Production of Bioethanol

Production of Bioethanol

JAYPEE UNIVERSITY OF ENGINEERING & TECHNOLOGY

FACULTY INCHARGE SUBMITTED BY: Mr. Rahul Shrivatava Aniket Chaki(101410)(Dept. of CHE Engg.) Vivek sharma(101451)

Selected processBioethanol can be produced by three processes: sugarcane processing, Cereal processing and lignocellulose processing. Among the most used Bioethanol production is by sugarcane.

Flowsheet

Process description 1.Preparation of the medium: Water is added to the molasses to bring down the sugar concentration to the desired level (usually 30 to 40 percent). A measured quantity of acid is then added so as to adjust the pH on the acidic side.

2.Addition of yeast: After adjusting the desired temperature, a yeast starter is allowed to be mixed thoroughly with the molasses mesh in the fermentation tank.

contd3. Fermentation: Fermentation by the yeast process starts and soon becomes vigorous. A large quantity of carbon dioxide is evolved during the process.

4. Separation of ethyl alcohol: The fermented medium contains alcohol as well as other volatile constituents and unused constituents of the molasses. Therefore, separation of ethyl alcohol from other impurities is necessary.

5. Distillation (Purification): Finally, alcohol is purified with the help of rectifying columns and stored in bonded warehouses.

Plant capacity 30 tons per day of bio ethanol from the rectification column (95% by weight)1 ton = 1000 kg Therefore, 30 tons per day= 1000*30 kg per day1 day = 24 hrsTherefore, 30 tons per day = 1000*30/24 kg per hr = 1250 kg/hrMass balance FERMENTERAssumptions : Molasses = 52% sucrose + 48% water 95% sucrose Bioethanol 10% less alcohol is produced due to pipe losses 1 kg=2.694*10^-3 kg Ammonium sulphate 1 kg=2.1544*10^-3 kg H2SO4 1kg H2SO4 = 0.2 kg H2O Density of ethanol: 0.789 kg/l Ratio of water to molasses is 4:1 Streams Input Mesh ( water + molasses Yeast culture + yeast cells Output CO2 Mixture of ethanol, water and biomass C12H22O11+H2O2C6H12O64C2H5OH+4CO2

CALCULATIONS342 kg of sucrose gives 184 kg of bio ethanol342 kg of sucrose will give 184*0.95=174.8 kg bio ethanolMolasses for 342 kg sucrose = 342/0.52=657.69 kg molasses174.8 kg bio ethanol requires 657.69 kg molasses Or 1 kg bio ethanol requires 3.76 kg of molassesDue to 10% pipe losses, 1kg bio ethanol requires =3.76+(0.1*3.76)= 4.136 kg of molassesAccording to our capacity (i.e. 1250 kg/hr), molasses required= 12,50*4.136 = 5170 kg/hr molassesWater added to molasses is 4 times of molasses = (4*5170)=20,680 kg/hr Therefore, total feed (i.e. Mesh) produced= (5170+20680) =25850 kg/hr

Since molasses contain 52% fermentable sugar in the form of sucrose, sucrose in the molasses (feed)=(0.52*5170)=2688.4 kg sucrose/hrFrom our reaction, we know that, 342 kg sucrose gives 174.8 kg pure ethanol; therefore 2688.4 kg sucrose/hr gives 1374.071 kg ethanol/hr.Yeast culture needed =5% by weight of mesh Therefore, yeast culture= (0.05*25850) =1292.5 kg/hrCell concentration=12.5 gm*kg of mesh So, cells present in the culture=12.5*10^-3 *25850 =323.125 kg cells/hAmmonium sulphate in 25850 kg/hr mesh= 69.6 kg/hr 1 kg =2.154*10^-3 kg H2SO4H2SO4 in 25850 kg/hr mesh= 2.1544*10^-3*25850=55.6912 kg/hrWater formed by 55.692 kg H2SO4=11.138 kg/hr

Water balance 1 kg H2SO4=0.2 kg H2OTotal water in=20680+11.138=20691.138 kg/hr342 kg sucrose requires 18 kg water therefore 2688.4 kg sucrose gives 141.494 kg/hr water.Water out =20691.138- 141.494=20549.64 kg/hr

CO2 producedMoles of CO2 produced is equal to the moles of ethanol produced. Moles of CO2 produced = moles of ethanol produced/46= 1374.071/46 = 29.871 kmol/hr

Biomass dx/ds=0.5g/g=(x-xo)/(s-so)Where, X is dry cell mass finallyXo is dry cell mass initiallyS is substrate mass finallySo is substrate mass initiallyXo=323.125 kg/hr cellsSo=2688.4 kg of sugar/hrS is the final weight of substrate or the left moles of ethanol=1374.071/46=29.871 kmol/hrAccording to the stoichiometry, 1 mole of sucrose equal to 4 moles of ethanol then the moles of sucrose reacted 29.871/4=7.468 kmol /hr

Initial mole of sucrose = 2688.4/342= 7.861 kmol/hrMoles of unconverted sucrose =7.861-7.468=0.393 kmol/hrKg of sucrose unconverted (s) final=0.393*342=134.406 kg /hrNow, X=1600.122 kg of cells/hrAlong with cells, about 50% water also goes out=0.5*1600.122=800.061kg water/hrsTherefore, wt. of biomass = 800.061+1600.122=2400.183 kg/hr.

Contd.. Material Balance across FermenterKg/hr(inlet) ComponentsKg/hr(outlet)Diluted Molasses5170Molasses20680Water20549.641292.5Yeast Culture323.125Yeast Cells55.69124H2SO455.692CO21314.324Bioethanol1374.071Biomass2400.183Sucrose134.406Residual Molasses1693.32027521.31727521.636Yeast treatment AssumptionsYeast culture needed is 5% by weight of meshCell concentration is 12.5g /kg of feedNutrients by ammonium sulphatepH control by H2SO4

Streams:Input H2SO4 Yeast culture + yeast cells Output Mixture of streams 5&6

Material balance across yeast treatment reactor Kg/hr (inlet)ComponentsKg/hr(outlet)55.69124H2SO455.69124323.125Yeast Cells323.1251292.5Yeast feed1292.1832400.183Biomass2400.1834071.494071.49Centrifuge Streams:Input Mixture of ethanol, water, biomass and sucroseOutput Mixture of ethanol, water and sucrose Biomass recycled

Material balance across centrifuge Kg/hr(inlet)ComponentsKg/hr(outlet)2400.183Biomass2400.1831374.071Bioethanol1374.071134.406Sucrose134.40620549.643Water20549.64324458.30324458.303Distillation column80% by weight of ethanol in distillate 2 % by weight of ethanol in bottom product

Streams:InputMixture of ethanol, water and sucroseOutput Distillate: 80% ethanolBottom: Vinasse% of alcohol in spent wash= 1374.071/ (24458.3-2400.183)*100 = 6.229 %

Calculations Overall material balance:F=D+RF=24458.3-2400.183 kg/hr22058.117=D+R

Component balance for ethanol:F*f=D*d + R*r22058.117*(6.229/100) =D*0.8+ (22058.117-D)*0.02D=1195.94 kg /hrR=20862.177 kg/hr

Material Balance across Distillation Columnkg/hr (inlet)componentskg/hr (outlet)1374.071Ethanol20684.046WaterEthanol (80%)1195.94Vinasse20862.17722058.11722058.117Rectification column95% by weight of ethanol in the distillate1% by weight of ethanol

Streams:Input Distillate from distillation columnRecycle from molecular sieve dehydratorOutput Distillate: 95% ethanolBottom: residue

Calculations Overall material balance:F=D+Rx+1195.94=R+1250x=R+54.06

Component balance:0.01*R+0.95*1250=0.97*(R+54.06)+0.8*1195.94 R=185.739 kg/hrx= 239.8 kg/hr.

Material balance across Rectification ColumnKg/hr(inlet)ComponentsKg/hr(outlet)1195.9480% Ethanol239.8Recycled Ethanol (97%)Residue185.739Ethanol (95%)12501435.741435.739Dehydration column Streams:Input Feed: Hydrous Ethanol (95% by weight of ethanol)OutputTop Product: Recycle stream to the rectification columnBottom Product: Anhydrous ethanol (99.5% by weight of ethanol)

Calculations Overall material balance D=x +E+W1250=239.8+E+W

Component balance 0.95*1250=0.995*E+0.97*239.8E=896.878 kg/hrW=113.22 kg/hr

Material balance across Dehydration ColumnKg/hr(inlet)ComponentsKg/hr(outlet)1250Ethanol (95%)Water113.22Anhydrous Ethanol (99.5%)896.878Recycled Ethanol (97%)239.812501250Overall Material Balance of the processkg/hr (inlet) Componentskg/hr (outlet) 5170 molasses 20680 water5603.523 1292.5 Yeast culture 323.125 yeast vinasse20862.177 Residue(rectification column)185.739Anhydrous ethanol (99.5%)896.878 55.692 H2SO4 CO2 27521.317 Total 27521.317Energy balance H=miHi (outlet)-miHi (inlet)Q-Ws=H+Ek+Ep

C12H22O11+H2O2C6H12O64C2H5OH+4CO2T=298K (assuming isothermal conditions)P=1atmEnergy Balance in fermenter:H=4(Hformation Ethanol) +4(Hformation CO2)-2(Hformation glucose)

Enthalpies of formation Hformation (Ethanol) =-276.5kJ/molHformation (CO2) =-393.5kJ/molHformation H2O (l) = -285.8 kJ/molHformation H2O (g) = -241.8 kJ/molHformation (glucose) (g) =-1250 kJ/molHformation (sucrose) (g) =-2220kJ/molTherefore, H= [4(-276.5) +4(-393.5)-2(-1250)] = -180kJ/mol

Calculations

Sucrose balance:Min of molasses=5170 kg/hrBut, sucrose content in molasses=52%Sucrose=0.52*5170 =2688.4 kg/hrMoles of sucrose=2688.4/342=7.860 kmolNout of sucrose= 1344.16/342=0.393 kmol

Water balance:Nin=20691.130 /18=1149.50 kmolesNout=20549.64/18=1141.64 kmoles

CO2 balance:Nout =13143.288/44=29.871 kmoles

C2H5OH balance:Nout= 13,740.71/46=29.871 kmoles

Energy Balance across the fermenter nin (kmol) Hin(kJ/mol) species nout(kmol) Hout(kJ/mol) 7.860-2220 C12H22O110.393-22201149.50-285.8 H2O1141.64-285.80-276.5 C2H5OH29.871-276.50-393.5 CO229.871-393.5Assumption:Power input=1.6 watt/kg of inputTotal input=275213.135kg/hrPower Input=Ws=440.341Ho =793.126 KWQ=H+Ws=793.126+440.341= 1233.47kw/hr

Distillation columnAssumptions:Temperature of distillate=82oC Boiling point of ethanol=78.5oC Boiling point of water=100oC Feed enters at 25oCHv = enthalpy of vaporization

H=49519.6089 kJQ=mCpT=HCp=43.99kJ/kgoCT=75oC , Therefore, Steam required, m=15kg/hr

For ethanol in distillate: = 38.58+5.516 = 44.034 kJ/molFor water in distillate: = 40.656+5.655-1.6211=44.69 kJ/molEthanol in residue: = 38.58+103.1*10^-3(100-25) =46.3125kJ/molWater in residue:

= 40.656+75.4*10^-3(100-25) =46.311 kJ/mol

Energy balance across the Distillation ColumnSpeciesFeedDistillateResiduenin(mol)Hin(kJ/mol)nout(mol)Hout(kJ/mol)nout(moles)Hout(kJ/mol)Ethanol29.871020.79844.0343.0746.3125Water1149.1134.0339245.0944.69904.0246.311Rectification columnAssumptions:Feed Temperature- 78.5oCDistillate Temperature-78.5oCResidue-100OC

H=10957.41292.71kJ/molQ=mCpT=H therefore, m= 3.32kg of steam/hr

Energy Balance across the Rectification column

SpeciesFeedDistillateResiduenin(mol)Hin(kJ/mol)nout(mol)Hout(kJ/mol)nout(moles)Hout(kJ/mol)Ethanol25.85025.8138.580.03440.797Water245.4890.1133.47240.656242.2040.656 Control strategies of distillation column

FC-Flow ControllerLC-Level ControllerPC-Pressure ControllerTC-Temperature ControllerTHANK YOU