JP3558800B2 - Control method of furnace pressure - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for controlling the internal pressure of a furnace, such as a boiler or an incinerator, for supplying and burning air and fuel as needed to generate exhaust gas.
[0002]
[Prior art]
The pressure inside the boiler, incinerator, etc., is controlled by combining an induction fan with a variable rotation speed and a damper that can be operated at a fixed opening.The rotation speed of the induction fan is fixed during operation, and only the opening of the damper is controlled. It was common to control the pressure inside the furnace by means of a furnace.
However, in the above method, there is a problem that the opening degree of the damper and the amount of air passing therethrough do not change temporarily, and furthermore, the change in the amount of airflow at a small opening degree of the damper is large, so that hunting easily occurs in the control system. Therefore, Japanese Patent Application Laid-Open No. Hei 5-231639 proposes a method of controlling the pressure in the furnace in order to solve such a problem.
FIG. 4 shows an overall block diagram of the furnace pressure control device described in the publication. The furnace pressure PV1 is detected by a furnace pressure sensor 50, and the furnace pressure is controlled while being compared with a furnace pressure instruction value SV1. The operation value MV1 is given to the damper 52 by performing the PID control in the unit 51, and the furnace internal pressure based on the opening degree of the damper 52 is controlled so as to approach the indicated value SV1. The operation value MV1 is a reference value PV2 (an arbitrary point at which the furnace pressure can be controlled) set as a reference value PV2 obtained by removing small fluctuations due to minute fluctuations in the furnace pressure through the primary delay filter 53. The operation value MV2 is input to the rotation speed control unit 55 of the induction ventilator 54 and sent to the induction ventilator 54, whereby the induction ventilator 54 is controlled.
[0003]
[Problems to be solved by the invention]
However, in the method of controlling the pressure in the furnace described in the above publication, the rotation speed of the induction ventilator 54 is controlled by the operation value MV1 of the damper 52. However, since the induction ventilator 54 has a large moment of inertia, the induction ventilation is actually performed. A delay of about several minutes occurs until the rotation speed of the ventilator 54 reaches a predetermined value. During this time, there is a problem that the furnace pressure cannot be accurately controlled. Or the combustion state in the furnace may be deteriorated.
Furthermore, the control method described in the above-mentioned publication has a problem that the system is complicated, the whole apparatus becomes complicated, and the adjustment thereof is troublesome.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of controlling the pressure in a furnace, in which the entire apparatus can be simply configured and the control is easy.
[0004]
[Means for Solving the Problems]
A method for controlling the internal pressure of a furnace according to claim 1, wherein the exhaust gas generated is discharged to the outside through a damper provided with a valve whose opening can be adjusted and an induction ventilator. a is, by detecting the pressure in the furnace by controlling the valve opening degree of the damper, a first control unit for controlling so that the pressure of the furnace is constant, the first control unit Operates independently, detects the valve opening of the damper by valve opening detecting means, and, when the valve opening is out of the proper control range, returns the ventilator to the proper control range. A second control unit having drive motor control means for changing the number of rotations by giving a predetermined control amount to the drive motor ,
In addition, the second control unit counts a fixed time after giving a constant control amount to the drive motor, and a timer means for not giving a new control amount to the drive motor when the count is within the count. have.
[0005]
In the method for controlling the furnace pressure according to claim 1 , the first control unit detects the furnace pressure and controls the opening and closing of a damper for controlling the amount of exhaust gas so that the furnace pressure is always constant. Control. A second control unit that operates independently of the first control unit detects a valve opening of the damper and determines whether the valve opening is within an appropriate control range. Is greater than the upper limit, the rotation of the drive motor of the induced draft fan is increased by a certain amount to increase the amount of air blown. As a result, the pressure in the furnace is reduced, so that the first control unit drives the damper so as to reduce the valve opening, whereby the valve opening falls within an appropriate range. If the valve opening is smaller than the lower limit value, the rotational speed of the drive motor of the induction ventilator is reduced by a certain amount. As a result, the pressure in the furnace increases and the first control unit issues a command in a direction to open the valve opening.
Further, in the second control unit, after giving a speed shift command to the drive motor of the induction ventilator, a predetermined time is counted by a timer to perform the next control. In general, since the inertia of the induced draft fan is large, it takes a considerable time to reach the given number of revolutions, and the provision of the timer stabilizes the operation of the control system.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.
Here, FIG. 1 is a block diagram showing a method of controlling the pressure in the furnace according to an embodiment of the present invention, FIG. 2 is a graph showing the relationship between the valve opening of a damper and the rotation speed of an induction ventilator, and FIG. Is an operation flow diagram of these.
[0007]
FIG. 1 shows an example in which a method for controlling the pressure in a furnace according to an embodiment of the present invention is applied to an incinerator (which may be a boiler) 10 which is an example of a furnace. The passage is provided with a damper 11 having a valve that opens and closes at an arbitrary angle and an induction ventilator 12 connected to the damper 11 to discharge generated exhaust gas to the outside. Further, the incinerator 10 is provided with an in-furnace pressure sensor 13 and sends its output signal to a first control unit 14 which performs PID control.
A reference value (SV) of the furnace pressure can be externally input to the first control unit 14, and an electric damper 11 is connected to the output side of the first control unit 14. % Can be controlled. The damper 11 is provided with a valve opening sensor 15 which is an example of a valve opening detecting means for outputting a valve opening. The output of the sensor 15 is input to a second controller 16.
[0008]
The second controller 16 is connected to input means 17 for an upper limit value (Vmax) and a lower limit value (Vmin) of an appropriate control range of the valve opening of the damper 11. The output from the second control unit 16 is supplied to an inverter (not shown) for controlling the drive motor M of the induction ventilator 12, so that the rotation speed of the drive motor M can be controlled.
[0009]
First, the first control unit 14 adjusts the valve opening of the damper 11 so that the furnace pressure becomes the reference value (SV).
Next, the operation of the second control unit 16 that operates independently of the first control unit 14 will be described with reference to FIGS. 2 and 3. The valve opening sensor 15 detects the valve opening of the damper 11. Then, this is input to the second control unit 16. The appropriate control range of the valve opening of the damper 11 is input to the second control unit 16 by the input means 17. The appropriate control range is determined by inputting an upper limit value Vmax (for example, 65 degrees) of the valve opening and a lower limit value Vmin (for example, 40 degrees) of the valve opening.
[0010]
Therefore, after the valve opening degree V of the damper 11 is input by the valve opening degree sensor 15 (step K1), it is determined that the valve opening degree V is equal to or smaller than the upper limit value Vmax of the valve opening degree (step K2). In this case, that is, when the valve opening V is larger than the upper limit value Vmax of the valve opening, the rotation speed of the drive motor M of the induction ventilator 12 is increased by a predetermined amount (for example, 200 rpm) (step K3). As a result, the displacement increases, so that the furnace pressure decreases and the first control unit 14 reacts to reduce the valve opening of the damper 11.
[0011]
Next, when the valve opening V is equal to or smaller than the upper limit value Vmax in Step K2, it is confirmed that the valve opening V is equal to or larger than the lower limit value Vmin of the valve opening (Step K4). Here, in the case of No, that is, when the valve opening V is smaller than the lower limit value Vmin, the rotation speed of the drive motor M of the induction ventilator 12 is reduced by a predetermined amount (for example, 100 rpm). As a result, the amount of exhaust gas decreases, and the pressure in the furnace increases. Therefore, the first control unit 14 controls the valve opening to open (step K5). When the above operation is completed, 1 to 3 minutes are counted by the medium timer T (step K6), and the above operation is repeated. Here, the reason why the middle timer T counts a relatively long time is that it takes time for the induced draft fan 12 to reach the predetermined rotation speed.
In the above, steps K2 and K4 constitute the valve opening detecting means, steps K3 and K5 constitute the drive motor control means, and step K6 constitutes the timer means.
[0012]
FIG. 2 shows this state. When the valve opening degree V of the damper 11 exceeds the upper limit value Vmax, the rotation speed of the drive motor M of the induction draft fan 12 increases, and the opening degree of the damper 11 gradually decreases. When the valve opening V of No. 11 is less than the lower limit value Vmin, it can be seen that the rotation speed of the drive motor M decreases and the damper opening gradually increases.
As described above, since the furnace pressure is kept constant and the valve opening is in the optimal control range, the control system can stably perform safe furnace pressure control.
[0013]
In the above embodiment, the reference value SV of the furnace pressure is one point. However, the reference value SV may have a certain width, thereby increasing the stability of the control system.
Further, in the embodiment, the incinerator has been described as an example, but the present invention is applicable to other furnaces as long as the furnace supplies air for combustion and has an induced draft fan. .
[0014]
【The invention's effect】
As is clear from the above description, the method for controlling the pressure in the furnace according to the first aspect has the first and second control units. However, since they operate independently, the configuration of the entire apparatus is extremely simple. It is.
Further, since the valve opening degree of the damper is always kept in the optimum control range, the control system is stabilized, and appropriate control of the furnace pressure is possible.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a method for controlling a furnace pressure according to an embodiment of the present invention.
FIG. 2 is a graph showing a relationship between a valve opening degree of a damper and a rotation speed of an induction ventilator.
FIG. 3 is an operation flowchart.
FIG. 4 is a block diagram illustrating a method for controlling the pressure in a furnace according to a conventional example.
[Explanation of symbols]
Reference Signs List 10 incinerator (furnace) 11 damper 12 draft ventilator 13 furnace pressure sensor 14 first control unit 15 valve opening sensor 16 second control unit 17 input means

Claims (1)

A method for controlling the internal pressure of a furnace that discharges generated exhaust gas to the outside through a damper provided with an opening-adjustable valve and an induction ventilator,
It detects the pressure of the furnace by controlling the valve opening degree of the damper, a first control unit for controlling so that the pressure of the furnace is constant,
Operating independently of the first control unit, the valve opening of the damper is detected by a valve opening detecting unit, and when the valve opening is out of the proper control range, the valve opening is set within the proper control range. A second control unit including drive motor control means for changing the number of rotations by giving a predetermined control amount to the drive motor of the induced draft fan in the returning direction ,
In addition, the second control unit counts a fixed time after giving a constant control amount to the drive motor, and a timer means for not giving a new control amount to the drive motor when the count is within the count. A method for controlling furnace pressure, comprising:

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