Pilot-Scale Membrane Systems

RWTH aachen university 1 m membrane module consisting of 42 perovskite tubes (with a length of500 mm and diameter of 15mm) housed in a heating chamber operating at = 850 °C and = 20 bar. fSource Reproduced from Ref [94], with permission from Elsevier) 

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As far as other MIEC membrane materials are concerned. Tan et al. developed a pilot-scale membrane system (shown in Figure 4.17) comprising 889 LSCF6428... 

Yeon S-H, Lee K-S, Sea B, Park Y-I, Lee K-H. Application of pilot-scale membrane contactor hybrid system for removal of carbon dioxide from flue gas. J Membr Sci 2005 257 156-160. 

The intrinsic rejection and maximum obtainable water flux of different membranes can be easily evaluated in a stirred batch system. A typical batch unit (42) is shown in Figure 5. A continuous system is needed for full-scale system design and to determine the effects of hydrodynamic variables and fouling in different module configurations. A typical laboratory/pilot-scale continuous unit using computer control and on-line data acquisition is shown in Figure 6. 

Following successful testing of the bubble jet system [3] at pilot scale, the plant was scaled to full technical size (2.5 m2 elements) and successfully tested. The anolyte flow-out of the elements showed a completely pulsation-free operation with all benefits for the membrane lifetime. Despite the rather good results of this first run a design review was started to improve the electrolyser element design. 

As was mentioned previously, an effective system, RNDS , has been developed to remove particular impurities from brine used in membrane electrolysis procedures. The basic concept of RNDS is to bring the feed brine into contact with an ion-exchange resin containing zirconium hydroxide for the adsorptive removal of impurities. For the removal of the sulphate ion from brine, commercial plants utilising RNDS are already in service. For the elimination of iodide and silica, pilot-scale testing is being planned. 

The process design principles of SLM, non-dispersive extraction, and hybrid hquid membrane systems need to be understood through bench scale experiments using feed solution of practical relevance. While the economic analysis of an ELM process can be performed from small scale experiments, such an analysis is difficult for other LM systems. In particular, availability and cost of hollow fiber membranes for commercial application are not known apriori. A simple rule of thumb for cost scale-up may not be apphcable in the case of an HE membrane. Yet we feel that the pilot plant tests would be adequate to make realistic cost benefit analysis of a liquid membrane process, since the volume of production in )8-lactam antibiotic industries is usually low. 

Unfortunately, it is difficult in the laboratory or even under pilot plant conditions to obtain large supplies of natural waters. Hauling of water is expensive at best, and the handling, detention, and storage of water in tanks and associated equipment can introduce iron and other metals which are even more troublesome than some of the scaling constituents normally present. Most laboratory and testing work on electric membrane stacks in pilot plants is done with solutions of sodium chloride. Testing with pure solutions of sodium chloride yields only an approximate idea of the true performance of membrane systems. Sometimes attempts are made to synthesize... 

A pilot-scale system was developed to detoxify 100 kg samples of CCA-treated wood (Christensen et al., 2004). The process consists of placing wood chips within the sample compartment (Figure 7.2). The sample compartment contains an electrolytic solution, which may be water, dilute oxalic acid, or 0.01 M sodium nitrate. The electrode compartments are filled with circulating 0.01 M sodium nitrate (Christensen et al., 2004, 232). During operation, ion-exchange membranes allow the arsenic and metals to pass from the sample into the electrode compartments, where they may be collected. 

The incomplete comprehension of mass transfer mechanisms in ED membrane systems is in all probability responsible for the difficult design of industrial plants and for their limited diffusion. For instance, in the food biotechnology sector ED applications are still in their infancy since quite a limited number of the novel processes studied so far in laboratory- and pilot-scales and reviewed here have been converted into industrial realities yet, except for the recovery of the sodium salt of unspecified organic acid from clarified fermentation broths, as well as amino and organic acids (Gillery et al., 2002). 

Adds, A. Lim, C. Grace, J. The Fluidized Bed Membrane Reactor System A Pilot-Scale Experimental Study Chemical Engineering Science 49, No. 24B (1994) 5833-5843. 

Frederico CF, Ludmila PA, Boam SZ, and Andrew L. Pilot scale application of the membrane aromatic recovery system (MARS) for recovery of phenol from resin production condensates. J. Memb. Sci. 2005 257 120-133. 

Yoon SH, Lee HS, and Kim CG. Comparison of pilot scale performances between membrane bioreactor and hybrid conventional wastewater treatment systems. J Mem Sci, 2004 242(1-2) 5-12. 

H.M. Adris, C.J. Lim and J.R. Grace, The fluidized bed membrane reactor system A pilot-scale experimental study. Paper presented at ISCRE 13, September 1994, Baltimore, MD, USA. 

In a typical example [20] 6.4 m of 0.2 pm membranes are used in a pilot scale operation, yielding average fluxes between 100 and 1251/m h in a installation working at 55°C. The concentration factor for the membrane installation varies between 6 and 12. Due to the extreme fouling nature of the feed, periodic cleaning is compulsory, but can be restricted to once a week. The system has been in operation since August 1992. The pay-back time is less than 3 years. 

In bench-scale tests, using hoUow-fiber membrane as support and a carrier concentration of 2 M the ethylene permeance was 4.6 X 10 barrer/cm with an ethylene partial pressure of 65 psia, while the selectivity C2H4/C2H6 was about 240. Same tests were carried out for separation of propylene from propane. The selectivity obtained was greater than 100 but this result was confirmed only at bench scale. In fact, in the large pilot system, the selectivity and flux dechned over some weeks due to loss of solvent and carrier and to the necessity of remove hydrogen from the feed gas to prevent reduction of Ag f carrier. Despite the result, this remains the first study on the use of facilitated transport membrane for gas separations on a pilot scale. 

The choice of membranes is critical and this requires careful evaluation. To save costs of testing, many operators try to perform bench-scale rather than pilot-scale experiments for an initial process evaluation. Stirred cell systems are commonly used for research purposes. 

Manufacturing processes are a second area for innovation. Scale-up of new membrane materials from the lab to pilot scale is a nontrivial task. Robust coating processes, flexible packaging, and more effective quality control tools could all improve the manufacturing yields and costs associated with membrane systems. This could have an immediate impact in areas where membranes are a technically viable solution, but are not currently economically competitive with alternate separation technologies. 

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