Acknowledgement


The author of this Plant Design Project express their grateful thanks and immense gratitude to Dr. Iqbal Mahmud, Professor of Chemical Engineering, Bangladesh University of Engineering and Technology(BUET),Dhaka-Bangladesh for his paternalistic guidance, advice and tolerance.

We also grateful for his helpful suggestions throgh the design project and assistance with our work. Working under his supervision was pleasant and rewarding.
The authers of this project are also indebted to Mr. Kamran Bakiar, Technical Director of Lever Brothers Bangladesh Ltd. for giving us permissinon to visit his plant. This visit leds us towards final completion of this plant design project.

Heartful thanks are also expressed to Mr. Rashed Iqbal, Pan room manager of Lever Brothers Bangladesh Ltd. for providing us necessary infromation regarding Soap Manufacturing Plant. The authors are also grateful to the management of Kohinor Cosmetics and Toileteries for giving us permission to visit their Soap Manufacturing Plant. Finally appreciation is also expressed to our friends for typing this project and VISIO Technical Software Co. for usning their software. 

TABLE OF CONTENTS

1.     Definition of the project

2.  Selection of the process and process description

3.     Design basis

4.     Process block diagram

5.     Process flow diagram

6.     Material balance

7.     Energy balance

8.     Equipment list

9.     Sizing of the equipment(PDF)

10. Mechanical design of major equipment

11. Piping and instrumentation diagram

12. Plot plane and equipment layout

13. Estimation of total capital investment and production cost(PDF)

14. Economic analysis (PDF)

15. References

DEFINITION OF THE PROCESS PLANT

A Soap manufacturing plant is to be set up at Kalurghat heavy industrial area in Chittagong, having a production Capacity of 40 tons of 86% Soap (Salt of higher fatty acid of sodium or potassium) on a summer day ( dry bulb temp. 35^oC & wet bulb temp.25^oC) including all off sites, auxiliaries, utilities and supporting facilities using Tallow and palm stearin as feed stock.

There will be 330 stream days a year and the corresponding production of Toilet Soap will be 13200 metric tons for the plant.

 The plant will also produce almost 3.6 metric tons of Glycerin per day which is essential ingredients  in pharmaceutical industries all over the world.

The composition of the product:

The composition of the raw materials is as follows:

Selection of the process and process description :                        Top

There are three major types of Saponification  processes for production of Soap from fatty acid of higher molecular weight.

The Saponification processes are  as follows:

1.     Full boiled Kettle process,

2.     Cold process saponification,

3.     Semi boiled process.

1.     Full boiled Kettle process:

In this process pan are circular or square in cross section, but taper to cone at the bottom and are generally lagged to conserve heat. Open steam coils in the cone section supply heat and agitation. Closed steam coils may also be present

 to supply heat without adding condensed steam. The bottom layer in any stages   of the boiling procedure is removed from pipelines. Similarly, the upper layer is removed through an adjustable swing pipe located part way down the kettle. 

This process supply completely saponified neutral soap containing ca 30 wt% water, a composition which, when hot, can be pumped to various finishing operations. The soap is washed free of soluble colored and odorous impurities and in subsequent processes is separated  as far as possible from Glycerol.            

2.     Cold process saponification:

This is the simplest of the batch saponification processes and requires a minumum of equipment. Since neither lyes nor nigre are separated, the glycol and impurities from the fats remain in the soap. The fat charge is simply melted in a vessel equipped with a mechanical stirrer, and the calculated amount of caustic soda solution is added with vigorous stirring. After emulsification and thickening, the mass is poured into frames where saponification is completed during cooling and saponification . The side of the frame are then removed, and the soap slab is cut into bars.

3.     Semi boiled process:

This is similar to the cold process, but a higher  temperature is used to speed saponification and permit adjustment of the alkali content before framing. The fat charge and alkali (which may be caustic potash for soft soap) are thoroughly mixed at 70 – 80^oC until the soap becomes smooth. Just prior to framing the soap may be perfumed and small amounts of sodium silicate or other builders may be added to laundry soap and free sand pumices etc. to abrasive hard soap.

From the above discussion it is clear that the Full boiled kettle process is more feasible then other process for commercial production of Toilet Soap. Much of the world’s  soap production still begins in open steel kettle or pans capable of processing batches of 1 – 2000 Kg soap.

So full boiled kettle process with some adopted modification has been chosen for Toilet Soap manufacturing. 

                                Process description:

Introduction:  

The plant has the capacity of 40 metric tons per day of  Toilet Soap ( as 86% Na- Soap) by a no. of batch operations based on saponification process.
The process consists of following sections:

1.     Crude Soap manufacturing section – PAN room,

2.     Glycerin recovery and purification section – which is a by-product of Soap manufacturing.

3.     Soap finishing and packing section.

Description:

►► Crude soap production section:

i.                    Oil weighting, blending and Bleaching:

First oil is weighted and blended in an open tank prior to bleaching. Vacuum bleaching is done here at around 5 mm HgP Vacuum. Moisture is freed here form oil so that oxidation can not be happened here in saponification operation. Because oxide will cause pyrolysis of the oil. Activated Earth is added here as a bleaching agent.

ii.                 Saponification :  

Main feed stock Tallow, palm stearin is charged in a Kettle type pan and Caustic soda is also added with is for saponification reaction to take place.

It is extremely slow process so heat is supplied here in the form of saturated steam at about 3 Bar (gauge) to boiling up the reactants involved in the PAN eractor (Kettle). Boiling time is about one to three Hrs depending up on the load

Crude Soap obtained from here is about 54% TFM

    iii     Washing (DPU):

All materials from the kettle is charged inclined open coutainer where brine solution and niger is flown counter clock wise with respect to product from Saponifier. This section separates Soap from the mixture and Glycerin is separated here.

iv.               Batch fitting and settling :

Crude Soap and Niger solution  thus obtained  from washing tank is charged into a batch fitting and settling tank. Here three additives are added:

a.     Caustic soda,

b.    Water,

c.     Brine solution.

Electrolytic parts are taken by electrolytic additives and soap is separated  and floated on the Niger solution due to density difference.

v.                 Soap base cleansing:

This  is actually a settling tank for soap. Soap is settled according to three layers:

a.     Aerated Soap ( 1 – 1 ½  feet thick layer  ) ,

b.    Neat Soap ( About 8 feet thick layer),

c.     High electrolytic Soap ( 1 – 1 ½  feet thick layer ),

      Remainder section of the tank consists of settled Niger. Time required is about           

      36 to 38 hrs for each batch operation.

       However Neat soap is our keen interest for further treatment.

vi.               Soap Drying :  

For drying purpose Soap is first heated in heat exchangers . Tow 1 – 2 exchanger is connected in series. Where Sat. steam is used as heating medium. Here Soap is heated up to 140^oC   for final Drying section.

Exit from exchanger in charged into a Screw type dryer with a nozzle of about 32 MM size. Soap is flown from top to bottom and is scraped by a scraper inclined about 270^o angle. Latent heat of vaporization is supplied by hot Soap (140^oC) and dried soap Soap thus obtained is about 40^oC.

vii            Stock pan and SFD:

Dried Soap is than charged batch wise in  mixer where various additives and odouring  substances are added in various proportions  to produce finished Soap. 

►► Glycerin Production section:

i           First treatment :

Neutral lye  after lye neutralization is charged into first treatment tank where three additives are added for its treatment:

a.      FeCl_3,

b.     HCl,

c.     Polyelectrolyte.

FeCl₃ is added to convert soap into ferric Soap,

HCl is added to neutralize the basic solution,

Polyelectrolyte is added for coagulation of ferric soap to remove it from the Glycerin part.

ii.          Filter press:

Plate and frame type filter press is used consisting of 32 plates. It removes sludge from glycerin solution.

iii.                Second treatment:

Caustic soda is added to convert FeCl₃ into Fe(OH)₃ to precipitate out from the glycerin solution.

iv.               Filter press:

Plate and frame type filter press is used consisting of 32 plates. It removes sludge from glycerin solution.

v.                 Double effect Evaporator:

A double effect evaporator is used to concentrate Glycerin solution from 12% to 30% (w/w). Natural circulation vertical tube calendria type evaporator is used for evaporation. 25 inch vacuum is applied in the last stage to boiling up solution at low temperature. Barometric condenser is used for condensation of vapor and steam ejector  is used to create vacuum at  desired level.  

vi          Finisher:

      An independent single effect evaporator is used after double effect evaporator      to concentrate Glycerin from 30% to 84% . Vacuum is applied here is about 28       inch HgP and mechanism is the same as mentioned above.

      vii        Still:

84% saturated Glycerin solution is fed into a packed bed distillation column. Here vacuum is applied at about 5 mm HgP(abs). At bottom after reboiler we get 95% pure Glycerin at about 154^oC. At top water (98.8%) is removed after condensation by a series of condenser consists of air cooled and batometric condenser .

     vii        Weighting, Drum Filling and ware housing:

About 95 to 98% Glycerin thus obtained is drummed in containers to supply in the near by pharmaceutical industries.

Design basis                                   Top

Design basis is the conditions in existence with which to design the project. These are the boundary conditions for the project. The following items should be included in design basis:

1.Geological data:

a) Load bearing capacity of the soil: 107 ton/m²

           Soil type:              normal

          Win content:      medium

 d) Process Chemicals

Component:

  4.     Raw material:

                                 Component                         Wt%

                                       Palm Sterene                                    61.54

                                       Coconut Oil                                      15.38

EQUIPMENT LIST:                                                                                Top