Common Stirrer Problems and Solutions

　　1: Reducing nonuniformity in phase, temperature or concentration to achieve the required process results.

　　2: Focusing on heat transfer, mass transfer, reactions and product properties.

　　II. How Much Mixing Is Enough? When Does Excessive Mixing Reduce Product Quality and Yield?

　　This depends on how sensitive product quality, selectivity and related factors are to stirring intensity and duration. These relationships require detailed experimental or simulation studies before process development and scale-up.

　　III. What Are the Consequences of Poor Stirring and Mixing?

　　Producing a product that meets process objectives is essential. If scale-up fails to deliver the required productivity, quality and performance, production costs can rise significantly. More importantly, the market opportunity may shrink while time and money are spent improving mixing.

　　Solving mixing problems during production can cost much more than evaluating and resolving them during process development. The expense can be substantial: losses attributed to poor stirring and mixing in the US chemical industry were estimated at approximately 5%. In 1989, the chemical industry alone lost billions of dollars. In 1993, a multinational chemical company also lost over one hundred million dollars because of poor mixing.

　　IV. How Can New Stirring and Mixing Problems Be Solved?

　　Communicate with operators and the chemists responsible for process development. Without this dialogue, the importance of mixing problems may remain underestimated. Engineers often focus only on geometric similarity and reaction conditions. Useful experimental results require a detailed understanding of mixing mechanisms; proceeding without it involves significant uncertainty.