Research On Characteristic Of Blended Fuels Of Municipal Sludge And Waste Cooking Oil

The thermal drying and combustion of the blended fuels fabricated by mixing municipal sludge?MS?with waste cooking oil?WCO?is a kind of disposal method,which can achieve the objective of reduction?harmlessness and resource utilization of the waste.The blended fuels fabricated by MS with different mixing ratios of waste WCO are to study about the drying characteristics?kinetic model?combustion characteristics?heat value?the interaction of their combustion characteristics due to WCO,providing theory and application foundation for the fuel treatment of MS and WCO.In order to reduce the water content of blended fuels,the constant temperature drying experiments of blended fuels with the different temperature and mixing ratios were carried out,and meanwhile the kinetic models were fitted.The research results showed that the higher the drying temperature was,the less drying time required was and the faster the drying rates was,but the decrease rate of the time decreased with the further increase of temperature.Due to the rollover phenomenon driven by the power of water boiling over 140?,in which the escape of free water recoincides with intermittent water,the corresponding time of coming to the maximum drying rate in the temperature ranges of 140-180?was delayed,but the corresponding dry basis moisture content had little change generally.What's more,the higher the mixing ratio was,the longer the drying time was,and the lower the drying rate was.The Midilli model was the best fitting model for fitting the drying process of blended fuels after comparing seven kinds of thin-layer drying models at different temperatures,which was also suitable for different mixing ratio.The effective moisture diffusion coefficient of the different ratio of blended fuels ranged from 5.85x10^-99.99x10^-8m²/s under temperature ranges of 80-180?,and the range of the activation energy value was 29.6⁴0.8kJ/mol.In addition,the activation energy value increased with the increase of mixing ratio,but the effective moisture diffusion coefficient did not decrease monotonously with the increase of mixing ratio.To research the utility value of the fuels,the experiment of calorific value and combustion of fuels were carried out by using oxygen bomb calorimeter and thermogravimetric simultaneous thermal analyzer,respectively,and at the same,the activation energy of combustion process was to be solved.As the results show,in the experiment of calorific value on blended fuels with the ratio of 1:0.1,1:0.2,1:0.3,1:0.4,0:1,which were dried at the temperature of 100,140 and 180?,the calorific value had nothing to do with the drying temperature.Besides,the calorific value presented a linear increase with the increase the mixing ratio.The addition of WCO greatly increased the calorific value of the blended fuels that at all mixing ratios was about 1.5 times more than that of the pure sludge.It showed that the addition of the WCO promotes the increase of the calorific value of the blended fuels,making the fuels more valuable.Furthermore,in the experiment of combustion characteristics on blended fuels dried at the temperature of 140?with the ratio of 1:0.1,1:0.2,1:0.3,1:0.4,0:1 at the heating rate of 10,20 and 30?/min,when the heat rate was 20?/min,the combustion process of MS and WCO were divided into 2 and 3 stages,respectively.Additionally,the combustion stage of the blended fuels could be divided into 2or 4stages as the mixing ratio differs,indicating that the addition of the WCO made the later stage combustion characteristics of fuels better.At the different heating rates,the burning rate and maximum peak value increased with the increase of heating rate,but the total weight loss rate was almost the same.The reaction kinetics was analyzed by two models of Ozawa-Flynn-wall?OFW?and Friedmen,namely model-free methods at different heating rates,and after the average activation energy was calculated,it was found that when the mixing ratio was 1:0.3,the average activation energy of the blended fuels reached the minimum with the values of 149.2kJ/mol?OFW?and 139.5kJ/mol?Friedmen?,respectively.To further understand the combustion process of the fuels,the interaction of combustion processes of blended fuels were studied by comparative method.As the results showed,the TG/DTG experimental curve and the TG/DTG theoretical curve were analyzed by comparative method,getting that the mass of the experimental residues was less than the theoretical residual and the effect on the interaction between the MS and the WCO was more obvious by the difference value?TG at high temperature.The coupling effects of them had positive significance for the promotion of the whole process of combustion.In the meanwhile,the combustion characteristic index?C,S?increased with the increase of WCO proportion at the heat rate of 20?/min,while the burnout temperature behaved oppositely,which suggested that the addition of WCO was beneficial for the combustion and burnout of MS.At different heating rates,most of the combustion characteristic parameters showed a linear growth trend with the increase of heating rate,while the rising rate of combustion characteristic indexes?C,S?showed a nonlinear increase,and moreover,the increase of these indexes suggested that the increase of heating rate not only could make up for the adverse effects of the ignition temperature and the burnout temperature,but also contributed to the combustion of fuels,so that the combustion of the fuels had better combustion effect and better comprehensive combustion performance.At last,Compared with the experimental combustion characteristic parameters and theoretical parameters,the experimental value of combustibility index C was larger than the theoretical one,which meaned that the combustibility of fuels with a certain addition of WCO?>1:0.1?was more combustible than expected in the early stage.The experimental burnout temperature was lower than that of theoretical one in the temperature of 85?or so,meaning that it was easier to burn.However,the WCO infiltrated into the inside of sludge would be more difficult to escape and decompose,and ignition point rose correspondingly,making the comprehensive combustion index S lower than the theoretical value.Therefore,the combustion process of the fuel was not a simple linear superposition by mixing ratio between the combustion of MS and WCO,but was the result of the intercoupling between them.