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The plastic film coating operations of a Chinese manufacturing company located in Jiaozuo City in Henan Province uses and emits a substantial amount of organic solvents to the atmosphere. The amount of solvents in the air emissions exceed 600 kg per hour of solvents consisting of Toluene, Methyl Ethyl Ketone (MEK) and Isopropanol (IPA). The combined value of these solvents is several million dollars per year.
In late 2008, the company commissioned a project to capture and recover their solvents for re-use in the plant. The system/process consists of an activated carbon adsorption system to remove the solvents, onsite regeneration of the carbon adsorbers using saturated steam and subsequent cooling and condensation of the solvent water mixture.
MEGTEC was chosen to design and supply a distillation system to recover two (2) separate purified and dehydrated product streams: 1) Toluene and 2) A blend of MEK and IPA while producing a clean wastewater stream.
Process Description
The condensate from steam regeneration of the activated carbon beds, consisting of water and solvent is sent to a decanter. In the decanter this mixture separates into a solvent layer and a water layer.
The solvent layer is first treated in a pretreatment column where an alkaline solution is added to minimize any color in the recovered solvent blend. It is then sent to a dehydration column where the water is carried to the top with some solvents while the dehydrated solvent blend flows to the bottom of the column. The solvent/water mixture from the column overhead is condensed and flows back to the decanter.
The dehydrated solvent mixture from the decanter is then sent to a separation column where a lower boiling top product and a bottom product are generated. Each of the two streams are condensed and sent to storage tanks for recycle.
The water layer from the decanter is sent to the stripping column where the overhead is the low boiling mixture of solvents and water which is condensed and sent back to the decanter. The bottoms from the column is water with less the 500 parts per million (ppm) of solvents.
The stripping and dehydration columns utilize random packing while the separation column is designed with valve trays. All three columns use external re-boilers and indirect steam to provide heat to the columns.
Project Execution
The system was designed by engineers located at MEGTEC Solvent Recovery Division offices in Vero Beach, FL and Columbus, Ohio.
The three (3) distillation columns and other process tanks were fabricated near Shanghai, China. Local supervision for the fabrication was provided by personnel from MEGTEC’s Shanghai, China facilities.
The pumps are procured from Chinese manufacturers and heat exchangers procured in the U.S and shipped to the plant site.
The PLC-based control panel was designed, assembled and tested in the U.S and shipped to the plant site.
Other components e.g. piping valves and instruments are all designed by MEGTEC and procured by the site general contractor. The contractor is also responsible for installing the system at the site based on drawings prepared by MEGTEC.
MEGTEC Distillation Systems
MEGTEC Systems, Inc. Solvent Recovery Division specializes in the design and supply of process equipment used to remove and recover volatile organic solvents (VOCs) from air and water emissions using adsorption, evaporation and distillation technologies.
MEGTEC distillation systems are widely used in the chemical and pharmaceutical industries to separate and recover solvents from solvent mixtures and solvent contaminated wastewater.
For more information about MEGTEC Distillation Systems, contact Paul Sengupta at 772-567-1320 or email info@megtec.com.
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