JPH0160734B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for determining the amount of fuel supplied and the amount of air supplied to each of a plurality of burners for heating a combustion furnace, based on the furnace temperature corresponding to each burner and the total air supply before distribution to each burner. The present invention relates to a temperature control device for a combustion furnace that maintains the temperature distribution within the furnace at a set temperature by controlling the air-fuel ratio, which is the ratio between the amount of fuel supplied and the total amount of fuel supplied.

Conventionally, temperature control devices for combustion furnaces have been used to control the air-fuel ratio of multiple burners installed in the combustion furnace individually according to the set temperature for each zone of the combustion furnace, in order to improve the temperature distribution inside the furnace. It was under optimal control. An example of this is the temperature control device shown in FIG.

This temperature control device includes a fuel pipe 2 and an air pipe 3 of each burner 1, a fuel flow detector 4, a fuel flow control valve 5, an air flow detector 6, and an air flow control valve 7.
and. and an air-fuel ratio calculator 8 which inputs each output from the fuel flow rate detector 4 and the air flow rate detector 6 and outputs a signal corresponding to the measured air-fuel ratio;
An air-fuel ratio regulator 10 receives the signal from the calculator 8 and the output signal R corresponding to the set air-fuel ratio from the air-fuel ratio setting device 9 and performs, for example, PI calculation to generate a correction signal S corresponding to the air-fuel ratio deviation. and a temperature controller 11 that outputs a flow rate setting signal Q according to the deviation between the furnace temperature detected by an internal furnace temperature detection device (not shown) and the furnace temperature set by a built-in furnace temperature setting device, and and a multiplier 13 which inputs the output via the low limiter 12 and the correction symbol S from the air-fuel ratio controller 10 to the flow rate setting signal Q from the temperature controller 11. Fuel flow rate correction signal P1
The multiplier 13 uses the valve control signal from the adder 14 which has been added together with the flow rate setting signal Q from the temperature controller
Subtractor 1 that subtracted the air flow rate correction signal P2 from
The fuel flow control valve 5 and the air flow control valve 7 are respectively controlled by other valve control signals from the control valve 5.

Therefore, in this case, the amount of fuel supplied and the amount of air supplied to each burner 1 are optimally controlled by the temperature controller 11 and air-fuel ratio setting device 9 provided individually for each burner 1; Since each combustion furnace requires an independent temperature control device and air-fuel ratio control device, temperature control of the combustion furnace has the drawback of requiring considerable equipment costs.

In addition, as a simplified temperature control device including this air-fuel ratio, as shown in FIG. There is a system in which the fuel flow control valve 5 is controlled by the output from 10, but even in this case, the air-fuel ratio is controlled in response to changes in one flow rate, so it does not respond to sudden changes. In addition to the fundamental drawback of delays, the need for expensive fuel flow rate detectors 4, air flow rate detectors 6, temperature regulators 11, etc. for each burner 1 makes it difficult to control the temperature of the combustion furnace. The disadvantage was that it required considerable equipment costs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature control device for a combustion furnace that can maintain a good temperature distribution in the furnace and can significantly reduce the equipment cost required for temperature control of the combustion furnace. Therefore, the present invention provides for a plurality of unit burners installed in a combustion furnace to be supplied with fuel from a main fuel pipe for fluid fuel supply and air from a main air pipe for air supply through branch fuel pipes for each unit burner. A fuel flow rate detector and an air flow rate detector are provided in the main fuel piping and the main air piping to detect the total fuel supply amount and the total air supply amount to the unit burner group. ,
Each branch fuel pipe and branch air pipe are provided with a fuel flow rate control valve and an air flow rate control valve for each unit burner, respectively.
Further, each burner is provided with a temperature regulator that detects the temperature inside the combustion furnace and generates a temperature difference output corresponding to the difference between the inside temperature of the furnace and a preset temperature, and furthermore, the fuel flow rate for each unit burner is adjusted. The flow rate controlled by the control valve and the air flow control valve is increased or decreased in a direction to eliminate the temperature difference according to the temperature difference output from the temperature controller for each unit burner, and the flow rate controlled by the fuel flow control valve and the air flow control valve is The flow rate ratio of the adjusted flow rate is calculated from the air-fuel ratio controller corresponding to the difference between the measured air-fuel ratio obtained from each output of the fuel flow rate detector and the air flow rate detector and the preset set air-fuel ratio. It is characterized in that the air-fuel ratio difference is changed in the direction of eliminating the air-fuel ratio difference by the air-fuel ratio difference output.

Next, the configuration of an embodiment of the present invention will be explained with reference to FIG. Note that the same numbers and symbols are used for the same components as those in FIGS. 1 and 2.

Fuel from a main fuel pipe 16 for fluid fuel supply and air from a main air pipe 17 for air supply are supplied to each of the plurality of burners 1 provided in the combustion furnace, and branch to branch fuel pipes 18 for each burner 1. The main fuel pipe 16 and the main air pipe 17 are provided with a fuel flow rate detector 4 for detecting the total amount of fuel supplied to each burner 1 and the total amount of air supplied to each burner 1. An air flow rate detector 6 is attached to the branch fuel pipe 18 and branch air pipe 19 for each burner 1, and a fuel flow control valve 5 and an air flow control valve 7 for adjusting the fuel flow rate and air flow rate for each burner 1 are attached. is installed. Further, in the combustion furnace, a temperature controller 11 outputs a flow rate setting signal Q according to the deviation between the furnace temperature detected by the furnace temperature detection device (not shown) corresponding to each burner 1 and the furnace temperature set by the built-in furnace temperature setting device. and a low limiter 12 for maintaining the furnace temperature above a certain level are provided for each burner 1. Furthermore, each output from the fuel flow rate detector 4 and the air flow rate detector 6 is inputted, and an output corresponding to the measured air-fuel ratio generated from the air-fuel ratio calculator 8 and an output corresponding to the set air-fuel ratio from the air-fuel ratio setting device 9 are generated. An air-fuel ratio regulator 10 that receives a signal R as an input and generates a correction signal S for PI calculation corresponding to an air-fuel ratio deviation is connected to all burners 1.
One is provided for each. Temperature controller 1
1, a fuel flow rate correction signal is sent from a multiplier 13 which receives the output from the temperature regulator 11 via the low limiter 12 and the output signal S from the air-fuel ratio regulator 10 as input. an adder 14 that adds P1 and inputs a valve control signal to the fuel flow rate control valve 5; and an air flow rate correction signal P from the multiplier 13 for the flow rate setting signal Q from the temperature controller 11;
a subtracter 15 that inputs a valve adjustment signal to the air flow rate adjustment valve 7 by subtracting 2, and a valve characteristic corrector that corrects the air-fuel ratio for each burner 1 by correcting the valve adjustment signal from the subtractor 15. 20 are provided separately for each burner 1.

Next, the operation of this embodiment will be explained.

In the combustion furnace temperature control device configured in this way, one common air-fuel ratio control device 21 corresponds to the fuel flow rate control valve 5 and the air flow rate control valve 7 of each burner 1, but each The air-fuel ratio for each zone of the combustion furnace corresponding to each burner 1 is determined by the correction amount by the valve characteristic corrector 20 for each burner 1, and therefore, the average air-fuel ratio of all burners 1 is set in the air-fuel ratio setting device 9. In this state, the air-fuel ratio of each burner 1 is corrected and set by a valve characteristic corrector 20 for each burner 1, and the furnace temperature is set by a furnace temperature setting device (not shown).

As a result, a correction signal S, which is a PI calculation of the air-fuel ratio deviation in a state where the measured air-fuel ratio based on the fuel supply amount and air supply amount to all burners 1 is compared with the air-fuel ratio set by the air-fuel ratio setting device 9, is sent to the air-fuel ratio controller. 10 to the multiplier 13 for temperature control for each burner 1, and the fuel flow rate control valve 5 and air flow rate control valve 7 of each burner 1 receive the flow rate setting signal Q from the temperature control device 11 for each burner 1.
The valve adjustment signal from the subtractor 15 is corrected by a valve characteristic corrector 20 in accordance with the air-fuel ratio of each burner 1. Therefore, the combustion furnace is essentially
As in the case of FIG. 1 in which an air-fuel ratio control device is provided for each burner 1, the air-fuel ratio and temperature are controlled for each burner 1.

In addition, in the case of a furnace with a small characteristic of the fuel and combustion air flow control valve or a small turndown ratio, a valve characteristic corrector 20 is used.
The low limiter 12 can be omitted depending on the set temperature of the furnace and the allowable fluctuation range, etc., and this temperature control can be performed separately for each zone of the furnace or at a position on the furnace, as shown in Fig. 4. It is also possible to control the temperature of an arbitrary number of burners 1 as a unit, such as burners 1 of
It can be provided for each.

In this way, the present invention targets the fuel supply amount and air supply amount supplied to each burner of a combustion furnace, and controls the temperature of each unit burner while collectively controlling the air-fuel ratio of the entire burner consisting of a plurality of unit burners. By controlling the temperature, it is possible to maintain a good temperature distribution in the furnace, and the equipment cost required for controlling the temperature of the furnace can be significantly reduced.

[Brief explanation of drawings]

Figures 1 and 2 are temperature control system diagrams of a conventional embodiment, Figure 3 is a temperature control system diagram of an embodiment of the present invention, and Figure 4 is a temperature control system diagram of another embodiment of the present invention. shows. 1...Burner, 4...Fuel flow rate detector, 5...
Fuel flow rate regulator, 6...Air flow rate detector, 7...
Air flow control valve, 8... Air-fuel ratio calculator, 9... Air-fuel ratio setter, 10... Air-fuel ratio regulator, 11... Temperature controller, 13... Multiplier, 14... Adder, 1
5... Subtractor, 16... Main fuel pipe, 17... Main air pipe, 18... Branch fuel pipe, 19... Branch air pipe, 21... Air-fuel ratio control device.

Claims (1)

[Scope of Claims] 1. For a plurality of unit burners provided in a combustion furnace, fuel from a main fuel pipe for fluid fuel supply and air from a main air pipe for air supply are distributed to each unit burner separately. A fuel flow rate detector and an air flow rate detector are installed in the main fuel piping and the main air piping to detect the total amount of fuel supplied and the total amount of air supplied to the unit burner group. A fuel flow rate control valve and an air flow rate control valve for each unit burner are provided in each branch fuel pipe and branch air pipe, respectively, and the temperature inside the combustion furnace is detected and set in advance to the temperature inside the combustion furnace. A temperature controller is provided for each burner to generate a temperature difference output corresponding to the difference from the set temperature, and the flow rate adjusted by the fuel flow rate control valve for each unit burner and the air flow rate control valve is adjusted to the temperature for each unit burner. The temperature difference output from the regulator is used to increase or decrease the temperature difference in the direction of eliminating the temperature difference, and the flow rate ratio between the flow rates adjusted by the fuel flow rate control valve and the air flow rate control valve is adjusted between the fuel flow rate detector and the air flow rate detector. The air-fuel ratio difference output from the air-fuel ratio controller corresponding to the difference between the measured air-fuel ratio determined by each output and the preset set air-fuel ratio is used to change the air-fuel ratio in a direction to eliminate the air-fuel ratio difference. Characteristic combustion furnace temperature control device. 2 Fuel from the main fuel piping for fluid fuel supply and air from the main air piping for air supply to multiple unit burners installed in the combustion furnace through branch fuel piping and branch air piping for each unit burner. At the same time, a fuel flow rate detector and an air flow rate detector are installed in the main fuel piping and the main air piping to detect the total fuel supply amount and total air supply amount to the unit burner group. A fuel flow rate control valve and an air flow rate control valve for each unit burner are provided in the fuel pipe and the branch air pipe, respectively, and an air-fuel ratio calculator is provided with outputs from the fuel flow rate detector and the air flow rate detector as inputs. An air-fuel ratio regulator is provided which receives an output corresponding to the measured air-fuel ratio and an output corresponding to the set air-fuel ratio from the air-fuel ratio setting device as input and generates an output corresponding to the air-fuel ratio deviation, and also detects the temperature inside the combustion furnace. A temperature controller that generates a temperature difference output corresponding to the difference between the temperature inside the furnace and a preset temperature is provided for each unit burner, and a fuel flow rate control valve and an air flow rate control valve are provided for each unit burner, One valve control signal is obtained by adding the output from a multiplier whose inputs are the output from the temperature regulator and the output from the air-fuel ratio regulator, and the output from the other valve is subtracted from the output from each temperature regulator. A temperature control device for a combustion furnace, characterized in that it is controlled by an adjustment signal. 3. The temperature of the combustion furnace according to claim 2, characterized in that the output from the temperature controller is input to the multiplier via a low limiter for maintaining the temperature of the combustion furnace above a certain level. Control device. 4. The second aspect of the present invention is characterized in that a valve adjustment signal is inputted to each unit burner-specific air flow rate control valve via a valve characteristic corrector for correcting the air-fuel ratio for each unit burner. The temperature control device for a combustion furnace according to item 1 or 3.