In the distant past, cleaning of furnace port necks and port mouths was a maintenance task many glass manufactures need not attend to. At the time furnace loads were not as high and the furnace campaign life was not as long as today, and furnace emissions were not a concern. Consequently, near the end of a campaign the operators often just “toughed it out” should they experience some problems with debris filled ports.
For those operators who did clean the ports and mouths it was generally done by a crew of 5 or 6 men using a large water-cooled rake or hook. This rake was made to extend through a hole in the regenerator target wall, across the checker pack and into the port neck.
This procedure often pulled large chunks of debris over onto the tops of the checker pack covering some of the checker openings. It then became another chore to remove these chunks from the regenerator or break them into small enough pieces to allow them to pass down thru the checker openings. All this was done hoping not to destroy the top courses of the checker setting.
In today’s world of smaller furnace crews and in many plants the elimination of the “hot repair crew,” the manpower necessary to do this labor intensive type work is no longer available. Hence this very important maintenance program goes the way of many important and well intentioned projects that can and does affect both furnace life and efficiency.
Fuse Tech / Hot Tech has developed a method of port cleaning which combines some of yesterday’s tools with today’s technology to make what we think is an improvement over the previous way of doing this important furnace maintenance.
The technique involves the use of ultra high water pressure lasers to attack the collected debris. The extreme pressures, up to 10,000 P.S.I, use very small volumes of water in the 2-3 gallons per minute range. The water readily vaporizes after it has done its job.
This method uses a water-cooled lance that reaches thru the regenerator target wall, across the checker pack and thru the port to the hot face. The lance is designed to “fire” the laser stream back toward the regenerator. Once the lance is in place a protective shield is placed in front of the hole to stop the debris from hitting the operator without obstructing their vision.
The water pressure is then turned on and increased to the level necessary to effectively remove the debris. The operator can then slowly move the lance across the port floor “blasting” the collected debris back into the regenerator. Because of the extreme pressure and the thermal shock of the water the debris comes out of the port in small pieces, which can fall through the checker pack to be removed below the rider arches.
This process is only done on the exhaust portion of the reversing cycle to assure that all the debris goes toward the regenerator and does not contaminate the glass bath.
The result of cleaning four ports on each side of this large float furnace was more than cosmetic. Because the combustion air flow had been chocked down by the debris to these four ports the fuel profile had been adjusted to compensate. After the ports were cleaned and the furnace fuels reprofiled, a fuel savings in excess of 5% for the same tonnage was reported, as well as an improvement in NOX.
This reduction in fuel is not only a cost savings, but often in older furnaces this reduction in fuel with resultant reduction in combustion air may be very helpful to relieve some furnace pressure on an old and heavily worn exhaust system.