1. Lecture 6 – Moisture Relationships
Announcements
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

2. Lecture 6 – Moisture Relationships
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 physically
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

3. Lecture 6 – Moisture Relationships
Sampling
Grain probe or trier (trucks or barges)
Diverter sampler (streams of material)
Ellis cup (material on a belt)
Samples divided by a Boerner divider… g samples
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

4. Lecture 6 – Moisture Relationships
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)
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

5. Lecture 6 – Moisture Relationships
Chemical method
Karl Fischer method: page 84
Electrical method
Moisture meters
Grain capacitance/conductance meter
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

6. Lecture 6 – Moisture Relationships
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 temperature
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

7. Moisture Relationships Chpt 3, Pages 81-105
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

8. Moisture Relationships Chpt 3, Pages 81-105
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

9. Lecture 6 – Moisture Relationships
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

10. Lecture 6 – Moisture Relationships
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
MCd as a function of rel. humidity and temperature
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

11. Lecture 6 – Moisture Relationships
Modified Henderson:
Chung-Pfost:
K, N, and C are constants specific to materials (Table 3.2, pg 92)
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

12. Lecture 6 – Moisture Relationships
Modified Henderson:
Chung-Pfost:
A, B, E, F, K, N, and C are constants specific to materials (Table 3.2, pg 92)
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

13. Lecture 6 – Moisture Relationships
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:
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

14. Lecture 6 – Moisture Relationships
Example:
Using the Modified Henderson and the Chung-Pfost Equations:
Determine the moisture content of rough rice at 20°C and 35% RH
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

15. Lecture 6 – Moisture Relationships
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?
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

16. Lecture 6 – Moisture Relationships
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.
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

17. Lecture 6 – Moisture Relationships
HW#5 Assignment
Problem 1:
A grain storage facility in Oklahoma must store soybeans at 11% mcw or less to prevent molding and rancidity due to the summer temperatures. The facility has kg at 9% mcw in storage. A producer would like to sell kg of his soybeans at 14.5% mcw to 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 so that the corn will not mold or become toxic. The corn is placed in the bin at 32% mcw. Safe storage takes place at 12% mcw If 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.)
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

18. Lecture 6 – Moisture Relationships
HW#5 Assignment
Problem 3:
An aeration equipment manufacturer is designing a system for an elevator facility to dry canola using ambient air aeration. The facility 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 to dry basis. You should have 6 moisture contents.
1/28/08
BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships