cre final project report

8/11/2019 CRE Final Project Report

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30,000 Metric Tonnes Per Annum Production


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Table of Contents

1. Introduction 2-3

2. Level 1 Decision: Batch Versus Continuous 3-4

3. Level 2 Decision : Input- Output Structure of The Process Output ......................... 5-9

4. Level 3 Decision 9-11

5.Reference 11

6.Appendix 12


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1. Introduction

One of the Methacrolein synthesis routes is from oxidation of isobutylene. From the

annual production capacity, about 428571.4286 kmol/yr benzene can be computed using

8000 operating hours for a year as about 760 hours of the rest time is for the plant

turnaround works. According to the information from the literature, the reactions involve in

the process are as follow:

Isobutylene + Oxygen Methacrolein + H2O

Isobutylene + 6O24 Carbon Dioxide + 4H2O (Eq. 1.1)

While yield and conversion of a reaction are defined as:

Yield, Y

Conversion, X For an adiabatic reactor with the inlet temperature > 50 oCand the reactor pressure 20 bar,

th i ld f th i b t l id ti ti


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Figure 0.1: Selectivity as a Function of Conversion

No catalyst is necessarily used for this reaction. The purity of the main product,

Methacrolein, required by the consumers is a minimum of 99%. The easily-available cheap

raw materials are pure isobutylene and oxygen with purity of 99%.

2. Level 1 Decision: Batch Versus Continuous

As referred to heuristic guidelines, for the process synthesis and flow sheeting, this process

is worth continuous mode. The reasons of the decision are mainly based on the capacity and

the nature of the reaction. This process produces more than 5,000 tons per annum and the

raw materials are only two: isobutylene and methanol. The reactions are not too complex

that would not require the use of well-controlled batch reactors. The demand is

considerably consistent and do not change much with years as it is free from any seasonal

difficulties.

At thi l l th l b l ld b t d i l b i t d l l t d th h


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Species Purity Price

Isobutylene 99% $40/MT

Methacrolein 99% $188/MT

Table 2.1: Prices of chemical species

1 Isobutylene + 1 1 Methacrolein + 1 H2O


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3. Level 2 Decision : Input- Output Structure of The Process Output

Since the raw materials costs normally falls in the range from 33 to 85% of the total

processing cost, these costs are essential to be estimated before any other detail is added to

the design.

As a rule of thumb in process design, it is desirable to recover more than 99% of all valuable

materials. Thus at the second level of decision, the mole balances are calculated for theoverall system in which the limiting reactant is 100% converted (various conversions are

evaluated inside the process and would appear in the third level of decision). Figure 3.1

depicts the input-output structure of the process

Process

1. Isobutylene

2 Oxygen

3Methacrolein (desired)

4Carbon Dioxide, Oxygen, Water

(a)


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Species Symbol Inlet Change Outlet

Isobutylene A FA -1- 2 PA

Oxygen B FB -1- 62 PB

Methacrolein C 0 1 Pc

Carbon Dioxide D 0 42 PD

Water E 0 +1-+41 PE

In total, other than PB, there are 6 unknown variables. Information available to solve those variables

can be detailed out as follows, based on the material and energy balance textbook (Felder &

Rousseau, 2005)

Number of unknown variables in the process 6

2 Independent reactions +2

5 equation of extent of reactions -5Composition of Ratio of Isobutylene to Oxygen in the feed -1

Total (Variables can be calculate specifying two more information available) 2

The remaining information is obtained from the purge composition which will determine the ratio of

excess for the whole process and design variable of the reactor which would be optimized based on

the economic analysis. This purge composition is actually governing the feed ratio too through the

mole balance of reactive unit.


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Table 0.2 Mole Balance in terms of conversion and yield for the Second Level of Decision

Species Symbol Inlet Change Outlet

Isobutylene A FA FA[-XY+X(1-Y)] FA[1-X]

Oxygen B FB FA[-XY+6X(1-Y)] FA[6-6X+5XY]Methacrolein C 0 FA[XY] FA[XY]

Carbon Dioxide D 0 FA[4X(1-Y)] FA[4X(1-Y)]

Water E 0 FA[XY+4X(1-Y)] FA[XY+4(1-Y)]

Total FA+FB FA(7+X-XY)

From the probability sketch, we can obtain:

Ratio ofIsobutylene to Oxygen=1:6


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Simplify

(

)

By Using Excel solver,

0 1

0.2

0.3

0.4

0.5

0.6

0.70.8

0.9

1

Yield, Y

Yield Vs Conversion


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As the result of the calculation, from the graph EP ($/yr) versus conversion in Figure 3.2, the

profit can be obtained at relatively high conversion.

As this economic potential is the annual profit that does not have to pay anything for capital

costs and utilities costs, all the analyses are just catering the sale of products (including by-

products) and the purchasing of raw materials. The next level of decisions would use the

range obtained from this level.

4000000

-3000000

-2000000

-1000000

0

1000000

2000000

3000000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

EP2($)

EP2 Vs Conversion


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4.1.2. Reactor Cost

The Cost of Reactor, V is the volume of the reactor.

Plug Flow Reactor, $PFR= (1.345V + 854.8) 375

0

10

20

30

40

50

60

0 0.2 0.4 0.6 0.8 1

Volume of PFR

(litre)

Conversion

Volume of PFR vs Conversion


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The previous economic analysis for the input-output structure considered only the stream

costs, i.e., products plus by-products minus raw material costs.

1E 09

-9E+08

-8E+08

-7E+08

-6E+08

-5E+08

-4E+08-3E+08

-2E+08

-1E+08

0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

EP3

EP3 Vs Conversion


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6.Appendix

X Y f(x,y) EP2($) rA -1/rA FA0 F(A)/-rA V(litre) Reactor Cost

Compressor

i nstallation

compressor

operation EP3($)

0.0875 0.870396 0.00E+00 -5010974 406.4409 0.0025 195116.3572 480.0608 7.701385246 324434.3862 857349858.2 360867.1837 -863046134.1

0.1375 0.867106 0.00E+00 -2191763 390.0046 0.0026 124636.0715 319.5759 12.28278074 326745.1275 565110852.7 236657.835 -567866018.6

0.1875 0.863554 0.00E+00 -877352 373.2916 0.0027 91775.8115 245.8555 15.64754462 328442.2303 425130453.3 189145.4608 -426525393.4

0.2375 0.859700 0.00E+00 -117496 356.2756 0.0028 72779.3990 204.2784 18.371723 329816.2378 342651653.1 162307.3415 -343261272.6

0.2875 0.855497 0.00E+00 376981.8 338.9257 0.0030 60417.4540 178.2617 20.70891746 330995.0602 288181441.7 144536.7484 -288279991.6

0.3375 0.850887 0.00E+00 723858.5 321.2058 0.0031 51745.5378 161.0978 22.79512226 332047.2898 249509312.8 131690.746 -249249192.3

0.3875 0.845797 0.00E+00 980082.2 303.0728 0.0033 45339.9452 149.6008 24.71361256 333014.9283 220654241.7 121873.8413 -220129048.3

0.4375 0.840131 0.00E+00 1176517 284.4750 0.0035 40429.0693 142.1182 26.52111526 333926.5875 198339922.8 114081.3214 -197611413.5

0.4875 0.833766 0.00E+00 1331301 265.3492 0.0038 36559.4767 137.7787 28.26033441 334803.8062 180623782.1 107726.0955 -179735011.1

0.5375 0.826537 0.00E+00 1455735 245.6168 0.0041 33448.6168 136.1821 29.96698104 335664.5961 166286368.9 102441.0528 -165268739.2

0.5875 0.818215 0.00E+00 1557154 225.1781 0.0044 30913.1556 137.2831 31.67459132 336525.872 154531943 97985.79687 -153409300.9

0.6375 0.808477 0.00E+00 1640410 203.9035 0.0049 28831.7508 141.399 33.41888802 337405.6516 144832158.3 94198.87535 -143623352.9

0.6875 0.796838 0.00E+00 1708664 181.6189 0.0055 27125.3995 149.3534 35.2432333 338325.8058 136843688.5 90972.37965 -135564322.7

0.7375 0.782537 0.00E+00 1763740 158.0813 0.0063 25748.5048 162.8814 37.20766349 339316.6153 130372001.6 88239.31318 -129035817.7

0.7875 0.764282 0.00E+00 1806095 132.9327 0.0075 24689.6367 185.7303 39.40752688 340426.1714 125378661.4 85970.61933 -123998963.6

0.8375 0.739637 0.00E+00 1834113 105.6054 0.0095 23989.1700 227.1586 42.02080301 341744.2425 122067237.1 84184.3566 -120659052.5

0.8875 0.703198 0.00E+00 1841250 75.0915 0.0133 23810.7463 317.0896 45.46638439 343482.1076 121222672.9 82981.57211 -119807886.5

0.9375 0.638878 0.00E+00 1801274 39.2223 0.0255 24810.1502 632.5529 51.29182912 346420.3163 125947715.6 82672.40113 -124575534.3

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