Volume 25, number 2, September 2011

Energy Efficiency and Increased Production: Central to the Success at Lantic

Lantic operates a cane sugar refinery plant that produces white, brown, liquid, and speciality sugars. The plant expansion, completed in December 2002, brought the plant’s cane sugar melting capacity from an average of 35 tonnes to 70 tonnes per hour. 

After that, Lantic’s managers wanted to improve productivity as well as the plant’s energy efficiency. To date, 512,000 GJ have been saved compared with 2005. All-out efforts by the employees, along with the support of Gaz Métro and its energy efficiency programs, helped Lantic achieve those results.

Expansion (December 2000)

Lantic was also operating a plant in the Maritimes. The decision was made in 2000 to transfer production to the Montréal plant. That decision had an impact on the refining capacity, which had to be increased from 35 tonnes to 70 tonnes per hour. The managers’ focus was therefore concentrated on achieving that objective. After consolidating activities and acquiring experience in the new setting, the managers then turned their attention toward optimizing production and improving energy efficiency.

First major project: Decolorization of sugar (Summer 2005) 

One of the steps in refining is to decolorize the sugar. The traditional method in sugar refining is to use activated carbon, a carbon granule made from animal bones. The process consists of a cascading series of steeping and washing in vessels filled with beds of carbonized organic materials mixed with water heated to 66°C. The decolorized sugar is pumped and circulated through several vessels until the specified decolorization is achieved. The decolorized diluted syrup then has to be concentrated through evaporation prior to the next step: crystallization.  

Decolorization, an “energy-guzzling” process, requires a large volume of hot water for the dilution and steam for the evaporation processes. An energy efficiency measure was introduced, which involved replacing the activated carbon by ion exchange resins.  

The new process uses vessels filled with synthetic materials, i.e. polymer resins. The syrup is pumped in and the resins act like a magnet, promoting ion exchanges between the minerals and the resins. When it leaves the vessels, the syrup is decolorized and, most importantly, not diluted and so it is ready for crystallization. A brine solution then regenerates the used resins, releasing and rejecting the minerals and repolarizing the resins. This first project had a payback period of 4 years.  

Integration through pinch analysis (Summer 2007)  

A major study was carried out in order to identify projects likely to contribute to improving the plant’s energy efficiency. The optimisation and production of steam were targeted with the goal of improving the plant’s competitiveness and increasing productivity.  

The pinch analysis involved raising the awareness of employees and gaining their cooperation as to the use of energy for the processes and services. These efforts rallied the employees around the goal of improving performance. The data collected turned out to be a mine of information that helped initiate an analysis of energy efficiency.  

Following a pinch analysis of the processes and services, a series of cost-effective and energy-saving projects were identified and an action plan drawn up.  

The pinch analysis produces composite curves, which helped determine the energy recovery potential using the streams from the processes, then those from the services. Nine projects were selected for their potential savings – about 14%.  

Replacing No.4 boiler burner (Spring 2009)  

The No.4 boiler produces about 50% of the refinery’s steam needs. It was therefore essential to optimize its efficiency. While the boiler was fitted with several performance-enhancing components, such as an economizer, an advanced combustion control system, an oxygen sensor, a modulating combustion blower, etc., the existing burner, from an earlier generation, had become obsolete. To optimize the design of a new burner, combustion simulations based on the size of the combustion chamber were carried out in order to maximize heat density, increase heat transfer and efficiency. This second project had a payback period of 2.5 years. 

 

Hybrid direct-contact economizer equiped with a natural gas burner

Energy recovery at the thermal power plant
(Spring 2010
)
 

A technical and financial analysis was carried out in order
to optimize the operation of the thermal power plant.
It highlighted the need to recover energy from the combustion products. The choice fell on a hybrid
direct-contact condensing economizer equiped with a natural gas burner. This equipment facilitates the thermal power plant’s activities in the summer, while guaranteeing a nominal capacity sufficient to efficiently meet maximum steam demands. The payback period was 3.1 years. 

 

Optimization of controls (2005-2011) 

The thermal power plant and the various plant processes are equipped with several controls, and their integration led to significant gains both in increased productivity and reduced energy intensity. 

Following the pinch analysis, work was undertaken to stabilize the boilers and processes that required steam, which resulted in the power plant operating with one less boiler by early 2007. A reduction of about 4% in energy consumption was recorded. 

At the beginning 2008, the master electronic controller for the thermal power plant was replaced, as well as the instrumentation. This increased opportunities for improvement, since more information was now available. The variability of the controls was revised to avoid perturbations on the steam system. There are therefore less rapid differences in the demand for steam and low-level alarms on the steam drum have also been reduced. 

At the start of 2010, those efforts, along with the installation of a new recuperator, led to a second boiler
and deaerator being shut down for 6-9 months each year, thereby generating annual savings of an additional 2%. 

Shutting down a boiler limits steam production and flexibility. However, concerted efforts by the operators of the thermal power plant and processes and by the maintenance personnel, ensures the reliability of the operations. Figure 1 illustrates the evolution of energy performance.

FIGURE 1 - Evolution of Energy Intensity

Conclusion 

The efforts by the employees, along with the help of specialists, led to refined sugar production being maintained at a higher level, generating savings of 512,400 GJ since 2005. 

Other projects identified will soon be undertaken from  a perspective of continuous improvement. 

   

Guy Desrosiers, Eng., CEM, CMVP
DATECH
Group