Batch treatment

The obvious batch treatment processor is the ultrasonic cleaning bath which is a readily available source of low intensity ultrasonic irradiation generally at a frequency of around 40 kHz. A reactor based on this design might require adaptation to provide chemically resistant walls, a sealed lid for work under an inert atmosphere and mechanical stirring. Using this 

Immerse the reaction vessel in a tank containing a sonicated liquid (most commonly an ultrasonic cleaning bath) thereby transmitting sonic energy through the reactor walls 

Use a reactor with walls which are themselves subject to direct ultrasonic vibrations via transducers bonded to the outer surfaces 

Immerse an ultrasonic source directly in the reaction medium 

Modified cleaning baths with fixed or submersible transducers 

Continuous injection of corrosion inhibitors is practiced in once-through systems where portions or batch treatment cannot be distributed evenly through the fluid. This method is used for water supplies, oil-field injection water, once-through cooling water, open annulus oil or gas wells, and gas lift wells. Liquid inhibitors are injected with a chemical injection pump. These pumps are extremely reliable and require little maintenance. Most chemical injection pumps can be adjusted to deliver the desired injection rate. 

Another form of continuous application is by the use of sbghtly soluble forms of sobd inhibitors. The inhibitor (such as glassy phosphate or silicate in the form of a cartridge) is installed in a flow fine where it is continuously leached out by passage of fluid through the cartridge. Inhibitors in the form of sticks or pellets are used in oil and gas wells to supply inhibitor continuously by their natural slow dissolution. 

Boilers, closed coohng water systems, and other closed circulating fluid systems can be treated with inhibitors with continuous injection. When such systems are started up after construction or major maintenance, the inhibitor is often injected at higher-than-normal concentration to permit rapid development of protective films. 

The most familiar example of batch treatment is the automobile cooling system. A quantity of inhibitor is added at one time to provide protection for an extended period. Additional inhibitor may be added periodically, or the fluid may be drained and replaced with a new supply. In most aerated, closed-loop cooling systems, it is important that the inhibitor concentration be measured occasionally to ensure that a safe level is maintained. 

Batch treatment is also used in treating oil and gas wells. An inhibitor is diluted with an appropriate solvent and injected into the annulus of open-hole wells or into the tubing of gas wells that have a packer. In this application, it is important that the inhibitor contacts all surfaces and that it has good persistence. Most wells require treatment about every two weeks. 

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Fabric preparation is often considered to be the most important stage to obtain good color yields, levelness, and brightness on wool fabric (104). This is done almost exclusively by an oxidative chlorination process, the most popular commercial methods using either a batch treatment with dichloroisocyanuric acid (DCCA), or a continuous fabric treatment with gaseous chlorine, called the Kroy process. 

Where activated carbon is a potential treatment technology, the first evaluation step is generally to run simple isotherms to determine feasibility. Isotherms are based on batch treatment where impurities reach equilibrium on available carbon surface. While such tests provide an indication of the maximum amount of impurity a GAC can adsorb, it cannot give definite scale up data for a GAC operation due to several factors ... 

Application of Corrosion Inhibitors. There are basically two main techniques used to apply corrosion inhibitors in drilling operations. In the first method inhibitors are added to the drilling fluid system either by mixing the additives through the rig s chemical hopper or through additions into the mud pit. The treatment can be achieved in two ways, batch treatment or continuous treatment. In some cases it may be necessary to use both types of treatment simultaneously. The second technique of applying is directly coating the corrosion inhibitors on the drillpipe. 

Batch Treatment. This treatment is accomplished by pumping manufacturer s recommended volume (with concentration up to 10,000 ppm or according to the manufacturer s recommendations for prevailing conditions) to batch down the drillpipe initially. Once the film is formed, the inhibitor concentration can be lowered for batch treatment at regular predetermined intervals. 

Once the microbiocide is selected, a method of application should be considered. The chemical can be introduced to the system by either batch treatment, continuous treatment or by a combination of both. For batch treatment, NACE provides an equation given below. This equation can be used to determine the concentration of chemical at any time during the eight hour period. The equation is... 

The frequency of the batch treatment, or slug treatment, depends on the actual field response. The continuous method of treatment is relatively more expensive and can be four times as expensive as the batch treatment. 

The simple calculations presented below will show that surface fluorination of rubbers with XeF2 is economically advantageous as compared with fluoro-rubbers. The amount ofXeF2 needed for batch treatment of 5000 O-rings made from EPDM rubber (diam. 10.2 x 1.5 mm) is approximately 20 g. That means that the cost ofthe XeF2 needed for one batch treatment, is 20 x 1.5 = 30 for 5000 O-rings or about 0.0006 each. It should be kept in mind that, as mentioned above, the price for fluororubber is thirty times that of EPDM. 

Chemical precipitation can be accomplished by either batch- or continuous-flow operations. If the flow is less than 30,000 gpd (21 gpm), a batch treatment system may be the most economical. In the batch system, two tanks are provided, each with a capacity of 1 day s flow. One tank undergoes treatment while the other tank is being filled. When the daily flow exceeds 30,000 gpd, batch treatment is usually not feasible because of the large tankage required. Continuous treatment may require a tank for acidification and reduction, then a mixing tank for chemical addition, and a settling tank. 

When a batch of slurry is aerated, its offensive odour soon disappears largely due to biodegradation. In batch aeration, the microbial respiration rate rises rapidly during the first 12h and then fails equally rapidly to a much lower level (12). Thus it is difficult and expensive to design a batch treatment reactor which is efficient in terms of use of aeration energy. It requires an aeration rate which continually varies in proportion to the changing respiration rate. 

In cases where low intensity irradiation is needed batch treatment could be as simple as using a large-scale ultrasonic cleaning bath as the reaction vessel. However the tank would need to be constructed of a material which was inert towards the chemicals involved. An appropriate grade of stainless steel might prove adequate or plastic tanks could be used. In the latter case however the transducer would need to be bonded onto a stainless or titanium plate and this assembly then bolted to the tank. A useful variant to this and indeed one which offers greater flexibility in use is the sealed, submersible transducer assembly (Fig. 7.17). With either system some form of additional (mechanical) stirring would almost certainly be needed. 

Biological treatment may be used to degrade the oil and grease fractions in drilling fluids prior to solids separation. Marks et al. [33] conducted batch treatment tests for drilling fluids and production sludges and demonstrated that biological treatment is feasible. However, more biokinetic tests are required for further evaluation. 

Semibatch Operations, The ion exchange column of Fig. 26.1(c) is an example of the batch treatment of solids in which the flow of fluid closely approximates... 

Where necessary and applicable, the specific ozone dose or the specific ozone absorption (best recorded and computed on-line) is recommended as the measure for analyzing process performance. Since in waste water ozonation, the ozone off-gas concentration often increases during the batch-treatment, the specific ozone absorption will not vary linearly with the treatment time. 

Method 4 simulate (approximate) the continuous-flow integrated process by a multisequential chemical/biological batch treatment or use the sequencing batch reactor (SBR) technology. 

Figure-6-4 Typical degradation profile (c(DOC)tlc(DOC)lf of a multi-sequential chemical/biologi-cal batch treatment process (after Jochimsen, 1997).

Table 6.8 shows that the fastest depletion of atrazine occurs under Fenton s reagent. Arnold et al. (1995) demonstrated that OH may react with Ch at low pH to produce HOC1 and Cl2, causing underestimation of Cl concentrations, but the results suggest that Cl- scavenging by OH was minimal. Dechlorination and dealkylation occur simultaneously, and the batch treatment showed that dechlorination occurred more readily with alkylated s-triazines. Chlorinated products accounted for a large part of s-triazines present upon completion of Fenton s reagent. 

Figure 14.4 is the three-dimensional view of the process. The figure illustrates the relative water head at different stages. Because of flexible design, Ultrox UV/oxidation treatment systems have a number of advantages (1) very few moving parts (2) operation at low pressure (3) minimum maintenance (4) full-time or intermittent operation in either a continuous or batch treatment mode (5) use of efficient, low-temperature, and long-life UV lamps and (6) use of a microprocessor to control and automate the treatment process (Zeff and Barich, 1992). 

S. Heinrich, G. Kruger, L Mori, Modelling of the batch treatment of wet granular solids with superheated... 

The use of biphasic reactors (with immiscible solvents) tries to overcome the restrictions described for monophasic reactors (miscible solvents) (1) the concentration of substrate or products in biphasic reactors could be increased even to g/L (instead of mg/L), depending on the solubility of the substrate in the immiscible solvent considered (2) the enzyme remains in the aqueous phase and can be easily recycled and (3) the solvent, after the enzymatic treatment and depleted in substrate, could be separated from the aqueous phase, used to extract the substrate and returned to the aqueous phase for a further batch treatment. 

This approach is also used to model batch treatments (4.6) with a high value of recycle and in which the produced chemicals are not too active, so they can be considered to live for a sufficiently long time and their concentration results homogeneous in the whole solution. In this case, the initial condition is the concentration of species i at time t = 0 ([S,-](=0)... 

This approach is also used to model batch treatments in which the recycle has a low or medium value In this case, two balances has to be drawn to characterize the discontinuous system one for the cell (4.8) and the other for the reservoir (4.9)... 

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