an minh tran - case 3 - cheg 407

Process Evaluation and Design II – Spring 2016

Process Evaluation and Design II – Spring 2016

CHEG 407 – A

CASE 3: PRODUCTION FRESH WATER FROM SEA

WATER BY MULTI-EFFECT EVAPORATOR SYSTEM

Instructor: Dr. Jacob R. Borden

Submitted by:

An Minh Tran

College of Engineering and Technology

McNeese State University

Date Submitted: May 3, 2016

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Table of Contents

Executive Summary.........................................................................................................................3

Introduction......................................................................................................................................3

Overall Process Description............................................................................................................3

Process with one Effect Evaporator System...........................…………………………………….4

A. Mass and Energy Balance………………..…………………………………………….5

B. Major Equipment List and Purchased Cost…………………………………………….8

C. Project Economics……………………………………………………………………...9

Process with three Effects Evaporator System……………………………………………..........11

A. Mass and Energy Balance…………………………………………………………….11

B. Major Equipment List and Purchased Cost…………………………………………...15

C. Project Economics…………………………………………………………………….16

Process with four Effects Evaporator System……………………………………………………19




Process with six Effects Evaporator System……………………………………………………..27




Options…………………………………………………………………………………………...33

Safety Concerns.............................................................................................................................34

A. Over Process………………………………………………………………………….34

B. Hazard and operability study (HAZOP)………………………………………………35

Conclusion and Recommendation.................................................................................................36

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EXECUTIVE SUMMARY

This report is a process design for the production of fresh water from sea water that contains 3.5

wt% salt. A multi – effect evaporator system that includes of number of effect, 1 boiler, and 1

condenser is used in this process. This paper provides a basic plant design with process flow

diagram, mass and energy balance, total equipment cost, economics analysis, and safety concerns

of the plant. The plant design basis is 400,000 pounds of fresh water is produced per day,

operating 300 days per year. The expected life of the equipment is 10 years and salvage value of

all equipment is 15% of the total equipment cost. Depreciate the equipment is calculated by

straight-line depreciation. Fixed charged are 15% of the installed cost of the evaporators

excluding depreciation. Maintenance charges are 5% of the total equipment cost. In this report,

the economics analysis is used base on different system with 1 effect, 3 effects, 4 effects, and 6

effects; then which option will give the highest total NPV will be chose to design the plant.

INTRORUCTION

Water is very important for human’s life. People drink water everyday to survive. The plants

need water in their photosynthesis process. Many factories use water for their cooling system.

Electricity can also produce by water; and many application of water in the real life. However,

because of the climate change and the increasing of population, souce of fresh water from nature

such as river or ground water seems like not enough to provide for human life. Besides, sea

water is the unlimit souce of water from natural. Therefore, a multi-effect evaporator need to be

designed to desalinate sea water to fresh water to provide for human life is very necessary.

OVERALL PROCESS DESCRIPTION

Sea water that pump to each evaporator is heated by hot steam which comes from the boiler.

After heated by hot steam, sea water turns to be hot vapor and is lead to the next evaporator to

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heat the next sea water flow of next evaporator. The cooling water on the other hand is pumped

to boiler. On next evaporater the sea water fed and the sea water coming from first evaporator are

heated by the steam coming from same evaporator to produce fresh water. Similarly, the process

keeps continuous until it goes to the last evaporator. At the last evaporator, the steam is cooled

by cooling water of the condenser. The figure below shown in the flow diagram of the Process

with four effect evaporator is used to make fresh water from sea water.

Figure 1: Flow Diagram of four Effects Evaporator System

PROCESS WITH ONE EFFECT EVAPORATOR SYSTEM

A. Mass and Energy Balance

With pressure of the boiler P = 40 bar, pressure of the effect P = 30 bar, and pressure of

condenser P = 1 bar, the base is given for mass flowrate of fresh water is 400,000 lb/day and is

5

produced from sea water that contains 3.5 wt% salt, from the steam tables combine with mass

and energy balance equations, the mass of brine coming out of effect, mass of cooling water

coming in to the condenser, mass of steam needed to heat up in the boiler, the heat duty of

natural gas that is required to heat up the steam in the boiler, the heat duty of condenser and its

area need to design to cool the hot stream are calculated.

Figure 2: Mass and Energy Balance Calculation for one Effect Evaporator System

Based on the values are calculated, the summary for mass and energy balance for the system is

shown in these figures below

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Figure 3: Mass Balance of the Process with one Effect Evaporator System

Figure 4: Energy Balance of the Boiler and one Effect Evaporator System

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Figure 5: Mass and Energy Balance of Condenser for one Effect Evaporator System

From those values of mass flowrate and heat duty that are calculated above, the unit such as

power of the pumps or area of evaporators are find out to estimate for equipment cost of the

project.

B. Major Equipment List and Purchased Cost

Figure 6: Cost Equipment Calculation for one Effect Evaporator System

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From those calculations that are presented above, the table of total equipment cost of process

is show in below

Name Unit of Size Value a b n Material Cost in 2010 Cost in 2016

Boiler Steam (liters/s) 9437.41 124000 10 1 Carbon Steel $ 218,374.07 $ 262,048.88

Condenser Area (m2) 64.01 1900 2500 1 Carbon Steel $ 161,929.16 $ 194,314.99

Effect 1 Area (m2) 40.29 330 36000 0.55 Carbon Steel $ 275,225.40 $ 330,270.48

Feed Pump Flow (liter/s) 2.12 8000 240 0.9 Carbon Steel $ 8,471.31 $ 10,165.57

Pump 1 Flow (liter/s) 3.19 800 240 0.9 Carbon Steel $ 8,681.82 $ 10,418.18

Total Equipment Cost $ 807,218.10 Table 1: Total Equipment Cost for one Effect Evaporator System

The total equipment cost for the process system with one evaporator equals $807,218.

C. Project Economics

1) Annual Depreciation

Annual depreciation is calculated by straight-line depreciation with the salvage value of all

equipment is estimated to be 15% of the equipment cost with the expected life of the

equipment is 10 years.

Total Equipment Cost $ 807,218.10 Salvage Value $ 121,082.72 Depreciable Asset Cost $ 686,135.39 Depreciation Rate/Year 10%Annual Depreciation $ 68,613.54

Table 2: Annual Depreciation for one Effect Evaporator System

Annual depreciation for one effect evaporator system is $68,613.54

2) Variables Cost of Production

To calculate variables cost of production, the number of water comes from cooling water of

condenser and steam for the boiler, electricity is used for the feed pump of sea water, and natural

gas is used for the boiler to heat water the run the system.

Utilities Consumption/day Cost $/unit Cost $/day Cost $/yearWater (gal) 3,953,301.72 0.005 19,766.51 5,929,952.58

Electricity (kWh) 731,531.69 0.046 33,650.46 10,095,137.3

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9Natural – gas (MM BTU) 714.69 2.178 1,556.60 466,981.00

Total variable cost $/year16,492,070.9

7Table 3: Variables Cost of Production for one Effect Evaporator System

From the table above, the main costs that effect to the variables cost of production are cost of

cooling water for the condenser and cost of electricity for the sea water feed pump. However,

based on mass balance, to produce 400,000 lb/day of fresh water, the flowrate of sea water is

414,508 lb/day, which is 2.12 liters/s, and this value is constant, so the electricity cost is

constant; therefore, the main utilities that effects to the changing variables cost of production is

volume flowrate of cooling water.

3) Annual Labor, Maintenance, and Fixed Charges

The calculation for annual labor, maintenance, and fixed charged are shown in table below with

the maintenance charged are 5% of the initial total equipment cost, and fixed charges excluding

depreciation are 15% of the installed cost of the evaporators

Number of operators/shift 2Operator salary $/hr 15Number of engineers 1Engineer Salary/season 25000Over head 100% labor cost Total labor cost $/year $ 632,000.00 Maintenance (5% Total equipment cost/year) $ 40,360.91 Fixed Charge ( 15% installed evaporator cost) $ 49,540.57

Table 4: Annual Labor, Maintenance, and Fixed Charges

4) Variables cost per gallon fresh water production

From all the costs that are calculated above, with 400,000 lb/day or 14.3 MM gal/day of fresh

water produce, the variables cost per gallon fresh water production is shown in table below

$/year $/gal of Water Utilities $ 16,492,070.97 $ 1.15 Depreciation $ 74,892.38 $ 0.01

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Labor $ 632,000.00 $ 0.04 Maintenance $ 40,360.91 $ 0.00 Fixed Charge $ 49,540.57 $ 0.00 Total $ 17,288,864.83 $ 1.20

Table 5: Variables cost per gallon fresh water production

From the table above, the cost of utilities is the highest cost that need to spend for the process.

5) Cash Flow and NPV Analysis

A cash flow analysis is done based on Annual Depreciation, Variables Cost of Production,

Annual Labor, Maintenance, and Fixed Charges for this project with the total is equal $17MM

each year. Net Present Value (NPV) method is applied to assess the economic value of the

project. A common Internal Rate of Return (IRR) of 8.5% is used for calculation. Tax is

incorporated and equals 28% of the net income. Desalinated water is sold for $1/gal. 400,000

lb/year or 14.3 MM gal/year of fresh water is produced. It means the revenue of this project

equals $14.3MM. The NPV of this plant is calculated in 10 years.

Year Cost Revenue Tax Cash Flow NPV Total NPV to year

0 $ 807,218.10 $ (807,218.10) $ (807,218.10) $ (807,218.10)

1 $ 17,288,864.83 $ 14,392,090.56 $ (811,096.79) $ (2,085,677.47) $ (1,772,825.85) $ (2,580,043.95)

2 $ 17,288,864.83 $ 14,392,090.56 $ (811,096.79) $ (2,085,677.47) $ (1,506,901.97) $ (4,086,945.93)

3 $ 17,288,864.83 $ 14,392,090.56 $ (811,096.79) $ (2,085,677.47) $ (1,280,866.68) $ (5,367,812.60)

4 $ 17,288,864.83 $ 14,392,090.56 $ (811,096.79) $ (2,085,677.47) $ (1,088,736.68) $ (6,456,549.28)

5 $ 17,288,864.83 $ 14,392,090.56 $ (811,096.79) $ (2,085,677.47) $ (925,426.17) $ (7,381,975.46)

6 $ 17,288,864.83 $ 14,392,090.56 $ (811,096.79) $ (2,085,677.47) $ (786,612.25) $ (8,168,587.70)

7 $ 17,288,864.83 $ 14,392,090.56 $ (811,096.79) $ (2,085,677.47) $ (668,620.41) $ (8,837,208.11)

8 $ 17,288,864.83 $ 14,392,090.56 $ (811,096.79) $ (2,085,677.47) $ (568,327.35) $ (9,405,535.46)

9 $ 17,288,864.83 $ 14,392,090.56 $ (811,096.79) $ (2,085,677.47) $ (483,078.25) $ (9,888,613.71)

10 $ 17,288,864.83 $ 14,392,090.56 $ (811,096.79) $ (2,085,677.47) $ (410,616.51) $ (10,299,230.22)Table 6: Cash Flow and NPV Analysis

Table above shown that the project is not profit if one desalinated water will sell for $1/gal for

one effect evaporator system.

PROCESS WITH THREE EFFECTS EVAPORATOR SYSTEM


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With pressure of the boiler P = 40 bar, pressure of the 1st effect P = 30 bar, pressure of the 2nd

effect P = 20 bar, pressure of the 3rd effect P = 10 bar, and pressure of the condenser P = 1 bar,

the base is given for mass flowrate of fresh water is 400,000 lb/day and is produced from sea

water that contains 3.5 wt% salt, from the steam tables combine with mass and energy balance

equations, the mass of steam and brine coming out of each effect, mass of cooling water coming

in to the condenser, mass of steam needed to heat up in the boiler, the heat duty of natural gas

that is required to heat up the steam in the boiler, the heat duty of condenser and its area need to

design to cool the hot stream are calculated.

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Figure 7: Mass and Energy Balance Calculation for three Effects Evaporator System



Figure 8: Mass Balance of the Process with three Effects Evaporator System

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Figure 9: Energy Balance of the Boiler and three Effects Evaporator System

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Figure 10: Mass and Energy Balance of Condenser for three Effects Evaporator System



project.


Figure 11: Cost Equipment Calculation for three Effects Evaporator System


is show in below


Boiler Steam (liters/s) 4093.07 124000 10 1 Carbon Steel $ 164,930.69 $ 197,916.82

Condenser Area (m2) 20.90 1900 2500 1 Carbon Steel $ 54,154.69 $ 64,985.63




Feed Pump Flow (liter/s) 2.12 8000 240 0.9 Carbon Steel $ 8,471.31 $ 10,165.57

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Total Equipment Cost $ 881,086.84 Table 7: Total Equipment Cost for three Effects Evaporator System

The total equipment cost for the process system with three effects evaporator system equals

$881,086.84







Table 8: Annual Depreciation for three Effects Evaporator System

Annual depreciation for three effect evaporator system is $74,892.38





Utilities Consumption/dayCost

$/unit Cost $/day Cost $/yearCooling water (gal) 1,063,043.26 0.005 5,315.22 1,594,564.88

Electricity (kWh) 731,531.69 0.046 33,650.4610,095,137.3

9Natural - gas (MM BTU) 309.97 2.178 675.11 202,532.89

Total variable cost $/year $ 11,892,235.16

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Table 9: Variables Cost of Production for three Effects Evaporator System











Number of operators/shift 4Operator salary $/hr 15Number of engineers 2Engineer Salary/season 25000Plant Manager 1Manager salary/season 37000Over head 100% labor cost Total labor cost $/year $ 1,560,000.00 Maintenance (5% Total equipment cost/year) $ 44,054.34 Fixed Charge ( 15% installed evaporator cost) $ 86,749.03





$/year $/gal of Water Utilities $ 11,892,235.16 $ 0.83 Depreciation $ 74,892.38 $ 0.01 Labor $ 1,560,000.00 $ 0.11 Maintenance $ 44,054.34 $ 0.00

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Fixed Charge $ 86,749.03 $ 0.01 Total $ 13,657,930.92 $ 0.95









lb/year or 14.3MM gal/year of fresh water is produced. It means the revenue of this project

equals $14.3 MM. The NPV of this plant is calculated in 10 years.

Year Cost Revenue Tax Cash Flow NPV Total NPV to year

0 $ 881,086.84 $ (881,086.84) $ (881,086.84) $ (881,086.84)

1 $ 13,657,930.92 $ 14,392,090.56 $ 205,564.70 $ 528,594.94 $ 449,305.70 $ (431,781.14)

2 $ 13,657,930.92 $ 14,392,090.56 $ 205,564.70 $ 528,594.94 $ 381,909.85 $ (49,871.30)

3 $ 13,657,930.92 $ 14,392,090.56 $ 205,564.70 $ 528,594.94 $ 324,623.37 $ 274,752.07

4 $ 13,657,930.92 $ 14,392,090.56 $ 205,564.70 $ 528,594.94 $ 275,929.86 $ 550,681.93

5 $ 13,657,930.92 $ 14,392,090.56 $ 205,564.70 $ 528,594.94 $ 234,540.38 $ 785,222.32

6 $ 13,657,930.92 $ 14,392,090.56 $ 205,564.70 $ 528,594.94 $ 199,359.33 $ 984,581.64

7 $ 13,657,930.92 $ 14,392,090.56 $ 205,564.70 $ 528,594.94 $ 169,455.43 $ 1,154,037.07

8 $ 13,657,930.92 $ 14,392,090.56 $ 205,564.70 $ 528,594.94 $ 144,037.11 $ 1,298,074.18

9 $ 13,657,930.92 $ 14,392,090.56 $ 205,564.70 $ 528,594.94 $ 122,431.55 $ 1,420,505.73

10 $ 13,657,930.92 $ 14,392,090.56 $ 205,564.70 $ 528,594.94 $ 104,066.81 $ 1,524,572.55 Table 12: Cash Flow and NPV Analysis

The NPV of this plant after 10 years is $1.5MM. The payback period is 2 years; the profit being

earned on the third year. With the NPV equal $1.5MM, which is 1.7 of the capital investment,

this project is worth implementing.

PROCESS WITH FOUR EFFECTS EVAPORATOR SYSTEM


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effect P = 20 bar, pressure of the 3rd effect P = 10 bar, pressure of the 4th effect P = 4 bar, and

pressure of the condenser P = 1 bar, the base is given for mass flowrate of fresh water is 400,000

lb/day and is produced from sea water that contains 3.5 wt% salt, from the steam tables combine

with mass and energy balance equations, the mass of steam and brine coming out of each effect,

mass of cooling water coming in to the condenser, mass of steam needed to heat up in the boiler,

the heat duty of natural gas that is required to heat up the steam in the boiler, the heat duty of

condenser and its area need to design to cool the hot stream are calculated.

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Figure 12: Mass and Energy Balance Calculation for four Effects Evaporator System



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Figure 13: Mass Balance of the Process with four Effects Evaporator System

Figure 14: Energy Balance of the Boiler and four Effects Evaporator System

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Figure 15: Mass and Energy Balance of Condenser for four Effects Evaporator System



project.


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Figure 16: Cost Equipment Calculation for four Effects Evaporator System


is show in below


Boiler Steam (liters/s)3552.1

112400

0 10 1Carbon Steel $ 159,521.07 $ 191,425.29

Condenser Area (m2) 19.36 1900 2500 1Carbon Steel

$ 50,293.17 $ 60,351.81

Effect 1 Area (m2) 15.17 330 36000 0.55Carbon Steel $ 160,937.50 $ 193,125.00




Feed Pump Flow (liter/s) 2.12 8000 240 0.9Carbon Steel

$ 8,471.31 $ 10,165.57

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Pump 1 Flow (liter/s) 1.20 800 240 0.9Carbon Steel

$ 8,282.97 $ 9,939.56


$ 8,194.46 $ 9,833.35


$ 8,135.62 $ 9,762.74


$ 8,128.77 $ 9,754.52

Total Equipment Cost $ 996,683.49 Table 13: Total Equipment Cost for four Effects Evaporator System

The total equipment cost for the process system with four effects evaporator system equals

$996,683.49






Table 14: Annual Depreciation for four Effects Evaporator System

Annual depreciation for four effect evaporator system is $84,719.28





Utilities Consumption/day Cost $/unit Cost $/day Cost $/yearCooling water (gal) 821,680.70 0.005 4,108.40 1,232,521.05 Electricity (kWh) 731,531.69 0.046 33,891.90 10,167,570.51Natural – gas (MM BTU) 269.04 2.178 585.97 175,790.74


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Total variables cost $/year 11,575,882.30Table 15: Variables Cost of Production for four Effects Evaporator System
















$/year $/gal of Water Utilities $ 11,892,235.16 $ 0.83

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Depreciation $ 74,892.38 $ 0.01 Labor $ 1,560,000.00 $ 0.11 Maintenance $ 44,054.34 $ 0.00 Fixed Charge $ 86,749.03 $ 0.01 Total $ 13,657,930.92 $ 0.95











Year Cost Revenue Tax Cash Flow NPV Total NPV to year0 $ 996,683.49 $ (996,683.49) $ (996,683.49) $ (996,683.49)1 $ 13,590,755.37 $ 14,392,090.56 $ 224,373.85 $ 576,961.34 $ 490,417.14 $ (506,266.36)2 $ 13,590,755.37 $ 14,392,090.56 $ 224,373.85 $ 576,961.34 $ 416,854.57 $ (89,411.79)3 $ 13,590,755.37 $ 14,392,090.56 $ 224,373.85 $ 576,961.34 $ 354,326.38 $ 264,914.59 4 $ 13,590,755.37 $ 14,392,090.56 $ 224,373.85 $ 576,961.34 $ 301,177.42 $ 566,092.01 5 $ 13,590,755.37 $ 14,392,090.56 $ 224,373.85 $ 576,961.34 $ 256,000.81 $ 822,092.82 6 $ 13,590,755.37 $ 14,392,090.56 $ 224,373.85 $ 576,961.34 $ 217,600.69 $ 1,039,693.51 7 $ 13,590,755.37 $ 14,392,090.56 $ 224,373.85 $ 576,961.34 $ 184,960.59 $ 1,224,654.10 8 $ 13,590,755.37 $ 14,392,090.56 $ 224,373.85 $ 576,961.34 $ 157,216.50 $ 1,381,870.60 9 $ 13,590,755.37 $ 14,392,090.56 $ 224,373.85 $ 576,961.34 $ 133,634.02 $ 1,515,504.62

10 $ 13,590,755.37 $ 14,392,090.56 $ 224,373.85 $ 576,961.34 $ 113,588.92 $ 1,629,093.54 Table 18: Cash Flow and NPV Analysis


earned on the third year. With the NPV equal $1.63MM, which is 1.63 of the capital investment,

this project is worth implementing.

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PROCESS WITH SIX EFFECTS EVAPORATOR SYSTEM



effect P = 25 bar, pressure of the 3rd effect P = 20 bar, pressure of the 4th effect P = 15 bar,

pressure of the 5th effect P = 10 bar, pressure of the 6th effect P = 4 bar, and pressure of the

condenser P = 1 bar, the base is given for mass flowrate of fresh water is 400,000 lb/day and is

produced from sea water that contains 3.5 wt% salt, from the steam tables combine with mass

and energy balance equations, the mass of steam and brine coming out of each effect, mass of

cooling water coming in to the condenser, mass of steam needed to heat up in the boiler, the heat

duty of natural gas that is required to heat up the steam in the boiler, the heat duty of condenser

and its area need to design to cool the hot stream are calculated.

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Figure 17: Mass and Energy Balance Calculation for six Effects Evaporator System

28



project.


Figure 18: Cost Equipment Calculation for six Effects Evaporator System


is show in below

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Name Unit of Size Value a b n Material Cost in 2010 Cost in 2016Boiler Steam (liters/s) 2969.32 124000 10 1 Carbon Steel $ 153,693.15 $ 184,431.78

Condenser Area (m2) 7.09 1900 2500 1 Carbon Steel $ 19,630.07 $ 23,556.09 Effect 1 Area (m2) 12.63 330 36000 0.55 Carbon Steel $ 145,565.34 $ 174,678.41 Effect 2 Area (m2) 12.73 330 36000 0.55 Carbon Steel $ 146,190.10 $ 175,428.12 Effect 3 Area (m2) 10.48 330 36000 0.55 Carbon Steel $ 131,398.89 $ 157,678.67 Effect 4 Area (m2) 7.37 330 36000 0.55 Carbon Steel $ 108,323.70 $ 129,988.44 Effect 5 Area (m2) 6.8143 330 36000 0.55 Carbon Steel $ 103,769.04 $ 124,522.85 Effect 6 Area (m2) 4.3441 330 36000 0.55 Carbon Steel $ 81,081.04 $ 97,297.25

Feed Pump Flow (liter/s) 2.12 8000 240 0.9 Carbon Steel $ 8,471.31 $ 10,165.57 Pump 1 Flow (liter/s) 1.00 800 240 0.9 Carbon Steel $ 8,240.82 $ 9,888.98 Pump 2 Flow (liter/s) 52.75 800 240 0.9 Carbon Steel $ 16,515.52 $ 19,818.62 Pump 3 Flow (liter/s) 48.92 800 240 0.9 Carbon Steel $ 15,957.56 $ 19,149.08 Pump 4 Flow (liter/s) 48.26 800 240 0.9 Carbon Steel $ 15,859.62 $ 19,031.54 Pump 5 Flow (liter/s) 47.32 800 240 0.9 Carbon Steel $ 8,522.38 $ 10,226.86 Pump 6 Flow (liter/s) 85.88 800 240 0.9 Carbon Steel $ 14,004.62 $ 16,805.54

Total Equipment Cost $ 1,172,667.79 Table 19: Total Equipment Cost for six Effects Evaporator System

The total equipment cost for the process system with six effects evaporator system equals

$1.172MM






Table 20: Annual Depreciation for six Effects Evaporator System

Annual depreciation for six effect evaporator system is $99,676.76


Total Equipment Cost $ 1,172,667.79 Salvage Value $ 175,900.17 Depreciable Asset Cost $ 996,767.62 Depreciation Rate/Year 10%Annual Depreciation $ 99,676.76

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Utilities Consumption/day Cost $/unit Cost $/day Cost $/yearCooling water (gal) 312,683.35 0.005 1,563.42 469,025.03Electricity (kWh) 731,531.69 0.046 33,650.46 10,095,137.39

Natural - gas (MM BTU) 225.43 2.178 491.00 147,299.22Total variable cost $/year 10,711,461.64

Table 21: Variables Cost of Production for six Effects Evaporator System













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$/year $/gal of Water Utilities $ 10,711,461.64 $ 0.74 Depreciation $ 99,676.76 $ 0.01 Labor $ 2,208,000.00 $ 0.15 Maintenance $ 58,633.39 $ 0.00 Fixed Charge $ 128,939.06 $ 0.01 Total $ 13,206,710.85 $ 0.92











Year Cost Revenue Tax Cash Flow NPV Total NPV to year0 $ 1,172,667.79 $ (1,172,667.79) $ (1,172,667.79) $ (1,172,667.79)1 $ 13,206,710.85 $ 14,392,090.56 $ 331,906.32 $ 853,473.39 $ 725,452.38 $ (447,215.40)2 $ 13,206,710.85 $ 14,392,090.56 $ 331,906.32 $ 853,473.39 $ 616,634.53 $ 169,419.12 3 $ 13,206,710.85 $ 14,392,090.56 $ 331,906.32 $ 853,473.39 $ 524,139.35 $ 693,558.47 4 $ 13,206,710.85 $ 14,392,090.56 $ 331,906.32 $ 853,473.39 $ 445,518.45 $ 1,139,076.92 5 $ 13,206,710.85 $ 14,392,090.56 $ 331,906.32 $ 853,473.39 $ 378,690.68 $ 1,517,767.60 6 $ 13,206,710.85 $ 14,392,090.56 $ 331,906.32 $ 853,473.39 $ 321,887.08 $ 1,839,654.67 7 $ 13,206,710.85 $ 14,392,090.56 $ 331,906.32 $ 853,473.39 $ 273,604.02 $ 2,113,258.69 8 $ 13,206,710.85 $ 14,392,090.56 $ 331,906.32 $ 853,473.39 $ 232,563.41 $ 2,345,822.10

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9 $ 13,206,710.85 $ 14,392,090.56 $ 331,906.32 $ 853,473.39 $ 197,678.90 $ 2,543,501.00 10 $ 13,206,710.85 $ 14,392,090.56 $ 331,906.32 $ 853,473.39 $ 168,027.07 $ 2,711,528.07

Table 24: Cash Flow and NPV Analysis


earned on the 2nd year. With the NPV equal $2.7MM, which is 1.6 of the capital investment, this

project is worth implementing.

OPTIONS:

From all the analysis economics parts that show in table 6, 12, 18, and 24, the more number of

effects evaporator, the higher NPV for this plant. The relation between number of effects

evaporator and NPV is shown in the table and graph below.

Table 25: Number of Effect to total NPV to 10th year

0 1 2 3 4 5 6 7

$(12,000,000.00)

$(10,000,000.00)

$(8,000,000.00)

$(6,000,000.00)

$(4,000,000.00)

$(2,000,000.00)

$-

$2,000,000.00

$4,000,000.00

# of Effecct Vs Total NPV

Number of Effect

Tota

l NPV

to 1

0 ye

ars

Figure 19: Number of Effect to Total NPV to 10th year

Number of Effect total NPV to 10th year1 $ (10,299,230.22)3 $ 1,524,572.55 4 $ 1,629,093.54 6 $ 2,711,528.07

33

From the table and the graph above, 6 effects evaporator system should be used to design the

plant because it gives the highest NPV value. Also, the main cost that need to spend that effect

the most changing to the NPV value is the cost of volume flowrate of cooling water for the

condenser. It is show in table and graph below.

Cooling Water Flowrate (MM gal/day) NPV to 10th year ($) 3.95 $ (10,299,230.22) 1.06 $ 1,524,572.55 0.82 $ 1,629,093.54 0.31 $ 2,711,528.07

Table 26: Cooling Water Flowrate to Total NPV to 10th year

- 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50

$(12,000,000.00)

$(10,000,000.00)

$(8,000,000.00)

$(6,000,000.00)

$(4,000,000.00)

$(2,000,000.00)

$-

$2,000,000.00

$4,000,000.00

1 effect

3 effects

4 effects

6 effects

Cooling Water Vs Total NPV

Figure 20: Cooling Water Flowrate (MM gal/day) to Total NPV to 10th year

The more effects evaporator, the less steam need to cool, so the less cooling water need to use in

condenser; therefore, the higher total NPV.

In conclude, system should be design with 6 effects evaporator.

SAFETY CONCERN

A. Overall Process

34

The chemicals involved in this process are sea water, and desalinated water. They are not

harmful so all the preventions for this plant are wearing protective gloves, safety goggles, and be

careful with the place that have hot steam.

B. Hazard and Operability study (HAZOP)

HAZOP Table and figure below is used for Steam at Boiler and Cooling Water in Condenser

Incident Effects RecommendationsLikelihoo

dSeverit

y DetectionOverall

RiskSTEAM OF BOILER

1Reverse Flow No steam in each effect

Check valves to prevent back flow and place a flow meter 1 10 3 30

2 No Flow No steam in each effect Place a flow meter 1 7 3 30

3 More FlowToo much steam in each effect

Place a flow meter and pressure transmitter 3 7 3 63

4 Less FlowLess steam in each effect, so less fresh water produce

Place a flow meter and pressure transmitter 3 5 3 27

5High Temperature Combust or over pressure

Place a Temperature Transmitter 5 3 5 75

6Low Temperature

Less steam in each effect, so less fresh water produce


7High Pressure Rupture steam tube

Place a pressure transmitter 3 5 3 45

8Low Pressure Rupture steam tube

Place a pressure transmitter 1 5 5 25

COOLING WATER OF CONDENSER

9Reverse Flow

Too hot of fresh water out of condenser

Check valves to prevent back flow and place a flow meter 1 7 3 21

10 No Flow No fresh water condense Place a flow meter 1 5 3 15

11 More FlowOver pressure and cause rupture Place a flow meter 3 5 5 75

12 Less FlowTemperature of Fresh water would increase Place a flow meter 3 5 3 45

13High Temperature

Temperature of Fresh water would increase


14Low Temperature

Temperature of Fresh water would decrease


15High Pressure Rupture cooling water tube

Place a Pressure Transmitter 3 5 3 45

16Low Pressure Rupture cooling water tube

Place a Pressure Transmitter 1 5 3 15

Table 27: HAZOP for Steam at Boiler and Cooling Water in Condenser

35

0 2 4 6 8 10 120

2

4

6

8

10

12

1

2, 9 3

4, 7 11, 12 15

6, 14

8, 10, 16

Boston square for Boiler and Condenser HAZOP

Likelihood

Seve

rity

5, 13

Figure 22: Boston square for Boiler and Condenser HAZOP

CONCLUSION and RECOMMENDATION:

This report is about a general plant design 400,000 lb/day of fresh water from sea water with 3.5

wt% salt. From all economics analysis, the system will have 1 boiler, 6 effects evaporator, 6

pumps and 1 condenser. The project requires $1.2 MM capital investment and annual $14.4 MM

cost for production. After 1 years, the investment starts to earn profit. At the end of year 10th,

NPV is about $2.7 MM. And the flowrate of cooling water is the most effective to changing

NPV value with the more effects evaporator, the less steam need to cool, so the less cooling

water need to use in condenser; therefore, the higher total NPV. And the recommendation for

this process is add the pressure transmitter, flowrate transmitter, and temperature transmitter in

each effect to guarantee the plant work well as its expectation.

an minh tran - case 3 - cheg 407

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