With the trade development, and the growth of industries, has become increasingly pounding the need for an accurate and responsible control of pollution, in the best respect for nature. In this regard, the analysis of the substances released into the atmosphere as a result of production cycles is crucial both to reduce the environmental impact and to respect the limits set by the regulations. In this context, solvents contained in the gases are filtered and recovered, in order to be able to be reused in production processes without harming the environment and while saving money.
The operation of a solvent recovery plant is outlined in four phases:
- The solvent is subtracted from the gas through the help of active carbons. The exhaust gases from the industrial process is first mechanically filtered, and further pushed towards the activated carbon cells. The pretreatment, and the following filtering, are intended to prevent the pollutants from being discharged directly into the atmosphere;
- The substance is then desorbed using steam. Once the filter reaches a state of saturation, indicated by the fact that the purifying capacity falls below a certain level, then starts the regeneration or the filter cleaning through steam. The steam then absorbs solvents from the carbons, and comes out soaked;
- The solvent is recovered from water through drying of the fluid. At this point, then the gas is condensed by means of a heat exchanger, and the liquid is brought to the distiller;
- The substance is distilled. The distillation begins with a decanter, where the liquid is decanted: this results in two substances, a heavier one (wet solvent), and a more liquid one (water impregnated with the solvent). The first is dried through a drying column and is then transported to a distiller where it is purified from imperfections and reinserted in the production cycle, the second will be sent to a reboiler where by evaporation at low temperature and subsequent condensation, the substance will be recycled.
More in detail, the active carbon solvent recovery plant is mainly formed by:
- Collection and conveying air network;
- Gases cooling and filtration system;
- Suction and expulsion fans;
- Activated Carbon Adsorbers;
- Nitrogen system for the regeneration of activated carbon;
- Row acetate condensation system at low temperature;
- Fridge group, water tower station and pumping system;
- Distillation columns to produce pure acetate from the raw one.
The main advantages of this system are:
- High removal efficiency and acetate recovery
- Low energy consumption and reactive
- Constant performance, unaffected by the gas
- Removal of odorous substances
- High quality of the recovered solvent
In this plant, the hazardous substances are made up essentially by the retrieved ethyl acetate based solvent contained in certain circuits of the structure, in particular:
- Condenser and raw recovery
- Crude tank service
- Distillation columns
- High-boiling tanks service, azeotropes, pure
A general ground plant ensures equipotentiality of the masses and a defense from lightning.