Pre-formulation in pharmaceutical manufacturing, Slides of Chemistry

Download Pre-formulation in pharmaceutical manufacturing and more Slides Chemistry in PDF only on Docsity!

Elementary Principles of

Chemical Engineering

Chapter 4a

Dr. Ibrahem Altarawneh

1

Course Contents

Chapter 4: Fundamental of material balances

Chapter 5: Single phase systems

Chapter 6: Multiphase systems

Chapter 7: Energy and energy balances

Chapter 8: Balances on nonreactive systems

Chapter 9: Balances on reactive systems

Example on a chemical process

Process Classification

Before writing a material balance (MB) you must first identify the type

of process in question.

• Batch – no material (mass) is transferred into or out of the system over the

time period of interest (e.g., heat a vessel of water)

Process Classification

• Semibatch – any process that is neither batch nor continuous (e.g., slowly

blend two liquids in a tank)

• Steady-State – process variables (i.e., T, P, V, flow rates) do not change with

time

• Transient – process variables change with time

Material (Mass) Balances (MBs)-No Reaction

• A material balance is simply an accounting of material. For a given

system in which no reaction is occurring (you will not be told this,

and will need to know this from the type of unit that is under

consideration; crystallizer, evaporator, filter, furnace, etc.),

• A material balance can be written in terms of the following

conserved quantities:

• Total mass (or moles)
• Mass (or moles) of a chemical compound
• Mass (or moles) of an atomic species

Some Basic Process Unit Functions

• Splitter – divides a single input

into two or more outputs of the

same composition (no reaction)

• Mixer – combines two or more

inputs (usually of different

compositions) into a single

output) (no reaction)

• Separator – separates a single

input into two or more outputs of

different composition (no

reaction)

Some Basic Process Unit Functions

• Reactor – carries out a chemical

reaction that converts atomic or

molecular species in the input to

different atomic or molecular

species in the output

• Heat exchanger – transfers heat

from one input to a second input

(no reaction)

• Pump – changes the pressure of an

input to that of the corresponding

output (no reaction)

General Mass Balance Equation

Suppose methane is a component of both input and output streams of a continuous process unit. What if the mass flow rates of methane in both streams are measured and found to be different?

1. Methane is being consumed as a reactant or generated as a product within the unit.
2. Methane is accumulating in the unit – possibly adsorbing on the walls.
3. Methane is leaking from the unit.
4. The measurements are wrong.

Material Balance Simplifications

• The following rules may be used to simplify the material balance

equation:

Accumulation = In – Out + Generation – Consumption

• If the system is at steady-state, set accumulation = 0

In – Out + Generation – Consumption = 0

• If the balanced quantity is total mass, set generation = 0 and

consumption = 0 (law of conservation of mass)

Accumulation = In – Out

• If the balanced substance is a nonreactive species, (neither a reactant

nor a product) or for non-reacting systems in general, set generation

= 0 and consumption = 0

Accumulation = In – Out

16 Input + Generation – Output – Consumption = Accumulation Input – enters through system boundaries. Generation – produced within system. Output – leaves through system boundaries. Consumption – consumed within system. Accumulation – build up within system. Two types of balances may be written:

1. Differential balances: indicate what happening in a system at an instant in time. Each term of the balance equation is a rate (rate of input, rate of generation, etc.) and has unit divided by time. Applied to continuous process. 2. Integral balances: describe what happens between two instants of time. Each term of the equation is an amount of the balanced quantity. Applied to batch process. A balance on a conserved quantity in a system is:

Example

Input + Generation – Output – Consumption = Accumulation

In terms of thousand barrels of oil per day, we have:

Thus, there was a net reduction in oil reserves during this time of year.

On average during the early part of 2009, the United States imported 12, thousand barrels of oil per day. There were also 5,191 thousand barrels of oil per day removed from oil wells. The nation exported 1,826 thousand barrels of oil per day and consumed 18,019 thousand barrels of oil per day. Write a balance on the oil in the nation.

Problems Involving Material Balances

Standard procedures will initially be developed for single-unit processes

• No reaction (Consumption=Generation=0)
• Continuous steady-state (Accumulation=0) Develop good habits now, and practise. Problems will get more complex as we extend the procedures to multiple-unit processes and processes with reaction Standard procedures are summarized in F&R Section 4.3 and include:
• drawing/labeling a process flow diagram (4.3a)
• selecting a basis of calculation (4.3b)
• setting up material balances (4.3c)
• performing a degree of freedom analysis (4.3d) Understanding the Concepts is not good enough. You will not be tested on Understanding the Concepts. You will be tested on your ability to solve balance problems, and to get the correct answer.

Example 2 : 1000 kg/h of a mixture of benzene (B) and toluene (T) containing 50 % benzene by mass is separated by distillation into two fractions, as shown. Calculate the unknown component flow rates in the output streams. Solution: