Incineration Of Salty Aniline Wastewater And High Temperature Corrosion In Fluidized Bed

The organic wastewater with high concentration cannot be disposed effectively by routine treatment methods because of high COD and salt content. Incineration processing is one of high efficient and environment friendly methods to treat the organic wastewater with high concentration, which can destroy hazardous substances as well as achieve energy recovery. It is significant for design and operation of fluidized to investigate the incineration of organic wastewater containing nitrogen as NO_x has been listed in the pollutant total control index. In the present dissertation, a set of fluidized bed incineration test facility was built and a series of experiments were performed to investigate salty aniline wastewater incineration, NOX emission, effect of additives on the NO_xOUT process and high temperature corrosion were studied. The main research contents are as follows:A set of universal semi-empirical formulas calculating heating values, and the amount of theoretic air and flue gas were derived from the representative date of aniline wastewater. It was established the heat balance equations on incineration of aniline wastewater in fluidized bed incinerator with ethanol as auxiliary fuel. It was also discussed the relations between the feeding rate of ethanol and HV of aniline wasteliquid, combustion temperature and air temperature. The minimum fluidization velocity （umf） was determined at elevated temperature ranges （25-1050℃）. The results showed that umf was almost stable for quartz sand at the temperature range of 25-1050℃, a new correlation to predict the umf was suggested based on the experimental date.The pyrolysis and combustion experiences of ethanol/aniline wastewater were conducted using Q5000IR thermogravimetric analyzer. It was calculated the curves and parameters of pyrolysis and combustion characteristic. The results showed that ethanol was helpful for improving the pyrolysis and combustion characteristic of aniline wastewater. At the same time, the burn-off characteristic was enhanced, and the ignition temperature, both activation energies of combustion and pyrolysis were reduced when the aniline wastewater was mixed with ethanol acted as combustion agent. On the other hand, it can be solved the kinetic parameters of ethanol/aniline wastewater pyrolysis and combustion processes using 1.0 and 0.8 order reaction models respectively.It was investigated the combustion behavior of salty aniline wastewater in a fluidized bed incinerator. The results showed that the combustion efficiency was 99.95% when the combustion temperature was up to 850℃.HCl emission was from the aniline wastewater incineration due to reaction between chlorides and bed materials （SiO2）. Fractional combustion and segmented combustion could improve the combustion efficiency and reduce HCl emission. The reduction of HCl emission was unsatisfactory using Ca agent at high temperature.The characteristic of NO_x emission from the incineration of salty aniline wastewater was investigated in a fluidized bed incinerator. The effects of incineration conditions on the emission concentration of NO_x were also studied as well. The results showed that the NO_x emission concentration decreased with increasing incineration temperature or salt content in aniline wastewater. However, high feeding rates may lead to low NO_x emission concentrations. When the excess air coefficient is lower than 1.0, the NO_x concentration rapidly decreases with decreasing in excess air coefficient. The NO_x concentration then presents a slow decreasing trend after α>1.1.The selective non-catalytic reduction （SNCR） of NO_x was researched using urea as a reducing agent （NO_xOUT process） in the incineration process of aniline wastewater on a fluid bed experimental system. Several sodium-containing additives such as Na2CO₃, NaOH and NaCl were added into the NO_xOUT system to improve NO_x reduction efficiency and enlarge temperature window, respectively. The results showed that the adding minute amounts of sodium additives improved the NO_xOUT performance significantly. The efficiency of NO_x reduction increased as with the addition of either aforementioned sodium additive was added to the NO_xOUT system. The NO_xOUT process was affected by the different sodium sources in accordance with an order: NaOH> Na2CO₃>NaCl. The sodium-containing additives provided ·OH free radicals to improve NO_x reduction at low temperature. The maximum efficiency of NO_x reduction was obtained as the NO_xOUT process was conducted at 900 ℃-950 ℃, a NH3/NO_x molar ratio of 1.5 and an excess air coefficient between 1.0 and 1.2. The molar reaction enthalpy, molar formation Gibbs function and constant of reaction rate were calculated using a thermodynamics method, the results of which confirmed that the NO_xOUT process in this work was available. Both ethanol and H₂O₂ were selected and used as NO_xOUT additive, the results showed that ethanol could improve the combustion and NO_x reduction at 850-950℃. The efficiency of NO_x conversion was improved with the addition of few H₂O₂.NO_xOUT kinetics of flue gas from the salty aniline wastewater incineration in a plug flow reactor was modeled by Chemkin software. The kinetics could be explained using the composition of 17 species and 30 reversible reactions without NaOH addition, but when NaOH was added as NO_xOUT additive, the kinetics is composed of 21 species and 46 reversible reactions. The NaOH additives provided OH free radicals to improve NO_x reduction in the NO_xOUT process.The accelerated corrosion performance of Fe-base alloy at high temperature beneath NaCl-quartz sand deposits was studied in flowing air. The surface morphology and composition were analyzed using scanning electron microscopy （SEM）, energy dispersive spectrometer （EDS） and X-ray diffraction （XRD）.The results showed that the corrosion rate was increased with the addition NaCl in deposits and corrosion temperature. The transformation way of Fe was following:Feâ†'FeCl₂â†'Fe₂O₃ under high temperature corrosion induced by NaCl-quartz sand. Element Cr in the Fe-base alloy could not show the better corrosion resistance under the present high temperature environment due to basic dissolution according to the basicity of the molten NaCl. The addition of kaoline in the NaCl-quartz sand improved the anticorrosion of Fe-base alloy significantly at high temperature.