Introduction
Adipic Acid
Adipic acid is one of the most important aliphatic acids with the following chemical formula ; COOH(CH2)4COOH. little of adipic acid occurs naturally but it is produced on large scale all around the world
Physical chemical properties
under the normal conditions (room tenperature and atmospheric pressure) adipic acid is an odorless,sour tasting solid present as awhite powder.the melting point of thr acid is 152c. it is soluble in polar solvents the solubility of adipic acid in water grows with increasing temperature
Application of adipic acid
adipic acid is an important chemical intermediate the main use of aa is a manufacture of nylon6,6 . nylon 6,6 is mainly used for production of fibers (fishing lines tires carpets home furnishing and in tough fabrics for backpacks parachutes luggage and business cases) and of resins. nylon resins sre used in electrcal connectors auto parts and items such as self lubricating bearings gears and cams
although thr main use of adipic acid is thr above written there are more ways of using adipic acid as can be seen from the figer.
Production of adipic acid
in 2006 the global AA capacity was around 2.8 million metric tons per year. the overall growth for AA is about 3% per year but the demand is growing faster in the year 2010 it was expected to be about 5-6% the most rapidly growing sector is the nylon one where during the past decade it was between 8-10% per year
Current industrial processes
adipic acid is produced by a two step oxidation process. the first one is oxidation of cyclohexane with air the second one is an oxidation of
a) a mixture of cyclohexane/cyclohexanol (called KA oil ) or
b) onoy of cyclohexanol with nitic acid
First step: Oxidation of cyclohexane with air
cyclohexane is obtained by the hydrogenation of benzene of from naphtha fraction in small amounts oxidation of cyclohexane was first performed in the yer 1940 by Dupont. the process is performed at temperatures between 150-180c under the pressure of 10-20 atm in the presence of Co or Mn organic salts . it is a two steps process oxidation and deperoxidation step. the rate limiting step of the process is the synthesis of hydroperoxide its concentration is optimized by carrying out the oxidation in passivated reactors and in the absence of transition metal complexes in order to avokd thr decomposition of hydroperoxide. the deperoxidation step in done in the second reactor , wher the catalyst amount and reaction coneition are optimixed allowing the OL/ONE ratio to be controlled . for the fact that both of the products are more reactive than the starting material , conversion of cyclohexane is kept low only about 5-7% in order to avoid consecutive reactions . the selectivity to KA oil is about 75-80% the by products are carboxylic acids amd cyclohexayl hydroperoxide . the unconverted cyclohexane is recycled scientific design company has developed a variation of this step , it consist in the addition of substantial quantities of anhydrous mera boric acid as alurry in cyclohexane to the first of a staged serier of oxidation reactors . no other catalydt is necessary . boric acid reacts with cyclohexanol to give a borate ester that stabilizes the products . conversion is as high as formed is easily hydrolysed by hot water to boric acid and cyclohexanol . after distillation a 99.5% OL/One mixture is obtained
CHAPTER2:
PROCESS DESCRIPTION:
Reactor 1:
in commercial use two approaches predominate the air oxidation of cyclohexane process; cobalt catalyzed oxidation and borate promoted oxidation. a third method the high peroxide process has found limited commercial use cobalt catalyzed air oxidation of cyclohexane is the most widely used method for producing acipic acid cyclohexane is oxidized with air at 150c to 160 and 810 to 1013kpa (about 8-10 atm) in the presence of the cobalt catalyst in a sparged reactor or multistaged column contactor.
several oxidation stages are usually necessary to avoid over oxidation the KA mixture cyclohexane on oxidation gives cyclohexane remains unreacted. unreacted ( excess) oxygen is drawn out from the product.
Distillation column:
oxidizer effluent is distilled to recover unconverted cyclohexane then recycled to the reactor feed. the resultant KA mixture may then be distilled for improved quality before being sent to the nitric acid oxidation stage . this process yields 75 to 80% mole percent KA with a kketone to alcohol ratio of 1:2 & water is completely removed KA mixtre consisting of ketonic alcoholic group and water is the bottom product.
Heat Exchanger
The lightly viscous mixture is then cooled from 150-85c using warer as a coolant.
Reactor 2:
the step in commercial production of adipic acid is nitic acid oxidation cyclohexanol and cyclohexanone mixture the reaction proceeds as follows:
cyclohexanol+nitric acid → adipic acid + NOX + H2O = HEAT
As the reaction is highly exothermic heat of reaction is usually dissipated by maintaining a high ratio (40:1) of nitric acid to KA mixture. nitric acid (50 to 60% ) and a copper vanadium catalyst are reacted with the KA mixture on a reactor vessel at 60 to 80c and .1 to .4 MPa. convresion yields of 92 to 96 % are attainable when usig high purity KA feed stock upon reeeaction nitric acid is reduced to nitrogen oxides NO2, NO ,N2O AND N2, the oxidation results into the formation of 94% adipic acid along with NOX, Salicylic acid m glutaric acid as by products m water and excess , HNO3
Vaccum Distillation Column
for enhancing the concentration of adipic acid up to 95% vaccum distillation of the mixture is done to remove water produced is the reactor2.
CRYSTALLIZER:
Now mixture is sent for crystallization to achieve up to 98% pure crystals of adipic acid crystals of adipic acid are obtained with small amount of mother liquor
CENTRIFUGE:
the mother liquor is separated from crystals here by washing with water in centrifuge for obtaining highly pure crystals of adipic acid crystals are sent to dryer.
DRYER:
Dryer is used to remove the water used for washing the mother liquor away from crystals in centrifuge. if water removal is not done then the crystals may remain impure and cause brittleness which are not suitable for handling and transportation. up to 99% pure crystals adipic acid are obtained , this purity is needed becayse these crystals are going to be used in the manifacturing of very important plastic Nylon
CHAPTER 3:
MATERIAL BALANCE:
MATERIAL BALANCE ON REACTOR 1:
REACTION:-
2C6H12 + 3/2
O2 80% C6H12O+C6H10O+H2O
17.86k.mole of C6H12 reacts with=1/2 * 17.86
C6H10O(Cyclohexanone):-
2k.moles of C6H12 reacts with = 1k.mole of C6H10O
=8.93 k.mole
As conversion is 80% so,
8.93 *
.8 * 78 =700.112 kg
H2O(Water):-
2k.moles of C6H12 reacts with = 1 k.mole of H2O1k.mole of C6H12 reacts with =1/2 k.mole of H2O17.86k.moles of C6H12 reacts with = 1/2 * 17.86
=8.93k.moleFor 80%conversion;
8.93 * .8 * 18=128.592kg2k.moles of C6H12 reacts with = 1.5 k.mole of O21k.mole of C6H12 reacts with =1/2 k.mole of O217.86k.moles of C6H12 reacts with = 1.5 * 17.86
=13.395k.mole13.395k.mole of O2
1k.
13.395k.mole mole of air 0.21k.mole of O2 63.78k.mole of airAs 25% excess air is supplied63.78 * 1.25=79.725k.mole of airSo O2 supplied;
79.725 * .21=16.74k.mole 16.74 *
32=535.75kg
O2 Unreacted
O2actually unreacted(before excess)=13.395 * 32 * 0.21
=85.73kg
O2 Unreacted
from excess=535.75 * 0.2
=107.15kg
Total
unreacted=107.15+85.73=192.6kg
Material
Balance on the Absorber
Reaction
1
2NO + O2 2NO2
Reaction
2
3NO2 + H2O 2HNO + NO
From
Reaction 1
NO=604.29/30=20.143k.moles
2k.moles of NO react=1mole of O2
1k.moles of NO react=1/2mole of
O2
20.143k.moles of NO react=1/2*20.143mole of O2
=10.0715*30=302.145
For
90% conversion=302.145*0.90=271.93
Material Balance on the vacuum Distillation
....................................
Material Balance on the Reactor 2
Reaction
3C6H12O + 2C6H10O +
18HNO3 5C6H10O4 +
12H2O + 9NO + 9NO2
Moles
of reactants
C6H12O =
714.285/100 = 7.1428 kmol
C6H10O =
700.112/98 = 7.144 kmol
HNO3 =
2700.1/63 = 42.85 kmol
C6H10O4 ( M.W. = 146 )
3
kmol of C6H12O
reacts with = 5 kmol of C6H10O4
1 kmol
of C6H12O reacts
with = 5/3
7.143
kmol of C6H12O
reacts with = 5/3 ( 7.143)
= 11.9 kmol
As
conversion is 94% so 11.9 * 146 * 0.94 = 1633.56 kg
H2O ( M.W. = 18 )
3
kmol of C6H12O
forms = 12 kmol of H2O
7.143
7 kmol of C6H12O
forms = 12/3 (7.143)
Hence
12/3
* 7.143 * 18 * 0.94 = 483.43 kg
NO (
M.W.= 30 )
3
kmol of C6H12O forms = 9 kmol of NO
1 kmol
of C6H12O forms
= 9/3
4.143
kmol of C6H12O forms = 9/3 (7.143)
Hence
9/3
* 7.143 * 30 * 0.94 = 604.29 kg
NO2 (M.W. = 46)
3
kmol of C6H12O forms = 9 kmol of NO2
1 kmol
of C6H12O forms
= 9/3
4.143
kmol of C6H12O forms = 9/3 (7.143)
Hence
9/3
* 7.143 * 46 * 0.94 = 926.58 kg
HNO3 (M.W. = 63)
3
kmol of C6H12O react = 18 kmol of HNO3
1 kmol
of C6H12O react = 18/3
7.143
kmol of C6H12O react = 18/3 (7.143)
Hence
18/3
* 7.143 *63 = 2700.05 kg
HNO3
unreacted
Material
Balance on the Distillation column
As C6H12 is completely removed from the top so;
Material
Balance on the Flash Drum
...........
Material
Balance on the Crystallizer
........................
Material
Balance on the Centrifuge
Solubility of HNO3 in Water =completely
Material Balance
on the Dryer
...............................................
CHAPTER 3:
ENERGY BALANCE:
Energy balance on the Reactor
Heat Inlet
Heat of reaction
Mass flow rate of nitric acid=162 kg
Mass flow rate of nitric acid=162 kg
Mass flow rate of water=578.67 kg
Mass flow rate of adipic acid=1633.156 kg
Mass flow rate of nitric acid=604.29 kg
Mass flow rate of nitrogen dioxide=926.58 kg
Mass flow rate of salisilic acid=120.8 kg
Mass flow rate
of giutaric acid=183.44 kg
Specific heat
capacity of nitric acid =.00174 kj/kg.k
Specific heat capacity
of water=4.2 kj/kg.k
Specific heat
capacity of adipic acid =2.44 kj/kg.k
Specific heat
capacity of nitric acid =1.0057 kj/kg.k
Specific heat
capacity of nitrogen dioxide =3.522 kj/kg.k
Specific heat
capacity of salisilic acid =0.66 kj/kg.k
Specific heat
capacity of giutaric acid =0.695 kj/kg.k
Q = m * cp * dt
= 4208.936 * 12.52444 * 60 =
629637.9 kj
Energy balance on the Dryer
Energy balance on the heat
exchanger
Mass flow rate
of giutaric acid=183.44 kg
Specific heat
capacity of nitric acid =.00174 kj/kg.k
Specific heat capacity
of water=4.2 kj/kg.k
Specific heat
capacity of adipic acid =2.44 kj/kg.k
Specific heat
capacity of nitric acid =1.0057 kj/kg.k
Specific heat
capacity of nitrogen dioxide =3.522 kj/kg.k
Specific heat
capacity of salisilic acid =0.66 kj/kg.k
Specific heat
capacity of giutaric acid =0.695 kj/kg.k
Q = m * cp * dt
= 4208.936 * 12.52444 * 60 =
629637.9 kj
Energy balance on the Dryer
Energy balance on the heat
exchanger
mass flow rate of cyclohexanol=714.285kg
mass flow rate of cyclohexanon=700.112kg
mass flow rate of water=128.592kg
mass flow rate of cyclohexane=300.0816kg
Q= m *cp * dt=1842.985* 5.42 * 60=158072.65kj
CHAPTER 5:
DESIGNING.
Heat Exchanger
Design
Background of
heat exchanger
Heat
exchangers are found in most chemical or mechanical systems. It’s a device that
transfers heat between one medium to another. Some of the
more common applications of
heat exchangers are found in heating,
air conditioning systems, radiators on internal
combustion engines, boilecondensers, and as preheaters
or coolers in fluid systems.These equipments are widely used
in many fields such as, power plants, petrochemical plants, petroleum refineries,
and natural gas processing.Because of heat exchangers come in so many shapes,
sizes, makes, and models, they are categorized according to common
characteristics.One common characteristic that can be used to categorize them
is the direction of flow the two fluids have relative to each other.
The
three categories are parallel flow, counter flow and cross flow as the
following figure
Figure
: Three flow arrangements categories.
Types of Heat exchangers
Plate
heat exchanger
DESIGN CALCULATIONS OF HEAT EXCHANGER
Inlet temperature of the process stream = T1
= 170oC
Outlet temperature of the process stream = T2 = 85oC
Inlet temperature of the water t1
= 25 o C
Outlet temperature of the water t2
= 55 o C
Mass
flow rate of the process stream
m = 2035.8 Kg/hr
Mass
flow rate of the Water m = .81904 Kg/hr
Cp of process
stream
Cp = 2.14 Kj/Kg o C
Cp of water Cp
= 4.18 Kj/Kg o C
Heat
duty
Q= m Cp ∆T
= 2035.8*2.14*85/3600
= 103.34kW
Mass flow rate of cooling water
=103.30/ 4.18*(55-25) = 81904 Kg/hr
LMTD
= 52.810 oC
Assumed Calculations
Value of
UD Assumed
UD = 400 W/m 2C
R = (T1-T2)/ (t2-t1 = 2.833
S = (t2-t1)/ (T1- t1) = 0.35
R & S intersect at fig 12.19 RC VOL 6 so from the value of Ft is 0.83
Del Tm = 0.83*52.810 =
43.83oC
Assumed Ud
= 400 W/m2.oC (rc vol6 table 12.1)
Heat Transfer Area
A= Q/UD∆T
=103.3
/43.83*400 = 5.8902m2
=103.3
/43.83*400 = 5.8902m2
TUBE DIMENSIONS
O.D. = 20 mm
I.D. = 16 mm
Length of tube
= Lt = 4.83 m
No. of tubes
= Ao/At = 5.8902/.303=53
Pt
= 1.25 ´ 0.020= 0.025m
Tube
Bundle Diameter
Db
= O.D* (Nt/K)1/n
For square
pitch pattern
n=2.291
K=0.156 (table 12.4 rc vol.6)
= 0.020*(20/.156)1/2.291
= 0.2163m m
No.
of tubes in centre row
Nr =
Db/Pt
= 0.3175/0.03125=10.1
Split ring floating head is selected. (From Figure
12.10 , volume 6)
BDC =
53mm=0.053m
Shell Diameter, Ds = Db+BDC= 0.21638+0.053=
0.2686 m
side heat transfer
coefficient Shell
Baffle spacing, lb = DS/5=
268.66/5= 53.72m m=.05372m
As =
= 0.0028879 m2
= 0.0028879 m2
Gs = M/As= 2035.8/0.0028879*3600= 195.945 kg/(s.m2)
Re, Reynold's number=Gs.do/µ= 469.8
jh = 2.4x10-1
(Fig. 12.31, Vol. 6)
Pr = Cpµ/k= 0.004675
hoc = (jH/do).k.Re.Pr1/3= (2.4x10-1/0.020)x0.2758x4.7026x102
(0.004675)1/3
= 260.243W/m .o C
Fn, Tube row
correction factor
(BC)
baffle cut is 25% of shell dia (rc
vol.6)
Baffle
cut height = 0.25xDs= 0.06716 m
Height
between baffle tips = 0.1350 m
Ncv
= 0.1350/0.025= 5.4
From
Fig 12.32, Vol. 6
Fn
=0.98
Fw, Window factor
Hb = (Db/2)-Ds(0.5-0.25)= 0.04115 m
Bundle cut, = Hb/Db=0.19 or 19%
Ra' = 0.16 (Fig 12.41, Vol. 6)
Tubes in one window, Nw = NtxRa'= 20x0.19 = 3.8
Rw = (2x3.8)/20 = 0.40
Fw = 1.06 (Fig. 12.33, Vol.
6)
Fb, Bypass correction factor
Ab = lb(Ds-Db)= 53.732(268.66-216.88)* 10-6= 0.002782m2
α = 1.35 (for turbulent flow from Vol. 6)
Fb = exp[-α.(Ab/As)(1-2(Ns/Ncv)1/3]
= 0.71006 (from Fig.
12.34, Vol. 6)
Fl, Leakage
correction factor
Fl = 1-βl(Atb+2Asb/Al)
Ct= 0.0008
(rc vol 6)
= 0.001490 m2
Cut = 25%, θ = 2.1 (Fig. 12.41, Vol. 6)
Cs=0.0032m (table 12.5)
= 0.002695 m2
AL/As = 0.5167
ΒL = 0.34 (Fig 12.35, Vol.6)
FL = 1-βl(Atb+2Asb/Al)= 1.08
hs = hoc x Fn x
Fb x Fw x Fl
hs = 260.243 x 0.98 x 1.06x .71006 x 1.08
hs =207.314 W/m2 .o C
AL/As = 0.5167
Shell
side Pressure Drop
Cross
flow zone
∆Pc = ∆Pi F'b F'L
Re = 654.5, for square pitch
jf = 8 x 10-2 (Fig. 12.36, Vol. 6)
us = .2153 m/s
∆Pi = 73.051 N/m2
F'b, bypass
correction factor for pressure drop
(α=4) for turbulent flow
F'b= exp[-α.(Ab/As)(1-2(Ns/Ncv)1/3]
F'b =0.3373
F'L, leakage
factor for pressure drop
β'l = 0.57( Fig. 12.38, Vol.6)
F'l = 1-β'l(Atb+2Asb/Al)
F'l = 0.7069
∆Pc = ∆Pi x F'b x F'l
∆Pc = 73.051 x 0.3373 x0.7069 = 17.41 N/m2
Window zone
∆Pw = F'l(2+0.6Nwu)ρuz2/2
For baffle cut 0.25, Ra = 0.16 (Fig. 12.41, Vol. 6)
Aw = (πDs2/4 x Ra) - (Nwπdo2/4)= 0.008123m2
uw = 0.076m/s
uz =
= 0.1279m/s
Nwu = Hb/Pt’= 41.154/25= 1.64
∆Pw = F'l(2+0.6Nwu)ρuz2/2= 15.734 N/m
End
zone
∆Pe = ∆Pi[(Nwu+Ncv/Ncv)]F'b
=
34.693 N/m2
Total pressure drop
Number
of baffles, Nb = 4.8/0.005373 - 1
Nb =
48.25= 87
∆Ps
= 2∆Pe + ∆Pc(Nb - 1) + Nb x ∆Pw
=156.00532 N/m2 or 0.2271Psi
Tube side Pressure drop
Re
= 8108.52 (for tube side)
jf
= 8.9 x 10-2 ( Fig. 12.24,
Vol. 6)
Np,
Number of passes = 2
∆Pt=
Np[8jf(L/di)+2.5]ρut2/2
∆Pt
= 2[8 x 8.9*10-2(4.88/0.016)+2.5]995*040952/2
∆Pt
= 4041.74 N/m2 or 0.58609 Psi
Tube side
Co-efficient
Mean temperature = (55+25)/2 = 40oC
Tube cross-sectional area = π/4 x d02= 201 mm2
As 2 passes are used so number of tubes per pass = 20/2 = 10
Total flow area = 10*201*10-6= 0.00201 m2
Mass velocity = .81904/0.00201= 407.48 kg/s.m2
ρ = 995 kg/m3
Water linear velocity, ut = 407.48/995 = 0.4095 m/s
The equation for heat transfer co-efficient below has been adapted
from data given by Eagle and Ferguson
hi = 4200(1.35+0.02t)ut0.8/di0.2
hi = 4200(1.35+0.02x40)0.40950.8/160.2
hi = 2491.79 W/m2.oC
Overall Design Co-efficient
kw = 45 (stainless steel)
1/hod = 0.0005 m2.o C/W
1/hid = 0.0002 m2.o
C/W (Table
12.3, 12.4, Vol.6)
Uo = 438 W/m2. o C
Tube side Pressure drop
Re = pdu/µ (for tube side)
=16827.42
jf = 4.3 x 10-3 (
Fig. 12.24, Vol. 6)
L/di= 1.83*10^3/21.8= 83.9
Np, Number of passes = 2
∆Pt= Np[8jf(L/di)+2.5]ρut2/2
∆Pt = 2[8 x 4.3*10-3*83.9+2.5]995*0.622/2
∆Pt = 2060 N/m2 or 0.298 psi
Heat Transfer Cofficient
hio = hi ´ ID/OD
hio =2468 W/m2 0C
Clean Overall Coefficient
Uc =1232.7 W/m2 0C
Introduction
What are HAZOPs
Standard
guidewords and their generic meanings
GUIDEWORD +
PARAMTER = DEVIATION
Preparation for
carrying out hazop
Record keeping
Assumptions
Resource
implications
Results of hazop
Benefits of
hazop
Cautions
Conclusion
INSTRUMENTATION AND PROCESS CONTROL
MEASRING DEVICES
PIPING NETWORK
The American National Standards Institute (ANSI) and
the American Petroleum Institute (API) have established detailed standards for
the most widely used components for piping systemMany of these standards contain
pressure-temperature ratings that will be assistance to engineers in their
design functions.
SELECTION OF PIPING
MATERIALS
COSTS FOR PIPING AND
PIPING SYSTEMS AUXILIARIES
Design Overall Coefficient Calculated
Centrifuge
Brief
Introduction
Classification of Centrifuges
These two categories can be further split into
subcategories,
Tubular bowl
High-speed,
vertical axis, tubular bowl centrifuges are used for the separation ofimmiscible liquids, such as water and oil, and for the separation of fine
solids. The bowl is driven at speeds of around 15,000 rpm (250 Hz) and the
centrifugal force generated exceeds 130,000N.
Disc bowl
The conical
discs in a disc bowl centrifuge split the liquid flow into a number of very
thin layers, which greatly increases the separating efficiency. Disc bowl
centrifugesused for separating liquids and fine solids, and for solids
classification
Scroll discharge
Parameters
Required For Designing
1: Volumetric Flow Rate
2:Length OF centrifuge
3:Volume OF bowl
4:Residence Time
5:Relative Centrifugal Force
6:Settling Velocity Of Prticles
Volumetric Flow Rate:
V= m/ρAVG
m=2150.97 kg/hr
ρavg = Xm ρ A.A
+ Xm ρS.A + Xm ρG.A + Xm ρN.A
V=1280.069 kg/m
Length Of Centrifuge:
L/D = 1.8
D = 1300 mm ,,,, D=1.3 m
L= 1.8 * 1.3= 2.34 m
L/D: Refrence; From
Patent ucdc 66.067 . 55/57002.237
D: Mcab - Smith , p#1067, CH#29
3:Volume Of Bowl:
V =
( π*D2 L/4)
= (3.14)*(1.3)2*(2.34)/4
V =
3.14 m3
Residence
Time
Settling
Velocity Of Particles
Dryer
Outlet
temprature of air
Mass
of air needed
Area of dryer
A =
1960.49 kg
Area= Ma /
G
Volume of dryer
Length of dryer
Residence time
Tr = k(Ln)/.5 / NDtanΦ (C)
DESIGN
OF DISTILLATION COLUMN
In industry it is common
practice to separate a liquid mixture by distillating the components, which
have lower boiling points when they are in pure condition from those having
higher boiling points. This process is accomplished by partial vaporization and
subsequent condensation
CHOICE OF PLATE TYPE
For
feed
|
component
|
Mass
Flow rate(kg/hr)
|
Molecular
wt
|
Kg
mole
|
Mole
fraction
|
|
C6H12
|
300.14
|
84.16
|
3.565
|
0.1425
|
|
C6H12O
|
714.285
|
100.152
|
7.1315
|
0.2855
|
|
C6H10O
|
700.112
|
98.15
|
7.133
|
0.2549
|
|
H2O
|
128.592
|
18
|
7.`44
|
0.2680
|
For Top product
|
component
|
Mass
Flow rate(kg/hr)
|
Molecular
wt
|
Kg
mole
|
Mole
fraction
|
|
C6H12
|
265
|
84.16
|
3.154
|
0.589
|
|
C6H12O
|
15
|
100.152
|
0.1497
|
0.02729
|
|
C6H10O
|
20
|
98.15
|
0.203
|
0.0379
|
|
H2O
|
33.2
|
18
|
1.844
|
0.
|
For
Bottom product
|
component
|
Mass
Flow rate(kg/hr)
|
Molecular
wt
|
Kg
mole
|
Mole
fraction
|
|
C6H12
|
35
|
84.16
|
0.4166
|
0.0212
|
|
C6H12O
|
699
|
100.152
|
6.978
|
0.3558
|
|
C6H10O
|
680
|
98.15
|
6.928
|
0.3552
|
|
H2O
|
95.25
|
18
|
5.2916
|
0.3698
|
Volatility
Calculation
Top product:-
αA =PAXB/PBXA
αA =0.97877*0.02797/0.0394*0.589
αA =1.775
Bottom product:-
αB =PAXB/PBXA
αB =2.142*0.3558/35.938*0.0212
αB =1.04
Average
Relative Volatility:-
αavg =
αavg =
αavg = 1.35
Key Component
Heavy Key component
C6H120
Light key component C6H12
Minimum
Reflux Ratio
1-q=∑ αi xif
αi-θ
αi= The relative volatility of component i with respect to some
reference
component, usually the
heavy key
Rm=∑αxid .
α-θ
Rm= Minimum ReflUX Ratio
Θ=0.75
1=(1.775)(0.1427)/()
Rm+1=1.8725-1
Rm=0.87
Rm= Minimum Reflux Ratio
α= Relative
Volatility
xid= Concentration of component /
in
the tops at minimum reflux
q= Thermal condition of feed
Θ2-1.75 θ+0.7004=0
Θ=0.75
We take
θ=0.75
Rm+1 = 1.8725-1
Rm=0.87
Minimum Number
of Plates
Minimum number of plates
are calculated by
using Fenske’s
equation
Nmin=ln[(xd/xb)LK(xd/xb)HK]
ln (α)
where
Nmin=ln[(0.589/0.02797(0.3558/0.012)]
ln (1.35)
Nmin=20
Optimum Reflux and Ideal Number
of Plates
Empirical relation.
|
R
|
R-Rm
R+1
|
(n+1)-(nm+1)
n+2
|
n
|
|
1
|
0.065
|
0.55
|
46
|
|
1.5
|
0.252
|
0.40
|
34
|
|
2
|
0.376
|
0.33
|
30
|
|
2.5
|
0.465
|
0.28
|
28
|
|
3
|
0.532
|
0.22
|
24
|
|
3.5
|
0.584
|
0.20
|
23
|
|
4
|
0.626
|
0.17
|
22
|
|
4.5
|
0.66
|
0.16
|
21
|
|
5
|
0.668
|
0.15
|
20
|
Reflux Ratio, R= 3
Ideal Number of Plates
N= 24
Eo = 0.68
Actual Number of
Plates
Eo= Number of Ideal Stag
Number of Real Stages
Number of Real Stages= 24/0.68
Feed tray location is found
by using Kirkbride
relation.
CHAPTER 6:
COST ESTIMATION
|
EQUIPMENT
|
COST($)
|
|
REACTOR
|
76000
|
|
DISTILLATION
COLUMN
|
87000
|
|
HEAT
EXCHANGER
|
43000
|
|
CRYSTALLIZER
|
41700
|
|
CENTRIFUGE
|
220300
|
|
DRYER
|
23860
|
|
Total
|
491860
|
CHAPTER NO 6:
HAZOP STUDY
Introduction
What are HAZOPs
HAZOPs are structured critical
examinations of plant or processes undertaken by an experienced team of company
staff in order to identify all possible deviations from an intended design,
along with the consequent undesirable effects concerning safety, operability
and the environment. The possible deviations are generated by
No (not, none)
none of the design intent is achieved
More (more of, higher) quantitative
increase in a parameter
Less (less of, lower) quantitative decrease in a
parameter
As well as (more than) An additional activity
occurs
Part of Only some of the design intention is
achieved
Reverse logical opposite of design intention
occurs
Other than (other) complete substitution, another activity
takes
Place
Other useful guide words include
Where else applicable for flows,
transfers, sources and
destinations
Before/after the step (or some part of it) is
effected out of
Sequence
Early/late the timing is different from the
intention
Faster/slower
the step is done/not done with the right timing
The deviations from the intended design
are generated by coupling the guide word with a variable parameter of
characteristic of the plant or process, such as reactants, reaction sequence,
temperature, pressure, flow, phase, etc. in other words:
Standard
guidewords and their generic meanings
No (not, none)
none of the design intent is achieved
Where else applicable for flows,
transfers, sources and
The deviations from the intended design
are generated by coupling the guide word with a variable parameter of
characteristic of the plant or process, such as reactants, reaction sequence,
temperature, pressure, flow, phase, etc. in other words:
GUIDEWORD +
PARAMTER = DEVIATION
For example, when considering a reaction
vessel in which an exothermic reaction is to be undertaken and one of the
reactants is to be added stepwise, the guideword “more” would be coupled with
the parameter “reactant” and deviation generated would be isothermal “runway”.
Systematic examinations are made of each
part of a plant or process using
these guidewords. Having examined one part of the design and recorded any potential hazards and operability problems associated with it, the study progresses to focus on the next part of the design or the next step in the operation. The examination is repeated until the whole plant has been studied for all major modes of operation. Recommendations for changes in design, operating procedure, materials or for referral outside for further consideration can then be made to overcome the problems which have been identified.
these guidewords. Having examined one part of the design and recorded any potential hazards and operability problems associated with it, the study progresses to focus on the next part of the design or the next step in the operation. The examination is repeated until the whole plant has been studied for all major modes of operation. Recommendations for changes in design, operating procedure, materials or for referral outside for further consideration can then be made to overcome the problems which have been identified.
The approach described above will
generate hypothetical deviations from the design intention.
The success or failure of study depends
on four aspects :
The accuracy of the design drawings and
other data used as the basis for the study
The technical skills and expertise of
the team
The ability of the team to use the
approach as an aid to their imagination in visualizing possible deviations ,
causes and consequences and
The ability of the team to maintain a
sense of the of proportion , particularly
When assessing the seriousness of the
hazards which are identified.
Careful thought must, therefore be given
to preparative work, team composition , keeping of records and so on.
Preparation for
carrying out hazop
The amount of preparation for a HAZOP
depends upon the size and complexity of the plant. Typically , the data
required consist of various drawings in the form of line diagrams ,flow sheets
.plant layout , isometrics and fabrication drawings, operating instructions ,
instrument sequence control charts ,logic diagrams and computer programmes.
Occasionally there are plant manuals and equipment manufacturer manuals. The
data must be accurate and sufficiently comprehensive. In particular, for
existing plant , line diagrams must be checked to ensure they are up to date
and that modifications have not been made since the plant was constructed.
Composition of the team to carry out a hazop
HAZOPs are normally carried out by a
multi-disciplinary team , including chemical engineers and chemists , with
members being chosen for their individual knowledge and experience in design ,
operations, maintenance or health and safety. A typical team would have between
4 and 7 members, each with a detailed knowledge of the way in which the plant
is intended to operate. The technique allows experts in the process to bring
their knowledge and expertise to bear systematically so that problems are less
likely to be missed. HAZOP is not a technique for bringing fresh minds to work
on a problem.
HAZOP studies generate recommendations
for design changes. The team should have the authority to agree changes there
and then , as progress is slow if every change has to be referred elsewhere for
a decision.
It is also essential that the team
leader is an expert in the HAZOP technique. The team leader ‘s role is to
ensure the team follows the procedure. He or she needs to be skilled in leading
a team of people who may not normally be responsible to him or her and the sort
of person who pays meticulous attention to detail.the team should have a
secretary to prepare notes after each meeting and to circulate them before the
next.
It is recommended that the team leader
should be an independent person,
i.e., this should not be somebody who is
closely associated with the plant under study. The team leader must have
sufficient technical knowledge to guide the study properly but should not
expected to make his technical contribution.it is beneficial if team members
have had some training in the HAZOP technique.
Record keeping
It is usual to record each step of a
HAZOP for all the physically meaningful deviations or, if a subset is used, to
include those requiring an action plus those which consider significant but
required no action because the existing protection was demed adequate. A
particularly useful type of record is the “Hazard file”.
This would normaly include:
A copy of the dat(flow sheets, original
and final process and instrument diagrams,running instructions,bar
sheets,models etc. used by the team during the examinations sessions and marked
by the study leader to show that they have been examined.
A copy of all the working papers ,
questions , recommendations , re-designs etc , produced by the team and others
as a result of the study. And
Confirmation that all the agreed actions
have been carried out .
The file should be retained on the plant
to provide a source of information for future use and in the event that changes
are subsequently contemplated by the operating personnel.
Assumptions
In a HAZOP study ‘operability’ is as
important as hazard and in most cases more operating problems are identified
than hazards. The HAZOP technique can therefore enable companies to use
resources more effectively and become more efficient as well as safer. It must
be remembered , however, theat the use of the HAZOP technique comes too late
for fundamental change in design. All that can usually be done is to add on
equipment or procedures to control the hazards that have been identified.
The techniques assumes a good level of
general management competence , in particular that the plant will be operated
and maintained in the manner assumed by the design team and in accordance with
good management and engineering practices .If these assumptions are not valid ,
then HAZOPs are of little value. It is no use identifying hazards if nothing is
to be done to manage and control the consequent risk; it is of little use
installing trips and alarms if they are going to be badly maintained. The time
spent on a HAZOP would be better spent improving management awareness and
commitment to provision of maintenance schedules, systems for controlling plant
modifications, and so on.
Resource
implications
HAZOPs are time consuming and on a
continuous plant can take , perhaps , up to half a day per main item of plant (e.g. still, furnace, reactor,
pipeline or transfer line, etc. ) depending on whether the plant is similar to
an existing one or completely new. For batch plants both the preparation of
data and the study itself will take longer , especially where the same
equipment is used to manufacture a range of different products.Meetings are
usually restricted to 3 hours , 2 or 3 days per week , to give the team time to
attend to their other duties and because people ‘s concentration wanes after 3
hours at a stretch. Many HAZOP studies can be completed in 5 to 10 meetings,
although for a small modification only one or two meetings may be necessary.
However, for a large project it may take several months even with 2 or 3 teams
working in parallel on different sections of the plant.
HAZOPs have major resource implications
which should not be under estimated. if HAZOPs are to be introduced to any
organization for the first time , it may be appropriate to apply the technique
to one or two problems to find out whether it is useful and can be applied
successfully.If so technique can grow naturally and be applied to larger
projects. For major projects, there may be six(or eight) different hazard
studies. A HAZOP study is often the third of these studies. Inherent safety is
usually covered in the second study.
Results of hazop
On completion of
a HAZOP study the likely outcomes are:
Some
improvements in operating/maintenance procedures, control programs and
instructions which may already have been implemented together with minor (low
cost) hardware alterations. These will have been put in hand as parts of the
study are completed.
Some proposed
changes may await the result of a more detailed quantitative assessment.
Major
recommendations will have yet to be implemented, possibly awaiting capital
sanction. And
The team members
will already have both a better understanding of the plan/process and a better
appreciation of potential hazards and risks than if the study had not been
carried out.
Benefits of
hazop
The
circumstances when HAZOPs are likely to produce benefits are:
·
During
the design or installation of any new plant or process, or major modification
to an existing one.
·
When
there are novel hazards such as environmental hazards and quality or cost
issues associated with the operation.
·
Following
a major incident involving fire , explosion , toxic release etc. and
·
To
justify why a particular code of practice , guidance note or industry code is
not to be followed.
Cautions
Even the most
rigrous HAZOP cannot be relied upon to foresee every hazard and some accidents
may well occur in the future .
When an accident
occurs on a plant which has undergone a HAZOP study , several questions of
particular significance should be asked :
·
Had
the set of conditions (deviations) which led to the incident been considered by
the HAZOP study team ? if not , could the team reasonably have been expected to
have done so ? and
·
If
such deviations and their causes had been considered , had the team made a
reasonable judgement of the likely frequency of the events and had concluded
that they were unlikely to occur and thus posed ‘ acceptable risks ?
In such
circumstances it is clearly important to document all the outcomes of study in
order to answer these questions .
Conclusion
HAZOPs are an
essential tool for hazard identification and have been used successfully to
improve the safety and operability of both new and existing chemical plant. The
technique is not confined to the chemical and pharmaceutical industries and has
also been used successfully in a number of other industries , including the
off-shore oil and food industries.
CHAPTER
NO 7:
INSTRUMENTATION
AND PROCESS CONTROL
INSTRUMENTATION AND PROCESS CONTROL
No plant
can operate until it is adeaqetly intrumented . the monitoring of temperature ,
pressure mfloqm level is necessary in almost every process in order to operate plant
in proper manner.
OBJECTIVES
OF CONTROL SYSTEM
Objectives
are
Ø To ensure the stability of the process
Ø To reduce the effect of external disturbances
Ø To optimize the overall process
Ø To keep the process variables within limit
Ø To give desire purity
Ø To Maintain the production composition
To
monitor and controle the operation of process there are seven hardware elements
as
Ø Process
Ø Measuring device
Ø Tranceducer
Ø Transmission lines
Ø Controller
Ø Final control element
Ø Recorder
PROCESS
It represent the material equipment together with physical and chemical
oprations
MEASURING DEVICE
The
instruments by which process is controlled
and und required enviroment is created
for process.
TRANSDUCER
It is
interface between process and control system and its job is to convert the
sensor signal into control system.
TRANSMISSION LINES
These lines carry signal from transducer to control
system. In modern systems transmission lines are not used as they reauire large
investment in capital cost. Now in modern system signal are transferred by
electrical signals which don’t require any transmission lines.
CONTROLLER
Controller
is the brain of whole plant. Its objective is to compare output signal and set
point and give correction to the system as required.
FINAL CONTROLE ELEMENT
Final
control element work on the instruction of controller.Final control
element mostly is control valve.
RECORDER
Recorder
, records the all process variable for monitoring purpose.
GENERAL
CONTROL SYSTEM
Following
are the general control system
Ø Open loop system
Ø Close loop system
Ø Feed backward system
Ø Feed forward system
Ø Combined control system
Ø Cascade control system
Ø Ratio control system
Ø Proportional control
Ø Proportional integral control
Ø Proportional derivative control
Ø Pid control
MEASRING DEVICES
In any
chemical process we usally measure
Ø Temperature
Ø Pressure
Ø Flow rate
Ø Level
PIPING NETWORK
The American National Standards Institute (ANSI) and
the American Petroleum Institute (API) have established detailed standards for
the most widely used components for piping systemMany of these standards contain
pressure-temperature ratings that will be assistance to engineers in their
design functions.
Some of the specific requirements for
piping system have been included in the Occupational Safety & Health
Administrations (OSHA) requirements.
SELECTION OF PIPING
MATERIALS
·
General
aspects that need to be evaluated when selecting piping materials are:
·
Possible
to exposure to fire with respect to the loss in strength.
·
Susceptibility
of the pipe to brittle failure or thermal shock failure when exposed to fire.
·
Ability
of thermal insulation to protect the pipe from fire.
·
Susceptibility
of pipe & joints to corrosion or adverse electrolytic effect.
·
Suitability
of packing, seals, gaskets and lubricants used on joints & connections.
·
Refrigeration
effect during sudden loss of pressure with volatile fluids.
·
Compatibility
with the fluid handled.
|
Metal Piping
Materials
|
Possible Material
Precautions and Alternatives
|
|
Metal
|
|
|
Iron(Cast,
Malleable & High Silicon)
|
Lack
of ductility & sensitivity to thermal & mechanical shock
|
|
Carbon
steel & Several low- alloy steels
|
Embrittlement
when handling alkaline or strong caustic fluids, conversion of carbides to
graphite during long time exposure to temperature above 4270C
|
|
High-alloy
stainless steels
|
Stress
corrosion cracking of austenitic stainless steels exposed to chlorides &
other halides; intergranular corrosion of austenitic stainless steel after
long time exposure to temperature between 4270C and 8710C
|
|
Nickel
& Nickel-base alloys
|
Grain
boundary attack of both materials not containing chromium when exposed to
sulfur at temperatures above 3150C
|
|
Aluminum
& Aluminum alloys
|
Corrosion
from concrete, mortar, lime, plaster, & other alkaline materials;
intergranular attack of alloys 5154, 5087, 5083 and 5456 when exposed to
temperature above 650C
|
|
Non-Metal
Piping Materials
|
|
|
Thermoplastics
|
Minimum
& Maximum operating temperature limits between -340C and 2100C
for thermoplastic piping material and -1980C 2600C for
thermoplastics used in linings, special precautions when used for
transporting compressed air or other gases
|
|
Reinforced
Thermosetting resins
|
Minimum
& Maximum operating temperature limits between 290C and 930C
|
COSTS FOR PIPING AND
PIPING SYSTEMS AUXILIARIES
Piping is a major item in the cost of
all types of process plants. These costs in a fluid-process plant can run as
high as 80% of the purchased equipment cost or 25% of the fixed-capital
investment. There are essentially two basic methods for preparing piping cost
estimations:
·
The percentage of installed equipment
method.
·
The material and labor takeoff method.
