RU2267119C2 - Mode of controlling indexes of quality of boiler water of boiler energy installations with natural and repeated compulsory circulation - Google Patents

Abstract

FIELD: the invention refers to heat-and-power engineering and refers to the questions of controlling water chemistry conditions of boiler installations with natural and repeated compulsory circulation and more specifically to express definition of the indexes of quality of boiler water( general salinity, contents of free alkali and relative alkali).

SUBSTANCE: the essence of the invention is in measuring in boiler water of electrical conductivity, a pH value and temperature. According to parameters received in the result of this measuring general salinity, contents of free alkali( alkali neutralization number) and relative alkali are defined and using metered meanings of these indexes water conditions in boiler installations are judged.

EFFECT: simplification of operative control of water conditions in boiler installations due to express definition with the help of tools of general salinity, contents of free alkali and relative alkali of boiler water.

Description

The invention relates to the field of power engineering and concerns the monitoring of water-chemical regimes of boiler plants with natural and multiple forced circulation, and more particularly to the rapid determination of boiler water quality indicators (total salt content, free alkali content and relative alkalinity).

Known chemical-analytical methods for determining these indicators, used, for example, for ship boiler plants. The salt content (salinity) of boiler water is evaluated on ships by the content of chlorine ions in it, which are the main impurity in the salt composition of water in ship boilers. The content of chlorine ions is controlled by titration of the boiler water sample with a solution of mercuric nitrate or silver nitrate in the presence of an indicator (Methods of analysis of water and aqueous media of marine power plants, pp. 53 and 57, RD 5.IM.YN. 037-88).

The content of free alkali (alkaline number) on ships is determined by titration of a water sample with a solution of sulfuric acid in the presence of an indicator (phenolphthalein or thymol blue), (ibid., P. 111).

The relative alkalinity of the boiler water is estimated by the ratio of the free alkali content to the dry residue of the boiler water (Yu.M. Kostrikin, N.A. Meshchersky, O.V. Korovina “Water treatment and water regime of energy objects of low and medium pressure”, reference book, Energoatomizdat, 1990 g, p. 60). The dry residue is determined by evaporation of the measured volume of filtered water, drying the residue at 105-110 ° C and weighing (Methods of analysis of water and aqueous media of marine power plants, p.65, RD 5.IMYAN. 037-88). That is, to determine the relative alkalinity, a qualified person needs to perform a number of laborious operations.

In stationary energy, the content of free alkali is estimated using the ratio of alkalinity for phenolphthalein to total alkalinity (Guidelines for the organization and scope of chemical control of the water-chemical regime in thermal power plants, RD 34.37.303-88, Tables 5 and 6). Total alkalinity is determined by the chemical-analytical method (titration of a sample of boiler water with an acid solution alternately with phenolphthalein and methyl orange indicators).

The main disadvantage of almost all chemical analytical methods is the complexity and complexity of the analysis, which requires special operator training and the need for specific equipment.

Also known is the method of instrumental determination of the salt content of boiler water used in stationary energy (Methodological guidelines for the organization and volume of chemical control of the water-chemical regime in thermal power plants, RD 34.37.303-88, table 6) - prototype.

It consists in measuring the specific electrical conductivity (SEC) of a boiler water sample that has been processed on an H-cation exchange column. As a result of the ion exchange of the cations of salts present in the boiler water (mainly sodium cations), an acid solution with a high electrical conductivity is supplied to the hydrogen cation in the device’s sensor (conductivity meter). In this case, the alkali present in the boiler is neutralized on the column with the formation of water according to the scheme

(H ⁺ -K is the exchange ion on H-cation exchanger) and does not affect the value of the electric conductivity of the filtrate (water after the column). According to the UEP of this filtrate, the salt content of the boiler water is calculated.

A significant drawback of this method is the relatively small exchange capacity of the H-cation exchange column and, therefore, the rapid development of its resource, which requires frequent regeneration of the H-cation exchange resin or its replacement. With a high content of dissolved impurities, typical for boiler water, the frequent regeneration of the H-cation exchange column makes it difficult to conduct operational control of its salinity. In addition, the speed of water passing through the column and the temperature of the sample taken affect the measurement result, which must be taken into account when using this method for controlling salinity.

A feature of the mineral composition of the boiler water is that it is mainly an alkaline solution of sodium salt, which must satisfy the condition w _ff ≥0,5SCH _Society (technical operation of thermal power stations and RF networks RD 34.20.501-95 p. 4.8.25). That is, the alkaline component of boiler water is hydrates. Therefore, the content of free alkali in it (alkaline number) with accuracy sufficient for the operation of boiler plants can be determined using the pH value.

The task of the invention is to significantly simplify the operational control of the water regime of boiler plants due to the rapid determination by instrumental means of total salt content, free alkali content and relative alkalinity of boiler water.

The specified technical result is achieved by the fact that in the known method for monitoring the quality of boiler water of boiler power plants with natural and multiple forced circulation, including measuring the electrical conductivity in the boiler water, pH and temperature, the total salt content is determined by the parameters obtained as a result of measurement, the content of free alkali (alkaline number) and relative alkalinity, and using the normalized values of these indicators judge the state of water No mode boiler plants.

Measurements of the total salinity and alkaline number and the maintenance of their normalized values make it possible to ensure the required steam quality and protection of the boiler internal surfaces against corrosion, and compliance with the requirements for the relative alkalinity value is to prevent alkaline corrosion (caustic brittleness) of the metal.

The concentration of free alkali, as well as the contribution of this alkali to the UEP of boiler water, is determined by the pH value, using analytical dependences and taking into account the temperature of the medium being measured. The total salinity is determined by the difference between the measured UEP of the boiler water and the determined UEP of the alkali, calculated on the concentration of salts. Relative alkalinity is estimated by the ratio of alkali concentration to the sum of the concentrations of salts and alkali.

The proposed method for determining the total salinity, alkaline number and relative alkalinity can be implemented using standard devices (pH meter and conductivity meter), using special tables, nomograms or graphs, as well as creating a new device that measures three parameters in boiler water (UEP, pH and temperature), and information on the quality of this medium reporting on six indicators (UEP, pH, temperature, total salinity, alkaline number and relative alkalinity). In this case, specific equipment required for chemical-analytical methods of control is not required, and the determination of these indicators can be performed by an operator who does not have special training.

Claims (1)

A method for monitoring the quality of boiler water in boiler plants of power plants with natural and multiple forced circulation, which includes measuring the electrical conductivity in the boiler water, pH and temperature, characterized in that the free alkali content (alkaline number) is determined by the parameters obtained as a result of the measurement and its specific electrical conductivity, total salt content in the form of a difference in the specific electrical conductivities of the measured boiler water and free alkali, Read on the concentration of salts, and as the ratio of the relative alkalinity of free alkali concentration to the sum of the concentrations of salts and free alkali and using the normalized values of these parameters are judged on the state of water regime boiler installations.