  This paper describes the design, construction principles and operations of
the distillation and stripping pilot plants tested at the Daya Bay Neutrino
Laboratory, with the perspective to adapt this processes, system cleanliness
and leak-tightness to the final full scale plants that will be used for the
purification of the liquid scintillator used in the JUNO neutrino detector. The
main goal of these plants is to remove radio impurities from the liquid
scintillator while increasing its optical attenuation length. Purification of
liquid scintillator will be performed with a system combining alumina oxide,
distillation, water extraction and steam (or N2 gas) stripping. Such a combined
system will aim at obtaining a total attenuation length greater than 20 m at
430 nm, and a bulk radiopurity for 238U and 232Th in the 10-15 to 10-17 g/g
range. The pilot plants commissioning and operation have also provided valuable
information on the degree of reliability of their main components, which will
be particularly useful for the design of the final full scale purification
equipment for the JUNO liquid scintillator. This paper describe two of the five
pilot plants since the Alumina Column, Fluor mixing and the Water Extraction
plants are in charge of the Chinese part of the collaboration.
