Group b sdl presentation
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This document discusses evaporators and their use in food processing, specifically for concentrating orange juice. It provides information on different types of evaporators, including natural circulation, rising film, falling film, and forced circulation evaporators. For orange juice concentration, falling film evaporators are most suitable due to their low energy costs, short retention times to avoid sugar loss, and ability to minimize scaling. The document also discusses considerations for hygiene, operating issues, and troubleshooting of falling film evaporators used for orange juice.
Group b sdl presentation
- 1. Not All Juices are Created Equal!Not All Juices are Created Equal! • 100% Pure or 100% Juice Guarantees 100% pure fruit juice • “Cocktail”, “Punch”, “Drink”, “Beverage” Terms which indicate diluted juice containing less than 100% juice, often with added sweeteners • “From Concentrate” Water is removed from whole juice to make concentrate; water is then added back to reconstitute juice • Fresh Frozen Freshly squeezed, packaged and frozen without pasteurization
- 3. Main FunctionsMain Functions Focus • Pre-concentrate foods prior to drying, freezing or sterilization: fruit juices, milk, coffee • Preservation by reducing water activity: molasses, condensed milk, evaporated milk • Convenient food for consumers or manufacturers: soups, pastes, fruit concentrates • Reduce transportation and storage cost Other Uses • Reboilers at bottom of distillation column
- 4. Elements of EvaporatorsElements of Evaporators Essentially evaporators consist of: • A heat exchanger (calandria): to transfer heat from low-pressure steam to the product under vacuum • A means of separating the vapours produced • Mechanical or steam ejector vacuum pump
- 5. Purpose of Vacuuming thePurpose of Vacuuming the Product SideProduct Side • Decreases boiling point of the liquid, thereby, the product boils relatively at low temperatures, thus minimising the heat damage
- 6. Types of evaporatorsTypes of evaporators for food processing include:for food processing include: Most Common • Natural Circulation • Rising Film • Falling Film • Forced Circulation Special Purpose • Batch pan • Wiped film • Plate tubular • Rising/Falling Film
- 7. Natural CirculationNatural Circulation Advantages: • Low capital and maintenance cost Disadvantages: • Unsuited for high viscosity products 100% LiquidPartial Vapour http://www.apv.com/Technologies/Downloads/Evaporator_HB.pdf
- 8. Rising FilmRising Film Advantages: • Good for highly viscous products Disadvantages: • Low heat transfer coefficient due to slow film development • Requires T difference greater than 25°F • Long residence times Vapour/ Liquid Separator Preheater http://www.apv.com/Technologies/Downloads/Evaporator_HB.pdf
- 9. Falling FilmFalling Film Advantages: • Operates with low T difference • Very short residence times Disadvantages: • Not suitable for highly fouling products http://www.apv.com/Technologies/Downloads/Evaporator_HB.pdf
- 10. Forced CirculationForced Circulation Advantages: • Suitable for products susceptible to scaling or crystallization Disadvantages: • High costs due to pump and piping requirements http://www.apv.com/Technologies/Downloads/Evaporator_HB.pdf
- 11. Which is right for you?Which is right for you? Two Major Criteria: •Is this equipment best suited for the duty? •Is the equipment arranged for the most efficient and economic use?
- 12. Concentrated Orange Juice PlantConcentrated Orange Juice Plant
- 13. CLASS EXCERISE!!! Which evaporator is right for making concentrated OJ?
- 14. Advantages of Falling Film EvaporatorsAdvantages of Falling Film Evaporators for Orange Juice Concentrationfor Orange Juice Concentration • Juice is fed from the top over the heating surface in a thin film, and falls with gravity, so low energy costs • Very small retention time, avoiding sugar loss • No stagnation of juice over the tube surfaces and minimized scaling • High evaporation rates
- 15. Falling Film EvaporatorsFalling Film Evaporators used in the making of Concentrated Orange JuiceConcentrated Orange Juice
- 16. Falling Film EvaporatorFalling Film Evaporator
- 17. Falling Film EvaporatorFalling Film Evaporator Production Rate? Typical Size? Typical Cost?
- 18. Falling Film EvaporatorFalling Film Evaporator Production Rate? 1,890,000 liters per day 500,000 gallons per day Typical Size? Typical Cost?
- 19. Falling Film Evaporator Production Rate? 1,890,000 liters per day 500,000 gallons per day Typical Size? 23 m high X 3 m wide or 75 ft high X 10 ft wide Typical Cost?
- 20. Falling Film Evaporator Production Rate? 1,890,000 liters per day 500,000 gallons per day Typical Size? 23 m high X 3 m wide or 75 ft high X 10 ft wide Typical Cost? $2,000,000
- 21. Juice contains 12% soluble solids. You want to obtain a concentrate of 65% soluble solids. How much water has to be removed? Q1 =100 kg/h X2 = 65% Q3 = ? Q2= ? X1 = 12% Assume 1 hr 0.12(100kg/hr) = 12 kg soluble solid 0.65Q2 = 12kg Q2 = 18.46 kg/hr Q = Q + Q Q = 81.54 kg/hr Mass BalanceMass Balance
- 22. i io oo h f r r k r f hU 1 ln 11 2 12 ++++= ( ) ∆ − = Tk Lg k hl L VLL µ λρρρ 3 13.1 TUAQ ∆= The heat transfer coefficient of the steam Governing EquationsGoverning Equations QQ →→
- 23. The heat transfer coefficient of the orange juice ( ) ( ) ( ) += L V V L VLLbD k hL µ µ ρ ρ 25.0 34.09.09.0 ReRe(Pr)3.1 b = 128 (for SI units) k Cp µ =Pr Korange = 0.148 + 0.00493W D = Tube diameter µ ρDV =Re V = Velocity W is % water content Cporange = 3851J/kg K ρorange = 1.03g/l µorange (70°F) = 89x - 2040 Governing EquationsGoverning Equations Where x = ° Brix
- 24. Operability IssuesOperability Issues • Operating window • Maintain plant operation during failures • Safe operation • Prevent damage to equipment • Startup and shutdown • Flexibility • Resiliency to disturbances • Monitor process and diagnose problems
- 25. Operability-FlexibilityOperability-Flexibility • Q=UA∆T Change Q by: • Affecting U • Affecting A • Affecting ∆T (∆T = Tsteam – Tproduct) http://www.cheresources.com
- 26. Affecting UAffecting U • Decrease velocity of feed (Increases U) – Increases residence time – Feed pipe sizing – Tube length ****Must be done during Design Stage****
- 27. Affecting AAffecting A • Use larger (smaller) tubes – Permitting more (less) H.T. • Nozzle – At top of evaporator – Can spread liquid out more – Caution: we must maintain even wetting ****Must be done during Design Stage****
- 28. AffectingAffecting ∆∆TT • Temperature Sensitivity – Juice spoiling temperature – Tsteam has a maximum • Preheating – Bring fresh juice closer to boiling point ∴decreasing ∆T • Increase Steam Pressure
- 29. CLASS EXCERISE!!! What special hygienic considerations must be taken into account when working with food products?
- 30. Hygiene ConsiderationsHygiene Considerations • Cleaning of equipment daily • Stainless Steel Construction • Ensure sanitary plant and working conditions • Food grade lubricants • Food grade storage containers/utensils
- 31. TroubleshootingTroubleshooting Falling Film - Orange Juice • Steam Hammer • Metal Erosion • Fouling & Solids Content
- 32. ReferencesReferences • http://www.niroinc.com/evaporator/esys.html • http://www.cheresources.com/evapzz.shtml • Geankoplis, Christie J., Transport Processes and Unit Operations, 3rd Ed., Prentice Hall, 1993, p. 263-267 • http://www.apv.com/Technologies/Downloads/Evaporator_HB.pdf