Volume 24, number 2, september 2010

Norampac Vaudreuil optimizes its steam system

The optimization of a steam system and its conversion into a closed system helps improve production while generating considerable savings.

Norampac, a division of Cascades Canada Inc., is the largest producer of cardboard in Canada and an important manufacturer of corrugated cardboard products. Norampac Vaudreuil annually produces 900 million square feet of corrugated cardboard packaging.

Norampac Vaudreuil wanted to improve the energy efficiency of its corrugator and better control the temperature of the rollers and hot plates in order to improve the quality of the cardboard.

The company called on the lalondesysthermique Group, a firm that is exclusively dedicated to the optimization of steam systems and processes that use steam. Starting from the premise that all components of a pressurized system are interdependent, the lalondesysthermique Group takes a global approach – the steam system is first analyzed as a whole, then each process is optimized individually.

The lalondesysthermique Group carried out the project in collaboration with Cascades’ Energy Intervention Group.

The initial situation

The steam at Norampac Vaudreuil is produced by a thermal oil system. The steam generator is supplied with water by a deaerator maintained at 100 psi. The deaerator is supplied by an atmospheric pressure tank, receiving fresh water (make-up water) and most of the condensate from the corrugator.

The corrugator is composed of two kinds of equipment: rollers (BHS and Langston) and hot plates.

The condensate extracted from the first section of rollers is directed toward the first in a series of flash tanks, from where the flash steam is directed toward the next section of rollers and so on. The steam is then directed toward the hot plates, which are also supplied one after the other. There are four sections of rollers and three sections of hot plates (see Figure 1).

Figure 1 - Initial situation

Figure 2 - Final configuration

The condensate from the flash tanks is directed toward an atmospheric pressure tank where it is mixed with fresh water. A significant quantity of steam is vented to the atmosphere at this stage (see also Informa-TECH Volume 23, September 2009). As well, some of the condensate is drained off to ensure it is adequately discharged.

The condensate and fresh water are then pumped toward the deaerator. A significant quantity of steam is vented to the atmosphere at this stage also in order to eliminate noncondensable gases (oxygen, carbon dioxide, nitrogen, etc.).

To avoid mechanical breakdowns due to water hammer, the start-up of the system takes six hours. Consequently, Norampac Vaudreuil prefers to keep its system under pressure throughout the weekend.

The project

The lalondesysthermique Group quickly arrived at the conclusion that the cascade configuration, which is an outdated standard, is no longer adapted to the needs of Norampac Vaudreuil. In fact, the configuration leads to a series of problems related to controlling pressures and discharging the condensate.

The project consisted of converting the existing system into a SCCS® (steam condensate closed system). In a SCCS®, all the energy from the condensate and flash steam is recovered and the noncondensable gases are eliminated throughout the whole system.

The system was reconfigured in order to eliminate all the flash tanks and replace them by steam traps to ensure that the condensate is discharged at high pressure.

The rollers and hot plates are now supplied by steam individually, which has several advantages from a technical point of view: simpler controls and fewer constraints with regard to operating pressures, much less downtime and easier diagnostics.

Mechanical noncondensable gas eliminators were strategically positioned on all the rollers and hot plates.

Many pipes on both the steam and the condensate side were reconfigured. The majority of the existing steam traps were replaced by more efficient models with better calibrated dimensions. (See Figure 2.)

Cost of work and savings

The interventions by the lalondesysthermique Group have had several positive impacts on operating costs, as well as on the performance of the processes.

The reduction in energy losses and the elimination of the noncondensable gases led to a radical reduction in natural gas consumption. The elimination of noncondensable gases also helped standardize and stabilize the temperature of the hot plates, reduce the consumption of chemical products and cut the time needed to start-up the system down to one hour. The new equipment is more durable, simpler and less expensive to maintain.

To ensure the sustainability of the benefits, operators were trained in the optimal operation of their steam system.

Cost of the work done $350,000
Reduction in consumption of gas per unit produced -25%
Annual savings in gas $170,000
Payback period (after grant) 20 months
Reduction in consumption of chemical products -50%

The savings were calculated in gigajoules of gas consumed per thousand square feet of cardboard produced. Consumption went from 0.08 GJ/unit produced in 2008 to 0.06 GJ in 2009. The project thus led to a reduction of 0.02 GJ/unit produced. The project also led to a significant reduction in the consumption of fresh water, which explains the reduced used of chemical products.

Jean-Francois Lussier, the lalondesysthermique Group
Marie-Joëlle Lainé, Eng., DATECH Group