acid scubber on dryer
- Thread starter DGC1
- Start date
- Location
- North West
There was a thread about this the other day, with a chap running one. Can’t remember what the thread was called though. I’ll have a look.
- Location
- North West
thanks
I did see that thread, just wondering if anyone else doing it to try and gauge how its working out
Fowler VF
Member
- Location
- Herefordshire
If you have ammonia coming out in your drying air then an air scrubber running with sulphuric acid in the water will definitely clean that right up. Solution in the scrubber will gradually turn to ammonium sulphate, quite a useful fertiliser solution. If anyone is interested in this I have some pretty large second hand scrubbers capable of dealing with 10,000 and 20,000 cubic feet per minute of air available. These could be very expensive items if you bought them new!
- Location
- Northumberland
Ask a silly question: Why don't these scrubbers re-condense the water vapour coming out of the dryer and put you back to square one? What's the acid consumption at those sort of air vols?
I’ve already had a private pm with DGC1 about our scrubber. We’re having a few teething problems, but slowly getting everything running. The acid consumption is pretty steep and won’t leave a massive profit for the AS, but I think it is something the EA will soon demand!
Would love to hear from anyone else.
Would love to hear from anyone else.
Fowler VF
Member
- Location
- Herefordshire
They can and often do re condense the water in the dryer exhaust air stream. All depends on just how warm the exhaust air is and just how saturated it is. If its very warm and high humidity then the washing action of the scrubber will cool it and condense. The exhaust from the scrubber will be high humidity, but cooler air so will carry less water overall. So it can end up that the scrubber actually "makes" water and fills up, equally it can happen that the exhaust from the scrubber will carry more water than was going in and it needs topping up with water. if there is too much re condensing going on then it can pay to warm the scrubber water a bit, so it doesnt cool the air so much.
As far as acid consumption goes its normally a direct correlation with the ammonia content. If you are using a lot of acid then there must be a lot of ammonia in the air. Equally if there is that much ammonia then you are recovering a lot of ammonium sulphate fertiliser as well. And as stated in a later post, if there is that much ammonia in the air then its a problem and before long EA are going to pick up on it.
Scrubber is normally just a tall chimney, tank at the base full of dose water, air blows up the chimney, though a layer of packing medium (normally plastic mesh and packers that look like plastic scrubbing brushes), water is pumped form the base tank and sprayed over the packing. Air to water contact is high due to the packing and the air gets washed, water trickles back into base tank, scrubbed air goes out the top. Things to watch out for are dust content in the air, this can block up the packing and can also react with the dosing chemicals, so increasing the chemical cost. Chemical added to base tank with a small dosing pump controlled by PH or whatever you want. I have built and used scrubbers running on acid, alkali, bleach, chlorine dioxide and all manner of stuff depending on what it is you need to scrub out of the air.
- Location
- Northumberland
Thanks, very interesting; only academic for me though. When I toyed with the viability of a plant a few years ago, I imagined drying/condensing the digestate, but didn't like the idea of all the N being lost.
We have installed a digestate evaporative system that works through a three stage vacuum process. it process 30,000m3 using 600kw of heat. We get 15,000m3 of distilled water and 800m3 of ammonium sulphate fert. it is difficult to be specific as we are only just post commissioning but it looks promising as always the technology comes from Germany
thanks Jim,
is the processing 15000m3 each unit so 2 x 15000 gives you the 30000cu?
did you manage to get the press/separation thing sorted out?
--
so 30000cu goes in and then treated with 600kw and backend is....
15000cu distilled water,
can this be discharged to stream?
or what are your plans with it....
800cu AS,
at ??% N?
what volume of sulphuric acid is needed to capture this 800T? app 200T?
is there a solid fraction as well? i.e a powder?
your project sounds really interesting and not many AD plants have advanced onto this sort of tech
is the processing 15000m3 each unit so 2 x 15000 gives you the 30000cu?
did you manage to get the press/separation thing sorted out?
--
so 30000cu goes in and then treated with 600kw and backend is....
15000cu distilled water,
can this be discharged to stream?
or what are your plans with it....
800cu AS,
at ??% N?
what volume of sulphuric acid is needed to capture this 800T? app 200T?
is there a solid fraction as well? i.e a powder?
your project sounds really interesting and not many AD plants have advanced onto this sort of tech