Dynamic And Thermal Study On Crushed Straw Material In Rotary Drum Fermentation And Ethanol Separation

China produces nearly 1 billion tons of straw every year.However,it has a low economic utilization level.The Advanced Solid State Fermentation technology(ASSF)is used to ferment crushed straw material to get ethanol.It increases the utilization level of straw.There are 3 technical problems which hinder further popularization and application of it.(1)It needs to study the law of material movement,heat generation and transfer in rotary drum.(2)It needs to develop a set of computer simulation method to simulate the movement,fermentation and heat transfer of material in rotary drum.(3)It needs a low cost method to separate ethanol from fermented material.Experimental equipment are designed and manufactured to solve the problems,such as a laboratory level ASSF drum and its sectional movement test platform.Computer simulation method was used too.The research route is:(1)Measure the mechanical and thermal parameters of crushed straw material,for they are the base of further study.(2)Study the movement law of material in rotary drum.(3)Study the heat generation of material fermentation in rotary drum.(4)Build a set of simulation method on material's movement,heat generation and transfer based on EDEM and API.(5)Find a low cost method to separate ethanol from fermented material,do the idealized modeling and cost analysis on it.(1)The mechanical and thermal parameters of crushed straw material,which includes the bulk density,repose angle,shear modulus,friction coefficient,and so on,are measured.For they are the base of further study and developing of simulation method.(2)The study on material's movement in ASSF drum contains two parts:the sectional and the axial.(1)Sectional:as the thermal conductivity of crushed straw material is low,the fermentation heat is easy to accumulate in the lower and center part of material bed,which leads to death of yeast.Rotary drum rotates the material bed to mix the particles and uniform the bed temperature.The uniform speed can be studied by studying the mixing speed of material layers.The mixing index Imix and complete mixing time tc were built based on image color analysis.The law of material movement and mixing is studied.For no-plate condition,the existence of material bed rotary cycle was discovered and the mathematical function to forecast tc based on filling rate and rotary speed of drum was regressed.For with-plate condition,complete mixing test was done to study the influence of number of plates and length of plates on tc.And tc is the smallest under influence of 4×0.55R plates.All the movement modes of material without plate or with different plate conditions have been analyzed and classified to a table.(2)Axial:the mean resident time of material(MRT)and axial diffusion of material(?R)in axial transfer are important to ASSF technology.Especially the MRT for it directly relates to the degree of fermentation.Complete test was done to study the influence of height and density of inner ring baffles on them.The optimum ring baffles condition is 0.55R height,central distance 50mm.(3)The heat generation power(P)of material was studied for the reason that the fermentation efficiency can be studied by studying P.P is affected by many factors.In simplified case,it can just investigate the effects of sugar content(S)and material temperature(T)on P.Complete fermentation tests were done.The initial sugar content S0 is 0.1 or 0.15 while the initial material temperature To is 18? or 24?.The bed's temperature and sugar distribution were got when the fermentation is stable.P was calculated.And the function of P is regressed.(4)The simulation method was developed based on the DEM software EEM.Based on comparing the macro movement(such as repose angle,section mixing velocity)of virtual material bed in DEM software EDEM and real material bed in test,a series of virtual particle parameters were got to build the simulation method of material's movement.Second develop programming was done on EDEM to import the heat generation and heat transfer models into the simulation method above.As a result,the simulation method on movement,heat generation and transfer of crushed straw material in ASSF was built.Based on it,some further study has been carried out.(5)Planar Thermal Source(PTS)was used to separate ethanol from fermented material instead of the current water steam method.Complete thermo gravimetric test was done on material to study and regress the model of ethanol evaporation from material by PTS.The cost model was added at last.The calculation result shows that the PTS method can significantly decrease the cost of ethanol separation than using the traditional separation method of water steam.The research above can provide theoretical guidance for the optimization of ASSF,which contains the structure and working conditions of rotary drum and the separation method of ethanol from fermented material.It serves on promoting the ASSF technology to extensive industrial application.