Development of Clean Utilization Technologies of Low-grade Coals Combined with Biomass

为了高效、清洁地利用低品位煤，煤与生物质混烧或共气化技术将有助于提高低品位煤的利用率。在本研究中，进行了生物质型煤燃烧、电加热间歇燃烧室、煤与生物质混烧、电加热落管炉、煤或生物质熔融盐气化炉等三种试验。对于生物质型煤的燃烧，由于生物质型煤中的生物质起到了点火触发的作用，生物质型煤的着火滞后时间和燃烧速度分别比煤型煤短和快。熟石灰可就地捕集型煤产生的SO2。在混燃实验中，生物质在混燃过程中对低品位煤的着火和燃尽有一定的促进作用。但是，混烧过程中NO和N2O的排放变化趋势与燃煤过程相似。与NOx相关的化学动力学模拟也可以解释实验得到的NOx行为的变化趋势。但非均相反应方式似乎影响了N2O的变化趋势。在生物质燃烧过程中，会产生粒径小于2μm的细小颗粒，形成灰尘颗粒。然而，生物质与煤一起燃烧时，生物质中的细颗粒物在燃烧过程中会被煤中的灰分捕获。熔盐煤气化炉似乎具有炉内脱硫、除尘和碳的催化作用。即使在相对较低的温度下，气化炉也有可能在没有气体净化系统的情况下产生清洁的合成气。

In order to utilize low-grade coals efficiently and cleanly, technologies of co-combustion or co-gasification of coal with biomass will contribute to enhancing utilization of low-grade coals. In this study, three kinds of experiments such as a biobriquette combustion, using an electrically heated batch combustor, co-combustion of coal with biomass, using an electrically heated drop tube furnace, and fundamental gasification of coal or biomass, using a molten salt gasifier, were carried out. For the biobriquette combustion, the ignition lag and burning rate of the biobriquette becomes shorter and faster than that of the coal briquette, respectively, since the biomass in the biobriquette plays a role for a trigger of ignition. Slaked lime can capture in situ SO_2 produced from the briquette. In the co-combustion experiments, the biomass can enhance ignition and burnout of the low-grade coal during the co-combustion. But, trend of NO and N_2O emissions during the co-combustion is similar with that during the coal combustion. The chemical kinetic simulation relating to NOx can also explain the trend of NOx behaviors obtained experimentally. However, heterogeneous reaction scheme seems to affect the trend of N_2O. In the biomass combustion, fine particulates with the particle size of less than 2μm are produced as ash particles. Burning the biomass with the coal, however, the fine particulates from the biomass are captured by the ash from the coal during the combustion. The molten salt coal gasifier seems to have such functions as in-furnace desulfurization, dust collection and catalytic action of carbon. It may be possible for the gasifier to produce a clean synthesis gas without a gas cleaning-up system even at relatively low temperature.