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首页> 外文会议>2001 International Ash Utilization Symposium Oct 22-24, 2001 Lexington, Kentucky, USA >Determination of the Available Si and Al from Coal Fly Ashes under Alkaline Conditions with the Aim of Synthesizing Zeolite Products
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Determination of the Available Si and Al from Coal Fly Ashes under Alkaline Conditions with the Aim of Synthesizing Zeolite Products

机译：合成沸石产品测定碱性条件下粉煤灰中有效硅和铝的含量

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Pure zeolites can be synthesized from silica extracts obtained from fly ash by alkaline leaching. The extraction potential of various types of European fly ashes was investigated under realistic process conditions (2 M NaOH; 90℃; L/S=3; 6h.) and found to vary from 1 to 130 g of SiO_2 per kg ash, using a single step process. However, during extraction zeolites are formed in the ash and this limits the amount of SiO_2 liberated, and thus the yield of pure zeolites to be produced from the extracts. The Al content in the extracts is almost negligible, showing that the liberated Al in the process is all used for crystallizing zeolites and hence consumption of Si. As zeolites form on the ash particles, this also makes the dissolution reactions to cease before completion. In order to avoid zeolite formation at an early stage and to determine the availability of SiO_2, experiments were done at 50℃, 2.5 M NaOH, L/S=20 and reaction times up to 72h. In this way the maximum extraction found increased up to 280 g/kg but still zeolites were found in the residues, showing that the maximum available amount of SiO_2 could not be maintained in the solution. Although the amount of available SiO_2 and Al_2O_3 will be related to fly ash characteristics, it turned out to be difficult to generalize this relation as for different ashes different assumptions were required to fit a model. The formation of zeolites is mainly influenced by the build-up of Al in the liquid phase. Therefore, Al-complexants were added to the solutions with the aim of suppressing the crystallization of zeolites. Zeolites were not detected in the residues, and although the extracted Al_2O_3 increased significantly, the amount of extracted SiO_2 was hardly affected. It is believed that with further development of those experiments and more insight in the glass fraction of the ashes, availability of Si and Al may be determined as a function of ash properties.
机译：可以通过碱浸从粉煤灰获得的二氧化硅提取物中合成纯沸石。在实际的工艺条件下（2 M NaOH； 90℃； L / S = 3； 6h。）研究了各种类型欧洲粉煤灰的提取潜力，结果发现每公斤灰分的SiO_2为1至130 g SiO_2。单步过程。但是，在萃取过程中，在灰烬中形成了沸石，这限制了所释放的SiO_2的量，从而限制了从萃取物中产生纯沸石的产率。提取物中的Al含量几乎可以忽略不计，这表明该过程中释放出的Al全部用于结晶沸石，从而消耗了Si。由于在灰烬颗粒上形成沸石，这也使溶解反应在完成之前停止。为了避免早期形成沸石并确定SiO_2的有效性，在50℃，2.5 M NaOH，L / S = 20的条件下进行了实验，反应时间长达72h。这样，发现的最大提取量增加至280 g / kg，但在残留物中仍发现了沸石，这表明溶液中无法保持最大可用SiO_2量。尽管可用的SiO_2和Al_2O_3的量与粉煤灰特性有关，但事实证明很难概括这种关系，因为对于不同的骨灰，需要不同的假设来拟合模型。沸石的形成主要受液相中Al堆积的影响。因此，为了抑制沸石的结晶化，向溶液中添加了铝络合物。在残留物中未检测到沸石，尽管提取的Al_2O_3明显增加，但几乎不影响提取的SiO_2的量。据信，随着那些实验的进一步发展和对灰分的玻璃分数的更多了解，可以确定Si和Al的可用性作为灰分性质的函数。

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