mass balance lecture
TRANSCRIPT
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Material Balance
Lecture by :
Ir. Dewi Tristantini MT. PhD.
University of Indonesia
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MaterialsBalance analysis (MB) is asystematic reconstruction of the way
in which a chemical element, acompound or material passes through
a natural cycle and/or its economicalbenefits. An analysis of the materialflow, usually is based on the origin of aphysical balance.
German investigation Committe, 1993
Definition
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Uses
day to day operation of process for
monitoring operating efficiency
Making calculations for design and
development of a process i.e. quantities
required, sizing equipment, number of items
of equipment
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Basic Knowledge
BASIS
The basis is the reference chosen for the
calculations in any particular problems. A
proper choice of basis frequently makes the
problem much easier to solve.
For selecting a suitable basis, ask yourself the
following questions:
1. What do I have to start with?
2. What answer is called for?
3. What is the most convinient basis to use?
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Basic Knowledge
CHEMICAL EQUATION AND STOICHIMETRY
Chemical equation provides both qualitativeand quantitative information essential for thecalculation of the combining moles of
materials involved in a chemical process.
Stoichiometry: quantitative relation ship
between reactants and products. Stoichiometric ratios: ratios obtained from the
numerical coefficients in the chemicalequation.
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Basic Knowledge
CHEMICAL EQUATION AND STOICHIMETRY
Chemical equation provides both qualitativeand quantitative information essential for thecalculation of the combining moles of
materials involved in a chemical process.
Stoichiometry: quantitative relationship
between reactants and products. Stoichiometryc ratios: ratios obtained from
the numerical coefficients in the chemicalequation.
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Basic Knowledge
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Basic Knowledge
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Example
Antimony is obtained by heating pulverized stibnite
(Sb2S3) with scrap iron and drawing off the moltenantimony from the bottom of reaction vessel.
Sb2S3+ 3Fe 2Sb + 3FeS
Suppose that 0.600 kg of stibnite and 0.250 kg of iron
turnings is heated together to give 0.200 kg of Sbmetal. Determine:
a. The limiting reactant
b. The percentage of excess reactant
c. The degree of completion (fraction)
d. The percent conversion
e. The yield
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Solution
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Solution
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Solution
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Its Very Simple Right ? =)
Just Like a Piece of Cake =)
Now Lets See The Real Mass Balance Calculation
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Conservation mass principle is used because it
indicates that:
Input Material = Output Material
whereas :
Units of measurements given in kg or moles or m3
per time
Material Balance
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Flow diagram
Graphic interpretation of the materials flows.It shows volumes, proportions, ecologicalrelevance among other characteristics.
Indicate the sequence or steps of theproductive process.
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Example 1: Input and Output diagram
Auxiliary materials
UnitOperation
Raw material
Product
(expected)
byproduct(usable)
Waste
Water Energy
Waste easilyassimilated by
theenvironment
Inert wastealways available
toxic/dangerouswaste
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Plant, Processor UnitOperation
Gaseous emissionsRawmaterials
Catalyst
Air/Water
Energy
Recycle
Reusable residues in otheroperation
Products
By-products
Wastewater
Liquid waste
Solid waste
Examples of Input and Output
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Examples of the Flow Diagram
Usage
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Mass balance filtration/centrifuge
feed suspension
wash water/solvent
solid
waste water filtrate
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Filtration
F1
5000 kg DM water
Impurity 55 kg
Water 2600 kg
API 450 kg
Water 7300 kg
Impurity 50 kg
API 2kg
Water 300 kg
API 448 kgImpurity 5 kg
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Mass balance - drier
feed
product
water/evaporated solvent
water/evaporated solvent
+ dried material
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Mass balance extraction/phase split
A + B
S
A + B
S + B
A = feed solvent; B = solute; S = extracting solvent
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Mass balances multiple units
Overall balance
Unit balances
Component balances
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Multiple units
E = evaporator; C = crystalliser; F=filter unit
F1 = fresh feed; W2=evaporated water; P3 = solid product;
R4 = recycle of saturated solution from filter unit
R4
E C FF1
W2
P3
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Mass balance procedures
1. Process description
2. Flowsheet
3. Label
4. Assign algebraic symbols to unknowns(compositions, concentrations, quantities)
5. Select basis
6. Write mass balance equations (overall, total,
component, unit)
7. Solve equations for unknowns
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ProblemsPROBLEMS
1. A cereal product containing 55% water is made at the rate of 500 kg/hr.
You need to dry the product so that it contains only 30% water. Howmuch water has to be evaporated per hour?
2. To prepare a solution of 50.0% sulfuric acid, a dilute waste acidcontaining 28.0% H2SO4 is fortified with a purchased acid containing
96.0% H2SO4 . How many kilograms of the purchased acid must bebought for each 100 kg of dilute acid?
3. An aqueous etching solution containing 8.8% KI is to be prepared toetch gold in printed circuit boards. The desired solution is to be formedby combining a strong solution (12% KI and 3% I2 in H2O) with a weak
solution (2.5% KI and 0.625% I2 in H2O)What should be the value of R, the ratio of the weights of the strong tothe weak solution, to make up the desired etching solution? What willbe the concentration of I2 in the final solution?