Method for minimizing material mixing during transitions in a material processing system

In a material processing system, a method for inhibiting mixing between a first material and a second material where the processing system has a piping system that includes a first pipe with a first effective diameter, the method comprising:

• providing a plurality of pipe pigs in the first pipe, the plurality of pipe pigs being sufficient to substantially fill a cross-section of the first pipe and to define a plug with a leading edge and a trailing edge such that the leading edge is in contact with the first material and the trailing edge is in contact with the second material;
• wherein each pipe pig has a nominal size that is smaller than the first effective diameter;
• and,
• wherein mixing of the first material and the second material is inhibited by the plug such that an amount of the first material present in the second material at the trailing edge is about 10% or less by volume and such that an amount of the second material present in the first material at the leading edge is about 10% or less by volume.