Single-Phase Systems These lie somewhere between the extremes of macro-and microfluids. ·Two-Phase Systems A stream of solids always behaves as a macrofluid,but for gas reacting with liquid, either phase can be a macro-or microfluid depending on the contacting scheme being used. 4 4 • Single-Phase Systems • These lie somewhere between the extremes of macro- and microfluids. • Two-Phase Systems • A stream of solids always behaves as a macrofluid, but for gas reacting with liquid, either phase can be a macro- or microfluid depending on the contacting scheme being used