JPS6315484B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion device used in various industrial furnaces such as heating furnaces, forging furnaces, and boilers, and other combustion equipment.

BACKGROUND ART As one of the energy saving measures in combustion equipment, burning a burner at a low excess air ratio is a simple and effective method and has recently become popular. However, low excess air ratio combustion is not always preferable, and high excess air ratio combustion may be preferable depending on the situation. For example, in burners designed for high temperatures or using preheated air, low excess air ratio combustion may be performed when the combustion equipment is still in the low temperature range, such as during startup, or when the air is insufficiently preheated. In many cases, combustion is not completed and unburned substances are emitted, resulting in unfavorable safety results.

The present invention has an extremely rational and simple configuration, and by making it possible to freely switch the air ratio, various conditions of the combustion equipment can be judged, and the burner can be set to high excess air ratio combustion for safety and energy saving. One of its features is that it can be easily used for low excess air ratio combustion.

By the way, in order to successfully perform low excess air ratio combustion, various problems must actually be solved. For example, in the combustion equipment mentioned above, an air preheater is often installed to further save energy.In this case, the ventilation resistance of such an air preheater changes depending on the preheating temperature, so the setting increases as the preheating temperature increases. There is a tendency for the air ratio to shift to the low air ratio side. In particular, if the air ratio deviates below 1.0, gas will enter the air preheater, leading to an abnormal temperature rise due to secondary combustion.
This may lead to undesirable results. Therefore, it is necessary to control the air ratio to correct this deviation.

As a general air ratio control method for controlling the air ratio, there is a method in which the exhaust gas components or the flow rates of fuel and air are fed back to the air ratio control section to control the air ratio control element.
In such a system, if there is a malfunction in the control system or measurement system, the correction cannot be performed accurately, and there is a risk that gas may be emitted or combustion may become unstable.

The present invention has an extremely rational and simple configuration, and by controlling the air ratio during combustion with a low excess air ratio, it is possible to control the air ratio during combustion at a low excess air ratio. If combustion becomes unstable, such as when an abnormality occurs in the control equipment for ratio, temperature, furnace pressure, etc., perform high excess air ratio combustion for safety, and when the condition is stable, One of the features is that low excess air ratio combustion is performed while correcting the influence of an air preheater on the air ratio.

The present invention will be described in detail below based on examples.

The figure shows the configuration of the present invention as a system diagram, in which reference numeral 1 is an air pipe, 2 is a fuel pipe, and 3 is a burner. A ratio control section A is provided. 1st
The air ratio control section A shown in the figure shows an embodiment in which a pressure proportional air ratio control method is applied.
, an air-fuel pressure proportional control valve 5 provided on the fuel pipe 2 side and having a function of making the fuel pressure proportional to the air pressure on the secondary side of the main control valve 4; and a fixed valve provided on the air pipe 1 and the fuel pipe 2. It consists of a throttle or resistor 6, 7 such as an orifice or a butterfly valve, and in this configuration, since the pressures of air and fuel are always in a proportional relationship, the air ratio is determined by the throttle or resistor 6, 7.
The air ratio is controlled by determining the aperture area ratio. Also, the air ratio control section A shown in FIG.
1 shows an embodiment in which a two-valve air ratio control system is applied, in which an air flow control valve 8 and a fuel flow control valve 9 are connected by a link 10, and the link 1
By adjusting 0, the air ratio is controlled to be approximately constant. In addition to these, the configuration of the air ratio control section A may be of any type.

Therefore, the first invention provides a throttle or a resistor 11 in the fuel pipe 2 on the downstream side of the air ratio control section A.
A first flow path 12 provided with a flow path 12 and a second flow path forming a bypass of the first flow path 12 and provided with a flow path blocking means 13.
The present invention is characterized in that an air ratio correction section B consisting of a flow path 14 is provided. The flow path blocking means 13 is a valve whose opening and closing are controlled by signals from a suitable restrictor, controller, etc., and for example, this valve is de-energized when the limiter, controller, etc. generates a shut-off signal. The structure shall be such that it can be fully closed by a return means such as a spring. Further, the aperture or resistor 11 of the air ratio correction section B is used when the air ratio control section A has a constrictor or a resistor 7 in the fuel pipe 2 as a component as shown in the embodiment of FIG. , this may also be used.

In this configuration, when the second flow path 14 is not blocked by the flow path blocking means 13 and can freely flow, the fuel flows between the first flow path 12 and the second flow path 1.
Since the air is supplied to the burner 3 through both of the air and air 4, it is possible to carry out low excess air ratio combustion at an appropriate air ratio within the range B shown by hatching in FIG. That is, for example, by controlling the air ratio control section A with a temperature controller and controlling the air ratio correction section B with a flow sensor, it is possible to perform combustion with a low excess air close to 1.0, which is effective for energy saving. Next, when desired, the second
If the flow path 14 of the
Since the air is supplied to the burner 3 only through the flow path 12, combustion with a high excess air ratio can be performed as shown by A in FIG.

Therefore, the first invention provides an appropriate limiter or controller for identifying stability or instability of combustion, for example, a temperature limiter for identifying instability at low temperatures of combustion equipment, a certain time limit at startup, etc. If the system is unstable, a timer is used, or if a malfunction in the control system is identified from the exhaust gas components, flow rate ratio, etc., the flow path blocking means 13 By controlling the It can be used easily. In the present invention, since the air ratio control section A is provided upstream of the air ratio correction section B that switches the air ratio in this manner, each of the above-mentioned combustions can be carried out stably.

With only the configuration of the first invention described above, when an air preheater for energy saving is provided in the air piping 1, the ventilation resistance of the air preheater changes depending on the preheating temperature, so the preheating temperature increases. As a result, the set air ratio shifts to a lower air ratio side, and therefore, when low excess air ratio combustion is performed, the air ratio shifts to 1.0 or less, causing secondary combustion of unused gas that has entered the air preheater. may cause undesirable results such as abnormal temperature rise. A control system and device for preventing this may be appropriate, but the second invention described below makes it possible to do this with an extremely rational configuration.

That is, the second invention is based on the second flow path 1 of the first invention.
4 is characterized in that, in addition to the flow path blocking means 13, a flow path adjusting means 15 is provided.
The flow path adjusting means 15 may be of any type as long as the flow rate through which it passes can be adjusted by an external signal, and it may be constructed integrally with the flow path blocking means 13 as shown in FIG. However, they may be configured independently as shown in FIG. Reference numeral 16 is an air preheater.

In such a configuration, the flow rate distribution between the first flow path 12 and the second flow path 14 is, for example,
4 becomes unable to flow, the standard air ratio (1.3) indicated in the energy saving judgment criteria or a higher excess air ratio is set, and when the second flow path 14 is free to flow and the flow rate is at its maximum, almost the theoretical The distribution shall be such that the air ratio is at or below the air ratio.

Therefore, when combustion is unstable, the second flow path 14 is made inaccessible in the same way as in the first invention, and high excess air ratio combustion can be performed on the safe side. When the shutoff means 13 is opened, the flow path adjustment means 15 is controlled by a control signal from a flow meter, exhaust gas component detection controller, etc., thereby reducing the ventilation resistance of the air preheater 16. The influence on the air ratio due to changes can be automatically corrected, and low excess air ratio combustion can always be performed at an appropriate air ratio. In particular, the present invention corrects the air ratio due to changes in ventilation resistance, rather than by direct control of the air ratio control section A as in the past. Since the correction is made by part B, combustion instability caused by malfunctions in the control system and measurement system of air ratio control part A is not induced.
It is characterized in that both high excess air ratio combustion and low excess air ratio combustion can be carried out stably.

As described above, the present invention provides a first fuel pipe that is provided with a throttle or a resistance in the fuel pipe on the downstream side of the air ratio control section that is provided across the air pipe and the fuel pipe leading to the burner.
Since an air ratio correction section is provided, which includes a flow path and a second flow path that bypasses the first flow path and is provided with a flow path blocking means, high excess air ratio combustion and low excess air ratio combustion can be achieved. Switching between specific combustion and specific combustion can be performed extremely easily and stably. Therefore, when combustion is unstable, high excess air combustion can be used to increase safety, and when combustion is stable, It is possible to achieve energy saving by performing combustion with a low excess air ratio, and has the great feature of being able to enjoy both safety and energy saving. Furthermore, the present invention provides a second aspect of the invention, in which the second flow path in the first invention is provided with a flow path adjustment means in addition to the flow path blocking means, and the flow path adjustment means allows the second flow path to be closed. Since the flow rate of fuel flowing through the second flow path can be adjusted, the difference in air ratio caused by changes in ventilation resistance when an air preheater is installed can be adjusted by adjusting the flow rate of fuel by the flow path adjustment means. The present invention has the great feature that it can be automatically corrected by adjustment, and in addition to the features of the first invention, extremely stable low excess air ratio combustion can be performed.

[Brief explanation of the drawing]

FIG. 1 is a system explanatory diagram of an embodiment of the first invention,
Fig. 2 is a system explanatory diagram of one embodiment of the second invention, Fig. 3 is a system explanatory diagram of another embodiment of the second invention, and Fig. 4 is a system explanatory diagram of an embodiment of the second invention.
The figure is an explanatory diagram of air ratio control in the present invention. 1... Air piping, 2... Fuel piping, 3... Burner, 4
...Main control valve, 5...Air-fuel pressure proportional control valve, 6,7
... Throttle or resistance, 8... Air flow control valve, 9... Fuel flow control valve, 10... Link, 11... Throttle or resistance, 12... First channel, 13... Channel blocking means,
14...Second flow path, 15...Flow path adjustment means, 16...
Air preheater, 17, 17'...flow meter, A...air ratio control section, B...air ratio correction section.

Claims (1)

[Claims] 1. In the fuel pipe on the downstream side of the air ratio control section provided across the air pipe and the fuel pipe leading to the burner,
An air ratio correction unit is provided, which comprises a first flow path provided with a restriction or resistance, and a second flow path forming a bypass of the first flow path and provided with a flow path blocking means,
When the second flow path is made inaccessible by the flow path blocking means at a desired time, high excess air ratio combustion is performed by supplying fuel to the burner only through the first flow path. In addition, when the second flow path is made freely flowable, fuel is supplied to the burner through the first flow path and the second flow path to perform low excess air ratio combustion. A combustion device characterized by: 2. In the fuel pipe on the downstream side of the air ratio control section provided across the air pipe and fuel pipe leading to the burner,
Air ratio correction consisting of a first flow path provided with a restriction or resistance, and a second flow path forming a bypass of the first flow path and provided with flow path blocking means and flow path adjustment means. If the flow path blocking means disables the flow of the second flow path at a desired time, the fuel can be supplied to the burner only through the first flow path to prevent high excess fuel flow. When air-ratio combustion is performed and the second flow path is made freely flowable, the flow path adjustment means adjusts the flow according to the combustion conditions, etc.
A combustion device characterized in that combustion is performed at a low excess air ratio while adjusting the amount of fuel flowing through the second flow path. 3. The combustion device according to claim 2, wherein the flow path blocking means and the flow path adjusting means are constituted by an integrated valve. 4. The combustion device according to claim 2, wherein the flow path blocking means and the flow path adjusting means are each constituted by independent valves. 5. The air ratio control section is a control section of a pressure proportional air ratio control system, and the restriction or resistance of the first flow path is configured to double as a restriction or resistance that is a component of the pressure proportional air ratio control system. A combustion apparatus according to claims 1 and 2, characterized in that: