Thread Content
During the hydrocracking reaction, the space velocity and reaction temperature complement each other within a certain range; that is, when increasing the space velocity while maintaining a certain degree of conversion, the reaction temperature can be increased to compensate for this, and vice versa. However, in industrial applications, the complementary range of variation for temperature and space velocity is actually limited. This is mainly determined by the following two factors: First, since the capital investment and operating costs of high-pressure fixed-bed hydrocracking units are quite high, and the operating technology is also quite complex, it is required that their continuous operation time be at least 18–24 months or longer ； Otherwise, frequent regeneration and start-stop operations are economically unreasonable. This requires that the process select the highest possible space velocity while ensuring a satisfactory operating cycle, so that the initial reaction temperature at startup is appropriate, thereby guaranteeing a sufficient temperature increase range throughout the entire operating cycle. Secondly, if an excessively high air velocity is used, it results in a higher initial reaction temperature, which in turn reduces the selectivity of the process and affects the yield of the desired product, leading to poor economic benefits; this is also not desirable. This situation may further deteriorate as operating time increases and the reaction temperature rises.