Numerical Simulation of Flow Field and Flow State Division in Thin-Film Evaporators

The flow field and flow state of thin-film evaporators are complex,and it is significant to effectively divide and quantify the flow field and flow state,as well as to study the internal flow field distribution and material mixing characteristics to improve the efficiency of thin-film evaporators.By using computational fluid dynamics(CFD)numerical simulation,the distribution pattern of the high-viscosity fluid flow field in the thin-film evaporators was obtained.It was found that the staggered interrupted blades could greatly promote material mixing and transportation,and impact the film formation of high-viscosity materials on the evaporator wall.Furthermore,a flow field state recognition method based on radial volume fraction statistics was proposed,and could quantitatively describe the internal flow field of thin-film evaporators.The method divides the high-viscosity materials in the thin-film evaporators into three flow states,the liquid film state,the exchange state and the liquid mass state.The three states of materials could be quantitatively described.The results show that the materials in the exchange state can connect the liquid film and the liquid mass,complete the material mixing and exchange,renew the liquid film,and maintain continuous and efficient liquid film evaporation.

Electrical properties of zinc-oxide-based thin-film transistors using strontium-oxide-doped semiconductors

Strontium-zinc-oxide（SrZnO） films forming the semiconductor layers of thin-film transistors（TFTs） are deposited by using ion-assisted electron beam evaporation. Using strontium-oxide-doped semiconductors, the off-state current can be dramatically reduced by three orders of magnitude. This dramatic improvement is attributed to the incorporation of strontium, which suppresses carrier generation, thereby improving the TFT. Additionally, the presence of strontium inhibits the formation of zinc oxide（ZnO） with the hexagonal wurtzite phase and permits the formation of an unusual phase of ZnO, thus significantly changing the surface morphology of ZnO and effectively reducing the trap density of the channel.

Development on the Technique of Total Recovery of Benzoic Acid Residue

Benzoic acid residue is solid waste produced from the production of benzoic acid by oxidizing toluene.Because it contained important chemical raw materials such as benzoic acid,benzyl benzoate and fluorenone,it is necessary to recover them from the residue.In this work the technique featured with high efficiency evaporation and vacuum distillation was developed to obtain total recovery and utilization of the benzoic acid residue.By controlling the operation temperature at 260℃ and the pressure of 16kPa in the rising and falling film evaporators,heavy components separated efficiently from the residue can be polymerized and the light components consisting of 63% of the residue entered into a benzoic acid vacuum distillation column.Keeping the temperature of polymerization at(280±10)℃,coumarone resin was produced after adjusting the softening point according to the market requirements.Vacuum distillation was operated under the following conditions:top temperature at 186℃,top pressure of 16kPa,bottom temperature at 240-250℃,reflux ratio being 3︰1.Benzoic acid of 98% purity was distilled out from the column as a side stream and the bottom product was crude benzyl benzoate.By the developed technique,the benzoic acid residue was splitted into three products,benzoic acid,crude benzyl benzoate and coumarone resin without any surplus waste.