Granulators are essentially rotary grinders that are used to grind scrap parts and melt delivery systems (sprues and runners) into feedstock sized granules for reprocessing. This allows the molder to reduce waste and produce components more cost effectively. Since these granulators will be used to cut polymers that are loaded with metal powders, the wear of the cutting blades is great. As such, the blades should be manufactured from carbide or a tool steel with high wear resistance. A design that allows resharpening of blades is desirable. Many granulators are designed so that the blades must be completely replaced when they are worn. The last consideration with respect to granulators is to have a granulator that is easy to clean thoroughly to avoid cross contamination between MIM materials. Having a granulator to serve each material may be desirable.
1.What are the different rotor designs used in granulators?2.What determines the size of the granulated particles?3.Where are granulators used in extrusion?4.What are four maintenance issues associated with granulators?5.What needs to be checked and serviced in a good preventive maintenance program for granulators?6.What is the difference between a granulator used to regrind film compared to a granulator designed to regrind profiles, pipe, and heavy stock?7.What are the differences in knives required for different resins?
Granulator machines are designed with high speed, medium inertia, open rotor body for fine grinding, with two, three, or five hardened steel knives. Granulators can grind material down to 0.177mm (80 meshes) or up to 5cm in size. Generally, the resulting particles vary in size from 3 to 20mm. Interchangeable qualifying screens with various diameter holes determine the final reduction size. With decibel ratings of less than 65Db, these units are ideal for placement at individual workstations. Granulators are sized by the dimensions of the cutting chamber and range in size from 20 25 to 40 88cm. Motor sizes range from 5 to 40HP. Complete systems can include air discharge units or conveyors, and can easily be integrated with existing shredder or grinder systems. Granulators have a smaller footprint than a full-sized grinder, but can still handle high volumes of product in the granulation process (Fig. 3.13) . Hammer mills accomplish size reduction by typically impacting at rates of 7000rpm and higher . A solid rotor for grinding scrap Cu wires, PCBs, metals, and plastics is used. These granulators are used for the sizing of plastics, nonferrous metals, heterogeneous materials, and enable to reach controlled output size in the recycling process with the use of classifier screens starting from 2mm diameter. The size of the granulators ranges between (1060 1800) (1700 1800) (2000) mm; power from 8 to 90kW, and weight from 0.7 to 4.2 tons.
Roll granulator, an indispensable basic production link of a large number of industrial and agricultural products, is involved in a wide range of national economy. Roll granulator is also a big energy consumer, and the pollution caused by working process is an important source of environmental pollution in China. Therefore the evaluation and optimization of the roll granulator design process is of great significance to both the manufacturers and the consumers.
The authors investigated the design, manufacture, and service process of a roll granulator in a building material equipment manufacturing group. It is a high-tech group, which manufactures large complex building material equipment for cement production line, such as cement mill, preheater system, rotary kiln, and stacker reclaimer. Due to complex structure, harsh working environment, long production cycle, and distributed manufacturing mode, it is difficult to implement the informatization construction of the building materials and equipment group. The development of new IT technologies brings opportunities for the group, which has established a complete data collection, mining, and analysis system around the PLC.
Take the roll granulator as an example, product design, manufacturing, and service mode of the group is shown in Fig. 5.5. When the company receives the order, the technician uses CAD and SolidWorks to design drawings according to customer requirements and imports the product design parameters, processing parameters, and material requirements into the enterprise resource plan (ERP) system through the product data management (PDM) system. Then, the production department organizes production according to the production details. IoT technology is used to collect real-time processing data of equipment and performance test data of products, while handheld terminals are used to collect progress data and quality inspection data. When all the components are processed, they are transported to the construction site for installation. When the product is put into use, the sensors and control system will collect the equipment operation data (such as energy consumption, vibration, and breakdown parameters) in real time and will upload it to the cloud platform. In addition, during the use and maintenance process, the customer also employs the after-sales service system to report problems and evaluations to the group and obtains continuous improvement. In this way, a large amount of data in PLC is collected and stored on the cloud platform for real-time monitoring and analysis. New IT has injected fresh energy to large complex equipment life cycle. These data will help build the DT for roll granulator and support designer for design evaluation.
The TSG consists of a barrel enclosing two co- rotating self-wiping screws. At the entrance, raw materials are fed into the transport zone and the granulation liquid is added via two nozzles, one for each screw, before the material reaches the mixing zone which consists of kneading discs (Fig. 1). The powder is hence wetted by the granulation liquid in this region. Further down, since the granulation occurs by a combination of capillary and viscous forces binding particles in the wet state, the wetted material is distributed, compacted and elongated by the kneading discs of the mixing zones, changing the particle morphology from small (microstructure) to large (macrostructure) (Vercruysse et al., 2012). The rotation of the screws conveys the material in axial direction through the different zones of the TSG by the drag and flow-induced displacement forces and thus causing mixing and granulation. The rheological behaviour of the material also changes based on liquid-to-solid ratio (L/S) (Althaus and Windhab, 2012).
Ring granulator crushers are used for coal crushing to a size that would be acceptable to or suitable for the mills/pulverizers, which then convert it into powdered coal. The essence of using a ring granulator is that it prevents both oversize and undersize coal; this helps with the quality of finished product and improves its workability. Due to the crushers strong construction, it is capable of being utilized for crushing various materials (e.g.,coal, limestone, lignite, gypsum) and other medium-to-hard friable items. Ring granulators are rugged and dependable and specially designed for continuous high-capacity crushing of materials. They are available with operating capacities from 40 to 1800 tons/hr or even more, with feed size of up to 500 mm.
Adjustment of clearance between the cage and the path of the rings is provided to take care of product gradation as well as to compensate for wear and tear of the machine parts and to maintain product size. The unique combination of impact and rolling compression makes the crushing action yield a higher output with less power consumption and a lower noise level. Here, the product is almost of uniform granular size with an adjustable range of <20 to 25 mm, and because the crushing action involves minimum attrition, minimum fines result. Further development from the conventional hammer mill through replacement of hammers by rings makes it possible to minimize both oversize and fines, thereby improving efficiency.
Ring granulator crushers work on an operating principle similar to a hammer mill, where the only change is that the hammers are replaced with rolling rings. This crusher compresses material by impact in association with shear and compression force. It is comprised of a screen plate/cage bar steel box with an opening in the top cover to introduce the material. The power-driven horizontal main shaft passes from frame side to frame side and supports a number of circular discs fixed at regular intervals along its length within the frame.
There are quite a few bars running parallel to the main shaft and around the periphery that pass through these discs near their outer edges. The bars are uniformly located about the center of the main rotating shaft. There are a series of rings, between the two consecutive disc spaces, mounted on each bar that are free to rotate on the bars irrespective of main shaft rotation.
The entire cage assembly, located below the rotor assembly, can be set at a desired close proximity to the rings by a screw jack mechanism that is adjustable from outside of the crusher frame. The rotor assembly, consisting of the shaft, discs, rings, etc., is fixed as far as the main shaft center line is concerned. This main shaft is carried in roller bearings from the box sides. The movable cage frame arrangement is provided so as to set its inner radius marginally larger than that of the ring running periphery.
When coal is fed from the top, the rings also rotate along with the shaft and around their own center line along the bars, which drag coal lumps and crush them to the desired size. After the coal has been crushed by ring granulator crusher, a vibrating screen grades the coal by size and then transports it via a belt conveyor. In this process, a dewatering screen to remove water from the product is optional.
The granulator consists of a granulation chamber, where the particle population is fluidized through an air stream with predefined pressure, temperature and humidity. Then a liquid solution or suspension is injected, which settles on the particles. Due to the low humidity and increased temperature the liquid fraction, i.e. the solvent or the external phase, is evaporated. The remaining solid forms a new layer on the particle surface. Typically, nucleation due to spray drying, particle agglomeration and breakage are in this configuration negligible. As one is in general interested in product particles with a defined particle size distribution withdrawn granules have to be sieved, which results in two additional fractions. The fine particles are directly sent back to the granulation chamber, whereas the oversized granules are send to a mill. There they are grinded to a specific size and then send back to the granulation chamber. It should be mentioned that due to this sieve-mill cycle a permanent generation of new particles is guaranteed, which hence allows a continuous process operation. The associated pilot plant and process scheme is depicted in Figure 1 (left and right). In Heinrich et al. (2002) a population balance model for the fluidized bed spray granulation with external product classification has been presented. There, it was assumed that the particles are almost spherical and can hence be described by one internal coordinate L, the particle diameter, giving rise to the particle size distribution n(t, L). The associated particle growth can be described by
In the continuous configuration of the fluidized bed spray granulation particles are continuously removed in order to achieve a constant bed mass, which correlates to a constant third moment of the particle size distribution. The particle flux being removed from the granulator is
where K is the drain, which has to be controlled such that the bed mass is constant. The removed particles nout(t,L) are then sieved in two sieves and separated into three classes: fines fraction Eq. (3), i.e. particles which are smaller than the desired product, product fraction Eq. (4), i.e. particles with the desired size and oversize fraction Eq. (5), i.e. particles being bigger than the desired product.
As has been shown in Radichkov et al. (2006) the qualitative dynamical behavior of the fluidized bed spray granulation with external product classification strongly depends on the process parameters especially the mill grade M.For sufficiently high mill grade, transition processes decay and the particle size distribution reaches as table steady state (Figure 2 left). Decreasing the mill grade below a critical value gives rise to nonlinear oscillations (Figure 2 right). Using the population balance model the critical mill grade, i.e. the mill grade where the qualitative change in the stability behavior occurs, can be derived by a one-parameter bifurcation analysis as depicted in Figure 3. It is important to mention that this qualitative behavior is not induced by the specific model formulation but is directly connected to the presented process configuration.
A ring granulator works on n operating principle similar to a hammer mill, but the hammers are replaced with rolling rings. The ring granulator compresses material by impact in association with shear and compression force. It comprises a screen plate/cage bar steel box with an opening in the top cover for feeding. The power-driven horizontal main shaft passes from frame side to frame side, supporting a number of circular discs fixed at regular intervals across its length within the frame. There are quite a few bars running parallel to the main shaft and around the periphery that pass through these discs near their outer edges. The bars are uniformly located about the center of the main rotating shaft. There are a series of rings in between the two consecutive disc spaces, mounted on each bar. They are free to rotate on the bars irrespective of the main shaft rotation. The entire cage assembly, located below the rotor assembly, can be set at a desired close proximity to the rings by screw jack mechanism adjustable from outside the crusher frame. The rotor assembly consisting of the shaft, discs, rings, etc., is fixed as far as the main shaft center line is concerned. This main shaft carries in roller bearings from the box sides. The movable cage frame arrangement is provided so as to set its inner radius marginally larger than that of the ring running periphery. When coal is fed from the top, the rings also rotate along with the shaft and around their own center line along the bars, which drags coal lumps and crushes them to the desired size. After the coal has been crushed by the coal crusher, a vibrating screen grades the coal by size and the coal is then transported via belt conveyor. In this process, a dewatering screen is optional to remove water from the product.
The feeder-blender-granulator system (see Figure 1a) consists of two feeders (API + excipient) that feed into a blender where the API and excipient are mixed due to convective/diffusive forces. The mixture of API/excipient is then continuously transported into a granulator whereby through the addition of liquid binder, the particles are formed into larger granules, to improve its flow and dissolution properties.
Each continuous feeder operates under closed-loop proportional-integral (PI) control whereby the feedrate is specified as the set-point and the feeder RPM is manipulated to ensure that the set-point is met. To model each feeder, set-point changes were made to the feedrate and the dynamic response was observed to follow a first order profile. Therefore, a first-order plus time delay (FOPDT) model was used to fit the data.
Here r is the vector of internal variables used to characterize the distribution and z is the vector of external coordinates used to depict spatial position. F(z,r,t) is the population distribution function (a.k.a. the number density function). The term r[F(z,r,t)drdt] would account for the rate at which the distribution evolves with respect to position and time due to the rate of consolidation. The term z[F(z,r,t)dzdt] accounts for the evolution of the distribution of the particle population with respect to spatial position. The function Rformation(z,r,t) and Rdepletion(z,r,t) accounts for the formation and depletion of particles respectively due to discrete aggregation and breakage phenomena. In the blender model, aggregation and breakage are neglected; therefore the PBM reduces to a two-dimensional model with respect to the vector z where z denotes the axial and radial direction. In the granulation model, the granulator is assumed to be well-mixed; therefore the PBM is a four-dimensional model with respect to r, where r denotes the volume fractions of the API, excipient, liquid and gas. Details of the blending model and granulation model can be found in .
Figure 2a depicts the total mass flowrate of powder that exits the blender and enters the granulator. It can be seen that steady state is reached by t=150s, whereby a step change is introduced to the rpm (rpm is doubled). This results in a sharp increase in the mass flow rate which gradually reduces to the original mass flowrate. Figure 2b depicts the average granule diameter upon particles exiting the granulator. It can be seen that in the first few seconds of operation, no powder enters the granulator as they are still being processed in the blender. Upon powder entering the granulator, there is a sharp increase in granule diameter as granules undergo aggregation and eventually a steady state is attained by t=150s, whereby the step change in rpm results in a slight immediate decrease in granule diameter (due to the sudden influx of more fine powder in the granulator). Eventually, this leads to more fine powder being aggregated and this results in an increase in granule diameter till a new steady state is achieved. Similar transient profiles are achieved for granule bulk density and granule API concentration (see Figures 2c and 2d)
A bimaterial catalyst support was obtained in a pan granulator with a composite sol-gel formulation based on -Al2O3 filler, boehmite binder and -Al2O3 beads. The resultant catalyst support shows a homogenous coating with a twenty micrometer thickness. Local mechanical properties of coating and interface are in the magnitude order of conventional -Al2O3 beads. Deposited metallic palladium nano-particles on this bimaterial are very preferentially located into the -Al2O3 coating as expected. Activity and selectivity of the bi-material catalyst show a huge improvement compared to the reference catalyst using conventional carrier.
This study demonstrated that bi-material catalyst are promising candidate for all industrial catalytic reactions that present intraparticular diffusion limitations as mechanical properties and catalytic performances are very satisfactory. It should be planned in the future to extend the concept to multifunctional catalysis.
Sand is the second most used natural resource after water. It is of high importance in the construction industry. As urbanization spreads around the world, more construction material is needed to build infrastructure in urban areas. It is being predicted that Sand will become the most sought after commodity of the 21st century, similar to oil in the 20th century.
Our endeavor in the platform is to make available alternate sustainable sources of sand that are ethically sourced to meet the varied requirements of the industry. And thus preserve the fast vanishing natural sources of sand.
Plaster Sand is is a very fine grade of sand used for internal and external render, plastering and screeding. It creates a smooth and even finish and can be used for filling cracks. The Fineness Modulus of this sand is not less than 1.4.
Concrete Sand is coarse in nature and primarily used in the manufacture of ready mix concrete and asphalt. The Fineness Modulus of this sand is between 2.3 to 3.2. It is graded and washed adequately to remove unwanted silt for optimum mix-design.
Masonry or Mortar Sand is a fine graded all purpose sand that can be used as a fill material, paver base and levelling agent. Its ultra fine texture and ease of use helps in projects where style and design are important. Fineness Modulus of this sand is between 1.15 to 2.95
Recycled sands are an environmentally friendly, cost effective alternative to natural sand. Produced from construction & demolition waste, recycled sands can be used for Mortar, concrete road construction, paver blocks and other street furnitures.
Silica sand is the primary component to produce flat glass for building and automotive use, container glass for foods, beverages and tableware. It provides the essential SiO2 component of glass formulation, and its chemical purity is the primary determinant of colour, clarity, and strength.
Silica sand is an essential part of the ferrous and non-ferrous foundry industry. Silicas high fusion point (1760C) and low rate of thermal expansion produce stable cores and molds compatible with all pouring temperatures and alloy systems.
CRF is a by-product of the quarrying industry and results from rock-crushing operation as waste, most of which passes through 6mm IS sieve. In the industry it is also known as quarry dust, stone dust or crusher dust. As per MORTH, quarry dust may be used in bituminous base course in construction of roads and highways. Landscapers use crusher dust for filling holes, as bedding for paving stones and more recently its applications have broadened to other areas.
Crushed stone sand is produced by crushing hard stones to less than 4.75mm particles by using roller crushers or vertical shaft impactors (VSI). Crushed stone sand has better particle shape and contains lower level of silt content when compared to CRF/crusher dust. In the construction industry crushed stone sand is used in mortars for brick laying and in concrete applications by suitably altering the mix-design.
Aggregates are inert granular materials such as sand that, along with water and portland cement, are an essential ingredient in concrete. 10 mm Aggregates are mainly used in ready mix concrete, asphalt/bitumen/concrete roads base and sub-base course, pavements, separately or mixed with other aggregates depending on the application.
Aggregates are inert granular materials such as sand that, along with water and portland cement, are an essential ingredient in concrete. 20 mm Aggregates are mainly used in ready mix concrete, asphalt/bitumen/concrete roads base and sub-base course, pavements, separately or mixed with other aggregates depending on the application.
Granular Sub Base (GSB) is natural or crushed material, used for road construction as a sub-base layer. Granular Sub Base is a layer in road foundation just above the compacted sub-grade layer. GSB or granular sub-base prevents capillary water from rising; its particle size is so designed that the capillary action stops and does not go beyond GSB layer. Secondly, it works like a drainage layer where water can pass without damaging other road layers. It is made from crushed stone aggregate or river bed material free from organic constituents. It conforms to Table 400-1 of MORTH specification, with the percentage passing 0.075mm size restricted to 5%.
Silt is the by-product of manufactured sand and separated during washing process. Typical silt consists of granular particles sized less than 0.075 mm. Good quality silt can be used in landscaping, as part of the mineral filler portion in hot mix asphalt paving mixtures or making cellular light-weight concrete (CLC) products as a replacement of fine aggregates in certain percentages.
In this study, the experimental investigation of model footing on crusher dust as an alternate granular soil with geotextile and geogrid as reinforcement is discussed. The experimental investigations were made separately with geotextile and geogrid with one to three layers in model tests at different relative densities. The bearing capacity was obtained from the load-settlement curve using the double-tangent method. The experimental results were validated through finite element analysis using commercial software Plaxis 3D. The friction between reinforcement and crusher dust is more than compared to that of natural sand, which may be due to surface roughness of crusher dust. The variations in bearing capacity of footing on geotextile and geogrid at different relative densities are compared in terms of bearing capacity factor N. A parametric study was also presented in terms of variations of bearing capacity ratio of model and real-scale footing.
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