Glycerin stream block

(f)   Ion Exchange:

•  15 – 20% glycerin along with impurities from the hydrolyser goes for ion exchange. •  Here salt and colour is removed from glycerin.

(g)   Triple effect evaporator:

•  The product stream from ion exchanger is sent to triple effect evaporator. •  The glycerin solution is concentrated in evaporator.

(h)   Vacuum still:

•  The glycerin obtained from vacuum still is called yellow glycerin. It is used for industrial use. •  The steam produced from evaporator is used in vacuum still to further concentrate the glycerin.

(i)  Mixer:

•  For removing color, yellow glycerin is treated with activated carbon in mixer.

(j)   Filter:

•  Activated carbon is separated from the solution. •  99% white glycerin is produced. The yield is 30 – 35kg per ton of soap produced.

30.3 Detergents

Detergents have better surface tension lowering action than soaps. Due to excessive foaming, it is unable to reduce organic content of sewage effluent. Biodegradation of detergent is an important environmental factor. Detergents react with hard water ions. Detergents are of four types - anionic, cationic, non- ionic and amphoteric. Most common type is anionic which is generally made up of sodium salts of an organic sulfate or sulfonate.

General method to make synthetic detergents: