materaial balance

8/14/2019 Materaial Balance

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Flow Sheets for Basic CHEN Unit Operations

Operations with Mass Transfer

1. DIVIDER/SPLITTER

a. The total balance is A=B+C

b. Composition of streams A, B and C is the same for each.

c. There in only one independent material balance since all compositions

are equal.

2. MIXER (Blender)

a. There are two or more entering streams.

b. There is only one exit stream, a "mixed" stream.

c. The streams can be any phase, gas, liquid or solid.

Splitter Feed, A

Splitter Exit 1, B

Splitter Exit 2, C

MIXER

Mixer Feed 2,B

Mixer Feed 1, F Mixer Product, E


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3. DRYER (Direct Heating)

a. Solvent stream leaves as a pure vapor and is solids free.

b. Exit dried solids are in the solid phase.

c. Dried solids may not be solvent free.

d. Feed can be solid, slurry or solution.

4. FILTER

a. Filtrate, the exit liquid, is solids free.

b. Filtrate is saturated with soluble component.c. The filter cake leaves with some liquid attached.

d. Concentration of stream E and liquid attached to the filter cake is the

same.

Dryer

Solvent, S

Dryer Feed, D Dried Product, E

Filter

Filter Cake

wet solids, S

Feed Solution

or Slurry, D

Filtrate

(Exit Liquid), E


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5. DISTILLATION

a. The more volatile components are in the distillate.

b. The less volatile components are in the bottoms.c. Separation is accomplished by boiling.

d. Perfect separation is not possible.

6. EVAPORATOR

a. Similar to drying, except both process streams are liquids.

Distillation

ColumnColumn Feed, F

Distillate, D

Bottoms, B

Evaporator

Solvent, S

Evaporator Feed, D Dried Product, E


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7. DEHUMIDIFIER

a. Feed stream contains a condensable component and a non-

condensable component.

b. Condensate is a liquid with the condensable component only.

c. The "dry gas" exit stream is saturated with the condensable

component at the T and P of the process.

8. HUMIDIFIER

a. The feed gas is not saturated.

b. The liquid is evaporated in the process unit.

c. The vapor exit product may or may not be saturated.

Dehumidifier

Condensate

liquid, S

Feed Gas

Moist Gas, DExit Gas, E

Humidifier

Volatile Feed

liquid, S

Feed Gas , DExit Gas

wetter gas, E


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9. GAS DRYER

a. Solvent is transferred from liquid phase to gas phase.

b. Unit can be split into two units for analysis- a direct dryer (as in 3)

and a mixer of the feed gas and the solvent mover to the gas phase.

10. LEACHING & EXTRACTION

a. The two liquid solvents must be immiscible.

b. They must have different S.G.c. At least one component is transferred from one solvent to the

other by difference in solubility.

d. The process is often called liquid-liquid extraction.

e. If one of the feed streams is a solid, the process is called

Leaching or liquid-solid extraction.

Gas Dryer

Dryer Feed, F

Feed Gas, GExit Gas, E

Dry Product, P

Extraction

Column

Light Solvent Feed, F

Heavy Solvent Feed, GExtract Liquid Out, E

Raffinate Liquid Out, R


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11. ABSORPTION (Gas Absorption) (DESORPTION)

a. Purpose of unit is to have the liquid absorb a component from the feed

gas. An absorber is often called a scrubber.

b. The liquid stream flows down through the tower by gravity.

c. The gas stream is pumped upwards through the tower.

d. No carrier gas is transferred to the liquid.

e. Generally no liquid solvent is transferred to the gas stream (check this

assumption).

f. Desorption is the same process as gas absorption except that the

component transferred leaves the liquid phase and enters the gas

phase. A desorber is sometimes called a stripper.

Absorber

Dirty Gas Feed, F

Feed Absorbing Liquid, GClean Exit Gas, E

Exit Liquid, P


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12. PARTIAL CONDENSER

a. The feed stream contains only condensable vapor components.

b. The exit streams, L and V, are in equilibrium.c. Condensation is caused by cooling and/or increasing pressure.

13. Flash Vaporizer, Flash Distillation

a. Same flow sheet as a partial condenser except the feed is a liquid.

b. Vaporization is caused by reducing the pressure and /or heating.

c. The Vapor and liquid streams are in equilibrium.

Partial

CondenserVapor Feed, F

Vapor Product, V

Condensed Liquid, L

Flash

UnitLiquid Feed, F

Vapor Product, V

Liquid Producd, L


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13. CRYSTALLIZER

a. Solid crystals are formed in the unit by a change in temperature.

b. The flow sheet for a crystallizer is often shown as a combination

crystallizer-filter.

15. REACTOR(Chemical Reactor, combustor, furnace, reformer)

a. The diagram shown is for a typical reactor that has two reactant feed

streams and a recycle stream.

b. If a single reaction takes place, put the conversion in the box.

c. A reactor is often named by the reaction taking place.d. A reactor is sometimes preceded by a fictitious mixer if the combined

reactor feed is specified or must be determined.

e. Multiple exit streams are shown to remind you to watch for exit

streams that separate because of their different phases.

Crystallizer

Crystallizer Feed, C Slurry Product, E

Reactor

Recycle Feed, R

Gas Products, G

Reactant 1 Feed, A

Solid Products, S

Reactant 2 Feed, B Liquid Products, L

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