The fouling in the tubular heat exchanger of Algiers refinery

Abstract

List of symbols AThe heat transfer external surface (m 2 ) a ⊥ , a c⊥ The fluid passage area at side tube and side calender, respectively (m 2 ) C P The heat-storage capacity (kJ/kg °C) C Pf , Cp c The heat-storage capacity (kJ/kg °C) d The fluid circulating density at side tube di Tubes interns diameter (m) d 0,e Diamètre externe des tubes (m) d 4 15 Density D c , D e Diamètre de la calandre et diamètre hydraulique, respectivement (m) f t The friction factor F The correction factor G t The mass speed fluid circulating at side tube (kg/h m 2 ) h i The heat transfer coefficient at internal film (kW/m 2 °C) h 0 The heat transfer coefficient at external film (kW/m 2 °C) h i0 The heat transfer coefficient at internal film brought back to the external surface (kW/ m 2 °C) J hf , J hc Coefficient de transfert pour le fluide froid et chaud, respectivement (kW/m 2 °C) l Tubes length (m) m The cold fluid mass flow (the crude oil) (m 3 /h) m f , m c Débit massique pour le fluide froid et chaud, respectivement (kg/s) m f⊥ , m c⊥ Mass flow for the cold and hot fluid, respectively, concerning the straight section (kg/s) MLDTThe difference logarithmic temperature (°C) n c , n tThe devices and the master keys numbers P e , P s Inlet and outlet pressure of the crude oil respectively (Pascal)Abstract Crude oil fouling in refinery preheat exchangers is a chronic operational problem that compromises energy recovery in these systems. Progress is hindered by the lack of quantitative knowledge of the dynamic effects of fouling on heat exchanger transfer and pressure drops. In subject of this work is an experimental determination of the thermal fouling resistance in the tubular heat exchanger of the crude oil preheats trains installed in an Algiers refinery. By measuring the inlet and outlet temperatures and mass flows of the two fluids, the overall heat transfer coefficient has been determined. Determining the overall heat transfer coefficient for the heat exchanger with clean and fouled surfaces, the fouling resistance was calculated. The results obtained from the two cells of exchangers studies, showed that the fouling resistance increased with time presented an exponential evolution in agreement with the model suggested by Kern and Seaton, with the existence of fluctuation caused by the instability of the flow rate and the impact between the particles. The bad cleaning of the heat exchangers involved the absence of the induction period and caused consequently, high values of the fouling resistance in a relatively short period of time.

The fouling in the crude distillation preheat train of Algerian reffinery

“…Additionally, most of the previous studies neglect the contribution of the particulate fouling and less information is available about this type of fouling in crude distillation unit. More to the point, Harche et al (7) performed an experimental study to determine the evolution of fouling resistance of a light crude oil in the preheat trains (PHT) of the crude oil distillation units of Algerian refinery. As consequent, their results show that fouling resistance reaches a maximum value about 2.7 m² °K /kW after 690 days in service.…”