DESIGN FINAL

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A/B designation for pumps means

two pumps in parallel - one is a spare

Smaller (<10 m^3) HE's are

usually double pipe

Decision Variables

variables manipulated in order to max/min OF

When is a zones analysis needed in a heat exchanger

when a different heat transfer coefficient is required for different phases (heating liquid, boiling, heating vapor)

Cost for BFW

when steam added and when condensate not returned to boiler plant

How should battery limit symbols be integrated in a PFD

white side of half moods faces the process

Centrifugal Pump

"Constant Head" Pump Good for lower flows/ smaller pressure differences

Positive Displacement Pump

"Constant Volume" pump Good for large flows or pressure differences

Default Heat Exchanger

1-2 Shell and tube heat exchanger (1 shell pass, 2 tube passes)

Reason for running columns at high P

Decrease diameter + allow cooling water to be used in condenser

Mixing vapor and liquid stream

Discouraged because two-phase flow isn't well understood

Mixing liquids

Done in a mixing drum with level control to control outlet flowrate Usually done w/ recycle DO NOT mix vapor + liquid streams

What is the usual objective function in engineering

Econ

Boiling Regimes

Keep temp differences below 50°C

Design Specs for Steam

LPS: 5 barg saturated w/ credit MPS: 10 barg saturated w/ credit HPS: 41 barg, saturated Take credit for steam unless steam is lost in the process

Shell and Tube Parameters

More extreme temperature in the tubes, higher pressure in tubes, corrosive/fouling in tubes, condensing/boiling fluid in shell

Mixing streams

Must be at same pressure + will not be at design flowrates

If temp > 250°C

Need a fired heater

If temp < 40°C If temp > 400 °C

Need refrigerated water Need special MOC

NPSH

Net Positive Suction Head Available must be higher than required

Plotting Optimization should result in ______ curves

Smooth if all variables are continuous

A/B Designation for Pumps

Spare Equipment

Expected in a Design Report for a Stream Table

Stream Number Temp Pressure Vapor Frac Total Mass + Mole Flowrate Component Flowrate

Diagram for Heat Exchanger generated by Aspen

T-Q Diagram - make sure there is no temperature crossover

What is the meaning of T-905?

The fifth tower in unit 9

The best thermodynamic method

The one that fits the experimental data

T-Q Diagram

You cannot cool below boiling temp

What is SRK suitable for

moderate pressures, 1/2 Pcrit

What determines column pressure

temperatures of reboilers and condensers

Topoligical Optimization

changes in arrangement of process equipment - can unwanted by-products/equipment be eliminated?

Pumps are located near

ground level

Flash Separations

Single-state distillation

Desuperheater

Allows steam to be made any any temp

Cooling water

Available at 30°C

What is PR suitable for

Better than SRK for higher pressures

Typical Pipe Characteristics

Can be threaded Connected by fittings Schedule number (thiccness) Nominal Diameter, Outer Diameter

PFD Requirements

Equipment listed at the top Battery-limit symbols (Half moons) for Raw Materials and Products Flags not needed if all streams numbered Basic Control System Horizontal Lines Dominate Vertical Number Streams left to right Add arrows for equipment inlet and change in direction Utility Streams appreviated (lps,mps,hps,bfw,fg,cw,rw) Mixing Tanks ONLY for liquids Condenser shown as partial/total Reactors are vertical

How to account for Frictional Losses

Equivalent Length or Velocity head method

Reason for Large Reflux Ratio

Feed is dilute in more volatile component separation between boilers very close high distillate concentration needed reduce stage numbers

The main thing that can be adjusted in a chemical plant

Flowrate - by changing a valve

How to find tank volume from outlet flowrate

Fout * 10 min holdup * 2 (vapor space)

Typical Heat Transfer Trends

Gas heat transfer bad, liquid better, water better liquid (phase change is best)

General info about azeotropes

Ideal thermo never predicts them concerning polar and "associating" (?) molecules, electrolytes

Cavitation

If fluid is too close to vapor pressure at the pump inlet can cause long-term damage Pumps do not like suckin on vapes

How to increase NPSHa

Increase the heigh difference between the storage tank and pump entrance Increase the initial presusre Decrease the vapor pressure by decreasing the temperature Decrease pipe length Increase pipe diameter

Always ____ before _____

Pump before heating

What equipment should have basic control/ regulation systems

Pumps, tank levels, reactors (temp), valves

What cost must be included with a refrigerant

Refrigeration equipment

Objective Function in Optimization

The thing that is max/min'd

Reactor Requirements

Thermal fluid in cocurrent to minimize hot spots Heat exchanger area and reactor volume must be matched Conversion vs. Selectivity + Kinetics

Boiler Feed Water

Used to make steam

If Pressure < 1 atm or > 10 atm

Vacuum and large equipment More expensive for reinforcement

remedy to thicc column

decrease RR + increase pressure

high (>= 20) reflux ratio suggests

difficult separation

low (<= 20) reflux ratio suggests

easy separation

Reason for running columns at vacuum

ensure temp sensitive components don't degrade + so highest temp steam can be used

Feed location for DC

feed should be at tray with same temp + composition

Column feed pressure must be _____ than column pressure

greater

Correction factor for heat transfer rate in HE's

needed when close approach on T-Q diagram or for heat integration F =1 for constant-temp phase change

MUMNE for Heat Exchanger Integration

obtains minimum utility use config, and min number exchangers

Zoned Analysis needed for HE design when

phase change due to different heat transfer coefficients

Reasons for hot Spot in PFR

reaction is fastest at high reactant concentration, which is at reactor entrance rate of heat gen exceeds rate of heat removal

how to decrease column height

reduce trays + decrease tray spacing

Increasing R/Rmin does:

reduces trays increases reboiler and condenser duties increases dolumn diameter

Multiple shell passes needed in HE when

small approach temps + not needed with phase changes


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