Study On Combustion Characteristics And Efficient Treatment Of Sludge In Fluidized Bed

With the acceleration of urbanization and the improvement of living standards of urban residents,the discharge of municipal sewage and sewage sludge production are increasing year by year.The domestic annual prodction of municipal sewage sludge is expected to reach 12.7 million tons(dry base)in 2020.The treatment and disposal of sludge has become an important problem restricting to the development of society and economics.Fluidized bed incineration technology has attracted wide attention from scholars at home and abroad and has been applied in sludge incineration treatment and disposal due to its wide fuel adaptability,stable operation,low flue gas pollution and less maintenance times.However,the sludge fluidized bed incinerator still has some problems such as high energy consumption and low equipment efficiency in the actual operation process.In view of the above situation,the paper mainly carried out a series of studies on the sludge fluidized bed incineration technology from how to improve efficiency.Firstly,the combustion characteristics of a bituminous coal and three kinds of sludge were compared by thermogravimetric-differential scanning calorimetry tests.Combustion kinetic parameters were calculated by Coats-Redfern integral method,and the interaction between sludge and coal during their co-combustion process was studied.The conclusions provided data support for the following research.In view of the two fluidized bed furnaces which are widely used at present,sludge incineration experiments were carried out on 0.5MW bubbling fluidized bed and 1MW circulating fluidized bed experimental benches.The temperature distribution,pollutant emissions and combustion efficiency were compared.The same experimental conditions were simulated by using Fluent software and non-premixed combustion model,and the characteristics of sludge incineration in these two types of furnaces were summarized.Combining with the above test results,this paper chooses the entrance and exit of incinerator as the breakthrough point to research on the method of improving sludge incineration efficiency in fluidized bed.Two kinds of sludge drying experiments were carried out on a self-made small batch sludge paddle dryer in laboratory to explore the relationship between sludge fuel size distribution and water content,so as to provide the data reference for choosing suitable sludge parameters into furnace.By comparing the physical parameters such as particle size distribution and density of sludge ash and coal ash,the necessity of improving the cyclone separator of fluidized bed boiler is explained.The influence of different parameters on separation efficiency is analyzed by theoretical calculation,and the separation efficiency under different structure and operation conditions is numerically simulated.The optimization of the current cyclone separator of fluidized bed is put forward.Finally,the paper takes a sludge drying and incineration project with designed treatment capacity of 700 tons/day as the research object.According to the monthly report data and field test data,the energy balance analysis of the system was carried out.The thermal efficiencies of six sludge dryers and two fluidized bed incinerators were calculated.The main operation parameters of the drying and incineration system were compared.The energy flow distribution and energy losses of the whole system are analyzed quantitatively based on the energy balance model.The relevant energy saving and consumption reduction measures are put forward based on the comprehensive analysis results.