DESIGN OF CONTINUOUS STIRRED-TANK REACTOR FOR LARGE-SCALE PHENOL PRODUCTION FROM CUMENE HYDROPEROXIDE __________________________________________________________ A written report Presented to the Chemical Engineering Department Faculty of Engineering University of Santo Tomas __________________________________________________________ In Partial Fulfillment of the Requirements of the Degree of Bachelor of Science in Chemical Engineering __________________________________________________________ By Hannah Mae R. Valensoy 5ChE-C DECEMBER 2014
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chehannahvalensoy.files.wordpress.com · Web viewThe reaction is first order kinetics and the most commonly used catalyst is a strong mineral acid such as sulfuric acid. Phenol has
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DESIGN OF CONTINUOUS STIRRED-TANK REACTOR FOR LARGE-SCALE PHENOL PRODUCTION FROM CUMENE HYDROPEROXIDE
Phenol is an aromatic organic compound which consists of a phenyl group bonded to a hydroxyl group. It is considered to be one of the most important starting material for various production of chemical products, such as phenol resin, bis-phenol A, aniline and some agricultural chemicals. Currently, there are four known processes being used commercially to produce phenol. But among the four stated processes, the major process used is the cumene hydroperoxide route, which accounts for about 90% of world capacity.
The basic reaction involved in the phenol production is the cleavage of cumene hydroperoxide to give the desired product, phenol and a useful by-product, acetone.
To give a brief explanation on how the process works, the cumene is oxidized into cumene hydroperoxide (CHP) which then decomposes to form phenol and acetone by using an acid catalyst. This process is very cost effective due to its mild reaction conditions and high percentage yield of phenol.
The reaction is first order kinetics and the most commonly used catalyst is a strong mineral acid such as sulfuric acid.
Phenol has been in the production since the early times of 1860s. Its early use was as an antiseptic. Towards the end of the 19th century, industrial scientists had found new uses for phenol in the synthesis of dyes, aspirin, and one of the first high explosives, picric acid.
For this particular report, a continuous stirred tank reactor was designed to produce 40,000 tons of phenol annually from the cumene hydroperoxide decomposition.
II. Feedstock and Operating Conditions
The cumene hydroperoxide which serves as the sole reactant for this process comes from the
oxidation of cumene into cumene hydroperoxide using a plug-flow reactor (PFR). The cumene
hydroperoxide (CHP) is now fed to a continuous stirred-tank reactor with H2SO4 as the catalyst. Heating
coil is used as the heating medium. The conversion of feed into product will occur isothermally at 65˚C
with a pressure of 2 atm. The order of the reaction is 0.5 (Kao, Chen-Shan & Duh, Yih-Shing., 1998) and
the overall conversion is 85%.
III. Material of Construction
The reactor will be made of a Grade 904L stainless steel cylindrical and ellipsoidal head as
material of construction. This type of stainless steel is a non-stabilized austenitic steel with low
carbon content. The high alloy stainless steel is added with copper to improve its resistance to
strong reducing acids, especially sulfuric acid. Grade 904L stainless steel is also resistant to stress
corrosion cracking and crevice corrosion. It is also non-magnetic, and offers excellent formability,
toughness and weldability.
Composition of Grade 904L stainless steel
Weight %
C 0.02
Mn 2
Si 1
P 0.045
S 0.035
Cr 23
Mo 5
Ni 28
Cu 2
Mechanical Properties
IV. Rationale for Equipment Selection
The stirred tank reactor can be considered as the basic chemical reactor. They are usually used
for homogeneous and heterogeneous liquid-liquid and liquid-gas reactions which suits it best for the
phenol production from cumene hydroperoxide decomposition. The presence of agitator in the
continuous stirred tank reactor is also significant because it increases the product yield of the
decomposition process. To sum up, continuous stirred tank reactors are suitable for reactions and/or
processes where good mass transfer or heat transfer is needed.
V. Material Balance
Component Mass Balance:
V CAO−V C A−¿V CAO−V C A−[V∗(k CA ) ]=0
Where:-rA = k*CA
0.5
-rA=1.007 mol/m3 min
Cumene Hydroperoxide (CHP)
CSTR
T=65˚C
30, 000 tons/year Phenol
13, 000 tons/year Acetone
Tensile strength(MPa)
490
Yield Strength(MPa)
220
Elongation(% in 50 mm)
36
Hardness 70-90
Energy Balance
VI. Equipment Design Theoretical Calculations
1. Design pressure and temperature
Based on working temperature + 30°C
T = 65°C + 30°C
T = 95°𝐶Based on working pressure + [10% of working pressure or 25 psi, depends on which is greater]
P = 202.65𝑘𝑃𝑎 + [25𝑝𝑠𝑖 𝑥 (101.325 𝑘𝑃𝑎)/(14.7 𝑝𝑠𝑖)]
P = 374.971 𝑘𝑃𝑎2. Calculation for reactor volume
mrb=30,000 ton/year
mrc=13,000 ton/year
MWb=94.111 kg/mol
MWc=58.079 kg/mol
Fb=mrb∗1000∗( 1MWb )∗( 1365 )∗( 1
24)
Fb=36.39 mol/hr
83.801 mol/hr CHP
T=25˚C
CSTR
T=65˚C
85% Products (Phenol + Acetone)
15% unreacted CHP
T=65˚C
Q generated (from agitation and heating coil)
Fc=mrc∗1000∗( 1MWc )∗( 1365 )∗( 1
24)
Fc=25.552 mol/hr
Let x=nao
0.85(x)=61.94
nao=72.87 mol/hr
0.15(nao)=10.931 mol/hr
Unreacted CHP=10.931 mol/hr
Total Fao=unreacted CHP + nao=72.87+10.931
Total Fao=83.801 mol/hr
Fao=83.801 mol/hr
ρa=1020 kg/m3
MWa=152 kg/mol
Xa=0.85
Cao= ρaMWa
Cao=6.711 mol/m3
vao= FaoCao
vao=12.487 m3/hr =0.25/hrƮ
V=vao* =(12.487)(0.25)Ʈ
V=3.122 m3
3. Dimensions of the reactor vessel
The reactor vessel will be in vertical orientation and with hemispherical head.
4. The rate of reaction in every instance must be established in the laboratory, and the
residence time or space velocity and product distribution eventually must be found from a
pilot plant.
5. The optimum proportions of stirred tank reactors are with liquid level equal to the tank
diameter, but at high pressures slimmer proportions are economical.
6. Power input to a homogeneous reaction stirred tank is 0.1–03kw/m3 (0.5–1.5hp/1000gal.)
but three times this amount when heat is to be transferred.
7. Ideal CSTR (continuous stirred tank reactor) behavior is approached when the mean
residence time is 5–10 times the length needed to achieve homogeneity, which is
accomplished with 500–2000 revolutions of a properly designed stirrer.
VIII. Equipment Specifications
Specification of reactor vessel Design dimensions
Diameter of the reactor 1.683 m
Height of the reactor 1.346 m
Aspect ratio 0.8
Head depth 0.842 m
Shell thickness (vessel) 0.01115 m
Shell thickness (head) 0.411 m
Diameter of the baffle (width) 0.1683 m
Type of impeller Four-pitched blade turbine
Number of blades 4
Agitator diameter 0.561 m
Height of agitator from tank bottom 0.561 m
Agitator blade width 0.1122 m
Input power 922.512 W
Agitator speed 14.703 m/s
IX. Rendered 3D-Model
REFERENCES
1. Green, Don W., Perry, Robert H. Perry’s Chemical Engineer’s Handbook, 8th edition. New York: McGraw-Hill, 2008
2. Sinnott, Rey., Towler, Gavin. Chemical Engineering Design, 5th edition. San Francisco: Elsevier, 2009
3. Levenspiel, Octave. Chemical Reaction Engineering 3rd edition.
4. Rules of thumb summary by Walas
5. Harriott, Peter. Chemical Reactor Design. New York: Marcel Dekker, Inc., 2002
6. Rengaraj, K., Selvin, Rosilda. Catalytic decomposition of cumene hydroperoxide into phenol and acetone. Applied Catalysis A:General 219 (2001) 125-129
7. Design of Ideal Continuous Stirred Tank Reactors http://www.rshanthini.com/tmp/CP303/set5.pdf
8. Rase, Howard F. Chemical Reactor Design for Process Plants, Volume two: Case studies and Design Data. New York: John Wiley & Sons.
9. Kao, Chen-Shan., Duh, Yih-Shing. Thermal decomposition kinetics of cumene hydroperoxide. Trans IChemE, Vol 76, Part B (1998)
Appendices for Calculations
Calculation for Q gained:
TO=25˚C
Tf=65 ˚C
FAO=83.801 mol/hr
Q=ΔHout-ΔHin+ΔHrxn
ΔHout= ΔHin=0
Q= ΔHrxn
ΔHrxn=ΔHR+ ΔHP+ ΔHF
At 25˚C:
ΔHFA=-475463.9
Residence time, =0.25 1/hrƮ*(M.Sittig, 1969)
ΔHFB=-165000
ΔHFC=-248000
ΔHF=[( ΔHFB+ ΔHFC)- ΔHFA] x Fao∗103
60
ΔHF=872.423x105 W
At Tave=65+252
=45˚ C :
CpA=2179.64
CpB=2154.558
Cpc=2241.623
ΔHR=[( CpA x MWA x Fao)]*(25-65)*160
ΔHR=-185.32x105 W
ΔHP=[(CpB x MWB X FB) + (Cpc x MWc x Fc)]*(65-25)*160