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Brewery Engineering Heating

Brewery Engineering Heating. Lecture 2. Brewery Engineering Lecture 2 - P 1. HEATING. BREWING ENGINEERING. Heating of liquids is required during the mashing and boiling steps in the brewing process Wort boiling has the highest energy requirement of any of the steps in the brewing process.

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Brewery Engineering Heating

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  1. Brewery EngineeringHeating Lecture 2 Brewery Engineering Lecture 2- P 1

  2. HEATING BREWING ENGINEERING • Heating of liquids is required during the mashing and boiling steps in the brewing process • Wort boiling has the highest energy requirement of any of the steps in the brewing process. • Depending upon the types of packaging operations a brewery might have, wort boiling can account for as much as 60% of the total heating (and/or steam) demand in the brewery. • Because of this people who design, own and operate breweries have expended a lot of effort to reduce energy demand, improve energy efficiency, and improve energy recovery from wort boiling operations Brewery Engineering Lecture 2 - P 2

  3. HEATING BREWING ENGINEERING • There are several ways that modern breweries can heat and boil wort in a brew kettle • Traditional direct-fired kettles • Kettles with internal heating systems (e.g. steam coils) • Kettles with external jackets (e.g. steam jackets) • Internal or external wortboilinig system (e.g. calandria) • Each type of equipment has advantages and disadvantages Brewery Engineering Lecture 2 - P 3

  4. HEATINGDirect Fired Kettles BREWING ENGINEERING • Direct-fired kettles are exactly what the name says – a kettle that has fire directly beneath it. • In a modern direct-fired brewery, the fire is almost always derived from burning natural gas, but historically, the fuel for the fire may have been wood, coal or peat Boil Vessel Grade Currents Firebox Enclosure Brick Support Brewery Engineering Lecture 2 - P 4

  5. HEATINGDirect Fired Kettles BREWING ENGINEERING • Because the heat is localized at the bottom of the kettle, the volume of wort that can be boiled in a single batch is usually a maximum of about 200 bbls. • A disadvantage of using direct-fired kettles is that they are relatively inefficient in transferring heat from the fire to the wort. • Additionally, the heating surfaces near the flame become very hot. This promotes carmalization and darkening and burning of the wort and the burnt wort requires frequent (every 2-5 batches?) cleaning. • Also, high evaporation rates are required in order to produce an effective, turbulent, vigorous boil. Evaporation rates of 10%/hr are common. Brewery Engineering Lecture 2 - P 5

  6. HEATINGInternally Heated Kettles BREWING ENGINEERING Boil Vessel • Internally heated kettles typically use steam coils that are actually inside the boiling vessel • Saturated steam, produced by an external boiler, is allowed to pass through the coils, condense, and then give up heat to the wort within the vessel. Currents Boil Vessel Coil Steam in Brewery Engineering Lecture 2 - P 6 Condensate Return out

  7. HEATINGInternally Heated Kettles BREWING ENGINEERING • Internally heated kettles typically use steam coils that are actually inside the boiling vessel • Use of steam coils allows use of larger boiling vessels because there is a larger surface area available for heat transfer. • Because the coil is completely surrounded by wort, heat transfer is more efficient • Additionally, coil heat-transfer surface temperatures are lower than with direct-fire systems, so there is less carmalization and wort burning Brewery Engineering Lecture 2 - P 7

  8. HEATINGInternally Heated Kettles BREWING ENGINEERING • Disadvantages of using internal steam coils are largely related to cleaning difficulty using conventional CIP systems. Build-up of “wort gunk” on coils reduces heat transfer efficiency and may require manual cleaning if excessive. • Also, because wort circulation relies on thermal currents and boiling, turbulence over the coils may not always be adequate to prevent some carmalization of wort from happening • Another disadvantage is the potential for corrosion of the coils and the possibility of introducing steam/condensate into the wort, or having wort back-flow into the steam delivery or condensate return piping. Brewery Engineering Lecture 2 - P 8

  9. HEATINGKettles w/ Steam Jackets BREWING ENGINEERING • An alternative to immersed-coil steam heating is to use a steam-jacketed vessel • This overcomes the difficulties associated with the need to clean the internal coils Currents Boil Vessel Steam in Steam Jacket Surrounding the Vessel Body Condensate Return out Brewery Engineering Lecture 2 - P 9

  10. HEATINGKettles w/ Steam Jackets BREWING ENGINEERING • Jacketed vessels, like direct-fired vessels, have the similar problem of achieving adequate, efficient heat transfer to obtain a satisfactory boil. • Although jacketed vessels have a lower tendency to foul than either direct-fired vessels or immersion-coil heated vessels, they will still require cleaning every 6-12 batches to ensure that effective heat transfer is maintained. • Because there is no cleaning issue with an immersion coil on a jacket-heated vessel, CIP systems are much more effective in cleaning than with an immersed-coil system Brewery Engineering Lecture 2 - P 10

  11. HEATINGExternal Wort Boiling Systems BREWING ENGINEERING • A more modern design uses an external heater (external wort boiler) which removes wort from the kettle and passes it through a heat exchanger for heating • These wort boilers achieve high rates of heat transfer by exploiting the two-phase flow and nucleate boiling situation within the system Currents Heat Exchanger Steam in Condensate Return out Pump Brewery Engineering Lecture 2 - P 11

  12. HEATINGExternal Wort Boiling Systems BREWING ENGINEERING • These systems operate at relatively low steam pressures (3.0-3.5 bar) to heat the wort in the heat exchanger • Turbulence in the boil is enhanced by the pump-induced movement of the wort through the heating loop • Because of these efficiencies, the classic 90 minute boil with 10%/hr evaporation loss can often be reduced to a 60 minute boil with only 5-6%/hr evaporative loss, without loss of wort/beer quality • This represents a significant improvement in efficiency and energy utilization Brewery Engineering Lecture 2 - P 12

  13. HEATINGExternal Wort Boiling Systems BREWING ENGINEERING • Additionally, because of the design, pre-heating of the wort can start when about 15% of the total kettle contents have been introduced into the vessel. This allows the kettle to heat in parallel with filling and be at a boil almost immediately when filled, thus improving vessel utilization • Also, since low-pressure steam in used, the rate of fouling of the heat-transfer surface is decreased • Because of this, the 16-32 batches between required “deep cleanings” may be achieved. This decreases brewhouse downtime and increases throughput. Brewery Engineering Lecture 2 - P 13

  14. HEATINGExternal Wort Boiling Systems BREWING ENGINEERING • One disadvantage of using external wort boiling is that the action of pumping increases shear forces on the wort. This can damage floc formation (trub or hot-break particles) and increase filtration/sedimentation times • Another disadvantage is the relative complexity of an external-boil system vs. other types, and the increased capital cost and maintenance costs that go along with increased system complexity. Brewery Engineering Lecture 2 - P 14

  15. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • It is important to understand how much hot water to add to a batch of colder water in order to obtain a particular temperature; you might desire to mash using something other than a single-temperature infusion mash (i.e. step-mash schedule) : Brewery Engineering Lecture 2 - P 15

  16. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • To achieve these “temperature steps”, hot water is added to the mash, and then the temperature is held relatively constant for a period of time in order allow enzymes to work at an optimal temperature for a particular kind of enzyme Hot water additions Brewery Engineering Lecture 2- P 16

  17. HEATINGMixing Waters of Different Temperatures • Here’s a sketch of the mash-tun that illustrates what’s happening when a hot-water addition occurs: BREWING ENGINEERING Hot Water Addition: Temp = 200 °F Mass (or Volume) = ??? Mash Water & Grain Bed: Tinitial = 122 °F Massinitial (or Volume) = 2500 lbs (300 gal) Tfinal = 140 °F Massfinal(or Volume) = ??? We want to figure out how much hot water is needed to achieve desired mash temperature Brewery Engineering Lecture 2- P 17

  18. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • Perhaps the easiest and most practical way to do this is to monitor the temperature of the mash as you are adding hot water, and stop the addition when desired temperature is achieved. • But you will still need to: • Be sure that your mash system is well-mixed to ensure as uniform a temperature as possible within the mash tun • Ensure temperature indicator is accurate • Ensure the hot addition water is hot enough to do the job without requiring excessive water volume • It’s always a good idea to build experience with your particular system, but it is also important to calculate the water volume and temperature requirements before mashing in order to be sure that your system can do what you need it to do. Brewery Engineering Lecture 2- P 18

  19. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • To determine the amount of water needed to achieve a particular temperature when mixed with another volume of water, it is useful to understand that heat will be transferred between the different-temperature waters • The temperature of the new mixture can be calculated by assuming an adiabatic system (heat not lost or gained from the overall system) and understanding that the heat lost by the hotter water will be equal to the heat gained by the cooler water (and grain bed). • To simplify the discussion and keep the calculations simple, let’s assume that we are working only with water Brewery Engineering Lecture 2- P 19

  20. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • The amount of heat required to increase the temperature of a particular amount of water by a specified amount is given by: • Where: • Q = heat required, BTU • m = mass of water, lbs • Cp = heat capacity of water, BTU/lb-°F • DT = temperature change of the water, °F Brewery Engineering Lecture 2- P 20

  21. HEATINGMixing Waters of Different Temperatures • Since the amount of heat gained by an amount of cooler water is equal to the amount that must be supplier by some amount of hotter water, • the following relationship is valid • Where: • Q1 = heat gained by cooler water, BTU • m1 =mass of cooler water, lbs • Cp1 = heat capacity of cooler water, BTU/lb- °F • DT1 = temperature change of the cooler water, °F • Q2 = heat provided by hotter water, BTU • m2 =mass of hotter water, lbs • Cp2 = heat capacity of hotter water, BTU/lb- °F • DT2 = temperature change of the hotter water, °F BREWING ENGINEERING = Brewery Engineering Lecture 2- P 21

  22. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • It is important to understand that the heat capacity terms, Cp1 & Cp2, are, for practical purposes, equal and have a value that is very close to 1 BTU/lb-°F • It is also important to understand that the DT terms, DT1 & DT2, are equivalent to the absolute value of (Tfinal – Tinitial) for the water in question • Example: if Tinitial = 122°F and Tfinal= 140°F, then DT = (140°F - 122°F) = 18°F Brewery Engineering Lecture 2- P 22

  23. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • We can now do a bit of algebra and rearrange the equations to calculate the amount of hot water that is needed to raise the temperature to a particular level: Brewery Engineering Lecture 2- P 23

  24. HEATINGMixing Waters of Different Temperatures • Since Cp2 ≈ Cp1 , we can cancel them out in the numerator and denominator: • And then expand the DT terms to get a useful equation: • Where: • m1 =mass of cooler water in lautertun, lbs • m2 =mass of hotter water being added, lbs • Tcoldfinal= final temp of originally-cooler water • Tcoldinitial = initial temp of originally-cooler water • Thotfinal= final temp of originally-hotter water • Thotinitial = initial temp of originally-hotter water BREWING ENGINEERING Brewery Engineering Lecture 2- P 24

  25. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • Let’s work an example to illustrate how this equation is used to calculate the amount of hot water that must be added to increase the temperature of the mash liquid. Here’s the system (assume we are working only with water): Hot Water Addition: Temp = 200 °F Mass = ??? Mash Water & Grain Bed: Tinitial = 122 °F Massinitial = 2500 lbs Tfinal = 140 °F Massfinal = Massinitial + Mass of hot water added = ??? Brewery Engineering Lecture 2- P 25

  26. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • For this system we have: • m1 = 2500 lbs • Tcoldfinal= 140°F • Tcoldinitial= 122°F • Thotfinal = 140°F • Thotinitial= 200°F Hot Water Addition: Thotinitial = 200 °F Mass = ??? Mash Water & Grain Bed: Tcoldinitial = 122 °F Massinitial = 2500 lbs Tfinal = 140 °F Massfinal = Massinitial + Mass of hot water added = ??? Brewery Engineering Lecture 2- P 26

  27. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • If we plug the values • m1 = 2500 lbs • Tcoldfinal= 140°F • Tcoldinitial= 122°F • Thotfinal = 140°F • Thotinitial= 200°F • Into the equation: Brewery Engineering Lecture 2- P 27

  28. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • We get: We need 750 lbs of hot water Brewery Engineering Lecture 2- P 28

  29. HEATINGMixing Waters of Different Temperatures • Since the final weight of the water in the mash tun = m1 + m2, the final weight of the water in the mash tun will be m1 + m2 = 2500 lbs + 750 lbs = 3250 lbs • Recall that the conversion factor for water between lbs and gallons is: • So we can also say that we had to add: • of 200°F water In order to accomplish our goal. BREWING ENGINEERING We need 750 lbs (89.9gal) of 200°F water to raise the temperature of 2500 lbs (300 gal) of 122°F water + 750 lbs (89.9 gal) new water to 140°F Brewery Engineering Lecture 2- P 29

  30. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • We can also calculate the final temperature of a mixture of known amounts of hotter and cooler water (m1, m2Tcoldinitial & Thotinitial known) by using a weighted average method: Brewery Engineering Lecture 2- P 30

  31. HEATINGMixing Waters of Different Temperatures • As an example, use: • m1 = 2500 lbs • Tcoldinitial = 122°F • m2 = 750 lbs • Thotinitial = 200°F • And substitute into: • To get: BREWING ENGINEERING Brewery Engineering Lecture 2- P 31

  32. HEATINGMixing Waters of Different Temperatures BREWING ENGINEERING • Since mass and volume are converted between one another by using a constant value for the density, this same “weighted average” approach is applicable if volume is know instead of mass • v1 = volume of cooler water (gallons) • v2 = volume of hotter water (gallons) Brewery Engineering Lecture 2- P 32

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