高温下煤灰热膨胀行为研究

为了更好地了解硅铝比在煤炭燃烧和气化过程中对炉体结渣和堵渣产生的影响,选取硅铝比不同的A、B、C三种煤样,在弱还原性气氛下,利用自主研制高温熔融装置,考察三种煤灰样在高温熔融炉中的形变情况,探究煤灰热膨胀行为。针对A煤样,将其灰化后分别添加SiO2和Al2O3,添加量为煤基的1%~5%,研究其高温下XRD物相变化、熔渣流动现象和熔渣表观形貌。结果表明:不同硅铝比的煤灰热膨胀行为存在差异,B、C煤灰产生明显热膨胀现象,A煤灰未出现此现象;添加SiO2的A煤灰产生明显热膨胀现象,而添加Al2O3却未出现膨胀过程。添加SiO2后的煤灰在高温下灰粘度会增加,气体较难透过粘稠液体相,造成煤灰在高温下会出现明显膨胀现象,进而会导致煤炭在燃烧和气化过程中出现炉体内壁的结渣和出渣口堵渣等问题。通过考察弱还原性气氛下,研究不同硅铝比对煤灰高温熔融过程形变的影响,为解决实际生产中气化炉结渣和堵渣问题提供理论依据。

Research of Thermal Expansion Behavior of Coal Ash under High Temperature

Three coal samples （referred to as A, B and C） with the different Si/Al ratio were selected to explore the thermal expansion behavior of the original ash by using the high-temperature melting device in weak reducing atmosphere. In order to better understand the silica alumina ratio in the process of coal combustion and gasification of the impact of furnace slagging, the high temperature XRD phase change and slag flow phenomenon and slag apparent morphology of Coal A with the addition of 1% to 5 % （air dry coal base） SiO2 and Al2O3 was studied in the high temperature tubing oven. The results indicated that different Si/Al ratio of original coal shows different thermal expansion behavior. Coal B and coal C ash melt produce significant thermal expansion phenomena, while thermal expansion phenomenon of coal A ash melt is not present. Coal A ash melt with the addition of SiO2 produced an obvious thermal expansion phenomenon and otherwise adding Al2O3 does not appear. After adding SiO2 coal ash viscosity would increase at high temperature, it is difficult for gas through the viscous liquid phase and promotes an expansive reaction under the high temperature, which leads to the coal in the process of combustion and gasification furnace lining the slagging problem such as slag and slag notch blocking. By investigating the weak reducing atmosphere, the study of different silicon ratio have influence on the ash melting process at high temperature deformation, which provide theoretical basis for solving the slagging and blocking slag problems in practical production gasifier.