Plant Applications

There are numerous general energy conservation practices that can be instituted at chemical plants [10]. Ten of the simpler ones are detailed below:

  • 1. Lubricate fans.
  • 2. Lubricate pumps.
  • 3. Lubricate compressors.
  • 4. Repair steam and compressed air leaks.
  • 5. Insulate bare steam lines.
  • 6. Inspect and repair steam traps.
  • 7. Increase condensate return.
  • 8. Minimize boiler blowdown.
  • 9. Maintain and inspect temperature-measuring devices.
  • 10. Maintain and inspect pressure-measuring devices.

Some energy conservation practices applicable to specific chemical operations are also provided below:

  • 1. Recover energy from hot gases.
  • 2. Recover energy from hot liquids.
  • 3. Reduce reflux ratio in distillation columns.
  • 4. Reuse hot wash water.
  • 5. Add effects to existing evaporators.
  • 6. Use liquefied gases as refrigerants.
  • 7. Recompress vapor(s) for low-pressure steam.
  • 8. Generate low-pressure steam from flash operations.
  • 9. Use waste heat for absorption refrigeration.
  • 10. Cover tanks of hot liquids to reduce heat loss.

Recycling can also be achieved in the recovery of energy through the use of waste as a fuel supplement or fuel substitute. Any waste may be processed in fossil-fuel-fired plants or in incinerators equipped with an energy recovery system. Usually, a variety of high-Btu wastes with different compositions are blended to produce a fuel with a certain specification.

Process/Operations Applications

For the purposes of implementing an energy conservation strategy, process changes and/or designs can be divided into four phases, each presenting different opportunities for implementing energy conservation measures.

  • 1. Product conception.
  • 2. Laboratory research.
  • 3. Process development (pilot plant).
  • 4. Mechanical (physical) design.

Energy conservation “training” measures that can be taken in the chemical process industry include the following:

  • 1. Implement a sound operation, maintenance, and inspection (OM&I) program.
  • 2. Implement a pollution prevention program [11,12].
  • 3. Institute a formal training program for all employees.

The following energy conservation practices are recommended at the plant’s “office” level [13]:

  • 1. Maintain air-conditioner efficiency, and reduce heated and cooled spaces.
  • 2. Maintain boiler efficiency.
  • 3. Use natural ventilation whenever and wherever possible, reduce air infiltration, and seal leaks in pipes and ducts.
  • 4. Raise office temperatures in summer.
  • 5. Lower office temperatures in winter.
  • 6. Use shading efficiently.
  • 7. Close windows and doors when and where applicable.
  • 8. Fix broken windows and other air leaks.
  • 9. Do not use lights unnecessarily.
  • 10. Turn off office equipment that is not in use.

Applications at Home

Domestic applications involving energy conservation have been divided into six topic areas. These include [14]:

  • 1. Cooling
  • 2. Heating
  • 3. Hot water
  • 4. Cooking
  • 5. Lighting
  • 6. New appliances

Specific suggestions are provided below for each of these topic areas.

1. Some key cooling suggestions include:

a. Before purchasing an air conditioner, determine how much cooling capacity is needed.

b. Consult the owner’s guide and follow maintenance recommendations for washing filter and vacuuming coils.

c. A whole-house fan can quickly pull large amounts of fresh air through the entire house. At night, this type of fan can draw in cool air from outside reducing the inside temperature enough to allow some occupants to run an air conditioner less often.

2. Some key suggestions regarding heating include:

a. Heating is the single biggest energy user in the house. A well-maintained heating system will hold down fuel costs and provide reliable comfort. The system should be checked periodically by a professional to assure efficiency.

b. When using the dryer, dry wash loads consecutively; the heat left over from the previous cycle will increase the efficiency of the dryer. It is important to clean the lint trap on the dryer prior to each use.

c. Let sunlight in by opening curtains, blinds, and shades over windows which face the sun to help keep the house warm and reduce heating needs. At night or when the sky is overcast, keep drapes and curtains closed to help keep the warmth indoors.

3. Some key suggestions regarding hot water include:

a. Proper maintenance assures the hot water heater’s efficiency. Drain a few gallons of water from the heater every 6 months to remove sediment that accumulates and reduces the heater’s efficiency. Consult the owner’s guide for other maintenance recommendations.

b. For families w'ith an automatic dishwasher, the hot water heater setting can safely be lowered to 130°F-140°F. Without a dishwasher, the setting can be lowered to 110°-120°.

c. Install low-flow showerheads in the shower to limit the flow of water to about 2 gal/ min. Once installed, these devices reduce hot water use by one-third without affecting water pressure.

4. Some key suggestions regarding lighting include:

a. A microwave oven is an energy-efficient alternative to a conventional oven. It cooks food more quickly, and it uses 70%-80% less electricity than a regular oven.

b. When cooking on top of a range, use pots and pans that are properly sized to fit the burners. A small pot on a large burner wastes energy.

c. When using a conventional oven, avoid “peeking” by opening the oven door. Each “peek” can lower the oven temperature by 25°.

5. Some key suggestions regarding lighting include:

a. If one prefers incandescent bulbs, try to use “energy saver” bulbs. These bulbs use halogen gases that allow the filament to burn brighter while consuming less electricity. According to the U.S. Department of Energy, the most popular light bulbs available are halogen incandescents, compact fluorescent lamps, and light-emitting diodes (LEDs). Although they can initially cost more than traditional incandescent bulbs, during their lifetime they save money because they use less energy.

b. Lighting controls or “timers” can help save energy dollars.

c. Consider using task lighting (lighting directed at a specific area) instead of overhead or general lighting, which may light unused area of the room.

6. Some key suggestions regarding new appliances include:

a. When shopping for a new appliance, check for the yellow Energy Guide label that indicates the unit’s energy efficiency. This is particularly important for appliances that use a lot of electricity, such as air conditioners and refrigerators.

b. For air conditioners, the Energy Guide provides an energy efficiency rating (EER). The higher the EER, the more efficient the air conditioner; thus, the more money and energy saved. Many utilities recommend an EER of 10 or higher.

c. For refrigerators and other appliances, the Energy Guide label provides the estimated yearly energy cost for operating the appliance based on an average national utility rate.

d. With any appliance, it is helpful to compare units in the same size range when trying to determine which model has the lowest annual operating cost.

e. Although very efficient appliances may cost more to buy, they pay for themselves through lower energy bills. For example, by purchasing a very efficient refrigerator, one could save up to $1200 over its life.

Obviously, individual effort by everyone can make things happen by preserving energy and winning the battle against wasting energy

Future Trends

Because energy has been relatively cheap and plentiful in the past, many energy-wasting practices have been allowed to develop and continue in all sectors of societies worldwide. There are high-horsepower, low-mileage cars; extensive outdoor lighting; and poorly insulated homes and buildings. Industries have wasted energy by discharging hot process water instead of recovering the heat and by wasting heat contained in flue gases that are discharged through power plant stacks. Waste hydrocarbons have been discharged or combusted with little consideration for recovering their energy and/or material value. There are many more examples, too numerous to mention. Elimination of these practices will, at least temporarily, reduce the rate of increase in energy demands and help reduce sustainability concerns. If conservation can reduce energy demand, it can also reduce the associated pollution; thus, conservation can be considered as an alternative to increased environmental management when regulators set any new source performance standards and ambient air quality standards for air emissions and wastewater effluent discharge limits.

The DOE (Department of Energy), EPA (Environmental Protection Agency), and other federal agencies should foster the development and implementation of energy-efficient industrial processes and practices. This type of program would contribute to

  • 1. Buying the time necessary to develop and introduce clean, renewable energy sources that eliminate sustainability problems
  • 2. Reducing the environmental pollution load, particularly if the United States someday reverts back toward coal
  • 3. Allowing clean energy resources that are conserved to be used in more critical applications in order to reduce sustainability concerns

The most dramatic energy improvements in the future probably will be developed by conservation in the industrial sector of the economy. According to the El A, in 2011, industry accounted for approximately 50% of the energy consumed in this country. Also, industry and commercial users might be more strongly motivated by the economic incentives offered by conservation than the other energy user sectors (e.g., residential, commercial, and transportation) since they can more easily pass on associated costs.

In addition to conservation, sustainability and green engineering concepts will also help reduce energy usage and demand in the future. Most of the activity in this area currently appears in the field of architecture and the so-called “fueled environment”.

References

  • 1. Theodore, M.K. Environmental Calendar, Theodore Tutorials, East Williston, NY, 2014.
  • 2. Theodore, L. Heat Transfer for the Practicing Engineer, John Wiley & Sons, Hoboken, NJ, 2006.
  • 3. Flynn, A.M., Akashige, T., and Theodore, L. Kern’s Process Heat Transfer, 2nd edition, Scrivener- Wiley, Salem, MA, 2019.
  • 4. Avallone, E.A., Baumeister, T., Ill, and Sadegh, A.M. 2007. Mark’s Standard Handbook for Mechanical Engineers, 11th edition, McGraw-Hill, New York.
  • 5. National Insulation Association. About insulation, 2015. http://www.insulation.org/about. Accessed December 21. 2015.
  • 6. Thurman, A. and Mehra, D.P. Handbook of Energy Engineering, 7th edition, Fairmont Press, Lilburrn, GA. 2013.
  • 7. Theodore, L., and Ricci, F. Thermodynamics for the Practicing Engineer, John Wiley & Sons, Hoboken, NJ, 2009.
  • 8. Sprague, B. Manufacturing Assessment Planner (MAP) Toolkit, Michigan Manufacturing Technology Center (MMTC) and CAMP, Inc. Ann Arbor. MI, 1999.
  • 9. http://www.energystar.gov.

10. Theodore, M.K. and Theodore, L. Introduction to Environmental Management,

11. Dupont, R.R., Theodore, L., and Ganesan, K. Pollution Prevention,

  • 12. Theodore, L. Chemical Engineering: The Essential Reference, McGraw-Hill, New York, 2014.
  • 13. Theodore, M.K. and Theodore, L. A Citizen’s Guide to Pollution Prevention (unpublished but copyrighted), Theodore Tutorials, East Williston, NY, 1992.
  • 14. Adapted from: A Guide to an Energy Efficient Home, Long Island Lighting Company, New York, not dated.

45 Heat Transfer and Heat

 
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