Miscellaneous - Process Design Practice - Lecture Slides, Slides of Process Engineering

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Miscellaneous

General Rule of Thumb –^

Based on discussions with industrial design engineers

-^

Each major piece of equipment results in approximately$1,000,000 in capital investment (including installation,engineering time, instrumentation etc. etc.)

-^

Thus

for

a

plant

with

a

reactor

and

two

distillation

columns, the typical price will be around $3,000,

-^

Remember, that this is “order of magnitude” estimation

Process Economics

Distillation Columns (Continued)–^

If identified diameter is beyond the curves found in P&T,assume (

for pricing purposes

) that the separation is

performed in NC columns in parallel all with the samespecifications.

-^

The number of columns required should be based onequal distribution of the cross-sectional area

NOT

the

diameter:

Equipment Sizing 2:

max

Aspen^

P&T 2

2

2

Aspen

2

2

2

P&T

2

Aspen

2

P&T D^

20ft

,^

D^

5ft^

Intuitive solution NC = 4 columns

A^

(20ft)

400ft

100ft

4

4

A^

(5ft)

25ft

6.25ft

4

4

A^

100ft

NC^

16 columns

A^

6.25ft ^

^



^



^

^

^

 

^



^

^

^

  

^

^

 

Heat Exchangers –^

Required information is usually the heat transfer area,apart from furnaces and fired heaters, which may beestimated based on the duty.

-^

Overall heat transfer coefficients can be found in P&T(p. 663 in 5

th^ ed.). Assume an average value.

–^

Assume inlet and outlet temperatures for utility stream.Sample calculations given P&T p. 693.

Equipment Sizing 3:

0

log mean

Q^

U^

A^

T

^

^

 

Q: Provided by AspenU: Found in P&T ∆T: Calculated after assuming temps.

Units to Include–^

Heaters, coolers and reactors

-^

Aspen will provide supply and target temperatures aswell as enthalpy change for each hot and cold stream

-^

Remember that a hot stream in pinch terminology willactually be TWO streams in Aspen

Pinch Analysis 1:

Supplytemp

Targettemp

∆H

Integration of streams should bedone using the HeatX model

B

1

2 3 4

Identifying the CP values (No phase change)–^

The

heat

capacity (CP)

of

a

stream

that

does

NOT

undergo any phase changes is readily calculated fromthe information provided by Aspen

Pinch Analysis 2:

Ts^

Tt

Q

CP = Q/

 T

Approximation

Pinch Analysis 4:

For mixtures with very different boiling pointsof the constituents the outlet temperatures inexchangers 1 and 2 will be quite different, butit will still give a better approximation than justan average over the entire temperature range.

Liquid @ T

s^

Vapor @ T

t

Q

Liquid @ T

s^

Liquid @ T

b

Q^1

Vapor @ T

b^

Vapor @ T

t

Q^2

Q^3

Can be specifiedin Aspen ashaving an outlet vapor

fraction of0.

Can be specifiedin Aspen ashaving an outlet^ liquid

fraction of0.

Specify outlettemperature at T

t

docsity.com

Units NOT to Include –^

Distillation columns and flash drums

-^

Due to dynamic implications, distillation columns shouldnot be directly integrated with the utility system

-^

Evaluate

all

columns

together

in

tabular

form

with

duties and temperature levels

-^

If there is a condenser with a temperature higher thana^

reboiler

in

another

column,

then

those

two

are

candidates for integration.

Pinch Analysis 5:

Evonik Site Visit – March 1 –^

What to bring?•^

Photo ID (drivers license is preferred)

-^

What not to bring?•^

Cameras (including camera phones)

-^

Cell Phone use is only allowed in buildings

-^

Guns, Drugs or Alcohol (I hope this one is obvious)

-^

What to wear?•^

Long Pants

-^

Closed Shoes (no sandals or flip flops)

-^

Shirts with Sleeves (no tank tops)

-^

Safety Glasses

Other Business

Evonik Site Visit – March 1 (Cont’d) –^

Tentative schedule

Other Business