| 摘要: | 工業快速的發展，造成了化石能源短缺與空氣污染嚴重。尋找替代可行能源及減少污染氣體的排放已為當前迫切之問題。而其中氫能為一種兼具環保與永續概念的能源，因此由於人類對於氫能的渴望及新技術的開發，擴大對氫能源的使用。因此本論文第一部分為整合Pd複合薄膜反應器與變壓吸附程序，進行甲醇水蒸汽重組產氫數值模擬研究。藉由兩者結合發現於薄膜反應器中增加進料流量時不利甲醇進行水蒸汽重組反應，甲醇轉化率下降，且對於滲透層內氫氣回收率亦減少，對於滲透層側氫氣的純度則會先升高後下降。當增加進料層壓力與降低滲透層壓力時無論氫氣純度及回收率皆越大。對於反應器之滲透層產物進入變壓吸附程序中顯示回沖洗比與進料吸附壓力愈大時，對於氫氣純化越好，而相對將減少其氫氣回收率。排氣壓力降低時，有助於得到純度90％H2，但相對的較不利於氫氣的回收。 結構性吸附劑相較於傳統填充吸附床系統可有效增加其分離能力，而塊狀結構為一種具有流動低壓降特性，因此非常適合發展應用變壓吸附程序。本論文第二至四部分為發展出塊狀結構吸附床模擬程式，首先第二部分為利用數值模擬丁烷與空氣混和氣於碳塗層陶瓷塊狀吸附床(carbon-coated ceramic monoliths)進行其貫流曲線，研究顯現貫流所需時間與長度成正比關係。增加流速不利於流體徑向質量傳送，因此貫流時間縮短。增加碳塗佈層厚度使質傳進入碳塗佈層進行吸附達到吸附相內濃度飽和時間也增加，因此也使得貫流時間增加。 第三部分為將碳塗層陶瓷塊狀吸附床應用於變壓吸附程序中分離丁烷與空氣混和氣及二氧化碳與氮氣混和氣，其結果顯示於純化丁烷/空氣應用於三步驟程序中增加碳塗佈層厚度可有效增加丁烷的純度。利用增加各步驟時間皆能增加純度，但回收率僅在逆向減壓產氣步驟時間增加時增加。對於純化二氧化碳/氮氣變壓吸附程序應用中碳塗佈層有較大之質傳阻力不利二氧化碳質傳擴散。因此利用增加停滯步驟的五步驟程序為最佳。 由於溫室氣體中二氧化碳的排放主要來自於燃燒化石燃料，而移除回收二氧化碳為減緩溫室效應之首要工作。本論文第四部分為探討利用塊狀碳吸附床(carbon monolithic adsorber)快速變壓吸附程序進行煙道氣中二氧化碳回收。模擬結果顯示於改變步驟時間中，藉由產氣潤濕步驟時間的增長能有效增進二氧化碳回收純度。此外對於相同壓力循環時間程序可藉由增加儲槽體積及縮短吸附床長度來提升二氧化碳回收純度。 As the industry fastly developed, it made shortage of fossile energy and serious air pollution. It is important to find out the renewable energy and reduce the emission of gas pollutant. Hydrogen energy is one kind of non-polluting and renewable fuel. As the people demend for more hydrogen energy and discoved new hydrogen production technology, it increased the utilization of hydrogen energy. The first part of study is to simulate hydrogen purification by applying composite palladium membrane reactor combined with pressure swing adsorption (PSA) hybrid process. This membrane reactor is adapted to produce hydrogen from methanol steam-reforming, where the permeated membrane hydrogen is mixed with sweep gas. The gas mixture from the membrane reactor is then fed into a dual-bed six-step pressure swing adsorption process, filled with zeolite 5A for hydrogen purification. The new-shape-structured materials, carbon monoliths, are characterized by straight parallel channels separated by thin wall, high void fraction and large geometric surface area, resulting in a low pressure drop under high flow rate and large contact area. These properties make carbon monoliths have the advantage on adsorption application. The second part of this study simulates the dynamic adsorption of butane on carbon-coated ceramic monoliths under isothermal condition. The parameters considered in the mathematical model include the mass transfer coefficient to the channel wall, effective diffusion within the pore structure and the axial dispersion model. The adsorption is expressed by the Dubinin-Radushkevich isotherm. The effect on increasing thickness of carbon-coated layer could raise the amount of adsorbate, although the thicker carbon layer would take longer time for stream diffusion to reach the saturated adsorption and breakthrough. Then the third part of this study develops mathematic model and simulates the adsorption separation of butane/air and CO2/N2 on carbon-coated ceramic monoliths for pressure swing adsorption processes under isothermal condition. In the three-step butane/air PSA process simulation study, increasing the thickness of carbon coated layer can increase the butane purity and recovery at the same valve value operation, but increasing the feed pressure will decrease the butane purity and recovery. For the other five-step pressure swing adsorption process for CO2/N2 on carbon-coated monoliths, when the mass transfer resistance between the gas and solid phase is small than that in the carbon coated layer, using an idle step is useful to improve the CO2 purity with an appropriate idle step time. The fourth part of study simulates the adsorption separation of CO2 from flue gas with 17% CO2 and 83% N2 on a carbon monolithic adsorber for a three-step rapid pressure swing adsorption process, which operates in the sequence of adsorption, rinse and desorption, under isothermal condition. The simulation results exhibit that the rinse step with a CO2 rich stream should be employed to enhance product purity. As to the effect of step time, increasing the rinse step time shows the greatest effect on increasing purity and decreasing recovery of CO2. Additinally, decreasing adsorber length and increasing rinse pressure are beneficial to improving the CO2 purity in production, but the CO2 recovery decreases at the same time. |
