Wastewater incinerators refer to technologies that use controlled high-temperature chemical reactions in the combustion chamber of the incinerator to destroy the molecular structure of various harmful substances in the wastewater and oxidize the wastewater into harmless substances such as CO2 and H2O. The wastewater incineration process can be divided into three stages: evaporation, gasification, and oxidation. The water in the wastewater first evaporates in a high-temperature environment, and the combustible components are in the form of mist droplets. Then, the organic matter is gasified, and high-molecular organic matter may be cracked into low-molecular compounds (the reaction temperature is about 700~800℃). Finally, the gaseous organic matter undergoes an oxidation reaction with the oxygen in the furnace to generate CO2 and H2O, which are discharged from the furnace with the flue gas.
The main characteristics of wastewater combustion are as follows: ① The combustion rate is inversely proportional to the square of the droplet size. The finer the liquid, the faster the combustion rate and the more complete the combustion. ② When the temperature is higher than 900℃, the oxidation reaction rate of the wastewater is fast and the burnout effect is good. When the temperature is lower than 850℃. The oxidation reaction rate is weakened, which limits the burnout effect. At this time, the atomization effect of the wastewater is required to be better, so as to improve the evaporation efficiency and improve the burnout effect; the atomization effect mainly depends on the particle size distribution within the large particle range of the atomized droplets. ③ These substances are highly corrosive. Second, the sodium salts produced in the combustion conversion reaction that are not carried away by the combustion gas react with the refractory materials of the incinerator, causing the lining materials of the incinerator to be damaged, affecting the normal operation of the incinerator.
1: Selection and material properties of refractory materials for the lining of wastewater incinerators
We found that during the use of wastewater incinerators. When the waste liquid spray atomization is normal, the erosion and stripping of the refractory material of the incinerator lining is mainly caused by the reaction between part of the waste liquid that is not fully burned and the waste liquid combustion products and the refractory bricks of the furnace wall lining, which produces a third molten compound on the surface of the refractory bricks that will damage them, causing cracks in the lining. The reacted compounds are easy to peel off from the surface of the lining, thereby taking away part of the lining refractory bricks with cracks, making the furnace inner layer gradually thinner. The upper inclined section and the 1/4 part of the middle straight section are the main mixing reaction areas, which are the areas where the atomized waste liquid and combustion products gather the most on the furnace wall. The contact reaction is the most serious in the parts with more waste liquid, so the erosion and peeling are the most serious; when the waste liquid spraying atomization is abnormal, most of the waste liquid is directly sprayed onto the furnace lining, causing the temperature of the local lining to drop sharply, forming a temperature difference with the surrounding furnace lining layer, thereby generating internal stress. When the internal stress exceeds the strength of the furnace lining, cracks will be generated. As time goes by, the cracks continue to expand and extend, and fractures will occur, causing the furnace lining to continue to peel off and become thinner. The upper inclined section and the upper 1/4 of the middle straight section are the parts that are most directly in contact with erosion, so the erosion and peeling are the most serious. For this reason, we must select refractory materials with good erosion resistance, high thermal shock resistance, and good high-temperature volume stability as the lining material of the incinerator.
2. Selection of refractory materials for lining
Considering that the lining of the incinerator is most susceptible to damage and the most serious damage in the upper 1/4 of the upper inclined section and the middle straight section, and considering the physical and chemical properties and economic costs of the materials, we selected zirconium-containing refractory castables and mullite bricks and corresponding matching refractory cement materials to rebuild the entire lining of the incinerator. This lining structure has achieved good results and provides a reference for the selection of refractory materials for the lining of similar incinerators. The reason why the lining layer can be used for so long is mainly because the refractory castable contains a certain amount of Zr2O3, which plays a certain role in resisting spalling and erosion. At high temperatures, the Zr2O3 in the refractory castable reacts chemically with AL2O3 to form a ZrSiO3 crystal form, producing monoclinic Zr2O3 that fills part of the pores of the refractory castable and prevents the corresponding chemical erosion.
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