新型燃烧方式下SO2脱除机理

对O₂/CO₂燃烧方式下SO₂的脱除机理进行了研究.静态实验和动态实验结果表明这种新型燃烧方式有利于降低SO₂的排放,SO₂脱除存在均相脱硫和多相脱硫的协同作用;新型燃烧方式下高CO₂浓度导致燃烧气氛中化学成分不同于传统的空气气氛,SO₂与燃烧气氛中存在的其他组分反应,生成硫的不同形态产物,SO₂只是其中的一种产物形态,导致SO₂总量排放减少;同时 O₂/CO₂燃烧气氛使燃煤中硫的氧化程度减弱;燃煤中本身所含脱硫剂存在优化的微观结构,该种结构有利于脱硫和对底灰中硫的吸附,也导致SO₂的排放量降低;CHEMKIN动力学计算结果进一步表征了以上机理.     

基于低温联合脱除的中低温Hg形态转化机理

与其他燃煤污染物联合脱除是解决燃煤汞排放问题的有效手段,促进Hg⁰向Hg²⁺的形态转化可以提高现有污染物控制装置对燃煤汞排放的控制能力。应用汞形态转化实验台,在中低温条件下研究分析Cl₂、SO₂、H₂O以及 NO₂对Hg⁰氧化过程的影响机理,结果表明,中低温条件下,10 μl•L^-1Cl₂可以氧化90%以上的Hg⁰。SO₂对Hg⁰形态转化过程的影响呈现区间性变化,按照SO₂浓度由小到大可划分为3个区间,只有在第（Ⅱ）区间内SO₂浓度才能显著影响Hg⁰的形态转化过程。H₂O与Cl₂反应的生成物HCl可以氧化Hg⁰,但其在中低温条件下氧化Hg⁰的能力弱于Cl₂,使得H₂O的存在抑制了Hg⁰的形态转化。将NO氧化为NO₂后进行脱除是低温条件下联合脱除的重要路线,NO₂在分解过程中释放出自由氧原子可以将Hg⁰氧化为HgO,这增强了低温条件下汞与NO_x联合脱除的技术可行性。     

改性活性半焦脱除烟气中SO2的反应动力学

在固定床反应器中，研究用改性活性半焦来脱除烟气中SO₂的动力学问题。考察半焦粒径、反应温度和空速对SO₂转化率的影响，建立了本征动力学方程。反应级数为一级，表观活化能为10.058 kJ·mol^-1，指前因子为69.622 2。     

烟气气相组分及Ca(OH)_2对KMnO_4氧化NO的影响机理

在固定床反应器中考察了KMnO₄氧化烟气中NO的过程,分析了烟气组分H₂O、O₂及SO₂对NO氧化过程的影响规律,得到了Ca（OH）₂对KMnO₄氧化NO的影响机理。实验结果表明,H₂O是KMnO₄氧化NO的必要条件;在含H₂O条件下,O₂可以提高NO氧化率。SO₂与氧化剂反应生成无水钾镁钒类复盐K₂Mn₂（SO₄）₃对NO氧化具有负面作用;Ca（OH）₂的加入提高了氧化剂表面的固体碱度从而促进氧化过程进行;通过添加Ca（OH）₂可以降低SO₂对NO氧化过程的负面影响。根据气体成分和产物分析可知,KMnO₄在钙基吸收剂表面氧化烟气中NO的机理可能是KMnO₄以离子态将吸附在氧化剂表面的NO和SO₂氧化为NO₂和SO₃,生成的NO₂、SO₃再传递到氧化位临近的碱性位被吸收。     

烟气气相组分及Ca（OH）2对KMnO4氧化NO的影响机理

在固定床反应器中考察了KMnO₄氧化烟气中NO的过程,分析了烟气组分H₂O、O₂及SO₂对NO氧化过程的影响规律,得到了Ca（OH）₂对KMnO₄氧化NO的影响机理。实验结果表明,H₂O是KMnO₄氧化NO的必要条件;在含H₂O条件下,O₂可以提高NO氧化率。SO₂与氧化剂反应生成无水钾镁钒类复盐K₂Mn₂（SO₄）₃对NO氧化具有负面作用;Ca（OH）₂的加入提高了氧化剂表面的固体碱度从而促进氧化过程进行;通过添加Ca（OH）₂可以降低SO₂对NO氧化过程的负面影响。根据气体成分和产物分析可知,KMnO₄在钙基吸收剂表面氧化烟气中NO的机理可能是KMnO₄以离子态将吸附在氧化剂表面的NO和SO₂氧化为NO₂和SO₃,生成的NO₂、SO₃再传递到氧化位临近的碱性位被吸收。     

O2/CO2气氛下煤燃烧SO2/NO析出特性

在水平管式炉上研究了O₂浓度、CO₂浓度、温度及石灰石添加等各参数对O₂/CO₂气氛下徐州烟煤和龙岩无烟煤燃烧过程中SO₂/NO排放特性的影响。结果发现,O₂/CO₂气氛下,烟煤和无烟煤燃烧SO₂/NO的析出规律与空气气氛下不同,同等O₂浓度下析出量比空气气氛下小。O₂/CO₂气氛下,随着O₂浓度的提高,烟煤和无烟煤SO₂/NO排放量均增大;随着CO₂浓度的升高, SO₂/NO排放量均减小。O₂/CO₂气氛下,石灰石添加对SO₂排放的抑制作用低于空气气氛下;石灰石添加对NO的排放有一定减排作用。对煤灰的元素分析显示O₂/CO₂燃烧对SO₂的抑制主要是由于煤灰的自固硫能力增强,而对NO的减排作用则是促进燃料N向其他含N气体的转换。     

O2/CO2气氛下煤燃烧SO2/NO析出特性

在水平管式炉上研究了O₂浓度、CO₂浓度、温度及石灰石添加等各参数对O₂/CO₂气氛下徐州烟煤和龙岩无烟煤燃烧过程中SO₂/NO排放特性的影响。结果发现,O₂/CO₂气氛下,烟煤和无烟煤燃烧SO₂/NO的析出规律与空气气氛下不同,同等O₂浓度下析出量比空气气氛下小。O₂/CO₂气氛下,随着O₂浓度的提高,烟煤和无烟煤SO₂/NO排放量均增大;随着CO₂浓度的升高, SO₂/NO排放量均减小。O₂/CO₂气氛下,石灰石添加对SO₂排放的抑制作用低于空气气氛下;石灰石添加对NO的排放有一定减排作用。对煤灰的元素分析显示O₂/CO₂燃烧对SO₂的抑制主要是由于煤灰的自固硫能力增强,而对NO的减排作用则是促进燃料N向其他含N气体的转换。     

煤燃烧时形态硫的析出及钙基添加剂的作用

在固定床反应器上进行了大同烟煤以及添加钙基固硫剂的样品在不同氧气浓度、不同升温速率下的燃烧实验.对所得到的SO₂逸出曲线采用Gaussian拟合,得到了各形态硫燃烧形成SO₂的温度范围以及影响形态硫逸出的反应条件.结果表明：随着升温速率增加,各形态硫燃烧释放SO₂的温度向高温区移动.氧气浓度升高,各形态硫燃烧释放SO₂的温度提前,而且它们之间的温度间隔缩小.加入的钙基添加剂中,CaO和Ca(OH)₂具有较高的固硫能力,而CaCO₃由于与SO₂反应困难,在低温阶段没有固硫效果;相反,由于它的催化作用,在低温阶段甚至促进了SO₂的释放.机械搅拌法和超声搅拌法加入的Ca (OH)₂由于高分散性,表现出比机械混合更好的固硫效果,其中超声的作用尤其明显.实验证明,固硫中间体CaSO₃在进一步燃烧形成CaSO₄的过程中会释放出一定量的SO₂.     

催化氧化-喷氨法从低SO2烟气中回收铵盐

利用TG-01型催化剂进行了催化氧化-喷氨法从低SO₂烟气中回收铵盐的研究。研究了各影响因素对SO₂氧化效率和喷氨成盐过程的影响。结果表明，空速对SO₂氧化效率影响较大，而氨硫比对成盐过程有较大影响。在空速1 500 h^-1、氨硫物质的量=1.85条件下，SO₂平均氧化效率达98.02%，产物为硫酸铵和硫酸氢铵的混合物。SO₂、硫酸雾及氨气均达标排放标准。     

三相循环流化床的小型冷模试验研究

三相循环流化床在化学工程、生物工程及废水处理等领域中均有着广泛的应用。试验采用固体取样法测定了反应器内的固含率分布；采用压降发测定了反应器内的气含率分布；采用压强脉动法确定了反应器在试验操作条件下的流型。试验结果表明：在试验考察范围内反应器的压强在轴向上均呈线性分布；固含率沿反应器轴向分布平缓；反应器内气含率随轴向位置的升高而缓慢增大，径向分布基本上是均匀的；气含率受配料浓度影响不大．受表观气速的影响较大；反应器各轴向位置脉动能量的主频范围差异不大。这表明整体上反应器全床均处于比较均匀、脉动较低的过渡流湍动状态。     

流化床与固定床耦合反应器中的颗粒磨损

在直径50mm的冷模流化床与固定床耦合反应器中,考察了活性炭颗粒在130～150℃及不同气速下的磨损情况,得到了不同气速下固定床中圆柱状颗粒的磨损率随时间的变化关系,同时分析了滞留在流化床、固定床及袋滤器中的细颗粒在不同气速下的粒径分布与质量分布.结果表明,颗粒在该耦合反应器中磨损严重,在0.212～0.424m/s气速下,固定床中颗粒质量损失可达3%～4%,流化床中颗粒平均粒径由200μm降至100μm以下.     

Modelling of hydrodynamics in a type I turbulent bed contactor

A simple model for the hydrodynamics in Type I TBC is developed for the prediction of hydrodynamic variables such as the phase holdups, bed expansion and pressure drop based on the model by Chern et al. (1983. Hydrodynamics of constrained inverse fluidization and semifluidization in a gas-liquid-solid system. Chemical Engineering Science 38, 1167). This is done by modelling the TBC as a packed bed with large porosities carrying countercurrent gas-liquid flow. The process parameters considered are gas and liquid velocities, particle size and density. The dependence of hydrodynamic variables on process parameters predicted by simulation agrees well with that reported in literature.     

三相循环流化床中的气液相界面积和传质系数

采用溶氧法测量了三相循环流化床中液相溶氧浓度的轴向分布,并按轴向扩散模型处理实验数据,优化得到气液体积传质系数kLa,同时用光纤探头测量了体系中的气含率和气泡大小分布,计算得到了气液相界面积a和气液传质系数kL,并研究了主要操作条件(表观气速、表观液速和固含率)对气液传质系数的影响规律.     

大颗粒三相环隙气升式环流反应器流体力学行为

研究了大颗粒体系气升式环流反应器的流体力学行为,考察了表观气速和颗粒质量分数对床层膨胀高度、循环液速和固含率分布的影响。实验结果表明,按颗粒的运动状态不同可以将反应器内的流动分为3个区域,即固定床区域、膨胀床区域和循环床区域,各流动区域内的流动行为存在显著差异。随着颗粒质量浓度的增大,起始流化气速和最小循环气速均显著增大。基于三相流化床的流化模型和环流反应器的特点建立了相应的数学模型,对大颗粒三相气升式环流反应器的起始流化气速和最小循环气速进行了预测,模型预测值与实验测量值吻合良好。     

Experimental and simulation study of the temperature distribution in a bench-scale fixed bed Fischer–Tropsch reactor

The temperature distribution in a bench-scale fixed bed Fischer–Tropsch reactor using Co-based catalyst was investigated under conditions of 2 MPa and 458 K at various syngas partial pressures and space velocities. The single-tube reactor had a diameter of 0.05 m, which is representative of the diameters used in industrial applications. With a special designed temperature measurement, the detailed temperature distribution in a bench-scale reactor was reported for the first time. The changes of maximum temperature in the bed and hot spot region were discussed at different N₂ flow rate and gas hourly space velocity. A 2D pseudo-homogeneous fixed bed reactor model was developed using ANSYS Fluent. A position-dependent heat-transfer coefficient, which considered more accurate in temperature prediction, was applied. The model was validated against both the reaction results and the measured temperatures. The inferred properties within the reactor were analyzed to give insight as to how to increase the reactor production capacity.     

INVESTIGATIONS OF THE BUBBLE PHASE BEHAVIOR IN A HIGH TEMPERATURE FLUIDIZED BED REACTOR WITH COALCOMBUSTION

The properties of bubbles in a bench-scale fluidized bed reactor, 30 cm in diameter, during coal combustion were determined by means of a newly developed cooled bubble probe and a data processing system at temperatures up to 850°C and fluidization indexes up to 10 in axial and radial positions in the bed. The fluidization index above 4 and the temperature have only slight effect on the bubble properties. Their variation along the height above the gas distributor is dominant.

Oxygen and Co₂-concentration profiles were measured in the bed and in the freeboard, and the o₂-profiles were calculated by means of measured bubble data and bubble models. A comparison of measured and calculated o₂-profiles indicates that the mass transfer rates between the emulsion and bubble phases are larger than the ones calculated by the models.     

Novel water treatment process — combined cationic ion-exchange bed and degasifier in a three-phase fluidized bed

A novel water treatment process, combining cationic ion exchange and bicarbonate removal in a countercurrent three-phase fluidized bed, was explored. The study was based around a laboratory scale bed. The different operating conditions and effluent quality were investigated. The results showed that concentrations of sodium and carbon dioxide in effluent decreased with increasing height of resin static layer and greater airflow velocity. The concentration of sodium and carbon dioxide in the effluent was lower than 0.1 mg/l and 5 mg/l respectively. Instantaneous conductivity that illustrated effluent quality was measured in different sections of the bed. A mathematical modeling which can simulate the changing of conductivity was built, the validity and applicability of the model for future prediction of effluent properties have been verified by the good agreement between the experimental and predicted values.     

The gas–liquid contacting effect on the operation of small scale upflow hydrotreaters

The effect of reactor geometry and bed dilution on the extent of gas oil hydrodesulfurization was tested by conducting hydrodesulfurization experiments in two laboratory reactors of different scale with non-diluted and diluted beds in ascending flow. The superficial gas and liquid velocities and the catalyst bed height were kept constant while the main difference between the two reactor scales was the reactor diameter. The diluted bed of the mini-reactor showed the best performance and its results were identical in upflow and downflow mode. The differences between the performance of the mini- and the bench-scale reactor operating in upflow mode have been investigated. Reactor performance simulation was attempted by a mathematical model that takes into account axial dispersion of the liquid phase and gas–liquid mass transfer. Bench-scale reactor operation was characterized by lower mass transfer rates than the corresponding mini-scale one. Combining model predictions and mock up operation it is concluded that the stronger mass transfer resistances calculated for the bench-scale reactor are associated with poorer gas distribution through the catalyst bed. Reduction of the bed diameter results in better gas–liquid contact by forcing the gas bubbles to distribute more effectively into the liquid phase.     

三相鼓泡淤浆床环氧乙烷合成反应器数学模拟及工程分析

建立了加压三相鼓泡淤浆床环氧乙烷合成反应器的数学模型 ,计入了催化剂颗粒在床层中沉降形成沿床高浓度分布对反应的影响以及由于惰性液相载体部分返混对传递的影响 ,进一步利用经实验验证的上述数学模型模拟不同表观气速、床高、反应器直径 (扣除传热元件截面积 )、进口乙烯摩尔分数等参数对床层中催化剂浓度随床高的分布、出口环氧乙烷摩尔分数、环氧乙烷选择率以及单位质量催化剂环氧乙烷年产量的影响 .通过模拟分析预示了工业三相床环氧乙烷反应器的合理尺寸、表观气速、环氧乙烷选择率以及时空产率 ,为工业化提供必要的设计依据