Chemical Technology N6 — Document
April 2020 — N6 — Chemical Technology
N6
2020
Nated Engineering
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Q1— Section header —
1.1Various options are given as possible answers to the following questions. Choose the answer and write only the letter (A D\ next to the question number (1.1.1
1.1.10\ in the ANSWER BOOK.
1.1.1Evaporation occur beneath the surface and added heat and mass transfer resistance are encountered: Water present on the surface Concept of the film Concept of the resistance to flow
1.1.2
1.1.3ONE of the foll owing cannot be dried by double drum drying: Dilute solution Heat sensitive organic material Concentrated solutions of highly soluble material Moderately heavy slurries
1.1.4ormation of solid part icles within a homogenous phase: Evaporation Drying Capacity Crystallisation
1.1.5Correct sequence of stages in evolution of a crystal:
1.1.6Phenomenon of boiling point of liquid (solvent\ becoming higher when another compound is added, meaning that solution ha s a higher boiling point than pure solvent: Boiling point rise due to material in solution
1.1.7Decrease in moisture conten t of air by operation in which water is transferred from vapour state to liquid state: Dehumidification Humidification Relative humidity Percentage humidity
1.1.8aturated vol ume of air versus temperature represented by curve of these lines: Air volume Humid heat Humidity
1.1.9Combining function of evaporator, crystalliser, dryer, size reduction unit and classifier: Flash dryer Drum dryer Spray dryer Rotary
1.1.10Difference between temperature of condensing steam in steam chest and temperature of boiling solution at liquid vapour interface in evaporator body: Temperature difference driving force Apparent temperature difference
1.2Indicate whether the following sta tements are TRUE or FALSE by writing only 'True' or 'False' next to the question number (1.2
1.2.10\ in the ANSWER BOOK.
1.2.1Salting occu rs when the third component act physically with the original solvent a mixed solvent in which the solubility of the solvent is sharply decreased.
1.2.2Homogenous nucleation occurs when the solid particles of foreign substance influence the nucleation process by catalysing an increase of the nucleation rate at any given super saturation or giving the infinite rate of super saturation.
1.2.3hysical process is the transfer of heat from one point to another which is often encountered in the chemical industry.
1.2.4In a typical drying rate curve, the falling rate period occurs when a part of the solid surface is no longer wetted by the liquid, the water area available for direct heat and mass transfer decreases.
1.2.5lash dryer operates by a timer which moves a flapper valve so that for a fixed period of time dry solid returns to the mixer and for another fixed period it is removed as product.
1.2.6Boiling point rise due to material is the phenomenon that the boiling point of a liquid (a solvent\ will be higher when another compound is added, meaning that a solution has a higher boiling point than a
1.2.7Conduction is the term given to the transfe r of energy through space by electromagnetic waves.
1.2.8Natural draught cooling tower s consist of an empty shell, constructed either of timber or ferro concrete, where the upper portion is empty and merely serve to increase the draught.
1.2.9In most industrial processes heat is transferred from one point to another under steady condit ions of temperature difference, length of heat flow path and cross sectional area and is called the condition of steady flow of heat.
1.2.10
1.3Choose a term f rom COLUMN B that matches a description in COLUMN A. Write only the letter (A K\ next to the question number (1.3.1
1.3.10\ in the ANSWER BOOK. COLUMN A COLUMN B
1.3.10Dryer operate d under vacuum, often with direct heating Dryer 1, m wide and 3, m long giving drying time of 5 to 120
1.4Complete the follo wing sentences by writing only the missing word or words next to the q uestion number (1.4.
1.4.10\ in the ANSWER BOOK.
1.4.1
1.4.2
1.4.3
1.4.4
1.4.5
1.4.6
1.4.7
1.4.8
1.4.9
1.4.1050
Q2— Section header —
2.1Discus each of the following regarding agitated film evaporators
2.1.1Operation principle (8\
2.1.2Advantages (6\
2.1.3Uses (4\
2.2List FOUR factors influencing the performance of spray. (4\
2.3Discuss the drying principle (10\
2.4Draw a labelled diagram of rotary dryer. (18\ [50]50
Q3— Section header —
3.1Write brief notes on each of the following:
3.1.1Initial breeding (5\
3.1.2(4\
3.1.3Enthalpy balance (8\
3.2List THREE classifications of nucleation groups. (3\
3.3Name TREE adva ntages of each of the following
3.3.1Forced circulation evaporator
3.3.2Flash dryer
3.3.3
3.4ndicate the transfer of heat in each of the following situations ith the aid of labelled diagram
3.4.1arallel resistance
3.4.2
3.5A student generate the following data while performing an experiment in the laboratory Water solution contains 78% (m/m\ starch. Temperature of solution is 361 Molar mass of
Q4— Section header —
4.1Define each of the following
4.1.1Equilibrium moisture content (4\
4.1.2
4.1.3
4.1.4Saturation volume (4\
4.1.5Magma (3\
4.1.6Evaporation (3\
4.1.7Drying (2\
4.2A laboratory is at an absolute pressure of 760 mmHg and contains 0,025 kg water vapour/k g dry air. The room temperature is 31, C. The saturated vapour pressure of water at 31, C is 4,63 k Pa.
4.2.1Prove that the saturated vapour pressure of wate r at 31, C is 4,63 k Pa. (3\
4.2.2Calculate the percentage humidity. (8\
4.2.3Calculate the relative percentage humidity. (8\
4.3Name THREE essential parts for long tube evaporator with upward flow and give ONE function of each. (6\ [50] TOTAL SECTION B:50
Multiple Choice Options
1C)The saturated
Topics Identified
1
Business Functions
Mark Allocation
Sections50 + 50 + 50 + 50 = 200 marks
Paper information
TitleDocument
SubjectChemical Technology
LevelN6
Document typeQuestion paper
Year2020
MonthApril
Pages11
Downloads6
Examination context
Decade2020s
Years ago6y
SeasonAutumn (SH)
Start dayWednesday
Exam periodApril 2020
Days since exam2,383
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