Regarding boiler water analysis

Superheated steam, saturated steam: SiO2 (≤20μg/L), conductivity (≤10μs/cm). Boiler feedwater: pH (9–11), Cl- (≤4mg/L), PO43- (5–15 mg/L), SiO2 (≤2.0mg/L), total alkalinity (≤3.0mmol/L), phenolphthalein alkalinity (≥0.1 mmol/L). Boiler water: pH (8.5–9.2), dissolved oxygen (≤15μg/L), conductivity (≤10μs/cm), total alkalinity (≤3.0mmol/L)

There are several types of moisture in boilers, and the specific parameters vary depending on the pressure level and evaporation capacity of the boiler. For these specific parameters, one can refer to national standards or industry standards for the power sector (with DL as the standard code for power-related standards). There are also differences between drum boilers and once-through boilers: Boiler feed water (deoxygenated water) – hardness, sodium ions, silicon, pH, conductivity, trace dissolved oxygen, azide; Steam condensate: pH, conductivity, TOC, sodium, silicon; Boiler water: pH, phosphates, silicon, dissolved oxygen, total iron, alkalinity; Boiler wastewater: pH, phosphates, silicon, total iron, turbidity, alkalinity; Steam quality: pH, conductivity, sodium, TOC. This information is provided for reference only.

(1) Suspended solids refer to the content of water-insoluble solid mixtures separated after filtration. The higher the suspended solids content, the more turbid the water is. For small industrial boilers, if purified tap water is used as the water source, it is not necessary to monitor the suspended solids level during operation. (2) Total hardness generally refers to the total amount of calcium and magnesium ions in water, and it is an important indicator for preventing scale formation in boilers. For boilers, the lower the hardness of the water, the better it is for preventing scaling. (3) Total alkalinity refers to the content of substances in water that can accept hydrogen ions. Since alkaline substances can react with hard substances to form loose sludge that can be removed through wastewater discharge, thereby preventing scaling in boilers, it is necessary to maintain a certain level of alkalinity in the water used in industrial boilers. However, if the alkalinity of the boiler water is too high, it can affect the quality of the steam and sometimes cause alkaline corrosion; therefore, the alkalinity of the boiler water should be kept within a certain range. (4) The pH value, which is the negative logarithm of the hydrogen ion concentration, is an indicator of the acidity or alkalinity of a solution. The pH range is 0 to 14; a pH of 7 indicates neutrality, while a pH above 7 indicates alkalinity. It is generally required that the water quality of boilers be at a certain level of alkalinity, which helps to prevent corrosion and scaling. (5) Dissolved oxygen refers to the amount of oxygen dissolved in water. Dissolved oxygen in water can easily cause corrosion of boiler equipment and water supply pipes, so it should be removed as much as possible. (6) Dissolved solids, conductivity, and chloride ions. Dissolved solids, also known as evaporation residue, can approximately represent the total salt content in water. Changes in the solid content dissolved in the boiler water directly reflect the degree of concentration of that water. When this content is too high, it can lead to a large amount of water being carried along with the steam, thereby deteriorating the quality of the steam; in severe cases, foaming may occur as well. Therefore, it is necessary to control this level by carrying out proper drainage. Since the measurement of dissolved solids is complex and time-consuming, conductivity or chloride ions, which are simpler methods to use during normal boiler operation, are generally used as alternatives. However, the ratio between these values must be determined through testing and corrected regularly. (7) SO32- (sulfite): This parameter is designed for boilers that use sodium sulfite to remove oxygen; boiler water without sodium sulfite contains no sulfites. (8) PO43- (phosphate): Phosphates can remove residual hardness, prevent scaling, and form a ferric phosphate protective layer on metal surfaces to reduce corrosion; therefore, phosphate-based treatment agents are often added to pots. Monitoring phosphate can help better control the amount of phosphate added. (9) Relative alkalinity refers to the ratio of the amount of free sodium hydroxide in the boiler water to the amount of dissolved solids. It is a parameter designed to prevent caustic embrittlement at the brazed or riveted areas of the boiler. For fully welded boilers, caustic embrittlement generally does not occur, so it is not necessary to control this parameter. (10) Oil content: Natural water generally contains no oil, so monitoring is not necessary under normal circumstances. However, when the water source is contaminated with oil, its oil content should be monitored to determine whether it can be used as boiler feed water. (11) Iron content refers to the total amount of iron ions present in the water. These are new control parameters for the feedwater of fuel and gas boilers that were added during the revision of water quality standards in 2001. This is mainly because fuel and gas boilers typically have a high heat load on their heating surfaces; if the feedwater contains high levels of iron, it can lead to the formation of iron oxide scale in the boiler, as well as corrosion beneath the deposits.