JPS58190618A - Combustion device - Google Patents

Abstract

PURPOSE:To facilitate the selective use of the combustion of high air ratio for the safety of a burner and the combustion of low air ratio for energy saving of the burner bya method wherein the air ratio is enabled to be changed over so as to judge various conditions in the combustion facility. CONSTITUTION:When a second flow passage 14 is not closed by a flow passage closing means 13 to make a free flow of fuel, the fuel is supplied to a burner 3 through a first flow passage 12 and a second flow passage 14, so that a combustion with low air ratio can be performed. In case that the second flow passage 14 is not enabled to have a flow by the flow passage closing means 13 if desired, the fuel is supplied to the burner 3 only through the first flow passage 12, so that a combustion with a high air ratio cab be performed. Thus, if the flow passage closing means 13 is controlled by the output of ''and'' of the sensing control device (a), (b) etc., an easy selective application of a combustion with a high air ratio and a combustion with a low air ratio can be performed.

Description

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

As one of the energy saving measures in combustion equipment, low air ratio combustion in burners has recently become popular as a simple and effective method.

However, low air ratio combustion is not always preferable, and high air ratio combustion may be preferable depending on the situation. For example, in a burner designed for high temperatures or using preheated air, if low air ratio combustion is 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 the air ratio switchable, it can be easily used for various air ratio combustion in combustion equipment and low air ratio combustion for energy saving. The characteristics are -.

By the way, in order to successfully perform low air ratio combustion, it is actually necessary to solve the problem of each bucket.

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 preheating temperature increases. There is a tendency for the set air ratio to shift toward a lower air ratio. In particular, if the air ratio deviates below 1.0, gas may enter the air preheater, which may lead to an abnormal temperature rise due to secondary combustion, resulting in unfavorable 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 this method, the correction cannot be performed accurately due to malfunctions in the control system or measurement system, 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 low air ratio combustion, in addition to the above, it is possible to
Alternatively, if combustion becomes unstable, such as when an abnormality occurs in the control equipment for air ratio, temperature, furnace pressure, etc., high air ratio combustion is performed for safety, and when the condition is stable. is characterized in that low 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,
Reference numeral 1 is an air pipe, 2 is a fuel pipe, and 3 is a burner.
The air piping 1 leading to the burner 3 and the return air ratio control section A shown in the fuel diagram show an example in which a pressure proportional air ratio control method is applied. A control valve 4, an air-fuel pressure proportional control valve 5 which is provided on the fuel pipe 2 side and has a function of making the fuel pressure proportional to the air pressure on the secondary side of the main control valve 4, and the air pipe 1 and the fuel pipe 2. It consists of a fixed orifice provided, a throttle such as a butterfly valve, or a resistor 6, 7. In this configuration, the pressure of air and fuel is always in a proportional relationship, and the air ratio is determined by the throttle or resistor 6, 7. The air ratio is controlled by determining the opening area ratio of 7.

Further, the air ratio control section A shown in FIG. 6 shows an embodiment in which an exchange valve air ratio control method is applied. The air ratio is controlled to be substantially constant by adjusting the link 10. In addition to these, the configuration of the air ratio control section A may be of any type.

Accordingly, the first invention provides a first flow path 12 provided with a throttle or a resistor 11 in the fuel pipe 2 on the downstream side of the air ratio control section A, and a bypass of the first flow path 12. However, the present invention is characterized in that an air ratio correction section B is provided, which includes a second flow path 14 provided with a flow path blocking means 13. 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, when the limiter, controller, etc. generates a shutoff signal, this valve is de-energized and springs etc. The structure shall be such that it can be fully closed by the return means. 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 such a configuration, when the second flow path 14 is not blocked by the flow path blocking means 13 and can freely flow, the fuel flows through both the first flow path 12 and the second flow path 14. Since the fuel is supplied to the burner 3, low air ratio combustion can be performed. Therefore, when the second flow path 14 is made inaccessible by the flow path blocking means 13 at a desired time, fuel is supplied to the burner 3 only through the first flow path 12.
High air ratio combustion can be performed.

Therefore, the first invention requires 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, If the system is unstable, use a timer, or if a malfunction in the control system is identified from the exhaust gas components, flow rate ratio, etc., use the respective detection controller a.

By controlling the flow path blocking means 13 using the logical product output such as b, it is possible to perform high air ratio combustion for safety when combustion is unstable, and to perform high air ratio combustion for safety when combustion is stable. Low air ratio combustion can be performed, and these can be easily used. 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 above, air distribution:・ When the pipe 1 is provided with an air preheater for energy saving,
The ventilation resistance of the air preheater changes depending on the preheating humidity, so as the preheating temperature rises, the set air ratio shifts to the lower air ratio side, and therefore, when low air combustion is performed,
If the air ratio deviates to 1.0 or less, unfavorable results such as an abnormal temperature rise due to secondary combustion of the gas that has entered the air preheater may occur. 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 characterized in that the second flow path 14 of the first invention is provided with a flow path adjustment means 15 in addition to the flow path blocking means 13.

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. 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 twentieth flow path 14 is determined according to the standard air ratio ( 1, 3) or higher, and the distribution is such that when the second flow path 14 is free to flow and is at its maximum flow rate, the air ratio is approximately equal to or lower than the theoretical air ratio.

Therefore, when the combustion is unstable, the second flow path 14 is made inaccessible in the same manner as in the first invention, and high air ratio combustion can be performed on the safe side, and the combustion becomes stable and the flow path is blocked. When the means 13 is opened, the flow path adjusting means 15
By controlling this using control signals from a flowmeter, exhaust gas component detection controller, etc., it is possible to automatically correct the influence on the air ratio due to changes in the ventilation resistance of the air preheater 16. Low air ratio combustion can be performed at a constant appropriate air ratio. In particular, the present invention corrects the air ratio due to changes in ventilation resistance by direct control of the air ratio control section A, as in the conventional method, by correcting combustion caused by malfunctions in the control system and measurement system of the bowl section A. It is characterized in that it does not induce instability and can stably perform high air ratio combustion and low air ratio combustion valves.

As described above, the present invention includes a first flow path in which a throttle or a resistance is provided in the fuel pipe on the downstream side of the air ratio control section, which is provided across the air pipe and the fuel pipe leading to the burner; An air ratio correction section is provided, which constitutes a bypass of the flow path and a second flow path provided with a flow path blocking means, making it extremely easy to switch between high air ratio combustion and low air ratio combustion. Moreover, it can be carried out stably, so when combustion is unstable, safety is increased by performing high air ratio combustion, and when combustion is stable, energy saving is achieved by performing low air ratio combustion. It has the great feature of being able to enjoy both safety and energy savings. 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 controls the second flow path. Since the flow rate of fuel flowing through the flow path can be adjusted, deviations in air ratio caused by changes in ventilation resistance when an air preheater is installed can be corrected by adjusting the flow rate of fuel using the flow path adjustment means. The present invention has the great feature that it can be automatically corrected, and therefore, in addition to the features of the first invention, low air ratio combustion can be performed extremely stably.

[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 an embodiment of the second invention, and Fig. 6 is a system explanatory diagram of another embodiment of the second invention. It is. 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 upstream control valve, 10... Link, 11...
- Throttle or resistance, 12... First flow path, 13... Channel blocking means, 14... Second flow path, 15... Channel adjustment means, 16... Air preheater, 17, 17'...flow meter, A...air ratio control section, B...air ratio correction section.

Claims (5)

[Claims] (1) A first flow path provided with a restriction or resistance in the fuel pipe on the downstream side of the air ratio control unit provided across the air pipe and fuel pipe leading to the burner; and a second flow path forming a bypass and provided with a flow path blocking means, and when the second flow path is made impossible to flow by the flow path blocking means at a desired time In this case, high air ratio combustion is performed by supplying fuel to the burner only through the first flow path, and when the second flow path is made freely flowable, the fuel is supplied to the burner through the first flow path. A combustion device characterized in that low air ratio combustion is performed by supplying air to a burner through a second flow path and a second flow path. (2) A first flow path provided with a restriction or resistance in the fuel pipe on the downstream side of the air ratio control unit provided across the air pipe and fuel pipe leading to the burner; A secondary bypass provided with a primary bypass and a flow path blocking means and a flow path adjustment means.
an air ratio control section consisting of a flow path, and when the flow path blocking means disables the flow of the second flow path at a desired time, the fuel is supplied to the burner through only the first flow path. By supplying high-air ratio combustion to
When the second flow path is made to freely flow, low air ratio combustion is performed while adjusting the fuel flow density of the second blood path by the nfJ flow path adjustment means according to the combustion conditions etc. A combustion device characterized by: (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 also serves 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 the combustion apparatus has the following configuration.