Capture more turbine energy with CHP
Frito Lay Takes the Step
An example of an ideal installation of a combustion turbine in a CHP installation is at the Frito-Lay plant in Killingly, Connecticut. This large scale producer of potato and corn snack products uses daily a quarter-million pounds each of corn and potatoes in a 24-hour manufacturing operation, with a peak electrical demand of 3.8 MWe and a minimum of 1.5 MWe.
In addition, the facility has a peak annual steam demand for up to 90,000 lbs/hr of saturated steam at 325°F for process applications. The minimal steam demand is on summer weekends, at 12,000 lbs/hr.
Because the plant was in an area with power reliability problems caused by distribution constraints, the plant had experienced significant interruptions in service. This created issues in terms of lost production, wasted stock in production and required re-inspections. According to Christopher Wyse, Communications Manager for Frito-Lay North America, the area also has high electric rates.
Further, the company needed additional steam generation capacity to keep up with growing production. Wyse indicates that they knew that “CHPs are common in other industries and have a proven reliability record, provided the owner follows a proactive maintenance program.” Beginning in 2006, working with consulting support from Dana Technologies, they investigated and began the engineering and permitting process to install a CHP system powered by a combustion turbine with heat recovery for process steam.
Major Part of Plant Energy Needs
In July, 2008 they began construction. The system uses a Solar Turbines 4.6 MWe Centaur 50 turbine with heat recovery by a Rentech HRSG, along with a Coen supplemental duct burner for additional and standby steam capacity. The turbine can provide nearly 100% of the site electrical requirement, and releases heat to generate 24,000 lbs/hr of steam without supplementary firing. With supplemental firing, the unit produces 60,000 lbs/ hr. This represents nearly 90% of the site steam requirement. The company maintains a connection to the electrical utility and purchases a small amount of power to maintain the connection.
After a short and trouble-free startup and commissioning, the system went into operation in March, 2009. In the first two years since beginning operation, the turbine had 96.5% availability. In that period, the CHP project has saved the company $930,000 in operating costs, as well as assuring improved reliability and reduced emissions.
Taking into account an incentive payment from the State of Connecticut, the payback on the project was calculated at 6.9 years. The current low natural gas prices are rapidly lowering the expect payback period. Also, this does not include the benefits to production from improved electrical reliability. On several occasions the plant was spared significant operating losses during grid power interruptions.
Dual Fuel Where Appropriate
Manufacturers do offer combustion turbine units designed for dual fuel operation – usually natural gas and fuel oil. In most parts of North America natural gas has a significant advantage in price. Lyons from Solar Turbines notes, “Dual fuel applications are more prevalent in the Northeast of the United States, where most of the large users have interruptible gas supply contracts. However in places such as California, Texas, Louisiana, etc. dual fuel is not as common.” Where dual fuel is necessary, most owners have a few day’s supply of fuel oil on hand to use as needed.
Another provider of combustion turbines for industrial and large commercial users is Kawasaki Gas Turbines – Americas. Kawasaki offers base load turbines in seven size classes from 600 kWe to 18 MWe. In addition, Kawasaki has a separate line of standby power turbines in sizes from 750 kWe to 4.8 MWe. The base load units would be the equipment suitable for heat recovery and full-time CHP operation.
As an example of CHP benefits, Kawasaki installed a 1.5 MWe cogeneration plant in 2007 for a major East Coast pharmaceutical company. The unit was supplied with an unfired heat recovery boiler providing over 11,000 lbs an hour of steam to the plant. The plant incorporated a KGTA pre-wired extended electrical skid which facilitated a quick installation on site.
This plant installation provides power plus steam at an overall 80% thermal efficiency rating. This plant also qualified for a state grant for its CHP energy savings. This facility uses Kawasaki Dry Low Emissions (DLE) technology ensuring lowered exhaust emissions, with NOx less than 20 ppm and CO less than 50 ppm.
Consider Your Application
Not every application will benefit from combustion turbine CHP, but if you have major thermal requirements for process steam or absorption cooling, plus a relatively continuous need for electric power, it may be your solution. An onsite plant can improve your power supply reliability, and could also lower your carbon footprint and reduce total emissions.
Help is Available
Ed Mardiat indicates that there are multiple sources for guidance in developing a CHP installation. “The first place I would recommend is the U.S. EPA CHP Partnership, which has developed several resources for CHP screening, spark spread analysis, emission calculators and a database for CHP incentives listed by state. Beyond that, I would recommend the owner find an engineering consultant that has experience preparing CHP Feasibility and Economic Investment Grade Audits at the specific type of facilities being considered.” For large energy users, industrial turbine CHP is here, and it’s better than ever.
- This story appeared in the Summer 2013 Gas & Technology supplement. See additional stories below.