Nitric oxide formation, coal

The control of nitric oxide emission from a fluidized bed coal combustor has been extensively investigated and it was found that the level of nitric oxide emission was determined by the relative contribution of nitric oxide formation and reduction processes. (l.,2) There is a great need for quantitative information concerning the rate of these processes.(2)... 

Badger and Dryden (1939) studied aerosol formation in batch and flow reactors. They were interested in the aerosol that forms in coal gas which also contains trace amounts of nitric oxide. The nitric Oxide reacts with diolefins in the coal gas, such as butadiene and cydopentadiene. to form products of low vapor pressure. These condense and produce a sticky aerosol present at concentrations usually less than 0.5 mg which may foul the gas transfer system. 

Nitric acid oxidation of coal, with or without oxygen, leads to the formation of complex mixtures of the benzenoid or aromatic type of organic acida Nitric acid oxidation of carbohydrates yfelds oxalic acid. Nitric acid of 50-76 per cent concentration at temperatures of 20-40 C oxidizes tetra-hydrofuran to good yields of succinic acid. Oxidation with nitric acid of a secondary aliphatic alcohol or an aliphatic ketone results in fistion of the aliphatic chain at the point of attachment of the functional group accom-... 

Nitrogen in the coal itself also contributes significantly to the formation of gases. Of the nitrogen oxides emitted in power station flue gas, 95% is nitric oxide (NO), which oxidizes rapidly in the atmosphere to form nitrogen dioxide (NO2) (Commission on Energy, 1981). 

Nitric oxide (NOx) is one of the main pollutants in combustion systems and rotary kilns are no exception particularly for pulverized fuel combustion. NOx formation depends on three factors, namely (i) the amount of nitrogen present in the fuel, (ii) the combustion temperature, and (iii) the stoichiometric conditions for the combustion reaction. Hence NOx production is classified into fuel NOx, thermal NOx, and prompt NOx. Some of the mechanisms for the formation of these species during pulverized coal combustion in rotary cement kilns have been described in commercial CFD packages (e.g., FLUENT, CINAR). 

The principal cause of acid rain is the combustion of fossil fuels that produce sulfur and nitrogen emissions. The primary sources are electrical power plants, automobiles, and smelters. Power plants produce most of the sulfur emissions and automobiles most of the nitrogen emissions. Other sources of acid rain include nitrogen fertilizers, jet aircraft, and industrial emissions. Just as in our discussion of ozone, numerous reactions are involved in the formation of acid rain. The process can be understood by considering the transformation of sulfur and nitrogen oxides into their respective acidic forms sulfuric acid and nitric acid. Sulfur, present up to a few percent in fuels such as coal, is converted to sulfur dioxide when the fuel is burned. The sulfur dioxide reacts with water to produce sulfurous acid, H,SO ,, that is then oxidized to sulfuric... 

Similarly, the chemistry of the nitrogen species in coal is also of some importance. Nitrogen oxides (Morrison, 1980) also contribute to the formation and occurrence of acid rain, in a similar manner to the production of acids from the sulfur oxides, yielding nitrous and nitric acids ... 

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