article, there was a hint about
“…to not preheat whole the wood-batch all at once, but to do it progressively, according to demand…”
That is “heat economy” at its best! And favours next start-up!
That reserves the (starting-up) heat to get the actual process going with “full quality” from the very beginning!
Or with other words: Not to spend the “budding” heat to
heat & dry all the wood-lot at once, but only the
“near-by” (above) fuel.
I see it as follows: The original construction was low and flat, which means a low layer of humid fuel above the “process”.
From this low level of fuel there was a “short” distance up and out (above the fuel) to the periphery cooler “sink down”.
But now, when higher silos are demanded, it would mean that the rising steam would just condens in the above cold layers of fuel!
To circumvent this, and still use higher silos, a chimney is needed to vent the rising steam up and out to the condensing mantel.
The diameter of this chimney would be ~2/3 of the nozzle-tip-circle diameter.
Starting at 1 – 2 hearth diameter(s) above the nozzles.
At the upper end it would have a T to distribute the rising flow to opposite sides of the condensing mantel.
Worth a try?