GasificationGasification is a process that converts biomass- or fossil fuel-based carbonaceous materials into gases, including as the largest fractions: nitrogen (N2), carbon monoxide (CO), hydrogen (H2), and carbon dioxide (). This is achieved by reacting the feedstock material at high temperatures (typically >700 °C), without combustion, via controlling the amount of oxygen and/or steam present in the reaction. The resulting gas mixture is called syngas (from synthesis gas) or producer gas and is itself a fuel due to the flammability of the H2 and CO of which the gas is largely composed.
Coal gasCoal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. It is produced when coal is heated strongly in the absence of air. Town gas is a more general term referring to manufactured gaseous fuels produced for sale to consumers and municipalities. The original coal gas was produced by the coal gasification reaction, and thus the burnable component consisted of mixture of carbon monoxide and hydrogen in roughly equal quantities by volume. Thus, coal gas is highly toxic.
CharcoalCharcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, called charcoal burning, often by forming a charcoal kiln, the heat is supplied by burning part of the starting material itself, with a limited supply of oxygen. The material can also be heated in a closed retort. Modern "charcoal" briquettes used for outdoor cooking may contain many other additives, e.
Water gasWater gas is a kind of fuel gas, a mixture of carbon monoxide and hydrogen. It is produced by "alternately hot blowing a fuel layer [coke] with air and gasifying it with steam". The caloric yield of this is about 10% of a modern syngas plant. Further making this technology unattractive, its precursor coke is expensive, whereas syngas uses cheaper precursor, mainly methane from natural gas. Synthesis gas is made by passing steam over a red-hot carbon fuel such as coke: (ΔH = +131 kJ/mol) The reaction is endothermic, so the fuel must be continually re-heated to maintain the reaction.
Producer gasProducer gas is fuel gas that is manufactured by blowing through a coke or coal fire with air and steam simultaneously. It mainly consists of carbon monoxide (CO), hydrogen (H2), as well as substantial amounts of nitrogen (N2). The caloric value of the producer gas is low (mainly because of its high nitrogen content), and the technology is obsolete. Improvements over producer gas, also obsolete, include water gas where the solid fuel is treated intermittently with air and steam and, far more efficiently synthesis gas where the solid fuel is replaced with methane.
Wood gas generatorA wood gas generator is a gasification unit which converts timber or charcoal into wood gas, a producer gas consisting of atmospheric nitrogen, carbon monoxide, hydrogen, traces of methane, and other gases, which – after cooling and filtering – can then be used to power an internal combustion engine or for other purposes. Historically wood gas generators were often mounted on vehicles, but present studies and developments concentrate mostly on stationary plants.
PyrolysisThe pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. Temperature can be understood as thermal vibration. At high temperatures, excessive vibration causes long chain molecules to break into smaller molecules. The word is coined from the Greek-derived elements pyro "fire", "heat", "fever" and lysis "separating". Pyrolysis is most commonly used in the treatment of organic materials. It is one of the processes involved in charring wood.
Coke (fuel)Coke is a grey, hard, and porous coal-based fuel with a high carbon content and few impurities, made by heating coal or oil in the absence of air—a destructive distillation process. It is an important industrial product, used mainly in iron ore smelting, but also as a fuel in stoves and forges when air pollution is a concern. The unqualified term "coke" usually refers to the product derived from low-ash and low-sulphur bituminous coal by a process called coking.
AnthraciteAnthracite, also known as hard coal and black coal, is a hard, compact variety of coal that has a submetallic lustre. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is the highest ranking of coals. Anthracite is the most metamorphosed type of coal (but still represents low-grade metamorphism), in which the carbon content is between 86% and 97%. The term is applied to those varieties of coal which do not give off tarry or other hydrocarbon vapours when heated below their point of ignition.
SyngasSyngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide, in various ratios. The gas often contains some carbon dioxide and methane. It is principally used for producing ammonia or methanol. Syngas is combustible and can be used as a fuel. Historically, it has been used as a replacement for gasoline, when gasoline supply has been limited; for example, wood gas was used to power cars in Europe during WWII (in Germany alone half a million cars were built or rebuilt to run on wood gas).
