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Design of stirred batch reactor
 

Design of stirred batch reactor

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  • (e.g. a continuous stirred-tank reactor model). An example of a continuous bioreactor is the chemostat

Design of stirred batch reactor Design of stirred batch reactor Presentation Transcript

  • Design Of Stirred Batch ReactorPresented 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 fermentssugars into ethanol, giving off carbon dioxide gas as a by product. Theprocess has been used since civilization began. Starch is made up oflong chains of glucose molecules coiled together. The starch must bebroken down into sugars that are only one or two molecules long forthe yeast to feed on.REACTION 305 KC6H12O6 (l)------------------> 2C2H5OH (l) + 2CO2 (g) 180 kPa∆H0r = -285 kJ /kg C2H5OH
  • REACTOR DESIGN• Reactor Selection• Process Design• Mechanical Design• Heat Calculation• Specification SheetREF: Chemical Process Engineering Design and Economics By Harry Silla
  • SELECTION OF REACTOROur 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 eachother for a long time.•Need to mix the nutrients, bio mass and molasses well together.•Visited MURREY BREWERY INDUSTRY RAWALPINDI where batchprocess 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 REACTORThe following table tells us that a stirred batch reactor is common for gas-liquidsystems.REF: Chemical Process Engineering Design and Economics By Harry Silla
  • BATCH REACTORREF: Chemical Process Engineering Design and Economics By Harry Silla
  • BATCH REACTOR•Fermenter modeled as a batch reactor.•Batch reactor consists of an agitator and ajacket around it for cooling purposes.•Reactants are filled in and allowed to react for acertain period of time without them exiting.•Jacket consists of agitation nozzles forproviding higher turbulence and hence betterheat 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 ajacket around it for cooling purposes.•Reactants are filled in and allowed to react for acertain period of time without them exiting.•Jacket consists of agitation nozzles forproviding higher turbulence and hence betterheat 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 48hrs.•2 fermenters are used because 1 would give usvery large dimensions.
  • PROCESS DESIGNIn sizing of a batch reactor, the following rate equations have to be followed tocalculate the reaction time; REF: Chemical Reaction Engineering By Octave Levenspiel
  • PROCESS DESIGNThe yeast being used is Saccharomyces cerevisiae. According to anexperimental research paper, for a conversion of 70%, the time takenfor the batch reaction is 48 hrs. The following equation was then usedto calculate the entire batch time.Where;tF ’ = Time needed for filling.tR = Time taken for reaction.tC’ = Time taken to cool.tE ’ = Time taken for emptying and cleaning.tB = 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’ ): 2 hrs. Cooling time (tC’) : 1.5 hrs. Reaction time (tR): 48 hrs. Emptying and cleaning time (tE’) : 0.5 hrs.Total time for batch (tB): 2 + 1.5 + 48 + 0.5 = 52 hrs. REF: Crystalline Chemical Industries
  • PROCESS DESIGNVolume of Fermenter:Conversion = 70%.Reaction Time = 48 hrs.Batch Time (tB) = 52 hrs.No. of Fermenters used =2Working Pressure of Vessel (P) = 180 kPaTemperature of Reaction = 32 oC.pH = 4.8Mass flow rate in (ml’) = 6700 Kg/hr.Density of Material in Fermenter (ρ’) = 1200 Kg/m3.
  • VOLUME OF FERMENTERNow;tB = 52 hrs.Density of Feed (ρ’) = 1200 Kg/m3.Now;ml’ = 6700 Kg/hrTherefore; Vr = 6700 x 52 1200 Vr = 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; VT = 1.30 x Vr = 1.30 x 290 = 377 m3.REF: Chemical Process Engineering Design and Economics By Harry Silla
  • Dimensions:H/D = 1.5VT = Π x (D2/4) x L = Π x (D2/4) x 1.5D = (3/8)Π x (D3)VT = 377 m3.Hence, putting in above equation;D = 6.8 m.H = 10 m
  • Now;Height of Dished Bottom =1m( From Literature)Therefore;Total Height = 10 + 1 = 11 m.
  • MECHANICAL DESIGNWALL THICKNESSFor the calculation of wall thickness we have to calculate the total pressurewhich 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 THICKNESSWall thickness = P x ri + Cc SEj – 0.6PMaterial = Carbon Steel.Working Stress of Carbon Steel,S = 94408 KN/m2.Joint Efficiency, Ej = 0.85Internal Radius, ri = 3.4 mCorrosion allowance = 2mm.Therefore wall thickness = 0.017 + Cc = 0.017 + 0.002 = 0.019 m = 19 mm.Therefore outside diameter = Di + 2t = 6.84 m. REF: Plant Design and Economics for Chemical Engineers Max S. Peters et al.
  • REACTOR HEADThere are three types of heads:•Ellipsoidal Head.•Torispherical Head.•Hemispherical Head.Ellipsoidal head is used for pressure greater than 150 psi and for lessthan that pressure we use Torispherical head. That is why we haveselected 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 Da = Dt/3 = 2.2 m Impeller Height above Vessel floor E = Da = 2.2 m Length of Impeller Blade L = Da /4 = 0.6 m Width of Impeller Blade W = Da /5 = 0.4 m Width of Baffle J = Dt/10 = 0.68 m No. of Impellers =3 No. of Impeller blades =6 Distance between 2 consecutive impellers = 2.2 m Shape Factors are S1 = Da/Dt = 1/3 S2 = E/Dt = 1/3 S3 = L/Da = 0.27 S4 = W/Da = 1/5 S5 = J/Dt = 1/10 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, 2002REF: Unit Processes in Chemical Engineering By Mccabe, Smith & Harriot
  • POWER REQUIREMENTPower no (Np )= 6.Shaft RPM (N)= 44 RPM = 0.7 rev/secPower = (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 DESIGNNo. of baffles = 4.Width of one baffle = Dt / 10 = 0.68 m.Height of baffle = 10 m.
  • VISUAL DISPLAY OF AGITATOR WITH DIMENSIONS
  • VISUAL DISPLAY OF FERMENTER WITH DIMENSIONSFRONT VIEW
  • VISUAL DISPLAY OF FERMENTER WITH DIMENSIONSCooling AgitatoJacket r 0.68 Width of 2.2 m m Baffle 6.80 m 6.84 mTOP VIEW
  • HEAT TRANSFER CALCULATIONCooling fluid used = Cooling Water.Cooling Jacket area available (A) = 17 m2This area is obtained from Table 7.3 in“ Chemical Process Engineering Design and Economics by Harry Silla”CW inlet temp = 20 oCCW outlet temp = 28 oCApproaches;• ΔT1= 32 – 20 = 12 0C• ΔT2= 32 – 28 = 4 0C LMTD = 7.3 0C = 7.3 0K REF: Chemical Process Engineering Design and Economics By Harry Silla
  • HEAT TRANSFER CALCULATIONHeat of Reaction; Q = ∆Hr = 1.1 x 106 kJ/hr Design Overall Coefficient = UD = 170 W/ m2. 0KNow; Heat Removable by Jacket; Qj = UD x A x LMTD = 23579 W = 8.5 x 107 kJ/hrSince the heat of reaction (1.1 x 106 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/hrMass flow rate of water = Q/( CpΔTM) = 33 Tons/hr REF: Chemical Process Engineering Design and Economics By Harry Silla
  • Identification Item Fermenter Item Name R-101 No. Required 8 Function Production of Industrial Alcohol by Fermentation Operation Batch Type Jacketed, Stirred Tank Reactor Volume 377 m3 Height 10 m Diameter 6.8 m Temperature 32oC Working Pressure 1.8 atm Batch Time 52 hrs Height to Diameter Ratio 1.5 Type of Head Torispherical Depth of Dished Bottom 1m Wall Thickness 0.019 m Head Thickness 0.021 m No. of Baffles 4 Width of Baffle 0.68 m Height of Baffle 10 mMaterial of Construction of Fermenter Carbon Steel
  • IdentificationItem AgitatorType Three 6-bladed Flat TurbineNumber of Blades 6Impeller Diameter 2.2 mLength of Blade 0.6 mWidth of Blade 0.4 mImpeller Above Vessel Floor 2.2 mSpeed of Impeller 44 RPMPower Required 60 hpIdentificationItem Cooling JacketFluid Handled Cooling WaterInlet Temperature 20oCOutlet Temperature 28oCFlow Rate 33 Tons/hr.Heat Transfer Area 17 m2UD 30 BTU/hr.ft2.oFRD 0.001 hr.ft2.oF/BTU