“If you define the problem correctly, you almost have the solution.”
– Steve jobs
Boiler water treatment is the conditioning and treatment of boiler feed water with the purpose of meeting three objectives. In order for boiler water treatment to be maintained, there must be a continuous heat exchange, protection for high-quality steam, and corrosion protection. Boilers are
designed to heat fluid, after which the vaporized or heated fluid will
exit the boiler and be used for heating applications and
various industrial processes like sanitation and cooking. The main types
of industries that use boilers include the pharmaceutical, textile, steel, and chemical industries.
If you want your boiler to remain
in good condition and be as efficient as possible, it’s important that
the water remains free from impurities, which means that water treatment
will be necessary. There are two methods that can be used for the
treatment of boiler water, which include external treatment and internal treatment.
Both of these processes rely on the conditioning process, which
essentially counteracts the hardness in water by introducing softening
agents to the water. Once these agents have been placed in the water,
most of the minerals, contaminants, and chemicals within the water
should be altered or removed completely. No matter which of these
methods you use, there are many effective chemicals that you can use to
keep the water free from impurities, which include everything from
oxygen scavengers to anti-scaling agents.
The following provides a guide on some of the more common chemicals that are used in boiler water treatment.
Oxygen Scavengers
Oxygen scavengers are designed specifically to reduce the amount of dissolved oxygen and oxides in the water. If you use a DO sensor and find that the amount of dissolved oxygen in your boiler water is too high, oxygen scavengers like hydrazine and sodium sulphite can effectively reduce both DO and oxides for purer water. Oxygen scavengers will typically passivate various metal surfaces as well, which helps to keep rust and other issues at bay.
When you introduce a chemical oxygen scavenger to your boiler water, you’ll be able to remove any residual oxygen from the feed water, protect the boiler from harmful chemical reactions, and reduce corrosion within the feed tank and return lines. Tannin chemicals and sulphite chemicals have proven to be particularly effective oxygen scavengers. If you decide to use sodium sulphite, this oxygen scavenger will act quickly and is particularly beneficial for
low-pressure applications. As for tannin, this chemical will remove oxygen from the water while also creating a corrosion resistant-film around the steel of the boiler.
The exact dose of an oxygen scavenger that you should use in your boiler depends on the type of scavenger that you’re using and whether the boiler is paired with a de-aerating heater. For testing purposes, you should always maintain 20 ppm of an oxygen scavenger in your boiler feed water. If you want to make sure that your boiler doesn’t corrode, it’s highly recommended that you make use of oxygen scavengers.
Alkalinity Builders
Alkalinity builders are designed specifically to raise the pH level of the water that they are placed in.
For steam boilers, it’s essential that pH levels remain high in order
to prevent corrosion, minimize the amount of silica plating in a
high-pressure boiler, and maintain proper efficiency of the boiler.
While it’s not always necessary to use an alkalinity builder if your
feed water has a high alkalinity, you should consider using alkalinity
builders in the event that the water in your boiler becomes too acidic.
All you need to do to determine the pH
level of your boiler water is to test it with a pH sensor. If the pH
levels have dipped too far, alkalinity builders will help you increase
the alkalinity of the water. When you increase the alkalinity of your
boiler feed water, you will be able to protect the feed line and hot
well from acid corrosion. The amount of this chemical that you require
all depends on how low the pH level is in your feed water.
The most common alkaline solutions for boiler water include sodium hydroxide and potassium hydroxide.
You can typically purchase these products with a 25 percent
concentration or a 50 percent concentration. If you need to
significantly increase the amount of alkalinity in your feed water, a 50
percent solution could be the most effective option for you. Some
alkalinity builders come with sludge conditioning polymers, which are
notably beneficial for high-temperature applications.
Amines
Amines are neutralizing chemicals that are able to keep the condensate pipe on a boiler from corroding.
Condensate water from a steam boiler can be highly corrosive to piping,
which can damage your boiler and cause you to make expensive repairs to
fix the issue. The three types of neutralizing amines that you can
obtain for boiler water treatment purposes include morpholine,
diethylaminoethano, and cyclohexylamine. While it’s possible to purchase
these neutralizing amines as a singular component, the majority of
solutions will be blended with all three.
When these amines are placed into your
boiler water, they will increase the condensate pH, which heavily
reduces the possibility of corrosion. Low pH within condensate piping is
known to cause high amounts of corrosion, which can lead to both
condensate leaks and steam leaks. Once this chemical has been applied to
the water in your boiler, you’ll be provided with increased boiler
reliability, cleanliness, and protection. While the condensate piping is
the main area of focus, this chemical will protect all condensate
systems. In order to determine if this chemical is needed, it’s recommended that you use a pH sensor to test the return condensate.
Anti-Scaling Agents
Anti-scaling agents are used to enhance the dispersive properties of any conditioning products that are being used in your boiler water. An anti-scaling agent is typically comprised of a blend of polymers and phosphates. These
anti-scaling agents are available as either natural or synthetic
chemicals. The most common natural polymers include tannins and
lignosulphonates, while the synthetic polymers available to you include
polystyrene sulphonates and maleic acrylate copolymer.
These chemicals act as softening agents
in order to minimize the buildup of scale in your boiler. Scaling can be
a significant problem for boilers because of how it causes the boiler
to be much less efficient. When harder impurities like magnesium salt
and calcium start to increase in your boiler water, they will eventually
become concentrated, which means that they will adhere to the tubes and
other surfaces in your boiler.
The most common contaminants for feed water that can cause scale to develop include magnesium, aluminum, calcium, iron, and silica. If
you don’t get rid of scaling as quickly as possible, it will first
lower the efficiency of your boiler. Eventually, it’s possible that the
affected tube will rupture or overheat. The amount of anti-scaling
agents that you use in your boiler water depends on how hard the water
has become and how much scale has formed. It’s recommended that you use
hardness test kits during water treatment with anti-scaling agents to
determine how effective these agents have been. With this information,
you can add more of the solution if necessary.
External and Internal Treatment of Boiler Water
s
The two types of treatment for boiler water include external treatment and internal treatment. With external treatment, the impurities are reduced or removed entirely from the water once the water has been taken outside of the boiler.
If the impurities in the feed water have reached very high levels that
could be damaging to the boiler, it’s recommended that you use the
external treatment method. When the feed water has been removed, it will
be purified and de-aerated. It can also be pre-treated through
evaporation, which produces somewhat pure vapor that can be condensed
and used during the treatment process. This treatment method is able to
provide softening to the water, reduce silica and alkalinity, remove
suspended matter, and reduce oxygen. However, the process can be
time-consuming and is oftentimes unnecessary.
As for the internal treatment of boiler water, this process calls for the conditioning of the impurities within the water, which means that the water is softened with softening chemicals like sodium phosphate and soda ash.
The main purpose of internal treatment is to properly reduce hardness,
sludge, and scavenge oxygen in the feed water. The only step involved in
the internal treatment process is to identify what type of softening
agent you’ll want to use. If you need to reduce scale buildup, the
softening agents that you introduce to the boiler water will react with
the magnesium and calcium compounds that are already in the water. With
the right combination, the unwanted impurities should soften and
dissolve.
If your primary goal is to condition sludge,
you can either use dispersion or coagulation. If the sludge in your
feed water is high, coagulation can help by forming large particles that
can easily be removed. If the sludge is at a relatively low level,
dispersion will break the sludge up and disperse it through the boiler
water. In most cases, internal treatment should be all that you require
to treat your boiler water.
Why Do You Need to Treat Your Boiler Water?
It’s important to treat your boiler water because
impurities in the water can cause a whole host of issues, which will
lead to you wasting money on equipment repairs if you don’t treat the
water instead. There are many problems that can develop if you
don’t treat your boiler water. For one, increasing levels of impurities
in the water will eventually cause scale to form in the boiler. Since
scale increases thermal resistance, your boiler will automatically be
less efficient. The tube itself can eventually overheat or completely
rupture, which would cost you a significant amount of money to repair.
While scale is the most common problem in
boilers, it’s also normal for the components within the boiler to
become corroded, which also makes the boiler less efficient. When
corrosion sets in, your boiler will start to degrade in quality, which
heightens the possibility that you will need to replace the boiler
sooner than you expected. If you’re using a boiler for food production
purposes, water treatment is essential if you want to make sure that the
food remains free from harmful impurities. The rate at which you treat
the water in your boiler depends on what you’re using the boiler for.
While it’s possible to treat your water every day, You should at least
treat the water once per week.
Maintaining High Quality Boiler Water
High-quality boiler water is important to the life of your boiler and will allow you to keep corrosion and other issues at bay. Scale
alone can cause tube failure, overheating, and efficiency loss, which
only serves to waste your money. No matter which industry you work in,
poor water quality can directly impact the necessary processes for your
company. If you purchase the right boiler as well, you’ll be provided
with a system that’s very reliable, relatively affordable with efficient
operation and highly effective at meeting the needs of your facility.
