Volume DRY I
Part 1 Introduction.
This part defines the drying process and also reviews the
drying manual volumes available throughout the field of drying
technology and explains how to use them to best effect. It was
issued in 1993.
Volume DRY I
Part 2 Drying fundamentals.
This part states the fundamental definitions used in drying
and covers the underlying science in depth, including the
following:
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moisture in gases (psychrometry) and moisture in materials
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stages of drying, mass transfer, drying kinetics and
equilibria
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physical, chemical and biological properties
-
heat transfer by conduction, convection, radiation and
dielectric heating
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generic heat and mass balances.
Section 2 describes how moisture is contained in materials.
The various definitions of moisture content (wet and dry
basis) and the binding mechanisms between moisture and solid
are explained. Likewise, Section 3 covers moisture in gases,
otherwise known as psychrometry. Humidity, saturation, wet
bulb and dewpoint temperatures are defined and explained and
the use of psychrometric charts is described.
Section 4 explains what factors regulate the overall drying
process. The relationships between moisture content, drying
rate and time are described and illustrated by means of drying
curves. The section also categorises the various stages of
drying and the fundamental mechanisms involved.
Section 5 covers the process of heat transfer to the solids to
carry out evaporation, by convection, conduction, radiation
and dielectric heating; the relevant correlations for heat
transfer to single particles, sheets and beds are listed.
Correspondingly, Section 6 describes mass transfer processes
within the solids and the gas. Theoretical models for drying
kinetics are briefly reviewed and practical representations
such as the characteristic drying curve are explained. Section
7 covers the equilibria set up between moisture in the solids
and vapour in the gas, and shows the effect of temperature and
humidity on equilibrium moisture content.
Section 8 gives in detail the heat and mass balances around
generic dryers, including convective, contact and vacuum
units, and noting the effect of gas recycle, direct-fired
burners and other refinements. Section 9 defines the physical
properties of gas, solid and solvent and methods for their
calculation. Heat capacity, enthalpy, dewpoint, psychrometric
constants and diffusion coefficients are included. does
likewise for materials handling, thermal and chemical
properties.
The Part concludes with a list of useful additional sources
and textbooks on drying, a comprehensive reference list and an
explanation of the SPS standard nomenclature. The Appendices
contain additional psychrometric charts and a list of
conversion factors between SI and Imperial units for all
parameters used in drying.
Volume DRY I
Part 3 Industrial drying practice.
This part covers, in general terms, the important features of
actual dryers, and shows how the fundamentals discussed in
Part 2 apply in real industrial situations. It includes the
following;
-
Types of industrial dryers and their classification
-
Market data on the use of the different dryers in industry
-
Process configurations; detailed heat and mass balances
-
Preliminary dryer selection and preliminary dryer design
-
Dryer ancillaries and operations and product quality.
Industrially available dryers are classified in Section 2 in
terms of the basic form of equipment (e.g. trays, fluidised
beds, rotary dryers). All significant types of dryer are
described and illustrated by line drawings and, in some cases,
photographs. Flowsheet features, such as gas recycle, and
novel dryers are mentioned.
Section 3, on market data, lists the different industries in
which dryers are used, with details of typical processing
duties and the types of dryers used for them. Energy use
statistics for the UK are also included.
Section 4 is a very brief outline of the procedures used in
selecting a dryer for a new application (the full method is in
Manual Volume DRY II Part 1). Some consideration of how the
dryer fits into the overall flowsheet is included.
Preliminary dryer design is covered in Section 5. This gives
an outline of the basic methods for setting up heat and mass
balances, use of psychrometric charts for calculating dryer
inlet and outlet conditions and required air flow, and other
rough initial sizing procedures. An outline of the principles
of the main methods for detailed dryer design is also
included.
Section 6 is on Dryer Operations, reviewing topics such as
safety, control and instrumentation, troubleshooting and
energy considerations. The discussion is in general terms;
specific aspects are covered in the Manual Volumes on
individual dryer types.
Section 7 covers costs and economics. The main factors
governing capital and operating costs are noted, and scaling
factors are provided for historical cost data.
Section 8 is an outline of product quality considerations,
covering: particle size considerations, product morphology,
bulk density, powder stickiness, reconstitution, odour and
secondary volatiles, and heat sensitivity.
DRY I Part 4:
Technological Update
The Drying Technological Update, released in 2004, is a
comprehensive review of developments in theory and practice
over the last 5-10 years, bringing the Drying technical area
of the Process Manual fully up to date. It follows a similar
structure to the Drying Manual itself, with most sections
relating directly to a specific Process Manual volume.
Section 2 covers advances in drying fundamentals, especially
in humidity and psychrometry.
Section 3 is a new review of the various drying software
programs available, with descriptions of all the Aspen Process
Tools covering drying.
Section 4 is an overview of the advances in drying equipment,
including novel dryers introduced in the last 10 years, and
industrial sectors in which notable developments have taken
place.
Section 5 is a major update of dryer design procedures, which
have been much better systematised and classified in recent
years, enabling a more effective breakdown between generic and
dryer-specific methods. Particularly important advances have
been made on batch dryers.
Section 6 notes advances in techniques for dryer selection,
particularly practical experience of applying the techniques
recommended in DRY 2 Part 1, and short-cut methods which have
been developed as a result.
Sections 7 to 12 cover new dryers and theoretical developments
which apply to specific types of dryer. Examples of
significant developments include analysis of fluidised bed
dryers, particle motion in rotary dryers, drying in cyclones
and computational fluid dynamics (CFD), especially for spray
dryers.
Section 13 reviews developments in knowledge on drying
kinetics and equilibria, and Section 14 looks at product
quality aspects such as stickiness and polymorphism.
Section 15 covers dryer operations, including safety, control
and instrumentation, and troubleshooting.
Section 16 lists and briefly reviews the Recommended
Procedures and Research Reports.
Section 17 looks at the dryer in the context of the overall
process, an important new field of analysis which has largely
developed since the late 1990's, with close links to
General Solids Processing (Mini-Manual) Volume 5. A
comprehensive reference list of approximately 150 recent
papers and publications is also included.
