Air Blown Bitumen Process
Last updated: 2026-10-01
Air Blown Bitumen Process: How Oxidation Turns Penetration Grade into Industrial Grade
Air blowing (oxidation) converts 1 metric ton of penetration-grade bitumen (60/70 or 80/100 pen) into approximately 0.92–0.97 tons of blown bitumen at 240–280°C, with air injected at 30–120 m³/hour per ton for 4–12 hours. The process raises softening point from ~45°C to 85–140°C and lowers penetration from 60–70 dmm to 10–40 dmm, producing industrial grades used in roofing, waterproofing, and pipe coatings. Blown bitumen typically trades at USD 380–520 per metric ton FOB, a 10–20% premium over penetration grade feedstock.
What Is the Bitumen Blowing Process?
Bitumen blowing is a controlled oxidation reaction. Refiners feed vacuum residue or penetration-grade bitumen into a blowing still, heat it to 240–280°C, and sparge air through the mass. Oxygen reacts with hydrocarbons, forming asphaltenes, increasing molecular weight, and hardening the product. The output — oxidized or "air blown" bitumen — is graded by softening point and penetration, not by the standard pen grades used for paving.
- Feedstock: vacuum residue, 60/70 pen, or 80/100 pen bitumen
- Catalyst (optional): ferric chloride (FeCl₃) at 0.1–0.5% by weight to accelerate reaction
- Air rate: 30–120 m³/hour per ton of bitumen
- Temperature: 240–280°C (above 300°C risks cracking and fire)
- Batch time: 4–12 hours depending on target grade
- Yield loss: 3–8% (light volatiles, off-gas)
| Variable | Typical Range | Effect on Product |
|---|---|---|
| Temperature | 240–280°C | Higher temp = faster reaction, harder product |
| Air rate | 30–120 m³/h/t | Higher rate = shorter cycle, more oxidation |
| Reaction time | 4–12 hours | Longer time = higher softening point |
| Catalyst (FeCl₃) | 0.1–0.5 wt% | Cuts cycle time 20–40% |
| Feedstock pen | 60/70–80/100 | Harder feed = harder finished grade |
Blown Bitumen Grades and Specifications
Oxidized bitumen is specified by softening point (ring and ball) and penetration at 25°C. The most traded grades in export markets are 115/15, 105/35, 95/25, and 90/40. The "115/15" label means softening point ≥115°C and penetration ≤15 dmm.
| Grade | Softening Point (°C) | Penetration (dmm, 25°C) | Primary Use |
|---|---|---|---|
| 115/15 | 112–118 | 10–20 | Roofing membranes, damp-proofing |
| 105/35 | 102–108 | 30–40 | Pipe coating, mastic asphalt |
| 95/25 | 92–98 | 20–30 | Waterproofing, adhesives |
| 90/40 | 88–92 | 35–45 | Industrial coatings, sealants |
| 85/25 | 83–87 | 20–30 | Specialty membranes |
- Softening point test: ASTM D36 (ring and ball)
- Penetration test: ASTM D5 (100 g, 5 s, 25°C)
- Solubility: ≥99.0% in trichloroethylene (ASTM D2042)
- Flash point: ≥230°C (ASTM D92) — safety-critical in shipping
Batch vs. Continuous Blowing
Refiners choose between batch blowing (small to mid plants) and continuous blowing (large export plants). The economics differ sharply.
| Parameter | Batch Process | Continuous Process |
|---|---|---|
| Capacity | 20–150 t/day | 300–1,500 t/day |
| Cycle time | 4–12 h per batch | Continuous, 24/7 |
| Labor | Higher (per-batch control) | Lower (automated) |
| Energy use | 1.5–2.5 GJ/t | 0.9–1.6 GJ/t |
| Product consistency | Good with tight control | Excellent, narrow spec bands |
| CAPEX | USD 0.5–2 million | USD 5–20 million |
| Best for | Niche grades, small orders | Bulk export, standard grades |
- Batch advantage: flexibility to switch grades between batches (e.g., 115/15 then 90/40)
- Continuous advantage: 15–30% lower unit cost at scale
- Hybrid setups: batch blowing with continuous air supply dominate mid-tier plants in the Middle East and Asia
Production Economics: Cost Breakdown
For a Middle East or Asian producer running 60/70 pen feedstock, the all-in cost of blown bitumen is typically USD 340–470 per ton, before freight and margin. The numbers below assume a 500 t/day continuous line.
| Cost Component | USD per Ton | Share of Cost |
|---|---|---|
| Feedstock (60/70 pen) | 300–400 | 75–82% |
| Fuel/energy | 25–45 | 6–10% |
| Labor and overhead | 10–20 | 3–5% |
| Catalyst and chemicals | 2–8 | 1–2% |
| Maintenance | 8–15 | 2–3% |
| Yield loss (4%) | ~14 | 3–4% |
| Total | 340–470 | 100% |
- Energy is the swing factor: plants running on natural gas at USD 3–5/MMBtu hold a 5–8% cost edge over diesel-fired units
- Yield loss matters: every 1% yield improvement on a 500 t/day line is worth roughly USD 550,000/year at a USD 450/t selling price
- Freight to Europe/Asia: USD 40–90/t in bulk, USD 60–120/t in drums or bags
Quality Control and Testing
Off-spec blown bitumen is a costly claim. Exporters run a fixed QC protocol per batch or shift.
- Softening point: every 2 hours during blowing (ASTM D36)
- Penetration: every 4 hours (ASTM D5)
- Flash point: once per batch (ASTM D92) — mandatory for IMO/IMDG shipping
- Solubility: once per batch (ASTM D2042)
- Density at 25°C: typically 1.01–1.06 g/cm³
- Loss on heating: ≤0.5% (ASTM D6)
Blown bitumen can be shipped in bulk (200°C heated tankers), drums (150–180 kg net), bags (25–50 kg), or jumbo bags (1,000–1,200 kg). Bulk is cheapest per ton but requires heated logistics; bagged material serves small markets in Africa and Southeast Asia.
FAQ: Bitumen Blowing Process
What is the bitumen blowing process in simple terms?
It is the injection of air into hot bitumen (240–280°C) to oxidize it, raising the softening point and reducing penetration. The result is a harder, more heat-resistant bitumen used in roofing and waterproofing.
How long does air blowing bitumen take?
A batch cycle runs 4–12 hours depending on target grade and air rate. Catalyzed processes using 0.1–0.5% FeCl₃ can cut this by 20–40%, so a 115/15 grade may take 5–7 hours instead of 9–10.
What is the yield of blown bitumen from penetration grade?
Yield is 92–97% by weight from 60/70 or 80/100 pen feedstock. The 3–8% loss is light hydrocarbons and off-gas burned or recovered in the thermal oxidizer.
What is the difference between penetration grade and blown bitumen?
Penetration grade (e.g., 60/70) has a softening point near 45–52°C and is used for roads. Blown bitumen has a softening point of 85–140°C and is used for industrial waterproofing, roofing, and coatings.
How much does blown bitumen cost per ton in 2024–2025?
Export prices run USD 380–520 per metric ton FOB, depending on grade, packaging, and origin. Bulk 115/15 from the Middle East sits at the lower end; bagged 90/40 from Asia can exceed USD 500.
Price Your Blown Bitumen Cargo with 6Tar
Before you commit to a blown bitumen order — bulk, drum, or bagged — run the numbers. The 6Tar cost calculator gives you landed cost per ton door-to-door: FOB price, ocean freight, drum or bag packaging, insurance, port charges, and inland delivery in one screen. Exporters and buyers use it to compare 115/15 vs. 105/35 offers across origins in under two minutes. [Open the 6Tar cost calculator →]