Yellow oil formation at acid gas removal unit in ethylene plant

The acid gas removal unit is a process unit of ethylene plant that employs caustic scrubbing technique to remove acid gases from the cracked gas stream. This process produces carbonyl polymer commonly called yellow oil. The first part of this thesis studied impacts of 3 factors, which are suspected to influence the yellow oil. formation. Oxygen is one factor that was studied by passing air through mixtures of acetaldehyde and caustic solution. Measure the amount of polymer formed by weighing the polymer solids. Repeat the test but passing nitrogen instead of air and compare the results. The two tests gave the same result. Temperature is the second factor that was studied by varying the temperature of reaction mixture of acetaldehyde and caustic solution on the water bath. Measure the amount of polymer formed by weighing the polymer solids. It was found that the amount of polymer solids increased with temperature. The third factor studied is the presence of iron solution in the system. Iron solution was added to mixtures of acetaldehyde and caustic solution to obtain10-100 ppm iron in solution. After the reaction, polymer solid was filtered through micro filter and weighted. The result showed no impact of iron solution on the amount of polymer formed. The second part of this study involved the use of inhibitor to reduce yellow oil formation. Inhibitors used in the study are hydrazine and hydroxylamine hydrochloride. Both chemicals have amine group that can react with carbonyl group. The test results showed that when the molar concentration of inhibitor was greater than the molecular concentration of acetaldehyde in the reaction solution no polymer was formed, indicating the effectiveness of the inhibitor in preventing yellow oil formation. The third part of the study investigated the effect of caustic soda concentration on the yellow oil formation. The test results indicated no impact of caustic soda solution on the yellow oil formation. The amount of yellow oil varied directly with the quantity of acetaldehyde in the system.