Electrode rod for detecting water-level, method of detecting water-level, method of controlling water-level in a boiler, and method of controlling water-level in a steam separator

Abstract

An insulating coating (6) formed of engineering plastic with high heat resistance, high-pressure resistance, and chemical resistance is formed on a surface of a water-level detecting electrode part (3) of an electrode rod for detecting water-level (1) attached to penetrate a metal container (5) communicating with a boiler (7) and including an external power supply connecting terminal part (2) projecting outside the container (5) and the water-level detecting electrode part (3) projecting inside the container (5). One side of a power supply (27) is connected to the external power supply connecting terminal part (2), and another side of the power supply (27) is connected to the container (5) for energization. An electrostatic capacity between the water-level detecting electrode part (3) and the container (5) is measured by using the insulating coating (6) formed on the surface of the water-level detecting electrode part (3) as a dielectric. The water-level of water to be brought into contact with the water-level detecting electrode part (3) in the container (5) can be detected from the electrostatic capacity. Proportional target water-level in the boiler (7) is set based on at least one of the burning capacity, vapor pressure, supply water temperature, and electrical conductivity of boiler water, and at least one of the burning capacity, vapor pressure, supply water temperature, and electrical conductivity of boiler water during operation of the boiler (7) is detected. A difference between the proportional target water-level to be specified by the detected values and actual water-level in the boiler (7) detected by the electrode rod for detecting water-level (1) is constantly calculated. A supply water amount is controlled such that water supply is stopped when the actual water-level exceeds the specified proportional target water-level and the water is supplied until the actual water-level reaches the specified proportional target water-level when the actual water-level falls short of the specified proportional target water-level. In this way, a good quality vapor with high dryness can stably be obtained, and a safe operation of the boiler can be conducted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a partial sectional front view showing an example of an embodiment of an electrode rod for detecting water-level in a boiler according to the present invention;

FIG. 2 is a schematic diagram showing an example of a schematic structure of a boiler system used for carrying out a method of controlling water-level in a boiler according to the present invention; and

FIG. 3 is a schematic diagram showing an example of a schematic structure of a boiler system used for carrying out a method of controlling water-level in a steam separator according to the present invention.

Claims

1. An electrode rod for detecting water-level, attached to penetrate a metal container through an insulator, for detecting water-level in the container including an external power supply connecting terminal part projecting outside the container, and a water-level detecting electrode part projecting inside the container, the electrode rod comprising an insulating coating formed of engineering plastic with high heat resistance, high-pressure resistance, and chemical resistance and formed on a surface of the water-level detecting electrode part.

2. An electrode rod for detecting water-level according to claim 1, wherein the engineering plastic comprises one of polyether ether ketone and a fluorine resin.

3. A method of detecting water-level employing the electrode rod for detecting water-level according to claim 1 or 2, comprising: connecting one side of a power supply to the external power supply connecting terminal part and connecting another side of the power supply to the metal container for energization; measuring an electrostatic capacity between the water-level detecting electrode part and the container by using as a dielectric the insulating coating formed on the surface of the water-level detecting electrode part; and detecting water-level of water to be brought into contact with the water-level detecting electrode part in the container from the electrostatic capacity.

4. A method of detecting water-level according to claim 3, comprising: providing to the container an adjusting electrode rod for detecting water-level for detecting specific water-level within a range of the water-level detecting electrode part; determining a difference between the specific water-level detected by the adjusting electrode rod for detecting water-level and water-level detected by measuring the electrostatic capacity; and adjusting the water-level to be detected by measuring the electrostatic capacity based on the difference.

5. A method of controlling water-level in a boiler employing the method of detecting water-level according to claim 3 or 4, comprising: setting proportional target water-level in a boiler from at least one of burning capacity, vapor pressure, supply water temperature, and electrical conductivity of boiler water; detecting at least one of the burning capacity, vapor pressure, supply water temperature, and electrical conductivity of boiler water during operation of the boiler; calculating constantly a difference between the proportional target water-level specified by detected values, and actual water-level in the boiler detected by the method of detecting water-level; and controlling a supply water amount by stopping water supply when the actual water-level exceeds the specified proportional target water-level, and by supplying water until the actual water-level reaches the proportional target water-level when the actual water-level falls short of the specified proportional target water-level.

6. A method of controlling water-level in a steam separator employing the method of detecting water-level according to claim 3 or 4, comprising: setting proportional target water-level in a steam separator from at least one of supply water temperature, burning capacity, and vapor pressure; detecting at least one of the supply water temperature, burning capacity, and vapor pressure during operation of the boiler; specifying the proportional target water-level by detected values; detecting actual water-level in the steam separator by the method of detecting water-level; calculating constantly a difference between the specified proportional target water-level, and the actual water-level; and controlling a supply water amount by stopping water supply to the boiler when the actual water-level exceeds the specified proportional target water-level, and by supplying water until the actual water-level reaches the proportional target water-level when the actual water-level falls short of the specified proportional target water-level.