气流床气化炉辐射废锅内灰渣的力学性能实验研究

气流床气化炉辐射废锅中易发生的积灰结渣现象会导致传热效率和生产能力的降低。灰渣特性中的力学性能反映了渣的黏合强度和脱除难易程度,是认识积灰结渣现象、有效除灰的基础,但针对辐射废锅中灰渣的力学性能研究较少。以某气化炉辐射废锅中不同位置实际渣块(停炉后取样的水冷壁渣和底部渣)和飞灰烧结渣为对象,实验研究了其化学组成、晶体矿物组成、熔融温度、样貌特征以及力学性能等特性。结果表明,辐射废锅水冷壁渣灰熔点更高,并含有更多钙铝晶体矿物;辐射废锅底部渣和飞灰烧结渣灰熔点较低并含有更多方解石晶体,其中飞灰烧结渣富集K和Na元素,非晶态物质较多。水冷壁渣微观结构相对规则,主要由灰颗粒以及微小的泡沫状空穴连接组成;飞灰烧结渣则存在有较多大小不一的空泡,且烧结温度越高导致粘结程度增大,并产生更大体积空泡,微观表面更光滑平整。辐射废锅中不同位置渣的力学性能有较大差异,其中壁面渣的弹性模量在550~750 MPa,抗压强度在20~22 MPa,较废锅底部渣和烧结渣的弹性模量(7~54 MPa)和抗压强度(1.2~3.0 MPa)大很多。底部渣和烧结渣的力学性能较为接近,但仍存在着较大的离散系数(0.35~0.50),这说明气流床气化炉辐射废锅中渣块力学性能变化范围大,与当地成渣温度、成渣细颗粒组分、熔融特性和孔隙率等性质密切相关。

Mechanical properties of slag in a radiant syngas cooler of entrained flow gasifier

The accumulation of ash and slag in a radiant syngas cooler(RSC)of entrained flow gasifier can reduce the heat transfer efficiency and the production capacity.The mechanical properties of slag,which determine the adhesion strength and the removal difficulty,are the key for the understanding of the slag deposit phenomenon and the effective ash removal.However,the researches on the mechanical properties of slag in the RSC are currently limited.The slag from different positions in the RSC(including the slag deposited on the wall tubes and the slag on the RSC bottom)and the sintered slag were investigated experimentally,including the chemical composition,crystal mineral composition,ash fusion temperature,microstructure,and mechanical properties.The results showed that the samples of slag deposited on the wall tubes had higher fusion temperature,forming crystal minerals with more Ca and Al than other samples.The slag deposited on the RSC bottom and the sintered slag contained more calcite,and the sintered slag was rich in K and Na and had more amorphous composition.The microstructure of the slag on the wall tubes was relatively regular,mainly composed of ash particles and small cavities,while there were many bubbles of different sizes in the sintered slag.Higher sintering temperature bonded the slag particle closer and produced larger bubbles,but smoothed the micro surfaces.The mechanical properties of slag were related to its positions in the RSC.The elastic modulus(E)and the compressive strength(σ)of the slag on the wall tubes were between 550 to 750 MPa and 20-22 MPa respectively,which were much larger than the elastic modulus(7-54 MPa)and the compressive strength(1.2-3.0 MPa)of the slag on the RSC bottom and the sintered slag.The values of E andσwere close among the slags on the RSC bottom and the sintered slag,but there were still large coefficients of variation(0.35-0.50).This indicates that the mechanical parameters of the slag from the RSC vary widely and are strongly related to the local slag forming temperature,the ash particle composition,the fusing characteristics and the deposit porosity.