STRIPS-Operator

Physicochemical relationships are such that soHd potassium chloride can be converted to soHd potassium nitrate ia a one-stage operation of the simplest kiad. The conversion takes place ia a stirred reaction system (Fig. 10). The overall separation is analogous to a rectification and stripping operation ia a distillation process. 

The Hquor is then treated with calcium hydroxide (milk of lime) which reacts with the fixed salts, mosdy ammonium chloride, to Hberate ammonia. The Hquor is regenerated in a steam stripping operation. 

Equation 32 represents the upper (or rectifying) operating line equation and equation 33 represents the lower (or stripping) operating line equation. The slopes L jV and L jV can vary, depending on heat effects. 

The McCabe-Thiele method employs the simplifying assumption that the molal overflows in the stripping and the rectification sections are constant. This assumption reduces the rectifying and stripping operating line equations to ... 

Condition of Feed (q Fine). The q line, which marks the transition from rectifying to stripping operating lines, is determined by mass and enthalpy balances around the feed plate. These balances are detailed in distillation texts (15). 

Experimental K g< and Ki a data are available for most absorption and stripping operations of commercial interest (see Sec. 15). The solute concentrations employed in these experiments normally are very low, so that Ki a — Ki/i and K g< Pt where pf is the total pressure employed in the actual experimental-test system. Unlike the individual gas-film coefficient /cg, the overall coefficient will... 

Recovery of the solvent, sometimes by chemical means but more often by distillation, is almost always required, and the recoveiy system ordinarily is considered an integral part of the absorption-system process design. A more efficient solvent-stripping operation normally will result in a less costly absorber because of a smaller concentration of residual dissolved solute in the regenerated solvent however, this may increase the overall cost of solvent recoveiy. A more detailed discussion of these and other economic considerations is presented later in this section. 

The design of a plate tower for gas-absorption or gas-stripping operations involves many of the same principles employed in distillation calculations, such as the determination of the number of theoretical plates needed to achieve a specified composition change (see Sec. 13). Distillation differs from gas absorption in that it involves the separation of components based on the distribution of the various substances between a gas phase and a hquid phase when all the components are present in Doth phases. In distillation, the new phase is generated From the original feed mixture by vaporization or condensation of the volatile components, and the separation is achieved by introducing reflux to the top of the tower. 

Desorption with Chemical Reaction When chemical reactions are involved in a stripping operation, the design problem can become extremely complex. In fact, much less is known about this very important process than is known about absorption. A classic work on this subject is that of Shah and Sharma [Trans. In.st. Chem. Tng., 54, 1 (1976)], which is recommended to those in need of more details. 

FIG. 22-42 Four alternative modes of contimioiis-flow operation with a foam-fractionation column (1) The simple mode is illustrated hy the solid lines. (2) Enriching operation employs the dashed reflux line. (3) In stripping operation, the elevated dashed feed line to the foam replaces the solid feed line to the pool. (4) For combined operation, reflux and elevated feed to the foam are both employed. 

Introducing the feed into the foam some distance above the pool makes for stripping operation. The resulting countercurrent flow in the foam further purines the bottoms, i.e., lowers C y. 

Time, e.g. performanee of eleaning, demolition or stripping operations out-of-hours . Rotation of jobs, and limitation of exposure, e.g. in eonfmed spaees, are also examples of partial segregation. 

The stripping operation takes place isothermally at 298 K and follows Henry s law. 

The a should be for the feed tray. However, the value of a = 2.8 should be accepted for feed tray conditions (not 158°F). It would not be if this were predominantly a rectifying or a stripping operation. 

Ammonia vapors from a stripping operation are to be condensed. Select the condenser pressure, which sets the top of stripper pressure, and design a condenser. Water at 90°F is to be used. 

A spherical preventer contains a packing element that seals the space around a drillpipe. This preventer is not designed to shut off the well when the drillpipe is out of the hole, although it allows stripping operations and some pipe rotation. Hydril Corporation, Shaffer and other manufacturers provide several models with different packing system designs for specific types of service. The ram-type preventer seals the annulus around the drillpipe however, each size of ram is designated for only one size of drillpipe. In other words, the preventer with 5-in. pipe rams can provide a seal only on 5-in. drillpipe. The preventer with blind rams is used to shut in the well if the pipe is not in the hole. If this type of preventer is activated with the pipe in the hole, the pipe can be cut. 

Efficient contact is produced between the phases in agitated gas-liquid contactors and, therefore, this type of equipment can also be useful for those absorption and stripping operations for which conventional plate or packed towers may not be suited. It may also be useful where the operation involves the contact of three phases—say, gas, liquid, and suspended solids. The latter application could be represented by the low-pressure polymerization of ethylene with solid catalysts (F5). 

Figure 2a shows the simplest possible model of an operating step, introduced by Fikes and Nilsson (1971) and known as the STRIPS operator. The preconditions are statements that must be true of the system and its surrounding world before the action can be taken. Similarly, the postconditions are statements that are guaranteed to be true after the actions corresponding to the specific operation have been carried out. The allowable forms of pre-, and postconditions should satisfy the following requirements ... 

The STRIPS operator is very simple and intuitively appealing. In attempting to use it for the synthesis of operating procedures for chemical processes, one finds immediately that it suffers from severe limitations, such as the following ... 

Nevertheless, early work in the synthesis of operating proeedures (Rivas and Rudd, 1974 Ivanov et al., 1980 Kinoshita et al., 1982 Fusillo and Powers, 1987) did employ various variants of the STRIPS operator on limited-scope problems with very useful results. Lakshmanan and Stephanopoulos (1987) also demonstrated the value of the STRIPS operators in ordering sequences of feasible operations during routine startup. 

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