JPH04148107A - Controlling method for pressure in furnace - Google Patents

Abstract

PURPOSE:To drive an induced draft fan at its maximum capability and stabilize the pressure in the furnace quickly by controlling the pressure in the furnace by operating a control damper provided in the exhaust gas return line. CONSTITUTION:The pressure PV0 in an incinerator 1 is detected by a detection end 9, and it is transmitted to a regulator 12 by a pressure transmitter 10. The regulator 12 for regulating the pressure in the furnace compares the furnace pressure with a set value SV by means of a PID regulator 11, carries out PID calculation, and operates a control damper 22 installed in an exhaust gas return line L to stabilize the pressure in the incinerator 1. With this arrangement in which the operational end of the pressure control is the control damper 22 installed in the return line L, the control damper 22 is opened or closed so as to supplement variations in the combustion exhaust gas by an exhaust gas return line L, and in the operation of an induced draft fan 5 it is operated at its maximum capability. Accordingly when the volume of the exhaust gas increases suddenly, the induced draft fan 5 sucks the exhaust gas at its maximum capability by closing the control damper 22 and the pressure in the furnace can be stabilized quickly.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an incinerator pressure control method for controlling the incinerator internal pressure of an incinerator in an incinerator for incinerating municipal waste, industrial waste, etc. by manipulating the exhaust gas flow rate. It is something.

[Prior art]

In incinerators for municipal waste, etc., it is necessary to maintain the internal pressure at a negative pressure at all times for safety reasons. If the negative pressure is too strong, the amount of air leaking from the furnace, exhaust gas cooler, gas treatment device, and exhaust gas duct will increase, resulting in an unfavorable state such as an increase in the amount of exhaust gas and an increase in the electric power of the induced blower. Therefore, the pressure inside the furnace needs to be controlled to an appropriate negative pressure.

Conventionally, the internal pressure of a general incinerator has been controlled using a simple controller as shown in FIG. In FIG. 2, 1 is an incinerator, 2 is a gas cooler, 3 is a gas treatment device, 4 is a remote control damper for adjusting the flow rate of exhaust gas, and 5
is an induced blower for sucking exhaust gas, and 6 is a chimney. The incinerator 1 is supplied with fuel 7 and combustion air 8 . 13 indicates a leak. The furnace pressure detected by the detection end 9 is sent to the controller 12 including the PID controller 11 by the pressure transmitter 10, and compared with the furnace pressure set value. The exhaust gas flow rate is adjusted by operating the operating damper 4.

However, although such a control system is sufficiently practical for general combustion furnaces, it is not suitable for stable furnaces such as heavy oil incinerators, such as incinerators that handle municipal waste that varies greatly in quality and quantity. In comparison, the fluctuations in the furnace pressure are severe;
It vibrates and is irregular, making stable control difficult with a simple controller like the one mentioned above.

As a countermeasure to this problem, there is an in-furnace pressure control device for which the present applicant has previously applied for a patent (Japanese Patent Application No. 171602/1982 (Japanese Patent Application Laid-open No. 49929/1983)). FIG. 3 is a diagram showing the configuration of this furnace pressure control device. In FIG. 3, the controller 12 includes a first-order lag filter 15, a subtracter 16, a nonlinear arithmetic unit 17, a differential arithmetic unit 18, a nonlinear arithmetic unit 19, and an adder 20. Differential calculator 18 and nonlinear calculator 19
A differential calculation output circuit 21 is formed.

In the furnace internal pressure control device having the above configuration, when the differential calculation output circuit 21 is not used, the furnace pressure of the incinerator 1 is transmitted to the pressure transmitter 10 as the output Pv0 and sent to the first-order lag filter 15.
The pulsation is absorbed and becomes the output Pvl. Output P
V, is the set value S of the PID controller 11 by the subtracter 16.
The difference with V is calculated and an output PV is output. Output PV
, outputs an output PV by the nonlinear arithmetic unit 17 with the gain changed depending on the case of sv<pv and the case of SV>PV.

That is, the gain when SV<PVI is selected to be larger than the gain when SV>PV.

PID in PID controller 11 with respect to output PV.
It performs the calculation and outputs an output MV, which passes through an adder 20 and outputs an output MV. In this case, since there is no input to be added, MV,=MV□.

The remote control damper 4 is operated by this output MV, but since the gain is changed as described above, the value of the output MY is smaller when SV>PVl.
, is larger than the case of . Therefore, SV<PV,
In this case, the operation speed of the remote control damper 4, which is the operating end, is increased, and thereby the pressure inside the furnace can be quickly prevented from increasing to positive pressure.

When using the differential calculation output circuit 21, the nonlinear calculation unit 1
7, the gain may not be changed depending on the magnitude relationship between SV and PV. The output Pv is differentiated by the differential calculator 18 and becomes the output yI. This output yI is output as an output y only when the differential value is positive in the nonlinear arithmetic unit 19. The output y1, the output MV as the basic operation amount from the PID controller 11, and the corrected operation amount signal MV in the adder 20 are used to operate the remote control damper 4, which is the operation end. Judging by the positive differential value that the furnace pressure is on the rise, the operation speed of the damper is increased by applying a larger amount of operation to the operating end, and the increase in furnace pressure is quickly suppressed, resulting in positive pressure. This prevents this from happening.

[Problem to be solved by the invention]

In recent years, exhaust gas treatment has become more sophisticated; in other words, while electrostatic precipitators have been the mainstream in the past, there has been a trend in recent years where exhaust gas treatment involves passing through bag filters, wet treatment, or filled beds with chemicals, which increases the pressure loss. In cases where exhaust gas treatment involves a large pressure loss,
In the method disclosed in No. 1602 (Japanese Unexamined Patent Publication No. 61-49929), the induction blower 5 temporarily became insufficient in capacity due to the delay in the remote control damper 4, and there was a risk that the pressure inside the furnace would become abnormally positive. . When the pressure inside the furnace becomes positive, combustion exhaust gas leaks out of the system, creating an undesirable problem in the working environment.

The present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide a furnace pressure control method that can quickly follow fluctuations in exhaust gas and stabilize the furnace pressure.

[Means to solve the problem]

In order to solve the above problems, the present invention provides an incinerator pressure control method for controlling the incinerator internal pressure of an incinerator for incinerating municipal waste by adjusting the flow rate of exhaust gas, and the incinerator exhaust gas is controlled by an induced blower. The exhaust gas cooler is configured to be induced and discharged into the atmosphere through an exhaust gas cooler, an exhaust gas treatment device, and a remote control damper, and the exhaust gas induced by the induced blower is transferred to the remote control damper inlet, the exhaust gas treatment device inlet, or the exhaust gas cooler. An exhaust gas return line is provided for returning to the inlet or the incinerator, a control damper is provided on the exhaust gas return line, and the control damper is controlled by the output of the furnace pressure adjustment needle, so that when the furnace pressure is high, the exhaust gas return flow rate is reduced. , when the furnace pressure is low, the exhaust gas return flow rate is increased. Further, the operating speed of the control damper is increased when the furnace pressure becomes positive by increasing the gain on the positive side of the set value of the furnace pressure regulator and decreasing the gain on the negative side.

In addition, detecting a sudden change in the pressure inside the furnace to positive pressure,
The control damper is characterized in that the control damper is operated at an early stage when the furnace internal pressure suddenly changes to positive pressure.

In addition, the combination of control that changes the gain on the plus side and minus side of the set value of the furnace pressure regulator and control that detects a sudden change in the furnace pressure to positive pressure and operates the control damper at an early stage. It is characterized by

[Effect]

As mentioned above, by using a control damper with the operating end of the pressure control installed in the exhaust gas return line, the exhaust gas return line L opens and closes to compensate for fluctuations in combustion exhaust gas, and the operating point of the induced blower is set at its maximum capacity. Therefore, when the amount of exhaust gas increases rapidly (when the pressure inside the furnace increases), by closing the control damper, the induced blower sucks the exhaust gas at its maximum capacity, quickly stabilizing the pressure inside the furnace. can be done.

In addition, by increasing the gain on the positive side of the set value of the furnace pressure regulator and increasing the operating speed of the control damper when the furnace pressure becomes positive, it is possible to quickly suppress the furnace pressure from becoming positive. can.

By detecting a sudden change in the furnace internal pressure to positive pressure and operating the control damper early if the furnace internal pressure suddenly changes to positive pressure, the furnace internal pressure is quickly suppressed from becoming positive. can.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing the configuration of a furnace internal pressure control device that implements the furnace internal pressure control method of the present invention. In this figure, parts with the same numbers and symbols as in FIGS. 2 and 3 indicate the same or equivalent parts (hereinafter, the same applies to other drawings).

As shown in Fig. 1, this furnace internal pressure control device has an induced blower
An exhaust gas return line L is provided for returning a part of the exhaust gas induced and discharged by the remote control damper 4 to the inlet of the remote control damper 4.
A control damper 22 is provided on the exhaust gas return line L.

In the furnace internal pressure control device having the above configuration, the furnace internal pressure PV of the incinerator 1 is detected by the detection end 9 and transmitted to the controller 12 by the pressure transmitter 10. In the controller 12 for adjusting the pressure in the incinerator, the PID controller 11 compares it with the set value S, performs PID calculation, operates the control damper 22 installed in the exhaust gas return line L, and controls the furnace of the incinerator 1. Stabilize internal pressure.

Here, when the remote control damper 4 starts the induced blower 5,
The manual damper is fully closed and the specified opening is maintained during operation (approximately fully open).
shall be. Here, the maximum capacity of the induced blower 5 is limited by the upper limit of the control damper 22.

Since the mass of municipal waste and the like input into the incinerator 1 varies, the amount of combustion exhaust gas also varies. As a result, the pressure inside the furnace also fluctuates. In order to stabilize this pressure, conventionally, the second
This was done by controlling a remote control damper 4 as shown in FIG. Therefore, the operating point of the induced blower 5 is set at a location where the capacity is suppressed. Therefore, by using the control damper 22 installed in the exhaust gas return line L as the operating end for pressure control as in this embodiment, the induced blower 5 The operating point is to operate at its maximum capacity. Therefore, when the amount of exhaust gas increases rapidly (when the pressure inside the furnace increases), by closing the control damper 22, the exhaust gas is sucked at the maximum capacity of the induced blower 5.
The pressure inside the furnace can be stabilized quickly.

FIG. 5 is a diagram showing the configuration of another furnace internal pressure control device that implements the furnace internal pressure control method of the present invention. This furnace internal pressure control system uses a controller 12 having the same configuration as the controller 12 shown in FIG. 3, and is configured so that its output controls a control damper 22 provided in the exhaust gas return line L.

In the furnace internal pressure control device shown in Fig. 4, the differential calculation output circuit 2
1 is not used, the pressure inside the incinerator 1 is sent to the first-order lag filter 15 by the pressure transmitter 10 as the output PVo, and the pulsation is completely absorbed, resulting in the output PV. Output PV,
A subtracter 16 calculates the difference between PV and the set value Sv of the PID controller 11, and outputs an output PV. Output Pv! The nonlinear arithmetic unit 17 outputs an output Pv with different toticanes when SV<PV, (7) and when SV>PVI (7).

That is, the gain when SV<PV is selected to be larger than the gain when sv>pV.

For the output P■, the PID controller 11
It performs the calculation and outputs an output MV, which passes through an adder 20 and outputs an output MV. In this case, since there is no input to be added, MV,=MV.

The control damper 22 installed in the exhaust gas return line L is operated by this output MV, but since the gain is changed as described above, the value of the output MV is as follows.
It is larger when SV<PV than when Sv>pv. Therefore, when SV<PV, the closing operation speed of the control damper 22, which is the operating end, is increased, thereby increasing the flow rate of exhaust gas released into the atmosphere through the chimney 6, and the pressure inside the furnace rises to achieve a direct ratio. You can quickly prevent this from happening.

When using the differential calculation output circuit 21, the nonlinear calculation unit 1
7, it is not necessary to change the gain due to the large/4% relationship between Sv and PV. The output PV is differentiated by the differential calculator 18 and becomes the output y1. This output y
l is output as an output y only when the differential value is positive in the nonlinear arithmetic unit 19. Output y3, PID controller 1
The output MV as the basic operation amount from 1 and the adder 20
, the corrected operation amount signal MV is obtained, and the remote control damper 4, which is the operation end, is operated. It is determined that the pressure in the furnace is on the rise when the differential value is positive, and a larger operation amount is given to the control damper 22, which is the operating end, to increase the closing operation speed of the damper, so that the pressure in the furnace increases quickly. to prevent positive pressure.

Incidentally, in the furnace pressure control devices having the configurations shown in FIGS. 1 and 4 above, an example is shown in which the return end of the exhaust gas return line L is connected to the inlet of the remote control damper 4, but the return end of the exhaust gas return line L is The connection part at the end is not limited to this, but it can be connected to the inlet of the gas treatment device 3 as shown in FIG.
It may be placed inside the incinerator 1 as shown in the figure.

〔Effect of the invention〕

As explained above, according to the present invention, the exhaust gas return line is provided to return the exhaust gas induced by the induced blower to the remote control damper inlet, the exhaust gas treatment device inlet, or the exhaust gas cooler inlet using the output of the furnace pressure regulator. Figure 1 shows the excellent effect of this invention in that the pressure inside the furnace is controlled by operating the control lever, so the induced blower can always be operated at maximum capacity, and the pressure inside the furnace can be quickly stabilized. FIGS. 2 and 3 are diagrams showing the configuration of a conventional furnace pressure control device, respectively. 6 and 7 are diagrams showing the configuration of other furnace pressure control devices for carrying out the furnace pressure control method of the present invention, respectively.

In the diagram, construction: incinerator, 2: gas cooler, 3:
...Gas treatment equipment, 4...Remote control Dan/To 5.
Induced blower, 6... chimney, 7... fuel, 8...
...Combustion air, 9...Detection end, 10...Pressure transmitter, 11...PID controller, 12...Controller, 15...-order lag filter, 16 ...Subtractor, 17...Nonlinear arithmetic unit, 18...Differential arithmetic unit, 19...Nonlinear arithmetic unit, 20...Adder, 2
1... Differential calculation output circuit, 22... Control damper, L... Exhaust gas return line.

Patent applicant: Ebara Corporation Agent: Patent attorney Takashi Kumatani (1 other person) No. Figure 5 No. Figure 6 Figure 7

Claims (4)

[Claims] (1) A method for controlling the internal pressure of an incinerator that incinerates municipal waste, industrial waste, etc. by adjusting the flow rate of exhaust gas, and the exhaust gas of the incinerator is controlled by an induced fan and an exhaust gas cooler. ,
It is configured to induce the exhaust gas through the exhaust gas treatment device and the remote control damper and discharge it into the atmosphere, and the exhaust gas induced by the induced blower is directed to the remote control damper inlet, the exhaust gas treatment device inlet, the exhaust gas cooler inlet, or the incinerator. A control damper is provided in the exhaust gas return line, and the control damper is controlled by the output of the furnace pressure regulator.
A furnace pressure control method characterized by reducing the exhaust gas return flow rate when the furnace pressure is high and increasing the exhaust gas return flow rate when the furnace pressure is low. (2) The operating speed of the control damper is increased when the furnace pressure becomes positive by increasing the gain on the positive side of the set value of the furnace pressure regulator and decreasing the gain on the negative side. The furnace internal pressure control method according to claim (1). (3) Detecting a sudden change in the furnace pressure to positive pressure,
2. The furnace internal pressure control method according to claim 1, wherein the control damper is operated at an early stage when the furnace internal pressure suddenly changes to positive pressure. (4) A combination of control that changes the gain on the positive and negative sides of the set value of the furnace pressure regulator and control that detects a sudden change in the furnace pressure to positive pressure and operates the control damper early. The furnace internal pressure control method according to claim 1, characterized in that: