Liquid heaters and vaporizers – Cleaning – Trapped circuit
Patent
1988-10-12
1990-02-27
Favors, Edward G.
Liquid heaters and vaporizers
Cleaning
Trapped circuit
210177, F22B 3748, F28G 900
Patent
active
049036424
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field:
The present invention relates to an apparatus for controlling injection of a chemical liquid in a boiler system which includes: a water supply control unit for keeping fluctuations in level of can water within upper and lower limit values, these fluctuations being concomitant with consumption of steam in the boiler system; water supplying means interlocked with and controlled by this water supply control unit; and chemical liquid supplying means, and more particularly, to an improvement in which a pH value and a concentration of can water in the boiler do not increase higher than needed.
2. Background Art:
In the boiler system, corrosion of a boiler can and scale adhesion thereto, which are caused by the action of can water, are typically restrained by injecting a chemical liquid (a rust preventive or a deoxidizer) into the can water. For injection of such a chemical liquid, an apparatus for controlling the injection of the chemical liquid which is illustrated in FIG. 1 has been used.
Referring to FIG. 1, connected to a boiler 1 are a water supplying pump 4 defined as water supplying means and a chemical liquid pump 5 defined as a chemical liquid supplying means to which the chemical liquid is fed from a chemical liquid tank 6. The boiler 1 is equipped with a combustion control unit 7 for controlling combustion so as to keep the vapor pressure of the boiler within a range of upper and lower limit values and a water gauge 11 for detecting upper and lower limit levels of water when controlling the supply of water to the boiler. A water level detecting signal SO can be transmitted from the water gauge 11 to a water supply control unit 3. From this water supply control unit 3, a water supplying signal S1 can be transmitted to the water supplying pump 4 and the chemical liquid pump 5.
In this arrangement, when basic injection of the chemical liquid is automatically or manually effected into the boiler filled with the can water, the pH value of the can water is somewhat increased, and the corrosion of the boiler just after initiating the operation is restrained. Subsequently, after initiating the boiler operation, when the level of can water is reduced down to the lower limit level as the boiler 1 consumes the steam, the water supply control unit 3 supplies the water supplying signal S1 to the water supply pump 4 and the chemical liquid pump 5 in response to the water level signal SO indicating the above-mentioned descent of water level to the lower limit value, and these pumps 4 and 5 are thereby actuated. On the other hand, when the level of can water rises to the upper limit level, the operation is stopped by cutting off the supply of the water supplying signal S1 in response to the water level signal SO indicating the above-described ascent of the can water level to the upper limit value. The water supply control is thus operated in a interlocking manner. The chemical liquid is injected into the can water at a constant ratio by means of the chemical liquid pump 5 concomitantly with the water supply by the water supply pump 4, thereby gradually increasing the pH value of can water, which has already been risen in a certain extent at the time of the basic injection, after starting the boiler operation. In this manner, the corrosion and the scale adhesion which are produced during the boiler operation can be restrained.
Based on the above-described conventional technique, the pH value is increased to a certain degree by effecting the basic injection of chemical liquid into the can water, and the chemical liquid is injected into the can water at the constant ratio to an amount of supplied water concomitantly with the intermittent water supply control after starting the operation. As a result, during continuation of the boiler operation, a concentration of the chemical liquid in the can water rises little by little because of concentration of the can water, and the pH value of the can water also gradually increases.
The restraining action of chemical liquid against corrosion and s
REFERENCES:
"Water Control in Boilers", by Japan Boiler Association, Oct. 15, 1967, pp. 179-189.
Jujita Tadao
Tamaru Nobuhiro
Ebara Corporation
Favors Edward G.
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