Changes in boiler feedwater standards?
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This post was last edited by zhang*aobin on 2016-1-16 at 10:52. Classification of boiler superheated steam pressure by standard/MPa. II. Quality standards for boiler feedwater: Hydrogen conductivity (25°C) (us/cm); Hardness; Dissolved oxygen; Iron; Sodium; Copper; Silicon dioxide; Oil; pH; Hydrazine; Ammonia. Standard values vs. expected values: umol/l, ug/l, mg/l (25°C), ug/l, mg/l. GB/T12145-1999: 5.9–12.6, --, ≤2, ≤7, ≤30, –, ≤5; Requirement for ensuring steam quality: ≤0.3, 9.0–9.5, 10–50; This parameter is not specified. GB/T12145-2008: 5.9–12.6, ≤0.30, --, ≤7, ≤30, –, ≤5; This parameter is not specified. Our company’s current standards: --, ≤2, ≤7, ≤30, --, 9.0–9.5, 10–50, 0.1–0.6. Our company uses circulating flow systems for boilers, and there are several issues that need to be analyzed by experts: 1. Why does the 2008 standard eliminate the requirement for analyzing oil content and pH value in feedwater, compared to the 1999 standard? 2. Is copper analysis only applicable when there is copper in the system? 3. The standard does not include ammonia analysis, but we do; is this unclear? 4. Could everyone share the metrics of their own factories? Active participation earns rewards! All chemicals used in our factory’s boilers: ammonia water, hydrazine, trisodium phosphate
Industrial boilers refer to boilers used for industrial purposes such as fuel-oil and gas boilers, coal-fired boilers, and biomass boilers. Water treatment for these boilers is an important aspect in ensuring their safe and efficient operation; it is also a crucial measure for preventing boiler accidents, saving fuel, and enhancing production efficiency. Natural water usually contains three types of impurities: suspended impurities (silt, oil, etc.), colloidal impurities (hydroxides of iron, aluminum, silicon, etc.), and dissolved impurities (dissolved gases and dissolved salts, etc.). These impurities can cause scale and sludge to form in the boiler, corrode the metal surfaces of the boiler, lead to foaming in the boiler water, bumping, water in the steam, and contamination of the steam. Sometimes they can also cause salt deposition and scaling in the superheater, resulting in superheater tube explosions. In particular, the formation of scale not only wastes fuel during combustion but also damages the heating surfaces ； It can also disrupt the water cycle and shorten the lifespan of the boiler. The reason for scale formation in industrial boilers is that, during the heating process of water, certain calcium and magnesium salts undergo chemical reactions that result in the precipitation of insoluble substances ； Moreover, the solubility of these calcium and magnesium salts decreases as the water temperature rises, and they precipitate once a saturated concentration is reached ； As the water in the pot continues to evaporate and concentrate, insoluble salts form precipitates. Water quality indicators are technical parameters that indicate the quality of water, and they are established based on water usage requirements and the characteristics of impurities. The main water quality parameters for boiler water are as follows: Suspended solids: the amount of water-insoluble substances obtained by filtering the water under specified test conditions. Salt content: Total amount of all salts dissolved in water ； The content of dissolved solids is often used as a substitute. Hardness: The total amount of calcium and magnesium salts dissolved in water. Hardness is further divided into temporary hardness and permanent hardness. Temporary hardness is the bicarbonate content of calcium and magnesium in water. Permanent hardness is the non-carbonate hardness in water, including sulfates and chlorides of calcium and magnesium, etc. pH value: The negative logarithm of the hydrogen ion concentration in water. Alkalinity: the total amount of substances in water that increase the concentration of hydroxide ions due to dissociation or hydrolysis ； Relative alkalinity: the ratio of the hydroxide alkalinity present in the boiler water to its salt content. In industry, water is classified into four categories based on its hardness: soft water (water with a hardness of less than 8 degrees, where 1 degree corresponds to 10 mg of calcium oxide per liter), moderately hard water (with a hardness between 8 and 16), hard water (with a hardness between 16 and 28), and ultra-hard water (with a hardness greater than 28 degrees). The main problems in water quality management at present are: some boilers still do not undergo water treatment, or fail to use effective water treatment methods properly ； The water quality supervision and management system is not strict enough ； Improper waste discharge control ； The technical skills of water treatment laboratory technicians are low, and a few of them lack a strong sense of responsibility. To ensure that all parameters of the boiler feedwater and boiler water meet the relevant standard requirements, to prevent scaling and corrosion during boiler operation and to maintain steam quality at acceptable levels, thereby ensuring the safe and economical operation of the boiler, it is necessary to carry out water treatment for the boiler. Common water treatment methods include chemical dosing inside the boiler and external softening (softening by precipitation and softening by ion exchange). When making a specific choice, it is necessary to take into account the characteristics of the furnace and the water; an appropriate treatment method can also be selected based on the relationship between the total hardness and total alkalinity of the water source.
GBT1576-2007 Standards for water quality in industrial boilers; GB/T12145-2008 Quality requirements for water and steam in thermal power generation units and steam-powered equipment
Is there any explanation that’s fresh and new to me? Ah, please, experts!