Experimental Study On Liquefaction Of Biomass In Supercritical Water

Along with the fossil fuel being used up and the global environment being destroyed badly, it is extremely urgent to develop a clean and renewable energy. If biomass is utilized reasonably, it is not only a renewable energy, but also a clean energy. In recent years, the liquefaction technology of supercritical fluid taking water as the solvent and reaction medium has got extensive research. Based on summarizing of many literatures, an experimental scheme that biomass was liquefied in supercritical water has been worked out, and then, a series of experimental researches have been carried out.A set of experimental equipment in which biomass is liquefied in supercritical water has been designed by us successfully. The maximum design temperature of the reactor is 450℃,and the maximum design pressure is 45Mpa. The reactor is heated by tin bath, so the reaction speed is quick. Test has proved that the equipment can meet the experiment request, and it has many advantages, such as: simplicity of operator, convenient of maintenance, no secondary pollution and high conversion ratio, and so on.In the experiment, essential component of the three kinds of biomass included woodiness, eupatorium coelestium and peanut shell has been analyzed, and it mainly include three component-cellulose, semi-cellulose and lignin. The mass content of cellulose is highest, and the semi-cellulose is lowest. The sum of the three components is more than 95%.Woodiness, eupatorium coelestium and peanut shell are liquefied in supercritical water, the gas products has tar smell; The liquefaction product shows acidly, the PH value is between 2.5 and 4.8; Some liquefaction products are unstable, so, in the course of conservation, the color turns from yellowish into the brown, and then there is a black deposition in the liquefaction products.The liquefaction products of cellulose, woodiness, eupatorium coelestium and peanut shell under different reaction temperature are analyzed by GC-MS. Its composition is quite complicated, and it contains dozens of organic matter. The main components are organic acid, furfural and other organic components contained methyl and methoxyl, such as aldehyde, ketone, phenol. And they contain 3~9 carbon atom. Compared the liquefaction products with others' research ofhydrolysates and pyrolysates of cellulose, semi-cellulose and lignin, the reaction are hydrolysis and pyrolysis when biomass is liquefied in supercritical water, so the final products are hydrolysates and pyrolysates of cellulose, semi-cellulose and lignin. Moreover, when the reaction temperature is above the critical temperature of water(374.3'C), the effect of reaction temperature on components of biomass is not obvious, but the effect of reaction temperature on components content of biomass is obvious.In addition, to determine the optimum conditions of the process, the effect of reaction temperature, volume of feed water and reaction mass on conversion rate has been studied. The optimum conditions of the process are summarized as: when the other reaction conditions are not changed, the reaction temperature should be adjusted to 370- 390℃; When the volume of the reactor is 20ml and other conditions are not changed, the volume of feed water should be adjusted to 10~ 11ml; The mixture ratio of reaction mass to the mass of feed water should be controlled between 1:10 and 1:20. Cellulose, woodiness, eupatorium coelestium and peanut shell are liquefied in supercritical water under the optimum conditions, the conversion ratio is higher and the experimental result is better.