Thinking of investing in a conveyor belt for your assembly line? It’s important to choose a conveyor that best suits the needs of your company. If you want to make an informed purchase, you might want to know the basic types of conveyors and match them with your business applications. The right belt can even help increase profit margin, streamline your assembly line, and contribute to company growth in ways that you might not picture at first. To start you off, here’s a rundown of the 8 basic types of conveyor belts, along with their applications.
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Image Source: New London Engineering
As the name suggests, the surface of this type of conveyor belt is made up of rollers that are selected to match production requirements, such as the weight or required speed of the products that will move along the belt. Shorter conveyor belts that fall under this type can be made up of just two rollers. However, as the distance between the two ends of the belt increases, more will be needed for the belt to function.
A roller bed setup is suitable for when items are loaded onto the belt with gravity. This is because manual loading can cause mechanical shock and damage the rollers. Roller bed conveyor belts are also a good option for transporting items over long distances as they reduce friction, making it easier for products to move along the belt.
APPLICATIONS: You can use these conveyor belts for packing, sorting, assembling, inspecting, and transporting items. Common applications of roller bed conveyor belts include postal sorting offices and airport baggage handling systems.
Image Source: Press Room Automation and Feed Fixtures
The flat belt conveyor belt is one of the most prevalent conveyor systems in use today. Flat belts are useful for internal conveyance, i.e. transporting items within a facility. This type of conveyor belt uses a series of powered pulleys to move a continuous flat belt, which can consist either of natural material or synthetic fabric (ex. polyester, nylon). Items are placed on top of the moving belt and carried from one end to the other.
Since its belts can be made of different kinds of materials, this type of conveyor belt is incredibly versatile. Optional features include center drives and nose bars depending on the requirements of a given application.
APPLICATIONS: Flat belt systems are often the conveyor of choice for industrial environments, wash down areas, and slow assembly lines. Fitted with the right belt, it can also convey small, soft, or irregularly shaped items without damaging them.
Image Source: Press Room Automation and Feed Fixtures
While flat belt conveyors use a single, continuous loop of material, modular conveyor belt systems use a single loop made of countless interlocked pieces, usually made of hard plastic. These segments can be removed and replaced individually, in contrast to having to discard the entire belt. They’re also easier to wash, as well as more resistant to sharp and abrasive materials. This makes modular belt conveyors simpler to maintain and repair than their flat belt counterparts.
Modular belt conveyors are well-suited to applications that involve travelling around corners. In fact, they can travel straight, go around a corner, and incline and decline using a single belt and the same motor all throughout. Technically, other types of conveyors can also accomplish this feat, but only with much customization and additional costs. Plastic modular belts also allow specific conveyor designs without compromising belt tracking. An example of this is a belt with greater width than length, which provides the support required to handle soft plastic bags, cardboard boxes, and shrink wrapped goods.
APPLICATIONS: This type of conveyor belt can be used to carry food products because it is easy to clean. Spacing between plastic segments are adjustable for applications where fluid should be either drained or retained as it is carried on the conveyor. The segments’ plastic composition also makes this conveyor belt useful for metal detection.
Cleated belt conveyors feature vertical cleats or barriers in their designs. These cleats can keep loose materials secure during inclines and declines, to provide consistent spacing between items, and more. Furthermore, cleats come in different shapes, each with its own application.
• Inverted Capital “T.” This type of cleat stands perpendicular to the belt surface, providing support and flexibility to handle delicate items. It is suited for light-duty jobs, such as transporting small parts, packaged items, and food products.
• Forward-Leaning Capital “L.” The wide base of this cleat makes it more resistant to leverage forces. Some cleats with this shape also have curved faces, which enables them to scoop granules. This type of cleat is designed to carry light- to medium-weight bulk material up steeper inclines.
• Inverted “V.” Cleats with this shape are usually 2 inches or less in height to allow for a troughing effect. They’re best for transporting abrasive, heavy, or large-piece bulk materials, as they can withstand heavy impacts.
• Lugs and Pegs. These kinds of cleats accommodate specific needs. For instance, they can promote run-off of liquids when used to transport washed fruit or vegetables. They’re also a cost-efficient cleat type for items that don’t need to be supported throughout the full belt width, such as rods and cartons. They can even be positioned to selectively move products exceeding a given size or to hold individual products in place.
An offshoot of the cleated belt is the elevator belt. Designed with regularly spaced partitions or scoops, it is designed to carry loose materials up a steep incline.
Image Source: Accurate Industrial
This type of belt conveyor uses a curved frame to carry items around corners, make tight transfers, or maximize available floor space. These belts’ curves can go up to 180°. True curved conveyors that do not have any straight runs can only use flat belts, as modular plastic belts require straight runs before and after curves.
APPLICATIONS: Curved belt conveyors are often used in bag handling systems to change items’ conveying direction.
Incline belt conveyors feature a center drive, gear motor, and take-up with a single or double nose. And instead of using a smooth-surfaced belt, this type of conveyor has a rough surface on the belt, ideal for carrying products up or down.
APPLICATIONS: These systems can cross over with cleated belt conveyors to transport products to different elevations while keeping them from falling off the line. Aside from transferring objects between floors, these conveyor belts are also suitable for boosting gravity flow systems.
Image Source: Food Engineering
If you’ve ever observed how donuts are manufactured in their shops, you might have seen this type of conveyor belt in action. Donut shops and other applications in the food and pharmaceutical industries often involve harsh washing and sterilization, in compliance with safety guidelines. Sanitary or washdown conveyors are specially designed to withstand the sanitary procedures for these applications. Conveyors under this type are usually fitted with flat wire belts, which are rugged and easy to clean.
APPLICATIONS: These conveyor belts can carry objects with extreme temperatures straight out of furnaces or freezers. In addition, machines in the food industry, in particular, must survive running through glaze, breading, or hot oil. Because they can securely handle both wet and greasy items, larger washdown conveyors with flat wire belts are also suited for offloading break bulk goods, like oil drums and crates, from ships.
There are several other kinds of conveyors tailored for different applications, although they are not as common as the previous types. Some of these are:
• Fiberglass Conveyor Belts – As the name implies, this type of conveyor belts are made of fiberglass. They are useful for tasks that require extreme temperatures.
• Metal Nub Conveyor Belts – This particular conveyor belt is fitted with metal nubs to better handle complex machines and their parts.
• Narrow-width Conveyor Belts – This type of conveyor belt is the best choice for handling small items.
• Back-lit Conveyor Belts – They come with a light fixture on the belt to aid with quality control.
• Vacuum Conveyor Belts – This particular conveyor belt creates suction to keep light products (sheets of paper, leaflets, etc.) on the line despite inclines and high speeds.
• Magnetic Conveyor Belts – This type of conveyor belt can transport materials that contain iron through equally spaced electromagnets that are placed within the bed of the conveyor.
• Sandwich Belt Conveyors – They use two face-to-face belts to securely carry items at steep inclines or even up a vertical run.
Keep this list in mind, and you can have a rough idea of what conveyor belt you’ll be looking for. However, it’s highly advisable to consult an expert before finalizing any equipment purchases!
Elixir Industrial Equipment, Inc. is one of the top industrial equipment suppliers in the Philippines. For 25 years and counting, we have provided our clients with cutting-edge industrial equipment as well as professional post-sales service. Aside from providing you with professional advice, we can even offer you the manufacturing solutions you’ve been looking for. If you’re strongly considering installing a conveyor belt along your assembly line, feel free to contact us today!
Looking into using conveyor belts to improve your assembly line? Hayama Industrial Corporation is a trusted name when it comes to the Design, Fabrication, Manufacturing, Rehabilitation, Installation, Commissioning of Packaging Equipment, Support peripherals, and auxiliaries including conveyor belts.
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An industrial filter press is a tool used in separation processes, specifically to separate solids and liquids. The machine stacks many filter elements and allows the filter to be easily opened to remove the filtered solids, and allows easy cleaning or replacement of the filter media.
Filter presses cannot be operated in a continuous process but can offer very high performance, particularly when low residual liquid in the solid is desired. Among other uses, filter presses are utilised in marble factories in order to separate water from mud in order to reuse the water during the marble cutting process.
Concept behind filter press technology
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Generally, the slurry that will be separated is injected into the centre of the press and each chamber of the press is filled. Optimal filling time will ensure the last chamber of the press is loaded before the mud in the first chamber begins to cake. As the chambers fill, pressure inside the system will increase due to the formation of thick sludge. Then, the liquid is strained through filter cloths by force using pressurized air, but the use of water could be more cost-efficient in certain cases, such as if water was re-used from a previous process.
History
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The first form of filter press was invented in the United Kingdom in 1853, used in obtaining seed oil through the use of pressure cells. However, there were many disadvantages associated with them, such as high labour requirement and discontinuous process. Major developments in filter press technology started in the middle of 20th century. In Japan in 1958, Kenichiro Kurita and Seiichi Suwa succeeded in developing the world's first automatic horizontal-type filter press to improve the cake removal efficiency and moisture absorption. Nine years later, Kurita Company began developing flexible diaphragms to decrease moisture in filter cakes. The device enables optimisation of the automatic filtration cycle, cake compression, cake discharge and filter-cloth washing leading to the increment in opportunities for various industrial applications. A detailed historical review, dating back to when the Shang Dynasty used presses to extract tea from camellia the leaves and oil from the hips in 1600 BC, was compiled by K. McGrew.[1]
Types of filter presses
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There are four main basic types of filter presses: plate and frame filter presses, recessed plate and frame filter presses, membrane filter presses and (fully) automatic filter presses.
Plate and frame filter press
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A plate and frame filter press is the most fundamental design, and may be referred to as a "membrane plate filter." This type of filter press consists of many alternating plates and frames assembled with the supports of a pair of rails, with filter membranes inserted between each plate-frame pair.[citation needed]
The stack is compressed with sufficient force to provide a liquid-tight seal between each plate and frame, the filter membrane may have an integrated seal around the edge or the filter material itself may act as a gasket when compressed.
As the slurry is pumped through the membranes, the filter cake accumulates and becomes thicker. The filter resistance increases as well, and the process is stopped when the pressure differential reaches a point where the plates are considered full enough.
To remove the filter cake and clear the filters, the stack of plates and frames are separated and the cake either falls off or is scraped from the membranes to be collected in a tray below.[2] The filter membranes are then cleaned using wash liquid and the stack is re-compressed ready to start the next cycle.[3]
M.W. Watermark Plate and Frame Filter PressAn early example of this is the Dehne filter press, developed by A L G Dehne (1832–1906) of Halle, Germany, and commonly used in the late 19th and early 20th century for extracting sugar from sugar beet and from sugar cane, and for drying ore slurries. Its great disadvantage was the amount of labor involved in its operation.[4]
(Fully) Automatic filter press
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An automatic filter press has the same concept as the manual filter and frame filter, except that the whole process is fully automated.[5] It consists of larger plate and frame filter presses with mechanical "plate shifters".[citation needed] The function of the plate shifter is to move the plates and allow rapid discharge of the filter cakes accumulated in between the plates. It also contains a diaphragm compressor in the filter plates which aids in optimizing the operating condition by further drying the filter cakes.[citation needed]
Fully automatic filter presses provide a high degree of automation while providing uninterrupted operation at the same time. The option of the simultaneous filter plate opening system, for example, helps to realise a particularly fast cake release reducing the cycle time to a minimum. The result is a high-speed filter press that allows increased production per unit area of filter. For this reason, these machines are used in applications with highly filterable products where high filtration speeds are required. These include, e.g. mining concentrates and residues. There are different systems for fully automatic operation. These include, e.g. the vibration/shaking devices, spreader clamp/spreader cloth version or scraping devices. The unmanned operating time of a fully automatic filter press is 24/7.[citation needed]
Recessed plate filter press
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A recessed plate filter press does not use frames and instead has a recess in each plate with sloping edges in which the filter cloths lie, the filter cake builds up in the recess directly between two plates and when the plates are separated the sloping edges allow the cake to fall out with minimal effort.[6] To simplify construction and usage the plates typically have a hole through the centre, passing through the filter cloth and around which it is sealed so that the slurry flows through the centre of each plate down the stack rather than inward from the edge of each plate. Although easier to clean, there are disadvantages to this method, such as longer cloth changing time, inability to accommodate filter media that cannot conform to the curved recess such as paper, and the possibility of forming uneven cake.[7]
Membrane filter press
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Membrane filter presses have a great influence on the dryness of the solid by using an inflatable membrane in the filter plates to compress remaining liquid from the filter cake before the plates are opened. Compared to conventional filtration processes, it achieves the lowest residual moisture values in the filter cake. This makes the membrane filter press a powerful and widely used system. Depending on the degree of dewatering, different dry matter contents (dry matter content – percentage by weight of dry material in the filter cake) can be achieved in the filter cake by squeezing with membrane plates. The range of achievable dry matter contents extends from 30 to over 80 percent. Membrane filter presses not only offer the advantage of an extremely high degree of dewatering; they also reduce the filtration cycle time by more than 50 percent on average, depending on the suspension. This results in faster cycle and turnaround times, which lead to an increase in productivity. The membrane inflation medium consists either of compressed air or a liquid medium (e.g. water).
Applications
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Filter presses are used in a huge variety of different applications, from dewatering of mineral mining slurries to blood plasma purification.[3] At the same time, filter press technology is widely established for ultrafine coal dewatering as well as filtrate recovery in coal preparation plants. According to G.Prat, the "filter press is proven to be the most effective and reliable technique to meet today's requirement".[8] One of the examples is Pilot scale plate filter press, which is specialized in dewatering coal slurries. In 2013 the Society for Mining, Metallurgy and Exploration published an article highlighting this specific application.[9] It was mentioned that the use of the filter press is very beneficial to plant operations, since it offers dewatering ultraclean coal as product, as well as improving quality of water removed to be available for equipment cleaning.[10]
Other industrial uses for automatic membrane filter presses include municipal waste sludge dewatering,[11] ready mix concrete water recovery,[12] metal concentrate recovery, and large-scale fly ash pond dewatering.[13]
Many specialized applications are associated with different types of filter press that are currently used in various industries. Plate filter press is extensively used in sugaring operations such as the production of maple syrup in Canada, since it offers very high efficiency and reliability. According to M.Isselhardt, "appearance can affect the value of maple syrup and customer's perception of quality".[14] This makes the raw syrup filtration process extremely crucial in achieving desired product with high quality and appealing form, which again suggested how highly appreciated filter press methods are in industry.
Assessment of important characteristics
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Here are some typical filter press calculation used for handling operation applied in waste water treatment:
Solids loading rate
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S=(B x 8.34 lb/gal x s)⁄A
Where,
S is the solid loadings rate inlb
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h
⁄ft2
.<r /> B is biosolids ingal
⁄h
s is the % solids/ 100.
A is the plate area in ft2.
Net filter yield
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N F Y = S × P T C T {\displaystyle NFY={\frac {S\times P}{TCT}}}
Where:
(S × P) gives the filter run time.[15]
Flow rate of filtrate
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u = 1 A d V d t = Δ P μ × ( R c + R f ) {\displaystyle u={\frac {1}{A}}{\frac {dV}{dt}}={\frac {\Delta P}{\mu \times (R_{c}+R_{f})}}}
Where:
Those are the most important factors that affect the rate of filtration. When filtrate pass through the filter plate, deposition of solids are formed and increases the cake thickness, which also increase Rc while Rf is assumed to be constant.[16] The flow resistance from cake and filter medium can be studied by calculating the flow rate of filtration through them.
If the flow rate is constant, the relationship between pressure and time can be obtained. The filtration must be operated by increasing pressure difference to cope with the increase in flow resistance resulting from pore clogging.[16] The filtration rate is mainly affected by viscosity of the filtrate as well as resistance of the filter plate and cake.
Optimum time cycle
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High filtration rate can be obtained from producing thin cake. However, a conventional filter press is a batch system and the process must be stopped to discharge the filter cake and reassemble the press, which is time-consuming. Practically, maximum filtration rate is obtained when the filtration time is greater than the time taken to discharge the cake and reassemble the press to allow for cloth's resistance.[16] Properties of the filter cake affect the filtration rate, and it is desirable for the particle's size to be as large as possible to prevent pore blockage by using a coagulant. From experimental work, flow rate of liquid through the filter medium is proportional to the pressure difference.[17] As the cake layer forms, pressure applies to the system increases and the flow rate of filtrate decreases.[7] If the solid is desired, the purity of the solid can be increased by cake washing and air drying.[18] Sample of filter cake can be taken from different locations and weighed to determine the moisture content by using overall material balance.[9]
Possible heuristics to be used during design of the process
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The selecting of filter press type depends on the value of liquid phase or the solid phase. If extracting liquid phase is desired, then filter press is among the most appropriate methods to be used.[19]
Materials
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Nowadays, filter plates are made from polymers or steel coated with polymer. They give good drainage surface for filter cloths. The plate sizes are ranged from 10 by 10 cm to 2.4 by 2.4 m and 0.3 to 20 cm for the frame thickness.[18]
Filter medium
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Typical cloth areas can range from 1 m2 or less on laboratory scale to 1000 m2 in a production environment, even though plates can provide filter areas up to 2000 m2. Normally, plate and frame filter press can form up to 50 mm of cake thickness, however, it can be push up to 200 mm for extreme cases. Recessed plate press can form up to 32 mm of cake thickness.[7]
In the early days of press use in the municipal waste biosolids treatment industry, issues with cake sticking to the cloth was problematic and many treatment plants adopted less effective centrifuge or belt filter press technologies. Since then, there have been great enhancements in fabric quality and manufacturing technology that have made this issue obsolete.[20] Unlike the US, automatic membrane filter technology is the most common method to dewater municipal waste biosolids in Asia. Moisture is typically 10-15% lower and less polymer is required—which saves on trucking and overall disposal cost.
Operating condition
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The operating pressure is commonly up to 7 bars for metal.[18] The improvement of the technology makes it possible to remove large amount of moisture at 16 bar of pressure and operate at 30 bars.[3] However, the pressure is 4-5 bars for wood or plastic frames.[18] If the concentration of solids in the feed tank increase until the solid particles are attached to each other. It is possible to install moving blades in the filter press to reduce resistance to flow of liquid through the slurry.[21] For the process prior to cake discharge, air blowing is used for cakes that have permeability of 10−11 to 10−15 m2.[9]
Pre-treatment of the slurries before filtration is required if the solid suspension has settled down. Coagulation as pre-treatment can improve the performance of filter press because it increases the porosity of the filter cake leading to faster filtration. Varying the temperature, concentration and pH can control the size of the flocs. Moreover, if the filter cake is impermeable and difficult for the flow of filtrate, filter aid chemical can be added to the pre-treatment process to increase the porosity of the cake, reduce the cake resistance and obtain thicker cake. However, filter aids need to be able to remove from the filter cake either by physical or chemical treatment. A common filter aid is Kieselguhr, which give 0.85 voidage.[21]
In terms of cake handling, batch filter press requires large discharge tray size in order to contain large amount of cake and the system is more expensive compared to continuous filter press with the same output.[3]
Washing
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There are two possible methods of washing that are being employed, the "simple washing" and the "thorough washing". For simple washing, the wash liquor flows through the same channel as the slurry with high velocity, causing erosion of the cakes near the point of entry. Thus the channels formed are constantly enlarged and therefore uneven cleaning is normally obtained. A better technique is by thorough washing in which the wash liquor is introduced through a different channel behind the filter cloth called washing plates. It flows through the whole thickness of the cakes in opposite direction first and then with the same direction as the filtrate. The wash liquor is normally discharged through the same channel as the filtrate. After washing, the cakes can be easily removed by supplying compressed air to remove the excess liquid.[18]
Waste
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Nowadays filter presses are widely used in many industries, they would also produce different types of wastes. Harmful wastes such as toxic chemical from dye industries, as well as pathogen from waste stream might accumulate in the waste cakes; hence the requirement for treating those wastes would be different. Therefore, before discharge waste stream into the environment, application of post-treatment would be an important disinfection stage. It is to prevent health risks to the local population and the workers that are dealing with the waste (filter cakes) as well as preventing negative impacts to our ecosystem. Since filter press would produce large amount of waste, if it was to be disposed by land reclamation, it is recommended to dispose to the areas that are drastically altered like mining areas where development and fixation of vegetation are not possible. Another method is by incineration, which would destroy the organic pollutants and decrease the mass of the waste. It is usually done in a closed device by using a controlled flame.[2]
Advantages and disadvantages compared to other competitive methods
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Many debates have been discussed about whether or not filter presses are sufficient to compete with modern equipment currently as well as in the future, since filter presses were one of the oldest machine-driven dewatering devices. Efficiency improvements are possible in many applications where modern filter presses have the best characteristics for the job, however, despite the fact that many mechanical improvements have been made, filter presses still remain to operate on the same concept as when first invented. A lack of progress in efficiency improvements as well as a lack of research on conquering associated issues surrounding filter presses have suggested a possibility of performance inadequacy. At the same time, many other types of filter could do the same or better job as press filters. In certain cases, it is crucial to compare characteristics and performances.[22]
Batch filter press versus a continuous vacuum belt filter
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Filter presses offer a wide range of application, one of its main propositions is the ability to provide a large filter area in a relatively small footprint. Surface area available is one of the most important dimensions in any filtering process, since it maximises filter flow rate and capacity. A standard size filter press offers a filter area of 216 m2, whereas a standard belt filter only offers approximately 15 m2.[22]
High-solids slurries: continuous pressure operation
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Filter presses are commonly used to dewater high-solids slurries in metal processing plants, one of the press filter technology that could deliver the job is the Rotary Pressure Filter method, which provides continuous production in a single unit, where filtration is directed via pressure. However, in cases where solids concentration in high-solids slurries is too high (50%+), it is better to handle these slurries using vacuum filtration, such as a continuous Indexing Vacuum Belt Filter, since high concentration of solids in slurries will increase pressure and if pressure is too high, the equipment might be damaged and/or less efficient operation.[22]
Current development
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In the future, market demands for modern filtration industry are going to become finer and higher degree in separation, and particularly on the purpose of material recycling, energy saving, and green technology. In order to meet increasing demands for higher degree of dewatering from difficult-to-filter material, super-high pressure filters are required. Therefore, the trend in increasing the pressure for the automatic filter press will keep on developing in the future.
The conventional filter press mechanisms usually use mechanical compression and air to de-liquoring; however, the efficiency of producing low-moisture cake is limited. An alternative method has been introduced by using steam instead of air for cake dewatering. Steam dewatering technique can be a competitive method since it offers product of low-moisture cake.[23]
References
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