New Boilers or Retrofits?

First Canadian Centre building was completed in 1982 and was the tallest building in Calgary at the time. By the year 2009 the two low-pressure boilers were almost 30 years old and an upgrade was needed to increase building efficiencies. Typically, boilers that are 30 years old and that have had good maintenance operate at an efficiency of about 75-80%. As an operations team it is understood that the steam is critical to the operation power and building. There is almost one-third of the buildings energy usage being used by the boilers, and system inefficiency is something that cannot be overlooked.
First Canadian Center was faced with 4 different options to increase the building efficiency regarding the boilers. The following are the options that were reviewed:

1. Replacing the steam system with hot water boilers: The steam boilers heat exchangers, air handling coils and distribution systems would all need to be replaced incurring high costs.

2. Joining District Energy: This option presents the same challenges and costs as with installing new hot water boilers.

3. Replacing the existing Cleaver- Brooks fire tube steam boiler with new steam boilers: The boiler plant has a 400ft boiler flue and this presented challenges in adopting new boilers. The boiler room is on the 4th floor and bringing in new boilers would require the demolition and reconstruction of multiple walls including the main fire rated stairwells and the building envelope.

4. Retrofitting the existing units with an efficient boiler burner: The 4 pass steam boilers are inherently the most efficient units.

After 2 years of research and consideration of all options it was determined that retrofitting the existing boilers was going to be the most cost-effective solution. The boiler pressure vessels were in good shape therefore the retrofit was viable.

The following were installed:

  • High-efficiency Cleaver-Brooks burners; Increasing the burner turndown rate reduces purge cycles and loss of stored heat through the stack.
  • Cleaver-Brooks Hawk PLC-based boiler control system with oxygen trim and parallel positioning; Monitors and manages combustion control.
  • Fuel-air characterization; Increases combustion efficiency by providing precise, repeatable fuel-to-air ratios throughout the boiler’s firing range.
  • Variable-speed combustion air-fan control; Improves air volume and velocity control throughout the firing range.
  • Lead-lag control; Multiple boiler capacity management to suit load conditions for reduced radiation and purge-cycle losses. This allows more controlled cycling of the boilers.
    Boiler 2 was retrofitted in 2010 and Boiler 1 was completed in 2011. This change has shown a reduction of 33% in natural gas consumption (from 50,000GJ vs 35,000GJ).
Year% Change from 2011
20110%
201214%
201312%
201415%
201532%
2016*61%*

*partial year

When starting this project the price of gas was between 10-12$/GJ, with this price it would show about a 4 year pay back. These changes have increased boiler efficiency by bringing its performance nearly up to today’s new boiler systems. The emissions were decreased from uncontrolled to low NOx. This change and innovation project has allowed First Canadian Centre to be awarded with the President’s Award for Sustainability from BOMA Calgary.

 

Alison Darling – Thorburn

BOMA Member

Submitted on behalf of the BOMA EH&S Committee

Aydan Aslan
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