JP2552995Y2 - Gas fired boiler combustion control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a combustion control device for a gas-fired boiler that performs ON / OFF combustion control or three-position combustion control.

(Conventional technology and its problems) A small gas-fired boiler that performs ON / OFF combustion control or three-position combustion control using a heat demand detection device, as shown in FIG. Stops combustion in response to a heat request stop signal from the request detection device,
The combustion is started in response to a heat request signal from the heat request detection device. When the steam pressure drops to the lower limit pressure and starts combustion, the boiler requires pre-purge, pilot burner ignition, pilot burner ignition confirmation and combustion preparation time from 40 seconds to nearly 1 minute until the main burner ignites. Combustion starts at a pressure lower than the lower limit pressure. For this reason, when the steam demand is large, there is a problem that the steam pressure drops below the required pressure that hinders the load side by the time the main burner is ignited. Therefore, if the lower limit pressure is set so as to be earlier by the combustion preparation time,
If the amount of steam used is low, such as when the use of steam is stopped, even if the steam pressure drops below the required pressure, there is almost no effect since steam is not used in that case, but
The steam pressure must be maintained in a high and narrow range, and the heat loss is increased, and wasteful combustion start and stop frequently occurs.

(Purpose of the invention) The present invention has been made in view of the above-mentioned problems. The purpose of the invention is to prevent the steam pressure from dropping below the required pressure when the steam demand is large and to reduce the steam pressure when the steam demand is small. It is an object of the present invention to provide a combustion control device which reduces unnecessary start and stop, has high load following, and can supply steam stably.

(Means for solving the problems) To achieve the above object, a temperature sensor for measuring the steam temperature in the upper header during combustion stoppage is installed, and a pressure SW or pressure sensor is used as a heat demand detection device. Attach.

A microcomputer incorporated in the combustion control device detects a change in the measured value of the upper header temperature, and detects a temperature change rate of steam. If the steam demand is high and the temperature change rate of the steam is larger than the set value, the prepurge is started before the heat request signal is transmitted so that the main burner can be ignited as soon as the heat request signal is transmitted. . Low steam demand,
When the temperature change rate of the steam is equal to or less than the set value, the prepurge is started after the heat request signal is issued, and then the main burner is ignited.

(Operation of the invention) By detecting the temperature change rate of the steam, the magnitude of the steam demand can be determined. If the steam demand is large, prepurge is performed before the heat request signal is transmitted, and the heat request signal is transmitted. Since the combustion starts immediately, the steam pressure does not become lower than the lower limit pressure at which the heat request signal is transmitted, and the problem that the pressure drops below the required pressure from when the heat request signal is transmitted until combustion starts occurs. do not do. When the steam demand is small, the pre-purge is performed after the heat demand signal is transmitted, and then the combustion is started. Therefore, the steam pressure becomes lower than the lower limit pressure at which the heat demand signal is transmitted. , The pressure does not drop below the required pressure, and the combustion start / stop interval is widened, so that the start / stop frequency can be reduced.

The heat request signal is transmitted at the same lower limit pressure, but the actual start of fuel is divided depending on the amount of steam demand when the heat request signal starts and after the fuel request time elapses from the heat request signal transmission,
Stabilization of steam pressure and prevention of unnecessary combustion start / stop can be achieved at the same time.

(Example) An example of the present invention will be described with reference to the drawings. A temperature sensor 3 is installed to measure the temperature in the upper header 2 of the gas-fired once-through boiler. A heat demand detection device 4 that outputs a heat demand signal or a heat demand stop signal by detecting steam pressure is attached to the boiler main body 1, and the heat demand detection device is connected to a combustion control device 10. The combustion control device 10 is connected to a blower 8, an air volume switching regulator 7, a main burner solenoid valve 5, a pilot burner solenoid valve 6, an ignition device 9, and a flame detection device (not shown). The device controls combustion. When the combustion control device outputs the start of combustion, first, a prepurge is performed by operating the blower, then the solenoid valve for the pilot burner is opened, and the ignition device is operated to ignite the pilot burner,
After that, the main burner solenoid valve is opened to start combustion of the main burner, and a combustion preparation time TC from when the combustion start is output to when the main burner is ignited is input to the combustion control device in advance.

When the steam pressure rises during combustion and a heat request stop signal is output from the heat request detection device to the combustion control device, the combustion control device measures the temperature inside the pipe at the upper header and measures the temperature transition for a certain period of time. I do. If the temperature change rate DT is larger than the constant value CL, a constant value CL is set so that the steam demand is large, and when the temperature change rate DT is larger than the constant value CL, combustion is required from the temperature change rate DT. To find the time TI. Compare TI and TC. If TI> TC, pre-purge is started immediately after TI-TC, and if TI <TC. If the temperature change rate DT is equal to or less than the constant value CL, the prepurge is performed by the heat request signal from the heat request detection device.

(Effects of the Invention) By implementing the present invention, it is possible to reduce the steam pressure when the steam demand is large and to reduce the frequency of starting and stopping the combustion when the steam demand is small, thereby providing an efficient and stable steam supply. Became possible.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a small gas-fired boiler using an embodiment of the present invention. FIG. 2 is an example of a time chart of the three-position combustion control of the gas boiler. FIG. 3 shows the progress of the steam pressure change in the case of the conventional combustion control.
In the embodiment of the present invention, the change in steam pressure when the steam demand is small shows a similar course. FIG. 4 is an example of a progress diagram of a change in steam pressure when the steam demand is large when the present invention is implemented. DESCRIPTION OF SYMBOLS 1 ... Boiler main body, 2 ... Upper header, 3 ... Temperature sensor, 4 ... Heat demand detection device, 5 ... Solenoid valve for main burner, 6 ... Solenoid valve for pilot burner, 7 ... Air volume switching adjustment , 8 ... blower, 9 ... ignition device, 10 ... combustion control device

Claims (1)

(57) [Scope of request for utility model registration] 1. A steam temperature detected by a temperature sensor provided in a steam portion in a boiler and a steam pressure generated by the boiler are detected. When the steam pressure falls below a lower limit pressure, a heat request signal is output. When the heat request stop signal is output, the signal from the heat request detection device that outputs a heat request stop signal is taken into the combustion control device. In the combustion control device of the boiler, the temperature change rate is detected by measuring the steam temperature change and the elapsed time after stopping the combustion by the heat request stop signal, and when the temperature change rate is less than the set value, The prepurge starts after the heat request signal is transmitted, and the main burner is ignited after the time required for combustion preparation has elapsed. If the temperature change rate is greater than the set value, the heat request No. By starting the prepurge before is transmitted, a combustion control device for a gas-fired boiler, characterized in that to be early ignition of Menbana.