In the summer of 2000, the facility's plant manager, Robert Bowman, decided it was time for the plant's 30-plus-year-old secondary water tube boiler to go. While the plant has a primary boiler that carries about half the load, the boiler Bowman wanted to replace served mainly as a backup and covered weekend loads. Some of the secondary unit's tubes had been removed, it didn't have an economizer, it had refractory problems, and its skin had been repaired a number of times.
"The desire to increase energy efficiency was a major part of the decision. The boiler served as our weekend load as well as a backup for the main boiler, and its combustion efficiency on the high end was OK, but on the low end, the radiation and combustion losses put it in the low 60% for thermal efficiencies," he said.
Weighing the Options
Bowman contemplated a number of options. First, he considered selecting a cogeneration unit that would produce electricity and steam, but the capital investment involved, combined with the cost of natural gas, made it prohibitive. Next, Bowman pondered the option of retrofitting the boiler. However, changing the tubes and refractory, and upgrading the combustion controls would have been costly and the unit still would have been inefficient on the lower end of operation.He also thought of replacing the unit with a new, or even used, large water tube boiler of the same type. That idea was shot down because it was cost prohibitive, and also because the existing boiler was basically landlocked in the building. Putting a similar unit in that space would have required removing part of the roof and lowering it in from above.
"So it came down to replacing it with smaller units that we could bring through the doors," Bowman said, adding that this familiarity with the Miura EX 300 BHPs from his previous job also made the decision easier. He had selected Miura boilers when he worked as engineering services manager with E.D. Smith (a food processor of jams, ketchup, salsas, pasta, and various other sauces). In that situation, the installation facilitated a staff reduction since Canadian requirements for boiler operators are tied to boiler size. By installing compact Miura boilers he reduced his staff requirement from three operating people per day (one each per three shifts) to only one day-shift person on at a time. This person's role became more focused on accomplishing maintenance.
Low-end Efficiency Achieved
Easing the operating staff wasn't the objective at Labatt. The project was justified on a payback of energy savings, Bowman said. "It would allow us to have higher- and lower-end efficiency and the multiple units would be able to handle increasing loads," he added. The installation, which was performed by a local contractor, Gimco (Markham, ON), went relatively smoothly.One of the main tasks was tearing out the existing boiler, and that went off without a glitch, Bowman said. One of the only challenges involved in the installation was that the boilers were delivered upright, when in order to get through the plant's doors, they had to be turned on their sides. However, there were no other significant problems.
The installation was complete in August 2000 and the results have impressed Bowman. The new Miura units now carry about 40% of the plant's needs. "We operate these boilers all the time to supplement our primary boiler to maximize our efficiencies. They run 30,000 lb/hr - 900 bhp [boiler horsepower,]" Bowman, said.
"There was about a 15% reduction in fuel for equivalent loads, and we have been getting good efficiencies on weekends that we never realized before. We could probably justify the addition of another 300 hp and 200 hp - they would give us more backup power and the smaller unit would better handle the smaller loads," he added.
