$9.$ Mull over the role of solvent flow rate in the absorption process.

a$.$ Why is there such a fuss about adjusting the solvent flow rate?

b$.$ What are the repercussions of operating above or below the ideal rate?

c$.$ How does the flow rate tie back to the concepts of NTU and HTU?

$10.$ Consider the practical impact of the Height of a Transfer Unit $($HTU$).$

a$.$ How do you go about calculating HTU, and why does it matter?

b$.$ What's the relationship between HTU and the column's total height?

c$.$ How do changes in the operating conditions affect HTU?

$11.$ Examine the decision$-$making process behind selecting packing materials for absorption columns.

a$.$ What criteria are used to select these materials?

b$.$ How do different materials impact the process's efficiency?

c$.$ What are the cost considerations in this selection?

$12.$ Unpack the concept of graphical methods for stage estimation.

a$.$ Why are graphical methods used, and what advantages do they offer?

b$.$ Can you break down the process of using these methods?

c$.$ How do you interpret the results from these graphical methods?