Experimental Research On Thermchemical Liquefaction Of Microalgae

Biomass based materials such like microalgae are abundant renewable resources in the world.Converting biomass materials into alternative petrochemical will release the dependence on fossile oils ofthe human society as well as to reduce the environment pollution. The purpose of this study was toinvestigate the liquefaction process for converting microalgae into bio-oil to develop a new approach to thereasonable and high efficient utilization of food process residues.The experimental research on thermchemical liquefaction of microalgae was crrarried out, maincontents as follows:1. The pyrolysis characteristics of Dunaliella tertiolecta was investigated by the thermogravimetric analysis.The experiments are carried out with a thermogravimetrc analyzer from ambient temperature to 900℃. Thekinetic analysis was performed by using a composite procedure involving the iso-conversional method andthe master plots method. Results showed that three stages appeared in the pyrolysis process with increasingtemperature. Moreover, the initial temperature of pyrolysis and the temperature at which the pyrolysis ratereaches the peak value rose with the heating rate increasing. The iso-conversional method indicated that thepyrolysis reaction can be dealt with as single reaction model, and the master plots method revealed thisprocess conforms to simple order reaction mode, F_n. The kinetic parameters, such as apparent activationenergy E_a, pre-exponential factor A and the kinetic exponent n, were determined, where the apparentactivation energy E_a is 146.3 kJ/mol, the pre-exponential factor is 4.28×10¹³ S^-1 and the kinetic exponent n is2.4.2. Direct liquefaction of Dunaliella tertiolecta dry powder and Dunaliella tertiolecta residue in sub-criticaland supercritical water was carried out in an 50ml autoclave. During the tentative experiment, Theinfluences of reaction temperature, reaction time, were inverstigated. Liquefaction results of Dunaliellatertiolecta dry powder and Dunaliella tertiolecta residue have shown that the highest liquefaction yield andbio-oil yield can be obtained at the condition of 340-380℃, 60min when feedstock ratio is 4g material/40ml water.3. The results showed that it was effcient to liquefy Dunaliella tertiolecta with ethylene glycol solvents as aliquefying solvent and 98% sulfur acid as a catalyst. Mathematical model for predicting the liquefactionyield was set up by central composite design and response surface analysis (RSA) on the basis of one-factortests. From a regression analysis, it appears that the individual effects (sulfuric acid content, thetemperature and the time), as well as the interactions between operating variables all have significanteffects on the liquefaction of microalgae, the liquefaction technology was optimized as follows: sulfuricacid content of 2.4%, the temperature of 170℃and the time of 33 min. The liquefaction yield reached97.02% at above-mentioned conditions.