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# Design and Calculation Methods for Uniflow Cyclones

By Ulrich Muschelknautz, MK Engineering |

*Uniflow cyclones can be effective solid-gas separation equipment when space is limited. Presented here are design and calculation methods for uniflow cyclones aimed at widening the industrial usefulness of these devices*

Cyclone separators are, in addition to fabric filters, electrostatic precipitators and scrubbers, the most commonly applied separators for removing solid particles from gases. They are used either to keep the exhaust air of a plant clean or to obtain powdery product from process gases. Compared to the other types of separators mentioned, cyclone separators have several major advantages. Their relatively simple and robust construction and operation result in comparatively low investment and operating costs in many cases. Also, they can be used in processes requiring high temperatures (up to 1,200°C), high pressures (over 100 bars) and high solids loads (for example, 30 kg solids per kg gas). Finally, they allow the reuse of the separated particles.

A competitive alternative to the standard cyclone for gas-solids separation is the uniflow cyclone. Like a pipe, a uniflow cyclone has gas and particles passing through it in only one direction. Clean gas and separated particles leave the device at the same end. The vortex flow is generated either by swirl vane inserts or by a tangential inlet at the entrance. Compared to standard cyclones, uniflow cyclones are much more compact, which makes them particularly interesting for applications with limited space. They also allow a simple and cost-effective implementation in piping systems.

Although the principle of uniflow cyclones has been known for a long time, few studies on design and calculation methods for this type of cyclone have been published. These investigations have been limited to specific applications of uniflow cyclones, such as a short-contact-time reactor for high-solids-loading gases [*1*]. This article provides information on fast design and calculation methods for the performance of uniflow cyclones, inlcuding separation efficiency and pressure drop. The performance data are aimed at widening the industrial use for uniflow cyclones, an accurate, reliable and inexpensive separation method.

## Design criteria for cyclones

In recent years, comprehensive experimental and theoretical studies of uniflow cyclones have strongly improved understanding of this equipment type and has led to approved design criteria and calculation methods, similar to those already available for standard cyclones. Applying those proven calculation models for both cyclone types, which are both based on the same physical concepts, indicates agreement with experiments on the following points:

- Uniflow cyclones can be more efficient than standard cyclones if the space is limited to close to the volume needed for the uniflow cyclone to achieve optimum performance, and the available pressure drop is low. In other words, uniflow cyclones can achieve a higher separation efficiency per volume if the available pressure drop is low.
- If volume and pressure drop are not restricted, standard cyclones are more efficient than uniflow cyclones, but require significantly more volume. The efficiencies of both cyclone types approach each other with decreasing gas volume flow and with increasing pressure drop, particle size and particle density of the feed.

## Cyclone operation

Cyclone separators have been in industrial use for over 100 years and still are the subject of intensive research and development (see Ref. 2 and 3, for example). A detailed description of physical fundamentals, designs, planning and commissioning, operation and maintenance of cyclone separators is given in Ref. 4.

The two essential performance parameters of a cyclone are its separation efficiency and its pressure drop. The latter determines its energy consumption. Goals of the cyclone design are generally to achieve the maximum possible separation efficiency with the lowest possible pressure drop for a given task. In addition, cyclone operation seeks to minimize erosion of cyclone walls by abrasive particles and prevent deposits on the cyclone walls in the case of adhesive particles, especially in areas of the cyclone with low flow velocity or flow detachment. And all of these design parameters ideally should be achieved with a limited construction volume.

In a cyclone separator, the gas to be purified from particles is set into a vortex flow with high vorticity (Figure 1). Due to the density difference between the particles and the gas, the particles sediment, under the action of centrifugal force, outward in the radial direction against the cyclone wall, where they move with the downwards rotating gas flow (only at high loads due to gravity) and are transported to the solids outlet. The cleaned gas exits the separation chamber, after reversal of direction, concentrically to the cyclone axis located at the gas outlet tube, also called the vortex finder.

The swirl is generated by introducing the particle-laden gas stream into the cyclone with a tangential component. This is realized either by a tangential slot, a spiral inlet or by an axial inlet with swirl vanes inclined to the vertical axis of the cyclone (Figure 2).

## Calculation models

For the computation of the performance data of standard cyclones, there are proven analytical models with high accuracy, which in practice, are often advantageous over numerical simulations with long computation times. One of those models is based on an equilibrium orbit concept according to Ref. 5 and is described in Ref. 2–3 and 5–13. This model has been applied successfully in a broad range of industrial applications (see for example, Ref. 14 and 15).

Similarly, industrial practice would benefit from a reliable analytical calculation model for uniflow cyclones. Previous analytical approaches to calculate the separation efficiency of uniflow cyclones are mostly based on the idea of a sedimentation process that takes place under the effect of centrifugal force. This concept insufficiently takes into account the drag force on the particles of the gas flowing inward toward the gas outlet. Since this drag force has a decisive influence on the cyclone separation efficiency, the models do not correctly reflect fundamental correlations, such as the dependence of the separation capacity on the vortex-finder diameter or the cyclone length. In addition, the re-entrainment of already separated particles from the cyclone wall into the clean gas and the influence of the solids loading on the performance data are not taken into account.

Against this background, a new analytical model was developed for the calculation of the separation efficiency and pressure drop of uniflow cyclones for practical design work. This model uses the same physical concepts as the equilibrium orbit model cited above. This approach makes sense because the principle of particle separation in both types of cyclones is the same: particle separation occurs through outward centrifugal forces generated by the swirl flow, reduced by the inward drag forces of the gas flowing to the gas outlet. The novel model has been validated with extensive experimental data [*16–22*].

** Calculation method for standard cyclones.** In standard cyclones, the separation efficiency depends crucially on the solids loading of the flow at the cyclone inlet. Solids loading is defined as the ratio of dust mass flow to gas mass flow, as shown in Equation (1).

**(1)**

The swirling flow can — similar to the gas flow in pneumatic transport — carry only a very limited dust load, the so-called limited loading. If the inlet loading (*µ*_{e}) exceeds the limited loading (*µ*_{lim}), the surplus particles are deposited on the wall of the separation chamber immediately after entry of the flow into the cyclone.

Thus, in the cyclone inlet region, a first separation stage takes place (also called wall separation). All particles carried by the vortex flow then undergo the second separation stage: the separation in the inner vortex of the cyclone. Figure 4 shows the wall separation very impressively in a standard cyclone with a diameter of 800 mm. With increasing solids loading at the cyclone inlet, an increasing portion of the incoming solids is deposited immediately after entry to the cyclone wall.

Figure 5 illustrates the influence of the solids loading on the course of the fractional efficiency curve, measured and calculated for a standard cyclone. For the case shown in Figure 5, the curve no longer drops to zero, but passes a minimum and increases as the particle size decreases. That is, finer particles are increasingly precipitated. This can be explained by a burying of fine particles below the solids strand on the wall deposited immediately after entry. The burying of fine particles increases with increasing solids loading at the entrance. For no burying to take place, this would be indicated by a steadily decreasing course of the fractional separation efficiency.

Similar behavior is also observed in uniflow cyclones (Figure 6). Immediately after entering the device, particles can form more or less pronounced strands at the cyclone wall, depending mainly on the curvature of the inlet vanes, the solids concentration and the mean particle size of the solids feed. In this case, the fractional efficiency curve passes a minimum similar to what has been observed in standard cyclones.

The model for standard cyclones, as described in the references, assumes a limited loading capacity of the gas stream splitting the separation process into two steps. At any solids loading, *µ*_{e}, in excess of this critical loading, *µ*_{lim}, the solids are immediately separated from the gas at the inlet to the cyclone. The solids remaining in the gas are separated in the cyclone barrel and in the inner vortex below the gas outlet tube with a second, inner separation efficiency, η_{i}. Total separation efficiency of the cyclone is described in Equation (2).

** (2)**

## Uniflow cyclone calculation

Analogous to the model for standard cyclones, it is assumed that both separation processes also occur in uniflow cyclones (Figure 7). The first separation takes place inside the swirl vane inserts for swirl generation and subsequently in the separation chamber due to exceeding the limited load ratio, *µ*_{lim}, of the uniflow cyclone. If the load ratio at the inlet *µ _{e}* exceeds the limited load ratio,

*µ*

_{lim}, the excess mass fraction will be removed immediately after the gas jet enters the cyclone, and only a small fraction that is restricted by

*µ*

_{lim}will undergo the centrifugal separation process in the inner vortex of the cyclones.

In a deviation from standard cyclones, uniflow cyclones have a third separation process that has to be taken into account. In contrast to standard cyclones, the solids discharge in uniflow cyclones is located close to the gas exit. Furthermore, a considerable part of the gas flow passes through the ring chamber between the cyclone wall and the vortex finder pipe before exiting through the gas outlet pipe. Due to these characteristics, particles carried into the ring chamber can be re-entrained back into the gas outlet. The re-entrainment rate depends on the cyclone geometry and on the operation data. The efficiency of the gas-particle separation within the ring chamber is denoted by η_{RC}.

Finally, the collection efficiency of the bunker has to be taken into account, as in standard cyclones. Thus, the total separation efficiency, as well as the fractional separation efficiency of the cyclone, are functions of those four single separation efficiencies (Figure 7).

The method for calculating the separation in the inner vortex has been described in detail elsewhere [*23, 24*]. For low loadings (*µ* close to 0.001), this separation mechanism is dominant and its efficiency is expected to be close to the total separation efficiency. With increasing solids loadings, the wall separation becomes more and more important and already below a solids loading of 0.01, the wall separation can become the dominant separation mechanism, depending mainly on the cyclone size, the tangential velocity at the inlet and on the size distribution and density of the particles.

Analogous to the calculation model for reverse-flow cyclones, the pressure drop of uniflow cyclones is calculated as the difference of the total pressures between a position in front of the cyclone inlet *o* and a position *m* far beyond the opening of the gas outlet where the swirl strength of the vortex flow in the gas outlet has decreased to approximately zero due to wall friction (Figure 8). As in standard reverse-flow cyclones, the total pressure drop is divided into three parts: the pressure drop in the inlet, *∆p*_{inlet}; the pressure drop in the separation chamber, *∆p*_{e}, between the mean entrance radius and the position *i* at the vortex finder radius *r*_{VF}; and the pressure drop, *∆p*_{i}, in the gas outlet tube, including the inlet pressure drop at the tube inlet between the position *i* and the measurement position *m*. At low loadings (below about 0.01), the third pressure-loss component, *∆p _{i},* accounts for the major part of the total pressure drop. The exact value depends on the geometry and operating data of the cyclone. At high loads (greater than 1),

*∆p*

_{i}is still roughly 50% of the total pressure drop.

The pressure drop calculation method is based on the same gas velocity field that is used to calculate the separation efficiency. Therefore, both calculation quantities are closely linked within this calculation model. In addition, the model allows the calculation of the pressure loss of a uniflow cyclone for any positions of the measuring point for the pressure in the gas outlet line, for example, at positions only a few inner diameters behind the gas outlet tube opening (that is, at a point where the gas flow still has a high vorticity). This is particularly useful for comparing calculation results with experimental data, as it is often measured within short distances to the gas outlet tube opening. For details of the pressure drop calculation, see Ref 24.

## Comparing cyclone types

The calculation models for standard cyclones and for uniflow cyclones described above allow comparisons between cyclone types in a systematic way. With respect to industrial applicability, a key question is what amount of particles both cyclone types can remove from specified gas-solids flows. To address this question, properly designed uniflow cyclones and standard cyclones for purifying four different gas volume flows between 24 and 6,640 m^{3}/h (air at 20°C, 1.013 bars) carrying 2 g/m^{3} dust are compared. All uniflow cyclones are geometrically similar and operate at the same static pressure drop of 4,000 Pa. The same applies to the four standard cyclones. In this example comparison, all considered cyclones are installed in a piping system with the same inlet and outlet gas velocity. The pressure drop is determined as the difference in static pressures between the inlet duct and the outlet duct. All cyclone configurations have been calculated for two dusts with different particle-size distributions (Table 1) and a particle density of 2,700 kg/m^{3}.

Uniflow cyclones for solving this problem have diameters between 30 mm (24 m^{3}/h) and 500 mm (6,640 m^{3}/h), whereas standard cyclones need diameters between 54 mm (24 m^{3}/h) and 900 mm (6,640 m^{3}/h), (Figure 9). The total lengths (including the length of the swirl generator) vary between 110 mm and 1,830 mm for uniflow cyclones, and between 150 mm and 2,580 mm for standard cyclones.

Thus, in the present case, uniflow cyclones are about 40% smaller in diameter and about 30% shorter than standard cyclones for purifying the same gas-solid flows at a given pressure drop, under typical conditions.

Note that an increase in the length of a uniflow cyclone beyond a value of *L _{c} /D*

_{c}~ 3 (Figure 8) does not improve its separation efficiency [

*22*]. This constitutes an essential difference compared to standard cyclones, where the separation efficiency increases with increasing separator height, since the cut-off size decreases with increasing height below the vortex finder (as long as this height does not exceed a critical value where the inner vortex starts to bend to the cyclone wall and to suck off particles into the gas exit).

Figure 9 shows the separation efficiencies calculated for those cyclones for semicoarse dust with a mean particle size of 50.5 µm (at the top) and for fine dust with a mean particle size of 15.5 µm (at the middle). The particle-size distributions of both dusts are given in Table 1.

The results indicate that for a specified particle feed, the difference between the standard cyclone and uniflow cyclone separation efficiencies decreases with decreasing gas volume flow and correspondingly with decreasing cyclone size. Furthermore, the difference between the separation efficiencies of both cyclone types becomes smaller with increasing particles size. Both effects can be traced back to the fact that the cut-off size of a uniflow cyclone in its present design, according to Figure 3, is slightly larger than that of a comparable standard cyclone.

A corresponding conclusion can be drawn regarding the particle density, which follows from the model approach described above. For higher particle densities than the one specified above, the gap between both separation efficiency curves (standard cyclone and uniflow cyclone) shown in Figure 9 will decrease, and vice versa.

In order to achieve a separation efficiency close to that of a standard cyclone, and also for larger gas volume flows, a multicyclone arrangement consisting of several parallel cyclones is preferable [*25*]. Figure 9b shows the separation efficiency of an arrangement of four parallel uniflow cyclones, each having half the diameter of the uniflow cyclones considered in Figure 9a. In addition, some space has been left between the cyclone cells. The comparison of Figures 9a and 9b indicates that by this measure, the separation efficiency of the uniflow cyclone is lifted up and comes very close to the values obtained by the standard cyclone in the case of separating semicoarse dust. Furthermore, the volume of the uniflow cyclone is still much more compact than that of the standard cyclone and the cyclone length has even been reduced (due to the smaller cyclone cells).

Besides the separation efficiency, the pressure drop is the other key parameter characterizing the performance of a cyclone. It can be reduced by geometrical modifications that slow down the gas velocities at the gas inlet or at the gas outlet, or both, usually at the expense of its separation efficiency.

To give an example, Figure 10 shows the separation efficiencies of standard cyclones and uniflow cyclones for the above considered gas flows between 24 and 6,640 m^{3}/h with diameters and lengths as used in the above study (Figure 9), but with reduced circumferential velocities, which strongly reduce the pressure drop to 1,000 Pa. By comparing with Figure 9, it can be seen that the pressure drop reduction distinctly affects the separation efficiencies for fine particles, whereas semicoarse particles can be removed with almost the same efficiency as that of the cyclones with high pressure drop. This applies to standard cyclones as well as to uniflow cyclones.

A well proven method in industry to reduce the pressure drop of standard cyclones without affecting the separation efficiency is to install swirl vane inserts into the vortex finder, as shown in Figures 11 and 12. This device transforms rotational energy into pressure [*11*]. Without that measure, the rotational energy will be lost due to dissipation in the gas outlet pipe. Up to 60% of the total cyclone pressure drop can be regained by swirl vane inserts, depending on the cyclone geometry and on the operation data. Similar results can be obtained by applying swirl vane inserts in the vortex finder of uniflow cyclones. For example, in a uniflow cyclone with a diameter of 300 mm (11.8 in.), a pressure-drop reduction by 43% could be achieved at a gas volume flow of 1,000 m^{3}/h, and by 40% at 2,500 m^{3}/h [*18*].

## Cyclones in limited space

Often, space available for dedusting a gas flow within an industrial plant is limited. If saving space is a high priority, or if there is a limited space available for purifying a given gas volume flow, the question arises whether under the space restrictions, a uniflow cyclone system may be preferable over its standard cyclone counterpart. This question is addressed by applying the above-mentioned calculation programs for standard cyclones and for uniflow cyclones.

To provide a fair comparison between both cyclone types, the most compact representative of a standard cyclone is considered. This is a cyclone with an axial inlet (Figure 2c), also called a swirl tube (Figure 14a). This cyclone type is preferably applied as a multicyclone series (that is, a system of many parallel cyclone cells within a common housing, and having a common solids hopper for solids discharge). Multicyclones are generally used to increase the separation efficiency beyond the level achievable by a single cyclone. Note that the minimum particle size that can be collected by a cyclone generally decreases with decreasing cyclone size. Principally, increasing the number of parallel cyclone cells and decreasing their size at the same time improves the efficiency of a multicyclone without changing the base area and without affecting its pressure drop, provided a uniform distribution of the gas and the solids feed into each single cyclone cell can be achieved, and bypass flows through the solids discharge openings from one cyclone cell to the other can be avoided. In many cases, this can be achieved to a good approximation by a proper design of the cell arrangement, the spacing between them, and the geometry of the housing inlet and outlet duct.

To compare both cyclone types, a typical industrial multiclone application has been considered and investigated in a systematic way. Various dedusting problems have been investigated, specified by the gas-solids feed, the available volume for the cyclone and its pressure drop.

In all considered cases, the gas feed per cyclone cell is 466 m^{3}/h (15,457 ft^{3}/h) air at ambient conditions with a gas density of ρ_{g} = 1.2 kg/m^{3} and a gas viscosity of 2 × 10^{–5} Pa s.

With respect to the particle feed, only fine powders are taken into consideration in order to make a meaningful comparison. Note that the difference between both cyclone types becomes most clear when considering the collection of fine particles. With increasing particle size of the feed, the efficiencies of both cyclone types increase and converge (Figures 9 and 10). Four fine powders are considered characterized by two different particle densities, ρ_{s} = 1,490 kg/m^{3} and ρ_{s} = 2,700 kg/m^{3}, and two particle-size distributions *Q*_{3} (d), which are assumed to be describable as Rosin-Rammler-Sperling-Bennett (RRSB) functions. The two sets of RRSB parameters are:

*d*_{min} = 0.2 µm, *d*_{max} = 200 µm, *d*’ = 25.5 µm, *n* = 0.95, *d*_{50} = 17.5 µm

*d*_{min} = 0.1 µm, *d*_{max} = 30 µm, *d*’ = 19 µm, *n* = 0.8, *d*_{50} = 12.2 µm.

In all considered cases the particle concentration is *S*_{0} = 2 g/m^{3}.

The volume occupied by a cyclone is mainly determined by its diameter and by its length. A uniflow cyclone generally requires about the same or even a shorter length (typically 2–3 cyclone diameters) to achieve optimum performance than a swirl tube [*22*]. Thus, only the cyclone diameter is varied to observe the influence of the available volume. The swirl tube diameter *D*_{c,ST} is varied between *D _{c,ST} / D*

_{c,UC}= 1.0 and

*D*

_{c,ST}/D_{c,UC}= 1.3, while keeping the uniflow cyclone diameter constant at

*D*

_{c,UC}= 124 mm. The pressure drop is varied between 500 Pa (0.073 psi) and 2,000 Pa (0.290 psi).

The results show that, under the operating conditions considered, a uniflow cyclone achieves a significantly higher separation efficiency than a swirl tube if the available volume is restricted to about the volume needed by the uniflow cyclone for separating the given gas-solids feed and if the available pressure drop is low, in accordance with experiments as is shown in Ref. *26*. For example, for a pressure drop of 500 Pa, the efficiencies can differ by up to 10%. If the volume and pressure drop are freely available, swirl tubes reach higher separation rates than uniflow cyclones, with the separation efficiencies of both cyclone types converging as the gas-volume flow, and consequently, the cyclone size decreases and the pressure drop, the particle size or the particle density increase.

The results described here are transferable to multicyclone systems. In many cases multicyclones use swirl tube cells. Analogously, multicyclones can be made from uniflow cyclone cells. Often these devices are used in space-limited applications; for example, as third-stage separators in fluid catalytic cracking (FCC) processes [*28, 29*].

Compared to swirl tubes, the higher efficiency per volume of uniflow cyclones at low pressure drop is especially advantageous in multicyclone applications with low pressure drop (for example purifying suction air in combustion engines [*27*]).

## Concluding remarks

Comparing standard cyclones with uniflow cyclones by applying well proven calculation models for both cyclone types indicates higher efficiencies, but also higher volume required for properly designed standard cyclones. However, if available volume is restricted to about the volume needed by a uniflow cyclone for its optimum performance, and if the pressure drop is low, a uniflow cyclone can be more efficient, in agreement with experiments. In other words, uniflow cyclones can achieve higher efficiencies per volume than standard cyclones if the available pressure drop is low. Furthermore, independent of any restriction regarding volume and pressure drop, the performance data of both cyclone types approach each other with decreasing gas-volume flow and increasing pressure drop, as well as particle size and particle density of the solids feed. Those results transfer to multicyclones systems consisting of many parallel cyclone cells.

*Edited by Scott Jenkins*

## References

1. Gauthier, T.A., Briens, C.I., Bergougnou, M.A., Galtier, P., Uniflow cyclone efficiency study.

Powder Technol., 1990, p. 217–229.

2. Knowlton, T. M., Cyclone separators. In: Wen-Ching Yang (ed). “Handbook of Fluidization and Fluid-Particle Systems.” Marcel-Dekker-Verlag, 2003.

3. Hoffmann, A.C. and Stein, L.E., “Gas Cyclones and Swirl Tubes,” Springer-Verlag, 2nd ed., 2007.

4. Kox, V., Lehmann, C., Muschelknautz, U., Ripperger, S. VDI-Richtlinie: VDI 3676 Abgasreinigung – Massenkraftabscheider (2018), p. 1–39.

5. Barth, W., Berechnung und Auslegung von Zyklonabscheidern aufgrund neuerer Untersuchungen. Brennstoff- Wärme- Kraft, Bd. 8, Nr. 1, 1956, S. 1–9.

6. Muschelknautz, E., Brunner, K. Untersuchungen an Zyklonen. Chem. Ing. Techn. 39, Nr. 9/10, p. 531–538, 1967.

7. Muschelknautz, E. Die Berechnung von Zyklonabscheidern für Gase.

Chem. Ing. Techn. 44, Nr. 1/2, 1972.

8. Muschelknautz E., Trefz M. Secondary flow and short circuit flow at the dust discharge end of cyclone separators. Calculation and design of multicyclones. 1. European Symposium Separation of Particles from Gases, Nürnberg, 19. bis 21.4.1989, Preprints S. 345–362.

9. Rentschler W. Abscheidung und Druckverlust des Gaszyklons in Abhängigkeit von der Staubbeladung. VDI Fortschritt- Berichte, VDI- Verlag, Düsseldorf, Reihe 3, Nr. 242, 1991.

10. Trefz M. Die verschiedenen Abscheidevorgänge im höher und hoch beladenen Gaszyklon unter besonderer Berücksichtigung der Sekundärströmung. VDI- Fortschr.- Ber., VDI- Verlag, Düsseldorf, Reihe 3, Nr. 295, 1992.

11. Greif, V. Reduzierung des Druckverlustes von Zyklonabscheidern durch Rückgewinnung der Drallenergie und Erweiterung der Grenzbeladungstheorie auf kleine und kleinste Staubbeladungen. VDI-Fortschr.-Ber., VDI-Verlag, Düsseldorf, Reihe 3, Nr. 470, 1996.

12. Muschelknautz, E., Greif, V. Cyclones and other gas-solids separators, in “Circulating Fluidized Beds” (Eds: J. R. Grace, A. A. Avidan, T. M. Knowlton), Blackie Acad. & Profess., London, p. 181–213. 1997.

13. Muschelknautz, U. Zyklone zum Abscheiden fester Partikel aus Gasen. VDI-Wärmeatlas, 12th ed., Springer, Berlin, Chapter 91-1, p. 1–20. 2018.

14. Muschelknautz, U., Muschelknautz, E. Abscheideleistung von Rückführzyklonen in Wirbelschichtfeuerungen. VGB KraftwerksTechnik 4/99.

15. Ipsen C., Roschek, D., Muschelknautz, U. Optimierung des Zyklonabscheiders einer zirkulierenden Wirbelschichtfeuerung – Theoretischer Hintergrund und Betriebserfahrungen. VGB PowerTech Journal 4/2014, S. 75–79.

16. Muschelknautz, U. Separation of coarse particles: New separator with low pressure drop. Proceedings of CFB-VII-Conference, Niagara Falls, Canada, 2002.

17. Würtl, R. Experimental investigation of uniflow cyclone performance. Diploma Thesis, MCI Management Center Innsbruck, Austria, 2007.

18. Foidl, F. Entwicklung von Leitapparaten zur Druckverlustminimierung in Gleich-stromzyklonen. Diploma Thesis, MCI Management Center Innsbruck, Austria, 2008.

19. Leitner, A. Einfluß der Staubart auf den Trenngrad eines Gleichstromzyklons. Diploma Thesis, MCI Management Center Innsbruck, Austria, 2009.

20. Reinalter, M. Minimierung des Partikelwiedereintrages in den Reingasstrom von Gleichstromzyklonen. Master Thesis, MCI Management Center Innsbruck, Austria, 2010.

21. Pattis, P. Entwicklung eines Gleichstromzyklons mit gezielter Strähnenführung. Master Thesis, MCI Management Center Innsbruck, Austria, 2010.

22. Muschelknautz, U., Pattis, P., Reinalter, M., Kraxner, M. Design criteria of uniflow cyclones for the separation of solid particles from gases. 10th International Conference on Circulating Fluidized Beds and Fluidization Technology – CFB-10, 2011.

23. Muschelknautz, U. Analytical approach for calculating the separation efficiency of uniflow cyclones.

Chem. Eng. Technol.35, 2012, No. 12, p. 2,099–2,106.

24. Muschelknautz, U. Analytical approach for calculating the performance data of uniflow cyclones. Proceedings oft he 22nd International Conference on Fluidized Bed Conversion, Turku, Finland, p. 929–934, 2015.

25. Muschelknautz, U. Performance comparison of uniflow cyclones and standard cyclones. Proceedings of the 12th International Conference of Fluidized Bed Technology, Krakau, Poland, 2017.

26. Muschelknautz, U. Design criteria of multicyclones in a limited space. 8th World Congress on Particle Technology, Orlando, Fla., 2018.

27. Greif, V. Multizyklon-Blöcke zur Staubabscheidung vor Verbrennungsmotoren – Ausle-gung und Betriebserfahrungen. VDI-Berichte 1511, p. 215–226. Düsseldorf: VDI-Verlag, 1999.

28. Kraxner, M., Muschelknautz, U., Karri, S.B., Cocco, R., Knowlton, T.M. Applicability of a Uniflow Cyclone as a Third Stage Separator in the FCC-Process. AIChE – American Institute of Chemical Engineers – Annual Meeting, Minneapolis, Minn., USA, 2011.

29. Krishnamurthy, S., Koves, W. Apparatuses and methods for gas-solid separations using cyclones. UOP LLC, Patent US-8419835 B2, 2013.

## Author

Ulrich Muschelknautz is managing director of MK Engineering Particle Removal Technology (Heinrich-Fuchs-Str. 101, 69126 Heidelberg, Germany; Phone: +0049-711-7262880; Email: um@mkengineering.de), an engineering office specialized in the process design of high-efficiency cyclones, scrubbers and pneumatic conveying systems. MK Engineering was founded in 1983 by Edgar Muschelknautz, an international expert in cyclone technology. Ulrich Muschelknautz has over 25 years experience in the design of industrial particle removal units. He has worked on projects in many industrial sectors, including power generation, petroleum refining, petrochemicals, chemicals, pharmaceuticals, food, recycling and others. Ulrich Muschelknautz was a professor of mechanical process engineering and fluid dynamics at the University for Applied Sciences MCI (Innsbruck, Austria) from 2005–2014, where he built a research group for particle removal technology. He has authored more than 60 scientific articles on particle removal technology. He holds a Diploma degree in physics from the University of Bonn (Germany), a doctoral degree in physics from the University of Stuttgart (Germany), and was a postdoctoral researcher at the Centre National de la Recherche Scientifique (CNRS), in Grenoble, France.

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**Supplier Process Engineer - Dell - Franklin, MA**

**Supplier Process Engineer - Dell - Franklin, MA**

**Chemical Engineer - National Fire Protection Association - Quincy, MA**

**SENIOR PROCESS ENGINEER - Air Products & Chemicals, Inc. - Allentown, PA**

**Reduce Explosion Risk in 2 Seconds with In Situ Oxygen Analysis**

**Tunable Diode Laser Spectroscopy in Critical Applications**

**Non-Contacting Gas Sensors Minimize the Risk of Corrosion to Plant Equipment.**

**5 ways to Optimize Production of Polymers and Intermediate Petrochemicals**

**7 Ways to Achieve Process Safety in Chemical Production**