鋼鐵廠飛灰製成高價值磁氧鐵礦觸媒回收再利用技術之研發
| 中文摘要 | 近年來，台灣地區的鋼鐵業每年產出約20萬公噸之集塵灰，其中以大量重金屬為主，且已被環保署認定為有害事業廢棄物。但因其粒徑微小，重金屬溶出機會高，容易發生生物吸入之可能性，亦會造成生物毒性累積之問題，而對人類健康及環境生物生存之嚴重危害，故研發作為一種高回收率且有效降低囤積量之高價值新興材料之來源，乃目前相當迫切之研發課題與有效做法。在不鏽鋼/碳鋼煉鋼廠中的飛灰以NiO/ZnO、鎳/鋅磁氧鐵礦(NiFe2O4/NiFe2O4)及鐵的氧化物或是其他可揮發性重金屬的化合物為主，其中具強磁性之NiFe2O4/NiFe2O4容易經磁選程序分離而純化，作為分解CO2之奈米級還原性觸媒。二氧化碳是目前主要之暖化潛勢溫室氣體(約占50~60%)，尤其是鋼鐵業、火力發電廠及石化業幾乎占大部分之排放量，因此如何降低CO2排放量之處理技術研發，早已引起世界各國高度重視；尤其對於環境生態危害及溫室效應所造成之全球暖化會直接造成影響，已成為國際亟需正視之環保重要議題。因此，本計畫主要目的分為兩大部分：(1)利用鋼鐵廠飛灰為原料，經過磁選分離之簡易程序，獲得高活性(high activity)與高比表面積(high specific surface area)奈米級NiFe2O4/NiFe2O4觸媒技術，並比較已研發成熟水熱法所合成出奈米級觸媒之特性差異；(2)觸媒先以H2還原後之特殊催化效果，並在中溫反應(573-673 K)及1 atm條件下，探討利用奈米NiFe2O4/NiFe2O4分解CO2，形成C微粒與O2之反應機制，達成CO2減量之目的；而C再進一步與H2反應產生有用能源甲烷(CH4, methanation))並予以回收再利用；並取得最佳CO2分解反應條件、反應動力及機制，評估氣體產物分佈及具高附加價值之甲烷回收效率，回送作為廠區能源再利用之可行性。另外，亦利用XRD、TEM、FE-SEM/EDS、XPS/Auger、FTIR/Raman、SSNMR、EPR、BET isotherm (ASAP)、XANES/EXAFS等貴重儀器，深入瞭解鋼鐵業飛灰及奈米級NiFe2O4/NiFe2O4觸媒之特性與界面化學及反應機制，以利後續提升分解CO2效果；並建立模擬煉鋼廠飛灰經磁選程序分離而純化NiFe2O4/NiFe2O4製程單元、進行工廠尾氣CO2之還原分解效率評估，以取得最佳NiFe2O4/NiFe2O4觸媒固定床操作條件、工程放大及經濟效益評估，以便提供後續基本工程設計之參考。另外，本計畫亦收集彙整國內外有關CO2之處理及回收減量技術等相關實務資料，預期本研發技術具有新穎性、高效率，低耗能、容易控制、方便現址連結配合廠區尾氣排放設備及甲烷回收再利用等多項優點，能有效而實際地解決鋼鐵業飛灰污染、CO2暖化潛勢溫室氣體排放量減量及各種產業未來必須面對更嚴苛CO2排放量管制及課稅政策之困境。 | ||
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| 中文關鍵字 | 奈米級鋅/鎳磁氧鐵礦觸媒、鋼鐵廠飛灰、催化分解二氧化碳 | ||
基本資訊
| 專案計畫編號 | EPA-102- U1U4-04-006 | 經費年度 | 102 | 計畫經費 | 1020 千元 |
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| 專案開始日期 | 2013/03/28 | 專案結束日期 | 2013/11/30 | 專案主持人 | 林錕松 |
| 主辦單位 | 永續發展室(停用) | 承辦人 | 林燕柔 | 執行單位 | 元智大學 |
成果下載
| 類型 | 檔名 | 檔案大小 | 說明 |
|---|---|---|---|
| 期末報告 | EPA-102-U1U4-04-006(定稿上傳版).pdf | 7MB |
| 英文摘要 | Recently, Over 0.2 million tons per year (TPY) of flyash hazardous wastes were produced from steel industries in Taiwan having high risk for enviroment or human beings. In stainless stell/carbon steel manufacturing plants, the NiFe2O4/ZnFe2O4 are major materials and can be easily speparated/purified using magnetic method or ball mill unit. Carbon dioxide is the main greenhouse gas of 50~60% with global warming potential (GWP) and plays a role in the greenhouse effect especially for the CO2 emission from steel companies, powder generation plants, and petrochemical industries. Experimentally, NiFe2O4/ZnFe2O4 catalysts were speparated from flyashes with the efficiency of 32-40% and further purified to obtain nanocatalysts with the efficiency of 15-20% using magnetic separation or ball mill methods. The optimal synthetic conditions of NiFe2O4/ZnFe2O4 catalysts were pH = 8.5 and stirring rate of 1,250 rpm at 453 K for 4 h using hydrothermal method. The XRD patterns indicated the NiFe2O4/ZnFe2O4 catalysts are spinel structure. Based on FE-SEM and TEM micrographs, the particle size ranged of 30-50 nm of NiFe2O4/ZnFe2O4 nanocatalysts were found. Decomposition of CO2 into carbon and oxygen was carried out within few minutes when it comes into contact with oxygen deficient nanocatalysts through incorporation of oxygen into catalysts. The pre-edge XANES spectra of Fe species in nanocatalysts exhibits an absorbance feature at 7,115 eV for the 1s to 3d transition which is forbidden by the selection rule in case of perfect octahedral symmetry. The EXAFS data showed that the nanocatalysts had two central Fe atoms coordinated by primarily Fe–O with bond distance and coordination number of 1.93 Å/2.01 Å and 3.38/3.88 for Ni/Zn nanoferrites, respectively. Based on 72 h durability test of ZnFe2O4/NiFe2O4 nanocatalysts, the decay of 40% was observed. Proposed deactivation mechanisms of the nanocatalysts may include: particle size increasing, carbon deposition/sintering or ZnCO3/NiCO3 deposition on the surface of nanocatalysts. Based on the theoretical calculation, the energy efficiency of the route from CO2 to CH4 is higher compared with the one from C or H2 combustion directly. The in-situ complicated offgases contains 15-20% CO2, it needs to be purified by pressure swing adsorption (PSA) before decomposition reaction in fixed-bed or fluidized-bed catalytic reactors at 300-350℃ and 1 atm. When CO2 contacts with oxygen deficient ferrites, decomposition of CO2 occurs by the incorporation of oxygen anions in the vacancies in the oxygen deficient ferrite thereby restoring the ferrite to stoichiometry at 1 atm and 573-673 K. At the same time, electrons are donated from the oxygen deficient ferrite to produce carbon or carbon monoxide. Next, the deposited carbon on the surface converts into methane (methanation) upon treatment with H2 (hydrogenation) while regenerating used ferrite to oxygen deficient ferrite. Decomposition of CO2, moreover, recovery of valuable methane using heat energy of offgas produced from steel companies, powder generation plants, and petrochemical industries is an appealing alternative for energy recovery. | ||
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| 英文關鍵字 | Zinc/nickel ferrite nanocatalyst, Steel plant flyash, Catalytic decomposition of CO2 | ||