%0 Journal Article
%T Design Mixers to Minimize Effects of Erosion and Corrosion Erosion
%A Julian Fasano
%A Eric E. Janz
%A Kevin Myers
%J International Journal of Chemical Engineering
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/171838
%X A thorough review of the major parameters that affect solid-liquid slurry wear on impellers and techniques for minimizing wear is presented. These major parameters include (i) chemical environment, (ii) hardness of solids, (iii) density of solids, (iv) percent solids, (v) shape of solids, (vi) fluid regime (turbulent, transitional, or laminar), (vii) hardness of the mixer's wetted parts, (viii) hydraulic efficiency of the impeller (kinetic energy dissipation rates near the impeller blades), (ix) impact velocity, and (x) impact frequency. Techniques for minimizing the wear on impellers cover the choice of impeller, size and speed of the impeller, alloy selection, and surface coating or coverings. An example is provided as well as an assessment of the approximate life improvement. 1. Introduction There are numerous applications of mixers that deal with erosive solids, especially in the minerals processing and power industries. In many of these applications, there is an erosion-corrosion synergistic effect on the wear of a mixer¡¯s wetted parts, particularly the impeller. This paper pulls together the authors¡¯ research with numerous articles on erosion and erosion corrosion to permit a designer to optimize the cost-based life of eroding mixer parts before replacement is required. There are a large number of factors that can affect the rate of erosion. Many of these factors have been known and studied to some extent:(i)chemical environment,(ii)hardness of solids,(iii)density of solids,(iv)difference in liquid and solid density,(v)percent solids,(vi)shape of solids,(vii)fluid regime (turbulent, transitional, or laminar),(viii)fluid rheology (e.g., pseudoplasticity),(ix)hardness of the mixer¡¯s wetted parts,(x)young¡¯s modulus of the mixer¡¯s wetted parts,(xi)hydraulic efficiency of the impeller (kinetic energy dissipation rates near the impeller blades),(xii)impact velocity,(xiii)impact frequency,(xiv)angle of impact. Theoretically the rate of volume loss of material is due to the kinetic energy lost when a particle impacts a material [1]. This would suggest a velocity exponent of 2. However, presented below, experimental velocity exponents have ranged from 1.5 to 4.0. The general form of the equation relating erosion rate to velocity is given by where volumetric erosion rate, constant (function of all parameters other than or ), particle velocity or relative velocity for rotating systems (impellers), velocity exponent (can also be a function of other parameters), and impingement angle. Most investigators have used this general equation form. Sapate and RamaRao
%U http://www.hindawi.com/journals/ijce/2012/171838/