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Food and Beverage

Winnipeg Oven Heat Recovery

  • Aug, 17 2011
  • Industry Sector:Food and Beverage

Challenge

In 2008, the company committed to replacing its aging Winnipeg fresh bread and rolls facility. The original facility was almost 100 years old and suffered from high costs to modernize the building and equipment. Hydro pricing had been increasing on average 3% per year, and natural gas pricing was increasing 22% over the first 6 months of 2008. Continuing at these cost increases, the plant would find utility costs becoming a significant factor in overall plant profitability. Cost savings for operating the plant could be realized by recovering waste heat for other uses inside the facility, and the capital and operational costs of the installation of a statute regulated steam system could be avoided.

 

The main stakeholders in this project were upper management, our production staff, central engineering, Air Management Technologies and Manitoba Hydro.

Strategy

The main goal of the heat recovery system was to negate the need for equipment and infrastructure costs to operate a conventional 50 BHP steam boiler system with its 70% overall gas to heat efficiency, and replace this with a system that would recover waste heat that is effectively 100% efficient. Avoiding the boiler plant at full loading would displace the need to combust over 1.7M BTU/hr of natural gas, avoid 172 lbs/hr of 10% boiler blow down water, and negate a boiler water treatment program that would have required wastewater monitoring and potential treatment. In the spring of 2008, Central Engineering completed a detailed review of the statute requirements of P95-92, The Power Engineers Act, to determine what design options and constraints would be encountered to build a heat recovery system, and compared this to the needs of a conventional steam boiler system. Manitoba Hydro was consulted for interpretation of some clauses of the Act and it was determined that, from a capital standpoint, heat recovery was a lower cost option. MB Hydro expressed interest at this time to support, via incentives, the installation of a heat recovery system depending upon design performance.

 

Air Management Technologies was contacted in early summer 2008, to provide a proposal for heat recovery to be incorporated in the overall plant design. In consultation with the oven suppliers, AMF and Bake-Tech, and the dough proofing supplier, Bake-Tech, a design was formed based upon a similar installation done two years previously at another Weston’s facility in the USA. Detailed design calculations indicated that the full boiler loading could be avoided, resulting in a potential net savings of 113,178 m3 of natural gas per year, with electrical consumption being held the same for both the heat recovery and conventional boiler options. Usage of potable city water was not needed for the heat recovery system, so boiler blow down issues would be avoided. Once the heat recovery design was completed, Manitoba Hydro was contacted in late summer 2008 to engage their support for the design and the offering of potential incentives.

 

In the fall of 2008, the main challenges for the system to proceed were to convince upper management that the design would be as reliable as a conventional steam system, and that the cost of ownership would be favorable. The reliability of the design concept was dealt with by consulting the USA facility where the original heat recovery system had been in operation for over 2 years. Topics related to capacity, reliable operational time, system maintenance and complexity for plant staff were discussed during several conference calls, and compared very favorably to a steam system. The resulting positive comments were forwarded to upper management decision makers. Cost of ownership was a comparison of capital outlay, labor costs, chemical costs and water usage costs between the heat recovery and steam systems. While capital outlay was found to be similar, secondary operational costs were found to be avoidable in the case of water and chemicals, or reduced in natural gas consumption.

Result

In the spring of 2009, upon completion of the construction of the new facility, the heat recovery system was put on line. Upon start-up, the cold start loading of both production line proofers was carried by the heat recovery from the rolls line only, validating the main design requirement of displacing the need for a steam boiler. In addition, the commissioning showed that a surplus of heat would be available for other secondary uses in the future, as the bread oven recovery unit was not in use at this time. Data collection presented to Manitoba Hydro during the months of July-August 2009 and during November 2009 showed that the heat recovery actually achieved was equivalent to 60,783 m3 of natural gas per year and 67,093 m3 of natural gas per year respectively. Scaled to the use of a 70% steam system, this gives a savings range of avoided natural gas consumption of 86,832 to 95,847 m3 per year, which is 76% of the designed target. The full potential savings of 113,178 m3 from the design could not be achieved due to the changes in production at the facility. The model required 24 hrs per day continual operations to keep the circulating fluid hot, but plant operations of 20 hrs per day allowed for cool down of the heat recovery fluid. Additionally, we learned that review of statute requirements in tandem with the governing utility would allow for a more complete understanding of design constraints and opportunities.

 

The business case to drive the heat recovery system resulted from net reductions in required capital and operational costs. The installation of a steam system would have required additional money to construct a separate steam plant building, a water treatment plant for boiler water, a wastewater treatment plant for boiler blow down, and more complex distribution piping. These extra costs were estimated at over $400,000. Operational costs would have been escalated with a steam plant due to chemical treatment programs, additional water use, and stationary engineering requirements. Chemical treatment programs cost on average $5000/yr for our facilities and water use savings would be nominal. Reallocation of stationary engineering salaries towards more technical maintenance staff was the preferred staffing option. Proven gas savings of 86,000 to 95,000 m3 gas per year amounted to a minimum of $27,000/yr in natural gas savings for this installation. Manitoba Hydro supplied a net incentive of $29,000 to the project upon supply of the verified gas usage data. The overall cost of project was $242,000, with year one total savings of $461,000 for operations and capital with ongoing savings of $32,000, excluding repairs and maintenance costs of the avoided steam plant building. The project embedded in the company psyche that heat recovery is economically viable, and would be the method of choice for future replacements or green field installation of systems requiring steam.

 

Read more about the Winnipeg Facility in the Natural Resources Canada OEE publication.

Website Links

http://oee.nrcan.gc.ca/industrial/technical-info/library/newsletter/archives-2010/Vol-XIV-no-15-aug15.cfm?attr=24#a

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