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Metal for stack of desulfurization plant
Q. Hello,
We have a HFO based power plant of 4MW near sea shore. We have a SOx scrubber with NaOH injecting for the fuel less then 1% sulfur content. The scrubber was designed for 1% sulfur. Recently we have received scrubber of 3% concentration & the Ph value of water has gone down to 4-6 for 2-3 months. We have made a stack of 80-meter high made of SS-304 of 2-mm thick with outer shell of MS-6mm thick. But we found the SS plate corroded at many places within 18 months of operation of the plant. Now we have to change the stack but which material be the best for this application. The chloride content in the make up water vary from 80-325 mg/lit of water.
Sanjay ShahHFO Based DG Power Plant - New Delhi, Delhi, India
2004
A. A high nickel-chromium alloy such as Hastelloy or Inconel will resist far more corrosion than SS. There are various grades and you should consult the vendor.
Guillermo MarrufoMonterrey, NL, Mexico
2004
A. Hi Sanjay,
Yours is not the first time that this has appeared on fin.com.
There is the concern of temperature but what one Company did was to make fibreglass stacks using the relatively high heat resistant Hetron l97 polyester ... with corrosion (of metals) occurring, of course, initially at the top.
These were made by Alcore Fabricating of Richmond Hill, Ontario for a U.S. Company called Custodis Chimney ... and I recall feeling vertigo when looking at the photos of the technicians installing the top 'crown' of the 200 foot high l0 foot diameter chimney in the Dominion Republic.
The FRP liners were made in l0 foot or so long sections, belled at one end, and lowered in from the top.
Temperature, if I recall correctly, was somewhere in the 250 F range whereas the modulus was extremely good.
Food for thought ... surely India has specialist chimney companies.
Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).
2004
aUse SS 904, That works like Hastelloy but cost is cheap.
Pavan Jainstainless. - Mumbai
2004
A. Hello, came across your questions in an email search this morning. My company make exhaust gas desulfurisation equipment for use in the marine environment. That is low pH and high chlorides which is a difficult medium for corrosion control.
I would agree with one of your answers that Inconel and Hastelloy are good choices as is titanium if the temperature remains below about 350-400 °C. You may also want to consider some of the high molybdenum stainless steels as a cheaper alternative SMO 254 is one but I'm not a metallurgist so there may be others.
Good luck,
- Littlehampton, UK
2005
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