Chemical Technology N6 — Document
August 2021 — N6 — Chemical Technology
N6
2021
Nated Engineering
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Q1— Section header —
1.1Various options are given as possible answers to the following questions. Choose the correct answer and write only the letter (A E\ next to the question number (1.1.1
1.1.5\ in the ANSWER BOOK.
1.1.1Which one of the following dryer ha baffles that distribute air uniformly and in which
1.1.2The formation of solid particles in vapour/snow Evaporation Drying
1.1.3The difference between the steam temperature and the apparent saturation temperature of the vapour leaving the evaporator mixture as determined from the pressure of the vapour
1.1.4The nucleation that occurs at low supersaturation where the growth rate of the crystals is optimum for good quality
1.1.5The volume occupied by unit mass of dry air plus any moisture the air may contain
1.2The following question is based on the five advantages of an agitated film evaporator. Complete the following sentences by filling in the missing word or words. Write only the word or words next to the question number (1.2.1
1.2.10\ in the ANSWER BOOK. This evaporator has the a materials, the evaporator keeps the
1.2.6ly
1.2.10sensitive product (10\
1.3Indicate whether the following statements are TRUE or FALSE. Choose the answer and write only True or False next to the question number (1.3.1
1.3.5\ in the ANSWER BOOK.
1.3.1ypical drying rate curve are based on experimental data of equilibrium moisture content at different times during the course of a drying operation
1.3.2Crystallisation from solution has industrial importan ce because of the variety of materials that
1.3.3Water is the only volatile material available in such large quantities that it can be considered valueless
1.3.4Chemical processes involving the transfer of heat from one point to another are often encountered in chemical industries
1.3.5Air conditioning unit in homes are practical application involving the unit operation of humidification and dehumidification
1.4The following diagram is of rotary dryer. Complete the diagram by filling in the missing labels . Write only the word or words next to the question number (1.4.1
1.4.10\ in the ANSWER BOOK. DIAGRAM (10\
1.5Give ONE term for each of the following descriptions by writing it next to the question number (
1.5.5in the ANSWER BOOK.
1.5.1The number of kilograms of water per k ilogram of dry solid when the drying limit has been attained by the use of air at any given temperature and humidity
1.5.2The formation of solid particles within homogeneous phase
1.5.3The process whereby fluid changes from the liquid state to the vapour state
1.5.4The number of kilograms vaporised per k ilogram of steam fed to unit
1.5.550
Q2— Section header —
2.1Write brief notes o each of the following
2.1.1Principle of drying (10\
2.1.2Initial breeding (5\
2.1.3Conduction (5\
2.2Differentiate between drying and freeze drying. (5\ 15040106
2.3A 1m long steel pipe with an inside diameter of 120 mm and a wall thickness of 80 cm carries steam at 200 C and is isolated by 50 mm asbestos. The inside temperature of the asbestos is 100
2.3.1The a rea of the steel pipe (2\
2.3.2The a rea of the pipe per asbestos (4\
2.3.3The l ogarithmic mean area (3\
2.3.4The h eat lost by the steel pipe per metr pipe (4\
2.3.5The i nside area of the asbestos (2\
2.3.6The o utside area of the pipe (2\
2.3.7The i nside temperature (8\ [50]50
Q3— Section header —
3.1Name THREE types of long tube vertical evaporator s. (3\
3.2
3.3Name SIX advantages of spray dryer. (6\
3.4Draw a labelled diagram of forced circulation evaporator and discuss its advantages in detail (10 + 3\ (13\
3.5Define the following terms:
3.5.1hring s rule and plot (5\
3.5.2Absorptivity (3\
3.5.3Stefan Boltzmann s law (4\ 15040106
3.6A water solution contains 72 % (m/m\ of glucose. In an evaporating operation where the mixture is at its boiling point, the temperature of the solution at the su face is 369 7 K.
Q4— Section header —
4.1Write brief notes on each of the following:
4.1.1The e ssential parts of the long tube evaporator and their functions (7\
4.1.2The c oncept of film (6\
4.1.3Percentage relative humidity (10\
4.1.4Dry bulb temperature (4\
4.1.5The s tart up operation of a heat exchanger (6\
4.1.6Growth related spurious nucleation (5\
4.2Name THREE uses of logarithmic mean temperature difference. (3\
4.3Write brief notes on equilibrium moisture content. (9\ [50] TOTAL SECTION B: 150 GRAND TOTAL: 200 1504010650
Topics Identified
1
Business Environments
Mark Allocation
Total200 marks
Sections50 + 50 + 50 + 50 = 200 marks
Paper information
TitleDocument
SubjectChemical Technology
LevelN6
Document typeQuestion paper
Year2021
MonthAugust
Pages9
Downloads5
Examination context
Decade2020s
Years ago5y
SeasonWinter (SH)
Start daySunday
Exam periodAugust 2021
Days since exam1,896
About Chemical Technology examination preparation
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