1. High Efficiency Cyclone Design Stairmand (1951) proposed a standard design of theCyclone separator for higher efficiency specifically, in 1951.
The basediameter of the cyclone separator is based upon the volumetric flow rate, andDimensions are derived from the base diameter of the cyclone separator inStairmand Design. Standard Procedure of High Efficiency Stairmand CycloneDesign 1 involves selecting a suitable inlet velocity which should preferablybe in the range of 20 to 30 m/sec.2.1. Factorsinfluencing the Cyclone SeparatorWith the above prominent parameters, some of themare constrained considering our conditions of the project objective. Particlessize diameter of 53 ?m iron ore sample is tested for particle sizeanalysis using laser interferometry and the results how that 176 ?m is the maximum particle size diameter with 0.172 ?m is the minimum diameter. 1.
806 ?m is found to be the average particle size in thedistribution range. Iron ore particles have the density of 4100 kg/m3 areused for the project objective. With the above mentioned constraints, theseparation efficiency can be influenced by controlling the inlet velocity andthe base diameter of the cyclone separator. Higher Velocity has to be chosenwith respect to the desired cut-off diameter for cyclone separation. Cut-offdiameter can be defined as the critical diameter of the particle up to which50% Separation efficiency is maintained in the particle size range. Theparticle diameters below cut-off diameter have lower separation efficiencybelow 50%.
To find the base diameter of the cyclone, InletVelocity of 22 m/s and maximum flow rate condition of 2000 litre per minutei.e., 0.
034 m3/s are used.Inlet area = = 1.5454 * 10-3 m2 1.5454 * 10-3= 0.1 D2 The diameter, D = 0.1243 m i.e.
, 12.43 cm which isapprox. 12.5 cm, is calculated as the base diameter of the cyclone separator.Theoretically, the Cut-off Diameter is calculatedby the following formula Cut-off Diameter = = 0.829 ?mVelocity more than 22 m/s could reduce the cut-offdiameter but also the base diameter (less than 10 cm).
Critical diameter ofreactor is 20 cm and at least half of it has to be maintained in cyclone toproper working of cyclone considering particle mass flow rate (0.0015 kg/s) andgas volumetric flow rate (0.034 m3/s).3.
CFD ModellingThe geometries attempted inthe paper are modelled using Solidworks and edited using ANSYS Workbench DesignModeler. The detailed description of the geometry is given by Fig.1.Cyclone separator schematic diagram showing different components3.1. Geometry DesignWith 12.
5 cm as basediameter, the other geometric dimensions of the cyclone separator are definedby the Stairmand Design which is as follows. Parameters Symbol notations Stairmand Design Proposed Design Inlet height a/D 0.5 0.625 m Inlet width b/D 0.
2 0.025 m Outlet diameter (vortex finder diameter) Dx/D 0.48 0.6 m Vortex insertion length S/D 0.5 0.
625 m Cylinder length H/D 1.6 0.200 m Cyclone total height Ht/D 4 0.500 m Solid outlet diameter Bc/D 0.4 0.50 m 3.2.
Modelling in Solidworks and ANSYS WorkbenchDesign ModelerThe geometry is saved in Solidworks editing formatand also in IGES format, which will be used in ANSYS Workbench Design Modelerfor further modelling and modifying the geometry necessary to meet therequirements of the workbench meshing platform for Hexahedral meshing. Fig.3.
Sliced Parts of the Cyclone Geometry and Meshing using ANSYS Workbench 3.3.MeshingThe paper also indicated thegeometry for the particular problem attained grid independence that reassures the mesh data pertaining to the geometrythat have been used to yield a reasonable prediction. The geometry issegregated as 3 blocks and meshed individually.
Unstructured Hexahedral gridelements are used. Total grid elements of 280,450 with 204,483 nodesare utilized in our simulation. Mesh Orthogonal Quality of 0.36 with Mesh Aspect Ratio of 8.36 have been found.3.4.
Governing EquationsUnsteady Lagrangian discrete phase model is utilised withsingle-gaseous phase flow is utilized to study the transient nature ofgas-solid phase physics and flow phenomena. The gas phase is modelled withReynold stress model with discrete phase model where the particles released fromthe CFB reactor are treated as inert particle materials. The governing Equations utilised in the simulation are as follows3.4.1.
Continuity EquationThe continuity equation is quintessential for solving any basicfluid flow computational problem and is based upon the law of conservation ofmass. For incompressible flow, , where isthe velocity vector components in the Cartesian co-ordinate dimensions, is the density of the gaseous phase. 3.4.
2.Momentum EquationsThe momentum equations of the three Cartesian co-ordinates areas follows. In the above equation, ?, ui are the density of thegaseous fluid, three components of the velocity in the space co-ordinatesrespectively.
Since turbulence is also included in the problem, ReynoldsAveraged Navier Stokes Equation is utilised for predicting the turbulence, where isthe time-averaged velocity function used to replace the fluctuating terms. Rij = is the Reynold stress term that requiresmodelling. The fluctuating terms are considered into the momentum equations forthe Reynolds averaged equation.
The interaction betweenthe flow and turbulent fluctuations include Mean pressure stress, mean viscousstress tensor and the Reynolds stress tensor.