Distillation stripping tower

The fat oil is fed to a splitter or stripping tower, where the absorbed tight constituents are separated from the oil by distillation. Usually the lean oil is the same material as the heavier part of the absorber feed, so that the bottoms from the stripper are split into lean oil, which is recycled to the absorber, and a stabilized gasoline product, which is passed on to subsequent processing operations. 

Transition metal oxides or their combinations with metal oxides from the lower row 5 a elements were found to be effective catalysts for the oxidation of propene to acrolein. Examples of commercially used catalysts are supported CuO (used in the Shell process) and Bi203/Mo03 (used in the Sohio process). In both processes, the reaction is carried out at temperature and pressure ranges of 300-360°C and 1-2 atmospheres. In the Sohio process, a mixture of propylene, air, and steam is introduced to the reactor. The hot effluent is quenched to cool the product mixture and to remove the gases. Acrylic acid, a by-product from the oxidation reaction, is separated in a stripping tower where the acrolein-acetaldehyde mixture enters as an overhead stream. Acrolein is then separated from acetaldehyde in a solvent extraction tower. Finally, acrolein is distilled and the solvent recycled. 

Approximate design equations applicable only to the case of pure physical desorption are developed later in this section for both packed and tray stripping towers. A more rigorous approach using distillation concepts may be found in Sec. 13. A brief discussion of desorption with cnemical reaction is given in the subsection Absorption with Chemical Reaction. ... 

The oil then goes to a stripping tower in which it is heated, releasing the dissolved gases these gases are recompressed and sent to a distillation column in which the propane and propylene are separated. The propane stream is recycled back to join the feed to the reactor preheater. The product stream from the distillation column contains 98% propylene, and the recycle stream is 97% propane. The stripped oil is recycled to the absorption tower. 

A typical distillate recovery system consists of a scrub cooler located at some point in the deodorizer vacuum system. The deodorizer vapor effluent is stripped of about 95% of the condensable organic material by direct contact in the cooler. The circulating distillate is then cooled to remove the heat of condensation before being returned to the stripping tower. Several equipment companies offer design/equipment packages for this. 

Figure P5.17 Phenosolvan plant—only one stream shown. Key 1, Tar-oil separation (gravity) 2. Saturation tower 3. Phenol extractor 4. Butyl-acetate recovery tower 5. Butyl-acetate stripping tower 6. Ammonia stripping tower 7. Atmospheric distillation tower 8. Vacuum distillation tower 9. Separator drum 10. Butyl-acetate circulating drum.

Before presenting cost data for plates and packings in distillation, absorption, and stripping towers, the following example is presented to estimate the purchase cost of an adiabatic, homogeneous, gas-phase reactor. 

The aqueous solution obtained in the scrubber, containing 15—25% formaldehyde, was fed into stripping tower to remove volatiles aqueous formaldehyde was collected as a side-cut distillate. High-boiling components were pumped off from the bottom of the column. The resulting 35—40% aqueous solution of formaldehyde was purified from acids with ion exchange resins, whereas other impurities were purified by solvent extraction to match industrial standards. 

The HETP of a packed-tower section, valid for either distillation or dilute-gas absorption and stripping svstems in which constant molal overflow can be assumed and in which no chemical reactions occur, is related to the height of one overall gas-phase mass-transfer unit Hqc by the equation... 

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. 

Certain refinery wastewater streams are treated separately, prior to the wastewater treatment plant, to remove contaminants that would not easily be treated after mixing with other wastewater. One such waste stream is the sour water drained from distillation reflux drums. Sour water contains dissolved hydrogen sulfide and other organic sulfur compounds and ammonia which are stripped in a tower with gas or steam before being discharged to the wastewater treatment plant. 

Tower bottoms-ACN, butadiene, with some butenes and acetylenes - are fed to a recovery/stripping column. The hydrocarbons are taken overhead and then rerun to meet product specifications. The stripping column bottoms, (ACN) is then remrned near the top of the extractive distillation tower. A small slipstream goes to the ACN recovery tower, where solvent is also recovered from the water wash streams. 

Ls = Liquid flowrate do wm stripping section of distillation tower, lb mols/hr... 

Most packed towers are used for mass transfer operations such as absorption, distillation, and stripping however, there are other uses such as heat transfer quenching and entrainment knockout. 

The hot feed enters the fractionator, which normally contains 30-50 fractionation trays. Steam is introduced at the bottom of the fractionator to strip off light components. The efficiency of separation is a function of the number of theoretical plates of the fractionating tower and the reflux ratio. Reflux is provided by condensing part of the tower overhead vapors. Reflux ratio is the ratio of vapors condensing back to the still to vapors condensing out of the still (distillate). The higher the reflux ratio, the better the separation of the mixture. 

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. 

---