anachronism
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aga said:
retention time calculation
- Thread starter saadat68
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Happy new year everyone. 
Just to continue the last development in this thread.
Has anyone tried to pump the red fumes back into the reaction liquid by peristaltic pumps or the likes.
Do you need peroxide then as well or will it give some affect anyway?
How about need for fume hoods, will it decrease if you recycle the fumes?
I kind of like the idea if we can use our chemicals to the max.
Just to continue the last development in this thread.
Has anyone tried to pump the red fumes back into the reaction liquid by peristaltic pumps or the likes.
Do you need peroxide then as well or will it give some affect anyway?
How about need for fume hoods, will it decrease if you recycle the fumes?
I kind of like the idea if we can use our chemicals to the max.
anachronism
Well-known member
- Joined
- May 31, 2016
- Messages
- 3,196
Yggdrasil said:Happy new year everyone.
Just to continue the last development in this thread.
Has anyone tried to pump the red fumes back into the reaction liquid by peristaltic pumps or the likes.
Do you need peroxide then as well or will it give some affect anyway?
How about need for fume hoods, will it decrease if you recycle the fumes?
I kind of like the idea if we can use our chemicals to the max.
Hey Ygg
4metals posted a pic of a closed loop system a few years ago utilising a condenser to take a lot of the Nitric back into the reaction vessel prior to the scrubbing of the gases. I'll try to find it and pop a pic up for you. Happy New Year to you too.
Jon
Thanks Jon.
In my ideal world our operations would be without fumes and so on, but we have to be practical in the real world.
If we can find workarounds and techniques that minimize our foot print, it would be magnificent.
Like distilling the HCl after use to azeotrope after it has been spent or the same about nitric.
I have not looked about the economic part of this, but the environmental part looks shining
Some day I will look into it ... I think :wink:
In my ideal world our operations would be without fumes and so on, but we have to be practical in the real world.
If we can find workarounds and techniques that minimize our foot print, it would be magnificent.
Like distilling the HCl after use to azeotrope after it has been spent or the same about nitric.
I have not looked about the economic part of this, but the environmental part looks shining
Some day I will look into it ... I think :wink:
That was stupid and arrogant of me.anachronism said:
Please accept my appologies Platdigger.
no worries
apology accepted
apology accepted
It's really nice to see everyone playing nice and getting along on this new year! It makes moderating easy.
H2O2 helps converting NO into NO2 but so does atmospheric oxygen too, so having a bleeder valve letting in some oxygen into the reaction vessel and then using refluxing condenser could stretch the amount of metal a certain amount of nitric could dissolve. In the simplest form a slow digestion in a large beaker with a watch glass or plate covering the top goes a long way.
For example the common knowledge is that it takes 1 ml nitric and 3 ml hydrochloric acid to dissolve one gram of gold. My best result so far is with an excess of hydrochloric acid and 28 ml nitric dissolved 53 grams of gold. That was with a beaker and a glass plate on low heat, not boiling. I haven't calculated how close I got to stochiometric values, maybe some day I'll do it for fun.
I have bought a professional refluxing condenser but I haven't tested it yet.
Happy new year everyone!
Göran
H2O2 helps converting NO into NO2 but so does atmospheric oxygen too, so having a bleeder valve letting in some oxygen into the reaction vessel and then using refluxing condenser could stretch the amount of metal a certain amount of nitric could dissolve. In the simplest form a slow digestion in a large beaker with a watch glass or plate covering the top goes a long way.
For example the common knowledge is that it takes 1 ml nitric and 3 ml hydrochloric acid to dissolve one gram of gold. My best result so far is with an excess of hydrochloric acid and 28 ml nitric dissolved 53 grams of gold. That was with a beaker and a glass plate on low heat, not boiling. I haven't calculated how close I got to stochiometric values, maybe some day I'll do it for fun.
I have bought a professional refluxing condenser but I haven't tested it yet.
Happy new year everyone!
Göran
Thanks Platdigger and anachronism.
The problems with HNO3 are varied.
It's relatively high vapour pressure of 48 mmHg basically means it wants to be a gas and escape into the big wide world instead of doing the work you set for it. Sulphuric acid tends not to do that as it's vapour pressure is just 0.001 mmHg. A simple experient with that is to get two small pots, put a few ml of sulphuric on one, nitric in the other, weigh them both, leave them out for a few days, then weigh again to see how much of each acid escaped. (conc sulphuric will actually Gain weight as it takes water from the air)
A you all know well, nitric is very reactive, so any ducting of the NOx gasses tends to get attacked, meaning that it doesn't last long and has taken some of the gas you were trying to save.
Lastly, nitric decomposes very easily, hence the orange fumes which are not the NO3 originally required.
Increasing the pressure of the reaction might squeeze more 'bang for your buck' out of the acid.
Although that might work, i have never tried that idea and it sounds like it could be quite dangerous !
The problems with HNO3 are varied.
It's relatively high vapour pressure of 48 mmHg basically means it wants to be a gas and escape into the big wide world instead of doing the work you set for it. Sulphuric acid tends not to do that as it's vapour pressure is just 0.001 mmHg. A simple experient with that is to get two small pots, put a few ml of sulphuric on one, nitric in the other, weigh them both, leave them out for a few days, then weigh again to see how much of each acid escaped. (conc sulphuric will actually Gain weight as it takes water from the air)
A you all know well, nitric is very reactive, so any ducting of the NOx gasses tends to get attacked, meaning that it doesn't last long and has taken some of the gas you were trying to save.
Lastly, nitric decomposes very easily, hence the orange fumes which are not the NO3 originally required.
Increasing the pressure of the reaction might squeeze more 'bang for your buck' out of the acid.
Although that might work, i have never tried that idea and it sounds like it could be quite dangerous !
On commercial scale silver digestions, a mixture of dilute nitric acid (usually less than 10% w/v) and 35% w/v H2O2 is used in the first scrubber to get the NO and most of the NO2 into nitric acid. That scrubber solution gets used for the the next dissolve.
Usually, most efficient to heat water and add fine silver granules or powder into the water, slurry and then pump in the nitric.
EDIT:
Keep in mind that in packed beds, your actual retention time might be considerably longer than the estimated residence time of a gas molecule due to a variety of effects (turbulence, tortuous pathways, etc).
How important is that for a scrubber for NOx? Don't know. I'd say I'd rather assume worst case scenario and make sure the BFRC doesn't escape!
Usually, most efficient to heat water and add fine silver granules or powder into the water, slurry and then pump in the nitric.
EDIT:
Keep in mind that in packed beds, your actual retention time might be considerably longer than the estimated residence time of a gas molecule due to a variety of effects (turbulence, tortuous pathways, etc).
How important is that for a scrubber for NOx? Don't know. I'd say I'd rather assume worst case scenario and make sure the BFRC doesn't escape!
This is a difficult thread to give anything but the most basic of answers. There are too many variables and all we were given was the column area. So simply stated, the retention time is the amount of time the fume remains in the packing of the scrubber. And that is just a function of the volume of the fume in the scrubber and the CFM flow of gas through the scrubber.
As Lou said, the type of packing effects how effective the scrubber actually is at reacting the fume. But for NOx in general a retention time of 8 seconds in the packed area of the scrubber is effective in a scrubber that recirculates the scrubber liquid. We do not know if the scrubbing liquid is being recirculated over the bed and if it is, what the flow rate is. And we do not know if the packing is one of the more popular tower packing types or if it is wiffle balls, marbles, or cut PVC pipe.
If you can provide a retention time of 8 seconds or better, there is an effective combination of packing, flow rate, liquid distribution, and chemistry to effectively scrub the NOx generated.
As Lou said, the type of packing effects how effective the scrubber actually is at reacting the fume. But for NOx in general a retention time of 8 seconds in the packed area of the scrubber is effective in a scrubber that recirculates the scrubber liquid. We do not know if the scrubbing liquid is being recirculated over the bed and if it is, what the flow rate is. And we do not know if the packing is one of the more popular tower packing types or if it is wiffle balls, marbles, or cut PVC pipe.
If you can provide a retention time of 8 seconds or better, there is an effective combination of packing, flow rate, liquid distribution, and chemistry to effectively scrub the NOx generated.
