Experimental Study On Combustion And Contamination Characteristics Of Zhundong Coal In Vertical Cyclone Furnace

The serious problems such as slagging and fouling on heating surface in the power station boilers during burning Zhundong Coal threaten the safe and economical operation of the boiler,which restrict its development and utilization.At present,research on Zhungdong Coal mainly focuses on pulverized coal boilers and fluidized bed boilers,so far there is no research on the use of Zhundong Coal in the slag tap boiler with cyclone furnace at home and abroad.A bench scale facilities of slap tap boiler with vertical cyclone furnace was designed,processed and installed in this study.And a comparative test study of Zhundong Coal was conducted on the slag tap furnace test bench and a dry bottom furnace test bench.Firstly,the coal quality characteristics of a typical Zhundong Coal was analyzed.The results showed that the alkali ratio of the coal ash is large;the ST of the coal ash was only 1140?;the temperature corresponding with 25 Pa·s is less than 1 450?,so it can be seen that the coal is suitable for using liquid ash removal.Then the structural design and thermal calculation of the front chamber of the cyclone furnace were completed according to the characteristics of the cyclone combustion mode.By scanning electron microscopy,energy spectrum analysis and laser particle size analyzer,the physical and chemical properties of the ash samples in furnaces with different slag removal methods in Zhundong Coal were analyzed.The ash samples of different positions along the flue gas flow in the cyclone furnace were taken to study the migration and enrichment of the main elements in the coal ash,and the main elements affecting the fouling were analyzed.Finally,the influence of different elements and slag disposal methods on the contamination characteristics of the coal ash were studied.Through the analysis of test results and data,the following conclusions are drawn:1)Zhundong Coal is completely burned on the slap tap boiler with vertical cyclone furncace,the carbon content of the ash is extremely low and the burning rate is high.2)The production of NOx can be controlled by changing the air distribution mode of the front chamber and adjusting the oxygen amount,due to high volatile and burning off rate of the coal.3)The components and contents of the Zhungdong slag samples in the dry bottom furnace test bench and the Zhungdong slag samples in the slap tap boiler with vertical cyclone furncace are basically the same,but the fly ash particle size distribution is quite different.The particle size of the fly ash in the slap tap boiler is less than 6.158?m,and the average particle size of the fly ash in the slap tap boiler is 1.896?m,only about one-eighth of the average particle size of the fly ash in the dry bottom boiler.The fine fly ash particles can increase the contamination in furnaces.4)In ash samples of the Zhundong Coal slap tap boiler,Na,Ca and S elements are enriched at ash samples in the low-temperature heating surface,but the content in the slag samples is relatively less.It can be seen that Na,Ca,S in coal ash are very difficult to be captured by slag on battom of flueway.5)By analyzing the typical particle components in the ash sample,it was found that some of Na and Ca combine with silica and alumina to form aluminosilicates,and some react with SO₂ in the flue gas to form alkali metal sulfates during the combustion process.The low-melting substance with strong adhesion is one of important reasons for fouling.6)With the increase of Na,Ca and Fe content in ash samples,the sintering strength gradually increases.At different temperatures,the sintering strength of the Zhundong Coal fly ash from the slag tap furnace is much higher than that of the Zhundong Coal fly ash from the dry bottom furnace.The results of the study show that the more serious fouling appear during burning the Zhundong Coal by the slag tap furance with cyclone boiler,and the fouling is more difficult to remove than the dry bottom furnace.