What is boiler water treatment?
Boiler water treatment is the conditioning and treatment of boiler feed water for the three purposes of continuous heat exchange, quality steam protection and corrosion protection. Boilers are designed to heat fluids, and then the evaporated or heated fluid will leave the boiler and be used for heating applications and various industrial processes, such as sanitation and cooking. Some of the major industries that use boilers are pharmaceutical, textile, steel and chemical industries.
If you want your boiler to remain in good condition and as efficient as possible, it is important that the water remains free of impurities, which means that water treatment is necessary. There are two methods of treating boiler water, an external treatment and an internal treatment. Both processes rely on a conditioning process that essentially counteracts the hardness in the water by introducing softeners into the water. Once these agents are placed in the water, most of the minerals, contaminants and chemicals in the water should be completely altered or removed. Whichever of these methods you use, there are many effective chemicals that can be used to keep the water free of impurities, including everything from de-oxidizers to anti-scalers.
Boiler treatment chemicals
A guide to some of the more common chemicals used in boiler water treatment is provided below.
Oxygen scavenger
Oxygen scavengers are specifically designed to reduce the amount of dissolved oxygen and oxides in water. If you use a DO sensor and find high levels of dissolved oxygen in your boiler water, deaerators such as hydrazine and sodium sulfite can effectively reduce DO and oxides, resulting in purer water. Deaerators also typically passivate various metal surfaces, which helps prevent rusting and other problems.
When you introduce chemical deaerators into boiler water, you will be able to remove any residual oxygen from the feedwater, protecting the boiler from harmful chemical reactions and reducing corrosion in the feedwater tank and return line. Tannin chemicals and sulfite chemicals have been shown to be particularly effective deaerators. If you decide to use sodium sulfite, this deaerator will work quickly and is especially suitable for low pressure applications. As for tannins, this chemical will remove oxygen from the water and also form a corrosion-resistant film around the boiler steel.
The exact dose of deaerator you should use in your boiler depends on the type of deaerator you use and whether the boiler is paired with a de-gas heater. For testing purposes, you should always keep 20 ppm of deaerator in the boiler feedwater. If you want to ensure that your boiler does not corrode, it is highly recommended that you use a deaerator.
Alkalinity generator
Alkalinity generators are specifically designed to raise the pH of the water in which they are applied. For steam boilers, it is important to maintain a high pH to prevent corrosion, minimize the amount of silica plating in high-pressure boilers, and maintain proper boiler efficiency. If your feed water has a high alkalinity, an alkalinity booster is not always necessary, but if the water in your boiler becomes too acidic, you should consider using an alkalinity booster.
All you need to do to determine the pH of the boiler water is to test it with a pH sensor. If the pH drops too far, an alkalinity builder will help you increase the alkalinity of the water. When you increase the alkalinity of the boiler feed water, you will be able to protect the feed lines and hot wells from acid corrosion. The amount of this chemical you need all depends on how low the pH of the feedwater is.
The most common alkaline solutions for boiler water include sodium hydroxide and potassium hydroxide. You can usually purchase these products in concentrations of 25% or 50%. If you need to significantly increase the alkalinity of your feed water, a 50% solution may be your most effective choice. Some alkalinity detergents come with sludge conditioning polymers, which can be particularly beneficial for high temperature applications.
Amines
Amines are neutralizing chemicals that prevent corrosion of condensate tubes on boilers. Condensate from steam boilers can be highly corrosive to the tubes, which can damage your boiler and cause you to make expensive repairs to fix the problem. The three neutralizing amines you can obtain for boiler water treatment purposes include morpholine, diethylaminoethanol and cyclohexylamine. While these neutralizing amines can be purchased as a single component, most solutions will be mixed with these three components.
When these amines are placed in boiler water, they increase the pH of the condensate, which greatly reduces the potential for corrosion. It is well known that low pH in condensate piping can lead to significant corrosion, which can lead to condensate leaks and steam leaks. Once this chemical is applied to the water in your boiler, you will gain greater boiler reliability, cleanliness and protection. While condensate piping is the primary area of concern, this chemical will protect all condensate systems. To determine if this chemical is needed, it is recommended that you test the return condensate with a pH sensor.
Scale Inhibitors
Scale inhibitors are used to enhance the dispersion properties of any conditioning product used in boiler water. Scale inhibitors typically consist of a mixture of polymers and phosphates. These antiscalants can be used as natural or synthetic chemicals. The most common natural polymers include tannins and lignin sulfonates, while synthetic polymers available for your use include polystyrene sulfonates and maleic acid ester copolymers.
These chemicals act as softeners to minimize scale buildup in the boiler. Scaling can be a major problem for boilers because it causes a significant reduction in boiler efficiency. When harder impurities such as magnesium salts and calcium begin to increase in boiler water, they eventually become concentrated, which means they can adhere to the pipes and other surfaces of the boiler.
The most common feedwater contaminants that can lead to scale formation include magnesium, aluminum, calcium, iron and silica. If you don’t get rid of scale soon, it will first reduce the efficiency of your boiler. Eventually, the affected tubes may rupture or overheat. Solenoid dosing pumps are usually used to add scale inhibitors. Mechanical diaphragm metering pumps are more suitable for large flow of chemicals. The amount of scale inhibitor you use in your boiler water depends on the hardness of the water and the amount of scale that forms. It is recommended that you use a hardness test kit to determine the effectiveness of these antiscalants when treating water with them.
External and internal treatment of boiler water
The treatment of boiler water is divided into two types: external treatment and internal treatment. With external treatment, once the water is removed from the boiler, impurities are reduced or completely removed from the water. If the level of impurities in the feed water is very high, it may damage the boiler and it is recommended that you use the external treatment method. After removing the feed water, it will be purified and degassed. It can also be pretreated by evaporation, which produces some pure steam that can be condensed and used in the treatment process. This treatment method softens the water, reduces silica and alkalinity, removes suspended matter and reduces oxygen. However, this process can be time consuming and is often unnecessary.
As for the internal treatment of boiler water, this process requires conditioning of impurities in the water, which means that the water is softened with softening chemicals such as sodium phosphate and soda ash. The main purpose of internal treatment is to properly reduce hardness, sludge and remove oxygen from the feed water. The only step involved in the internal treatment process is to determine which type of softener you want to use. If you need to reduce scale buildup, the softeners you introduce into the boiler water will react with the magnesium and calcium compounds already present in the water. With the right combination, unwanted impurities should be softened and dissolved.
If your main goal is to regulate sludge, you can use dispersion or coagulation. If the sludge level in the feedwater is high, coagulation can help by forming large particles that can be easily removed. If the sludge is at a relatively low level, dispersion breaks up the sludge and disperses it through the boiler water. In most cases, internal treatment should be all you need to treat the boiler water.
Why do you need to treat your boiler water?
Treating your boiler water is important because impurities in the water can cause a host of problems, and if you don’t treat the water, this will cause you to waste money on equipment repairs. There are many problems that can occur if you don’t treat your boiler water. For one thing, the increased level of impurities in the water will eventually lead to the formation of scale in the boiler. Since scale increases thermal resistance, your boiler will automatically become less efficient. The tubes themselves may eventually overheat or rupture completely, which will cost you a lot of money in repairs.
While scale is the most common problem in boilers, it is also normal for parts inside your boiler to corrode, which can also reduce the efficiency of your boiler. When corrosion begins, your boiler will begin to lose quality, which increases the likelihood that you will need to replace your boiler sooner than expected. If you are using your boiler for food production purposes, water treatment is essential if you want to ensure that your food is free of harmful impurities. The rate at which you treat the water in your boiler depends on the purpose for which you are using the boiler. While it is possible to treat water daily, you should treat water at least once a week.
Maintaining high quality boiler water
High-quality boiler water is important for the life of your boiler, allowing you to avoid corrosion and other problems. Scaling alone can lead to pipe failure, overheating and loss of efficiency, which only wastes your money. No matter what industry you work in, poor water quality can directly affect your company’s essential processes. If you also purchase the right boiler, you will get a system that is very reliable, relatively affordable and operates efficiently and effectively to meet the needs of your facility.
You can choose from several types of boilers, each with its own advantages and disadvantages. If you need equipment or resources that can help you test your boiler water and maintain proper boiler water treatment, contact Apure today to learn more about the services and products we offer.
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