The revision of production processes is based on darn, results and exp
erience gained from a wide range of tools and instruments, It is there
fore important to critically examine the limits and meaningfulness of
these tools and instruments as they apply to process revision, Followi
ng a description of a normal revision procedure, the limits and meanin
gfulness of the information obtainable by modelling, experiment and fu
ll-scale operation are discussed as a basis for process revision. Part
icular emphasis is placed on fundamental operational information obtai
ned from production plant. in addition, tools specially developed for
process revision are presented and evaluated. The common theme of thes
e tools is the ability to provide improved material balances of operat
ing processes. Some of the better known process evaluation tools are a
lso considered. The main feature of these tools is the abstraction of
the task of individual unit operations as a starting point for possibl
e process improvements.