大气污染控制LectureControlofPrimaryParticulates.ppt

Air Pollution Questions for the Last Lecture Answer Answer Particles too large for Stokes’ Law Particles too Small for Stokes’ Law Lecture 9 Control of Primary Particulates Lecture 9 Control of Primary Particulates Lecture 9-1 The nature of Particulate Pollutants Ⅰ Types of Particles collection devices Ⅰ Types of Particles collection devices The general idea of wall collection device 2.Gravity settlers (2) Block flow model (2) Block flow model collection efficiency (2) Block flow model (2) Block flow model (3) Mixed flow model Mixed flow model and Block flow model Shortcoming of Gravity settlers Ⅲ Centrifugal Separators Ⅲ Centrifugal Separators Ⅲ Centrifugal Separators Questions for the Last Lecture The general idea of wall collection device Ⅲ Centrifugal Separators (3) gas flow and efficiency Because rectangular inlet is arranged tangentially to the circular body of cyclone, so that the entering gas flows around the circumference of the cylindrical body, not radically inward. ① Outer helix around the outer part of the cylindrical body with downward component. ② Inner helix is at the center of cylindrical body, flowing upward to the gas outlet. 旋风除尘器 (3) gas flow and efficiency (3) gas flow and efficiency L — the length of the flow path N — the number of turns that the gas makes the traversing the outer helix of the cyclone D0 — the outer diameter of the cyclone (3) gas flow and efficiency (4) Cut diameter (4) Cut diameter A Multiclone (5) Pressure drop of cyclone (6) Location of cyclone. Ⅳ Electrostatic Precipitators (ESP) The basic idea of all ESPs is to give the Particles an electrostatic charge and then put them in an electrostatic field that drives them to a collecting wall. (2) The charge on the particles by field charging ε — dielectric constant of the particle,1 for vacuum, 4-8 for typical solid particles. ε0 — the permittivity of free space, 8.85×10-12 C/(V·m) D — particle diameter. E0 — the local field strength. (3) Electrostatic force (3) El