PROJECT DESCRIPTION
BACKGROUND
The precipitated silica production process generates as by-product a high conductivity salt stream that is poured into natural channels after passing through treatment plants. The main salt generated in the process is sodium sulphate (Na2SO4) that must be removed, along with other components such as colloidal silica, by washing which generates a large water consumption. For each ton of precipitated silica produced, 0.75 tons of Na2SO4 are obtained as a by-product and this generates a discharge of 40 m3 (30 g/l). European production of precipitated silica in 2018 reached 720 000 tons (2 500 000 tons worldwide) with big growth expectations during the coming years. It is estimated that this industry is spilling about 500 000 tons of sodium sulphate into European natural channels. Spills from the precipitated silica industry (as well as other industrial and domestic spills) contribute to an increase in the natural salinisation of rivers. The excess salinity is a factor that conditions the survival of natural organisms and communities, the biodiversity, and the ecological balance of the entire ecosystem. This problem is especially important in summer seasons where river flows are minimum, and the salinity concentration can reach naturally maximum recommended parameters (250 ppm-sulphate ion). These saline discharges also generate problems in water treatment and purification facilities, corroding their equipment and slowing down the digestive processes, generating high economic costs for administrations.
OBJECTIVES
LIFE ZEROSILIBRINE is a pilot project to demonstrate the application of an innovate technology for the treatment of precipitated silica wastes, an environmental challenge with no feasible current solution. This project has been designed by IQE to upscale small-scale results (2m3/h) to a pre-industrial scale (40m3/h) and validate it before the construction of a full industrial installation (120m3/h) after the LIFE project. The implementation of a Circular Economy strategy in precipitated silica sector help mitigate the environmental impact caused by the discharge of the by-product generated (sodium sulphate). This will be achieved by recovering 100% of the water for the production process itself (reduction of water collection and reuse of the discharge water as process water) and recovering sodium sulphate as a high-purity product with commercial value.
The specific objectives are the following:
- Demonstration of the technical feasibility of the reverse osmosis stage by means of the 40m3/h installation recovering 80% volume of the production process effluent of precipitated silica reusing the water recovered in the same production process;
- Validation of the operating costs of the reverse osmosis process and validation of the economic feasibility of the manufacture of high purity anhydrous sodium sulphate;
- Validation and optimisation of the evaporation-crystallisation stage with a small prototype (1-2m3/h) from 80% to 100% of the discharge volume until obtaining a commercial anhydrous sodium sulphate;
- Study the anhydrous sodium sulphate by-product characteristics with primary sodium sulphate manufacturer;
- Study the potential technology replicability and transfer to other chemical processes and/or industrial sectors.
LIFE ZEROSILIBRINE will contribute to achieving the objectives of the EU Circular Economy Action Plan, Water Framework Directive, and the EU Chemicals Strategy for Sustainability.
RESULTS
Expected results:
- Construction and validation of a reverse osmosis pilot plant (40 m3/h) for concentrating the effluent from the precipitated silica production process (from 30 g/l to 120 g/l);
- Permeated water of 252 800 m3/year redirected to silica process as osmotised water;
- Concentrated effluent of 20 800 m3/year with 130 g/l concentration redirected to silica process;
- 400 ton/year of anhydrous sodium sulphate obtained through evaporation;
- 3 000 m3/year of osmosis water redirected to silica process;
