Biturox process

Bitumen is a naturally occurring black residue that is mainly used for asphalt. Bitumen is made up of naturally decomposing organic materials and is often referred to as asphalt. The traditional method of refining crude oil to create bitumen is through direct distillation from the heavy oils. (See. Bitumen) Atmospheric distillation as well as vacuum distillation are used to separate the lighter petrochemical and fuel fractions from the non-boiling bitumen at the bottom. The atmospheric residue is heated to temperatures between 300 and 350 degrees CELSIUS and fed into a vacuum distillation column which allows the fractions to separate and leave the heaviest fraction, namely the short residue, to be left behind. The Biturox® method of bitumen processing makes use of a different method known as Oxidation, to produce quality bitumen. Oxidation chemically changes crude oil residues and other refinery feedstock so that bitumen can be produced. A higher quantity of bitumen can be yielded by chemical conversion of middle crude oils that are preferably used at refineries to produce fuels. The Biturox® system allows a constant control over the whole process of production and the properties of the bitumen can be custom tailored.

History

The Biturox® process was first developed by OMV in Austria in the early 1970s and Pörner Ingenieurgesellschaft mbH (web), situated in Vienna Austria, holds the protected rights and licencing for designing Biturox® plants. By 1978 the first Biturox® license was granted by Pörner to NIOC Isfahan in Iran. Since then the Pörner group has been planning as well as implementing more than 40 Biturox plants all over the world.

Technology

In contrast to conventional bitumen production, the Biturox method chemically integrates the bitumen by air oxidisation, this process is known as “Mild Air Blowing”. The bitumen quality, being refined, depends on the harmonized balance of its chemical components, Saturates, Aromatics, Resins and Asphaltenes. The Biturox® process is utilised to create and preserve valuable aromatic components and to optimise the ratio between Resins and Asphaltenes. Besides the residue obtained from vacuum distillation, a variety of high molecular weight refinery components can be used as feedstocks for the Biturox® Process. The key element of the Biturox® process is the loop reactor. It is an air-lift reactor with an agitator which processes the thermo-chemical conversion of selected raw materials by air oxidation.

The parameters of the process, eg. pressure and temperature, can be controlled exactly and are able to occur under continuous and repeatable conditions. Oxygen utilisation is kept just below 100 per cent in the reactor, resulting in safe operation and short processing times and low operating costs. Due to gentle and efficient oxygen introduction, local overheating and thermo-cracking in this process is limited resulting in a minimum of coke build up. The shorter residence time in the reactor also allows for the saving of the valuable resin components. Due to an optimum air/feed ratio, Biturox® Plants yield less off-gas than traditional blowing units, which minimizes atmospheric emissions. The reactor off-gas, consisting of nitrogen, steam and some light hydrocarbons, is lead through a knockout drum which separates the hydrocarbons and through an incinerator to combust the waste components. In specialised cases heat recovery and desulphurisation can be used to treat and utilise the off-gas.

The resulting bitumen from the Biturox process shows reduced thermal susceptibility. Tailored special bitumen grades (so called Multi-grades) behave like stiff grade bitumen at high temperatures and soft grade at low temperatures. This allows for a longer service life for the roads and minimizes the cost because the road layers can have a reduced thickness.

Research and Development

Feedstocks from refineries can be very different so individual research and development needs to be conducted for each Biturox® application. Through this process the chemical composition of the bitumen can be adjusted to create the best quality bitumen possible at the most economical condition. The Biturox Bitumen Research Center is situated near the OMV refinery in Vienna, Austria and uses the experience and knowledge gathered through hundreds of pilot tests executed on the most representative crude bases. Over 30 years of knowledge can be accessed from this data bank and utilised for each project.

Tailored solutions can be designed following the in-depth pilot studies that involve the following:

• Screening of the raw materials
• Establishing the best feedstock composition
• Oxidation tests in the pilot plant
• Verifying the processing parameters as a basis for the plant design
• Production of reference samples of each of the products

Features of bitumen produced by the Biturox Process

• Increased stiffness against rutting
• High resistance against fatigue
• Better adhesive properties
• Better resistance to ageing
• Good compatibility for polymers and ability to emulsify