Soap Saponification Section

Soap saponification section is a set of equipment that are used in the saponification process (the first stage in the soap making process). Saponification can be of two types -

• Batch type
• Continuous process type

Batch Method
Semi boiled saponification for obtaining medium quality soap is attained by simple mixing and heating in a crutcher (soap mixer) and is used for producing small (1 to 5 tonnes) batches household or laundry soap. Any impurities in the raw materials will be present in the final obtained soap and there is no wasted discharge to the drain.

Completely boiled saponification for producing high quality soap is done in kettles. This is the most common method of soap making and can be used to make laundry or toilet soap. The completely boiled soap is washed during the process to remove any glycerin or impurities. Batch size is usually 25 to 50 tonnes and 3 to 5 kettles are used in this process. The plant outputs are generally 1 to 5 tonnes per hour. The technique can be used to produce soap of international quality standards. Some wastes may require to be discharged to the drain if glycerin is not recovered from these wastes (called lye).

Continuous Process
Continuous saponification process is suitable for producing different grades of soap of different quality standards. This system is not suitable to manufacture soaps at the production rate of less than 50 tonnes of soap per day. The system can be designed to achieve soap production rates in excess of 200 tonnes per day.

In the continuous process technique, raw materials are accurately metered using a special pump to the saponification reactor. Following the reaction, the clean soap is separated from the by-product of the reaction (rich in glycerin). The separation occurs in two main stages, at first in the rotating disk column, and secondly through centrifuge separation. The clean soap can be pumped to the storage, or directly to the vacuum spray drying section.

Because of the high value of glycerin, the plants generally come with a glycerin recovery section to purify and retain the glycerin

Saponification Pan
Saponification pan is a hemispherical vessel, the bottom of which is made of thick steel plates. The bottom of the pan is heated using firewood or by means of diesel burners. The boiling mixture is stirred with the help of crutches and due to the direct heating, the soap mixture requires to be continuously stirred for homogenous mixing. Boiling is carried out till the complete neutralization is achieved, after which the soap is taken to drying section for further process.

It is important to take care to ensure that soap does not stick to the bottom as if it sticks it may get burnt. The technique is a manual process and needs continuous stirring.

Saponification Vessel
Saponification vessel is a cylindrical vessel with a cone shaped bottom. At the inner side, the vessel has circular coils that have holes and steam is injected from these holes. In the case, soap is obtained by full boiled method, the layers of soap and lye separates out. When soap is obtained by full boiled process layers of soap and spent lye separates out. The spent lye goes to the bottom and the soap to the top. The spent lye is drained from the valve at the bottom of vessel and as the lye is drained, soap begins coming out of the valve. As the heating of soap mixture is done with steam there is no chance of soap getting burned. The vessel can be used to obtain quality soap.

Continuous Vacuum Spray Drying Process
In the continuous vacuum spray drying process technique, the clear soap from saponification section is taken to the soap feed tank after being filtered. After this the soap is sprayed into the spray drier where the desired vacuum can be maintained using a vacuum system. As the soap is flashed from the soap nozzles into the vacuum chamber, vacuum is removed. The soap sticking to the spray drier walls can be scrapped with the help of a scrapper that can be adjusted. The dried soap falls into the duplex vacuum plodder and the duplex soap descends from the top noodle plodder. Vacuum is sustained within the chamber that connects the plodders and the soap comes out of the plodder in the bar form. These bars are then cut into desired forms and stamped.

Good laundry bar soap can be obtained using the continuous vacuum drying process. For toilet soap, a duplex plodder fitted with noodle plate is used. As the soap comes out rotating knives cuts the soap noodles. The soap noodles produced and obtained from the stage are further finished to get high quality toilet soap.