.1. EvGT system without CO2 capture (reference system, System I)
A sketch of the EvGT system [33] is shown in Fig. 1. Water is
heated close to saturated conditions by the compressed air in the
aftercooler and exhaust gas in the feedwater heater and the economizer.
The heated water enters at the top of a humidification
tower and is brought into counter-current contact with the compressed
air that enters at the bottom of the tower, which is a column
with a packing that is either structured or dumped. Some
water is evaporated and the air is humidified. The water evaporates
at the water boiling point corresponding to the partial pressure
of water in the mixture, i.e., water evaporates below the
boiling point corresponds to the total pressure in the tower. Therefore,
low temperature heat, which cannot be used to evaporate
water in a boiler, can be recovered in an EvGT cycle. Since the
water vapor content in the air increases as the air passes upward
through the tower, the evaporation temperature also increases.
This ensures a close matching of the air and water temperature
profiles and small exergy losses compared to evaporation in a conventional
steam boiler. The EvGT system has a high efficiency, because
the waste heat from the gas turbine exhaust gas can be
recovered efficiently through the humidification of compressed
air in the humidification tower, the economizer and/or the
recuperator.
3.2. EvGT with chemical absorption system (System II)
A sketch of the EvGT system with chemical absorption c