Carbon capture is an important possibility to reduce carbon dioxide emissions. To be able to study the startup process of such an amine-scrubbing process, a startup model of a postcombustion-capture plant (pcc-plant) was developed in the Modelica language and validated with measured data from a pilot plant in Heilbronn, Germany. Afterward, the process was scaled up in the model to handle the entire flue-gas flow of a 875 MW coal-fired power plant, resulting in three parallel capture plants. A case study was carried out to investigate the startup process of the pcc-plant in detail, indicating that the startup time increased drastically when the plant is operating at partial load. The startup time for a cold start from the beginning of steam flow to a 90% carbon-capture rate is t = 1900 s at full load and t = 11 075 s at 15% load. The total heat demand in the reboiler of one pcc-plant is 326 GJ at full load and 370 GJ at 15% load. Other results show that the startup time increases linearly with increasing total amount of solvent and that the steam flow rate and solvent flow rate have a high impact on the startup time.