Experimental And Mechanism Study On Pyrolysis Of Typical Algae Biomass

The rapid development of social life,the serious depletion of fossil fuels and the worsening environmental pollution have prompted people to pay more attention to renewable energy.Algae are considered to be a renewable energy with great potential because of its high photosynthesis efficiency,high yield and non-occupation of cultivated land.In this paper,three kinds of algae,nannochloropsis,spirulina and sargassum,were selected to study the effect of different temperatures(400 °C,500 °C,600 °C,700 °C)and the use of catalysts(HZSM-5 and HUSY)on algae pyrolysis products.According to the proximate analysis and elemental analysis of the three kinds of algae,it can be seen that the volatile matters accounting for 60-80%,and the calorific value are relatively high.TG and DTG curves of algae were measured by thermogravimetric analysis at the heating rate of 10 °C/min.The results show that the pyrolysis process of different algae is mainly divided into three phases,i.e.dehydration,decomposition and the formation of char.The experiments were conducted by pyrolysis-photoionization time-of-flight mass spectrometry for on-line analysis of algae pyrolysis combined with Py-GC-MS for offline analysis.The three algae components are different,thus the pyrolysis products and distribution are also very different.Nannochloropsis are mainly composed of a large number of lipid,a small amount of protein and carbohydrates.For lipids,the major structures are triglycerides,steroid compounds,and phospholipids.The main decomposition reactions of lipid are decarboxylation,decarbonylation,glycerol cleavage and steroid decomposition.Spirulina are composed of a large number of proteins,small amounts of lipids and carbohydrates.The main pyrolysis pathways of protein are decarboxylation,deamination,depolymerization,and cyclization.The main components of sargassum are lignocellulosic,the pyrolysis path of lignocellulosic are mainly dehydration,glycosidic bond cleavage,ring opening reaction and rearrangement reaction.According to the analysis of the pyrolysis results at different temperatures,it shows that the temperature has a great influence on the pyrolysis products.The higher temperature can promote the cleavage of the chemical bonds and promote the pyrolysis reaction.Both HZSM-5 and HUSY catalysts have great influence on the product distribution of oalgae pyrolysis.The signal intensities of light olefins,monocyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons are obviously increased after adding catalyst.The catalyst can effectively promote the denitrification,deoxygenated and cyclization.Due to the different pore size of HZSM-5 and HUSY catalyst and acidity,the catalytic results are obviously different.The HZSM-5 catalyst has a high silica-alumina ratio and a high catalytic activity.HUSY catalyst has a large pore sizes,resulting in more catalytic pyrolysis products of the microalgae,especially of the macromolecular mass.