It’s 2009 and the agricultural giant, Cargill, has expanded significantly over the last decade
into the production of renewable carbon monoxide, CO, generated from agricultural solid
waste. The Cargill CO pipeline currently produces 16 [t/h] of renewable CO at 2.5 [bar] (a) and
25 [°C], containing 0.25 [%] (mol/mol) CO2. However, the return on investment when selling
the renewable CO at fuel value for electrical power generation has been less that desirable
from the perspective of senior management. Another sustainable technology has created an
opportunity to upgrade the renewable CO. Cargill has developed a technology to convert their
expansive monosaccharide feedstocks into propene via fermentation, producing 3 [t/h] of
renewable propene from several first generation production facilities at 2 [bar] (g) and 30
[°C]. In addition, Cargill has committed to investing heavily into the production of MW-scale
water electrolysis, producing H2, using renewable electricity. Senior management have set
their sights on adding greater value to these renewable resources by producing sustainable
chemicals from the propene, CO and H2.
R&D efforts in Cargill’s world class laboratories has led to the development of processing
steps, able to convert CO and propene into isobutanol via hydroformylation and
hydrogenation reactions. Isobutanol is an attractive drop-in fuel, which augments Cargill’s
vision towards sustainability in the transport market. The technology remains in the
developmental stages, but senior management would like you to evaluate a conceptual
design within a preliminary cost framework. By-product production of n-butanal and
isobutene remain a challenge and the focus of further R&D effort. Cargill estimates that
another three years of R&D effort is required starting in 2010 prior to commencing the two
years of plant construction and commissioning. The R&D budget per annum for this project is
$3,000,000 over the three year period.
For the hydroformylation reactor, Reaction 1 represent the conversion of propene, CO and
H2 to isobutanal using an in-house catalyst developed at Cargill. Reaction rates are expressed
in [kmol/(m3
·h)] and partial pressure in the ‘Vapour’ phase in [kPa]. The activation energy, E,
is expressed in [kJ/kmol]. Similarly, Reaction 2 represents the synthesis of the
hydroformylation by-product, n-butanal, associated with the catalyst mechanism. In the
laboratory, a plug flow reactor has typically been operated at 150 [°C] and 4 [bar] (g).
𝑟1 =
589 · 𝑒
𝑅·𝑇 · 𝑃𝐶3𝐻6
· 𝑃𝐻2
(1 + 0.89 · (1 + 0.2) · 𝑃𝐶3𝐻6
𝑟2 =
85.6 · 𝑒
𝑅·𝑇 · 𝑃𝐶3𝐻6
· 𝑃𝐻2
(1 + 0.22 · (1 + 1.8) · 𝑃𝐶3𝐻6
For the hydrogenation reactor, Reaction 3 represents the conversion of isobutanal to
isobutanol with renewable H2 using a newly developed catalyst in the chemistry laboratories.
Reaction rates are expressed in [kmol/(m3
·h)] and the molar concentration in the ‘Liquid’
phase in [kmol/m3]. The activation energy, E, is expressed in [kJ/kmol]. Similarly, Reaction 4
represents the synthesis of the dehydration by-product, isobutene, and Reaction 5 the aldol
condensation by-product, 3-hydroxy-2,2,4-trimethylpentanal, associated with the catalyst
mechanism. In the laboratory, a continuous stirred tank reactor has typically been operated
at 100 [°C] and 15 [bar] (g).
𝑟3 = 1.3 · 1012
· 𝑒
𝑅·𝑇 · 𝐶𝑖𝑠𝑜𝑏𝑢𝑡𝑎𝑛𝑎𝑙
𝑟4 = 1.5 · 1014
· 𝑒
𝑅·𝑇 · 𝐶𝑖𝑠𝑜𝑏𝑢𝑡𝑎𝑛𝑜𝑙
𝑟5 = 9.0 · 1012
· 𝑒
𝑅·𝑇 · 𝐶𝑖𝑠𝑜𝑏𝑢𝑡𝑎𝑛𝑎𝑙
𝑟5− = 9.0 · 1011
· 𝑒
𝑅·𝑇 · 𝐶3−hydroxy−2,2,4−trimethylpentanal
Your department has recommended the use of UNIQUAC Property Package from past
experience with this component system, estimating all unknown binary coefficients using
UNIFAC VLE estimation. Your department has made the thermodynamic data for the
components available to you.
Table 1 outlines the economic considerations. Furthermore, the techno-economic
department has forecast the pricing for feedstocks and products as in Table 2. Table 3 details
the CE Plant Cost Index (2006 – 2015).
Table 1 – Economic parameters associated with isobutanol process.
Economic Parameters Unit Value
Capital for major equipment
Major Equipment Purchase
Cost + Internals
(Knovel reference material)
Towler, G., and Sinnott, R.K., (2012),
Chemical Engineering Design: Principles,
Practice and Economics of Plant and Process
Design, Butterworth-Heinemann, 2nd edition,
Location factor with respect
to US Gulf Coast
[-] 0.75
Installed cost – ISBL factor [-] Hand
OSBL [% of ISBL] 25
Working capital
(Returned in final year)
[% of Fixed Capital Investment] 10
Commissioning cost [% of Fixed Capital Investment] 5
Return on Investment
Plant life [years] 20
Annual inflation [%] 2
Linear depreciation [years] 10
Annual corporation tax [%] 30
Discounted Rate of Return [%] 9
Fixed Operating Cost
Labour rate per shift worker [$/annum] 45,000
Number of shift teams [-] 4
Number of shift team
members (excluding
[-] 3
Supervisory labour [% of Operating Labour] 25
Direct Salary Overhead [% of Operating + Supervisory
Maintenance [% of ISBL] 3
Property taxes & insurance [% of ISBL] 1
Rent of land / buildings [% of Fixed Capital Investment] 1
General plant overhead [% of Total Labour +
Allocated Environmental
[% of Fixed Capital Investment] 1
Interest charges (capital) [% of total capital investment] 2.5
Economic Parameters Unit Value
Production Costs
Cooling water [$/m3
] 2.5
Process water [$/m3
] 1.2
Steam 22 [bar] (g) [$/t] 22
Electricity [$/kWh]
(including maximum demand)
Table 2 – Economic parameters associated with isobutanol process.
Economic Parameters Unit Value
Long Term Average Pricing
Hydrogen [$/kmol] 2.0
Carbon monoxide [$/kmol] 5.6
Propene [$/kmol] 33.7
isobutanal [$/kmol] 86.5
n-butanal [$/kmol] 74.3
[$/kmol] 15.1
isobutanol [$/kmol] 125.0
isobutene [$/kmol] 39.3
Methane (natural gas) [$/MMBTU] 2.5
Table 3 – CE Plant Cost Index from 2006 – 2015.
CE Plant Cost Index Value
2007 525.4
2008 575.4
2009 521.9
2010 550.8
2011 585.7
2012 584.7
2013 567.3
2014 576.1
2015 556.8
For heat exchangers, assume an overall heat transfer coefficient of 1,500 [W/(m2
·K)] in the
absence of a phase change. Where a phase change occurs, assume an overall heat transfer
coefficient of 10,000 [W/(m2
All potential products have a purity specification of > 99 [%] (mol/mol] and are stored at
ambient temperature