石灰石煅烧/碳酸化过程中微观结构的演变特性

对石灰石煅烧/碳酸化过程中微观结构的演变特性进行了研究.结果表明:石灰石不同煅烧/碳酸化阶段产物的氮吸附/脱附等温线为Ⅳ型,并在煅烧过程和碳酸化初期存在H1型吸附滞后环;石灰石煅烧产物的比表面积和比孔容随煅烧时间的增加呈线性增加,而碳酸化产物的比表面积和比孔容随碳酸化时间的增加呈指数规律迅速衰减;石灰石完全分解产物的孔容分布曲线呈双峰结构,随着煅烧反应的进行,双峰峰值不断增大,而碳酸化反应导致峰值减小;微孔、中孔和大孔对孔容积和孔面积的增加贡献不同,微孔只对孔面积的增加有一定的贡献,而中孔和大孔对孔容积和孔面积的增加皆有较大的贡献;随着比表面积和比孔容的增大,石灰石煅烧转化率呈线性增大趋势,而CaO的碳酸化转化率呈指数衰减.     

CaO闪蒸改性试验研究

文章在固体颗粒孔径增扩仪和高压给水器试验装置上对CaO进行了孔径闪蒸增扩改性试验，用压汞仪对CaO的孔径分布、比孔容积和比表面积进行了测定。结果表明，在一定的压力和温度下，闪蒸试验能够增大CaO的小孔孔径，增加孔容积和比表面积。CaO孔径增加能够减少硫化过程中的孔闭塞，提高钙的利用率。     

不同工况和粒径下飞灰孔隙结构的实验研究

通过氮气等温吸附(77K)方法对不同燃烧工况下燃煤电厂排放的不同粒径飞灰的孔隙结构进行了测试、分析,并通过BET法计算了其比表面积.低压下的吸附等温线和高压下的脱附等温线分别用HK方法和BJH方法解析.结果表明:飞灰的比表面积和孔容积随着氧浓度和钙硫比的增加而增大,随着煤焦比的减小而增大;随着粒径的减小,飞灰孔隙结构变得发达,特别是粒径小于2.5μm时,比表面积、孔容积明显增大.     

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。     

煤粉粒燃烧模糊孔模型

本文利用压汞仪研究了８种原煤及其不同燃尽度的焦样中的孔隙结构,发现大孔的孔容积构成了煤的孔容积的绝大部分,小孔的孔面积构成了煤的孔面积的绝大部分。基于试验结果和理论推导,作者提出了一种新的孔结构模型──模糊孔模型。模糊大孔和模糊小孔分别控制孔内的传质和化学燃烧过程。文中给出了煤粒燃烧过程的控制方程,并对单颗煤粒内部的燃烧过程进行了数值求解,研究了孔隙率、比表面积,颗粒尺寸等结构参数对煤焦反应性的影响,而且与Ｓｍｉｔｈ的试验结果进行了比较。     

石灰石分解特性及微观结构迁移规律研究

采用自建的热重分析仪进行石灰石煅烧分解的热重实验,得到了温度、煅烧气氛及粒径对石灰石分解过程的影响规律,利用扫描电镜(scanning electron microscopy,SEM)和比表面积及孔隙度分析仪重点考察了分解过程中煅烧产物微观结构的迁移变化规律。研究表明:温度是影响石灰石煅烧的关键因素,温度越高,反应越快;CO2分压和粒径的增大对石灰石分解反应有一定的抑制作用;石灰石煅烧产物比表面积和比孔容随煅烧时间的延续快速增加。超过完全分解时间继续煅烧,煅烧产物产生烧结,比表面积和比孔容减小;原始石灰石几乎为无孔形态,随着煅烧过程的进行,微孔、中孔和大孔出现,呈双峰结构分布,煅烧开始至2.5 min时段内中孔增长较多,2.5～6.5 min时段内微孔和大孔快速生成,烧结导致孔的数量减少。     

煤热解的孔隙结构特性

在同热解时间与相同粒度,不同热解终温的实验条件下,利用马弗炉热解龙坪煤获得煤焦试样;用N2气体吸附/脱附方法进行实验研究。实验结果表明:在此实验条件下,不同热解终温下煤焦颗粒试样大体上均是Ⅱ型等温线(或包含Ⅱ型等温线);煤焦的孔径较小,主要是微孔与小孔,且含有少量的中孔及大孔。在热解终温不断提高的实验条件下,孔的结构及种类变得复杂多样化,孔的比表面积及孔容积总体上呈现增加上升的趋势,表明提高热解终温有助于龙坪煤的热解。     

粒径及孔隙结构对石灰石脱除CO_2能力的影响

利用热重分析仪,在不同煅烧及碳酸化反应温度条件下,对比了不同粒径石灰石煅烧和碳酸化反应转化率。采用氮吸附实验,比较了不同煅烧条件下,不同样品的孔隙结构变化规律。实验表明:样品粒径和孔隙结构特征共同影响碳酸化转化率;微米级粒径的石灰石样品煅烧后具有较高比表面积,因此转化率较高;随着石灰石样品粒径增大,CaO比表面积减少,碳酸化转化率下降;伴随着比表面积的减少,样品平均孔径增大,具有较大孔径的CaO一方面减少了孔隙堵塞情况的发生,另一方面也能够容纳更多的CaCO_3,这些因素导致了随着石灰石样品粒径增大,碳酸化转化率反而提高,继续增大石灰石粒径,煅烧后的较大的孔径无法弥补比表面积下降所带来的不利影响,碳酸化转化率降低。     

部分气化后半焦的孔隙结构

用氮气等温吸附(77K)的方法测量了原煤及加压、常压部分气化后半焦的BET比表面积，并利用BJH法计算了孔比表面积、孔容、孔径和孔分布。结果表明，原煤在转化为半焦的过程中，孔隙结构变得发达，比表面积明显增大；半焦的孔比表面积和孔容积分布曲线存在两个明显的峰值，部分气化后的原煤2nm左右的微孔及中孔会较大幅度地增加，3．8nm左右的中孔有进一步的扩展，且该孔径占主导地位。     

石灰石静态煅烧特性的研究

在实验室ＡＳＡＰ２０００比表面积测定仪上,研究了两种石灰石煅烧后得到的ＣａＯ的微观结构特性,讨论了煅烧时间,煅烧温度和石灰石粒径对ＣａＯ比表面积,平均孔径的影响。     

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.     

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。     

闪蒸处理对石灰石脱硫性能的影响

在自制的固体颗粒孔径增扩仪上对石灰石进行了闪蒸改性试验,并在气流反应器上对样品进行了煅烧和脱硫试验研究。结果表明,闪蒸改性处理能够增大石灰石的孔径,而且,在石灰石孔径增扩后,孔增之间的交联性得到了提高,比表面积稍有减少。石灰石经闪蒸改性后煅烧产物CaO的孔径向大孔方向偏移,同时由于闪蒸改性使反应气体的输运性能得到了较大的改善,减少了煅烧过程中烧结的影响,从而比表面积有了大幅度增大。在相同的试验条件下,闪蒸改性后样品的脱硫效率得到了明显提高。     

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。     

循环流化床锅炉脱硫飞灰的水活化实验研究

以310 t/h循环流化床锅炉脱硫飞灰为原料,在不同的水活化条件下进行活化机理的实验研究,探讨了水活化温度、活化时间、活化水量对灰中游离氧化钙水合反应转化率的影响规律,并研究了水活化对孔隙结构的影响。结果表明:水活化过程中,水合反应与消耗氢氧化钙的胶凝反应同时进行;水活化过程中氢氧化钙含量呈现快速上升、慢速上升、缓慢下降的规律;随活化温度提高,水合反应与胶凝反应速率均提高,中期持续时间缩短,活化时间一定时,活化温度存在最佳值;活化水量的增加,可以加快水合反应与胶凝反应速率,活化时间处于后期时,活化水量存在最佳值。     

Preparation of Ni/SiO2 using silicon-rich-biomass as source for acetic acid steam reforming

In this paper, four kinds of silicon-rich biomass (rice husk, rice straw, peanut shell, corncob) were used as raw materials for SiO₂ extraction by heat treatment method. And the extracted SiO₂ was applied to prepare Ni/SiO₂ catalyst for acetic acid (AcOH) steam reforming. Various characterization methods were used to analyze the purity, structure and specific surface area characteristics of SiO₂ extracted from different sources. It was found that the silica prepared by acid washing and calcination (AWC) had larger specific surface area, abundant pore channels and larger pore volume. By water washing and calcination (WWC), K₂O impurity would be remained in SiO₂, which might dissolve SiO₂ during the calcination process, generating an increase in the pore size and a decrease in the specific surface area. While the CaO impurity in SiO₂ promoted the dispersion of the active components and enhanced the interaction between the active component and the carrier. A series of reforming catalysts were prepared by using the obtained SiO₂ as carriers. It was found that the lifetime of catalyst from low to high was Ni/RS-SiO₂ <Ni/PS-SiO₂ <Ni/RH-SiO₂, which was in the opposite order of K₂O content. Acid washing was beneficial for the enhancement of Ni/RH-AC-SiO₂ activity, and the increase of Ni/RS-AC-SiO₂ stability. Among the four catalysts, the Ni/RH-AC-SiO₂ catalyst exhibited the highest carbon conversion (100%) and hydrogen yield at 600 °C, which may be because that the acid washing removed the metal oxide impurity K₂O. And its large specific surface area, the concentrated pore size distribution, and the suitable interactions between the support and carrier may also contribute to its high catalyst activity.     

NO and SO2 removal and pore structure evolution during reburning with calcium magnesium acetate blended peanut shell

Calcium magnesium acetate (CMA) was an effective material for the NO reduction and SO₂ removal simultaneously by using reburning technology. To further improve its NO reduction rate, the peanut shell blended with CMA was used as the reburning fuels. Effects of the Ca/S molar ratio and temperature on the NO reduction and SO₂ removal were investigated. Pore characteristics of solid samples at different temperatures were also studied. Results show that peanut shell addition improves the NO reduction and SO₂ removal during the CMA reburning process. A Ca/S molar ratio ranging from 2 to 3 is a reasonable range for this technology. At lower temperatures, NO reduction and SO₂ removal ratios are much smaller because of the poorly developed pore structure and tar blocking. With increases in temperature, both ratios increase significantly due to the well-developed pore structure caused by volatile matter release and CMA calcination. At a temperature of 900 °C, the SO₂ removal ratio increases slowly because of the partial surface sintering of CaO and because some pores are blocked by the pollutants.     

循环流化床锅炉飞灰的水活化与脱硫

循环流化床飞灰中含有较高的氧化钙和未燃碳，将飞灰水活化后能提高飞灰中钙的利用率．在热重分析仪上，对不同条件下水活化的飞灰脱硫性能进行了实验研究．结果表明，水与飞灰混合干燥条件对其脱硫效果没有明显的影响，而水钙摩尔比是活化程度的最大影响因素，活化水钙摩尔比为．4是较好的活化飞灰脱硫效果的下限．通过比较飞灰水活化前后的孔径结构和比表面，探讨了含钙飞灰脱硫效果改善的机理．