Balance Model for Energy Optimization

Against the backdrop of rising energy costs, energy-intensive manufacturing processes in different sectors are under increasing pressure. Considerable cost cutting is possible through mass and energy optimization schemes. This led to a collaboration with Stora Enso Sachsen GmbH (paper manufacturer) through the INFOR117 Project.

Model Application Scheme

What makes the energy saving in a paper industry worthwhile to other manufacturing sectors? Almost two-thirds of the energy (20 % of the production cost) is spent in drying of paper, thus indicating a huge energy (and of course money) saving potential.

Capturing the energy saving potential

At the outset, energy integration in the paper manufacturing facility should be made more effective through schemes such as: better monitoring of process variables, improvement in the operating point (or range) of the process, installation of heat recovery systems (e.g. at heat exchangers), use of heat pumps and replacement of high energy streams (steam) with waste heat streams. Most of these techniques are standard recipes which are readily available in the market. However they are designed without giving any consideration to the specific aspects of a manufacturing facility and also provide no quantitative evidence of the potential benefits. The paper manufacturers lack a tool, which optimally calculates with a holistic perspective, the possibilities to meet all heat requirements through the existing heat sources within the facility, thus minimizing the need for use of fresh energy sources. 

Sankey Diagram

As part of a funded project at TU Dresden, Germany, a facility (paper manufacturing) related balance model was developed and implemented. This model is based on the mass and energy flow networks, location of process control units, staff (operators and managers) experience and additionally measured process variables. This balance model was automated to incorporate real time data. The model represents the actual state of a system with accuracy depending on the location and density of sampling points where a resolution down to individual heat exchangers is possible. This tool also demonstrates the effects of implementing one or more of the energy-saving techniques and helps in deciding beforehand, for or against a particular technique. 

additional advantages

In addition to identifying and assessing the energy saving potential, techniques can be designed on the basis of automatic model application. A constant review and evaluation of the obtained data will benefit the plant operations.

• Detailed Understanding of Complex Processes: A clear representation of the interdependent components in the system, which was not possible up to now, was used to develop strategies for optimized operations.
  

Heat Recovery against Ambient Temperature

• Diagnosing and Monitoring: To detect malfunctions in the heat exchangers, measurement equipment (sensors) and valves.

Leakage in Valves

• Long-term Analysis: Behaviour of interdependent processes over a long period of time becomes visible and gradual processes (fouling in heat exchangers) and seasonal fluctuations can be analyzed. The long-term analysis can also be done retrospectively, provided that past data are available and changes to the system are documented.

Publications

• Energy Optimization through Capturing of Energy-saving Potential, Presentation, Zellcheming, Wiesbaden, 29^th June 2011, Dixit, O.; Kamischke, R.; Schinke, L.; Kuitunen, S.; Treppe, K.
• Wettbewerbsfaktor: Energieeinsparpotenziale - Brennstoffeinsparung und Reduktion von Emissionen, Presentation, Österreichische Papierfachtagung, Graz, 8^th June 2011, Kamischke, R.; Schinke, L.; Kuitunen, S.; Dixit, O.; Treppe, K.
• On identifying and capturing the energy-saving potential, ipw The magazine for the International pulp and paper Industry, (2011) No. 5, pp. 26-30, Treppe, K.; Dixit, O.; Kuitunen, S.
• Fallstudie zur Abwärmenutzung mittels Wärmepumpe, Wochenblatt für Papierfabrikation 2011 No. 1, pp. 26 - 29, Treppe, K. ; Pinnau, S.; Kuitunen, S.
• Energie-Audit 2.0 - Bilanzmodell zur energetischen Optimierung, Wochenblatt für Papierfabrikation 2010 No. 09, pp. 748 - 753, Treppe, K.; Kuitunen, S.
• Untersuchung des Energieeinsparpotenzials in der Trockenpartie von Papiermaschinen, Presentation: Zukunft Forum Papier - Die Österreichische Papierfachtagung, Graz, 26^th to 28^th May 2009, Treppe, K.; Zelm, R.