Stripping distillation columns

For absorption or stripping distillation columns, the most commonly-used plates are perforated plates, because they are cheapest to make and of well-established design. 

There are a number of additional modes of operating a distillation column. These include partial condenser open steam introduced at the column bottom without a reboiler enriching distillation column stripping distillation column operation with a side stream, etc. We will briefly describe each one of these in the context of equilibrium stages/ plates and constant molal overflow. 

Figure 8.1.26. (a) Enriching distillation column (b) stripping distillation column. 

Figure 2 illustrates the three-step MIBK process employed by Hibernia Scholven (83). This process is designed to permit the intermediate recovery of refined diacetone alcohol and mesityl oxide. In the first step acetone and dilute sodium hydroxide are fed continuously to a reactor at low temperature and with a reactor residence time of approximately one hour. The product is then stabilized with phosphoric acid and stripped of unreacted acetone to yield a cmde diacetone alcohol stream. More phosphoric acid is then added, and the diacetone alcohol dehydrated to mesityl oxide in a distillation column. Mesityl oxide is recovered overhead in this column and fed to a further distillation column where residual acetone is removed and recycled to yield a tails stream containing 98—99% mesityl oxide. The mesityl oxide is then hydrogenated to MIBK in a reactive distillation conducted at atmospheric pressure and 110°C. Simultaneous hydrogenation and rectification are achieved in a column fitted with a palladium catalyst bed, and yields of mesityl oxide to MIBK exceeding 96% are obtained. 

After flashing the propylene, the aqueous solution from the separator is sent to the purification section where the catalyst is separated by a2eotropic distillation 88 wt % isopropyl alcohol is obtained overhead. The bottoms containing aqueous catalyst solution are recycled to the reactor, and the light ends are stripped of low boiling impurities, eg, diisopropyl ether and acetone. A2eotropic distillation yields dry isopropyl alcohol, and the final distillation column yields a product of more than 99.99% purity. 

Determining the number of theoretical and actual trays in a distillation column is only part of the design necessary to ensure system performance. The interpretation of distillation, absorption, or stripping requirements into a mechanical vessel with internal components (trays or packing, see Chapter 9) to carry out the function requires use of theoretical and empirical data. The costs of this equipment are markedly influenced by the column diameter and the intricacies of the trays, such as caps, risers, weirs, downcomers, perforations, etc. Calcvdated tray efficiencies for determination of actual trays can be lost by any unbalanced and improperly designed tray. 

Ni-Si recovery of HP Processes involving cone. H2SO4 processes. Sulphur stripping columns. Distillation columns containing acidic chlorides. Handling acid sludges processes impellers, propeller shafts, fasteners. Demisters in desalination plants refrigerating brines. Salt production. Evaporators steel... 

FIG. 19 Formation of hydrochloric acid. SC, stripping column LS, liquid separator DC, distillation column. 

The idea is best explained with an example. Suppose the base level in a distillation column is normally held by bottoms product withdrawal as shown in Fig. 8.4a. A temperature in the stripping section is held by steam to the rcboiler. Situations can arise where the base level continues to drop even with the bottoms flow at zero (vapor boilup is greater than the liquid rate from tray 1). if no corrective action is taken, the reboiler may boil dry (which could foul the tubes) and the bottoms pump could lose suction. 

In this process developed by Lurgi [17], the phenolic effluent is contacted with the solvent in a multistage mixer-settler countercurrent extractor (Fig. 10.8). The extract, containing phenol, is separated into phenol and solvent by distillation and solvent is recycled to the extractor. The aqueous raffinate phase is stripped from solvent with gas, and the solvent is recovered from the stripping gas by washing with crude phenol and passed to the extract distillation column. 

Whether or not a variable is independent may be more difficult to determine in other cases. For example, a distillation column with a side stripper is shown in Fig. 1. The side stripper in Fig. 1(a) has a reboiler and that in Figure 1 (b) is stripped with steam. Under the program, the liquid side stream which feeds the side stripper must be set. Also, in the column arrangement of Fig. 1(b) the amount and enthalpy of the steam fed must be set, since it constitutes an external feed. For illustration, we assume that the bottom product from the reboiler of the main column has... 

Figure 1 Flowsheet of the RCH/RP hydroformylation process 38 1 Continuous flow stirred tank reactor,424 2 Phase separator, 3 Stripping column, 4 Distillation column, 5 Heat exchanger, 6 Falling film evaporator, 7 Liquid vapor separator.

In the process using sulfuric acid (see Figure 1) this acid was, and in many instances still is, added to the weak nitric acid produced by an AOP before the mixed acid was fed to the top of a distillation column. The feed has been preheated in some processes to minimize the vapor load in the distillation column. Enough sulfuric acid was added to the feed so that the vapor leaving the top of the column was at least 98% nitric acid. Live steam was added to the base of the column to provide the heat for the column and the stripping vapor required to... 

Fig. 4. Flow diagram of the Ruhrchemie/Rhone-Poulenc process (137) 1, continuous-flow, stirred tank reactor 2, phase separator 3, stripping column 4, distillation column 5, heat exchanger 6, falling film evaporator 7, liquid-vapor separator.

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