Method of converting a furnace to oxygen-fuel while it is operating and aburner block assembly

A method has been developed for converting a hot, operating furnace to oxy-fuel avoiding the problems of the past. This method comprises removing an old burner from the furnace, drilling a cylindrical hole, with its axis generally aligning with the axis of the opening in the old burner block, through the old burner block, removing the cut out portion, inserting a refractory tube in the new hole, and fastening an oxy-fuel burner onto the furnace to join in a sealing and or biased relationship with the outside end of said tube.

BACKGROUND 
During the last few years it has become desirable to convert air-gas or 
air-oil fueled furnaces, such as glass making furnaces or melters, to use 
oxygen instead of air or preheated air. Since the air-gas or air-oil 
burners use a refractory burner block having an internal flame containing 
or directing configuration that is undesirable for the preferred oxy-fuel 
burners, it has been necessary in the past to tear out the old burner 
blocks and replace them with new burner blocks having the desired internal 
configuration. 
It is desirable to make such a conversion hot and while the melter 
continues to operate because to turn off and cool down the melter is 
extremely expensive. Removing the old burner blocks and installing the new 
blocks while the furnace is hot is difficult, time consuming, and 
disruptive to the process causing a costly effect on the process. Also, 
tearing out the old burner block often damages the surrounding wall 
reducing the life of the melter or requiring hot repairs. Where the 
furnace is old and the surrounding wall is in less than good condition it 
is often too risky and the furnace must either await a rebuild for 
conversion or the furnace must be rebuilt before the life of the 
refractories is expended, both of which are costly. 
SUMMARY OF THE INVENTION 
A method has been developed for converting a hot, operating furnace to 
oxy-fuel avoiding the problems of the past. This method comprises removing 
an old burner from the furnace, drilling a cylindrical hole, with its axis 
generally aligning with the axis of the opening in the old burner block, 
through the old burner block, removing the cut out portion, inserting a 
refractory tube in the new hole, and fastening an oxy-fuel burner onto the 
furnace to join in a sealing and or biased relationship with the outside 
end of said tube. This method can also be used to convert a hot banked or 
cold furnace without damaging the walls of the furnace. Preferably the 
cylindrical hole is made by core drilling such that the outside diameter 
of the drill is less than the diameter of a tunnel in the old burner block 
at the hot end of the old burner block so that the cutting end of the core 
drill does not reach the hot end of the old burner block. This minimizes 
or avoids getting refractory particles into the furnace and the work 
product in the furnace. Preferably a gasket made from refractory fiber is 
used to form a seal between the oxy-fuel burner and the cold end of the 
refractory tube. 
To make the conversion faster and less work at the job site, it is possible 
to preassemble the new refractory tube, gasket seal, and the oxy-fuel 
burner into a single unit to be installed in the bored out old burner 
block.

DETAILED DESCRIPTION 
An air-fuel burner, whether the air is preheated or not, requires a burner 
block that has a bell or cone shaped internal opening or tunnel to contain 
the flame, with the small diameter of the tunnel joining with the burner 
and the largest diameter of the tunnel lying adjacent with the interior of 
the furnace or melter. FIG. 1 shows a typical air-fuel burner block 2 
mounted in a sidewall 4 of a furnace, such as a glass melter. The notched 
ears 5 on the exterior face of the burner block 2 are for holding a metal 
plate which the air-fuel burner mounts on. The burner block 2 has an 
internal opening 6 that is generally cone shaped in this figure, but which 
can also be bell shaped and versions thereof. 
The burner block 2 is normally mortared at the joints 8 with the wall 4 to 
prevent its movement in the wall. This, and a ceramic joint in the hottest 
portion near the interior caused by condensed volatiles and subsequent 
reaction with the refractories, prevents the block from being forced out 
of the wall of the furnace. To remove the burner block from a used furnace 
requires chipping the block out from the wall, which invariably causes 
pieces of refractory to enter the furnace causing problems, bad glass when 
the furnace is a glass melter. Other problems, as mentioned above, make 
removing the old burner blocks 2, which often number ten or more, very 
difficult and risky, particularly while trying to continue to operate the 
furnace while the conversion is taking place. 
Preferred oxy-fuel burners, such as the CLEANFIRE.TM. oxy-fuel burner 
supplied by Combustion TEC, Inc. of Orlando, Fla., because of the lower 
volume of gases these burners emit, need a burner block having a 
cylindrical opening or tunnel, like the block shown in FIG. 2, and are not 
operable effectively using the air-fuel shaped burner blocks tunnels. This 
type of burner and burner block are disclosed in U.S. Pat. No. 5,199,866, 
which disclosure is hereby incorporated here by reference. The present 
method overcomes the problems of the prior art method of tearing out the 
old burner blocks 2 to install new burner blocks 9 having the desired 
cylindrical tunnel. 
Using the new method it is not necessary to shut down the furnace and there 
is little or no risk of significantly damaging the walls of the furnace. 
According to the new method an air-fuel burner is shut off of an operating 
furnace and removed from its mount on the sidewall and from the burner 
block. A piece of refractory fiber blanket cut to fit tightly into the hot 
end portion of the tunnel in the burner block is compressed and inserted 
into the open tunnel to the hot end where it expands to block the flow of 
furnace gases from coming through the tunnel. 
Next, a core drill having a diameter slightly larger than the new 
refractory tube is positioned so that its axis is aligned with the axis of 
the tunnel of the old burner block and a core 10 of the old burner block 
is cut out so that it can be removed, as shown in FIG. 3. Preferably, a 
typical water cooled core drill is used and the water fed to the cutting 
edge of the tool removes refractory dust generated by the cutting tool out 
the bottom of the cut or tunnel 11. Also preferably, the diameter of the 
core drill will be somewhat less than the diameter of the large end of the 
tunnel so that the cutting will be completed at a point 12 before the 
inside face 14 of the block is reached to prevent dust and fine particles 
of refractory generated in the final portion of the cut from dropping into 
the furnace. The center core 10 of the old burner block 2 is removed 
leaving the outer part of the old block 3, the joints 8 and the wall 4 in 
place and undisturbed. The enlarged tunnel 11 left by removing the inner 
core 10 can be quickly plugged by inserting a piece of refractory 
insulator previously cut by the same core drill or a plug of refractory 
fiber to prevent escape of furnace gases. 
A refractory tube 16 (see FIG. 4) having an outer diameter slightly smaller 
than the hole 11 made by the core drill and a length slightly shorter than 
the length of the new tunnel 11 is prepared for insertion into the hole 
11. Any good thermal shock resistant refractory compatible with the old 
burner block and the operating conditions can be used. For use in a glass 
melting tank or furnace ZED 3, manufactured by Zedmark Refractories 
Company of Dover, Ohio is preferred. The interior diameter of the 
refractory tube 16 is that required for the particular burner used. The 
length of the tube 16 is approximately the same as the length of the old 
burner block, but can be slightly shorter or longer. A refractory fiber or 
insulator plug is inserted into the outer end of the tube 16 to block the 
gases while it is being installed. A uniform layer about one sixteenth of 
an inch thick of refractory mortar, preferably 716 Zircon manufactured by 
Didier Taylor Company of Cincinnati, Ohio or other compatible refractory 
mortar is applied to the outer linear surface of the tube 16, the 
refractory plug in the tunnel of the old block is removed and the new tube 
16 is pushed into the tunnel formed by the removal of the inner core 10 of 
the old block 2 until the trailing end of the tube is about one sixteenth 
to about one half inch or more from the outer exposed surface of the outer 
portion 3 of the old block 2, as shown in FIG. 4. 
A ring or donut shaped gasket 18, having the dimensions of the cross 
section of the refractory tube 16 is cut from a refractory, mineral or 
glass fiber blanket to make a gasket. A suitable material is a one inch 
thick refractory fiber blanket, FIBERFRAX.TM., sold by the Carborundum 
Company of Niagara Falls, N.Y., having a density of about eight lbs./cubic 
foot. Other thicknesses and densities of material would be suitable so 
long as the fiber doesn't melt, adequate resistance is exerted by the 
material to compact it to a good seal, and so long as the burner doesn't 
bottom out on the tube 16 before a good seal is made. An easy way of 
making the gasket is to set the refractory tube 16 on end on the blanket 
and cut the blanket around the outside and the inside of the tube 16 using 
a sharp knife. This should be done at the very beginning before turning 
off the air-fuel burner. This gasket is now packed into the slight recess 
in the tunnel of the remaining portion 3 of the old block 2 and adjacent 
to the outside end of the installed refractory tube. Normally the 
compressible refractory or glass fiber gasket 18 will remain in place by 
the expansion force it exerts on the tunnel of block 3, but if necessary 
one face of the gasket can be dipped into the 716 Zircon mortar and 
adhered to the outside end of tube 16. 
The new oxy-fuel burner is ready for installation. The new burner is 
installed by first sliding steel plate 19 containing studs 24 onto the 
ears 5 of the block 3 and sliding the oxy-fuel burner with its mount 22 
onto the studs 24 and tightening it with nuts on the studs 24 such that 
the front portion of the burner engages and compresses gasket 18 to form a 
good seal. The burner is hooked up to oxygen and fuel and turned on. This 
procedure is repeated on each air-fuel burner to be converted to oxy-fuel 
until the conversion is complete. 
FIG. 5 is a vertical view of the remaining outer portion 3 of the old 
burner block 2 with the new tube 16 mounted therein as seen from inside 
the furnace. The gap 24 is formed by the inner diameter of the original 
tunnel of the old burner block 2 and the outer diameter of the new 
refractory tube 16 in the preferred embodiment. The gap 24 extends only a 
short distance in to the wall, e.g. about 0.5 inch and its outer diameter 
decreases as it proceeds into the wall. 
Using this process the wall of the furnace is undamaged and there is 
inconsequential impact on the process and production. About one hour is 
required to convert each burner to oxy-fuel using this procedure versus 
three to four hours with the old process of removing the old burner 
blocks. Also, unlike the old process, this new process avoids getting 
refractory into the glass when converting a glass melter avoiding process 
problems and glass scrap encountered in the past using the old procedure 
of conversion. 
To reduce conversion time still further and to make conversion more 
convenient, the new refractory tube 16, the gasket 18 and the oxy-fuel 
burner 20, including plate 19, mount 22 and studs 24 or their equivalent, 
can all be preassembled into a single unit and then installed as a single 
unit after the center portion 10 of the old block is removed in the above 
described method of conversion. 
Further modifications in this new procedure will be obvious to those 
skilled in the art and their use is considered part of the present 
invention.