Development of high efficient power generation system with CO_2 recovery

为了开发一种高效的化学链燃烧发电系统，我们进行了多方面的实验研究，并取得了以下成果.循环固体介质的发展在所提出的系统中，燃料在一个反应器中被金属氧化物氧化，还原金属在另一个反应器中被空气氧化。该方案不需要额外的能量就能回收CO_2，并能高效发电，同时避免了NO_x的生成。这些特性是由在两个反应器之间循环的固体介质带来的。除了已经用作反应介质的NiO/YSZ之外，我们开发了两种更有前途的候选物，即，NiO/NiAl_2O_4和CoO-NiO/YSZ。对NiO/NiAl_2O_4和CoO-NiO/YSZ颗粒进行了循环试验（600 ℃下H_2还原，1000 ℃下空气氧化）。与NiO/YSZ颗粒相比，这两种颗粒在反应10次后仍能保持其微观结构、机械强度和反应活性.避免碳沉积当燃料含有碳时（例如，NiO/YSZ颗粒在50%CO-25%H_2O-25%N_2气氛下，600 ℃时，可完全避免积炭，此时的水蒸气浓度远低于水蒸气重整.固定床反应器实验在固定床反应器中，用H_2或CH_4还原颗粒状固体介质，用空气氧化。通过GC-Mass检测来自反应器的废气。通过这些实验，为下一步设计实用反应堆提供了有价值的信息。

In order to develop a high-efficient power generation system based on chemical-looping combustion, we have carried out various experiments, and the following results were obtained.1. Development of circulating solid mediumIn the proposed system, fuel is oxidized by metallic oxide in a reactor and reduced metal is oxidized by air in another reactor. This scheme yields CO_2 recovery without any extra energy, high-efficient power generation, and avoidance of NO_x formation. These characteristics are brought by the solid medium that is circulated between two reactors. In addition to NiO/YSZ that has been used as a reaction medium, we developed two more promising candidates, i.c., NiO/NiAl_2O_4 and CoO-NiO/YSZ.2. Repeatability of solid mediumCyclic test (reduction by H_2 at 600ﾟC and oxidation by air at 1000ﾟC) was conducted using NiO/NiAl_2O_4 and CoO-NiO/YSZ particles. In comparison with NiO/YSZ paricle, these two particles have benefits for maintaining their microstructure, mechanical strength, and reactivity even after 10cycles of reaction.3. Avoidance of carbon depositionWhen the fuel contains carbon (e.g., Co or CH_4), NiO/YSZ had good resistance against carbon deposition as compared to NiO/NiAl_2O_4 and CoO-NiO/YSZ.For NiO/YSZ particle, carbon deposition can be completely avoided at the atmosphere of 50% CO-25%H_2O-25%N_2 at 600ﾟC,where this steam concentration was found to be much lower than that in steam reforming.4. Experiments in fixed-bed reactorPellet-shaped solid medium was reduced by H_2 or CH_4 and oxidized by air in the fixed-bed reactor. The exhaust gas from reactor was detected by GC-Mass. From these experiments, we got valuable information for the next step to design practical reactor.