吸附制冷用复合吸附剂的吸附性能

固体吸附式制冷因具有环保和节能两大优势,成为国内外竞相开发的热点,尤其是将其用于新型空调系统和太阳能应用产品方面的开发研究备受关注．但从实用化研究成果来看,还远不满足工业化条件,其主要原因之一是受吸附制冷工质对（吸附剂-制冷剂）的性能制约．目前,国内外关于吸附制冷工质对的研究报道比较多,所采用的吸附（工）质仍然以水、甲醇、乙醇和氨为主,对于吸附剂的研究进展比较快,已从当初单一组分吸附剂的选用发展到目前多组分、复合吸附剂的研制．研制性能优良的吸附剂被认为是推动固体吸附式制冷工业化的关键之一．     

Effects of capillary condensation on adsorption and thermal desorption dynamics of water in zeolite 13X and layered beds

The effects of capillary condensation on the adsorption and thermal desorption dynamics of water in zeolite 13X beds and layered beds with zeolite 13X/silica gel or zeolite 13X/alumina were experimentally and theoretically studied. As the equilibrium isotherm of water on zeolite 13X pellet was found to be most favorable at a low relative humidity and indicated capillary condensation at a high relative humidity, it was possible to construct a non-isothermal model that included capillary condensation and that could successfully predict plateaus of temperature and concentration profiles in thermal regeneration. In adsorption breakthrough, by using a feed in the capillary condensation range of the isotherm on zeolite 13X, the breakthrough curve showed a shock wave in the low concentration and a proportionate pattern in the high concentration. In thermal desorption breakthrough, the desorbed water at the upper part of the bed was re-adsorbed at the lower part of the bed, and that re-adsorption mainly occurred in the capillary condensation range of the isotherm. Therefore, even though an adsorption was performed at a feed in the favorable range of the isotherm, and could be well predicted with type I isotherm, its desorption dynamics should be predicted by using the isotherm model with its consideration of capillary condensation. The layered bed with silica gel or alumina did not have any advantage over the zeolite 13X bed with respect to adsorption breakthrough performance. However, compared to the zeolite 13X bed, the complete regeneration time in the layered bed was drastically shortened due to a greater variation of the amount of equilibrium adsorption of water under temperature on both silica gel and alumina. In addition, since an increase in temperature led to a greater decrease of the amount of equilibrium adsorption of water on silica gel than on alumina, a layered bed with silica gel obviously could be regenerated more efficiently than a layered bed with alumina.     

Modeling of Drying of Gaseous Mixtures in TSA System with Fixed Bed of Solid Desiccants

A nonisothermal, nonequilibrium mathematical model was developed to theoretically analyze adsorptive drying of gaseous mixtures containing water and volatile organic compounds (VOCs). The analysis concerns a four-bed cyclic temperature swing adsorption (TSA) system. The two fixed beds are formed of silica gel primarily as the water vapor adsorbent. The other two consist of activated carbon as the adsorbent of the organic component (e.g., benzene, isopropanol). In the model, possible insignificant interactions among the VOCs and water during adsorption and desorption were neglected. The following parameters were considered to study their effect on the process efficiency: relative humidity of the inlet gas, temperature of the purge gas, and height of the adsorbent beds. Simulation results showed that both the shape of the adsorption isotherm and heat effects played an important role in the breakthrough behavior of water vapor adsorption on silica gel. The model accurately simulated experimental data taken from literature.     

沼气变压吸附剂吸附性能比较

研究了工程上常用的3种吸附剂CO2吸附剂硅胶、13X分子筛和碳分子筛在高压(0.1~1 MPa)下对CO2和CH4的吸附容量、稳定性和选择性,以确定其在沼气变压吸附分离中应用的可行性. 结果表明,硅胶的吸附稳定性非常好,0.1 MPa时吸附选择性系数为8~10,能有效分离CH4?CO2;13X分子筛对CH4和CO2吸附容量最高、吸附选择性最好,重复使用5次CO2的吸附容量略有下降;以CH4的损失率作为评价标准时,13X分子筛吸附CH4的损失率最低. 降压不能使被碳分子筛吸附的CH4完全解吸,吸附位不能充分释放,不适用于CH4与CO2的分离.     

磷化氢在改性13X分子筛上的吸附行为

为回收工业废气中的磷化氢(PH3)并资源化,采用浸渍法制备了一种CaCl2改性13X分子筛吸附剂,通过容积法研究了25—70℃PH3气体在改性13X分子筛上的等温吸附行为。结果表明,在实验条件范围内25,40,55,70℃下PH3的饱和吸附量(质量分数)分别为2.528,1.901,1.591,0.925mg/g。Freundlich吸附等温方程很好地模拟了改性13X分子筛对PH3的等温吸附,Langmuir和Henry吸附等温方程对吸附平衡数据的拟合效果不佳表明了改性13X分子筛表面吸附位的不均匀分布。当初始吸附量为0.10mg/g时,等量吸附热值最大,为17.81353kJ/mol,即等量吸附热不超过18kJ/mol,过程为物理吸附,便于PH3气体的解吸。     

吸附制冷用复合吸附剂的吸附等温线推算

用真空重力法测定了水和乙醇在自制复合吸附剂上的吸附等温线。采用由微孔填充理论导出的吸附平衡方程对所测得的等温线进行了拟合,计算相应的吸附热;对用Clausius Clapeyron方程推算吸附等温线的方法进行了讨论,并推算有关吸附等温线。结果表明:水在自制复合吸附剂M1 0001和M1 9906上平衡吸附量的推算值与实测值之间的相对误差<10%;乙醇在自制复合吸附剂上的推算误差<15%。给出了推算等温线和获得等压线的简便方法。     

硅藻-氯化锂复合除湿剂制备及吸附性能

以硅藻为多孔基质,氯化锂为浸渍盐,配制了硅藻-氯化锂复合除湿剂。采用麦克公司生产的ASAP2020物理吸附仪测量了复合硅藻的比表面积、孔径等微观结构参数。通过对吸附仪的改进,对复合除湿剂的水蒸气吸附性能进行了测试研究,并与纯硅藻基质以及常见硅胶除湿剂的吸附性能进行对比。氮气吸附测试显示复合除湿剂的比表面积、孔体积参数较纯硅藻基质有明显下降,表明氯化锂颗粒充分浸入到硅藻孔隙中。水蒸气吸附测试表明复合硅藻除湿剂的吸湿性能较纯硅藻基质及硅胶除湿剂有着显著提高。此外,基于Polanyi吸附势理论对复合除湿剂吸附特征曲线的拟合研究发现复合除湿剂的吸附特征曲线包括3个部分。     

吸附法控制航空煤油中微生物的研究

航空煤油中的水质量浓度对微生物的生长影响显著,而微生物对飞机的危害非常严重。水质量浓度越高,微生物含量越多,对飞机的危害也就越大。与传统的添加抗微生物添加剂等化学方法相比,利用硅胶和3A,4A,5A和13X 4种型号分子筛作为航空煤油中的水吸附剂,由静态吸附实验得出:选择3A分子筛作为吸附剂,吸附时间为180 min、每100 mL航空煤油吸附剂投入量为2 g和粒径为80目,此时除水效果最佳,能将航空煤油的水质量浓度从1.2×10-4mg/L降为8×10-6mg/L;同时以航空煤油中的微生物为指标,通过以上改进优化条件能够将航空煤油中微生物从1 000个/mL降为5个/mL或者无菌状态。     

不同干燥剂转轮的除湿性能

以除湿量和除湿性能系数作为评价指标, 对3个不同干燥剂转轮的除湿性能进行了实验研究。对比分析了处理空气入口温度和相对湿度、处理风速、再生风速、转轮转速以及再生温度对各个转轮的影响, 得到了转轮的除湿量和除湿性能系数的变化趋势。结果表明:在处理侧温度较高的情况下, 聚苯硫醚(PPS)/PPM各半转轮相比PPS硅胶转轮和PPM分子筛转轮, 除湿性能是最好的;PPS硅胶转轮更适用于高湿度工况环境;而处理风速的增大有利于提高PPM分子筛转轮的性能;再生温度从60℃提高到80℃, 3个转轮的除湿量和除湿性能系数增大1倍左右。     

13X分子筛静态脱除含硫模型化合物的吸附研究

采用噻吩/正己烷配制出含硫模型化合物,以13X分子筛为吸附剂,在常压条件下,用静态吸附法评测了吸附时间、吸附温度、含硫模型化合物浓度等吸附条件对吸附剂脱硫性能的影响。实验结果表明:13X型分子筛在6 h时吸附基本达到饱和,并对其吸附动力学、热力学及吸附等温曲线的研究,发现此吸附反应为放热反应,并求出吸附焓变及熵变,确定吸附反应为二级反应。     

低温吸湿复合吸附剂的制备及吸湿性能

针对冷库结霜严重制约其经济性的问题,化学固体吸附除湿防霜技术逐渐得到重视。本文将对水吸附能力较强的金属卤化物与容易定型且传热传质性能较好的分子筛相结合,制成复合吸附剂,建立了低温情况下吸附材料的吸湿性能测试系统,并进行了大量测试,给出了多种材料在-5℃、-10℃、-15℃下的吸湿量及吸湿速率变化,实验结果表明复合吸附剂的吸附性能与单纯的分子筛相比有了明显的改善,13X型分子筛浸渍浓度20%的Na Br溶液所得试样吸湿量和吸湿速率性能优越,复合过程中损失较少,成本低,可作为复合吸附剂应用于冷库除湿系统中。     

ADSORPTION OF WATER VAPOR ON MOLECULAR SIEVE 13X

Adsorption isotherms of water vapor on molecular sieve 13X were obtained at 288, 298, and 308 K. The isotherms were of Type 1 and exhibited hysteresis upon desorption. The heat of adsorption data indicated that water was held on the surface by physical forces and the molecular sieve 13X provided a heterogeneous surface for the water vapor. The equilibrium data were correlated by the Polanyi potential theory and the theory of the pore volume filling proposed by Dubinin and co-workers.     

多孔材料烷烃/烯烃分离技术的研究

以模拟油品为原料,在小型固定床（200 mL）反应器上考察了硅胶、γ-Al₂O₃、13X分子筛、Y分子筛及ZSM-5分子筛等多孔材料对烷烃/烯烃的吸附分离性能;其中硅胶的烷烃/烯烃分离效果最好,在吸附温度为40 ℃、压力为0.5 MPa、解吸剂为正辛烷/甲基环己烷的条件下,烷烃/烯烃分离度最高达到0.81;与其他类型硅胶相比,平均孔径为4~6 nm的B型硅胶传质效果更好,吸附-脱附过程更易趋于平衡。经过焙烧和溶剂再生的吸附剂,与新鲜剂相比,分离效果没有明显的降低。     

Mercury removal from hydrogen gas streams

Type 13X molecular sieve and chromic acid on silica gel have been examined as sorbents for the removal of mercury vapour from hydrogen at atmospheric pressure and, chiefly, ambient temperature. The molecular sieve had a very low capacity for mercury. Chromic acid on silica gel had a much higher capacity but this was much reduced by the presence of water vapour in the hydrogen.     

Separation of fatty acid methyl esters from tall oil by selective adsorption

Fatty acid methyl esters (FAME) and resin acids (RA) were separated from tall oil by selective adsorption. Commercial nonmodified molecular sieve 13X was used as adsorbent. The adsorption isotherms of fatty acids (FA), FAME, and RA on molecular sieve 13X at 25°C were determined using various solvents. The solvents were methanol, ethanol, isopropanol, acetone, benzene, hexane, isooctane, petroleum ether (40–60°C), and petroleum naphtha (80–180°C). With each solvent, FA and RA were adsorbed to a greater extent than FAME. Adsorption isotherms for RA and FAME in binary adsorption systems were also determined using petroleum ether, petroleum naphtha, benzene, and isopropanol. For each component in the binary adsorption, the equilibrium amounts are lower than the values for pure component adsorption. The adsorption of FAME decreased in the presence of RA markedly in petroleum ether and petroleum naphtha. This fact may be the indication of the phenomenon of selective adsorption. Separation was accomplished by adding a solution of esterified tall oil in solvents used in the binary adsorption systems, through a column packed with molecular sieve 13X. With petroleum naphtha, FAME and RA were recovered in yields of 93 and 94%, respectively, from esterified tall oil. Petroleum naphtha gave the best results. The effects of particle size of adsorbent and flow rate of solvent on the efficiency of the separation were also investigated in fixed-bed column studies. The particle size of adsorbent did not apparently alter the results. Changes in the particle size should not significantly change the number of available adsorption sites in a microporous molecular sieve.     

离子凝胶复合吸附剂的制备及空气取水性能

制备了一种LiCl复合可得然离子凝胶,并将其首次用于空气取水性能研究。在不同吸附温度、吸附湿度的开式环境中,完成了复合吸附剂的水蒸气吸附特性研究。探究了浸渍盐的质量浓度对复合吸附剂吸附性能的影响。根据目标工况,完成了复合吸附剂组分的优化配比。对优化后的离子凝胶进行了吸附动力学和等温吸附特性研究。结果表明,15% LiCl溶液复合而成的可得然吸附剂综合性能最佳。在35℃&75%RH下,该复合吸附剂的吸附量高达3.30g/g,是传统硅胶复合吸附剂的6.6倍;在55℃&40%RH工况下实现1.66 g/g的水量脱附,是硅胶复合吸附剂的3倍。在25℃&75%RH下,可得然复合凝胶吸附剂的吸附速率K高达3.48×10^-3s^-1;该离子凝胶复合吸附剂的研究,为吸附式空气取水技术提供了基础支持。     

新型高效复合吸附剂开发及系统仿真

针对一种新型高效复合吸附剂开展了吸附性能实验研究,并假想将该复合吸附剂装填于一固体吸附式空调样机吸附床内进而开展仿真研究。对比研究表明该复合吸附剂不但具有比硅胶强得多的吸附能力,而且再生温度较低。装填该复合吸附剂的吸附式空调不但可以获得比装填纯硅胶时高得多的比制冷功率SCP,而且系统性能系数COP也明显高于纯硅胶系统。     

硅酸盐矿物和传统吸附型干燥剂

传统吸附型干燥剂,包括活性炭、硅胶、活性氧化铝和合成沸石等,利用其孔道结构和表面属性发挥吸湿作用.硅酸盐矿物蒙脱石、海泡石和坡缕石具有成分和结构上的相似性和吸湿能力,是良好的干燥剂材料.相对于传统吸附型干燥剂,蒙脱石、海泡石和坡缕石的优势在于资源丰富,对环境无污染和价格低廉等.坡缕石可弥补蒙脱石和海泡石某些应用上的不足.     

活性炭-疏水硅胶复合吸附剂吸附油气

开发出一种上层为活性炭、底层为疏水硅胶的复合吸附剂,并与活性炭、硅胶单独吸附汽油蒸气进行比较,发现不同吸附剂及油气质量浓度对吸附容量及吸附热有大的影响。研究活性炭与硅胶不同体积比对吸附质量比和温度的影响,得出最佳体积比为1∶1。这样高质量浓度油气先被底层的硅胶吸附,低质量浓度的油气再被上层的活性炭吸附,从而综合利用了硅胶的不燃烧及活性炭吸附质量比高的特点,从工艺技术上降低了活性炭吸附放热的安全问题,进而还可适当提高活性炭有效吸附容量。