Study On Combustion And Pyrolysis Characteristics Of Seaweed And Oil Shale

There is an abundant of biomass resources on the earth.Exploiting and using biomass resources cannot only ease the energy crisis arising as a result of economic development,but also mitigate environmental problems.The first generation biofuels,which are generated from food and oil crops,have some shortcoming,such as small biological yield,the occupation of cultivated land.Besides,the weather is seriously than before and the rapid economic growth demand more energy.All above mentioned promotes more experts and scholars to focus on second generation biofuels-seaweed.Compared with traditional biofuels,seaweed have high fat content,fast growth and short growth cycle,a strong environmental adaptability,no occupation of cultivated land and reduction of carbon dioxide emission,etc.Thus,seaweed are recognized as the most potential alternative to fossil fuels.Many countries in the world are dedicated to study the technology of seaweed biomass.This paper studied the characteristics of seaweed and oil shale by an improved drying oven,thermal gravimetric analysis,tube reactor flue gas analyzer and microwave pyrolysis systems,etc.Many useful conclusions can be obtained from this paper.The characteristics of pyrolysis waste.have been studied through the microwave pyrolysis systems in this dissertation.The study results will provide a new technology roadmap and theoretical instruction for waste treatment.Drying characteristics of seaweed and oil shale under different moisture content,dry thickness and the drying temperature were studied.The fitting results of common thin-layer drying model showed that ?Logarithmic model? is the best one.The effective moisture diffusion coefficient of seaweed is 1.03×10-8².38×10-8m2/s.The values of activation energy and pre-exponential factor of seaweed are Ea=17.35kJ/mol and D0=3.61×10-3m2/s.The effective moisture diffusion coefficient of oil shale is 2.73×10-8¹.34×10-7m2/s.The values of activation energy and pre-exponential factor of seaweed are Ea=32.91kJ/mol and D0=1.82×10-3m2/s,respectively.With the increase of temperature,the effective moisture diffusion coefficient is increased.Thermogravimetric analysis is carried out to investigate decomposition characteristics of seaweed in different atmospheres and different heating rates.In N2 atmosphere,only one main decomposition stage occurs at 140-550°C?devolatilization?.However,in CO₂ atmosphere,two main decomposition stages are observed,occurring at 140-560°C and 790-1000°C;The total residual mass in CO₂ atmosphere?16.86%?is less than in N2 atmosphere?23.12%?;In CO₂ atmosphere,the maximum kinetic parameters?E,n,A?occur in the fourth stage,while the minimum kinetic parameters occurs in the second one.The kinetic parameters of second stage in CO₂ atmosphere are quite similar to those in N2 atmosphere.Thermogravimetric?TG?analysis and kinetic modeling are applied to study the effects of alkaline earth and alkali metal compounds on catalytic thermal decomposition of microalgae.When alkaline earth and alkali metal compounds are added,the initial thermal degradation temperatures increased by about 3.2-10.2K,and the final temperatures reduced by about 3.5-9.4K.The results show that CaO,MgO,K2CO₃,BaCO₃ and Na2CO₃ may shorten the time of pyrolysis,implying that alkaline earth and alkali metal compounds may promote the process of thermal degradation of organic matters.The first maximum weight loss rate is in the order of Na2CO₃ > CaO > K2CO₃ > BaCO₃ > MgO > no additive.Em?weight means activation energy?varies from 99.60 to 134.05 kJ kJ mol-1,which implies ignorable overall activation energies?Em?after alkaline earth and alkali metal compounds are added.Co-pyrolysis characteristics of seaweed and oil shale were studied by thermal gravimetric analysis.The results showed that the main pyrolysis zone of blends was 210-610°C,which close to that of pure seaweed,but different from oil shale;seaweed and oil shale exist synergy in the solid-solid phase during their co-pyrolysis.Seaweed and eucalyptus in the process of pyrolysis can be seen that exist several similar through TG and DTG curves.The seaweed and eucalyptus exist synergy in the solid-solid phase during their co-pyrolysis;Different atmosphere has important influence on material pyrolysis.With the increase of heating rate,temperature,the peak of the heating rate and the amount of residue will has a tendency to increase.The emission characteristics of flue gas pollutants produced from seaweed and oil shale combustion were studied,using a lab-scale electrically heated tube furnace.The results showed that release time and completion time of CO,H₂ and NO had a trend of decrease gradually with the temperatures rise of the seaweed.The peak concentration was increased and then decreased,The average concentration,gas volume,gas quality and elements conversion rate increased first and then decreased also;The release rate of CO and H₂ increase;largest elements conversion of C,H and N was 30.87%?600??,2.78%?600??and 30.99%?700??.As combustion temperatures rise of oil shale and seaweed mixture,release time and completion time of CO,H₂,NO and SO₂ also showed a trend of decrease gradually.The gas volume,gas quality decline and then increase;The release rate of CO and H₂ increase,The burning of oil shale,The largest elements conversion rate of C,H,N and S was 78.88%?400??,4.85%?600??,1.52%?700??and 96.24%?600??.The mixture of Seaweed and oil shale,will promote the process of combustion reaction and inhibit the production of H₂.The impact of microwave power,microwave absorber,different mixture ratio and the amount of raw materials on the microwave pyrolysis of seaweed and oil shale are studied.The results showed that,in N2 atmosphere,The temperature increases by adding microwave absorber.The maximum oil production were 26.47% by adding NaH₂PO₃,and then were ZnCl2?19.6%?.The metal oxide?CuO,MgO and CaO?has a little influence on the rise of temperature of the oil shale.The maximum gas production were obtained by adding CuCl2.The three metal oxide?CuO,MgO and CaO?can promote the increase of oil production in the microwave assisted pyrolysis of seaweed,the largest oil production were obtained by adding MgO.The maximum gas production and weight loss is obtained from the pure sedweed.The pyrolysis temperatures can be improved by adding oil shale in the seaweed.The oil and gas production were the biggest as the proportion of oil shale and seaweed is 9:1;Seaweed and eucalyptus mixed pyrolysis oil is biggest?24.87%?when the proportion of seaweed and eucalyptus is 3:7;The largest gas production is 65.40% when the proportion of seaweed and eucalyptus is 5:5;there are synergies in the mixed pyrolysis of seaweed and eucalyptus,and the synergy is most obvious when the ratio is 1:1.The effects of microwave pyrolysis temperature on pyrolysis products,regulation of gas yield and the composition of the gas were investigated.The results showed that the temperature of municipal solid waste under microwave pyrolysis was quickly increased.Microwave pyrolysis of municipal solid waste exhibited short pyrolysis time.The solid component was decreased from 55% to 26%,the liquid component was increased from 21.52% to 27.83%,the pyrolysis gas component was increased from 12% to 35% with microwave pyrolysis temperature increased from 400? to 600?.The gaseous products were composed of hydrogen,carbon monoxide,methane,carbon dioxide and hydrocarbon,et al.Methane content was increased with the increasing of temperature.The content of hydrocarbon reached at the top in 500?.Hydrogen content was low in 450?,and quickly improved with the temperature above 550?.Those results obtained from microwave pyrolysis provide foundational data for the new utilization of municipal solid waste resources.