Brown coal heating value

Briquettes have a heating value of 16.7-23.4 MJ/kg (7, 200-10,000 Btu/lb) or from 2—3 times the value of a typical brown coal primarily because of the moisture loss. 

Rhenish brown coal has an average ash content of about 4 % (mf), a volatile matter of about 52 % (maf) and a lower heating value of 25.6 MJ/Kg of coal (maf). The final analysis of the coal under maf conditions shows the following average composition ... 

Figure 8. Heating value of the brown coal lithotypes as a...

Lignite (brown coal) is the least mature of the coal types and provides the least yield of energy it is often crumbly, relatively moist, and powdery. It is the lowest rank of coal, with a heating value of 4000-8300 Btu per pound. Most lignite mined in the United States comes from Texas. Lignite is mainly used to produce electricity. 

The lowest rank of coal that contains recognizable plant structures heating value <8300 Btu per pound on a mineral matter-free basis carbon content 60%-70% w/w (dry ash-free basis) often called brown coal in the UK, Europe, and Australia... 

Another potential advantage of low-temperature char involves its production from very low-rank fuels, such as lignite or brown coal. These abundant fuels have very low heat value (Chapters 2 and 9)... 

Many coals contain, or generate, considerable quantities of volatile matter (Chapters 8 and 9) and will also evolve tar at approximately 450°C (840°F). In this simple combustion method, heat is transferred ahead of the flame front by radiation and convection causing the distillation of the volatile tar matter at temperatures below the ignition temperature. The purpose of the secondary air is to bum the volatile matter and in simple appliances it is not difficult to supply the necessary air, but there is rarely sufficient turbulence to mix it with the volatiles and thus the temperature in the zone above the bed can easily fall below the value where ignition is possible. As a result, there may be the emission of a yellow-brown smoke containing pollutants such as hydrocarbons and the oxides of sulfur and nitrogen. 

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