Application Of Immobilized Enzymes In The Circulating Cooling Water System With Diesel Leakage

Due to the poor quality of heat exchanger,backward sealing technology,aging pipelines and improper operation in the recirculating cooling water system,oil leakage exists ubiquitously in the oil refineries of China.The mixing of leaking oil and recirculating cooling water in the system will not only affect the efficiency of heat exchange of the system,but aggravate the corrosion of the equipment.Thus,it is imperative to develop proper water treatment agents applicable to the system suffering from oil leakage to improve the quality of recirculating cooling water and ensure the normal operation of the system,which is also an effective way to save and utilize freshwater resources.The dissertation mainly focused on the application of immobilized enzyme in the recirculating cooling water system in the circumstance of oil leaking.The content consists of four aspects as follows:?1?Synthesizing mesoporous SiO₂ microspheres,the enzyme carrier,using sol-gel method and characterizing them with TEM,BET and FT-IR;?2?Immobilizing laccase,lysozyme and lipase with synthesized SiO₂ microspheres to investigate the properties of the three enzymes and analyzing the effect of corrosion inhibition of them;?3?Co-immobilizing lysozyme and lipase with physical adsorption and optimizing the immobilization conditions with Design Expert software;?4?Applying the co-immobilized lysozyme and lipase to simulated recirculating cooling water system and analyzing its effect in the condition of diesel leakage.The conclusions obtained from the experiment are as follows:?1?The diameter of the synthesized SiO₂ microspheres were uniformly distributed within 2-3nm.The average diameter was 2.55 nm and the specific surface area was 1088.9 m2/g;?2?The optimal condition of immobilizing laccase using SiO₂ microspheres were that the concentration of glutaraldehyde was 0.75%?v/v?,reaction time was 8h,the addition amount of enzyme was 0.04L/L,the fixed time was 10 h,reaction temperature was 40?and the pH of the solution was 4.In the recirculating cooling water with diesel concentration of 80mg/L,the corrosion inhibition rate reached the peak?49.23%?when the addition amount was 0.8g/L;?3?The optimal condition of immobilizing lysozyme using physical adsorption was that the lysozyme concentration was 0.8 g/L,immobilization time was 10 h,the pH was 6.5 and the ionic concentration of buffer solution was 50mmol/L.In the recirculating cooling water with diesel concentration of 80mg/L,the corrosion inhibition rate reached 78.21% when the addition amount was 0.7g/L;?4?The optimal condition of immobilizing lipase was that the lipase concentration was 2g/L,immobilization time was 8h,the pH was 8 and the ionic concentration of buffer solution was 25mmol/L.In the recirculating cooling water with diesel concentration of 80mg/L,the corrosion inhibition rate reached 61.7% when the addition amount was 0.8g/L;?5?Based on the results of single-factor experiment,the respond surface methodology?Box-Behnken?was conducted to investigate the optimal conditions of co-immobilizing lysozyme and lipase and corrosion inhibition.The optimal condition of co-immobilizing lysozyme and lipase was that the lysozyme concentration was 0.88 g/L,the time of immobilizing lysozyme was 11.81 h,the lipase concentration was 2.07 g/L and the time of immobilizing lipase was 9.22 h.The inhibition rate also reached the peak of 86.10% in the same optimal condition of co-immobilzation;?6?A filter column was made by using co-immobilized bi-enzyme and activated carbon with volume ratio of 1:2.The diesel concentration in the outlet of the column decreased significantly to 2.1mg/L.In addition,the corrosion rate of the outlet was 0.0818mm/a,dropping by 61.16% comparing with the corrosion rate of original water?0.2106mm/a?.