MANUFACTURING OFPHOSPHORIC ACID

Presented By

Sagar Mahajan Aniket Mali

Exam No. B120215939 Exam No. B120215940

BE Chemical

Under Guidance of

Prof. H L Kamble

Department of Chemical Engineering

AISSMS College of Engineering, Pune-01

1

1. Introduction

2. Literature Survey

3. Selection of Process

4. Process Description

5. Material Balance

6. Energy Balance

7. Equipment Design

8. Cost Estimation

9. Plant Layout

10. Safety

11. Conclusion

12. References

2

In this project, we are going to analyze the production of

phosphoric acid by wet process

Phosphoric Acid is made from Phosphate Rock

Figure 1: Structure 3

Food-grade phosphoric acid is used to acidify foodsand beverages such as various colas

Teeth whiteners to eliminate plaque.

As a chemical oxidizing agent for activated carbonproduction

As a cleaner by construction trades to remove mineraldeposits, cementations smears, and hard water stains

As a pH adjuster in cosmetics and skin-care products

As a dispersing agent in detergents and leathertreatment

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Sr . No.

Patent Title Author Patent No Process Raw Material Parameters

1. Process of manufacturing phosphoric acid

Casimer c Legal,Jr Pasadena

et al

US2504544Wet Process

Sulphuric acid & phosphate rock

P2O5=33%Cao=45.79%Composition:-Fluorine=3.66%Moisture=0.70%Conversion = 98%

2. Method of manufacturing wet process phosphoric acid

Asalchi Matsubara,Yoshito Yasutake

US3416887 Wet

Process

Phosphate rockH2SO4

P2O5=40%

So3=2-2.5%H2SO4=15-50%

Table 1: Literature Survey

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Sr . No.

Paper Title Author Paper no Process Raw Material Parameters

3. Method of

preparing wet

process

phosphate acid

Feng

et al

US7172742

B2

Wet

Process

Decomposing

phosphate rock

in sulphuric

acid

Liq-solid ratio-2.3-2.7SO3 -0.09g/L

H3PO4-33-39wt%

P2O5-30-35%

Production=80%

4. Phosphoric

Acid

(Dryden’s

Outline of

Chemical

Technology,

3rd Ed.)

M. Gopal

Rao

Page No

150-153Wet

Process

Phosphate Rock

H2SO4

Phosphate Rock- 2.5 T

H2SO4 – 2.0T

CaSO4 – 2.7 T

Phosphoric Acid:

• Molecular formula : H3PO4

• Molecular weight : 98 gm/mole

• Melting point : 42.4ºC

• Boiling point : 213ºC

• pH: 1.5 (0.1 N aq. sol)

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Different process are needed because of different rock and gypsum disposal systems

Two general types of processes are used

Wet Process

Thermal process

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The processes that use phosphated minerals which are decomposed with an acid, are known as ‘Wet Process’

There are 3 Types of Wet Processes:

Nitric

Hydrochloric

Sulphuric

The process using sulphuric acid is most common and particularly used for fertilizer grade phosphoric acid

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Main Reaction:

3CaO + P2O5 Ca3(PO4)2

Ca3(PO4)2 + 3H2SO4 3CaSO4 + 2H3PO4

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• SO3 + H2O H2SO4

• 2CaO + 2F2 2CaF2 + O2

• CaF2 + H2SO4 + 2H2O 2HF + CaSO4.2H2O

• 6HF + SiO2 H2SiF6 + 2H2O

• CaO + H2O Ca(OH)2

• Ca(OH)2 + H2SO4 CaSO4.2H2O

• Al2O3 + 3H2SO4 Al2(SO4)3 + 3H2O

• Fe2O3 + 3H2SO4 Fe2(SO4)3 + 3H2O

• CO2 + H2O H2CO3

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Figure 2: PFD 12

Phosphate Rock: Ground to 200Mesh

Reaction Time: 4 – 6 Hr

98% conversion

By-Product: Gypsum(CaSO4.2H2O)

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1000 kg/day of Phosphoric Acid

Batch of 8hr

Slurry Feed ratio 1:2.5

Excess H2SO4 =1.4

98% Ca3(PO4)2 conversion

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COMPOUND CONTRIBUTION (%)

P2O5 32

CaO 49

SiO2 5

F 4

Al2O3 2

Fe2O3 2

CO2 1

SO3 2

Moisture 1

16

% by mass

Table 2: Rock

1

2

3

4 Vent720.05 Kg Rock

+

1925.13 Kg Water

734.67 Kg H2SO4

Table 3: Material Balance for Reactor

To

Filter

17

3 5

6

Liquid to Sedimentation Tank

Gypsum

+

Waste

Assuming 85%

Filter efficiency

From

Reactor

Table 4: Material Balance for Filter

18

6

7To

Evaporator

Table 5: Material Balance for Sedimentation Tank

From

Filter

19

8

7

10

Water Vapours

To

Evaporator IIFrom

Sedimentation Tank

Table 6: Material Balance for Evaporator I

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11

STEAM

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483.29 Kg

483.29 Kg

9

13

From Evaporator I

Table 7: Material Balance for Evaporator I

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14

10

12

483.29 Kg

483.29 Kg

Water Vapours

To

Evaporator III

12

16

Water Vapours

To

CondenserFrom Evaporator II

Table 8: Material Balance for Evaporator I

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17

13

15

444.47 Kg

444.47 Kg

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Table 9: Properties of Components

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Ca3(PO4)2 + 3H2SO4 + H2O 3CaSO4.2H2O+ 2H3PO4

Formula ∶ ∆𝐺𝑓𝑅 = ∑(𝑝𝑖 × ∆𝐺𝑓𝑖)𝑝𝑟𝑜𝑑𝑢𝑐𝑡 − ∑(𝑟𝑖 × ∆𝐺𝑓𝑖)𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡

where ∆𝐺𝑓𝑖 = Gibbs free energy of ith component

𝑝𝑖 = Stoichiometry of Product

• ∆𝐺𝑓𝑅 = 3 × −1797.44 + 2 × −1111.68 − [ 1 × −3884.84 +

3 × −690.06 + (6 × −237.18)]

• ∆𝑮𝒇𝑹 = -237.58KJ/Kmol

• Reaction is feasible

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Base Temperature : 298 K

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Table 10: Total Heat of Reaction for 1 Batch

∴ −∆𝐻𝑅 = 3448.526 KJ

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1

2

3

4 Vent

To

Filter298 K

343 K

298 K

Table 11: Total Heat of Reaction for 1 Batch

Heat to be Added by Jacket = 354055.907 KJ

Steam of 105oC is used at 0.64 Kg/min-batch

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3 5

6

Liquid to Sedimentation Tank

Gypsum

+

Waste

Assuming 5%

Energy Loss

From

Reactor343 K

339.5 K

339.5 K

Table 12: Energy Balance for Filter

6

7To

Pre-Heater

Table 13: Energy Balance for Sedimentation Tank

From

Filter

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8

339.5 K

337.5 K

337.5 K

Assuming 3%

Energy Loss

First Effect: Wsʎs + WF(tf-t1) = W1ʎ1

Second Effect: W1ʎ1 + (WF-W1)(t1-t2) = W2ʎ2

Second Effect: W2ʎ2 + (WF-W1-W2)(t2-t3) = W3ʎ3

WF-W1-W2-W3 = WP

Steam Supplied: 483.2913 Kg

Vapours Out: 1329.191 Kg

Average Heat Transfer Area Required = 36m2

Steam Economy: 2.75

Table 14: Energy Balance for MEE

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We calculated the total volume of input material

Volume of reactor is taken in 10% excess

Diameter, Height and Thickness of reactor

assuming 𝐿

𝐷=1.5

Various stability checks

Total weight of the reactor

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Volume of cylinder = 𝜋𝑅2𝐻

Weight = 𝜋𝐷𝐻𝑡𝑝

Tangential Stress = 𝑓𝑡 =𝑃 (𝐷𝑖+𝑡)

2𝑡

Stress due to Internal Pressure = 𝑓1 =𝑃×𝐷𝑖

4𝑡

Stress due to Weight = 𝑓2 =𝑊

𝜋(𝐷𝑖+𝑡)×𝑡

𝑓𝑎 = 𝑓1 + 𝑓2

𝑓𝑟 = [𝑓12 − 𝑓1𝑓𝑎 + 𝑓𝑎

2 + 3𝑓22]0.5

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Table 15: Design of Reactor

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Calculated the total volume of input material

Volume of tank is taken in 20% excess

Calculations same as for reactor

Diameter, Height and Thickness of tank assuming 𝐿

𝐷=1.5

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Table 16: Design of Sludge Separator

We calculated number of tubes required.

Pitch of tube: 75mm (Triangular)

𝐴 =𝑁×0.866×𝑆𝑇

2

𝛽𝛽 = 0.9

Area of Central down-take = 40% of CSA (Tubes)

Diameter of Tube Sheet

Thickness of Calendria

Thickness of Tube Sheet

𝐾 =𝐸𝑆×𝑡𝑆 𝐷𝑜−𝑡𝑆

𝐸𝑡×𝑁𝑡×𝑡𝑡(𝐷𝑡−𝑡𝑡)𝐹 =

𝐾

2+3(𝐾)

𝑡𝑡𝑠 = 𝐹 × 𝐷𝑜 ×0.25×𝑃

𝑓

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Area of Drum

𝑅𝑑 =𝑉

𝐴

0.0172×𝜌𝑙−𝜌𝑣𝜌𝑣

Rd =0.8

Thickness of Vapour Space.

Design for all 3 evaporators will remain same

As the heat transfer area required is equal.

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Table 17: Tubes and Calendria Specifications

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Table 18: Vapour Space and Head Specifications

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Figure 2: CFD – Geometry of Evaporator

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Table 20: Equipment Cost

Final Equipment Cost is 30% excess for supports, pumps, etc.

Therefore, FCE = 1.3 × 2858522.5 = 3716079.3

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Table 19: Material Cost

Fixed Capital (FCI)

Working Capital (WCI)

TCI = FCI + WCI

= 24773862 +17279693 = ₹ 4,20,53,555

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Manufacturing Cost

General Expenses

TPC = Manufacturing Cost + General Expenses

= 24773862 +17279693 = ₹ 1,50,93,453

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Selling Price of H3PO4(SP)= ₹ 80

Operating Time = 330 Days/Year

Capacity of Plant= 1000 Kg/Day

Taxes = 30% of GP

Income = SP × Capacity × Cycles

= 80 × 1000 × 330 = ₹ 2,64,00,000

Gross Profit (GP)= Income – TPC = ₹ 1,13,06,547

Net Profit = GP – Taxes = ₹ 79,14,583

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Rate of Return:

𝑟 =Net Profit

Total Capital Investment× 10

=7914583

42053555.8× 100 = 𝟏𝟖. 𝟖𝟐%

Pay-out Period:

T =Total Capital Investment

Net Profit + Depreciation= 5.08 𝑌𝑒𝑎𝑟

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After the process flow diagrams are completed and before

detailed piping, structural, and electrical design can begin,

the layout of process units in a plant must be planned

This layout can play an important part in determining

construction and manufacturing costs

Must be planned carefully with attention being given to

future problems that may arise

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Operational convenience and accessibility

Economic distribution of utilities and services

Type of buildings and building-code requirements

Health and safety considerations

Waste-disposal requirements

Auxiliary equipment

Space available and space required

Roads and railroads

Possible future expansion

The principal factors to be considered are :-

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Figure 3: Plant Layout

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Keeping the number of incidences and accidents zero

Having a robust and dynamic safety program

Major Hazard is Fire

Using inherently safe equipment

Carrying out independent audit from competent organizations

Abide by all the Govt. laws and hold sacred all the engineering ethics

Regular training and drill of the employees and workers

Creating safety policies

Developing and monitoring safety programs

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• Wet process was selected for the production of Salicylic Acid.

• Production capacity was selected as 1 Ton/Day after studying supply and demand data.

• From analysing the residence time of the process, three batches per day were selected.

• Energy balance was done for entire process.

• Design of the equipments was done.

• Costing of equipments was done.

• Plant layout is drawn.

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R K Sinnott , “Chemical Engineering Design,” 4th ed.,

Elsevier Butterworth-Heinemann (2005)

J P Holman, “Heat Transfer”, 6th ed., McGraw Hill Book

Company (1986)

Donald Q Kern, “Process Heat Transfer,” McGraw Hill

Book Company (1988)

Robert H. Perry, “Perry's Chemical Engineers' Handbook,”

8th ed., McGraw Hill (1934)

V. V. Mahajani and S. B. Umarji, “Joshi’s Process

Equipment Design”, 5th edition, Trinity Publications.

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