Manufacturing of Phosphoric Acid

Manufacturing of Phosphoric Acid

INTRODUCTION

Phosphorous acid is the backbone of all the phosphorous industries. All the phosphatic compounds are prepared from phosphoric acid. The rock phosphate available in India utilized   to   prepare   phosphoric acid.

Rock phosphate is available near Matar, Daman, Motra and other places in Udaipur district, Rajasthan state new deposits located at Nawana, mata Deharadun, U.P. in India. About 90% of phosphoric acid is used to produce fertilizers, such as calcium and ammonium phosphates. The greatest proportion of white phosphorous is used to make pure phosphoric acid.

Phosphoric acid is an important intermediate chemical product. It is used by the fertilizer industry. In 1980 the worldwide production capacity for H₃P0₄ yielded about 33 million tones of P₂0₅ equivalent. P204 equivalent contains in phosphate rocks and phosphatic fertilizer in phosphate rocks and phosphatic fertilizer.

About 98% of the world P₂0₅consumption involves fertilizers industry. Although there are many technologies available to produce different liquids of phosphatic fertilizers, so that phosphoric acid is not unavoidable intermediate.

Phosphate   ore   are   of   two   major   geological   origins.

(1) Sealimentary

(2) Igneous & Metamorphic.

The most easily mined phosphates are found in the great sealimentary basins. Generally these sealimentary deposits are association with matter devised from linings creatures thus they contains organic compound most phosphate ore, whatever their origin. They have to be concentrated before they can be consumed or sold.

At the benefaction or concentrated different technologies may be used to treat the same ore for removal of signal or associated impurities. This of rise to further varieties in the finished is concentrated product. It is clear therefore that phosphoric acid technology having to rely on row material of great and permanently fluctuating composition.

Phosphoric acid merely number of continuous series of amorphous condensed phosphoric acid which extended from pure phosphorous pentaoxide (P₂0₅) to 0 phosphoric acid. The HCI processes are more economical in India because of availability of chlorine and due to scarcity of native sulphate and H2S04.

In early days, small quantities of phosphoric acid were produced by leaching super phosphate with a weak H2S04 but this was letter abandoned in favour of direct production of phosphoric acid from phosphoric rock or bones.

Older plants aquitated phosphate rock with 30% to 40% H₂S0₄ in batch tanks and then separated the phosphoric acid from gypsum on fitter bed requirements were that the fitter or presses became dogged.

Filtration was slow, excessive quantities of water were used to wash residue and the filter had to be continuously cleaned and frequently repaired because of extremely corrosive nature of the acid.

The first and most probably most important attempt to modernise chemical engineering application of this process and to make it feasible for large quantity production was by the application of continuous counter current decantation using Dorr-type of C- air lift aquitator and it is this system of continuous decantation which has come to know as the Dorr system.

The maximum strength of acid obtained with his counter current decantation method washing was around 20% to 22% P₂0₅. The recoveries were high and labour requirement were low, but the plant costs were considered due to large equipment and the tremendous amount of load. And building requirement.

Nordengren   and     his     associates     first     attempted   to produce directly a very strong 40% to 50% P₂0₅ and this lead the production of anhydrous calcium sulphates they carried out the digestion under pressure and at elevated temperature but the problems of suitable MOC was serious and filtration of this strong hot acid extremely difficult.

The darision chemical corporation has also proposed a very novel method of producing cone. Fluorine H₃P0₄. It is claimed that an acid with upto 54% P₂0₅ can be produced by this process.

The process following a very new approach to this problem has been proposed by Jhon-N olerian for producing high cone, and high purify H₃P0₄ or alternatively a high analysis material for uses distance shipment. This can be used for production of cone. H₃P0₄by digestion with a mix of cone. H₂S0₄ and 60% H₃P0₄ giving a pyrophosphoric acid. Which rapidly hydrates to 0- H₃P0₄ acid. The calcium sulphate is filtered off and washed and it is eliminate that 70% H₃P0₄ can be produced.