Polymer quality and production cost of industrial polymerization production not only depend on the polymerization reaction technology but also on the structural type of polymerization reactor. Mixed-tank reactor is an important polymerization reaction device which needs professional model selection and design to solve the quality and energy transferring problems, so that to produce products of superior quality and reduce cost.
Design and engineering enlargement of mixed-tank reactor almost have difficulties of all the mixing reactors as shown below:
(1) High requirements on product quality. For example: product molecular weight, molecular weight distribution, average grain diameter, granulometric distribution and particle morphology, etc. all have high requirements.
(2) Complicated variety of polymer system. For example: heterogeneous system, highly viscous non-Newtonian system and variable viscosity system, etc.
(3) Flow complexity in mixing tank. For example: randomness of three-dimensional flow, complicated shape and boundary conditions of mixer.
(4) Great heat effect during the polymerization process. Strict requirements on reaction temperature control; special design on heat transfer components and mixer.
(5) Large scale polymerization device.
We have university-industry cooperation for many years. We learnt a lot of valuable experience and theoretical guidance on polymerization reaction technology and device, developing mixing device for various polymerization processes and applying them into industrial production successfully.
Medium will go through or become viscosity state during many technology processes, for example:
(1) Concentration, evaporation, solvent recovery and desiccation on viscous medium (cream).
(2) Mixing and reaction of wet powder.
(3) Treatment on slurry of high concentration.
(4) Polycondensation, mass polymerization and solution polymerization.
(5) Devolatilization of polymer.
(6) Other phase changing processes (process from liquid→ slurry→ cream→ wet powder→ dry power).
Tank type mixing device cannot finish above process due to the problems below:
(1) Along with the reduction of volatile component, viscosity of medium will increase hundreds of times or even thousands of times rapidly. Tank type mixing device cannot exceed its limitation and will overload finally.
(2) Viscous medium will agglomerate or attach on the mixer and mixing shaft. No update on the surface and the evaporation area will decrease.
(3) Mediums attach to the inner tank wall will reduce the heat-transfer capability greatly.
According to the technological features and special medium property, we researched the horizontal single shaft self-cleaning mixing reactor and horizontal double-shaft self-cleaning mixing reactor that are suitable for wet medium, cream and high viscosity medium treatment. Self-cleaning mixing reactor integrates machinery, chemical engineering and heat transfer as one, using the smallest device to generate the highest productivity.
Unit operations in fine chemical engineering, medicine and pesticide have many types and respective features. For common physical process like distillation, cooling, dissolving, concentration and some homogeneous reactions of kinetic control, mixing is not the controlling factor; all common mixing devices (like standard glass lined reactor) can meet the technological requirement, so the design focuses are mainly the energy consumption and cost.
However, mixing device of most unit operations still need professional design, including continuous nitration, chlorination, addition, condensation, substitution, fluorination, acylation, sulfonation, aminolysis, oxidation, extraction, crystallization, hydrolysis and washing, etc. How to find the key problem of each process and design accordingly mainly depends on the long-term engineering experience and abundant knowledge. We find the essence of problem and match the chemical characteristics and transmission characteristics of reaction to get the best technology effect.