水合煅烧改性CaO孔隙的实验分析

水合煅烧是改善CaO脱硫性能的一种有效方式，从改变水钙比和煅烧温度两个影响因素出发，实验研究了高温煅烧后CaO颗粒孔隙特性的变化，并结合TGA实验测定了水合煅烧CaO的脱硫性能的改变效果，最后从孔隙内液体相变析出的膨化作用与毛细作用两个角度解释了实验现象。     

CaO颗粒水合制备工艺的优化及其性能的CFBR实验研究

为了降低脱硫反应产物层的扩散阻力对于CaO颗粒脱硫反应的影响，提高脱硫反应速率和CFB-FGD工艺中的烟气脱硫率，必须降低CaO颗粒粒径。将分析纯CaO颗粒分别与去离子水和4种分散剂溶液进行水合反应并根据悬浮液分散度对脱硫剂制备工艺进行了必要的优化。对分析纯CaO颗粒与去离子水反应得到的Ca(OH)2颗粒悬浮液和分析纯CaO颗粒与0．006mole／l的(NaPO3)6溶液反应得到的Ca(OH)2颗粒悬浮液分别与飞灰混合、干燥、研磨得到的脱硫剂性能在自行设计制造的小型循环流化床热态实验台(CFBR)上进行了实验研究。实验结果表明：在600℃～800℃范围内，CFBR的烟气脱硫率达到最大值。提高Ca(OH)2悬浮液的分散度是降低CaO颗粒覆盖层厚度和提高脱硫剂在CFB-FGD工艺中的烟气脱硫率的有效方法之一。图3表5参9     

氧化钙脱硫过程反应动力学研究

利用7种不同粒径大小的CaO颗粒以热重分析方式进行脱硫反应实验，反应温度分别为680,750,890℃，得到了各种脱硫剂的实时转化率曲线，并针对热重分析实验的特点对变晶粒模型进行改进得到了脱硫反应动力学方程式，通过与热重分析实验相比较的方式获得SO2气体在产物层中的扩散系数和化学反应速度常数值，结合SEM分析了温度对脱硫反应的影响原因，得到了气体在产物层中的扩散系数与粒度之间满足幂函数关系，颗粒具有分形特性的结论，解释了以往实验给出的实验数据的分散性问题。     

CaO颗粒烟气脱硫反应最佳反应温度的实验研究

CaO颗粒的烟气脱硫反应受到烟气成份、温度和CaO颗粒自身特性的综合影响。通过实验研究和对前人工作的总结,证明了CaO颗粒在烟气脱硫循环流化床中的最佳反应温度为800℃。在此温度下,基本上避免烟气中NO和CO2等成份对脱硫反应的竞争反应;基本上回避了CaO等晶体的再结晶过程引起的脱硫反应速率的降低;使脱硫反应产物的主要成份变成CaSO4。CaSO4的热解温度比较高,脱硫产物的稳定性较好,不会对大气造成二次污染。     

水蒸气对CaO颗粒脱硫反应转化率的影响

用固定的SO2浓度和干空气、湿空气为载气,对4种CaO样品进行了系列TGA实验研究,结果表明,模拟烟气中含有水蒸气时,水蒸气能够提高CaO颗粒脱硫反应中的转化率．随着反应温度的提高,CaO转化率的相对提高幅度逐渐降低,而绝对提高幅度却逐步增加．模拟烟气中没有包含CO2、NOx等成分,回避了碳酸盐反应和硝酸盐反应对实验结果的干扰．由于CaO样品的性质覆盖了分析纯CaO和工业级石灰,水蒸气对于CaO转化率的提高作用对工业级石灰的烟气脱硫反应有一定参考价值．     

水合反应和氧化铁对CaO颗粒脱硫反应作用的Arrhenius表达

将水合反应对CaO颗粒脱硫反应的促进作用归纳为水合反应的活化作用和将氧化铁对CaO颗粒脱硫反应的促进作用归纳为CaO颗粒活性中心数量的增加的观点,从化学动力学角度而言是不够清晰的。本文通过TGA系列实验证明了CaO的水合活化反应和氧化铁在Ca0颗粒的脱硫反应中的作用本质是提高指前因子,并对水合反应和氧化铁的作用机理进行了对比分析。     

EtOH调质CaO粒径对其脱硫效果影响的实验研究

就CaO经乙醇水溶液调质前后粒径对其脱硫率的影响进行了实验研究,发现小粒径下的CaO经调质后脱硫率提高程度要较大粒径下明显。就两种典型粒径下的CaO探讨了燃烧炉温度、Ca/S等因素对脱硫率的影响。借助于SEM重点对两种典型粒径下调质及脱硫前后的CaO大尺寸孔隙分布要优于小粒径下的CaO,而小粒径下调质后CaO所获得的大孔隙分布相对改善程度要好于大粒径下得到的孔隙分布改善。     

多孔脱硫剂孔结构的特性

多孔脱硫剂孔结构的特性对脱硫效果有着重要的影响.借助压汞分析微观手段对脱硫剂孔结构的特性进行了大量的实验,表明脱硫剂的孔径分布满足高斯函数分布形式,建立了SO2和多孔CaO反应的孔分布数学模型.通过计算表明,脱硫剂颗粒中不同的孔径大小具有不同的CaO转化率,孔径范围在100～600nm之间的孔具有较高的CaO转化率.研究结果可为脱硫反应过程的实际应用提供理论指导.     

石灰石煅烧产物CaO的孔隙特征模拟及实验研究

为了研究石灰石煅烧产物 CaO 的孔隙特征与脱硫过程的关系,建立了 CaO 孔结构特征的数学模型,利用模型计算了 CaO 内部孔的比表面积和孔容积,计算值与实测值吻合良好.重点对0～5 nm,5～20 nm,20～100 nm及>100 nm 4个孔径范围进行了分析,结果表明:在 3 种试样中,试样 A 的粒径最大,孔径分布最宽,函数峰值所对应的孔半径及平均孔半径最大;试样 B 的粒径居中,但是孔径分布最窄,函数峰值所对应的孔半径及平均孔半径最小;粒径最小的试样 C,煅烧时可能部分烧结,导致函数峰值所对应的孔半径及平均孔半径比试样 B 大.在 3 种试样中,试样 B 的有效孔径(5～20 nm)所占的比例最大,由此预测其脱硫效果最好,选取上述 3 种粒径石灰石煅烧产物进行脱硫实验,实验结果与预测结果一致.     

纳米TiO_2催化煤燃烧的实验研究

研究了纳米TiO2在有、无CaO脱硫的工况下,对汶南褐煤和内蒙烟煤的催化燃烧效果.通过热重曲线,从着火温度、失重量、放热量等燃烧特性方面,对实验结果进行了分析.结果表明:在无CaO脱硫时,纳米TiO2使烟煤的着火温度下降15 ℃,褐煤的燃尽温度降低了32 ℃;在有CaO脱硫时,纳米TiO2使褐煤的着火温度下降17 ℃,烟煤的燃尽温度降低了8 ℃,同时褐煤、烟煤的燃烧反应活化能分别降低了5.9 kJ/mol和1.3 kJ/mol,褐煤的发热量升高.XRD图谱中没有新物质生成也证明了纳米TiO2的催化燃烧作用.这一结果为燃烧脱硫的同时,提高煤的燃烧效率,节约用煤量提供了理论依据.     

高CO2浓度下石灰石硫化特性实验研究

借助热重分析天平、扫描电子显微镜、氮吸附仪对石灰石在高CO_2浓度下的硫化特性进行了研究．实验结果表明,高CO_2浓度下石灰石直接硫化时Ca的最终转化率及在高硫化程度时的硫化速率均比CaO-SO_2硫化高很多．测得直接硫化反应由化学反应控制时的表观活化能为93．5 kJ/mol,且表观活化能随Ca转化率的升高而增加．直接硫化所形成的CaSO_4产物层表现出多孔性且比较疏松,而且产物层的比孔容积和平均孔径均随温度的升高而呈指数增长．     

Fundamental study of heterogeneous KCl sulfation under oxy‐fuel combustion conditions

Under oxy‐fuel combustion condition, SO₂ in the flue gas would be accumulated by recirculation, which is conducive to the heterogeneous sulfation reaction of alkali metals. In the present study, experiments were conducted in a fixed bed to investigate the effects of operating parameters and mineral additives (SiO₂, CaO, and Fe₂O₃) on the heterogeneous sulfation of potassium chloride under oxy‐fuel combustion atmosphere. According to the results here, the heterogeneous sulfation reaction was a kinetically controlled process, with the activation energy of 93.6 kJ/mol. The reaction orders with respect to SO₂, O₂, and H₂O were determined as 1, 0.6 and 0 (H₂O involved in the reaction). While the reaction would be promoted obviously in the absence of H₂O. The rate law of heterogeneous sulfation of potassium chloride was derived based on the experimental data. Compared with air combustion, the heterogeneous sulfation rate was lower under oxy‐fuel combustion. All the mineral additives employed would affect the sulfation reaction. The sulfation reaction can be catalyzed by Fe₂O₃. While CaO would suppress the reaction by competing for SO₂ with KCl. The reaction between CaO and SO₂ could also be catalyzed by Fe₂O₃. Besides, SO₂ was more reactive towards CaO than KCl.     

Experimental study on pore distribution characters and convert rate of CaO

During the reaction between calcium sorbents and SO2, calcium sorbents are first calcined and converted into CaO. CaO can be obtained by calcining Ca(OH)2or CaCO3. The porosity of the sorbent is increased because of calcination and is decreased because of sulfurization. In the calcination process H2O or CO2 is escaped from the particles and pores are formed in particles. The reaction or convert rate of CaO is influenced strongly by the pore structure characters. From Ca(OH)2 to CaO the escape velocity of H2O or its mass transfer is one of the key factors influencing the pore forming. During calcination process different healing velocity, different heating time and temperature were suggested. The temperature rising rate and calcining temperature play important role to the pore structure. The convert rates of CaO obtained through different calcining conditions were investigated experimentally. Some interesting results were showed that the calcium utilization of CaO particles is determined not only by the special surface area and total pore volume, but also by pore-size distribution. The main factor influencing the sulfation is the pore diameter distribution at lower sulfation temperature. For higher reaction temperature specific volume is the important reason. But pore-size distribution is strongly influenced by heat flux and temperature in the calcining process.     

石灰石直接硫化实验研究

进行了在高CO2浓度下石灰石直接硫化实验研究。实验研究了温度、CO2分压、O2分压及SO2浓度对石灰石直接硫化的影响。结果表明,温度对直接硫化反应速率影响很大,随温度的升高直接硫化速率增大,在所试验的时间内,当温度为1173K时,Ca转化率可以达到87%,当转化率≈0时,测得表观活化能为93.5kJ/mol,且表观活化能随Ca转化率的升高而增加;与温度相比,CO2分压对石灰石直接硫化几乎没有影响,增加CO2分压只是延缓石灰石的分解,提高石灰石的分解温度;在5%以下随O2分压的增加,直接硫化速率随之增加,O2分压超过5%以后,O2分压对石灰石直接硫化就没有什么影响;随SO2浓度的增加,直接硫化速率升高。     

钙基脱硫剂孔隙分形特性的实验研究

分形维数是描述分形结构特性的一个重要参数,其反映了结构的规划程度。通过实验的方法,研究钙基脱硫剂在不同温度,气氛及烧结时间等煅烧条件下,对孔结构分形维数的影响,以及分形特性对脱硫剂的硫化能力的影响。结果表明煅烧温度对CaO孔结构的分形维数影响较小;CaO孔隙的分形维数随着煅烧气氛中的CO2浓度的增加而减小,随着烧结时间的延长而减小,脱硫剂硫化过程中形成的不可进行孔隙量随着分形维数的增大而增大。     

基于逾渗理论的CaO吸收CO2动力学模型

石灰石循环吸收是一种高效而经济的减排烟气中CO2的技术,然而其循环效率降低较快,吸收剂利用率较低.为了对循环吸收过程有很好的认识,改善吸收剂的利用率,将逾渗理论应用于CaO与CO2反应模型中,对CaO颗粒吸收烟气中CO2的过程进行描述.实验数据与模型数据相结合,表明新的模型可以很好地对吸收过程进行描述:烟气中CO2体积分数对CaO转化率的影响主要在反应初期的化学反应阶段;小粒径CaO颗粒在一定程度上可以提高CaO的钙转化率.该研究为提高循环吸收效率提供理论指导.     

Sulfation in lead–acid batteries

Virtually, all military land vehicle systems use a lead–acid battery to initiate an engine start. The maintainability of these batteries and as a consequence, system readiness, has suffered from a lack of understanding of the reasons for battery failure. Often, the term most commonly heard for explaining the performance degradation of lead–acid batteries is the word, sulfation.Sulfation is a residual term that came into existence during the early days of lead–acid battery development. The usage is part of the legend that persists as a means for interpreting and justifying the eventual performance deterioration and failure of lead–acid batteries. The usage of this term is confined to the greater user community and, over time, has encouraged a myriad of remedies for solving sulfation problems. One can avoid the connotations associated with the all-inclusive word, sulfation by visualizing the general “sulfation” effect in terms of specific mechanistic models. Also, the mechanistic models are essential for properly understanding the operation and making proper use this battery system. It is evident that the better the model, the better the level of understanding.     

Steam-gasification of biomass with CaO as catalyst for hydrogen-rich syngas production

Biomass is extensively considered as a feed-stock for bio-chemicals and bio-fuels production. Among all options for the utilization of biomass, gasification process is more popular because of its environmental advantages. In this study, biomass gasification with CO₂ removal by CaO sorbent was simulated by using a commercial simulator. The model accuracy was validated with reported results from steam only gasification of biomass in presence of CaO. The system was evaluated through tar yield, carbon conversion, gas quality and H₂ yield by varying the reaction temperature, steam flow rate and CaO flow rate. The hydrogen yield enhanced slightly from 187.32 ml/g to 198.49 ml/g with the increase of CaO/B from 1.0 to 1.5. However, a further enhancement in CaO/B from 1.5 to 2 sharply enhanced the hydrogen yield approximately 1.55 times (from 198.49 ml/g to 308.54 ml/g).     

钠盐对钙基脱硫剂烧结动力学的影响及孔结构的生成模型

从离子迁移现象出发探讨了钠盐杂质对CaO烧结动力学的影响.采用不等径团聚体,代替传统认为CaO晶粒都是同一尺寸的物理概念,进而通过空位缺陷方程,推导出固态离子扩散系数,从而实现对CaO烧结过程中物理结构不断变化的模拟.利用向钙基脱硫剂中添加钠盐以得到不同杂质含量的方法,研究了温度、杂质含量对CaO烧结的影响.通过实验数据和模型计算结果比较,证明了该模型的合理性.     

双流化床生物质气化及CO2捕获的模拟

用Aspen Plus建立了双流化床气化和燃烧模型,对生物质在双流化床中气化及CaO吸收合成气中的CO2过程进行了模拟研究;探讨不同反应条件:气化温度、蒸汽与生物质的质量配比(S/B)以及CaO循环量与生物质的质量配比(Ca/B)对合成气成分的影响,为该类型工业反应器的研发提供了理论依据.模拟分析结果表明:气化温度低于700℃时,CaO能很好地吸收气化过程中产生的CO2并促进平衡反应向产氢方向进行;在温度为650℃及CaO作用下,S/B在0.6～1.7内对合成气成分的影响不大;CaO的加入能够有效地改善合成气的组成,合成气中氢气浓度能达到95％以上,氢气产量达到52 mol/kg.