Distribution And Migration Patterns Of Chlorine During The Heat Treatment Of Dregs And Coal

The dregs biomass is mainly composed of the roots,stems and leaves of plants.It has complex shapes,high water content,and low energy density.The content of chlorine and heavy metals are relatively high.During the burning process,it is easy to produce PCDD/Fs.The dregs and coal co-combustion would effectively improve the combustion activity and increase the calorific value.Under the conditions of anaerobic pyrolysis,there will be no formation of PCDD/Fs.In this paper,low-rank coal?Shenmu coal?and traditional Chinese medicine slag were used.Firstly,the pyrolysis parameters of coal and drags were studied by TG-FTIR analysis method,and dynamic model was established to obtain the kinetic parameters of the co-pyrolysis process;Analysis of gas components in co-pyrolysis of coal and dregs by infrared analysis.Then,studied on co-pyrolysis and co-combustion of coal and dregs by using double temperature zone tube furnace.After combusting the coke?semi-coke?obtained by pyrolysis,Combining analysis methods of EDS and XRD,analysis chlorine ions in gases,solids,and liquids obtained from the experiment was performed by suing ion chromatography.Studying the release of chlorine and distribution rate of chlorine in three phases after co-combustion and co-pyrolysis.Draw the following conclusions:?1?With the increase of the proportion of dregs in the mixture,the reactivity decreased,but the reaction rate increased.The gas components that co-pyrolysis of the dregs and coal are mainly small molecules such as CO₂,hydrocarbons,acids,ketones,carboxylic acids,and esters,and the release rules of HCl are also very different.?2?The chlorine in the pyrolysis tar of the mixed sample mainly comes from the decomposition of the dregs.The temperature increases,the distribution rate of chlorine increases in the tar and gas,the increase rate in the low temperature zone is higher than that in the high temperature zone,and the chlorine transferred into the gas is far less than the tar and coke.?3?Comparing the chlorine release between the direct combustion and pyrolysis solid combustion product of the sample,the chlorine precipitation rate curves of the two have similarities in the shape trends,but they differ greatly in value.This is due to coke?semi-coke?produced after low-temperature pyrolysis,it's volatile matter and organic compounds are not completely release or decomposed,and are basically the same as the original sample after combustion.However,in the process of pyrolysis,the physical structure and properties of the sample have changed,so that the chlorine form is also simpler than the original sample structure,so it is different from the original sample combustion,the weight loss rate of semi-coke combustion is reduced,the rate of weight loss is large,the chlorine release rate increases,etc.The alkali metals in the dregs would facilitates the release of chlorine from the mixture.The presence of alkali metal in the dregs facilitates the release of chlorine from the mixed sample.The direct combustion of the dregs and coal is much greater than the amount of chlorine that is combusted after pyrolysis,and less chlorine is emitted during coke combustion.Dioxins can be effectively avoided during combustion.