Batching tanks

Batch Percolators The batch tank is not unlike a big nutsche filter it is a large circiilar or rectangiilar tank with a false bottom. The solids to be leached are dumped into the tank to a uniform depth. They are sprayed with solvent until their solute content is reduced to an economic minimum and are then excavated. Countercurrent flow of the solvent through a series of tanks is common, with fresh solvent entering the tank containing most nearly exhausted material. In a typical ore-dressing operation the tanks are 53 by 20 by 5.5 m (175 by 67 by 18 ft) and extract about 8200 Mg (9000 U.S. tons) of ore on a 13-day cycle. Some tanks operate under pressure, to contain volatile solvents or increase the percolation rate. A series of pressure tanks operating with countercurrent solvent flow is called a diffusion battery. 

Dispersed-Solids Leacbing Equipment for leaching fine solids by dispersion and separation includes batch tanks agitated by rotating impellers or by air and a variety of continuous devices. 

Figure 5-25B. For a first order reaction, the ratio of time in a continuous tank to the time in a batch tank for various percentages of reaction completion. By permission, Oidshue, J. Y. [29].

Ideally, the oxygen scavenger is added continuously rather than periodically shot-dosed where batch tanks are employed, there should not be more than one day s supply of oxygen scavenger in the tank. The tank contents should not be agitated any longer than necessary, to avoid aerating the mix. 

An agitated batch tank, is used to dissolve a solid component from a solid matrix into a liquid solvent medium, as in Fig. 1.18, Geankoplis (1983). 

Case B. Gas-Liquid Mass Transfer to a Batch Tank... 

An nth-order homogeneous liquid phase reaction is carried out in a batch tank reactor. 

The conversion X in the batch tank is given by X = 1 - y, which becomes... 

Bench-Scale Equipment for Batch/Tank Reactors... 

When a batch tank is being filled with reacting liquid, the material balance is... 

Ujhidy and co-workers studied the thermal ring closure of )V-(3-chloro-phenyl)aminomethylenemalonate (250) to 7-chloro-4-hydroxyquinoline-3-carboxylate (759, R = Cl, R1 = H) in Dowtherm A containing 5% or 10% of paraffin oil at 230°C, 235°C, 240°C, 245°C, 250°C, and 255°C in different reactors (a continuous tank reactor, a batch tank reactor, a cascade of... 

Knowing the effective pumping capacity of agitation and crosssectional area of the pilot-batch tank, bulk fluid velocity is obtained by using Equation (16). 

Willeman et al. [26] modeled the enzyme-catalyzed cyanohydrin synthesis in a stirred batch tank reactor. Assumption of a mass transfer limitation (Figure 9.3b) is made, which results in a low concentration of substrate in the aqueous phase, thus suppressing the non-enzymatic reaction. In a well-stirred biphasic system the enzyme concentration was varied, keeping the phase ratio constant A maximum rate of conversion is reached at the concentration where mass transfer of the substrate becomes limiting. Further increase of enzyme concentration does not enhance the reaction rate [27]. The different results achieved by the two groups are explained by the different process strategies. No mass transfer limitation could be detected by Hickel et al. because the stirring rate in the aqueous phase was not varied [26]. 

Powders are dissolved either directly in the main mix tank or premix tank or indirectly using a vortex-type mixer (Figure 8.1) where powder is dropped into the vortex of a horizontally mounted pump head recirculating the fluid from and to the batch tank. Some specialised versions of this mixer can handle very viscous blending applications (50,000 cP or more). 

In a batch unit, the water to be demineralized is fed into a batch tank under pressure until the batch tank is full. The filling of the tank is controlled by a level controller and an automatic valve, AVt. The full batch tank of water to be demineralized is pumped through the membrane stack by a dilute pump, D, and recirculated back through the tank until the desired effluent conductivity of the water is achieved. The... 

The pumping out of the batch tank at the end of the cycle lowers the level in the batch tank which signals valve AV1 to open again and a new batch of undemineralized water comes into the system. The cycle is repeated automatically for an indefinite period. The salts removed in the stack from the dilute stream are absorbed in a concentrated stream loop being pumped by concentrating pump C. Enough water is continuously added under control of valve CV and rotameter R to make up for the amount of water blown down as brine. The proportion of water which must be wasted as brine is determined by the chemical composition of the water to be treated. The blowdown is adjusted so that the least soluble salt component in the feed water will remain in solution. 

Either anhydrous dextrose or dextrose monohydrate can be obtained by crystallization. Monohydrate crystallizers are large horizontal, cylindrical batch tanks or... 

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