The Volatilization And Removal Mechanism Of Chorine And Fluorine Gas During Pyrolysis And Combustion Of Hazardous Waste From Chemical Engineering

Incineration is an effective method for the disposal of the hazardous waste from chemical industry. The fluorine and chlorine content of the wastes from some specific chemical industry is well above that of other wastes. The volatilaization and removal mechanism of the fluorine and chlorine gas from these wastes are rarely studied. This thesis is funded by National High-Tech Research and Development Program of China (863Program)(2007AA061302) and National High-Tech Research and Development Program of China (863Program)(2007AA061302). The key research contents and conclusions are as follows.The volatilization characteristics of two typical hazardous wastes during pyrolysis were studied. The fluorine gas HF, SiF4and BF3were found in IR spectrum during the pyrolysis of fluoroborate residue. NaBF4in the sample was decomposed into BF3and NF before700℃. Some of the BF3was hydrolyzed to HF. The NaF was also hydrolyzed to HF at high temperature. BF3and HF could react with SiO2in the sample before600℃.To quantify the emission of the fluorine and chlorine gas during the combustion of fluoroborate residue, a tubular furnace combined with a Gasmet analyzer was used. HF was found to be the dominant fluorine gas after the gas emitted passed through a high temperature secondary combustion chamber. Around68%of the fluorine in the material was transformed into HF.Since the HF and HCl concentration in flue gas was too high when pure fluoroborate residue was incinerated, it was co-disposed with ibuprofen in the plant. The release of HF and HCl was also studied in a tubular furnace. Their concentration could meet the Chinese standard when treated by semi-dry cleaning method in the plant. And the removal efficiency of HF and HCl by CaO was also studied.Chlorinated aromatics could be produced during the combustion of the waste with chlorine from chemical industry. Mono-chlorinated benzene was used as surrogate to study the mechanism of nucleophilic substitution of chlorinated aromatics on V2O5/TiO2surface, which was the first step of the decomposition of dioxin like compounds on catalyst surface. The mechanism was neither an SN1reaction, nor a general SN2reaction. The energy barrier and total energy change on different surface were compared. The reaction was most possibly to occur on anatase (001) surface.The thermal behavior of bio-ferment residue was studied by TG-FTIR study. Since the similar behavior to MSW was found, the residue was co-incinerated in a CFB designed to dispose MSW. The main parameters during co-incineration were within the allowance when bio-ferment residue was not added. And all the pollutant emissions, including HF, HCl and PCDD/F, could meet Chinese standard.