流化床中RDF焚烧时CO、SO2和HCl的生成

在非均匀布风流化床中进行了垃圾衍生燃料(RDF)与煤的混烧试验，测量了H2O、CO、CO2、NO、N2O、HCl、SO2等污染物质的排放特性．结果表明与单纯燃烧RDF相比，混烧时的CO生成量大大下降；SO2生成浓度较低，而HCl的生成量比单纯烧煤时明显增加．

Formation of CO, SO2 and HCl during RDF incineration in a fluidized bed

The refuse-derived fuels-RDFhas the advantage of high heating value and is easily combusted. The potential application of RDFis co-firing with coal and instead of some coal in the boiler. The heating value of RDFmay attain 24MJ·kg^-1, similar with that of coal. Due to the high content of volatiles in RDF (more than 70%), a large quantity of volatiles is likely to release during RDFincineration. If the pollutant emissions can not be controlled very well, the limit of environmental standard will not be guaranteed. On the other hand, the contents of harmful elements in coal or RDFare very different. For coal, the content of nitrogen or sulfur is higher and the content of chlorine is very lower, on contrary, to those in RDF (normally with a higher content of chlorine and lower sulfur content). Therefore, during co-firing RDFwith coal, the interaction of pollutants NO_x, SO_x, HCl and ash may occur and the combustion properties of co-firing cannot be predicted only by the results of burning pure coal or pure RDF. The internally circulating fluidized bed (ICFB) is applied to investigate the pollutant emissions during co-firing RDFwith coal. In the ICFB, the air plenum is separated as two equal boxes. Then the primary air separately enters the bed from air boxes with high or low air velocity. Unevenly distributed fluidized air induces a large-size internal circulating flow of solid particles in the dense bed which may improve the properties of lateral diffusion. The cross section of the furnace is 500mm×240mm in the dense phase zone and 800mm×280mm in the freeboard. The total height of the furnace is 4500mm. Concentrations of pollutants in the flue gas were measured by Fourier Transform Infrared (FTIR) spectrometry (Gasmet DX-3000). In the tests, the concentrations of the species, such as H₂O, CO, CO₂, NO, NO₂, N₂O, HCl, SO₂, CH₄, C₂H₂, C₂H₄, C₂H₆ and C₆H₆ were measured online with 2% error. The concentration of oxygen was measured by an oxygen analyzer (TEMET 19) with 0.2% error. The results indicated that when co-firing RDFwith coal, the formation of H₂Owas relatively higher than burning pure coal because of the higher content of hydrogen. The average concentration of H₂Oattains 8% during pure RDFincineration, compared with 4.5% during pure coal combustion. The concentration of COemission during firing pure RDFwas relatively higher and fluctuates sharply. During co-firing RDFwith coal, the formation of COdecreased rapidly and the fluctuation of COconcentration became smaller because of the lower content of volatiles in coal. In pure RDFincineration, the concentration of N₂Owas relatively higher, about 100mg·m^-3. But it was only half of this value during co-firing. The concentration of SO₂ was relatively low because calcium and alkali metals in the ash of coal could absorb SO₂. Due to the higher content of chlorine in RDF, the formation of HCl significantly increased compared with the combustion of pure coal.