Neutralisation loop reactor

For the manufacturer of 70% AD SLES and 70-75% AD coco-PAS, rheological changes that take place during the neutralisation stage start-up can result in very high apparent viscosities (K is about 100 Ns/m or 100 000 cP) and thus hi pressure drops in the neutralisation loop reactor. This has implications for the mechanical design of pumps, mixers, pipe sizing and equipment lay-out. 

Much of the colour produced during sulphonation is contained in the spent acid. The upper layer in the separator, which contains around 90% alkylbenzene sulphonic acid (the remainder being primarily dissolved sulphuric acid) is also removed from the separator and neutralised with sodium hydroxide solution or with sodium carbonate solution to yield the active paste. When sodium hydroxide is used a considerable amount of heat must be removed. This is done in the third loop reactor of this process, the neutralisation heat exchanger (also known as the neutraliser). If sodium carbonate solution is used, the neutralisation is much less exothermic and no heat exchanger is needed at this stage. 

For Ballestra plants running a wider range of products like alkylbenzenes, alcohols and ethoxylated alcohols, the double-step neutralisation system is recommended. This system allows neutralisation to occur in two steps 95% of the neutralisation occurs in the first loop reactor, always working under strong caustic conditions and neutralisation is cpmpleted in the compact intense mixer second step, in series with the first. This procedure may be followed for LAB-SA neutralisation. 

Standard loop neutralisers use caustic soda solution as neutralising agent. Other agents such as aqueous or s ydrous ammonia, caustic potash, or ethanolamine can also be used. In addition liquid additives such as ethyl alcohol and urea solutions will blend with the paste in the loop reactors. 

Various loop-type reactors, consisting of a circulation pump, homogeniser (where the acid is introduced in Ae circulating alkaline paste) and heat exchanger, are used for the complex neutralisation step. 

The loop circulating reactor outlined above expresses in chemical engineering terms, the characteristics of a perfect mixer. This type of reactor presents the following characteristics required for the neutralisation step ... 

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