| It is difficult for municipal solid waste(MSW)to make refuse derived fule(RDF),because of its complicated composition and high humidity.This papar took the MSW under 80mm particle size as the object,aiming at reducing the moisture content and improving the calorific value.The biodrying technology is regarded as a good solution to reduce water content of MSW.Based on the process optimization control of the organic matter degradation and water removal,investigating the effects of different process parameters on the biodrying performance and determining the quantitative evaluation indicators of biodrying performance.In addition,the contributions of degradation of biochemical components to total organic losses and heat generation and utilization during biodrying were calculated.On this basis,a pilot scale test was studied to verify the biodrying performance,and analyzed the feasibility of biodrying technology from technology,economy and environment three aspects.The results could provide an theoretical basis and data support for Large-scale application of biodrying technology of MSW.Results of this study showed that:(1)Addition of bulking agents to MSW produced less leachate,higher moisture-removal rates,and consumed less organic matter.Bulking with cornstalks achieved the highest water-removal rate and biodrying index.Lipids and cellulose were the main components of organic losses in all treatments and adding a bulking agent changed the sequence and extent of degradation of biochemical components.Evaporation heat was the main component of heat consumption,accounting for 58.1-60.7%of the total energy consumption.Addition of 15%cornstalk(wet basis)was the recommended bulking agent.(2)When total aeration volume was relatively low and remained the same,the change of ventilation method had no significant effect on biodrying performance.As the continuous aeration rate increased,the water removal rate,biodrying index and evaporation heat also increased.The aeration rate of 0.5 L·kg-1DM·min-1 achieved the highest water-removal rate(0.5kg·kg-1)and biodrying index(4.12),and 68.3%heat consumption used for evaporation.When the aeration rate was higher than 0.5 L·kg-1DM-min-1,it had a negative effect on biodrying performance;When total ventilation rate at a certain situation,increasing of turning frequency could not improve the biodrying index.The function of turning can be achieved through increasing aeration.The recommended parameters for biodrying are a continuous continuous aeration rate of 0.4-0.5 L·kg-1DM·min-1,and turned every 3 days.(3)Mixed inoculation of 5%biodrying product enhanced the biodrying performance,the biodrying index reached 4.96.There was no significant effect on the biodrying performance when the amount of inoculation increased.Covered inoculation of 10%biodrying product had the lowest moisture content(<20%).The moisture content of covering material increased to 49%,which could be used as the initial inoculum of next biodrying reaction.(4)The order of importance of factors affecting biodrying index was aeration rate(AR)>C/N ratio>moisture content(MC).The recommended parameters for biodrying are an AR of 0.4 m3·h-1 and a C/N ratio of 21?24 with MC of 60%.The order of importance of factors affecting maturation of compost was C/N ratio>aeration rate>moisture content.The recommended parameters for composting are an AR of 0.2 m3·h-1 and a C/N ratio of 24-27 with MC of 65%.(5)The combustion rate,combustion ratio and final burnout values decreased during biodrying.The organics degradation had almost no influences on the ignition performance.The combustible indexes and comprehensive combustion characteristic index decreased during biodrying.Bulking with wood peat had the highest ignition and combustion ratio,while combustion rate and final burnout values were the lowest.The biodrying process made the combustion easier due to lower apparent activation energy.(6)In pilot scale,the moisture content of MSW decreased from 57.04%to 18.1%,changing of moisture content with time during biodrying can be expressed by linear equation.The VS degradation rate was 22.1%,and moisture removal rate was 81.6%,achieving a high biodrying index(6.35).(7)The total costs of biodrying was 60 CNY·t-1(wet weight of MSW),the same with the cost of landfill.The pollution emissions during biodrying was lower than that during composting.The process of biodrying is considered to be a good solution for reducing the water content of MSW from technology,economy and environment three aspects. |
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