Waste Acid Tar Removal

[cdb]

All,
In the process, H2SO4 is used as a reactant and formation of the final product produces large quantities of ammonium bisulfate (NH4HS04). A "waste" stream comprised of NH4SO4 + organics + (excess)H2SO4 is sent to a kettle where live steam is sparged into the mixture to boil off any trapped product and organics. Tars are formed readily in the vessel and are an extensive cost($$ and enviromentally) when shutdown and cleaning are required. A spare vessel is always on standby.

I would value information in the any of the following areas:

1. Chemical solutions which hinder the formation of such tars??? And are heavy enough to partition with the heavies in the vessel

2. Adequate filter materials for continuous filtering(i.e. polypropylene, polyethylene)??

3. Separation techniques other than the kettle approach?

Thanks for the consideration.

 

[DeltaCascade]

The high salt and free mineral acid concentrations make this challenging. More info on process would always help. Wonder what others in your industry are doing and why and all that...

1) I wonder if polymerization inhibitors are available, perhaps like those used for vapour phase ethylene compressors. BetzDearborn Inc. Process Division (not the water treatment division) supplies inhibitors for the latter and perhaps could help... although your process is a liquid phase one.

2) Filter materials? ...

I wonder if walnut-shell media filters could help reduce organics loading to the kettle. This media is used in oilfield produced water filtration, typically removing oil down to 2 ppm (see

http://elibrary.usfilter.com/priv_elib/Objects/

40166_usfwalnut.pdf). Backwash water could be high enough in orgranics such that they may be decanted off. However, this may only work for insoluble organics (like oil in water).

Your reference to synthetic materials makes me think of reverse osmosis membranes. Perhaps there is opportunity for that.

3) Alternate Separation Techniques -

Reverse osmosis is all that comes to mind with present info.

Oh, perhaps also biological decomposition (eg: trickling filter), although high salt content, and low pH, may be restrictive.

Perhaps some other oxidation process, such as supercritical oxidation??

In water treatment, to remove organics such as humic acid from surface waters, anion exchange membranes are used. They are regenerated with NaCl brine. The backwash water would have the organics and the waste salt, altough simply concentrating the organics and adding the waste salt may not help your process.

Perhaps activated charcoal filters. Regenerated with steam to remove organics, perhaps they would avoid tar formation.

Solvent extraction and later distillation of solvent?

 

[Muggle]

Not sure of the process your involve with here, and really need more information, but if the treatment is to remove/oxidize the nitrogen and sulphate, electrolytic treatment would produce this, and catalytic enzyme would reduce/liquify any organics. You could discuss the process with Orenda Technologies (800-322-1648) as I beleive they would have a better grasp on the process your involved with here and could recommend treatment regime that would not be as expensive as RO or as limiting as trickle/biological filtration.

Dave Orlebeke
Aquatic Technologies

 

[hacksaw]

cdb,

why not burn it in your spent acid furnace?

If the tar is particulary heavy then you may need to trace the piping. You do have to watch out for solids produced in the furnace as they can play havoc down stream.

The are several processes that regenerate such feeds. I would not attempt to design a new one.

 

[hkmtx]

Have you considered a sand filter or clay (DME) precoated filter followed by activated carbon treatment to remove the bulk of the organics prior to steam stripping?

 

[NicLindeque]

Hi,

if you need help with what to do with the tar acids, vissit our website

http://www.ffs-refiners.com

. We have a tar cleaning fasility wich processes 80m3/h of tar from the coal to pure gas process by means of separation, centrifuging and filtration. We have through the years experimented with varios types of plastics and rubbers to find materials that can withstand high temps and chemmical attacks from solvents within tar streams.