Experimental Study On The Semi-continuous Anaerobic Treatment Of Rehmannia Residue

The world is facing the pressure from environment pollution and energy shortage,By using the anaerobic biological technology to dispose the solid waste,can make the reducing pollution and producing energy come true.Traditional solid or semi-solid anaerobic reactor efficiency is very low,so it is eagerly to carry on the corresponding research of high-efficiency anaerobic reactor for the development of the application and anaerobic digestion technology,and anaerobic kinetics research is the key to highly efficient anaerobic device design and reaction process control.Chinese medicine six ingredient rehmannia pill production process will produce a large number of residues,the residue is rich in nutrients,compared with the high fat high salt in eat hutch garbage and high mineral content of municipal sludge and heavy metals,rehmannia residue is preferably in anaerobic digestion.The process of extracting effective components rehmannia steamed and vacuum distillation,can be regarded as the pretreatment of anaerobic digestion,it can promote the dissolution of the plant cells,and improve the efficiency of anaerobic digestion.Obviously,Rehmannia residue dispose by anaerobic treatment not only can dispose biomass solid wastes,but also can produce clean energy.Based on rehmannia residue in the process of Chinese medicine six ingredient rehmannia pill production as the research object in this paper,so as to find the characteristics of anaerobic digestion under laboratory conditions,according to the methane production potential,the best fixation rate and the effect of spoil disposal,we make sure the optimum reaction conditions for sequencing batch type and semi-continuous anaerobic digestion experiment,and analysis the methanogenesis kinetics.The process of anaerobic metabolism jointly completed by a variety of flora,of which the product is relatively complicated,but in the case of domesticated completed anaerobic bacteria flora,its ultimate objective production is methane.Obviously,in the zero order reaction stage,the anaerobic bacteria proliferation is not restricted by the substrate concentration,methane yield per unit time is only related to anaerobic bacteria group of biomass.Therefore,thispaper put forward for the first that we can use the apparent increment volume ΔV of methane in per unit time in zero order reaction to represent the increment of anaerobic microorganisms Δx,and according to the anaerobic reaction kinetics characteristics of rehmannia residue derived its apparent proliferation kinetics of anaerobic bacteria.And,we design the semi-continuous anaerobic treatment operation mode based on the above research results,Study on the material balance analysis of semi-continuous anaerobic digestion reactor in a single feeding cycle,trough derived rehmannia residues in the substrate in semi-continuous anaerobic digestion reactor and get the volume biogas production rate,volume loading,relation between production of methane and the effective volume of the reactor,relation between the amount of feeding and spoil disposal parameter model.In this study,we provide new train of thought to represent the amount of anaerobic microorganisms,and provide theoretical basis for reactor design and process control of using the semi-continuous anaerobic digestion to dispose organic solid waste.The main research results in this paper are as follows1.The characteristics of the rehmannia residues in anaerobic fermentation(1)Batch feeding repeated experiments shows that the methane production rate of rehmannia residues is 92.8mL/g · VS,and it means that rehmannia residues is suitable for fermentation as a kind of fermentation raw material.Set TS as 10%、15%、20% and 25% respectively.Compared the volume of methane comparative analysis of the total methanogenic anaerobic reactor,methanogenesis kinetics constants,the best TS was 15%.Set the spoil disposal mass as 1/4、1/6and 1/8 respectively,the cycle of spoil disposal is three days,analysis of the anaerobic reactor zero order reaction stage accumulated from domestic production and methane production rate,we make sure that the best spoil disposal mass and spoil disposal cycle should be according to the change of anaerobic bacteria flora proliferation.2.The start-up operation of sequencing batch feeding and semi-continuous feeding anaerobic digestion experiment.(1)With the substrate to inoculum ratios were 1:2(expressed as raw material)in a sequencing batch feeding.The feeding cycle is 7 days,the reaction has been operatingcontinuously for 4 cycles,there exists little change in the cumulative methane production within the four cycles of the same continuous feeding,but the first day’s methane production percentage of the total amount is increased from 52.88% to63.95%,the more the biomass of the beneficial bacteria increases,the faster the conversion rate of the same feeding will be.Here are obtained by calculations that the kinetics constants at the zero-order reaction: 143.1ml/h,150.2mL/h,159.5mL/h and170.7mL/h.(2)After analysis the anaerobic fermentation kinetics model of rehmannia residues with Sequencing batch feeding,it provides the following analytic result: the methane producing process within one cycle falls into two stages.The first stage is 0~20h,during which time the beneficial bacteria is in a stable growth phase for the no substrate competition,and the cumulative methane production is at zero level reaction with a linear increase.It’s linear equation is y1=106.88t1+81.667,wherein y1 represents the cumulative methane production(mL)at the time of t1(h,0< t1<20).The second one is 20~168h.In this stage,the metabolic pattern of the beneficial bacteria is at the first-order reaction as well as in the rate-limiting phase of hydrolysis and acidification without VFA accumulation.Its equation is y2=3140 1-e-0.0337t2,wherein y2 is the cumulative methane production at the time of t2(h,20< t2<168).The correlation between the measured data and the fitting curve respectively are:R2=0.9901 and R2=0.9921.(3)Set the feeding cycle as 10 hours in the semi-continuous anaerobic digestion of the rehmannia residues,the analysis results show that the zero-order reaction kinetic constants-k respectively are: 240.47mL/h、254.39mL/h、264.45mL/h and 279.75mL/h,the semi-continuous reaction has been operating continuously for 160 hours,the production of cumulative methane during this period is 36833 mL,and dispose 1173 g rehmannia residues in total.The methane production during the zero-order reaction period in 10 hours is increasing gradually which is related to the increase of biomass.3.The analysis of the anaerobic bacteria flora proliferation regularity.After the formula deduction,we found that the relationship between the biomass of anaerobic bacteria flora and the cumulative methane produced per unit during thezero-order reaction period.We derived and modified the microbial proliferation rate defined equation:xt=x0eμt,the Monod equation:μ=dXand so on,Curve fitting the natural logarithm of the methane production in semi-continuous anaerobic fermentation with the reaction time in a cycle,and it provides the apparent specific growth rate of the anaerobic bacteria flora and its generation period.According to the self-built anaerobic fermentation model of generated methane,which includes sequencing batch feeding and semi-continuous feeding,we predict and comparative analyse the differences and advantages in the process of anaerobic digestion reaction between these two feeding mode by curve fitting.The kinetic model provides the following analytic result: With the same effective volume of the anaerobic fermentation reactor,the capacity of dispose rehmannia residues and the production of cumulative methane in semi-continuous feeding anaerobic digestion are 2.9 times than that in sequencing batch feeding mode.Study on the material balance analysis of semi-continuous anaerobic digestion reactor in a single feeding cycle,trough derived rehmannia residues in the substrate in semi-continuous anaerobic digestion reactor and get the volume biogas production rate,volume loading,relation between production of methane and the effective volume of the reactor,relation between the amount of feeding and spoil disposal parameter model.