Reclamation Research Of Purple Root Water Hyacinth In Sub/Supercritical Water

The salvage quantity of purple root water hyacinth in Dian Lake (in Yunnan Province) is very large each year. The exploitation of utilize of it has always bothering us for a long time because of its high moisture (>90%), high content of heavy metals. The sub/supercritical water can make purple root water hyacinth efficient conversion come true and during the direct dispose of purple root water hyacinth, water work as the reaction medium can also hydrolysis and extract purple root water hyacinth molecules. Withing high added value products like oil and gas fuel and high heavy metals of residue during the process.The paper analyzed the technological conditions of purple root water hyacinth reclamation(gasification and liquidation)in sub/supercritical water systematically. The results show that, the main reaction is the liquidation of purple root water hyacinth in sub/supercritical water at lower temperature (280-380℃). Liquid product is influenced by reaction time, temperature and catalyst significantly. The yield has the tendency to become higher and then reduce with the increase of temperature and eaction time. Under this experimental condition, the optimum technological conditions is:when the reaction temperature is 340℃, reaction time is 45min, the yield is 73.22%. The yield is 87.64% when adding catalyst Pd/Al2O3 at 5min and 340℃, it is higher 50% than without catalyst. It shows that catalyst can shorten the reaction time significantly. Liquefaction intermediate component shows that the bases are alcohols, phenols like phenol and phenol,4-ethyl-, hydrocarbons like alkane and olefin, acids like fatty acids, oxygenated chemicals like esters, ketone, aldehydes, pyridine, naphthalene etc. Biodiesel can be obtained after refining.When temperature is higher than 400℃, the main product is gas. Comparing with temperature and feed loading, the reaction time did not significantly affect on the gas yields, especially at longer times.The results indicated that the yields of gases increased with temperature, H2 and CH4 reached 7.33 and 5.07 mol/kg respectively at 550℃ with a reaction time of 50 min and a 4.8 wt% loading. Adding the Ru/C catalyst, the rate of gasification of carbon and hydrogen vaporization rate reached 90% and 120% respectively. Using self-made Ru/CZ selective catalyst can improve the hydrogen production rate and selectivity of hydrogen. The kinetic analysis indicated that the hydrogen gasification efficiency (HGE) was more sensitive to temperature than carbon gasification efficiency (CGE) and the gasification behavior of water hyacinth in supercritical water followed the psudo-first-order kinetic under the experiment conditions.By analyzing the composition of liquefaction products of different temperature and reaction time, the reaction mechanism of purple root water hyacinth in sub/supercritical water was studied, the results show that, in the action of sub/supercritical water, the purple root water hyacinth firstly decomposed to produce small molecules such as phenol, Phenol,4-ethyl and most of the macromolecular esters and diethyl oxygen-containing compounds etc., with the temperature and the reaction time prolonged, gradually transformed into most of the small molecules, in the majority with phenolics, and finally get the product gas. The phenols are difficult to convert. The analysis of the residue of the liquid solid residue indicated that heavy metals mainly existed in the residue, and the content of heavy metals in the residue did not reach the standard of hazardous waste.In conclusion, reaction temperature and residence time are the key factors to influencing the oil yields and gas yields. Oil production has advantage in lower temperature, gas production has advantage in higher temperature. The research work provided the basis of purple root water hyacinth reclamation in sub/supercritical water and laid the foundation for the technical generalization.