Dealkalizers play a crucial role in the reduction of excess an-ions in the ion exchange process. Dealkalization is highly applicable in commercial settings; it helps in reducing alkalinity in both boilers and cooling towers. The application of dealkalizers reduces the application of softeners and chemicals in commercial processes, which leads to reduction of operation costs. Dealkalizers also prevent corrosion, helping equipment and storage units last longer.
What is Alkalinity?
The term alkalinity refers to water’s ability to neutralize an acid. Water contains three types of alkalinity: bicarbonate (pH 4.3 to 8.3), carbonate (pH 8.3-10) and hydroxide (pH greater than 10). Most natural water sources contain high levels of bicarbonate.
Effects of Alkalinity
Alkalinity affects the production of various good and services, especially in commercial industries that use boilers such as brewers. During steam production, bicarbonate and carbonate ions breakdown into Hydroxide (OH) and carbon dioxide (CO2); once the cooling process begins, the steam condenses; the CO2 dissolves and reacts with the hydroxide to form carbonic acid (H2CO3), a highly corrosive substance. The presence of carbon dioxide, hydroxide and bicarbonate also creates further corrosion.
The different corrosion-prevention additives in the market offer a costly dealkalization solution. They also cause corrosion on equipment when applied repeatedly. Additionally, you can only measure their effectiveness by the amount of carbonic acid they control. This makes alkalinity the determining factor in deciding the number of cycles at which boiler can operate safely. Operating a boiler for short cycles increases running and energy costs significantly.
In the treatment of alkalinity, dealkalization is only applicable to boilers that operate at less than 700 psi, with feed water that contains 50 ppm alkalinity or less, and receives above 1,000 gallons of make-up water (added to replace water lost through steaming or blow downs). You can apply several dealkalization methods to raw water, such as:
Split Stream Dealkalization
During stream dealkalization, you place two parallel beds with a strong acid cation; one bed serves as the sodium cation exchange softener while the other one operates in hydrogen form as the cation vessel of the demineralizer. During dealkalization, water flows between both beds: the sodium based bed contains the alkalinity while the hydrogen contains zero alkalinity. Both streams of water are then degasified, removing all the carbon dioxide.
Chloride Anion Dealkalizers
Chloride anion dealkalizers use the ion exchange system with filtration systems that contain an anion resin. You can use either salt or a salt-caustic combination for the resin regeneration. Salt is applicable to water with 10 grains or less, while salt-caustic requires that you soften the water before feeding it in into the dealkalizer. The softening prevents scale buildup in the boiler.
The use of membranes is quite popular in water treatment. Proper application of reverse osmosis eliminates almost all the carbon dioxide from feed water. Reverse osmosis also removes over 98 percent of dissolved minerals, reducing both blow down and alkalinity. Through these, you can increase boiler cycles by 50.
Weak Acid Dealkalization (WAC)
WAC offers a cost saving solution when the ratio of water hardness to alkalinity exceeds one. WAC resins exchange hydrogen for the hardness synonymous with alkalinity in water, and then degasification helps in the removal of carbon dioxide. In extreme cases, you can add caustic to raise water PH levels.
Each of the dealkalization methods offers its advantages and disadvantages. Speak to water professionals to help you assess the best method for your commercial system. The professionals will analyze your raw water and measure the operating parameter of your boiler to find the most effective dealkalization method.