temperature of sulfuric acid) or lower and the tube is subjected to dew point corrosion, which must be avoided.

  1 controls the air, feed water, and temperature (main steam temperature) system of the boiler unit including the auxiliary steam supply system (22, 23, 24) from the acid dew point detection means 31. The detected value of the inlet temperature of the air preheater 10 obtained is evaluated, and it is confirmed that the low temperature side metal temperature of the air preheater 10 is not lower than the dew point of sulfuric acid gas. Control of water supply and main steam temperature system.

  According to the present embodiment, since the auxiliary steam is not supplied from the steam drum of the other boiler unit to the steam air preheater when starting the boiler in the DSS operation or the WSS operation, the power generation efficiency of the other boiler unit is not lowered. A hot start or a warm start can be performed.

  The present invention can be used for starting a boiler for DSS operation or WSS operation for thermal power generation, but can also be used for starting other boilers.

It is a figure which shows the structure of the boiler unit to which the starting method of the boiler of this invention is applied. It is the figure which showed the starting method (a) of the boiler of this invention compared with the starting method (b) of the conventional boiler. It is a schematic block diagram of the boiler unit which showed the first half of the boiler starting method of this invention. It is a schematic block diagram of the boiler unit which showed the second half of the boiler starting method of this invention. It is a schematic block diagram of the boiler unit which showed the state at the time of normal driving | operation. It is a schematic block diagram of the boiler unit which showed the state in the stop. It is a schematic block diagram of the boiler unit which showed the first half of the starting method of the conventional boiler. It is a schematic block diagram of the boiler unit which showed the second half of the starting method of the conventional boiler.

Explanation of symbols

1 Pulverized coal fired boiler 2A Furnace (own can)
2B furnace (other cans)
6mil 10 air preheater (AH)
11 Primary ventilator (PAF)
12 Intrusion ventilator (FDF)
13 Chimney 14 Water supply pump 15 Eco-saving device 16 Evaporating pipe 21 Steam drum 23 Auxiliary steam header 25 Steam air preheater (SAH)
31 Steam drum

Claims (6)

  When starting the boiler, if it is ensured that the exhaust gas temperature of the boiler is higher than the acid dew point, which is the condensation temperature of sulfuric acid, do not supply auxiliary steam from the steam drum of other furnaces to the steam air preheater. Start the boiler by operating the forced draft fan, and start supplying auxiliary steam from the steam drum of the furnace to the steam air preheater when the pressure of the steam drum of the furnace rises to a predetermined value. The boiler starting method characterized by this.   The boiler startup method according to claim 1, wherein the boiler startup is a boiler startup in a midnight stop startup operation of thermal power generation.   The boiler startup method according to claim 1, wherein the boiler startup is a boiler startup during a weekend stop startup operation.   The inlet temperature of the air preheater is detected, and when it is confirmed that the exhaust gas temperature of the boiler is an inlet temperature that is equal to or higher than the acid dew point, the boiler is started by operating the forced air blower. The boiler starting method according to any one of claims 1 to 3.   5. The supply of auxiliary steam from the steam drum of its own furnace to the steam air preheater is started when the pressure of the steam drum of its own furnace rises to a predetermined value of 4 MPa. The startup method of the boiler in any one of. The boiler startup method according to any one of claims 1 to 5, wherein the boiler is a pulverized coal fired boiler or an oil fired boiler.

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