Petroleum Refining. By Jean-Pierre Favennec, Robin Baker, https://books.google.lu/books?id=V6VTqs2KgWQC&pg=PA127&lpg=PA127&dq=gas+desulphurisation+refers+to+-flue&source=bl&ots=AdLINAX2OB&sig=jGtlPsIE5F2yOfA26gUxUzeuF6I&hl=en&sa=X&redir_esc=y#v=onepage&q=gas%20desulphurisation%20refers%20to%20-flue&f=false (en)