Caustic-wash treating

The solvent is 28 CC-olefins recycled from the fractionation section. Effluent from the reactors includes product a-olefins, unreacted ethylene, aluminum alkyls of the same carbon number distribution as the product olefins, and polymer. The effluent is flashed to remove ethylene, filtered to remove polyethylene, and treated to reduce the aluminum alkyls in the stream. In the original plant operation, these aluminum alkyls were not removed, resulting in the formation of paraffins (- 1.4%) when the reactor effluent was treated with caustic to kill the catalyst. In the new plant, however, it is likely that these aluminum alkyls are transalkylated with ethylene by adding a catalyst such as 60 ppm of a nickel compound, eg, nickel octanoate (6). The new plant contains a caustic wash section and the product olefins still contain some paraffins ( 0.5%). After treatment with caustic, cmde olefins are sent to a water wash to remove sodium and aluminum salts. 

When both HjS and mercaptans are to be removed in the light ends treating plant, the amine scrubbing tower precedes the caustic washing step. If the order were reversed, the large quantity of HjS present would "fix" the caustic. Also, the caustic will act to remove any final traces of HjS when it follows the scrubbing tower. 

Several processes use the principle of an alkali (caustic) wash, which is a process in which distillate is treated with sodium hydroxide to remove acidic contaminants... 

Isomerization processes produce sour water and caustic wastewater. The ether manufacturing process utilizes a water wash to extract methanol or ethanol from the reactor effluent stream. After the alcohol is separated, this water is recycled back to the system and is not released. In those cases where chloride catalyst activation agents are added, a caustic wash is used to neutralize any entrained hydrogen chloride. This process generates a caustic wash water that must be treated before being released. This process also produces a calcium chloride neutralization sludge that must be disposed of off-site. 

Removal of the objectionable odors due to the presence of H2S and mercaptans is the objective of the fuel sweetening process. Several methods can be utilized to remove these undesirable compounds including caustic washing, copper chloride sweetening, sulfuric acid treating, Merox processing, and hydrotreating. These methods will be discussed below. 

Caustic wash the process of treating a product with a solution of caustic soda to remove minor impurities often used in reference to the solution itself. 

Sulfur compounds such as alkyl and aryl thiols are treated with concentrated alkaline solutions in a process known as sweetening and cresols and xylenols are recovered from spent caustic washes, producing sodium cresolates/ xylenolates. 

If the naphthalene is to be used in processes involving hydrogenation over nickel catalysts the hot pressed or purified" naphthalene is subjected to further treatment. Treatment with sulfuric acid followed by washing removes some of the impurities that are still present. A subsequent caustic soda treat followed by vacuum or steam distillation results in the production of refined naphthalene with a melting point of 79° to 79.8° C. (melting point of pure naphthalene 80° C.). For the removal of... 

The traditional method of manufacturing is by a separation method (like most traditional methods) with a solvent extracted and dewaxed base oil as the usual feedstock. By reaction of either a paraffinic or a naphthenic base oil with oleum, aromatics are converted to the corresponding sulfonic acids and separate out. This may require several mixing steps to complete reaction of all the aromatics. Paraffins and naphthenes are essentially unaffected by the acid treatment.7 After separation of the sulfonic acids, the remaining oil, now free of aromatics, is neutralized with caustic, washed with alcohol, and finally treated with bauxite or clay. Figure 11.1 provides a schematic for this type of process. 

As already described in the previous section, great care must be taken to properly treat all cumene recycle streams. This is typically done by caustic washing to neutralize and separate organic acids and phenol see especially [21]. 

Caustic Washing. A flowsheet of the type of Fig. 11.3 may be used, involving stagewise contacting. In the first extractor H2S is removed by a prewash of caustic, as outlined above. The next three stages are used for countercurrent extraction of the mercaptans from the gasoline with aqueous sodium hydroxide, and the treated gasoline is water-washed to remove... 

Mix valve pressure drop should be about 10 psi for good mixing. On our caustic wash facility, we had a static mixer. This meant no adjustment could be made. Usually, one should increase mix-valve pressure drop when inadequate treating is reported. 

A caustic wash is typically followed by a water wash. This will remove entrained caustic from the treated hydrocarbon. Also, water washing is commonly used to remove salt from crude oil. 

In early designs, the reaction heat typically was removed by cooling water. Crude dichloroethane was withdrawn from the reactor as a liquid, acid-washed to remove ferric chloride, then neutralized with dilute caustic, and purified by distillation. The material used for separation of the ferric chloride can be recycled up to a point, but a purge must be done. This creates waste streams contaminated with chlorinated hydrocarbons which must be treated prior to disposal. 

Caustic soda is removed from the carbonate—bicarbonate solution by treating with a slight excess of hard-burned quicklime (or slaked lime) at 85—90°C in a stirred reactor. The regenerated caustic soda is separated from the calcium carbonate precipitate (lime mud) by centrifuging or rotary vacuum filtration. The lime mud retains 30—35% Hquid and, to avoid loss of caustic soda, must be weU-washed on the filter or centrifuge. Finally, the recovered caustic solution is adjusted to the 10% level for recycle by the addition of 40% makeup caustic soda. 

More recendy, the molten caustic leaching (MCL) process developed by TRW, Inc. has received attention (28,31,32). This process is illustrated in Eigure 6. A coal is fed to a rotary kiln to convert both the mineral matter and the sulfur into water- or acid-soluble compounds. The coal cake discharged from the kiln is washed first with water and then with dilute sulfuric acid solution countercurrendy. The efduent is treated with lime to precipitate out calcium sulfate, iron hydroxide, and sodium—iron hydroxy sulfate. The MCL process can typically produce ultraclean coal having 0.4 to 0.7% sulfur, 0.1 to 0.65% ash, and 25.5 to 14.8 MJ/kg (6100—3500 kcal/kg) from a high sulfur, ie, 4 wt % sulfur and ca 11 wt % ash, coal. The moisture content of the product coal varies from 10 to 50%. 

To produce a moulding composition, aniline is first treated with hydrochloric acid to produce water-soluble aniline hydrochloride. The aniline hydrochloride solution is then run into a large wooden vat and formaldehyde solution is run in at a slow but uniform rate, the whole mix being subject to continuous agitation. Reaction occurs immediately to give a deep orange-red product. The resin is still a water-soluble material and so it is fed into a 10% caustic soda solution to react with the hydrochloride, thus releasing the resin as a creamy yellow slurry. The slurry is washed with a counter-current of fresh water, dried and ball-milled. 

About 250 ml of a reaction mixture obtained by the electrolytic reduction of nitrobenzene in sulfuric acid solution and containing about 23 grams of p-aminophenol by assay is neutralized while at a temperature of 60° to 65°C, to a pH of 4.5 with calcium carbonate. The calcium sulfate precipitate which forms is filtered off, the precipitate washed with hot water at about 65°C and the filtrate and wash water then combined. The solution is then extracted twice with 25 ml portions of benzene and the aqueous phase is treated with 0.5 part by weight, for each part of p-aminophenol present, of activated carbon and the latter filtered off. The activated carbon is regenerated by treatment with hot dilute caustic followed by a hot dilute acid wash, and reused a minimum of three times. 

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