Volume 25, number 2, September 2011

Industrial Dryers: Energy Now Recoverable

Today’s energy issues pose substantial challenges to equipment designers to make technologies efficient and utilization economical. Industrial dryers present the same challenges, and Québec has a good number of these. Recovering energy at dryer vents is quite difficult, since the lint (dried textile fibre) discharged with the hot, humid air, has to be handled well to avoid clogging the exchanger.

LintX from Airex

Under Gaz Métro’s Innovative Technology Program, Airex Industries proposed a system that would both recover the energy and manage the lint discharged from the dryers at Buanderie Blanchelle in Saint-Jean-sur-Richelieu. The plant, almost 60,000 ft2 in size, handles 6.7 million kilos of laundry per year. The Natural Gas Technologies Centre (NGTC) set up a demonstration project, installing measuring equipment on one of the laundry’s dryers.

Buanderie Blanchelle has been in business since 1977, principally serving clients in the health sector. It washes, dries and irons all sorts of textile products (bed linen, lingerie etc.) typical of that market. The laundry prides itself on staying at the leading edge of technology in its operations, hence its interest in an innovative technology project.

Buanderie Blanchelle has a dozen dryers that are used continuously to dry the treated textiles. The dryers were installed in 2008; the company operates six days a week.


The pilot project was run on one of the 12 dryers. The dryer is fed continuously and automatically. The lots of textiles are fed randomly, based simply on the availability of a dryer. A typical dryer can treat between 125 and 187.5 kg per lot and evaporate up to 5.9 kg of water per minute. The nominal consumption of natural gas is 34.95 m3 per hour. The average temperature taken in the exhaust air was 89.1oC. After projection, the measurements taken during the tests indicate that the annual consumption of natural gas by this type of dryer is 47,804 m3.

The choice of drying cycle is based on the lot sent to the dryer. The type of textile determines the temperature and the length of the drying cycle. The dryer burner modulates the supply of natural gas to maintain the temperature required for drying.

The energy recovery system at the Buanderie Blanchelle transfers heat from the hot, humid air vented outdoors to the air inlet of the same dryer.

LintX (energy recovery system)

LintX, the recovery system designed by Airex, is a heat recuperator fitted with a plate-type heat exchanger. The recuperator includes a system for removing lint from the dryer exhaust air, thus reducing the risk of clogging the heat exchanger. The system consists of a lint filter fitted with a cutter that limits the accumulation of lint on the filter, and a collector that removes the lint from the filter so the system does not have to be stopped periodically to remove the lint.

Results :
The results obtained during the measuring period are shown in this table.

  Reference case (dryer only) Dryer coupled to LintX Natural gas savings with LintX % energy saving
Annual consumption of natural gas (m3) 47,804 40,162 7,642 15.99%
Average natural gas consumption per cycle (m3 par cycle) 7.36 6.19 1.17
Average consumption of natural gas per kilo of wet textiles (m3/kg) 0.0478 0.0401 0.0077

Throughout the entire measuring period, no excess lint was ever observed on the surface of the heat exchanger. Note that the type of dryer used by Buanderie Blanchelle is fitted with a quite effective primary lint collection system.

The savings measured during the demonstration project were in the order of 16% on an annual basis, which represents a very attractive savings potential for all laundries in Québec. Since many industrial laundries like Buanderie Blanchelle have several dryers in their plants, it could be worthwhile integrating the all-in-one system of energy recovery to take advantage of the potential savings.

 

Marc Beauchemin, Eng., CEM
DATECH Group