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Slurry Piping Design

Slurry Piping Design

This document discusses the design considerations for slurry piping systems. It describes key factors like slurry characteristics, concentration, critical velocity, friction loss calculation… The design of the system is governed by following general considerations: a) 'o solid deposition in system. b) 'o change in slurry composition from inlet to outlet of the system. c) inimum wear and tar or erosion. The design and engineering of the system components is discussed in the following order: i) ine sizing and pressure drop. ii) Special consideration iii) #umps for slurry. iv) *nstrumentation.

Line Sizing And Pressure Drop

The basic steps in design are as follows :+.+ *dentify slurry characteristic .+. Select slurry concentration +.- Select trial pipe si!e+. alculate critical velocity+./ ompare design velocity with critical velocity+.0 alculate design friction loss+.1 alculate system pressure gradient and pump discharge pressure 2"planations and 3 or clarifications relevant t o each of above steps are discussed below.

Slurry Characteristics

Slurries can be classified into broad categories as homogenous or heterogeneous. The type of slurry dictates rheological properties and there fore characteri!ation is important.

Homogeneous Slurry

*n this type of slurry , solid particles are uniformly distributed in liquid medium. Such slurries are characteri!ed by high concentration of solids having small (fine) particle si!e .Typical e"amples are sewage sludge, clay slurry. Such slurries usually e"hibit non5'ewtonian flow behavior (effective viscosity changing with shear rate) . a6ority of them show behavior like 7ingham plastic (no shear rate up to yield stress and 'ewtonian behavior for stress beyond yield stress).

Heterogeneous Slurry

The solids are not uniformly distributed in liquid in such Slurries .*n a hori!ontal pipe the concentration of solids is higher at lower levels and lower at upper levels .Such a Slurry is characteri!ed by low concentration of large si!e particles . #hosphate rock Slurry is typical e"ample of this type.

Mixed e!"#ior of Slurry

any Slurries encountered in industry may show behavior in between homogeneous and heterogeneous. This would be more so when particles of different si!es constitute the Slurry . *n such a situation dominant characteristics have to be identified and design procedure adopted to arrive at safer design . 8 typical e"ample of this type is Slurry of coal particles in water.

Slurry concentration

Solid concentration of Slurry becomes an important consideration for following reasons: Solids concentration governs the Slurry specific gravity (and hence pumping cost) and sometimes the rheoloy of the Slurry.8t certain solid conc entration Slurry may b e difficult to trans port or unstable. *n su ch situations solids concentration would have to be selected for proper transportation. Solids concentration in static settled Slurry would be a useful guidance in this respect. 9enerally solid concentration +5+/ & below static settled Slurry concentration would prove stable and convenient for handling.Solid concentrations in settled Slurries could depending on nature of solid, vary over a wide range (+5/&) 9enerally solids with particle si!e of .5./ micron may form a stable Slurry for solid concentration up to &.

Trial pipe si!e selection

Since the throughout of Slurry (volume 3time) is known selection of pipe si!e (particularly pipe *nside dia) will determine the velocity of Slurry through the pipe(vol. flow rate ; velocity

Calculate critical velocity

alculations of critical velocity for homogeneous Slurry is now described as below:>or heterogeneous Slurries the procedure is little comple" . The details of the procedure for heterogeneous Slurry are available in an article by 8ude et. 8l (+)>or homogeneous Slurry , the procedure for calculating critical velocity is as follows:8) *f the Slurry shown 'ewtonian beha vior , then critic al =eynolds?s 'o.'=ec is considered as + and critical velocity is calculated.7) *f the Slurry is non5'ewtonian type and e"hibits 7ingham plastics type behaviour, then he procedure adopted for calculating critical velocity is as follow: $.% &se '!"rt (s!o)n "s fig.*+ to '"l'ul"te ,e' 2nter the chart (>ig.) with value of '@e , find the value critical =eynolds 'o. '=ec.*n present case '=ec ; 0 (say)7./ alculate critical velocity (Ac)ritical velocity can be calculated by using one of the following relationships: