Sulfuric Acid as an Dehydrating Agent

Concentrated sulfuric acid readily absorbs water from the air (desiccating or dehydrating agent). It is thus used to dry the air used in the contact process. Hydrated crystals can be dehydrated with concentrated sulfuric acid.

Industrial use of Sulfuric Acid as a Dehydrating Agent

Sulfuric acid is used in a variety of industrial processes two known processes covered in the syllabus include the dehydration of ethanol and esterification. Sulfuric acid can be used as a dehydrating agent in the contact process as well.

Hydrous Air + H2SO4(l) -> Anhydrous Air H2O*H2SO4

CuSO4*5H2O(s) -> CuSO4(s) + 5H2O(l)

Carbohydrates such as sugars can also be dehydrated.
C12H22O11(s) -> 12C(s) + 11H2O(g)
C(s) + 2H2SO4(l) -> CO2(g) + 2SO2(g) 2H2O(l)

The mixture caramelises, turning brown then black (black porous solid is mainly carbon). The heat from the reaction turns water to steam, causing the mass to expand. Carbon react with sulfuric acid in a second step to produce sulfur dioxide, carbon dioxide and water.
Concentrated sulfuric acid is also used to dehydrate ethanol to produce ethene, and is also a common catalyst to manufacture esters.