以變壓吸附法捕獲中高溫水煤氣轉化反應氣中二氧化碳之模擬

Capturing CO2 from water-gas-shift reaction effluent gas by pressure swing adsorption at mid-high temperature

施育豪(Yu-Hau Shih)

指導教授 ： 周正堂

國立中央大學/工學院/化學工程與材料工程學系/碩士(2011年)

摘要

本研究探討之對象為煤炭氣化燃燒發電技術燃燒前捕獲從水煤氣轉化器出來之氣體中之二氧化碳，本研究使用K2CO3-promoted hydrotalcite吸附劑在中高溫(水煤氣轉化反應器出來之溫度)進行二氧化碳捕獲，剩下以氫氧為主的氣體再送進燃氣輪機燃燒發電。以減少先降溫分離再升溫燃燒造成之能源損耗。
本研究先以程式驗證K2CO3-promoted hydrotalcite的突破曲線與脫附曲線，證明本程式模擬K2CO3-promoted hydrotalcite吸脫附行為的可信度，再驗證以一塔五步驟5A沸石分離二氧化碳/氫氣的程序，證明本程式在完整變壓吸附程序二氧化碳分離技術的可信度。
本研究以一塔四步驟程序，雙塔六步驟程序在假設從水煤氣轉化反應器出來在的氣體在含水進料與無水進料的情況下探討步驟時間、壓力、流量、塔長、P/F ratio等操作條件對二氧化碳產物之純度與回收率的影響。由模擬結果可知一塔四步驟二氧化碳純度較高。雙塔六步驟可提高二氧化碳回收率，卻造成二氧化碳濃度下降。本研究中二氧化碳的純度與回收率皆可達到90%以上。在無水的條件下， 一塔四步驟最佳操作值為二氧化碳濃度98.72%，回收率97.96%， 雙塔六步驟最佳操作值為二氧化碳濃度90.15%，回收率98.98%，在含水的操作條件下， 一塔四步驟最佳操作值為二氧化碳濃度99.3%，回收率97.57%，雙塔六步驟最佳操作值為二氧化碳濃度93.58%，回收率99.23%。
本研究第二階段變壓吸附程序進料來源為第一階段變壓吸附程序含水進料操作條件下一部分塔頂產物降至常溫除水而得，以CO與H2為主，第二階段變壓吸附程序為以AC5-KS吸附劑雙塔六步驟程序分離CO/H2，可達到99%以上純度之氫氣，此時回收率為93%。

關鍵字

二氧化碳 ； 氣化複循環發電技術 ； 中高溫 ； 變壓吸附

並列摘要

An integrated gasification combined cycle (IGCC) is a potential electric power technology that turns coal into synthesis gas, which can be burned to generate power. In this study, pressure swing adsorption (PSA) is utilized to capture CO2 from outlet stream of water-gas-shift reactor of IGCC process at nearly 400C with K2CO3-promoted hydrotalcite adsorbent, avoiding energy loss of capturing CO2 at room temperature, and the purified H2 at 400C is sent to gas turbine for generating electrical power.
In this study , we first simulate breakthough curve and desorption curve of K2CO3-promoted hydrotalcite, proving the accuracy of our program that we can simulate adsorption and desorption of K2CO3-promoted hydrotalcite correctly.We also simulate 1-bed 5-step process of CO2/H2 separation utilizing 5A zeolite adsorbent, proving the accuracy of our program.
Adsorbent K2CO3-promoted hydrotalcite adsorbs CO2 at mid-high temperature and does not adsorb other gases ,such as CO ,H2 and H2O. Non-moisture inlet condition (water is removed before entering PSA process) and moisture condition is studied in simulation at the 1st stage CO2 PSA , and two PSA processes,1-bed 4-step process and 2-bed 6-step process, are studied to separate CO2 from syngas.
1-bed 4-step PSA process generates better purity of CO2 and 2- bed 6-step PSA process have better recovery of CO2.Both of them could achieve above 90% purity and recovery of CO2. For non-moisture inlet ,the best result of 1-bed 4-step process is with CO2 purity of 98.72%and a recovery of 97.96%, and the best result of 2-bed 6-step process is with CO2 purity of 90.15% and a recovery of 98.98%.For moisture inlet ,the best result of 1-bed 4-step process is with CO2 purity of 99.3%,and a recovery of 97.57%,and the best result of 2-bed 6-step process is with CO2 purity of 93.58% and a recovery of 99.23%.
The inlet of the 2nd stage H2 PSA coming from part of the top product of the 1st stage CO2 PSA with moisture inlet is reduced to room temperature to remove water content and to perform H2 purification at room temperature.The main compositions of the 2nd stage inlet gas are CO/H2.We use AC5-KS adsorbent and 2-bed 6-step process to separate CO/H2.It can achieve 99% purity and 93 % recovery of H2.

並列關鍵字

Pressure Swing Adsorption ； carbon dioxide ； Integrated Gasification Combined Cycles ； mid-high temperature

參考文獻

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