Study of vapor/gas permeation using thin immobilized liquid membrane

To improve liquid membrane selectivity and stability for removal of vapor and gases from a gas stream, a thin immobilized liquid membrane (ILM) has been studied. Low vapor pressure liquid solvent/solutions were immobilized in part of the micropores of a hydrophilic, hydrophobic or ceramic hollow fiber substrate. To prepare such thin ILMs, three approaches were used: evaporation of the a volatile solvent; acrylic acid-grafted hollow fibers providing a thin hydrophilic layer; pressurization technique. For removal of volatile organic compound (VOC), a thin ILM of silicone oil incorporated in the micropores of a hydrophobic hollow fiber with a silicone rubber coating yielded a highly VOC-enriched permeate and increased separation factor. The same ILM was stable over an extended period (6 months - 2 years) demonstrating the potential utility of such an ILM-based hollow fiber device for VOC-N2/air separation. A mathematical model was successfully developed to describe the VOC-N2 permeation-separation in a hollow fiber permeator having this special type of membrane containing a thin ILM. Grafting method used for the preparation of a thinner ILM resulted in various hollow fibers having different hydrophilic layer thickness. These fibers were used to study the effect of various glycerol-based and aqueous liquid membranes immobilized in the thin hydrophilized part of the fiber. Glycerol-based ILMs resulted in low CO2 permeances in the range of 1*10-6 cm3/cm2*s*cmHg for enclosed atmosphere application; aqueous based ILMs has much better performance. A pressurization technique was used to prepare a thin ILM in porous hydrophilic and ceramic substrates. It was shown that when appropriate asymmetric hollow fibers substrates were used, increase in CO2 permeance was achieved

Removal of VOCs from waste gas streams by cyclic membrane separation techniques

In this study, new separation techniques called Flow Swing Membrane Absorption Permeation (FSMABP) and Flow Swing Membrane Permeation (FSMP) were used for the removal of the volatile organic compounds (VOCs). In both cases, processes are cyclic in terms of feed flow while desorption of the VOCs is constantly taking place. The transport mechanism in the FSMABP process is selective permeation followed by absorption of the VOCs into the stagnant nonvolatile absorbent liquid on the shell side of the membrane module and then desorption through a similar polymeric membrane. In the FSMP process, VOCs selectively permeate through the membrane into the shell side due to the partial pressure difference across the membrane. Hollow Fiber Modules (HFM) which were used for this experimental work were effective in removing various VOCs from gas streams. High percent removal of VOCs in case of FSMABP and FSMP was achieved at lower feed flow rates and shorter cycle times. Organic contamination in the feed gas stream could be almost totally removed to obtain highly purified treated gas. The advantage of the FSMABP process is that the enrichment of the permeate is much higher compared to the FSMP. Low nitrogen solubility in mineral oil ensures that the permeate is much more concentrated in VOCs, thus facilitating not only removal of organics but also recovery of these commercially valuable solvents. For the same process inlet conditions, lower concentrations of the treated stream were achieved in FSMP. Silicone coated membrane used in this experimental work showed reasonable high selectivity for VOCs over nitrogen

Heat transfer between moving beds of solids and a vertical tube

Heat transfer to moving packed beds of solids has been studied extensively but predictions are usually specific to the experimenter's own equipment. In order to obtain a more general predictive equation, the heat transfer coefficient was measured for a single vertical tube immersed in a moving packed bed of glass beads, sand, or copper in air at atmospheric pressure and compared to measurements performed by independent researchers with various experimental configurations. High speed photography was used to observe the motion of the particles as they flowed past the heated wall. The particle separation from the wall could not be determined. There was little interchange of the wall particles with the particles in the bulk beyond the wall layer. Likewise, the particles in the layer adjacent to the wall showed very little rotational or cross-flow motion. A numerical method, based on the unsteady state conduction equation, was developed to predict the heat transfer coefficient between the wall and the flowing bed of solid particles. This method could be used to predict the experimental heat transfer coefficients obtained provided the correct value of the particle separation from the wall was used in the numerical solution. This separation cannot be predicted a priori so that the numerical method is, therefore, not suitable for predicting the heat transfer coefficient. The experimental data showed good agreement with the analytic solution obtained by Mickley and Fairbanks (1) at long contact times. At short contact times, the data do not agree with the Mickley and Fairbanks solution but the heat transfer coefficient tends to level off at an asymptotic value. An empirical correlation was obtained by which the contact time at which the data depart from the Mickley and Fairbanks solution may be predicted. The following equation, was found to be valid for the data of the present work and for data of other researchers who used different geometries in their work. tcr/dpρs= 0.3622 + 9.691 L. This equation may be used in conjunction with the Mickley and Fairbanks solution to predict the heat transfer coefficient for a given flowing packed bed over a wide range of contact times

Pressure Swing Absorption Device and Process for Separating CO{sub 2} from Shifted Syngas and its Capture for Subsequent Storage

Using the ionic liquid (IL) 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]) as the absorbent on the shell side of a membrane module containing either a porous hydrophobized ceramic tubule or porous hydrophobized polyether ether ketone (PEEK) hollow fiber membranes, studies for CO{sub 2} removal from hot simulated pre-combustion shifted syngas were carried out by a novel pressure swing membrane absorption (PSMAB) process. Helium was used as a surrogate for H{sub 2} in a simulated shifted syngas with CO{sub 2} around 40% (dry gas basis). In this cyclic separation process, the membrane module was used to achieve non-dispersive gas absorption from a high-pressure feed gas (689-1724 kPag; 100-250 psig) at temperatures between 25-1000C into a stationary absorbent liquid on the module shell side during a certain part of the cycle followed by among other cycle steps controlled desorption of the absorbed gases from the liquid in the rest of the cycle. Two product streams were obtained, one He-rich and the other CO{sub 2}-rich. Addition of polyamidoamine (PAMAM) dendrimer of generation 0 to IL [bmim][DCA] improved the system performance at higher temperatures. The solubilities of CO{sub 2} and He were determined in the ionic liquid with or without the dendrimer in solution as well as in the presence or absence of moisture; polyethylene glycol (PEG) 400 was also studied as a replacement for the IL. The solubility selectivity of the ionic liquid containing the dendrimer for CO{sub 2} over helium was considerably larger than that for the pure ionic liquid. The solubility of CO{sub 2} and CO{sub 2}-He solubility selectivity of PEG 400 and a solution of the dendrimer in PEG 400 were higher than the corresponding ones in the IL, [bmim][DCA]. A mathematical model was developed to describe the PSMAB process; a numerical solution of the governing equations described successfully the observed performance of the PSMAB process for the pure ionic liquid-based system

Pressure Swing Absorption Device and Process for Separating CO{sub 2} from Shifted Syngas and its Capture for Subsequent Storage

Using the ionic liquid (IL) 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]) as the absorbent on the shell side of a membrane module containing either a porous hydrophobized ceramic tubule or porous hydrophobized polyether ether ketone (PEEK) hollow fiber membranes, studies for CO{sub 2} removal from hot simulated pre-combustion shifted syngas were carried out by a novel pressure swing membrane absorption (PSMAB) process. Helium was used as a surrogate for H{sub 2} in a simulated shifted syngas with CO{sub 2} around 40% (dry gas basis). In this cyclic separation process, the membrane module was used to achieve non-dispersive gas absorption from a high-pressure feed gas (689-1724 kPag; 100-250 psig) at temperatures between 25-1000C into a stationary absorbent liquid on the module shell side during a certain part of the cycle followed by among other cycle steps controlled desorption of the absorbed gases from the liquid in the rest of the cycle. Two product streams were obtained, one He-rich and the other CO{sub 2}-rich. Addition of polyamidoamine (PAMAM) dendrimer of generation 0 to IL [bmim][DCA] improved the system performance at higher temperatures. The solubilities of CO{sub 2} and He were determined in the ionic liquid with or without the dendrimer in solution as well as in the presence or absence of moisture; polyethylene glycol (PEG) 400 was also studied as a replacement for the IL. The solubility selectivity of the ionic liquid containing the dendrimer for CO{sub 2} over helium was considerably larger than that for the pure ionic liquid. The solubility of CO{sub 2} and CO{sub 2}-He solubility selectivity of PEG 400 and a solution of the dendrimer in PEG 400 were higher than the corresponding ones in the IL, [bmim][DCA]. A mathematical model was developed to describe the PSMAB process; a numerical solution of the governing equations described successfully the observed performance of the PSMAB process for the pure ionic liquid-based system

Kraft black liquor delivery systems

Improvement of spray nozzles for black liquor injection into kraft recovery furnaces is expected to result from obtaining a controlled, well-defined droplet size distribution. Work this year has centered on defining the capabilities of commercial black liquor nozzles currently in use. Considerations of the observed mechanism of droplet formation suggest a major revision is needed in the theory of how droplets form from these nozzles. High resolution, high sensitivity video has been shown to be superior to flash x-ray as a technique for measuring the droplet size distribution as well as the formation history. An environmentally sound spray facility capable of spraying black liquor at temperatures up to normal firing conditions is being constructed before data acquisition continues. Preliminary correlations have been developed between liquor properties, nozzle design, and droplet size. Three aspects of nozzle design have been investigated: droplet size distribution, fluid sheet thickness, and flow and pressure drop characteristics. The standard deviation about the median droplet size for black liquor is nearly the same as the for a wide variety of other fluids and nozzle types. Preliminary correlation for fluid sheet thickness on the plate of a splashplate nozzle show the strong similarities of black liquor to other fluids. The flow and pressure drop characteristic of black liquor nozzle, follow a simple two-term relationship similar to other flow devices. This means that in routine mill operation of black liquor nozzles only the fluid acceleration in the nozzle is important, viscous losses are quiet small. 21 refs., 53 figs., 10 tabs

Solubilities of CO₂ and Helium in an Ionic Liquid Containing Poly(amidoamine) Dendrimer Gen 0

In this study, measurements of the solubilities of pure carbon dioxide, pure helium, and a feed mixture of 40% CO₂–He balance were carried out in the ionic liquid, 1-butyl-3-methyl-imidazoliumdicyanamide ([bmim]­[DCA]). Measurements were also made in its solution containing 20 wt % and 30 wt % poly­(amidoamine) (PAMAM) dendrimer Gen 0 with and without moisture. A pressure-decay dual-transducer apparatus was employed at temperatures of 323, 353, 363, and 373 K and at pressures up to 1.38 MPa (∼200 psig). Henry’s law constants of pure CO₂ and pure helium were determined at different temperatures for the ionic liquid. Pseudo-Henry’s law constants for each of CO₂ and helium in a 40%–60% feed gas mixture were also determined. Solubility selectivities of carbon dioxide to helium for all liquid absorbents were also calculated at each temperature. Carbon dioxide was absorbed much more in these studied liquids, compared to helium. In addition, carbon dioxide absorption increased considerably when the amine was added to the ionic liquid and then increased several-fold when moisture was present in the amine–ionic liquid solution, compared to the CO₂ absorption by the ionic liquid