Rotamix Mixing Systems
- The Rotamix Concept
- System Components
- Rotamix Applications
- CFD Modelling
What is Rotamix?
Designed and developed by Vaughan Company, the Rotamix process mixing system is today’s most cost effective means of mechanical hydraulic mixing, consisting of an engineered arrangement of internal nozzle assemblies fed by an externally-mounted Vaughan chopper pump. With over 700 systems installed, Rotamix can be applied in circular, rectangular and oval tanks and basins, as well as other unique process configurations such as egg-shaped digesters, CSO tunnels, pump stations and sludge lagoons.
Using custom engineering and CFD software, each Rotamix system is designed to meet individual application requirements and to achieve the desired mixing effect for the process.
QUALITY & PERFORMANCE
- Rotamix System Guarantee provides GUARANTEED* active volume mixing performance
- Includes a factory 10 year full replacement nozzle warranty* against wear and corrosion
- State-of-the-art Computational Fluid Dynamics (CFD) modelling for mixing design verification
- Vaughan Company’s 50+ years of solids handling and wastewater process experience
* Contact Pump Systems for further details.
OPERATION & MAINTENANCE
- Vaughan chopper pump conditions solids for better digestion whilst preventing clogging
- Can be used in conjunction with self-priming pumps for suction lift or complete pump down
- No rotating parts within the process and no scheduled nozzle maintenance is required
- Integrated scum nozzles and foam suppression systems to help fight process problems
- Reduces confined space entry
ENERGY & FLEXIBILITY
- Ability to intermittently mix any tank or process, reducing operation and energy costs
- Mixing pump can be used to transfer tank contents, eliminating the need for additional equipment
- Shown to enhance methane gas production within anaerobic digesters for co-generation
- Variable speed drive operation to reduce pump speed can provide further energy savings
How does Rotamix work?
The Rotamix system incorporates several basic principles of physics and hydraulics, including uniform field of flow, vortical field of flow, induced flow and surface contact. Combined together, this unique mixing concept optimises solids contact due to the homogenous state.
Rotamix system nozzle assemblies developed by Vaughan Co. create multiple directional discharge points in order to evenly distribute flow. This approach allows the system to focus on problem areas within a process and eliminates the need for any rotational equipment within a particular process such as gearboxes, crankshafts, pins or any other high-maintenance moving parts.
Mixing flows are distributed through each nozzle simultaneously, which allows for very rapid development of rotation, maximising solids contact to optimise system performance. The Rotamix system is specifically developed to eliminate the “tea cup” phenomenon – a problem with most rotational mixing methods. Rotamix evenly distributes flow to both inner and outer portions of the tank, preventing pressure zones from developing and prohibiting solids from migrating towards the center of the tank. Mixing energy is distributed across the tank center floor, raising and drafting solids outwards towards the periphery, where in a circular tank, the greatest degree of natural rotational speed occurs.
Dual-Zone Mixing
The highly efficient "dual-zone" mixing pattern created by Rotamix provides complete mixing of both rotational zones, allowing the system to produce very high active volume mixing rates with relatively low flows.
Induced Flow
High velocity Rotamix nozzle assemblies increase the effective mixing volume by inducing entrained fluid over a long distance, significantly increasing the overall mixing effect over a large volume.
Surface Contact
Continuously chopped solids not only eliminate nozzle clogging, but also enhance sludge quality. Digester efficiency is further increased by further reducing solids size and increasing surface contact.
Rotamix Nozzle Assemblies
The Rotamix system uses fixed nozzle assemblies that are available in a range of single and dual nozzle configurations, depending on the tank geometry and volume of liquid to be mixed. Rotamix nozzle assemblies are designed for permanent installation inside a tank or digester. Once the assemblies are installed and nozzles aimed to factory specified angles, they are permanently tightened. No further adjustment required and there are no moving or rotating parts within the process.
Rotamix nozzle assemblies and their components are constructed from heavy-duty ductile cast materials that are then glass lined and hardened to Rockwell 70C for abrasion resistance, reduced friction, and to eliminate struvite adhesion. The tapered Rotamix nozzle barrels are a minimum 1 inch wall thickness for long-term wear protection. The entire assembly is white metal sandblasted and then powder coated with 3M™ Scotchkote™ Fusion Bonded Epoxy Coating, which is a one-part, heat-curable coating for superior surface protection. Each Rotamix nozzle assembly is covered by a 10-year full replacement warranty against wear and corrosion.
Vaughan Chopper Pump
Powering the Rotamix system is the heavy-duty Vaughan chopper pump. Vaughan’s proven technology and experience in manufacturing chopper pumps over the past 50 years ensures long-term low maintenance, and the highest reliability of any chopper pump. Continuously chopper solids not only eliminate the risk of nozzle clogging, but enhance sludge quality. Digester efficiency is increased by further reducing solids size and increasing surface contact.
Some of the key benefits offered by the Vaughan chopper pump include:
- Patented chopping action conditions solids to eliminate clogging and improve sludge quality
- Main wearing components are heat-treated to Rockwell 60C+ hardness for impact & abrasion resistance and to extend service life
- Over-sized bearing and shafting design extends pump life – B10 minimum bearing life 100,000 hours
- Heavy-duty Vaughan “flushless” cartridge seal prevents sludge dilution by eliminating the need for external flush systems (other seal configurations available)
- Back pull-out casing design with externally adjustable cutting clearances allows ease of servicing without needing to disconnect suction and discharge piping
- Available in a range of configurations, including horizontal end suction and self-priming
- Non-Clog Performance Guarantee on every pump
Highly Flexible
The flexibility in Rotamix’s design means that it can be adapted to a wide range of applications and unique processes including cylindrical, rectangular, oval and egg-shaped digesters and tanks. Rotamix application nozzle assemblies are offered in single and double nozzle configurations and can be supplied as wall-mounted, pipe-mounted or floor-mounted units. This provides flexibility of nozzle placement so that the mixing system can be tailored to the process.
Foam & Scum Protection
Foaming and excessive surface scum build-up are two process problems that can seriously affect a digester’s ability to operate at full capacity. Vaughan Co. has available a scum nozzle and Foambuster foam suppression system that can help in controlling surface scum and digester foam when all else fails.
Located at the upper level of the digester, the scum nozzle is designed to provide added upper mixing just below the surface to effectively re-suspend floating solids and to prevent stratification, while the Foambuster nozzle creates an even spray across the top of the sludge surface to break down foam after it is generated. Because Rotamix’s mixing energy will rotate the upper surface of the tank below the stationary Foambuster, most of the upper digester surface foam is broken down by the Foambuster spray.
Unlike other forms of foam control that use liquids from outside of the process, Vaughan Co.’s scum and Foambuster nozzles are designed to be integrated with the main mixing system. By using digester sludge with flow provided from the Vaughan mixing chopper pump, digester dilution problems are avoided.
Applications
WATER & WASTEWATER
- Anaerobic digesters
- Sludge storage tanks
- Sludge blend tanks
- Thickened sludge tanks
- Bio-solids blend tanks
- FOG reception & blend tanks
- Acid-phase digesters
- Egg-shaped digesters
- Equalisation basins
- Influent channels
- Skimmings & wastings pits
- CSO tunnels
- Anoxic zones
- Septage receiving tanks
- Alum sludge
- Lime slurry storage
- Ground water storage
INDUSTRIAL
- Anaerobic digesters
- Food & meat process wastes
- Recycled wastes and bio-solids
- Pulp & paper black liquor
- Refinery waste containment
- Textile waste
- Mining fine solids suspension
- Tannery & wool scour wastes
Computational Fluid Dynamics
Computational Fluid Dynamics (CFD) is a form of fluid mechanics that uses numerical methods and algorithms to solve and analyse problems involving fluid flow, the techniques of which are similar to finite element stress analysis. Essentially, fluid volumes are broken down into hundreds of thousands of volume elements to be analysed. The final results can then be plotted in various formats as described below.
The CFD modelling software used at Vaughan Co. for analysis is among the top programs available in the world for this type of detailed computer flow modelling work. Over the past 8 years, Vaughan Co. has evaluated well over 1000 different wastewater, sludge and bio-solids systems for use with its products. All Rotamix mixing system designs are supported by CFD analysis, either by standard modelled geometries, or using customised models individualised to meet specific application parameters on a consultation basis.
Velocity Plots
Shown as cross-sections through vertical or horizontal planes, velocity plots help to describe mixing energy distribution within the tank. Velocity plots have proven that small diameter nozzles producing high velocities provide more complete mixing than larger diameter low-velocity nozzles designs using equal amounts of energy. Higher velocities allow flow patterns to travel farther, while inducing significantly more entrained fluid. Unlike systems that use a standard non-clog pump, the Rotamix system is able to safely use smaller diameter nozzles without the risk of plugging, as whole solids are continuously reduced in size by the Vaughan mixing chopper pump.
Pathline Plots
Pathline plots illustrate the path of flow for a particle starting at any given point. The plotted path shows the actual movement of the particle around the tank, confirming both horizontal and vertical movement within the mixing pattern. Pathline plots are useful for showing particle movement in a tank that has reached steady state (a period of time determined to ready a steady state of mixing with a tank) and can also be used to show the re-suspension of a particle from a point on the tank floor.
Isosurface Plots
Rotamix nozzles are strategically aimed to spread mixing energy to all regions and levels of the tank. Isosurface plots can be used to illustrate the effect of the high velocity Rotamix nozzle plumes as they drive tank mixing. Isosurface plots are often also used to assess tracer washout simulation results by focusing on specific areas of concentration inside the tank after a given period of mixing time.
Tracer Burst Analysis
In addition to all of the standard CFD simulations available for Rotamix, Vaughan Co. has also developed the unique capability of being able to generate lithium chloride tracer washout test simulations using their software. Tracer washout testing can be an expensive and time consuming method of performance testing in the field. Vaughan Co.’s computer models have proven to be over 97% accurate when evaluated against actual field test results, providing additional peace of mind to the customer that they are receiving the best and most effective mixing solution for their process.
Rectangular Tanks
Rectangular tanks usually require additional mixing energy depending on the sludge rheology in each application.
Egg-Shaped Digesters
In spite of their volume and height, egg-shaped digesters can be very effectively mixed across all levels by Rotamix.
