Manufacture Of H2so4 Past Times Contact Process

Manufacture of H₂SO₄  By Contact Process.

"Manufacture of H2SO4  By Contact Process" There are ii major processes for the Manufacture of H₂SO₄ on Commercial-scale:

1. Lead Chamber Process.
2. Contact Process.

But nosotros are to hash out entirely the "contact process".

Contact Process.

Principle of contact process:

Sulphur dioxide is obtained past times burning of sulphur or atomic set out 26 pyrites. SO₂ is converted into SO₃ . SO₃ So formed is dissolved into sulphuric acid to larn oleum or pyrosulphuric acid, which is diluted amongst H2O to larn sulphuric acid of required concentration.

Conditions for the maximum yield of SO3:

The conversion of SO₂ to SO₃ is a reversible exothermic process

According to Lechatelier's principle, the next conditions, should move fulfilled to larn the maximum yield of SO₃.

Temperature:

Optimum temperature betwixt 400 - 500°C is maintained, in addition to hence the reaction may occur amongst a reasonable speed.

Pressure:

High line per unit of measurement area is required to favor the reaction to the forrard direction. Mostly the gases are given the line per unit of measurement area of 2 atmospheres.

Excess of Oxygen:

A slight excess of oxygen inwards the reaction mixture Of SO₂ in addition to O₂ favours the reaction towards the forrard direction. The best results are obtained when the ratio of O₂ to SO₂ is 3:2.

Catalyst:

At 400 - 500°C the charge per unit of measurement of reaction is rattling depression because the reaction is exothermic. In fellowship to keep a reasonable some normally used catalysts are:

1. Fe₂O₃ amongst a petty total of CuO.
2. V₂O₅.
3. Pt – MgSO₄.

But now-a-days V₂O₅ is used because it is cheaper in addition to is non easily poisoned. Anyhow, V₂O₅ cannot to recovered afterwards use.

Chemical Reactions in H₂SO4 Manufacture.

Following are the major chemic reactions.

Plant Uses:

The constitute which is used inwards the contact process is sketched below inwards the shape of a menses canvas diagram.

Procedure:

The constitute which is used for the grooming of H₂SO₄ is consisted of iv major parts:

1. Sulphur burners.
2. Purification unit.
3. Preheater in addition to contact tower
4. Absorption tower.

Let us hash out these units i past times one.

Sulphur burners.

In sulphur burners, SO₂ is produced from sulphur or atomic set out 26 pyrites (FeS2)

Purification Unit.

The gases which nosotros larn from sulphur burners contain

1. Sulphur dioxide = 7%
2. Oxygen = 10%
3. Nitrogen = 83%

But at that topographic point is a lot of impurities as

1. As₂O₃.
2. Sulphur dust.
3. H₂SO₄ fog.

All these impurities human activeness equally a toxicant for the catalytic surface. In fellowship to purify SO₂ from impurities next stages are necessary.

Dust Remover:
Heavy dust particles are removed. For this utilisation mechanical atmospheric precipitation is carried out amongst the help of steam.
Cooling Pipes:
The gases are cooled upward to 100°C inwards this unit.
Scrubber:
The cooled gases are washed past times a spray of water SO₂ gas is non absorbed past times H2O at high temperature.
Drying tower:
The wet which is carried past times the gases from the scrubbers is removed past times concentrated H₂SO₄. The tower is packed amongst coke or flintstone stone. H₂SO₄ is sprayed from the top.
Arsenic Purifier:
This comprise precipitated Fe(OH)3, which is placed on horizontal shelves. It absorbs As₂O₃.
Testing Box:
A potent beam of low-cal is thrown against the gases inwards fellowship to banking concern check that the gases are absolutely complimentary from dust and As₂O₃.

Contact Tower.

First of all the gases are sent to preheater, where the gases are heated upward to 400 - 500°C. 

The hot gases immediately piece of occupation into into an atomic set out 26 cylinder, which is called a contact converter or tower. It is fitted within amongst vertical atomic set out 26 tubes. These tubes are packed amongst platinised asbestos catalyst.

The incoming gases circulated some the hot tubes in addition to SO2 is converted to SO3.

This reaction is highly exothermic. The oestrus in addition to hence produced raises the temperature to most 500°C. But the charge per unit of measurement of menses of the gases is in addition to hence adjusted that the temperature of converter is kept some 400 - 500°C.

Absorption Unit.

The SO3 obtained from the contact tower is sent to the absorption tower from the bottom. It meets the descending steam of conc. H₂SO₄. It forms oleum or fuming sulphuric acid. It is diluted amongst the calculated quantity of H2O to get H₂SO₄ of required concentration