Stripping operation transfer unit

Extrapolation of KgO data for absorption and stripping to conditions other than those for which the origin measurements were made can be extremely risky, especially in systems involving chemical reactions in the liquid phase. One therefore would be wise to restrict the use of overall volumetric mass-transfer-coefficient data to conditions not too far removed from those employed in the actual tests. The most reh-able data for this purpose would be those obtained from an operating commercial unit of similar design. 

A well-established concept in the design of stripping operations in the chemical processing industries is the use of equations in which the height of the unit required is expressed as the product of two terms the number of transfer units (NTU), a measure of the difficulty of the operation to be carried out, and the height of a transfer unit (HTU), a measure of the height required in order to carry out an operation of unit difficulty. The advantage of this procedure is that the effectiveness of a particular unit is directly reflected in the value of the HTU. On the other hand, the advan-... 

Actions shifting hazardous waste from one environmental medium to another. Many of the waste management, treatment and control practices used to date have simply collected pollutants and moved them from one environmental medium to another, as follows (a) collection of pollutants from air and water via pollution control devices, which are then legally disposed of in land disposal sites, and (b) transfer of volatile pollutants from surface impoundments, landfills, water treatment units, groundwater air stripping operations, to the air through evaporation. 

Lj = Liquid flowrate down stripping section of distillation tow er, lb mols/hr Light key component in volatile mixture Internal reflux ratio Actual external reflux ratio Minimum external reflux ratio Molecular weight of compound Total mols steam required Number of sidestreams above feed, n Number of theoretical trays in distiUation tower (not including reboiler) at operating finite reflux. For partial condenser system N includes condenser or number theoretical trays or transfer units for a packed tower (VOC calculations) Nb = Number of trays from tray, m, to bottom tray, but not including still or reboiler Nmin = Minimum number of theoretical trays in distillation tower (not including reboiler) at total or infinite reflux. For partial condenser system,... 

An aqueous waste stream containing 1.0 weight percent NHj is to be stripped with air in a packed column to remove 99 percent of the NHj. What is the minimum air rate, in kilograms of air per kilogram of water, if the column operates at 20°C How many transfer units are required at twice the minimum air rate ... 

A computer simulation for the distillation of ethanol and water shows that the second theoretical stage from the bottom would operate with a stripping factor of 3.0. How many liquid phase mass transfer units are equivalent to that theoretical stage ... 

Stripping is carried out either in compact, packingiess flash strippers or in conventional stripping columns. The conventional columns operate with a number of transfer units calculated on the basis of the required efficiency (from 3 to 5 transfer units). When ori ginat S concentrations are high (>15 gd ), these two processes are combined. 

Lj and are the pure liquid and inert gas loading rates, respectively, in units of Ib-moles/hr-ft. The second expression is the operating line on an equilibrium diagram. In all scrubbing application, where the transfer of solute is from the gas to the liquid, the operating line will lie above the equilibrium curve. When the mass transfer is from the liquid to the gas phase, the operating line will lie below the equilibrium curve. The latter case is known as stripping . 

The GS enriching process is a counter-current gas-liquid extraction done at a pressure of 2000 kPa in a sieve tray tower with the upper half operating at 30 C and the lower at 130 C. ( 5) In the top half of the tower, feedwater extracts deuterium from the upflowing cold H2S, reaching a maximum at the centre of the tower. The recycled lean H2S entering the lower hot half of the tower strips deuterium from the water, which then leaves the system depleted in deuterium. A cascade of several stages is used to reach the desired feed concentration for the final water distillation or finishing unit. Transfer between cascades can be either by gas or liquid from the centre of the tower. 

In a typical fluid catalytic cracker, catalyst particles are continuously circulated from one portion of the operation to another. Figure 9 shows a schematic flow diagram of a typical unit W. Hot gas oil feed (500 -700°F) is mixed with 1250 F catalyst at the base of the riser in which the oil and catalyst residence times (from a few seconds to 1 min.) and the ratio of catalyst to the amount of oil is controlled to obtain the desired level of conversion for the product slate demand. The products are then removed from the separator while the catalyst drops back into the stripper. In the stripper adsorbed liquid hydrocarbons are steam stripped from the catalyst particles before the catalyst particles are transferred to the regenerator. 

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