Pengaruh Injeksi Phosphate terhadap Parameter pH, Silika (SiO2), dan Residual Phosphate (PO43-) pada Boiler Water

Abstract

Research has been carried out on the effect of phosphate injection on pH, silica (SiO2) and residual phosphate (PO4 3-) parameters in boiler water at PT. PLN Indonesia Power PLTU Pangkalan Susu PGU. Boiler water used at PT. PLN Indonesia Power PLTU Pangkalan Susu PGU is demineralized water which goes through various stages in removing mineral salts. Several boiler water parameters are pH, silica (SiO2), and residual phosphate (PO4 3-). These parameters have predetermined quality standards, if they do not meet the quality standards it will cause corrosion, scaling, carry over, and others. To overcome this, chemical injection is carried out, namely phosphate injection with the right dose and pump openings in accordance with applicable regulations, namely 0-100%, which can increase the pH and reduce silica levels that cause scaling. pH analysis is carried out by rinsing the multimeter electrode first with demineral water, then dipping it into the sample (boiler water), and recording the pH seen on the multimeter. Silica (SiO2) analysis was carried out by making a Hexammonium Molybdate solution, a 1,2,4-Acid Reducer solution, and a 10% Oxalic Acid/10% Tartaric Acid solution, then the three solutions were homogenized with the sample (boiler water) then the silica content was measured using using a silica meter. In the analysis of residual phosphate (PO4 3-), a Hexaammonium molybdate-ammonium metavanadate-nitric acid solution was made, then the solution was homogenized with the sample (boiler water) then phosphate analysis was carried out using a UV-Visible spectrophotometer with a wavelength of 880 nm. From the results of the pH analysis of boiler water for units 3 and 4 from the first week to the fourth week, namely in unit 3 it was 9,30, 9,25, 9,22, and 9,29, and in unit 4 it was 9,21, 9,19, 9,17, and 9,16. For analysis of silica (SiO2) content in boiler water for units 3 and 4 from the first week to the fourth week, namely in unit 3 it was 81,00 ppb, 99,28 ppb, 100,51 ppb, and 118,12 ppb, as well as in unit 4 was 38,33 ppb, 36,68 ppb, 35,82 ppb, and 37,20 ppb. And for analysis of residual phosphate (PO4 3-) levels in boiler water for unit 3 and unit 4 from the first week to the fourth week, namely in unit 3 it was 0,71 ppm, 0,63 ppm, 0,51 ppm, and 0,63 ppm , and in unit 4 it was 0,40 ppm, 0,37 ppm, 0,36 ppm and 0,31 ppm. In accordance with the Chemical Operation Manual 1st Edition published by SINOHYDRO CO. LTD. and Base Practice from Pangkalan for pH in boiler water, namely 9,0-9,7, for silica (SiO2) in boiler water, namely <450 ppb and for residual phosphate (PO4 3-) in boiler water, namely 4-6 ppm, then all data Unit 3 and Unit 4 meet these standards. And with the provision that the pump stroke opening for phosphate injection is 0-100%, the actual pump stroke opening at PT. PLN Indonesia Power PLTU Pangkalan Susu PGU for phosphate injection meets these requirements, namely 80% with an actual dose of 4 ppm.