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By Mike Pehanich, Plant Operations Editor | 01/09/2007
Soaring energy costs — and the chronic risk that they will only climb higher — have altered the economics of the food processor’s supply chain. One way processors can get a grip on energy is to maximize the efficiency of equipment on processing and packaging lines.
Kettle Foods has one of the largest commercial solar arrays in the Pacific Northwest on top of its plant. It generates approximately 120,000 kWh per year.
“The market is being challenged by high energy prices,” says Ted Worlick, engineering director for Schneider Electric (www.us.schneider-electric.com), Palatine, Ill. “A lot of companies saw their natural gas bills double. Now we’re at a new high plateau for natural gas. Electricity costs continue to head upward.”
The challenge is doubled in that processors, who are finally running plants at higher capacity utilization rates, cannot — and should not — sacrifice manufacturing output with equipment replacement or plant modifications. But processors do need to make energy investments that create savings over the long term.
Despite the enormous burden to operations costs that soaring fuel bills have added in recent years, many food companies have yet to take important energy-savings steps: from developing comprehensive energy programs to replacing or modifying equipment to making the necessary plant upgrades to save big energy bucks.
Incredibly, some companies have barely scratched the surface when it comes to processes and procedures to identify waste and save significantly on fuel costs. Heat recovery, capital projects for energy conservation and investment in energy control optimization continue to come on strong and have become more sophisticated — especially for companies that already have plucked the low-hanging fruit with the simplest changes in plant practices.
Manufacturers have put energy efficiency high on their priority lists. “We’ve addressed energy efficiency in heating and cooling, pumping, homogenizing, and fluid and product movement,” says Jim LeClair, technical director for APV Invensys (www.apv.invensys.com), WHERE. “Mixing, too. The more efficiently your equipment uses energy, the lower your cost of ownership (the sum of energy and maintenance costs). Your payback comes back quickly.”
Today’s high efficiency centrifugal pumps, for example, have added 20-30 percent energy efficiency on top of the overall performance efficiency of the pumps, compared to pumps of the 1970s and ’80s. “We have gone from 45 percent pump efficiency to 75-85 percent efficiency. That means for every horsepower you put into a pump, you are getting an average 70 percent return. That’s a significant difference,” says LeClair.
Those are the kinds of savings plant personnel frequently overlook. But the addition of small improvements – even on systems as seemingly inconsequential as clean-in-place systems — can add up to big savings.
Heat exchangers have been other key targets for energy savings. New designs operate more efficiently at lower pressure. Heat exchangers operating at 75 psi today may work as effectively as those that operated at 100 psi in the past.
Manufacturers have focused on pressure and efficiency of heat exchangers to lower energy requirements.
“The lower the pressure drop required to maintain adequate pressure, the less pumping your equipment will need to do,” explains LeClair. “As for the efficiency of heat exchange or the heat exchange pump, it is determined by the thickness of the plate and how (flows — port to port and cross flow — across the plate.”
Energy-efficient designs can have significant long-term impact on plant energy costs. For example, LeClair touts APV’s corrugated tubular heat exchanger for its energy efficiency. “The corrugated tube creates more turbulence and produces a better mixing of heat.”
Homogenizers and mixers that require lower pressure to operate also are proving their worth in energy savings.
“The more efficiently you can make a homogenizing valve, the less pressure you’ll need and the less energy you will use,” says LeClair. In dairy operations, for example, taking a homogenizer’s 1,800 to 2,600 psi requirement down to 1,100 psi will result in a huge energy savings.
“We have valve systems that will take pressure requirements down to 100 psi. That’s $10,000 to $20,000 savings just due to the pressure difference in one year,” says LeClair.
Simply replacing drafty old doors with modern, energy-efficient ones can be a big energy saver, as discovered by Truitt Bros.
Processors can justify equipment purchases and energy management programs only when they have adequate data. Good data facilitates negotiation for better energy rates. Knowing energy requirements at every significant point in the plant makes it easier to identify problems with power systems and to lower power demand charges. It can also reduce downtime and help avoid blackouts.
Motors are always candidates for efficiency upgrades. Rockwell Automation published a study in 2002 showing the food industry was able to effect total energy cost savings of 12.4 percent in applications with high motor system content by implementing efficiency measures.
Baldor Electric (www.baldor.com), Fort Smith, Ark., the world’s largest manufacturer of motors, often quotes a U.S. Dept. of Energy report that claims “electric motor-driven systems used in industrial processes consume some 679 billion kWh, or 63 percent of all electricity used in U.S. industry.” It’s easy to see how even a small efficiency increase in a motor, multiplied by the millions of motors out there, can add up to huge reductions in electricity use.
In 1992, the Energy Policy Act established minimum efficiency standards for industrial electric motors made after October 1997. But Baldor estimates only 10 percent of all motors in use today comply with those minimum efficiency levels.
The greatest gains in energy savings come when processors can integrate improvements from as many of the components of energy consumption as possible. In addition to motors, these include motor controls, power distribution, transmissions and plant floor equipment and processes.
Energy audits, of course, always precede such efforts. Plant drawings and utility bills come into play. Measurements of energy consumption at key points of the operation are critical. Motors driving processing and packaging equipment should be monitored often.
Strategies for improvement include load profiling, measuring electrical consumption over time; demand management to control electrical loads and to avoid demand penalties; and co-generation and the addition of backup energy measures.
In the late 1990s, Kraft Foods engineers lamented that the difficulty of demonstrating return on investment for capital expenditures indefinitely delayed needed boiler upgrades. They were not alone. Much of the food industry was guilty of the same penny-wise, pound-foolishness, for which processors paid dearly as energy prices skyrocketed.
“When processors should have made investments in the 1990s, capital dollars didn’t go into energy systems,” says Schneider Electric’s Worlick. “A lot of systems are 15 to 30 years old. We see more attention to them today. Companies are looking at ways to make older systems more efficient, but energy efficiency measures are still fighting hard for attention today.”
Companies that avoided upgrades to steam generators and heat recovery systems in the past might want to reconsider. A lot of companies passed up steam trap systems to capture waste heat, steam vent losses and boiler stack losses a few years back. Worlick says they may want to take a second look today.
“The economics that come into play are different today,” he says, identifying ionic stack economizers and other pieces of heat recovery equipment surrounding boilers as savings-makers. “If you have a place to put steam back into the process, you are now seeing one- to two-year payback."
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