Thread Content
Since the 1980s, development of pressurized hydrocracking technology with operating pressures of 6.0 Mpa–10.0 Mpa has also become active, and several units have been put into industrial use. However, due to limitations such as product quality, conversion concentration, raw material adaptability, and unit flexibility, medium-pressure hydrocracking still finds it difficult to replace high-pressure hydrocracking. When processing the same raw material, the first difference lies in product quality. Reaction pressure has a significant impact on product quality; whether it is the aromatic content and smoke point of jet fuel, or key physical and chemical properties such as aromatics content and cetane number in diesel, the quality of products obtained through high-pressure hydrocracking is much better. The smoke points of the jet fuel produced by medium-pressure hydrocracking are not up to standard, and the BMCI value of the tail oil is too high, which makes it unsuitable as a feedstock for ethylene production ； From the perspective of the requirements for clean diesel in the 21st century, a high content of aromatics in diesel – particularly polycyclic aromatics – is not a desirable characteristic for high-quality diesel. From this perspective, high-pressure hydrocracking is an important method for directly producing clean fuels. Next is the depth of transformation. Under medium-pressure conditions, if inferior raw materials are used, the conversion rate remains around 20-40%; higher conversion rates accelerate the deactivation of the catalyst, making it difficult to maintain operation over a long period of time ； Conversely, to increase the conversion rate at medium pressure, it is necessary to use higher-quality raw materials. Therefore, high-pressure hydrocracking clearly has advantages if it can produce high-quality light oils from heavy vacuum distillates at high conversion rates, while also exhibiting strong adaptability to variations in feedstock. Finally, a comparison from an investment perspective. Research conducted by the French Institute of Petroleum (IFP) on the same 1.5 million tons per year hydrocracking unit showed that high-pressure hydrocracking operates at a pressure that is 1/4 higher than that of medium-pressure hydrocracking; it achieves a 20% higher conversion rate, a 50% longer catalyst life, higher capital costs of 26%, and higher operating costs of 23%. However, the payback period for the investment is only 0.1 year longer. Given the current level of hydrocracking technology developed in our country, under medium-pressure conditions (total pressure less than 12.0 Mpa), it is only possible to process oils with a dry point not exceeding 420–450°C (i.e., normal third-grade and first-stage reduced oil) ； For some paraffin-based oils with low impurity content, such as Daqing oil (whose dry point can reach 470–500°C), as well as heavier feedstocks (such as reduced naphtha and reduced kerosene), high-pressure hydrocracking technology (with a total pressure greater than 16.0 Mpa) must be employed to ensure the operational cycle of the facility, the degree of conversion, and product quality.