Wash tower

In general, the sulfolane extraction unit consists of four basic parts extractor, extractive stripper, extract recovery column, and water—wash tower. The hydrocarbon feed is first contacted with sulfolane in the extractor, where the aromatics and some light nonaromatics dissolve in the sulfolane. The rich solvent then passes to the extractive stripper where the light nonaromatics are stripped. The bottom stream, which consists of sulfolane and aromatic components, and which at this point is essentiaHy free of nonaromatics, enters the recovery column where the aromatics are removed. The sulfolane is returned to the extractor. The non aromatic raffinate obtained initially from the extractor is contacted with water in the wash tower to remove dissolved sulfolane, which is subsequently recovered in the extract recovery column. Benzene and toluene recoveries in the process are routinely greater than 99%, and xylene recoveries exceed 95%. 

In both cases, the carbonate ion concentration increases and eventually equiUbrates in the system, releasing carbon dioxide in the stripping column and thereby reducing product purity. Hence, a small caustic wash tower is employed to remove any carbon dioxide that is Hberated in the stripper. 

Berieselungs-blitte, /. (Cdlulose) wash box, -klihler, m, trickle cooler, spray cooler, -turm. m. wash tower scrubbing tower, scrub-... 

Riesel-turm, m. trickling tower, spray tower, washing tower, -wasser, n. trickling water irrigation water. 

FIG. 21 Process for manufacture of tetrapropylene benzene. BC, benzene column D, dryer IC, intermediate column R, reactor RR, rerun column ST, settling tank W, wash tower. 

A liquid/liquid separation of product and catalyst is done in separate vessels after the reaction has taken place. The reaction mixture is sent to a gas separator and from there to a counter current washing tower (a simple phase separator is shown in the figure) in which the effluent is treated with aqueous Na2C03. The acidic HCo(CO)4 is transformed into the water soluble conjugate base NaCo(CO)4. The product is scrubbed with water to remove the traces of base. The oxo-crude goes to the distillation unit. 

As one of the first processes, the decaffeination of green coffee beans was applied on the industrial scale [6]. Zosel proposed three possibilities for the decaffeination. In the first, the moistened green coffee beans are extracted in a pressure vessel at 160 to 220 bar. The caffeine diffuses from the beans into the C02, which is fed into the washing-tower [8],... 

In the washing-tower the caffeine is washed out from the CO2 with demineralized water at 70 to 90°C. After 8 to 12 hours, depending on the coffee raw material, all of the caffeine is in the washing water, which is degassed and the caffeine recovered by distillation of the washing water. Thereby, the caffeine concentration in the beans is reduced from the initial 0.9 to 1.8% down to 0.08%. For the decaffeination of one kg raw coffee about 3 to 5 liter washing water is necessary. 

Description Hydrocarbon feed is pumped to the liquid-liquid extraction column (1) where the aromatics are dissolved selectively in the sulfolane water-based solvent and separated from the insoluble non-aromatics (paraffins, olefins and naphthenes). The non-aromatic raffinate phase exits at the top of the column and is sent to the wash tower (2). The wash tower recovers dissolved and entrained sulfolane by water extraction and the raffinate is sent to storage. Water containing sulfolane is sent to the water stripper. 

Scrubbers for tar removal have a large disadvantage, which is the tar condensate and scrubber water. Several institutes have experiences with scrubbers (mostly wash towers and Venturi scrubbers), however, hardly any data can be found in open literature. Wash towers only remove part of the tars (typically 40%) whereas Venturi scrubbers can have much higher efficiencies of 80% or higher. 

The large-scale plants which have so far been realized for the decaffeination of tea and coffee and for the extraction of hops and spices are now established. These are in general one-stage plants in which the extract is separated by adsorption on activated carbon or by pressure reduction. The tendency now is to replace adsorption by absorption in washing towers. 

The bottom of this tower, a mixture of C4 and ether produced in the second stage, is recycled to the first column while the overhead stream (C4 and ethanol) is sent to the alcohol extraction tower. In this column, ethanol is removed by counter-current washing with alcohol-free water while C4 raffinate, isobutene-free, is sent to battery limits. The stream water/ethanol is finally sentto an additional fractionation tower where the ethanol-free water, recovered as bottom stream, is recycled to the washing tower, and the overhead ethanol/water azeotropic stream is recycled to the reaction stages. 

Coffee extract solution from reservoir is pumped to apacked column filled with, for example, Rashig rings, stainless steel spirals, etc. The coffee liquor flows downward over the packing and is contacted by upward flowing supercritical CO2. Caffeine is extracted from the coffee liquor which exits at the bottom of the column, and the caffeine-laden CO2 stream leaves the extraction column and enters the water wash tower (which is also a packed column) where the CO2 is stripped of its caffeine. The caffeine-free CO2 is recirculated to the coffee liquor extraction tower, and the caffeine-water solution is evaporated and the caffeine recovered. 

Sight glasses Caustic-wash-tower top-section spray arrestor Submerged glandless circulating pump... 

The reaction effluent, mainly consisting of isobutylene, methanol and unconverted MTBE, is sent to a counter-current washing tower (2) to separate out methanol, and then to two fractionation towers to separate isobutylene from unconverted MTBE, which is recycled to the reactor (3) and from light compounds (4). The produced isobutylene has a product purity of 99.9-" wt%. 

The methanol/water solution leaving the washing tower is fed to the alcohol recovery section (5), where high-quality methanol is recovered. 

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