<< 4. Would a gate valve or a ball valve be better for each of the
> valves (2" and 3/4")? I don't want fine control, basically just
> on/off. I was thinking ball valves? >>
> I would say to use the ball valve.>>
I just went and looked at ball v's gate valves, and while I thought I
would prefer to use the ball, in a 2" size, gate valves are about
half the price, and look to be solid metal construction, compared to
the plastic components in the ball valve. Does anyone know anything
about the comparability of the seal maintained by both?
<< If you are able to use your long column, I would suggest to do so.
> you will be able to get the "right" amount of separation in the
> better separate the heads. But my suggestion would be is to have
> valve AFTER the column and its packing BEFORE the N/S head. This
> you open your pot still valve, and close off the N/S head, all of
> and fluid in your packed column would be able to return to the
> escape through your pot still valve. Otherwise I would believe that
> would trap some good alcohol vapor in the packet column when you
> switch over to your pot still.>>
You bring up a good point here - and one I have had a couple of off
group dicussions with others about.
Basically, there is going to be some retention of vapour in the
column around the time of switchover. If the valve is at the bottom
of the column, obviously it is liable to be lost - either condensed
in the column or taken off to the angels.
However if the valve is at the top of the column, as you say, it
cannot be lost - but I would query if it is actually usable, as it
will remain in the column (??) to keep the pressure equal -
therefore, some good ethanol vapour will still be in the column even
after the tails are coming through the pot still section. Does
anyone have any comments on this? Any idea what type of volume
(condensed vapour volume - i.e. lost ethanol) we are talking about?
The way I see around this is:
1. After foreshot come through, the still gets turned off. This has
to be done, so I can swap the water connections from the N/S head to
the pot still jacket condenser.
2. In this off time, I have to wait for the vapour temp in the head
to decrease below 40 degrees or so, otherwise I will loose vapour -
this takes around 10 minutes from experience.
3. Once this time is up, I swap the condenser connections over.
Then open the pot still valve(3/4"), and close the N/S column valve
4. Power then goes back on (at half power!)
I think this minimises vapour losses - there probably will be a small
amount in the column, but I think it will be negligable, especially
considering I am talking about 25L - 50L runs. It also negates any
possibility of pressure buildup in the boiler.
What do you think?