Dust removal characteristics of fabrics used in pulse-jet filters

Dust removal characteristics of three fabrics used in pulse-jet filters were investigated. All fabrics were polyester felt but had different surface characteristics; fabrics with an untreated surface, a singed surface, and a surface with a microporous PTFE laminate were used. Three dusts (fly ash, limestone, and granite dust) were tested on each fabric at each of three filtration velocities (50, 75 and 100 mm/s), so that a total of 27 different operating conditions were examined. Both fabric cleaning efficiency, defined as the fraction of deposited dust that is removed from the fabric by cleaning, and system cleaning efficiency, defined as the fraction of deposited dust that reaches the hopper during a cleaning cycle, were measured for each operating condition.Resultant data fell into three groups. Group 1, consisting of the PTFE-laminated fabric collecting all dusts, had the highest fabric and system cleaning efficiencies. Group 2, consisting of limestone and granite dust deposited on untreated and singed fabrics, had the poorest fabric cleaning efficiency but a system cleaning efficiency intermediate between the other groups. Group 3, consisting of fly ash deposited on untreated and singed fabrics, had fairly high fabric cleaning efficiency but the lowest system cleaning efficiency; much of the fly ash removed from these fabrics probably redeposited on the fabrics instead of falling to the hopper. Fabric cleaning efficiency was independent of the filtration velocities tested here and dependent on the dust deposit areal density.     

A heat and mass transfer study—analysis of continuous processes for the coloration of polyester fabric. II. Modelling and characteristics of the (polyester) fabric heating

First it is shown how the equations used for the numerical solution of the transient heat transport to a body can be reduced to the simple transport model (of Paper I), which is commonly used in the textile literature for estimating the heat transfer coefficient (h) of the various fabric heating equipment. During the thermal treatment of a fabric that can be approximated by a geometrically stable homogeneous plate, the simple transport model should not be used for calculating h in cases of high heating rate equipment (e.g., direct contact units) instead; the numerical solution should be used. For a fabric that becomes geometrically unstable during a thermal treatment, like polyester knits, the h value obtained by fitting the numerical solution to the fabric heating rate measurement becomes an apparent coefficient that is the function of the fabric thermal history rather than the equipment heating efficiency. However, if the objective of the modelling is to represent the geometrically unstable fabric heating rate, the simple transport expression is a viable alternative to an otherwise intricate model.     

Vapor phase dyeing of synthetic fibers with disperse dyes

Dyeing of synthetic fibers by the heat transfer process of disperse dye vapors is performed by contacting white receptor polyester or polyamide fabric with other dyed polyester fabrics (donor) under the influence of heat. The dye vapours flowing away will diffuse across the very slight air gap enclosed between the inner donor and receptor surfaces under the applied pressure. It is found that the dye uptake by the receptor fabric is dependent on the original dye content of the donor fabric, transfer temperature and dwell time. The released dye from the donor fabric under the influence of heating is found to be dependent on the original dye content of the donor fabric as well as the transfer temperature. The efficiency of the dye transfer is also attributed to the original shading of the donor fabric. Evaluation of the imparted colors on the receptor fabric (polyester, polyamide) obtained by heat contact with the same donor fabric showed visually the same colour level up to the 13th run. Thermodynamic interpretation of the standard affinity (Δu⁰) and heat of dyeing (ΔH⁰) as well as the partition coefficient of the dye show that the dyeing process has an exothermic character. The rate controlling step in this dyeing process is found to be dependent on the diffusion of the dye vapors into the fiber phase.     

聚乳酸复合空气过滤材料的制备及性能研究

以分子质量为7万的聚乳酸（PIA）为原料,分别用不同的溶剂制得两种纺丝液,并采用静电纺丝法将其分别纺在水刺无纺布和熔喷无纺布上,采用TSI8130仪器对阻力和效率进行测试,比较两者的过滤性能。结果表明：当纳米纤维膜厚度为2mm左右时,水刺非织造布与纳米纤维的复合材料过滤效率从近乎0提高到45．88％,当纳米材料厚度为1mm左右时,提高到26．12％;熔喷非织造布分别与1mm和2mm厚度的纳米纤维膜复合后过滤效率分别提高了23．7％和24．6％,但缺点是过滤阻力提高。     

热处理工艺对PBO纤维拉伸性能影响

针对研究较少的聚对苯撑苯并双恶唑(PBO)纤维热处理工艺进行研究,通过控制热处理气氛、热处理温度、热处理停留时间和预加应力4个参数,对初纺丝PBO(PBO–AS)纤维的热处理工艺进行优化,得到拉伸性能大幅提高的PBO–HM纤维。利用电子织物强力仪对PBO–HM纤维的拉伸性能进行测试,发现热处理氛围为N2时PBO–HM纤维的性能更为优异;热处理温度控制在550℃以下时,热处理温度越高,热处理后得到的PBO–HM纤维的拉伸弹性模量越高,但热处理停留时间延长会使拉伸强度降低;预加应力有助于PBO–HM纤维拉伸弹性模量的增加。经分析得出,最优热处理温度为550℃,热处理停留时间为53.3 s,预加应力为5.48 c N/dtex,得到的PBO–HM的拉伸性能较优。     

Aligned carbon nanotube sheet high efficiency particulate air filters

Aerosol filters, made with conventional micro-fiber fabrics, are designed to efficiently capture small particles from the air. Filters constructed of nano-fiber fabric structures provide even greater filtration efficiency than conventional micro-fiber fabrics due to their higher surface area and smaller pore size. Carbon nanotubes (CNTs) are very small diameter fibers that have the potential to be integrated into filters to further increase particle capture efficiency. In this study, CNT sheets, drawn from millimeter tall CNT arrays, were integrated between traditional micro-fiber fabrics to produce aerosol filters. The filtration performance of the novel filters showed that when the number of CNTs layers increased, the filtration efficiency increased dramatically, while the pressure drop also increased. In order to meet high efficiency particulate air (HEPA) filter requirements with a reasonable pressure drop, CNTs were laid in a cross-plied structure within the filter. The results demonstrated that the three layer cross-ply structure provided 99.98% filtration efficiency at 0.3 μm particle size at a 10 cm/s face velocity, making it a viable method for producing low basis weight HEPA filters utilizing CNTs as the main filtration component.     

Design of three-dimensional gradient nonwoven composites with robust dust holding capacity for air filtration

Air pollution has seriously threatened public health in developing countries. However, it is still a big challenge for fabricating a filter with high filtration efficiency, low air resistance, and long service life. Herein, we report a facile strategy to fabricate a multilayered nonwoven composite with a functionally gradient structure for air filtration by a combined method of needle-punch, melt blown, and corona charging techniques. Our integrated multilayer needle-punched/melt blown composite filter could achieve a high filtration efficiency up to 99.52 ± 0.01%, a low pressure drop of 136.87 ± 0.49 Pa, and a satisfied quality factor of 0.03898 ± 0.0001 Pa⁻¹ for sodium chloride particles with an aerodynamic diameter of 0.26 μm at the airflow rate of 85 L min⁻¹. More importantly, the resultant filter exhibited a large dust holding capacity of 23.5 ± 0.41 g m⁻², which indicates a long service life. It is expected that our multilayer needle-punched/melt blown composite fabric may not only serve as a good candidate for air filtration, but also provide a new sight for designing the air filtration materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47827.     

常用过滤材料的分类总结及性能测试

从使用温度的角度分类总结了常用滤布材料的性能,并测试了几种常见滤布样品的断裂强度、透气性、透水性、以及鼓泡孔径等性能。测试数据对今后过滤机实际作业中滤布材料的选择提供了可靠的参考依据。     

A study on the characteristics of improvement in filtration performance by dust precharging

A hybrid dust-collector combining electrostatic charging with fabric filtration was developed and its performance characteristics were evaluated. Charged particles build porous dendritic structure on the filter surface by electrostatic attraction, increasing the collection efficiency of dust particles and reducing the pressure drop through the deposited dust layer and filter media. The cleaning performance of the dust layer is improved because the dendritic structured dust layer may be removed more easily by pulse jet cleaning flow. The results of the experiment showed a reduction of fine particle emission by 37% and 13% energy saving by precharging dust particles before filtration.     

生物质石墨烯纺黏非织造布的制备及其过滤性能

为了提高复合非织造布的过滤效率,采用水热合成法制备生物质石墨烯炭分子筛,将其加入纺黏非织造布里,对非织造布的过滤效果进行了研究。结果显示:添加了生物质石墨烯炭分子筛的纺黏非织造布的过滤效率比普通纺黏非织造布的过滤效率提高了31%。再将其与普通熔喷非织造布复合,制成的复合熔喷非织造布的过滤效果均高于普通熔喷非织造布,最大过滤效率达到了96.6%。     

Improving the flame retardant properties of polyester-cotton blend fabrics by introducing an intumescent coating via layer by layer assembly

Layer by layer (LBL) assembly technique was used to deposit multilayer coating containing phosphorus-nitrogen onto the surface of fibers to improve the flame retardancy of polyester-cotton (PET-COT) blended fabric. Ellipsometer results confirmed that polyallylamine hydrochloride (PAH), melamine (MEL), and ammonium polyphosphate (APP) grew linearly on silicon wafer during the LbL process. The LOI value of coated PET-COT fabric was increased from 20.8% of pristine fabric to 28.4% by the presence of about 9 wt% coating. Besides, this intumescent nanocoated PET-COT fabric was self-distinguished during the vertical burning test. Thermogravimetric analysis under both nitrogen and air atmosphere revealed that the initial degradation temperature of the coated sample was decreased and the char residue amount was significantly improved during combustion. The flame resistance performance evaluation by pyrolysis combustion flow calorimeter indicated that this coating effectively reduced the peak heat release rate of PET-COT matrix. The scanning electron micrographs of char residue demonstrated that the char formation in the condensed phase and free radical caption in the gas phase was responsible for the improved flame retardancy. It is suggested this unique facile coating technology with low cycles and high efficiency has great potential to produce commercially available flame retardant polymeric-cotton blend fabrics.     

Giving polyester textile materials high water repellency by treating them with a solution of tetrafluoroethylene telomers

It was shown that solutions of tetrafluoroethylene telomers in acetone form a coating on the surface of fabric which forms a thin fluoropolymer film after heat treatment and gives polyester fabrics a high level of water repellency. Methods of acting on the fibre material that allow additionally increasing the degree of water repellency due to regulation of the thickness and ordering of the fi lm and acting on the microrelief of the fabric were revealed. Preliminary chemical activation of the polyester material and an abrasive effect on its water-repellent coating are proposed for this purpose.     

Fabrication of a Bio-Based Superhydrophobic and Flame-Retardant Cotton Fabric for Oil–Water Separation

It is an urgent task to develop environmentally friendly and flame retardant durable oil–water separation materials. A green TA/B@PDA coating derived from bio-based materials such as tannic acid (TA), borax (B), and polydopamine (PDA) is deposited on cotton fabric through facile dip-coating method and step-by-step assembly method. A series of methods are used to characterize the as-prepared cotton fabric. PDA provides a reactive interface, while n-dodecyl mercaptan enhances the hydrophobicity of the surface with a water contact angle (WCA) and shedding angle (SA) of 153.3° ± 1.2° and 9° ± 0.8°, respectively. The as-prepared fabric exhibits outstanding oil/water separation efficiency (>98.5%) for various types of oil, and wear resistivity, washability, and reusability. Meanwhile, combustion test and limit oxygen index (LOI) test show that the modified fabric has excellent flame retardant performance. The cone calorimeter test (CCT) indicates that compared with the pristine cotton fabric, the peak heat release rate (PHRR) and total heat release (THR) of the TA/B@PDA cotton is decreased by 50% and 32%, respectively. Through the analysis of char residues, the flame retardant mechanism is studied. This method provides a general green way for the construction of superhydrophobic surfaces, and can be further applied to the broad fields of durable oil–water separation.     

Interaction between the Surface Properties of the Textiles and the Deposition of Cationic Softener

In this study we categorised the surface properties of different knitted fabrics by their electro-kinetic behaviour and liquid up-take phenomena of the knitted textiles in order to understand the interaction of the surface properties of the textiles with cationic softener deposition. The electro-kinetic and liquid uptake properties of textiles were measured by their zeta-potential and liquid absorption ability. We also examined the influence of fabric softener on the surface characteristics of the textiles. We used solvent extraction followed by cationic titration to determine the cationic softener level present on the textiles. The major finding of this study was the different behaviour of individual loads and mixed loads in terms of cationic pick up from the rinse cycle softener. Fibre type plays the most critical role in determining the zeta potential of the fibre, filtration efficiency and water retaining capability of the fabrics, which in turn play the most important role in softener deposition on the textile. The charge on the textile surface is negative; this plays a key role in the deposition of the cationic softener in both kinds of loading conditions. Capillary diffusion could be a key parameter only in the individual load condition. It was found that there is a significant reduction in the liquid adsorption weight when fabrics are treated with levels of softener that are much higher than those associated with normal consumer use. As soon as the fabric comes into contact with the liquid, the fabric softener molecules transfer from the fabric to the liquid and reduce the surface energy of the liquid. This results in an increase in the wetting weight of the fabric.     

编织滤布自身性能对过滤的影响

从滤布的自身性能出发,分析归纳总结了编织滤布的纱线类型、线密度、纤维支数,捻度,编织方法和精整加工对过滤的影响,在此基础上,依据各种性能对过滤性进行了排序。对今后过滤介质的选用以及发展提供了可靠的参考依据。     

影响PA6浸胶帘子布定负荷伸长率的因素

阐述了影响 PA6浸胶帘子布定负荷伸长率的因素。结果表明 :浸胶热处理工艺中主要是拉伸区、定型区温度高低、张力大小影响浸胶帘子布定负荷伸长 ;原丝定负荷伸长率小于 11.5 %才能确保浸胶帘子布定负荷伸长小于 80 %和外观质量 ;浸胶帘子布吸湿会造成浸胶帘子布定负荷伸长率增长。     

采用陶瓷膜动态过滤在漂染废水处理中的应用

将陶瓷膜动态过滤技术与絮凝技术相结合,对染料废水和漂染废水进行预处理,充分发挥动态过滤生产能力高,过滤效果好以及陶瓷膜易清洗、再生、使用寿命长等优点,研究表明,这种综合技术对污水处理可以取得比较好的效果;研究同时还表明絮凝预处理方法、操作条件对过滤速率及过滤效果均会有明显的影响,应综合考虑生产能力及废水处理效果两方面的因素,选择最宜操作参数。     

Characteristics of electrostatic cyclone/bag filter with inlet types (lab and pilot scale)

The main purpose of this study was to investigate experimentally the characteristics of an electrostatic cyclone/bag filter with inlet types (upper and bottom inlet) in order to overcome the low collection efficiency for submicron particles and high pressure drop, which were the main problems of general fabric bag filters. The experiment was performed to analyze the collection efficiency and pressure drop of the electrostatic cyclone/bag filter compared with that of conventional fabric bag filters with various experimental parameters such as the inlet type (upper and bottom), inlet velocity (filtration velocity) and applied voltages. From the results, the upper inlet type showed a slightly higher pressure drop reduction ratio as 40–90% than that of bottom inlet. In addition, the electrostatic cyclone/bag filter represented an increment of over 5% for the collection efficiency of submicron particles (around 1 Μm) in comparison with the general fabric filter. Presented at the Int’/Sym. on Chem. Eng. (Cheju, Feb. 8–10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

Performance characteristics of air intake pleated panel filters for internal combustion engines in a two-stage configuration

Previous numerical studies that have used computational fluid dynamics (CFD) and experimental software to address the effects of the geometric parameters of pleats on the pressure drop and air flow rate through a fibrous filter are analyzed. The analysis establishes that using a test dust with gradually smaller particle sizes (10, 5, and 1?μm) results in a more intense increase in the filter pressure drop, thus decreasing the service life of the filter. The benefits of using a multicyclone as the first stage of air filtration are discussed. Selecting the air filter by determining the active surface of the filter medium A_c based on the allowable filtration rate is not sufficient; to select the filter medium of a motor vehicle air filter, the dust mass retained per unit of filtration area (mass loading of dust k_m) must be known for a specific allowable pressure drop Δp_fdop. New methods and conditions for determining the mass loading of dust k_m for filter paper and non-woven fabric in single-stage and two-stage filtration systems are presented. The characteristics of the separation efficiency and filtration performance as well as the pressure drop of a filter set comprising a single cyclone and a filter element with a specific filter medium surface are determined. The effects of the particle size distribution of the dust in the air downstream of the cyclone on the mass loading of dust k_m of the filter paper and non-woven fabric in a two-stage filtration system are presented. The mileage of a truck fitted with a single-stage or two-stage filtration system in a “multicyclone–panel filter” configuration is estimated based on the calculated mass loading of dust k_m of the filter paper and non-woven fabric.

© 2018 American Association for Aerosol Research     

高温气体过滤除尘脉冲反吹再生过程的研究进展

叙述近年来高温气体过滤除尘技术的实验和理论研究进展,指出脉冲反吹再生过程是高温气体过滤除尘过程持续操作的关键。操作参数以及结构设计(包括喷嘴直径、喷嘴与文氏嘴之间的距离、喷嘴出口速度以及文氏嘴结构等)对除尘工艺过程和再生效果具有很大影响。分析了脉冲反吹过程中所涉及的传递现象数值模拟,以期更为深入地了解反吹再生过程的气流流动与能量传递规律,以指导和优化过滤装置的操作参数和结构设计。