5 A new generation of wet FGD systems, pioneered in the mid to late 1990's, improved mass transfer, which resulted in the usage of more compact absorbers that are estimated to require 50 percent less material, compared to an older generation of wet FGD systems.
Mass transfer was improved by the wet FGD systems that began to appear from the mid 90s to the late 90s.
The newer wet FGD systems had a negative effect on mass transfer when they first came out.