Experience Gained from Setting Up Cycle Chemistry with the Use of Film-Forming Amines at Thermal Power Stations Equipped with Combined-Cycle Plants

Abstract

The list of thermal power stations equipped with combined-cycle plants (CCPs) at which chelamine is used as a correcting reagent is presented. The advantages of this reagent and advisability of using it are pointed out. The main drawbacks of cycle chemistries based on film-forming amines are formulated, namely, low pH values in the low-pressure boiler water with high pH values in superheated low-pressure steam and high concentrations of ammonia in superheated steam. The effect the concentration of a complex reagent has on the water and steam quality parameters during the operation of a 110 MW combined-cycle unit in its nominal mode is outlined. Measures taken for optimally conducting the cycle chemistry with metering complex reagents as applied to a CCP are considered. The results from regime-adjustment tests of the cycle chemistry of a heat recovery steam generator with metering a complex reagent are described. It has been revealed that in case of using Type 906 H chelamine, the specific electrical conductivity of the H-cation sample of high-pressure superheated steam exceeds the values prescribed by the temporary regulations, and that the pH of the low-pressure circuit's boiler water is at the lower limit of the range prescribed by these regulations. A transition for using Type BRW 150H reagent, which is characterized by a lower distribution ratio between boiling water and saturated steam, has been done. The results obtained from the regime-adjustment tests in the cases of using chelamine of types 906H and BRW 150H were subjected to a comparative analysis. It has been revealed that the replacement of the chelamine type (with the reagent concentration remaining the same) resulted in a higher concentration of sodium, higher conductivity of the H-cation sample, and higher pH value of low-pressure feed water. It has been shown that with a lower concentration of Type BRW 150H reagent, the main quality indicators of feed water, boiler water, and low- and high-pressure steam are within the their standardized ranges and have stable values. It is pointed out that the specific consumption of Type BRW 150H reagent is a factor of 2 lower than in case of metering Type 906H reagent.