[Gasification] Condensing heat exchanger

[AJH]

On Fri, 15 Sep 2006 11:03:47 -0700 (PDT), Steve Carroll wrote:

>Does anyone have any ideas on building a condensing
>heat exchanger?  I figure most people on this list
>with condensor experience are just trying to cool 
>their gas down before mixing it with secondary air.  I
>am trying to cool the combusted gasses and recover the
>energy from the heat of vaporization (heating
>application, not for ICEs).

What will you do with the condensate? I don't think you'll get it
clean enough to discharge unless you have extremely good combustion.

I'll throw a few thoughts into the pot because I've been looking at
this, mainly to do with burning wet wood.

I was looking for simplicity and low cost, so my thoughts were on the
lines of an water filled,insulated, plastic barrel under the flue with
a stainless steel plate heat exchanger near the top and under the
water level. The water for an underfloor heating system runs through
this plate heat exchanger constantly, hopefully with a return <25C.
Water drawn from the bottom of the barrel is pumped up in a fine spray
into the vertical flue, this spray then condenses out any water vapour
in the flue gas and cools it to somewhere around 50C, obviously the
remaining flue gas is saturated at this temperature. We'd need to look
up a psychometric chart to see how much water was being lost this way
but I expect it to be around 30 grams per cu metre.

At the bottom of the barrel some loose rocks of chalk or broken
concrete, to neutralise the acidity. An overflow pipe from the bottom
led up the outside to a level just above the heat exchanger to
discharge. I am almost certain that this arrangement would not pass
environmental limits for discharge into a water course in UK.

Andrew Heggie ( follower of Heath Robinson ;-))