April 20, 2011

Process Intensification - 2, Static Mixers

My last post was focussed on general & brief overview of process intensification abbreviated PI. The term may be new to almost half of the population but we use it somewhere or somehow knowingly or unknowingly in our current life also.

As explained earlier, the miniaturisation is the key word for PI as best & smallest explanation. However, it can be simple on one side like static mixers and very complicated like immobilized solvents for absorption & desorption OR SDR (spinning disc reactor) etc. on the other side.

So instead of discussing it in general, let us go through these specific examples of PI equipments & how can we utilize them in our life...CHEMICAL life...; our first item is - Static Mixers.

According to wikipedia, the static mixers were invented by the Arthur D. Little Company in 1965. This device was licensed to the Kenics Corporation and marketed as the Kenics Motionless Mixer.

Static Mixers
A very simple piece of equipment & very easy to understand yet fully misunderstood by many of us. The basic image of an static mixer is the take a piece of pipe & fill it with any packing and your static mixer is ready. YES.....& ......NO.

YES.....because of its general construction......NO because improper design can lead to many failures and because of that you are not using it for real applications where it is more beneficial.

These mixers can be utilized for various purposes e.g. For slow Gas & Liquid Reactions where the BCT is very high & therefore, many benefits can be achieved by using SM for this type of slow reactions. Another example where we can use them effectively are homogeneous & quick mixing of liquid liquid systems.

In such cases, the benefits are many like BCT is reduced so the capacity can be enhanced from the same size of system OR the system volume can be reduced and hence the inherent safety is increased. The yields will be better due to complete or higher utilization of GAS, more uniform product due to lesser side product formation etc.

Can you think of any other good use of static mixers???

Now Let us classify SM in broad categories & how to estimate pressure drop.

1. LPD - Low pressure drop mixers for low viscosity applications.
2. ISG - Interfacial Surface Generator for high viscosity applications.

Now to estimate the pressure drop in a SM, following is the process.
First Assume the Mixer Diameter.

  1. First Calculate the Reynold No as Nre = 6.31 w / mu D = 3161 Q sg / mu D

  2. If Nre is < 500 the flow is laminar. Use either Fig.1 for LPD or Fig.3 for LLPD or Fig.5 for ISG mixers to estimate the pressure drop per element.

  3. If Nre > 500 the flow is turbulent. The pressure drop per element is estimated from Fig.2 for LPD or Fig.4 for LLPD & Fig.6 for ISG mixers.

  4. Multipy the pressure drop per element by the number of elements to obtain the estimated pressure drop through the mixer.

  5. For turbulent flow, multiply the estimated pressure drop by the specific gravity and the correction factor K to obtain the actual pressure drop as below -

    K = 1.1 for mu upto 10 cp.
    K = 1.3 for mu from 10 to 100 cp.
    K = 1.5 for mu from 100 to 1000 cp.
    K = 1.6 for mu from 1000 to 5000 cp.

  6. For laminar flow, the pressure drop is proportional to the viscosity. So for Figures 1, 3, & 5 which are based on a fluid having a viscosity of 10,000 cps, the actual pressure drop is calculated as follows

    Actual DP = Cal DP x Actual Viscosity / 10000

  7. Now if calculated total pressure drop is more than allowable pressure drop use next higher diameter.

Some of the information & Graphs are from Staticmixers.com website.

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April 06, 2011

ISO - Standard or Business - 4

Continuing discussion on useless nature of ISO from previous post, the next one is on the actual spread of ISO business. This reflects how it can be utilized to earn quick money by many incompetent professionals just by using some jargons & those who are more vocal than others.
See my First Three Posts on ISO-1, ISO-2 & ISO-3

In fact, this is the best 'QUICK MONEY SCHEME' for everyone who are looking for some easy job, no actual output, only vocal & very good money for all collectively where the payee is also happy & reviever will always be happy in any case.

DO YOU AGREE.........

It is useful to suppliers to sell easily in the name of ISO systems. It is useful to so called (conformity assessment) professionals as they are very much essential in order to understand the code & implement it in the RIGHT way - hence so much employment is generated by ISO for those who can Interpret the code, it doesn't matter if they understand the technical process or value chain or not.

So purposefully the ISO code is written in such a manner that you can use the language as per your own interpretation and if you are more professional you hire some specialist & he will explain you the simple english in a complicated manner. (Without understanding your prcoesses, this is the beauty of the system that they don't need to understand your process).

And the purpose is to develop a community which can earn quickly & easily and in my personal opinion & view, this is the biggest & successful MLM system in the world. you earn & promote others to join as a consultant. Some may argue that they have a very good system of certification of consultants / experts & they are again regularly reviewed........So what......After all it is beneficial for them so they have to have some system in the eyes of customers, but no one failed.

So we can have any one as an ISO assessment specialist. The level of these specialist is such that they even do not know benchmarking - and anything told by operating person is accepted by them as a benchmark (Generally people start from worst achieved figures for continual improvement targets). Pitty???????? How can you be efficient & that's why I said this is not the fault of the system, it is implementation which is faulty. Error in the system is that it allows to take these side routes becasue of many reasons as listed one by one here and I will compile all of them at the end of this series, if possible for me because of time constraints.

These are only one or two points which I am raising through this Blog as & when they come to my mind. If I go in detail or anyone else (I would love to invite you to write your frank opinion on this issue as a guest writer) each point can become a single chapter covering its impact on entire value chain - May be in future I'll do that if time permits.

Learning -3 It is beneficial to many becasue it is made so. It should be taken as a system not as a saleable product & if MLM is stopped, it may be more useful.

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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