Abstract:

The oil vaporization of crude oil in heat exchanger often causes lots of problems. Domestic refineries often use pressure holding valves to build the higher pressure in the heat exchanger before pre-flash column to reduce the rate of oil vaporization, but the higher pressure has certain adverse impact on the efficiency of heat exchange. The simulative analysis was conducted for a heat exchanger with pressure holding valves before pre-flash column of a 12.0 Mt/a crude oil distillation unit by PRO/II software. The results show that with the inlet pressure of heat exchanger rising from 1.2 MPa to 2.2 MPa, the energy recovered from the heat exchanger network reduces by 8.24% and the subsequent atmospheric furnace load increases by 1.65%, the air cooler load and cooling water are increased by 4.73% and 1.64%, respectively. Two stage pre-flash drums solution is suggested to solve the problem. The results of three cases were compared with or without pressure holding valve and the two pre-flash drums solution. The results indicate that the two stage pre-flash drums solution can not only maintain the operating pressure in a reasonable range, but also recycle more low-temperature heat, and the atmospheric furnace load is reduced by 5.30%.

Key words: heat exchanger, oil vaporization, pressure holding valve, two pre-flash drums