【作者】 孙文寿；

【导师】 谭天恩； 吴忠标；

【作者基本信息】 浙江大学 ， 化学工程， 2001， 博士

【摘要】 石灰石/石灰因价廉易得而一直作为湿式烟气脱硫（FGD）的两种主要的吸收剂。为提高脱硫率和石灰石/石灰的利用率，可采用适宜的添加剂。本研究以两种不同结构的旋流板塔和双搅拌釜为实验设备，首先对几种无机和有机添加剂进行了筛选实验，进而对效果较好的添加剂进行了详细的实验研究和理论探讨。 实验表明，硫酸镁、硫酸钠及腐植酸钠均能有效提高石灰石脱硫过程的脱硫率，而造纸黑液的效果相对较小。实验同时确定了适宜的添加剂浓度。还对效果较好的硫酸镁和腐植酸钠混合添加剂的强化效果进行了试验。在实验的基础上，分析了添加剂的强化机理。 对筛选出的三种添加剂强化石灰石/石灰脱硫过程，研究了pH值、液气比及进口SO₂浓度对脱硫率的影响规律，得出了回归公式，并对这些操作参数的影响机理进行了分析。 对镁强化石灰石/石灰脱硫过程，详细测定了不同浓度硫酸镁强化下脱硫率、pH值等随脱硫反应时间等的变化情况，分析了不同pH值范围时的反应机理，确定了适宜的pH值操作范围，得出了τ（pH₀）、η（pH₀）回归式，计算了石灰石/石灰的利用率。实验和分析表明，在不同pH值范围，脱硫反应的化学过程是不尽相同的；添加硫酸镁能促进石灰石/石灰的溶解，延缓pH值的降低，在相同pH值下又能有效提高脱硫率，故可提高石灰石/石灰的利用率。本文同时对镁强化石灰石和镁强化石灰脱硫过程进行了分析对比。 在常规旋流板塔上，对钠强化石灰石脱硫过程进行了研究，测定了脱硫率、pH值等随时间的变化情况，分析了pH值对脱硫率、石灰石溶解速率等的影响规律。在与工业操作相近的温度条件下，测定了脱硫率和压降随塔板数的变化情况，得出了平均单板效率与塔板数之间的关系式。 依据实验结果，分析认为硫酸钠、硫酸镁和腐植酸钠均能促进石灰石的溶解，从而延缓浆液pH值的下降。根据理论分析，导出了添加剂强化下石灰石溶解的数学模型公式，可满意地关联实验结果。 以双搅拌釜为实验设备，测算了三种添加剂强化下及非强化石灰石脱硫过程的液相传质系数、反应增强因子及气相总传质系数，对其变化规律进行了分析对比。 为全面了解添加剂的影响，也测定了添加剂强化石灰石/石灰脱硫浆液的沉降速率、沉降时间、脱硫渣固含量以及脱硫清液密度等，分析对比了强化与非强化时的异同。更多还原

【Abstract】 The two main absorbents in wet flue gas desulfurization(FGD) process are limestone and lime because of their cheapness. The S02 removal efficiency and limestone/lime utilization can be increased by using adequate additives. In this dissertation, some inorganic and organic additives were experimentally selected. The selected effective additives were further tested in detail and the enhancement mechanism was analyzed theoretically. The tests were conducted on two kinds of rotating-stream tray(RST) scrubbers and a stirred tank.Experiments demonstrated that magnesium sulfate, sodium sulfate and sodium humate could effectively increase SO2 removal efficiency, while the promoting effect of black liquor was relatively low. The adequate additive concentrations were determined. The effects of magnesium sulfate mixed with sodium humate were also tested. The enhancement mechanism was analyzed based on the experiment results.For the limestone/lime FGD process enhanced by the three selected additives, effects of pH value, liquid-to-gas ratio, inlet SO2 concentrations on removal efficiency were investigated, and the regression equations were obtained. Meanwhile, the operating factors’ affecting mechanism was analyzed.For the magnesium-enhanced limestone/lime FGD process, changes of SO2 removal efficiency and pH value with time were experimentally studied. The reaction mechanism at different pH range was analyzed and the adequate operating pH range was determined. According to the experimental data, the regression equations of *(pH0) and 77(pH0) were obtained and the limestone/lime utilization was calculated. Experiments and analyses showed that the reaction mechanism was different at different pH range; and that adding magnesium sulfate could promote the dissolution rate of limestone/lime, slow down the descent of pH value, achieve higher SO2 removal efficiency at the same pH value and therefor increase limestone/lime utilization. Furthermore, Magnesium-enhanced limestone FGD process was compared with that of lime.Sodium-enhanced limestone FGD tests were conducted on normal RST scrubber. Changes of SO2 removal efficiency and pH value with time were measured and the effects of pH value on S02 removal efficiency and dissolution rate of limestone were analyzed. The effects of plate number on SO2 removal efficiency and pressure drop were tested at temperature approximated to industrial operating value. The relation between the average plate efficiency and plate number was obtained.It was shown that magnesium sulfate, sodium sulfate and sodium humate could all increase limestone dissolution rate and therefor slow down the descent of pH value. Based on theoretical analysis, a mathematical model of limestone dissolution enhanced by additives was developed. The model could correlate test data with good results.The liquid-phase mass-transfer coefficient, enhancement factor and over-all gas-phase mass-transfer coefficient of limestone FGD processes with and without additives were obtained by experiments conducted on stirred tank. The results were compared and analyzed.To understand the additive-enhanced limestone/lime FGD process all-sidedly, the slurry setting rate and setting time, indissoluble solid content of the filter cake, and density of the slurry supemate were measured. The results were compared with that of non-enhanced process.更多还原