Grey System Theory is applied to study the influence of the coal properties on the emissions of nitric oxides from fluidized bed coal combustion. Grey correlation coefficients for the emissions of nitrous oxides and nitric oxides in relation to the contents of nitrogen and carbon, fixed carbon, volatile matter, nitrogen fractions in char, and volatile, and the O/N ratio, fuel ratio, etc., are calculated. A large correlation coefficient of coal property means that the emission of nitrous oxides and nitric oxides is in close relation with the relevant property, in other words, the relevant coal property is the main affecting factor for nitrous oxides and nitric oxides formations. The calculation results show that the N2O emission is determined mainly by the nitrogen carbon content, fixed carbon, and the nitrogen fraction in char. While the carbon content, fixed carbon, nitrogen fraction in char mainly influence the NOx emission and nitrogen and hydrogen contents, it suggests that combustion of high rank coal with high nitrogen content in fluidized bed emits more nitrous oxides and nitric oxides. The O/N and fuel ratios are not important for emissions of nitrous oxides and nitric oxides compared with other factors. And the results are in agreement with experimental data.

Kinetics of natural gas reburning is modeled on the basis of GRI3.0 and the method of Gear. The calculation results indicate that the model agrees with experiments. HCN, NHi and HCCO play an important role in the reburning system. Injecting NH3 and increasing the fraction of HCCO in the reburning system will promote NO reduction. Injecting natural gas at the places wherein the fraction of NO is highest is a benefit to de-NOx. There exists an optimal value of ratio of natural gas: NO for reburning system. The influences of temperature, excess oxygen ratio and pressure are also discussed in the reburning system.

In this paper, many rules about N2O and NOx emission under fluidized bed combustion conditions were found by experiments. The research results indicate that CaO, CaSO4, Fe2O3 and char have important influence on decomposition of N2O; co-combustion of coal and biomass are effective measures to low N2O and NOx emission.