Overview
Producer gas is a combustible mixture obtained by passing air over hot carbonaceous material (coke, coal, charcoal or biomass) so that partial oxidation converts solid fuel into a gas. It is distinct from natural gas and pipeline gases in that it is manufactured on site and has a relatively low energy content per unit volume because of dilution by nitrogen when air is the oxidant.

Typical composition and properties

The fuel is mainly a mixture of carbon monoxide and hydrogen together with large proportions of inert nitrogen and smaller amounts of carbon dioxide and light hydrocarbons. Because air is usually used as the gasifying agent, the resulting gas has a low calorific value and is relatively cool compared with gases produced with pure oxygen or steam.

Production processes and equipment

Producer gas is formed in a gasifier or producer where the solid fuel is heated in a controlled oxygen supply. Common reactor types include fixed-bed (updraft and downdraft), fluidized-bed and entrained-flow designs. The feedstock may be metallurgical coke (made by destructive distillation of coal), raw coal, wood or other biomass.

Uses and historical context

Historically, producer gas supplied lighting, heating and motive power before widespread availability of petroleum fuels and natural gas. During fuel shortages in the 20th century it was used to run internal-combustion engines in vehicles and for stationary power. Today producer gas is still used in some industrial furnaces, small power systems and combined heat-and-power installations where local solid fuels are abundant.

Cleaning, safety and limitations

  • Raw producer gas contains tars, soot, ash and other contaminants requiring filtration and scrubbing for many uses.
  • Carbon monoxide in the gas is toxic, so handling and leak prevention are essential.
  • Compared with oxygen- or steam-blown synthesis gases, producer gas has lower energy density and higher nitrogen content, limiting its suitability where high calorific value is needed.

Terms often contrasted with producer gas include "water gas" (made by passing steam over hot carbon) and "syngas" (a hydrogen–carbon monoxide mixture produced under controlled conditions for chemical synthesis). The choice of process and oxidant determines composition and suitable applications.

Notable fact: producer gas systems can provide fuel from local solid resources but require thorough gas cleaning and careful design to be efficient and safe.