Knowledge is Power—A Look at Energy-Saving Equipment Options
Knowing what you use and acting to conserve could save you thousands

By Al Jenneman

No doubt you recently checked the gas mileage on your car. Most of us nowadays have an in-dash computer that will tell us instant and average miles per gallon. You feel it’s important because that tank that used to cost you $30 now costs you $60 or more.
Checking and improving the “gas mileage” of your laundry is just as economically and environmentally important because you’ve probably experienced the same percentage increase—or more!

Gas mileage, you say? Well, let’s refer to it as “gas unit consumed per unit produced.”
The laundry industry generally has boiled this down to a common denominator in the industry of “therms per 100 weight.” Some managers calculate therms per “soiled” 100 weight and some use “clean dry weight” as a production unit. Clean dry weight seems to have surfaced as the preferred unit, because clean dry weight is more consistent. Soiled weights may contain anywhere from 5-20% soil by weight, and thus skew your study, as soil conditions vary.

Whether you use “soiled weight” or “clean dry weight” units doesn’t really matter. The important factor is to know what the terms per 100 weight consumption is for your laundry(s).

Knowledge is power. You can fix what you know is a problem, but you will not fix what you do not know is a problem and miss the profit-enhancement opportunity it presents.

How low can you go?
Part of the laundry industry’s dilemma is that there is no “benchmark” or standard for fuel consumption per pound. There is no benchmark on what the standard therms per 100 weight should be in an industrial laundry in Peoria, IL, washing 25% volume (by weight) in mats and 75% uniforms. But as an industry, we are getting closer to arriving at that number as we receive more data from laundries.

A major industrial chain reports that it budgets 1.8-2 therms per 100 weight in gas, while food and beverage or hospitality plants say they are “all over the map” on therms per 100 weight, some operating under 2, and others over 4 therms/100 weight. Hospital laundries also vary significantly on this figure. Some report 2.2-therms/100 weight, while others are over 4.
One therm per 100 weight is a huge cost factor. One industrial laundry recently reported an energy cost of $1.20 per therm.

Save energy or add volume to increase profit?
If you are operating at 2.75 therms per 100 weight and you deliver 25 million lbs. annually, your fuel cost is $825,000 annually—or 4.9% of revenue if you operate at 70 cents per lb. revenue. When you install energy-recovery equipment and “tighten up the ship” where you lower your therms per 100 weight to 1.8, your annual fuel cost is $540,000 annually or a $285,000 annual fuel cost reduction.

You could 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 $2,375,000 in annual revenue is not easy. You have to have the available market first, and then you have to add garments, mats, linen, napkins or whatever else, plus machinery and labor, in order to improve your bottom line by an equal amount.

The investment in energy recovery equipment could cost less than the additional rental goods, machinery, associated labor and cost of sales, while providing a more attractive return on that investment.

Where does all that natural gas go?
A detailed breakdown on where all that natural gas is consumed can be difficult, but basically it goes to distinct areas of the plant and laundry process:

1. Wash aisle (water heating)
2. Dryers, conditioners
3. Flat work, pressing or tunnel finishing
4. Building and office heating.

Although not always the case, generally gas is consumed in approximate equal amounts in the wash aisle, dryers and various forms of finishing.

This article was not designed as a detailed engineering study, but rather to enhance your awareness of “total fuel consumption per unit washed.”

Heating water does not have to be the highest gas consumer
In the wash aisle, water heating can be the largest consumer of natural gas via the water heating system, generally through the steam boiler. Water heating loads are in direct proportion to the change in temperature or “delta T” needed to raise water from ambient cold temperatures, which average about 60ºF around the United States, to the required wash aisle temperature which averages about 100ºF (60-160ºF) in most laundries.

If you cross section laundries that meter boiler and dryer gas separately, most consume about 66% of the total natural gas used via the boiler and 34% through the dryers. That 66% boiler gas is then broken down further. Generally, 66% of the boiler gas goes to water heating and the balance to steam used in finishing. Therefore, of a $30,000 monthly gas bill, about 44% goes to water heating and the balance to drying and finishing.

For the sake of study, let’s look at the “therms/100 weight” used in heating water for an 800 lb. load of medium-soiled linen using 2.4 gallons per lb., 50% hot water at 160ºF. We also are going to use the following values in calculating therms consumed:
1 British thermal unit (Btu = Heat required to raise 1 lb. of water 1 degree F.
1 therm = 100,000 Btu
1 therm = 1 CCF on your fuel bill
1 boiler horsepower (HP) = 33,472 Btu
Delta T = change in temperature in degree F
Cold water is 60ºF
Hot water in wash wheel is 160ºF
Boiler combustion efficiency is 80%
Boiler system (Btu output in steam versus Btu input in gas) efficiency is 65%

Therefore:
800 lb. x 2.4 GPP = 1,920 gallons of water
50% hot = 960 gallons per lb. (hot)
960 gallons delta T (100ºF) x 8.33 lbs. per gallon = 799,680 Btu required in the wash wheel
Note: This figure does not include live injection in the wash wheel to maintain the 160ºF for hot water.

However, to deliver 799,680 Btu to the wash wheel with a 65% efficient boiler system, this number has to be divided by the boiler system’s efficiency to obtain required boiler gas input in Btu.

Thus, the gas input is: 799,680 divided by 65% system efficiency or 1,230,276 Btu gas input to deliver 799,680 Btu to the washer.

799,680
.65 = 1,230,276 Btu in gas

One therm of natural gas is 100,000 Btu. Therefore this 800 lb. load consumes 12.30276 therms of gas or 1.54 “therms per 100 lbs.” to heat water.

12.30 therms
8 = 1.54 “therms/100 weight”

If we break down the dryer gas consumption, it could be calculated like this:

Assume two 400 lb. loads or an 800 lb. total. Moisture retention after extraction = 50% or 400 lbs. of water. Evaporation of 400 lbs. of water in the drying process with the dryer at 50% efficiency is calculated as follows, assuming the goods and retained water enters the dryer at 80ºF ambient temperature.

1,200 lbs. of goods and water x delta T = Btu
1,200 lbs. x (212ºF - 80ºF) = 158,400 Btu required

For this calculation we are going to assume dryer efficiency at 50%.

158,400 Btu
50% efficiency = 316,800 Btu input in gas

316,000
100,000 Btu/therm = 3.16 therms of gas

3.16 therms of gas divided by 8 hundred weights = .39 therms/100 weight

We are now at 1.54 to heat water + .396 for drying or 1.936 therm/100 weight so far.

Flatwork ironers’ gas consumption can be high
Now, let’s run this load thru the flatwork ironers, assuming it takes 60 minutes to do so. An ironer consumes about 2.5 boiler horsepower (HP) per roll/per hour so an 8-roll ironer uses about 20 HP per hour (8x2.5=20). Delivering 20 HP per hour to the ironers at a 65% boiler system efficiency means that 669,440 Btu/hr (20X 33472), is delivered to the ironer because 1 HP = 33,472 Btu. A boiler system therefore consumes

669,440 Btu output divided by
.65 boiler system efficiency = 1,029,907 therms in gas to heat an 8-roll iron or

1,029,907 Btu divided by 100,000 Btu per therm = 10.299 therms/hr

10299 therms
8 = 1.287 “therms of 100 weight”
Here is the total “therms consumed per 100 weight”:
1.54 water heating
0.39600 dryer(s)/conditioning

1.287 ironer/finishing

3.22 “therms/100 weight” consumed to wash, dry and finish an 800 lb. load of table linen.

How to reduce therms/100 weight with heat recovery
The goal is to reduce therms per 100 weight closer to a benchmark of say 2.2 therms per 100 weight or lower. How is this cost effectively accomplished without undermining quality? Heating water can be the largest gas consumer in this example, as demonstrated above.
You may be able to reduce water consumption (check with your chemical supplier), but with the industry having reduced total water by 50% or more over the past 5-10 years, how much further can you go without installing water reuse or recycling equipment?

Water temperature rise is the largest factor left after “gallons per lb.” is minimized. A good heat-recovery system will reduce your delta T by 50% because most (heat reclaimers) will produce 110ºF-preheated water with wastewater at about 120ºF. Therefore, when using wastewater heat recovery, the therms per 100 weight in water heating would drop by 50% to .77 (from 1.54 as previously calculated above), thus bringing our therm per 100 weight to .77 + .396 + 1.287 or 2.453 therms per 100 weight—simply by utilizing and maintaining a good heat reclaimer.

Other cost-effective devices
There are two more extremely cost-effective energy recovery devices that will significantly reduce water-heating costs. The first additional item is the Direct Contact Condensing Boiler Economizer. Typically, these devices recover 600,000 Btu/hr per 100 hp of actual fired boiler load when fed preheated water from a heat reclaimer at about 100-110ºF. These economizers normally add a 20ºF rise to the hot water portion of the makeup water flow. (This average temperature gain is calculated from an average of hundreds of installations of Direct Contact Economizers operating in commercial, institutional and industrial laundries.) How does this system affect the therms per 100 weights in our example? A 20ºF rise on the 110ºF preheated water from the wastewater heat recovery system means the delta T is now only 30ºF (160-130ºF) on the 960 gallons of hot water in our formula. The Btu required is now at 960 x 30ºF x 8.33 or 239,904 Btu. With our boiler system at 85% efficiency—because stack loss is eliminated—the Btu gas input is 239,904 ÷ .85 = 282,240. That’s down from 1,540,000 prior to wastewater heat recovery and the 770,000 Btu after wastewater heat recovery. Water-heating related therms per 100 weights is now 282,240 ÷ 8 = .3528 therms per 100 weights on that 800 lb. load.

We are now down to .3525 (water heating) + .396 (dryers) + 1.287 (flatwork) ironers or a total of 2.034 therms/100 weight.

Flash Steam Recovery System
The last and most cost effective energy recovery device in terms of R.O.I. is the Vent Condenser or Flash Steam Recovery System. Flash steam generally amounts to at least 5% of the boiler steam output, even when the traps are perfectly maintained, and can be as high as 10% of the boiler steam output. Hundreds of vent condensers now on line show the average temperature rise they typically add to the hot water makeup flow is 8ºF. If we add this 8ºF to the hot water makeup flow the delta T in hot water now becomes (160ºF - 138ºF) or 22ºF. The Btu delivered to the washer becomes 960 x delta T 22 x 8.33 or 175,930 Btu. A boiler system efficiency of 90% after the installation of the flash steam condenser means the gas input now drops to 175,930 Btu ÷ .9 or 195,477 Btu input down from the original 1,540,000 input to heat water alone without any form of heat recovery. Water heating Btu input is now a total of 195,478 therms ÷ 8 or .24434 therms per 100 weight.

Total therms per 100 weight is .24434(water heating) + .396 (dryers) + 1.287 (ironers) or 1.93 therms per 100 weight and thus very near the 1.8 to 2.2 therms per 100 weight benchmark, proving this IS an attainable goal.

How would a 1.29 therms per 100 weight gas reduction affect your bottom line?
Here is how to determine that number. Divide your (clean dry) 100-weight poundage into the therms you presently consume in the same time frame (generally per month or a natural gas billing period).

Example:
monthly purchased natural gas therms = 60,000 CCF
Monthly 100 weights processed= 20,000
Therms per 100 weight consumed = 3.0

If you reduce your gas consumption from 3 therms to 2 therms per 100, you would avoid the purchase of 1 therm per 100 weight. If you wash 24 million lbs. per year, your annual fuel cost avoidance (at $1.20 per therm) = 200,000 x $1.20 or $240,000 annually.

Here are some other ways to significantly reduce your fuel bill or therms/100 weight:
Check your steam and water systems for leaks. These leaks can cost $1,000s/year.
Make certain your heat recovery system is delivering to its design performance specifications. Add capacity and/or clean and maintain it. Tempering cold water with heat recovery reduces your percentage of hot water and related gas consumption.

Balance your system so fresh water is flowing along with wastewater the majority of the hour. A clock installed on the wastewater pump starter and on the fresh water make up valves will indicate what percent of the hour they are operating.

Look into additional energy-recovery systems such as direct contact economizers or vent condensers for maximum energy recovery.

Check your dryer’s seals. Poor dryer seal maintenance significantly reduces dryer efficiency and increases gas consumption.

Clean dryer baskets to maintain airflow and efficiency.

Reduce or eliminate live steam injection in the wash wheel as much as possible. Live steam injection increases boiler make up water, increases boiler feed water chemistry and increases boiler blow down requirements.

Recently, a major upper-Midwest industrial launderer reported gas consumption at 1.2 therms per 100 weight (clean dry) and going down! Their goal is 1 therm per 100 weight. Energy-conservation measures along with excellent plant maintenance provided a significant portion of this low therms per 100 weight consumption.

Knowing your therms per 100 weight and doing what it takes to lower gas consumption will significantly improve your bottom line while maintaining quality. TR

Al Jenneman is executive vice president of sales and a 23-year veteran of Kemco Systems Inc., Clearwater, FL. He previously operated a large steam-generating facility for a major U.S. leather tanner in Milwaukee, WI. Contact him at ajenneman@kemcosystems.com or 800/ 633-7055 ext. 230.