粉煤灰中钙的结晶相及其随粒径的分布关系

Crystal phase and distribution of calcium in fly ash with particle size

粉煤灰中的含钙相结晶形式多样,粉煤灰的活性状态也相应受到含钙相及含量的影响。粉煤灰用于水泥、混凝土等建筑材料中时,其含钙结晶相也会严重影响安定性、凝结时间等。通过对4种不同粉煤灰的粒径分布、结晶相,以及每种灰的含钙结晶相随粒径变化的研究,初步确定粉煤灰中含钙结晶相的分布规律为:对累积粒径基本相当的粉煤灰而言,循环流化床灰的粒径呈单峰分布,煤粉炉灰的粒径呈双峰分布。含钙结晶相中的硫酸钙结晶只存在于循环流化床灰中,在煤粉炉灰中几乎不存在。结合粒径来看,煤粉炉灰的含钙结晶相主要为Ca(OH)_(2)、CaO、少量碳酸钙等,均集中在粒径<0.106 mm的细灰中。循环流化床灰的含钙结晶相主要包括Ca(OH)_(2)、CaO、硫酸钙、碳酸钙等,炉内脱硫的灰中还有钙黄长石、铁酸钙。炉外脱硫的循环流化床灰,Ca(OH)_(2)、CaO只存在于粒径<0.044 mm的灰中,粒径≥0.106 mm的灰中只有碳酸钙。炉内脱硫的循环流化床灰,粒径≥0.044 mm的灰中出现钙黄长石、铁酸钙等矿物。

The crystalline forms of calcium-containing phase in fly ash are diverse,and the active state of fly ash is correspondingly affected by the crystal phases containing calcium and their contents.When fly ash is used in cement,concrete and other building materials,its calcium-containing crystalline phases will also seriously affect stability,setting time,etc.In this paper,through the study of the particle size distribution and crystalline phases of four different fly ashes,as well as the changes of calcium-containing crystal phase of each ash withparticle size,it is preliminary determined that the distribution law of calcium-containing crystalline phase in fly ash is as follows:for fly ash with basically the same cumulative particle size,the particle size of circulating fluidized bed ash is single-peak distribution,and the particle size of pulverized coal furnace ash is bimodal distribution.Calcium sulfate crystals in calcium-containing crystalline phases are only present in circulating fluidized bed ash and are almost absent in pulverized coal furnace ash.Combined with the particle size,the calcium-containing crystalline phases of pulverized coal furnace ash are mainly Ca(OH)_(2),CaO,and a small amount of calcium carbonate,all of which are concentrated in fine ash with a particle size of<0.106 mm.The calcium-containing crystal phase of circulating fluidized bed ash mainly includes Ca(OH)_(2),CaO,calcium sulfate,calcium carbonate,and there are also calcium yellow feldspar and calcium ferrite in the ash desulfurized in the furnace.Circulating fluidized bed ash for desulfurization outside the furnace,Ca(OH)_(2),CaO only exists in ash with a particle size of<0.044 mm,and only calcium carbonate in ash with a particle size of≥0.106 mm.The circulating fluidized bed ash of desulfurization in the furnace,the ash with particle size≥0.044 mm appeared calcium yellow feldspar,calcium ferrite and other minerals.