Compound additives of phosphorus-free scale inhibitor for low-temperature multi-effect distillation seawater desalination
The synthesized scale inhibitor AA-AM-HPA terpolymer and several scale inhibitors were selected to carry out a series of phosphorus-free scale inhibitor compound experiments.A dynamic test was carried out by simulating the low temperature and negative pressure evaporation circumstance of LT-MED and the corrosion inhibition performance of scale inhibitors was investigated.Moreover,the mechanism of scale inhibition and corrosion inhibition was explored by electrochemical test and SEM.The results show that MA-AA and AA-AM-HPA have the best scale inhibition effect at the mass ratio of 2:1,and the static scale inhibition rate is 78.50％.The corrosion rate of HA177-2 aluminum brass is 0.127 mm/a at 67℃ when the seawater concentration is doubled.Besides,the results of dynamic simulation test show that when the dosage is 5 mg/L,the scale inhibition rate of calcium and calcium sulfate of the compound scale inhibitor reaches 70.45％and 89.71％,respectively,which is better than that of the selected commercial scale inhibitors.In addition,the electrochemical test and SEM results show that the main mechanism of scale inhibition is lattice distortion,and the compound additive belongs to a mixed-type inhibitor,which mainly suppresses anode reaction.What's more,the compound scale inhibitor reflects a threshold effect.Considering the scale inhibition and corrosion inhibition performance and economy,the dosage of scale inhibitor is recommended to be 5-10 mg/L.
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