Keropok lekor ( Malay pronunciation: [kəropoʔ lekor] ; Jawi : كروڤوق ليكور ) is a traditional Malay fish cracker snack originating from the state of Terengganu , Malaysia . It is made from fish and sago flour and seasoned with salt and sugar. It is slightly greyish and gives off a fishy taste and smell which becomes more prominent as it cools down after frying. The word lekor is said to be derived from a Terengganu Malay word meaning "to roll".
34-399: It is usually made by grinding fish or vegetables into a paste, mixing it with sago , and then deep-frying it. It comes in three main forms: lekor (long and chewy), rebus (steamed), and keping (thin and crispy). There are two types of keropok lekor which are the keropok lekor goreng and keropok lekor rebus - the former are shaped like sausages with a chewy texture and fried whereas
68-468: A grinder is a machine for producing fine particle size reduction through attrition and compressive forces at the grain size level. See also crusher for mechanisms producing larger particles. In general, grinding processes require a relatively large amount of energy; for this reason, an experimental method to measure the energy used locally during milling with different machines was recently proposed. Autogenous or autogenic mills are so-called due to
102-418: A 28 MW (38,000 HP) motor. A SAG mill with a 44' (13.4m) diameter and a power of 35 MW (47,000 HP) has been designed. Attrition between grinding balls and ore particles causes grinding of finer particles. SAG mills are characterized by their large diameter and short length as compared to ball mills. The inside of the mill is lined with lifting plates to lift the material inside the mill, where it then falls off
136-433: A ball mill, each material having its own specific properties and advantages. Key properties of grinding media are size, density, hardness, and composition. The grinding chamber can also be filled with an inert shield gas that does not react with the material being ground, to prevent oxidation or explosive reactions that could occur with ambient air inside the mill. Ball milling boasts several advantages over other systems:
170-466: A certain similarity to roller crushers and roller presses for the compacting of powders, but purpose, construction and operation mode are different. Extreme pressure causes the particles inside of the compacted material bed to fracture into finer particles and also causes microfracturing at the grain size level. Compared to ball mills HPGRs achieve a 30 to 50% lower specific energy consumption, although they are not as common as ball mills since they are
204-401: A hopper leads to a material bed between the two rollers. The bearing units of one roller can move linearly and are pressed against the material bed by springs or hydraulic cylinders. The pressures in the material bed are greater than 50 MPa (7,000 PSI ). In general they achieve 100 to 300 MPa. By this the material bed is compacted to a solid volume portion of more than 80%. The roller press has
238-408: A large screw mounted vertically to lift and grind material. In tower mills, there is no cascading action as in standard grinding mills. Stirred mills are also common for mixing quicklime (CaO) into a lime slurry. There are several advantages to the tower mill: low noise, efficient energy usage, and low operating costs. A VSI mill throws rock or ore particles against a wear plate by slinging them from
272-460: A newer technology. A similar type of intermediate crusher is the edge runner, which consists of a circular pan with two or more heavy wheels known as mullers rotating within it; material to be crushed is shoved underneath the wheels using attached plow blades. A rotating drum causes friction and attrition between rock pebbles and ore particles. May be used where product contamination by iron from steel balls must be avoided. Quartz or silica
306-406: A spinning center that rotates on a vertical shaft. This type of mill uses the same principle as a VSI crusher . Ball mill A ball mill is a type of grinder filled with grinding balls, used to grind or blend materials for use in mineral dressing processes, paints, pyrotechnics, ceramics, and selective laser sintering . It works on the principle of impact and attrition: size reduction
340-408: A type of grinder , is a cylindrical device used in grinding (or mixing) materials like ores , chemicals, ceramic raw materials and paints. Ball mills rotate around a horizontal axis, partially filled with the material to be ground plus the grinding medium. Different materials are used as media, including ceramic balls, flint pebbles, and stainless steel balls. An internal cascading effect reduces
374-614: Is a device, often a structure , machine or kitchen appliance , that breaks solid materials into smaller pieces by grinding, crushing, or cutting. Such comminution is an important unit operation in many processes . There are many different types of mills and many types of materials processed in them. Historically mills were powered by hand or by animals (e.g., via a hand crank ), working animal (e.g., horse mill ), wind ( windmill ) or water ( watermill ). In modern era, they are usually powered by electricity . The grinding of solid materials occurs through mechanical forces that break up
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#1732854805434408-486: Is arranged eccentrically on a so-called sun wheel. The direction of movement of the sun wheel is opposite to that of the grinding jars (ratio: 1:−2 or 1:−1). The grinding balls in the grinding jars are subjected to superimposed rotational movements, the so-called Coriolis forces. The difference in speeds between the balls and grinding jars produces an interaction between frictional and impact forces, which releases high dynamic energies. The interplay between these forces produces
442-412: Is commonly used because it is inexpensive to obtain. A rotating drum causes friction and attrition between steel rods and ore particles. But the term 'rod mill' is also used as a synonym for a slitting mill , which makes rods of iron or other metal. Rod mills are less common than ball mills for grinding minerals. The rods used in the mill, usually a high-carbon steel, can vary in both the length and
476-405: Is done by impact as the balls drop from near the top of the shell. A ball mill consists of a hollow cylindrical shell rotating about its axis. The axis of the shell may be either horizontal or at a small angle to the horizontal. It is partially filled with balls. The grinding media are the balls, which may be made of steel ( chrome steel ), stainless steel, ceramic, or rubber. The inner surface of
510-414: Is partially filled with balls , usually stone or metal , which grind material to the necessary fineness by friction and impact with the tumbling balls. Ball mills normally operate with an approximate ball charge of 30%. Ball mills are characterized by their smaller (comparatively) diameter and longer length, and often have a length 1.5 to 2.5 times the diameter. The feed is at one end of the cylinder and
544-404: Is reported to have been used for grinding flint for pottery in 1870. In case of continuously operated ball mill, the material to be ground is fed from the left through a 60° cone and the product is discharged through a 30° cone to the right. As the shell rotates, the balls are lifted up on the rising side of the shell and then they cascade down (or drop down on to the feed), from near the top of
578-422: Is widely used in production lines for powders such as cement, silicates, refractory material, fertilizer, glass ceramics, etc., as well as for ore dressing of ferrous and non-ferrous metals. The ball mill can grind ores and other materials, wet or dry. There are two kinds of ball mills according to their ways of discharging material: grate type, and overfall type. Many types of grinding media are suitable for use in
612-569: The Hukki relationship . In stirred mills, the Hukki relationship does not apply and instead, experimentation has to be performed to determine any relationship. To evaluate the grinding results the grain size disposition of the source material (1) and of the ground material (2) is needed. Grinding degree is the ratio of the sizes from the grain disposition. There are several definitions for this characteristic value: [REDACTED] In materials processing
646-610: The cost of installation and grinding medium is low; the capacity and fineness can be adjusted by adjusting the diameter of the ball; it is suitable for both batch and continuous operation; it is suitable for open and closed-circuit grinding; it is applicable for materials of all degrees of hardness. Aside from common ball mills, there is a second type of ball mill called a planetary ball mill . Planetary ball mills are smaller than common ball mills and mainly used in laboratories for grinding sample material down to very small sizes. A planetary ball mill consists of at least one grinding jar which
680-491: The cylindrical shell is usually lined with an abrasion-resistant material such as manganese steel or rubber lining. Less wear takes place in rubber lined mills. The length of the mill is approximately equal to its diameter. The general idea behind the ball mill is an ancient one, but it was not until the Industrial Revolution and the invention of steam power that an effective ball milling machine could be built. It
714-417: The diameter. However, the smaller the rods, the larger is the total surface area and hence, the greater the grinding efficiency. SAG is an acronym for semi-autogenous grinding. SAG mills are autogenous mills that also use grinding balls like a ball mill. A SAG mill is usually a primary or first stage grinder. SAG mills use a ball charge of 8 to 21%. The largest SAG mill is 42' (12.8m) in diameter, powered by
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#1732854805434748-549: The discharge is at the other. Ball mills are commonly used in the manufacture of Portland cement and finer grinding stages of mineral processing. Industrial ball mills can be as large as 8.5 m (28 ft) in diameter with a 22 MW motor, drawing approximately 0.0011% of the total world's power (see List of countries by electricity consumption ). However, small versions of ball mills can be found in laboratories where they are used for grinding sample material for quality assurance. The power predictions for ball mills typically use
782-521: The following form of the Bond equation: where Another type of fine grinder commonly used is the French buhrstone mill, which is similar to old-fashioned flour mills . A high pressure grinding roll, often referred to as HPGRs or roller press, consists out of two rollers with the same dimensions, which are rotating against each other with the same circumferential speed. The special feeding of bulk material through
816-475: The latter is boiled. Keropok lekor should not be confused with keropok keping. The snack is eaten with special homemade chili blends that are particular to Terengganu and sold there; though modern innovations like adding mayonnaise and cheese sauce (the combination known locally as "keropok cheese") may also be available. This Malaysian cuisine -related article is a stub . You can help Misplaced Pages by expanding it . Grinder (milling) A mill
850-440: The manufacture of black powder , but cannot be used in the preparation of some pyrotechnic mixtures such as flash powder because of their sensitivity to impact. High-quality ball mills are potentially expensive and can grind mixture particles to as small as 5 nm , enormously increasing surface area and reaction rates. The grinding works on the principle of critical speed. Critical speed can be understood as that speed after which
884-450: The material to a fine powder. Industrial ball mills can operate continuously, fed at one end and discharged at the other end. Large to medium-sized ball mills are mechanically rotated on their axis, but small ones normally consist of a cylindrical capped container that sits on two drive shafts ( pulleys and belts are used to transmit rotary motion). A rock tumbler functions on the same principle. Ball mills are also used in pyrotechnics and
918-526: The plates onto the rest of the ore charge. SAG mills are primarily used at gold, copper and platinum mines with applications also in the lead, zinc, silver, alumina and nickel industries. Tower mills, often called vertical mills, stirred mills or regrind mills, are a more efficient means of grinding material at smaller particle sizes, and can be used after ball mills in a grinding process. Like ball mills, grinding (steel) balls or pebbles are often added to stirred mills to help grind ore, however these mills contain
952-420: The purposes of structural fill or land reclamation activities. Aggregate milling processes are also used to remove or separate contamination or moisture from aggregate or soil and to produce "dry fills" prior to transport or structural filling. Grinding may serve the following purposes in engineering: In spite of a great number of studies in the field of fracture schemes there is no formula known which connects
986-437: The self-grinding of the ore: a rotating drum throws larger rocks of ore in a cascading motion which causes impact breakage of larger rocks and compressive grinding of finer particles. It is similar in operation to a SAG mill as described below but does not use steel balls in the mill. Also known as ROM or "Run Of Mine" grinding. A typical type of fine grinder is the ball mill . A slightly inclined or horizontal rotating cylinder
1020-764: The shape of particles, provide for mechanical alloying , mixing, producing powders and changing materials properties. An open source ball mill has been designed that can be fabricated with a 3D printer for a few hundred dollars. It is able to be operated both on grid for lab work and off grid with solar photovoltaics and a battery for field work. Blending of explosives is an example of an application for rubber balls. For systems with multiple components, ball milling has been shown to be effective in increasing solid-state chemical reactivity. Additionally, ball milling has been shown effective for production of amorphous materials. It may also be useful to separate gases such as hydrogen and store them in powder form. A ball mill,
1054-405: The shell. In doing so, the solid particles in between the balls and ground are reduced in size by impact. Ball mills are used for grinding materials such as mining ores, coal, pigments, and feldspar for pottery. Grinding can be carried out wet or dry, but the former is performed at low speed. Ball mills are used often in scientific work to reduce the particle size , eliminate agglomeration, change
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1088-408: The steel balls that are responsible for the grinding of particles start rotating along the direction of the cylindrical device, thus causing no further grinding. Ball mills are used extensively in the mechanical alloying process, in which they are used for grinding and for cold welding, producing alloys from powders. The ball mill is a key piece of equipment for grinding crushed materials, and it
1122-459: The structure by overcoming the interior bonding forces. After the grinding the state of the solid is changed: the grain size, the grain size disposition and the grain shape. Milling also refers to the process of breaking down, separating, sizing, or classifying aggregate material (e.g. mining ore ). For instance rock crushing or grinding to produce uniform aggregate size for construction purposes, or separation of rock, soil or aggregate material for
1156-436: The technical grinding work with grinding results. Mining engineers, Peter von Rittinger , Friedrich Kick and Fred Chester Bond independently produced equations to relate the needed grinding work to the grain size produced and a fourth engineer, R.T.Hukki suggested that these three equations might each describe a narrow range of grain sizes and proposed uniting them along a single curve describing what has come to be known as
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