Introduction
DME (dimethyl ether) is an easy to liquidate, clean, colorless gas. It has a significant
potential for increased use in car fuel, for the production of electricity, and in domestic
applications such as heating and cooking.
It can come from a wide range of sources, including renewable (biomass, waste, agricultural
products) and fossil (natural gas and coal).
The DME is now more widely used as a clean burning substitute for LPG (liquified
petroleum, diesel and petrol) in the personal care industry (as a harmless aerosol propellant)
for decades.
As LPG, DME is gaseous at normal temperature and pressure but changes to the liquid if the
pressure or cooling is modest. DME is easier to transport and store with this simple
liquefaction.
These and other characteristics such as high oxygen content, lack of sulfur or other toxic
compounds, and ultra-clean combustion make DME a flexible and promising alternative in
the global mix of clean renewables and low carbon oil.
DME can be made from a wide range of sources, including gas, coal, pulp and paper mill
waste, forest products, agricultural by-products, industrial waste and fuel crops such as
switchgrass.
Today, global production is mainly through dehydration of methanol, but DME can also be
produced from synthesized gas, which is either produced through carbon gasification or
biomass gas refurbishment. Direct synthesis of DME is the most efficient among the different
processes for chemical conversion of natural gas. [ CITATION abo19 \l 1033 ]
DME is used primarily as an aerosol propellant. It is miscible with most organic solvents, has
a high solubility in water, and is completely miscible in water and 6% ethanol [1]. Recently,
the use of DME as a fuel additive for diesel engines has been investigated due to its high
volatility (desirable for cold starting) and high cetane number. The production of DME is via
the catalytic dehydration of methanol over an acid zeolite catalyst. The main reaction is
(B.1.1)
In the temperature range of normal operation, there are no significant side reactions. B.1.1
Process Description
A preliminary process flow diagram for a DME process is shown in Figure B.1.1, in which
50,000 metric tons per year of 99.5 wt% purity DME product is produced. Due to the
simplicity of the process, an operating factor greater than 0.95 (8,375 h/yr) is used.
Figure B.1.1 Unit 200: Dimethyl Ether Process Flow Diagram
Fresh methanol, Stream 1, is combined with recycled reactant, Stream 14, and vaporized
prior to being sent to a fixed-bed reactor operating between 250°C and 370°C. The single-
pass conversion of methanol in the reactor is 80%. The reactor effluent, Stream 7, is then
cooled prior to being sent to the first of two distillation columns: T-201 and T-202. DME
product is taken overhead from the first column. The second column separates the water from
the unused methanol. The methanol is recycled back to the front end of the process, and the
water is sent to waste water treatment to remove trace amounts of organic compounds.
In this project our goal is to calculate plant capital cost, manufacturing cost for the year 2019
using UAE as the location for plant construction, in addition to calculating the payback
period and the rate of return on investment both for discounted and undiscounted time cases.
Given:
WC= 20% FCI
1st year = 60% FCI
2nd year = 40% FCI
LC = 6% FCI
Salvage value = 10%
Detailed Calculations:
1. Estimating the Capital Cost
To calculate the capital cost first calculate the bare module cost.
Where
and
Then include the Includes Contingency and Fees at 15% and 3% of the previous cost
Then calculate the CBMo ( total direct and in direct cost ) from the following table
Then use the following equation to find to gross roots cost
Finally adjust the cost by multiplying it by the location factor using the following table
Heat Exchangers
There are 8 heat exchangers in the unit of each one operation at different pressure and has
different area so the cost of each one has to be done.
Sample calculations for E-201:
-Where K1 and K2 K3 for heat exchangers from appendix A(Turton et al)
= 4.8306, -0.8509,0.3187 respectively.
-A=99.4 m2
- Pressure of 15 bar
So plugging all the values, Cp(2001)= $25263.54 so Cp(2019)= $396149.08
Since the pressure is not atmospheric so it has it be corrected.
We have to calculate the Bare module cost to get the total cost:
Where
The values of B1 and B2 for floating-head heat exchangers from Table A.4 are 1.63 and 1.66,
respectively.
The pressure factor is obtained from Equation A.3.
(A.3)
From Table A.2, for pressures >15 barg, C1 = 0.1587C2 = -0.2992 C3 = 0.1413, and from
Equation A.3, Fp = 1.00521. Using data in Table A.3 for shell-and-tube heat exchangers with
both shell and tubes made of carbon steel (Identification Number = 1) and Figure A.8, FM =
1. Plugging all the values, Fbm = 3.298
So CBM = $396149.08(3.29) = $1303330.48
The following tables shows all the prices for all 8 heat exchangers.
Heat Exchagers Cpº (2001)($) Cpº (2019)($) FBM CBM
E-201 252263.54 396149.08 3.29 1303330.48
E-202 833083.27 1308255.54 3.29 4304160.72
E-203 25521.34 40078.15 3.29 131857.11
E-204 18308.8 28751.73 3.29 94593.21
E-205 181056.47 284327.08 3.29 935436.08
E-206 23517.1 36930.73 3.29 121502.11
E-207 18317.6 28765.55 3.29 94638.67
E-208 18315.2 28761.78 3.29 94626.27
Total CBM 7080144.66
Towers
There are 2 towers in our process, the sample calculations will done of T-201.
For T-201 there are 22 ss trays with a height of 15.8 m and D= 0.79m and operating at 10.6
bar.
The costs of the tower and trays are calculated separately and then added together to obtain
the total cost.
For the tower,
Volume = πD2L/4 = (3.14159) (0.79)2(15.8)/4 = 7.7446 m3
By using the equation but instead of A it will be the volume founded:
From Table A.1 Equipment Cost Data to Be Used with
K1= 3.9474, K2=0.
4485 , K3=0.1075 for V= 7.7446 m3
So Cp (2019) = $15026.47 and
For Trays,
K1= 2.9949 ,K2=0.4465 , K3=0.3961 From Table A.1
Tray (tower) area = πD2/4 = 0.49 m2
So using this equation:
Cp(2019) = $1231.655
The following tables is for both towers prices in our process:
Towers Cpº (2001) Cpº (2019)($) FBM CBM
($)
T-201 10356.35 16263.38 6.51 105874.62
T-202 12563.17 19728.92 5.89 116203.36
Total CBM 222077.99
Vessels
There are 3 vessels in the unit of each one operation at different pressure and has different
size parameters so the cost of each one has to be done.
Sample calculation for V-201:
cpo is found using the following graph
Where the volume is 3.86521 m3
By intersecting the volume with the horizontal curve cpo/m3 = 1890$/m3
cpo (2001) = cpo/m3 x m3 = 1890$/m3 x 3.86521 = 7305.04 $
I2 619 .2
Cp°(2019) = Cp° (2001) * ( ) = (7305.04 $) ( ) = (7305.04 $) (1.57) = 11471.67$
I1 394 .3
- Pressure of 1.1 bar
We have to calculate the Bare module cost to get the total cost:
Where
The values of B1 and B2 for horizontal vessels from Table A.4 are 1.49 and 1.52,
respectively.
Since the pressure is the atmospheric so no need to correct it
∴The pressure factor is 1.
And FM = 1 since it’s a carbon steel.
FBM = 1.49 + 1.52 (1x1) = 3.01
So CBM = $11471.67 (3.01) = $34529.74
Repeat the calculations for all the vessels.
The following tables shows all the prices for all 3 vessels.
Vessels Cpº (2001)($) Cpº (2019)($) FBM CBM $
V-201 7305.04 11471.67 3.01 34529.74
V-202 4852.6 7620.42 6.35 48389.64
V-203 4602.39 7227.49 3.62 26163.52
Total
CBM: 109082.90
Pumps ( P-201 A/B)
Reciprocating
P = 14.7
Using this graph it was determined from the Ws= 7.2KW that the purchased cost of Pump
per unit shaft power is 2500$//KW
Values of B from table A.4 B1 = 1.89 B2 = 1.35
Values of C from table A.2 C1 = -0.245382 C2 = 0.259016 C3 = -0.01363
Identification no.26 FM = 1.4
Cp° (2001) = (2500$/KW) (7.2KW) = 18000$
I2 619
Cp° (2019) = Cp° (2001) * ( ) = (18000$) ( ) = (18000$) (1.57) = 28260$
I1 394
= (-0.245382) + (0.259016) (log10 (14.7)) + (-0.01363) (log10(14.7))2
Fp = 1.0924
= (28260) (1.89 +1.35 (1.4)(1.0924) = 111758.0134
Pumps Cpº (2001)($) Cpº (2019)($) FBM CBM
P-201(A/B) 18000 28266.80 3.95 111653.87
P-202(A/B) 2500 3925.94 4.16 16331.93
P-201(A/B) 3120 4899.58 4.49 21999.11
Total CBM 149984.91
Reactor
There is only on reactor in the whole unit and it’s a packed bed reactor
calculations for R-201:
since there is no values of k’s of the packed bed reactor or graphs
cpo is found from outside source = 13,500$
I2 619 .2
Cp°(2019) = Cp° (2001) * ( ) = (13,500$) ( ) = (13,500$) (1.57) =21195$
I1 394 .3
FBM is taken form bare module factor table.
So CBM = $21195 x (4) = $84780
Total CBM of the equipment = 7646090.85$
CTM = 9022387.206 $
CBMo = 133.5$
∴ CGR=4511260.353
Adjusting the cost by the location factor from the table = 1.07
The fixed capital cost = 4827048.578$
2. Manufacturing Cost
To Calculate the COM this equation has been used without Depreciation.
The following variables has to be estimated:
Where FCI is the Grass root cost which is found in the previous calculations which has a
value of $4827048.578.
1.To Find Cost of operation Labor COL:
This equation has been used where Nnp is the summation of all equipment in the process.
Nnp= 17
NOL= (6.29+0.23(17))0.5 = 3.1937 number of operators per shift.
Operating Labor = (3.1937)(4.5)= 14.37 15
Note: Where 4.5 is the number of operators needed to provide this number of shifts is [(1095
shifts/yr)/(245 shifts/operator/yr)] or approximately 4.5 operators. Four and one-half
operators are hired for each operator needed in the plant at any time
Labor Cost COL(2001)= 14.37($52900)= $740600/yr
Labor Cost COL(2019)= $740600(1.57)= $ 1193608.65/yr
Cost Of Operating Labor (COL)
NoL 3.1937
Opearting Labor 14.37165
Cost (2001) 760260.285
Cost(2019)/yr 1193608.65
2.Finding Cost of Utilities & Waste Treatment
CUT= 2% of FCI
CWT= 1% of FCI
Where FCI= $4827048.04
96540.960
Utilities Cost ($/YR)(CUT) 8
Waste Treatment Cost ($/yr) 48270.480
(CWT) 4
3.Finding Cost of raw material CRM:
Since fresh methanol is the first fresh feed of a molar flow rate of 259.7 kmol/h and a
stream factor of 0.9.
Cost of methanol (2006)= 0.295$/kg
619.2
Cost of methanol (2019)= 0.295$/kg( )= 0.3656$/kg
499.6
So, Mass flow rate (kg/hr) = 259.7 kmol/h * 32.0416 kg/kmol = 8321.089 kg/hr
Yearly Cost of methanol = 8321.089 kg/hr (24)(365)(0.90)(3656$/kg)= 23916399.5/yr
so, by plugging all the values into the equations:
COM= $33722709.65
