Device and method for softening hard water by using carbon dioxide in flue gas

Abstract

The invention discloses a device and a method for softening hard water by using carbon dioxide in flue gas. The device comprises a water inlet system, a pH adjusting system, a gas inlet system, a reaction tower system and a solid-liquid separation system. According to the method, firstly, hardness ion-containing water enters the pH adjusting system and the pH value is adjusted to about 10 by using an alkaline adding system and a stirring system; then, the water enters the top of a reaction tower; the flue gas enters the bottom of the reaction tower through the gas inlet system; the flue gas and the hard water are in countercurrent contact, so that CO2 in the flue gas is dissolved in water under an alkaline condition and is converted into CO3<2-> which reacts with Ca<2+> so as to generate CaCO3 precipitate, and Mg<2+> reacts with OH<-> to generate Mg(OH)2 precipitate; the adsorbed and purified flue gas is discharged from a gas outlet; and the reacted mixed liquid enters the solid-liquid separation system, and the softened water is obtained after the solid-liquid separation is carried out. The device and the method have the advantages that CO2 in the flue gas is used for softening the hard water, the shortcomings of high investment, high operating cost and high mud yield in a conventional hard water softening treatment technology are overcome, the flue gas is purified while the hard water is softened, and the good effect of treating wastes with wastes is achieved.

Description

technical field [0001] The invention relates to the technical field of water treatment, in particular to a device and method for softening hard water by using carbon dioxide in flue gas. Background technique [0002] Industrial boilers are widely used, but most boilers have strict requirements on the hardness of feed water. Hardness is caused by calcium and magnesium ions in water. It is divided into temporary hardness and permanent hardness. Temporary hardness is formed by bicarbonate of calcium and magnesium, and permanent hardness is mainly formed by sulfate and hydrochloride of calcium and magnesium. Groundwater and some surface water have high hardness, especially in the northern water-scarce areas. Direct use of groundwater with high hardness as boiler feed water will cause scaling and corrosion inside the boiler, affect heat transfer efficiency and equipment safety, and cause energy waste. Therefore, it is necessary to soften the feed water. The commonly used soften...

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Problems solved by technology

[0003] The boiling method is simple to operate, but the energy consumption is high, and it is only suitable for the removal of temporary hardness

The chemical method has less investment at one time, but the amount of dosing is large during operation, the operating cost is high, and the amount of sludge generated is relatively large

Ion exchange resin exchange capacity is limited, easy to saturation, requires frequent regeneration, complex operation and easy to produce secondary pollution, only suitable for treatment of low hardness water

The one-time investment cost of the membrane method is high, and the hardness ions are easy to scale on the membrane, causing fouling and membrane life, and the operation energy consumption is high

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