Batch recycle system

Figures 22a, b provides a schematic representation of the pilot scale reactor. Essentially it is a rectangular parallelepiped limited by two parallel windows made of borosilicate glass and operated as a slurry reactor inside the loop of a batch recycling system. Irradiation of one of the reactor faces is obtained using two tubular lamps that were placed along the focal axis of two parabolic reflectors made of specularly finished aluminum (Brandi et al., 1996, 1999, 2002). The specific information concerning the experimental device is presented in Table 9, and more details can be found in Satuf et al. (2007b).

With feed and bleed or batch recycle systems some or all of the water that has already been processed by the stack is mixed with feed and returned via a recirculation pump. Recycle is inherently less efficient than once-through flow in both stack utilization and in energy consumptions since the same solution must be pumped and desalted repeatedly and then remixed with a more concentrated solution. However, the increased flexibility in process control makes recycle systems attractive for small-scale operations where stacks are over-sized to handle varying loads. Feed and bleed is useful for operations where the enriching stream needs to be as concentrated as possible. Ten-fold enrichment or 90% recovery of some feed waters as diluate can be achieved by concentrate recirculation if solubility limits of the dissolved substances are not exceeded in the concentrate stream. 

Given the choice of a batch rather than continuous process, does this need a different approach to the synthesis of the reaction and separation and recycle system In fact, a different approach is not needed. We start by assuming the process to be continuous and then, if choosing to use batch operation, replace continuous steps by batch steps. It is simpler to start with continuous process operation... 

The normal boiling points of the materials are given in Table 4.6. Synthesize a continuous reaction, separation, and recycle system for the process, bearing in mind that the process will later become batch. 

Appropriate setting of two on-off valves (Fig. 1) allows the system to be operated either as a batch recycle reactor or as a continuous-flow steady-state recycle reactor. 

Reaction, Separation and Recycle Systems for Batch Processes... 

Suppose Table 1-1 represents the yield obtained vs. time for each reactor cycle. If the reactor cycle is 8 hours and produces 15,000 lb of product per batch, then if the cycle time were cut to 5 hours the yield would be 13,250 lb per batch. The rates of production would be 1,875 lb / hr for the former and 2,650 lb / hr for the latter. For a plant operated 8,000 hours per year this would give a production rate of 15,000,000 lb / yr for the former and 21,206,000 lb / yr for the latter. A change of this sort would necessitate no increase in reactor capacity, but it would require changes in the recovery and recycle systems other than those solely due to the increase in capacity. 

The Terra-Kleen solvent extraction technology is an on-site, batch-process system that uses a proprietary solvent to remove hazardous organic constituents from soils. The treatment system uses a solvent regeneration system that concentrates the extracted contaminants and then recycles the extraction solvent. The treated soil can often be returned to the site. The concentrated contaminants are usually transported off-site for disposal. 

Recently, a new rhodium recycling system was described that takes advantage of amphiphilic ligands such as Ph2ArP (Ar = 3-hydroxyphenyl, 4-carboxyphenyl). The corresponding rhodium complexes are active in the hydroformylation of 1-octene and can be separated from the products by acidic or basic extraction into water. After neutralization of the aqueous phase, the rhodium species could be extracted into a new batch of octene, with toluene as a solvent. The recovered catalyst retained only up to 87% of its activity (72). 

The experimental study of solid catalyzed gaseous reactions can be performed in batch, continuous flow stirred tank, or tubular flow reactors. This involves a stirred tank reactor with a recycle system flowing through a catalyzed bed (Figure 5-31). For integral analysis, a rate equation is selected for testing and the batch reactor performance equation is integrated. An example is the rate on a catalyst mass basis in Equation 5-322. 

Some older facilities operate with no recycle, and transfer of water occurs as either batch advance or continuous advance. Most commonly, the systems are continuous advance where the water is moved by a small pump attached to each steep tank (Figure 9.8). In older batch advance systems, one large pump serves an entire battery. 

Finally, some remarks on the operation of mechanically agitated gas-liquid reactors are worth mentioning. The mode of operation (i.e., batch, semibatch, continuous, periodic, etc.) depends on the specific need of the system. For example, the level of liquid-phase backmixing can be controlled to any desired level by operating the gas-liquid reactor in a periodic or semibatch manner. This provides an alternative to the tanks in series or plug flow with recycle system and provides a potential method of increasing the yield of the desired intermediate in complex reaction schemes. In some cases of industrial importance, the mode of operation needs to be such that the concentration of the solute gas (such as Cl2, H2S, etc.) as the reactor outlet is kept at a specific value. As shown by Joshi et al. (1982), this can be achieved by a number of different operational and control strategies. 

The 1973 petroleum crisis intensified research on coal liquefaction and conversion processes. The technology developed in this field was later harnessed in chemical recycling of plastics. Mastral et al. [32], for example, employed two different batch reaction systems (tubing bomb reactors and magnetically stirred autoclave) and a continuous reactor (swept fixed bed reactor). Chemical recycling techniques such as pyrolysis [28, 33-38] or coliquefaction with coal [39, 40] convert plastic wastes into hydrocarbons that are valuable industrial raw materials. 

In this reaction, however, both the reactant and the sulfur product are insoluble and could interrupt process continuity by deposition and clogging if installed in the continuous portion of a recycle system. Furthermore, the sodium salt solution from the regenerator can be isolated for batch reaction with an inexpensive insoluble metal oxide, such as lime slurry. 

In the single-pass system, the feed stream passes through the system only once, and there is no recycling. In a recycling system, a recirculation pump is used to recycle the retentate stream. For small-scale applications, a batch system can be used, as shown in Fig. 19. 

Using a batch recycle mode, oily wastewater was treated in the photoassisted advanced oxidation systems. Their results indicated that UV/H2O2 oxidized oily compounds into organic acids with the efficiency being greater at acidic pH. The oxidation rate was enhanced in the presence of Fe " ". 

A batch recycle reactor (Fig. 12-1), operated differentially and used for the gas-phase photolysis of acetone, has a volume of 62.8 cm, while the total volume of the system is 6,620 axr. Runs at 97°C and 870 mm Hg pressure were made at different initial concentrations of acetone in helium. Typical data for conversion to C2H6 are as given below for varying initial concentrations (gram moles per liter). The products of photolysis are primarily CjHe and CO, according to the overall reaction... 

Damiano, D., Wang, S. S. (1985). Improvements in ethanol concentration and fermentor ethanol productivity in yeast fermentations using whole soy flour in batch, and continuous recycle systems. Biotechnology Letters 7 135-140. 

Naot, I., and D.R. Lewin, Analysis of Process Dynamics in Recycle Systems Using Steady State Flowsheeting Tools, Proc. 4th IFAC Symposium on Dynamics and Control of Chemical Reactors, Distillation Columns and Batch Processes (DYCORD 95), Helsingor, Danish Automation Society, Copenhagen (1995). 

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