JP2008101842A - Abnormality detecting method of combustion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abnormality detecting method of a combustion device capable of easily detecting not only abnormality in supply systems for fuel and air but also abnormality in an overall combustion device in an early stage. <P>SOLUTION: In this abnormality detecting method of the combustion device controlling the combustion by controlling flow rates of fuel and air or an opening of a flow rate control valve, the relationship between the opening of flow rate control valve and the flow rates is determined in advance, and the abnormality is determined when both measured values depart from an allowable range of the relationship. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for detecting an abnormality in a combustion apparatus installed in a heating furnace, an annealing furnace, or the like.

  With the development of industry, a wide variety of energy is consumed, but it must be burned in the process of converting chemical energy, such as liquid, gas, solid, etc., into energy that is easy to use, such as heat, electricity, mechanical energy, etc. It will be accompanied by a phenomenon. Combustion requires fuel and air (oxygen). The basis of combustion control in a combustion device is that the ratio of air flow rate to fuel flow rate is always within a predetermined appropriate range no matter how the combustion load changes. It is to control while maintaining.

  As a combustion control method for that purpose, a parallel type in which the fuel flow rate and the air flow rate are controlled in parallel by the output signal of the temperature controller, the air flow rate is first controlled by the output signal of the temperature controller, and further the fuel flow rate by the actually measured air flow signal There are known an air-advanced type that controls the flow rate, a fuel-advanced type that first controls the fuel flow rate based on the output signal of the temperature controller, and further controls the air flow rate based on the measured fuel flow rate signal.

  In the conventional combustion control method, the flow control of fuel and air is generally performed by controlling the valve opening degree of the flow control valve. For example, in Patent Document 1, a relationship between a load of gas fuel to be burned and a valve opening is obtained in advance, a valve opening for a load designated by the relationship is selected, and a fuel flow rate is set so as to be the opening. A control method for a gas combustion apparatus for controlling a control valve is disclosed.

By the way, when the combustion apparatus installed in a heating furnace, an annealing furnace, or the like loses the flow rate balance between fuel and air, there is a risk that a fire may extinguish or a serious trouble such as abnormal combustion or explosion may occur. Therefore, the detection of abnormality in the combustion device is extremely important, and monitoring of the actual flow rate (actual value) with respect to the fuel and air flow rate setting value (target value) and the actual valve with respect to the setting value of the flow control valve opening A system that detects an abnormality by monitoring the opening is generally employed.
JP-A-11-270843

  The above abnormality detection method assumes that the value displayed on the flow meter of fuel or air or the display value of the valve opening of the flow control valve is correct until it gets tired, and then performs abnormality detection. is there.

  However, the display of the flow meter or the valve opening may not represent a true value. For example, the valve opening and the actual flow rate do not necessarily have a linear relationship, and an error is likely to occur when the flow rate control is performed via the valve opening control. Also, there may be an abnormality in the flow meter or the flow control valve itself. In such a case, the display of the flow meter and the flow control valve opening is not different from the set value, and therefore, it is not possible to detect an abnormality only by these monitoring.

  Even if the flow meter and valve opening indication are correct, if there is a problem in other parts of the combustion device, for example, if the fuel or air supply pipe is clogged, the flow control valve Even if the opening of the is increased, the actual flow rate does not increase. Furthermore, if a burner is blocked or a flue is clogged, if it is mild, it can be handled by flow control or valve opening control. The above-mentioned abnormality cannot be detected only by monitoring the degree.

  For this reason, with the conventional abnormality detection method that monitors only the flowmeter of the fuel or air or the flow control valve opening, the combustion control is performed in an abnormal direction, or the abnormality is not made until the situation becomes serious. Since it cannot be found, there is a great risk that the fuel / air balance will be lost, causing serious troubles such as misfire, abnormal combustion, and explosion, or causing serious troubles in the combustion apparatus itself.

On the other hand, a method is known in which the CO or O ₂ concentration contained in the exhaust gas of the combustion apparatus is analyzed, and the abnormality of the combustion apparatus is detected from the result. However, this method has a problem that real-time abnormality detection is difficult because gas analysis can be performed only intermittently, and it takes time until results are obtained, and is not practical.

  Accordingly, an object of the present invention is to propose a combustion apparatus abnormality detection method capable of early and simply detecting abnormality not only in fuel and air supply systems but also in the entire combustion apparatus.

Inventors repeated examination in order to solve the said problem which a prior art has.
As a result, the target value and actual value of the flow rate of the fuel and air and the flow control valve opening are compared with each other, and it is not determined whether or not the combustion control is normally performed. The relationship with the flow rate is obtained in advance, and if the measured value of the flow control valve opening and the flow rate is within the predetermined allowable range of the above relationship, it is determined to be normal, and if it deviates from that range, it is determined to be abnormal. As a result, it was found that the above problems could be solved, and the present invention was completed.

  That is, the present invention obtains the relationship between the valve opening and the flow rate in advance in a combustion apparatus abnormality detection method for performing combustion control based on the flow rates of fuel and air or the valve opening of the flow control valve. However, the abnormality detection method for the combustion apparatus is characterized in that an abnormality is determined when the value deviates from a predetermined allowable range.

  In the method of the present invention, the relationship between the valve opening and the flow rate is a relationship between the valve opening and the flow rate of the flow rate control valve actually measured in a normal state.

  Further, the method for determining an abnormality in the present invention is a method of comparing a flow rate obtained from a relationship between a normal valve opening and a flow rate at a certain valve opening and a flow rate measured at the time of abnormality determination, The absolute value of the deviation or the difference between both flow rates deviates from a predetermined allowable range.

  According to the present invention, by sequentially confirming that the relationship between the flow rate of the fuel or air and the valve opening is within a predetermined allowable range, even if there is no apparent abnormality in the combustion device, the flow meter or flow control Abnormalities such as valve abnormalities, burner nozzle clogging, clogging of the fuel or air supply system or exhaust system, and changes in pressure loss in the system can be detected at an early stage, and an alarm can be issued. Therefore, by applying the abnormality detection method of the present invention in addition to the conventional abnormality detection method, not only early abnormality detection or early repair of the combustion device is possible, but also improvement of safety and realization of stable operation are realized. Also contributes.

  FIG. 1 schematically shows a combustion control system diagram of a conventional combustion apparatus. For example, in the case of a fuel-advanced control system, a temperature controller (TIC) is usually connected to a combustion apparatus (burner). The difference between the actual temperature measured with the attached thermometer and the target temperature is given as an output signal to the fuel flow controller (FIC-F), and the FIC-F determines the target value to eliminate the difference. Then, the fuel flow meter or the fuel flow control valve is instructed to control the fuel flow rate or the valve opening, and the air flow controller (FIC-A) is empty in the actual fuel flow or valve opening signal. Using a signal multiplied by the fuel ratio coefficient as a target value, an instruction is given to the fuel flow meter or the flow control valve to control the air flow rate or the valve opening.

  In the combustion apparatus, the abnormality is detected by constantly monitoring whether or not the target values and the actual values of the flow rates of the fuel and air or the valve opening coincide with each other. However, as described above, in the above abnormality detection method, when there is an abnormality or an error in the valve opening degree of the flow control valve or the display of the flow meter, the optimum combustion control is not always performed. Also, if the fuel or air supply piping is clogged, the nozzle is blocked, or the air fan is abnormal (belt slip, rotational speed abnormality, etc.) It is impossible to detect an abnormality because it can be dealt with by expanding the number of times, and when an abnormality is detected, it often leads to a serious trouble.

  Therefore, as shown in FIG. 2, the present invention obtains the relationship between the valve opening and the flow rate in advance in a combustion apparatus that performs combustion control based on the flow rates of fuel and air or the valve opening of the flow control valve. When the relationship between the two deviates from the predetermined allowable range, it is determined that there is an abnormality, that is, the fuel or air flow control valve opening or flow rate display (measured value) is relative to the target value (set value). The relationship between the valve opening and the flow rate in a normal state is determined in advance, the allowable range predicted from the relationship is set, and then the measured valve opening and Check whether the flow rate relationship is within the above-mentioned tolerance range, and if it deviates from that, adopt an abnormality detection method that determines that the valve opening and flow rate are normal even if the display is normal It was decided.

  As for the relationship between the valve opening and flow rate of the flow control valve, the characteristic curve described in the purchase specifications of the flow control valve may be used, but the relationship between the valve opening and flow rate is Therefore, in order to detect an abnormality with higher accuracy, it is preferable to use the relationship between the valve opening degree of the flow control valve and the flow rate actually measured in an actual machine during normal operation. For reference, FIG. 3 shows the relationship between the valve opening and the flow rate when the butterfly valve measured with an actual machine is normal.

  Further, in the present invention, as a method of determining an abnormality, a flow rate obtained from the relationship between a normal valve opening and a flow rate at a certain valve opening is compared with a flow rate measured at the time of abnormality determination, and both flow rates are determined. It is preferable that the absolute value of the deviation or the difference between the two flow rates deviates from a predetermined allowable range. Here, the deviation is the ratio of the flow rate at the time of abnormality determination to the normal flow rate (flow rate at the time of abnormality determination / normal flow rate), and the absolute value of the difference between the two flow rates is (normal It is desirable to set the permissible range appropriately depending on the level of abnormality detection accuracy required.

  As a result, for example, if there is an error in the flow meter or valve opening indication of the fuel supply system pipe, even if the target temperature of the combustion device is secured, the display of the flow meter of the fuel supply system Since the relationship between the valve opening degrees of the flow rate control valves deviates from the predetermined allowable range, it can be understood that either the flow meter or the valve opening degree is abnormal.

  Also, for example, if the fuel supply system piping is clogged, the combustion control function will increase the valve opening of the fuel control valve to ensure the flow rate and achieve the target combustion temperature. Therefore, no abnormality is detected only by comparing the target value of the conventional fuel flow rate with the actual measurement value. However, even in such a case, looking at the relationship between the valve opening and the flow rate of the fuel control valve, the valve opening to obtain the same flow rate is larger than that at normal time, Can be detected.

  Further, for example, when slip occurs between the pulley of the air fan that supplies air and the belt, and the slip is light, the air flow control valve is opened by increasing the valve opening degree. Since the flow rate can be secured, no abnormality is detected by the conventional method. However, according to the method of the present invention, the relationship between the valve opening degree and the flow rate of the air flow control valve deviates from the predetermined allowable range, so that it is possible to easily detect an abnormality.

  As described above, according to the abnormality detection method of the present invention, it is possible to detect an abnormality over the entire combustion apparatus that could not be detected conventionally with high accuracy and before a serious trouble occurs. Further, the abnormality detection method of the present invention is not contrary to the conventional combustion control method in which the actual value (PV) is compared with the target value (SV) and controlled, and is used for the conventional combustion control. Since the existing instruments can be used as they are, it is possible to complement the conventional abnormality detection method by combustion control and realize more excellent abnormality detection at low cost.

  The abnormality detection technology of the present invention is not limited to the abnormality detection method of the combustion device, but the technical field for controlling the flow rate of gas or liquid using a flow meter and a flow control valve, the target value and the actual value. It can be applied to all technical fields where control is performed in comparison.

It is a schematic diagram explaining the control system figure of the conventional combustion apparatus. It is a figure explaining the abnormality detection method of this invention. It is a graph which shows the valve opening degree and flow rate of a butterfly valve.

Claims (3)

In an abnormality detection method for a combustion apparatus that performs combustion control based on the flow rates of fuel and air or the valve opening of a flow control valve, the relationship between the valve opening and the flow is obtained in advance, and the relationship between the two is within a predetermined allowable range. An abnormality detection method for a combustion apparatus, characterized in that an abnormality is determined when deviating from the above. 2. The combustion apparatus abnormality detection method according to claim 1, wherein the relationship between the valve opening and the flow rate is a relationship between the valve opening and the flow rate of the flow rate control valve actually measured during normal operation. The method for determining an abnormality is to compare the flow rate obtained from the relationship between the normal valve opening and the flow rate at a certain valve opening with the flow rate measured at the time of abnormality determination, The abnormality detection method for a combustion apparatus according to claim 1 or 2, wherein the absolute value of the difference deviates from a predetermined allowable range.

Images