CENTRIFUGAL
OVERVIEW
Figure 1 1 Diagram of the centrifugal system with intermittent line A
1 Assistive devices; 2 Distribution trough; 3 Intermittent centrifuge; 4. Container for raw honey A; 5 Container containing diluted bile A; 6 Sand sugar
Figure 1 2 Diagram of the continuous centrifugation system for road B
1 Horizontal assistant; 2 Distribution trough; 3 Continuous centrifuge equipment; 4 Container for bile B.
Figure 1 3 Diagram of continuous centrifugation system for line C
1 Horizontal assist device; 2 Distribution trough; 3 Continuous centrifuge equipment; 4 C2 bile container; 5 Return sugar barrel; 6 Container for molasses.
Sugar centrifugation involves the high-speed rotation of vats to separate sugar crystals from molasses using centrifugal force This process yields sugar A, brown molasses (raw honey A), and white bile (diluted honey A) The centrifugal force effectively dissociates the solid-liquid phases, allowing for the distinct separation of components.
Young sugar is a mixture of sugar crystals and molasses, characterized by a high solid phase ratio and viscosity To effectively separate the sugar crystals from the molasses, centrifugal filtration is employed, utilizing centrifugal force as the primary method Alternative separation techniques like centrifugation and gravity sedimentation are also applicable, but centrifugal filtration proves most efficient for this specific mixture.
When an object rotates around an axis, it experiences a centripetal force directed toward the center of rotation According to Newton's third law, there is an equal and opposite reaction, known as centrifugal force, which acts outward from the center Thus, centrifugal force is the reaction to the centripetal force experienced by a rotating object.
Centrifugal force plays a crucial role in separating granulated sugar from molasses in a centrifuge As the centrifuge rotates, it generates force that causes the liquid molasses to splash out through the machine's side mesh, while the solid sugar remains behind This process effectively separates the bile from the young sugar, ensuring a clean extraction.
To enhance centrifugal force, one can either increase the turntable's diameter or the number of revolutions, allowing for a quicker rise in rotation speed compared to diameter However, it is crucial to assess the material quality to ensure that the speed increase remains within the permissible limits.
The comparison of various centrifuges involves calculating the ratio of gravitational force to the centrifugal force acting on the centrifuge mass This relationship is defined by the dissociation value, which represents the ratio of centrifugal force to weight, as well as the ratio of centrifugal acceleration to gravity The dissociation value serves as a key characteristic of the centrifuge, expressed mathematically as f = F/G.
When designing a centrifuge, maximizing the centrifugation value is essential To achieve higher speeds, it is crucial to appropriately reduce the size of the wheel while maintaining the stability of the turntable.
As the centrifuge spins, the sugar introduced into the rotating plate experiences centrifugal force, causing it to press against the plate's wall This pressure allows honey to flow through the sugar crystal layer and exit via the floor hole in the plate wall The centrifugal force effectively compresses the sugar layer against the mesh wall, facilitating the separation process.
TREATING YOUNG SUGAR BEFORE CENTRIFUGATION
1.2.1 The dilution of young sugar
The high concentration of molasses, combined with the high stickiness of the molasses, makes the transport and distribution of young molasses more difficult.
To effectively dilute young sugar, add hot water to the outlet of the aid tank for uniform distribution The recommended dilution ratio is approximately 2% of the young sugar's total volume.
When diluting young sugar, some crystals will inevitably dissolve To further reduce the viscosity of raw sugar and minimize the re-dissolving of undissolved sugar, heating can be used as a combined or alternative method.
According to studies, the viscosity of molasses decreases by 50% or the ability to break down bile increases by 50% when the temperature is increased by 5.
Heating can be done in the vat or by means of a coiled tube in a gully or rapid heating devices.
1.2.3 Devices containing young sugar before centrifugation
The young sugar after semen is discharged into the distribution trough to stir well and distribute to the centrifuges.
The young sugar dispenser resembles a small aid box positioned above the centrifuges and should have a capacity to handle the volume of young sugar required for processing within 15 to 30 minutes It features a U-shaped or closed cylindrical trough equipped with a screw-type stirrer operating at speeds between 1 to 8 rpm To prevent the settling of sugar crystals, a rake-style stirrer is installed at the bottom, functioning at 3 rpm Additionally, the trough is inclined towards the centrifuge and includes a dedicated drain hole for each unit.
Figure 1 4 Screw-type road distribution trough
In actual production, another type of trough is also U-barrel type but has a square hollow shaft with paddle-type stirrer suitable for feeding the granules to each centrifuge.
For road C, the distribution trough typically features a two-shell design or incorporates a heating element that uses hot water to elevate the temperature of the young road, thereby reducing its viscosity Alternatively, it may consist of a closed cylindrical horizontal distribution trough equipped with a propeller-type stirrer, which does not have a heating system In such cases, a separate device is often utilized to heat the material before it enters the centrifuge.
1 Raw road distribution trough; 2 Electric heating; 3 Continuous centrifugation; 4 Line load screw.
Heating the slope with a resistor has many advantages:
- The length of the road is short.
-> Thus, reducing the risk of crystals being re-dissolved and fully adapted to continuous centrifuges.
The optimal heating limit in the aid box or in the distribution trough is about
50 - 55, but with the small line resistance heating device, it saves very little time at high temperature, so it can be easily raised to 57.
The young sugar heater consists of two concentric tubes, with the sapling traveling through the space between them These tubes act as electrodes, generating a potential difference that facilitates the heating process As the molasses moves through the centrifuge, it is rapidly heated by a gravity-driven device, ensuring a steady and continuous flow without any downtime between heating and centrifugation.
FACIAL SEPARATION CENTRIFUGE
The molasses separation process is crucial for achieving high-quality products by effectively separating crystalline substances from molasses This process must ensure mass production while maintaining clear separation of bile and bile dilute, optimizing water usage, and adhering to production conditioning standards.
To perform a rotation test, manually rotate the wheel multiple times to ensure there are no issues Once confirmed, lower the shot, open the molasses branch, and press the power button to initiate a slow rotation of the centrifuge Monitor the speed as it increases.
To ensure even distribution of sugar in the barrel, it is essential to lift the massecnite outlet Key factors influencing the feed time include the concentration of massecnite and the centrifuge speed.
Due to its high concentration and viscosity, non-C has a slower charging speed compared to non-A, operating at a machine speed of 150-200 rpm If loaded at higher speeds, it becomes challenging for the massecnite to adhere evenly to the machine's grid wall.
+ For non A: Because of the lower viscosity, it is usually loaded at a speed of about 250-300 rpm to avoid unevenly distributed massecnite.
In addition, the charge speed is controlled to suit the characteristics of the centrifuge being used.
Charge: massecnite materials are filled with rotating barrels, to improve equipment productivity but should not be too full, avoiding the phenomenon of massecnite thrown out to increase process losses.
For massecnite have a large, equal and low viscosity We can increase the amount of charge.
For small-sized massecuite with uneven consistency, false chimneys, and high viscosity, the charge is minimized Non-B and non-C types maintain a molasses layer that is thinner than that of young A sugar, facilitating easier separation.
After charging, the massecnite layer in the entrance chum will be scratched into the rotating wheel of the device.
After loading, the speed gradually increases to its maximum, causing centrifugal forces to separate most of the massecuite, which then flows into the molasses branch This molasses is commonly referred to as brown sugar.
The duration of the separation molasses depends on:
+ The thickness of the massecnite layer: the larger molasses separation time.
+ Viscosity: The large molasses viscosity makes the time of separation of molasses even more.
+ Grain size and quality: if the grain is large and equal in size, the molasses separation time decreases.
+ Rotary barrel size: large size and large grid area, molasses separation time decreases.
To effectively eliminate sticky molasses from the surface of sugar crystals, it is essential to wash them with water Even after the initial separation of molasses, a thin brown membrane may still adhere to the crystals Therefore, a thorough washing is necessary to completely remove this remaining layer of molasses.
- The process of washing the sugar (this is the process of using water to remove molasses and at the same time is the process of diffusion of sugar).
Water initially dissolves some sugar outside the crystal, creating a sugar solution As centrifugal force acts, this sugar water passes through the crystal membrane, a process that occurs simultaneously with diffusion Ultimately, the sugar water exits through the sieve holes, resulting in the formation of sugar.
In locally concentrated and very densely, only the amount of water cannot be dissolved enough, so it is required to wash further with steam.
For low-grade sugars, sugar B may only need to wash the water, while sugar C should not washed, as they will be reprocessed during production.
The molasses after washing the sugar is called white molasses, washed molasses or diluted molasses.
+ Often use hot water with a temperature of > 60 o C or overcizzly hot water >
The washing water utilized in the sugar production process constitutes approximately 2-3% of the total massecuite amount, with the specific quantity varying based on crystal grain size Larger crystals require less water, as excessive water usage can lead to deformed crystal angles, diminishing the sugar's sparkle and increasing the amount of molasses that needs to be recooked.
+ Water quality: no turbidity, no impurities or odors, often use condensation water to wash.
+ After washing the water, use saturated vapor with pressure of 3-4 at to continue washing.
+ The amount of steam used is about 2-3% of the amount of massecnite. The purpose of the steam-ejector process:
+ Steam easily passes through small gap between crystals, raising temperature, reducing viscosity to help the centrifuge process occur better.
+ When the heat is lost, it condenses into water and washes the sugar crystal again.
+ High temperature steam will make the crystal drier In addition to the preliminary drying effect, which makes the sugar grain shinier, it also reduces lump of sugar.
To maintain the quality of finished non-A sugar, it is essential to utilize wash water and wash steam effectively In contrast, for non-B and non-C sugars, any washing should be minimal and only performed when necessary.
Separated molasses and diluted molasses:
Washing sugar removes the molasses that adheres to the surface of the sugar crystals, but it also leads to the dissolution of some sugar crystals This process results in a higher concentration of molasses purity than the original sugar purity.
It is crucial to properly separate molasses and to timely open the diluted branch of molasses to prevent mixing, which can negatively impact its purity and complicate purity control during the cooking process.
1.3.5 Stop and discharge the road
+ After washing by steam, close the steam valve, brake the machine and discharge the sugar.
+ The entire duration of the completion of the centrifugal process called the centrifugal cycle
FACTORS AFFECTING THE CENTRIFUGAL PROCESS
Centrifuge is the fundamental factor that determines the effectiveness of molasses separation, in addition to a number of other factors that affect the process.
The quality of massecnite is an important factor that greatly affects the rate of separation of molasses.
The speed of separation molassesis affected by the size of sugar crystal grain, the viscosity of massecnite or the stickiness of the molasses.
The crystal grain of the massecnite are moderately sized and arranged regularly, a gap between crystals grain very large and easily separate molasses.
If the particle size is uneven, especially there are many mischievous, when it comes to the process of molasses feces it is easy to choke the net.
If a beam occurs, it is extremely difficult to separate the bile between the crystals.
Molasses exhibits high viscosity, making the centrifugation process challenging To address this issue, it is essential to effectively reheat the massecnite, particularly for massecnite C.
To optimize washing time and enhance the flow rate of molasses, it is essential to manage viscosity effectively by increasing hot water usage and introducing steam into the rotating barrel Additionally, employing hot air in a closed barrel can prevent sugar from cooling, further accelerating the flow of molasses.
The worker possesses comprehensive knowledge of molasses separation operations, including the quality indicators of massecuite and the ability to assess the degree of separation and humidity of refined sugar By optimizing centrifuge performance, the centrifugal process significantly enhances sugar quality while minimizing losses and reducing energy, electricity, and water costs.
CLASSIFICATION OF CENTRIFUGAL PROCESS
The centrifugal process is once sequenced according to the stages of bile sorting cycle Start, recharge, declassify, wash the road, stop the machine and discharge the sugar.
Centrifuge twice In the first centrifugation without steam washing, also known as pre-centrifugation The bile removed is bile.
After the molasses is separated, the sugar is transferred to a tank located beneath the preliminary centrifuges In this tank, young sugar is produced by mixing it with a higher purity density than its female bile, or by combining it with tea bile or hot water to achieve the proper concentration for the centrifuge process This mixture is then transported to the second centrifuge, known as the complete centrifuge, where it can be washed with water or steam, resulting in diluted bile.
The dual centrifuge method effectively produces high-quality sugar while ensuring optimal separation of bile; however, it necessitates the use of two centrifuges This bile-defecation process, commonly referred to as re-sieve, is typically employed for young C sugar.
1.5.3 C line double bile (C line re-sieve)
+ Increases the ability to recover roads and ensures the safety of erratic treatment of the end line for reuse
+ Remove a large amount of starch in sugar i.e increase the quality of sugar
The C path through the preliminary centrifuge leads to the discharge of C sand into the lake barrel, where it is recycled into magma The road substance, bile B, is diluted to 70°Bx and heated to 70°C before being pumped onto the distribution trough of the finished centrifuge The redistributed C sugar then falls into the sugar lake barrel, mixing with magma C Additionally, the rich C bile from the finishing centrifuges is utilized for cooking C, rather than cooking B.
LOW SUGAR TREATMENT AFTER CENTRIFUGATION
The sugar lake concept involves utilizing raw materials like bile or hot water combined with sand sugar, which is derived from the centrifugation process This mixture, known as young sugar or magma, is processed to achieve the desired concentration It is then sifted to produce higher quality sand sugar or to create various types of premium cooking sugars.
In factories producing white sand sugar, the process involves diluting B sugar from the centrifuge into a magma-like state, similar to young sugar cooking The B sugar is transported via a screw to a sugar slurry device, where it is mixed with an appropriate amount of tea molasses or clean water, achieving a dilution concentration of 86-91% Maintaining the correct concentration is crucial; if it's too high, pumping becomes difficult, while a concentration that is too low can lead to significant sugar dissolution, negatively impacting production efficiency.
Cane sugar recovery involves utilizing hot water and, if needed, saturated steam to fully dissolve sand sugar into a concentrated sugar solution This process transforms the sugar into a higher-grade raw material suitable for producing young sugar.
Cane sugar recovery is essential for optimizing the use of equipment, steam, electricity, and water in white sand sugar factories The C sand line undergoes a resuscitation process, converting it into syrup with a concentration equal to or greater than tea density This syrup is then filtered to eliminate impurities and treated with SO2 to further reduce color, alongside molasses cooked with young sugar A.
Technology requirements:must completely dissolve the sand sugar into syrup with the appropriate concentration or it will interfere in the cooking of young A sugar.
Load screws are essential for transporting low-level road materials, particularly round particles with high stickiness They are commonly utilized in the movement of sand B and sand road C, facilitating efficient transfer to road lakes and road regression equipment.
Figure 1 6 Cane sugar screw conveyor
A screw conveyor features a U-shaped trough with a spiral shaft resembling a chicken intestine, supported at both ends Due to the length of the trough, it includes a mid-support pillow for stability This type of conveyor is commonly used for transporting abrasive road particles, making it ideal for moving materials from low-level roads to road lake equipment or for road regression applications.
EQUIPMENT
1.7.1 Flat bottom Weston discontinuous centrifuge
- This type of centrifuge is commonly used for sand road A and sand road B at a speed of 960 rpm or a highway centrifuge for road C at a speed of 1,450 - 1,850 rpm.
Figure 1 7 Flat bottom Weston discontinuous centrifuge
1 Mesh basket, 2 Rotary, 3 Support pillow, 4 Cone, 5 Ledge, 6 Rotary barrel, 7 Engine, 8 Coupling, 9 Engine stop brake
The machine features a 6th rotating crankshaft connected to the 2nd axis, along with a barrel that is supported by a 3-axis pillow, allowing it to hang freely The base is equipped with a 4th cone at the 5th ledge, which is manually raised during discharge The barrel rotates within a fixed shell, enabling bile separation through a grid as the centrifuge directs it into a container Typically, the centrifuge incorporates two copper mesh panels, with the outer plate having holes measuring 5 × 5 mm and the inner plate having 0.5 × 5 mm holes A rubber-cushioned lock on the shaft bearing permits slight vertical movement, preventing issues like vibration and bending when uneven raw materials are introduced The centrifuge operates through a 7-engine system connected by coupling 8, with a brake 9 for stopping, and includes a steam and water drainage system for cleaning.
The centrifuge operates on a continuous inertial principle, typically installed on the ground The feed enters through a fixed tube into the bottom of the rotating barrel, where centrifugal force propels the material against the barrel wall, causing it to move upwards Bile is expelled through an opening in the barrel wall, while the clarified liquid is discharged from above the rotating barrel.
DRYING SUGAR
OVERVIEW
1 Centrifugal zone; 2 Sugar dryer; 3 Sieve; 4 Packing area; 5 Silo;
6 Special sugar production zone; 7 Transport vehicle; 8 Warehouse.
2.1.1 Purpose of sugar drying process
After centrifugation, washing with hot water results in an initial moisture content of 1-2% at approximately 60°C, while steam washing yields a humidity level of 0.7-1.0% at around 80°C At these moisture levels and temperatures, proper bagging and storage are not feasible.
To prevent sugar from clumping and changing texture while achieving a shiny finish, it is essential to dry the sugar properly This process involves reducing the temperature to match the ambient conditions and lowering humidity to just 0.05% Ensuring these conditions is crucial for maintaining product quality and meeting safety standards during storage and distribution in the market.
Figure 2 1 Diagram of drying system and finished product
Thus, the purpose of sugar drying is to bring sugar to the appropriate humidity, increase the storage time, make the finished sugar shiny, not damaged or deformed during storage.
2.1.2 The principle of sugar drying
Use the heat released from the sugar itself after centrifugation, or use hot air to evaporate the water on the road surface.
The main factors affecting the drying rate of sugar:
The grain size of granulated sugar and the thickness of its layer significantly impact drying time An increased surface area for water evaporation accelerates the drying process However, if the sugar crystals are too small and the layer is excessively thick, moisture diffusion becomes challenging, resulting in a slower drying speed.
The amount of water contained in the sugar is dried: if the granulated sugar after centrifugation has high moisture, the drying time will be prolonged.
High air temperature combined with low relative humidity leads to strong hygroscopicity and rapid drying However, excessively high temperatures can negatively impact the quality of sugar during the drying process.
Drying equipment: different equipment structure, drying speed is also different.
2.1.3 Methods of drying crystalline sugar
After centrifugation, granulated sugar typically exits at temperatures exceeding 80°C To achieve optimal drying, we cool the sugar naturally, utilizing its residual heat However, this method is time-consuming and presents challenges in controlling the final product Additionally, fluctuations in moisture content post-centrifugation can significantly impact drying efficiency.
To effectively reduce moisture in sugar, first dry the air to lower its relative humidity before placing the sugar in the dryer This method ensures that the granules come into contact with the dry air, allowing them to absorb moisture efficiently As a result, the drying time is minimized, and the final moisture content of the sugar can be precisely controlled.
SOME EQUIPMENT IN THE SUGAR DRYING PROCESS
2.2.1 Equipment for conveying granulated sugar from centrifuge to sugar dryer
2.2.1.1 Vibrating conveyors transporting sugar (Vibrating floor)
1 Sieve surface; 2 Connecting rod; 3 Eccentric swing arm; 4 Eccentric wheel;
5 Sugar after centrifugation; 6 Vibrating chute.
Vibrating sieves are strategically positioned beneath centrifuges to facilitate the efficient transport of sugar released during the centrifugation process These vibrating screens play a crucial role in conveying the sugar to the bottom of the bucket while allowing it to cool and dry slightly during transit Importantly, the design ensures that the sugar remains intact and does not get crushed, making this method particularly effective for transporting materials like sand.
The vibrating sieve consists of a deep, flat-bottomed steel trough equipped with several tweezers featuring dynamic joints It operates through a motor with an eccentric arm, generating vibrations that cause the chute to move back and forth.
In the sugar manufacturing industry, using a lifting bucket is a type of equipment used to transport bulk materials (sand lines) from low to high in the vertical direction.
1 Bucket load; 2 Chain load; 3 Bucket load body; 4 Sprocket.
The system features two buckets equipped with sprockets, which are mounted on a chain at equal intervals A motor drives the lifting bucket via a reducer, allowing it to transport sand from the bottom as it ascends Upon reaching the top of the tower, the bucket reverses direction, releasing the sand to fall freely and effectively drying the road naturally.
This bucket design occupies minimal space; however, it can easily break granulated sugar, leading to dust formation and challenges in handling and classification When utilizing a conveyor dryer for natural drying, it is advisable to forgo the lifting bucket and instead employ a vibrating sieve to direct the material flow to the dryer efficiently.
At present, rotary drum dryer is being widely used in the sugar drying industry.
1 Air intake door; 2 Caloriphe; 3 Loading door; 4 Gears; 5 Rotary barrel; 6. Belt; 7 Exhaust gas pipes; 8 Conveyor belt; 9 Door outlet after drying; 10.
The machine consists of a cylindrical barrel that is placed horizontally and tilted slightly from the ground from 3 to 6° Box 5 rests on belt 6 thanks to the
The 11 support roller system facilitates the movement of the dryer via a transmission system, with gear 4 rotating at 3 to 8 rpm Sugar enters the revolving drum through inlet 3, where it undergoes drying and cooling before being discharged through door 9 and conveyed to the bagging unit via conveyor 8 Air is heated by the caloriphe 2 unit, which moves in the same direction as the sugar, and exits the dryer through the recovery cyclone Automatic controls manage the air temperature both entering and exiting the dryer.
The machine operates by introducing wet material into the top of a rotating barrel, where it is stirred by inner blades This stirring action ensures that the material is thoroughly exposed to hot air, facilitating moisture removal As the machine rotates, the material is gradually moved from the top to the end of the barrel, achieving the desired level of dryness before being discharged through the unloader.
The structure of this type of dryer is similar to a vibrating type dryer.
1 Distribution segment; 2 The boiling segment; 3 The selection screening section; 4 Air chamber;
5 Current guide plate; 6 Micro-perforated sheet; 7 Adjustable brake plate; 8.
9 Air; 10 Road; 11 Powdered sugar; 12 Finished sugar;13 Lump sugar.
Figure 2 6 Schematic diagram of fluidized bed dryer
1 Wet road; 2 Hot air; 3 Cold air; 4 Air out; 5 Dry sugar.
Fluidized bed drying is an efficient method characterized by rapid drying speeds and high production capacity In this process, cane sugar is placed on perforated plates, where hot air is blown through the holes from below, directly contacting the granulated sugar's surface When the airflow reaches a specific velocity, it creates a smooth sugar layer that mixes uniformly with the air, causing it to rise to the conveyor belt, resembling boiling water At this stage, the sugar layer detaches from the conveyor belt, supported by a cushion of air underneath.
The continuous vibration of the drying machine allows the sugar layer to float within the airflow, minimizing friction against the fine mesh This process helps prevent damage to the crystal angles, ultimately enhancing the brightness and quality of the sugar crystals.
Typical boiling floor dryer: total length 13m, width 1m, inside the division in
3 segments: distribution segment, boiling segment and selection segment.
The road is transitioned to the distribution segment, ensuring an even distribution of road movement At the conclusion of this section, a wiper is installed to regulate the thickness of the sugar layer prior to entering the boiling stage.
The boiling segment consists of an air chamber, a precision perforated plate, and a top cover It features two curved air current plates in the lower layer, ensuring even air distribution to optimize the drying rate Hot air enters the lower air chamber, flows through the tiny holes of the plate, and moves into the boiling section before being expelled through the top cover.
The sand line from the boiling section comes out through the selection section and divides into 3 types of sugar of different sizes.
High drying effect, usually drying at the boiling point for only 12 seconds. The total drying and sieve time is 70-80 seconds.
+ Average yield per hour of 7.61 tons of sand sugar is equivalent to the yield of 1,500 tons of sugarcane per day.
+ Materials for making extremely small perforated panels
SUGAR PRESERVATION
Possible phenomena when storing sugar
- This phenomenon most often occurs and is most important during storage.The air entering the warehouse will condense to the surface of the sugar crystal,making the sugar moist.
The primary cause of sugar clumping is the premature packaging of sugar before it has cooled and dried completely When the external temperature suddenly drops, the moisture surrounding the sugar crystals can become oversaturated, leading to the formation of new crystals that gradually bond together, resulting in clumps of sugar Other factors may also contribute to this phenomenon.
- Some microorganisms and molds turn sugar into butiric acid and lactic, xitric, acetic acid
- After the sugar is moist, there are many yeasts that make the sugar metabolize
Microorganisms present in sugar cane can survive the production process and reactivate under low temperatures or suitable conditions To mitigate this issue, it's crucial to focus on thoroughly cleaning sugar cane bran and minimizing the duration of cleaning and drying sugar crystals.
- It is also caused by sugar moisture Because when moistened sugar is susceptible to microorganisms and can cause the metabolism of sugar.