What is a Pusher Centrifuge?
Pusher centrifuge is a continuous filtering apparatus that typically finds application in mineral and chemical industries for solid-liquid separation. Centrifugal devices are being used for more than 60 years now for dewatering fairly large crystals. They feature a unique design that efficiently minimizes crystal breakage, impurity and moisture in the discharged cake. Pusher centrifuge is employed for quick and efficient separation techniques and works on two fundamental principles: filtration and sedimentation.
The use of filtration usually depends on the size of the particles that need to be processed because they need to be large enough to build a cake that is adequately porous to facilitate the liquid flow through it. Examples include peeler, pusher and vibration screen. Sedimentation on the other hand, involves allowing the heavier phase to pass through the lighter one. The heavy phase containing fine solids collects on an imperforate surface. Examples include disk nozzle centrifuge and decanters.
Features of Pusher Centrifuge
A pusher centrifuge comes with hydraulic drive arrangements for different capacity requirements.
- The safety features available in a pusher centrifuge include gas tight arrangement, interlock mechanism for the front lid, anti-vibration interlock, safety guard, and pressure relief valve for high capacity, large units.
- Pusher centrifuges come with a variety of screen cross sections to suit different process requirements. Filter screen options include looped slotted screen, milled screen and welded screen.
- Feeding options also vary vastly depending on different feeding arrangements and include hydrocyclone, pre-thickener and screw feeder.
- All electric panels come with safety interlocks and fully programmable logic controls for efficient operations that save time, effort and money.
- The cooling coils fitted inside the reservoir of the hydraulic system help maintain optimum temperature levels.
- The separation pusher features a robust base that provides solid support to the entire rotating assembly.
Operation of Pusher Centrifuge
- The pusher centrifuge is constantly fed from the top with the slurry that needs to be filtered.
- A feed distributer evenly distributes the slurry for gentle acceleration and reduced breakage of particles. This improves efficiency and aids in quick filtration.
- A major portion of the slurry gets filtered during the first stage, pushing the discharged cake to the next stage.
- During the second stage of filtration, the cake is pushed further into the discharge chute.
- The residual solids accumulated in the discharge chute are then scraped off.
- The liquids separated from the slurry are discharged through the liquid discharge arrangement depending on the solid-liquid separation requirements.
Parameters That Affect Pusher Centrifuge Performance
Some important variables that impact the performance of pusher centrifuge include:
Size of the Particle: For any pusher centrifuge to produce maximum throughput, it is necessary that the particle size be as large as possible. The size and shape of the crystals determine the efficiency and functioning of the centrifuge as the crystal size increases, the surface area for every unit mass decreases. When there is less surface area for the moisture to bind to, it results in a drier cake.
The Viscosity of the Mother Liquor: The drainage rate of the pusher centrifuge is also affected by the viscosity in addition to porosity. As the viscosity increases, the solid-liquid separation is subjected to added resistance which consequently, de-rates the throughput.
Particle Attrition: When the pusher plate movement combines with the feed funnel’s acceleration, some particles break and compact, increasing the volatile matter in the discharge cake. When the centrifugal force is low, the conveying of cake takes place gently in a single stage, resulting in low particle attrition.
Quality of the Cake: The cake quality is measured in terms of volatile matter and purity. The amount of volatile matter in the cake is a function of the centrifugal force and the associated residence time. So, increasing the centrifugal force would increase the solid-liquid separation force and thereby facilitate faster drainage.
Slurry Concentration: Increasing the feed slurry concentration makes it easier to process more solids for any given amount of feed. So, in order to achieve more throughput; the feed concentration must be increased.
Applications of Pusher Centrifuge
The pusher centrifuge finds application in various industries including chemical, waste treatment and inorganics. Notable applications include plastics, rocket fuels, organic intermediates, food processing, ammonium sulfate, sodium bicarbonate, borax, borates, potash, sulfides, chlorates and chromates. Plastic applications include PVC, polypropylene, polyethylene and a number of other resins. Pusher centrifuges are also used for different soda ash applications, for waste water treatment, for cotton seed delinting, and for extracting nitric acid from adipic acid.
Advantages of Employing a Pusher Centrifuge for Solid-Liquid Separation
A pusher centrifuge offers several advantages of which, the most distinct is quick and efficient solid-liquid separation. A pusher centrifuge offers high throughput consistently, while ensuring high purity and low moisture in the discharged cake. The recent design modifications made in pusher centrifuge have successfully reduced energy consumption in a wide range of applications. Other advantages include an even feed distribution and consistent product quality.
Author Bio:
Jigar Patel is the director of Oriental Manufacturers. He believes in the power of good functional designs and its ability to boost productivity and drive growth. Fuelled by his passion for innovative designs and all things EPC, Jigar took to blogging about all the information and technical know-how he has amassed over the years. He writes on topics related to process machinery production, turnkey solutions, best industry practices and his personal insights!