Got the printer to assist drawing functions initially...
First we have to set the mind to what a blasting nozzle really does!
Most have in mind what happens ahead of a blasting nozzle in the open.
The beam rips with it and pushes a lot more than the beam flow itself.
All this added volume comes in from the sides, and in a closed passage, from behind.
So, a nozzle-beam does not transport anything else, if the admittance to the beam is "prohibited"!
Now, if the nozzle blows a beam in a compact char-mass,
it burns a "channel" for the rushing insucked gases and air toward the hearth center.
The char constitutes a real resistance for the gases to be sucked in by the beam.
But we can help this "inflow" driwen by the sucking beam! And benefit the pyrolyse gases rehandling!
With a ringformed cavity around the center-glow, the out-streaming gases are easily re-routed to the sucking beams instead of sneeking down toward the restriction.
A loose metallic cylinder stands on the nozzle-shafts, and in the upper end a conical metal ring is welded to this loose cylinder.
Easily removed upwards for cleaning, if the silo funnel is kept high enough and it also is removable.
Let's see if the nozzle-area picture can be transported; the acceptable transport programmes have been changed again... jpg, jpeg, png, gif.