Module design, membrane technology

The catalytic esterification of ethanol and acetic acid to ethyl acetate and water has been taken as a representative example to emphasize the potential advantages of the application of membrane technology compared with conventional distillation [48], see Fig. 13.6. From the McCabe-Thiele diagram for the separation of ethanol-water mixtures it follows that pervaporation can reach high water selectivities at the azeotropic point in contrast to the distillation process. Considering the economic evaluation of membrane-assisted esterifications compared with the conventional distillation technique, a decrease of 75% in energy input and 50% lower investment and operation costs can be calculated. The characteristics of the membrane and the module design mainly determine the investment costs of membrane processes, whereas the operational costs are influenced by the hfetime of the membranes. 

Over the course of development of the membrane technology, RO module designs, as shown in Figure 8.4, evolved. They are tubular, plate-and-frame, spiral wound, and hollow hne-hber modules. In the tubular design, the membrane is lined inside the tube which is made of ordinary tubular material. Water is allowed to pass through the inside of the tube under excess pressure causing the water to permeate through the membrane and to collect at the outside of the tube as the product or permeate. The portion of the influent that did not permeate becomes concentrated. This is called the concentrate or the reject. 

Continuous development of membrane processes applied in nuclear technologies is of considerable interest. Implementation of new membrane materials with high chemical and radiation resistance, and new module designs allow spreading applications of membrane processes into different fields of nuclear industry. The main barriers in the use of membrane methods are the... 

TNG (Holland) designed a rectangular module (TNO transversal-how membrane module) contaming hollow hbers. The system performs with high mass-transfer coefficients and low-pressure drops. Furthermore, it shows a good scale-up potential. The module is commercialized by XTO Membrane Technology. 

Abstract This chapter is devoted to the state of the art of the most important aspects of high temperature ceramic air separation membranes for oxygen production and oxidation processes. Aiternative technologies, operational principle, fields of application, energy efficiency and cost aspects, materials science, module design, and sealing will be discussed. 

Before this technology can be applied on a full-scale as envisaged in our conceptual module design, the end-users should gain sufficient trust in long term performance and reliability of this membrane solution. We believe that to achieve this, first, a number of smaller on-site production facilities must be set up. Only through wide publication of the information obtained in those demonstration plants can significant industrial application be expected. 

In general, membrane science research can be divided into seven major areas, that is, material selection, material characterization, membrane fabrication, membrane characterization and evaluation, transport phenomena, membrane module design, and process performance. Among these areas, materials chosen for membrane fabrication are the most important part in the membrane technology and this phenomenon can be reflected by the significant amount of technical articles published in the literature. 

The relative competitiveness of the two processes is determined primarily by the relative cost of energy and membranes. The dramatic drop in membrane costs evident in Figure 14 is due to economies of scale associated with mass production, improvements in membrane transport properties (water transport rates and salt rejection), and careful attention to feed pre-treatment and module design to reduce fouling and increase lifetime. These cost reductions in combination with the current cost of energy make membrane processes the preferred technology for future desalination plants. 

Microfiltration plants are also being installed in membrane bioreactors to treat municipal and industrial sewage water. Two types of systems that can be used are illustrated in Fig. 7.6. The design shown in Fig. 7.6(a), using a crossflow filtration module, was developed as early as 1966 by Okey and Stavenger at Dorr-Oliver [17]. The process was not commercialized for another 30 years for lack of suitable membrane technology. In the 1990s, workers at Zenon [15,16] in Canada and... 

In this chapter we have shown that the main trend in Pd-based membrane development is towards thinner membranes, particularly composite membranes. The relatively demanding operation conditions in many important applications require further work in terms of membrane development in combination with optimisation of reactor design and operation conditions. The encouraging industrial involvement in the development of the membrane, module and reactor technology is a key factor for successful implementation. Current state-of-the-art shows capability of small scale industrial membrane production of the most common Pd-based composite membranes. Their stability has been verified for thousands of hours under realistic conditions, but in processes free of some of the most hazardous components, e.g. sulfur. 

---