JP5384401B2 - Boiler water level control method - Google Patents

Description

  The present invention relates to a method and an apparatus capable of stably controlling the water level of a boiler even when the boiler load varies.

  In conventional boilers, when the boiler water level is continuously controlled, so-called measurement value control is performed in which the water level to be controlled is directly measured by a transmitter or the like, and PID (proportional integral derivative) control is performed based on the measurement value. Usually done. In some cases, such as when an advance operation is required, the steam flow rate may be supplementarily measured to improve controllability.

  However, in this measurement control, the pipe to the water level transmitter (water level detector) is clogged with rust due to corrosion factors, and the water level cannot be measured accurately, and the water level control becomes unstable. The current situation is that the maintenance is complicated and the usability is not always good. Furthermore, in many cases, only the water level of the boiler is captured and an independent control loop is formed, and control in consideration of the boiler load (combustion state) is not performed, so that the water level control may become unstable depending on the boiler load situation.

Japanese Patent No. 4059554 JP 2007-170814 A

  The boiler provided with the water supply amount calculating means of Patent Document 1 calculates the water supply flow rate from the water level detection time interval at the electrode instead of the water supply flow meter. In the present invention, the amount of water supply is a measured value from a flow meter. The boiler drum water level control device disclosed in Patent Document 2 performs water level control by adding the steam flow rate and the water supply amount to the detected water level, and is a three-element control.

  The problem to be solved is that in the conventional boiler water level control method, the piping to the water level transmitter is clogged with rust and the like, so that the water level cannot be measured accurately and the water level control becomes unstable. The water level control becomes unstable depending on the load condition.

  The present invention relates to a physical quantity of water level necessary for controlling the water level of a boiler, an instantaneous feed water flow rate of the boiler, an instantaneous fuel input amount, a combustion amount indication value from a control panel, an instantaneous evaporation amount generated from the boiler, and a boiler The main feature is to use the calculated water level that is calculated by taking into account the amount of water held by the boiler body depending on the load. In addition, since the present invention may cause a deviation from the actual water level only by the calculated water level, the calculated water level is corrected at any time using an electrode rod for water level detection, and the water level is controlled by the water level. It is said. In addition, it is characterized by providing advanced water level control at low cost by eliminating the water level transmitter itself.

  In the boiler water level control method of the present invention, in the boiler water supply control, instead of using either the directly measured value of the boiler water level or the detected value, either the measurement or calculation of the amount of water entering or exiting the boiler is performed. The current boiler water level is calculated from the value, and the result is used to control the boiler water level.

  In this method, in addition to the amount of water entering and leaving the boiler, the amount of change in the amount of retained water in the boiler that changes depending on the load state of the boiler may be added to the calculation. In addition to the calculation, the amount of water discharged by blow may be added to the calculation. In addition, the amount of change in the specific volume of can water that changes depending on the pressure state of the boiler may be added to the calculation.

  In these methods, several boiler water levels are detected by electrodes, the current actual water level is detected from the on / off signal of the electrodes, and if there is a difference between the calculated water level and the detected actual water level, the calculated water level is set to the actual water level. The calculation water level may be corrected to match.

  Also, in these methods, as the amount of water used for the calculation, the signal of the feed water flow meter attached to the boiler is taken into the boiler control panel, and at this time, from the temperature of the feed water and the pressure in the boiler simultaneously measured, The volume of water converted to the state in the boiler body may be used.

  Furthermore, in these methods, as the amount of water discharged outside the boiler system used for the calculation, the signal of the steam flow meter attached to the boiler equipment is used, or the signal from the fuel flow meter attached to the boiler is used. Either the evaporation amount calculated from the heat generation amount of the fuel and the boiler efficiency, or the evaporation amount calculated from the maximum boiler evaporation amount and the current boiler load factor may be used.

  The boiler water level control device of the present invention includes a boiler, a steam / water separator connected to the boiler, a water level detector connected to the steam / water separator, and a steam flow meter connected to the steam / water separator. A steam extraction pipe provided with a water level detection electrode and pressure sensor provided in the water level detector, a water supply pipe connected to a steam separator and provided with a water supply pump and a water supply flow meter, and combustion of a boiler A fuel supply pipe with a fuel flow meter and a fuel flow control valve, a blower with an air amount adjustment damper connected to a boiler combustor, and a control panel for controlling the boiler, The feed water pump is connected to the control panel via an inverter, and the steam flow meter, the electrode, the pressure sensor, the feed water flow meter, the fuel flow meter, the fuel flow control valve, and the air amount adjustment damper are Connected to the control panel It is characterized in Rukoto.

  In the boiler level control method and apparatus of the present invention, there is an advantage that the level control can be stably performed even with respect to the occurrence of rust in the pipe to the level transmitter and the fluctuation of the boiler combustion load. Further, there is an advantage that stable water level control can be performed without using a water level transmitter.

FIG. 1 is a block diagram showing a boiler water level control device of the present invention.

  The objective of stably controlling the boiler water level was realized by controlling the water level calculated by calculation, that is, the calculated water level.

  Hereinafter, although the Example of this invention is described based on FIG. 1, this invention is not limited to the following Example at all, It can implement by changing suitably.

  FIG. 1 shows a boiler water level control device. The boiler water level control device of this example includes a boiler 1, a steam / water separator 2 connected to the boiler 1, a water level detector 3 connected to the steam / water separator 2, and the steam / water separator 2. Connected to a steam extraction pipe 5 connected with a steam flow meter 4, a water level detection electrode 6 and a pressure sensor 7 provided in the water level detector 3, and a steam separator 2, A water supply pipe 12 provided with a feed water flow meter 11 and a boiler combustor 13, a fuel supply pipe 16 provided with a fuel flow meter 14 and a fuel flow control valve 15, and a boiler combustor 13 connected to an air A blower 18 provided with a quantity adjusting damper 17 and a control panel 20 for controlling the boiler are provided. 21 is an electrode rod, 22 is a LIC (liquid level indicating controller), 23 is LB (calculated water level), that is, a calculated water level as a result of performing each calculation.

In the apparatus configured as described above, the feed water pump 10 is connected to the control panel 20 via an inverter 24, and the steam flow meter 4, the electrode 6, the pressure sensor 7, the feed water flow meter 11, and the fuel. The flow meter 14 is connected to the control panel 20. In this configuration, for example, by controlling the rotation speed of the inverter 24, the amount of water supply is changed in the water supply control of the boiler.
The fuel flow rate adjusting valve 15 and the air amount adjusting damper 17 are connected to a driving source 25, and the driving source 25 and the control panel 20 are connected. 26 is a feed water thermometer, and 27 is a main steam valve.

  In the apparatus shown in FIG. 1, instead of the conventional measurement control of water level control, the feed water flow rate and evaporation amount (evaporation amount or steam flow rate given from the combustion amount or boiler load) measured in the calculator of the boiler control panel, And the water level control of a boiler is performed by the water level (calculated water level) calculated by the calculation which considered the retained water amount etc. of the boiler which changes with respect to various boiler load conditions.

The boiler water level is calculated by the following equation.
LB = (Qw−Qs−ΔVw) / S
LB: Boiler water level (m)
Qw: Boiler water supply per unit time (m ³ )
Qs: Boiler evaporation per unit time (based on saturated water) (m ³ )
ΔVw∝f (−MV): Change amount of boiler water volume (m ³ )
MV: Boiler load factor (%)
S: Boiler cross-sectional area (m ² )

  Qw in the equation captures a signal from the feed water flow meter 11 attached to the boiler. Qs in the formula measures the evaporation amount of the boiler (1) directly with the steam flow meter 4. (2) The fuel flow rate to the boiler is taken into the control panel 20 from the fuel flow meter 14, and the evaporation amount is calculated by calculation with the boiler efficiency. (3) The amount of boiler evaporation at that time is calculated from the load factor (MV) of the boiler. The calculated value is obtained by such a method. For ΔVw in the equation, an arithmetic expression obtained by measuring the amount of retained water for each MV by a test in advance and using it is used. S in the formula is a sectional view of the boiler determined by the shape of the boiler.

  A boiler with many load fluctuations can be operated stably by controlling the water level.

DESCRIPTION OF SYMBOLS 1 Boiler 2 Air-water separator 3 Water level detector 4 Steam flow meter 5 Steam extraction pipe 6 Electrode 7 Pressure sensor 8 Water pipe 10 Feed water pump 11 Feed water flow meter 12 Feed water pipe 13 Combustor 14 Fuel flow meter 15 Fuel flow control valve 16 Fuel Supply pipe 17 Air amount adjusting damper 18 Blower 20 Control panel 21 Electrode rod 22 LIC
23 LB
24 Inverter 25 Drive source 26 Feed water thermometer 27 Main steam valve

Claims (7)

In the water supply control of the boiler, instead of using one of the boiler water level was values and detected directly measured value, do any of the measurement and calculation of the amount of water into and out of the boiler, by the following numbers 1 from that value A boiler water level control method characterized by calculating a current boiler water level and controlling the boiler water level using the result.
(Equation 1)
LB = (Qw−Qs−ΔVw) / S
LB: Boiler water level (m)
Qw: Boiler water supply per unit time (m ³ )
Qs: Boiler evaporation per unit time (based on saturated water) (m ³ )
ΔVw∝f (−MV): Change amount of boiler water volume (m ³ )
MV: Boiler load factor (%)
S: Boiler cross-sectional area (m ² )   The boiler water level control method according to claim 1, wherein, in addition to the amount of water entering and leaving the boiler, the amount of change in the amount of water held by the boiler, which changes depending on the boiler load state, is added to the calculation.   The boiler water level control method according to claim 1 or 2, wherein in addition to the calculation, the amount of water discharged by blow is added to the calculation.   The boiler water level control method according to claim 1, 2, or 3, wherein the amount of change in the specific volume of the can water that changes depending on the pressure state of the boiler is added to the calculation.   The boiler water level is detected at several locations by the electrode, the current actual water level is detected from the on / off signal of the electrode, and if there is a difference between the calculated water level and the detected actual water level, the calculated water level is adjusted to match the actual water level. The boiler water level control method according to any one of claims 1 to 4, wherein the correction is performed.   As the amount of water used for the calculation, the signal of the feed water flow meter attached to the boiler is taken into the boiler control panel, and at this time, it is converted into the state of the boiler body from the temperature of the feed water measured simultaneously and the pressure in the boiler. The boiler water level control method according to any one of claims 1 to 5, wherein the volume of the water is used. As the amount of water discharged outside the boiler system used for calculation, use the signal of the steam flow meter attached to the boiler equipment, or the signal from the fuel flow meter attached to the boiler, the heat value of the fuel, and the boiler efficiency The boiler water level according to any one of claims 1 to 6, which uses either the amount of evaporation calculated from the above, or the amount of evaporation calculated from the maximum boiler evaporation amount and the current boiler load factor. Control method .

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