Lima Ana T, Ottosen Lisbeth M, Ribeiro Alexandra B, Hansen Henrik K
Department of Sciences and Environmental Engineering, Faculty of Sciences and Technology, New University of Lisbon, Caparica, Portugal.
J Environ Sci Health A Tox Hazard Subst Environ Eng. 2008 Jul 1;43(8):844-51. doi: 10.1080/10934520801974327.
Ashes from biomass combustion contain many macro and micro nutrients and its reuse in agricultural fields could be beneficial. In the case of straw ash, however, the content of Cd is often too high for the ash to be utilized this way. In Denmark the limiting concentration for spreading the ash in agricultural land is 5.0 mg Cd/kg and in order to utilize the nutrients in the straw ash it is necessary to decrease the Cd content to meet this limiting concentration. It has been previously shown, at a laboratory scale, that the Cd concentration can successfully be decreased by an electrodialytic method. Results from scale-up of the electrodialytic method to pilot scale are the focus. The capacity of the pilot plant was approximately 40 L ash suspension (2 kg ash). During the treatment, 40% of the Cd was removed from the straw ash, and the final obtained concentration was 6.8 mg Cd/kg. Although this concentration still exceeds the limiting concentration, valuable experience concerning the practical operation through scale-up was obtained. In addition, the experiments are a good basis for further scale-up and optimization of the process for improved Cd removal to meet the requirements. A very important finding consisted in the control of the osmotic water flux that emerged from the electrode compartments into the ash suspension during treatment.
生物质燃烧产生的灰烬含有许多常量和微量营养元素，在农田中再利用可能有益。然而，就秸秆灰而言，镉含量往往过高，无法以这种方式利用。在丹麦，在农业土地上施用灰烬的限制浓度为5.0毫克镉/千克，为了利用秸秆灰中的养分，有必要降低镉含量以达到这一限制浓度。此前在实验室规模已表明，通过电渗析法可成功降低镉浓度。本文重点关注电渗析法扩大到中试规模的结果。中试装置的处理能力约为40升灰悬浮液（2千克灰）。处理过程中，40%的镉从秸秆灰中去除，最终获得的浓度为6.8毫克镉/千克。尽管该浓度仍超过限制浓度，但通过扩大规模获得了有关实际操作的宝贵经验。此外，这些实验是进一步扩大规模和优化工艺以提高镉去除率以满足要求的良好基础。一个非常重要的发现是控制处理过程中从电极室进入灰悬浮液的渗透水通量。
