13.Study on deposition characteristics of particulate matterin asymmetric heating tube of supercritical unit

Abstract:

Corrosion deposition on the heating surface of supercritical units can lead to a decrease of 9． 46% to 12． 40% in heat ex-change efficiency，seriously threatening the safe operation of supercritical units． However，there are relatively few existing studies onthe particle migration mechanism under asymmetric heating conditions． Therefore，by introducing a custom function of circumferentialasymmetric heat flux density，the mathematical characterization under asymmetric heating boundary conditions can be achieved． Forthis purpose，an innovative analysis model for the migration and deposition of corrosion products under the semi-circumferential heatingcondition of Φ14 mm × 2 mm × 3 000 mm was constructed． And the interaction mechanism between the non-uniform distribution of cir-cumferential heat flow and pipe diameter，particle size，inlet temperature and mass flow rate was further studied． The research resultsshow that the particle mass concentration on the hot side wall is generally lower than that on the cold side． When the particle diameteris within 1 μm，a better deposition effect occurs at the vertical tube wall on the cold side of the particles． Particles will generate con-centrated deposits approximately 1 meter long on the cold side wall surface in the trancritical region． Meanwhile，the second concentrat-ed deposits will also occur at a distance of 1 000 mm before and after the trancritical region on the hot side wall surface．

Keywords: vertical pipeline; particle deposition; half-cycle heating; supercritical unit; numerical simulation