Why is sodium phosphate added to the boiler?

pH value and PO3 concentration are important indicators for controlling the quality of water in boiler feedwater. Initially, when the boiler was not heated, there were no precipitates in the feedwater, the hardness was low, and its quality remained constant. As the evaporation rate of the boiler increases, the concentrations of calcium and magnesium ions in the boiler water rise, leading to an increase in the electrical conductivity of the boiler water. When the concentration of calcium and magnesium ions in the boiler water exceeds their solubility, some of these ions precipitate out. They then settle on the inner walls of the boiler tubes, in dead corners, collection boxes, etc., or adhere to the evaporation surfaces of the boiler, forming water-insoluble calcium and magnesium compounds. At this time, the salt content and sediment in the furnace are usually reduced by adjusting the flow rates of the fixed-flow and continuous-flow systems. However, when the evaporation rate of the boiler reaches a certain level, it is uneconomical to rely solely on periodic or continuous drainage to control the conductivity or salt content of the boiler water. Moreover, if too much water is drained, it can easily disrupt the steam-water circulation in the boiler, affecting its safe and stable operation. At this point, to meet the requirements of the quality standards for boiler steam and water, it is necessary to continuously add sodium diphosphate, an antiscalant capable of removing calcium and magnesium ions and their compounds, into the boiler. This substance converts the hard salts formed by calcium and magnesium ions into insoluble, less viscous light water sludge, which is then removed through the boiler’s regular or continuous drainage systems. The dosage of Na3PO4 should be adjusted based on the test results. After adding it for a period of time, and once the steam quality meets the requirements and the boiler is operating properly, continuous dosing should be adopted with the dosage maintained at that level. To ensure that a non-precipitating, lightweight water slag is always formed in the furnace, phosphates should be added to the alkaline furnace water, maintaining a certain excess of phosphates in it; meanwhile, the levels of PO3 and pH in the furnace water must be monitored during operation.

To ensure water quality, reference is mainly made to four indicators: conductivity, phosphate, pH, and silica. For specific theories, refer to the comments above and Baidu

Thank you. May I ask what purpose the accumulator in the turbine compressor system serves?

Received, the talk upstairs was excellent!