Over the past 10 years, the landscape of the North America pulp and paper industry has seen a dramatic change. The reoccurring themes have been old, inefficient equipment, lower demand and higher energy costs. Including lumber and pulp and paper, forestry accounts for 35% of Canada's total energy consumption; to succeed in the new millennium, the industry has had to find ways of becoming more efficient, and of reducing costs.
One of the more popular choices for energy cost reduction has been the addition of biomass boilers. The forest industries have been increasing their use of wood wastes that otherwise would be burned, buried or land filled, to the point that the forest industries meet more than one- half of their energy needs themselves with self-generated biomass wastes. Although typically defined as wood residues such as bark or hog fuel, biomass also now includes the plant effluent, de- inked mud, and other residues.
The White Birch Papers plant in Quebec City is not unlike many of the other newspaper paper mills in North America. In order to survive, it took the necessary steps in modernizing the plant and with the same energy concerns, installed a high efficiency biomass boiler in 2006 to lower energy costs. One of the keys to high efficiency boilers is to pre-dry the biomass before feeding into the boiler. This is accomplished at White Birch Paper with a rotary dryer followed by ducting up to two 50’0” tall sizing cyclones, that sit 130 feet off the ground. The larger particles fall out of the rotary dryer onto a conveyor, which then feeds into the boiler. The hot air and fines from the outlet are sucked up into the cyclones where the fines are separated and sent into the boiler while the hot air is sent back to the feed end of the rotary dryer to pre-dry the biomass.
The biomass is comprised of 40% plant effluent and 50% de-inked mud. The two cyclones are made of 3/16” thick SS304 due to the slightly corrosive (SO2) environment of the plant effluent. The cyclones operate under negative pressure (air pulled through and not pushed) due to the high flammability of the dried effluent and are equipped with an extinguishing system of water nozzles. Only one fire has occurred since the commissioning and this was due to leaky seals on the rotary valves and flange connections. Normal operating temperature at the top of the inlet is 95°C and 65°C at the cone outlets.
After 18 months of operation, the cyclones started showing signs of wear, requiring the replacement of several sections. Replaceable liners made of AR400 steel plates were installed for the inlet and upper barrel section.
The lower 10’0” diameter cone was also replaced and fabricated using AR400 plate.
Over the following year, wear continued to manifest itself in both cyclones, requiring several maintenance interventions. Due to all the patching and uneven surfaces, the wear rate continued to increase, thus becoming a cause for concern.
The steam plant maintenance superintendent at the time had heard about a cyclone-lining project completed a year earlier at a nearby cement plant utilizing KALCRET, a cement bonded wear compound. He inquired about the possibility of doing the same with his cyclones. Initial discussions about lining the inside of the cyclones with KALCRET were held in June of 2009, but due to short outage periods, the decision was taken to install AR liners during the September outage.
An inspection in January 2010, showed once again severe wear on all the AR liners and the concern now was with the original steel being too thin to receive any more liners.
The Solution:
After several more discussions and meetings, it was concluded that lining the cyclones with KALCRET offered two major advantages; the 50’0” high cyclones would not need replacing, representing a significant cost savings and, the logistics were much simpler.
The contract was awarded to Abresist Kalenborn Inc. of Pointe-Claire, Quebec to line the bifurcated inlet section and both cyclones, an area totaling approximately 3,000 ft2. The turnkey project was handled entirely by the Canada Kalprotect installation team, including the mobilization of cranes, scaffolding and installation of all materials.
It was determined that KALCRET-BTS sprayable material would be used for each entire cyclone with the exception of the bifurcated inlet area and lower cones. For safe and proper installation of the scaffolding, the first three sections of cones were removed and lowered to ground level. These lower cones would be completely replaced with new steel lined with KALCRET-BTX trowellable compound.
A wire mesh anchoring system was installed on all surfaces receiving the KALCRET wear compound. The inlet area and cyclone roofs were lined with the BTX trowellable KALCRET, while the bull nose was protected using an engineered KALOCER ceramic tile.
Using the spraying equipment, quick work was made of the remaining 2000 ft2, where 50 ft2 per hour of KALCRET-BTS was applied. The new lower cones, now lined with KALCRET-BTX, were then positioned back into place and re-assembled. Final touch ups and one final site
clean up were followed by demobilization on schedule.
According to Louis Senechal, project manager, “the benefits of the KALCRET lining were noticed immediately after start- up as the operators were able to control the temperature and airflow much more effectively which will allow for a more precise and efficient operation of the boiler.”
Increases in equipment wear life, as well as an improved operating efficiency, were just two of the benefits of the KALCRET abrasion resistant wear compound.
Lining the remaining 1000 ft2 of duct leading into the cyclones is already being discussed for the next outage.
The White Birch Papers plant in Quebec City is not unlike many of the other newspaper paper mills in North America. In order to survive, it took the necessary steps in modernizing the plant and with the same energy concerns, installed a high efficiency biomass boiler in 2006 to lower energy costs. One of the keys to high efficiency boilers is to pre-dry the biomass before feeding into the boiler. This is accomplished at White Birch Paper with a rotary dryer followed by ducting up to two 50’0” tall sizing cyclones, that sit 130 feet off the ground. The larger particles fall out of the rotary dryer onto a conveyor, which then feeds into the boiler. The hot air and fines from the outlet are sucked up into the cyclones where the fines are separated and sent into the boiler while the hot air is sent back to the feed end of the rotary dryer to pre-dry the biomass.
The biomass is comprised of 40% plant effluent and 50% de-inked mud. The two cyclones are made of 3/16” thick SS304 due to the slightly corrosive (SO2) environment of the plant effluent. The cyclones operate under negative pressure (air pulled through and not pushed) due to the high flammability of the dried effluent and are equipped with an extinguishing system of water nozzles. Only one fire has occurred since the commissioning and this was due to leaky seals on the rotary valves and flange connections. Normal operating temperature at the top of the inlet is 95°C and 65°C at the cone outlets.
After 18 months of operation, the cyclones started showing signs of wear, requiring the replacement of several sections. Replaceable liners made of AR400 steel plates were installed for the inlet and upper barrel section.
The lower 10’0” diameter cone was also replaced and fabricated using AR400 plate.
Over the following year, wear continued to manifest itself in both cyclones, requiring several maintenance interventions. Due to all the patching and uneven surfaces, the wear rate continued to increase, thus becoming a cause for concern.
The steam plant maintenance superintendent at the time had heard about a cyclone-lining project completed a year earlier at a nearby cement plant utilizing KALCRET, a cement bonded wear compound. He inquired about the possibility of doing the same with his cyclones. Initial discussions about lining the inside of the cyclones with KALCRET were held in June of 2009, but due to short outage periods, the decision was taken to install AR liners during the September outage.
An inspection in January 2010, showed once again severe wear on all the AR liners and the concern now was with the original steel being too thin to receive any more liners.
The Solution:
After several more discussions and meetings, it was concluded that lining the cyclones with KALCRET offered two major advantages; the 50’0” high cyclones would not need replacing, representing a significant cost savings and, the logistics were much simpler.
The contract was awarded to Abresist Kalenborn Inc. of Pointe-Claire, Quebec to line the bifurcated inlet section and both cyclones, an area totaling approximately 3,000 ft2. The turnkey project was handled entirely by the Canada Kalprotect installation team, including the mobilization of cranes, scaffolding and installation of all materials.
It was determined that KALCRET-BTS sprayable material would be used for each entire cyclone with the exception of the bifurcated inlet area and lower cones. For safe and proper installation of the scaffolding, the first three sections of cones were removed and lowered to ground level. These lower cones would be completely replaced with new steel lined with KALCRET-BTX trowellable compound.
A wire mesh anchoring system was installed on all surfaces receiving the KALCRET wear compound. The inlet area and cyclone roofs were lined with the BTX trowellable KALCRET, while the bull nose was protected using an engineered KALOCER ceramic tile.
Using the spraying equipment, quick work was made of the remaining 2000 ft2, where 50 ft2 per hour of KALCRET-BTS was applied. The new lower cones, now lined with KALCRET-BTX, were then positioned back into place and re-assembled. Final touch ups and one final site
clean up were followed by demobilization on schedule.
According to Louis Senechal, project manager, “the benefits of the KALCRET lining were noticed immediately after start- up as the operators were able to control the temperature and airflow much more effectively which will allow for a more precise and efficient operation of the boiler.”
Increases in equipment wear life, as well as an improved operating efficiency, were just two of the benefits of the KALCRET abrasion resistant wear compound.
Lining the remaining 1000 ft2 of duct leading into the cyclones is already being discussed for the next outage.
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