Pyrolysis Kinetics And Pyrolysis Liquefaction Technology Research On Marine Macro-algae Biomass

In recent years, in the face of dual pressure of global energy and environments, accelerating thedevelopment and utilization of new energy resources has become a common action around the world.Biomass energy is one of most important renewable energies. And pyrolysis is one of the mostpromising methods of biomass utilization in the near future and it arouses researchers' extensiveattention around the world. Study on biomass pyrolysis kinetics which can obtain their pyrolysisparameters t is of great significance toward judging mechanism and influence factors and optimizingreaction conditions. The results of this study provided the useful information for designing apyrolytic processing system using biomass as feedstock. Researchers have already carried outextensive studies on terrestrial biomass thermochemical properties and pyrolysis liquefaction works,and some terrestrial biomass pyrolysis studies have already been realized industrialization, butmacro-algae biomass related research started late, and a lack of thorough and systematic researcheson the pyrolysis characteristics and kinetic mechanism has a serious impact on the progress ofbio-fuel production and industrialization by pyrolysis and liquefaction from macro-algae biomass.In this thesis, several kinds of common macro-algae were investigated by thermogravimetryAnslysis (TGA) and differential scanning calorimetry(DSC) methods on pyrolysis characteristics andkinetics for screening the suitable macro-algae species as feedstock for bio-fuel production bypyrolysis and liquefaction. And then Enteromorpha prolifera and Macrocystis pyrifera withabundant bioresources and good thermochemical properties were focused on and investigated ontheir pyrolytic characteristics and kinetics mechanisms. On basis of previous studies Enteromorphaprolifera materials pyrolysis experiments were conducted on a laboratory scale using self-mixingdownflow circulating fluidized bed reactor. And a specified volume of bio-fuel and bio-oil wereobtained and then purified and characterized. The main research contents and results are as follows:1. Fixed Enteromorpha, floating Enteromorpha, Ulva lactuca L., Laminaria japonica,Asparagus schoberioides kunth and Undaria pinnatifida (Harv.), which are six kinds of marinebiomass, are the focuses of this study. Simultaneously, cornstalk, which is grass biomass, andsawdust, which is lignocellulosic biomass, are reference samples. Non-isothermal thermogravemetricanalysis was used to investigate the process of pyrolysis and thermolysis kinetics. The basicpyrolysis characteristics, including the earliest temperature of precipitation of volatiles Ts, the peakweight loss rate Dmax, the peak weight loss temperature Tmax, the index of pyrolysis productsrelease r and other parameters, were studied using TGA method and TG-DTG-DTA curves. Theresults showed that the whole process of pyrolysis of biomass could be divided into three stages:dehydration, dramatic weight loss and slow weight loss. The Ts of macro-algae is significantly lowerthan other two kinds of terrestrial biomass, and floating Enteromorpha has lowest stability ofpyrolysis and a good combustion characteristics. At the same time, corresponding activation energyE and frequency factor A were obtained by Coats-Redfern method. It was found that the pyrolysisreaction mechanism functions of three kinds of biomass are different. For marine biomass, Avrami-Erofeev model is fit for low temperature region, and second-order reaction is fit for high temperatureregion. The most probable mechanism functions of grass biomass is second-order reaction model and that of lignocellulosic biomass is Zhuralev, Lesokin and Tempelmen (Z-L-T) function model,respectively. In addition, the process of pyrolysis with sodium carbonate and alumina showed thatthe catalytic effect of the sodium carbonate is more obvious than the latter. With the increase ofcatalyst content, Tmax and E decreased continuously, and Dmax increased in varying with differentsamples.2. The materials of Enteromorpha prolifera, Macrocystis pyrifera, cornstalk and sawdust wereinvestigated on the components of cellulose, hemi-cellulose and lignin by concentrated sulfuric acidhydrolysis, dilute sulfuric acid hydrolysis and hydrochloric acid hydrolysis method. The pyrolysischaracteristics and kinetics of this four biomass were studied by TGA method. The pyrolysisexperiments were performed up to800C at heating rates of5,10,20and30C/min in a dynamicnitrogen flow of50cm3/min. The results showed that four stages appeared in this thermal degradationprocess. The influence of different heating rates on the process of biomass pyrolysis was investigatedby non-isothermal method. With heating rate increasing, the initial temperature and peak temperatureof pyrolysis shifted to a higher value and there is an obvious inorganic volatilization process in thefinal stage of marine biomass. The composition difference of biomass was also studied by FT-IR,which confirmed the influence of the composition difference of biomass on pyrolysis characteristicsand kinetics. The activation energies of four samples for pyrolysis were respectively calculated byFWO, KAS and Popescu methods. The best mechanism functions of this four biomass were alsodeduced. The results showed that with the reaction degree increased all of the activation energy ofthis four biomass increased. The results of the best mechanism functions acquired by Popescumethod showed that the equation ln[-(1-α)]4is the optimal mechanism function for Enteromorphaprolifera and Macrocystis pyrifera, and the equation ln[-(1-α)]3is the optimal mechanism functionfor cornstalk and sawdust.3. Enteromorpha prolifera was selected as the object biomass and its cellulose, hemi-celluloseand lignin were extracted and analyzed by different methods. Then thermal characteristics andkinetics were investigated at different heating rates by TGA and DSC methods. The kinetic character-istics parameters, including the earliest temperature of volatiles emission, the peak weight loss rateand the peak weight loss temperature, and so on, could be obtained with these methods. The resultsshowed that the pyrolysis processes of the three components are similar with one another, forexample the whole process all can be divided into three stages: dehydration, dramatic weight lossand slow weight loss. The themostability of them follows the order of lignin> hemicellulose>cellulose. The results of the best mechanism functions acquired by Popescu method showed that theequation f(α)=[ln(1α)]3is the optimal mechanism function for cellulose and ligin, and the equationf(α)=[ln(1α)]4is the optimal mechanism function for hemicellulose. At the same time, theactivation energy, pre-exponential factor and the function of weight loss rate of the sample byPopescu method have been obtained. At different heating rates, there are some differences amongthem, especially along with the increase of the heating rates, the TG and DTG curves all movedtowards the high temperature region, but the rate of weight loss decreased.4. The green tide Enteromorpha prolifera biomass powder was used as raw materials, and alaboratory scale circulating fluidized bed fast pyrolysis experiment was conducted with a certain amount of pyrolysis bio-oil obtained. Subsequently, Enteromorpha prolifera pyrolysis oil physicaland chemical properties (including color, odor, density and pH) were assessed, and the pyrolysiscrude oil and light oil separated by extraction were analyzed using TGA and DSC technology,Fourier transform infrared spectroscopy(FT-IR) and GC-MS technologies. The results showed that,the light oil is rich in alkanes, furans, aldehydes, phenols and aromatic chemicals. The study resultssuggested that green tide Enteromorpha prolifera biomass as raw materials for bio-oil production bypyrolysis has good feasibility and great potential.