Experimental Study On Characteristics Of Zhundong Coal Ash Deposition

China’s rich of coal,shortage of oil and gas can not be changed,so the situation that coal in China’s primary energy consumption in the dominant position can not be changed recently.Zhundong coal,because of its large reserves and excellent quality,will be highquality thermal coal in the future.However,since it is rich in more alkali metals,it causes that the tail-heating surface will be serious fouling and corrosion in the actual operation of the boiler,which greatly limits the promotion and application of Zhundong coal.Therefore,the research in fly ash deposition characteristics of the coal for the large-scale apply to ensure the safe and stable operation of power generation equipment is of great significance.In this paper,two typical Zhundong coal are selected,namely,the Jiangjunmiao(JJM)and the Wucaiwan(WCW).The two kinds of coal are different in industrial analysis.The JJM contains more Si and Al elements,while the Ca content is less.In the use of two kinds of coal in the muffle furnace 350℃ prepared as the raw material can maximize the assurance of alkali metal retaining in the ash.The main crystalline compounds 、microstructure and the element migration laws were characterized by XRD,SEM and ICP-AES.At the same time,the physical characteristics of fly ash deposition and the deposition rate are analyzed.The results show that the results are more realistic.Finally,the differences of the ashdeposition characteristics of the two kinds of coal are compared and analyzed,and the conclusion is drawn.First,this paper transforms the one-dimensional visualized sedimentation furnace,seals the feeding device and increases the buffer mouth so that the feeding material is more uniform and does not clog.At the same time,the center cross tube is expanded and the test bed can accommodate multiple probes,and then introduces the definition of two physical characteristic parameters,as well as the introduction of the test methods.Secondly,the deposition characteristics under different probe diameters are studied.The diversity of JJM and WCW are consistent.The fly ash deposition height and ratio of deposition increase with the increase of probe diameter,but the ash morphology is different.The JJM appeared in the initial deposition layer,and the uniform coverage of the probe,for the follow-up ash deposition to provide a better breeding ground,and WCW in the center of the probe are more fouling,which cannot form a uniform initial sedimentary layer.Most of the ash particles deposite in the center of the inertial collision.In the case of comprehensive comparison,the height of the WCW fly ash is higher than that of the JJM,but the ratio of deposition is less than that of the JJM.It is also shown that the initial deposition layer of the JJM can adsorb more ash particles.Then,the deposition characteristics of different probe temperatures are studied.The difference between WCW and JJM was great.For the JJM,the height and ratio of deposition of fly ash decreased with the increase of probe temperature.On the contrary,combined with XRD,SEM and digestion-ICP-AES results,the content of Na in the study was lower than that in the bottom ash,but the content of Fe was much higher than that of the bottom ash.For the alkali metal is volatile,so it exists corrosion phenomenon,and solidify Fe in the phenomenon of deposition of ash.At the 350℃ of probe temperature,XRD found Na2SO4 this easily contaminated material,while the SEM The results showed that there was a large range of agglomeration and sintering in the low probe temperature of the JJM,which will make the ash more polluted on the surface of the probe.For the WCW,the Ca content in the ash is higher,The Na content of ash is higher than that of bottom ash,and the content of Fe is higher than that of bottom ash,which indicates that Na is weak in the WCW and is less corrosive to the probe.SEM showed that the WCW particles are melted at the high probe temperature,and the surface of the particles was smooth and no fine particles were bonded,but the molten surface of the JJM is attached with more fine ash particles.When the probe temperature was 450℃,K2Ca(SO4),a low melting point calcium salt,was found in the XRD results,resulting in a decrease in the ash melting point,contamination at high probe temperatures,and promoting fouling.In the transverse double probe and longitudinal double probe experiments,the height variation of fly ash deposition is increased in three stages.First,the accumulation of rapid initial sediments is followed by the rapid deposition stage.After about 300 minutes,in the vertical stage double-probe experiment,the upper layer fouling reaches the stable deposition stage,and the phenomenon of falling shedding-deposition-shedding occurs repeatedly,while the sublayer probe is relatively stable,but ash height is lower.The stable fouling height of the horizontal double probe is higher than that of the longitudinal double probe,because the vertical double probe upper layer is affected by the airflow and the ash,leading to the occurrence of shedding.Finally,the difference of fly ash deposition between two typical Zhundong coal is compared,and it is concluded that the JJM is a deposition mechanism with volatile alkali metal as the controlling factor,while the WCW is the deposition mechanism with the low melting point calcium salt as the controlling factor.