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Energy Savings Opportunities:
- Change Boiler Efficiency – Flue gas oxygen is measured during the annual tuning of the boiler’s positioning-type air-fuel ratio controller. The controller does not include feedback from an oxygen sensor. There may be an opportunity to improve the efficiency of the boiler by lowering the excess oxygen present in the flue gases. The plant should continue to evaluate the costs and benefits of a robust, automatic control system. If an automatic controller is not cost effective, there may be an opportunity to decrease stack oxygen levels slightly during the annual tuning of the existing controller. For the purposes of the ESA we assumed a potential decrease in boiler flue gas oxygen from approximately 5% to 2.5%. Note: The plant should measure carbon monoxide during the boiler tuning efforts. The presence of carbon monoxide indicates the presence of unburned fuel in the boiler furnace.
- Change Boiler Efficiency – Boiler no. 3 is fitted with a stack economizer. There is an additional opportunity to increase efficiency by adding a stack economizer to one or two more boilers. For the purpose of the ESA we conservatively assumed a potential 90 deg F reduction in stack temperature (from 385 to 295 deg F).
- Change Condensate Recovery Rates – There may be an opportunity to increase the high pressure (125 psig) steam condensate recovery rate to approximately 60% (from 50%) by modifying the piping associated with the steam coil space heaters.
- Implement Steam Trap Maintenance Program – The plant has a relatively small number of steam traps (approximately 30). Nevertheless, there is an opportunity to realize some savings by implementing a steam trap maintenance program.
- Implement Steam Leak Maintenance Program – There is an opportunity to realize some savings by fixing steam leaks throughout the facility. Some of the leaks are at valves and pipe fittings, others are from loose-fitting doors or ineffective water seals on steam blanchers.
- Condensing Boilers for Heating Sanitation Water – There is an opportunity to reduce fuel use by heating sanitation water with small and efficient condensing boilers instead of the relatively large and less efficient package boilers. This project would include the installation of a new 3.5 MMBtu/h condensing boiler and associated electrical connection for a draft fan, stainless steel exhaust ducts, and plumbing. The new condensing boiler would be installed on the sanitation tanks being maintained at 125oF, while the average inlet temperature of the water is 80oF. The new condensing boilers are capable of accepting very low return water temperature that leads to condensing exhaust gases. The boilers and its heat exchangers are fabricated with materials that allow them to withstand the impacts of condensation of boiler flue gases.
- Improve Insulation – Several insulation opportunities were identified using E3+ software.
- Sanitation water tank (125 deg F)
- Tunnel defrost water tanks (3 tanks, 100 deg F, outdoors)
- Tunnel defrost water tank (100 deg F, indoors)
- Blancher water line (6” diameter, 170 deg F)
- Boiler steam valves (8” valves, 10 pcs.)
- Continuous cookers
- Boiler blowdown lines
- Chill water lines (6”)
- Multiple Boiler Optimization –There is an opportunity to develop a systematic approach to boiler operations that ensures that steam demand is always being met with the most economical combination of boilers. Such a system was once installed at Norpac but, for reasons that are not clear, the system has been out of service for many years.
Other Options Considered:
Several potential energy savings opportunities were found to be impractical or uneconomic.
1. Change Boiler Blowdown Rate - Boiler makeup water quality and the low condensate return rates associated with this plant’s type of end use equipment contribute to a current blowdown rate of approximately 10.5% of the feedwater flow rate. There may be a cost- effective opportunity to reduce the boiler blowdown rate from 10.5% to 3.0% using either softener chemicals or a reverse osmosis (RO) system; however, our initial and informal cost estimates for these systems led us to conclude that they may be uneconomic. The plant should further investigate the existing controller set-points and the costs of softener and RO systems to determine the economic merits of reducing the boiler blowdown.
The following turbine-related projects were considered and rejected because the economics are unfavorable:
2. Install a combustion turbine (gas turbine) and heat recovery steam generator
3. Install a condensing steam turbine generator or steam turbine driven chiller
4. Install a backpressure steam turbine generator or steam turbine driven chiller
The potential energy savings opportunities summarized on page 1 include estimated time horizons for implementation. The opportunities are categorized as near-term, medium-term, or long-term according to the general guidelines below.
- Near-term opportunities include actions that can easily be attained in less than one year. Examples include improvements in operating activities, equipment maintenance, and relatively low cost actions or purchases.
- Medium-term opportunities would typically require one to two years to implement and would require additional engineering and economic analysis. Examples include capital equipment purchases and moderate changes to the plant’s steam system or processes.
- Long-term opportunities typically require two to five years to implement. Examples include new technologies or significant changes to either the steam system or the plant’s processes.
||% of Savings Opportunities
Management Support and Comments:
The Stayton plant production manager and Norpac corporate engineer participated in this Energy Savings Assessment. Their active participation and collective experience made this a productive ESA. The Norpac team will continue to use the DOE suite of steam tools to quantify additional energy savings opportunities in Stayton and at other Norpac facilities.