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الأربعاء، 5 نوفمبر، 2014

Study The Corrosion of CO2 Removal Unit in Ammonia Process

Title: Study The Corrosion of CO2 Removal Unit in Ammonia Process
Author        : Mahmoud Fawzy Abou-Zaid Hamada
Collection   : Ph.D. Chemistry
Abstract:
The CO2 absorber is one of the largest pressure vessels in the ammonia plants which are suffering from severe corrosion problems worldwide. The aim of present study is to investigate the corrosion behavior of AI06 carbon steel absorber for CO2 removal in amine promoted hot potassium carbonate solution (Benfield solution). The present study simulates C02 removal unit in ammonia production process at Abu Qir Fertilizers and Chemical Industries Company (Alexandria, Egypt) and many other plants all over the world. A typical Benfield solution contains hot potassium carbonate K2C03, potassium bicarbonate KHC03, diethanol amine (DEA) as a promoter and Potassium metavanadate KY03 as corrosion inhibitor. The galvanic corrosion rate of carbon steel and stainless steel couple in this system was measured in absence of corrosion inhibitor found to be in the range from ll S mm / y to 5.9 mm / y depending on concentration of chemicals in the solution and operating parameters, the corrosion rate was measured by weight loss: echnique through measuring dissolved iron in the solution in relation to different
operating parameters such as solution velocity, solution temperature, K2C03, CO2 .oading, DEA and the effect of the presence of solution contaminants. In general .ncreasing solution velocity, solution temperature, K2C03, CO2 loading and the presence of solution contaminations increase the corrosion rate. However the increase of DEA in solution decreases the corrosion rate. Surface morphology study revealed presence of non .miform porous solid layer of corrosion product on carbon steel surfacend. The present system was successfully passivated with KY03 which added to the solution in the form of vanadium pentoxide, Y205 and Potassium oxide K20. The vanadium pentavalent V5 + reduced to the lower tetravalent state y4 + .The v "can passivate the steel surface by anodic: 'xidation of the iron to magnetite Fe304.The passivation process was carried out in relation .c different operating parameters such as effect of corrosion inhibitor concentration, solution velocity, solution temperature, K2C03, Presence of Diethanolamin (DEA), the Presence of O2 during Passivation process, effect carbon steel surface conditions and effect :: - dynamic addition of inhibitor .Corrosion rate decreased to be in the range from 0.008 -: nJyto 0.245 mm / y depending on concentration of chemicals in the solution, the way of:.; plying the inhibitor and operating parameters during passivation. Surface morphology s.udy revealed the formation of passive layer on carbon steel surface

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