| With the global shortage of fossil energy and the increasing demand for fuel,finding new and renewable clean energy has become one of the most urgent tasks for mankind.China is a large agricultural country.The incineration of the remaining cellulosic straw materials causes great environmental pollution.The method of converting cellulosic into ethanol can not only solve the energy demand,but also protect the environment.However,enzymatic hydrolysis of lignocellulose without pretreatment is usually less effective because the stability of cellulose structure makes it difficult for enzyme or bacteria to attack.The existing pretreatment methods mainly include grinding,irradiation,microwave,steam explosion,ammonia fiber explosion,supercritical carbon dioxide and its explosion,alkaline hydrolysis,liquid hot water pretreatment,organic solvent treatment,wet oxidation,ozone decomposition,dilute acid and concentrated acid hydrolysis and biological pretreatment.In this paper,the pretreatment technology of corn straw cellulose,the relationship between substrate and enzyme,the optimization of microbial degradation conditions,the engineering design of cellulose ethanol and the comprehensive utilization of by-products were studied.The main work is as follows:1.The effects of different pretreatment methods on corn straw were studied.The effects of different pretreatment processes on chemical composition,morphology,fiber length,BET specific surface area and pore diameter of materials were discussed.The preliminary evaluation of different pretreatment technologies was carried out.The one-step blasting method has a certain destructive effect,and some peeling and holes appear on the surface of the fiber.However,in terms of the change of fiber appearance size and fiber length,it does not significantly reduce compared with the raw material.The two-step method of "blasting + dilute acid cooking" made the sample size changed significantly,fiber fracture,length shortened,fiber surface holes increased,pore diameter increased,specific surface area increased.Although dilute acid cooking is helpful to reduce the fiber size and increase the porosity and specific surface area of the material,it is a serious equipment corrosion problem and the treatment time is long.The mechanical pre-treatment can significantly reduce the length of the fiber cells,promote the fiber cell fracture and fiber separation brooming,and then increase the specific surface area of the fiber,improve the accessibility of enzyme,and increase the effect of enzyme treatment.Finally,the enzymatic hydrolysis characteristics of the samples treated with "Silk rubbing + blasting" were analyzed.2.Through the study on the conditions of C5 yeast,the fermentation conditions with higher ethanol concentration and yield were obtained,and a strain with the best ethanol yield was obtained by comparing several different C5 yeast.Compared with the liquefying mash of glucose and corn,no matter the primary or secondary fermentation activity of the seed is better after dilution.The effect of different inoculation amount was further studied.The xylose utilization rate of high inoculation amount was high,but the acetic acid content was high,which was not conducive to C5 yeast fermentation.It was found that the sugar alcohol conversion rate of the experimental group added yep was more obvious than that of the experimental group added corn syrup and inorganic salt.Penicillin was used as antibacterial agent in NBS automatic fermentation tank to study the influence of p H,nutrition and dissolved oxygen on CO fermentation.Finally,the performance of different C5 fermentation strains was studied.The xylose utilization rate of CIBT yeast was the highest,and the utilization rate of CIBT yeast reached 87% in 48 hours.It was found that the performance of CIBT strain was the best.3.Based on the water,alcohol,aldehyde,ester,acid,etc.in the metabolites formed during the fermentation process of the cellulose enzymatic hydrolysate,the specific physical properties of cellulose fuel ethanol have been determined.At the same time,with the help of the thermodynamic method,the component separation sequence,and Aspen Plus to developed the whole process computer simulation,which provided a powerful research method for the design and optimization of the process flow.The lignocellulosic biomass(corn stover)used in this chapter as the raw material to produce fuel ethanol,simulated the distillation process,and conduct research on the development of the 10,000-ton cellulosic ethanol process package.Also,the factors that affect the acid value of fuel ethanol were analyzed.The research results in this chapter have certain guiding value and significance for the technical and economic evaluation and engineering design of the cellulosic ethanol production process.4.Using the ethanol fermentation residue of corn stover,which contains a large amount of lignin and silica as raw materials,the structure of the lignin-silica composite was analyzed by using specific surface area,infrared spectroscopy,scanning electron microscopy and thermogravimetric analysis.The lignin-silica composite surface exhibits a good adsorption performance towards methylene blue,while the ?-? interaction with methylene blue molecules and electrostatic attraction affected the adsorption performance of the material pair.The ligninsilica composite porous material prepared from the ethanol fermentation residue of corn stover has simple operation,cheap raw materials,and more importantly,the good adsorption effect.Therefore,the lignin-silica composite porous material can be used as a cheap adsorbent for effectively removing dye wastewater.5.With the aid of computer simulation,a powerful research method was provided for the design and optimization of the technological process.Based on the cellulosic ethanol pilot test process,a mathematical model of the cellulosic fuel ethanol process was established.Through the simulation results,the material and energy of the cellulosic ethanol production process can be strictly accounted for,and a variety of options can be evaluated and optimized,which not only saves a lot of manpower and material resources,but also contributes to the development and improvement of future technologies. |
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