Primary Gas

(or semicoking gas), a combustible gas formed upon low-temperature dry distillation of solid fuels. The composition and yield of primary gas depend on the nature of the fuel used and on the semicoking method.

The main combustible components of primary gas are methane (20–50 percent), hydrogen (15–20 percent), carbon monoxide (7–10 percent), and unsaturated hydrocarbons (7–15 percent). The noncombustible inert component is carbon dioxide, the content of which may reach 50 percent in the distillation of brown coals and peat. The yield of primary gas varies from 80 to 100 cu m per ton and the heat of combustion ranges from 8 × 10³ to 34 × 10³ megajoules per cu m, or 2,000–8,000 kcal per cu m. Primary gas is usually used at its site of production as a gaseous fuel.