Optimization of Reagent Methods for Sedimentation of Solid Formations in Water Softening Systems
Keywords:
НАКИПЬ, УМЯГЧЕНИЕ, ОСАЖДЕНИЕ, ИЗВЕСТЬ, ПРОДУКТ РЕАКЦИИ, ДОЗИРОВАНИЕ РЕАГЕНТОВAbstract
The article analyzes the advantages and disadvantages of using various reagents for water softening by the sedimentation method of hardness cations in sedimentation tanks or clarifiers.
It is shown that the lime as a reagent has a number of advantages over other reagents. The advantages are as follows: when softening water with lime, the carbonate index of the treated water decreases – the product of calcium hardness and alkalinity, the reaction product is obtained in a solid form and can be used in the construction industry or other industries and agriculture, the commercial product contains the largest (by compared with other reagents) the content of the active substance (up to 35,7 kg-eq/t of the reagent), due to the low equivalent mass of the reagent, low specific consumption of the lime per unit volume of treated water.
The disadvantage of using lime as a reagent for water softening by the sedimentation method of scale-forming agents is its low solubility, as a result of which up to 96 % of the active substance in the dosed solution is in the form of the suspension. The dosed solution dissociates in the reactors of the separators - precipitators as the dosed reagent enters the reaction. There are special requirements to ensure the uniformity of the reagent dosing. The violation of the requirements leads to the deterioration in the stability indicator of the treated water as a result of the apparatus transition - precipitators to the hydrocarbonate mode of operation. This increases the dispersion of the sludge and, accordingly, its removal into the clarified water. Achieving the uniformity of the lime suspension is ensured by increasing the efficiency of mixing the solution in a feed mixer and using the circulation of the solution through the pipeline at the suction of the metering pumps.
The analysis of changes in the component composition of the treated water: hydrocarbonates, carbonates and hydrates, as well as its electrical conductivity with an increase in the dose of lime is presented. The indicator of the minimum electrical conductivity of water occurs symbatically with a change in the content of hydrates. The indicator of the minimum content of hardness cations slightly lags behind the indicator of the minimum content of hydrates, which indicates the advisability of using the hydration mode of operation of reactors - precipitators.
The extreme dependence of the conductivity index of the treated water, taking into account the change in its component composition, shows the advisability of using systems for correcting or regulating the dosage of lime according to the value of conductivity approximately 25 % higher than its minimum value.
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