Importing　hotwind　to　the　direct-discharged　chimney　of　flue　gas　desulphurization　(FGD),　in　which　secondary　dehydration　device　is　installed,　could　lower　the　outlet　moisture　content　and　solve　the　problem　of　chimney　rain　effectively.　In　order　to　examine　the　influence　of　hotwind　on　the　flow　characteristics　and　optimize　the　structure　of　the　chimney　dehydration　device　to　match　the　dehydration　capacity　and　running　resistance,　discrete　phase　model,　RNG　k-Ε　double-equation　turbulence　model　and　component　transport　model　based　on　calculation　fluid　dynamics　(CFD)　were　adopted　to　build　a　hydrodynamic　model　to　describe　the　flow　field　inside　the　chimney.　The　variation　of　temperature,　velocity,　pressure　and　moisture　content　in　the　chimney　with　and　without　hotwind　and　the　optimal　angle　of　blade　of　the　rotating-stream　tray　were　obtained　by　the　numerical　simulation.　With　hotwind　added,　the　outlet　temperature　rises　3　K,　outlet　velocity　is　increased　0.6　m·s-1,　outlet　pressure　is　decreased　55　Pa,　outlet　moisture　content　is　reduced　29　mg·m-3,　and　the　optimal　angle　of　blade　is　45°.　Compared　with　the　angle　of　42°　in　applications,　the　optimal　angle　makes　the　running　resistance　decrease　108　Pa　with　negligible　increase　in　moisture　content.　The　simulation　results　are　in　the　range　for　practical　use,　verifying　the　rationality　and　feasibility　of　the　simulation.　The　simulation　provides　theoretical　bases　for　optimizing　the　internal　structure　of　chimney　and　directing　the　sample　locations　in　the　project.　©　All　Rights　Reserved.