ABSTRACT
The economics of a process must be evaluated at a very early stage in its development. Then, as the process is moved from bench-scale to pilot plant to design and then to construction, the economics must be re-evaluated at timely intervals. Contingency allowance is an allowance for problems which have not yet been identified. The amount allowed for contingencies can cause a great deal of argument on a project because it can have a large effect on the economics. The method of depreciation allowed by the federal and state governments in the US, and national and regional governments in other countries is subject to frequent changes and needs to be checked before a detailed economic evaluation can be carried out. The flow diagram is then used to prepare an on-plot investment estimate, an off-plot investment estimate and a utilities summary. These serve as the major input for the manufacturing cost and for the economic evaluation.
