Study On The Properties Of Caragana Biomass Carbonization And Activation

Biomass is a kind of renewable energy that is of much value. It has so many advantages such as clean, low cost, economic, rich in source and energy, wide application and easy to get and so on. It is of great practical significance to increase the development and utilization of biomass resources, especially under conditons that today resources are shortage and environment deterioration more and more seriously.As biomass energy, Caragana is a kind of excellent shrub resource, which is widely disstributed in "Three North"areas such as northeast,northwest and north China. The adaptability and survival rate of Caragana is considerably high, and as well as its ability of branching and regeneration. The branches of Caragana need to be choped every three to five years, so the period of choping for Caragana is short, and the yield is high. This study makes full use of the advantages of Caragana, such as abundant resources, easy to obtain, and high yield, and the branches during choping period is fullly utilized in this paper. Its carbonization and activation properties is studied in this paper, so as to improve its application value further more.Caragana is used as research object, and its pyrolysis mechanism is studied by DSC, TG, DTG technology, the main components and their variation trend of Caragana carbon under different conditions were determined. The pyrolysis experimental results show that Caragana pyrolysis can be divided into four stages:drying stage (25℃～150℃), pre carbonization stage (150℃～200℃), carbonization stage (200℃～580℃) and calcination stage (580℃), respectively. Carbonization process will be lagging with the heating rate increased. Carbon yield and the volatile content decreases with the increase of carbonization temperature, but ash content and fixed carbon content show opposite trend, and carbonization time hardly has no influence on above indexes. Under the condition of this experiment, conclusion can be drawed that the best carbonization process for Caragana is that the final carbonization temperature is 500℃, and remaining 1 hour after achieving 500℃.Under this condition, Caragana carbon yield is 47.07%, the content of fixed carbon 37%, ash content 49%, and volatile matter 14%.This paper uses steam activation and phosphoric acid activation to create activated carbon, at the same time its adsorption properties are studied. Steam activation experiment results show that both Caragana activated carbon yield and iodine adsorption value will decline with temperature increased or time extended. And the best activation process for Caragana under this experimental conditions is that activation temperature 600℃, activation time 2 hours, the activated carbon yield under these conditions was 65.59%, and the iodine adsorption value is 221mg/g. Phosphoric acid activation experiment results show that activation temperature is the most significant fator to activated carbon yield and iodine adsorption value, other factors such as the volume fraction of phosphoric acid, the comprehensive effect of the ratio of liquid to solid and activation time will also effect the activated carbon yield and its properties. For activated carbon, the effects sequence of each single factors is that activation temperature> activation time> the volume fraction of phosphoric acid>the ratio of liquid to solid; for iodine adsorption value, the sequence is that activation temperature> the ratio of liquid to solid> the volume fraction of phosphoric acid> activation time. The best activation process for Caragana by phosphoric acid activation under this experimental conditions is that activation temperature 400℃, the volume fraction of phosphoric acid 40%, the ratio of liquid to solid 3:1, activation time 120min.The activated carbon yield under these conditions was 31.90%, and the iodine adsorption value is 666mg/g, which is much larger than that of commercial activated carbon(146mg/g).By contrasting many indicators such as iodine adsorption value, microstructure, specific surface area, total pore volume and pore size, conclusion can be drawed that the comprehensive performance of Caragana activated carbon is much better than that of commercial activated carbon. Therefore, Caragana is suitable to be used as large surface area activated carbon raw material. The datas and conclusions in this study provide theoretical basis and support for optimization and selection of Caragana carbonization and activation process.