Rheological properties of baking soda

USE

Many household uses: cooking and cleaning.

TEST EQUIPMENT

Instrument: powder flow tester (PFT)

Tank: 230 cc, 6 inches in diameter (standard volume)

Lid Type: Pallet Lid, 33cc, 6 inch diameter

Wall cover, 2B finish, 6 inches in diameter

Test Type: Flow Function Test, Wall Friction Test

Temperature: Room temperature (70-72 ° F)

Humidity: 48%

METHOD

A Brookfield powder flow tester, equipped with Powder Flow Pro software for automated instrument control and data acquisition, was used to test this brand's baking soda. The baking soda was poured into the bin, and the scraping tool was then used to evenly distribute the powder throughout the bin. After recording the sample weight and entering it into the software, a standard flow function test and then a wall friction test were performed. The time required for each test was 25 minutes and 13 minutes respectively.

MEASURED PARAMETERS

Fluidity: Very cohesive to cohesive

Wall friction: 35 ° to 27 °

TO ANALYSE

Hopper shape: Conical

Critical arch dimension: 90.2 mm (3.55 in.)

Rat hole diameter: Depends on tank diameter

RESULTS

Figure 1 shows the fluidity of baking soda at different levels of consolidation stress. These results show that baking soda is generally cohesive except at very low levels of consolidation stress where it begins to fall into the very cohesive range (less than 1.5 kPa).

Note: Flow function data is indicated by the red line. When interpreting a flow function graph, the data is read from right to left. The rightmost data point indicates the powder flow rate when the hopper is full; the leftmost data point indicates the powder flow when the hopper is nearly empty. Purple lines are standard flow indices that distinguish different types of flow behavior across levels of consolidation, ranging from “free fluid” (lower segment) to “non-fluid” (upper upper segment).

Figure 1: Flow function graph of baking soda La

Figure 2 shows the friction angle of the wall at different levels of normal stress. The wall friction angle represents the friction between the sliding powder and the wall of the hopper. In this test, a 304 stainless steel cover was used, illustrating what the friction would look like if the baking soda was in a 304 stainless steel hopper. At a low normal stress of about 0.5 kPa, the angle effective wall friction is about 35 ° and drops to about 27 ° at higher levels of normal stress (4.75 kPa).

Figure 2: Baking Soda Wall Friction Graph

CONCLUSION

Baking soda is a powder that is very cohesive at low levels of consolidation stress and cohesive at high levels of consolidation stress. This means that the baking soda may have problems with its flow when the hopper empties. Possible flow problems include camber (when the powder forms a cohesive bridge over the outlet); this provides a conservative estimate to prevent arcing, provided the minimum hopper outlet dimension exceeds this value. The critical dimension of the rat hole depends on the diameter of the tank. The rat hole (when powder only flows from the center leaving the rest of the static material against the walls) can be automatically calculated by Powder Flow Pro once the bin diameter is entered. The critical arch dimension for this material in this test was determined by Powder Flow Pro to be 3.55 inches (90.2mm);