The influence of different alkalization agents

i.e.NH3

Na3PO4

and NaOH

in boiler water upon the pH value of boiler water has been analysed

the calculation method for pH value of boiler water under low phosphate treatment mode being given

and the relationship curves between pH value of boiler water and the PO3-4 content in boiler water in different boiler water treatment systems and their typical application being also given.Results of study show that as listed in the following:(1) during the time of calculating the pH value of boiler water

if PO3-4 is less than 2 mg/L

the Na3PO4 can be handled as one-dimentional strong alkaline;(2) under condition of NaOH and Na3PO4 content inboiler water is lower

the effect of ammonia in boiler water upon the pH value is remarkable;(3) the existing on-line monitoring data of steam-water quality

such as feed-water conductivity

PO3-4 in boiler water

as well as proportioning ratio of NaOH and Na3PO4·12H2O in making up the dosage can be substituded into the calculation formula of pH value in boiler water

the pH value of boiler water can be conveniently calculated out

giving effective guidance to pH value control of boiler water

and can judge the accuracy of pH value measurement for boiler water;(4) the relationship curves in defferent boiler water treatment systems are useful to select the suitable boiler water treatment mode.