Note On High Air to Cloth Ratio Bag Filters

In past OEM’s have generally been offering bagfilters for product handling with A/C ratio as 1m/min and purge air pressure of to ! bar"

 ALSTOM Alstom supplies bag filters with Optipow pulsevalves with lower air pressure of # to $ bar as incase of our C%&M line ' and #" A/C ratio for our bag filters is 1 m/min.SCHEUCH(cheuch say that they operate their EMC)EnergyMinimising Concept* bag filters with 1+# bar airpressure, depending on the -ind of dust" Possible A/C ratio can be up to 1. m/min ma!. 

.he lower air pressure also results in longer lifeof bags".hey also say that they have achieved years lifewith 0$ needle felt bags in a -iln/raw millapplication with '2C during direct operation"In India they have supplied a bag filter for -ilnfor .hyssen3rupp India, impri/une for an abroadpro4ect in the 5ulf region, which is still undererection" Contact partner is Mr" Malay 6A(, .elno"'/'!$ ' $71In India there is no EMC bag filter in operation,the nearest is in Emirates in a ball mill cementgrinding plant for the separator filter while allothers are in Europe""#$Mr (hah of erry has informed the following8PT$E membrane bag suppliers use %ig% A/C ratio ofappro! 1.& to 1.' m/min..he .9E membrane is very thin, hardly 'micrometers thic- laminated either on a needlefeltbase material or on a glass fabric" .he membrane issupposed to give anti stic- property which formsthe basis of low pressure drop and high A/C ratio"

 

:ote8 they have a very low air permeabilitycompared to needlefelts" ;e have seen a number of failures because themembrane brea-s creating holes after a shorttime, leading to particles entering the filtermedia and getting stored beneath intact membrane".his leads to a sudden rise in pressure drop and/orrise in emissions in due course A good e<ample is Indo &ama Cement for their slagand clin-er grinding , who initially used 5orete<bags ) homopolymer acrylic bags laminated with .9Emembrane* and had severe differential pressureproblems after paying a fancy price for the bags"(ince then they have stopped buying membrane bagsand instead are using 1= homopolymer acrylicneedlefelts at a much lower cost"&eport is attachedin a separate file" Attached please also find another file on negativereference list where we have analysed so many bagswith this failure including some in India" ;ith A/C ratio as high as these even ordinaryneedlefelts will come under severe stress as muchmore gas has to pass through it and resulting inshort bag life, increased pressure drop and highemissions as particles will penetrate " .heabrasive nature of the slag will brea- thethin .9E membrane" Conclusion(It appears from the above that it is better tostic- to conventional A/C ratio of 1 m/min for bagfilters handling product with conventional filtermedia depending upon application">owever,we maydiscuss in detail with suppliers during technocommercial discussions before coming to finalconclusion"