Side Stream Configuration

An increasing number of SSCs are used in the chemical and petroleum industries. They offer a cost-effective way of producing three products from a single column in some separations 

Similarly, the concentration of B first increases above the feed as the less volatile component C decreases in the first column of the indirect sequence. The concentration of 

---

In the side-stream configuration, the MLSS is pumped through the membrane module. Side-stream systems typically use tubular membranes. Fouling is controlled by a well-defined flow velocity in the range of l-4m/s, generating a turbulent crossflow. Figure 9.7 shows a schematic view of a side-stream system. 

Le-Clech, P., Jefferson, B. and Judd, S.J. (2003) Impact of aeration, solids concentration and membrane characteristics on the hydraulic performance of a membrane bioreactor. Journal of Membrane Science, 218,117—129. Le-Clech, P., Jefferson, B. and Judd, S.J. (2005) Comparison of submerged and side-stream tubular membrane bioreactor configurations. Desalination, 173, 113-122. 

The development of thermally coupled systems started with attempts to find energy-saving schemes for the separation of ternary mixtures into three products. One of the first industrial applications was the side rectifier configuration for air separation. The side stripper configuration followed naturally. By combining the two we obtain the fully thermally coupled system of Petlyuk, Platonov, and Slavinskii [Int. Chem. Eng., 5, 555 (1965)] see Fig. 13-67h. It consists of the prefractionator which accepts the ternary feed stream followed by the main column that produces the products (product column). 

A cost analysis and comparison between two anaerobic processes for the treatment of wastewater was also carried out by Pillay et al. [6.23]. The first configuration consisted of a conventional system coupling a digester with a sedimentation unit. In the second configuration the sedimentation step was replaced by a membrane separation unit treating a side stream. Pillay et al [6.23] report that for a 60 Ml d plant the MBR process results in capital savings of about 27 % when compared with the classical configuration. 

The above flowsheet can be simplified tremendously by catalytic distillation. Figure 7.32 depicts a conceptual configuration. The RD column consists of a reactive zone at the top, and a distillation section at the bottom. The reaction mixture is sent to a purification column, from which ethylbenzene is obtained as top distillate. A side-stream containing PEB is sent to transalkylation for EB recovery. Obviously, the feasibility of this process depends largely on the availability of an active and selective catalyst. For zeolites the optimal operating conditions are about pressure around 3 MPa, temperature less than 200 °C, and reaction rate capable to give a space-time of 5 h" for almost complete ethylene conversion. 

Each equipment symbol shown in Table 1.1 corresponds to the simplest configuration for the represented operation. More complex versions are possible and frequently desirable. For example, a more complex version of the reboiled absorber, item (5) in Table 1.1, is shown in Fig. 1.7. This reboiled absorber has two feeds, an intercooler, a side stream, and both an interreboiler and a bottoms reboiler. Acceptable design procedures must handle such complex situations. 

While the major control considerations have been discussed in the previous three chapters, several loose ends remain. These loose ends pertain to controls that usually command less attention than others, such as reflux and level controls, and to those controls that are not applied in the majority of columns but are critical to some. The latter group includes side-stream drawoff controls, differential pressure control, and feed preheat control. Poor configuration of any of these loose ends can be just as troublesome as the poor practices described in relation to the major controls. 

Subject to availability of an external recycle stream, as well as spare capacity in the column section below the side draw, configuration 19.6c can also be used. However, this scheme is energy-wasteful and will usually accomplish little more than the IVC. 

While the net flows patterns for each structure are now clearer, it still remains difficult to comprehend the effects of changing the reflux in one CS in the rest of the column. The reflux ratio in a specific CS is an important parameter in finding feasible structures and therefore it is necessary to fully understand these effects. As shown in previous chapters, the reflux in a specific CS is a limitless parameter valid anywhere from negative to positive infinity. Notice howev that in the side-stripper configuration, for example, that the liquid stream is split into two parts. 

In this case, the flow rate and AA purity of the side stream and the distillate rate are used as three specifications. The flow rate of Liquid Main out and Vapor Main out should be specified as the remaining two specifications. The mass- and energy-balance of the base case were obtained by activating this configuration (Figure 9.12). 

Schematic representation of MBR configurations (a) submerged MBR and (b) side-stream MBR. 

Biocatalytic membrane reactor configuration, (a) Side-stream (b) submerged. 

The objective of this study is to investigate the process configuration illustrated in figure 2c. Therefore the dehydration of the ternary mixture acetone, isopropanol and water into pure components in one distillation column combined with a hydrophilic membrane unit located in the side stream of the column is analysed. The water-depleted retentate from the permeation zone is returned back to the column while the permeate is removed out of the process. In this configuration, the operation conditions for the membrane separation is more suitable because the side stream can be placed near the maximum concentration of the most permeating component which leads to an increased driving force and consequently to smaller membrane areas. 

In this section, two load disturbances are introduced to test the proposed column configuration. The overall control strategy, shown in Figure 9.26, is also implemented here. The only difference is a side stream at Stage 10 with the flowrate controlled at 50 kg/h. The two load disturbances considered are feed F3 water molar composition +10% changes and feed F3 m-xylene component flowrate +20% changes. 

---