Investigation of waste gase cooling after high-temperature electrothermal fluidized bed furnaces

Abstract

Analysis of recent studies and publications. Analysis of the flow char diagram for electro-thermal fluidized bed furnace for graphite purification shows that their significant disadvantage is the increase in the amount of flue gases in the afterburner by almost 30-50 times. This feature complicates their further processing and increases the size and cost of the entire system.
Purpose of research. The aim of this investigation is enhancing the existing process flow diagram of heat utilization and exhaust gas cleaning after electrothermal fluidized bed furnaces for refining graphite by means of a surface-cooled radiation cooler with water cooling, and respectively study the influence of cooler’s regime and geometric parameters on the cooling degree of the dust-laden gas flow.
Presentation of the main research material. Parametric studies of heat and mass trans-fer processes in a radiation cooler were performed theoretically on the basis of the devel-oped mathematical model. The model took into account the processes of radiation-convective heat transfer in the dust-laden gas flow, the dependence of thermophysical properties of gas and material on temperature, as well as the thermal effects of the phase transition.
With the results of the calculations it was found that the main factors that lead to deep cooling of the exhaust gases, apart from length, are the increase in the channel’s diameter, maintain the gas-dynamic mode of the furnace with minimal flue gas output and dust concen-tration. At the same time, the initial temperature of the gases and the addition of "cooling" dust are characterized by a negligible effect on the final temperature at a given length of the heat exchanger. It is shown to ensure the reliability of the radiation cooler, it is recommended to intensify the heat transfer from the cold coolant, to add "cooling" dust and to protect steel walls with carbon felt.
Conclusions. For the first time, for the conditions of high-temperature electrothermal fluidized bed furnaces for graphite refining, the dependence of "cooling" dust additives to flue gas pollination on cooler’s efficiency was determined.
The design of the gas cooler for the given electrothermal furnace of 1000 kgph produc-tivity was developed: a surface of heat exchange of 2,2 m2; channel diameter 100 mm; length 7.0 m. The temperature of the smoke at the outlet does not exceed 930C. The design provides for the presence of a layer between the graphite insert and the steel wall made of graphite felt with a thickness of 10 mm.