Emissions biomass combustion

Polycyclic aromatic hydrocarbons (PAHs, sometimes also called polynuclear aromatics, PNA) are a hazardous class of widespread pollutants. The parent structures of the common PAHs are shown in Fig. 4 and the alkylated homologs are generally minor in combustion emissions. PAHs are produced by all natural combustion processes (e.g., wild fires) and from anthropogenic activity such as fossil fuels combustion, biomass burning, chemical manufacturing, petroleum refining, metallurgical processes, coal utilization, tar production, etc. [6,9,15,18, 20,24,131-139]. 

Jaegle L. Steinberger L. Martin R.V. and Chance K. (2005). Global partitioning of NOx sources using satellite observations Relative roles of fossil fuel combustion, biomass burning and soil emissions. Faraday Discuss., 130, 407 -423, doi 10.1039/b502128f. 

Several issues clearly remain regarding how blending biomass and coal will affect combustion performance, emissions, fouling and slagging propensities, corrosion, and ash salability. Nevertheless, several utilities have tested biomass/coal co-firing in utility boilers and the Electric Power Research Institute funded a study in 1997 to establish biomass co-firing guidelines.580... 

Unterberger S. et al. (1998) Optimisation of the combustion and emission behaviour of wood burning systems - an experimental and numerical approach. Biomass for Energy and Industry, 1456-1459. 

Although the gasifier product itself has low levels of NOx, the total systems emissions of this product must be carefully scrutinized. When clean biogas is eventually burned, NOx will be produced, as it is in most combustion systems with all fuels. The use of biogas rather than solid biomass fuels provides the opportunity to better control the combustion process, which can potentially result in lower NOx emissions. As such, gasification offers potential environmental emissions advantages over combustion alternatives. However, NOx may still occur as the gas is burned, and appropriate NOx control technologies may be needed. 

Methanol also seems to biodegrade quickly when spilled and it dissolves and dilutes rapidly in water. It has been recommended as an alternative fuel by the EPA and the DOE, partly because of reduced urban air pollutant emissions compared to gasoline. Most methanol-fueled vehicles use a blend of 85% methanol and 15% gasoline called M85. Building a methanol infrastructure would not be as difficult as converting to hydrogen. While methanol can be produced from natural gas, it can also be distilled from coal or even biomass. In the 1980s, methanol was popular for a brief time as an internal-combustion fuel and President Bush even discussed this in a 1989 speech. 

Grate-fired combustors are in use for old biomass-fired plant, while fluid bed combustors are rapidly becoming the preferred technology for biomass combustion because of their low NOx emissions. 

A popular small-scale thermal biomass conversion method is combustion in grate furnaces. To meet the emission regulations for such a furnace, the operating conditions and design of the furnace have to be chosen carefully. Numerical models, known as computational fluid dynamics (CFD), can support the making of these choices, provided that accurate sub-models for the phenomena occurring in the oven are available. 

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