The Exergy Analysis And Energy Integration Of Wax Oil Hydrocracking Unit

With crude oil becoming heavier and deteriorating, urban smog problems are gradually getting national attention. The environmental requirements are more stringent, but the demand for gasoline, diesel and other light oil is increasing. Then the processing capacity of heavy distillate hydrotreating, hydrocracking and other secondary processing technology has been fairly rapid development, which has played an irreplaceable role in the refining industry. Domestic hydrocracking unit energy consumption is about from 30kgEO/t to 60kgEO/t, high above the foreign advanced level.Therefore, energy optimization of hydrocracking units is very necessary.According to an annual output of 1.5 million tons wax oil hydrocracking process unit in a refinery, the energy consumptionof which is about 51kgEO/t,the thesistakes advantage of process simulation software for accurate simulation.Effective energy analysis and pinch technology were combined for calculating and analyzing major equipments, then existing heat exchanger network was reformedand simulated to give energy-saving programs. From a global perspective of the energy integration for the preliminary study, the project has acertain significance.The accurate simulation of wax oil hydrocracking unit was achieved.Single segment series and cold high pressure column and light hydrocarbon absorber vacuum tower were used to describe the process.The thesis was based on the basic production data of wax oil hydrocracking units, which took advantage of Aspen Plus software to establish a strict mathematical model for each unit module in the process.By adjusting the parameters of the model, the simulation results and calibration data will achieve a good agreement, the relative error does not exceed 10%, so the simulation results can accurately reflect the actual operation of the production unit.Exergy analysis for unit equipment and pinch analysis for system energy were used to diagnose the energy bottleneck and energy saving potential.The exergy analysiswas regarded as a guide so as to get the energy balance calculation and exergy analysis of the main units such as pumps, heating furnace, reactor, distillation, heat exchangers and air coolers, then the distribution of exergy loss rate will be obtained and the exergy loss of the units will be found out. At the same time, pinch analysis was used to have a in-depth analysis for the existing heat exchanger network.The required minimum amount of heat utilities is 20968kW, the minimum amount of cold utility is 26558kW, there are still 45550kW saving space of the existing heat exchanger network.At last, energy-saving renovation projects and the energy integration programs were put forward. Under the condition of maintaining the existing process unchanged, the pinch technology was regarded as a theoretical basis for two energy-saving projects of heat exchanger network of wax hydrocracking unit. For the first energy saving program, the amount of hot utility savings is 42.2%, the amount of cold utility savings is 38.5%; for the second energy saving program, the amount of cold utility savings is 44.9%, the amount of hot utility savings is 51.5%. In addition, energy integration between distillation column T1007 and T1009 and wax hydrocracking process was discussed, total utilities will reduce 0.46kgEO/t compared with background process, so as to realize the purpose of energy saving.