Steam, used in most significant amounts in chemical pulping, bleaching, evaporation, and drying processes, is the biggest energy carrier used in a pulp and paper mill and fuel input to the boilers is usually the largest share of the energy consumption. Consequently, improving the energy efficiency of the steam system holds a significant potential for reducing the energy consumption in a mill.
Steam system details may vary from mill to mill. In general, however, the system has two main parts: the boiler and the steam distribution system. There are several measures that should be considered for these parts. In improving the energy efficiency of steam systems, it is essential to dopt a systems approach and optimize the system by assessing optimization opportunities both with the demand (i.e., end uses) and the supply of steam.
| Technology or Measure | Energy Savings Potential | CO2 Emission Reduction Potential Based on Literature | Costs | Development Status |
|---|---|---|---|---|
| Boiler Process Control | An audit in a a mill in the US identified an opportunity to save $475 000 (2002 dollars) annually with the optimization of the boiler operations with a control system. Estimated payback time was less than 6 months (Kramer et al., 2009. p.45) | Commercial | ||
| Improved steam distribution systems insulation | The U.S. DOE estimates that the installation of removable insulation on valves, pipes, and fittings can reduce steam system energy use by 1-3% (U.S. DOE 2006c). | Case studies from the U.S. pulp and paper industry indicate that the payback period for improved insulation is typically less than one year (IAC 2008). | Commercial | |
| Reduction of Flue Gas Quantities | Boiler energy consumption can be reduced by 2 to 5% (Kramer et al., 2009. p.45). | Commercial | ||
| Insulation maintenance | As part of an energy use and energy efficiency opportunities case study of ten different pulp and paper mills in Illinois, it was shown that installing or improving insulation on pipes and valves could save (on average) over 3,800 GJ (Chimack et al. 2003). | The U.S. DOE estimates that (as of 2002) roughly half of U.S. pulp and paper mills could significantly benefit from insulation improvements and installation, and that these mills could reduce their boiler fuel use anywhere from 3% to 10% if such improvements are pursued (U.S. DOE 2002b). | Commercial | |
| Reduction of Excess Air |
|
|
Commercial | |
| Steam trap improvement | Commercial | |||
| Improved Boiler Insulation | Savings of 6-26% can be achieved, if improved insulation is combined with improved heater circuit controls. | Commercial | ||
| Steam trap maintenance | Energy savings for a regular system of steam trap checks and follow-up maintenance is conservatively estimated at 10% (Jones 1997; Bloss et al. 1997). | Several industrial case studies suggest that investments for repair or replacement steam traps are very low, resulting in a payback period of only a few months or less (IAC 2008). | Commercial | |
| Boiler maintenance | The lack of boiler maintenance can end up costing a steam system up to 30% of initial efficiency over two to three years (Galitsky et al. 2005a). On average, the energy savings associated with improved boiler maintenance are estimated at 10%. | Improved maintenance may also reduce the emission of criteria air pollutants. | Commercial | |
| Steam trap monitoring | Employing steam trap monitoring has been estimated to provide an additional 5% in energy savings compared to steam trap maintenance alone (Galitsky et al. 2005a). | Employing steam trap monitoring has been estimated to have a payback period of around one year (Galitsky et al. 2005a). | Commercial | |
| Condensate return | The U.S. DOE estimates that this measure can lead to a 1.5% reduction in boiler fuel use at U.S. pulp and paper mills, at an average payback period of around 15 months (U.S. DOE 2002b). In a specific example, the U.S. DOE reports that a large specialty paper plant reduced its boiler makeup water rate from about 35% of total steam production to less than 20% by returning additional condensate; annual savings were around $300,000 (U.S. DOE 2004a). | Commercial | ||
| Leak repair | The U.S. DOE estimates that repairing leaks in U.S. pulp and paper mill steam distribution systems could lead to fuel savings of around 2% (U.S. DOE 2002b). | Case studies of U.S. pulp and paper mills in the IAC database suggest a payback period for this measure of less than one year (IAC 2008). | Commercial | |
| Minimizing boiler blow down | Case studies from the pulp and paper industry suggest that automatic blow down systems can have a payback period of just six months (Focus on Energy 2006a). The U.S. DOE estimates that improving blow down practices can lead to annual boiler fuel savings of around 1.1% (U.S. DOE 2002b). | Commercial | ||
| Flash steam recovery | Where feasible, this measure can be easy to implement and can save considerable energy. | The potential for this measure is site dependent, as its cost effectiveness depends on whether or not areas where low-grade heat is useful are located close to steam traps. | Commercial | |
| Blow down steam recovery | Examples of blow down steam recovery in the pulp and paper industry suggest a payback period of around 12 to 18 months for this measure (Focus on Energy 2006a). The U.S. DOE estimates that the installation of continuous blow down heat recovery systems can reduce boiler fuel use by around 1.2% (U.S. DOE 2002b). | Commercial | ||
| Flue gas heat recovery | Typically, one percent of fuel use is saved for every 45°F (25°C) reduction in exhaust gas temperature (Ganapathy 1994). A conventional economizer would result in savings of 2-4%, while a condensing economizer could result in energy savings of 5-8% (Gardner 2008). However, the use of condensing economizers is limited to boilers using clean fuels due to the risk of corrosion. | The U.S. DOE estimates that the installation of boiler feedwater economizers can reduce boiler fuel use by around 3.5% (U.S. DOE 2002b). | Commercial | |
| Burner replacement | As part of an energy use and energy efficiency opportunities case study of ten different pulp and paper mills in Illinois, it was shown that improving boiler combustion efficiency, using blow down steam energy rather than live steam to preheat makeup feedwater, and installation of stack economizers could save (on average) over 9,500 GJ per year (Chimack et al. 2003). | For example, the payback time for a new burner that provides a boiler efficiency improvement of 2% will be around one year (U.S. DOE 2004a). In one example from the pulp and paper industry, replacing circular oil burners with more efficient parallel throat burners with racer type atomizers had a payback of approximately one year (Focus on Energy 2006a). The U.S. DOE estimates that upgrading burners to more efficient models or replacing worn burners can reduce the boiler fuel use of U.S. pulp and paper mills by around 2.4% with a payback period of around 19 months (U.S. DOE 2002b). | Commercial | |
| Steam distribution controls | Commercial |
This Energy Guide discusses energy efficiency practices and energy-efficient technologies that can be implemented at the component, process, facility, and organizational levels.
U.S. DOE estimates that U.S. pulp and paper plants could reduce boiler fuel use by around 2.3% by reducing excess air (Kramer et al., 2009. p.45).