# FAQ

##### Frequently Asked Questions.

NIKIFOS is the only one company in the world, which offers very powerful and user friendly Software. This includes professional software support for the Solid – Liquid Separation sector with the focus on the Cake Formation of Suspensions and on Hydrocyclones. These are based on the more than 35 years of Research and Practical experience of Prof. Nicolaou.

For customers not using our Software we can guarantee a professional and
objective consultancy with a fast and low cost solution for your Solid Liquid
Separation projects. Furthermore, we offer Courses on Solid-Liquid Separation
in form of Video Conferences or by visiting you at your place. The long
teaching experience of Prof. Nicolaou with its vivid presentations is a
guarantee for effective courses. Duration and main topics of the courses can be
adjusted to the needs of your company.

NIKIFOS specializes in Filter and Filter Centrifuge apparatuses for the cake filtration of
suspensions of any scale (industrial, Pilot or laboratory). These are Continuous
Filters for vacuum or pressure filtration (Belt Filters, Drum Filters, Disc
Filters and Pan Filters) as well as Batch Filters (Pressure and Vacuum
Nutsches, Filter Presses, Filter Press Automats, Candle Filters, Pressure Leaf
Filters) and Filter Centrifuges (Horizontal and Vertical Peeler Centrifuges,
Vertical Basket Centrifuges, Inverting Filter Centrifuges, Pusher Centrifuges).

Furthermore we are specialized on Hydrocyclones. The Software CYCLONPLUS is a unique, powerful and user-friendly program for the Design and Performance Calculation of Hydrocyclones.

Regarding the apparatuses mentioned in
the previous question, NIKIFOS is the best solution for proper apparatus
selection, optimal design and performance calculation, judgment of the
performance of apparatuses in operation as well as suggestions for the performance
improvement. This is due to this main reason: We are the only company with
powerful, user-friendly and for practically reliable software combined with
more than 35-years of focused research and practical experience in this
sector. This results in an objective and professional support as well as in the
time and costs minimization for your projects.

Our Software are the result of more than 20 years of intensive
and focused development. It includes up to date theory, more than 35-years
research and practical experience of our director Prof. Dr. Nicolaou, as well
as the feedback of our customers. They are characterized by the user
friendliness and their practical reliability. This is due to the adaptation
parameters, which are used in the mathematical models and are determined by the
analysis of test data in laboratory or pilot scale.

Aside from the modules for the Design and Performance Calculation of the SLS-Apparatuses, our programs include powerful modules for the Analysis of Test Data. This enables the user-friendly correction of the test data leading to the determination of accurate adaptation parameters.

Also, the interface between Analysis and Simulation modules enables the automatic transfer from the Analysis to the Simulation modules of entered and determined material parameters. Databases for Suspensions and Apparatuses are also included in the programs. Graphs and Tables of the programs can be copied and pasted in other programs like Excel and Word, enabling the easy preparation of your report and further data processing.

By using our Software, you can process your projects
more reliably and in a much shorter time with less cost. Your reports will be more
convincing, and you can impress your customers by including theory-based
diagrams and tables. It is not an exaggeration to say that some projects cannot
be satisfactorily processed without the use of our programs. Your projects can
become more interesting. Also, the needed experiments are minimized because you
know exactly which experiments you have to do in order to get the necessary
adaptation parameters for the reliable calculation of your apparatus.

Furthermore, our Software is a big contribution for
establishing a common language among the filtration specialists. Because the communication
can be based on common theory-based parameters which are used in the programs. Our
programs are also ideal tools for training purposes.

All NIKIFOS programs are licensed on a yearly basis.
If you are seriously interested in the programs, just contact us and we will
respond immediately. We can contact you via a Video Conference explaining to you
the program(s) you wish to license.

Please notice that we do not deliver any DEMO-Version.
If you are seriously interested in licensing one or more of our programs, then
we will send you first an official offer and after getting your purchase order,
the hardware protection will be sent to you (one USB-WIBU key of the company
WIBU SYSTEMS for each license) with the code and the expiration date for the
software you will order. The installation of the programs can be downloaded
from our Website (see Downloads –menu). If the programs are installed for the
first time on your computer, you have also to install the WIBU key driver. This
installation can also be downloaded from our Website.

Since the phenomenology of the processes taking place
in a SLS-Apparatus is very complex, any simulation of the performance of a
SLS-Apparatus cannot be reliable if the needed material parameters in the
mathematical models themselves are not reliable. A practical accuracy for the
needed parameters can only be achieved if experiments with a representative
suspension are carried out and if these experiments are analysed with the help
of the mathematical models used in the programs.

The drastic reduction of the needed tests is due to
the use of the mathematical models which serve as a guide for the experimental
planning. The only tests needed are the ones which enable us to get the
necessary adaptation parameters.

The first
task for the filtration specialist should be to determine the porosity of the
filter cake, the standard cake permeability or cake resistance (cake resistance
is the inverse value of the cake permeability) and the cake compressibility as
well as the filter medium resistance.

The cake
permeability (pc) can be considered as the efficiency parameter for the cake
formation (filtration) step. The higher the cake permeability for a given
suspension (that means for a given mother liquid viscosity, suspension solids
volume content (Cv), with Cv equal to the solids volume related to suspension
volume and the given cake porosity) and for a given pressure difference and
filtration time, the higher the suspension amount, which is filtered. For
higher cake permeability and for a given cycle time, that means higher dry
solids and higher filtrate flow rates leading to higher productivity. The cake
permeability does not only determine the above-mentioned productivity but also
influences the cake moisture content. And in case of cake washing, the wash out
content in the cake is also influenced. The higher the cake permeability, the
lower the cake moisture content, and the lower the wash out content in the
discharged cake (if all other influencing parameters are considered constant).

The cake
permeability pc (m^{²}) is the better parameter to express the filterability
of a given suspension than the cake resistance α
(m/kg) because it enables the comparison of the filterability for different
suspensions.

When using the cake permeability, two suspensions with the same cake permeability have the same filterability (specific filtrate volume flow rate) when the mother liquid viscosity and the pressure drop (Δp/hc) are the same. This cannot be said when using the cake resistance α (m/kg). In that case, two suspensions with the same cake resistance α can have the same filterability if in addition to the mother liquid viscosity and the pressure drop, the bulk density of the dry solids is the same.

The complex phenomenology of the steps taking place during the filter cycle time (cake formation and the optional steps of cake washing, cake squeezing and cake deliquoring) does not allow any filter performance simulation for given geometrical and settings parameter with practical accuracy if the material input parameters are not reliable. Still, based on our experience from the analysis of many test data, it is possible for some parameters which have to normally be determined by analysis of test data, to use average default values. This concerns the efficiency parameters for cake deliquoring, cake washing and cake squeezing as well as some other parameters, which are of minor importance for the simulation reliability.

The use of average values for the efficiency parameters of all mentioned steps (except the efficiency of the cake formation step) is of course acceptable if the result parameter of the given step is not very important. For example, if we demand minimal possible cake moisture content of the discharged cake, then of course the use of default (average) efficiency parameter cannot be acceptable and deliquoring experiments should be carried out and analysed.

Yes.

When talking about the filter performance we mean the filter area-specific dry solids mass flow rate (if the solids is the product) or the specific filtrate flow rate (if the liquid is the product) and the moisture content of the discharged cake. In case of cake washing, we have additionally the wash out content of the discharged cake.

The filter performance depends on the material, filter geometrical and filter setting parameters. For every step (cake formation and the optional steps of cake washing, cake squeezing, cake deliquoring), we always have to consider two parameters: the efficiency and the kinetic parameter. The efficiency and kinetic parameters are dimensionless and the only parameters, which determine the filter performance. The efficiency parameter of a definite step answers the question “How well has it performed?” and the kinetic parameter “How far are we from the equilibrium state?”.

For example, if we want to judge the performance of the deliquoring step (cake moisture content), no matter which apparatus we have and which suspension, it is only important to determine the value of the efficiency parameter and of the kinetic parameter. For users of FILOS and CENTRISTAR these are the ad1-parameter (efficiency of the deliquoring step) and the K-parameter (kinetic parameter of the deliquoring step). Knowing that the ad1-value can vary between 0.1 and 0.5 and having for example a value of ad1=0.2, we know that the deliquoring efficiency is low (bad deliquoring). A cake cracking for example can be the reason. Knowing that a kinetic parameter of K=5 is a reasonable value for an acceptable cake moisture content and having for a given application K=200, we know that the deliquoring time is too high and we lose productivity (low dry solids flow rate) without a significant decrease of the cake moisture content. Only for the case that the cake moisture content should be as low as possible and the expected dry solids rate is not important, only then very high values of the kinetic parameter should be allowed.

Similarly, for the cake washing we have as washing efficiency the Dn-parameter and as kinetic parameter the washing ratio w (w=volume of used washing liquid related to the volume of the cake voids). Usually an average Dn-value is Dn=2. By determining the Dn-value, we can judge how good is the cake washing. An average w-value is w=2 to 3. Having too high w-values means that the wash liquid consumption is too high and vice versa.

The efficiency parameters for the cake formation and
for the optional steps: Washing, Squeezing and Deliquoring of the filter cake (Deliquoring
is defined as liquid removal from the cake by a gas pressure difference) are
material parameters, which should be always determined by laboratory or pilot
tests. Only reliable values of the efficiency parameters can give reliable
filter performance results.

In the ideal case we would expect that the efficiency
parameters are pure material parameters and do not depend on the apparatus type
and size. It can be said, that for a given apparatus and a given size the
efficiency parameters do not depend on the filter settings. In reality, the
efficiency parameters depend more or less on the filter type and size.

For example, it is expected that efficiency parameters
determined by analysis of laboratory nutsche test data will be different from
the efficiency parameters when using an industrial filter centrifuge. For the
same suspension, the difference of the efficiency parameters between for
example a laboratory nutsche and a filter centrifuge is what causes the scale
up problem. That is the reason why pilot tests are in some or in many cases
necessary because the efficiency parameters from the pilot tests are nearer to
those of the industrial application.

Still the laboratory tests are of great importance. Because
normally the efficiency parameters gained from laboratory tests are expected to
be higher than those for the industrial application are, by simulating the
filter performance with the use of the efficiencies from the laboratory tests,
we can determine the best possible performance of the industrial filter. Furthermore,
by comparing the efficiency parameters from the analysis of laboratory test
results with the efficiency parameters determined from the analysis of pilot
test results (one reliable pilot test could be enough) a scale-up factor for
each efficiency parameter can be determined.

According to the above, it is very important to emphasize
that we do not have only one scale-up factor but as many scale-up factors as
the number of performance parameters for the given application: A scale up
factor for the dry solids flow rate, for the cake moisture content and for the
wash out content of the discharged cake (if the cake has to be washed). And the
scale –up factor for a given performance parameter can be define as the ratio
of the corresponding efficiency parameter gained from the analysis of the pilot
test results and the efficiency parameter gained from the analysis of
laboratory test results. To make it clear: If we want to have the scale –up
factor for the dry solids flow rate (cake formation step), we have to divide
the cake permeability determined from the analysis of the pilot test results by
the permeability gained from the analysis of the laboratory test results.
Similarly, the scale up factor for the cake moisture content (deliquoring step)
is the ratio of the ad1-values of the pilot and the laboratory tests. The same
with the scale –up factor of the wash out content (washing step): that is the
ratio of the Dn-values of the pilot and the laboratory tests.

From the above we can conclude that we have different
scale-up factors for each performance parameter and the scale-up factor can be
defined as the efficiency reduction factor. This factor is expected to be less
than one and is determined by dividing the efficiency of a definite performance
parameter determined from pilot test results by the efficiency determined from
laboratory test results. By determining the scale-up factors for different
suspensions and different filter types, a database can be established, which
will allow us in the future to use reliable scale-up factors without having to
do any pilot tests. That is now just a vision and an inspiration for intensive
research work.