Capital Cost for Retrofit

As an example, one very common retrofit situation is the replacement of distillation column internals to improve the performance of the column. The improvement in performance sought is often an increase in the throughput. This calls for existing internals to be removed and then to be replaced with the new internals. Table 2.8 gives typical 

Column modification Cost of modification (multiply factor by cost of new hardware) 

Installation of new trays 1.0-1.4 for the same tray spacing 1.2- 1.5 for different tray spacing 1.3- 1.6 when replacing packing 

As far as utilities and off-sites are concerned, it is also difficult to generalize. Small retrofit projects are likely not to require any investment in utilities and off-sites. Larger-scale retrofit might demand a major revamp of the utilities and off-sites. Such a revamp of utilities and off-sites can be particularly expensive, because existing equipment might need to be modified or removed to make way for new utilities and off-sites equipment. 

This estimate should not be treated with any confidence. It will give an idea of the costs and might be used to compare retrofit options on a like-for-like basis, but could be very misleading. 

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Figure 10.9 Non-dominated solutions for maximization of utility cost savings and minimization of capital cost for retrofitting EF to an HMD system, considering reboiler duty as utility credit (plot a) optimal values of decision variables corresponding to the Pareto-optimal front are in plots b-e.

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