The carbon dioxide in the exhaust gas needs to be absorbed in a solvent such as diethanolamine $($DEA$).$ The solubility of $C{O}_2$ in DEA is inversely proportional to the temperature of the gases. Thus, the exhaust gases must be cooled sufficiently for the efficient functioning of the carbon capture system. A substantial part of this cooling can be accomplished by internal heat recovery which involves transferring this heat to other process streams in the plant which require heating.

The process streams along with their inlet and $($target$)$ outlet temperatures and thermal capacity rates are summarised in table $1.$ Any external heating will be provided by burning natural gas which costs $\frac{110}{M}Wh$ any external cooling will require electric input from the grid which costs $275/$MWh$.$

Table $1$: Main process streams

$\backslash$table$[[$Stream$,m^{}{c}_p,$Temperature in$,$Temperature out$],[,MW.K^{-1},C,{?}^{?}C$