After the shutdown of the waxy crude oil pipeline, the wax⁃crystals in the crude oil will gradually separate out when the temperature in the pipe falls below the wax precipitation point. According to the variation of viscoelasticity of waxy crude oil with temperature in temperature drop process, a method for dividing the temperature⁃drop stage during the shutdown of pipeline was put forward by using the relation of the storage modulus, loss modulus and loss angle with temperature. The temperature drop process was divided into three stages with the critical point of wax precipitation point and the temperature point when the storage modulus and loss modulus were equal (loss angle equaled 45 degrees). Taking the Huage pipeline as an example, FLUENT was used to describe the temperature drop process and calculate the solution. In addition, crude oil with different properties was selected to verify the method, and the rule of temperature drop in waxy crude oil pipeline was obtained.

A cationic natural polymer flocculant has been prepared by reacting cationic reagent with the parent peanut shell．The peanut fibre epoxypropyltrimethylammonium chloride (PNET) flocculanting property and its application was examined and the preparation conditions were studied．Through orthogonal experiment the best synthesize conditions are: mass fraction of NaOH 15%,alkali temperature 20 ℃,alkali time 1.5 h,PNET is produced at 80 ℃ for 3 h by mixing 1 g cationic reagent with 10 g peanut shell．The flocculanting properties of PNET has been studied using sludge, lives dirty water and electroplating dirty water．The dehydrate efficiency can reach 89.0％,the phosphorus and chromium removal ratios can reach 58.3％，74.0％, respectively．