Contact-batch unit operation

The flexibility of the batch-contact unit makes it adaptable for many varied industrial applications, and this adaptability has done much to extend the use of carbon. Until recently the batch-contact unit operation was employed in all liquid-phase purifications that require a decolorizing type carbon. 

The capacity of the tank will depend on the amount of liquid to be processed and on the time of treatment, which must include time for filling and emptying. The tank should be equipped with an agitating device to enable the carbbn particles to meet fresh portions 

From Active Carbon the Modern Purifier, published by West Virginia Pulp and Paper Company, New York reprinted by courtesy of copyright owner. 

Filter cloth is commonly used for dressing a filter, although for some applications, fine mesh wire screen or paper is appropriate. The real function of the filter cloth or other membrane is to furnish a support for the real filter medium, namely, the bed of deposited solids that form the filter cake. The ability to maintain maximum flow of clear filtrate depends on furnishing a filter cake of proper permeability. 

The conveying pipes may be made of materials compatible with the processed liquid rubber hose or suitably lined pipes are serviceable for corrosive fluids. Sharp bends are to be avoided. 

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For the other contacting patterns of Fig. 24.2 plug G/plug L cocurrent, mixed G/mixed L, plug G/mixed L, mixed G/plug L, mixed G/batch L see Levenspiel (1996) Chapter 42, or recall the equations and methods from your lessons in mass transfer and unit operations. 

Conoco operated a stirred tank Pfaudler glass-lined reactor for the batch S03 sulfonation of detergent alkylate. The plant utilized over-the-fence S03 converter gas (8% S03 in dry air) having 6-8 h batch cycles (264). Allied Chemical Company provided details for batch S03 sulfonation (265,266) and Conoco also published their procedure for S03 batch sulfonation (267). Andrew Jergens Company patented a cyclic batch sulfonation and sulfation process introducing nondiluted S03 vapors into a venturi contacter that emitted reaction product into a stirred reservoir tank where it was recycled from the reservoir vessel through a heat exchanger and back to the venturi in the cyclic loop. The unit operated in a vacuum (268). Derived color quality was unspecified. 

Nowadays it is sometimes argued that each chemical reactor is unique and a systematic classification of chemical unit operations makes little sense. However, a classification based on the nature of the way different phases/substances are brought into contact with one another tends to dominate hence there are packed, fluidised, and spouted bed reactors, bubble column reactors, batch stirred tank reactors, etcetera. 

The extraction equipment consists of a mixer, where the solvent and the mixture of solutes are mixed in an agitated vessel, after which the two layers are made to separate in a settler tank. The equipment may be operated in batch or continuous mode. For batchwise extraction the mixer and the settler may be the same unit, whereas for continuous operation the mixer and the settler must be separate pieces of equipment. If several contact stages are required, a series... 

Figure 3 in introduces the Coxsackie Sewage Treatment Plant (STP). The plant s special wastewater chlorination facility, a combined chlorine contact chamber (CCC) second-phase final settler unit, is shown in Fig. 4. This section introduces the sludge chlorination facility of Coxsackie STP and its operational data. At Coxsackie STP, data generated during 19 batches of sludge chlorination are summarized in Tables 10-12. Characteristics of the underflow from the sludge dewatering beds for nine of those...

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