JPH03199892A - Control of amount of supply gas for waste heat boiler - Google Patents

Abstract

PURPOSE:To respond the load fluctuation of a heat source quickly and change the amount of supply gas to prevent the generation of back pressure fluctuation and trouble accompanied by the same by a method wherein the objective opening degree of a flow amount changing means is corrected based on the detecting result of a pressure loss generated in a waste heat boiler to regulate the opening degree of the same. CONSTITUTION:The control of the opening degree of a damper 4 is effected in accordance with an opening degree command given from an opening degree control unit 10 while the opening degree control unit 10 is provided with the detecting result of the supplying amount of fuel for a heating furnace 2 from a fuel meter 20, arranged on the half way of a fuel supplying system for the heating furnace 2, and with the detecting result of a pressure loss, generated in a waste heat boiler 1, from a pressure difference detector 21, interposed between the inlet side and the outlet side of a waste heat boiler 1, respectively. The opening degree control unit 10 is provided with a bypass flow amount operator 11, a damper opening degree control operator 12, a corrector 13 and an adder 14 while the detecting value of the supplying amount of fuel, which is detected by the fuel meter 20, is given to the bypass flow amount operator 11 and the detecting result of a pressured loss, detected by the pressure difference detector 21, is given to the corrector 13. Accordingly, when a sudden load fluctuation is generate in the heating furnace 2, the supply amount of gas for the waste heat boiler 1 is changed quickly so as to follow the sudden fluctuation whereby the back pressure increase of the waste heat boiler 1 and the increase of pressure in the heating furnace 2, which is accompanied by the back pressure increase, can be prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is arranged in the middle of a waste gas passage of a heat source such as various industrial heating furnaces, diesel engines, gas turbines, etc., and is operated by the residual heat of the waste gas. The present invention relates to a method for controlling the amount of gas supplied to a waste heat boiler.

[Prior art]

The waste gas discharged from industrial heating furnaces such as metal smelting furnaces as a result of internal combustion retains a large amount of residual heat.In order to effectively utilize this residual heat, waste heat is A heating furnace equipped with a boiler has been put into practical use. In this waste heat boiler, the amount of gas supplied has conventionally been controlled in order to recover as much heat as possible. FIG. 4 shows the implementation state of this supply gas amount control. A model waste heat boiler l is located in the middle of the waste gas passage 3 of the heating furnace 2.
It is arranged to recover the heat retained in the waste gas flowing through it. A bypass passage 5 equipped with a damper 4 as a flow rate changing means is arranged in parallel with the waste gas passage 3, and both are integrated on the downstream side of the waste heat boiler 1.
An exhaust fan 6 is installed further downstream from this position. The waste gas generated as a result of combustion inside the heating furnace 2 is discharged through the waste gas passage 3 and the bypass passage 5 by the operation of the exhaust fan 6; The amount of waste gas, that is, the amount of gas supplied to the waste heat boiler 1 increases (or decreases) as the opening degree of the damper 4 in the middle of the bypass passage 5 becomes smaller (or larger).
Become. The opening degree of the damper 4 is adjusted according to an opening command signal given to it from an opening degree control section 30. A detection result is provided from a temperature detector 31 disposed downstream of the waste heat boiler 1. And the opening control section 30 is
When the exhaust gas temperature given from the temperature detector 31 is high,
An operation is performed to give a signal to the damper 4 to reduce its opening degree, and as a result of this operation, the amount of gas supplied to the waste heat boiler 1 increases, resulting in an increase in the amount of recovered heat.

[Problem to be solved by the invention]

However, in this supply gas amount control method, since the opening degree of the damper 4 is adjusted according to the temperature of the waste gas after passing through the waste heat boiler 1, which is detected by the temperature detector 21, the opening degree of the damper 4 is adjusted. When a sudden load change occurs, the opening degree is not changed promptly to follow the change, and the back pressure of the waste heat boiler 1 increases, resulting in an increase in the internal pressure of the heating furnace 2. there were. In industrial heating furnaces, there is generally an upper limit to the furnace internal pressure, and the increase in furnace internal pressure that occurs as described above can cause various problems in terms of maintenance of the heating furnace 2, such as damage to the furnace wall and blowing out of combustion gas. invite.

That is, implementation of the conventional supply gas control method in the waste heat boiler 1 impedes maintenance of the heating furnace 2, and cannot be said to be a desirable method.

The above-mentioned difficulties similarly occur in a waste heat boiler disposed in the waste gas passage of a heat source other than the heating furnace 2, such as a gas turbine or a diesel engine.

The present invention has been made in view of the above circumstances, and is capable of changing the supply gas amount with high response to load fluctuations occurring in a heat source, thereby preventing back pressure fluctuations and the associated inconveniences. It is an object of the present invention to provide a method for controlling the amount of gas supplied to a waste heat boiler.

[Means to solve the problem]

In the method for controlling the amount of gas supplied to a waste heat boiler according to the present invention, a bypass passage equipped with a flow rate changing means is provided in parallel to the waste gas passage of a heat source, and by adjusting the opening degree of the flow rate changing means, a bypass passage is provided in the middle of the waste gas passage. In the method of controlling the amount of gas supplied to a disposed waste heat boiler, the amount of gas generated inside the heat source is calculated using the amount of fuel supplied to the heat source, and the calculated amount of gas is set in advance. When the amount exceeds the fixed amount, a target opening degree of the flow rate changing means is determined so that an amount equivalent to the difference between the two flows through the bypass passage, and this result is based on the detection result of the pressure loss occurring inside the waste heat boiler. The present invention is characterized in that the opening degree is adjusted to achieve the corrected target opening degree.

[Effect]

In the present invention, the load fluctuation of the heat source is regarded as the amount of fuel supplied to the heat source, the bypass flow rate to the bypass passage is determined from the generated gas amount calculated based on this, and the flow rate changing means is opened to realize this. Feedforward control is performed to adjust the temperature, and the amount of gas supplied to the waste heat boiler is maintained at a predetermined amount with high responsiveness to prevent back pressure from increasing.
The adjustment amount of the opening degree is corrected based on the pressure loss occurring inside the waste heat boiler, a predetermined amount of gas to be supplied to the waste heat boiler is ensured, and as much waste heat as possible is recovered.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is a schematic diagram showing the implementation state of the method for controlling the amount of gas supplied to a waste heat boiler according to the present invention (hereinafter referred to as the method of the present invention).

In the figure, l is a waste heat boiler disposed halfway in the waste gas passage 3 of the heating furnace 2, and the waste gas passage 3 has a bypass passage 5 equipped with a damper 4 as a flow rate changing means in the middle. They are installed in parallel. Both roads 3.5 are unified on the downstream side of the waste heat boiler 1 and communicated with the exhaust port via the exhaust fan 6, and the waste gas generated as a result of combustion inside the heating furnace 2 is
Due to the operation of the exhaust fan 6, the waste gas is discharged through the waste gas passage 3 and the bypass passage 5. At this time, the amount of waste gas flowing through the waste gas passage 3, that is, the amount of gas supplied to the waste heat boiler 1, is changed according to the opening degree of the damper 4, as in the conventional case.

Now, in the method of the present invention, the configuration of the control system for adjusting the opening degree of the damper 4 is different from the conventional method. The opening degree of the damper 4 is adjusted in accordance with an opening degree command given from an opening degree control section 10, and this opening degree control section 10 includes a fuel gauge disposed midway in the fuel supply system to the heating furnace 2. 20, the detection result of the amount of fuel supplied to the heating furnace 2 is detected from the differential pressure detector 21 interposed between the inlet and outlet sides of the waste heat boiler 1.
The detection results of the internal pressure loss are given respectively.

The opening control section 10 includes a bypass flow rate calculator 11, a damper opening degree calculator 12, a corrector 13, and an adder 14, and the detected value of the fuel supply amount by the fuel meter 20 is sent to the bypass flow rate calculator 11. Further, the pressure loss detection result by the differential pressure detector 21 is provided to the corrector 13. The bypass flow rate calculator 11 calculates the amount of waste gas to be made to flow through the bypass passage 5 side, that is, the amount of passing gas 2, and calculates the amount of fuel supplied to the heating furnace 2 i1.
For example, an arithmetic expression G (x) as shown in the following expression is set for calculating from x.

z = G (x) −Ko ・KI ・x−y
−=(1) However, Ko is a constant, K1 is a constant determined depending on the type of fuel supplied, and (the first term on the right side of Equation 11 represents the total amount of waste gas generated by combustion inside the heating furnace 2. In addition, y is the rated gas amount of the waste heat boiler 1. Therefore, the passing gas amount 2 determined by equation (1) is the deviation between the total amount of waste gas and the rated gas amount of the waste heat boiler 1. , if this is achieved in the bypass passage 5, the amount of gas supplied to the waste heat boiler 1 will be kept below the rated gas amount y, regardless of the amount of waste gas generated from the heating furnace 2. The back pressure of boiler l is maintained below a predetermined pressure.
Ko, KI, and y are input into the bypass flow rate calculator 11 in advance. The bypass flow rate calculator 11 is connected to the fuel gauge 2
Using the detected value of the fuel supply amount X that is sequentially input from 0 to
It is calculated according to Formula 11, and the calculation result is given to the damper opening degree calculator 12.

The damper opening degree calculator I2 has a relationship established between the opening degree 2' of the damper 4 and the amount of passing gas 2 generated in the bypass passage 5 as shown in FIG. It is set as an arithmetic expression F (z) for determining the opening degree 2'. The damper opening degree calculator 12 calculates the target value of the damper opening degree 2' in the damper 4 using the target value of the passing gas amount 2 given from the bypass flow rate calculator 11, and this result is sent to the adder 14. It is given.

On the other hand, the corrector 13 uses the detected value of the pressure loss in the waste heat boiler 1 given from the differential pressure detector 21.
A correction amount α (positive or negative value) of the damper opening required to optimize this pressure loss is calculated by fixed value calculation, and this result is given to the adder 14.

The output signal of the adder 14, that is, the target value of the damper opening degree 2' calculated sequentially by the damper opening degree calculator 12, is sent to the damper 4 using the correction amount α calculated by the corrector 13. The corrected target opening degree is given as an opening command signal, and the opening degree of the damper 4 is successively adjusted to match this target opening degree.

That is, the method of the present invention carried out as described above calculates the total amount of waste gas generated inside the heating furnace 2 from the amount of fuel supplied to the heating furnace 2, and adjusts the amount of gas supplied to the waste heat boiler 1 to a predetermined value. Feedforward control calculates the amount of gas passing through the bypass passage 5 necessary to maintain the gas amount below the rated gas amount and adjusts the opening of the damper 4 to achieve this, so sudden load fluctuations in the heating furnace 2 are avoided. Even if the waste heat boiler 1
The amount of gas supplied to the waste heat boiler 1 is changed accordingly, and an increase in the back pressure of the waste heat boiler 1 and an accompanying increase in the internal pressure of the heating furnace 2 can be prevented.

Furthermore, the damper 4 is determined to achieve the above-mentioned amount of passing gas.
Since the target opening degree of is corrected based on the pressure loss inside the waste heat boiler, fluctuations in the amount of gas supplied to the waste heat boiler 1 due to disturbance in the pressure balance between the waste gas passage 3 and the bypass passage 5 can be prevented. This is effectively suppressed, and as much waste heat as possible can be recovered in the waste heat boiler 1.

FIG. 3 shows the changes in pressure loss that occur before and after the waste heat boiler 1 when the amount of fuel supplied to the heating furnace 2 is changed.
It is a graph showing a comparison between the case where the method of the present invention is carried out and the conventional method in which the damper 4 is given a predetermined opening degree corresponding to the fuel supply amount.

As is clear from this figure, the fuel flow rate is approximately 50% of the maximum flow rate.
In response to the opening of the damper 4 that starts after reaching , in the conventional method, a sudden decrease in pressure loss occurs, whereas in the method of the present invention, there is no fluctuation in pressure loss. , is maintained at a substantially constant value, and it can be seen that fluctuations in the furnace pressure in the heating furnace 2 are effectively suppressed by implementing the method of the present invention.

Table 1 also shows the amount of waste heat recovered by implementing the method of the present invention in comparison with that by the conventional method. Note that the values in this table are percentage values assuming that the waste heat recovery amount obtained in the waste heat boiler 1 by supplying the rated gas amount is 100χ, and the fuel flow rate is based on the maximum flow rate in the heating furnace 2 being I.
It is a percentage value of OOX.

In the method of the present invention, the fuel flow rate to the heating furnace 2,
In other words, regardless of the load on the heating furnace 2, the amount of waste heat recovered is always the same as when the rated gas amount is supplied.
In the conventional method, as is clear from the decrease in pressure loss that occurs inside the waste heat boiler 1 as shown in Figure 3, a sufficient amount of gas supply cannot be secured, and as a result, As is clear from Table 1, the amount of waste heat recovered also decreases as the load on the heating furnace 2 increases.

In this embodiment, a case has been described in which the heat source is an industrial heating furnace 2, but the heat source is a gas turbine.

It goes without saying that method 1 of the present invention can be applied to heat sources such as diesel engines that generate waste gas that retains residual heat through internal combustion.

Further, the flow rate changing means in the bypass passage 5 is not limited to the damper 4 shown in this embodiment, and other flow rate changing means may be used.

〔effect〕

As detailed above, in the method of the present invention, the amount of gas passing through the bypass passage and the target opening degree of the flow rate changing means to achieve this are determined from the amount of generated gas calculated using the amount of fuel supplied to the heat source. Since feedforward control is performed based on this target opening degree, it is possible to control the amount of supplied gas that follows load fluctuations with high responsiveness, reducing the increase in back pressure of the waste heat boiler and the resulting inconvenience caused to the heat source. This can be prevented, and since the target opening degree is corrected based on the pressure loss inside the waste heat boiler, a predetermined amount of gas to be supplied to the waste heat boiler can be ensured, and as much waste heat as possible can be supplied to the waste heat boiler. The present invention has excellent effects such as a large amount of recovery.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the implementation state of the method of the present invention, Fig. 2 is a graph showing an example of the relationship between the damper opening degree and the amount of passing gas, and Fig. 3 is a waste heat boiler in the method of the present invention and the conventional method. FIG. 4 is a graph showing the results of comparing the pressure loss before and after, and is a schematic diagram showing the state of implementation of the conventional supply gas amount control method. 1... Waste heat boiler 2... Heating furnace 3... Waste gas passage 4... Damper 5... Bypass passage 10... Opening degree control section 20... Fuel gauge 21.
・Differential pressure detector

Claims (1)

[Claims] 1. A waste heat boiler in which a bypass passage equipped with a flow rate changing means is arranged in parallel to the waste gas passage of the heat source, and the opening degree of the flow rate changing means is adjusted to provide a waste heat boiler disposed in the middle of the waste gas passage. In the method of controlling the amount of gas supplied to the heat source, the amount of gas generated inside the heat source is calculated using the amount of fuel supplied to the heat source, and when this calculated amount of gas exceeds a predetermined amount set in advance, both A target opening degree of the flow rate changing means is determined so that a deviation equivalent to A method for controlling the amount of gas supplied to a waste heat boiler, characterized in that the opening degree is adjusted to achieve a target opening degree.