氣力揚昇幫浦應用於海域甲烷水合物輸送之初步研究

Abstract

甲烷水合物具備了多項的能源特性，是最近相當受到注目的一項替代能源，而在台灣西南外海就有發現大量甲烷水合物，若能對此處的甲烷水合物進行開採，對於台灣將有很大的幫助。 本研究將以氣力揚昇幫浦(airlift pump)作為輸送機制，多流體模式(multi-fluid model)作為理論基礎，來對海域甲烷水合物顆粒之輸送做研究。由於甲烷水合物會因輸送過程中壓力降低而分解出甲烷氣，此情形將會對整個輸送行為造成影響，因此本研究中將把此現象納入考慮，並以數值計算的方式來對流態為穩態時之海域甲烷水合物輸送做計算，並對其數值結果做討論。 由計算結果得知管中的混合流體之流體性質(包括相佔有率、相速度…等)會隨著流體之輸送而產生變化，越靠近管出口時，變化越劇烈。而在水合物顆粒的分解上，由於其分解速率極慢，因此對於整個系統而言影響極小，若想達到Hamaguchi, et al.(2003)所提的自行氣力揚升(self-air-lift)之程度，恐怕需要對整個輸送系統做一些改變。然而未分解的甲烷水合物反而適合其輸送。

The methane hydrate is a chemical substance of multiple energy characteristics, which has been regarded as a future energy resource. It is found that there are a lot of methane hydrate reserve in the South –Western sea area of Taiwan. It is beneficial for us, if we can exploit the methane hydrate commercially. The concept of this study is to use the airlift pump to transport marine methane hydrates from the sea bed up to a plant ship, in which a multi-fluid model is employed. In the transport process, the methane hydrate will decompose into methane gas and water as the pipe pressure decreasing. In this study a three phase flow behavior will be analyzed numerically in order to develop a commercialized methane hydrate recovery system. According to the analysis of the transport process, the fluid characteristics in the pipe are always changing, especially when the fluid is close to the upper pipe outlet. Because the decomposition time rate is too small, its influence is quiet limited. It is necessary to have some changes, if the “self-air-lift” concept proposed by Hamaguchi et al. (2003) can is to realized. However, the methane hydrate itself is easier for transportation.