The Reason For Corrosion On The Overhead Circulation Of Atmospheric Tower And Selection, Synthesis Of Inhibitor In Processing Crude Oils With High Acid Value

In recent years, due to processing of high-acid crude oil, the overhead circulation of atmospheric tower appeared frequently corrosion perforation, leak, pump salt deposition and other new issues, the production of the device, safety, equipment corrosion were severely affected. In this work, the reason of corrosion on the overhead circulation of atmospheric tower, the synthesis and selection of inhibitor compounds were studied, which has important meaning to the work safety of refinery.In this paper, Salt deposition on atmospheric tower was analyzed by chemical and instrumental methods. The results showed that the main ingredient of the salt deposition was ethylenediamine hydrochloride which formed salt in high temperature without wat er. Appropriate amount of ethylenediamine can slow down corrosion by neutralization. however large amount of its injection will cause corrosion and salt; The investigation of the factors affecting salt hydrolysis illustrated that both the naphthenic acid and acetic acid had promotive effect on salt hydrolysis. Meanwhile, the hydrolysis rate increased with the increase of the acid value. Therefore, crude oils with high acid value promoted hydrolysis o f the salt and caused corrosion.The analysis results of overhead condensed water, top cycle oil and corrosion products showed overhead condensed water contained chloride, iron, sulfur ions, the top cycle oil of atmospheric contained a certain amount of chloride ions, mercaptan, but without elemental sulfur; The ion chromatographic qualitative analysis showed that top cycle oil contained small molecular carboxylic acid; The results of XRD and EDX indicated that corrosion products mainly were iron sulfide, iron chloride, iron oxide etc., so the hydrogen chloride and hydrogen sulfide are the main cause of corrosion.At the same time, through the analysis of samples on atmospheric tower circulation and line-one,s when washing tower, there was S, without the S2-; Solid sediments contained ethylenediamine hydrochloride, iron sulfide, iron chloride, hydroxy iron oxide, etc.; The brown liquid beads of line-one,s contained Fe2+, C l- and ammonium or amine; the pH of the water containing C l- and ethylenediamine hydrochloride on overhead circulation of atmospheric tower was 8.6~9.2,; Floc of O il-water interface contained FeO(OH), Fe(OH)3, etc.. All of these results further showed that the hydrogen chloride and hydrogen sulfide w ere the main cause of corrosion.Selection of neutralization corrosion inhibitor and oil-soluble corrosion inhibitor, the results of the evaluation of corrosion performance showed that NJZ, NJY had good corrosion effect. The influence factors of synthesis of a new type corrosion inhibitor(CIA) were studied, the best conditions were concluded: the time of synthesis cinnamyl imidazoline was 7 h, temperature was 230℃, mole ratio of cinnamic acid and divinyl three amine was 1:1.2; The temperature of synthesis of CIA was 80℃, molar ratio of cinnamyl imidazoline and the acetic anhydride was 1-0.6. The inhibition efficiency can reach 87.97% when the concentration of corrosion inhibitor was 100μg/g and temperature was 50℃.