SAL College of Engineering Department Of Chemical Engineering ALA PRESENTATION Subject: Chemical Process Industries 1 Topic: Manufacturing of Phosphoric Acid Prepared By: Divya D Patel (131130105040) Ketan B Patel (131130105042) Guided By: Greeshma Nair

Introduction Phosphoric acid also known as orthophosphoric acid or phosphoric(V) acid is a mineral (inorganic) acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way. The term phosphoric acid can also refer to a chemical or reagent consisting of phosphoric acids, such as pyrophosphoric acid or triphosphoric acid, but usually orthophosphoric acid. The concentration of phosphoric acid is normally expressed as %P2O5(percent phosphoric anhydride) rather than % H3PO4 (percent phosphoric acid).

Properties of Phosphoric Acid Molecular formula H3PO4 Molar mass 98.00 g/mol Density 1.885 g/ml (liquid) Melting point 315.50 K (anhydrous) 302.47 K (hemihydrates) Boiling point 431 K, 486 K Decomposes Solubility Soluble in ethanol Refractive index (nD) 1.34203 Viscosity 2.4-9.4 cP(85%aq. Soln.) 147 cP (100%)

Structure of Phosphoric Acid H3PO4

Production Wet process Thermal process Dry kiln process Phosphoric acid can be produced by 3 main commercial methods: Wet process Thermal process Dry kiln process

Wet Process: Thermal Process: Wet process is by far the most common route and the acid can be used in phosphate fertilizers production. (DAP). Thermal Process: Thermal process phosphoric acid is of a much higher purity and is used in the manufacture of high grade chemicals, pharmaceuticals, detergents, food products, and other nonfertilizer products. Dry Kiln Process: The last method, using a rotary kiln, is a promising alternative because of its reduced environmental footprint and potential cost saving.

The Full Manufacturing of Phosphoric Acid by the Wet Process Phosphoric acid is produced from fluorapatite, known as phosphate rock, Ca3(PO4)2, by the addition of concentrated (93%) sulfuric acid in a series of well-stirred reactors. This results in phosphoric acid and calcium sulfate (gypsum) plus other insoluble impurities. Water is added and the gypsum is removed by filtration along with other insoluble materials (e.g. silica).

Although the reaction takes place in stages involving calcium dihydrogen phosphate, the overall reaction can be represented as: Ca3(PO4)2 + 3H2SO4 + 6H2O 2H3PO4 + 3CaSO4·2H2O The product from the 'wet process' acid is impure but can be used, without further purification, for fertilizer manufacture (see below). Alternatively it can be evaporated further to ca 70% P2O5, a solution called super phosphoric acid which is used directly as a liquid fertilizer. To make industrial phosphates, the acid is purified by solvent extraction using, for example, methyl isobutyl ketone (MIBK) in which the acid is slightly soluble and concentrated to give 60% P2O5 content. This acid can be further purified using solvents to extract it from heavy metals and defluorinated (by evaporation) to produce a product of food grade quality.

Figure – Dependance of Calcium Sulphate Hydrate Crystallisation on Temperature and P2O5.

Annual production of Phosphoric Acid: World : 38 million tones Europe : 4 million tones North America : 10 million tones Asia : 14 million tones

The Advantages of Wet Process in Production of Phosphoric Acid: There is no phosphate rock quality limitation On-line time is high Operating temperatures are low Start-up and shut-down are easy Wet rock can be used (saving drying costs)

The Disadvantages of Wet Process in Production of Phosphoric Acid: Relatively weak product acid (26-32% P2O5) High energy consumption in the acid concentration stage 4-6% P2O5 losses, most of them co-crystallised with the calcium sulphate

Common Uses of Phosphoric Acid:

Uses of Phosphoric Acid: Phosphoric acid is one of the most widely known and used acid. This acid is also known as orthophosphoric acid and is a mineral acid. Removal of Rust Use in Processed Food Medical Uses Phosphoric acid is used as the electrolyte in phosphoric acid fuel cells. As a catalyst in the hydration of alkenes to produce alcohols, predominantly ethanol.

TECHNOLOGICAL STATUS OF INDIAN INDUSTRY(CAPACITY IN TONNES P2O5) Sr. No. Manufacture Installed Capacity Process Licensor Engineering Contractor 1 Paradeep Phosphates Ltd. (under construction) 2,25,000 Jacobs International Inc. with Indian associate Hindustan Dorr Oliver Ltd. Hindustan Dorr Oliver Limited 2 FACT Limited, Cochin 1,18,800 Societe-de-Prayon Belgium through FEDO 3 Coromandel Fertilisers Ltd. 91,000 Dorr Oliver, USA USA 4 FACT Limited Udyogmandal 33,000 Dorr Oliver.U.S.A. Dorr Oliver, Ltd

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