Acid plant - Inlet Quench

[bphil]

For those of you who are familiar with the Inlet quench of smelter's sulfuric acid plant, as you may expect, we are experiencing corrosion problem on this equipment...

The inlet quench is the area where hot SO2 (300 C) gas coming from Nickel or Copper smelter is quenched by weak acid spraying. Almost everything has been tried in this environment and everything is failing (Hastelloy C276, 904L, Alloy 20 and refractory lined 904L).

In a specific location of this equipment we have the following conditions:

3-10% H2SO4 mist
200-300 °C
No significant buildup

Here are my questions: Could I use lead bonded steel or lead bonded stainless steel for this environment? Will the lead resist the sulfuric acid concentration at the temperature? Has anybody ever tried lead in those concentration and temperature?

Thanks if somebody has an answer, if you don't have a solution, I'll understand as this is a generalized problem throughout all acid plants.

Phil

 

[unclesyd]

I don't have by Sulphuric Acid Plant data anymore but there were what was called Lead Chamber Sulphuric Acid Plants. I can remember where the all the lead was used.
The essential construction materials were lead and a refractory

 

[CeraTeccy]

you might also want to consider ceramic materials, depending of the dimensions.

H.

 

[hacksaw]

what level of florides are you seeing?

 

[bphil]

Hacksaw,

There is some fluoride but the actual concentration is unknown. I would say that the fluoride concentration is somewhere between 0 - 500 ppm.

Phil

 

[mqas]

Phil,

I know this is an old thread but would be interested to know if you found a solution to this problem or have you tried any other material combinations which have subsequently failed.


Regards

 

[bphil]

mqas,

At two of our operations we are testing brick lined stainless steel. The stainless is first lined with a rubber lining and then brick lined. This is the most promising solution so far. The stainless is only there in case the lining fails. If it does give good service life, the next design would be made out of carbon steel.

At this point I consider this part of the process a consumable that we have to replace every two years approx.

Phil

 

[sulphuric]

The inlet to the quench tower is a region that is exposed to varying conditions from hot to cold and wet to dry. Most quench towers have a 90 deg elbow at the inlet and the gas flow through this elbow tends to follow the outside of the elbow. At the inside of the elbow, back currents and eddies are formed that draw wet cold gas into the elbow. Materials can be specified for either hot dry conditions or cold wet conditions but not where conditions vary from one to the other. You probably have found that the mortar in the joints is the first to go. Once there is significant mortar loss, bricks may start to fall out. Without mortar, there is a leak path for weak acid to the metal shell which very quickly gets corroded away.
I believe that a correction of the flow profile in the inlet elbow will prevent the back currents and give a well defined interface between hot/cold wet/dry conditions so that the proper materials of construction can be specified.

 

[gmasuch]

We operate a fluid bed roaster, and following our precips at 300C we enter a venturi to quench to 60C. 10% SO2, some acid mist. The Lurgi venturi is carbon steel with carbon brick lining, with tangential solution inlet at the top to keep the inlet bricks well wetted. The cover was carbon steel with clad 276, but developed holes after 12 yrs. We have installed carbon steel clad with 254SMO a few years ago.... still looks okay. The venturi bricks appear to be perfect after 24 years.

Hope this helps.