Separation of Suspended Solids by （悬浮物的分离）.pdfVIP

Chapter 4 Separation of Suspended Solids by Sedimentation Processes 4.1 SETTLING OF DISCRETE PARTICLES IN AN IDEAL FLOW TANK In an horizontal flow settling tank, the suspension to be clarified flows horizontally through the tank and the suspension settles out on the floor of the unit. The classical theory of Hazen (1904) and Camp (1946) is based upon the concept of an ideal horizontal flow settling zone free from inlet and outlet disturbances in which particles settle freely at their terminal settling velocities as in quiescent conditions. The flow is steady and the velocity of the fluid is everywhere uniform. It is assumed that initially the particles are uniformly distributed over the cross-section of the flow and particles that settle out are not re-entrained. Flocculation, turbulence and other effects are absent. Referring to Fig 4.1 it can be seen that a particle follows a path determined by the vector sum of its settling velocity v and the horizontal flow velocity v . Particles entering the tank at water surface level and having t h v = v , where v /v = H/L, will just reach the tank floor in the tank flow-through time. Particles having a t 0 0 h settling velocity greater than v0 will also reach floor level, while those particles having settling velocities less than v will be removed from the fluid in the ratio v /v . 0 t 0 h v vR settling o zone H Area BH vh sludge zone B