BITUMEN HANDBOOK 2014 - page 12

11
1.1. Bitumen production technologies at ORLEN Asfalt
1.1.1. Production of Paving Grade andMultigrade Paving Bitumens
ORLEN Asfalt manufactures Paving Grade Bitumens and BITREX Multigrade Paving Bitumens using systems
where vacuum residue from crude oil processing is oxidised. They are classified as 
1
semi-blown or air-rectified
bitumens.
Bitumen oxidation is a very complex chemical and physical process. In terms of chemical processes, it involves
intensepolymerisationand condensation leading toparticlegrowth. Chemical reactions takingplace concurrently
produce oxygen compounds, with the associateddehydrogenative condensation causingC-C (carbon-carbon)
bonds to appear. This produces resins and asphaltenes at the expense of naphthenic aromatic hydrocarbons.
The reaction types andmechanism depend on the reaction’s temperature. The physical nature of the reaction
is evidenced by the stripping of lighter hydrocarbons from the liquid to the gaseous phase through steam
distillation. It is an exothermic process, whichmeans that heat is produced by the reaction.
1.1.1.1. Biturox technology vacuum residue continuous oxidation system
PavingGradeandBITREXMultigradePavingBitumens aremanufacturedbyORLENAsfaltmainly in the continuous
oxidation process based on BITUROX® technology, licensed from Austrian company Pörner. The process
involves continuous, uninterrupted feedstock batching to the reactors and continuous discharge of products
to storage tanks. Theprocess continuity ensures product homogeneity. The process is alsomarkedby optimum
utilisation of oxygen for oxidation and excellent hydrodynamic properties of the reaction.
The heart of the system is composed of Biturox® reactors. They are cylindrical, vertical pressure vessels fitted
with a central cylinder and an agitator with three turbines on a single shaft, placed inside the cylinder. Air
forming large bubbles moves upwards inside the cylinder, and is collected at two levels by coalescing plates
andbroken into smaller bubbles by the agitator’s turbines. This renews the reaction surfaces. Intense oxidation
takes place in the entire volume, using less air andover a shorter residence time. The air flow is selected so that
the quantity of oxygen in the off gas is 2÷5% (v/v)
2
. Air movement and operation of the agitator produce
liquid circulation in the reactor – an upward movement in the inner cylinder, and a downward movement
in the external cylinder space. The heat of oxidation is collected from the reactor by the evaporationof process
water, injecteddirectly toprocess air immersionpipes. Thequantityof processwater precisely controls theprocess
temperature. The resultant steam helps to remove undesirable by-products from the bitumen, such as gases
and light oxidised distillate and increases production safety. Bitumen is discharged from the external cylinder
space of the reactor, from the level above the feedstock inlet, and is cooled in bitumen coolers. Subsequently,
it is sent to bitumen storage tanks, where it ismixed and tested for quality. Bitumen distribution to road and
rail tankers takes place at sealed loading stations. The process is controlled by the distributed DCS system.
1) According to Eurobitume’s nomenclature, paving-grade bitumens manufactured by ORLEN Asfalt are “
semi-blown
” or “
air-
rectified
” bitumens, with the Penetration Index lesser than or equal to 2.0, whereas industrial bitumens are (“
oxidised
”)
bitumens, and their Penetration Index is greater than 2.0 [source:
Physical differentiation between air-rectified and oxidised
bitumens. Technical Committee Task Force. Eurobitume, 15.04.2011
]
2) (v/v) means volumetric proportions, whereas (m/m) stands for weight proportions
Bitumen production
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