In this article, I will share types of feed water treatment and how they work. Feed water treatment is one of an important processes done to enhance the efficiency of a boiler.
Fee water is used in steam generation in a boiler. The water fed into the boiler is called feed water.
So, before the water is fed into the boiler, it has to be treated first, and these processes that the feed water undergoes is what I will be talking about in this article.
Without wasting time, let me share the types of feed water treatment.
Types of feed water treatment
Feed water treatment is categorized into the following types;
- Mechanical feed water treatment.
- Chemical feed water treatment.
- Thermal feed water treatment.
1. Mechanical feed water treatment
Mechanical feed water treatment involves filtration and coagulation.
Filtration is all about removing solid contaminants from the feed water.
The water is passed through a filter medium that removes the solid contaminants such as sand, gravel, stops and plastics.
These solids contaminants are left on the filter medium while the water passes across through the pores.
This process of feed water treatment is not effective because it can’t eliminate the dissolved solid contaminants (magnesium, calcium, silica, iron etc) from feed water and that is why other methods are employed.
Coagulation involves adding chemicals in feed water and mixing it which causes the formation of the insoluble jelly clump that absorbs and entangles the fine suspended matter that wouldn’t be removed by simple filtration.
After the gelatinous flocculent absorbs and entangles the impurities on top of the water they are then swept away easily since they are floating thus leaving the water free of these impurities.
You have to know that coagulation is termed as the mechanical and chemical treatment of water.
The mechanical side of this treatment is that the jelly layer that is formed on the top of the water is removed by sweeping it away while the chemical side is when the chemical reaction between the alkalinity of the water and the chemical added (coagulate) results in the formation of the insoluble flocs.
2. Chemical feed water treatment.
There are quite several processes used in chemical feed water treatment.
Before I share these processes that feed water treatment involves, I would like you to know something.
Chemical feed water treatment involves of removal of dissolved solids in water.
The dissolved solids can be magnesium, calcium, iron, and silica.
These solids can’t be removed from the feed water through filtration.
These are the chemical process used in feed water treatment;
- Zeolite softener.
- Ion exchange.
- Demineralization.
- Dealkanization.
1. Zeolite softening process of feed water treatment
The zeolite softening process of feed water treatment involves the exchange of ions which aims at eliminating calcium and magnesium ions.
The zeolite softener has a salt cap that consists of the zeolite compounds which are silicates of aluminium and sodium.
These zeolites are released into the hard water which ends up exchanging the ions of magnesium and calcium replacing them with sodium.
Sodium is used in the zeolite softening process because it’s a softening salt.
The zeolites are regenerated by passing a solution of sodium chloride, sodium aluminium orthosilicate or sodium zeolite through the ion exchange resin bed.
This method of feed water treatment eliminates the permanent and temporary hardness of the water.
2. Ion exchange process of feed water treatment
The ion exchange process of feed water treatment involves of exchange of ions that are a result of water hardening and replacing them with softening salts.
This is how the ion exchange process of feed water treatment works; the main components of ion exchange are exchange resins which are supersaturated with a loosely held solution of sodium.
As the hard water containing calcium and magnesium enters the ion exchanger, the ions of magnesium and calcium are attached to the ion exchange resin bed.
The action of these ions (calcium and magnesium) attaching themselves to the resin bed will result in the loosely held solution being released into the water.
And the water leaving the ion exchanger is eventually free of calcium and magnesium.
The downside is that the ion exchange resin bed will become saturated with calcium and magnesium and for these to be removed a fluid with a salt brine solution is flashed in the ion exchanger.
3. Demineralization process of feed water treatment
From the word demineralization, this process of feed water treatment involves the removal of all inorganic salts by the process of ion exchange.
This process is quite similar to the ion exchange process that I have just talked about in the above section, the differences come in how they all work.
The demineralization process setup consists of two tanks that contain different ions and a piping system that conveys water throughout the system.
This is how the demineralization process of feed water treatment works; water enters the first tank that contains strong acid cation resin in form of hydrogen.
When water enters the first the dissolved salts in feed water will form corresponding acids thus leaving the first tank cation-free and low PH.
The water will then flow to the second tank that contains strong base anion resin in the form of hydroxides.
When the water enters this second tank, the corresponding acids from the first tank will be neutralized by a strong base anion resin bed in form of hydroxides.
After the water is demineralized it’s taken out of the tank with a neutral pH.
The process is just as simple as that!
4. Dealkanization process of feed water treatment
The process of dealkanization also involves ion exchange to remove unwanted ions from the feed water.
The main difference between dealkanization process from the ion exchanger, zeolite softening and demineralization process is that dealkanization removes carbonates ions, exchanging them for chloride ions.
The working principle of dealkanization process involves the exchange of ions by removing carbonate ions from feed water and exchanging them with chloride ions.
Chloride is used in dealkanization process because it’s a softening salt also.
To recharge the dealkanizers salts are used and to enhance the efficiency of the resin beds they have to be treated with an additional caustic solution.
3. Thermal process of feed water treatment
The thermal process of feed water treatment involves heating the feed water.
Increasing the temperature of feed water removes the dissolved gasses from the water.
The higher the temperature of feed water the lower the solubility of gasses in it.
Feed water heaters and deaerators are used to remove dissolved gasses from the feed water.
If you want to know more about feed water heaters and how they work you should read the article below.
You might like this: Feed Water Heaters: Functions, Types, Advantages And Operation
Final thoughts
Feed water treatment is essential since it increases the efficiency of steam boilers.
The impurities in the feed water boilers are capable of far worst things than decreasing the efficiency of the boiler.
Check the article below to know the effects of these impurities in a boiler.
You might like this: Effects of Impurities of Feed Water In Boiler (+Prevention)
There is still much to learn about the feed water treatment process such as the design of the components used, their efficiencies, advantages and disadvantages and so forth.
What I have shared has barely scratched the surface of what you need to know about these processes.
Do your research to find out more about the feed water treatments.
Thanks for reading the article, if you have any questions leave a comment. Have a great time learning and see you in my next piece.
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