1 Ethyl Acetate Design Project University of California Santa Barbara Omid Borjian Executive Summary The catalytic conversion of ethanol to produce ethyl acetate has shown to be a profitable market. We designed a plant to optimize the production of ethyl acetate, while minimizing operating and production costs and undesired side products. We found that the reaction was best suited for a 41m 3 plug flow reactor operated at 285 o C and 1 atm. Feeding 120 MM kg/yr of ethanol into the reactor produced 100 MM kg/yr of ethyl acetate to be sold along with 5 MM kg/yr of hydrogen for a total profit before taxes of a total of $43.6 MM$/yr. To start the plant a total capitalized investment (TCI) was approximated to be $28.8 MM with a net present value of the project (NPV proj ) to be $102 MM and net present value percent (NPV % ) of 32.7%. The internal rate of return (IRR) was found to be 113.5%. The discussed numbers are approximations, and flexible approach should be considered when plant production commences. The plant design accounted for market fluctuations, and the process control was purposely designed simplistically. They are, however, a good basis to gain an understanding of the plant’s general function and expectations.
60
Embed
Ethyl Acetate Design Project - ideangineideangine.com/Ethyl_Acetate_Design_Project.pdf · Ethyl Acetate Design Project ... distillation column that removed water in the process, ...
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
Ethyl Acetate Design Project
University of California Santa Barbara
Omid Borjian
Executive Summary
The catalytic conversion of ethanol to produce ethyl acetate has shown to be a profitable market. We
designed a plant to optimize the production of ethyl acetate, while minimizing operating and production
costs and undesired side products. We found that the reaction was best suited for a 41m3 plug flow
reactor operated at 285 oC and 1 atm. Feeding 120 MM kg/yr of ethanol into the reactor produced 100
MM kg/yr of ethyl acetate to be sold along with 5 MM kg/yr of hydrogen for a total profit before taxes
of a total of $43.6 MM$/yr. To start the plant a total capitalized investment (TCI) was approximated to
be $28.8 MM with a net present value of the project (NPVproj) to be $102 MM and net present value
percent (NPV%) of 32.7%. The internal rate of return (IRR) was found to be 113.5%. The discussed
numbers are approximations, and flexible approach should be considered when plant production
commences. The plant design accounted for market fluctuations, and the process control was purposely
designed simplistically. They are, however, a good basis to gain an understanding of the plant’s general
function and expectations.
2
Goals and Introduction
With an increasing industrial demand for ethyl acetate, many have found successful ways to create a
marketable business for the production and distribution of ethyl acetate. This increasing demand has
also initiated industry to develop commercial processes, such as that by DAVY Process Technology, for
large production of ethyl acetate. The GSI Process Feasibility Group has developed a plant that will be in
direct competition with Davy Process Technology. In this plant, ethyl acetate will be synthesized via the
interaction of ethanol with a catalyst consisting of 94% copper oxide, 5% cobalt oxide, and 1% chromium
oxide. Unfortunately, under these conditions ethanol can react to form ether acetaldehyde or diethyl
ether. Diethyl ether is a side product that is of lesser importance and may not be profitably sold. While
diethyl ether does not need to be disposed of and can be burned, in this initial profitability design and
analysis, heat exchange interactions were not taken into account and any credits able to be obtained
from burning the diethyl ether were not accounted for. In addition to ethyl acetate and diethyl ether,
this system of reactions will also produce hydrogen and water. Through the use of a flash drum, the
hydrogen will be separated from the system and be sold for further profit.
The primary challenge is to create an optimally profitable amount of ethyl acetate, while working
around an azeotropic solution involving the ethyl acetate, ethanol, and water. Since in this system the
selectivity is constant over reactor conversion, a higher conversion was able to be chosen without loss of
selectivity. Once a specific conversion is selected, a separation system is able to be designed and the
equipment and streams of the system are able to be cost and implemented into a cost diagram. To
ensure profitability, an economic analysis will be run on the five most important economic parameters.
Conceptual Design
Various factors were taken into consideration when making design decisions to optimize the plant
profitability. These factors consisted of reactor volume, reactor temperature and pressure, along with
other equipment constrictions. The system was found to be optimized at a reactor conversion of 90%
with a recycle stream to the reactor.
Using Douglas’s Conceptual Design hierarchy (Douglas, 2011), ideal stoichiometric mole balances were
developed to find the flow rates of the inlet, outlet, and ideal recycle streams. Using the kinetic data
provided from the GSI technical data sheet, a graph of reactor volume versus reactor conversion was
3
constructed for varying temperatures and pressures (Doherty, 2011). Analysis of the chart provided a
minimal reactor volume, which facilitated the selection of optimal operating conditions. It essential that
a minimal reactor volume is shown for cost analysis shows reactor cost grows exponentially as a
function of reactor volume. The reactor optimally operated at 285 oC and 1 atm.
The reaction was run in a heat exchanger with circulating heating fluid because in order to run the
endothermic reaction isothermally. A shell-and-tube heat exchanger was utilized to combine the
costing of the reactor and heat exchanger. Maintaining the heating fluid at the desired temperature
was the primary factor regarding the reactor operating cost. To approximate the heat produced in the
reactor, and thus cost the reactor, the heat capacities were assumed to be constant with respect to
temperature.
The separation consisted of a split block that separated out the diethyl ether, a flash drum that
separated out the hydrogen, two distillation columns that separated out ethyl acetate, and one
distillation column that removed water in the process, purifying the ethanol recycle stream. The flash
drum was optimized at 1 atm and 255 K, allowing for approximately 100% of the hydrogen to exit the
column in the vapor stream. It was particularly challenging to separate the ethanol, ethyl acetate, and
water because they contain azeotropes that prevent separation of individual species. Each distillation
column was designed at specific pressures and temperatures that avoid azeotropes by analysis of
ternary maps as shown in Appendix B. Flash drum calculations were designed in the attached MATLAB
code (Appendix D) and the three distillation columns were designed in ASPEN as shown in Appendix B
To solve the distillation systems multiple trials were run in ASPEN to determine which design was most
effective. Firstly, processes with conversions of 70%, 80%, and 90% were simulated in ASPEN and
compared. Conversions of 80% and 90% showed to be far more profitable than that of 70%. Reactor
size and cost drastically grow exponentially as conversion surpasses 90%. Thus, we set 90% conversion
as a maximum possible conversion for the reactor. Secondly, purge stream and waste disposal analysis
was run. Since the remaining unwanted products were easily burned and did not require an additional
disposal cost, running the process with three distillation columns and a recycle stream or two distillation
columns and disposing the remaining products were both viable options. As depicted in the process
flow diagram (PFD), the former design proved to be more profitable as shown in the economic section.
4
Azeotrope Conceptual Design
Designing a system that separates an azeotropic mixture is particularly challenging because the
conventional methods, Gilliland, Fenske and Underwood equations, were not adequate to calculate the
number of stages, V/F ratio, and the distillation feed stage for a specified recovery. This interaction
between the components makes complete separation impossible unless the mixture is operated at a
different pressure (pressure-swing distillation) or added another component (entrainer) to break the
azeotrope. In our design, the first method was sufficient.
Using ASPEN PLUS, a ternary map of ethanol, water, and acetyl acetate was acquired for the system as
shown in Figure 1 below. Depending on the location of feed compositions, we adjusted the pressure to
obtain the maximum separation distillation boundary. In the first and second column, the high
concentration of ethyl acetate was removed by running the distillation at highest possible pressure, 15
atm. We were able to conceptually extract ethyl acetate with 99.99% purity from bottoms of the
columns. In the third column water was separated out the bottom of the column at atmospheric
pressure. Knowing the behavior of the equilibrium curves and tie lines, we specified reflux ration,
distillate, and bottoms compositions for the column in such way that the rectifying and stripping curves
cross each other simultaneously when the system converges. We used ASPEN PLUS to design and
calculate the total number of stages, feed stage, and V/F ratio to obtain the required separation.
Figure 1 Ternary map of ethanol, water, and ethyl acetate at 12 atm.
5
Process Control
In the design of the process control we used the standard feedback controllers used in the flash unit and
distillation units to adjust the pressure, temperature, liquid level, reflux ratio, and stream composition.
Our reactor operates isothermally, which required the temperature controller to adjust the temperature
of the feed stream. Fluctuations may occur as the species are reacting.
The recycle stream from the third distillation column enters a recycle surge tank, which is regulated by
signals from the composition controller on the products stream. A valve on the purge stream interacts
with the recycle surge tank’s liquid level controller, which opens to prevent an over flow in the surge
tank. The pressure inside the flash unit and the first two distillation units are controlled by adjusting a
valve on the top vapor stream. The liquids are driven inside the units via pumps to ensure a steady drive
of flows in and out of the system. Lastly the ethanol feed flow rate is controlled by another flow
controller based on the production rate. Figure 2 shows the process control diagram with every
controller listed in Table A.4 with the corresponding controlled and manipulated variables. A larger view
of Figure 2 is referenced in Appendix B.
Flash
Unit
Distillation
Unit1
Distillation
Unit2
Distillation
Unit3Recycle Surge Tank
Mixer
Split Block
Wastes Stream
Purge
Stream
LC
23
Cooling water
TC
24
Bot3
LC
19
FC
1
E stream, w1
Cooling Water
TC
3
Cooling water
LC
5
PC
4
Steam
TC
2
Reflux3
AC
20
Steam
AC
18
Cooling Water
Condenser3
Top3
LC
17
AC
13
Condenser2
Reflux2
LC
12
Top2
Cooling Water
Condenser1
Reflux1
LC
7
Top1
AC
8
Hydrogen
PC
11
PC
6
AC
22
Reactor
Bot2
LC
15
AC
16
Steam
Bot1
Steam
LC
9
AC
10
EA Stream, w2
Products
W Stream
Waste water
FC
21
TC
13
Cooling water
Figure 2 Process Control Flowsheet
6
Economic Design and Analysis
While the basis of most of the plant design decisions were products of the conceptual design, the
reactor conversion and reactor temperature were decided based on the final economic analysis run on
the conceptual design of the system. This analysis was further justified by the reactor volume, pressure,
and temperature relationship.
The economic analysis run on the conceptual design consisted of graphing the net present value of the
project (NPVproj), the net present value at year zero (NPVzero), the risk associated with the project (NPV%),
the return on investment before taxes (ROIbt) based off of the total investment (TI), and the total
capitalized investment (TCI) against the reactor conversion of 80% and 90% for two different situation as
seen in Figures 3 through 4. Other economic figures are located in Appendix C. (While Figures 3
through 4 only show situations at 80% and 90%, it should be noted that an initial analysis was done for
70%, 80%, and 90% which showed 80% and 90% to be the more profitable reactor conversions). The
two different situations analyzed for the system at each reactor conversion revolved around the recycle
stream. One design analyzed the profitability to have less distillation columns and purge the potential
recycle stream, while the other proved that the design of a distillation column with a recycle stream was
more profitable. (The first situation is indicated on the figures by a 0.05 addition to the conversion). The
trends on these figures were then analyzed to find the most profitable reactor temperature and
conversion. The most profitable combination was based off of the two parameters NPVproj and NPV%.
Economically, the most desirable combination would maximize both of these quantities leading to the
highest net plant worth at the time of project conception with the least amount of risk associated with
the project. For this project a risk of less than 15% was not acceptable since ethyl acetate is a
commodity chemical.
7
Figure 3. Net present value of the project versus the reactor conversion with the operating point highlighted.
Figure 4. The net present value percent of the project versus reactor conversion with the operating point highlighted.
Since it was found that for all alternatives analyzed the NPV% was much higher than 15%, process design
was chosen by optimizing NPVproj (Mellichamp, 2011). By optimizing NPVproj, this allowed for the plant
worth to be maximized. This optimization was found to be consistent with the temperature of 285 oC,
and the separation system that consisted of three distillation columns and a recycle stream to the
reactor which corresponds to 0.9 on the figures presented previously.
Operating Point:
T = 285 oC and P = 1
atm
Operating Point:
T = 285 oC and P = 1
atm
8
Economic Cash Flow Analysis
The conceptual and economic design executed in HYSYS provided a framework to calculate the fixed
capital and the fraction of working capital as well as the predicted profit before taxes utilizing the
conceptual design MATLAB program (Appendix D). Discounted cash flow analysis as well as a sensitivity
and fluctuation analysis was then performed using the previously mentioned results.
The economic model used in this analysis was created on the basis that the finance and construction
interest rates, the fractions of startup capital and salvage value, the amount of fixed capital spent during
the construction years, the fraction of profit before taxes made in the ramp up years, and the operating
and fixed capital costs were all reasonable approximations. The finance interest rate was assigned a
value based on colloquial knowledge that normal finance rates range from three to five percent but can
be as high as ten percent. With this knowledge, an eight percent finance rate was chosen in order for
the calculations of project value to be conservative.
An average construction rate was taken to be approximately 7% based on data and examples from
Evaluating Plant Profitability in a Risk-Return Context (Mellichamp, 2011). Again to keep the plant value
calculations conservative a construction rate of 10% was chosen for the cash flow analyses. This will
reduce the risk of calculating financial data that would indicate an exaggerated profit. The fractions of
startup capital and salvage value were based on the fact that the startup capital would be only a small
portion of the fixed capital and the amount salvaged from sales after decommissioning of the plant
would be even significantly smaller. Fixed capital spending rate in the construction years was chosen
assuming that less of the fixed capital would be spent in the first year, when the final plant designs are
being finalized and plant construction is minimal. In the second year during plant construction, the
majority of the fixed capital is used.
The ramp-up fractions were chosen assuming that in the first few years, profitability will be lower than
expected. This is believed to be true since ethyl acetate is a commodity chemical and market
competition exists, which is expected to cause low initial profit. Finally, the operating and fixed capital
costs were based on the factors that could not be assumed to be negligible. In both of these
calculations offsite costs, or outside battery limit (OSBL) costs, were assumed to be negligible, while the
onsite costs, or inside battery limit (ISBL) costs, were assumed to greatly affect these two economic
calculations. ISBL costs were considered to be the most important costs but not all of these costs were
consider in the model calculations. Among others, the cost of pumps and mixers were assumed to be
9
negligible. Ultimately, the fixed capital costs included the costs for the separation system (three
distillation columns), the heat exchanger reactor and multiple other pieces of heating equipment. The
reactor cost was assumed to be negligible in comparison to the heat exchanger and only the heat
exchanger portion of the reactor was cost.
The operating costs included the cost for the separation system, the cost for additional heating and
cooling operations, and the cost for heating the Dowtherm used to keep the reactor isothermal. These
were assumed to be the main costs that would affect the calculation for the operating cost, and costs
such as the plant electricity were assumed to be negligible. Once these values were all chosen
(Appendix C), a second economic analysis was performed to find the sensitivity of the base case to
variations in specific parameters, and to determine relative maximum finance rate, minimum selling
price of ethyl acetate, and the maximum cost of ethanol before the NPVzero is equal to zero. The results
of this analysis are summarized below in Table 2 with variations listed in Table 1.
Table 1. The variations performed on the base case.
Variation Number Alteration Performed
Variation 1.a/b Increase/decrease the cost of the ethanol
Variation 2.a/b Increase/decrease the value of ethyl acetate
Variation 3.a/b Increase/decrease the construction rate.
Variation 4.a/b Decrease/increase the finance rate.
Abnormal 1 New political leadership drastically lowers tax rate.
Abnormal 2 Competitor enters market in year 5 reducing profits.
Sell Price Drop How low can the selling price of ethyl acetate go?
Raw Material Raise How high can the cost of ethanol go?
IRR At what finance rate does the NPVzero equal zero?
10
Table 2. A summary of the results of the sensitivity and dependence analysis run on the base case plant
design produced in the HYSYS and ASPEN simulation.
Variation Change Variable
Variable Originally
Variable Changed To
NPV(0) NPVproj Percent Deviation From Base Case
NPV(0) NPVproj
Base Case NA NA NA 118.08 101.24 NA NA
Variation 1.a
Ethanol Price
$0.70/kg $1.00/kg 3.85 3.30 96.74 96.74
Variation 1.b
Ethanol Price
$0.70/kg $0.40/kg 232.32 199.18 96.74 96.74
Variation 2.a
Ethyl Acetate Value
$1.30/kg $1.50/kg 178.66 153.18 51.31 51.31
Variation 2.b
Ethyl Acetate Value
$1.30/kg $1.10/kg 57.50 49.30 51.31 51.31
Variation 3.a
Construction Rate
10% 15% 117.99 101.16 0.08 0.08
Variation 3.b
Construction Rate
10% 5% 118.17 101.32 0.08 0.08
Variation 4.a
Finance Rate
8% 3% 156.30 147.32 32.36 45.53
Variation 4.b
Finance Rate
8% 13% 91.17 71.40 22.79 29.47
Abnormal 1
Tax Rate 50% 35% 155.65 133.45 31.82 31.82
Abnormal 2
b's (fraction of P_bt made)
b1 = 0.5, b2 = 0.8, b3 = 1
Varying Less Than 1
101.40 86.94 14.12 14.12
Sell Price Drop
Ethyl Acetate Value
130.5 MM $/yr
91.4 MM $/yr
0.00 0.00 NA NA
Raw Material Raise
Ethanol Price
85.1 MM $/yr
124.2 MM $/yr
0.00 0.00 NA NA
IRR Finance Rate
8% 106.8% 0.00 0.00 NA NA
This analysis showed that the two parameters that have the most effect on the economics of the plant
are the price of ethanol and the value of the ethyl acetate, causing deviations from the base case of 97%
11
and 51% as seen in Variation 1.a through Variations 2.b. Base case changes in the finance rate,
construction rate, and tax rate produced relatively small percent deviations. However, between the
interest rates the one with the largest effect on the plant profitability was found to be the tax and a
large drop in this interest rate was further analyzed.
The final analysis that was done on the economics was a fluctuation analysis which focused on a
potential drop in ethyl acetate worth and rise in ethanol worth to discover how much fluctuation the
project could withstand before the project risk was too great. While the fluctuation analysis does look
slightly at a raise in ethyl acetate worth and drop in ethanol worth, the main focus is on the ethyl
acetate worth dropping and the ethanol worth increasing because it is a primary concern that with the
addition of this plant to the market that price of ethyl acetate will be forced down since it will be in
greater supply. Also, an increase in ethanol worth is analyzed because this process adds additional value
to ethanol and it is likely that the addition of the plant will cause the demand for ethanol to increase.
After the fluctuation analysis was completed, it was obvious that this project is worth further
investigation if it is projected that the value of ethyl acetate will not drop much below $1.00/kg and the
cost of ethanol will not increase much higher than $0.80/kg. This boundary is indicated in the
fluctuation analysis table (Table 3) by the brown coloring between the green and red.
Table 3. Fluctuation analysis of the risk of the project based on the ethanol and ethyl acetate prices.
Table is focused on drop in ethyl acetate since it is a primary concern that the market will not be able to
withstand the current selling price of ethyl acetate once GSI enters the market.
Sell Price
Raw Material MM $/yr 56.1 61.0 66.3 72.0 78.3 85.1 91.9 99.3 107.2 115.8
Establishes the ROI_BT Based on TI (also TCI ) and the Annual % Increase of NPV (Normalized by TCI )
Fixed Capital and Profit_BT are the two independent variables.
CR and FR can be chosen independently. WC and SV are converted from inventory to Profit_BT in Year 10.
using Capitalization =
NPV Increase per Year
35
Appendix D: MATLAB code
Design2Varying clear; clc; %number of plots making PlotNumber = 1; %need to know values %selectivity s = 10/11; %flow rates Pea_kg = 100*10^6; %kg/yr Pea = Pea_kg*1000*(1/88.105); %mol/yr [=] MM kg/yr*1000g/kg*mol/g Ps = 2*Pea; %mol/yr Fa = 2*Pea/s; %mol/yr Pde = Pea*(1/s - 1); %mol/yr Pw = Pea*(1/s - 1); %mol/yr %density in g/L = g/cm^3*(1 cm^3/0.001 L) da = 0.789*(1/0.001); CuOdensity = 6.31*(1/0.001); CoOdensity = 6.44*(1/0.001); Cr2O3density = 5.22*(1/0.001); catdensity = 0.94*CuOdensity+0.05*CoOdensity+0.01*Cr2O3density; %molecular weight in g/mol MWa = 46.07; %molar densities = density*(1/MW) mda = da/MWa; %g/L*(mol/g) = mol/L %costs Cost_pea = 1.30; %ethyl acetate $/kg Cost_a = 0.70; %ethanol $/kg Cost_s = 0.31; %hydrogen $/lb %reactor conversion xa = 0.01:0.01:1; %equipment temperature and pressure reactT = 498:20:558; %K reactP = 1:3:10; %atm
36
%need to know values R = 1.987; %cal mol^-1 K^-1 R2 = 0.082057; %L atm K^-1 mol^-1 for m = 1:1:PlotNumber for p = 1:1:length(reactP) for t = 1:1:length(reactT) for h = 1:1:length(xa) %calculating recycle flowrate = mol/yr Ra(h) = 2*Pea/s*((1-xa(h))/xa(h)); %total molar flow rate leaving reactor = mol/yr TFLR(h) = Pea + Ps + Pde + Pw + Ra(h); %mole fractions leaving reactor za(h) = Ra(h)/TFLR(h); zea(h) = Pea/TFLR(h); zs(h) = Ps/TFLR(h); zde(h) = Pde/TFLR(h); zw(h) = Pw/TFLR(h); %total molar flow rate to separation system = mol/yr %after removing all diether with split block %after removing all hydrogen TFTS(h) = Pea + Pw + Ra(h); %mole fractions zas(h) = Ra(h)/TFTS(h); zeas(h) = Pea/TFTS(h); zws(h) = Pw/TFTS(h); %solving for reactor volume %K's Ka(t) = exp(5890/(R*reactT(t))-6.40); %atm^-1 Ks(t) = exp(6850/(R*reactT(t))-7.18); %atm^-1 k(t) = exp(-16130/(R*reactT(t))+16.25); %mol hr^-1 g-cat^-1 Pain(p,h) = reactP(p); %(mol/L)*(K)*(L atm K^-1 mol^-1) = atm Paout(p,h) = reactP(p)*za(h); %atm step(p,h) = (Pain(p,h) - Paout(p,h))/100; Pa = Paout(p,h):step(p,h):Pain(p,h); %mol/L Psin(p,h) = 0; Psout(p,h) = reactP(p)*zs(h); step2(p,h) = (Psin(p,h) - Psout(p,h))/100; ps = Psout(p,h):step2(p,h):Psin(p,h); for g = 1:length(Pa) %concentration of acetaldehyde is zero funct(h,g) = 20*10*(1+Ka(t)*Pa(g)+Ks(t)*ps(g))^2/(k(t)*Ka(t)*Pa(g));
37
end AreaUnderCurve(p,t,h) = trapz(Pa,funct(h,:)); %hr g-cat/L tau(p,t,h) = AreaUnderCurve(p,t,h); %catalyst weight catW(p,t,h) = Fa*tau(p,t,h)*(1/8765.81277); %mol/yr*(hr g-cat/mol)*conversion = g-cat %reactor volume [=] m^3 Vreact(p,t,h) = 2*catW(p,t,h)*(1/catdensity)*0.001; end end end end for p = 1:1:length(reactP) for t = 1:1:length(reactT) for h = 1:1:length(xa) vol(h) = Vreact(p,t,h); end if p==1 && t==1 plotcolor = 'b'; end if p==2 && t==1 plotcolor = 'g'; end if p==3 && t==1 plotcolor = 'r'; end if p==4 && t==1 plotcolor = 'k'; end if p==1 && t==2 plotcolor = 'b'; end if p==2 && t==2 plotcolor = 'g'; end if p==3 && t==2 plotcolor = 'r'; end if p==4 && t==2 plotcolor = 'k'; end if p==1 && t==3 plotcolor = 'b'; end if p==2 && t==3 plotcolor = 'g'; end
38
if p==3 && t==3 plotcolor = 'r'; end if p==4 && t==3 plotcolor = 'k'; end if p==1 && t==4 plotcolor = 'b'; end if p==2 && t==4 plotcolor = 'g'; end if p==3 && t==4 plotcolor = 'r'; end if p==4 && t==4 plotcolor = 'k'; end hold on; fig1 = figure(1); set(fig1,'Color','white') ylim([0 100]) ylabel('Reactor Volume (m^3)') xlabel('Reactor Conversion') plot(xa,vol,plotcolor) end end Design2Conversion clear; reply = input('Reactor Temperature in Celsius: ', 's'); if reply == '225' reactTC = 225; plotcolor = 'c'; end if reply == '255' reactTC = 255; plotcolor = '--b'; end if reply == '285' reactTC = 285; plotcolor = '--k'; end %number of plots making PlotNumber = 1;
%Cooling fluid == water Tfin = 4.4+273; %Cooling fluid temperature in K Tfout = 10+273; %Cooling fluid temperature out in K %fraction of start up capital = SU/FC = alpha_su alpha_su = 0.1; %fraction of fixed capital spent in start up years a_2 = 0; a_1 = 0.3; a0 = 0.7; %fraction of p_bt obtained in start up years = 3 startupyrs = 3; b1 = 0.5; b2 = 0.8; b3 = 1.0; %construction rate = CR, finance rate = FR, tax rate = TR, complementary tax rate = TRC CR = 0.1; FR = 0.08; TR = 0.5; TRC = 1-TR; %sigma_b = used in NPV0 calculation; note need to change if start up yr > 3 sigma_b = b1*(1+FR)^-1+b2*(1+FR)^-2+b3*(1+FR)^-3+(1+FR)^-3*((1-(1+FR)^-7)/FR); %sigma = used in NPV0 calculation; not for n = 10 years = lifetime of plant sigma = (1-(1+FR)^-10)/FR; % needed values PS = 2; % project start time PL = 12; % project lifetime for m = 1:1:PlotNumber for h = 1:1:length(xa) %calculating recycle flowrate = mol/yr if h == 1 || h == 3 Ra(h) = 2*Pea/s*((1-xa(h))/xa(h)); end if h ==2 || h == 4 Ra(h) = Fa*(1-xa(h)); end %calculating total ethanol flow to reactor = mol/yr Fain(h) = Fa + Ra(h); %outlet temperature of reactor T_out2(h)=T_in-(dH0_a*Fa+dH0_b*Pea+dH0_c*Pde)/(Fain(h)*Cp_a); %total molar flow rate leaving reactor = mol/yr TFLR(h) = Pea + Ps + Pde + Pw + Ra(h); %mole fractions leaving reactor za(h) = Ra(h)/TFLR(h); zea(h) = Pea/TFLR(h); zs(h) = Ps/TFLR(h); zde(h) = Pde/TFLR(h); zw(h) = Pw/TFLR(h); %total molar flow rate to separation system = mol/yr %after removing all diether with split block TFTS(h) = Pea + Pw + Ra(h) + Ps;
44
%mole fractions zas(h) = Ra(h)/TFTS(h); zeas(h) = Pea/TFTS(h); zws(h) = Pw/TFTS(h); zss(h) = Ps/TFTS(h); %solving for reactor volume %K's Ka = exp(5890/(R1*reactT)-6.40); %atm^-1 Ks = exp(6850/(R1*reactT)-7.18); %atm^-1 k = exp(-16130/(R1*reactT)+16.25); %mol hr^-1 g-cat^-1 Pain(h) = reactP; %(mol/L)*(K)*(L atm K^-1 mol^-1) = atm Paout(h) = reactP*za(h); %atm step(h) = (Pain(h) - Paout(h))/100; Pa = Paout(h):step(h):Pain(h); %mol/L Psin(h) = 0; Psout(h) = reactP*zs(h); step2(h) = (Psin(h) - Psout(h))/100; ps = Psout(h):step2(h):Psin(h); for g = 1:length(Pa) %concentration of acetaldehyde is zero funct(h,g) = 20*10*(1+Ka*Pa(g)+Ks*ps(g))^2/(k*Ka*Pa(g)); end AreaUnderCurve(h) = trapz(Pa,funct(h,:)); %hr g-cat/L tau(h) = AreaUnderCurve(h); %catalyst weight catW(h) = Fa*tau(h)*(1/8765.81277); %mol/yr*(hr g-cat/mol)*conversion = g-cat %reactor volume [=] g-cat*(cm^3/g-cat)*(m^3/1000000 cm^3) = m^3 Vcat(h) = catW(h)*(1/catdensity); %cm^3 Vreact(h) = 2*Vcat(h)*(10^-6); %m^3 %finding dimensions of reactor %assume tube diameter is 2 cm, and length of reactor is 10 m d = 2/100; %m r = d/2; %m hcyl(h) = Vreact(h)/(pi*r^2); %m %number of tubes in heat exchanger Ntubes(h) = hcyl(h)/10; %surface area of tubes A(h) = 2*pi*r*10*Ntubes(h); %m^2 Aft(h) = A(h)*10.76; %ft^2 %Reynolds number Calculations NEED TO CHECK %mol/yr*g/mol*cm^3/g*1/m^2*m^3/cm^3*yr/s = m/s velocity(h) = Fain(h)*MWa*(1/dagcm)*(1/(pi*r^2))*(1/100)^3*(1/31556926); %PROBLEM HERE???
45
visa = 0.001095; %kg m/s^2 s/m^2 = kg s^-1 m^-1 %g/cm^3*m/s*m*m*s/kg*1kg/1000g*(100cm/m)^3 = unitless Re(h) = dagcm*velocity(h)*d*(1/visa)*(1/1000)*100^3; %Flash Drum Calculations %We assume there is a split block between the reactor and the reactants that gets rid of diethyl %We need to bring the feed's temperature as low as 320K to flash the hydrogen from the rest of the species %componenets entering the flash drum %%% Hydrogen BP: 20.3K (-253C) %Antoine Constants in K and Bar A1=3.54314; B1=99.395; C1=7.726; % Ethyl Accetate BP: 350K (77.1C) %Antoine Constants in K and Bar A2=4.22809; B2=1245.702; C2=-55.189; % Ethanol BP: 351K (78C) %Antoine Constants in K and Bar A3=5.37229; B3=1670.409; C3=-40.191; % Water BP: 373K (100C) %Antoine Constants in K and Bar A4=4.65430; B4=1435.264; C4=-64.848; z_E(h) = zas(h); z_EA(h) = zeas(h); z_H(h) = zss(h); z_W(h) = zws(h); F_flash(h) = TFTS(h); %mol/yr %Operating Pressure P_drum=1; %bar %Operating Temperature Note:we need to adjust this to get maximum separation T_drum=255; %K %Antoine equation %psat all in bar psat_H=10^(A1-B1/(T_drum+C1)); %bar psat_EA=10^(A2-B2/(T_drum+C2)); %bar psat_E=10^(A3-B3/(T_drum+C3)); %bar psat_W=10^(A4-B4/(T_drum+C4)); %bar K1=psat_H/P_drum; K2=psat_EA/P_drum; K3=psat_E/P_drum; K4=psat_W/P_drum; k1=1/(K1-1); k2=1/(K2-1); k3=1/(K3-1); k4=1/(K4-1); % Solve Rachford-Rice equation numerically to find a=V/F: a(h)=fzero(@(a) z_H(h)/(k1+a) + z_EA(h)/(k2+a) + z_E(h)/(k3+a) + z_W(h)/(k4+a) , .5); %Hydrogen molar composition in the bottoms xflash_H(h)=z_H(h)/(1+a(h)*(K1-1)); %Ethyl acetate's composition in the bottoms xflash_EA(h)=z_EA(h)/(1+a(h)*(K2-1)); %Ethanol molar composition in the bottoms xflash_E(h)=z_E(h)/(1+a(h)*(K3-1));
46
%water molar composition in the bottoms xflash_W(h)=z_W(h)/(1+a(h)*(K4-1)); %Hydrogen molar composition in the vapor stream yflash_H(h)=K1*xflash_H(h); %Ethyl acetate's composition in the vapor stream yflash_EA(h)=K2*xflash_EA(h); %Ethanol molar composition in the vapor stream yflash_E(h)=K3*xflash_E(h); %water molar composition in the vapor stream yflash_W(h)=K4*xflash_W(h); %Bottoms flow rate L_flash(h)=(1-a(h))*F_flash(h); %Vapor stream flow rate V_flash(h)=a(h)*F_flash(h); %Gamma need to be varying??? %Compressor 1 %molar density of fluid to compressor [=] mol/L mdcompfluid1(h) = xflash_H(h)*mds + xflash_EA(h)*mdea + xflash_E(h)*mda + xflash_W(h)*mdw; %volumetric flow rate = flow rate to compressor/molar density [=] ft^3/min %mol/yr*L/mol*0.0353146667ft^3/L*(1yr/525948.766min) = ft^3/min qin1(h) = L_flash(h)*(1/mdcompfluid1(h))*0.0353146667*(1/525948.766); hp1(h) = ((3.03*10^-5)/gamma1)*Pin_comp1*qin1(h)*((Pout_comp1(h)/Pin_comp1)^gamma1-1); bhp1(h) = hp1(h)/0.8; %Distillation Columns Height_1(h) = 3*0.61 + 0.61*D1stages(h); Height_2(h) = 3*0.61 + 0.61*D2stages(h); Height_3(h) = 3*0.61 + 0.61*D3stages(h); Diameter_1(h) = 1/6*Height_1(h); Diameter_2(h) = 1/6*Height_2(h); Diameter_3(h) = 1/6*Height_3(h); PeaT(h) = D1Bflow(h)*z_D1Bea(h) + D2Bflow(h)*z_D2Bea(h) + D3Bflow(h)*z_D3Bea(h); PsT(h) = yflash_H(h)*V_flash(h); PwT(h) = D1Bflow(h)*z_D1Bw(h) + D2Bflow(h)*z_D2Bw(h) + D3Bflow(h)*z_D3Bw(h); PaBot(h) = D1Bflow(h)*z_D1Ba(h) + D2Bflow(h)*z_D2Ba(h) + D3Bflow(h)*z_D3Ba(h); PeaT_kg(h) = PeaT(h)*MWea*(1/1000); %kg/yr PsT_kg(h) = PsT(h)*MWs*(1/1000); %kg/yr PwT_kg(h) = PwT(h)*MWw*(1/1000); %kg/yr PaBot_kg(h) = PaBot(h)*MWa*(1/1000); %need in kg/yr IN(h) = Fa_kg; OUT(h) = Pde_kg + PeaT_kg(h) + PsT_kg(h) + PwT_kg(h) + PaBot_kg(h); %Costing % Revenue % R = EA val + H2 val - A cost (Water Sellable???) % R($/yr) = ($/kg)*(mol/yr)*(g/mol [MW])*(kg/1000g) [=] $/yr
47
Sell(h) = Cost_pea*PeaT(h)*MWea*(1/1000); Pay(h) = Cost_a*Fa*MWa*(1/1000); %$/lb*mol/yr*(g/mol [MW])*(0.0022lbs/g) Extra(h)= Cost_s*PsT(h)*MWs*0.0022; R(h) = Sell(h)-Pay(h)+Extra(h); %Operating Cost Calculations % Operating Costs are the utility cost to run that piece of equipment % C = React + Sep System %cm^3*$/kg*g/cm^3*1kg/1000g*2/yr CatCost(h) = Vcat(h)*Cost_cat*catdensity*(1/1000)*2; %use Dowtherm over steam %using a process furnace to circulate the Dowtherm %operating cost is the cost fuel %$/kg*MJ/yr*kg/kJ*10^6J/MJ*1kJ/1000J %Cost_Heat(h) = reactsteamcost*abs(QrJ)*(1/Hsteamreact)*(10^6/1000); %MJ/yr*(1.62 $/MM Btu)*(10^6 J/MJ)*(1 Btu/1055 J)*(1 MM Btu/10^6 Btu) = $/yr Cost_Heat(h) = abs(QrJ)*1.62/1055; React(h) = CatCost(h) + Cost_Heat(h); %$/yr %compressor operating cost utilityreq1(h) = bhp1(h)/0.9; %hp hptokW = 0.75; %1 hp = 0.75 kW [=] kW/hp opcostcomp1(h) = utilityreq1(h)*hptokW*operating_hours*electricity_cost; %distillation operating cost %Condenser Costs = coolant %coolant = refrigerated water coolant_cost = 5.7; %$/GJ %$/GJ*J/s*(GJ/10^9 J)*(31556926s/yr) C_1(h) = coolant_cost*abs(D1cond(h))*(31556926)*10^-9; C_2(h) = coolant_cost*abs(D2cond(h))*(31556926)*10^-9; C_3(h) = coolant_cost*abs(D3cond(h))*(31556926)*10^-9; %Reboiler = heater %$/kg steam_cost1 = 6.74/1000; steam_cost2 = 2.38/1000; %kJ/kg H_steam1 = 1755; H_steam2 = 2213; %$/kg*kg/kJ*J/s*31556926s/yr*1kJ/1000J R_1(h) = steam_cost1*abs(D1reboil(h))*(1/H_steam1)*31556926*(1/1000); R_2(h) = steam_cost1*abs(D2reboil(h))*(1/H_steam1)*31556926*(1/1000); R_3(h) = steam_cost2*abs(D3reboil(h))*(1/H_steam2)*31556926*(1/1000); dist_op_cost(h) = C_1(h)+C_2(h)+C_3(h)+R_1(h)+R_2(h)+R_3(h); Sep(h) = opcostcomp1(h) + dist_op_cost(h); C(h) = React(h)+Sep(h); %$/yr % Profit Before Tax = Revenue - Operating Costs P_bt(h) = (R(h) - C(h)); %$/yr %Equipment Cost Calculations %installed costs %Reactor Installed Cost