利用液-固多階式流體化床去除海砂中的鹽分

因近年來建設遽增，砂石需求量也大幅增加，但河川砂石的蘊藏量日竭，而且盜採問題層出不窮，危及環境與公共安全。有鑑於日本及英國等國開發利用海砂之成功經驗及台灣優渥的地理環境，若能去除海砂中之鹽分，擬定正確使用對策，則可解決部分砂石來源。本研究利用含錐形段之逆流式多階流體化床浸取及洗滌海砂，藉著錐形段之廣粒徑範圍的操作特性，以及逆流式多階流體化床之優點來去除海砂中的鹽分，使其符合CNS1240中華民國國家標準，並達到節省水量、縮短清洗時間、縮小系統體積以及連續操作獲得高處理量的目標。研究結果顯示，逆流式多階流體化床的穩定操作條件參數有一定的範圍，若不在穩定範圍內，則會發生液體氾濫(Flooding)或是固體堵塞(Choking) 的現象，導致操作中斷。系統的穩定操作範圍，隨著液體進口流量及固體進料流率的增加而縮小，隨階數的增加而變廣，在操作的過程中發現，因為溢流管的設置而產生特殊的流體化現象，使粒子有明顯的橫向移動，與學者Singh A. et al.(2008)所提出之掃流流體化現象(cross-flow fluidization)相符合。除鹽實驗方面，利用逆流式多階流體化床裝置去除海砂中的鹽分，於二階床操作時可達固液比範圍為0.55?1.4之間，三階床操作時，其固液比範圍為1.29?3.23，已經達到每1m3的海砂其處理水量為0.5公噸之相同比例，同時，固液比為3.23，操作時間約為2 分鐘之操作為最適化的操作條件，且海砂殘餘含鹽量可降至0.0348％，除鹽率高達88％，頗具實用價值。

關鍵字

錐形段；逆流式多階流體化床；固液比；液固流體化床；外部溢流管；海砂除鹽；掃流流體化現象

並列摘要

Because the recent years developed rapidly, the sand and crushed stone demand also largely increases. But the river sand and crushed stone reserves date uses up, moreover the robber picks the question to emerge one after another incessantly, endangers the environment and the public security. Base on the successful experience of Japan and British in developing and using sea sand and Taiwan liberal geographical environment, if can remove salt content in the sea sand and draws up the correct using countermeasure, then may solve the partial sand and crushed stone origin. This study use countercurrent multistage fluidized bed which contains the cone-shape section for leaching and washing sea sand. To take advantage of the characteristic of broad particle size distribution in cone-shape section and the virtues of countercurrent multistage fluidized bed to desalt in sea sand and make its salt content to conform the CNS national standards. The target in this study achieves saving water, volume, reducing cleaning time as well as the continuous-running to obtain the high process load. The experimental results show that the stable operation region in countercurrent multistage fluidized bed has a fixed range. The stable operation region in the system decreases with increasing liquid flow rate and solid feeding flow rate and increases with increasing the number of stages. In the process, the special phenomenon as a result of the downcomer. The solid flow move across the stage from the location of the downcomer on the cone-shape section to the location of the downcomer on the column section, resulting in the cross-flow fluidization. In the experiment of desalination in sea sand by countercurrent multistage fluidized bed. The solid feeding flow rate over the liquid inlet flow rate in two stages operation can achieve between 0.55 to 1.4 and it can achieve 3.23 in three stages operation. It already achieves the experts’ expectation which is each 1m3 sea sand its processing water volume is 0.5 metric ton.

並列關鍵字

desalination ； sea sand ； liqid solid fluidized bed ； countercurrent multistage fluidized bed ； external downcomer ； cross-flow fluidization

參考文獻

1983/ 4416859 (1983).

Mono-Size, Binary and Multi-Size Particles in a Liquid Fluidized Bed Classifier,"

Chemical Engineering Science 57, 991-1002 (2002).

DiFelice, R., 'Hydrodynamics of Liquid Fluidisation,' Chemical Engineering

Characteristic of Tapered Fluidized Beds,' AIChE Journal 37(11), 1668-1672 (1991).

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利用液-固多階式流體化床去除海砂中的鹽分

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