August 09, 2010

ISO - Standard OR Business - 2

In continuation to my previous post on the topic.....

2. Claims & Reality?

Now first on ISO claims itself that - ISO standards also serve to safeguard consumers, and users in general, of products and services - as well as to make their lives simpler. HOW???????????????

Safeguard consumers & users - How???? To understand this we will start from the first Clause of ISO manual which is related to SCOPE - Scope of coverage of activities under ISO. This is the biggest loophole & biggest problem in the entire ISO standard which is used as an escape route wherever troublesome processes are involved.


The classic example:

Why the Soft drink companies do not specify the presence of pesticides in their product and then why not they do specify the limit of these pesticides which has been already proved by many international organizations. This is very prominent especially in India due to local government regulations, but ISO do not work on local regulations - They claim to be “International Standards”. Don't forget that these companies are also certified by ISO for their Indian operations.

So the first learning or flaw is that for any one kind of product there should be an internationally acceptable quality parameters (If you claim to be an International Standard - else ISO is not required because each country is already having its own standards & therefore nobody requires another standard which do not ask for improvement to an international level and just try to sell you a certificate with which your business can fetch more money – I doubt this also because the image of ISO is so diluted that there is no credit or premium for it) e.g. for a toothpaste of non-fluoride nature it should not have already identified harmful ingredients beyond the prescribed limit.

The first difference is that ISO says – You specify the quality but how it can be true especially for consumer products. So for this category of FMCG etc the quality is not the content of the product in terms of purity but in my opinion it is the limit of harmful contents in the product, then only it can safeguard the customer.

The example – according to one report (I do not have any legal binding here – this is based on the reports published & broadcasted in newspapers & TV channels), one of the government agency found the objectionable content in cold drinks of two world famous companies (everybody knows them) in India beyond the prescribed limit.

Even if we assume that it was qualifying local standards (Indian in this case) then how can ISO allow manufacturing a product for which WHO or any other world / international organization has set a different limit as harmful content? If it is so, then ISO is not an international standard OR I can say not following international standard.

One may argue that ISO is not setting quality of product its basically setting the quality standard for processes. OK then I must say they should not claim – “ISO standards also serve to safeguard consumers and users in general” the first line of their claim.

In fact, no activity of ISO can be related to safeguarding the interest of consumers, business partners, employees etc. I will put some example for them in the next few posts one by one. Yes, they have only one interest by partnering with some of the foreign business groups, who will ask manufacturers of any third world country to have ISO to qualify as their standard supplier. This way they put cost pressure on developing countries & simultaneously providing business to ISO.

Learning -1 Each product should have internationally specified limits for each harmful content which should be essentially written on the product. This should be the first condition of having ISO in any country any region on this globe.



Disclaimer - This is a series of my personal views on ISO systems, its implementation, Effectiveness etc. They do not carry any legal issue related to my personal views under the human right of "Freedom of Speech".

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July 26, 2010

ISO - Standard OR Business - 1

I am going to write a series on ISO system, its implementation practices, effectiveness, it's claims etc. in several parts in the form of a series. Anyone can put their frank opinion & comments on these write ups. We are not going to comment on ISO as organization but we are commenting on the systems, its effectiveness & industries which are implementing it.

Again this is not for criticism of any agency or organization; it is my experience sharing on actual implementation & loop holes in the system & its effective implementation.

I will show - How the basic purpose of this standard is defeated by standard itself - And my real experience no standards management expert or ISO expert who is responsible for its implementation is concerned about it - even after accepting these problems
resistively.

For reality purpose, we are referring the website quotes or matter from ‘ISO’ website.


1. Why Standards Matter?

This is the first question, the official website of ISO present to us, in a very nice & surely positive manner. It is soon justified that without ISO systems the product quality, incompatibility, cost and, safety are compromised.

One better paragraph on site says that - "ISO standards contribute to making the development, manufacturing and supply of products and services more efficient, safer and cleaner. They make trade between countries easier and fairer. They provide governments with a technical base for health, safety and environmental legislation. They aid in transferring technology to developing countries. ISO standards also serve to safeguard consumers, and users in general, of products and services - as well as to make their lives simpler." (Source : ISO Website)

Read on further claims - "When things go well - for example, when systems, machinery and devices work well and safely - then it is because they conform to standards. And the organization responsible for many thousands of the standards which benefit society worldwide is ISO." (Source : ISO Website)

Yes, Standards do matter & definitely help in making processes efficient, safer & cleaner as claimed but the difference do not lie in making a "voluminous standard", it lies in actual implementation & practice. The way ISO is implemented is totally useless as standard itself provides ways & means to enjoy bypasses to the spirit of the standard.

Therefore, it is neither helpful in making processes efficient as some or the other way is available to bypass the system nor safer or cleaner. ( How - You will see it through examples in the next parts of this series - Be patient).

There is no health, safety & environment improvement by implementing ISO....In fact, it is creating more problems to the environment - by using more papers - more documents - more consumption of power due to late sitting of ISO staff in organization to complete the time targets - late sitting for preparing for audits - many formats but only one line on one paper sheet - etc. etc. etc....

Even though I am not saying ISO system is bad - Mind it I am repeating - I say, ISO system needs further improvements in terms of its effectiveness.

The first problem I see is - to allow the manufacturer to go selectively. We will discuss this in next part.....



Disclaimer - This is a series of my personal views on ISO systems, its implementation, Effectiveness etc. They do not carry any legal issue related to my personal views under the human right of "Freedom of Speech".

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July 12, 2010

MVR - Use it for Higher Benefits


In my last post, I mentioned some background about mechanical vapor re-compression.

In this post I am going to illustrate some benefits out of MVR system.

In general they must be seen as energy saving schemes in the current scenario of high energy costs in most of the processes. The need to recover or re-utilize energy is essential in thermal separation processes such as evaporations, distillation etc.

Following are the general options available in the industry out of which MVR is the most unutilized or neglected one while being the most efficient one.

1. Multi Effect evaporation (MEE)
2. Vapor re-compression
a. Thermal recompression
b. Mechanical recompression



I am not covering other options as they are well known as my focus here is to mainly emphasize on the benefits of MVR. However, for comparison purpose we will start with MEE only.

MEE
In a multi effect evaporation plant, the vapors produced in the first effect are utilized as the heating medium of the second effect and so on. This effectively reduces steam consumption in proportion to the number of effects. Ideally unit mass of vapor on condensation can evaporate unit mass of liquid. The vapors generated at the first effect are condensed in the second stage to further evaporate the liquid from the second stage and so on. A temperature gradient of about 7-10°C is maintained between stages for maximum efficiency.

So a triple effect evaporator would consume only 35-36% of the energy in comparison to a single effect system. Thus for each kg of steam input to first effect we can theoretically produce 3 kg of evaporation, practically it would be as below because of efficiency of evaporation in the subsequent systems. So let us work on some nos.

The efficiency of 95% is assumed in all evaporation systems through out this comparison

Feed to first effect (say) – 1 Kg steam
The evaporation from first effect – 0.95 Kg steam
The evaporation from second effect – 0.90 Kg steam (i.e. 0.95 x 0.95)
The evaporation from third effect – 0.86 Kg steam (i.e. 0.90 x 0.95)

So total evaporation possible in a 3 stage MEE is = 0.95+0.90+0.86 = 2.71

This is generally the overall economy ratio of a 3stage MEE system. This means for every kg of live steam fed to the system you can remove 2.71 kg of water from the MEE system. Thus, the so called COP is 2.71.

Thermal recompression
Now let us see thermal recompression system which is nothing but an ejector system which boosts the pressure of first effect evaporation by using higher pressure steam so that it can be utilized in the next effect. The major difference is that it requires high pressure steam to elevate the pressure of evaporated steam and may or may not require pressure gradient in the system which is essential in MEE.

Initially, heating steam is used to initialize evaporation. The vapors evaporated are compressed to higher pressure and temperature by steam jet ejector, condensed back for heat recovery and the residual vapors are taken to second stage for condensation / heat recovery. The amount of surplus energy contained in the residual vapor corresponds to the amount of energy supplied for steam jet ejector operation. This is taken as additional heat input / work done for recovery of large heat content of the evaporated vapors

So by theory practically the economy ratio is 1 for thermal compression system as whatever energy we put into the system in terms of motive steam is recovered back in the condenser of the next stage.


MVR
So now it’s a turn of MVR system. The process is that the initial vaporization is done using steam or electrical heater to initiate the process & then system may balance itself if you run only one stage of evaporation (by inherent nature of the process & economy ratio you do not need more than one stage practically unless there is a huge requirement or some mechanical issue is involved). So let us now see the calculations.

Every kg of steam initiated from the system is already having its latent heat. Let us assume that the process is near atmospheric condition. So the latent heat is ~2257 KJ/Kg at 100 C & 1 bar.

Now this steam is taken by the compressor & compressed to bit higher pressure. The energy required for compression is given as electrical energy which is increased by the efficiency terms over & above the theoretical requirement. This compression energy depends on pressure ratio. Generally MVR are currently designed to a pressure ratio limit of 1.5. So if the compressor is increasing the pressure to say 1.5 bar then the work done by compressor is

W = (P2 – P1) x Vs x 100

W = specific work done = KJ/Kg
P2 = final pressure = 1.5 bar
P1 = initial pressure = 1.0 bar
Vs = specific volume of steam = 1.67 M3/Kg

So the energy required is

W = (1.5 -1.0) x 100 x 1.67 = 83.5 KJ/Kg

Now let us assume overall efficiency of compression process including electrical, transmission efficiencies is 60%. Then total actual energy requirement is

W = 83.5/0.6 = 139 KJ/Kg

This means by putting an energy of 139 KJ/Kg, we can recover the latent heat of 2257 KJ/Kg out of steam. Therefore by definition of COP of the process, it is

COP = 2257 / 139 = 16.2

This means that one stage of MVR is equal to 16 stages of MEE in terms of energy efficiency. This also means that energy equal to one kg of steam put into an MVR will or can evaporate 16 Kg of steam from the system.

Benefits
Now in terms of cost of energy, theoretically the power cost is double than steam cost. So effectively the ratio will be 16.2/2 = 8. Thus, effectively the operation cost can be reduced by 8 times in comparison to MEE or any other option.

Following are the other advantages

  1. Low specific energy consumption i.e. energy consumed per kg of product.

  2. Unmatched Higher Performance co-efficient i.e. the overall economy of the operation.

  3. Gentle evaporation of the product due to low temperature differences and hence useful for temperature sensitive operation. In fact it is never a problem for any material because it operates only at very low delta T.

  4. No load or reduced load on cooling towers as there is no CW condenser in the system.

  5. Simplicity of process, operation & maintenance.












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June 29, 2010

Mechanical Vapor Re-Compression

You may have seen the term Mechanical vapor compression or re-compression. It is basically the compression of vapors. The main difference is the general compression is used for gases not for vapors while this term is used for compression of vapors.

You know the difference in VAPOR & GAS...I am not going to cover it here.

The term is derived mainly from the compression of steam evaporated from the evaporators. It seems that the need got generated from the large scale desalination plants where very large amount of water is to be evaporated economically. So some brilliant chemical / mechanical engineer (I don't know him) thought about the use of some compression device so that evaporated steam it self can be used for heating purpose. It can be visualized from the diagram below.





The short description of the process is as below.

1. Unheated wastewater is fed to the liquid vapor separation tank (1) and is heated to a boil by the electric heating element (6).

2. Recirculation pump begins circulating heated water through the main heat exchanger (2) and back into the separation tank (1).

3.Steam flows up through the mist pad (8) to inlet side of vapor compressor (4).

4.Compressed steam from vapor compressor (4) is forced through the steam side of main heat exchanger (3) giving up latent heat to the counter flowing water from the separation tank (1).

5.High temperature distillate flows out of the main heat exchanger (3) to feedstock heat exchanger (7) giving up sensible heat to feedstock wastewater.

6.Upon reaching steady state, cold feedstock wastewater is fed at a constant rate through the feedstock heat exchanger (7) to raise temperature before feeding to recirculation loop.

7.Concentrate is periodically discharged based on temperature, conductivity or time from separation tank (1) to concentrate tank (9) through residue pump (10).

Benefits of MVR
The beauty of MVR is that by putting in a fraction of energy into comprssor, we can recover entire latent heat of steam. Thus it can produce a COP of >15. Though it has got many limitations but the economy ratio of 15 (Simply understand it this way - that one MVR evaporator is equal to 15 Multi Effect Evaporators running on successive levels.)

I will try to show one practical example with calculations in the next post as & when I get some more time from my schedule.

Work On it NOW....

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June 17, 2010

Drive Through ATM

Here is another truth....
Drive through ATM is a new concept & may be popular soon in Europe & then in the rest of the world.

The story goes like this....

A sign in the Bank Lobby reads: "Please note that this Bank is installing new "Drive-through" teller machines enabling customers to withdraw cash without leaving their vehicles. Customers using this new facility are requested to use the procedures outlined below when accessing their accounts. After months of careful research, MALE & FEMALE procedures have been developed. Please follow the appropriate steps for your gender."


MALE PROCEDURE

1. Drive up to the cash machine.
2. Put down your car window.
3. Insert card into machine and enter PIN.
4. Enter amount of cash required and withdraw.
5. Retrieve card, cash and receipt.
6. Put window up.
7. Drive off.

FEMALE PROCEDURE

1. Drive up to cash machine.
2. Reverse and back up the required amount to align car window with the machine.
3. Set parking brake, put the window down.
4. Find handbag, remove all contents on to passenger seat to locate card.
5. Tell person on cell phone you will call them back and hang up.
6. Attempt to insert card into machine.

7. Open car door to allow easier access to machine due to its excessive distance from the car.
8. Insert card.
9. Re-insert card the right way.
10. Dig through handbag to find diary with your PIN written on the inside back page.
11. Enter PIN.
12. Press cancel and re-enter correct PIN.
13. Enter amount of cash required.
14. Check makeup in rear view mirror.
15. Retrieve cash and receipt.
16. Empty handbag again to locate wallet and place cash inside.
17. Write deposit amount in check register and place receipt in back of checkbook.
18. Re-check makeup.
19. Drive forward 2 feet.

20. Reverse back to cash machine.
21. Retrieve card.
22. Re-empty hand bag, locate card holder, and place card into the slot provided.
23. Give appropriate one-fingered hand signal to irate male driver waiting behind you.
24. Restart stalled engine and pull off.
25. Redial person on cell phone.
26. Drive for 2 to 3 miles.
27. Release Parking Brake

JUST A JOKE............

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June 07, 2010

How True...???


Few lines, which are true for those whosoever read them. Here they are.....Tell us your comments what do you feel ??....??....??

  1. Whenever I find the key to success, someone changes the lock.

  2. To Err is human, to forgive is not a COMPANY policy.

  3. The road to success??.. Is always under construction.

  4. Alcohol doesn't solve any problems, but if you think again, neither does Milk.

  5. In order to get a Loan, you first need to prove that you don't need it.

  6. All the desirable things in life are either illegal, expensive, fattening or married to someone else.


  7. Read More.....


  8. Since Light travels faster than Sound, people appear brighter before you hear them speak.

  9. Everyone has a scheme of getting rich?.. Which never works.

  10. If at first you don't succeed?. Destroy all evidence that you ever tried.

  11. You can never determine which side of the bread to butter. If it falls down, it will always land on the buttered side.

  12. Anything dropped on the floor will roll over to the most inaccessible corner.

  13. As soon as you mention something?? if it is good, it is taken?. If it is bad, it happens.

  14. He who has the gold, makes the rules ---- Murphy's golden rule.

  15. If you come early, the bus is late. If you come late?? the bus is still late.

  16. Once you have bought something, you will find the same item being sold somewhere else at a cheaper rate.

  17. When in a queue, the other line always moves faster and the person in front of you will always have the most complex of transactions.

  18. If you have paper, you don't have a pen??. If you have a pen, you don't have paper?? if you have both, no one calls.

  19. Especially for engg. Students----
    If you have bunked the class, the professor has taken attendance.

  20. You will pick up maximum wrong numbers when on roaming.

  21. The door bell or your mobile will always ring when you are in the bathroom.

  22. After a long wait for bus no.20, two 20 number buses will always pull in together and the bus which you get in will be more crowded than the other.

  23. If your exam is tomorrow, there will be a power cut tonight.



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May 28, 2010

Pressure Swing Distillation - Use it Economically - 2

In the last post we discussed a bit about azeotropes & refreshed ourselves on basics.

So basically because of deviations from ideality (Raoult's Law), liquid mixtures form azeotropes.

Now, the phase envelope at different pressure suggest that the azeotropes shift due to change in pressure and this is our best tool to be utilized in the industry instead of going for extractive distillation where other solvent is used to carry over more of one component than other thus breaking the azeotrope.

Let us understand the conventional azeotropic distillation system, its basic, benefit & limitation.

The conventional method of separation of binary azeotropes have been through addition of another solvent to shift the equilibrium by forming ternary azeotrope. This is called azeotropic distillation.

The common example is to separate ethanol & water using cyclohexane. The ternary azeotrope of 7% Water, 17% Ethanol & 76% Cyclohexane boils off at ~62 C. So in the binary azeotrope of 95.6 % Ethanol and 4.4% Water, just enough cyclohexane is added to remove the water in 7 to 76 ratio which removes all water with some ethanol leaving almost pure ethanol at the bottom.

For example - For 100 Kg of ethanol azeotrope (means 4.4 Kg water) requires 4.4 x 76 / 7 = 47.8 Kg of Cyclohexane. This will carry all water i.e. 4.4 kg of water, 47.8 Kg of cyclohexane & 10.7 Kg Ethanol.

So WHAT????????????

This is just an example of azeotropic distillation where it can be used effectively, but just think if the azeotrope of ethanol water is say 60:40 in place of 95.6 & 4.4. Will it be possible by same system of cyclohexane let us see...

In this hypothetical case, 40 Kg water requires 434 Kg of cyclohexane & how much ethanol it will carry....97 Kg. SO It is not possible because all ethanol is also carried to top distillate & practically no separation.

So now you have fair idea about the benefits & limitations of azotropic distillation.

Therefore, I would like to explain something more which is more beneficial.

Pressure Swing Distillation
As explained earlier, the azeotrope composition varies with change in pressure. This can be understood from the following diagram.



In the above figure, you can clearly see that the azeotrope point is shifting towards right side at high pressure.

So if let us say point B = 30% of component A is at azeotrope now this mixture if pressure is raised will become point C at high pressure & then distillation can continue to point D of another azeotrope at that higher pressure.

So now if I again subject point D to same low pressure then it will become point E at low pressure but distillation can continue. So I can achieve 100% of component A.

This can be applied to any system without any issue and you have following benefits.

1. You do not need any third component.
2. You do not need two more columns for removal of solvent - one for solvent removal from light component & one for solvent removal from heavy component.
3. So more hardware cost.
4. So more energy cost also.
5. PSD (Pressure Swing Distillation) is very simpler to design.
6. No losses of components.
7. No Bulk quantities handling hence very low cost of operation.
8. Many more.........I am not in a mood to loist down all.

Now I will give you one practical example.....which I personally handled.
Ethanol & Ethyl acetate also forms azeotropes & I came across one such system with large quantities. So instead of considering Az Disitll I used PSD.

In this case, We came across an Az mix of ~69% Ethyl acetate (EA) & 31% Ethanol (EtOH). When we ran Aspen Simulation for PSD, we fixed the pressure of first column as 5.5 Bar (After Optimization) & 300 mm Hg for second column.

Now feed was sent to first column & we could recover EA from bottom as 99.9% pure and top was fed to vacuum column at 300 mmHg pressure. Here we coul dseparate 99.9% EtOH from bottom again. the top cut from second column was recycled to first column and thus there was no loss.

I also used it for separation of cyclohexane, EA & EtOH separation later on & my experience shows that slight moderate pressures of 2 to 5 bar can change azeotropes significantly.

So now on try to use it for your benefit & get the recognition from your Boss.

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May 10, 2010

Pressure Swing Distillation - Use it Ecnomically - 1

All the process engineers must have come across the term azeotropic distillation in some or the other way. Most of the time the conventional approach of handling an azeotropic mixture is to carry out extractive distillation using some solvent.

Very easy know. So many lists of such solvents are available in the literature or on internet and then we go ahead with that age old philosophy.

You know, I NEVER follow conventinal things. So Pressure Swing Distillation (which is now becoming more popular) is an effective answer to such problems.

To define it & understand it properly, I would like to first cover up few basics of azeotropes which you may be knowing if you were good in theory during your college days.

Azeotrope - means a mixture of liquid which generates vapor of same composition as that of liquid.



There are two types of azeotropes - Negative azeotropes & Positive Azeotropes.

Negative Azeotropes are those in which the azeotropic boiling point is higher than any of its constituent's boiling point e.g. the mixture of Formic acid & water as given on wikipedia.



Positive Azeotropes are those in which the azeotropic boiling point is lesser than any of its constituent's boiling point e.g. the mixture of Chloroform & Methanol.



Now curves represented in above diagrams are simple T-x-y OR P-x-y curves which are commonly found in distillation textbooks, but what we forget or do not know is that these curves are pressure dependant curves. This means the phase envelope changes with change in system pressure. So if you alter the pressure of the system the azeotrope point or composition will change. You can find it out how? YES...Whenever something goes out of track always remember RAOULT's LAW.

Rest in next post.........


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April 20, 2010

Understanding Impellers

In the last post, i discussed about use of shear / dispersion component based impellers for most of the chemical applications in place of pitch blade trubines. Based on that our readers are asking for the coverage of all types of impellers for general understanding.



Therefore, I am giving some brief details on different mixing agitators.

I am starting the post from categorization of applications where they are used to understand their selection in a better manner. There are three basic categories of mixing applications as mentioned in previous article also.

1. Gas Liquid mixing.
2. Liquid Liquid mixing.
3. Solid Liquid mixing.

Now for all of these cases, there are three basic type of agitators.

1. Axial Impellers
2. Radial or Shear Impellers.
3. Special Impellers.

So let us first start understanding Axial impellers.

Axial Impellers
In this category of impellers the major action or fluid movement is in vertical or axial direction of impeller shaft & therefore, named as axial impellers.

The major impellers in this category is a pitch blade turbine, where different types of blades, at different angles, in different blade width are used for different services. the general design is a 3 blade impeller or more approapriately a propeller, which is used.





The above design is a propeller with 3 blades similar to chemineer AP-3 and lightinin A-100 etc. However the difference is up-pumping or down-pumping. You can guess how & which one is up and which one is down pumping in nature. The up pumping means the flow goes up near the shaft of the impeller & vice-versa for the down pumping.

The power no is very low for these impellers however, it is higher than some specially designed hydrofoil shapes of these blades. So variations are as below.











All the above impellers are axial in nature with wide variation in flow characteristics, power consumption, mixing pattern etc. Now let us go to Radial Impellers.

Radial Impellers
In this category of impellers the major action or fluid movement is in the same plane of rotation or it is shearing in nature & therefore, named as radial / shear impellers.

The major impellers in this category is a rushton turbine, where different types of blades, in different blade width & shape are used for different services. the general design is a 6 blade (flat) turbine which is also more commonly known as rushton turbine.











Special Impellers
The thrid category of impellers is the special design of impellers which are used mainly for specific services mostly involving highly viscous liquids e.g. anchor, helical etc.











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March 25, 2010

Selection of Right Impeller

Its a long time since I wrote my last post in Aug'2009. Now I am retrying to find out some time out of my schedule to the benefit of all of you again. So I thought to start with this info on agitators design.



Generally in small chemical industries & particularly by different agitator designers pitch blade turbines are suggested for most of the mixing applications. But, before you select any agitator just based on the suggestion from your vendor or from some knowledge from books, re-think in terms of your process.

First & most important thing is to understand the process requirement. The process means following three major categories.

1. Gas Liquid applications.
2. Liquid Liquid applications.
3. Solid Liquid applications.

Now in most of the specilaity chemical companies the second category i.e. liquid liquid mixing is the most used application. This is the area of problem during selection of impellers, because most of the literature suggest pitch blade turbines in these cases without understanding or emphasizing on the basic chemistry & mixing need.

In my opinion, based on my experience, it is important to understand the requirement of process e.g. in case of mixing need for two liquids, it is not necessary that only homogeneous mixing is sufficient but you need to understand how the reaction rate is changing with respect to fine mixing. Means, if you use more shattering or shear during mixing does it imapct on reaction rate?

I am sure in case of mass transfer controlled reactions it is going to help a lot significantly. If you do not believe, then try changing one of your impellers & see the impact.

In such cases, the shear forces provided by flat blade turbine (FBT, Rushton) or by CD-6 turbine is much higher & very useful for increasing the reaction rate by providing fine liquid dispersion. PBT will not be my choice in this case as it does not provide any radial or shear component in mixing.






This is one example of going against well written suggestions.

Similarly in case of solid liquid mixing requirement, I am again not in favor of using PBT every time. In such cases, it depends on process behavior. if you need to break lumps or if you need to avoid formation of lumps you should have some radial mixing component along with axial component.

For example, if liquid is viscous or lump formation is to be avoided, use shear component to your advantage.

Conclusion
In my opinion mostly the shear or dispersion is helpful in case of chemical reactions, whether it is liquid liquid mixing or liquid solid mixing.

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