生物质发电锅炉产生的飞灰一般用作建筑原料和肥料生产的辅料，然而飞灰中的有害成分会降低建筑材料的稳定性，造成农田重金属富集。因此，飞灰原料的预处理和适用性改善成为关键。以生物质电厂飞灰为原料，筛分得到粒径<0.2 mm的细灰，将细灰与去离子水配制浆液，采用超声辅助浸出、过滤处理；考察超声时间、浆液温度、固液质量比对宏量金属元素K、Na、Zn、Ca以及4种微量重金属元素Co、Cr、Ni、Pb浸出的影响规律，并探索适宜的操作参数。结果表明，试验采用的细灰富含CaO、SiO2和K2O。对于宏量金属元素，超声时间1～30 min，随时间延长金属元素浸出质量浓度和浸出量增大且趋向恒定，而Ca2+由于发生碳酸化反应而先增大后缓慢减小。浆液温度25～70 ℃时，浆液浸出生成Ca2+离子和碳酸盐化受温度影响尤其显著，随浆液温度升高，Ca2+浸出质量浓度先增大后减小，其他金属元素浸出质量浓度和浸出量均增大。固液质量比1∶3～1∶6时，随固液质量比减小，金属元素浸出质量浓度降低，而金属元素浸出率增大。超声时间20 min、浆液温度50 ℃、固液质量比1∶5时，钾元素浸出率达到47.22%。超声时间、浆液温度和固液质量比对于微量重金属元素的浸出过程存在一定影响，在试验参数范围内重金属浸出率和浸出量维持在很低水平。典型操作参数为：超声时间30 min、浆液温度25 ℃、固液质量比1∶5时，Co、Cr、Ni和Pb四种重金属元素浸出率分别低于0.10%、0.30%、0.05%和0.10%。综合考虑技术系统实施和运行成本，适宜的超声时间为15～20 min、浆液温度为40～50 ℃、固液质量比为1∶3～1∶5。通过对比超声处理的浸出液和残渣中关键碱金属元素、硫和氯元素，宏量可溶性元素大量迁移至滤液中，且微量重金属含量极低，浸出液用作肥料和土壤调节剂具有现实意义。由于可溶性碱金属盐以及氯化物的滤出，残渣中其含量明显减少，有利于将其用作工业建材原料。

The fly ash produced from biomass power generation boilers is generally used as building materials and auxiliary materials for fertilizer production. However,the hazardous components in fly ash can reduce the stability of building materials and cause the enrichment of heavy metals in farmland. Therefore,the pretreatment of fly ash raw materials and the improvement of suitability are the key issues. In this study,fly ash from biomass power plant was used as raw material to obtain fine ash with particle size <0.2 mm by sieving. Fine ash and deionized water were prepared into slurry,which was treated by ultrasonic-assisted leaching and filtration. The effects of sonication time,slurry temperature,solid-liquid mass ratio on the leaching of macroscopic metal elements K,Na,Zn,Ca,and four trace heavy metal elements Co,Cr,Ni,Pb were investigated. The appropriate operating parameters were explored. The results show that the fine ash used in the experiment is rich in CaO,SiO2 and K2O. For macroscopic metal elements,the leaching concentration and leaching amount of metal elements increase and tend to be constant with the time prolonging within 1-30 minutes of sonication. While Ca2+ increases first and then decreases slowly due to carbonation reaction. In the range of slurry temperature from 25 ℃ to 70 ℃,Ca2+ generation and carbonation are significantly affected by temperature. With the increase of slurry temperature,the leaching mass concentration of Ca2+ increases firstly and then decreases,but the leaching mass concentration and leaching amount of other metal elements increase. In the range of solid/liquid mass ratio 1∶3 to 1∶6,the leaching concentration of metal elements decreases and the leaching rate of metal elements increases with the decrease of solid/liquid mass ratio. When sonication time is 20 min,the slurry temperature is 50 ℃,and the mass ratio of solid to liquid is 1∶5,the leaching rate of potassium reaches 47.22%. Sonication time,slurry temperature and solid-liquid mass ratio have certain effects on the leaching process of trace heavy metals. The leaching rate and amount of heavy metals remain at a very low level within the parameters explored in the experiment. In the typical operating parameters:the leaching rates of cobalt (Co),chromium (Cr),nickel (Ni) and lead (Pb) are lower than 0.10%,0.30%,0.05% and 0.10% for 30 min of sonication time,25 ℃ of slurry temperature,and 1∶5 solid-liquid mass ratio. Considering the implementation and operation cost of the technical system comprehensively,the suitable sonication time is 15-20 minutes,the slurry temperature is 40-50 ℃,and the mass ratio of solid to liquid is 1∶3-1∶5. By comparing the key alkali metal elements,sulfur and chlorine elements in the leaching solution treated by ultrasonic-assisted leaching and the residue,a large number of macro-soluble elements migrate into the filtrate,and the content of trace heavy metals is very low. It is of practical significance for the leaching solution to be used as fertilizer and soil regulator. Due to the leaching of soluble alkali metal salt and chloride,the content in the residue is reduced significantly,which is favorable for its use as the raw material of industrial building materials. 

0 引言

1 试验

   1.1 试验原料与方法

   1.2 试验测试与表征

2 结果与讨论

   2.1 生物质细灰成分分析

   2.2 超声时间对浸出效果的影响

   2.3 浆液温度对浸出效果的影响

   2.4 固液质量比对浸出效果的影响

   2.5 微量重金属元素的浸出特性

   2.6 滤洗残渣特性分析

3 结论