JPS60226604A - Controller for temperature of steam from coal burning boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a steam temperature control device for a boiler.

Conventional steam temperature control for coal-fired boilers is a method that measures the steam temperature to be controlled and maintains the steam temperature at a set value using a feedback method using a proportional integral function to calculate the difference from the set value.

Methods for keeping the steam temperature at the set value include cooling water spray, burner tilt, gas recirculation, and gas damper methods for drum-type boilers, and water-fuel ratio methods for supercritical pressure boilers in addition to drum-type boilers. It is taken.

On the other hand, the current trend is to drastically reduce the number of soot blowers used in coal-fired boilers in order to save energy, but operating the soot blower also has a great effect in removing dirt from heat transfer surfaces. In the conventional control method based on the deviation between the steam temperature and the set value, the deviation of the steam temperature becomes large (and is becoming large).

However, according to the conventional method, when the amount of heat absorption on the heat transfer surface decreases, the soot blower is operated according to a command from the soot blower startup board, which improves the heat absorption on the heat transfer surface, and the outlet of the heat transfer surface The steam temperature rises. In order to lower this increased temperature, it is necessary to spray a large amount of cold water into the desuperheater to lower the air temperature at the inlet lid of the heat transfer surface.

However, in the past, control was performed by the outlet steam temperature of the heat transfer surface, and although the soot blower operation would improve heat absorption and thereby lower the inlet steam temperature, a momentary deviation would occur, resulting in a reduction in heat absorption. The drawback was that the warmer was delayed in operation.

The present invention has been made to solve these conventional problems, and takes into consideration the fluctuations in steam temperature that inevitably occur when cleaning the heat transfer surface by operating the soot blower, and makes it an advance operation of the current control method. Therefore, it is an object of the present invention to provide a steam temperature control device that eliminates steam temperature fluctuations during operation of a soot blower.

A preferred embodiment of the present invention will be described in detail below with reference to the drawings.

The drawing shows an example of a steam temperature control device for a coal-fired boiler equipped with a soot blower.

The temperature measured by the steam temperature detector 1 is determined by the steam temperature setting device 2.
The deviation is calculated by the controller 3A, and the cold water control valve 4 is opened and closed to spray cold water onto the steam exiting the heat transfer surface 5A in the desuperheater 6 to lower the temperature. After heat absorption, the steam temperature measured by the steam temperature detector 1 is made to have no deviation from the setting device 2.

Therefore, in this embodiment, the soot blower 7 is placed on the heat transfer surface 5B.
is installed, the heat transfer surface becomes dirty with ash, the heat absorption of the heat transfer surface 5B decreases, the cold water control valve 4 closes and eventually becomes fully closed, and if it gets even more dirty, the steam temperature will drop below the set temperature. Become. At such times, the soot blower 7 operates to clean the dirt on the heat transfer surface 5B. As a result, if the heat absorption of the heat transfer surface 5B becomes good, it is naturally necessary to lower the inlet temperature of the heat transfer surface 5B. In order to lower this inlet temperature, the cold water control valve 4 must be opened.

Therefore, the soot blower activation signal from the soot blower activation board 8 is added to the calculation signal of the controller 3B and the calculation signal of all controllers 3A as a preceding signal for steam temperature control, and is used as an opening/closing signal for the cold water control valve 4.

As described above, when the heat absorption amount of the heat transfer surface 5B decreases, the soot blower 7 is operated by a command from the soot blower activation board 8. The operation of the soot blower 7 improves the heat absorption of the heat transfer surface 5B, and the outlet steam temperature of the heat transfer surface 5B increases.

In order to lower this increased temperature, it is necessary to spray a large amount of cold water into the desuperheater 6 to lower the inlet steam temperature of the heat transfer surface 5B. This operation necessarily needs to occur when the soot blower 7 operates.

Therefore, before the temperature measured by the steam temperature detector 1 deviates from the steam temperature setting device 2, the soot blower operation signal from the soot blower activation board 8 is sent to the controller 3B to detect the rise in steam temperature caused by the operation of the soot blower 7 and the increase in steam temperature. Calculate the opening direction amount of the cold water control valve 4 to offset, add it to the calculation signal of the controller 3A as a preliminary operation, operate the cold water control valve 4, and perform control to reduce fluctuations in steam temperature due to the operation of the soot blower 7. do.

Therefore, according to the present invention, temperature fluctuations due to the operation of the soot blower can be reduced by incorporating the steam temperature fluctuation value during operation of the soot blower of a coal-fired boiler into the steam temperature control circuit as advance operation information.

[Brief explanation of drawings]

The drawing is a diagram showing an example of a steam temperature control device for a coal-fired boiler according to the present invention. l...Steam temperature detector, 2...Steam temperature setting device, 3A,
3B...Controller, 4...Cold water control valve, 5A. 5B...Heat transfer surface, 6...Desuperheater, 7...Soot blower,
8.◆Soot blower starting board.

Claims (1)

[Claims] A steam temperature control device for a coal-fired boiler, characterized in that a steam temperature fluctuation value during operation of a soot blower of the coal-fired boiler is incorporated into a steam temperature control circuit as advance operation information.