Recycle operation modes

A refiner has many operation mode choices if the required octane number of the pool can be met by recycle of the methlypentanes, the refiner can choose... 

FIGURE 1.1 Yields of LCO and bottoms vs. conversion. Bottoms oil yield monotonically decreases as conversion, while LCO yield experiences a peak (overcracking point). Recycling operation enables FCCU to run at conversion close to LCO yield peak with little or no bottoms penalty compared to max gasoline mode. 

An alternative carrier-gas system uses a condensable gas, such as steam, as the carrier sweep fluid. One variant of this system is illustrated in Figure 9.7(d). Low-grade steam is often available at low cost, and, if the permeate is immiscible with the condensed carrier, water, it can be recovered by decantation. The condensed water will contain some dissolved organic and can be recycled to the evaporator and then to the permeate side of the module. This operating mode is limited to water-immiscible permeates and to feed streams for which contamination of the feed liquid by water vapor permeating from the sweep gas is not a problem. This idea has been discovered, rediscovered, and patented a number of times, but never used commercially [37,38], If the permeate is soluble in the condensable... 

The different operation modes used in microbial fermentations are employed also in animal cell cultivation. Although many different classifications can be adopted, the most general is the one that considers the following operation modes batch, fed-batch, continuous, and perfusion, which is a continuous mode with cell recycle/retention (Castilho and Medronho, 2002). 

Due to an always high water contents at the reactor inlet, the eventual internal water loop (as described in Fig. 8.3) should not be a problem. However, if co-current and countercurrent operation is compared (Fig. 8.28), a clear difference between these two operation modes is found only for the water concentrations, whereas the gain in space-time yield is limited to around 10 %. This can be attributed to the high recirculation rate of the liquid, whereas in both experiments the gas phase was vented after one pass. Therefore, the gas-liquid operation was of the cross-flow-type rather than pure co-current or countercurrent To identify the effect of pure co-current or countercurrent operation, the gas phase should also be recycled. 

A non-periodic plant operating mode defined over a given time horizon is considered. Mixed storage policies, shared intermediated states, material recycles and multipurpose batch plant equipment units with continuous sizes, are allowed. 

The design of SMBR processes has to take into account the requirements of different types of reactions. Therefore, different types of flowsheets and operating modes can be chosen. As with a semi-continuous operation, a process without section IV (regeneration of the solvent), a five-section process or a four section process without recycle of the eluent may be advantageous. Relevant design criteria for the SMBR are discussed in Section 8.4. 

As shown in Fig. 5, three potential commercial modes of operation to produce DME have been investigated by Air Products. The first operating mode uses an oxygen-blown coal gasifier with recycle of the synthesis gas. The coproducts of this process mode are methanol and DME, which have applications in the fuel and petrochemical industry. Per-pass CO... 

A fourth alternative for carrying out the naphthalene extraction utilizes the dissolving capacity of near-critical liquid CO2. This operating mode is illustrated in figure 6.1 by the LV tie line. Liquid CO2 is employed to dissolve and extract the naphthalene from the mixture, and the liquid solution leaving the extractor is heated to vaporize the CO2 and recover the naphthalene. The CO2 is then condensed and recycled to the extractor. 

Operation Modes Different operation modes including batch, fed-batch, continuous and multistage cultivation, cell recycling, and immobilization have been implemented and optimized to maximize 1,3-PD production from glycerol. These operating strategies are illustrated in detail as follows. 

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