Experimental Study On The Fouling Of Heat Exchangers In The Crude Distillation Unit

With the worse of the crude oil property, it is necessary to solve the fouling of heat exchangers in the crude distillation unit (CDU). So far, systematic experimental study on the crude oil fouling feature is absent at home, the quantitative experimental data is even less, which holds up the development of the cleaning technology. The thesis which is aimed at this situation researches the fouling character of the SuiZhong 36-1 sour crude oil.At the moment, the studies of the crude oil fouling character mainly focus on the measurement of the fouling resistance and fouling rate, the disquisition of effective forecasting models, the investigation of the heat interchange operation condition, and so on. The thesis, on the basis of the thermal conduction rule, firstly analyzed the experiment approach and theory on the measurement of the thermal fouling resistance, and secondly self-designed the autoclave test apparatus, simulated heat transfer surface and fouling in crude oil, applied the King-View soft to acquire and record the surface temperature, bulk temperature, heating capacity, by means of analyzing the change of the heat transfer coefficient to obtain the fouling resistance and fouling rate, and investigated the effect of the heat interchange operational condition on crude oil fouling according to the fouling rate.Bulk temperature, surface temperature, Reynolds number and pressure effects have been established. With increasing surface temperature, deposition increased on the heat transfer surface, induction period cut down, fouling speeded up, the initial surface temperature from 310℃increased to 380℃, fouling rate augmented about six times. Contrast to the surface temperature, the film temperature effect on the crude oil fouling was stronger, the activation energy of 28.5kJ/mol was determined. At a constant surface temperature, bulk temperature elevated in the range of 200℃to 280℃, bulk chemical reaction enhanced in crude oil, the thermal fouling resistance and fouling rate increased. Reynolds number has a very complex effect on the fouling, at constant surface temperature, bulk temperature and pressure, the thermal fouling resistance and fouling rate presented a reductive trend with continuously increasing the rotation Reynolds number from 7000 to 12760, which showed that the deposition and adhesion or the chemical reaction near the thermal bound layer controlled the whole fouling reaction. The present laboratory findings demonstrated that fouling rate was to vary as Reynolds number to the -0.35 power. The fouling tendency was almost identity at different pressure conditions. The pressure had a very small effect on the crude oil fouling, even negligible.On the end, the thesis proposed three improved respect to the Polley threshold fouling model on the basis of experimental data, and check the veracity of the modified model.