Problems with boiler feed water and demineralized water?

Boiler feed water is demineralized water; demineralization involves removing calcium and magnesium ions to prevent scaling, and boiler feed water must be demineralized water

Desalinated water is obtained by treating groundwater through mechanical filters, activated carbon filters, and precision filters, followed by desalination via reverse osmosis. After acid-base adjustment using a mixed-bed reactor, this desalinated water is sent to a deaerator for heating and deoxygenation, after which it can be fed into boilers; the water before being fed into the boilers is known as boiler feedwater.

Boiler feed water with a high pressure rating must also be deoxygenated

We call water from which calcium and magnesium ions have been removed “soft water”. It is produced using an ion exchanger. The water used in our company’s old boiler (SHW6) must be deoxygenated. According to the tutorial: “Deoxidization is required when the rated evaporation capacity of the boiler is 6t or greater.”

Boiler feed water can also be condensate

Boiler feed water must be demineralized water, that is, soft water from which calcium and magnesium ions have been removed through a series of chemical treatment processes, with conductivity and pH levels meeting the specified standards. Deoxygenation must also be carried out before entering the boiler. Sometimes, some of the condensed water is also used as boiler feedwater after being collected.

Desalinated water is soft water in which ions such as calcium, magnesium, silicon, and iron have been removed using methods such as microfiltration, ion exchange, and membrane filtration. Boiler feedwater refers to deionized water that has undergone deoxygenation and chemical treatment; it is necessary to use deionized water, which is then deoxygenated in a deoxygenator and has its pH value adjusted to 9-10 before being used as boiler feedwater.

Desalinated water refers to water from which cations and anions have been removed through exchange towers. It is divided into primary desalinated water and secondary desalinated water; primary desalinated water has a SiO2 level of ≤100 mg/L, while secondary desalinated water is an even purer form of water obtained by treating primary desalinated water with mixed-bed resins, with a SiO2 level of ≤20 mg/L； Generally, medium-pressure boilers use first-stage deionized water, while for low-pressure boilers, softened water is sufficient; softened water refers to water from which Ca2+ and Mg2+ have been removed ； High-pressure boilers must use two-stage deionized water. For boilers equipped with turbines, feedwater refers to water whose temperature has reached 215°C after passing through the low-pressure heater, deaerator, feedwater pump, and high-pressure heater. This feedwater enters the boiler economizer directly, while the deionized water goes into the deaerator; there it is deoxygenated together with the condensate from the turbine, and then it enters the high-pressure heater via the feedwater pump. In other words, the deionized water is only a part of the boiler feedwater. For boilers without turbines, demineralized water enters the deaerator; after deoxygenation, it is pumped by a feed pump to the economizer.

Generally, demineralized water must be deoxygenated before being sent to the boiler, and then supplied as boiler feed water to the boiler system

For small low-pressure boilers, softened water is sufficient; a water softener and deaerator are used, followed by the addition of chemicals before the water is sent to the boiler. Medium-pressure boilers require demineralized water, which is obtained using reverse osmosis membranes – these membranes not only remove hardness from the water but also eliminate approximately 97% of ions as well as all organic substances. The water quality is better than that of softened water; after desalination, it is fed into the boiler after adding chemicals. In short, desalinated water is not necessarily used in boilers, and boiler water does not necessarily have to be desalinated.

The **boiler feedwater quality standards** can be checked

Desalinated water is soft water to which ions such as calcium, magnesium, silicon, and iron have been removed. Boiler feed water is deionized water after deoxygenation or recycled condensate water. Boiler water with a pH value adjusted to 9-10. So there is still a certain difference between the two.

Boiler water equipped with a superheater must be desalted.

Desalinated water and boiler feed water are different; boiler feed water is prepared from desalinated water. Desalinated water is soft water after the removal of ions such as calcium, magnesium, silicon, and iron. Desalinated water is deoxygenated, and chemicals such as sodium phosphate and diammonium compounds are added to adjust its pH value to a specific level before it can be used as boiler feedwater.

I also believe that there is a difference between desalinated water and boiler feed water; boiler feed water must be demineralized water, that is, water from which ions such as calcium, magnesium, silicon, and iron have been removed. In addition, larger boilers require oxygen removal, and the water quality must meet the requirements specified in GB1576-2001 \"Water Quality for Industrial Boilers\" or those for thermal power plant boilers.

Desalinated water is obtained by treating groundwater through mechanical filters, activated carbon filters, and precision filters, followed by desalination via reverse osmosis. This desalinated water is used to prevent scaling in boilers. After its pH value is adjusted – we use ammonia to keep the pH between 8.5 and 9.2 – the water is sent to a deaerator for oxygen removal; we employ atmospheric thermal deailers that heat the water to around 104 degrees Celsius to remove oxygen and other gases from it, thereby preventing damage to the boiler’s structure and avoiding corrosion. Once this is done, the water can be pumped into the boiler using a feed pump, and the water before entering the boiler is known as boiler feedwater. Generally, it must first be heated in a economizer before being sent to the steam drum. Once inside the steam drum, chemical treatment is also required (we use phosphates to adjust the pH value to between 9 and 11, ensuring that the water in the boiler’s steam drum remains alkaline and protecting the structure of the steam drum). This post was last edited by bobo315 on 2009-2-12 08:13

The experts upstairs discussed things in a very professional and insightful manner. I’m not majoring in waterways; it’s confusing! What exactly are demineralized water, soft water, and deionized water? What is an exact definition?