The Research Of CaO Treatment Municipal Sludge Effects On Sludge Thermal Drying And Mathematical Modeling

Municipal sludge is a kind of solid waste with utilizat ion value.With the increase of sludge production year by year,the government began to encourage multi-resour c e utilizat ion to solve the problem of sludge treat ment and disposal better.But the bottleneck of resource utilizat ion is the municipal sludge has high moisture content.Thermal drying is the best way to reduce water content of municipal sludge after mechanical dewatering,but there are some problems such as high energy consumptio n and expensive equipment.A lot of research on sludge treatment methods at present,and few studies have been done on the strengthening and strengthening principle of drying process and on providing basic data for the development of equipment through mathematical modeling.In this paper,the optimum proportion of CaO as conditioning reagent was studied and the strengthening principle of drying process was analyzed by SEM.O n this basis,the effects of temperature and thickness of the sludge layer on drying process were studied by stirring and crushing.The energy consumption of drying process was detected and analyzed by DSC.Finally,the sludge drying process was reproduced by mathematical modeling.The following conclusions can b e drawn:1)The addition of CaO can reduce the initial moisture content of sludge,increase the volume of sludge and increase the solid mechanism after sludge drying.The drying rate was the fastest,resulting in the formation of smaller sludge particles,t he change of muddy characteristics,and the existence of gaps between the particles with the C ao:sludge=20:100 was added.The addition of CaO can increase the solid mechanism in the sludge and increase the resistance of moisture diffusion from the slud ge interior to the sludge surface.With the increase of the amount of CaO,the resistance increases continuously.2)There are three stages in the drying process:acceleration,deceleration and stabilization.The faster the average drying rate with the lowe r the thickness and the higher the temperature,and the shorter the time required to reach the maximum drying rate.The increase of temperature accelerates the drying rate,but the benefits by the increase of temperature decrease gradually.The drying time decreases with the decrease of thickness of the sludge layer,but the benefits of the decrease of thicknes s of the sludge layer is gradually increasing.With the increase of temperature and the decrease of sample thickness,the maximum of drying rate deviates to low moistur e content.3)The results show that the energy consumption of the pure sludge drying process is higher than that of the conditioning sludge,and with the increase of temperature,the theoretical energy consumption and the test energy cons umption are increased.The growth rate of test energy consumption of pure sludge is higher than that of the conditioning sludge.C ompared with pure sludge,the test energy consumption of the conditioning sludge in the heat drying process can save 10.858%heat energy at 120?and 5.538%at 240?.It has good energy saving effect at 240?,and the best energy saving effect at 150?and 180?.4)The mathematical model was established in the following form:MR=a*exp(-kt~n)+bt,and the model form of drying rate constant is:k=ax~2+bx+c in this paper.And then the effective diffusion coefficient(Deff)and activation energy(Ea)of the first stage and the second stage of the deceleration are calculated.