Development of high efficient power generation system with CO_2 recovery

为了开发一种基于化学环燃烧的高效发电系统，我们进行了各种实验，得到了以下结果：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。该方案在不消耗额外能量的情况下回收CO_2，发电效率高，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NiO/YSZ作为反应介质外，我们还开发了两种更有前途的候选介质，即NiO/NiAl_2O_4和co -NiO/YSZ.2。采用NiO/NiAl_2O_4和co -NiO/YSZ颗粒进行了固体介质循环试验（H_2在600ºC下还原，空气在1000ºC下氧化）的重复性研究。与NiO/YSZ颗粒相比，这两种颗粒在经过10次循环反应后仍能保持其微观结构、机械强度和反应活性。当燃料中含有碳（如Co或CH_4）时，与NiO/NiAl_2O_4和Co -NiO/YSZ相比，NiO/YSZ具有良好的抗碳沉积能力。3 .对于NiO/YSZ颗粒，在600ºC的50% co -25% h2o -25% n_2气氛下可以完全避免积碳，其蒸汽浓度远低于蒸汽重整。在固定床反应器中，用H_2或CH_4还原球团状固体介质，用空气氧化球团状固体介质。采用气相色谱-质谱法对反应器废气进行了检测。从这些实验中，我们得到了下一步设计实用反应堆的有价值的信息。

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.