Pre-treatment technologies were researched for wood feedstock, in order to alter structural and compositional impediments, to improve conversion rates and increase yields, for electricity ge…Full description
This document gives a superficial description of the saponification reaction and the differential method to find the rate law.
To determine the stoichiometric, the heat of reaction, and the rate constant of the reaction between sodium thiosulphate and hydrogen peroxide in an aqueous medium.
CONTINUOUS STIRRED TANK REACTOR (40 L)
design of PFR
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Design Of Stirred Batch Reactor
Presented By: SAQIB RAUF
What is bio-reactor • A bioreactor may refer to any manufactured or engineered device or system that supports a biologically active environment • In one case, a bioreactor is a vessel in which a chemical process is carried out which involves organisms or biochemically active substances derived from such organisms. This process can either be aerobic or anaerobic. These bioreactors are commonly cylindrical, ranging in size from litres to cubic metres, and are often made of stainless steel.
Cont.. • A bioreactor may also refer to a device or system meant to grow cells or tissues in the context of cell culture. These devices are being developed for use in tissue engineering or biochemical engineering
Classification of bio-reactors • On the basis of mode of operation, bioreactor may be classified as • Batch • Fed batch • continuous • Organisms growing in bioreactors may be • Suspended • Immobilized
WHAT IS FERMENTATION? Enzymes break down starch into simple sugars, and yeast ferments sugars into ethanol, giving off carbon dioxide gas as a by product. The process has been used since civilization began. Starch is made up of long chains of glucose molecules coiled together. The starch must be broken down into sugars that are only one or two molecules long for the yeast to feed on. REACTION 305 K
Reactor Selection Process Design Mechanical Design Heat Calculation Specification Sheet
REF: Chemical Process Engineering Design and Economics By Harry Silla
SELECTION OF REACTOR
Our system is gas-liquid system. We select a batch stirred tank reactor. This is due to the following reasons: We need to have the bio mass and molasses in contact with each other for a long time. •
Need to mix the nutrients, bio mass and molasses well together.
•
Visited MURREY BREWERY INDUSTRY RAWALPINDI where batch process was taking place. •
Concentration and temperature of the species is uniform through out.
•
REF: Chemical Process Engineering Design and Economics By Harry Silla
SELECTION OF REACTOR The following table tells us that a stirred batch reactor is common for gas-liquid systems.
REF: Chemical Process Engineering Design and Economics By Harry Silla
BATCH REACTOR
REF: Chemical Process Engineering Design and Economics By Harry Silla
BATCH REACTOR
Fermenter modeled as a batch reactor.
•
Batch reactor consists of an agitator and a jacket around it for cooling purposes. •
Reactants are filled in and allowed to react for a certain period of time without them exiting. •
Jacket consists of agitation nozzles for providing higher turbulence and hence better heat transfer. •
REF: Chemical Process Engineering Design and Economics By Harry Silla
BATCH REACTOR
Fermenter modeled as a batch reactor.
•
Batch reactor consists of an agitator and a jacket around it for cooling purposes. •
Reactants are filled in and allowed to react for a certain period of time without them exiting. •
Jacket consists of agitation nozzles for providing higher turbulence and hence better heat transfer. •
REF: Chemical Process Engineering Design and Economics By Harry Silla
BATCH REACTOR
There are 2 fermenters installed in parallel.
•
According to a journal, the conversion is 70 % and for that conversion the reaction time is 48 hrs. •
2 fermenters are used because 1 would give us very large dimensions. •
PROCESS DESIGN In sizing of a batch reactor, the following rate equations have to be followed to calculate the reaction time;
REF: Chemical Reaction Engineering By Octave Levenspiel
PROCESS DESIGN The yeast being used is Saccharomyces cerevisiae. According to an experimental research paper, for a conversion of 70%, the time taken for the batch reaction is 48 hrs. The following equation was then used to calculate the entire batch time.
Where; tF’ tR tC’ tE’ tB
= Time needed for filling. = Time taken for reaction. = Time taken to cool. = Time taken for emptying and cleaning. = Time taken for the entire batch operation.
REF: Journal of Tokyo University of Fisheries, Vol 90, pp. 23-30, 2003 REF: Chemical Process Engineering Design and Economics By Harry Silla
Time required for the entire batch operation: Charging
time (tF’ ): Cooling time (tC’) : Reaction time (tR ): Emptying and cleaning time (t E’) : hrs.
2 hrs. 1.5 hrs. 48 hrs. 0.5
Total time for batch (tB): 2 + 1.5 + 48 + 0.5 = 52 hrs.
REF: Crystalline Chemical Industries
PROCESS DESIGN Volume of Fermenter: Conversion
= 70%.
Reaction Time
= 48 hrs.
Batch Time (tB)
= 52 hrs.
No. of Fermenters used
=2
Working Pressure of Vessel (P)
= 180 kPa
Temperature of Reaction
= 32 oC.
pH
= 4.8
Mass flow rate in (ml’)
= 6700 Kg/hr.
VOLUME OF FERMENTER Now; tB Density of Feed (ρ’)
Now; ml’ Therefore;
= =
52 hrs. 1200 Kg/m3.
= 6700 Kg/hr V r V r
= 6700 x 52 1200 = 290 m3.
REF: Chemical Process Engineering Design and Economics By Harry Silla
Now; We allow 30% of volume of fluid as the free space in the fermenter. Hence; With 30% allowance; V T
= 1.30 x V r = 1.30 x 290 = 377 m3.
REF: Chemical Process Engineering Design and Economics By Harry Silla
Dimensions: H/D V T
V T
= 1.5 = Π x (D2/4) x L = Π x (D2/4) x 1.5D = (3/8)Π x (D3) = 377 m3.
Hence, putting in above equation; D
= 6.8 m.
H
= 10 m
Now; Height of Dished Bottom ( From Literature)
=1m
Therefore; Total Height
= 10 + 1 = 11 m.
MECHANICAL DESIGN WALL THICKNESS For the calculation of wall thickness we have to calculate the total pressure which is the sum of static pressure and operating pressure of the fermenter.
Static Pressure (Ps)
= ρ’ x g x H = (1200 x 9.81 x 10)/1000 = 129 kPa.
Total Pressure at base
= Ps + P = 309 kPa.
Maximum allowable pressure = 1.33 (309) = 410 kPa. REF: Plant Design and Economics for Chemical Engineers Max S. Peters et al.
WALL THICKNESS Wall thickness
+ C c = P x ri SE j – 0.6P Material = Carbon Steel. Working Stress of Carbon Steel,S = 94408 KN/m2. Joint Efficiency, E j = 0.85 Internal Radius, ri = 3.4 m
Corrosion allowance
= 2mm.
Therefore wall thickness
= 0.017 + C c = 0.017 + 0.002 = 0.019 m = 19 mm. = D i + 2t = 6.84 m.
Therefore outside diameter
REF: Plant Design and Economics for Chemical Engineers Max S. Peters et al.
REACTOR HEAD There are three types of heads: •Ellipsoidal Head. •Torispherical Head. •Hemispherical Head.
Ellipsoidal head is used for pressure greater than 150 psi and for less than that pressure we use Torispherical head. That is why we have selected a Torispherical head. REF: Chemical Process Engineering Design and Economics By Harry Silla REF: Coulson & Richard Chemical Engineering, Vol 6.
TORISPHERICAL HEAD
= 0.019 + 0.002 = 0.021 m = 21 mm.
REF: Chemical Process Engineering Design and Economics By Harry Silla REF: Coulson & Richard Chemical Engineering, Vol 6.
MECHANICAL DESIGN AGITATOR DESIGN Agitator Dimensions are: Impeller Diameter Impeller Height above Vessel floor Length of Impeller Blade Width of Impeller Blade Width of Baffle No. of Impellers No. of Impeller blades Distance between 2 consecutive impellers Shape Factors are S1 = Da/Dt = 1/3 S3 = L/Da = 0.27 S5 = J/Dt = 1/10
Da = Dt/3 E = Da L = Da /4 W = Da /5 J = Dt/10
= 2.2 m = 2.2 m = 0.6 m = 0.4 m = 0.68 m =3 =6 = 2.2 m
S2 = E/Dt = 1/3 S4 = W/Da = 1/5 S6 = H/Dt = 1.5
Tip Velocity = 3 – 6 m/sec Tip Velocity = 5 m/sec Tip Velocity = π x Da x N Speed of Impeller = N = [5/( π x 2.2)] x 60 = 44 RPM REF: Heuristics in Chemical Engineering Edited for On-Line Use by G. J. Suppes, 2002
POWER REQUIREMENT Power no (Np )= 6. Shaft RPM (N)= 44 RPM = 0.7 rev/sec Power = (Np x N3 x Da5 x ρ)/gc = 52 hp. Now, Assuming the impeller is 85 % efficient: Actual Power required = 52/0.85 = 60 hp.
BAFFLE DESIGN No. of baffles Width of one baffle Height of baffle
= 4. = Dt / 10
= 0.68 m. = 10 m.
VISUAL DISPLAY OF AGITATOR WITH DIMENSIONS
VISUAL DISPLAY OF FERMENTER WITH DIMENSIONS
FRONT VIEW
VISUAL DISPLAY OF FERMENTER WITH DIMENSIONS
Cooling Jacket
Agitato r
2.2 m
6.80 m 6.84 m
TOP VIEW
0.68 m
Width of Baffle
HEAT TRANSFER CALCULATION Cooling fluid used
= Cooling Water.
Cooling Jacket area available (A)
= 17 m2
This area is obtained from Table 7.3 in “ Chemical Process Engineering Design and Economics by Harry Silla”
ΔT1= 32 – 20 = 12 0 C ΔT2= 32 – 28 = 4 0 C LMTD = 7.3 0 C = 7.3 0 K REF: Chemical Process Engineering Design and Economics By Harry Silla
HEAT TRANSFER CALCULATION Heat of Reaction; Q = ∆H r = 1.1 x 106 kJ/hr Design Overall Coefficient = UD = 170 W/ m2. 0K Now; Heat Removable by Jacket; Q j = UD x A x LMTD = 23579 W = 8.5 x 10 7 kJ/hr Since the heat of reaction (1.1 x 10 6 kJ/hr) < heat removable by jacket (8.5 x 107 kJ/hr ) Our design for a cooling jacket is justified in comparison with a cooling coil.
Now Cooling water Flow rate can be calculated as: Heat to be removed from reactor = 1.1 x 106 kJ/hr Mass flow rate of water = Q/( CpΔTM) = 33 Tons/hr REF: Chemical Process Engineering Design and Economics By Harry Silla
