熱化學사이클을 위한 金屬 酸化物의 酸化 還元 特性 = Redox characteristics of metal oxide for thermochemical cycle

다국어 초록 (Multilingual Abstract)

To develop oxygen carrier for chemical-looping reaction, we have investigated that various oxygen carrier, NiO/ZrO_(2), NiO/YSZ, NiO/NiAl_(2)O_(4) and NiO/AIPO_(4), were examined by TGA.
Hydrogen fuel is reacted with metal oxide (reduction of metal oxide), and then the reduced metal is successively oxidized by air. The oxygen carriers were prepared by dissolution and semi sol-gel method. The diameters of them were set at 2mm and 105~150㎛.
A various kinds of oxygen carriers were determined by reacitivity and regenerability. Oxygen carrier consists of metal oxide and binder. NiO, CoO, Fe_(2)O_(3), NiO-Fe_(2)O_(3) and NiO-CoO particles are used as metal oxide. Binders are ZrO_(2), YSZ, NiAl_(2)O_(4) and AIPO_(4). The results of experiment could be summarized as follows.
1. Characteristics of Redox reaction with various metal oxides in oxygen tarriers.
The metal oxide(NiO, CoO, Fe_(2)O_(3), NiO-Fe_(2)O_(3) and NiO-CoO) used to oxygen carrier are estimated.
The times required for their complete conversion in reduction were within 400s and in oxidation were within 600s.
In single metal oxides, NiO/YSZ and CoO/YSZ have good reactivity and good reduction and oxidation rate. In oxidation of CoO/YSZ, time required for complete conversion was increased by tailing.
The behavior of double metal oxide of NiO-CoO particles was similar to those of single metal oxide. For the particle of NiO-Fe_(2)O_(3), both the reduction and oxidation rates are lower than those of NiO-CoO particle. But Fe_(2)O_(3) have an advantage in cost and in environmental sound.
Result by kind of metal oxide showed that NiO and Fe_(2)O_(3) can choose by suitable metal oxide in oxygen carrier.
2. Characteristics of Redox reaction with various binders in oxygen carriers.
In oxygen carriers, NiO/YSZ and NiO/NiAl_(2)O_(4) have good reduction and oxidation rates. Also they have good regenerability. In case of NiO/AIPO_(4), for the early few cycles, rates of reduction and oxidation were slightly change, but they were almost the same after the third cycle. It has lesser 20% than NiO/YSZ in reactivity. NiO/NiAl_(2)O_(4) Particle had advantage of material cost as compared with NiO/YSZ. In XRD patterns, NiAl_(2)O_(4) as spinel type had been formed between metal oxide NiO and binder Al_(2)O_(3) during calcinations process above 1100℃. Therefore, the NiO/NiAl_(2)O_(4) was simply prepared will be one of good candidates to take the place of NiO/YSZ.
3. Characteristics of Redox reaction of NiO/YSZ against mixing ratio.
We observed redox reaction of NiO/YSZ against mixing ratio.
As ratio of metal oxide in oxygen carrier increases, reaction velocity decreased.
The oxygen carrier that weight ratio of NiO/YSZ was 6/4 stabilized within 100s in reduction and oxidation. Therefore, we have confirmed that favorable weight ratio of NiO/YSZ was 6:4.
4. Regenerability of oxygen carriers
All redox reaction repeated 10 times. In 10 times redox reactions, the reactivities of NiO/YSZ and NiO/NiAl_(2)O_(4) were superior to those of other oxygen carriers relatively.
Especially, both NiO/YSZ and NiO/NiAl_(2)O_(4) showed fast reaction rate and about 100% of oxygen conversion during all redox reactions.
The NiO/YSZ and NiO/NiAl_(2)O_(4) calcined at temperature of 1300℃ showed the most superior performance.
The NiO/NiAl_(2)O_(4) Prepared by oil-dropping coagulation showed high reaction rate, regenerability and mechanical strength until the contents of NiO was 80wt.%.

목차 (Table of Contents)

• 목차 = ⅰ
• Ⅰ. 서론 = 1
• Ⅱ. 문헌적 고찰 = 5
• 2.1. CO_(2)의 저장기술 = 5
• 2.2. CO_(2)의 분리 공정 = 5
• 2.3. 매체 순환식 연소 = 9
• 2.4. 산소운반매체의 특성 = 10
• 2.4.1. 산소운반매체에서 금속산화물의 역할 = 10
• 2.4.2. 산소운반매체에서 바인더의 역할 = 12
• 2.5. 산소운반매체의 제조 방법 = 13
• 2.5.1. 함침법 (Impregnation method) = 13
• 2.5.2. 졸겔법 (Sol-Gel method) = 16
• 2.5.3. 용해법 (Dissolution method) = 20
• 2.6. 산소운반매체의 구형제조를 위한 공정 = 21
• 2.6.1. ODC법에 의한 구형의 알루미나 제조 = 21
• 2.6.2. RPG법을 이용한 산소운반매체의 구형 제조 = 22
• 2.7. 매체의 선정 = 24
• 2.8. 주요 각국의 연구동향 = 28
• Ⅲ. 실험 = 29
• 3.1. 시약 = 29
• 3.2. 산소운반매체의 제조 = 29
• 3.2.1. 용해법 = 29
• 3.2.2. 졸겔법 = 34
• 3.3. 균일한 구형매체 제조를 위한 방법 = 34
• 3.3.1. ODC법 = 34
• 3.3.2. RPG법 = 37
• 3.4. 실험 장치 및 방법 = 37
• Ⅳ. 결과 및 고찰 = 41
• 4.1. 산소 운반 매체의 기계적 강도 = 41
• 4.2. 매체의 반응성 - 반응온도의 영향 = 42
• 4.3. 금속산화물의 종류에 따른 영향 = 47
• 4.4. 바인더의 유무 및 안정화에 따른 영향 = 48
• 4.5. 바인더의 종류에 따른 영향 = 51
• 4.6. AIPO_(4)의 처리에 따른 효과 = 53
• 4.7. 하소온도에 따른 영향 = 55
• 4.8. 공업용 YSZ와의 비교 = 58
• 4.9. NiO와 Fe_(2)O_(3)의 혼합 산화물 매체의 비율에 따른 영향 = 58
• 4.10. NiO와 CoO의 혼합 산화물 매체의 비율에 따른 영향 = 61
• 4.11. 금속산화물의 종류에 따른 전환율과 내구성 = 63
• 4.12. NiO와 Fe_(2)O_(3)의 혼합 비율에 따른 전환율과 내구성 = 69
• 4.13. NiO와 CoO의 혼합비율에 따른 전환율과 내구성 = 73
• 4.14. 바인더의 유무 및 종류에 따른 전환율과 내구성 = 73
• 4.15. NiO/YSZ 입자의 하소온도에 따른 전환율과 내구성 = 81
• 4.16. NiO/YSZ 입자의 혼합비율에 따른 전환율과 내구성 = 84
• 4.17. NiO/AIPO_(4) 입자의 혼합비율에 따른 전환율과 내구성 = 93
• 4.18. NiAIP-2와 NiAIP-4 매체의 전환율과 내구성비교 = 97
• 4.19. ODC법으로 구형제조한 NiO/NiAl_(2)O_(4) 입자의 혼합비율에 따른 전환율과 내구성 = 100
• Ⅴ. 결론 = 107
• 1. 금속산화물의 종류에 따른 환원/산화반응 특성 = 107
• 2. 바인더의 종류에 따른 환원/산화반응 특성 = 107
• 3. 금속산화물과 바인더의 비율에 따른 환원/산화반응 특성 = 108
• 4. 산소운반매체의 반응성과 반복된 환원/산화반응시 내구성평가 = 108
• References = 110
• ABSTRACT = 116
• Appendix = 120