Week 2: A Great Process Takes Great Planning

Lecture

In this week’s lecture, we reviewed some of the chemical engineering processes that we could use to extract coffee efficiently. We learned that a unit operation is an equipment used in a chemical process for extracting a chemical. We were told to identify the unit operations in our process flow diagrams (PFD). We were also told that critical operating conditions should be added to our PFD to make the process more specific. Some of the many conditions we could consider were temperature, flow rate, particle size, and extraction time. Some of the possible operating conditions in detail:

The ways of measuring the concentration of coffee were introduced to us. Some possible ways include drying and measuring the coffee, using light absorption spectroscopy, and electrical conductivity.

Planning

Our PFD became more detailed and some of the plans changed. We decided that the chemical we are looking for from turmeric is curcumin due to its health benefits. One of our operation conditions was to make the shred the turmeric 0.5-2.0 mm. We did not want the turmeric to be too small because then we could over-extract it and percolation would be difficult. We did not want the turmeric too big because they could be under-extracted, and the solvent would go down too fast. Our group decided to freeze the turmeric first so that the extraction would be more efficient. After that, the turmeric will be filtered and heated up in a beaker between 59-68°F so that the process will be efficient, yet safe. Since ethanol is flammable, we made sure that the temperature is nowhere near its flammability temperature so that our laboratory would not set on fire. After heated up and the ethanol evaporated, the final product, curcumin would be left. Below is the PFD for the process:

We can apply this PFD to coffee, which is similar to tumeric.

Labs: Making the Coffee Calibration Curve

By making a calibration curve, we can use the slope of the curve to find the concentration of the coffee in the experiment. To create the curve, we made several cups of coffee with different concentrations and measured their conductivity in order to see the relationship.

In order to make the curve, ¼ cup of instant coffee had to be measured.

After measuring the instant coffee, 1 cup of hot water was measured and mixed with instant coffee. We used hot water so that the instant coffee would dissolve better in the water. We made sure that the solution was homogenous so our data can be as accurate as it can be.

To prepare the 2nd cup, we measured ¼ cup of cup #1’s coffee and ¾ cup of water into the 2nd cup to keep the amount of water a fixed constant.

We keep repeating the steps of dilution for each cup until we have 9 cups of coffee. Below is the picture of the 9 cups with different concentration of coffee from cup #1 to cup #9.

While we waited for the coffee cups to cool down, we did the calculations for concentration of coffee. Since we know the amount of instant coffee in grams (19 g) and the amount of water present in the cup (0.236588 L), we are able to calculate cup #1’s concentration by dividing the mass of the instant coffee by the volume of the water. After finding the concentration of cup #1, we can find #2 by understanding that since cup #2 contains ¼ cup of coffee and ¾ cup of water, we would divide the concentration of cup #1 by 4. Finding the concentration for cup #3 and so forth, we take the cup’s concentration before it and divide it by 4. Below are the calculations for cup #1 and #2.

After calculating the concentration, most of the cups of coffee are at the same temperature. Since temperature affects conductivity, we want the cups to have the same temperature of coffee. As we used the conductivity probe (measuring it 3 times), the 9 cups’ conductivity were collected:

Using the data, we created the calibration curve.

That is all for this week! Thank you and tune in next week!