Characteristics and reactivity of rapidly hydrated sorbent for semidry flue gas desulfurization

Semidry flue gas desulfurization with a rapidly hydrated sorbent was studied in a pilot-scale circulating fluidized bed (CFB) experimental facility. The desulfurization efficiency was measured for various operating parameters, including the sorbent recirculation rate and the water spray method. The experimental results show that the desulfurization efficiencies of the rapidly hydrated sorbent were 1.5-3.0 times higher than a commonly used industrial sorbent for calcium to sulfur molar ratios from 1.2 to 3.0, mainly due to the higher specific surface area and pore volume. The Ca(OH)2 content in the cyclone separator ash was about 2.9% for the rapidly hydrated sorbent and was about 0.1% for the commonly used industrial sorbent, due to the different adhesion between the fine Ca(OH)2 particles and the fly ash particles, and the low cyclone separation efficiency for the fine Ca(OH)2 particles that fell off the sorbent particles. Therefore the actual recirculation rates of the active sorbent with Ca(OH)2 particles were higher for the rapidly hydrated sorbent, which also contributed to the higher desulfurization efficiency. The high fly ash content in the rapidly hydrated sorbent resulted in good operating stability. The desulfurization efficiency with upstream water spray was 10-15% higher than that with downstream water spray.     

A biomass-supported Na2CO3 sorbent for flue gas desulfurization

A novel sorbent for SO2 removal has been investigated. The sorbent is obtained by conventional incipient wetness impregnation of abandoned biomaterials (straw or dried leaves) with an aqueous solution of Na2CO3. A material with the composition 80 wt % Na2CO3/straw shows a desulfurization activity which is both higher and faster than that of the reference sample Na2CO3/gamma-Al2O3. The breakthrough and stoichiometric SO2 adsorption efficiencies for 80 wt % Na2CO3/straw reach 48.9% and 80.6%, respectively, at a temperature of 80 degrees C. The adsorption efficiencies are almost constant in the temperature range 70 to 300 degrees C. According to IR and XPS analysis the main products observed on the spent sorbent are sulfite below 150 degrees C and sulfate at 300 degrees C. The Na2CO3 in 80 wt % Na2CO3/straw can potentially be recycled by the oxidation of the straw with concomitant reduction of the sulfite species to elemental sulfur, making the proposed process CO2 neutral.     

Iron blast furnace slag/hydrated lime sorbents for flue gas desulfurization

Sorbents prepared from iron blast furnace slag (BFS) and hydrated lime (HL) through the hydration process have been studied with the aim to evaluate their reactivities toward SO2 under the conditions prevailing in dry or semidry flue gas desulfurization processes. The BFS/HL sorbents, having large surface areas and pore volumes due to the formation of products of hydration, were highly reactive toward SO2, as compared with hydrated lime alone (0.24 in Ca utilization). The sorbent reactivity increased as the slurrying temperature and time increased and as the particle size of BFS decreased; the effects of the liquid/solid ratio and the sorbent drying conditions were negligible. The structural properties and the reactivity of sorbent were markedly affected by the BFS/HL ratio; the sorbent with 30/70 ratio had the highest 1 h utilization of Ca, 0.70, and SO2 capture, 0.45 g SO2/g sorbent. The reactivity of a sorbent was related to its initial specific surface area (Sg0) and molar content of Ca (M(-1)); the 1 h utilization of Ca increased almost linearly with increasing Sg0/M. The results of this study are useful to the preparation of BFS/HL sorbents with high reactivity for use in the dry and semidry processes to remove SO2 from the flue gas.     

Key factor in rice husk Ash/CaO sorbent for high flue gas desulfurization activity

Siliceous materials such as rice husk ash (RHA) have potential to be utilized as high performance sorbents for the flue gas desulfurization process in small-scale industrial boilers. This study presents findings on identifying the key factorfor high desulfurization activity in sorbents prepared from RHA. Initially, a systematic approach using central composite rotatable design was used to develop a mathematical model that correlates the sorbent preparation variables to the desulfurization activity of the sorbent. The sorbent preparation variables studied are hydration period, x1 (6-16 h), amount of RHA, x2 (5-15 g), amount of CaO, x3 (2-6 g), amount of water, x4 (90-110 mL), and hydration temperature, x5 (150-250 degrees C). The mathematical model developed was subjected to statistical tests and the model is adequate for predicting the SO2 desulfurization activity of the sorbent within the range of the sorbent preparation variables studied. Based on the model, the amount of RHA, amount of CaO, and hydration period used in the preparation step significantly influenced the desulfurization activity of the sorbent. The ratio of RHA and CaO used in the preparation mixture was also a significant factor that influenced the desulfurization activity of the sorbent. A RHA to CaO ratio of 2.5 leads to the formation of specific reactive species in the sorbent that are believed to be the key factor responsible for high desulfurization activity in the sorbent. Other physical properties of the sorbent such as pore size distribution and surface morphology were found to have insignificant influence on the desulfurization activity of the sorbent.     

微生物烟气脱硫技术及其研究方向

微生物烟气脱硫 ,是用含有脱硫菌的溶液作循环吸收液、以粉煤灰中Fe2 O3被离子化后产生的铁离子作催化剂和反应介质、以脱除烟气中SO2 的一项新技术 .从能源、酸度、温度、需氧类型等方面综合考虑 ,氧化亚铁硫杆菌、氧化硫硫杆菌、氧化亚铁硫螺菌可作为三层滤料生物滤池脱硫的菌种 .而选育适宜性和稳定性更强、使用寿命更长的高效菌和合适的生化反应器 ,是脱硫菌种研究的趋势 .     

Effect of solids concentration distribution on the flue gas desulfurization process

A dry flue gas desulfurization (FGD) process at 600-800 degrees C was studied in a pilot-scale circulating fluidized bed (CFB) experimental facility. Various fresh sorbent distribution types and internal structures were modeled numerically to investigate their effect on the gas-solid flow and sulfate reaction characteristics. Experimental results show that, after the fresh sorbent supply was stopped, the desulfurization efficiency declined rapidly even though the sorbent recirculation was maintained. Therefore, the fresh sorbent is the main contributor to the desulfurization process and the primary effect of the recirculated sorbent was to evenly distribute the fresh sorbent and to prolong the sorbent particle residence time. The numerical results demonstrate thatthe desulfurization efficiency varied greatly for the various fresh sorbent bottom injection methods. The desulfurization efficiency of the bottom-even injection method was 1.5 times that of the bottom two-sided injection method. Internal structures effectively improved the fresh sorbent solids concentration distribution and the desulfurization efficiency. Optimized internal structures increased the desulfurization efficiency of the bottom two-sided injection method by 46%, so that it was very close to that of the bottom-even injection method with only a 4.6% difference.     

白泥在电厂烟气脱硫中的应用研究

由于白泥的钙含量高,颗粒粒径很小,可以考虑利用造纸厂碱回收白泥代替石灰石用于电厂烟气脱硫。试验表明,Ca/S比取1.0～2.0时,白泥溶液对SO2去除率可达到90%以上。白泥用于烟气脱硫在技术经济上是可行的。     

固体颗粒对三相循环流化床蒸发器性能的影响

讨论了汽-液-固三相循环流化床蒸发器中,固体颗粒的运动规律及其对循环流化床蒸发器的传热及防、除垢性能的影响,建立了加入固体颗粒形成的汽-液-固三相流动沸腾传热准数经验关联式。实验结果表明,三相流循环蒸发器具有良好的蒸发性能。     

汽-液-固三相流化床蒸发器浓缩食品液体的实验研究

介绍了三相流化床蒸发器的结构特点，对其传热和防、除垢性能进行了研究；论述了把汽-液-固三相流化床蒸发器应用于食品液体浓缩的可行性。研究结果表明：汽-液-固三相流化床蒸发器具有良好的传热和防、除垢性能，在食品工业中具有一定的应用前景。     

惰性粒子流化床蒸发器浓缩南瓜汁的传热研究

根据惰性粒子流化床蒸发器的结构特点,将其用于浓缩南瓜汁,讨论了惰性粒子在流体中的运动情况及其对循环流化床蒸发器浓缩南瓜汁的传热性能的影响,建立了汽-液-固三相流动沸腾传热准数经验关联式.实验结果表明,该准数经验关联式的计算值与实验值吻合较好.     

Effect of near-wall air curtain on the wall deposition of droplets in a semidry flue gas desulfurization reactor

The wall deposition of droplets is an important issue affecting the desulfurization efficiency and operating stability of semidry flue gas desulfurization (FGD) reactors. Various near-wall air velocities, near-wall air flow inlet heights, and spray characteristics were analyzed numerically to investigate their effect on the gas-liquid flow and droplet deposition characteristics. The analytical results show that the near-wall air curtain effectively reduces the wall deposition of droplets in the semidry FGD reactor. The droplet deposition ratio decreased rapidly with increasing near-wall air velocity due to the increased gas flow rates and the altered gas velocity distribution. The near-wall air flow inlet height had an optimum value due to the rapid decline of the near-wall air momentum along the reactor height. The optimum distance between the near-wall air inlet height and the droplet injection height was 1.2 times that of the droplet vertical movement distance before deposition based on the linear droplet movement. For commonly used spray characteristics in the semidry FGD process, i.e., droplet diameters of 50-150 microm, spray angles of 10-70 degrees and droplet initial velocities of 20-100 m/s, the droplet deposition ratio with the addition of the near-wall air curtain varied slightly with the droplet diameter and the spray angle but increased rapidly with the initial droplet velocity. Therefore, for the semidry FGD processes, the near-wall air curtain is an effective method to reduce the wall deposition of droplets for various droplet diameters and spray angles while the initial droplet velocity should be carefully controlled to reduce the wall deposition of droplets and improve the operating stability.     

三相循环流化床蒸发器浓缩葡萄糖溶液的传热研究

研究了三相循环流化床蒸发器浓缩葡萄糖溶液时的传热性能,分析了一些主要操作因素对传热性能的影响,给出了传热系数与主要操作参数的经验关联式,讨论了三相循环流化床蒸发器的防、除垢性能。      

流化床干燥工艺对稻谷糊化特性的影响

本文以不同干燥温度、缓苏时间、降水幅度为因素对稻谷进行流化床干燥-缓苏实验,研究其干燥后的米粉糊化特性变化,并分析干燥后米粉糊化指标的相关性。结果表明:单次降水幅度（1.5%、2.25%、3.0%）、缓苏时间（1、2、3 h）和干燥温度（45、50、55、60、65℃）对稻谷干燥后不溶性直链淀粉含量、峰值粘度、崩解值、消减值有极显著影响（p<0.01）;降水幅度与缓苏时间交互作用对干后稻谷的不溶性直链淀粉含量、崩解值影响显著（p<0.05）;稻谷不溶性直链淀粉含量、消减值与崩解值呈显著负相关（p<0.01）,峰值粘度与崩解值呈显著正相关（p<0.01）。干燥温度45℃、单次降水幅度在1.5%、缓苏时间3 h工艺条件下,峰值粘度、崩解值相对较高分别为（2282±13.09）c P、（755±27）c P,不溶性淀粉含量和消减值相对最低9.29%±0.37%、（906±98）c P,干燥后稻谷的各项品质保持良好。      

烟气净化用针刺滤料耐腐蚀性能研究

针对过滤材料使用寿命短的问题,根据相关标准,对8种滤料覆膜前后的面密度、厚度、透气率进行测试,并采用pH值=5的硫酸水溶液、pH值=9的氢氧化钠水溶液和去离子水对滤料进行处理,利用断裂强力表征滤料耐酸碱腐蚀性能的优劣.研究表明:8种滤料覆膜后,面密度的变化幅度为-8.8％～8.0％,厚度的变化值为-0.21～0.84 ...     

流化床制备大黄鱼仔稚幼体微胶囊饲料的应用研究

将基础饲料先制成球丸,用流化床制备乙基纤维素包衣的微胶囊饲料。微胶囊饲料粒径为150～840μm的达70%。微胶囊饲料的包含率和脂类包埋率分别为97.2%±1.7%、63.2%±3.7%,在35.0‰的NaCl溶液中浸泡20、40、60min,氮保留率分别为73.6%±2.6%、65.8%±3.5%、53.7%±4.2%。扫描电镜(SEM)观察微胶囊饲料表面为均匀光滑一致的包衣膜,形状规则且无粘连现象。将微胶囊饲料饲喂15日龄大黄鱼25d作为实验组,对照组饲喂冷藏桡足类。实验结束时,实验组大黄鱼鱼苗的成活率虽显著低于对照组,但体重大于对照组。     

烟气净化用滤料表面改性及其性能

为改善过滤材料的使用性能,满足焦化厂除尘工况的使用要求,选用聚四氟乙烯乳液对玄武岩针刺滤料(X)、氟美斯针刺滤料(F)、玄武岩与氟美斯复合针刺滤料(XF)进行表面改性,并根据相关标准对滤料改性前后的热学性能、耐氧化性能、抗静电性能进行了测试。结果表明:3种滤料表面改性前后均为放热反应,表面改性前后热分解外推起始温度均在350℃左右,焦炉烟气平均温度在230℃,均高于使用温度,符合使用要求;经氧化剂处理,3种滤料表面改性后断裂强力损失率均值较小,说明抗氧化性能改善;表面改性前X滤料的感应静电等级为A级、F滤料的感应静电等级为A级、XF滤料的感应静电等级为C级,表面改性后X滤料、F滤料、XF滤料的感应静电等级均为B级。     

Experimental and parametric study on drying of green peas in spouted bed

Drying of Green Peas (Pisum sativum) was studied experimentally in a lab‐scale spouted bed. Experiments were carried out at different operating conditions, and the effect of inlet air temperature and its flow rate, bed height (initial mass of wet particles) and average diameter of particles were examined on performance of dryer and rate of drying. The obtained experimental results were fitted by an exponential form equation to model the drying kinetic behaviour of green peas in a spouted bed. The fitting parameters are presented in the form of mathematical correlations as a function of operating parameters. As expected, it was found that by increasing inlet air temperature and air‐flow rate, the rate of drying increases, but by increasing the bed height and diameter of particles, the rate of drying decreases. The results can help the design engineers to choose the optimum drying conditions for industrial applications.