Manufacture of Sulphuric acid - contact process

Question 1

Production of So2 - Units behind it

Answer 1

Blower - For passage of purified air

Sulphur or pyrite burners - for production of Sulphur dioxide by burning sulphur or iron pyrites

Question 2

Purification unit - things behind it

First 3

Answer 2

Dusting tower - For removal of dust particles by downward blow of steam
cooling pipes - For cooling the gas by passage through isolated pipe
Scrubbing tower - further removal of impurities by downward spray of water

Question 3

Purification unit - things there

next 3

Answer 3

Drying tower - for drying moist gas by downward spray of H2SO4
Arsenic purifier - For removing arsenic oxide by passage over ferric hydroxide
Testing box - for testing purity of gas by passage of light in darkened room

Question 4

Catalytic oxidation -

things needed

Answer 4

Contact tower - For catalytic oxidation of SO2 to SO3 by passage of sulphur dioxide and oxygen through iron tower packed with Vanadium pentoxide catalyst initially heated to 450*

Question 5

Absorption of SO3 - things needed

Answer 5

For absorption of sulphur trioxide vapours by descending steam of conc.H2SO4

Question 6

Dilution of oleum

Answer 6

Dilution tank - for dilution of oleum by flow of requisite amount of soft water

Question 7

What will be formed when sulphur burnt in air ? The colour of the flame ?

Answer 7

Sulphur dioxide will be formed also some traces of sulphur trioxide
pale blue flame

Question 8

Impurities present in the mixture

Answer 8

dust particles , arsenious oxide

Question 9

What happens if the impurities are not removed ?

Answer 9

It tends to deactivate or poison the catalyst

Question 10

Dust particles are removed in

Answer 10

dusting and scrubbing tower

Question 11

What is the role of excess oxygen in Catalytic reaction ?

Answer 11

Excess oxygen favours the forward reaction

Question 12

Why vanadium pentoxide is preferred to platinized asbestos ?

Answer 12

Since it is comparatively cheaper and less easily poisoned or susceptible to impurities

Question 13

Promoters used -

Answer 13

V2O5 is compressed to threads and mixed with a promoter usually potassium oxide to enhance he activity of the catalyst

Question 14

catalyst only initially heated why ?

Answer 14

Since the reaction is exothermic the heat produced maintains the temp 450 to 500 *C

Question 15

why high pressure is not used even when it favours higher yeild ?

Answer 15

High pressure may cause damage to the lead pipes , resisting tower and decompotion of porous catalyst