PROCESS OPTIMIZATION TO MINIMIZE ENERGY USED IN FOOD PROCESSING
- 1. by ABDUL REHMAN B TECH FOOD TECHNOLOGY
- 2. ▪ The food processing industry sector is large, growing, and competitive contributing millions to nation’s economy. ▪ The products manufactured in these industries includes meat products, dairy products, preserved fruits and vegetables, grain mill products, bakery products, sugar and confectionery products, fats and oils, beverages, and other miscellaneous food products. ▪ Energy use in the food industry is examined by cost of fuels and electricity.
- 3. ▪ Heating and cooling process was the most energy consuming process in the food industry taking up 44.6% of the total energy inputs. ▪ Boiler losses accounted for an average of about 22% of energy inputs. ▪ Wet corn milling is the most energy intensive industry in food processing sector with a 15% share of the total energy used. ▪ The beet sugar industry is second in energy use with 7% weightage. ▪ Soy-bean oil mills, malt beverage, and meat packing plants take about 5% each of the total energy use in this sector. Image Source: Energy Conservation http://www.sustainablefoodservice.com
- 4. Typical mass and energy flows in a food processing facility.(Reprinted from Muller,D.C.A., Marechal,F.M.A.,Wolewinski,T., and Roux, P.J.,Appl. Thermal Eng., • Horizontal flows represent the transformation of raw materials into food products and by-products. • Vertical flows represent energy and water. • Maximizing the horizontal flows and minimizing the vertical flows will minimize the production costs and environmental impact.
- 5. ▪ High-grade or high-quality energy sources provide more organized forms of energy than low-grade sources. ▪ The energy sources that have a high grade include kinetic energy of moving matter, gravitational potential energy, and electrical energy, which can be converted into another energy form with small energy losses. ▪ Chemical energy has an intermediate grade, followed by high-temperature heat and low- temperature heat. Image source: Energy management and efficiency for Food Processing Industries Alan P Rossiter, Beth P Jones 2015 by the American Institute of Chemical Engineers, WILEY
- 6. ▪Increase in energy efficiency is accomplished mainly by the integration of complex heat flows within processing facilities. ▪This can be achieved by making a wise choice of production routes, raw materials, and energy carriers is required to significantly improve energy efficiency and process economics simultaneously.
- 7. ▪According to the first law of thermodynamics, the sum of anergy (lost energy) and exergy (available energy) is constant. ▪Exergy eventually ends up in the desired products. ▪Also, exergy can always be converted into anergy while anergy can never be converted into exergy. ▪Therefore, it is important to delay the degradation of exergy as long as possible in a processing facility.
- 8. ▪ In thermodynamics, the exergy of a system is the maximum useful work possible during a process that brings the system into equilibrium with a heat reservoir, reaching maximum entropy. ▪ Can be lost in two ways: ✓Internal energy losses due to the irreversibility of the process itself. ✓External energy losses in the waste streams that do not reach equilibrium with the environment. Energy and Exergy:A Comparative difference
- 9. ▪ The exergy destruction due to irreversibility is Exdestruction = Exin − Exout = T0ΔS Where, T0 is the environmental temperature in Kelvin ΔS is the generated entropy during conversion ▪ The exergy stored in the waste steams is determined by Exwaste = Exout − Exproduct
- 10. Process Energy Efficiency Exergy Efficiency Source: Adapted from Dincer, I., Hussain, M.M., and Al-Zaharnah, I., Energy Policy, 33, 1461, 2005.
- 11. Process Energy Efficiency Exergy Efficiency Source: Adapted from Dincer, I., Hussain, M.M., and Al-Zaharnah, I., Energy Policy, 33, 1461, 2005.
- 12. ▪ Thermal processes such as pasteurization and sterilization, chilling and freezing, and evaporation and drying are energy-intensive unit operations used in the food industry for food preservation and safety. ▪ The energy saving opportunities for each unit operations include three aspects: 1. Improvement of energy efficiency in existing units 2. Replacement of energy-intensive units with novel units 3. Use of renewable energy sources, particularly food processing wastes Image Source: Unit Operations in Food Processing, R L Earle
- 13. ▪ According to the results from Simpson et al. (2006), retort insulation can reduce 15%–25% of current energy consumption depending on selected conditions. ▪ An increase in the initial temperature of food products can reduce the peak energy demand in the order of 25%–35%. ▪ Thus, operating practice can also reduce the peak energy demand during retorting.
- 14. ▪ Ozyurt et al. (2004) designed a liquid-to-liquid heat pump for pasteurization. ▪ Hot pasteurized milk is cooled by the evaporator of the heat pump while the cold raw milk is heated by the condenser of the heat pump. ▪ For the pasteurization temperature at 72°C and coagulation temperature at 32°C, the measured COP of the heat pump ranged from 2.3 to 3.1. ▪ In this way, The heat pump system can save 66% of the primary energy compared to traditional plate and double jacket milk pasteurization systems.
- 15. ▪ Heat pumps have been used to increase the drying efficiency of convectional air dryers (Perera and Rahman, 1997). ▪ A heat pump can also be used to extract heat from a low-temperature energy source such as geothermal energy through its evaporator and upgrade the extracted heat to a high-temperature heat source at its condenser for drying (Kuzgunkaya and Hepbasli, 2007). ▪ Supercritical fluids such as supercritical carbon dioxide can be used to remove moisture from foods (Brown et al., 2007). ▪ Supercritical CO2 drying has been found to generate more favorable re- hydrated textural properties than the air-dried equivalents.
- 16. ▪Food processing facilities make heavy use of refrigeration. It is estimated that the refrigeration systems use as much as 15% of the total energy consumed worldwide. ▪Generally, energy conservation for refrigeration unit operations can be achieved by: ✓ Improved insulation ✓ Best practice ✓ Use of novel refrigeration cycles powered by waste heat
- 17. ▪ Biot number is the ratio of the internal resistance to the external resistance, which is expressed as (Singh and Heldman, 2001) Bio= hl 𝑘 where l is a characteristic dimension of the food body m is the radius of a round shaped body and half of the thickness of a fl at shaped body h is the surface convective heat transfer coeffi cient (W/m2 °C) k is the thermal conductivity of foods (W/m°C) ▪ For higher efficiency in cooling and freezing, the Bio value should not exceed 5 (Mattarolo, 1976)
- 18. ▪ The increasing energy prices and efforts for the reduction of CO2 emission, improving the energy efficiency had become an important consideration in sustainable establishment of food processing plants. ▪ For this reason, Energy efficiency improvement and waste-heat recovery in the food industry have been a focus in the current scenarios. ▪ This can be achieved by replacement of conventional energy with novel technologies as well as techniques to replace traditional energy-intensive unit operations for pasteurization and sterilization, evaporation and dehydration, and chilling and freezing in the food industry.