2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships1AnnouncementsLecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships2–Measuring moisture content•Oven drying…most common•Distillation, chemical reactions, electrical resistance or capacitance, near infrared spectroscopy, nuclear magnetic resonance•Variation due to how water is bound…chemically or physicallyLecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships3–Sampling•Grain probe or trier (trucks or barges)•Diverter sampler (streams of material)•Ellis cup (material on a belt)•Samples divided by a Boernerdivider…100-200g samplesLecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships4–Convection Oven Method•ASAE Standard S352.1, grain and seeds–Numbered dishes are heated for 1 hour–Grain is placed in dishes and in oven–Removed and placed in desiccator to be brought to room temperature and weighed–Heating times and temp vary by material–Wheat, oats, rye…130°C, 19 hr, 22hr, or 16 hr respectively (just an example)Lecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships5–Chemical method•Karl Fischer method: page 84–Electrical method•Moisture meters•Grain capacitance/conductance meterLecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships6–Equilibrium Moisture Content (EMC)•Material moisture content when equilibrium occurs during the exchange of moisture between material and air–Equilibrium Relative Humidity•RH of air when equilibrium occurs–Relationship varies with temperatureLecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships7Moisture RelationshipsChpt 3, Pages 81-1052/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships8Moisture RelationshipsChpt 3, Pages 81-1052/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships9Equivalent Relative Humidity, % (40% seed oil content) Temperature, °F 20 30 40 50 60 70 80 20 4.9 4.5 4.1 3.8 3.6 3.4 3.2 30 6.5 5.9 5.5 5.1 4.8 4.5 4.3 40 8.1 7.4 6.8 6.3 6.0 5.6 5.3 50 9.6 8.8 8.1 7.6 7.1 6.8 6.4 60 11.3 10.3 9.6 9.0 8.4 8.0 7.6 70 13.1 12.1 11.2 10.5 10.0 9.3 8.9 80 15.4 14.2 13.2 12.3 11.6 11.0 10.5 90 18.6 17.2 16.0 15.0 14.2 13.5 12.8 Lecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships10•Two equations for predicting EMC–Henderson or modified Henderson Equation–Chung-Pfost equation•Each has 2 forms:–EMC as a function of temperature and MCd–MCdas a function of rel. humidity and temperatureLecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships11–Modified Henderson:–Chung-Pfost:•K, N, and C are constants specific to materials (Table 3.2, pg 92)Lecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships12–Modified Henderson:–Chung-Pfost:•A, B, E, F, K, N, and C are constants specific to materials (Table 3.2, pg 92)Lecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships13–When all you know is the % dry matter as fat and % dry matter as nitrogen free extract (% carb which does not include fiber), use this equation from Vemuganti and Pfost:Lecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships14–Example:•Using the Modified Henderson and the Chung-Pfost Equations:–Determine the moisture content of rough rice at 20°C and 35% RHLecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships15–Example:•Using the Modified Henderson and the Chung-Pfost Equations:–If the air temperature is 22°C, what does the rh need to be to dry corn to 15% MCw?Lecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships16–Example:•Compute the final moisture content after thoroughly mixing 60 kg of 18% MC corn with 40 kg of 12% MC corn.•Compute the final moisture content after mixing 30 kg of 18% MC corn with 40 kg of 12% MC Corn.Lecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships17HW#5 AssignmentProblem 1: A grain storage facility in Oklahoma must store soybeans at 11% mcwor less to prevent molding and rancidity due to the summer temperatures. The facility has 16380 kg at 9% mcwin storage. A producer would like to sell 13600 kg of his soybeans at 14.5% mcwto the facility. A) Should the manager of the facility buy this canola to mix with the seed already in storage? B) How many kg of soybeans can the manager buy under these conditions?Problem 2:A drying system must remove excess moisture content from corn sothat the corn will not mold or become toxic. The corn is placed in the bin at 32% mcw. Safe storage takes place at 12% mcwIf the bin holds 175,000 bushels, how much water should the drying system remove to achieve the necessary moisture content? (note the conversion necessary for bushels and kg or lbs.)Lecture 6 – Moisture Relationships2/2/2009 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships18HW#5 AssignmentLecture 6 – Moisture RelationshipsProblem 3:An aeration equipment manufacturer is designing a system for an elevator facility to dry canola using ambient air aeration. Thefacility manager wishes to be able to accept 15% mc canola. Generally canola would be harvested in June. If the Mesonet says that the rh average for June is 60% and the average temperature is 85°F., what is the driest the manager can expect to dry the canola under these conditions?Problem 4:Convert each of the moisture contents in problems 1 - 3 to dry basis. You should have 6 moisture
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