design of distillation column- meth- water

Batch Still Volume 6000 lts

Operating pressure 760 mmHg

Feed Composition

Component %w/w

Methanol 11%

Water 89%

100%

Properties of solvents

Component Sp.gr MWLatent heat Antonie Coefficient

Kcal/kg A B C

Methanol 0.78 32 263 8.08097 1582.271 239.726

Water 1.00 18 540 8.07131 1730.63 233.426

Loading factor for Structured packing 1.5

Heating Medium Steam

Saturated pressure 2 bar (g)

Saturated Temperature 142 °C

Latent heat 512 kcal/kg

Cost of Steam 0.9 Rs/kg

Main Condenser Cooling medium Cooling water

Inlet temperature 6 °C

Outlet temperature 11 °C

Percentage of operating load 85 %

Cost of cooling water (Rs/TR)

Vent Condenser Chilling medium Chilled brine

Inlet temperature -5 °C

Outlet temperature -3 °C

Percentage of average operating load 15 %

Cost of cooling water (Rs/TR)

Cost of Electricity 4.5 Rs/unit

m/s (kg/Cu.M)0.5

Avg. Specific gravity of Methanol-Water feed mixture 0.98

Feed Quantity 5854.8 kgs

Component wf mass (kg) Mol. Wt Moles mol.frMethanol 0.110 644 32 20.1 0.07Water 0.890 5211 18 289.5 0.93

1.000 5855 309.6 1.00

Recovery of Methanol as % of total Methanol in feed 30 %

Distillate Quantity 194 Kgs

Component % w/w mass (kg) Mol. Wt Moles mol.frMethanol 0.995 193.2 32 6.0 0.99Water 0.005 1.0 18 0.1 0.01

1.000 194.2 6.1 1.00

Bottom residue Quantity 5661 Kgs


1.000 5660.6 303.5 1.000

Bubble Point calculation for distillateOperating pressure of the column 760 mmHgBubble temperature 64.74095 °C

ComponentAntonie Coefficient Vap. Pr mol. Fr

A B C mmHgMethanol 0.99 8.08097 1582.271 239.726 765.7971 0.9987Water 0.01 8.07131 1730.63 233.426 184.9603 0.0022

1.00 1.00

Relative volatility of Methanol over water 4.14

Bubble Point Calculation for feedOperating pressure of the column 760 mmHgAssumed temperature 95.76734 °C

Componentmol. Fr Antonie Coefficient Vap. Pr mol. Fr mass mass fr.

x A B C mmHg kgs w/wMethanol 0.07 8.08097 1582.271 239.726 2315.893 0.198 6.34 0.31Water 0.93 8.07131 1730.63 233.426 651.8174 0.802 14.43 0.69

1.00 1.00 20.77 1.00

Relative volatility of IPA over water 3.55

Bubble Point Calculation for final residueOperating pressure of the column 760 mmHgAssumed temperature 96.93434 °C

Componentmol. Fr Antonie Coefficient Vap. Pr mol. Fr

x A B C mmHgMethanol 0.046 8.08097 1582.271 239.726 2404.733 0.147Water 0.954 8.07131 1730.63 233.426 680.2944 0.854

1.000 1.000


mol. Fr x y=Psat*x/P

y=Psat*x/P

y=Psat*x/P

G33

Goal seek to achieve Sum(y)=1 by adjusting the Bubble temperature (Indicated in Red)

G44

Goal seek to achieve Sum(y)=1 by adjusting the Bubble temperature (Indicated in Green)

G55

Goal seek to achieve Sum(y)=1 by adjusting the Bubble temperature (Indicated in Blue)

Average relative volatility, Alp 3.83

For a Total Condenser system

6Minimum no. of trays, N 5

Minimum reflux ratio

4.39

Actual Theoritical Add Feed with 50% Packing Height (M)

Reflux ratio L/D+1 N+1 N Total N packing eff. Str. Packing Random Pak

5.3 0.14 0.485 10 11 22 7.5 13.4

18.0 0.72 0.140 6 7 13 4.5 8.0

Note :

Column diameter calculation

Option-1 : Considering MellaPak Structured Packing

Reflux ratio L/D 5.3Internal reflux ratio L/V=R/(R+1) 0.84Average molecular weight of Distillate 32 kg/kmolDuration of Batch distillation 0.72 hrsAverage rate of distillation collection 270 kg/hr

Molar flow rate of distillate 8.45 kmol/hrLiquid flowrate Molar flow rate 45 Kmol/hr

mass flowrate 1421 kgs/hr 0.39 kgs/sVapour flowrate Molar flowrate 53 Kmol/hr

Mass flowrate 1691 kgs/hr 0.47 kgs/sColumn operating pressure 760 mmHgVapour density 1.15 kg/Cu.M 0.07 lb/Cu ftDensity of Liquid 781.10 kg/Cu.M 48.76 lb/Cu ftPacking Loading Factor F 1.50Column Cross Sectional Area 0.292 Sq. MDiameter of the column 0.609 M

Reboiler Heat Load Calculation

Boil-up rate 1690.9 kgs/hrLatent heat of boiling liquid 264.4 Kcal/kgHeat Load of Reboiler 491746.0 Kcals/hr

960.4 kgs/hrTotal Steam consumption for I fractionation 691.5 kgs/batch

Condenser Load

Latent heat of condensing Methanol-water mix 264.4

Nmin+1 = log(xDl/xDh)(xBh/xBl)/log(Alphaavg)

(L/D)min = (1/(Alp-1))((xlD/xlB)-Alp(xhD/xhB))

(L/D)-(L/D)min N-Nmin

1. For Structured packing, Packed ht is calculated considering 4 no. of theoritical stages per mtr of Packing. Hpacking=N50% eff*4

2. For Random Packing, 1" Pall ring is considered and height of packing is calculated considering HETP=1 (Ref. Ludwig Page no. 212, Table 9-36). HETP Act=HETPEst*1.5 and Hpaking=HETPAct*Ntotal

3. Use gilliland plot for entering values in (N-Nmin)/(N+1). Ref. Ludwig Vol-2 Page-11 Fig 8-14

m/s(kg/M3)1/2

Quantity of Steam required at 2 kg/cm2 (g)

C68

From Gilliland Plot Pg. No. 11, Ludwig Vol-2

G69

Mellapak : 4 theoritical stages per Mtr. packing

H69

1" Pall ring : HETP=1.25*0.8=1 Ref. Ludwig Pg. 212, Table 9-36

F88

Vary the value of distillation duration to achieve the required column dia

F100

Goal seek for column dia (610mm in this case) by adjusting Duration of batch distillation (Indicated in Red)

Condenser load 447041.8 Kcals/hr147.8 TR

Cooling water circulation rate at 6°C temp. diff 74.5 Cu. M/hr


Feed Quantity 5660.621 kgs


1.000 5661 303.5 1.00




1.000 228.8 7.2 1.00



1.000 5431.8 296.3 1.000




1.00 1.00





1.00 1.00 20.06 1.00





1.000 1.000



y=Psat*x/P

y=Psat*x/P

G33


G44


G55






8.31



10.0 0.15 0.480 10 11 21 7.0 12.6

18.0 0.51 0.180 6 7 13 4.5 8.0

Note :









970.8 kgs/hrTotal Steam consumption for II fractionation 1441.4 kgs/batch

Condenser Load








m/s(kg/M3)1/2


C68


G69


H69


F88


F100



Feed Quantity 5432 kgs


1.000 5432 296.3 1.00




1.000 118.6 3.9 1.00



1.000 5313.1 292.4 1.000




1.00 1.00





1.00 1.00 19.11 1.00





1.000 1.000



y=Psat*x/P

y=Psat*x/P

G33


G44


G55






15.33



18.4 0.16 0.485 9 10 20 6.6 11.8

35.0 0.55 0.230 6 7 13 4.4 7.9

Note :









996.6 kgs/hrTotal Steam consumption for III fractionation 1368.3 kgs/batch

Condenser Load








m/s(kg/M3)1/2


C68


G69


H69


F88


F100



Feed Quantity 5313 kgs


1.000 5313 292.4 1.00




1.000 43.8 1.5 1.00



1.000 5269.3 291.0 1.000




1.00 1.00





1.00 1.00 18.57 1.00





1.000 1.000



y=Psat*x/P

y=Psat*x/P

G33


G44


G55






21.44



25.7 0.16 0.485 8 9 19 6.3 11.3

40.0 0.45 0.280 6 7 14 4.5 8.1

Note :









1033.9 kgs/hrTotal Steam consumption for IV fractionation 731.8 kgs/batch

Condenser Load








m/s(kg/M3)1/2


C68


G69


H69


F88


F100


COD REDUCTION CALCULATION FOR METHANOL STREAM

+ +

MW 32 32 44 18Moles 1 1.5 1 2Kgs 32 48 44 36On 1mg of Acetone basis :mg 1 1.5 1.375 1.125

Basis : 1 kg of effluent.

Initial FinalSolvent Content in effluent 11% w/w 1.39% w/w

110000 mg/l 13902.8 mg/lCOD of effluent 165000 mg/l 20854.2 mg/l

Percentage reduction in COD 87.4 %

Cost Saving due to COD Reduction

Oxygen requirement 0.17 kg/l

Quantity of effluent per month 75.60 KLQuantity of Oygen required per month 13076.91 KgsAir equivalent to oxygen 395384 Cu. m/monthEquivalent operating hrs of compressors 138.3845 hrsMotor Power of compressor 10 hpPower consumption Per month 1057 kW hr

Per year 12687.09 kW hrCost saving (Rs/Annum) 58360.61

Reduction in effluent per batch 0.1209 731.8602 LEffluent reduction per annum 110657 LSaving due to effluent reduction per annum Rs. 88525.81

CH3 - OH 1.5O2 CO2 2H2O

COST SAVING DUE TO METHANOL RECOVERY

Feed Distillate Bottoms

Qty (kgs) Purity Qty (kgs) Purity % Qty (kgs) Purity %

I Fractionation 5854.8 11.00% 194.2 99.5% 5660.6 8.0% 0.72 5.3 960 1691 1421

II Fractionation 5660.6 7.96% 228.8 98.5% 5431.8 4.1% 1.48 10.0 971 1691 1537

III Fractionation 5431.8 4.15% 118.6 95.0% 5313.1 2.1% 1.37 18.4 997 1676 1589

IV Fractionation 5313.1 2.12% 43.8 90.0% 5269.3 1.4% 0.71 25.7 1034 1655 1593

585.5 4.29 990

Cost due to steam ConsumptionSteam Consumption

Cost of steam generation 1.25 Rs/kg Cost of Power 4.6 Rs/unit

ParticularsSteam Duration

(kgs/hr) (hrs) (kgs) (Rs) Pump-1 5 1.50 100% 5.73 26.4

I Fractionation 960 0.72 692 864 Pump-2 5 0.00 100% 0.00 0.0

II Fractionation 971 1.48 1441 1802 Pump-3 5 0.05 100% 0.19 0.9

III Fractionation 997 1.37 1368 1710 Pump-4 5 0.08 100% 0.31 1.4

IV Fractionation 1034 0.71 732 915 Pump-5 5 0.00 100% 0.00 0.0

Total Steam Cost per recovery batch (Rs) 5291 Pump-6 7.5 8.00 100% 45.84 210.9

4233 52.07 239.5

Cost due to Chilled water usage

Cost of Chilled Water 4.9 Rs/kg Cost due to operation of Agitator

ParticularsDuration Total TR Cost Agitator prime mover power 12.5 hp

(TR) (hrs) (kgs) (Rs) Duration of operation 10 hrs

I Fractionation 125.7 0.72 90 443 Operating load 100%

II Fractionation 127.0 1.48 189 924 Power consumption 96 units

III Fractionation 130.4 1.37 179 877 Cost of operating agitator (Rs) 439

IV Fractionation 135.3 0.71 96 469

Total Chilling Cost per recovery batch (Rs) 2714 148

Cost due to Chilled brine usage

Cost of Chilled brine 10.3 Rs/kg

ParticularsDuration Total TR Cost

(TR) (hrs) (kgs) (Rs)

I Fractionation 22.2 0.72 16 164

II Fractionation 22.4 1.48 33 343

III Fractionation 23.0 1.37 32 325

IV Fractionation 23.9 0.71 17 174

Total Chilling Cost per recovery batch (Rs) 1007

Cost saving due to Solvent recovery

ParticularsRec. Sol Rate Savings

UtilizationKgs Rs/kg (Rs)

I Fractionation 194.2 18 3,495 Substitute for Incinerator fuel

II Fractionation 228.8 18 4,119 Substitute for Incinerator fuel

III Fractionation 118.6 15 1,780 make up for brine solution

IV Fractionation 43.8 8 351 will be sold as spent solvent

Total Saving (Rs/batch) 9,745

Cost advantage due to recovery (Rs/distillation batch) 54

Savings due to solvent recovery (Rs/Annum) 8,215

Fractionation details

Duration (hrs)

Reflux ratio

Steam Con. (kg/hr)

Vap. flow rate (kg/hr)

Liq. flow rate (kg/hr)

Total Steam

Steam Cost

Pump No.

Installed hp

Duration (hrs)

operating load

Power cons. hp

Power Cost (Rs)

Chilling Load

Chilling Load

design of distillation column- meth- water

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