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.

By thermogravimetric analysis (TGA), the influences of different catalysts on the ignition and combustion of municipal solid waste (MSW) have been investigated in this paper. MSW combustion can be divided into two steps. One is the emission and combustion of volatiles, and the second is the combustion of char. The existence of catalysts in the first step enhances the emission of volatiles from the MSW. When the concentration of volatiles around the MSW is high enough, the MSW ignites. The action of catalysts in the second step of MSW combustion may be as a carrier of oxygen to the MSW char. Two indices have been used to compare the characters of ignition and combustion of MSW under different catalysts. One is the temperature when the rate of conversion of the MSW is at 5%, while the other is the combustion when the temperature is at 850℃ in the TGA system. By comparing the different values of the two indices, the different influences of the catalysts on the ignition and combustion of MSW have been studied.

The influences of alkali and alkali-earth salts on the combustion of municipal solid waste (MSW) have been studied by thermogravimetric analysis (TGA). In the presence of alkali and alkali-earth salts, the combustion of MSW become easier than that of non-catalyzed MSW. By comparing the different temperatures when CRCM (conversion ratio of combustible matter) is 5%, and CRCM when temperature reaches 1123 K, the different influences of catalysts on the ignition and burn off of MSW can be obtained. The kinetic model of catalytic combustion has also been investigated in this paper. The catalytic importance sequence to ignition of MSW is described as: CaO-CaCl24KOH4K2CO34KCl4Na2CO34MgO 4NaOH4BaCO34CaO. The catalytic importance sequence to burn off of MSW is described as: Na2CO34NaOH4 CaO-CaCl24MgO4KCl4K2CO34KOH ¼ BaCO34CaO. According to the activation energy of combustion, the catalytic importance sequence for the first combustion process is described as KOH4 > K2CO34 > NaOH4 > CaO2 > CaCl24 > Na2 > CO34 > MgO4 > KCl4 > Ba > CO34 > CaO, the catalytic importance sequence for the second combustion process is described as KOH4 > MgO4 > NaO > H4 > CaO2 > CaCl24 > Na2 > CO34 > CaO4 > KCl4 > K2 > CO34 > BaCO3.

Pyrolysis of waste tyres was carried out with a two-stage bed reactor. Thewaste tyres were first pyrolysed in a fixed bed reactor, and then the evolved pyrolysis gases were passed through a secondary catalytic reactor filled with two types of zeolite catalysts, which were ultrastable Y-type (USY) and ZSM-5 catalyst. The catalytic temperatures were examined to determine their influence on the yield of product from the pyrolysis-catalyst of waste tyres. The results indicated that with the increase of catalytic temperature, the gas yield increased at the expense of oil yield. The light fractions (<220 8C) distilled fromthe derived oils with the two catalystwere analyzed by gas chromatography/mass spectrometry (GC/MS). It showed that there was a dramatic increase in the concentration of single ring aromatic compounds in the light fractions of the derived oils after catalysis. For example, toluene reached a value in the light fraction of 11.62 wt%, benzene 1.6 wt%,m/p-xylene 12.27 wt%and o-xylene 4.42 wt%, with the catalysis ofUSY catalyst, at the pyrolysis temperature, catalysis temperature and catalyst/tyre ratio of 500, 400 8Cand 0.5, where the light fraction was about 71 wt%in the derived oil. The yield of aromatic hydrocarbons in the derived oils were related to the different properties of the two catalysts such as the pore size which influenced the selectivity, and the silica/alumina (Si/Al) ratio which influenced the number of active sites on the catalyst surface.

In this paper, an ultrastable Y-type (USY) zeolite was investigated with two-staged pyrolysis-catalysis of waste tyres. Waste tyres were pyrolysed in a fixed bed reactor and the evolved pyrolysis gases were passed through a secondary catalytic reactor. The main objective of this paper was to obtain high concentration of certain aromatic hydrocarbons suitable to be used as a chemical feedstock rather than a liquid fuel, and the influence of catalyst/tyre ratio on the product yield and composition of derived oils. The light fraction (boiling point < 220℃) was distilled from the derived oil prior to be analyzed with gas chromatography/mass spectrometry (GC/MS). It showed that the increase of catalyst/tyre ratio resulted in high yield of gas at the expense of the oil yield. The high catalyst/tyre ratio favored to increase the concentration of light fraction (<220℃) in oil. Increasing the catalyst/tyre ratio resulted in significant changed in the concentration of benzene, toluene, xylenes and the alkyl aromatic compounds. For benzene and toluene, the highest concentration was obtained at the catalyst/tyre ratio of 0.5. The concentration of xylenes increased with the increasing of catalyst/tyre ratio.

A zeolite catalyst of ultrastable Y-type (USY) was investigated in the research of two staged pyrolysis-catalysis of scrap tyres. Scrap tyres were pyrolysed in a fixed bed reactor and the evolved pyrolysis gases were passed through a secondary catalytic reactor. The main objective of this paper was to investigate the effect of zeolite USY on the yield of products and the composition of derived oil. The influences of several parameters such as pyrolysis temperature, catalytic temperature, catalyst/tyre ratio, heating rate, etc. on the yield of the derived oil, char and gas were investigated. It showed that the increase of catalytic temperature and catalyst/tyre ratio resulted in high yield of gas at the expense of the oil yield. For example, when the catalyst/tyre ratio increased from 0.25 to 1.0, the yield of gas increased from 30.5 to 49.9 wt.%, and the oil yield decreased nearly two-fold from 31.6 to 12.7 wt.%. The concentration of light naphtha (boiling point < 160℃) was also investigated in this study. And the high catalyst/tyre ratio favored to increase the concentration of light naphtha (<160℃) in oil. In order to study the composition of derived oil, a distilled fraction (<280℃), which was 92.5 wt.% of the oil obtained from catalytic pyrolysis of scrap tyre at a pyrolysis temperature, catalytic temperature and catalyst/tyre ratio of 500, 400℃ and 0.5, respectively, was analyzed with gas chromatography/mass spectrometry (GC/MS). The distillate was found to contain 1.23 wt.% benzene, 9.35 wt.% toluene, 3.68 wt.% ethylbenzene, 12.64 wt.% xylenes, 1.81 wt.% limonene and 13.89 wt.% PAHs, etc., where the single ring aromatics represented a significant potential use as chemicals.