Abstract:
The global soap market was around USD 43 billion in 2023 and is expected to grow to
USD 67 billion by 2033. Soap prices have been increasing over the years for many
reasons, and the current economic crisis in Sri Lanka has also worsened the situation. In
this regard, the current project aims to develop a user-friendly semi-automated batch
soap manufacturing unit for domestic-scale users to produce soap bars at a lower cost.
This also helps in decentralizing the soap manufacturing process. Mixing, heating and
moulding are the basic unit operations involved in the unit. A stainless-steel container,
which can stand at a higher temperature, was used as the main reactor. Four heat
elements (PTC heaters) were attached to the main reactor for heating purposes. A
stainless-steel agitator was used to mix the reactants. A motor (RS 775) was used to
agitate the reactants, which can speed up to 1200 rpm. Load cells (HX 711) were used
to weigh the reactants and products in the main reactor. Small storage tanks were used
to store all the reactants. NaCl, H3PO4, fragrance and colouring agents were introduced
to the reactor using solenoid valves, while mini pump motors (solar pump) were used to
pump H2O and coconut oil to the reactor. A screwdriver was used to introduce NaOH
powder to the reactor. A brush DC motor (DC 775) was used to rotate the screwdriver.
All the instruments were calibrated prior to use in the unit. The entire setup was
powered by SMPS unit (12V,10A). Arduino boards (UNO and Nano), relay modules,
display models, I2C bus modules, keypads, and thermocouples were used to semi
automate the operations of the unit. Most of the time, due to the presence of impurities
as well as machinery and human errors, the actual mixing ratios of the reactants differ
from the stoichiometric ratios. In this experiment, after a few trial-and-error studies, it
was found that mixing 50 mL of coconut oil with 15 mL of H2O and 15 g of NaOH is
the best combination to produce the soap bar. These promising results encourage the
commercialization of the unit. Further studies are planned to improve the quality of the
produced soap from the setup.
