| Bio-drying is a new kind of economy, energy saving, environmental protection reduction technique, it evolved in the aerobic fermentation, and will become more and more attention in the economic and the present development situation of our country. This article summarizes the current domestic and foreign sludge treatment and disposal technology; and proposes a new process Bio-drying technology in the tunnel reactor to solve the defects of present in aerobic composting. Article adopt combined method with theoretical analysis, numerical simulation, pilot scale test, engineering application to research the variation of characterization factor and control factor under the conditions of different reflux ratio, and propose the best bio-drying process parameters. The article focus on the use of kinetic, mass transfer and heat transfer theory to analysis of internal mechanism in the process and basic characteristics of sludge bio-drying. The results are applied to engineering to test, guide the design and operation control of engineering. The completion of the main research work and results are summarized as follows:1. The experiment build Special closed type bioreactors based on the material balance calculation, structure design, ventilation design, mixing system design, to research the variation of Pile temperature, moisture content, density, C/N, calorific value, specific heat capacity and other characterization factor under the conditions of different reflux ratio. The result show that:The initial moisture content at around 60%, the C/N is about 20:1 and with 40% reflux ratio is a kind of economical and practical initial operating condition. Sludge bio-drying moisture content can be decreased from 61.3% to 38.7% after 13d fermentation under that condition.2. This study used Ventilation and turning rate as the control factor to Study on the effects of bio-drying. Research shows that the effect on pile temperature is small by increased frequency of turning rate. The initial temperature is higher, the time of turning back to the initial temperature is shorter. The average rate of the return temperature of the reactor at high temperature stage and the cooling stage is 6.31～12.13 and 2.84～3.72 times of the heating period. The maximum removal water rate can reach 0.56% by turning 1 times. In tunnel reactor, the best technological parameter for the bio-drying is turning 1 times with the ventilation 0.1,0.2,0.25 m3·min-1·m-3 in the heating period, the high temperature phase and cooling period respectively.3. This study used a kinetic model to simulate the dynamic degradation process of organic matter on the bio-drying, and considering the influence of temperature, turning rate, moisture content, oxygen volume fraction and the free air space on the degradation coefficient, Innovative convert pile turning factors into the temperature correction factor, and modified organic matter degradation model. Verified with experimental values, mean relative deviation is 0.15%, the simulation results of organic matter degradation rate in the heating period, the high temperature phase and cooling period is 3.23%、85.38%、11.39% respectively. High temperature period is an important stage in the degradation of organic matter.4. According to the water quality balance principle, this study use the amount of organic matter produced water, the amount of removal water by ventilation and turning pile as dynamic variable factor to establishment of water mass balance model for bio-drying. The result of simulated show that the amount of removal water by ventilation and turning pile respectively accounted for 86.99% and 13.01% of the total amount of removal water. the amount of removal water by ventilation is 3.14-8.26 times compare with turning pile, ventilation removing water effect is more significant.5. Considering the gradient parameters influence on the dynamics process of bio-drying, this study use the finite volume method derived volume averaged governing equations, taking the engineering conditions as the research object, establish a bio-drying mathematical model that the changes of temperature, moisture, pressure can be described with time and space. And using the model simulate the effects of different ventilation modes on the water concentration,the result of simulated show that moisture removal effect is best by adopting the intermittent ventilation way of ventilation 20min, stop 20min. Considering the practical application of engineering, engineering application can adopt the intermittent ventilation way of ventilation 2h, stop 2h.6. According to the results of the study, the article propose the main bio-drying process parameters, and carry on the Engineering experiment under winter and summer conditions, Detect the changes in the law of Pile temperature, moisture content, Bulk density and other characterization factor, project has achieved good application effect, and the article introduces and summary the characteristics of the demonstration project and complete sets of equipment, provides the reference of engineering machinery and integrated use in tunnel reactor for bio-drying. |
PDF Full Text Request