KR102086250B1 - Boiler Enthalpy Automatic Control Circuit On Classified By Coal Property - Google Patents

Abstract

According to the present invention, disclosed is an automatic boiler enthalpy control circuit for each fuel property. For example, the automatic boiler enthalpy control circuit for each fuel property selects one of classified high-calorie, medium-calorie, and low-calorie combustion fuels, calculates set point enthalpy for the selected combustion fuel to determine a feed water flow rate, and changes the enthalpy curve of a design separator to feed forward when combustion fuel property changes so that the feed water flow rate is controlled.

Description

Boiler Enthalpy Automatic Control Circuit On Classified By Coal Property}

The present invention relates to a boiler enthalpy automatic control circuit for each fuel phase.

The conventional coal-fired boiler enthalpy control circuit derives an enthalpy process variable (PV) by measuring the change in pressure and temperature of the separator outlet when the fuel properties are changed, and controls the control variable according to the PV change. Variable, CV) is added to or subtracted from the Feed Water Set Point to control the main steam pressure and temperature. Large changes in fuel properties during boiler operation lead to changes in main steam pressure and temperature, and the main steam pressure and temperature are stabilized by the enthalpy control circuit.

However, when the enthalpy control circuit was operated, it took considerable time for the main steam to stabilize. In addition, as the stabilization time increases, a larger control circuit is driven to correct the main steam pressure drop, causing a swing phenomenon of the main steam pressure.

The present invention provides a boiler enthalpy automatic control circuit for each fuel phase.

The boiler enthalpy automatic control circuit for each fuel property according to the present invention is a boiler enthalpy automatic control circuit for each fuel property, wherein one of the classified high calorific value, medium calorific value and low calorific value combustion fuel is selected, and a set point enthalpy is selected for the selected combustion fuel. The water supply flow rate may be determined by calculation, and the feed water flow rate may be controlled by changing the design separator enthalpy curve when the properties of the combustion fuel are changed and feed forward.

The design separator enthalpy curve may be provided by arranging input and output amounts for each of the high calorific value, the middle calorific value and the low calorific value combustion fuel.

Then, the calorie design separator enthalpy is subtracted from the calorific design separator enthalpy, multiplied by 0.5, and the value obtained by subtracting the calorific design separator enthalpy from the set point enthalpy is selected to select a curve.

In addition, after subtracting the heavy heat design separator enthalpy from the calorie design separator enthalpy and multiplying by 0.5, the flow rate may be increased when the value of the heavy heat design separator enthalpy is subtracted from the set point enthalpy.

In addition, after subtracting the heavy heat design separator enthalpy from the calorie design separator enthalpy and multiplying by 0.5, the flow rate may be reduced if the value obtained by subtracting the heavy heat design separator enthalpy is smaller than the set point enthalpy.

Boiler enthalpy automatic control circuit according to the present invention improved the existing boiler enthalpy control circuit to select the Design Separator Enthalpy curve according to the high calorie fuel and low calorie fuel. Accordingly, the existing design separator enthalpy curve is used when using medium calorie fuel, and it can be automatically converted into high calorie and low calorie curve according to the change of separator enthalpy PV to derive the feed water set point for each situation.

1 is a logic circuit illustrating a boiler enthalpy automatic control circuit according to an embodiment of the present invention.
2 is a logic circuit illustrating a curve automatic selection circuit of a boiler enthalpy automatic control circuit according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily practice the present invention.

1 is a logic circuit illustrating a boiler enthalpy automatic control circuit according to an embodiment of the present invention.

By adding selection logic, it is possible to improve feedwater system control response by adding feed forward concept by changing Design Separator Enthalpy curve in case of drastic fuel property change. Each Design Separator Enthalpy curve is shown in the table below.

division High Calorie Fuel F (X) Heavy Calorie Fuel F (X) Low Calorie Fuel F (X) Input Output Input Output Input Output One 0 2880 0 2960 0 3080 2 315 2880 315 2960 315 3080 3 525 2680 525 2820 525 2860 4 787.5 2600 787.5 2720 787.5 2750 5 1050 2570 1050 2625 1050 2745 6 1120 2550 1120 2600 1120 2710 7 1500 2550 1500 2600 1500 2710

2 is a logic circuit illustrating a curve automatic selection circuit of a boiler enthalpy automatic control circuit according to an embodiment of the present invention.

Design Separator Enthalpy curve automatic selection circuit. The selection circuit formula is made as follows and the Design Separator Enthalpy curve is automatically selected through the Transfer Function according to whether the ⓛ or ⓗ signal is operated.

division Formula Signal ① (High Calorie Design Separator Enthalpy-Medium Calorie Design Separator Enthalpy) × 0.5-Heavy Calorie Design Separator Enthalpy> Set Point Enthalpy L action ② (High Calorie Design Separator Enthalpy-Medium Calorie Design Separator Enthalpy) × 0.5 + Heavy Calorie Design Separator Enthalpy <Set Point Enthalpy H action

Meanwhile, examples of logic operations according to FIGS. 1 and 2 are as follows.

First, the Separator Enthalpy Process Variable (b), Heat Capacity (a, ④) and the calculated values (Divide a / b, ③) are basically the Boiler Input Demand. ) Is calculated by subtracting Total Superheater Spray Flow (6) from (Feed Water Set Point) and calculating (⑤, ⑦) to form the final Feed Water Set Point. .

 When the fuel properties are changed, the enthalpy process variable (PV) is derived by measuring the pressure and temperature changes of the separator outlet and the control variable (CV) according to the PV change is supplied to the water supply set point ( It controls the main steam pressure and temperature by adding or subtracting the feed water set point. Large changes in fuel properties during boiler operation lead to changes in main steam pressure and temperature, and the main steam pressure and temperature are stabilized by the enthalpy control circuit.

On the other hand, in the boiler enthalpy automatic control circuit according to an embodiment of the present invention, when the calorific value fuel combustion can be started by selecting ① curve selection.

However, if high calorie fuel is introduced, the separator enthalpy (PV) is increased.

Further, accordingly, the calculated values Divide a / b and ③ are reduced, and the heat capacity (Heat Capacity, a and ④) is reduced.

In addition, the value of ⑤ increases, the value of ⑥ decreases, and the value of ⑦ increases to a negative value, thereby increasing the set point feed water.

In addition, the separator outlet temperature is increased to reduce the enthalpy deviation value to a negative value.

Meanwhile, the Design Separator Enthalpy is almost constant, and the set point enthalpy decreases due to an increase in the negative error of the Separator Enthalpy PID circuit.

The high-calorie curve ② may be automatically selected by a design separator enthalpy curve automatic selection circuit, so that feed forward may be performed.

On the other hand, due to the curved transition, the design separator enthalpy is greatly reduced, and the set point enthalpy (⑧) is greatly reduced, thereby increasing the water supply flow rate.

Therefore, the automatic control of the boiler enthalpy for each fuel property according to an embodiment of the present invention can greatly contribute to improving the boiler water system rapid response and stable facility operation by applying the optimum design separator enthalpy in the event of rapid heat change.

What has been described above is just one embodiment for implementing the boiler enthalpy automatic control circuit for each fuel property according to the present invention, the present invention is not limited to the above embodiment, as claimed in the following claims Without departing from the gist of the invention, those skilled in the art to which the present invention pertains to the technical spirit of the present invention to the extent that various modifications can be made.

Claims (5)

In the boiler enthalpy automatic control circuit for each fuel property,
One of the classified high calorie, medium calorie and low calorie combustion fuels,
A set point enthalpy is calculated for the selected combustion fuel to determine a feedwater flow rate,
When a change in the properties of the combustion fuel by changing the design separator enthalpy curve, feed forward to control the feed water flow rate,
A boiler enthalpy automatic control circuit for each fuel phase that selects a curve compared to a set point enthalpy after subtracting the heavy heat design separator enthalpy from the calorific design separator enthalpy and multiplying by 0.5. The method of claim 1,
The design separator enthalpy curve is a boiler enthalpy automatic control circuit for each fuel property provided by arranging the input and output for each of the high calorific value, medium calorific value and low calorific value combustion fuel. delete The method of claim 1,
The fuel enthalpy automatic control circuit for each fuel phase which increases the flow rate after subtracting the heavy heat design separator enthalpy from the calorific design separator enthalpy and multiplying by 0.5, and then subtracting the heavy heat design separator enthalpy from the set point enthalpy. The method of claim 1,
The boiler enthalpy automatic control circuit for each fuel phase, which reduces the flow rate when the calorific value design separator enthalpy is subtracted from the calorific design separator enthalpy and multiplied by 0.5, and the value of the calorific value design separator enthalpy is smaller than the set point enthalpy.

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