Process vessels and plant for gas capture

A gas scrubbing apparatus including at least two modules, each module including at least one process vessel for a gas scrubbing process, each process 5 vessel being selected from an absorber, a regenerator, a scrubber, a reboiler, a heat exchanger or a combination thereof. Each process vessel has top wall, a base wall, and at least three sidewalls formed from a cementitous material. Each process vessel has inlet and outlet ports for fluid entering and leaving the process vessel when in use, formed within at least one of the top wall, base 10 wall, or sidewall of each process vessel. The sidewalls of each process vessel define a polygon shaped cross-section, and at least one side wall of a first process vessel in a first module can be connected or abutted to at least one side wall of a second process vessel in a second module. 15 Figure 6