7/22/2019 CBE 40 Midterm Review

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CBE 40 Fall 2013 Midterm Review

Concepts:

What do ChemEs do? What is a chemical process? Representing processes with Process Flow Diagrams Design and analysis Basic unit operations Flow chart conventions Using phase (boiling points) in separations Steady state, transient processes Continuous, Batch, Semi-batch processes Conservation of mass Steady state materials balances Drawing system boundaries Conversion Use of recycle and bypass streams, e.g. to increase conversion Modified conservation equation with reaction Materials balances with reaction, using stoichiometry Limiting and Excess reactants Using Ideal Gas Law to convert volume to moles Operating equations as design tools Process Economics Capital costs, depreciation, lifetime Return on Investment Economies of scale Estimating quantities

Outline:

1. What ChemEs doa. Chem Es design and analyze processes in which physical & chemical changes

yield useful things.

b. Processes are represented using boxes and arrows with process flowdiagrams.

c. To analyze the process, we ask questions: quantify inputs and outputs, is itworth it? (economics)

d. Design and development of processes that will be successful commerciallyand/or will make the world a better place require creativity and innovation

(R-brain). Analysis in Chem E is a methodology that involves algebra and

calculus (L-brain)

2. How do we design a process? Goals:a. Minimize costs: materials, equipment, energyb. Good product: high quality, purity, durabilityc. Minimize waste, HSE effectsd. Comply with regulations (EPA, FDA)

3. Separationsa. By phase: condensation, evaporation, crystallization, distillationb. By size: filtration, membranes (liquid or gas)c. By affinity (chromatography, adsorption, absorption, leaching)

7/22/2019 CBE 40 Midterm Review

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CBE 40 Fall 2013 Midterm Review

d. Other (solubility differences, density differences (i.e. centrifugation)4. Process flow diagram units and conventions see PFD Units and Conventions in

bSpace resources

5. Conservation Equation: Rate of accumulation = rate of inputrate of outputa. What quantities are conserved? (mass, energy, linear & angular momentum,

electrical charge)

b. At steady state, accumulation = 0c. Transient processes are important for starting, stopping, controlling

processes

6. System boundaries: we can draw a box around an entire process and/or around asingle unit mass conservation is true for any system

7. Conversion:a. You can use conversion to follow a reactantb. Using recycle and bypass can increase the overall conversion rate in a

process with a reactor

8. Conservation Equation with Reactiona. Use stoichiometry: number of each type of atom is always conservedb. Determine which reactant is limiting and which are excessc. Using Ideal Gas Law to convert volume to molesd. Modify conservation equation to include generation and consumption by

reaction for a component i:

rate of accumulationi=

rate of inputi+ rate of generationirate of outputirate of consumptioni

9. Creating operating equations with variables in the mass balance allows us to pluginto Excel or another calculation system and make comparisons what do we want

to optimize & why?

10.Process Economicsa. Costs: Capital cost & depreciation, operating costsb. Profit = Revenue Costsc.

What goes into pricing? (profit margin, substitute goods, perceived value)d. Return on investment (ROI)

e. Economies of scale (cost ratio vs. capacity ratio, residence time effects)Study Tip:Solve problems. Practice, practice, practice!