Elroy is Here to Stay
…A few words about UNIFAC…
Interaction parameters for VLE
■ Fredenslund A, Gmehling J, Rasmussen P. 1977. VaporLiquid Equilibria Using UNIFAC. Elsevier, Amsterdam.
■ Hansen HK, et sl. 1991. Ind. Eng. Chem. Res. 30:2352–2355
■ Wittig R, et al. 2003. Ind. Eng. Chem. Res. 42:183–188
Interaction parameters for LLE
■ Magnussen T, et al., HK, et sl. 1981. Ind. Eng. Chem. Fund.
Interaction parameters for heats of mixing
■ Dang D, Tassios DP. 1986. Ind. Eng. Chem. Process Des. Dev.
(for VLE)
Poling et al. 2001
et al.
Soup of CH3, OH and H2O groups
Soup of CH3OH and H2O groups (molecules)
Design Project: Polylactic Acid
Preliminary design and economic analysis for a plant
producing 300 million lb/yr of polylactic acid polymer from a
feed stream of crude lactic acid.
Technical and economic aspects of design
Procedural aspects of course
Haven’t I seen this somewhere before?
Technical and economic aspects of design
Advantages of polylactic acid
Seriously cool biodegradable thermoplastic polymer. To be
addressed by YOU in Interim Report #0
Direct polymerization of lactic acid? Um… NO!
Condensation reaction
Rate decreases with increasing MW
Depolymerization reaction
Creates cyclic dimer lactide
Polymerization of lactide
Ring opening
Low-MW poly(lactic acid) = pre-polymer = source of lactide
Pre-polymer MW 1,000–5,000 (400–2500)  1,000
Decent high-MW PLA: MW > 100,000
Poly(L-lactic acid), PLLA
“The L-isomer constitutes the main fraction of PLA derived
from renewable sources since the majority of lactic acid from
biological sources exists in this form.”
“PLA polymers with L-content greater than ∼90% tend to be
crystalline while those with lower optical purity are
Lim LT, et al. 2008.
Progress in Polymer
Science 33:820–852
“PLA articles which require heat resistant properties can be
injection molded using PLA resins of less than 1% D-isomer.”
(Lim LT, et al. 2008. Progress in Polymer Science 33:820–852)
Design project
Pretend as if L-isomer is the only one that exists. Can use Dproperties.
Real life: minimize racemization by minimizing residence time
and avoiding high temperature (< ~200 oC for PLLA)
(22) + (38)
Gruber PR, et at. 2001. US Patent No. 6,326,458 B1
Evaporator/pre-polymer reactor
Falling film, agitated thin-film, wiped film
Multiple effects
Vacuum to reduce minimize racemization
E.g. falling film – one pass down inner
walls of tube. Good for heat sensitive
materials, viscous liquids.
Less detail in design (except for fivemember groups)
Falling film
McCabe LT, et al.
Horizontal wiped film
Towler G, Sinnott R.
Do we need to talk about evaporators?
Lactide reactor (evaporator)
Will be supplying more information about reaction and
catalyst (tin(IV) butyl-tin tris(2-ethylhexanoate); FASCAT®
9102, Atochem North America Inc.). Watch Update page.
Feed 180–250 oC
Pressure 2–60 mm Hg
Residence time 2 – 10 min
Film thickness 0.5–8 mm
Physical properties
Lim LT, et al. 2008.
Progress in Polymer
Science 33:820–852
Do we need to talk about mass transfer with chemical
Components: lactide, lactic acid, water
Condenser temperature (and therefore pressure) is limited by
cooling water temperature
Reboiler temperature (and therefore pressure) is limited by
maximum tolerable temperature (avoid decomposition,
Avoid freezing of all components
Must establish all pure-component phase diagrams, and find
suitable operating window
Must feed UniSim accurate vapor pressure and activity
coefficient parameters
Consider pressure drop (trays versus packing)
We do not need to talk about distillation.
Points to watch for
Low pressure process. Lecture on vacuum systems. Tight
Energy integration.
Required level of detail in technical design
Specify type; size/dimensions; temperature, pressure and
composition of input and output lactic acid/polylactic acid
streams, and output vapor stream; and required amount of
steam. The requirements for your design of the
evaporator/pre-polymer reactor (i.e., the unit combining the
functions of (22) and (38)) are relaxed in the sense that it may
be a rough estimate. For the lactide reactor (60) you must
present a more detailed design. In particular, you must
specifically determine a film thickness based on mass transfer
considerations, and incorporate this choice into your design.
The choice of lactic acid feed, and the pressure and basic
configuration for the evaporator/pre-polymer reactor and
lactide reactor must be established by 9 March (Decision
Point 1).
Note: five-member groups must develop a more detailed
design also for the evaporator/pre-polymer reactor.
Distillation column
You must develop a detailed design of the distillation column
specifying reflux ratio and boilup ratio; temperature, pressure
and composition of feed, distillate and bottom product
streams; column height above feed and below feed, and
column diameter; type of packing or trays; and thermal duty
and heat transfer area for reboiler and condenser.
The distillation is a particularly important part of the process.
Calculations can be made by yourself or using UniSim. If you
use UniSim, then you must provide it with substantial
amounts of physicochemical property data on lactide, which is
not included in the library of available components. Relying
on the base estimation package based only on MW and boiling
point will be grossly inaccurate and therefore unacceptable.
You must also carefully check the properties of lactic acid, and
augment them as necessary. Start the distillation model early
to be sure you produce a converged model that reasonably
approximates reality.
Do not underestimate the amount of work involved in getting
this unit operation right. If you use UniSim, then you must
also prepare one or more McCabe-Thiele diagrams that
explain your design and roughly check the numbers.
The pressure, VLE data and configuration for your distillation
process must be reported by 30 March (Decision Point 2).
Heat exchangers
Determine and state thermal duty, heat transfer area,
temperature and pressure of input and output streams, and
type of heat exchanger.
Fluid lines
Your design must include sizes of all lines between units (must
be standard sizes), and pump power for each line. These
specifications must be reported by 20 April (Decision Point 3).
You must also specifically select the pump for the line from
the hold tank (44) to the lactide reactor (60). (The term “fluid
transfer mechanism” used throughout Gruber et al.’s patent
means pump.)
Flow sheet
Your completed design (and in particular, report) must contain
a neat, computer-generated, detailed flow diagram. It should
resemble Towler and Sinnott’s Figure 2.8 (p. 39). It may not be
a UniSim flowsheet.
Streams must be labeled, with information about each stream
(temperature, pressure, phase, composition) tabulated below
by number. Information must be given in units customary
among engineers in this country (not Planet X on the galactic
rim), i.e., flow rates in lb/h or kg/h, pressures in psi or kPa,
temperatures in °F or °C, dimensions in ft or m, and pipe sizes
in in. Although you might use other units in calculations, they
must be converted into acceptable units in your final
presentation. Also, you should retain extra significant figures
in order not to let round-off error corrupt your calculations.
However, you should ultimately report only a reasonable
number of digits. Net: a flow rate expressed as, e.g.,
1.344789002 × 108 g/week WILL NOT FLY with Elroy or any of
your project supervisors.
(a) Materials available
Lactic acid at $0.69/lb for 50% solution, $0.78/lb for 88%
solution, f.o.b.
FASCAT® at $12/lb, f.o.b.
(b) Services available
Steam, 150 psig, saturated: $15 / 1000 kg
Cooling water, 60 psig, 30 °C supply, 40 °C return:
$0.20 / 1000 gal
Process water (chilled), 60 psig, 15 °C: $1.50 / 1000 gal
Electricity: $0.06 / kWh
Wastewater treatment: $3.00 / 1000 gal
(c) Product specification
Polylactic acid (PLA), 200,000 MW, sells for $1.00/lb
(d) On stream time
Assume 8000 hours / year
Economic analysis
Assume 20-year project life, 6% annual effective interest rate,
40% tax rate.
Results and criteria specifically to be addressed in your final
report are: fixed and working capital investment,
manufacturing cost, and revenue; return on investment
(minimum acceptable 15% after income tax), and net present
Base capital cost estimates mainly on tables in Towler and
Sinnott (especially Table 7.1 (pp. 314–317) and Table 7.2 (pp.
322–324)), which yield reasonable study estimates. Do NOT
expend effort contacting actual vendors for quotations on
specific pieces of equipment.
As with process stream variables, figures from the economic
analysis should be reported with a reasonable number of
digits, especially as your cost estimates will be subject to ±30%
error or more. In other words, report e.g. a net present value
as $12,400,000, not $12,364,078.92.
As with process stream variables, figures from the economic
analysis should be reported with a reasonable number of
digits, especially as your cost estimates will be subject to ±30%
error or more. In other words, report e.g. a net present value
as $12,400,000, not $12,364,078.92.
…just reminding us that Elroy is here to stay…
Procedural aspects of course
Industrial participants
Paul Ameis (VanDeMark Chemical)
Dr. David Courtemanche (Dupont)
Dr. Rich Fickelscherer (Falconeer)
Dr. Vasilis Papavassiliou (Praxair)
Dr. William Schatmach (Praxair)
Regular meetings and progress reports
Meetings with project supervisors
Meeting #
Week of
09 February
23 February
09 March
30 March
20 April
Group meetings with
Ameis, Fickelscherer, Papavassiliou, Scharmach
Ameis, Fickelscherer, Papavassiliou, Scharmach
Ameis, Fickelscherer, Papavassiliou, Scharmach
Ameis, Courtemanche, Fickelscherer, Papavassiliou, Scharmach
Sign-up sheets posted on MN’s office door; sign up early
Must talk with four different supervisors during semester
All members of group must be present at meeting (grade
penalty for absence)
Bring questions
Progress reports
Schedule &
due date
09 Feb.
by 4:00 pm
23 Feb.
by 4:00 pm
09 Mar.
by 4:00 pm
due date
Bring to
Mtg. #0
Bring to
Mtg. #1
Bring to
Mtg. #2
Interim #3
30 March
by 4:00 pm
Bring to
Mtg. #3
Interim #4
20 April
by 4:00 pm
Bring to
Mtg. #4
Final report
4 May
by 4:00 pm
Interim #0
Interim #1
Interim #2
Introduction and literature review; solutions of
VLE problems posed
Preliminary definition of process streams and
units; preliminary flow sheet
Flow sheet with all mass and energy balances
completed; analysis of production costs and
revenues; Decision Point 1 — Choice of feed, and
evaporation parameters determined
Preliminary economic evaluation of flow sheet;
Decision Point 2 — distillation parameters
Provisional final flow sheet with all mass and
energy balances completed; designs as
requested for all process units; provisional final
economic evaluation; Decision Point 3 — line
sizes determined, and specified pump selected
Final report
Must be received in time for supervisors to have a look before
meeting. Also bring paper copy to meeting.
Composition of grade for design project
Report #0
Meeting #0 (preparedness and quality of discussion)
Report #1
Meeting #1 (preparedness and quality of discussion)
Report #2
Meeting #2 (preparedness and quality of discussion)
Report #3
Meeting #3 (preparedness and quality of discussion)
Report #4
Meeting #4 (preparedness and quality of discussion)
Final Report
Final Presentation
SEAS Senior Design Expo
% of grade
Haven’t I seen this somewhere before?
Yes I have… several times!
CE 317 fall 2012
CE 318 spring 2013
CE 329 fall 2013
Batch fermentation kinetics based on Monod’s equation
CE 407 spring 2014
Consider distillation of a saturated vapor feed stream comprising 24 mole percent
L-lactic acid (light component) and 76 mole percent L-lactide (heavy component).
The desired product is the heavy component, L-lactide, and it should be
contaminated by only 0.4 mole percent L-lactic acid in the bottom product. The
distillation is carried out at a pressure of 10 mm Hg.
(a) What is the maximum percent recovery of L-lactide in the bottom product that
could theoretically be achieved with an infinite number of stages?
(b) Suppose the distillation is run such that the distillate has 48 mole percent Llactic acid, the reflux ratio is 1.5 times the minimum reflux ratio, the column is
fitted with a total condenser, and the trays all have a Murphree efficiency of 70%.
Answer the following questions. (i) What is the temperature of the distillate
stream? (ii) What is the percent recovery of L-lactide in the bottom product? (iii)
How many trays are required, and on which tray should the feed enter?
VLE data for binary mixtures of L-lactic acid and L-lactide at 10 mm Hg are provided
hM = 70%: 14 stages
hO = 70%: 13 stages
CE 427 fall 2014
Lactide process safety
Chemical hazards
…just reminding us that Elroy is here to stay…
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