碱金属碳酸盐对CaO高温固硫促进作用地研究

提高ＣａＯ的固硫是对煤炭燃烧污染防治的研究热点。采用热天平测试研究在ＣａＯ中添加不同碳酸盐的固硫反应的进程,并采用等效粒子模型处理实验数据,计算了表面化学反应控制阶段及产物层扩散控制阶段的动力学参数。实验及计算结果表明,ＣａＯ固硫反应初期为表面化学反应控制阶段,后期转为产物层扩散控制阶段。以碱金属碳酸盐为催化剂,能固硫反应前期的化学反应控制阶段的反应活化能下降,并按Ｌｉ,Ｎａ,Ｋ,Ｃｓ的顺序依次递     

添加剂对氧化钙固硫促进作用的机理探讨

探讨了添加剂对石灰石固硫促进作用的机理,添加剂改变了ＣａＯ的孔结构,孔分布和表面性质,添加剂在一定程度上催化了ＣａＯ与ＳＯ２的表面化学反应;由于添加剂所加离子的掺杂,引起固硫产物层晶格的缺陷,大大提高了产物层扩散系数;添加剂的加入,改变了钙基固硫剂中钙的化学形式。生成熟的含钙化合物,它们与ＳＯ２反应活性更高,或形成了高温下更稳定的多元化合物,添加剂及其燃烧的条件可以改变固硫最终产物。     

添加剂对型煤固硫促进作用的研究

研究了添加剂对型煤高温（１２００℃）固硫效果的影响．实验发现：ＭｇＯ对Ｃａ（ＯＨ）２固硫反应有较强促进作用;在钙基固硫型煤中同时加入硅酸盐和Ｆｅ２Ｏ３,可大大提高固硫效果,其ＸＲＤ图表明灰渣中形成了一些耐高温物质和 ＣａＳＯ４复盐（Ｃａ３Ａｌ６Ｏ１２·ＣａＳＯ４）;并得出 ＭＳ型煤的Ｃａ（ＯＨ）２和 ＭｇＯ加入摩尔比和固硫率关系的回归方程．     

石灰石与SO2反应动力学的研究

石灰石与ＳＯ２的高温短时的硫酸化反在夹带流反应器中被实验研究，硫酸化反应是一个两阶段反应：初始是一个非常快的零级表面反应且活化能的２１．０ｋＪ／ｍｏｌ，接着是活化能为８０．１ｋＪ／ｍｏｌ的产物层扩散控制反应，初始阶段约０．３ｓ．吸收剂的种类、Ｃａ／Ｓ比、停留时间、反应温度和ＳＯ２分压影响着脱硫反应速率，脱硫反应过程能用缩芯模型来模拟。在Ｃａ／Ｓ＝２、１０００℃Ｔ ２Ｓ的实验条件下，喷射Ｆ－石灰石能     

CaO固硫反应缩芯动力学模型

建立CaO固硫反应的未反应缩芯动力学模型,通过模型计算,考察了宏观反应、灰层扩散控制、气膜扩散控制和化学扩散控制条件下,反应温度、CaO粒径对固硫反应特性的影响.结果表明,提高反应温度、延长反应时间和减小CaO粒径,有利于提高CaO转化率,其中减小CaO粒径对于提高CaO固硫效果最为明显.模型计算结果与实验结果分析表明,未反应收缩芯模型可较好地描述CaO-SO2固硫反应的宏观动力学,其中影响CaO固硫反应的最主要因素是化学反应扩散控制,提高CaO固硫效率最有效的方法是减小CaO粒径.     

高有机硫煤燃烧固硫的研究

以高有机硫煤──贵定煤为研究对象，以ＣａＯ，ＣａＣＯ＿３为固硫剂，对影响固硫作用的温度、Ｃａ／Ｓ摩尔比、固硫剂比表面等因素进行了研究。发现：有机硫析出温度低，过程短。确定燃烧固硫最佳条件，应充分考虑煤中硫的赋存形态和固硫剂的性质。实验表明，ＣａＯ固硫的最佳工况条件是炉温为９５０℃，Ｃａ／Ｓ＝３；ＣａＣＯ＿３固硫的最佳工况条件是炉温１０００℃，Ｃａ／Ｓ＝３。     

CaO—SiO2—P2O5—H2O系统中CBC材料的溶胶—凝胶过程研究：II.凝胶的…

利用ＸＲＤ，ＩＲ，ＳＥＭ及＾２９Ｓｉ，＾３１Ｐ－ＮＭＲ等测试技术研究了ＣａＯ－ＳｉＯ２－Ｐ２Ｏ５－Ｈ２Ｏ系统中干凝胶在烧成过程中的物相变化及物相间发生的化学反应，认为凝胶在烧成过程的不同阶段发生的主要化学反应如下：（１）６７３～７７３Ｋ，由Ｃａ２Ｐ２Ｏ７和Ｃａ（ＮＯ３）２．４Ｈ２Ｏ反应生成了ＯＨＡｐ；（２）７３３～８７３Ｋ，由Ｃａ２Ｐ２Ｏ７和ＣａＯ反应生成了β－Ｃ３Ｐ；（３）８７３～９７３Ｋ；由Ｃ     

氧燃烧方式下石灰石直接固硫反应模拟

氧燃烧方式下高浓度CO2气氛使得石灰石与SO2的气固反应存在直接固硫和间接固硫两种方式。在热重分析仪上进行了石灰石直接硫化的实验,考察了温度、SO2浓度对直接固硫反应的影响。基于球形颗粒气体扩散理论,在未反应收缩核模型的基础上推导出一种从实验数据计算化学反应速率常数和SO2反应级数的新方法。同时在已有研究的基础上改进了产物层扩散系数的计算方法,并采用未反应收缩核模型对不同温度、SO2浓度条件下石灰石直接固硫反应进行模拟,模拟结果与实验结果较为吻合。在所建立模型的基础上定性讨论了温度、孔隙率、平均孔径对产物层有效扩散系数的影响,发现温度对有效扩散系数影响很显著,而孔隙率、平均孔径的影响较小。     

3C2S.3CaSO4.CaF2的形成动力学

３Ｃ２Ｓ．３ＣａＳＯ４．ＣａＦ２是水泥生产中应用氟硫复合矿化剂时重要的中间化合物。本文首次较完整地研究了３Ｃ２Ｓ．３ＣａＳＯ４．ＣａＦ２的形成动力学，认为３Ｃ２Ｓ．３ＣａＳＯ４．ＣａＦ２在９３５℃左右迅速形成，其固相反应可用Ｇｉｎｓｔｌｉｎｇ动力学模型很好地描述。固相反应的扩散控制元是ＣａＯ，反应活化能力２４６ｋＪ／ｍｏｌ．９３５时反应速率常数为２．８０×＾Ｓ＾┑。同时还得到了反应的热力学函数值。     

CaO-SiO_2-P_2O_5-H_2O系统中CBC材料的溶胶凝胶过程研究 Ⅱ凝胶的烧成过程

利用ＸＲＤ，ＩＲ，ＳＥＭ及２９Ｓｉ，３１ＰＮＭＲ等测试技术研究了ＣａＯＳｉＯ２Ｐ２Ｏ５Ｈ２Ｏ系统中干凝胶在烧成过程中的物相变化及物相间发生的化学反应。认为凝胶在烧成过程的不同阶段发生的主要化学反应如下：（１）６７３～７７３Ｋ：由Ｃａ２Ｐ２Ｏ７和Ｃａ（ＮＯ３）２·４Ｈ２Ｏ反应生成了ＯＨＡｐ；（２）７７３～８７３Ｋ：由Ｃａ２Ｐ２Ｏ７和ＣａＯ反应生成了βＣ３Ｐ；（３）８７３～９７３Ｋ：由ＣａＯ和ＳｉＯ２反应生成βＣ２Ｓ。因此粉末材料的主要晶相有：ＯＨＡｐ，βＣ３Ｐ和βＣ２Ｓ，其中Ｓｉ和Ｐ之间有相互固溶现象。     

钙基吸收剂碳酸化实验研究

对CaO吸收CO2反应的特性进行了实验研究,采用未反应收缩核模型分析碳酸化反应动力学特性.结果表明,化学反应速率常数在650℃～750℃范围内基本为一常数,产物层扩散系数随着温度的增加而增大.化学反应控制段的活化能Ea=29.70 kJ/moL,产物控制段的活化能Ea=92.80 kJ/moL.温度一定时,随着CO2体积分数增加,碳酸化反应速率加快,转化率增大.     

Study of the sulfation kinetics between SO2 and CaO catalyzed by TiO2 nano-particles

The catalytic activity of TiO₂ nano-particles, prepared by a sol-gel method, was studied when added in the reaction between SO₂ and CaO. The reaction products were analyzed by infrared spectrophotometry (IR) and specific surface area analysis and the kinetics and mechanisms of the sulfation catalyzed by the addition of TiO₂ are discussed. The results indicate that nano-TiO₂, which serves as an active catalytic center, enhances O₂ transfer and is helpful in the diffusion of SO₂ from the product layer to the inner unreacted CaO. As a result, the desulfurization efficiency increased. The results also suggest that the SO₂ and NO must both be removed simultaneously in order to keep the sulfation rate. The desulfurization reactions are first order for SO₂ concentration and zero order for O₂ concentration and include two zones, the surface reaction zone and the product layer diffusion zone, with later being the rate limiting step. The apparent activation energy of the desulfurization reaction decreased with the addition nano-TiO₂ as compared to that without. The unreacted shrinking reaction core model was used to investigate the reaction kinetics and was shown to describe the course of desulfurization. Lastly, the results obtained through calculation agree with the empirical data.     

Effect of characteristics of calcium-based sorbents on the sulfation kinetics

The microstructure and pore structure of limestone and shell as desulfurization sorbents during calcination and sulfation were investigated using the scan electron microscope and the porosimeter, respectively. The sulfation process and kinetics were analyzed by thermo-gravimetric method and modified grain reaction model. The results show that the doped alkali metal salts may improve microstructure and product diffusion of sorbent during high temperature sulfation, and enhance the initial reaction rate and the final CaO conversion of sorbents. The kinetic parameters of desulfurization with shells present compensation effect. There are linear relationships between logarithms of the pre-exponential factor ln k₀, ln D₀ and activation energies E_a, E_p, respectively. The activity of sorbent can not be exactly evaluated only by activation energies because of the compensation effect; and the k, D_s under certain experimental conditions can reflect the activity of sorbent. The particle pore diffusion and product layer diffusion control principally the rate of sulfation reaction. The pore size and structure and crystal lattice defects concentration caused by impurities or additives are the main factors to affect the sulfation capability of sorbent. There is an optimum content of alkali metal salts in the sorbent within a certain range of sulfation temperature, which helps sorbent to form a better microstructure and obtain higher reactive activity.     

微波固相法制备铁酸锌脱硫剂的硫化动力学

通过微波与常规固相法制备了铁酸锌高温煤气脱硫剂,使用X射线衍射（XRD）、氮吸附、扫描电子显微镜（SEM）以及X射线光电子能谱（XPS）对两种不同焙烧方式制备的脱硫剂的物相组成、织构形貌和表面元素进行了表征。数据显示微波焙烧制备的脱硫剂具有孔隙结构丰富、表面金属元素含量高、结合能低等优点。使用热天平对铁酸锌脱硫剂硫化行为进行了研究,根据等效粒子模型计算了两种脱硫剂与硫化氢气体反应的动力学参数,得到了硫化反应动力学方程,并在固定床上对其煤气脱硫性能进行了考察。结果表明硫化过程分为化学反应控制区和颗粒内扩散控制区。微波焙烧制备脱硫剂的化学反应活化能和颗粒内扩散活化能较低,说明其在硫化氢气体脱除上具有更高的活性。在模拟煤气气氛下,相比常规焙烧方法制备的脱硫剂,微波制备的脱硫剂的脱硫性能显著提高,具有更高的硫容和更长的精脱硫时间。     

氧化铝厂赤泥剂的固硫反应动力学特性研究

采用热分析法研究了山东铝业公司赤泥和石灰石固硫反应过程,利用等效粒子模型计算分析了其固硫反应动力学参数,并在此基础上利用压汞仪、SEM分析了赤泥煅烧前后的微观结构,探讨了赤泥固硫机理,为利用氧化铝生产中排放的大量赤泥代替石灰石用作燃煤固硫剂提供了理论依据.结果表明,赤泥的钙利用率是相同条件下石灰石的2～3倍,赤泥煅烧后较石灰石具有更多的中孔和较大的比表面积,可提高化学反应速度和反应深度;另外,赤泥中较多的三氧化二铁和碱金属盐也可提高赤泥固硫反应速率常数和有效扩散系数,但温度过高会降低固体熔点而易导致烧结,削弱其固硫活性.     

缓冲体系中辉钼矿电氧化浸出研究

主要对缓冲体系中辉钼矿电氧化浸出行为进行了考察,最优的浸出工艺参数为液同比25∶1,搅拌速度400 r/min,NaCl浓度4 moL/L,Na_2CO_3浓度10 g/L,pH=9,室温,Mo浸出率可达到99.5%,且电流效率达到61%,而非缓冲体系电流效率仅为39%;浸出动力学表明,浸出过程表观活化能为8.56 kJ/mol,反应界面有固体产物生成,过程受固膜扩散控制.     

烟气脱硫传质-反应阻力特性分析

主要分析脱硫反应中形成产物层之前的传质反应特性.研究发现,可用蒂勒（Thiele）数来描述以同时反映化学反应速率、扩散速率的影响.脱硫剂颗粒形成产物层之前的转化率仅由蒂勒数决定,随其增加而降低,与此阶段持续时间无关.分析表明,颗粒半径、孔隙率、孔隙分布方式等都可能会改变在产物层形成过程中的转化率和过程特性.粒径较小时,产物层形成过程的转化率随粒径增大而降低;粒径增大到一定程度后,在较大粒径范围内转化率基本不随粒径变化而变化;孔隙率越大,形成产物层时转化率越高.     

Direct Sulfation of Calcium Carbonate Using the Variable Diffusivity Approach

The direct sulfation of calcium carbonate was investigated in the temperature range of 600–900 °C under atmospheric pressure. Thermogravimetric analysis was employed to study the direct sulfation reaction. A gas mixture containing 3300 ppm sulfur dioxide in 5 vol.‐% oxygen and 95 vol.‐% carbon dioxide was passed through 3–5 mg of sorbent. The influence of particle size was studied using three different levels of particle average diameter. A variable diffusivity shrinking core model was applied to interpret the time‐conversion data. The conversion dependent effective diffusivity in the porous sulfated layer was estimated based on the two mechanisms in series, i.e., pore diffusion and solid product layer diffusion. By applying the activation energy data for chemical reaction, available in the literature, the reaction rate constant, and the solid product layer diffusivity with Arrhenius type temperature dependency were estimated as adjustable parameters. The variation of fractional conversion with time can be reasonably predicted by using the developed model and the estimated parameters.     

FeS的水蒸汽高温氧化动力学

通过测定脱硫速率。研究了FeS的水蒸汽高温氧化动力学FeS的水蒸汽氧化产物为Fe3O4，未反应物转变成类磁黄铁矿相（Fel-aS）反应初期铁先于硫被氧化，较致密的Fe3O4产物层形成后，流与铁同时被氧化实验数据与界面化学反应和固体产物层扩散共同控制数学模型结果相吻合。反应活化能和扩散活化能分别为122DkJ／mol和90．2kJ／mol．增加水蒸汽流量可使产物层粒度变细，孔隙度降低流量为240ml／s时，脱硫速率出现极大值     

Useful experimental technique for the study of heterogeneous reactions

The heterogeneous CaO/SO₂ reaction has been thoroughly investigated by developing a series of new experimental techniques including the TGA reactor, the volulmetric reactor and the entrained flow reactor. The heterogeneous system is designed in such a way that most of the gas film and pore diffusion resistances are reduced. The modelling of each step related to the reaction is discussed while the chemical reaction and product layer diffusion are emphasized as the main influences on the SO₂removal. The unchanging size shrinking core model is used to describe the reaction progress with a two stage assumption which has been confirmed in the TGA reactor: first, a very fast surface reaction, followed by a product layer diffusion controlled reaction. It was found from the experiments that the SO₂-partial pressure aat the very beginning is very important for a high removal efficiency during the initial reaction period.