JPS5932713A - Air flow rate control process for boiler - Google Patents

Abstract

PURPOSE:To improve a combustion of entire boiler and improve an efficiency of the boiler by a method wherein a combustion chamber is divided into several sections for each of the burners, an air flow rate for each of the compartments is controlled in the most appropriate way, an air fuel ratio control at a low flow rate ara is improved, and in turn a correction causing an entire air fuel ratio of the boiler to be the most appropriate one is applied. CONSTITUTION:A burner 6 is divided into several units and air flow rate is controlled in response to each of the fuel flow rates, wherein upon energization of boiler, an air flow rate is calculated in reference to a differential pressure 37, a fuel flow rate is calculated at a function generator and proportional integrator in reference to a fuel pressure 54 so as to control the damper 3. In turn, in case of low loading condition, the air flow rate is controlled to a specified value and under a normal loading condition, an entire air flow rate 51 is controlled to the most appropriate value in response to a total fuel volume 52, so that upon energization the total air volume is kept at the desired value by controlling it by a damper 3 and in turn in case of normal operating condition, by correcting it with a function generator, proportional integrator and multiplier in reference to a flow rate of heavy oil 53. In order to improve a controlling of the damper 8, FDF outlet draft is performed by an air register in case of starting an operation and is performed with the damper 3 under a normal operating condition. Thereby, a stable combustion and an efficiency of the boiler are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to air flow rate control in a boiler, and particularly to a method for suitably controlling the air-fuel ratio of each burner.

The conventional boiler air flow rate control method, as shown in Fig. 1, controls the total air flow rate (detector 51) of the boiler l to a specified value, but the air-fuel ratio of each burner 6 is not controlled. This was a cause of combustion instability in burners and oil and gas mixed combustion burners.

That is, the total amount of air light (detector 51) is controlled by the damper 3 of the forced draft fan 2 (hereinafter referred to as FDP) in accordance with the total heavy oil flow rate (detector 52) of the boiler 1, and Since the air-fuel ratio is not controlled, the combustion conditions differ between the upper and lower stages of the burner 6, or between the morning and the afternoon, and suitable combustion cannot be expected.

On the other hand, when starting up the plant, for the safety of the boiler 1, it is necessary to maintain the air flow rate above the specified value regardless of the number of ignitions of the burners 6 (Fig. It is necessary to control the amount of air in the combustion burner 6 to just the right amount by letting the amount between 1 and 12 escape from the air register (23 in FIG. 2) of the burner that is not ignited.

However, in the conventional method, a large number of burners are controlled at once, and the total amount of fuel in the burners is determined from the common header pressure at the inlet of the burners, and the air flow rate of the burners is calculated from the differential pressure between the FDF outlet and the furnace. However, the air-fuel ratio of each burner cannot necessarily be controlled appropriately. moreover,
In the conventional system, as shown in Fig. 3, the upper limit value 13 and the lower limit value 15 are set for the optimum air-fuel ratio curve 14 for each burner on the flow rate side #1, and the burner main pipe pressure is set at I''. D
If the pressure difference between the F outlet and the furnace exceeds the upper limit set value fc, open the air register, and if the pressure difference falls below the lower limit set value,
The bar is closed by so-called 0N-OFF control.
Since the airflow lid of the boiler is controlled, the air-fuel ratio in the burner section cannot be maintained properly, resulting in unstable burner combustion, smoke color, and unburned matter being discharged from the boiler, resulting in secondary pollution. It was a triggering factor.

For the purpose of the present invention, in order to maintain stable combustion in each burner section, the combustion section is divided into several burner units and each is controlled independently. The present invention provides a light amount control method.

The present invention provides means for controlling the air-fuel ratio of individual burners,
It separates the combustion chamber into several burner units and optimally controls the air flow rate in each compartment, and as a means to overcome the problem of difficulty in measuring the amount of 151 in the low flow area. The burner fuel main pipe pressure and the compartment/furnace differential pressure t (as a pressure signal) are measured, and the flow rate is determined from these to improve air-fuel ratio control in the low flow range. At the same time, the air-fuel ratio of the entire boiler is determined, and this is the optimal one. By adding such corrections, the overall combustion and efficiency of the sipoiler can be improved.

In addition, in order to improve the air flow control by the compartment population damper, as a means to control the population pressure to a specified value, by opening and closing the IP register at startup, and by opening and closing the IP register at normal times, Add a method to control with Rodanba.

An embodiment of the present invention will be described below with reference to FIGS. 5 and 6.

In the boiler combustion system diagram (Fig. 5), the combustion section of the burner 6 is divided into Xe burner units, and each compartment has an air flow rate adjustment damper 8, an air flow rate 7, and a fuel flow! A detector 53 is provided to control the air flow itt according to the fuel #Lft in each compartment.

By the way, when the boiler is started, the number of burners ignited is small and it is difficult to measure the air flow rate in each compartment.
, the fuel flow rate from the burner main pipe fuel pressure 54 to the function generator 3
2, and this deviation signal is calculated by the proportional integrator 34 to control the FDP robot 3.

On the other hand, when the load is low, the boiler usually adjusts the air flow rate to the specified value.
When under load, it is necessary to control the air flow rate 51 of the entire boiler to the optimum value according to the total fuel amount 52, so at startup, the FDP is set to 1. l+! !
The required air flow rate value obtained by the function generator 34 is calculated from the compartment heavy oil flow rate 53 controlled by the constant C unit, and the deviation signal of the total air flow is calculated by the proportional integrator 3.
By correcting the signal calculated in step 4 via the p1 multiplier 42, the total air amount p and t1 can be maintained at the target value. FIG. 7 shows the relationship between the air flow rate and the heavy oil flow value.

In addition, to improve the controllability of the compartment damper, it is necessary to maintain the FDP outlet pressure at a specified value.
At startup, FDP output rod draft air register 23,
Normally, the FDP person performs 3 Romero dampers. In addition, in the figure, 4 is a heavy oil pump, 5 is a heavy oil flow rate control valve, 9 μF' DF output draft detector, 10 is a compartment furnace differential pressure detector, 16 is a stable combustion characteristic diagram line, 31 is a burner main tube pressure, and 21 is a Land box, 22 is the inside of the furnace, 37 is the compartment furnace differential pressure, 40 is the switch, 41ii: A J generator, 42μ multiplier, 53 is the compartment heavy oil flow rate, 54 is the conversion header pressure. be.

According to the present invention, the 1-tal air-fuel ratio of the boiler, and
The air-fuel ratio of each burner can be controlled stably from plant start-up to normal load range, resulting in stable boiler combustion and improved plant efficiency.Also, since boiler combustion can be performed stably, load changes can be achieved. We can also expect the rate to improve.

[Brief explanation of the drawing]

Figure 1 is a conventional boiler combustion system diagram, Figure 2 is a sectional view of the combustion section of the burner, Figure 3 μ is a diagram of stable combustion characteristics of a heavy oil burner, and Figure 4 is a boiler code 1 air Flow rate setting factor,
FIG. 5 is a system diagram of the compartment combustion boiler of the present invention, FIG. 6 is a system diagram of the air flow control system of the present invention, and FIG. '7 is a stable combustion curve diagram of the boiler. 7... Compartment artificial fuel flow value detector, 8...
・U 7 Rod damper with bartment, 9... Compartment artificial fuel flow value detector, 37... Conhartment furnace differential pressure, 53... Conhartment heavy oil flow rate, ≠1 3rd--high ~1 Master pipe oil pressure $4 You idiot! ;prisoner

Claims (1)

[Claims] 1. In a compartmental combustion boiler in which the combustion chamber of a boiler consisting of a large number of burners is divided into units of several burners, a means for measuring the fuel flow rate and air flow rate in the compartment, and a means for controlling the air flow m in the compartment. The Danhara installation is a method for controlling the air flow rate of a boiler, characterized by controlling a compartment rotor so that the air-fuel ratio of the burner is optimized.