Material · draft · confidence 0.88
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claude-sonnet-4-6
A dark, viscous liquid byproduct recovered from raw coke oven gas during the cooling and scrubbing stages of byproduct recovery. Coal tar is a complex mixture of hundreds of organic compounds, predominantly polycyclic aromatic hydrocarbons (PAHs) including naphthalene, anthracene, phenanthrene, pyrene, and benzene. It is a primary feedstock for the tar chemicals industry (producing refined naphthalene, anthracene, pyrene, creosote, and electrode pitch for aluminum smelting anodes), carbon black production, and road binder applications.
Common forms
- Crude coal tar (as recovered from the collecting main)
- Refined coal tar (after distillation into fractions)
- Coal tar pitch (residue after distillation; used for carbon electrode manufacture and roofing)
Common sources
- Recovered from by-product coke oven batteries during carbonization of coking coal
Composition
Complex mixture of ~300 organic compounds. Major classes: polycyclic aromatic hydrocarbons (PAHs, ~60–80 wt%), phenols, pyridines, quinolines, thiophenes, and aliphatic compounds. Key fractions by distillation: light oil (<170°C), carbolic oil (170–210°C), naphthalene oil (210–230°C), wash oil (230–270°C), anthracene oil (270–350°C), pitch (>350°C residue, ~55–65 wt% of tar).
Hazards
- Carcinogenicity — coal tar contains numerous IARC Group 1 human carcinogens (benzo[a]pyrene and other PAHs). Coal tar pitch volatiles are listed as a confirmed carcinogen. Occupational exposure associated with elevated rates of skin, scrotal, and lung cancers.
- Fire hazard — combustible liquid; vapors ignitable above flash point (~60°C).
Properties
- density: Approximately 1.18–1.22 g/cm³ at 20°C.
- viscosity: High viscosity at ambient temperature; must be heated for pumping and processing.
- calorific_value: ~35–38 MJ/kg; historically used as a fuel but now preferentially refined for chemical products.
Connections
Outgoing
- Has hazard → Coke Oven Emissions — Coal tar contains IARC Group 1 human carcinogens (benzo[a]pyrene, other PAHs). Coal tar pitch volatiles are a confirmed occupational carcinogen.
- Manufactured by → Cokemaking — Coal tar is recovered during cooling and scrubbing of raw COG in by-product coke oven operations.
Incoming
- Produces ← Cokemaking — Heavy viscous liquid byproduct recovered from raw COG in by-product ovens. Contains PAHs, phenols, pyridines; refined for tar chemicals, electrode pitch, and carbon black.