The Study On Steam Explosion Pretreatment Technology And Application Of Bio-Cellulose Materials

Bioenergy is rich in resource and reproducible which can be convert into clean fuels—solid,liquid and gas. Scholars began to study the mechanism and the influence factors of conversion at the aim of improving the biomass conversion efficiency at the beging of 1990s. Among these problems how to eliminate or decrease the hindrance of lignin to the cellulase is the difficulty of research.It is because the complex structure of hemicellulose, cellulose and lignose in the biomass stalk that pretreatment on biomass must be done to destory the physical sturcture of biomass and have them seprated effectively if we want to enhance the conversion rate . The aim of pretreatment is to separate or remove the lignin and increase the porosity and accessibility of cellulase to the straw stalk, thereby to improve the cellulose and hemicellulose conversion rate of the biomass straw stalk. The pretreatment methods can be classified into four kinds: physical pretreatment, chemical pretreatment, physical and chemical pretreatment and biological pretreatment. Though the scholars has made many achievements in pretreatment research, the pretreatment method with high efficiency, low cost and to the biomass straw stalk had never been found till today. So it is still the key technology of bioenergy utilizing in high grade to found the pretreatment technology if we want to increase the conversion and utilization efficiency of biomass, it is also the goal that scholars and entrepreneurs hardly pursuited.The steam explosion technic was first used into the paper pulp production, which is one kind of physical pretreatment method. Up to now, there is still no report on significantly increasing the cellulose conversion by steam explosion pretreatment technic. even more; there is no report about the study on the mechanism of anaerobic fermentation with steam explosion pretreated stalk straw. More and more scholars began the research of steam explosion technic in recent years; we can make a conclusion that they are all belong to steam spout or swollen technic in fact by analyzing their technics parameters and the pretreatment result. Because that the real biomass explosion occurred only when it was released out of high pressure vessel within 1 second. The explosion technics reported at present were not the real steam explosion technic indeed, which always cost about several ten seconds to several minutes to spout the biomass out of the boiler. So the good result could not be achieved with these kinds of pretreated technics. The steam eject technology was introduced in the steam explosion equipment in this study. The new steam explosion technique can complete the high density release of energy only in 0.00875s, so the straw stalk was break down easily. Lots of explosion experiments of straw stalk have been done and the result of the biogas anaerobic fermentation and saccharification experiments with the steam explosion pretreated straw stalk showed that the pretreatment effect was satisfied.The author's study was perfectly reflected in this doctoral dissertation, including:(1)The study is mainly focus on impact factors of steam pretreatment and optimization of the steam explosion parameters. Through the two index: structure variety (the content of hemicellulose, cellulose and lignose) and saccharification rate of steam exploded corn stalk we can weigh the impact of factors on the pretreatment effect and found the main impact factors , the best parameters of steam explosion pretreatment technics. Accordingly, lots of experiments with the different combination of pressure, retained time, moisture content and the loaded density have been done, the physical,chemical and the structure analysis of the steam exploded straw stalk were carried through. The optimal steam explosion pretreatment parameters were found. Dual-steam explosion experiments have been done in this study; the result showed that the pretreated ability of dual-steam explosion technic was significant higher than the ordinary steam explosion.(2)To validate the effect and applicable value of the steam explosion technic, the experiments of anaerobic fermentation on steam exploded corn stalk under normal and moderate temperature have been done, which with the TS concentration of 5%. The result showed that the biogas prodution and the methane content of per gram dry steam exploded corn stalk were all increased than the contrast test, the COD removal ratio was high. The starting and closing time of anaerobic fermentation was all about 10 days earlier exploded under the condition of 3.0Mpa and 90s than the unpretreated straw stalk.(3) The saccharification experiments of steam exploded corn stalk showed that the saccharification ratio was increased than the contrast test. The steam explosion with addition of chemical have been done to look for efficiency pretreatment technic, the chemicals such as HCl, NaOH, Na2SO4 and ammonia were added into the corn stalk during the steam explosion process. Though the saccharification ratio of steam exploded corn stalk that used HCl as addition was higher than that use the other chemical as addition, the effect of chemical addition was not so useful in increasing the saccharification ratio of steam exploded corn stalk. The prodution rate decreased along with the increaseing of retained time in the experiments of fermentation for fuel ethanol under the pressure 3.0Mpa, but it increased under the condition of low pressure.(4)The analysis on microstructure of steam exploded corn stalk with SEM showed that the degree of damage to structure of the steam exploded corn stalk increased along with the increase of pressure and retained time. The better saccharification effect can be achieved with the steam explosion pretreatment condition of high pressure and short retained time. The crystallinity of steam exploded corn stalk increased to some extent than the unpretreated.(5)Equipment improvement. The effect of steam explosion was proved by a series of experiments, the problems such as the seal, retained time, the needed steam pressure, the thermal insulation etc were found. The corresponding improvement of steam explosion test-bed design have been done, which perfects the performance further. The moderate steam explosion was established according to the experiments on the test-bed. Also the study will provide basis for the design and manufacture of equipment industrialization.