Solid/ Liquid Separation

by Tarleton; Wakeman

• ISBN13: 9781856174190
• ISBN10: 1856174190
• Format: Hardcover
• Copyright: 2005-11-04
• Publisher: Elsevier Science

Summary

The separation of solids from liquids in an industrial setting is a complex process involving specialised equipment and expertise: some would say that there is still an element of 'black art' about it. A clear understanding of the principles involved is essential if perfection in separation is to be achieved. This volume, written by two acknowledged experts in the field, provides that understanding. It takes a sequential and logical route through the major factors affecting industrial separation: the properties of liquids and particles; the fluid dynamic background to the filtration process; the use of gravity in the processes plus the formation, deliquoring and washing of filter cake. The whole is fully illustrated and supported by references to the literature.

Table of Contents

Preface	ix
Introduction	1	(18)
The separation process	1	(12)
Solid/liquid separation in the process flowsheet	4	(2)
Filter media	6	(4)
Cake and depth filtration	10	(1)
``Laws'' of filtration	10	(3)
Particle and liquid properties in filtration	13	(5)
Particle shape	13	(1)
Particle size	14	(1)
The solution environment	15	(3)
The nature of the fluid	18	(1)
Conclusions -- Perfection in separation!	18	(1)
Fluid dynamic background to filtration processes	19	(53)
Motion of particles in a fluid	19	(7)
Gravity settling at low concentrations	22	(2)
Settling in a centrifugal field	24	(1)
Suspensions with high concentrations of solid - hindered settling	25	(1)
Darcy's Law	26	(2)
Darcy's Law in filtration	28	(1)
Permeability and specific resistance	28	(10)
The Kozeny-Carman equation	29	(4)
Permeabilities calculated from cell models	33	(1)
Properties of porous media	34	(2)
The friction factor for particulate beds	36	(2)
Depth filtration (clarification)	38	(6)
Capture mechanisms	38	(4)
Modelling the capture process	42	(1)
Deposition and scour	43	(1)
Flow through fibrous and woven media	44	(7)
Flow through nonwoven, random fibre media	44	(1)
Monofilament woven media	45	(5)
Multifilament woven media	50	(1)
Cake deliquoring -- multiphase flow in porous media	51	(9)
Capillary pressure and threshold pressure	52	(1)
Relative permeability and capillary pressure	53	(4)
Application to cake deliquoring	57	(1)
Other deliquoring models	58	(2)
Cake washing -- Hydrodynamic dispersion	60	(8)
The equations of hydrodynamic dispersion	62	(3)
Washing deliquored filter cakes	65	(2)
Other models for cake washing	67	(1)
Expression -- deliquoring by compression	68	(3)
Conclusions	71	(1)
Gravity clarification and thickening	72	(24)
Basics of gravity settling	72	(4)
Batch sedimentation	73	(1)
Types of sedimentation	74	(2)
Clarification	76	(3)
Thickening	79	(16)
Relating batch test data to thickeners	80	(5)
Thickener area	85	(3)
Thickener depth	88	(4)
Zone sedimentation models	92	(1)
Compression subsidence models	92	(1)
Zone settling vs. compression subsidence models	93	(2)
Conclusions	95	(1)
Filtration: cake formation	96	(66)
Relationships between process variables	100	(4)
Compressible cake filtration	104	(14)
Pressure conditions in a compressible filter cake	105	(2)
Working relationships for compressible filtration	107	(1)
Effects of pressure on filter cake properties	108	(1)
Other factors affecting filter cake properties	109	(7)
Expressions for the solids mass deposited	116	(1)
Expressions for suspension concentration	116	(1)
Relationships between cake thickness and filtrate volume	117	(1)
Basis for filtration calculations	118	(11)
Constant pressure operation	119	(7)
Constant rate operation	126	(2)
Variable pressure-variable rate operation	128	(1)
Filtration tests to determine cake formation data	129	(4)
Filtration onto cylindrical elements	133	(4)
Constant pressure filtration	134	(1)
Constant rate filtration	135	(2)
Filtration in centrifuges	137	(6)
Centrifugation rate and filtrate flow rate	138	(4)
Cake thickness dynamics	142	(1)
Filtration from suspensions of Non-Newtonian liquids	143	(1)
Process calculations	144	(12)
Optimisation of cycle times	152	(4)
Advanced models of cake filtration	156	(5)
Constitutive properties	158	(2)
Models incorporating interparticle interactions	160	(1)
Conclusions	161	(1)
Cake deliquoring	162	(34)
Threshold pressure and irreducible saturation	163	(5)
Irreducible saturation of vacuum or pressure deliquored cakes	166	(1)
Irreducible saturation of centrifuge cakes	166	(2)
Design charts for deliquoring	168	(9)
Vacuum and pressure deliquoring	171	(1)
Centrifugal deliquoring	172	(1)
Gravitational drainage	173	(1)
Experimental validation of the design charts	173	(4)
Example calculations for deliquoring	177	(15)
Summary of deliquoring calculations for vacuum and pressure filters	179	(8)
Effects of particle size, cake thickness and pressure difference	187	(1)
Summary of deliquoring calculations for centrifugal filters	187	(5)
Cake cracking	192	(3)
Stresses in partially saturated filter cakes	192	(3)
Conclusions	195	(1)
Cake washing	196	(51)
The wash liquid and washing curves	198	(7)
Measurement of washing curves	199	(3)
Representation of washing data	202	(1)
``Washing efficiency''	203	(2)
Cake washing models for design	205	(7)
Continuous washing processes	212	(10)
Correction factors for full scale filters	215	(5)
Washing deliquored filter cakes	220	(1)
Cake washability	221	(1)
Reslurry washing	222	(6)
Multiple reslurry systems	223	(3)
Countercurrent multiple reslurry systems	226	(2)
Multiple washing filter installations	228	(17)
Rotary vacuum filter flow sheets	229	(7)
Countercurrent washing on belt filters	236	(9)
Conclusions	245	(2)
Expression (compression deliquoring)	247	(19)
Experimental evaluation of expression	249	(3)
General treatment of experimental expression data	250	(2)
Interpretation of expression data	252	(9)
Analysis of the first stage -- cake formation	252	(2)
Analysis of the second stage -- cake consolidation	254	(7)
Expression on curved (2-dimensional) filter media	261	(1)
Factors affecting expression characteristics	261	(4)
Expression rate increase by inserted strings	263	(1)
``Torsional'' expression	264	(1)
Conclusions	265	(1)
Membrane filtration	266	(30)
Membrane filtration processes	268	(12)
Crossflow filtration vs. normal (cake) filtration	270	(1)
How much permeate could be produced?	270	(1)
Membrane fouling and concentration polarisation	271	(3)
Fouling by proteins and other biological materials	274	(2)
Fouling by inorganic particulates - effects on MF performance	276	(4)
Ultrafiltration	280	(7)
Rejection	280	(1)
Mass transfer analysis	280	(2)
Determining the mass transfer coefficient	282	(1)
The diffusion coefficient	283	(3)
Limiting flux	286	(1)
Limiting concentration	287	(1)
Microfiltration	287	(4)
Filtration rate equations	287	(1)
Deadend filtration	288	(2)
Crossflow filtration	290	(1)
Critical flux operation	291	(3)
Deposit characteristics	292	(2)
Conclusions	294	(2)
List of notation	296	(11)
Bibliography and additional bibliography	307	(21)
Index	328