13-06-2012, 11:11 AM
Air Blowing of Bitumen &Extraction of Aromatics
AIR BLOWING OF BITUMEN.pptx (Size: 121.08 KB / Downloads: 74)
What is air blowing?
This is an oxidation process which involves the blowing of air through the asphalts, either on a batch or a continuous basis, with the short residue at a high temperature.
What is the Feed ?
Residuum's of vacuum distillation unit
Deasphalting operations
Solvent extracts
Objective:(Why it is done?)
Bitumen production by straight run vacuum distillation does not meet the market product quality requirements.
To Produce different better grades of Bitumen having qualities such as ductility penetration index API gravity.
Blowing will yield a harder and more brittle bitumen (lower penetration, higher softening point, high molecular)
Process description
Asphalt from various sources are mixed and heated to a temperature of 200 -2100C and send to the reactor.
Air is blown through the bitumen by means of an air distributor located at the bottom of the column. The air is not only the reactant but also serves to agitate and mix the bitumen.
During oxidation temperature increases rapidly and hence cooling coils are made available with reactors.
Straight chain hydrocarbons are dehydrogenated to form polycondensed aromatic hydrocarbons of high molecular wt during air blowing
Steam and water are sprayed into the vapour space above the bitumen level, the former to suppress foaming and dilate the oxygen content of waste gases and the latter cools the vapours to prevent after-burning.
Gases are allowed to escape into refinery combustion system after being stripped from water.
Product i.e. air blown bitumen is obtained from the bottom of reactor.
Other product Cut back bitumen-obtained by blending with suitable solvents(basically liquid bitumen)