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Do You Know How Many Therms You're Using?

Bruce Beggs |

MALIBU, Calif. – Natural gas and fuel oil prices have been on the rise in recent years, and industry veteran Al Jenneman doesn’t see that trend ending anytime soon. Thus, it’s vitally important, urges Jenneman, sales executive vice president from Kemco Systems, that commercial laundries regularly monitor their energy efficiency and adjust their operations accordingly.
This can be calculated using therms per hundredweight, he says, which is a critical and oftentimes cost-saving measuring stick.
“I’ve been in most every commercial laundry of any significant size, especially independent plants, in the United States, Mexico, Canada and even Europe,” Jenneman told the operators attending the 2006 Tech/Plant Summit hosted by the Textile Rental Services Association of America (TRSA). “One of the first questions I ask the operator is what he is running on therms per hundredweight. I would say that maybe one out of 10 can tell me what he is operating at on therms per hundredweight.
“Some of the larger chains do monitor therms per hundredweight and do budget therms per hundredweight. If they’re outside of that budget, that tells them immediately that they need to do something about their plant efficiency. If you know where you are in therms per hundredweight, then you can do something about it. If you don’t know, then it’s very difficult to make the kinds of adjustments you need to get that gas usage in line with where it should be.”
If operating efficiently, an industrial laundry plant should be at 1.8 to 2 therms per hundredweight, Jenneman says. On the linen side, he’s seen the number range widely from 1.6 to 4.3. “The plants I’ve seen that are at 4.3 generally don’t have any energy recovery equipment operating at all.”SAVE ENERGY OR ADD VOLUME?
So, why are energy-recovery equipment and an understanding of therms per hundredweight important?
If your laundry operates at 2.75 therms per hundredweight and delivers 25 million pounds annually, its annual fuel cost is $825,000 – or 4.9% of revenue if operating at 70 cents per pound, Jenneman says.
When energy-recovery equipment is installed and the laundry “tightens up the ship” to lower therms per hundredweight to 1.8, the annual fuel cost is $540,000, or a $285,000 annual reduction.
“If you look at this $285,000 ‘annual revenue enhancement’ this way, if you operate at a 12% profit margin, you would have to add $2,375,000 in annual revenue to produce this $285,000 annually in profit.”
Adding nearly $2.4 million in revenue annually wouldn’t be easy, he adds. You have to have the available market first, then pay for the additional textiles, machinery, labor and other expenses to boost your bottom line by an equal amount.
A brand-new boiler will produce 80% fuel-to-steam efficiency, based on the Btu [British thermal units] entering the burner in the form of natural gas and the Btu leaving the header in the form of pounds per steam, Jenneman explains. But overall steam boiler efficiency – typically around 67% – is dictated by losses in the transmission.
Percentages of efficiency succumb to part loading loss, zero loading loss, blow-down loss, distribution loss, flue loss, radiation loss and condensate and flash steam loss, he says. “Flash steam losses are probably the biggest sin, and the easiest thing to fix in the laundry with a vent condenser.”
Jenneman offered a formula by which laundries can calculate what gaining just 10 degrees in heat could mean to their performance.
“If you take 25 gallons [of water] per minute times a 10-degree temperature rise times 500, that’s 125,000 Btu per hour,” he explains. “At 65% boiler system efficiency, the consumption in gas is then 192,308 Btu per hour. With 100,000 Btu per therm, that means that 25 gpm at 10 degrees Delta T [the change in temperature in degrees Fahrenheit] is going to consume 1.923 therms per hour. If you’re paying $1.20 a therm, which is probably the going rate today, every 10-degree change on every 25 gallons a minute is costing you, or is worth to you, $2.31 an hour.”
If the laundry operates one shift or 2,080 hours per year, the thermal increase is worth $2.31 multiplied by 2,080, or roughly $4,800 annually per 10 F on 25 gpm. Laundries operating at higher flow rates obviously stand to gain greater benefit.
“There isn’t a plant that I’ve been in that I couldn’t squeak another 10 degrees out of if I had to,” he asserted.GREATEST AREAS OF ENERGY LOSS
Jenneman summarized the greatest areas of lost energy in a laundry:1. Wastewater heat recovery.
Either there’s no wastewater-heat recovery equipment in place, or the equipment isn’t properly maintained. Items of interest should be the condition of the wastewater pump, condition of the four-way valve, proper chemical cleaning and proper system balancing. Waste pump and tank inlet valves need clocks to assist in balancing wastewater pumps, Jenneman advises, and makeup valves should be on 90% of every day.2. Heat reclaimer performance is limited because the tempered-water tank is too hot.
Solutions include adding a blend valve, and adding a cool-down heat exchanger in the case of a healthcare tunnel.3. No boiler stack heat recovery.
This is the second most serious loss of recoverable heat next to wastewater heat recovery, Jenneman says.4. Flash steam due to poor trap maintenance.
No trap is 100% efficient, so flash steam recovery is a must, he says. It offers the fastest return on investment of all heat recovery.5. Dryer seals are bad.6. Boiler blow-down and makeup water are excessive due to a poor return system or too much live injection.7. Plant airflow is too negative in the winter, causing boiler and dryer combustion efficiency loss.
“I’ve been in plants where you could hardly open the front door,” Jenneman says. “They close up all the doors and windows because they don’t want that 20-degree air to come into the building, but natural gas has to have a lot of air to run a decent combustion efficiency.”8. Cooling water for hydraulic systems isn’t recovered or reused.9. A water-reuse system isn’t implemented when warranted.10. The laundry’s chemical supplier effectively has control of utilities, i.e., gas, water, electricity.
This arrangement could see your supplier lower his costs at your expense, Jenneman warns.11. Short-loading machines.
Loading a 900-pound machine with only 450 pounds of goods effectively doubles all utilities.12. Overdrying or overconditioning.13. Poor extraction efficiency.
This means more drying and conditioning and slower ironing, leading to greater gas consumption.14. Boiler system leaks.
Look at valve stems, excessive blow-down, and condensate return.15. Lack of insulation.
Consider insulating around tanks, headers, condensate return lines and steam lines.16. Direct-contact water heaters operating in recirculation too often.
Wastewater heat recovery yields 50 F on average if working properly and in balance, Jenneman says. Boiler economizers normally add 20 F to 25 F in heat recovery to the hot-water makeup flow. Vent condensers normally add 10 F to the total water flow.
“Today, if you’re over 2.5 therms per hundredweight, you’re wasting energy dollars.”
 

About the author

Bruce Beggs

American Trade Magazines LLC

Editorial Director, American Trade Magazines LLC

Bruce Beggs is editorial director of American Trade Magazines LLC, including American Coin-Op, American Drycleaner and American Laundry News. He was the editor of American Laundry News from November 1999 to May 2011. Beggs has worked as a newspaper reporter/editor and magazine editor since graduating from Kansas State University in 1986 with a bachelor’s degree in journalism and mass communications. He and his wife, Sandy, have two children.

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