Agitated vessels, temperature

Framing. The framed bar process is by far the oldest and the most straightforward process utilized in the production of bar soaps. The wet base soap is pumped into a heated, agitated vessel commonly referred to as a cmtcher. The minor ingredients used in soap bars such as fragrance or preservative are added to the wet soap in the cmtcher or injected in-line after reduction of product stream temperature. The hot mixture is then pumped into molds and allowed to cool. 

A common process task involves heating a slurry by pumping it through a well-stirred tank. It is useful to know the temperature profile of the slurry in the agitated vessel. This information can be used to optimize the heat transfer process by performing simple sensitivity studies with the formulas presented below. Defining the inlet temperature of the slurry as T, and the temperature of the outer surface of the steam coil as U then by a macroscopic mass and energy balance for the system, a simplified calculation method is developed. 

Heating or cooling of process fluids in a batch-operated vessel is common in the chemical process industries. The process is unsteady state in nature because the heat flow and/or the temperature vary with time at a fixed point. The time required for the heat transfer can be modified, by increasing the agitation of the batch fluid, the rate of circulation of the heat transfer medium in a jacket and/or coil, or the heat transfer area. Bondy and Lippa [45] and Dream [46] have compiled a collection of correlations of heat transfer coefficients in agitated vessels. Batch processes are sometimes disadvantageous because ... 

The crystallizer was an agitated vessel with an Inside diameter of 9.0 cm and a volume of about 1 1. It was equlppet with four vertical baffles, a water jacket to keep the solution temperature constant, and a nozzle through which nitrogen gas was Introduced In several experiments to suspend a speed crystal more effectively In the solution. Agitation was accomplished with a 5.0 cm stainless steel marine propeller having three blades driven by a variable speed motor. 

The objective of absorption equipment is to provide intimate contact between the liquid concerned and gas, thus facilitating the absorption process. When a large volume of gas is absorbed per unit volume of liquid, a marked rise in temperature may result and devices for the removal of the heat evolved are then an important feature of the equipment. Apart from packed towers, the types of equipment described here include agitated vessels, bubble-plate towers, cooler-absorbers and spray towers. 

There is an intimate and often very complex interrelation between the performance of an agitated vessel and the system geometry, the properties of the processed materials, and the operating conditions. In some cases the true complexity of a mixing situation may not be appreciated. Particularly in scale-up problems, the physical nature of the mixing in a process may be as important a factor as the proper reaction temperature or reactant ratios. Thus, another objective of this review is to demonstrate that agitation is a process variable of major significance. 

An agitated vessel may be operated in either a continuous, batch, or semi-batch mode. In continuous operations, the typical heat-transfer requirement is to maintain a set process temperature by either adding or removing heat, depending on the chemical reaction involved. In batch operations, the heat-transfer process can have a number of different functions at different stages of the operation. Examples include the ... 

In situations where either phase conld be disparsed. the pbese being added is normally the dispersed phase that is, in an agitated vessel one phme is being mixed and a second phese is added. As concentrations, temperature, and physical properties chenge. phase inversion may occur. 

TRANSIENT HEATING OR COOLING IN AGITATED VESSELS. Consider a well-agitated vessel containing m kilograms or pounds of liquid of specific heat Cp. It contains a heat-transfer surface of area A heated by a constant-temperature medium such as condensing steam at temperature 7. If the initial temperature of the liquid is T , its temperature at any time tr can be found as follows. The basic relation for unsteady-state heat transfer is... 

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