Appendices Appendix A – Ethanol Market Analysis and Projections ....................................................... 22 Appendix B – Preliminary Material Balance ........................................................................... 24 Appendix C – Derivation of the Kinetic Rate Law .................................................................. 26 Appendix D – MSDS for Ethanol, Acetic Acid, and Acetaldehyde ........................................ 30 Appendix E – Environmental Regulations ............................................................................... 31 Appendix F – CSTR Volume and Productivity Determination .............................................. 32 Appendix G - TPXY Data for Components in System ............................................................ 33 Appendix H - Sizing the Molecular Sieve ................................................................................. 34 Appendix I – Design of Separation Section of Process ............................................................ 36 Appendix J - ChemCAD Process ............................................................................................... 37 Appendix K - ChemCAD Report Summary............................................................................. 39 Appendix L – Economic Analysis .............................................................................................. 51 21
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Appendix L – Economic Analysis 51 - Josh Staiger Design Final Report... · Table B.1. Material balance for the ethanol production process Stream # Glucose Water Yeast Air Ethanol
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Appendices Appendix A – Ethanol Market Analysis and Projections ....................................................... 22 Appendix B – Preliminary Material Balance ........................................................................... 24 Appendix C – Derivation of the Kinetic Rate Law .................................................................. 26 Appendix D – MSDS for Ethanol, Acetic Acid, and Acetaldehyde........................................ 30 Appendix E – Environmental Regulations ............................................................................... 31 Appendix F – CSTR Volume and Productivity Determination.............................................. 32 Appendix G - TPXY Data for Components in System ............................................................ 33 Appendix H - Sizing the Molecular Sieve ................................................................................. 34 Appendix I – Design of Separation Section of Process ............................................................ 36 Appendix J - ChemCAD Process............................................................................................... 37 Appendix K - ChemCAD Report Summary............................................................................. 39 Appendix L – Economic Analysis.............................................................................................. 51
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Appendix A – Ethanol Market Analysis and Projections
Currently, both the international and US ethanol market are in the growth stage. The overall global ethanol production is a little less than 20 billion liters/year, and the production is expected to exceed 50 billion gallons by 2010 [14]. An analysis of the ethanol U.S. market shows that the demand for ethanol is expected to rise in the forthcoming years with a projected 10% per year market growth.
Dem
and
(in m
illio
ns o
f dol
lars
)
Figure A.1. Projected U.S. Ethanol Market Growth [15]
Historically, ethanol demand has been steadily climbing at 7.5% a year. However the market has been projected to increase at an average rate of 10% through 2010 to almost 5 billion gallons per year (bgy) depending on several factors [16, 15]. (Figure D.1) The gradual phase out of MTBE in several states, and possibly the country, will be the primary driver for an increased demand for ethanol as a replacement oxygenate in fuels [2].
Dem
and
(in m
illio
ns o
f)
Figure A.2. Projected U.S. Market Demand with MTBE ban [17]
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Figure A.3 shows that the price of ethanol is projected to steadily rise over the next 10
years regardless of the future of MTBE. This indicates that the investment of selling ethanol in the fuels industry would be profitable.
Figure A.3. Ethanol price projection for the next 10 years without MTBE phase out or RFS [18]
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Appendix B – Preliminary Material Balance A preliminary material balance for the ethanol manufacturing process was conducted using a block flow diagram consisting of the feed
preparation, reactor, and recovery sections. Figure A.1 shows the block flow diagram for the ethanol process while Table A.1 shows the stream table and mass balance for the process. Table A.2 summarizes the product quantities, purities, and states produced from the ethanol process.
Table B.2. Product summary for the purities and amounts produced
Product Purity Quantity (kg/yr) State Carbon Dioxide ~100% 259 E 6 Gas Acetic Acid ~99% Acetic Acid, with impurities 4.00 E 6 Liquid 95% Ethanol 95% Ethanol, 5% Water 94.74 E 6 Liquid 100% Ethanol 100% Ethanol 209 E 6 Liquid DDGs 97% dead yeast and nutrient, 3% Water 290 E 6 Solid
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Appendix C – Derivation of the Kinetic Rate Law The general fermentation reaction is A → C + R where A is the substrate or glucose, C is
the yeast cell, and R is the rate-depressing component or ethanol. The Monod equation describes the kinetics of the fermentation process:
( )⎟⎟⎠
⎞⎜⎜⎝
⎛+
=MA
CAobsC CC
CCkr [C1]
n
*R
Robs C
C1kk ⎟⎟
⎠
⎞⎜⎜⎝
⎛−= [C2]
where ri = Reaction Rate with respect to species i [=] quantity formed/(L⋅hr) k = Reaction Rate Constant [=] 1/hr kobs = Observed rate constant [=] 1/hr n = Toxic Power [=] Unitless Ci = Concentration of species i [=] g/L CM = Monod or saturation constant [=] g/L CR* = Ethanol Poison Concentration for Yeast [=] g/L
The yield, y, is defined by Equation C3 and the space time, τ, is defined by Equation E4.
y = ⎟⎠⎞
⎜⎝⎛
RC [C3]
τ = ⎟⎠⎞
⎜⎝⎛
vV [C4]
The constants of CR*, n, CM, and k must be determined.
Determination of kobs and CM
The equation for τ can also be written as:
⎟⎟⎠
⎞⎜⎜⎝
⎛⋅⎟⎟
⎠
⎞⎜⎜⎝
⎛+=
Aobs
M
obs C1
kC
k1τ [C5]
A plot of τ vs. ⎟⎟⎠
⎞⎜⎜⎝
⎛
AC1
will yield linear curves of the form y = mx + b where
b = ⎟⎟⎠
⎞⎜⎜⎝
⎛
obsk1 [C6]
m = ⎟⎟⎠
⎞⎜⎜⎝
⎛
obs
M
kC
[C7]
Thus, the value for kobs may be determined from the inverse of the intercept. The value for CM may then be calculated by multiplying the slope by the kobs.
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CR = 81.3 g/Lτ = 1.5853(1/CA) + 7.1185
R2 = 0.9971CR = 61.29 g/L
τ = 0.8935(1/CA)+ 3.4738R2 = 0.9907
CR = 29.19 g/Lτ = 0.6241(1/CA) + 2.7177
R2 = 0.9983
CR = 4.37 g/Lτ = 0.5541(1/CA) + 2.4128
R2 = 0.9974
-10
-5
0
5
10
15
20
25
30
-10 -5 0 5 10 15 20 2
1/CA (1/g)
τ (h
r)
5
Figure C.2.Linear Regressions for Dr. Breakthrough Kinetic Data at Various CR
The yield of the reaction [1] is closest to the data set with R/C = 4.88, or with CR = 81.3 g/L, so the appropriate data set was used to find the values for kobs and CM, as shown below:
kobs = 7.1185hr
1intercept
1= = 0.1405/hr
CM = = obskslope× 0.1405/hrmol/L1.5853hr ×⋅ = 0.2227 mol/L The calculations are shown in Table E.3 for all of the data sets.
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Table C.1. Calculations used for the calculations and graphs in the determination of the rate constants.
The three-year average of annual arithmetic mean concentrations at each monitor within an area is not to be at or above this level.
51 µg/m3 51 µg/m3
24-hr
The three-year average of the annual 98th percentile for each population-oriented monitor within an area is not to be at or above this level.
66 µg/m3 66 µg/m3
Respirable Particulate Matter (2.5 microns or less) (PM2.5)
Annual
The three-year average of annual arithmetic mean concentrations from single or multiple community-oriented monitors is not to be at or above this level.
15.1 µg/m3 15.1 µg/m3
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Appendix F – CSTR Volume and Productivity Determination
Table F.1. shows the spreadsheet used to calculate the reactor volume and productivity.
Table F.1. Excel spreadsheet used to determine CSTR volume and productivity.
vol. flow 629035 L/hr k 0.431 1/hr Go 1.284182 g/L n 0.3678 - Yo 0 g/L E* 85.5 g/L Eo 68.56589 g/L Km 0.2227 g/L e/g 0.434 y/g 0.108 Insert Sheet Numbers Here: Gi 136.1845 Vol. Flow In 610576 L/hr Ei Glucose Flow In 83151 kg/hr Ethanol Flow In 9859 kg/hr Vol. Flow Out 647494 L/hr Glucose Flow Out 831.5 kg/hr Ethanol Flow Out 44396 kg/hr Reaction Rate (y) 0.202482 Reaction Rate (g) 1.874833 Reactor Volume 426,800 L - Productivity 80.92087 g/L.hr Conversion Iterate! 0.99057
The flow values were obtained from the ChemCAD simulation of the process, which is shown in Appendix J. The volume of the CSTR was calculated from the CSTR design equation, as shown in Equation F1.
A
Ao
rXF
V−
= [F1]
where V is the reactor volume in liters, FAo is the input flow of glucose, X is the conversion with respect to glucose, and –rA is the rate law with respect to the glucose. The rate law was converted between different species by using the yield data from Dr. Breakthrough, as shown in Equation F2.
A
C
rr
yield = → yield
rr C
A = [F2]
The reactor was optimized with respect to the volume productivity, or VP, which is defined by Equation F3.
hLg ][
VF
VolumeReactor Produced EtOH of Flow MassVP R
⋅=== [F3]
The effect of key variables on the volume productivity was studied and the values for each variable were selected to maximize the VP for the reactor.
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Appendix G - TPXY Data for Components in System
Figure G.1. TPXY Data for Ethanol/Water at 1 atm by UNIFAC
Figure G.1 shows that an EtOH/Water azeotrope occurs for 95 wt% EtOH, and a method other than distillation must be used to achieve pure EtOH. From Figure G.2 shows the water/acetic acid azeotrope.
Figure G.2. TPXY Data for Water/Acetic Acid at 1 atm by UNIFAC
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Appendix H - Sizing the Molecular Sieve Based on the Chemcad simulation, 1405 kg/h of water had to be removed from a 25621 kg/h
stream consisting of 95 wt% ethanol to produce anhydrous alcohol. The following physical parameters were available [20]:
Quality of Adsorbent: q* = 0.103 adsorber kg
OH kg 2
Heat of Adsorption: molkJ9.42Hads =
Density of Adsorbent: 3ads mkg1210
mLg 21.1 ρ ==
Density of Solution: 3sol mkg789
mLg 789.0 ρ ==
The assumptions used in the design of the molecular sieves are the following:
− Liquid feed is a homogenous 2 component system − Model sieve as a plug flow system − EtOH is not adsorbed and the molecular sieve is initially free of EtOH − Process is isothermal − Total mole change is negligible – No accumulation within the system − No axial dispersion The vessel volume must be calculated from the mass of adsorbent required to remove the
water in the ethanol stream. The mass of the adsorbent required to remove the specified amount of water in a one hour time basis was calculated using q*:
adsorbent of kg 13643OH kg 0.103
adsorbent kg 1OH kg 1405m2
2ads =⋅= [H1]
The volume of the adsorbent was calculated by dividing mads by ρads:
adsorbent of kg 1210
m 1kg 36431 ρm
V3
ads
adsads
3m 11.275=⋅== [H2]
To determine the dimensions of the molecular sieves, a heuristic was used to determine the optimum L/D ratio of 3 for process vessels [21].
322
ads m 11.275(3D)2DπL
2DπV =⎟
⎠⎞
⎜⎝⎛=⎟
⎠⎞
⎜⎝⎛= [H3]
Solving Equation H3 yielded a diameter of 1.685 m corresponding to a vessel length of 5.06 m. The space time, τ, was calculated for the molecular sieves. The volumetric flow of the feed to the separator was calculated:
hm 47.32
789kgm 1
hrkg 25621V
33
sol =⋅= [H4]
Thus, the τ was determined to be 20.8 min, as shown below:
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min 20.8 ==== hr 347.0
hm 32.47
m 11.275VV
3
3
sol
adsτ
The volume and space time must be corrected by a safety factor. This value was determined from uptake curves to be 50% at an operating temperature of 40ºC [20]. Thus, the corrected volume for the molecular sieve was 16.9 m3 and the corrected space time was 31.2 min. The new dimensions were calculated by solving Equation H3. Based on heuristics, the optimum diameter was 1.93 m and the corresponding length was 5.79 m.
Four molecular sieves will be rotated as they become saturated to ensure a pseudo-state process. When one molecular sieve vessel becomes saturated with water, the water will be desorbed by spraying hot air at a temperature of 200ºC. The mass of 1405 kg/h of water can be converted to 78056 mol/h, which requires 930,162 W to adsorb:
W930162==⋅=⋅=hkJ3348583
watermol1kJ 9.42
h watermol 78056 Hn Q adsOH2
[H5]
According to a heuristic, the optimum temperature approach,ΔTlm, is 15ºC and the typical heat transfer coefficient, U, is 60 W/(m2·C) [21]. A proposed schematic of the heat exchanger is shown in Figure H.1.
ΔT = 15ºC
Air 200ºC
Air 55ºC
Water 185ºC
Water 40ºC
Water Desorption
Figure H.1: Proposed schematic of heat exchanger to desorb water from molecular sieve Based on these values, the area of a heat exchanger can be calculated to be 1034 m2:
2m 1034=⋅
⋅
=Δ⋅
=C )15(
CmW)60(
W(930162)TU
Q A
2lm
[H6]
The amount of air required for the adsorption can be calculated from Equation A7. Q = m·Cp·ΔT [H7] From Chemcad, the specific heat of air, Cp, is 1001 J/(kg·C). Thus, the mass of air required is equal to 23071 kg/h.
hkg 23071==
⋅⋅
=Δ⋅
=s
kg 41.6C )145(
CmJ)0011(
sJ (930162)
TCQ m
2p
air
The water in the air will be removed in a flash tower before the air is recycled to the desorption process. The heat exchanger and desorption process will be incorporated in the final process flow design.
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Appendix I – Design of Separation Section of Process The flash units and distillation columns used to recover CO2 and separate acetic acid and acetaldehyde from water were designed based upon technical heuristics for equipments sizes, operating conditions and performance. Additionally, design parameters were varied in ChemCAD process simulations to test the performance and feasibility of the process. The following heuristics were applied in the design of the distillation towers in ChemCAD:
− Height of the column can not exceed 300 ft high due to safety issues. − The column cannot have more than 150 trays if the tray spacing is 2 ft. − The temperature constraints depending on materials of construction are:
· Most processes designed to operate between 40 and 260ºC · Towers can operate between -200 and 400ºC
− The ratio of L/D is between 2 and 20. − The economically optimum number of stages is 2Nmin. − The economically optimum reflux ratio is 1.2Rmin. − The sequence of separations:
· Perform easiest separation first, as defined by fewest trays · If relative volatility or feed composition is similar, then remove components
individually as overhead products · Separate components in order of decreasing volatility: CO2, acetaldehyde, ethanol,
water, acetic acid For the Chemcad simulation, the heuristics were applied in the following manner:
− To have a reasonable tower size, the reflux ratio was increased so that fewer stages are required to obtain the desired separation
− To minimize the boiler duty, feed streams were preheated using the excess heat of streams from other parts of the process through a heat integration network The sequence of separations was based on the order of volatility: − · Flash units were used to remove the most volatile components when the components
were present in large quantities Because of its volatility, CO- 2 was recovered using a vacuum unit and purified
using a distillation tower. ile water was the most abund· Wh ant component, it was not the easiest component to
separate first because of its relative volatility and azeotropes
Ethanol for internal use 2.8 $/gal Ethanol for sale 1.2 $/gal
Table L.3 is a summary of calculations for depreciation using the five year MACRS method. Table L.4 and L.5 summarizes the calculations for the NPV and the IRR for the project.
Table L.3. Summary of calculations for depreciation.