ENVIRONMENTAL & SAFETY ISSUES: Energy Savings through Furnace Efficiency
According to the U.S. Department of Energy, industry is responsible for more than one-third of all the energy used in the United States with the majority coming from natural gas and petroleum and electricity coming in a distant third.1 The tendency in many cases is to attempt to negotiate advantageous supply rates either directly with suppliers or more often through power brokers in attempt to control or “lock in” stable rates.
Controlling and conserving energy at the source can be just as strategic and can often yield greater savings. Companies are aware that their heat-treatment processes are inefficient and continue to operate their systems at less than optimal performance largely because of three reasons:
- The way they calculate capital expenditure payback
- Using old analyses that do not take into account the benefit of new technologies
- Improper furnace operations
PaybackA comprehensive payback analysis not only takes into account projected supply rates but also includes tax benefits, operational efficiency improvements, increased quality and other labor cost savings in operations, maintenance and downtime. Cost accounting practices are often very good at capturing the direct savings while disregarding indirect savings. Those working around heating operations know that these additional costs are very real. A strategic payback analysis should attempt to identify all costs, which means measuring and putting value to what you don’t know. Some companies have found it effective to develop a cross-sectional energy team with a purpose to focus on cost reduction at the source.
New TechnologiesThe pace at which new energy-efficient technologies are hitting the market is nothing short of overwhelming. Sorting through the latest and greatest technology can be time consuming and cumbersome, but it is necessary for competitive distinction because the savings are substantial. Take into account a product from Sidel Systems USA, Inc. that has an ASME-approved waste heat recovery unit capable of boosting the energy efficiency of a natural gas or LP boiler by up to 15%.2 Vendor management is essential in this phase. A good start is to map out your needs and then sort vendors into categories. Make them work for it.
Improper Furnace OperationThere are many parts of a process that will yield lost energy, including heat losses through furnace walls, inadequate burner performance, negative pressure in the furnace and air infiltration. As a result, progressively managed companies have considered or implemented some form of heat-recovery system to utilize high exhaust temperatures. But before this can be taken advantage of, heat losses should be minimized.
Furnace linings are being updated to newer materials, such as ceramic modules, that offer very high insulating values, fast thermal cycling and less maintenance than firebrick. According to the Office of Energy Efficiency of Canada (http://oee.nrcan.gc.ca), outer shell temperatures of 500°F-600°F can be reduced to 100°F with the modular ceramic insulation lining.
A burner optimization tune-up can immediately reduce the amount of energy needed. Also consider the use of regenerating burners to allow for a higher combustion air temperature that will cut down on natural gas demand.
Negative pressure can be experienced in any furnace because they are designed to maintain pressure under full load conditions. A small load may require less heat, which would alter the airflow design. This can present a negative pressure inside the furnace, leading to air infiltration and inefficient operation. To ensure optimum pressure is maintained for variable furnace loadings, a pressure controller can be used to regulate the flue damper.
Air infiltration within the furnace is a function of both the pressure inside the furnace and the condition of the insulation and seals of the furnace. By maintaining positive pressure within the furnace and conducting regular maintenance on insulation and door seals, major energy loss can be minimized by preventing cold outside air from entering the furnace and also by eliminating cold spots within the furnace load that may lead to quality issues.