Volume
SLS IIA : Cake Filtration - Fundamentals and Design.
Volume SLS IIA : Part
1 Introduction
This part
describes briefly the scope and contents of Volume IIA
Volume SLS IIA : Part
2 Modelling filtration processes
This part contains some
basic definitions and simple models which can be used
to simulate filtration processes. Only models of practical
use to industrialists are included; other models given
in the literature are difficult (or impossible) to use
in practical situations. The models in this part can
be used to estimate filtration characteristics from
particle properties and to extend the range of data
so minimising the amount of testwork required.
Volume SLS IIA : Part
3 Filter design and optimisation
This part describes the
general approach for designing new filters.
Volume SLS IIA : Part
4 Testwork
This part describes simple
laboratory scale equipment which can be used to simulate
full scale filters, and shows how the tests should be
carried out. The laboratory scale equipment includes
vacuum filters, pressure leaf filters, chamber filters,
batch compression filters and belt presses. Procedures
for laboratory-scale testing cover flocculation, precoating,
thickening, and other pretreatment methods, as well
as chamber filling, cake formation, dewatering by gas
blowing, washing, compression and discharge.
Volume SLS IIA : Part
5 Analysis of data
This part shows, with the
aid of worked examples, how the data from the testwork
should be treated. It also shows how the data can be
extended to give an optimum design by using the equations
given in Part 2.
Volume SLS IIA : Part
6 Alternative definitions.
This part gives definitions
and equations which are alternatives to those given
in Part 2. In general, these are equations which are
not recommended but which the reader may find in the
literature. Where appropriate, the relationship between
the recommended and alternative equations are given.
Volume SLS IIA :
Part 7 Nomenclature
Volume SLS IIA : Part
8 References
Existing
Reports
The
reduction in the moisture content of filter cakes. (SAR
6) (Rev)
The methods
of dewatering covered are gas blowing including hot
gas and steam blowing; gravity and centrifugal drainage;
and mechanical compression in batch machines (filter
presses, diaphragm presses) and continuous machines
(belt presses, screw presses, rolls on vacuum filters).
The report is concerned more with the process of dewatering
rather than with equipment. For each method, the report
describes the mechanisms, the theoretical models and
design methods. The report shows how to optimise the
performance by manipulating process variables or by
flocculating the feed. A selection guide is given to
allow the user to decide which method to use.
The
washing of cakes and thickened slurries. (SAR 50)
The basic
concepts of reslurry and displacement washing are first
explained. Then methods are described for carrying out
laboratory test work for obtaining washing data. Methods
are given for calculating the performance of single
and multi-stage co-current and counter-current operations
from the test data. Fundamental models for predicting
the behaviour of cakes during washing are described.
There is a description of the washing arrangements for
gravity, vacuum, pressure, compression, centrifugal
and membrane filters and for sedimentation equipment,
screens and washing columns. The design and selection
of spray nozzles, weirs and wash troughs is discussed
with particular attention to the problem of applying
small amounts of wash liquid. Selection of the wash
liquid is discussed in relation to viscosity, density,
temperature, polarity, volatility and reactivity. Methods
of controlling the volume and temperature of the wash
liquid and effluents are described. Optimisation of
the washing stage is discussed in relation to drum,
belt and leaf filters as is the relation between cake
formation, dewatering and washing.
The
sizing of vacuum filters. (DR 20)
The report
presents in logic diagram form a procedure for sizing
filters. The procedure requires that data should be
collected on the process limitations, on the properties
of the feed stream, and the required properties of the
product streams. Decisions can then be made on the type
of filter to use and on which variables are available
for optimisation. A suitable cloth is selected at this
stage. Test work should then be done with a representative
sample of slurry and should simulate full-scale conditions
as closely as possible. The leaf test is used for most
of the test work but the CST test and pilot-scale testing
may play some part. Design factors are given for scaling
up the results from the leaf test. Methods of optimising
the design are given for six different filter applications.
The final stage is to consider the mechanical design
of the filter and to specify the ancillaries.
Dewatering
by gas blowing. (DR 25)
The report
describes design methods for dewatering of filter cakes
by gas blowing, in the absence of evaporation effects.
The methods can be used for vacuum or pressure filters
and give rate of desaturation and gas flow required.
A quick method is given in which dewatering characteristics
are calculated from known cake properties. This method
requires no test work but is suitable only for initial
costing. The main design method requires a limited amount
of test work but correlations are given to extrapolate
the data to longer dewatering times and thicker cakes.
Design factors are given for scale-up to full size.
Details of the test work required are given and the
analysis of the results is illustrated with worked examples.
Alternative methods of dewatering cakes are discussed
and methods of optimising the design given.
Volume
SLS IIB : Cake Filtration - Equipment.
Volume SLS IIB : Part
1 Introduction
This part
gives an overview of the volume including sections on
the scope and contents. It also gives a glossary of
terms used in the volume.
Volume SLS IIB : Part
2 to 10 Nutsches
Parts 2-10 each describe
the available equipment options. They show when to use
one option in preference to another and give advice
on the installation, operation and maintenance of the
equipment. Some information on compression filters can
be found in Volume IIA.
Volume SLS IIB : Part
11 Control of filters
This part provides a checklist
of factors which should be considered when deciding
how to control a cake filter. It is illustrated with
examples of typical control methods. Different methods
of control are reviewed and the requirements of a control
system are listed. Typical control variables and manipulated
variables are given for various filtration operations.
Typical control strategies are given for a number of
types of filter.
Volume SLS IIB : Part
12 Ancillary equipment
This part helps the reader
to select ancillary equipment for cake filters. It covers
safety and layout as well as specific pieces of equipment
such as tanks, pumps and valves.
Volume SLS IIB : Part
13 Performance improvement
This part consists of a
check list of possible ways of improving filter performance.
A computer program based on this Part (CAKEFIMP) is
on the CD-ROM.
