流化床内CaO循环碳酸盐化／煅烧实验研究

以石灰石为吸收剂在流化床反应器内对CaO循环吸收C0:以及循环煅烧特性进行了实验研究.结果表明:当吸收温度为650℃时,在稳定吸收阶段,反应器出口气体中C0:体积分数不超过3%,表明CaO吸收剂在流化床内能有效吸收CO2.随循环反应次数的增加,CaO吸收剂循环反应活性下降,使得稳定吸收CO2阶段所持续的时间随循环次数的增加而减少.CaO吸收剂比表面积和孔隙率随循环反应次数的增加而减少,因此会导致CaO转化率随循环次数的增加而快速降低.     

基于钙基的吸收增强式水气变换反应实验研究

利用CaO能同时催化水气变换反应和吸收CO2的双功能特性,在流化床反应器上进行了基于钙基CO2吸收剂的吸收增强式水气变换过程的实验,研究了反应温度、H2O/CO比对水气变换反应的影响,讨论了石灰石对水气变换的催化作用,分析吸收剂循环反应活性下降特性并进行了乏吸收剂水蒸气活化改性实验。实验结果表明,在400～600oC范围内,升高温度同时提高CaO的催化和CO2实验吸收能力。增加H2O/CO比例有利于水气变换反应中CO转化率的提高,但当H2O/CO比例高于2时,水蒸气对水气变换的促进作用减弱。石灰石只有在高于700℃时才体现出一定的催化效果。钙基吸收剂催化活性和CO2吸收能力均随循环次数的增加而下降,通过水蒸气活化可以部分恢复CaO反应活性,提高钙基吸收剂在吸收增强式水气变换循环过程中的利用效果。     

碳酸钙循环煅烧_碳酸化吸收CO_2的热力学分析

针对CaCO3的煅烧/碳酸化反应(CCR)循环吸收CO2的方法,基于ASPEN PLUS平台进行了热力学模拟.以增压循环流化床作为碳酸化反应器,采用O2/CO2气氛下燃烧的常压循环流化床作为煅烧炉.根据系统吉布斯自由能最小原理计算了当碳酸化过程中的平均转化率为0.7和新鲜吸收剂添加量为8 kg/s时,经过多次煅烧-碳酸化反应后系统脱碳效率为74%.排放烟气中的CO2浓度为5.3%及煅烧炉回收的CO2浓度为95.6%,并模拟出了排放烟气中的产物成分,得出了烟气再循环比例与O2/CO2体积比的关系.同时计算了不同平均碳酸化转化率时吸收剂的添加量与脱碳效率和排放烟气中CO2体积浓度的关系.     

Effect of pH Value on Reaction Property of CaO/MgO Sorbent Prepared by Sol-Gel Combustion Method

针对多循环反应过程中钙基吸收剂的CO2吸收能力随循环次数增加而迅速衰减的问题,采用溶胶-凝胶燃烧法,在不同前驱体溶液pH值条件下制备CaO/MgO吸收剂,并在卧式固定床反应器上进行了20次循环的煅烧/碳化试验,对其吸收CO2的活性及循环反应稳定性进行了研究.结果表明：采用溶胶-凝胶法合成的CaO/MgO吸收剂与干物理混合法及湿化学法合成的相比,具有更好的CO2吸收性能;对于采用尿素溶胶-凝胶燃烧法合成的CaO/MgO吸收剂,前驱体溶液pH值越小,制备的CaO/MgO吸收剂颗粒越小,比表面积越大,CO2吸收能力越高.     

基于石灰石的CO2吸收循环特性多参数线性回归分析

基于热重分析法（TGA）测试2种钙基吸收剂的CO2循环特性，引入多参数线性回归统计分析方法，确定了反应参数（循环次数、碳酸化反应时间、煅烧温度及煅烧气氛）与循环反应速率和转化率之间的关系，引入评价函数F推导了各参数对吸收剂循环吸收特性的影响程度．结果表明：通过对不同反应机理阶段分别建立回归方程，准确描述了不同参数条件下钙基吸收剂的CO2吸收循环过程；在化学反应控制阶段，反应时间对吸收效率的影响最为显著，而进入扩散反应控制阶段后循环反应次数成为决定因素．     

固体CaO颗粒吸收CO2特性分析

随着温室效应对全球气候的影响越来越显著,世界上将有更多国家关注温室气体的排放问题.温室气体中CO2的排放量最大,被认为是引起全球变暖的主要原因,有在短期内改变气候的可能.现今许多国家都在研究减排与隔离CO2的措施,希望能够开发一种高效、低成本的CO2吸收技术.相对于其它的吸收剂,CaO具有高吸附量、低制备成本、较长循环使用寿命及良好抗磨特性而成为优选的高温CO2脱除剂,CaO循环吸收CO2技术在工业操作中也较为简单.主要通过分析煅烧/吸收温度、添加剂、CaO颗粒内部孔结构和分布以及烟气中其它主要成分对CaO吸收性能的影响,为CaO吸收CO2性能的改善提供一定的理论基础.     

钙基吸收剂脱碳的模型建立及参数研究

针对天然气联合循环(NGCC)电厂烟气CO_2脱除问题,对钙基吸收剂循环煅烧与碳酸化CO_2脱除法进行了研究.利用Matlab建立数学模型,并分析了碳酸化反应温度、碳酸化塔床料量、循环吸收剂摩尔流量以及补充吸收剂摩尔流量对CO_2捕集率的影响.结果表明:由于NGCC电厂烟气中CO_2摩尔分数较低,为达到90%CO_2捕集率(rcc),其碳酸化反应温度应为594℃,明显低于燃煤电厂的碳酸化反应温度(650℃);随着循环次数的增加,吸收剂的吸收能力明显下降;在补充吸收剂摩尔流量(F_0)一定时,r_(cc)随着单位发电量碳酸化塔床料量(W_(CaO))和循环吸收剂摩尔流量(F_R)的增加先大幅增加,后趋于稳定;在W_(CaO)一定时,rcc随着F_0和F_R的增加而增加,但当F_R增加到一定值时,碳酸化塔中床料量不足,使得进入其中的CaO颗粒转化率未全部达到最大平均转化率X_(ave),r_(cc)反而下降.     

基于钙基吸收剂煅烧/碳酸化循环吸收CO2研究进展

对钙基吸收剂煅烧/碳酸化循环吸收CO2的最新研究进展进行了阐述,包括反应条件对钙基吸收剂吸收CO2的影响,如压力、颗粒粒度、反应时间及SO2存在等因素,和提高钙基吸收剂吸收CO2的各种方法,如采用添加剂、进行水合反应等.提出了一种提高钙基吸收剂吸收CO2能力的可能方法:对钙基吸收剂进行闪蒸改性,以优化吸收剂的孔隙结构.     

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．     

高温CO2吸附/吸收剂的研究进展

化石燃料火电厂是CO2主要排放源,直接脱除高温烟气中的CO2可以减少系统的能量损失,CO2高温吸附剂和吸收剂的开发研究得到重视。本文主要对高温CO2吸附剂中的碳基吸附剂、沸石、类水滑石化合物及高温CO2吸收剂中的锂基吸收剂和钙基吸收剂等进行分析比较：经过化学改性的类水滑石化合物在140℃以上具有高温吸附剂中最高的CO2吸附能力,钙基吸收剂中的PCC（沉淀碳酸钙）和CaO／CB12Al14O33在600℃或更高温度下具有较高的吸收能力和循环反应活性。针对上述高温吸附,吸收剂目前存在的问题,提出以研究高温吸附／吸收机理,提高循环吸附／吸收CO2能力和改进其制备工艺作为今后研究的重点。     

CaO循环吸收CO2的实验研究

对CaO与CO2的循环反应特性进行实验研究,分析了影响CaO转化率的因素及CaO转化率随循环次数的变化趋势,实验结果表明：CaO转化率随温度和CO2体积分数的增加而增加,颗粒粒径对其影响较大;CaO转化率随循环次数的增加而降低,在循环次数达到一定值后,CaO转化率降低到某一值后不再发生较大的变化,在不同温度下,CaO转化率随循环次数的增加而降低的趋势有所不同。     

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.     

CFB-FGD 工艺中Ca(OH)2颗粒悬浮液最大分散度的实验研究

CFB-FGD工艺中的CaO颗粒粒径偏大，CaO转化率比较低．降低CaO颗粒粒径的途径之一是优化脱硫剂制备工艺．为此，研究了用5种不同制备工艺得到的Ca(OH)2颗粒悬浮液和悬浮液中Ca(OH)2颗粒的算术平均粒径．实验结果表明，采用0．006mol／L的六偏磷酸钠溶液与CaO水合反应得到的Ca(OH)2颗粒悬浮液的分散度增加了6．62倍，Ca(OH)2颗粒的算术平均粒径降低到了1053nm．这是一种简单、有效、经济的脱硫剂制备工艺．     

Hydrogen production via steam reforming of coke oven gas enhanced by steel slag-derived CaO

Steel slag, a waste from steelmaking plant, has been proven to be good candidate resources for low-cost calcium-based CO₂ sorbent derivation. In this work, a cheap and sintering-resistance CaO-based sorbent (CaO (SS)) was prepared from low cost waste steel slag and was applied to enhance catalytic steam reforming of coke oven gas for production of high-purity hydrogen. This steel slag-derived CaO possessed a high and stable CO₂ capture capacity of about 0.48 g CO₂/g sorbent after 35 adsorption/desorption cycles, which was mainly ascribed to the mesoporous structure and the presence of MgO and Fe₂O₃. Product gas containing 95.8 vol% H₂ and 1.4 vol% CO, with a CH₄ conversion of 91.3% was achieved at 600 °C by steam reforming of COG enhanced by CaO (SS). Although high temperature was beneficial for methane conversion, CH₄ conversion was remarkably increased at lower operation temperatures with the promotion effects from CaO (SS), and CO selectivity has been also greatly decreased. Reducing WHSV could increase methane conversion and reduce CO selectivity due to longer reactants residence time. Reducing C/A could increase methane conversion and hydrogen recovery factor, and also decrease CO selectivity. When being mixed with catalyst during SE-SRCOG, CaO (SS) with a uniform size distribution favored methane conversion due to the high utilization efficiency of catalyst. Promising stability of CaO (SS) in cyclic reforming/calcination tests was evidenced with a hydrogen recovery factor >2.1 and CH₄ conversion of 82.5% at 600 °C after 10 cycles using CaO (SS) as sorbent.     

Study on kinetics of desulfurization reaction by cao particles

In this paper, TGA was employed in the desulfurization reaction with different CaO particles to investigate the dynamical behavior and the effect of particle size. The changing grain model was revised to describe the reaction kinetics characteristic. The effect of temperature on the reaction was analyzed using scanning electron microscope (SEM) photos of CaO particles. The diffusion coefficient of SO₂ in the product layer and the chemical reaction rate constant were acquired through comparison between TGA experimental data and the reaction dynamics equations. It was found that the diffusion coefficient of SO₂ in the product layer was proportional to some power of the particle radius and the CaO particles can be depicted by fractal geometry. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(5): 391–401, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10108     

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).     

Prediction model for methanation reaction conditions based on a state transition simulated annealing algorithm optimized extreme learning machine

Methanation is the core process of synthetic natural gas, the performance of the entire reaction system depends on precise values of the reaction condition parameters. Accurate predictions of the CO conversion rate of the methanation reaction can eliminate time-consuming and complex steps in experiments and speed up the discovery of the best reaction conditions. However, the methanation reaction is an uncertain, highly complex, and highly nonlinear process. Thus, this paper proposes a machine learning prediction model for the methanation reaction to facilitate the subsequent search for optimal reaction conditions. The reaction temperature, pressure, hydrogen–carbon ratio, water vapor content, CO₂ content, and space velocity were selected as the condition variables. The CO conversion rate was the optimization objective. An extreme learning machine (ELM) was selected as a prediction model. Because the input weights and bias matrices of the ELM are randomly generated, an ELM based on a state transition simulated annealing (STASA-ELM) algorithm is proposed. The STASA algorithm was used to optimize the ELM to improve the accuracy and stability of the model. Five additional sets of experimental data were designed for the experiment, and the error between the experimental and predicted values was small. Thus, the STASA-ELM algorithm can accurately predict the conversion of CO for different values of reaction conditions.     

A simulation study on the enhancement of the shift reaction by water injection into a gasifier

Although coal gasification is a clean and efficient use of coal, a reduction of CO₂ emissions is needed to mitigate global warming. The aim of this study was to improve the thermal efficiency of fuel production and electricity generation by dry coal feed gasification. The primary cause of thermal efficiency loss is steam use in a water-gas shift reactor. The shift reactor, installed downstream from the gasifier, uses a catalyst to adjust the H₂/CO ratio of the syngas. We have proposed a new process in which water is injected at the outlet of the gasifier and is vaporized to enhance the extent of the shift reaction. This process utilizes the high temperature of the syngas, which is sufficient for the shift reaction to occur without a catalyst. We have developed a model that incorporates the shift reaction velocity to evaluate our proposed process. In an optimized 5-stage water supply case, we found that the CO conversion reaches 9.9% at a water/syngas ratio of 0.14 mol/mol (water/CO = 0.25 mol/mol); the CO conversion needed for dimethyl ether production is 31%. This new process can improve the efficiency and reduce the cost of coal gasification.