| In this paper,through the static scale inhibition and disperse iron oxide deposition test, a high performance of combined scale-corrosion inhibitor was selected,and its overall performance has been studied;The combined scale-corrosion inhibitor was applied to the quantity of recirculating water of 5 tons/h of the pilot plant to study the effect on the conventional physical and chemical indicators of water quality and microbial indicators of the cooling water system;Through the hanging patch test of the three materials of the carbon steel,copper and stainless steel in the pilot plant,dynamic corrosion performance of combined scale-corrosion inhibitor to the three materials of the carbon steel,copper and stainless steel was studied;Iron bacteria in the biofilm of the surface of the most serious corrosion of the three materials was isolated and purified,using 16S rDNA methods to identify the strain:On this basis,the carbon steel hanging piece which suffered the most serious corrosion was selected for the representative,and the preliminary study of iron bacteria corrosion mechanism was carried out.The main results of this research were summarized as follows:(1)The combined scale-corrosion inhibitor selected was compounded of poly-aspartic acid and polyacrylic acid,whose performance was excellent.The static calcium carbonate and calcium phosphate scale efficiency were 92.8%and 96.4%,respectively.The light transmission rate can reach 37.6%,and the dispersion capacity of iron oxide deposition was high.(2)The combined scale-corrosion inhibitor was reduced according to the pharmacy proportion,named B1,B2,B3,using the water sources of pilot test device-tap water as pilot water for the tests,through the static calcium carbonate scale inhibition and disperse iron oxide deposition test,the performance of B1,B2,B3 was evaluated.The results showed that: Before 12d,6d and 6d.the inhibition efficiency of calcium carbonate scale of B1,B2,B3 were above 85%,respectively.Using 85%as the inhibition efficiency criteria for judging the received,the cost of B3 was 0.07 yuan/(ton of water·day),which was only 50 pencent of B1 and B2,compared with the conventional scale and corrosion inhibitor formulations,it can save 75%-77%of pharmaceutical costs,and the economic efficiency was very impressive;The light transmission rate of B3 was 38.9%,and there was no significant difference compared with B1 and B2.Considering the three considerations of economic cost of pharmacy,the dispersion of iron oxide deposition and scale inhibition ability of pharmacy,B3 was selected to pilot study and dosing time was determined to 6d. (3)Conduct comprehensive performance study of the B3 results showed that:it has good adaptability to calcium ion,alkalinity and temperature.Under the condition of the concentration of calcium ion less than 200 mg/L,alkalinity less than 500 mg/L and the temperature less than 60℃,the rate of scale inhibition of B3 can reach 80%or more;The static scale inhibition efficiency was 85%or more,the static corrosion rate of B3 for carbon steel,stainless steel and copper can reach more than 60%after a month of action time,and it had good compatibility with the antiseptic in scale and corrosion performance;The dynamic bio-degradation rate of PAA in the compound pharmacy can reach 87.6%on the sixth day,therefore the integrated performance of B3 was excellent.(4)Add combined scale-corrosion inhibitor B3 to the pilot plant can ensure that the physical and chemical water quality indicator values of the circulating water were in line with industrial cooling water design standards(GB50050-2007) in the corresponding circulating cooling water quality standards.(5)The test results of the hanging patch in the pilot plant showed that polysaccharide content and iron bacteria of the biofilm in carbon steel,copper and stainless steel surfaces increased along with the running time.The polysaccharide content and the number of bacteria of the biofilm in carbon steel,copper and stainless steel surfaces in the No.1 pilot plant which was as comparison increased more quickly than those No.2 pilot plant to which combined scale-corrosion inhibitor and combined antiseptic were added.The polysaccharide content in the biofilm of carbon steel,copper and stainless steel surfaces in pilot plant No.1 increased from 0.080g/m2,0.096 g/m2,0.136 g/m2 in 14th day to 0.433 g/m2,0.447 g/m2,0.680 g/m2 after 98th day,respectively.The number of iron bacteria increased from 19 CFU/cm2,0 CFU/cm2,19 CFU/cm2 in 14th day to 57900 CFU/cm2,73 CFU/cm2,3480 CFU/cm2 after 98th day,respectively.The polysaccharide content in the biofilm of carbon steel,copper and stainless steel surfaces in pilot plant No.2 increased from 0.026 g/m2,0.096 g/m2,0.039 g/m2 in 14th day to the 0.226 g/m2,0.302 g/m2,0.179 g/m2 after 98th day,respectively.Compared with that of No.1 pilot plant,the number of iron bacteria in the biofilm of carbon steel,copper and stainless steel surfaces in pilot plant No.2 was more less,and the maximum was also only 23 CFU/cm2.(6)The addition of combined scale-corrosion inhibitor B3 to the pilot plant changed the the correlation between the number of iron bacteria in biofilms of carbon steel surface with corrosion rate of carbon steel,making no correlation between the number of iron bacteria in biofilms of carbon steel surface with corrosion rate of carbon steel.After 98 days of running time,its rate of dynamics corrosion to carbon steel and copper was also above 60%, indicating that it had good corrosion inhibition performance to carbon steel and copper which were metal materials suffering relatively severe corrosion in cooling water system. (7)The16S rDNA genetic identification on the iron bacteria after the separation and purification results showed it belonged to Sphaerotilus,which indicated that iron bacteria played an important role in microbiologically influenced corrosion in the circulating cooling water system.
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