Screening And Performances Research On Green Water Treatment Agent For Central Air Conditioner Cooling Water

In order to solve the problems of scaling and copper-iron corrosion in cooling water system of central air conditioners,and overcome the disadvantage of high phosphorus content in existing water treatment agent,which may lead to water eutrophication.Through single factor test,mixing experiment and orthogonal test,a kind of environmentally friendly,non-phosphorus and free of heavy metal compound scale and corrosion inhibitor was developed by layers of screening and optimizing.Static scale inhibition test,rotary coupon test and electrochemical method were used to evaluate the corrosion and scale inhibition performance of the compound water treatment agent,as well as its adaptability on different conditions of water quality(pH value,temperature,hardness,alkalinity,concentration of Cl~-).The inhibition property and inhibition mechanism were explored by scanning electron microscopy,electrochemical test,X-ray diffraction,and energy spectrometer.Finally,the environmental and economic benefits of the compound water treatment agent were analyzed.The main results of this research were summarized as follows:(1)The optional green scale inhibitors are HPMA,PASP,PESA,POCA,ATMP by investigation,and their preferential order on anti-scale performance is as follows:HPMA>ATMP>POCA>PESA>PASP.Mixing test results of scale inhibitors indicated that there had no anti-scaling synergies between HPMA and ATMP,as well as between HPMA and POCA,while HPMA and low concentration of surfactant STA had excellent anti-scaling synergies.(2)The optional green corrosion inhibitors are sodium N-lauroyl sarcosinate,sodium gluconate,sodium tungstate,sodium molybdate,sodium citrate and sodium humate by investigation.Contrast test showed that only sodium N-lauroyl sarcosinate had excellent anti-corrosion performance both on A3 carbon steel and T2 red copper.Mixing test results of corrosion inhibitors indicated that there had no anti-corrosion synergies between sodium N-lauroyl sarcosinate and sodium molybdate,as well as between sodium N-lauroyl sarcosinate and sodium tungstate,while sodium N-lauroyl sarcosinate and ATC had excellent anti-corrosion synergies on T2.(3)Series of optimization experiments showed that the best ratio of the compound formula is HPMA 16mg/L+STA1.5 mg/L+sodium N-lauroyl sarcosinate 75mg/L+ATC2.0mg/L.(4)Water quality conditions(pH,temperature,hardness,alkalinity,concentration of Cl~-)had great effect on anti-scale and anti-corrosion performance of the best compound formula.Scale and corrosion inhibition rate can still remain at around 80%even in the worst water condition.Accordingly,the compound water treatment agent had good adaptability to water quality variation,and it can effectively solve the problems of scaling and copper-iron corrosion in central air conditioners system.(5)The scale and corrosion inhibition mechanism of the best compound is as follows:The compound water treatment agent can adsorb on active growing point of specific CaCO3 crystal face,which resulted in distortion of crystal lattice,thus hindered the crystal growth.The compound agent can also form a layer of dense adsorption film on metal surface,which can hinder the contact of metal surface with the corrosive ions in the medium.The electrochemical tests showed that the compound reagent was a kind of mixing type inhibitor for A3 carbon steel,and mainly suppressed anode polarization,while for T2 red copper was a kind of anodic inhibitor.(6)The best inhibitor compound obtained by screening had excellent environmental and economic benefits,which is expected to be applied in cooling water of central air conditioners.