What causes high silica in boiler water?
When pressure increases inside the boiler system, colloidal silica gets converted into ionic silica . Further concentration of the silica along with dissolved solids also increases due to steam generation in the boiler system.
How do I reduce silica in my boiler water?
After silica enters the boiler water, the usual corrective action is to increase boiler blowdown (to decrease the boiler water silica to acceptable levels) and then to correct the condition that caused the silica contamination.
How do you reduce silica in water?
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. Lime softening utilizes the addition of lime (calcium hydroxide) to remove hardness (calcium carbonate and magnesium carbonate) ions by precipitation.
Why should the presence of silica in boiler water be avoided?
Impurities that form deposits Sulfate and silica generally precipitate directly on the boiler metal and are much harder to condition. Silica (sand) if present in water can form exceedingly hard scale. Suspended or dissolved iron coming in the feedwater will also deposit on the boiler metal.
How do you remove silica build up?
Treatment for silica depends on the form it’s in. It may be possible to remove with a simple filtration process if it’s in a particulate form. If it’s in a colloidal form it may require some chemical addition such as magnesium salts which then need to be followed by filtration or a reverse osmosis (RO) system.
What happens to boiler if water contains silica?
Silica is the only boiler water salt which vaporizes at pressures below 2400 psig. It can vaporize at pressures as low as 400 psig. This has caused deposition problems in numerous turbines. The solubility of silica in steam increases with increased temperature: silica becomes more soluble as steam is superheated.
What is unreactive silica?
Unreactive silica is polymerized or colloidal silica, acting more like a solid than a dissolved ion. Silica, in the colloidal form, can be removed by a RO but it can cause colloidal fouling of the front-end of a RO.
Do water filters remove silica?
Removing Silica from Water Silica is a hard, ceramic/sand like mineral formed from Silicon and Oxygen. It is frequently found in water supplies as a colloid or in ultra fine particulate form. Water softeners don’t remove it and carbon filters don’t remove it, neither do Iron filters or cartridge filters!
Which water has the most silica?
Mount Kirishima water has the highest silica content in the world (silica is commonly found in volcanic rock). The mountain has erupted several times in the last 1,000,000 years, forming natural aquifers underground. The area is also known as one of Japan’s most rain heavy regions.
Why boiler drum silica increases after the boiler trips?
Silica build-up is monitored inside the boiler drum. The silica concentration is distributed between the water and vapour phases in a boiler. As the temperature and pressure are increased, more silica becomes present in the steam.
Does RO remove silica?
Reverse osmosis (RO) is by far the most efficient way to remove colloidal and dissolved silica, which can be found in high concentrations in brackish water. The presence of silica and its ability to foul membranes limits the use of silica… plant.
How does silica increase in boiler drum?
How is silica distributed in a gas boiler?
It has been demonstrated that for any given set of boiler conditions using demineralized or evaporated quality make up water, silica is distributed between the boiler water and the stream in a definite ratio. This ratio depends on water pressure and boiler water pH as shown in the picture on the right.
What is the maximum amount of silica in boiler water?
On the left: Maximum boiler water silica allowable to mantain less than 0.02 ppm silica in the steam The most significant factor is to maintain low silica concentrations in the boiler water. This can be gained through external treatment equipment for make up water or monitorning and controlling the condensate contmination.
What is Silica scale in boiler?
Silica scale is not normally found in boiler systems except in minute quantities. It can be admitted to the system when severe carryover occurs in evaporators processing water with a high Silica content.
When is silica added to the system?
It can be admitted to the system when severe carryover occurs in evaporators processing water with a high Silica content. Other sources of such feedwater may be high Silica river or raw fresh water as well as distilled/deionized or unprocessed fresh water which has been stored and taken from cement-washed or silicatecoated tanks.