The hydrocarbon kicker removes hydrocarbons from the gas stream while
leaving the SO2 concentration unaffected. It operates on a selective
permeation principle using differential pressure to force hydrocarbon
molecules to pass through the tube wall. The differential pressure is created
across the tube wall as sample gas passes through a capillary tube which
reduces its pressure. The sample gas is then fed to the shell side of the
hydrocarbon kicker.