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We have a plate heat exchanger as a reactor feed/effluent heat exchanger in DHT unit. this exchanger is very sensitive to debris/catalyst fine/ceramic ball chips.., accordingly a fine mesh (cone shape) is installed upstream the exchanger on the reactor effluent line. This filter is doing great by catching all scales and preventing them getting into the exchanger. However, when the Dp increases across the filter, we have to shutdown the unit and clean it. I'm looking for online cleaning, such as a dust collector, cyclone or whatever thing appropriate. the filter is installed in a piece that is same size as the piping and with no spare to avoid block valves in the reactor circuit.
 
Answers
22/02/2009 A: Marcello Ferrara, ITW SrL, mferrara@itw.it
ITW Online Cleaning can be performed to remove heavy hydrocarbon deposits without opening any cover. Recently, we also developed a novel technology to modify/dissolve polymeric deposits.
03/02/2009 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
If you can provide an isometric, digital image, line pressure, flows and operating temperatures, I'm confident we would be able to offer an Online cleaning alternative.
03/02/2009 A: Lindsay McRae, Pall Corporation, Lindsay_McRae@pall.com
Feed filters on DHT feed are reasonably common to protect feed exchanger and also the fixed bed reactor from fouling. A similar concept can be used on effluent stream to protect effluent side of exchanger from fouling if that is the problem here.
To protect heat exchanger on the effluent side, we'd recommend the installation of duplexed high temperature filters (either metallic large bore filter or high temperature disposable filter elements) with a high surface area to minimise the filter cleaning or replacement frequency.
(Note: In-line conical 'witches hat' type strainers will have a low surface area so regular cleaning would be needed which you rightly identify is problematic). We would normally recommend a duplexed unit but it could also be a simplexed filter unit with a bypass to enable filter cleaning / replacement without taking the DHT unit offline. That would be a lot more practical and workable than the existing in-line conical strainer installed.
Duplexed filters would enable one to be on-line while the other is offline or being cleaned. You would need isolation valves of course to enable that.
This would be likely to be the most cost effective solution. The TSS level in such a DHT effluent stream would generally allow this to be effective and not too maintenance intensive. An automatic self cleaning backwash filter could do the job too but typically would that be a multi-million dollar investment, plus would produce a highly contaminated backwash fluid stream which would need to be reprocessed or downgraded. An automatic backwash filter would not be justifiable compared to a properly sized cleanable metallic or high temperature disposable filter in my view.