Study Of Slurry Concentration And Flow Pattern In Polyolefine Reactor

Slurry concentration and flow pattern, as the basic parameters of the multi-phase flow, were very important to the design of the reactors and the optimized operation of the process. Reliable measuring techniques are therefore needed as well in academia as in industry for the rational description and the design of multiphase reactors. A novel acoustic emission (AE) technique were used to measure slurry concentration of the stirred tank and the loop reactor coupled with a fluidized bed, and flow pattern of the loop reactor coupled with a fluidized bed. Slurry systems generally released various AE signals comprised of particle-particle or particle-chamber collisions impact sound, particle-particle or particle-chamber friction sound, and liquid turbulence in the reactor. Therefore, measurement of AE energy and analysis could reflect the slurry concentration and flow pattern in reactors. The innovative results could be summarized as following:1. Two models of the slurry concentration in a stirred vessel, E-C_s model and R— C_s model, was proposed to explore the quantitative relationship between AE energy, stirring rate, and slurry concentration, by use of wavelet transform, on basis of the mechanism that AE signals with different frequencies emitted when solid and liquid impacted with the wall. The E—C_s model applied to be measured on the upper part of the tank wall, when the stirring rate was greater than the critical stirring rate. The R-C_s model applied to be measured on everywhere of the tank wall, when the stirring rate was greater than the critical stirring rate. AE signals were analyzed by using of 8 scales wavelet transform when the stirring rate was greater than the critical stirring rate. Based on the experimental data, the model parameters were estimated. Take the case of water and sands slurry system, the average absolute relative error between the calculated values and the actual vales of the slurry concentration was 7.62 %. Take hexane and polyethylene slurry system as another example, the average absolute relative error between the calculated values and the actual vales of the slurry concentration was 23.4%. Takehexane and polyethylene slurry system in the stirred vessel of CX polyethylene technique for account, the average absolute relative error between the calculated values and the actual vales of the slurry concentration was 43%. The results showed that this model could predict the slurry concentration with fairly good accuracy.2. Slurry concentration in the loop reactor coupled with a fluidized bed was measured with the use of AE technique. The results demonstrated that frequencies of acoustic emission emitted by the particle-chamber collisions were greater than 10 KHz. AE signals were analyzed by using of 8 scales wavelet transform. The energy ratio in special frequency spectrum(i?) increased monotonically with the increase of the apparent slurry concentration in the high consistency stock area of the fluidized bed and the loop. The results showed that the slurry concentration could be measured by analyzing R .3. The system of water and headings was used as an example and investigated under the slurry concentration at 0.15 g?cm"3 and at the velocity 7 m?s"' in the loop. Secondary flow in the bend of the loop was verified by AE technique. The energy and energy ratio in special frequency spectrum were used to characterize the apparent slurry concentration. The energy or energy ration on the outboard were much greater than that on the inboard. The results showed that secondary flow in the bend of the loop really existed.4. The system of water and headings was used as an example and investigated under the slurry concentration ranged from 0.03 to 0.15 g?cm"3 and the velocity ranged from 3 to 7 nvs"1 in the loop. Size separation of particles in the loop reactor coupled with a fluidized bed was measured with the use of AE technique and photography. AE technique showed the consistent results with the photography that particles with different size could be separated well in the loop reactor coupled with a fluidized bed by controlling the speed of the slurry in the loop. And the distribution efficiency (D) was defined to characterize the size separation in the reactor. The results showed that D increased with the increase of slurry velocity in the loop.5. Distributions of the acoustic emission in the axial direction and the radial direction in fluidized bed and loop were measured, under the apparent slurry concentration was 0.15 g?cm"3 and at the stirring rates ranged from 3 to 7 m's'1. It was found that the acoustic emission distributed evenly along the radial direction in fluidized bed and loop except the bend of the loop, and unevenly along the axial direction in fluidized bed and loop. There were a particle level and a high consistency stock area in the fluidized bed, as the energy of acoustic emission could be divided into two section with different size and there was a maximal value. The particle level increased with the increase of slurry velocity, and the high consistency stock area decreased with the increase of slurry velocity. Distribution of the acoustic emission energy along the axial direction in loop were similarly symmetric distribution, the energy of the first point in the ascending tube was greater then others, and order of AE energy magnitude in the ascending tube was the same as in the descending tube, but the average AE energy in the ascending tube was greater than that in the descending tube.