Dealkalization systems find applications in the following areas:
Boiler Feedwater Treatment: Dealkalization systems are used to lower the alkalinity of water used as feedwater in boiler systems. High alkalinity can lead to scale buildup and crack formation in boilers. Therefore, having low alkalinity in boiler feedwater ensures the efficient and safe operation of boilers.
Drinking Water Treatment: Dealkalization is used in drinking water treatment plants to enhance the palatability of drinking water. Reducing alkalinity can improve consumers' acceptance of water.
Chemical Industry: Some chemical processes require water with low alkalinity. Dealkalization systems can be employed to meet this need.
Paper and Pulp Industry: The production of paper necessitates the use of water with low alkalinity. Dealkalization systems provide the required water quality in this industry.
Food and Beverage Industry: Low alkalinity water may be essential for specific processes in the food and beverage industry to ensure product quality.
Marine Applications: Dealkalization systems are used in marine applications to reduce the alkalinity of water, particularly in marine water treatment systems.
Dealkalization systems are widely used in industrial applications where reducing alkalinity is necessary. These systems can improve water quality, extend equipment life, and reduce operating costs.
Difference Between Dealkalization and Demineralization
Dealkalization and demineralization are both water treatment processes aimed at reducing the mineral content of water, but they serve different purposes and target different chemical components. Here are the key differences between these two terms:
Purpose
Dealkalization: Dealkalization aims to reduce the alkalinity level of water. Alkalinity refers to the concentration of carbonate (CO3²-), bicarbonate (HCO3-), and hydroxide (OH-) ions in the water. This process primarily targets reducing high alkalinity, especially in applications like boiler water preparation.
Demineralization: Demineralization aims to remove ions from water generally. These ions can be both positively charged cations and negatively charged anions. Demineralization removes hardness, salts, and other ions and is often preferred to obtain high-purity water.
Process
Dealkalization: Dealkalization is typically carried out using anionic resins. Anionic resins capture negatively charged ions in the water and reduce alkalinity.
Demineralization: Demineralization can involve both cationic and anionic resins. Cationic resins capture positive ions, while anionic resins capture negative ions. This combination purifies water from the majority of ions, resulting in high-purity water.
In summary, while dealkalization and demineralization processes may use similar methods, they have different objectives. Dealkalization aims to reduce alkalinity, while demineralization aims to reduce the overall mineral content of water, often to obtain high-purity water.
Dealkalization Systems
Dealkalization systems are water treatment systems used to reduce the alkalinity of water.
Flow of Water: A flow path is created for water to come into contact with the cationic resins, allowing the water to interact with the resins.
Ion Capture: Cationic resins capture positively charged ions in the water, releasing hydrogen ions (H+) in their place. During this process, the pH of the water may decrease.
Regeneration: Over time, the ion-exchange capacity of cationic resins becomes exhausted, and the resins become saturated. Therefore, regeneration is required after a certain period. The regeneration process involves the use of acid (typically hydrochloric acid). The acid releases the positively charged ions held by the resins and reactivates the resins.
Disposal of Regeneration Ions: During regeneration, the resulting brine solution (containing acid and ions) is either disposed of or treated. This brine solution is considered waste.
Operation: After regeneration, dealkalization systems are ready for reuse and continue to produce low-alkalinity water.
Dealkalization is commonly used in boilers operating at temperatures below 700 psi. It is suitable when the alkalinity level of feedwater is 50 ppm or lower, and makeup water is added to the boiler in quantities of 1000 gallons or more per day.
The alkalinity of raw water can be reduced through various methods. For example, when reverse osmosis membrane filtration is used, it is observed that carbon dioxide can be almost completely removed, and approximately 98% of dissolved minerals can be eliminated. This helps reduce alkalinity and remove scale-limiting minerals.
Chloride anion dealkalizers operate similarly to ion-exchange water softeners. Salt or a salt-caustic combination can be used for resin regeneration. The water’s hardness should be less than 10 grains if salt is used. If a salt-caustic combination is used, water softening should be performed first. Dealkalization typically requires water softening to prevent boiler scale formation.
Weak acid dealkalization offers cost advantages when the ratio of water hardness to alkalinity is one or greater. In this method, the water’s alkalinity is reduced through hydrogen exchange, and caustic may be added if a pH increase is desired.
Split-stream dealkalization utilizes two strong acid cation beds. One bed operates in sodium to soften the water, while the other works in hydrogen to remove the water’s alkaline properties. Sulfuric acid is typically used to regenerate the hydrogen-form bed, and the feedwater flow is split between the two beds.
Dealkalization processes work similarly to water softeners, using ion exchange to remove unwanted ions from water. However, while water softeners work to remove calcium and magnesium ions, dealkalization processes remove carbonate ions by exchanging them with chloride ions. Dealkalizers, like water softeners, use salt during the regeneration process. However, unlike water softeners, dealkalizers operate with the additional use of a caustic solution during regeneration. This caustic solution raises the pH levels and enhances resin efficiency.
Dealkalization processes make the water softer by reducing its alkalinity. This is particularly important in boiler water preparation, where it helps prevent scale buildup and damage to equipment. These systems are commonly used in industrial facilities and power plants.