JP2862604B2 - Combustion protection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a fuel control device, and more particularly to a combustion control suitable for preventing an accident such as an explosion due to abnormal combustion in response to a decrease in air flow required for fuel. Related to a protective device.

[Prior Art] In a conventional combustion apparatus, a method has been adopted in which an abnormal state of combustion is detected by a fire detector, and when a misfire state is detected, fuel is shut off. However, since fire detectors detect unstable flames during combustion, it is difficult to stably detect the combustion state, and there are many problems to use as a protection device, and various types of products have been improved. , Has been developed.

FIG. 4 shows an example of using a cross limit circuit, which is a typical example.

In the state where the air flow is insufficient with respect to the fuel flow, the fuel control by the illustrated device does not increase the fuel, and at the same time, the air flow is larger than the fuel flow.
A method of providing a selection circuit in a control signal has been adopted.

In addition, in the cross limit circuit, a constant control width is provided to perform the limiting operation so that it does not operate due to fluctuations during normal control.Therefore, in the limited operation state, a certain deviation remains and the operator's correction Operation was required. This corrective operation is an emergency and may cause erroneous operation.
There was a need for a method for preventing operator misoperation.

Further, in the example of use of the cross limit circuit shown in FIG. 4, the circuit operates on the upstream side of the automatic manual switching device, and does not function in the operating state.

[Problems to be Solved by the Invention] The prior art has only a cross limit circuit even when the air-fuel ratio becomes abnormal in fuel control, and a corrective operation by manual operation is required, but an erroneous operation preventing means at the time of manual operation is required. Had not been taken. Further, even if the air flow rate drops abnormally, only protection by a flame detector is provided.

For this reason, when the air flow rate is reduced by half with respect to the fuel flow rate, or in the manual operation state where the protection operation by the cross limit circuit is not applied, and when the operation terminal goes out of control, the flame detector may not detect the complete flame misfire. And fuel protection was inadequate.

For this reason, in the above prior art, explosion accidents cannot be protected, and several accidents are reported annually.

An object of the present invention is to prevent these accidents from occurring, and to provide a fuel protection device that operates promptly and reliably when the air-fuel ratio becomes abnormal in fuel control, and provides a plant state quantity. Based on the above, it is intended to perform reliable combustion protection and prevent erroneous operation.

[Means for Solving the Problems] The object of the present invention is achieved by the following configurations.

That is, in a fuel device having combustion flow rate detection means, fuel flow rate control means, air flow rate detection means, and air flow rate control means, a fuel flow rate signal from the fuel flow rate detection means or a signal having a functional relationship with the fuel flow rate and an air flow rate detection An air-fuel ratio calculating means for calculating an air-fuel ratio based on the air-flow ratio signal from the means, and an air-fuel ratio calculated by the air-fuel ratio calculating means. A combustion protection device characterized in that an interlock mechanism is provided which does not permit an increase in fuel even if the manual automatic operation devices of the flow control means and the air flow control means are manually operated.

[Operation] The air-fuel ratio is calculated by the air-fuel ratio calculating means based on the fuel flow rate signal from the fuel flow rate detecting means from the fuel flow rate detecting means or the signal having a functional relationship with the fuel flow rate and the air flow rate signal from the air flow rate detecting means. When the air flow detection value decreases to a set value at which the fuel cannot be continued based on the air-fuel ratio obtained by the air-fuel ratio calculation means, an interlock mechanism is provided in each of the fuel flow control means and the air flow control means. Is provided, the fuel supply amount does not increase even if this operation end is set to manual operation.

Embodiment FIG. 1 shows an embodiment of the present invention.

Fuel flow transmitter 1, air flow transmitter 2, excess air flow correction characteristic relay 3 for fuel flow, comparison ratio calculation relay 4, air-fuel ratio decrease detector 5, and air flow lower limit detector 6
(Here, if the control range is within the range of the upper limit and the lower limit, for example, the trip limit is the lower and lower limits.) , Unit trip.

In FIG. 1, the result of calculating the ratio of the air flow rate to the fuel flow rate is output as air-fuel ratio signals 21, 22, and 23. Also, air flow signals 24, 25, 26
An air flow rate lower limit detector 6 is installed in the air conditioner, and the air flow rate lower limit value is taken out as a contact signal. If any two of the three contacts are operating based on these two contact signals, an AND circuit 14 that trips the unit is configured to ensure the operation of the equipment. Even so, a functionally similar circuit can be configured. The OR circuit 16 constitutes a circuit that causes a unit trip even if any two circuits operate.

When the unit trip fuel cutoff valve is fully closed based on the circuit shown in FIG. 1, the operation of the interlock mechanism shown in FIG. 2 is performed.

In this case, it is an interlock block diagram showing a protection device that adds an operation prohibition interlock to the decrease operation circuit of the air selector station 11 due to a decrease in the air-fuel ratio and adds an operation prohibition interlock to the increase operation circuit of the fuel selector station 12. . Timer 13 for timed operation, AND
It comprises a circuit 14 and a NOT circuit 15 which means the opposite of the condition.

In FIG. 2, if the air-fuel ratio reduction state is continuously detected for several seconds on the condition that the air control system is manual, the air selector station 11 operates so that the reduction operation cannot be performed. Similarly, in the fuel system, in the fuel system manual state, the fuel selector station 12 prohibits the fuel increase operation when the air-fuel ratio lowering state is detected for several seconds. Next, instead of the circuit for fully closing the unit trip fuel cutoff valve shown in FIG. 1, the circuit shown in FIG. 3 is used to perform the operation for fully closing the unit trip fuel cutoff valve, and then the interface shown in FIG. 7 shows an embodiment in which the operation of the lock mechanism is performed.

This circuit is used for co-firing boilers with many types of fuels. The total fuel flow rate 7 is taken out from the control unit as the fuel flow rate, and two load signals MW8, which are boiler outputs, are used. The structure is similar to that of FIG. With this device,
Although a highly reliable circuit configuration is possible, the circuit can also be configured with only one load signal system and one air flow rate system. By setting the characteristic relay 3 as an air flow rate with respect to the load in consideration of the excess air ratio, the same function as the embodiment shown in FIG. 1 can be obtained.

[Effects of the Invention] According to the present invention, the unit is stopped and the fuel is shut off without continuing the abnormal state of the fuel even in the abnormal state of the fuel control apparatus or the runaway of the operating end, so that the fuel system Can be protected, and serious accidents such as explosions can be prevented.

Even in the manual operation, there is an effect that the manual operation can be stably performed by interlocking so that the operation in the direction in which the fuel deteriorates cannot be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of an air-fuel ratio lowering unit trip detecting circuit according to the present invention, FIG. 2 is a circuit diagram of a manual operation prohibiting circuit when the air-fuel ratio is lower according to the present invention, and FIG. FIG. 4 is a cross-limit circuit diagram of a conventional control device of a fuel ratio reduction unit trip detection circuit. 1. Fuel flow rate detecting means 2. Air flow rate detecting means

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yasuhiro Yamachi 4-6-6 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi, Ltd. (56) References JP-A-63-108114 (JP, A) JP-A-58- 142115 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F23N 5/24 F23N 1/02

Claims (1)

(57) [Claims] In a fuel system having combustion flow rate detection means and fuel flow rate control means, and air flow rate detection means and air flow rate control means, a fuel flow rate signal from the fuel flow rate detection means or a signal having a functional relationship with the fuel flow rate is provided. The air flow rate signal from the air flow rate detection means has reduced the air flow rate detection value to a set value at which fuel cannot be continued based on the air-fuel ratio calculation means for calculating the air-fuel ratio and the air-fuel ratio obtained by the air-fuel ratio calculation means. In this case, an interlock mechanism that does not allow an increase in fuel even when the manual automatic operation devices of the fuel flow rate control means and the air flow rate control means are manually operated is provided.