Simulation And Energy-saving Research On Catalytic Cracking Unit

Catalytic cracking is a crucial part of the petroleum refining process,enabling conversion of heavy petroleum fractions into lighter products with higher added value.The International Energy Agency(IEA)reports that global production of light oil from catalytic cracking units currently exceeds 110 million tons per year,accounting for over 20% of total petroleum product output.However,catalytic cracking units consume significant energy and generate substantial waste heat and gas,leading to energy waste and environmental pollution.Thus,research into energy savings for catalytic cracking units is necessary.In our energy use analysis of the plant,we employed two thermodynamic analysis methods-enthalpy and exergy-to assess the plant’s energy use.Enthalpy analysis showed that actual energy consumption increased by 119.84 MJ/t and 215.32MJ/t for electricity and flue gas,respectively,compared with baseline energy consumption,indicating substantial energy-saving potential.Our analysis further demonstrated that the desorption tower bottom reboiler,stabilization tower bottom reboiler,and main fractionation tower were the primary equipment causing losses,with values of 498.39 k W,710.46 k W,and 3980.24 k W,respectively.Based on the plant process simulation and energy use analysis,we proposed energy saving ideas for the catalytic cracking plant based on operational optimization.We optimized 13 independent operation variables using a Python-Aspen Plus integrated optimization platform with genetic algorithm and NSGA II algorithm.The minimum plant energy consumption,maximum plant product yield,and maximum plant product revenue were determined as the three optimization objective functions.Single-objective optimization using genetic algorithm resulted in an 11.35% reduction in energy consumption and 2.17% and 1.88% increases in product yield and revenue,respectively,compared to current operating conditions.The NSGA II algorithm was used to optimize two bivector functions: minimum plant energy consumption maximum product yield and minimum plant energy consumption-maximum product revenue.After optimization,product yield increased by 1271.6 kg/h and the relative yield increased by 1.31% at the same product yield as current working conditions,and energy consumption of the plant reduced by 10.69% at the same product yield as current working conditions.In summary,our proposed energy-saving approach for catalytic cracking plants through operational optimization using optimization algorithms can be applied to other chemical plants,providing new ideas for energy-saving optimization.