High-tech plants designed to abate and then to recover the solvent content present in a stream, by means of activated carbon adsorption and regeneration cycles.
Steam solvents recovery plants Solvent recovery plants are units for the purification of the gaseous emissions containing VOC (Volatile Organic Compounds) which have a double function:
When applicable, this technology therefore has a significant advantage, as it is beneficial not only from an environmental standpoint but economical as well, with quick payback (even three years). Brofind’s long-standing experience in the sector allowed us to install solvent recovery plants in a variety of industrial fields (printing, flexible packaging, adhesive tape, chemical, etc.) with treatment potential ranging from 2,500 to 300,000 Nm3/h of air. Depending on the nature of the recovered solvents, there are two different types of plants according to the technique used to regenerate the activated carbon:
The solvent recovery plant with steam regeneration is suitable for solvents that do not dissolve in water as recovery is carried out by separation of the aqueous phase with the solvent. This technology is based on the following operating cycle: Pre-treatment and extraction The solvent laden air coming from the production cycle and extracted by the main fans, must first of all be filtered to eliminate any solids therein through the installation of a suitable filtering system. The flow rate of the air extracted from the plant is normally adjusted by inverters applied on the main fans, in turn managed by a pressure controller located upstream of the plant: this system allows for considerable energy-saving when the air flow rate is below the design value. A cooling unit then brings the air to a temperature suitable for adsorption, below 60°C, as this is more efficient at low temperatures. The temperature is only one of the parameters to be assessed, as special attention must also be paid to the moisture of the emission: over 60-70%, the amount of water adsorbed by the carbon increases exponentially, thereby reducing its efficiency and leading to malfunctions. Adsorption The polluted air flows in specific adsorbers in which an activated carbon fixed bed captures the solvent; the purified air can then be released into the atmosphere through the stack. Each plant is supplied with several adsorbers working in parallel. Each of them is kept in the adsorption phase as long as the outgoing TOC (Total Organic Carbon) concentration complies with the pre-established limit; when this value is reached, the saturated adsorber is placed in the regeneration phase (see below). Using an analyser to monitor TOC (Total Organic Carbon) concentration automatically optimises plant operation, activating regeneration only when the limit is reached at the stack; this way consumption can be reduced to a minimum according to the actual incoming solvent load.
Distillation For the plant to recover a mixture of solvents, a distillation section of the solvents might need to be installed to separate them from each other.
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