Marsina sodium silicate production technology operates by direct attack of silica sand with caustic soda, to produce sodium silicate solution, a raw material largely used as agglomerating agent in the manufacture of powder detergents.
Starting from silica sand with SiO2 content of minimum 98%, the plant allows to obtain a sodium silicate solution at 48°Bé density and ratio SiO2/Na2O in the range 1.6 ÷ 2.0.
The production process is based on batch-wise operations.
Standard plant capacity is 100 ton/day.
MAIN PLANT SECTIONS
Typical plant is composed of the following main sections:
- Raw materials dosing
Complementary units/sections available are the following:
- Caustic soda dissolving unit
- Water softening system
- Liquid raw materials storage
- Finished product storage
- Utilities production units
Sodium silicate solution is obtained by chemical attack of silica sand with caustic soda through a two-steps reaction path, as per following reactions:
2NaOH → Na2O + H2O
Na2O + nSiO2 → Na2O*nSiO2 n = 1.6 ÷ 2.0
Caustic soda fed to the reactors undergoes a dissociation generating sodium oxide which, in its turn, reacts with silica contained in the sand so producing sodium silicate.
The reaction process, occurring in presence of 12 bar pressure saturated steam, is carried out batch-wise inside stirred reactors, autoclaves type, where silica sand, caustic soda solution at 50% and water are charged in appropriate quantities.
The total exothermicity of the reaction path is 135 kcal/kg of reacted NaOH (100%).
At 48°Bé density, the finished sodium silicate solution contains 41.8% of dry material, the remaining being water.
The plant includes the following sections:
Raw materials dosing
Solid and liquid raw materials dosing is carried out by means of reactors weighing systems.
Opportunely sieved silica sand is charged into the reactors by means of screw conveyors while caustic soda solution and water are fed by pipes, carefully respecting the quantities required by the batch.
Two autoclaves type reactors, working in parallel configuration, are generally foreseen.
Operating conditions maintained in the reactors during the 8 hours cycle are: pressure 11- 12 bar and temperature 188-192°C.
Sodium silicate solution leaving the reactors at high temperature is cooled down to a temperature suitable for the following treatment of filtration.
Filtration of sodium silicate solution
Sodium silicate solution is carefully filtered before its final storage.
Filter-press type filter is used.
The plant is fully automatic to minimize number of necessary operators.All operations are controlled and regulated by advanced PLC system, guiding the plant to the achievement of product specifications.