The Macroscopic Dispersion Of The Transfer Process Strengthed By Liquid-Continuous Impinging Streams

The strengthening factors of production efficiency and production process are often influenced by factor of heat and mass transfer and other factors, especially the flow field of the reactor in petrochemical and metallurgical equipments. The Liquid-continuous impinging streams reactor(LISR) is a new reactor in the chemical equipments. The source of excellent performance comes from the enhancing characteristics of mixing and dispersing. A large number of experimental results show that the LISR is not only good at dispersing and promoting the reaction efficiency, but also significantly improving product performance, so these advantages for searching for LISR of mixing and diffusion process has the necessity. At the same time, structure characteristics and dispersion characteristics exist in the LISR, especially fluid macroscopic dispersion characteristics affects efficiency of fluid mixing and dispersion efficiency, in the time domain, macroscopic dispersion is in advance of the microscopic dispersion, and macroscopic dispersion in excess of microscopic dispersion time required, so less macroscopic dispersion time can greatly shorten the total mixing time. But at present this research is not enough, the majority results of the fluid mixing and dispersing performance are from experimental method.The research is on the basis of previous experimental model and structure size, physical and geometrical model multiple grid is constructed by using pretreatment software Gambit. Then using the CFD-Fluent having numerical simulation analysis for LISR fluid macroscopic dispersive characteristics in flow field with different structure and operating conditions, the distribution laws for macroscopic dispersion characteristics with changes in various parameters are carried out.The main results inclueding: the maximum amplitude of pressure fluctuations of the inclined paddle is 16.3911 Pa, and the spiral surface paddle is 3.8017 Pa; The average shear stress of the inclined paddle reactor along the Z-axis is 0.0272 N/m2, the standard deviation of fluid component fraction in the Z-axis is 0.0226, and mixing time is approximately 2.5s; While the average shear stress of the spiral surface paddle in the Z-axis is 0.0204 N/m2, the standard deviation of fluid component fraction in the Z-axis is 0.0400, and mixing time is approximately 3s; In addition, the volume average turbulent kinetic energy produced of inclined paddle reactor is 0.0401 m2/s2, and the spiral surface paddle is 0.0185 m2/s2.When the blade speed is 1500r/min, the average of maximum pressure is 245.923 Pa and maximum turbulent kinetic energy is 0.168m2/s2; Moreover, increasing the blade speed makes the fluid macroscopic mixing time is shorter, but when the blade speed increases to a certain extent, changing in macroscopic mixing time required with the blade speed is not obvious, and increasing the spacing of draft tube has no obvious influence for maximum velocity of the fluid. The axial average pressure in stable time will first increases and then decreases, when draft tube spacing is 40 mm, the maximum value is the 6.432 Pa. The radial average pressure in the stable time will decreases first and then increases. When draft tube spacing is 60 mm, the maximum value is 99.367Pa; the turbulent kinetic energy decreases, the maximum value is 0.088m2/s2; Meanwhile, with the increasing of the draft tube spacing, the impacting area is also larger, macroscopic mixing time required will extend slowly, and the fluctuation effect weaken and maintain about 2.5s.The simulation results show that the the mixing performance of LISR with inclined paddle is better than the other one, and the component mixing of the inclined paddle is more uniform than the spiral surface paddle. As the impeller speed increases, the fluid was thrown inside LISR draft tube collide with each other in order to enhance compression, along between the fluid and the fluid energy into the more, until the energy is close to saturation, the fluid dispersion effect is not further enhanced. When the blade speed increments to 1500r/min, the average maximum pressure value for this condition, as 245.923 Pa, the maximum turbulent kinetic energy is 0.168m2/s2, and the turbulent kinetic energy is significantly greater than the average volume blade speed is 500r/min arising volume average turbulent kinetic energy, this time with a better macro dispersion; draft tube spacing in ascending order from small to large, the maximum velocity of the fluid movement is substantially similar; the average axial pressure after first increased and then decreased, when the draft tube spacing of 40 mm When a maximum value is 6.432Pa; radial pressure in the steady pressure decreases and then increases the mean time, a maximum value of 99.367 Pa when the draft tube spacing of 60mm; turbulent kinetic energy showed a decreasing trend, a maximum of 0.088m2/s2; at the same time, when the draft tube spacing increases, LISR the impact area is correspondingly increased, which led to the mixing time becomes longer, but the overall change is not great, results show that the draft tube spacing will affect LISR volume impact area, thereby enabling the fluid material within the impact area per unit volume of the collision intensity becomes weak macro-mixing and dispersing effect will be relatively weak. In summary, when the paddle type is the inclined paddle, the paddle speed is 1500r/min, the diversion tube spacing is 40 mm, and the optimal dispersion effect is the best.