Mass Balance Basics

We will see the next topics:

• Mass Balance Principle and Equation
• Mass Balance in 2 Units (No Reaction)
• Mass Balance in 2 or More Units (No Reaction)
• Recycle and Bypass in Mass Balance
• Mass Balance in Reactive Systems
• Chemical Equilibrium in Mass Balance
• Multiple Reactions in Mass Balance
• Mass Balance of Atomic and Molecular Species
• Mass Balance with Purge Systems
• Combustion in Mass Balance

Let's go!

Basic Principle of Mass Conservation: No creation or Destruction of Mass!

There is only transformation...

We present an examples so you get the best of the Topic!

The Mass Balance Equation is presented:

Inlet - Outlet + Production - Consumption = Accumulation

The accumulation term is generally a derivative... In steady state we will ignore this fact!

The Differential Mass Balance is recommended for Continuous Processes (Steady State)

The Integral Mass Balance is recommended for Batch or Semi-Batch Processes (Transient State)

The type of Processes are presented once again... We will perform some exercises!

Steady State Problem... We see how the accumulation term is cancelled and since there is no reaction the consumption and production terms are cancelled as well!

We will work with Inlet = Outlets

We solve this Batch Problem. Hexane will be evaporated with air. At the end you finish with NO hexane at all...

The accumulation term here is a derivative of mass with respect of time!

How to read and draw Flow Diagrams.

Its very important to be able to read the diagrams and get information and data that will help you understand the process.

If you get written data or any type of extra data, is very important that you draw the diagram and write down every data! Then you should be able to solve you problem!

Its very important to be able to scale-up and scale-down. This is done generally by calculating a Factor.

Basis of calculation is important to establsih on "what base" is the problem based?

We analyze our first system: A system with no reaction, in one single unit!

We apply the Mass Balance Equation to this example of Water and NaOH. The idea is to dilute the original Brine to a less concentrated one.

Sometimes you are going to stumble upon a problem with not enough data and you will ask yourself if you either need more data or if you just made a mistake.

We start this study of "Degree of Freedom". This methodology allows us to know if the system is completely set or if it has some degree of freedom (i.e you can set the variables)

We use the "variable counting" vs. "equation couunting".

Its very important to use INDEPENDENT equations. If you count a dependent equation, the you will not be able to solve the system!

Degre of Freedom Analysis Example. I like this example since you get to see how we apply the method of DOF Analysis.

Important to mark that you should account all the variables, even though you know you have the data. Explicit data such as:

X = 10

is an explicit equation that you should also take into consideration!

The proposal of this Methodology to attack Mass Balance Equations is totally recommended!

You may use other approaches but they should be similar to these one!

We apply the methodology to an example.

A real life example of how we could Apply the Mass Balance Equation to a "Egg Factory"... Even though we are using "eggs" as a currency, we could still use "mass"

Exercise for Labeling Streams in a Mass Balance Problem

We perform an analisys of the degrees of freedom in a Distillation Column

We perform a Mass Balance on a Distillation Column. Be sure to get how we apply the inlet = outlet reduced mass balance equation.

Humidifying Air: This process is contrary to "drying" air which will be studied in Exercise#08

A simple mass balance of different solutions of Sulfuric acid (H2SO4). Mass Balance Equation reduces to Inlets equals Outlets

Application of the Mass Balance Equation to a Wet Sugar Factory. Remember that there are two substances and we can apply 2 mass balances!

Dry Air and Humidity (water) are common mixture in ambient air. Normal operations require dry air, therefore the air must be dried.

Flow of CO2 in a pipeline. We use geometry of the pipeline...

This are basic Mass Balance Problems. We will add up extra "features" to these type of problems such as:

• More Unit Operations
• Recycle, Bypass and Purge
• Reactions
• Combustion

Be sure you get the idea, these set of problems is very important for you to continue in this course!

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The next exercises will be based on these type of problems!

Mass Balance in 2 units with no reaction. Last section was about 1 unit, now we add an extra unit. Things get more complex now. Be sure to understand the "sub-system" concept!

An applied example of a Mass Balance with two units and no reactions!

An exercise using 2 units. Be sure to get the Mass Balance in the Sub-Systems!

The next exercises will include at least 2 or more units! This is just an introduction. In the next Section you will study multiple units

This topic is actually an extension of Mass Balance with no Reaction on 1 Unit and 2 Units. The Mass Balance is still in Steady State. We apply the balance in differente sub-sustems now!

Multiple set of units in a Concentration of a Brine. Since all the set are equal, you may get a standard formula for the "nth" unit.

Please refer to next sections if you need more Solved Problems of Mass Balance with 2 or MORE!

Lets see a little bit of theoretical concepts of Plant Design. We use Recycle and Bypass to improve the process. It is very basic but very powerful!

We apply this concept to a process. Be sure to get how we set the basis of calculation!

We introduce the application of Bypass. In this example, some fresh juice is mixed in the end due to the flavour conditions.

In this crystallization process you will use multiple units!

In this crystallization process you will use multiple units!

We apply the concept of Recycle in each unit.

We apply the concept of Recycle in each unit.

Recycle and Bypass Applications will be included in many other exercises in the next sections! Just keep doing exercises and you will find more recycle and bypasses!

This is an introduction for Mass Balances with Reactions! We still work in steady state but we will now add the Produciton and Consumption terms!

Its very important that you know how to apply the MAss Balance equation to each. Please take the time to review the Stoichiometry Topics... Eventhough is no topic of Mass Balance, you will need them!

A Stoichiometry review: the stochiometric coefficeints and factors

A Stoichiometry review: How to balance a chemical equation. The Mass Balance depends on 100% of the balanced equation.

A Stoichiometry review:

1. Limiting reactant - ONE species that will react totally
2. Excess reactatns - one or more species that will NOT react totally

A Stoichiometry review: Conversion is very important specially in reaction proesses such as reactors or even in combstion!

Conversion is based on the feed mateial vs the outlet material.

A Stoichiometry review: Extent of Reaction

Is similar to conversion but it is based on the stoichiometric factor of each of the species. This will help us A LOT in the Mass Balance Problems!

Examples of the use of Extent of Reaction.

We've seen conversion before. Its important to note that the conversion may be based on either the Global Process, or the Single-Pass Conversion of that single unit!

The reference changes since the inlet value is different!

A simple reaction of oxidation. Be sure to balance the equation and solve!

Another Reaction Mass Balance to form Ethyl Bromide

Production of the famous pigment Titanium Dioxide. We use a lot of reactions and mass balances which is important since many processes are like this one

Production of the famous pigment Titanium Dioxide. We use a lot of reactions and mass balances which is important since many processes are like this one

If you need more help or exercises for chemical reaction, check out the next sections, these included more chemical reaction exercises! Good luck!

Chemical Equilibrium Theory. This Course's Scope has nothing to do with Chemical Equilibrium but with the applciation of Mass Balance in Chemical Equilibrium Systems.

Application of the concepts of Chemical Equilibrium to a Real-Life Problem

We start now another process which include a chemical reaction. Be sure to balance correctly the equation, account for each species and perform the Balance Equation in Steady Sate.

We start now another process which include a chemical reaction. In this special case we include EQUIBLIRUM Be sure to balance correctly the equation, account for each species and perform the Balance Equation in Steady Sate. Then use the equilibrium constant and perform the operations!

We apply the equilibrium reaction to methanol

Chemical Equilibrium problems are not typical in Mass Balance Problems. You WILL study these type of problems in Equilibrium Thermodynamics or Physical Chemistry problems...

Please refer to Problem #20. This Problem includes 2 reactions and an Equilibrium.

An overview of what happens when we add MORE reactions on the process. Essentialy the basics are known but we need to adapt it for multiple reacitons!

Yield is important since we want to maximize it in a process. We are going to see how could we maximize it using just Mass Balance Theory. This is a typical Reactor Engineering Topic

Selectivity is essentially, how is the reactant "selecting" the path of reactions. We have multiple reactions and we want one in specific.

The higher the selectivity, the better performance of reactions we will have.

How to apply the Extent of Reaction in Multiple Reactions Systems. Please refer to the Applied Exmaples #1 and #2!

We apply the extent of reaction to multiple reactions!

We apply the extent of reaction to multiple reactions!

We apply Multiple Reactions and Equilibrium concepts!

Multiple reactions and side reactions. Balance Equations, apply extent of reactions and solve for the mass balances

Multiple Reactions in the same process!

Mass Balance application to the production of Formaldehyde.

Production of Methyl Chloride... in multiple reactions. Be sure to account for each extent of reaction correctly.

Production of Methyl Chloride... in multiple reactions. Be sure to account for each extent of reaction correctly.

So far we've only seen the Mass Balances of Molecular Species (H2O, CO2, N2)... But we could also do Mass Balances on the Atomic Species.

The main advantage is that atoms cant be created or destroyed so they have the form:

Inlet = Outler

Even though there is a reaction occuring in the system!

Applying the Atomic Species Balance to an example

Applying the Atomic Species Balance to an example

Production of Iso-Octane. A series of recycles are included...

Production of Iso-Octane. A series of recycles are included...

Production of Iso-Octane. A series of recycles are included...

Refer to Problem #26 for more Atomic Species Mass balances.

As with Recycle and Bypass, we will find convenient for reaction systems to have a purge.

Many systems will not be able to eliminate inert material. The amterial will accumulate in the sytem and this should not be possible!

We are working in Steady State so we need to find a way to mantain the steady State... The Purge!

Application of a Purge system to a Process. This is Part 1.

Application of a Purge system to a Process. This is Part 1.

A process of methanol production. An atomic specis mass balance is applied on Carbon, Hydrogen and Oxygen. There is also a Purge System Included

Refer to problem #31 if you need an extra problem of a Pruge System. Remember that a Purge is only a stream and may be treated as a Product Stream!