NZQA Expiring unit standard
17619 version 4
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Title
Explain the efficient crystallisation, decanting, washing and filtration
of a-lactose monohydrate
Level
4
Credits
24
Purpose
People credited with this unit standard are able to: explain
factors which influence the primary crystallisation of -lactose
monohydrate; explain factors which influence the efficiency of
decanting and washing of -lactose monohydrate; and explain
factors which influence the efficiency of lactose refinery
filtration.
Classification
Dairy Manufacturing > Dairy Technology
Available grade
Achieved
Entry information
Critical health and
safety prerequisites
Open.
Explanatory notes
1
Primary crystallisation refers to the first crystallisation stage following concentration of
lactose by evaporation.
2
Showering refers to formation of excess small crystals at the expense of fewer, larger
crystals.
Outcomes and evidence requirements
Outcome 1
Explain factors which influence the primary crystallisation of -lactose monohydrate.
Range
optimum conditions, sub-optimal effects, process variables.
Evidence requirements
1.1
Concentrate feed variables to the third-stage evaporation process are explained
in terms of their influences on the nucleation rate and crystal growth rate.
Range
feed variables include but are not limited to – saturation level, %
total solids range from second-stage evaporation, temperature.
Primary Industry Training Organisation
SSB Code 101558
 New Zealand Qualifications Authority 2016
NZQA Expiring unit standard
1.2
The degree of supersaturation of the lactose in solution during crystallisation is
explained in terms of its influence on crystallisation.
Range
1.3
viscosity variables may include but are not limited to – proteins,
oligosaccharides, temperature.
Seeding methods are explained in terms of their influences on the nucleation
rate and crystal growth rate.
Range
1.7
impurities may include but are not limited to – minerals, proteins,
calcium phosphate.
Lactose slurry viscosity variables are explained in terms of influences on the
nucleation rate and crystal growth rate.
Range
1.6
heat transfer influences may include but are not limited to –
mixing, type of cooling medium, time.
Impurities in the lactose slurry are explained in terms of their influences on
nucleation rate, crystal growth rate and evaporator fouling.
Range
1.5
crystal nucleation rate and growth rate, showering, yield.
The temperature and rate of cooling of the lactose slurry are explained in terms
of factors which influence heat transfer and the nucleation rate and crystal
growth rate.
Range
1.4
17619 version 4
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dry-seeding, wet-seeding, self-seeding.
Lactose crystal size distribution is explained in terms of influences on the
nucleation rate and crystal growth rate.
Outcome 2
Explain factors which influence the efficiency of decanting and washing of -lactose
monohydrate.
Evidence requirements
2.1
Decanting and washing of -lactose monohydrate is explained in terms of the
effect of each of the major process steps on the composition of streams within
and leaving the process.
Range
2.2
major process steps may include but are not limited to – solid-bowl
decanting, hydrocyclones, screen-bowl decanting.
Decanting of -lactose monohydrate is explained in terms of the influence of
feed concentration (crystal composition) on separation efficiency.
Primary Industry Training Organisation
SSB Code 101558
 New Zealand Qualifications Authority 2016
NZQA Expiring unit standard
17619 version 4
Page 3 of 4
2.3
Washing of -lactose monohydrate is explained in terms of the influence of feed
concentration (crystal composition) and feed rate on product through-put and
wash water volumes.
2.4
Decanting and washing of -lactose monohydrate is explained in terms of the
effects of plant faults versus plant operation settings.
Range
plant faults may include but are not limited to – screen bowl failure,
hydrocyclone nozzle wear, level control, pump wear, foaming;
effects may include but are not limited to – high crystal loading,
coarse crystals, reduced localised and/or overall separation
efficiency, pressure reductions.
Outcome 3
Explain factors which influence the efficiency of lactose refinery filtration.
Evidence requirements
3.1
Lactose refinery is explained in terms of the purpose of filtration.
3.2
Lactose refinery filtration is explained in terms of the influences of variables in
‘dirty liquor’ (unfiltered lactose) feed.
Range
3.3
Lactose refinery filtration is explained in terms of the functions, principles of
operation, and optimum ratios of filtration additives.
Range
3.4
variables in 'dirty liquor' feed may include but are not limited to –
solids concentration, temperature, viscosity, flow rate, particle size
distribution.
activated carbon, diatomaceous earth, polyelectrolyte.
Lactose refinery filtration is explained in terms of the influences of filtration plant
variables.
Range
filtration plant variables may include but are not limited to –
surface area, pore size of filter media, filter element geometry.
3.5
Lactose refinery filtration is explained in terms of functions and critical
transitions of the pre-coating, filtration, cleaning and hold cycles.
3.6
Lactose refinery filtration is explained in terms of the function and principles of
operation of the main filtration and ancillary plant.
Range
filtration and ancillary plant may include but is not limited to – feed
tank and feed pumps, circulation loop, additive preparation and
dosing, filter pressure vessels, air pressure equipment, filter
configuration, clean liquor tank, polishing filters.
Primary Industry Training Organisation
SSB Code 101558
 New Zealand Qualifications Authority 2016
NZQA Expiring unit standard
17619 version 4
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This unit standard is expiring. Assessment against the standard must take place by
the last date for assessment set out below.
Status information and last date for assessment for superseded versions
Process
Version Date
Last Date for Assessment
Registration
1
25 November 2000
31 December 2017
Revision
2
13 June 2003
31 December 2017
Rollover and
Revision
3
26 January 2007
31 December 2017
Review
4
15 October 2015
31 December 2017
Consent and Moderation Requirements (CMR) reference
0022
This CMR can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
Please note
Providers must be granted consent to assess against standards (accredited) by NZQA,
before they can report credits from assessment against unit standards or deliver courses
of study leading to that assessment.
Industry Training Organisations must be granted consent to assess against standards by
NZQA before they can register credits from assessment against unit standards.
Providers and Industry Training Organisations, which have been granted consent and
which are assessing against unit standards must engage with the moderation system that
applies to those standards.
Requirements for consent to assess and an outline of the moderation system that applies
to this standard are outlined in the Consent and Moderation Requirements (CMR). The
CMR also includes useful information about special requirements for organisations wishing
to develop education and training programmes, such as minimum qualifications for tutors
and assessors, and special resource requirements.
Primary Industry Training Organisation
SSB Code 101558
 New Zealand Qualifications Authority 2016