TABLE OF CONTENTS In previous chapters aspects of the chemistry involved in the design of 'greener' processes and products have been discussed, along with the techniques for minimizing and controlling waste. Most of the discussion has centre on what chemists can do, but, as highlighted in Chapter 2, engineering also has a vital role to play. In this chapter some engineering aspects of green process development are examined; the use of these technologies can lead to safer, cleaner and more cost-effective processes.
Scale-up from the laboratory is not always straightforward, and what may appear to be a green efficient reaction on the bench may not result in a green process without appropriate development, including the correct choice of reactor and other plant equipment. Chemical processes can be divided into two main types, batch and continuous; most fine chemicals and pharmaceuticals are made in batch reactors whilst the majority of bulk chemicals are made in continuous plants. Semi-batch plants are used in some cases; these processes involve additional ingredients being added at certain stages into an otherwise batch process. Multi-purpose plants tend to go hand in hand with batch processing; these are relatively common in the fine chemicals industry, most bulk processes using dedicated plant. Reactor choice and operation can have a dramatic effect on the overall eco-efficiency of a process.
A typical batch reactor (Figure 8.1) will be made of stainless steel or glass-lined steel. Stainless steel vessels have better heat transfer characteristics than their glass-lined...
