JPH112403A - Boiler apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate reliably an acid dew-point temperature of exhaust gas evolved from a boiler and maintain the high efficiency of the boiler by controlling an exhaust gas temperature to an optimum level. SOLUTION: This boiler apparatus is provided with a regenerative air preheater 2 for recovering heat from exhaust gas evolved from a boiler 1, which uses fuel containing a sulfur component, and with a controlling means adapted to control a temperature of the exhaust gas at an outlet of the regenerative air preheater 2. The concentration of SO3 contained in the exhaust gas from the regenerative air preheater 2 is measured by an SO3 measuring instrument 12 and, at the same time, moisture contained in the exhaust gas from the regenerative air preheater 2 is measured by a moisture measuring instrument 15. An acid dew-point temperature of the exhaust gas is calculated by a dew-point temperature operation unit 13 on the basis of both of a measured value of the SO3 concentration obtained by the SO3 measuring instrument 12 and a measured value of moisture obtained by the moisture measuring instrument 15, whereby an exhaust gas temperature is controlled so that the exhaust gas temperature becomes higher than the acid dew-point temperature. Further, an ammonia injection quantity at an inlet of a dust collector 16 for the exhaust gas is controlled by an ammonia injection nozzle 18 on the basis of the measured value of the SO3 concentration obtained by the SO3 measuring instrument 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler control method, and more particularly to a boiler apparatus suitable for optimizing an exhaust gas temperature and maintaining a high boiler efficiency.

[0002]

2. Description of the Related Art As shown in FIG.
The air temperature in the air duct 11 at the inlet of the regenerative air preheater 2 installed for recovering heat from the exhaust gas of the boiler 1 is measured by the air thermometer 5, and the outlet gas temperature of the gas duct 10 is measured by the gas thermometer 4. The average temperature calculator 6 calculates the low-temperature end metal temperature of the regenerative air preheater 2, which is obtained as an average value, and compares it with a predetermined set value by the comparison calculator 7. The control signal transmitter 8 operates the steam flow regulating valve 9 for controlling the steam flow to the steam air preheater 3 to change the air temperature in the air duct 11.

However, the set value of the comparator 7 is determined from the viewpoint of preventing the elements of the regenerative air preheater 2 from corroding and clogging. If flue gas denitration is installed at the outlet, it is determined based on the expected maximum value of the SO3 concentration in the exhaust gas in consideration of the time-dependent change in the SO2 oxidation rate of the catalyst, etc. The temperature became higher than necessary, and sufficient consideration was not given to boiler efficiency.

Further, the SOx concentration in the exhaust gas is measured, and the SO3 concentration is calculated from a preset SO2 oxidation rate.
Although there is a method of determining the set value, there is a problem that it cannot cope with a case where the SO2 oxidation rate changes with time.

Further, there is a conventional method in which an acid dew point meter is installed in the gas duct 10 and the set value is determined by directly measuring the dew point. In this method, a sensor and an electrode coated with an electrolyte are placed in a gas, and the dew point is measured using electric conductivity. However, there are the following problems.

(1) To place the sensor and the electrode in the gas,
When the ash is contained in the exhaust gas, the sensor and the electrode are covered with the ash and cannot be measured.

(2) If unburned carbon is present in the ash in the exhaust gas, the conductivity changes and accurate measurement cannot be performed.

(3) Chloride (CaCL2, MgCL2)
) Or sulfides (eg, MgSO4) cannot be measured accurately.

(4) Acid ammonium sulfate (NH 4 HSO)
If 4) is present, accurate measurement cannot be performed because the gas condenses on the sensor at a gas temperature of about 230 ° C. or less.

[0010]

The above prior art does not take into consideration the point of improving the efficiency of the boiler, and has a problem that the exhaust gas temperature becomes unnecessarily high and the boiler efficiency decreases. There is also a problem that it is difficult to accurately measure and evaluate the SOx temperature and the dew point meter.

An object of the present invention is to reliably evaluate an acid dew point temperature, optimize an exhaust gas temperature, and maintain a high boiler efficiency. In addition, there is a need to reduce the operation history by minimizing the amount of injected ammonia.

[0012]

In order to solve the above problems, the present invention mainly employs the following configuration.

A boiler apparatus comprising: a regenerative air preheater for recovering heat from exhaust gas from a boiler using a fuel containing sulfur; and control means for controlling the temperature of the exhaust gas at the outlet of the regenerative air preheater. Measuring the concentration of SO3 in the exhaust gas from the regenerative air preheater, calculating the acid dew point temperature based on the measured value, and controlling the exhaust gas temperature so that the exhaust gas temperature exceeds the acid dew point temperature. Boiler equipment.

[0014] Further, the moisture in the exhaust gas from the regenerative air preheater is measured, and the acid dew point temperature is calculated from the measured moisture value and the measured SO3 concentration value.

[0015] Further, the amount of ammonia injected into the dust collector at the inlet of the exhaust gas is controlled based on the measured SO3 concentration.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An overall configuration according to an embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, 1 is a boiler, 2 is a regenerative air preheater, 3 is a steam air preheater, 4 is a gas thermometer, 5
Is an air thermometer, 6 is an average temperature calculator, 7 is a comparison calculator,
8 is a control signal transmitter, 9 is a steam flow control valve, 10 is a gas duct, 11 is an air duct, 12 is an SO3 meter, 13 is a dew point temperature calculator, 14 is a comparison calculator, 15 is a moisture meter, 16
Denotes a dust collector, 17 denotes an ammonia flow control valve, 18 denotes an ammonia injection nozzle, 19 denotes a control signal transmitter, and 20 denotes a filter.

The exhaust gas from the gas duct 10 that has exited the boiler 1 undergoes heat exchange with the air in the air duct 11 in the regenerative air preheater 2 and is then sent to the chimney (not shown) in the gas duct 10 and discharged. You. The combustion air of the air duct 11 supplied to the boiler 1 is sent after the heat is recovered from the exhaust gas of the gas duct 10 by the regenerative air preheater 2.

A steam air preheater 3 is installed in the air duct 11 of the regenerative air preheater 2 for the purpose of controlling the element low-temperature metal temperature and the exhaust gas temperature of the regenerative air preheater 2. Steam flow rate adjusting valve 9
To control the inlet air temperature of the regenerative air preheater 2.

Inlet air duct 1 of regenerative air preheater 2
1. Thermometers 5 and 4 are installed in the outlet gas duct 10, respectively. An average value = low-end metal temperature is calculated by an average temperature calculator 6 based on the measured values. By comparison, the steam flow control valve 9 of the steam air preheater 3 is operated.

At the inlet of the dust collector 16 installed downstream of the gas of the regenerative air preheater 2, there is an ammonia injection nozzle 18, which controls the opening of the ammonia flow control valve 17 to control its flow rate. .

Next, the interrelationships between the components in the overall configuration of the embodiment of the present invention and the operation thereof will be described below.

Outlet gas duct 10 of regenerative air preheater 2
A SO3 meter 12 is installed in the vicinity of to measure the SO3 concentration in the exhaust gas. The measurement of SO3 is performed by putting the exhaust gas sucked from the gas duct 10 into the SO3 meter 12, passing it through the column of the reagent to develop color, and performing colorimetric analysis. Barium chloranilate used as a reagent is a substance with very low solubility, but when sulfate ions come, they are replaced by chloranilate ions to form barium sulfate (BaSO4), and chloranilate ions are liberated. This is to determine the density.

Since the SO3 meter 12 is installed outside the duct, there is no problem of ash adhesion.
Sulfides, chlorides, and the like are removed by installing a filter 20 in the suction tube to improve measurement accuracy. Dew point temperature calculator 13
, The acid dew point temperature is calculated, and the measured value of the gas thermometer 4 is compared with the comparison arithmetic unit 14. The acid dew point can be evaluated by the following formula.

T = 20 log ₁₀ V + a where V is a constant determined by the SO3% and a is a constant determined by the moisture in the gas. Therefore, if the moisture in the exhaust gas is measured by the moisture meter 15, the acid dew point can be more accurately evaluated.

If the acid dew point temperature from the dew point temperature calculator 13 is higher than the measured gas temperature value from the gas thermometer 4,
In order to prevent corrosion of the downstream equipment after the gas duct 10, the opening of the steam flow regulating valve 9 is increased (the regulating valve 9 is opened) to increase the steam flow to the steam air preheater 3, and the steam air The outlet air temperature of the preheater 3 is increased to control the exhaust gas temperature to be higher than the acid dew point temperature (the regulating valve 9 is opened).

Conversely, when the acid dew point temperature from the dew point temperature calculator 13 is lower, control is performed to close the steam flow control valve 9 so as to satisfy the low end metal temperature set value of the regenerative air preheater 2. I do. In a boiler having a large amount of SO3 in exhaust gas, an ammonia injection nozzle 1 provided at an inlet of a dust collector 16 is used.
Ammonia is injected from 8 and reacted with SO3 to remove as ammonium sulfate in the dust collector 16. Therefore, the ammonia flow control valve 17 is operated and controlled according to the change in the concentration measured by the SO3 meter 12.

As described above, the present invention measures SO3 in exhaust gas and optimizes and controls the temperature of the exhaust gas and the amount of ammonia injected into the dust collector according to the concentration.
When the temperature of the exhaust gas at the outlet of the air preheater of the boiler using the fuel containing sulfur is lower than the dew point temperature of sulfuric acid, the sulfuric acid precipitates and causes corrosion of downstream equipment such as the gas duct 11, so that the temperature does not fall below the dew point temperature. Control.

Since the dew point temperature of an acid is determined by the SO3 temperature and the amount of moisture in the exhaust gas, if the SO3 concentration or the amount of moisture is also measured and the gas temperature is controlled so that the exhaust gas temperature does not fall below the dew point temperature, the temperature of the exhaust gas can be reduced. Is not unnecessarily high, so that the efficiency of the boiler is not deteriorated.

Further, if the amount of ammonia injected into the dust collector is controlled in accordance with the increase or decrease in the SO3 concentration, useless ammonia consumption can be suppressed, so that the operating cost does not increase.

Another embodiment of the present invention is shown in FIGS. In the embodiment of FIG. 2, a bypass air duct 21 and a bypass air flow adjustment damper 22 are provided from the inlet to the outlet of the regenerative air preheater 2, and the bypass air flow adjustment damper 22 increases the bypass air amount of the bypass air amount duct 21. Thus, the amount of air passing through the regenerative air preheater 2 was reduced, the amount of heat exchange in the regenerative air preheater 2 was reduced, and the exhaust gas temperature in the gas duct 10 was increased.

In the case of FIG. 3, a bypass gas duct 31 and a bypass gas flow rate adjusting damper 32 are installed on the gas side of the regenerative air preheater 2 to increase the amount of bypass gas in the bypass gas duct 31 so that the exhaust gas temperature in the gas duct 10 is increased. Is higher.

In each of the embodiments shown in FIGS. 2 and 3, FIG.
There is no steam type air preheater 3 shown in the embodiment, and the system can be simplified.

FIG. 4 shows that the SO3 meter 12 is converted to a regenerative air preheater 2.
An embodiment in the case of being installed on the upstream side of a gas is shown. In this case, when the denitration device 41 is installed between the boiler 1 and the boiler 1 and the regenerative air preheater 2, SO
There is an effect that the change with time of the oxidation rate can be accurately monitored.

FIG. 5 shows the SO3 concentration and the acid dew point temperature in the exhaust gas.
The relationship is shown in The SOx concentration in the gas largely depends on the S content in the fuel. The SO2 oxidation rate changes due to the catalytic action of vanadium and the like attached to the boiler heat transfer surface and the denitration catalyst.
Since the oxidation rate may increase to the extent, the SO3 concentration is 0 to 200 ppm depending on the fuel specifications and the operation time.

[0036]

As described above, according to the present invention,
If the SO3 concentration is low and the dew point temperature is lower than the gas temperature, operate at the lowest gas temperature that satisfies the low end metal temperature setting required to prevent corrosion and blockage of the air preheater. Only when the dew point temperature rises high,
If the operation is performed while the exhaust gas temperature is raised so as to exceed the dew point temperature, the exhaust gas temperature can be minimized, so that the reduction in boiler efficiency can be minimized and high efficiency operation can be achieved.

Since the dew point temperature can be accurately evaluated,
In addition to making it easy to monitor the change over time in the SO3 concentration, the temperature of the exhaust gas can be accurately set to the dew point or higher, and the regeneration type air preheater 12
By changing the material of the low-temperature side element from enamel coating material to corrosion-resistant steel, it is possible to reduce equipment costs.

Further, since there is no SO3 condensation on the element, the amount of ash adhering to the element is reduced, and the operation frequency and steam consumption of the soot blower are reduced.

Furthermore, the amount of ammonia injected at the inlet of the dust collector 16 can be saved, and the operation history can be suppressed.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a system diagram showing a second embodiment of the present invention, and is a configuration diagram in which a bypass duct is provided in an air preheater.

FIG. 3 is a system diagram showing a third embodiment of the present invention, and is a configuration diagram in which a bypass duct is provided in an air preheater.

FIG. 4 is a system diagram showing a fourth embodiment of the present invention.

FIG. 5 is a graph showing the relationship between SO3 concentration in exhaust gas and acid dew point temperature.

FIG. 6 is a system diagram around an air preheater in the related art.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 boiler 2 regenerative air preheater 3 steam type air preheater 4 gas thermometer 5 air thermometer 6 average temperature calculator 7,14 comparison calculator 8,19 control signal transmitter 9 steam flow control valve 10 gas duct 11 air duct 12 SO3 meter 13 Dew point temperature calculator 15 Moisture meter 16 Dust collector 17 Ammonia flow control valve 18 Ammonia injection nozzle 20 Filter 21 Bypass air duct 22 Bypass air flow control damper 31 Bypass gas duct 32 Bypass gas flow control damper 41 Denitration device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideaki Iwamoto 6-9 Takaracho, Kure City, Hiroshima Prefecture Babkotsuk Hitachi Kure Factory

Claims (3)

[Claims] 1. A regenerative air preheater for recovering heat from an exhaust gas of a boiler using a fuel containing a sulfur component, and control means for controlling a temperature of the exhaust gas at an outlet of the regenerative air preheater. In the boiler device, the concentration of SO3 in the exhaust gas from the regenerative air preheater is measured, and the acid dew point temperature of the exhaust gas is calculated based on the measured value, so that the exhaust gas temperature exceeds the acid dew point temperature. A boiler device for controlling exhaust gas temperature. 2. A regenerative air preheater for recovering heat from an exhaust gas of a boiler using a fuel containing sulfur, and control means for controlling a temperature of the exhaust gas at an outlet of the regenerative air preheater. In the boiler device, while measuring the concentration of SO3 in the exhaust gas from the regenerative air preheater, measuring the moisture in the exhaust gas from the regenerative air preheater, the SO3 concentration measurement value and the moisture measurement value A boiler device which calculates an acid dew point temperature of exhaust gas from the boiler. 3. The boiler apparatus according to claim 1, wherein the amount of ammonia injected at the dust collector inlet of the exhaust gas is controlled based on the measured SO3 concentration.