Evaluation of the performance of bimetal mixture from scrap iron, copper wire and nickel oxide as oxygen carrier in chemical klooping combustion of Philippine coal using thermgravimetric analysis

• Main Author: Sokuntheany, Kheang
• Format: text
• Language: English
• Published: Animo Repository 2014
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/4700
• Institution: De La Salle University

Chemical looping combustion (CLC) is the latest and perhaps the most effective carbon capture technology in the last decade. In CLC, the oxygen used for the combustion is from the metal oxide, so there is no direct contact between fuel and oxygen from the air. The advantage of CLC is that it produces energy from fossil fuel wherein the flue gas produced is just a mixture of steam and carbon dioxide (CO2). Hence, the separation of CO2 has no significant energy penalty, because we just allow the steam to condense. In this study, Semirara coal of the Philippines was used as fuel in order to investigate the performance of six types of bimetal oxide samples as oxygen carrier. Moreover, the effect of hold temperature, coal to metal oxide mass ratio and metal1/metal2 mass ratio on conversion of coal-oxygen carrier mixture were also studied. Two different temperatures of 700oC and 900oC were chosen to be the hold temperature. The mass ratio of 25:75 and 75:25, were selected for coal to metal oxide mass ratio and metal/metal mass ratio in order to evaluate their effect on the conversion of the coalmetal oxide in chemical looping combustion. Furthermore, the effect of the number of redox cycle on the conversion was also investigated. Based on the statistical analysis, the significant parameters are the coal to metal mass ratio and also the interaction between temperature and coal to metal mass ratio for Cu-Fe mixture. The coal/metal oxide mass ratio is the significant parameter in the case of Ni-Fe mixture as oxygen carrier (OC). The higher conversion of up to about 70% was obtained for all samples with the coal to metal mass ratio of 75:25 for both bimetal mixture. Moreover, it was noticed that temperature has a relationship with the metal1/metal2 mass ratio. For the samples, which were high in treated copper and NiO content, performed well at the low temperature only. However, at high temperature of 900oC, the reactivity of those bimetal oxide samples were dramatically decreased because of agglomeration. For bimetal oxide as oxygen carrier (OC) in CLC with coal, the relationship between temperature and metal1/metal2 mass ratio was also considered to be important. The mass of low melting point metal oxide such as treated copper wire and NiO should not be too high in the bimetal mixture in order to avoid agglomeration problems which can cause the deactivation of OC particle during high temperature coal- CLC performance. The ratio of 25:75 of metal1/metal2 mass ratio would be a suitable for the bimetal mixture in CLC with coal at the high temperature of 900oC. Redox cycle study of the six samples with their corresponding specific conditions showed that at the highest temperature of 900oC, 25Cu75Fe performed well its role as OC in coal CLC process because no particle sintering problem was observed. On the other hand, at the lowest temperature of 700oC, 75Ni25Fe showed high reactivity without any sign of particle agglomeration from the 2nd to the 5th cycle . From redox cycle study,we can also conclude that the six bimetal oxide samples can be reoxidized back to the original oxide form in order to perform their role again as OC. Nevertheless, the ability of re-oxidation of bimetal oxide will change depending on the type of mixture and the metal1/metal2 mass ratio.