Hi Steve,
The feed gas temperature influences the kinetics of CO2 absorption reaction and equilibrium CO2 content in rich solution. This temperature is also guiding the heat requirement in your stripping section. Re-boiler duty in stripping section will increase if you bring down the inlet temperature too much. Therefore, an optimum temperature ( operating range) is normally selected to meet the product purity and specific energy requirement of CO2 removal process selected.
This temperature is normally fixed by licensor by taking care of many aspects including CO2 slip, height of the column, type of packing , rich solution loading, specific energy requirement, water balance etc. As others have highlighted, the feed gas temperature for sure should not be at 90C but at a moderate temperature of 65-75C. I would suggest you to contact your CO2 removal licensor for the best advice.
You can see the impact of feed gas temperature by running aspen simulation model for DEA based CO2 removal process.
Kind regards,
Satyajit