| Biomass energy has two prominent advantages of environmental friendly and renewable compared with petrochemical energy. At present, utilization and conversion of biomass energy has become one of major topical issues, and is widely concerned by governments and scientists around the world. Biomass heat conversion technology is an important area of biomass energy research and development. The technology includes direct combustion, thermal gasification, pyrolysis liquefaction and other forms, but, biomass fast pyrolysis liquefaction technology has been paid great attention because it provides liquid fuels as an alternative of petrochemical energy.Biomass fast pyrolysis liquefaction technology, with the basic characteristics of high heating heat transfer rate, medium temperature, very short residence time and rapid condensation, taking the liquid bio-oil as the targeted product, has the advantage of converting the low-grade and low-energy density biomass into high-grade solid, liquid and gaseous commercial-value fuels which have high energy density and are easy to storage and transport. There is much research on pyrolysis liquefaction of wheat straw, rice straw, corn stalk, sawdust and so on, but not much research on oil crops straw at home and abroad.In this study, representative oil crops straw wastes were chosen as raw materials by respect of abundant biomass resources in China. Quality analysis, evaluation of energy value, pretreatment and pyrolysis liquefaction of all the oil crops straw (rape straw, earthpea straw and sesame straw) were studied based on biomass fast pyrolysis liquefaction bench device. Analysis and evaluation of bio-oil was taken by advanced analytical tools. Through the studies above, conclusions were made as follows:1. Study on quality and pretreatment of oil crops straw(1) Quality of oil crops straw (including rape, earthpea and sesame) were studied by industry, element and calorific value analysis and the results showed that ash and moisture contents of three kinds of oil crops straw were about 5% and 10% respectively; cellulose content was high and the highest reached 45%, but hemicellulose and lignin contents were low; the calorific values were between 16 and 18 MJ·kg-1. Based on related mechanism of biomass fast pyrolysis, it was suggested that oil crops straw was suitable to be raw materials of fast pyrolysis liquefaction; The total sum of three elements C, H, O were all above 98% , meanwhile N, S elements were lower in the oil crops straws. N element content of earthpea straw was 1.57% which was the highest and S element content of rape straw was 0.85% which was also the highest. They were consistent with the straws own characteristics.(2) Pretreatment of oil crops straw was studied and the results were as follows: by washing, pickling and oven drying, ash of rape straw was almost deashed and the moisture content was declined; according to raw straw the cellulose and hemicellulose contents were improved 9% and 5% respectively. It was shown that physico-chemical properties of de-ashing rape straw were better than that of raw rape straw, and it had an important significance for exploring effcts of de-ashing on biomass pyrolysis. Particle size of oil crops straw was lower than or equal to 0.9 mm diameter, by drying, crushing, screening and other treatments. The pretreatment could meet technology needs of biomass fast pyrolysis.2. Study on oil crops straw fast pyrolysis liquefaction process and pyrolysis products distribution.(1) Oil crops straw fast pyrolysis liquefaction process was studied systematically for the first time and the results were shown that fluidized bed reactor was suitable to the straw biomass fast pyrolysis liquefaction, and could get higher yield of bio-oil at the conditions of pyrolysis temperature between 450℃and 550℃, the velocity of feeding 2 kg·h-1, blowing feed wind speed 10 m·s-1 and fluidizing wind speed 15 m·s-1.(2) Effects of materials species, particle diameter, pyrolysis temperature and de-ashing treatment on oil crops straw pyrolysis products distribution were investigated and the results were as follows: bio-oil yields of three kinds of oil crops straw (including rape, earthpea and sesame) were different due to different contents of their cellulose, lignin and hemicellulose; 50% yield of earthpea straw bio-oil was highest, followed by 45% yield of sesame straw bio-oil, and 42 % yield of rape straw was the lowest. Cellulose content of earthpea straw was the hightest in the oil crops straw. Pyrolysis temperature is a crucial parameter of biomass pyrolysis process and products distribution. Bio-oil yield increased with pyrolysis temperature increasing between 450℃and 480℃, but decreased because of the aggravation of the secondary cracking while the temperature was above 480℃. It was always shown that non-condensed gas yield had an improving trend with temperature increasing, but char yield had a continuous decline. Straw particle diameter had little impact on pyrolysis products when its particle size was less than 1 mm.(3) The yield of straw bio-oil was improved by 14% and reached 56%, after the raw materials was deashed and the best pyrolysis temperature of de-ashing straw had increased by 20℃to 30℃.3. Analysis and evaluation of oil crops straw bio-oil(1) Physico-chemical characteristics of oil crops straw bio-oil were studied and the results were as follows: at normal temperature, the bio-oil was highly acid with pH between 2.65 and 3.80; flash point about 43℃was low but ignition characteristic was poor due to high moisture content about 35%; viscosity between 4.64 and 5.64 mm2·s-1, and pour point range from—28 to—19℃, range from 2 to 5℃higher than solidifying point, were shown that it had better low-temperature flow ability; density between 1127 and 1154 kg·m-3 was higher than fossil fuels; ash content less than 1% and remnant char was about 10%; calorific value between 18 and 21 MJ·kg-1 was about half of fossil fuels. Element analysis showed that nitrogen and sulfur contents were low and the oil was clean and little pollution, but C/H was low and reached about 0.65, meanwhile, oxygen content was high and reached between 42% and 47%, so the oil needed to be further refined in order to enhance its quality and value.(2) Oil crops straw bio-oil was analyzed by the means of FTIR and GC-MS and the results showed that the bio-oil contained complex components. These main components consisted of the polyphenol, ketones, acetate, alcohols, aldehydes and organic acid, and so on. In the same analysis conditions, oils from different raw materials could be detected remarkable differences in compound compositions and contents, and the content sequence was the same as the order of different raw materials bio-oil yields. All these conclusions had the important guiding significance on the choice of raw materials for biomass fast pyrolysis liquefaction, as well as study on application technoloty of bio-oil.De-ashing treatment could improve bio-oil yield and had great influence on components of the bio-oil. Under the same anlysis conditions, the contents of detected components in de-ashing rape straw bio-oil were two times higher than rape straw bio-oil; especially, ketones and phenols contents were improved by about 16% and 10% respectively.
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