Suggested Design Projects – 2015-2016
1.
C4 Operations Optimization
(recommended by Gary Sawyer, Consultant – formerly ARCO, Lyondell-Basell)
Background
“Crude C4s” are a mix of butanes, butenes, and butadiene produced from steam crackers. “Cat BB”
is a similar stream from refinery catalytic crackers, but generally lacking in butadiene.
The components in these streams have value in different markets. Two of them, butadiene and 1butene, are valuable monomers and are recovered and sold in pure form. Isobutylene has some
market as a monomer if in high purity, but most of it is converted to high octane fuel additives
MTBE or ETBE (methyl- or ethyl- tertiary butyl ether). There are several options for cis- and
trans- 2-butene:




Feed to an alkylation unit along with isobutane to make high grade motor fuel called
“alkylate”
Skeletal isomerization to an equilibrium mix of isobutylene and butenes, and feed to an
MTBE unit to recover isobutylene value.
Feed to a metathesis unit along with ethylene to make propylene.
Olefin isomerization to an equilibrium mix of 1- and 2-butenes, and recover the 1-butene
for sale.
A less desirable alternative is to hydrogenate the butenes to n-butane, which can be returned to the
steam cracker as feedstock.
A typical large petrochemical company or steam cracking operation will have a variety of
processing operations at their disposal. It is an ongoing challenge to optimize the options for
processing various C4 streams, given changing market conditions, feedstock compositions, and
equipment limitations. There may be a “base load” from internal operations that does not fully
utilize all the equipment capacity, creating an opportunity to purchase additional feedstock.
A rather typical but not universal sequence is shown below in simplified fashion. The term “Raff”
refers to raffinate from extractive distillation of butadiene.
C4 Processing Terminology
Crude
C4
Raff 1
Butadiene
Raff 2
Isobutene
In this design problem, we consider the following processing options.
1
Raff 3
1-Butene
Unit Operation
Comments
Butadiene Extraction
Extractive distillation. Several licensors.
Recoveries high 90s%. Selective
hydrogenation of unreacted butadiene
required.
Contained isobutylene is reacted with
methanol / ethanol. High conversion
required if 1-butene is to be recovered
Contained 1- and 2-butene react with
ethylene to make propylene. ~50%
conversion per pass. Recycle possible.
Conventional distillation requires no
butadiene or isobutene.
Isobutylene, 1-butene, and 2-butene go to
chemical equilibrium at high temperature.
~5-10% losses to “heavies” per pass
Equilibrates 1- and 2-butenes without
skeletal isomerization. Minimal losses.
Reacts isobutylene, 1-butene, and 2-butene
with isobutane to make alkylate gasoline.
Sulfuric acid or HF processes.
MTBE / ETBE
Metathesis
1-Butene
Skeletal Isom
Olefin Isomerization
Alkylate
Capacity
Limitation
To be
determined
via literature
search and
consultation
with faculty /
industrial
advisor(s)
Utility Costs
To be
determined
via literature
search and
selected
rigorous
modeling
Deliverables and Scope of Work
You have been hired by the Operations Planning department of a large petrochemical company to develop
a model that will optimize the production plan on a weekly basis, and will be used to determine
opportunities to buy supplemental feedstock. You must give a live demonstration of this model at the
final oral presentation, which shows how results change with changing input. You may choose any
platform you are most familiar with – spreadsheet, ASPEN PLUS, or mathematical modeling tool – but
the user interface should be an important aspect of your model design. The model should arrive at the
optimal process configuration given the capacity constraints of each unit and pricing assumptions. The
major units can be treated as a whole – you do not need to model all the reactors, columns, heat
exchangers, etc. Each major unit has a typical utility consumption available from the licensor; where
licensor data is not available, rigorous modeling can be used to establish a characteristic utility
consumption, expressed in terms of energy per unit of product.
It is suggested you take the following approach:
1) Review Literature and set model inputs. Become familiar with the operation of each unit.
Determine what capacities have been built. For this design problem, select a capacity limit near
80% of the largest practical scale. This may be adjusted later. Capacity limitations may be on
total throughput, or amount of recovered material. For example, an MTBE unit will not
produce as much from a dilute feedstock as a feedstock rich in isobutylene. Determine utility
consumptions as suggested by the licensor or rigorous modeling.
2) Characterize typical crude C4s and Cat BB. Literature searches and on-line product specs will
establish range compositions for these streams. Select three or four examples across the range
to use as available feedstocks in the optimization model.
2
3) Determine pricing scenarios Establish two or three pricing scenarios (high, middle, low) for
the following compounds.
a.
b.
c.
d.
e.
f.
g.
Ethylene
Propylene
1-Butene
Methanol
MTBE
Butadiene
N-Butane and i-Butane
There are relationships that must be recognized. Ethylene and propylene prices tend to track
together. 1-Butene is a co-monomer in polyethylene and its price is generally slightly above
that of ethylene. MTBE tends to track with gasoline prices. See the references below for
possible pricing resources.
4) Develop your model. Begin by laying out the units in block diagram form and show the
possible connections between them. Calculate overall material balances and product values
from each unit. Create an input “page” or “dashboard” showing input assumptions and output
value generation. The heart of the model will be determining where the output from one unit
operation should go to the next to optimize values. Remember the constraints established
earlier on unit capacity.
References – Unit Operations
Robert A Meyers, Handbook of Petrochemicals Production Processes, 2005, McGraw-Hill. ISBN:
9780071410427. A reference for Butadiene Extraction and Metathesis (as UOP Oleflex)
Robert A Meyers, Handbook of Petroleum Refining Processes, 3rd edition, 2004, McGraw-Hill.
ISBN: 9780071391092. A reference for Alkylation, MTBE, skeletal isomerization (UOP Olefin
Isomerization)
References – Economics
Nexant presentation, “Butadiene: Feedstock supply challenges and volatile demand”, 16 May
2014.http://www.apic2014.com/download/SR%201-%20NEXANT%20
%20Anna%20Ibbotson%20%20Butadiene%20Feedstock%20Supply%20Challenges%20and%20Volatile%20Demand.pdf.
http://www.platts.com/news-feature/2014/petrochemicals/pgpi/ethylene
http://www.platts.com/news-feature/2014/petrochemicals/pgpi/propylene
http://www.icis.com/resources/news/2012/01/16/9523382/us-chemical-profile-butadiene
https://www.quandl.com/data/WSJ/BUTANE-Butane-normal-Mont-Belvieu-Texas
www.eia.gov for gasoline prices (and hence MTBE)
3
2.
Manufacture of Isoprene via Fermentation
(recommended by Rick Bockrath, Consultant – formerly DuPont)
You are the head of the techno-economic group at All Rubber, Inc. Your CEO stops by to discuss
the joint development between Danisco (now part of DuPont) and Goodyear to manufacture
isoprene via fermentation of sugar. He wonders if he should approach the two companies about
their technology. Before doing so, he wants your group to do an in-house analysis of the
technology to see if the “view is worth the climb”. Assume a 50,000 ton/yr plant. Since this is an
in-house analysis you will need to make many assumptions and so carefully document them. State
them explicitly in your report, so that the CEO may understand the uncertainty in your design and
economic projections. Remember this may be a game-changer and the long-term future of All
Rubber may depend on the quality of your analysis. If your results look promising then the
assumptions will be reviewed with DuPont/Goodyear for verification or modification. He wants
you to develop a plant design and determine operating costs to see if it is likely to be viable or can
be safely ignored for now. Since he has many contacts with Goodyear he doesn’t know if it is a
threat or an opportunity to work with them on commercialization.
During the meeting you discuss the market dynamics with him. You both know that natural rubber
is essentially 100% cis-polyisoprene and so a successful new route to isoprene could be a game
changer. Demand is growing, especially in India, China and South America, and it remains fairly
stable in North America and Europe. Rubber pricing had been growing dramatically up to 2009,
but since then has slumped about 50%. You both agree that prices will likely recover and continue
to rise. Since palm oil and rubber plantations often compete for the same land, rubber pricing can’t
get too low or owners will switch from rubber to palm oil which appears to be a growing trend in
Asia. Obviously the price of natural rubber puts a cap on the price that isoprene can command via
this route. You will need to make an assumption about how much of the natural rubber price can be
assigned to the isoprene monomer venture (someone has to earn a profit for the polymerization
step). Since it is a potential game-changer, the CEO wants you to not only determine the likely
current technology situation (investment and cost) but to carefully list which more favorable but
reasonable assumptions would move it from un-economical to economical if your analysis says it is
likely to be un-economical.
You start your work by pulling up the patents from the joint venture. You discover to your dismay
that it is extensively patented and the typical patent is 350 pages long. In addition, the patents mix
biochemistry with engineering in a confusing way. You hire an outside microbiological consultant
to review the patent estate. She comes back the next week and makes the following observations:
1) It looks like E. coli is the production platform. She cautions you that other microbes are
claimed too, but E. coli shows up in many of the examples. E. Coli is a very, well understood
platform.
2) There has been a raft of recent patent issuances but she doesn’t think they should be the basis of
your analysis. Most of them were filed in 2009 and so they probably lag the real technology
status significantly.
3) She suggests you focus on U.S. Patent Application 20130164809 A1, Chotani,
G. K., et al., June 27, 2013, "Production of Isoprene under Reduced Oxygen Inlet Levels,”
which seems closer to commercial conditions.
4) She also suggests you look at U.S. Patent 8,470,581, which has “the safety stuff in it”.
5) Finally, she says that U.S. Patent Application 2011/0178261 A1, Feher et al., June 11, 2011,
“Purification of Isoprene from Renewal Resources,” talks about the refining section although it
is imbedded among biochemistry pathway examples, etc.
4
6) Some of the patents talk about lignocellulosic (LC) feedstocks, but given that this is brand new
technology, she expects the first plant to be based on glucose from a source like Cargill. LC is
probably the long term goal though. Given the complexity of LC feedstock impurity profiles
(including many inhibitory chemicals), she suggests you look only at glucose for now.
7) She suggests that you use the following information for fermenter design. She is basing it on
U.S. Patent 2013/0164809 A1 with assumed improvements.
Pathway: C6H12O6 + 3.41 O2 = 0.370 C5H8 + 4.15 CO2 + 4.52H2O
Rate (Figure 10): 2.2 g/hr/L with e coli concentration of 15 g/L (dry cell weight)
The rates in the figure are actually lower, but she assumes the process has been further
improved since the application filing.
8) She mentions an article by Gregory Benz, “Large-Scale Microbial Production of Advanced
Biofuels: How Big Can We Go?" to help in fermenter sizing (to be provided by Dr. Bockrath).
9) She offers to consult as needed.
You noticed in your cursory review of the patents that the vast majority of the examples use a feed
gas with 9.97% O2. You realize that this is the MOC (minimum O2 concentration) for isoprene.
Danisco/Goodyear clearly want the feed gas to be below a flammable level of isoprene in the
presence of O2. Since you have no data to support the use of air itself, you should assume a feed
gas of 9.97% O2. This means you will need a diluent. You are to evaluate two sources – N2 from a
liquefaction plant or from membranes, which can make (95% N2), or by recycling the fermenter
off-gases, which will be further depleted in O2 by passing through the fermenter.
Obviously, the design needs to meet likely Federal and state emissions regulations. Recover and
recycle process materials to the maximum economic extent. Also, energy consumption should be
minimized, to the extent economically justified. The plant design must also be controllable.
Patent Figure 10. Isoprene titer in a 15 L fermenter
References
Available from Dr. Bockrath.
5
3.
New Sorbent-Based Oxygen Production Method
(recommended by Matthew Targett, LP Amina)
Overview
Investigate the science and characterize the economic viability of novel low-cost sorbent-based
oxygen production. A number of new mixed ion electrically conducting (MIEC) materials are
being researched by a number of teams globally for the purposes of various oxygen transport
applications.
One application of these new materials is as a selective oxygen sorbent, potentially offering a lowcost alternative means of producing oxygen from air. Given the early stage of research efforts, only
a scant amount of information is available on such compounds and it is not expected that any
commercially available materials are at low enough cost or sufficiently high performance levels to
serve as adequate sorbents at this time.
Figure 1. Maturity versus total investment time for oxygen separation technologies
http://decarboni.se/sites/default/files/publications/112031/sota-report-dense-ceramic-membranesoxygen-separation-air.pdf
It is not clear at present what plant and reactor design is required for these new sorbent materials to
be commercially successful. The objective of this project is thus to design a plant suited to the
unique oxygen production mechanism of MIEC materials to achieve cost-effective oxygen
production at a commercial scale. Project teams will need to model two different oxygen plant
production scenarios:
1) A 10,000 metric tonnes O2/day plant producing a mixture of 25% oxygen by weight with CO2
(40,000 tonnes/day total for mixture). Assume a sale price per tonne for the O2 component of
the mixture commensurate with the median bulk cryogenic oxygen price in the region where
you choose to locate your plant.
2) A 10 metric tonnes/day oxygen plant with at least 99% O2 purity and a sale price per tonne
comparable to a PSA oxygen plant of the same scale operating in your location.
For both of the above plant capacities and O2 prices, design a process and facility using notional
properties for a new high-performance MIEC sorbent provided in the section on Sorbent
Assumptions and in the Appendix. Use engineering and financial projections to determine best-,
6
base-, and worst-case scenarios for both plants. Take a systems approach in producing your
business model, and refer to business models and approaches currently used in the oxygen
production industry. Upon completing your analysis, specify minimum acceptable enhancements to
the adsorption/desorption kinetics of the baseline MIEC sorbent material that would be required to
enable your facility operation to achieve a 25% improvement in profitability.
Background on Technology
This project is aligned with carbon capture and energy efficiency initiatives. The 10,000 tonne per
day facility supports carbon capture goals by providing an option for low-cost oxygen supply using
MIEC materials, with minimal electric power consumption relative to current oxygen production
methods. Oxy-combustion is a leading option for large-scale power plants with CO2 capture, but
the cost of O2 is a critical factor in making the economics viable. The O2 production unit may
contribute up to 33% of capital cost and 67% of the power consumption of a power plant with CO2
capture. Cryogenic air separation is currently the leading option for providing the oxygen required
by oxy-combustion hydrocarbon power plants, but it involves high electric power consumption
(parasitic load on the power plant) and is cost-prohibitive.
A more efficient, inexpensive means of pure oxygen production is also desirable for small scale
oxygen consumers. Current PSA oxygen sorbent systems such as those using silver zeolites
consume significant amounts of electric power, scale poorly to large plant sizes, and have oxygen
purity limitations. Your 10 tonne per day plant will address this market.
Figure 2: Oxy-combustion Power Plant
http://www.netl.doe.gov/research/coal/energy-systems/advanced-combustion/oxy-combustion
7
Focus Areas for Commercialization Portion
In your engineering assessments as well as economic and facility costs predictions, some aspects
you will need to include are:
Design:
‐ A notional design for sorbent reactors appropriate for both the 10,000 tpd and 10 tpd production
targets, with particular attention in the design to preventing excessive heat buildup due to the
highly exothermic adsorption process.
‐ Consideration of MIEC sorbent degradation and poisoning concerns given your reactor designs
and choice of process gasses.
‐ Auxiliary equipment requirements for your plant
‐ A brief exploration of integration of the 10,000 tpd facility into a natural gas fired oxycombustion plant.
Costing:
‐ Location of facility (assume 10 tpd and 10,000 tpd plant are in same location)
‐ Price projections for the fuel source and/or electricity your reactor will utilize
‐ Price projections for sweep gas or process gases used and/or coproducts, if any. Assume CO2
from a natural gas fired oxy-combustion power plant is available onsite at 50°C and 1
atmosphere. Assume it is available at no cost and is essentially pure and sulfur-free. You must
account for the equipment required for processing CO2 to your desired temperature and
pressure, but do not consider the power plant itself.
‐ Fixed and variable costs (e.g., cost of facility and operations – CAPEX, OPEX)
‐ Return-on-investment in the form of expected Internal Rate of Return (IRR) for the given O2
sale price and quantity, assuming oxygen price increases at the same rate per year as inflation
(assume yearly inflation level appropriate for plant location)
‐ Carbon credits/taxes and potential impact on project economics
In judging the competitiveness of your plant design in a given location, you should take into
account the political and economic landscape of the energy industry and the impact of climate
change regulations. Also, take into account the changing nature of energy policy, such as
incentives for construction of low-carbon power plants, incentives for energy efficient small-scale
oxygen production facilities, and other regulations that may give you an upper hand (carbon credits,
cap and trade, etc).
To determine plant and reactor performance, a thermodynamic model of sorbent bed operation is
required. In modeling reactor performance, refer to MIEC sorbent assumptions and material
properties in the Sorbent Assumptions section and in the Appendix. For this model, you will need
to solve coupled heat- and mass-transfer equations. Create a model of adsorption and desorption
for your sorbent reactor design based on one-dimensional time-dependent heat- and mass-transfer
partial differential equations (PDEs) to achieve the required rate of O2 production and cost targets.
Refer to the Appendix for example PDEs and equations defining sorbent properties. At least one
person in the project team must be capable of using software such as MATLAB and COMSOL to
numerically solve PDEs using finite-element (FEM) numerical approximations. Use the numerical
model to qualitatively and quantitatively guide your reactor design development. Graphs of
temperature and reaction kinetics over time and position are desired.
8
Sorbent Assumptions
-
-
The MIEC sorbent price is $40/kg, and can be resold as scrap for $15/kg at the end of plant life.
Assume material degradation is minimal, but avoid process gases or other incompatible
materials which, based on your research, may degrade MIEC sorbents.
The sorbent material only works in the temperature range of 400°C-1,000°C due to its defect
chemistry.
To achieve low-oxygen partial pressures required for desorption, you may use a sweep gas such
as carbon dioxide or steam, or you may use a vacuum system.
For your reactor, you may design a Temperature-Swing Adsorption (TSA) process, a PressureSwing Adsorption (PSA) process (with or without vacuum), or a TSA-PSA process. Reactor
configuration can take whatever form the project team determines is optimal for your approach
(i.e., sorbent bed, small channels, etc.), but must be based on direct use or modification (within
reason) of existing industrial equipment and processes.
Assume the material to be exothermic in adsorption and equally endothermic in desorption with
constant enthalpy of adsorption:
∆
180
References
Refer to the PDF research papers included in project statement package
Oxygen applications to oxy-combustion:
http://futuregenalliance.org/futuregen-2-0-project/oxy-combustion/
Small-scale PSA production of oxygen:
http://www.ou.edu/class/che-design/a-design/projects-2007/Oxygen%20Generator.pdf
Refer to Appendix
Note: The creator of this project is not based in Philadelphia. Many or all interactions will be
through SKYPE, phone, and/or email. His group will meet from 4:30-5:30 p.m.
Appendix
PDE equations for a PSA bed system, and MIEC Sorbent Properties
∙
Oxygen balance:
∙
Linear Driving Force Model:
∙
∗
∙
∙
0
,
= average amount of oxygen adsorbed at a particular discreet bed element position z.
Energy Balance:
∆ ∙
∙
∙
∙
∙
1
∙
∙
∙
0
The assumptions for the above equations are:
- no heat accumulation and a state of constant thermal equilibrium between the bulk gas phase
and the sorbent bed*
9
-
no radial heat transfer*
no heat transfer with the reactor walls*
diffusivity of gas species can be determined using the Lennard-Jones equation for gas diffusion
*
-
Your reactor design should contain provisions to effectively manage heat to prevent
excessive temperature buildup given that adsorption is highly exothermic.
A function modeling the adsorption and desorption constant (k) is shown below. Assume that
the adsorption constant is constant for all T and P. Assume the desorption constant is a strong
function of P:
2.0 ∙ 10 1.6 ∙ 10
∙ ln
0
0.21
0.21
0.21
- Adsorption capacity as a function of temperature and pressure is modeled as follows:
∗
8.355 ∙ 10
∙
1.346 ∙ 0.0876 ∙ ln
∗
0,
10
1.1343 ,
10 10 4.
Biobutanol
(recommended by Bruce M. Vrana, DuPont)
Prior to the advent of the petrochemical industry, which made the process uneconomic, acetone, nbutanol (BuOH) and ethanol (EtOH) were produced together by fermentation, using one of several
Clostridia strains. The advent of the petrochemical industry shut down nearly all BuOH production
by fermentation, with the vast majority of world capacity coming from hydroformylation of
propylene, the so-called Oxo process. Although it can be used as a fuel additive, BuOH is
primarily used as a chemical intermediate in the manufacture of butyl acetate and butyl acrylate,
and as a solvent.
Your company, a small startup, is working on a new chemical route to BuOH from ethanol, making
renewably-sourced BuOH that would be attractive to some industrial customers, provided the price
is competitive with petrochemical BuOH. However, it has come to management’s attention that
another startup, Cobalt Technologies, is touting their fermentation route to biobutanol. They have a
several year head-start on your company, and have demonstrated fermentations at the 100 m3 scale.
Cobalt is exploring opportunities to retrofit existing U.S. corn EtOH plants to make BuOH, and has
even announced plans to build a plant to make bio-butadiene from BuOH in Asia in 2017.
As the only company employees with a degree from a department that includes “bio” in its name,
you have been assigned the task of deciding whether Cobalt’s fermentation route poses a threat to
your business plan. Since contacting Cobalt directly could be “anti-competitive,” management has
forbidden any contact with Cobalt or LS9, the company where the 100 m3 fermentation was
demonstrated. You must base your analysis solely on public information obtained from a literature,
patent and Internet search.
Assume that Cobalt is successful in negotiating the retrofit of an existing 50MM gpy EtOH plant to
make BuOH. Based on published EtOH plant designs, which you will also need to find in your
search, since your company has no EtOH plant experience, determine what their process mass and
energy balance would be, what their process design should be, how they would best make use of the
existing assets to commercialize their process, and what equipment they would need to add or
change.
In addition to normal considerations for a fermentation process (such as sterility), water balance is a
significant issue, since EtOH plants are primarily in the corn belt, where water is scarce. All
process water is evaporated and recycled, and there is no process water discharge from the typical
EtOH plant. Assume that Cobalt would fall under the same restrictions. Also, it is reasonable to
assume that Cobalt will produce a dried animal feed product equivalent to the DDGS (dried
distiller’s grains with solubles) made in a dry grind corn EtOH plant.
Your company’s process, still under development, is projected to be cost competitive with
petrochemical BuOH. The basic question you need to answer is whether Cobalt can compete on a
price basis with petrochemical BuOH, beating you to the market and capturing the lion’s share of
the renewably-sourced or bio-n-butanol market. Or are they only a competitive threat under certain
assumptions or scenarios. Or are they unlikely to be a competitive threat at all. The only relevant
business information that your company has is its projection for BuOH price, of $2,900/tonne, in
2016 dollars.
You will need to make many assumptions to complete your design, since you have no data, and
patent applications and the internet will only tell you so much. State any assumptions explicitly in
your report, so that management may understand the uncertainty in your design and economic
projections before deciding whether to continue on as planned, or change strategies. Test your
11
economics to reasonable ranges of your assumptions. If there are any possible “show-stoppers”
(i.e., possible fatal flaws, if one assumption is incorrect that would make the design either
technically infeasible or uneconomical), these need to be clearly communicated and understood by
management.
The plant design should be as environmentally friendly as possible, at a minimum meeting Federal
and state emissions regulations. Recover and recycle process materials to the maximum economic
extent. Also, energy consumption should be minimized, to the extent economically justified. The
plant design must also be controllable and safe to operate.
Reference
Try a Google search. Help will be provided if needed.
12
5.
Lignin to Adipic Acid
(recommended by Bruce M. Vrana, DuPont)
Several cellulosic ethanol plants in the U.S. are beginning, or have recently begun, to produce fuel
ethanol from cellulosic feedstocks such as corn stover. This second generation ethanol is mandated
in the RFS2 regulations and production is expected to increase significantly over the next few
years.
In addition to ethanol, these plants make a coproduct consisting primarily of lignin. Lignin is a
heterogeneous mixture of largely-aromatic polymers that provides plant cell walls their structural
strength and recalcitrance to biologic attack. The old joke in the industry has been that you can
make anything from lignin except money. But the National Renewable Energy Lab (NREL) is
working to change that.
They have genetically modified P. putida to funnel many lignin model compounds to cis,cismuconic acid. They also demonstrated an integrated process from plant-derived lignin to muconic
acid, followed by high yield recovery and hydrogenation to adipic acid. Adipic acid is the
dicarboxylic acid produced industrially in the largest quantity. It is used primarily as a monomer to
make nylon 6,6, used for fibers and engineering polymers.
Your company makes adipic acid from the conventional petrochemical process. You have been
assigned the task of deciding whether this NREL process is a threat to your business in the near
term, in the longer term with further work, or whether it needs significant new inventions to be
competitive.
Thus, you should design the process that NREL has demonstrated to see if it is already competitive.
However, it seems likely that further improvements in the process may be necessary for it to be
competitive. So you should build all your process models (for example in ASPEN PLUS) and your
economic model recognizing that you will likely need to test the sensitivity to various process
parameters that have been demonstrated. Then determine where NREL should focus its effort to
make the overall process commercially competitive with existing adipic production.
Assume that lignin is available at a price of half of its fuel value in your economic projections.
This is because a boiler to generate steam and electricity from lignin is expensive, and this capital
would be avoided if an alternative use for lignin is found. You may also assume that there will be
several cellulosic ethanol plants operating in the U.S. corn belt in the 25-30MM gallon per year
capacity range. You will need to decide the best commercialization path for the NREL technology
– a small plant built at each ethanol plant, or a larger plant that takes lignin from several ethanol
plants. The only relevant business information that your company has is its projection for adipic
acid price, of $1,800/tonne and the price of hydrogen of $1,100/tonne. All prices are forecasts by
your marketing organization for long term average prices, expressed in 2016 dollars.
You will need to make many assumptions to complete your design, since the data you have is far
from complete. State them explicitly in your report, so that management may understand the
uncertainty in your design and economic projections before deciding how to respond to this
potential competitive threat (or opportunity) from NREL. Test your economics to reasonable
ranges of your assumptions. If there are any possible “show-stoppers” (i.e., possible fatal flaws, if
one assumption is incorrect that would make the design either technically infeasible or
uneconomical), these need to be clearly communicated and understood by management.
13
The plant design should be as environmentally friendly as possible, at a minimum meeting Federal
and state emissions regulations. Recover and recycle process materials to the maximum economic
extent. Also, energy consumption should be minimized, to the extent economically justified. The
plant design must also be controllable and safe to operate.
Reference
Vardon et. al., “Adipic acid production from lignin”, Energy Environ. Sci., 2015, 8, 617.
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6.
Direct Route to Phenol From Benzene
(recommended by Bruce M. Vrana, DuPont)
Phenol is a major chemical intermediate used in a variety of other products. Phenolic resins are
used in a wide range of products, including printed circuit boards. Phenol is a raw material to make
polycarbonate, used in CD, DVD and Blu-ray discs. Phenol can be converted to caprolactam and
ultimately nylon-6, or to adipic acid and ultimately nylon-6,6, both used for fibers and engineering
polymers. There are a wide variety of other applications for this versatile intermediate.
Phenol is conventionally made from cumene using the following chemistry:
O
H3C
H3C
CH3
OH
CH3
OH
+
H
O2
H3C
O
+
CH2
+ H3C
CHP (cumene
Cumene
hydroperoxide)
This route has several drawbacks. Growth in demand for propylene has exceeded the growth in
supply, driving propylene prices higher. Also, one mole of acetone is made per mole of phenol.
The acetone must be sold at a reasonable price in order to have favorable economics on making the
phenol. Although acetone has numerous uses, phenol producers often have difficulty selling the
byproduct at an attractive price. Effectively, this process converts high value propylene into low
value acetone. In fact, although you could sell more phenol, your company has decided to not
expand phenol capacity if it produces acetone as a coproduct.
A team of scientists at the Council of Scientific and Industrial Research (CSIR) in New Delhi has
recently patented a direct process from benzene to phenol. Their vapor-phase process uses air to
oxidize benzene directly over a supported copper-chromium catalyst with about 95% yield at 28%
conversion of benzene.
Your company is considering licensing this technology. Your team has been assembled to
determine whether the process will be economical before engaging in any discussions with CSIR.
Because these negotiations can be sensitive, your management has forbidden any form of contact
with anyone at CSIR during your design. You may use only information that you can find in the
public domain, in the patent, on the Internet, etc. The objective is to obtain a license at the lowest
possible price, so you do not want to tip off your company’s interest in the process until your
engineering analysis is complete.
Based on data in the patent, design the optimum process to make 500MM lb/yr of phenol from
benzene at your plant complex on the U.S. Gulf Coast. You will need to focus on the process to
make phenol, not the process to make the catalyst, which you can assume will be produced for you
by a catalyst vendor. Benzene is available on site for $1,100/tonne. Phenol is worth $2,000/tonne
to your company. All prices are forecasts by your marketing organization for long term average
prices, expressed in 2016 dollars.
You will need to make many assumptions to complete your design, since the data you have is far
from complete. State them explicitly in your report, so that management may understand the
15
CH3
uncertainty in your design and economic projections before approaching CSIR to discuss a license.
Test your economics to reasonable ranges of your assumptions. If there are any possible “showstoppers” (i.e., possible fatal flaws, if one assumption is incorrect that would make the design either
technically infeasible or uneconomical), these need to be clearly communicated and understood
before proceeding.
The plant design should be as environmentally friendly as possible, at a minimum meeting Federal
and state emissions regulations. Recover and recycle process materials to the maximum economic
extent. Also, energy consumption should be minimized, to the extent economically justified. The
plant design must also be controllable and safe to operate. Remember that if the negotiations are
successful, you will be there for the plant start-up and will have to live with whatever design
decisions you have made.
Reference
U. S. Patent 8,772,552, July 8, 2014, assigned to Council of Scientific and Industrial Research.
16
7.
Propylene Oxide from Propylene
(recommended by Bruce M. Vrana, DuPont)
Propylene oxide (PO) is an important intermediate in the manufacture of propylene glycol (PG),
polyether polyols and many other products. PG is in turn used to make unsaturated polyester
resins, environmentally-friendly antifreeze, cosmetics, etc. The conventional PO processes have
many drawbacks. The chlorohydrin process produces chlorinated byproducts, both organic
compounds and inorganic salts, which must be disposed of. Other processes generally produce a
co-product, such as styrene, which can adversely affect the economics of producing PO. These
drawbacks have prevented your company from expanding production of PO.
Several companies have researched directly oxidizing propylene to make PO. But these efforts
have been unsuccessful because the allylic protons are easily oxidized.
A team of scientists at the Council of Scientific and Industrial Research (CSIR) in New Delhi has
recently applied for a patent for a catalyst that oxidizes propylene to PO in high yield. Propylene
conversions of up to nearly 50% are reported with selectivities of 100% (except for one data point).
Your company is considering licensing this technology. Your team has been assembled to
determine whether the process will be economical before engaging in any discussions with CSIR.
Because these negotiations can be sensitive, your management has forbidden any form of contact
with anyone at CSIR during your design. You may use only information that you can find in the
public domain, in the patent application or other patents or applications from CSIR, on the Internet,
etc. The objective is to obtain a license at the lowest possible price, so you do not want to tip off
your company’s interest in the process until your engineering analysis is complete.
Based on data in the patent, design the optimum process to make 200MM lb/yr of PO from
propylene at your plant complex on the U.S. Gulf Coast. You will need to focus on the process to
make PO, not the process to make the catalyst, which you can assume will be produced for you by a
catalyst vendor. Chemical grade propylene is available as a coproduct at your plant site for
$1,100/tonne. Propylene oxide can be sold for $2,500/tonne. All prices are forecasts by your
marketing organization for long term average prices, expressed in 2016 dollars.
You will need to make many assumptions to complete your design, since the data you have is far
from complete. State them explicitly in your report, so that management may understand the
uncertainty in your design and economic projections before approaching CSIR to discuss a license.
Test your economics to reasonable ranges of your assumptions. If there are any possible “showstoppers” (i.e., possible fatal flaws, if one assumption is incorrect that would make the design either
technically infeasible or uneconomical), these need to be clearly communicated and understood
before proceeding.
The plant design should be as environmentally friendly as possible, at a minimum meeting Federal
and state emissions regulations. Recover and recycle process materials to the maximum economic
extent. Also, energy consumption should be minimized, to the extent economically justified. The
plant design must also be controllable and safe to operate. Remember that if the negotiations are
successful, you will be there for the plant start-up and will have to live with whatever design
decisions you have made.
Reference
U.S. Patent Application 20140364636, published December 11, 2014 by workers at Council of
Scientific and Industrial Research
17
8.
Design of Manufacturing Facility for Oleosin 30G
(recommended by Daniel Hammer and Miriam Wattenbarger, UPenn)
Recombinant amphiphilic proteins are used to make self-assembling structures such as bilayer
vesicles or micelles for drug delivery or imaging of patients or for surfactant use in the chemical
and food industries. Oleosin, a natural protein found in plants, is a natural surfactant with a triblock arrangement of amino acids with a hydrophilic N-terminus, a central hydrophobic block, and
hydrophilic C-terminus. The Hammer lab has produced recombinant oleosin in E. coli, isolated and
purified oleosin, and made self-assembled structures with oleosin. The oleosin vesicles produced
are more stable than phospholipid vesicles. With the ability to modify the oleosin gene before
insertion into E. coli, the oleosin sequence can be modified to optimize the structure and allow
targeting for particular applications
The goal of this project is to design an oleosin manufacturing facility based on the research lab
protocols for recombinant oleosin developed in Dr. Dan Hammer’s lab. Dr. Hammer has recently
established a company, Oleocor, to pursue commercialization of his oleosin work which will
require the design a larger scale facility to make oleosin.
The manufacturing facility should produce 1 kg/year of dry powder oleosin. The lab protocols will
need to be modified for the larger facility. The process for making pharmaceutical grade oleosin
will require a high purity (> 99%) and removal of endotoxins. A lower grade oleosin can be
produced for use as a surfactant for non-pharmaceutical applications in the chemical and
agricultural industries (~95%). Oleosin for the food industry may have purification specifications
between the pharmaceutical and chemical grade products.
The economic analysis should evaluate the current market for competitive products and the
feasibility for producing the three grades of oleosin. Recommendations should include which
process is most feasible and discuss any costly steps that deem the process unprofitable. Research
and development for particular steps to reduce the cost should be presented.
The plant design should be as environmentally friendly as possible, and should allow for the
recovery and recycling of the process materials when possible.
References
Vargo, K. B. et al, Spherical Micelles Assembled from Variants of Recombinant Oleosin, Langmuir
2014 30: 11292.
Vargo, K. B., Self-assembly of Tunable Protein Superstructures from Recombinant Oleosin. PNAS
2012. 109:11657.
18
9.
High-temperature Pebble-bed Nuclear Reactor with “Lego” Modular Design
Improvements
(recommended by Adam A. Brostow, Air Products and Chemicals)
Background
Figure 1 shows the process PFD of MIT’s High-temperature Pebble-bed Nuclear Reactor. The
system comprises a primary and secondary helium circuit. Helium in the primary circuit is heated
to a high temperature in the nuclear reactor core. Helium in the secondary circuit is heated in the
intermediate heat exchanger (IHX) against helium in the primary circuit to avoid possible
radioactive contamination. It is then expanded in a series of expanders (isentropic turbines). Some
of those turbines directly drive compressors (so-called companders). Then, the working fluid is
expanded in a generator-loaded turbine to produce electric power. The expanded stream is cooled
in the recuperator (economizer) heat exchanger, further cooled in a precooler, compressed, reheated
in the recuperator, and sent back to the IHX. This is the so-called Brayton power cycle. The
nuclear reactor is of pebble-bed type, which eliminates the possibility of a meltdown and is
inherently safer than other types.
Figure 8, in A Future for Nuclear Energy: Pebble Bed Reactors (see Literature), shows a variation
of the cycle with three expanders, rather than two, a different compressor arrangement, and slightly
different conditions.
Figure 1 MIT Pebble-Bed Nuclear Reactor Power Cycle
19
Figure 2 shows the supercritical CO2 Brayton cycle developed by the Sandia National
Laboratories.
Figure 2 CO2 Brayton cycle
Figure 3 shows a Supercritical Brayton cycle applied to a nuclear power plant similar to the ones
shown on Figures 1 and 2.
Figure 3 Supercritical Brayton cycle
20
Figure 4 (U.S. Patent Application 20120216536) shows a supercritical CO2 Brayton cycle applied
concentrated solar power plant.
Figure 4 Supercritical CO2 Brayton cycle applied concentrated solar power plant
Design Problem
An MIT-type modular, nuclear, power plant supplies 120 MW of electricity. Helium, as working
fluid, is believed to be well suited for high temperature applications. However, helium requires
exotic equipment and easily leaks out of the system. Equipment sizes are large.
This assignment is to model the helium-based plant as described in the literature using the ASPEN
PLUS process simulator and to try to improve it by replacing helium in the secondary circuit at
least partially with supercritical CO2 (S-CO2) while maintaining the modular character of the
design.
Another part of the assignment applies the same S-CO2 design to the high-temperature,
concentrated, power plant also producing 120 MW of electricity. Because the design is modular, at
least some modules should be identical, the difference being the possibly lower maximum
temperature and primary circuit working fluid (oil, molten salt, etc.).
The students, then, would compare short-term and long-term economics of the two variants: nuclear
and renewable.
21
References
A Small Modular Reactor That is Being Built Now! by Andrew C. Kadak, Ph.D.
A Future for Nuclear Energy: Pebble Bed Reactors by Andrew C. Kadak
High Temperature Gas Reactors by Andrew C. Kadak
MIT PEBBLE BED REACTOR PROJECT by Andrew C. Kadak
Modularity of the MIT Pebble Bed Reactor for Use by the Commercial Power Industry by Jaime E.
Hanlon-Hyssong
Design of a Heat Exchanger for Pebble Bed Reactor Applications by Jesse Russell Schofield
Development of a Supercritical Carbon Dioxide Brayton Cycle: Improving PBR Efficiency and
Testing Material Compatibility by Chang Oh et al.
OVERVIEW OF SUPERCRITICAL CO2 POWER CYCLE DEVELOPMENT AT SANDIA
NATIONAL LABORATORIES by Steven A. Wright et al.
Review of High-Temperature Central Receiver Designs for Concentrating Solar Power by Clifford
K.Ho
U.S. Patent Application 20120216536: Supercritical Carbon Dioxide Power Cycle Configuration
for Use in Concentrating Solar Power Systems by Zhiven Ma et al.
Become an Inventor: Idea-Generating and Problem-Solving Techniques with Element of TRIZ, SIT,
SCAMPER, and More by Adam Adrian Brostow:
http://www.amazon.com/Become-Inventor-Idea-Generating-Problem-SolvingTechniques/dp/1508936838
The above book talks, among other things, about principles such as Division (modularity),
Universality, Putting to Different Use, and reusing a solution from another domain. It gives
examples from former senior design projects. One can use division not only to how the plant is
designed, but also how it is simulated.
22
10.
Cocoa Liquor, Butter, and Powder Production
(recommended by Stephen M. Tieri, DuPont)
Chocolate has been called the "food of the gods”; and while a sweet treat for many across the
world, it is also a thriving $100 billion per year global industry. Chocolate is an agricultural
product, and similar to wines, a product whose finished character and flavor are dependent on
numerous items; including genetics, climate, soil, and processing practices.
Through a recent acquisition, your company now has a food and beverage ingredients business,
with a range of product offerings. As the chocolate industry continues to sustain steady growth, the
company believes there are favorable expansion economics for the Chocolates and Cocoa
Derivatives business. As a part of this new business, the company acquired new cocoa processing
technology with an advertised potential to provide more uniform product mixing properties, reduce
cost, offer manufacturers more flexibility in processing, and provide reduced fat content offerings.
Traditional methods of extracting cocoa powder from the fermented bean have been described as
complex, difficult, and expensive. The standard practice involves processing the bean into cocoa
nibs and then cocoa liquor. The liquor is then treated to separate the components cocoa butter from
cocoa powder. This separation is usually completed by processing the liquor, leaving a solid mass
which is cooled and milled to produce fine powder used in confectionary and beverage applications.
However, in pressing this liquor into a cake form, some residual cocoa butter is left in the resulting
powder, potentially rendering the product lumpy and insoluble when mixed with water or milk for
chocolate flavored drinks. Most manufacturers add lecithin or a similar dispersing agent to prevent
this problem, which increases both the production cost and fat content of the final product.
Furthermore, the typical cocoa nib mechanical processing methods, employed to isolate high
quality cocoa butter from cocoa powder, operate at high pressures and result in both relatively
expensive equipment and high maintenance costs. As this pressing step is typically a batch
operation, the step time is dominated by the rate and extent to which the fat can be removed from
the cocoa mass; with long batch press times required to achieve high cocoa butter yield.
Additionally, the minimum practical limit of fat removal for the pressing technology is ~11%,
potentially as low as 9-10% for certain varieties of cocoa plants/beans.
The newly developed process technology employs solvent extraction to separate cocoa fat from
cocoa mass, and achieve a desirable cocoa butter yield and provide a low fat, and preferably fatfree, cocoa powder product. The company is marketing the low fat and fat-free products as
providing a more user friendly product for manufacturers of consumer chocolate products and
beverages. Among the claimed attributes of this novel technology, the reduction in process
investment and operating costs, are enabled by the elimination of one or more traditional processing
steps.
Development laboratory and pilot testing indicate the fat-free powders resulting from the new
technology exhibited particle-size distributions identical to standard cocoa powders (with 10-12%
residual fat) and no differences in subsequent customer processing were observed. The particle size
was found to have been controlled during grinding of the nibs to form liquors, with the particle size
maintained downstream irrespective of the butter extraction technology (solvent vs. press).
Your project team has been assembled to quantify the value of the new process technology,
compared to a traditional chocolate process in terms of plant investment and manufacturing cost;
and to design a commercial plant to produce 120 M tonnes/yr (thousand metric tons per year) of
cocoa liquor, butter and powder based on the optimal technology. The business and marketing
team determined the necessary residual fat content targets in your cocoa powder products are < 2%
and < 0.5% for the “Low Fat” and “No Fat/Fat Free” grades, respectively. All cocoa liquor, butter
23
and powder products must have less than 1 ppm residual solvent. The cocoa liquor, butter, and
low-fat powder products must be of Food Grade quality, fit for human consumption, and meet all
FDA and other regulatory standards. In addition to the process equipment, the facility is expected
to have some amount of onsite storage for both raw materials and products.
Your company management is currently considering two potential locations for this new facility;
Tema, Ghana or Sao Paulo, Brazil. Your team is expected to evaluate these siting options, and
identify the preferred location. Your company expects to secure long-term cocoa bean supply
agreements, based on your recommendation. To support your evaluation of the geography options
for this facility, the company internal project and accounting resources suggest the use of 0.92 and
0.96 as location factors for Ghana and Brazil, respectively. Cocoa beans and other process
materials are expected to be sourced locally at current market pricing.
The plant design is expected to be as environmentally friendly as possible, and as necessary as
required by state and federal emissions legislation. It is expected that the facility will include
emission control equipment as a part of the process design. Recover and recycle process materials
to the maximum economic extent. Material use and energy consumption should be minimized, to
the extent economically justified. The plant design must also be controllable and safe to operate.
As the process technology integration and design team, you will be there for the start-up and will
have to live with whatever design decisions you have made.
You will need additional data beyond that given here and listed in the references below. Cite any
literature data used. If required, make reasonable assumptions, state them, and indicate whether
your design or economics are sensitive to the assumptions you have made.
References
International Cocoa Organization, http://icco.org/
Low-Fat Cocoa Powder, U.S. Patent 7709041 B2; May 2010
Method and Arrangement for Processing Cocoa Mass, Resulting Products, U.S. Patent 6361814;
March 2002
Method for Processing Cocoa Mass, U.S. Patent 6610343; August 2003
Producing Cocoa Powders With Different Cocoa Butter Contents by Liquefied Gas Extraction on
Substantially the Same Production Line, U.S. Patent Application 20040071847; April 2004
Process for Producing Cocoa Butter and Cocoa Powder by Liquefied Gas Extraction, U.S. Patent
Application 20040071848; April 2004
Chocolate Composition, U.S. Patent 8293314 B2; October 2012
Dispersible Cocoa Products, U.S. Patent 7201934 B2; April 2007
www.ams.usda.gov
http://www.eia.gov/forecasts/steo/
24
11. Propane Dehydrogenation by Autothermal Reforming
(recommended by John A. Wismer, Arkema)
The market for propylene has been shifting dramatically over the past decade. Historically,
propylene has been supplied as a by-product of refinery catalytic crackers and olefins plants that
use naphtha or gas oil feedstocks. However, in recent years the decline in US gasoline
consumption combined with the displacement of naphtha by ethane as a feedstock for olefins
crackers has led to a decline in by-product propylene production. These trends are expected to
continue for the foreseeable future as new ethane-supplied crackers come on stream. As a result,
propylene will be increasingly supplied by on-purpose production. Although ethylene metathesis
may play a bigger role in the future if ethylene prices drop as expected, the current preferred onpurpose route is propane dehydrogenation. This has typically been done in catalytic high
temperature reactors. Considerable heat input is required to satisfy the endothermic heat of reaction
and the conversion per pass is equilibrium limited. The separation of propylene from propane is
very energy intensive.
A competitive technology to direct dehydrogenation is oxydehydrogenation. In this technology,
oxygen or air is co-fed to the reactor to react exothermically with the hydrogen produced by
dehydrogenation6. The heat of the combustion reaction is used to supply the heat requirement for
the dehydrogenation reaction. Furthermore, the consumption of hydrogen allows the equilibrium
conversion of propane to increase. The higher propylene content of reactor effluent allows for less
energy intensive C3 separation.
The technology as practiced is described by a promotional brochure of the licensor3. The first US
plant to use this technology was announced in 2014. One design concern is making sure the oxygen
gets distributed along the reactor’s axial length to smooth out the temperature profile and minimize
non-selective C3 oxidation2. Presumably, enough CO2 is generated that some type of CO2 removal
process will be needed1. Also, steam is added to allow the reactor to run at elevated pressure while
keeping the hydrocarbon partial pressure low, which is critical to maximizing the equilibrium
conversion. The ASPEN PLUS equilibrium reactor simulations can also evaluate whether steam is
useful in scavenging any CO by way of the water-gas-shift reaction.
In propylene production, another focus of R&D work, which has become especially important for
PDH processes, is C3 splitting. Conventional distillation can require up to 200 theoretical stages
and reflux ratios >10. Among the alternative methods that have been partially explored include
pressure-swing adsorption, reactive distillation, facilitated diffusion and membrane separation.
There is some indication that a hybrid process using both distillation and membranes may be
optimal5. A recent membrane development is to use a hybrid of resins and zeolite. One member of
this family is ZIF-84. Although not yet commercially available, it is showing promise in both C3
splitting and CO2 purification. Your design should explore whether this type of membrane
separation has merit. A previous design group evaluated a less efficient membrane and showed it
have good economic potential8. Your evaluation can essentially update their analysis using the
ZIF-8 performance data and the higher propylene content of oxidative dehyrogenation reactor
effluent.
The plant should be sized for 500 kT/yr of propylene.
References
1) Intratec Solutions, “Propane dehydrogenation: Oxydehydrogenation,” Chemical Engineering.
Volume 122, No. 3 , March 2015, p.44
25
2) Rytter, E., et al., US2003/0139637A1 “Method and reactor for autothermal dehydrogenation of
hydrocarbons,” July 24, 2003
3) The Uhde STAR Process – Oxydehydrogenation of light paraffins to olefins – Promotional
Brochure available at Thyssen Krupp website
4) Pan, Y. “Effective separation of propylene/propane binary mixtures by ZiF-8 membranes,
Journal of Mebrane Science 390-391 (2012), 93-98.
5) Benali, M., ‘Ethane/ethylene and propane/propylene separation in hybrid membrane distillation
systems – Optimization and economic analysis”, Separation and Purification Technology, 73
(2010), 377-390.
6) Herauville, V. “Catalytic Dehydrogenation of Propane”, publishhed by NTNU Dept of
Chemical Engineering, June 2012 at:
www.diva-portal.org/smash/get/diva2:629220/FULLTEXT01.pdf
7) Kaneko, S., “Dehydrogenation of propane combined with selective hydrogen combustion over
Pt-Sn bimetallic catalysts”, Applied Catalysis A:General 356, 2009, 80-87.
8) Li, D. et al., “Membranes for Olefins Separations” CBE 459 Design Report, April 3, 2012.
26
12.
Brine Wastewater from Desalination Processes
(recommended by Arthur Rempel and Kyra Berger, CBE 459 Students, Penn)
Clean water sources have recently become a scarce commodity across the globe. Brazil has reported
its worst drought in the past 50 years [1], while South Africa expects a 32% downfall in maize
production this year alone due to a shortage of clean water. And, of course, California is
domestically affected, where all 12 of its clean-water reservoirs are at abnormally low levels (and
have been, for some time now.)
One available method to produce clean water focuses on desalination. Desalination is a process
that removes salts and other minerals from untreated water, producing water that is clean for both
human consumption and irrigation [2]. Ocean water makes up approximately 97% of the Earth’s
total water supply [3], suggesting that desalination is an attractive option as a clean water source –
especially for coastal regions, like the three aforementioned areas.
Desalination is typically conducted either using multistage flash thermal vacuum evaporation,
where saline water is boiled at extremely low pressures with excess heat, or reverse osmosis
membrane separation (ROMS), a process by which contaminated water is forced through a series of
semi-permeable membranes at high pressures to filter out salts, minerals, and residual metals.
Currently, only 1% of the Earth’s clean water supply is produced using desalination, although the
UN predicts that by the year 2025, “14% of the world’s population will be encountering water
scarcity [4].” Furthermore, the Western Hemisphere’s largest desalination plant is projected to
open in May of 2016 in southern California [5], which will theoretically provide 50 million gallons
of drinking water per day to the San Diego county area.
Unfortunately, high
costs (as compared to
other clean water
sources) accompany
the
desalination
process,
predominantly due to inefficient
energy
consumption and ample
wastewater byproduct, usually referred
to as brine water.
Figure 1. General schematic of the desalination process
Brine water is highly concentrated salt water, which also contains other impurities like precious
metals that were used to purify the water during the desalination process. Due to its high salt
concentrations (typically about 30%, whereas ocean water usually spans the 1-5% range), brine
water will sink upon reentering the ocean, detrimentally affecting marine life and posing major
environmental concerns. Currently, a plethora of permits and federal regulations are required for
disposing brine water in sewer systems or in the ocean, which significantly contributes to the high
economic and energetic costs associated with desalination.
That is, the desalination process can consume as little as 3kWh/m3 (ROMS) [2], although this value
can reach anywhere from 13.5 up to 25.5kWh/m3, in the case of thermal desalination. For context,
fresh-water supplies typically require a maximum of 0.2kWh/m3 for treatment – significantly less
than any desalination process. Desalinated water costs on average $2,000 per acre-foot (1acre-foot
27
is about 3.26x105 gal, or the equivalent amount of water consumed on average, annually by a family
of five) [5], which is four times as much as money spent on water from fresh sources; these high
costs typically arise due to the difficulty in managing the brine by-product. Storage facilities
charge, on average, between $2.00 and $2.50 to store one cubic meter of brine [8], which, in the
case of the aforementioned desalination plant, would equate to somewhere between $378,500 and
$473,125 per day, assuming that one gallon of brine is produced for every gallon of purified water
[5].
A series of brine management strategies exist and are implemented in desalination plants across the
globe, although they are extremely dependent on a variety of variables: location, land availability,
air moisture content, legal/federal permitting requirements, and economic feasibility.
Brine concentrators and evaporation ponds are attractive options – both methods allow for
additional water recovery from brine wastewater (up to 94%) [7], and completely remove the salts
from the environment “by ultimately sequestering the remaining brine in a landfill or in a closed
and sealed evaporation pond.” Thus, the combination of these brine concentrators and evaporation
ponds are deemed environmentally desirable. Figure 2 shows a general schematic of General
Electric’s brine concentrator [9].
Sadly, however, excessive costs
and energy consumption are
accompanied
by
these
environmental benefits, rendering these processes infeasible
more often than not. Brine
concentrators typically con-sume
between 60 and 100 kWh per
1,000 gallons of brine – assuming
a cost of $0.77/kWh, a brine
concentrator
will
generally
require $4,600-$7,700 per day to
process 1 mgd (million gallons
per day) of brine [8]. Or, in the
case of the plant from above, a
Figure 2. General Schematic of a brine concentrator
daily charge between $230,000
and $385,000. Notice that these
costs are between 20-40% lower
than those of the storage facility mentioned earlier, but they are not feasible or efficient by any
means.
Table 1 below further illustrates the high costs associated with treating 10 mgd of brine with these
two strategies as compared to other methods [7]. Additionally, Table 2 depicts the energy
consumption pertaining to all of the specified methods, clearly highlighting the excess energy
required for brine concentrators in comparison to the other methods.
Table 1. Costs of evaporation ponds and brine concentrators compared to other strategies
28
Table 2. Energy consumption of various brine-wastewater treatment methods
In addition to energy and management costs, brine wastewater also suffers from economic
opportunity costs due to the lack of recovering useful byproducts. These byproducts may consist of
selenium, nitrates, gypsum and calcium compounds, which “are widely used in the building
industry for drywall, plaster, and cement [10].” Other byproducts could consist of magnesium salts,
which are useful in the medical industry, and boron, which is a recent hot topic in high-efficiency
electronics. Finally, if purified appropriately, any recovered sea salt could be sold as a raw material
to further increase profitability.
We are interested in studying whether it is possible to improve the brine concentrator/evaporation
pond system in terms of both energy and cost, since their environmental benefits are unprecedented
among other common brine-management techniques. If possible, this would not only be
economically attractive to investors and desalination firms, but would also give rise to a new,
affordable, clean, and abundant water resource.
As such, this design project aims to study the thermal treatment of brine wastewater and
subsequently perform an in-depth economic analysis to determine whether brine concentrators and
evaporation ponds can become more cost-effective waste management strategies for desalination
plants. First, we will create a scaled-down experimental set-up of a brine concentrator, which,
alongside ASPEN PLUS simulation modeling, will allow us to somewhat mimic a brine
concentrator, providing us with a basis for the scaled-down energy consumption of our brine
concentrator/evaporation pond.
We then plan on examining the energy consumption required to purify various brine samples after
altering elements of the design process, including but not limited to: batch vs. semi-continuous vs.
fully continuous, and chemical composition (for example, using organo/carbocatalysts or anticaking
agents). Additionally, we plan on exploring the possibility of purifying brine wastewater solutions
and subsequently extracting economically valuable byproducts as a method of reducing both costs
and wastes, increasing efficiency in the long run. Ideally, the results obtained from these various
alterations will allow us to project any possible energy gains in the brine treatment process using
concentrator and evaporation ponds, and in turn, lead to economic benefits and cost reductions for
the respective brine management strategies.
References
[1]http://www.usatoday.com/story/news/world/2015/07/24/historic-droughts-wreak-havoc-usabrazil-n-korea/30513289/
[2]https://en.wikipedia.org/wiki/Desalination#Energy_consumption
[3]http://www.noaa.gov/ocean.html
[4]http://www.globalwaterintel.com/desalination-industry-enjoys-growth-spurt-scarcity-starts-bite/
[5]http://www.mercurynews.com/science/ci_25859513/nations-largest-ocean-desalination-plantgoes-up-near
29
13.
Recycling of Neodymium and Dysprosium from Neodymium-Iron-Boron Magnets
used in Wind Turbine Generators
(recommended by Connor Lippincott and Alan Dai, CBE 459 Students, UPenn)
Introduction/Motivation
In 2010 and 2011, the US Dept. of Energy released its Critical Materials Strategy, which outlined
the importance of various materials in the clean energy economy, including rare earth metals1. They
not only addressed the uses of these materials in new and developing clean energy technologies, but
described their supply challenges as well. Among those materials deemed most important to clean
energy and experiencing the worst supply risks are the rare earth metals neodymium (Nd) and
Dysprosium (Dy), both in the short term (from 2011-2015) and the medium term (2015-2025).
These two metals have magnetic and thermal properties that make them ideal for use in wind
turbine generators and electric vehicle motors. However, like the other rare earth elements in the
critical materials list, production is dominated by China, which has both the abundant natural
resources along with lax regulations that allow it to provide more than 95% of the world’s rare earth
elements since 2011.1 Worsening the supply problem is China’s strict quotas, which restrict much
of their production from being exported to the United States and other countries. While DOE has
encouraged the development of better (more economically viable and environmentally responsible)
extraction, separation, and processing methods to increase supply, along with the seeking
alternatives to lower demand, they have also highlighted the need for better recycling of the current
rare earth products, such as Nd-Dy magnets.
Despite the Critical Materials Strategy being developed in 2011, the rare-earth economy is still as
relevant as ever. Recent developments include the bankruptcy of Molycorp, the sole U.S. miner
and producer of rare-earth elements, which was almost a direct result of China’s control on the
global rare-earth market, as the relaxation of their export quotas burst the rare-earth market
“bubble” that formed in the past 5 years.2 Other companies are still seeking rare-earth production
methods as an alternative from Chinese suppliers.3,4 A new, efficient solution to the supply
problem would combat further market volatility and revitalize U.S. production of rare earths. In
2013, DOE established the Critical Materials Institute (CMI) at Ames Laboratory to specifically
research solutions to just this problem.5 In a press release on June 30, 2015, the CMI announced a
new method for recycling samarium-cobalt magnets, which contain a variety of rare earths, with
promising commercial viability.6 Recycling of rare earth-products is not only more cost efficient
and environmentally benign compared to mining and extraction processes, but as the CMI
researchers note, manufacturers can “retain quality control of the composition of their materials and
can be confident of the grade of their product” when running the recycling process themselves.
However, it is estimated that less than 1% of all rare earths are recycled today13. Recently with the
DOE mandate, many groups other than the Ames Laboratory see an opportunity and are developing
recycling methods.
Project Proposal
This project seeks to recycle Nd and Dy from used neodymium-iron-boron permanent magnets. In
these magnets, Nd is responsible for the main magnetic properties, while Dy is added primarily for
thermal stability. Different applications require different amounts of Dy – for instance, hard disk
drives contain no Dy, while magnets used in wind turbine generators contain 4-8 wt% Dy12. To
recover Nd and Dy for reprocessing into other magnet types, the elements must be separated from
each other and other components. Many rare-earth separation processes exist, as these elements
often need to be extracted from the same ores due to their chemical similarities, but these
similarities make even the most efficient process prohibitively slow, harsh, and expensive. For
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instance, the popular method in China for large-scale separation of rare-earth elements involves
multi-step, liquid-liquid extraction preceded by liberal treatment with strong acids.
An alternate recycling strategy is based on a method developed by Dr. Eric Schelter of the Penn
Dep't. of Chemistry8. This process involves the use of a novel tripodal nitroxide ligand, H3TriNOx.
The ligand’s structure gives it the ability to selectively separate rare-earth metals based on different
sizes of metal cations. The smaller Dy3+ ion forms the monomer [Dy(TriNOx)thf] when dissolved
in benzene, while Nd3+ forms the dimeric [Nd(TriNOx)]2. These two complexes have drastically
different solubility in benzene, leading to a separation factor, SNd/Dy= 359, which is ten times better
than the industrial standard, the MIII-HCl-HDEHP extraction method9. After the separation, the
H3TriNOx ligand is recycled, giving the process greater sustainability and cost-effectiveness.
To use this separation technique, in this project, a process from NdFeB magnets to the purified rareearth metals will be developed. First, the rare earths will be separated from the iron and boron
contained in the magnets by acid dissolution and then precipitation of the rare earths10. Then, the
rare-earth metals will be separated into their RE(TriNOx) species. Both compounds will be treated
with oxalic acid, creating RE2(C2O4)3 compounds and recycled H3TriNOx. In addition to designing
and streamlining the separations process, the project will attempt to create a small-scale version of
the reactor to demonstrate the viability of the process.
Potential Process Flowsheet – see Figure 1 and description below
1) Acid Dissolution:
● Feed 1: Scrap NdFeB magnets (Stream A)
○ Solid mixture, pre-crushed into small pieces
○ Varying composition: 29% - 32% Nd, 64.2% - 68.5% Fe, 1.0% - 1.2% B, 0.8% - 1.2%
Dy
○ Assume no plastic or impurities in simplest case
● Feed 2: Acid : H2SO4 (sulfuric acid) - cheaper and more widely used already in REE
processing than HCl
○ 2M H2SO4 suggested to keep sulfates in solution (else more water needs to be added)14
● Reaction: Acidification of metal components of magnet to form
○ Scrap dissolves readily without heating or agitation
■ Room temperature, atmospheric pressure
○ Weight ratio of acid to scrap of 2:1 or higher needed14
■ Fully dissolves scrap and be acidic enough to prevent oxidation of Fe2+ to Fe3+
(the latter of which would form a precipitate)
■ 1M H2SO4 at 2:1 ratio -> pH ~ 1.0, complete dissolution, no Fe ppt
■ 1:1 ratio -> pH ~ 3.0, incomplete dissolution, Fe ppt observed
○ Safety: exothermic, H2 evolution during dissolution
● Outlet: FeSO4, Nd2(SO4)3, Dy2(SO4)3, B (Stream B)
2) Rare Earth Double Salt Precipitation:
● Feed 1: Metal sulfates in aqueous, acidic leach solution (Stream B)
● Feed 2: NaOH (Stream C)
○ Add enough to raise pH to 1.5
○ 20 mL saturated NaOH solution per 400 mL leach solution = optimum ratio
■ Data: 99.47% RE recovery, double salt has 32.3% Nd, 2.91% Fe14
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●
●
●
Reaction: Formation of NaRE(SO4)2 double salt which precipitates out and is easily filtered.
OH- serves to raise pH of solution.
○ T = 25C, P =1 atm
○ Kinetics: After 60 min, negligible additional recovery of RE for ammonium salt14
■ Assume similar kinetics for sodium salt in simplest case
Outlet 1: FeSO4, B, pH 1.5 solution (Stream D)
○ Can be further processed by selectively precipitating Fe or B
Outlet 2: Filter and dry to obtain solid NaRE(SO4)2 salt (Stream E)
3) Conversion to Rare Earth Fluoride Salts
● Feed 1: Solid NaRE(SO4)2 salts (Stream E)
● Feed 2: Aqueous HF leach solution (Stream F)
○ 10 mL HF in 100g H2O most effective at converting RE and reducing residual Na+ and
SO42- content14
○ Add water to HF first before adding to double salt to obtain more easily filtered fluoride
salt
● Reaction: NaRE(SO4)2 + HF -> RE(F)3 + Na+ and SO42- impurities
○ Assume ambient conditions (no T, P given)
○ Kinetics: 15 min adequate for complete conversion of double salt and minimizing
impurity levels14
● Workup:
○ Filter to obtain solid RE(F3) salt and filtrate with minimal RE and Fe content
○ Wash RE(F)3 3-4 times with 1:2:10 weight ratio HF to RE(F)3 to H2O to half ion impurity
content.14
○ Dry RE(F)3.
● Outlet 1: Solid mixture of Nd(F)3 and Dy(F)3 (Stream G)
● Outlet 2: Filtrate with mainly HF, H2O, with some Na+, SO42- ions, minimal RE and Fe (not
shown in flowsheet)
○ Possible recycle stream back into step 3
4) Separation of Dy and Nd via Precipitation of Dy(TriNOx)
● Feed 1: Solid, dry mixture of Nd(F)3 and Dy(F)3 (Stream G)
● Feed 2: H3TriNOx and K[N(SiMe3)2] in THF (Stream H)
● Feed 3: N2 purge (not shown in flowsheet)
● Reaction 1: (Batch)
○ H3TriNOx + K[N(SiMe3)2] + RE(F)3 -> RE(TriNOx) + H+, K+, H[N(SiMe3)2], F○ Kinetics: T = Room temperature (25C), reaction time <= 12 hr8
● Workup:
○ Filter and drain liquids, wash solid RE(TriNOx) ppt with THF (collect and recycle THF
wash)
○ Extract RE(TriNOx) with DCM into reactor with heater/vacuum (not shown on
flowsheet)
■ Maybe explore more benign solvent
○ Remove DCM until solution is saturated (collect and recycle DCM)
○ Layer THF onto saturated DCM solution to obtain pure, solid RE(TriNOx)THF
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○
○
●
●
●
Isolate RE(TriNOx)THF (evolve THF/filter solid RE(TriNOx)THF)
Dissolve in toluene to ppt Dy(TriNOx)
■ Separation factor of Nd vs. Dy: SNd/Dy= 359 which is ten times better than the
current industrial separation standard, the MIII-HCl-HDEHP extraction method.8
■ a.k.a. 50:50 mixture of Nd:Dy enriched to 95% Nd complex in liquid
phase and 95% Dy complex in solid phase in one separation step
○ Filter to obtain solid Dy(TriNOx), Nd2(TriNOx)2 in solution
Outlet 1: Nd2(TriNOx)2 in toluene (Stream I)
Outlet 2: Solid Dy(TriNOx) (Stream J)
Main thermophysical and transport properties only relevant for bulk solvent (toluene)
5) Conversion of RE(TriNOx) to RE Oxalate Product
Nd:
● Feed 1: Nd2(TriNOx)2 in toluene (Stream I)
● Feed 2: Aqueous solution of oxalic acid (H2C2O4)
● Reaction: 3H2C2O4 + Nd2(TriNOx)2 -> Nd2(C2O4)3 + 2H3TriNOx
○ Kinetics: T = Room temperature (25C), reaction time <= 2 hr14
● Workup:
○ Filter and wash with DCM to obtain solid Nd2(C2O4)3 and H3TriNOx in filtrate
● Outlet 1: Solid Nd2(C2O4)3 Product (Stream L)
● Outlet 2: H3TriNOx in filtrate (Stream K)
Dy:
● Feed 1: Dy(TriNOx) (Stream I)
● Feed 2: Aqueous solution of oxalic acid (H2C2O4)
● Reaction: 1.5H2C2O4 + Dy(TriNOx) -> .5 Dy2(C2O4)3 + H3TriNOx
○ Kinetics: T = Room temperature (25C), reaction time <= 2 hr14
● Workup:
○ Filter and wash with DCM to obtain solid Dy2(C2O4)3 and H3TriNOx in filtrate
● Outlet: Solid Dy2(C2O4)3 Product (Stream M)
● Outlet 2: H3TriNOx in filtrate (Stream K)
Figure 1
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6) Recycling of H3TriNOx ligand (not detailed on flowsheet)
● Extract filtrate with DCM
● Dry organic extracts with drying agent (e.g. MgSO4)
● Remove drying agent by filtration
● Remove solvent from filtrate to obtain H3TriNOx
○ Could initially extract with THF so that this step is unnecessary
Challenges, Economics, and Additional Options
There are some definite challenges in this process design. The sensitivity to air and water has not
been completely defined. But, creating an air- and water-free process free would endanger
economic feasibility. Also, the cost and time investment in synthesizing the H3TriNOx ligand is
potentially high. The ability to recycle the ligand is promising, but streamlining the synthesis is a
necessary step towards success.
Economics
●
●
●
●
Can compare to current RE liquid-liquid extraction methods (by $/kg cost of Nd/Dy obtained)
○ Jan 2015: Nd stable at ~$100/kg, Dy stable at ~$500/kg
○ Note additional benefits of recycling over mining, etc.
Available data:
○ Data for popular industrial 100+-stage LLE RE separation process
Can compare to emerging RE magnet recycling methods (see PROCEEDINGS OF THE
52nd CONFERENCE OF METALLURGISTS)
Add on to existing equipment for magnet recycling (that didn’t separate the rare earths from
each other)
Additional Options
●
●
●
●
Sensitivity analysis: vary Dy content of feed
Fe and B processing
Relax assumptions:
○ Include other metals in magnet scrap: Al, Co, Pr
○ Include generic plastics in magnet scrap
Alternate method of separating Fe and REE
References
1. “Critical Materials Strategy.” U.S. Department of Energy. Dec. 2011. Web. 25 Jul. 2015.
http://energy.gov/sites/prod/files/DOE_CMS2011_FINAL_Full.pdf
2. Miller, J. W.; Zheng, A., “Molycorp Files for Bankruptcy Protection.” The Wall Street Journal.
25 Jun. 2015. Web. 25 Jul. 2015.
http://www.wsj.com/articles/SB10907564710791284872504581069270334872848
3. Matich, T., “Rare Earth Salts’ Separation Process Could Be Key for Producers Outside China.”
Investing News. 10 May 2015. Web. 25 Jul. 2015. http://investingnews.com/daily/resource-
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investing/critical-metals-investing/rare-earth-investing/rare-earth-salts-separation-processcould-be-key-for-producers-outside-china//
4. Matich, T., “Rare Element Resources COO Jaye Pickarts Talks Rare Earths Separation and
Competing with China.” Investing News. 23 Jun 2015. Web. 25 Jul. 2015.
http://investingnews.com/daily/resource-investing/critical-metals-investing/rare-earthinvesting/rare-element-resources-china-rare-earth-separation/
5. “Ames Laboratory to Lead New Research Effort to Address Shortages in Rare Earth and Other
Critical Materials.” U.S. Department of Energy. 9 Jan. 2013. Web. 25 Jul. 2015.
http://energy.gov/articles/ames-laboratory-lead-new-research-effort-address-shortages-rareearth-and-other-critical
6. Nlebedim, I.; Millsaps, L.. “New CMI process recycles magnets from factory floor.” The Ames
Laboratory. 30 Jun. 2015. Web. 25 Jul. 2015 https://www.ameslab.gov/news/newsreleases/new-cmi-process-recycles-magnets-factory-floor
7. Lerner, E., “Penn Research Simplifies Recycling of Rare-earth Magnets.” University of
Pennsylvania. 17 Jun. 2015. Web. 25 Jul. 2015. http://www.upenn.edu/pennnews/news/pennresearch-simplifies-recycling-rare-earth-magnets
8. Bogart, J. A.; Lippincott, C. A.; Carroll, P. J.; Schelter, E. J., "An Operationally Simple
Method for Separating the Rare-Earth Elements Neodymium and Dysprosium" Angew. Chem.
Int. Ed. 2015, 54, 8222–8225
9. Gupta, C. K; Krishnamurthy, N., Extractive Metallurgy of Rare Earths, CRC, New York, 2005,
pp. 1–484.
10. Lyman, J.W.; Palmer, G.R., “Recycling of neodymium iron boron magnet scrap.” Report of
Investigations 9481 (United States, Bureau of Mines). 3 Nov 1993. Web. 25 July 2015.
http://stacks.cdc.gov/view/cdc/10223/cdc_10223_DS1.pdf
11. Rai, D; Felmy, A.R.; Fulton, R.W., Journal of Solution Chemistry 24: 879-895 (1995).
12. “The Important Role of Dysprosium in Modern Permanent Magnets” Arnold Magnetic
Technologies. 12 Jan. 2012. Web. 28 Aug. 2015.
13. “Rare Earth Recycling”. Molycorp. 2013. Web. 28 Aug. 2015.
http://www.molycorp.com/technology/rare-earth-recycling/
14. Gschneidner, KA; Eyring, L. Handbook on the physics and chemistry of rare earths. 1978.
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