The main plant is situated in Casone in the borough of Scarlino (Province of Grosseto). It covers approximately 140 hectares of land that had previously, in the 1960’s, been agricultural land. The plant has an annual capacity of approximately 600,0000 tons.
The process of obtaining sulphuric acid using locally mined pyrite was abandoned many years ago, and today the plant achieves its production cycle using sulphur as its base; this is purchased in both liquid and solid form. The production cycle is composed of combustion whereby the sulphur is burned in the presence of air in order to produce sulphurous process gas. Sulphuric acid is produced at the Nuova Solmine plant using the ‘contact process’: sulphur dioxide (SO2) produced and by its catalytic conversion, sulphuric dioxide (SO3) is generated. The SO3 gaseous mix is then cooled in a water exchanger and sent to the absorption towers. The sulphuric acid molecule H2SO4 is a result of the process of absorption of SO3 in water H2O.
SO3 + H2O H2SO4
This process is distinguished for the two aspects that make it particularly ‘virtuous’ from a point of view of both energy and environment: 1) the absence of waste or of intermediate stages in production (as opposed to the original procedure of baking the pyrite) and 2) the significant heat production generated by the process that allows a large quantity of energy to be produced with zero emission of greenhouse gases, given that sulphur combustion and its successive oxidation do not produce any carbon dioxide gas emission (greenhouse gas).
The production plant is classified as a ‘basic inorganic chemistry’ industrial process and falls within the category of process plants with a high accident risk (D.Lgs 334/99) because of stocking the product ‘fuming sulphuric acid – oleum that contains free SO3.
Nuova Solmine constantly maintains and updates its structures and machineries, keeping its plants at their best in order to guarantee efficiency and environment care.
DEMINERALISED WATER, STEAM AND ELECTRIC ENERGY
The demineralised water production plant is fed with river and well water that have first been sterilised, filtered and softened. After this treatment the waters flow into three lines of reverse osmosis.
This treated water supplies the production plants for the production of steam; a minor part is used to produce a special sulphuric acid, so-called ‘accumulator acid’.
The Serravalle Scrivia plant produces demineralised water exclusively for internal use while the Scarlino plant,( with a production capacity of 100m3/h, and stocking capacity of 1200m3,) uses a part of the water to produce steam. The remaining water is sold to neighbouring industries for use both internally and for bottling. Steam is produced at the Scarlino plant from the heat produced from the combustion of sulphur and methane.
The energy generated by the sulphuric acid exothermic process is used to produce electric energy.
The energy thus produced (6000V) is used in the plant or transformed (130KV) in the sub-station so that it can be put into the national grid to which the power plant is connected. Approximately half of the normal production of energy is sold and the remaining part is for consumption by the Nuova Solmine plant.