Research On The Effect Of Pyrolysis Reactor Collection System On The Characteristic Of Bio-oil And The Application Of The Pyrolysis Products

The coal and fossil fuel shortage and globle warming problems have become bigthreats to the sustainable development of our society. With the depletion of fossilenergy reserves in the world, renewable energy sources have attracted significantattention. Biomass is a clean, cost-effective, CO₂neutral and low sulfur contentrenewable material which can be used for heat and fuel production. Thermal pyrolysisis a thermochemical process in the middle temperature （300-500℃） with the absenceof oxygen, atmospheric pressure. Bio-oil was produced using fast pyrolysis andbiochar was produced using slow pyrolysis method. Bio-oil is a complicated mixtureof organic compounds with water containing almost all kinds of organic compoundssuch as aether, ester, aldehyde, ketone, hydroxybenzene, alcoholic, organic acid andetc. As the bio-oil has the characteristic of high water content, high solid, low heatingvalue, it is difficulty to use as liquid fuel. The effects of collection system （selectivecondensation and hot vapor filtration （HVF）） on the characteristic of bio-oil wereinvestigated in this paper. And then bio-oil/desiel emulsion and bio-oil steamingreforming were used to investigate the application of bio-oil. The effect of thetemperature on the characteristic of biochar and the biochar combustion behavie werealso investigated.The numerical simulation （FLUENT） was used to simulate the process of fluidizedbed reactor. The solid volume, gas velocity and the pressure drop were simulated. Theresults showed that the pressure drop was1500Pa with the gas velocity of0.15m/s.In the real experiment, the effect of the carrier gas velocity with the pressure drop was also investigated. The results showed that the pressure drop is increased with theincrease of gas velocity at first. It is tending towards stability after0.13m/s and thepressure drop is1400Pa. The numerical simulation result fit the experiment data verywell.The fast pyrolysis of pine sawdust was conducted in a fluidized bed reactor with aselective condensation system. The selective condensation and electrostaticprecipitator were used to condense the pyrolysis vapours. The average yields ofbio-oil, the gases and the char were41.5%,43.3%,15.2%respectively. It was foundthat the condensed oils in the condenser1#contained higher water content and ratio ofcollected water content of oil was86.2wt%. The bio-oil condensed in the lattercondenser has a lower water content, higher pH value, higher heating value, higherkinetic viscosity compared to the former one. Analysis of1#,4#and5#bio-oil withGC-MS showed that102types of chemical compounds were detected and most of thecompounds were condensed at different condensers. Therefore, the selectivecondensation is useful to separate the water and chemical compounds from bio-oilcompared with direct contacting condensing. The selective condensation andelectrostatic precipitator can condense the pyrolysis vapours selectively. The gasproducts were mainly CO, H₂, CO₂, CH₄and C₂-C₄’s. It was also found that there arelarge amount of hydrogen and oxygen in the bio-char. A lot of bonds such as-NH,-CH-,-C=C-,-CH₃,-C-O-C-were found in the char samples. It was observed that thesurface morphology of pine sawdust particle changed after pyrolysis, and it becamethinner.Fast pyrolysis of rice husks in a fluidized-bed reactor was reported in this paper. Theeffect of HVF on the characteristic of bio-oil was investigated. It was found that thetotal bio-oil yield decreased and that the bio-oil has a higher water content, higher pHvalue, and lower alkali metal content when a HVF is used in the system. Analysis ofthe bio-oil with GC-MS showed that the molecular weight of the chemical compoundsdecreased after HVF. The content of C₂-C₄’s gases from gas products was decreasedafter HVF. The bio-char has many chemical bonds and its alkali metal content ishigher compared to the bio-oils. Bio-oil from the rice husks was used to emulsion with diesel. The temperature,percentage of the emulsifier, time and the percentage of bio-oil were investigated inthis paper. The results showed that the emulsion temperature should be at60℃andthe suitable percentage of emulsion was10%. The emulsion fuel can get a stable timemore than72h if the bio-oil percentage less than10.Steam reforming of two kinds of bio-oil from rice husks fast pyrolysis was conductedfor hydrogen production at three temperatures （650,750and850℃） with Ni-basedcatalyst in a fixed-bed reactor. Mole fractions of H₂and the CO₂increased, while thevolume fraction of CO, CH₄and C₂-C₄gases decreased with the increase of thetemperature from650to850℃. The highest H₂efficiency was45.33%whenadditional water was added at850℃for F1bio-oil. Bio-oil with lower content ofchemical compounds has a higher H₂efficiency, but its hydrogen volume wasdecreased. Analysis of the liquid condensate showed that most of the organiccompounds were circularity compounds. Carbon deposition can decrease the bio-oilconversion, and it was more readily formed at750℃.The slow pyrolysis of white ash, switch grass and corn stover were used as thefeedstock at three temperatures （300,400and500℃）. The results showed that theyield of the biochar and bio-oil were decreased and the volume of syngas wasincreased with the increase of the temperature. The yield of the biochar was26-41%.The carbon sequestration rates canbe60wt%. The pH, heating value and solid contentof the biochar were increased with the increase of the temperature. FT-IR showed thatthere are a lot of chemical ponds in the biochar, and they were decreased with theincrease of the temperature. The SEM-EDS analysis showed that the structure hascarbon fiber at higher temperature, and the content of alkali metals （Na, K, Ca, Mg）were increased with the increase of temperture. The main content of the syngas wereCO、CO₂、H₂and CH₄.The mole fraction of CO and CO₂were decreased and the molefraction of H₂and CH₄were increased with the time. More H₂and CH₄wereproduced at high temperature.The combustion characteristic and kinetic behaviour of the biochar were studied byusing a thermogravimetric analyzer at four heating rates （5,10,20and50K min-1）. The FWO and KAS methods, two commonly used isoconversional methods, wereapplied to estimate the effective activation energy, and the master plot method wasused for the determination of the kinetic model f（α）. The kinetic parameters of biocharcombustion are obtained as follows: f（α）=（1-α）^3.3, A=6.20×10¹²s^-1, E=212.524kJmol^-1.