The monitoring of the water-chemical mode of steam boilers using the pH value of boiler water

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The monitoring of the water-chemical mode of steam boilers using the pH value of boiler water

This article describes the technology of boiler water quality control with the control of the pH value of boiler water and the value of its electrical conductivity. Examples of this control are provided. The conditions under which this control is sufficiently effective are specified.

 

Is it possible to control the entire water-chemical mode ( WCM) of a steam boiler by measuring only the pH and electrical conductivity of the boiler water?

Theoretically, Yes. In practice, the success of this control will be determined by the accuracy of pH and electrical conductivity measurements.

It should be noted that all of the following applies to low-pressure steam boilers that are not direct-flow, I.e. boilers in which the boiler water is formed by repeated evaporation of feed water.

The boiler water quality parameters are as follows:

 - the alkalinity at phenolphthalein (P) and methylorange (M), mol/l;

- salinity (S), mg/l;

- the relative alkalinity of the boiler water (A), %.

All four indicators of boiler water quality are related, i.e. the value of each indicator depends on the values of other indicators.

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1 Comment

  1. How is the hardnes (Ca?)  control. Which is de Pressure limits? Thank you 

    1 Comment reply

    1. This method is for boilers with an ion exchange softening of feed water. I also tried this method for water treatment schemes with reverse osmosis and softening. It means that in this case, the boiler water has only one pH value at a certain value of electrical conductivity. And with this pH value, the boiler water does not contain calcium or magnesium. If the boiler water begins to get calcium or magnesium, the pH value of such water will decrease, but the value of electrical conductivity remains the same. On this basis, we can understand that the boiler water receives hardness salts. I have tried this method on boilers up to 13 bar. But I think it can work at higher values. The main conditions are an ion exchange softening of feed water and a source of water supply with more or less constant ionic composition.

      Of course, this is an indirect method of controlling the hardness of feed water.