Frequently Asked Questions.
NIKIFOS is a Chemical Engineering Company with more than 20 years focused activity on Solid-Liquid Separation, serving customers with powerful and user friendly Software, offering Courses in Solid-Liquid Separation and professional Consultancy. Companies dealing with the cake forming filtration of Suspensions as well as with Hydrocyclone applications can mostly benefit from our services. These are companies of the Pharmaceutical and Chemical Industry, Mineral Processing, Food Technology and Environmental Technology as well as manufacturers of Filters, Filter Centrifuges, Hydrocyclones and Filter Media. As last, we want to mention Research Institutes and Consultancy Companies dealing with Solid –Liquid Separation.

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). The Design and Performance Calculation of these Apparatuses is one of the main jobs of the Software FILOS (for Continuous and Batch Filters) and CENTRISTAR (for Batch Filter 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.

Last but not the least, is the professional support of Prof. Nicolaou, which is offered to the Software users at any time.

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.

For the Downloading of the program installations, you need a username and a password, which will be provided to you. You can install the programs in any of your computers, but you can run the programs only if you have a not expired WIBU-key inserted in a USB-port of your computer. This has the advantage that you do not depend on a special location or an internet connection. Usually, the programs are licensed yearly. Only in very special cases, we can offer you to buy the programs. Because of this, you do not have a big financial risk. In the worst case that you want to discontinue working with the programs, you can cancel the licensing one month before of the expiration of the current licensing year at the latest. Otherwise, the licensing continues automatically for the next year. We offer discounted prices for the case that a customer orders more than one program.

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 so-called theory-based plotting of the experimental results enables first the correction of the test data because wrong measurements are made “visible” in the theory-based diagrams. Only after the correction of wrong data, we can achieve analysis result values for the material parameters with practical accuracy.

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.

Taking the cake formation step as an example, we need only 3 experiments in a laboratory scale with different pressure differences in order to determine the cake permeability/cake resistance, the cake compressibility and the filter medium resistance. In case that the cake compressibility can be neglected, only one good test is enough. The theory-based analysis of laboratory tests for data correction and achieving reliable adaptation parameters for the laboratory scale reduces automatically the number of pilot tests (if these are necessary at all) just to one pilot experiment only in order to determine the scale-up factor.

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 is the most important parameter and can be considered as the main efficiency parameter of the cake formation step. The lower the cake porosity, the cake compressibility, and the higher the cake permeability the more efficient is the cake formation step. For the optional steps of cake washing, cake squeezing and cake deliquoring one efficiency parameter for each of these steps has to be determined by analysis of test data. Both programs: FILOS and CENTRISTAR enable the reliable determination of efficiency parameters for each step: cake formation, cake washing and cake deliquoring by using the Analysis modules of these programs. The cake squeezing efficiency is determined by the squeezing analysis module of FILOS.

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 and the cake compressibility are the key parameters for the selection of the proper filter apparatus and for the reliable calculation of the filter performance (see Simulation modules of FILOS and CENTRISTAR). By using the cake permeability and compressibility, a suspension typology can be established. Depending on the suspension type, definite types of filters can be selected as the most appropriate filters for the given application.

The cake permeability pc (m²) 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 explanation that the use of α (m/kg) is better when the surface of the cake is not even, since the cake height measurement is not needed for the determination of α, is not steadfast because two cakes of the same suspension with the same specific dry solids mass but different cake height distribution have automatically different filterability and that means different α -values.

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.

Still there are two parameters, which should always be determined experimentally. These are the cake porosity and the cake permeability/cake resistance. It can be enough to do just one experiment (the simplest way is a test with a laboratory vacuum apparatus) and from this experiment determine these two parameters. If for this test the cake formation step and other optional steps are tested, then the efficiency parameters of these steps can also be determined, and average default values are not needed.


The programs (FILOS and CENTRISTAR) consider for each filter apparatus a set of material parameters which are typical for them. Because of this, a simulation of the performance of any apparatus with material parameters which are representative for the given apparatus can be done very fast. This is a great help to get a rough approximation of the expected filter performance. Of course, such simulation results cannot be used for guarantee purposes.

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.

Finally, due to the above considerations, we should never judge the performance of a filter apparatus by considering the performance parameter of only one step but by considering all performance parameters. That means for a given application we should say: A definite apparatus for the given suspension, given geometrical and settings data has a definite dry solids flow rate, a definite cake moisture content and a definite wash out content in the discharged cake (if the cake is washed). It is wrong to compare the performance of different apparatuses by comparing for example only the dry solids flow rate or only the cake moisture content. A separate consideration of the performance parameters can only be done if the other performance parameters are not important for the given application.

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.

FILOS and CENTRISTAR enable the reliable determination of the efficiency parameters for all steps by analysing the test results (see Test Data Analysis modules of these programs). These user-friendly Analysis modules enable the detection and the easy correction of wrong measurements by using theory-based diagrams. By excluding wrong measurements, reliable values of the efficiency parameters can be determined. 

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.

And finally: Reliable efficiency parameters are necessary for the reliable calculation of the performance of industrial filters. That is, among others, the main task, or the main result of the Analysis modules of the filtration programs and that is why the test data Analysis modules are extremely important because they provide us the values of reliable efficiency parameters for each step as precondition for reliable performance calculations for the given Industrial filter apparatus.