Repeat Exercise 10.25, but substitute the following...

Repeat Exercise 10.25, but substitute the following specifications for the specifications of vapor distillate rate and reflux rate: Recovery of $n \mathrm{C}_{4}$ in distillate $=98 \%$ Recovery of $i \mathrm{C}_{5}$ in bottoms $=98 \%$ If the calculations fail to converge, the number of stages may be less than the minimum value. If so, increase the number of stages, revise the feed location, and repeat until convergence is achieved.

Repeat Exercise 10.25, but substitute the following specifications for the specifications of vapor distillate rate and reflux rate:
Recovery of $n \mathrm{C}_{4}$ in distillate $=98 \%$
Recovery of $i \mathrm{C}_{5}$ in bottoms $=98 \%$
If the calculations fail to converge, the number of stages may be less than the minimum value. If so, increase the number of stages, revise the feed location, and repeat until convergence is achieved.

Key Concepts

Feed Stage Location Optimization

Optimal placement of the feed in a distillation column can significantly impact the separation efficiency and overall column performance. Identifying the best feed location involves balancing the relative volatilities of components and matching the feed condition with the existing column profiles for effective separation.

Reflux Rate and Vapor Distillate Rate

Operating parameters such as the reflux rate and vapor distillate rate are essential in controlling the separation within the distillation column. They influence both the internal flow dynamics and the energy consumption of the process, thereby affecting the separation efficiency and the attainment of the recovery specifications.

Theoretical Stages and Column Efficiency

The number of theoretical stages is a key parameter in distillation design, representing ideal equilibrium stages needed for separation. Practical design often requires comparing these ideal stages with actual column stages while considering stage efficiencies, and adjustments may be needed if the design does not meet the minimum stage requirements.

Distillation Column Design

This concept involves establishing the framework for separating mixtures using the differences in volatility between components, which is central to process design and optimization. It requires determining the number of theoretical stages, the configuration of the column, and operational parameters such as feed location and reflux rate to achieve the desired separation performance.

Component Recovery Specification

In distillation, ensuring a specified recovery of a particular component in either the overhead or the bottoms product is critical. This concept is about setting and meeting performance targets for product purity and yield, which directly impacts the design and operation of the separation process.

Iterative Convergence in Numerical Calculations

Numerical methods used in distillation design, such as simulation and iterative calculations, rely on convergence to a solution. This concept encompasses adjusting process parameters, like the number of stages or feed location, in the simulation until a stable and feasible design meeting all specifications is achieved.

Transcript

00:01 So we're continuing our work around physical chemistry here and we're going to be taking a look at a distillation column.

00:08 So the first thing we can calculate here, we will look at the molar flow rate.

00:16 So the calculation we need for this is as follows.

00:37 So then we just plug in our values.

00:53 We go value of 1 .95 kilomol per hour.

00:59 Continuing on, we have a molar flow rate of the residue.

01:03 So we've just calculated for the feed.

01:06 So now the moll flow rate for the residue.

01:09 N equals n b, add in d.

01:16 So what we have is 195, subtract 85.

01:24 That leaves us with 110 kilomol per hour.

01:33 Next we can look at the mole fraction.

01:36 So the mole fraction calculate using the following equation, n .0.

01:41 Xpd is equal to n b xpb add n d xpd so our mole fraction here is 0 .405 mole so moving on to the second part now so we're solving for temperature so our equation 1 equals xp add xh then we can rearrange that because it is also equal to y pep divided by p, p, star, t, v, temperature, add yhp over ph star tv.

02:40 So we rearrange for temperature, we find temperature, and it is 37 .3 degrees celsius.

02:48 Once we've plugged in our values, the next thing we can take a look at is solving for the volumetric flow rate of the vapor out of the top of the column.

02:59 V.

03:00 V is equal to n .vrt divided by pv.

03:05 Plug in our values...

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