Chemical Forums
Specialty Chemistry Forums => Chemical Engineering Forum => Topic started by: ananya on March 19, 2006, 12:40:06 PM
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Benomyl is a fungicide powder. Dry solid benomyl fungicide is powdered in Jet mill where highiy compressed air from a compressor is sent to jet mill. Below is the process flow. Feed- pre blender-dump tank- jet mill-cyclone seperater-post blender- powdered product. The bottom product of the cyclone seperater which has some ungrinded particles goes to post blender and top product which is of fine powder with air is sent through air filter bags, powder is retained in filter and sent to packing. powder is very fine as it ground by jet mill than than other mehods of grinding. The main problem is the moisture content of the powder as it is powdered by air 0.5% where the permissible limit is 0.25%.Due to 0.5% moisture content the life time of powder is reduced from 3 years to 1 year. cost of drier is high and it is not advisible to dry the powder using drier. can the inlet air through the air compressor be made dry or is there any other way to control the moisture content.
Details:-
The compressor is reciprocating type.
Air to product ratio in Jet mill is 240 cfm @ 3 Kg/sq.cm of product per minute.
Feed quantity per hour to jet mill - 250 Kgs.
During milling the air pressure in jet mill is 3 Kg/square.cm
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You obviously identified the solution in your problem statement, ie. to provide dry air in your process, instead of directly drawing air from the environment. If you intend to use a compressor to remove moisture from air, then you must employ the Joule-Thomson effect to cool the air from room temperature to below zero degree celcius, so that water in the air will solidify.
Things to note:
you don't want the free expansion of air to occur near the compressor, in case the ice chokes the compressor.
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this is the same method how water and carbon dioxide is removed from air before air was furthur cooled to obtain liquified nitrogen.
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Thank you for your reply . your suggestion will be helpfull to me.
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The most economical way to dry the air to this process is via a pressure-swing adsorption air drier. Many companies sell these units that dry the air down to -40 deg. dew point. This is the method of choice in the industry for dry air.
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Thank you for your reply TexasChE .
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Can anyone give other suggestions
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http://www.gas-plants.com/pressure-swing-adsorption.html
http://www.gas-plants.com/products/compressed-air-dryer.html
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Passing air through a desiccant bed is another option for drying air. It is more cumbersome than the other method mention previously. You have to revitalize the desiccant compound when it becomes saturated. The revitalizing method could be baking the desiccant compound.
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Thank you all
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You could bubble the air through methanol .
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Would that add methanol fumes to the air stream?
I doubt that would be desired for the original posting.
You could bubble the air through methanol
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Hi billnotgates,
You are probably correct .
cheers,
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Ananya:
On the off chance that you are still looking for an air drying system: almost any process plant (petroleum refinery, petrochemical plant, chemical plant.etc.) that uses pneumatic control instruments has an instrument air system. Such instrument air systems include compressors and filters as well as air driers that produce air with a water dew point as low as -40 °F to -100 °F.
If you do an "advanced" Google search for the word "drying" and the phrase "instrument air", you will find a great many vendors who offer instrument air drying systems.