Boiler water quality is of prime concern to all boiler operators. Typically, silica exists in two forms in the water supply: (1) reactive silica; and (2) colloidal silica. systems should be analyzed to determine the source. EXTERNAL TREATMENT Most of the unit operations of water treatment (Table 39.2) can be used alone or in combination with others to adapt any water supply to any boiler system. There are no primary or secondary regulations for general silicates in drinking water, although there is a maximum contaminant level of seven million fibers longer than 10 microns for asbestos. Silica is a major culprit behind the build-up of hard and dense scale inside the boilers and turbines of power generation plants. NOTE -In case of recovery boilers operating at low boiler pressures of I.5 to 2.0 Calcium, magnesium, sodium, potassium, bicarbonate, sulfate, chloride, nitrate, and silica typically make up most of the dissolved solids in water. solids in boiler water Blowdown - Removes boiler water with a high concentration of solids which is replaced by feedwater containing a low concentration of solids WATER ... Silica 6 0 % Condensate 50 Basic Boiler Calculations. 3. 5.1 Control of silica in boiler feedwater and boiler water is necessary to minimize the formation of scale-forming silicates that decrease heat transfer in the boiler. 7 common food sources of silica you MUST know! After the steam is used it is then dumped to the main condenser. Disadvantages of Scale formation (1) Wastage of fuel : Scales have a poor thermal conductivity so the rate of heat transfer from boiler to inside water is greatly reduced. Silica, in amounts ranging from less than 1 to over 100 ppm, is found in all natural water supplies. In rain hail and snow, silica content range from 1 to 2.8 ppm. An increase in temperature results in an increase in electrical conductivity. Another important source of silica in water is the sand watertreatments filter. Anthropogenic source of silica is relatively very small. The anion resin appears to be doing its job, i.e. This ratio, called the distribution ratio, depends on two factors: boiler pressure and boiler water pH. This can be written as: Example 3.12.3. For boiler water, the conductivity increases at the rate of approximately 2% (of the value at 25°C) for every 1°C increase in temperature. There are no other sources of water as the ST condenser is an air cooled type, with no inleakage. Slowdown: Control of the concentration of chemicals in the boiler water by bleeding off a portion of the water from the boiler. Magnesium phosphate has a surface charge that can cause it to adhere to tube surfaces and then collect other solids. EXTERNAL TREATMENT Most of the unit operations of water treatment (Table 39.2) can be used alone or in combination with others to adapt any water supply to any boiler system. C,}Px9Â8°�aP˜2‚çúTHaQØš…@Ñ Á¯2NH¦@µÃ0u…!ŒÚ¿hRáœ:‹pV.Â(I Í\Œ…±G ec™Ÿ$zÉ©N`Ìc‰Á®T†`Í ƒI¯r2+EˆJƒL%ph2G“a8g uƒS7D'çb4 Another common source of excessive impurities in steam is inadequate attemperation spray water purity. Left improperly treated All impurities in the spray water enter directly into the steam. Other impurities such as silica and iron can be tied up by dispersants and chelants and remain suspended in the boiler water where they can be removed by continuous surface or bottom blow down. Such water is troublesome for boiler feed because of the formation of scale. The main natural source of silica is mineral quartz. Calculate the feedwater composition (impurities) from make up and condensate analysis below Total Hardness M Alkalinity TDS In order to avoid these problems, the quality guidelines shown in Table IV have been adopted. nÅ’U,Áš,Á÷[ÃT?0d²Èk4­8^¡½ï1MWmßxÍ!´¢³³V#†W7JøÆ5'ܬî,q‚ÍdPÖKIPÕtûÒk54³áì'Ò°ğgÃù–qv»“Úã–Ñ�‚íäóõ飼õm‰�ºyì¸İÊEã©Õƒ˜ëS—XUu’kúMOeJKE‡k�Õj9 %°!7É‚Ã# 3-2.8.5.2. Silica is found in almost all rocks and susceptible to weathering. Standard Methods for the Examination of Water and Wastewater accepts a TDS constant of 0.55-0.7, though if the water source is known to be high in calcium or sulfate ions, a constant of 0.8 may be used 13. For example, many higher-pressure boilers will require a higher quality of water with less contaminants than some lower-pressure boilers. Whether or not these subunits are joined together depends on the conditions of polymerization. If boiler water is at a very low hardness, then raw water may be. 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