| Coal is needed for thermal power in our country,and when the coal burns,it will release sulfur dioxide which has huge impacts on the ecosystem and human activities.Therefore,it is necessary to use desulfurization technology to capture sulfur dioxide.Ammonia desulfurization,as a new technology for capturing sulfur dioxide,has the feature of high efficiency.Ammonium sulfite is one of the products of ammonium desulfurization process,if it can be turned into ammonium sulfate,which will be used as a fertilizer,then can bring economic benefits.The traditional oxidation process of ammonium sulfite is conducted in the oxidation tower with air as oxidant.However,due to the low mass transfer efficiency of the oxidation tower and low solubility of oxygen in water,the mass transfer of oxygen from air to the liquid phases is low,resulting in a long oxidation time of ammonium sulfite.These drawbacks significantly limit the application of ammonia desulfurization technology.In view of the above problems,this thesis used the rotating packed bed（RPB）as a reactor to enhance the oxidation of ammonium sulfite by ozone.The influences of different operating conditions in the three processes on the utilization percentage of ozone（η）and the oxidation percentage of ammonium sulfite（X）were studied.The results are shown below:1.By the study of the rotational speed,when it increased from 0 rpm to400 rpm,the utilization efficiency of ozone increased from 68.6%,54.2%and78.1%to 100%,99.3%and 99.5%,respectively,in the air-sourced ozone circulation oxidation,oxygen-sourced ozone continuous oxidation and oxygen-sourced ozone circulation oxidation processes,indicating that RPB can enhance the mass transfer of ozone between gas phase and liquid phase.2.By a comparison of the oxidation percentages of ammonium sulfite in the air circulation oxidation,oxygen continuous oxidation and oxygen circulation oxidation processes with those in the air-sourced ozone circulation oxidation,oxygen-sourced ozone continuous oxidation and oxygen-sourced ozone circulation oxidation processes,respectively,it was found that the X improved significantly in the ozone-based processes,and the oxidation percentages of ammonium sulfite increased from 15.7%to 35.6%（ozone concentration 10 mg/L,circulation time 15 min）,7.7%to 69.6%（ozone concentration 60 mg/L）,25%to 65.7%（ozone concentration 60 mg/L,circulation time 6 min）,respectively.3.In the studies on the air-sourced ozone circulation oxidation,it was found that the X rose with the rise of the liquid circulation time,gas flow rate,liquid flow rate and temperature,and declined with the rise of the incipient concentration of ammonium sulfite.It was also discovered that with the rise of rotational speed and p H,the oxidation percentage of ammonium sulfite increased first and then decreased.The reaction order and the apparent reaction rate constant of ammonium sulfite oxidation were determined by the half-life method as 0.32 and 3.04×10-3(mol·L-1)0.68·min-1,respectively,and the reaction rate equation of ammonium sulfite oxidation was obtained.4.In the studies on the oxygen-sourced ozone continuous oxidation,it was discovered that X rose with the rise of the temperature,ozone concentration and gas flow rate,but when the initial concentration of ammonium sulfite and liquid flow rate declined,the oxidation percentage of ammonium sulfite declined.It was also found that with the increase of rotational speed and p H,the oxidation percentage of ammonium sulfite increased first and then decreased.5.In the studies on the oxygen-sourced ozone circulation oxidation,it was found that X rose with the rise of the liquid circulation time,gas flow rate,liquid flow rate,ozone concentration and temperature,and declined with the rise of the initial concentration of ammonium sulfite.When the rotational speed rose,the oxidation percentage of ammonium sulfite rose first and then remained almost unchanged.With the increase of p H,the oxidation percentage of ammonium sulfite increased first and then decreased. |
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