5.2 Colloidal silica that is not removed by boiler water pretreatment processes may be solubilized in the boiler and thus contribute to the dissolved silica concentration in the boiler. Unreactive silica is polymerized or colloidal silica… After the colloid is destroyed, this silica which firstly was “hidden” suddenly appears. Most raw surface waters contain colloidal silica together with other colloidal particles. As a result, it can cause problems with deposits being formed as well as scaling. No other units of measurement are included in this standard. 5.2 Colloidal silica that is not removed by boiler water pretreatment processes may be solubilized in the boiler and thus contribute to the dissolved silica concentration in the boiler. Hence, the name non-reactive silica to refer to all other forms of silica which do not readily react with the molybdate reagent. Ion exchange will remove this as long as … All of the non-reactive, or colloidal, silica is rendered soluble above 600 psig and hence all of the silica in the boiler is, theoretically, capable of being vaporized. Both dissolved and total … Select Accept cookies to consent to this use or Manage preferences to make your cookie choices. pH, cationic conductivity, iron, copper, chloride, dissolved oxygen, silica… This “anything” can be polymeric or can be combined with iron, aluminum, potassium, sodium or organics. In the analyses of various surface and ground waters, silica content range from 1 … The lower level of impurities also reduces corrosion rates in the boiler. purifying boiler feed water has been to use chemically regenerated ion-exchange deionization. R.O. 1.3 This test method determines total silica, and does not distinguish between soluble and insoluble forms. Silica … In high enough … 1.2 This test method is applicable in the range from 25 to 250 μg/L of silica as SiO2. Often, colloidal silica is also defined as “anything” that will be retained by a 0.22 micron filter. Standard References. Ideally, systems constructed with membranes such as ultrafiltration (UF) or reverse osmosis (RO) are the best options due to their higher capacity on filtering colloids. Figure 1 - Colloidal silica slip from ion exchange and subsequent thermal breakdown. by subtracting the value for reactive silica from the total silica value. The surface of colloidal silica in … CASE 3 –COLLOIDAL SILICA REMOVAL Customer Jindal Power Ltd, Raigarh, Chattisgarh Raw Water Source Surface water Problem •Colloidal silica in raw water created problems on turbine in power plant Flow m3/hr 100 x 3 Streams Inlet Colloidal Silica … Lime softening is one of the most common methods for removing silica from water such as make up to cooling towers, make up to boilers or boiler blow down water. Products and Services / Standards & Publications / Standards Products, Active Standard ASTM D4517 | Developed by Subcommittee: D19.03, Permissions to reprint documents can be acquired throughCopyright Clearance Center   It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Depending on the water source, time of the year, rainfall quantity, etc, there can be more colloidal silica in the water. Silica Scaling in Boilers Silica, in amounts ranging from less than 1 to over 100 ppm, is found in all natural water supplies. Removing silica, which is the dioxide of silicon (SiO2), can be difficult; is found in many raw water sources in different concentrations and forms—mostly dissolved, suspended, or colloidal. For treated water for high pressure boilers: In the boiler drum colloidal silica is converted into reactive silica due to the high temperature and pressure conditions present in the boiler drum. The presence of even small residuals of colloidal silica in water can dramatically cause high silica levels and depression in pH in the boiler water. ... Colloidal Silica Particles: Effect of Particle Size, Langmuir 2005, 21, 5761-5769. Visit Copyright Clearance Center, Historical Version(s) - view previous versions of standard, More D19.03 Standards Based on the above, there could be a situation where the demineralized water from an ion exchange system may have residual reactive silica below 10 ppb, which is a good number, but there could be some colloidal silica which is not measured neither by the lab testing or the on-line silica analyzer. The field test for silica will detect only reactive silica. We and third parties such as our customers, partners, and service providers use cookies and similar technologies ("cookies") to provide and secure our Services, to understand and improve their performance, and to serve relevant ads (including job ads) on and off LinkedIn. Chemicals to react with feedwater hardness 2. Concentration range should not be extended by dilution. Ion exchange resins usually are not capable on removing colloidal silica. A complete boiler water treatment program may include: 1. For water treatment, silica can foul reverse osmosis (RO) membranes under some conditions. Such occurrence undoubtedly exists, but it is reasonably certain that complete clarification will remove this form of siliceous material. membrane (0.0001 micron), the membrane separates the silica from the water. Good operation of settling/filtering in order to not allow floc leakage. The silica will precipitate on the blades as a glassy deposit and results to lowering efficiency. Typically, silica exists in two forms in the water supply: (1) reactive silica; and (2) colloidal silica. 1.4 Re mov al of Non re active silica There are atleast two methods for removing non-reactive silica from boiler feed water : - Pretreatment of water ( coagulation and clarification) - Ultrafiltration 1.4.1 Pre tre atme nt of wate r Difficulties in removing non-reactive silica from the fact that it is not present as a simple colloidal … Water Treatment for Silica as small suspended silicate particles (colloidal silica). Owing to its volatility, … Non-reactive silica thus includes polymerized (aka polymeric), colloidal and insoluble silicates (aka suspended or granular silica). 1.6 This standard does not purport to address the safety concerns, if any, associated with its use. The presence of excessive levels of silica in boiler feed or makeup water is critical. Normally silica is present in a weak acidic form. Engineers at the plant found that the silica impurities in the boiler water were high, necessitating frequent blowdown operations that consumed large volumes of water and wasted heat energy. Proper maintenance of water chemistry helps in minimizing corrosion, deposition, and scaling problems in boiler and turbine and prevents costly shutdown and material replacement. It is important to control the … The documents listed below are referenced within the subject standard but are not provided as part of the standard. There are 2 forms of Silica in water, colloidal silica … The immediate result is a sudden raise in silica concentration in the boiler water. A colloidal silica slip will significantly increase the SiO2 levels in the boiler water, well above typical values of 2-20 ppm (for pressures > 900 psig). Silica-content of water are very critical to High Pressure Steam boiler system as it is volatile enough that it can carry over to the vapor partition and can deposit on turbine. Treatment of boiler feed water is required for preventing excessive heat transfer equipment fouling and erosion of turbine blades. To promote optimum performance downstream, filtration of boiler feed water streams allows an industrial boiler or power plant to meet the stringent requirements for more efficient boiler performance. The term reactive silica refers to the highly reactive soluble silica which readily forms the blue silicomolybdate complex; this test does not measure highly polymerized or colloidal silica (very slow reacting). This is a widely ... it offers better removal of colloidal silica and dissolved Volatilization and carryover of silica with the steam may cause hard, glassy siliceous deposits to form on turbine blades that reduce turbine efficiency. Especially if colloidal silica is present in the makeup water. 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