Research On Naphthenic Acid Corrosion In The Dynamic State Of High Temperature

Naphthenic acid corrosion is a kind of corrosion form which usually occurs at the location of crude oil distillation unit and high temperature parts. With the growing shortage of oil resource, more and more inferior crude oil was supplied, and the problem of hyperthermia naphthenic acid corrosion has been one of the issues desiderating to be solved urgently in today’s refinery industry. This thesis mainly research on the performance of hyperthermia naphthenic acid corrosion in dynamic state. A corrosion test unit of high temperature and high flow-rate naphthenic acid corrosion was used to simulate how the pipe fitting like elbow, reducer and straight pipe would be corroded in refinery, and then according to those test results we can discovery the trend of typical materials(20# mild steel and 304 stainless steel) between naphthenic acid corrosion rate and temperature, flow rate and incidence. Combining test results and the conclusion of numerical simulation, we can reveal the relationship between wall shear stresses and corrosion rate when the temperature and TAN is constant. Lastly, we can realize the mapping between input and output parameters with the help of visual studio software.By the hyperthermia naphthenic acid corrosion experiment research some conclusions are drawn as follows. Firstly, corrosion products were oil-soluble iron naphthenate and 304 stainless steel would lose metallic luster after experiment and became brownness from silver. While 20# mild steel surface would be covered by black corrosion products and with the increase of temperature the stickiness became stronger. Secondly, there was no simple liner relationship between the corrosion rate of naphthenic acid and temperature, if the temperature within the range of 280~320 ℃ the corrosion rate decreased with the temperature increased, while if the temperature between 320~360℃ the other way around. Thirdly, the faster the fluid velocity was, the more serious corrosion as responded. Fourthly, with the incidence increased from 0°to 90°by the structure changed of straight pipe, reducer, elbow, the corrosion rate rose in turn. Lastly, the corrosion rate of 20# mild steel is 3~5 times that of 304 stainless steel.The results of fluent numerical simulation as follows. Firstly, the greater the fluid flow velocity was, the greater would be the wall shear stresses. Secondly, Newton fluid’s flowing in straight pipe, reducer and elbow at same velocity was analysed, it was gained that their area-weighted average wall shear stresses increased successively. Thirdly, taking the test results into account and found that if the temperature and TAN was constant the corrosion rate would increase with the increasing of wall shear stresses under the condition of pure naphthenic acid. So, by wall shear stresses estimating naphthenic acid corrosion was reliable.Lastly, building the projected curve of naphthenic acid corrosion rate with the least square method, and the predicted results was compared with experiment results and the accuracy of this projected curve is showed. With the help of visual studio software we can realize the mapping between input and output parameters.