Introduction: What is bitumen?

Ever heard of bitumen? Maybe… But what is bitumen exactly? Bitumen is a semi-solid hydrocarbon product produced by removing the lighter fractions (such as liquid petroleum gas, petrol and diesel) from heavy crude oil during the refining process. Bitumen and bituminous products are often used for their adhesive and waterproofing properties and are therefore sometimes referred to as binders. Depending on the application, the climatic and loading conditions that the bitumen will experience in service, different types of bitumen are produced.

Bitumen uses: asphalt and roofing

Bitumen is often used in asphalt production and roofing applications. Its waterproofing and adhesive properties make it a suitable base product for these applications.

Bitumen plays an important role in road construction. Asphalt is a mixture of a bituminous binder with mineral aggregate (stone), sand and filler, typically containing approximately 5%W/W bitumen. There are over 4,000 hot mix asphalt plants in Europe alone, producing some 300 million tonnes of asphalt per year.

Membranes made of bitumen are water repellent and flexible which make them ideal for waterproofing applications. Bitumen membranes are widely used for waterproofing of low slope roofs. It is estimated that bitumen membranes annually cover over 200 million square metres of roof.

Industrial odour control in the case of bitumen fumes

Bitumen are usually stored and handled at temperatures up to 200 – 230°C.  During storage and handling of bitumen at high temperatures, small quantities of bitumen fumes are generated, which are responsible for the typical odour of bitumen. Bitumen fumes contain particulates, hydrocarbons (VOC) and hydrogen sulphide (H₂S). The quantity of fumes depends on the handling and storage temperature of the bitumen.

Table 1: Typical aromatic organic molecules in bitumen fumes

Hydrogen sulphide can concentrate in confined spaces of bitumen storage tanks and escape into the atmosphere during handling. Areas around vents can contain H₂S, resulting in the typical odour of rotten eggs.

Bitumen fume also contains small quantities of Polycyclic Aromatic Hydrocarbon (PAH) compounds and therefore exposure levels should be kept to a minimum to avoid irritation effects for workers handling hot bitumen.

Odour emissions are one of the key concerns for manufacturers of bitumen membranes and asphalt. The industry has implemented several measures for reducing odour output. Examples are the placement of higher stacks, the implementation of fine dust filters, scrubbers, and the covering of storage areas. In some cases these measures are not sufficient and neighbours continue complaining about the odour emissions… DESOTEC’s industrial odour control system is set to tackle persistent odour emissions, even after the initial odour removal measures (like water scrubbing etc.)!

DESOTEC’s odour control system for bitumen fumes

In a European bitumen roofing membranes production plant, air is extracted from several emission points for odour control:

• Stream 1: Air coming from bitumen mixing plant
• Stream 2: Air coming from bitumen waterproof membrane production line
• Stream 3: Air coming from bitumen storage tank

Although this mixed stream was treated with a water scrubber, it was still causing some odour. The process conditions after the wet scrubber were as follows:

• Total flow: 25,000m3/h max
• Temperature: 22°C
• VOC (mainly Alkanes) and H2S removal
  • VOC inlet concentration 50-60 mg TOC/m3
  • Treatment objective: Odour removal
  • Relative humidity: Saturated
  • Pressure: Ambient
  • No dust

An AIRCON^® H filled with AIRPEL 10 with piping and demister was plugged in between the scrubber and the stack. It proved to be an effective odour control system.

Another manufacturing plant had, especially in summer time, odour complaints from the neighbours. The installed scrubbing was not efficient during the summer time to treat the emissions of the production facility. The process conditions after the wet scrubber were as follows:

• Flow: 30,000 m³/h
• Temperature: 30 °C
• Relative humidity: after scrubber (100%)

To solve the seasonal odour emission, the customer selected DESOTEC’s activated carbon mobile filter solution AIRCON^® V filled with AIRPEL 10-4.

Are you in need for an efficient odour control system for your industry? Don’t hesitate to contact us about our tailored odour control solutions!

At DESOTEC’s facilities, all used carbon is analysed so the right measures can be taken for handling and removing the saturated carbon out of the mobile filters. All molecules that were adsorbed on the activated carbon at the customers’ site, are desorbed inside DESOTEC’s reactivation furnaces. These contaminants are then fully destroyed, in accordance with National and European legislation, by an incineration and neutralisation setup. The entire installation and it's emissions are under continuous on-line monitoring, which guarantees that only harmless water vapour is seen exiting the chimney.