Starch and starch processing

In ancient times, starch was extracted from wheat and used as an additive in medicines and as glue.

This base sediment was then dried in the sun. Our ancestors later proceeded in a similar way to obtain potato starch from grated potatoes. In Europe, the starch industry developed as an ancillary trade to agriculture. The simplest devices were used, and they were only developed into special processing machines in the course of industrialisation. This improved purity, yield and cost structure.

History of starch

ca. 3500 BC

Starch is used as a glue and smoother for papyrus leaves

ca. 200 BC

Written record of a process description for obtaining starch from grain from Greece and Egypt

700 - 1300

Starch is used for colour lightening and smoothing in paper manufacturing.

1400

Starch serves as an ironing aid for stiffening garments.

1600

Starch is a base ingredient for cosmetic powder, makeup and hair dyes

1700

Starch is extracted from maize and potatoes in the USA

1770

Starch glue is used for yarn dressing

1811

Chemical modification / starch saccharification by acid catalysis

1890

In Germany, there are about 250 companies that manufacture starch

Today

In Germany, about 2600 people work in 14 factories in the starch industry. Starch production in Europe about 12 million tonnes.


Raw materials for obtaining starch in Europe are potatoes, wheat and maize, while outside Europe the starch is also extracted from field crops such as manioc and rice. Today, the commercial product starch (C6H10O5)n may contain a maximum of 3% foreign substances. In the international starch market, it has been established that the raw protein content of cereal starch may not exceed 0.58% in the dry matter, and 0.13% in potato starch.



 

average starch content in percent by weight

Amylomaize content in the starch

Wheat

60-70

20-26

Maize

62-70

0-85

Wrinkled peas

30-40

50-80

Rice

70

0-25

Barley

60-70

60-70

Potato

10-20

20-28

Gene-manipulated potato

10-20

0

Crop plants with their approximate content of starch and amylomaize

Low-protein wheat starch is extracted for dietary nutrients (e.g. coeliac disease). The Codex alimentarius (FAO/WHO Food Standards) defines starch as gluten-free if the protein content (gluten) is less than 20 mg/kg. Modern analysis methods can detect residual protein contents of less than 5 mg/kg.

Starch consists exclusively of glucose and is the actual energy source of the vast majority of plants. It is produced by photosynthesis with glucose as

n C6H12O6 – (n-1) H2O   –>    (C6H10O5)n

 Glucose                                    Starch

an intermediate stage and deposited in the plant tubers and seeds of the plants in the form of starch grains. Thousands of glucose molecules link with one another in in a helix and form a starch molecule, which in turn becomes embedded in the starch grain.

Enzymes determine the configuration and structure of the starch grains. They can form a long strand through glycosidic linkage of the glucose molecules. This structure is called amylomaize. If side chains are attached to the strand, it is called amylopectin.


The molecular similarity between the starch and cellulose molecules is interesting. Starch is the energy depot of the plants, whereas cellulose forms their cell framework – with impressively high strength and elasticity, when one thinks of wood or 4 metre- hemp stems.

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Depending on whether the anomeric OH group of the sugar A is in the α (= bottom) or β position (= top), an α-glycosidic or a β-glycosidic bond forms.

The numbers 1,4 and 1,6 indicate the respective C-atoms in the glucose molecule.

Starch is formed from the α-bond.

Every glucose molecule has different branches. These OH groups of neighbouring molecules link. Water is formed. This is how the bond between two glucose molecules is formed. Starch granulates consist of thousands of glycosidically linked glucose molecules

Cellulose is formed from the β-bond.

When opposite OH groups bond with each other, a chain of glucose monomers is formed. We find this type of the molecule in cellulose, the stabiliser of all plants.

Similarity of the molecular structure of cellulose and starch

The starch grains differ in size depending on the type of starch. The diameter of the starch particles in potatoes can be more than 100 µm, those in wheat 2 to 35 µm, those in maize 5 to 25 µm and those in amaranth only 0.5 to 3 µm. The starch grains in wheat starch are distributed bimodally (frequency distribution with two maxima). This can be used on the one hand to produce a high-purity A-wheat starch (20 – 35 µm) and on the other to produce a small-grained B-wheat starch (2 – 10 µm) with higher impurity.

 Starch normally has an amylomaize content of 14 % to 27 % and an amylopectin content of 73 % to 86 %. However, special plant breeding also produces starch types that contain up to 99 % amylopectin or up to 85 % amylomaize.

 

Amylomaize

Amylopectin

Iodine binding capacity

20%

0 bis 1%

Colour of the iodine complex

deep blue

red-violet

Solution stability

instable

stable

Thickening performance

low

high

Retrogradation; reversal of previously agglutinated starch

irreversible

reversible

Gel formation/ cross-linking

strong and fast

little and slow

Distinguishing features of the two starch components: amylomaize and amylopectin

Starch is insoluble in cold water, but the starch corns can reversibly swell slightly, increasing their volume by up to 28 %. The swelling retrogrades if water is withdrawn from the starch.

Native starch can bind water or moist goods well, but not permanently for the most part and particularly not at varying temperatures. Starch is therefore modified to accelerate, control and stabilise its gelatinisation, to stiffen fluids and stabilise their consistency irrespective of the influences of heat/cold or stirring movements.

Modified starches can exhibit hydrophilic as well as hydrophobic properties. Starch is thus adapted to the needs of the producer. In the food sector, these are in particular convenience products https://www.amixon.com/de/blog/amixon-mischer-fuer-instant-food and the dough conditioner industry with the process steps cooking, baking, roasting, shock frosting, thawing and influencing of the Maillard reactions.

© by amixon GmbH

© by amixon GmbH

Batch mixing versus continuous mixing. What are the advantages and disadvantages of the processes?

Basically, a batch mixing operation allows more flexibility than a continuous mixing plant. This is one of the reasons why batch blending plants are far more common than continuous blending plants.

In the batch mixer - on the left - the operation is carried out in batches. Only when the individual components have been poured in does the mixing tool start to rotate. The mixer changes the position of all particles in relation to each other by three-dimensional flowing of the goods. The state changes from "unmixed" to "technically ideally mixed". Then the discharge takes place.

In continuous mixing - on the right - the components involved are continuously fed to the mixer in the correct mass proportion. The material flows are homogenized in the mixer and the mixed material is continuously discharged.

The actual mixing task is somewhat easier here, because the so-called continuous boiler flow has already created a homogeneous mix base. The material flows carried in are comparatively small in relation to the already homogenized vessel contents. The average residence time can be 0.5 to 3 minutes.

Isn't the dosing technology the key technology in terms of in terms of mixing quality and reproducibility in continuous mixing?

Yes, it is undoubtedly the decisive process that cannot be compensated. Continuous mixing plants have been established since accurate powder feeders exist, which have high "short-time accuracies". When selecting dosing systems, gravimetric dosing systems should be given priority.

Depending on the product and the industry, each blending operation has its individual characteristics. What criteria should one consider when choosing between continuous mixing and batch mixing?

A continuous mixing process is advantageous

  • if a short defined residence time is required; e.g. defined deagglomeration, spontaneous build-up granulation during liquid addition, or if spontaneous chemical reactions take place, which may be exothermic.
  • when the formulation consists of only a few components
  • when the formulations are are standardized and the qualities of the components are assured
  • if large quantities of the same or a similar product are produced, possibly even in three layers (bulk goods such as basic nutrients in grain mills, basic chemical active ingredients, washing powders, plastics, building materials)
  • if the mixed goods are to be packaged directly without intermediate storage

A batch blending operation is then advantageous

  • if complex preparation processes are involved, e.g. multistep mixing processes, or mixing processes with overpressure or vacuum application takes place
  • if laboratory analysis must take place before filling
  • if quality assurance insists on batch control and if cleaning must be carried out after each preparation
  • if many components are involved. This is the case for baby food, dietetic nutrients, baking agents, spice preparations, stabilizers, instant food, seasonings, ....
  • when it is a matter of made-to-order production with different recipes for each operation (food supplements, spice preparations for meat companies, flavors for the food industry, instant meals, instant beverages,...).

The conical mixer shown above can conveniently perform both mixing processes when resting on load cells. The requirement for continuous mixing is the presence of the dosing systems. 

Please come to Paderborn with your products. We will be pleased to demonstrate the mixing processes to you!

Three essential types of modification can be distinguished

Physical:

  • through heat treatment, grinding, pre-gelatinisation, roller drying, extrusion or agglomeration. This treatment need not be declared for food. The inexpensive roller drying or the more expensive spray drying is used, depending on the cold solubility desired. The latter is usually combined with a fluidised bed agglomeration if the starch is to exhibit particularly good instant properties.

Chemical:

  • Starch is suspended in water in a stirred tank and, after adding a small quantity of acid or alkali, carefully heated without reaching the gelatinisation temperature. After adjusting to a specific pH value, a modifying agent is added. After neutralisation, washing, filtration and drying, the starch has completely changed properties. If starch is chemically converted, degraded, or treated with dextrin, esterified, etherified or oxidised, then it must be declared in food as an additive with an E-number or as modified starch.

  • If the crystalline structure of the starch grains is to be largely retained despite effective modification, the method of chemical cross-linking of the starch molecule groups with the help of suitable hydroxyls such as ethylene, propylene oxide or dicarboxylic acid can be used. This reduces the solubility of the starch, increases the gelatinisation temperature and, depending on the degree of cross-linking, eliminates retrogradation.

Enzymatic:

  • Enzymatic hydrolysis of starch is a highly effective process in which the starch can be saccharised to produce sweetener. Just as they can organise and bond molecular structures as well as forming molecular chains and side chains, enzymes can also split those starch molecules. As opposed to chemical splitting, enzyme-catalytic hydrolysis of starch takes place more slowly, but also at a lower temperature. The corresponding enzymes can be extracted from moulds, bacteria or the pancreas of cattle. Following the conversion, the enzymes are flushed completely from the starch derivative or deactivated. The degree of starch degradation can be set precisely so that a large number of products are available (starch syrup). This is no declaration obligation for this form of modification. Alternatively, the starch can also be split with an acid (acid hydrolysis).

  • Maltodextrin, for example for instant beverages, spice preparations, fruit preparations and ice cream, can be obtained effectively in this way. Starch is suspended in water with alpha-amylase and heated slowly while stirring slowly. There are defined stirring and dwell times at different temperatures in order to promote the most complete enzymatic splitting possible. The suspension is then washed several times, centrifuged and dried.

  • A particularly gently and effective method of contact drying takes place in the vacuum-mixer dryer from amixon®. With particularly low temperatures and a gentle circulation flow, high drying rates are achieved extremely quickly.

© by amixon GmbH

© by amixon GmbH

Mixer, synthesis reactor, vacuum dryer

What are typical criteria for determining whether the system should have a flat bottom or a conical bottom? 

The product that is discharged from the machine at the end should be either a powder or a liquid. There is no general answer to this question. In principle, both systems have similar performance.

Both systems achieve first-class mixing qualities - regardless of the consistency of the material. A wide variety of stock properties can occur during the synthesis reaction or during vacuum drying. The stock properties can change massively; from 

a. suspended-pumpable to
b. viscoplastic-highly viscous to
c. granular-lumpy and then to
d. powdery-granular.

All this takes place conveniently in both systems. The drive torques can be large depending on the material properties:

  • If the vertical installation space is limited, then the flat-bottom reactor is preferable.
  • If the resulting mix is particularly well free-flowing, then the cone reactor will probably have better residual discharge properties.
  • If the products are abrasive or particularly corrosive, then regular inspection must take place inside. If a synthesis reactor, vacuum dryer is to be walked on from time to time by people - for the purpose of repair or weld hardfacing - then the flat-bottom system is preferable. In large apparatuses it is possible to stand upright.
  • If bulk densities and filling levels fluctuate massively during the synthesis reaction, then the cone system should be given preference, because a cone mixer can tolerate very large differences in filling level.
  • If price considerations "cost per m³ useful volume" are dominant, then the flat-bottom system will probably be more suitable.
  • If particularly high pressures are present inside the reactor, then the cone system could offer advantages.
  • If maximum large heat exchanger areas (m²/m³) are to be provided in the dryer/reactor, then the cone apparatus is also advantageous.
  • If the end product should be a viscous, pasty mass, then the cone reactor offers the better possibility of product discharge.

We can continue this list if we know your requirements and products. 

Please feel free to contact us or visit us with your mixed products. We will be pleased to demonstrate the reactions and vacuum drying.

The integrity of a native starch is simple to establish if the starch grains are observed microscopically with polarised light. The double refraction makes native starch grains appear iridescent with a dark cross, while processed starch grains have a monochrome appearance without a cross – obviously because their crystalline structure has been destroyed.

If starch is heated as an aqueous suspension, then the starch grain is destroyed above a certain temperature, the swelling increases again and amylomaize emerges from the grain. This process is called gelatinisation. The viscosity increases, as does the clarity of the starch/water mixture and its electrical conductivity. It is a structurally viscous solution whose viscosity decreases the more the solution is stirred or sheared. In the course of cooling, the solution clarifies, the glucose chains align in parallel and form new hydrogen bonds. Depending on the type of starch, a more or less stable gel is formed.

This structurally viscous behaviour is exactly opposite to the initial state. Wet starch (water-in-starch suspension) is dilatant. The higher the shear stress, the more the viscosity increases. In special cases, drive components and mixing tools can even break or plastically deform due to the blocking effect.

Type of starch

Gelatinisation temperature [°C]

Swelling capacity (-fold)

Potato

56 - 66

1 000

Maize

75 - 80

24

Wheat

80 - 85

21

Rice

61 - 78

20

Waxy corn

63 - 72

64

The gelatinisation of starch is of great importance in various industrial applications

© by amixon GmbH

© by amixon GmbH

A "Viscograph" or a "Rapid-Visco-Analyzer" provides a clear measuring technique for comparing the curing characteristics of different starches. A starch-water suspension is heated and cooled under constant stirring. The stirring resistance is measured continuously and plotted over time.

Starch suspensions sometimes flow poorly because their viscosity increases when the starch suspension is agitated. With the synthesis reactor / vacuum dryer shown above, you can prepare even highly complex formulations. Ideal mixing is usually always possible.

You can modify, mix, thermally treat and thermally dry your starch in various forms under vacuum application. Vacuum drying works particularly quickly, especially at low temperature levels.

Further properties of liquefied starch are texture (sliminess) and turbidity, film formation, gel formation and retrogradation. No matter where starch is used in the food industry, it should be tasteless and it should improve the end application in the interests of the consumer. Furthermore, it should positively support the mouthfeel to match the respective food.

  • a cake topping should be cold swelling and quick to prepare, support the creamy taste, but have lasting elasticity and shape stability when cutting the cake slices.

  • a spray-dried baby food should have good instant properties and a suitable liquid consistency

  • a milk-based fruit dessert or a yoghurt should feel refreshing, cooling, but by no means sticky or furry in the mouth, but on the other hand it should be easy to portion and behave drip-free in the high-performance filling machine.

  • a grill sauce should be easy to dispense from the bottle and wet the grilled food in a thick layer with high viscosity despite the effect of heat, but unfold the spice flavours in the mouth in a natural way while chewing.

  • a breadcrumb coating powdered with starch or a baking dough should cover the food evenly and adhere firmly, no matter whether the food is eaten immediately or first deep frozen, packed and stored.

  • an instant beverage powder should disperse quickly and lump-free in the liquid phase even after a long storage period
  • in a multi-stage fluidised bed process, even volatile or oxidation-prone liquids can be microencapsulated with the help of starch.


Starch gelatinisation is an endothermic process – similar to when crystals go into solution. Thus, heat must be supplied accordingly. In Germany, most types of starch are interchangeable; especially if they are used in modified form. Potato starch is usually more expensive than grain starch because the potato tubers are only available seasonally and few by-products are produced during manufacture. At the moment, the supply of wheat starch is increasing because wheat gluten in particular is becoming increasingly important as a by-product. Wheat gluten / wheat protein has always been a valued by-product that had been made available in dried form for the bakery industry or for animal fodder. Today, wheat gluten also serves as the basis for meat substitutes and has become comparatively expensive. This makes the extraction of starch from wheat increasingly interesting.

The total consumption of starch in Europe is about 12 million tonnes, with an increase of about 2% per year. In the USA, the increase is about 4%, in South America about 4.5% and in Asia as much as 7% per year. About 10% of the starch produced worldwide is used in the chemical industry, about 30% in the paper and corrugated cardboard industry, 30% in the food industry and about the same amount is modified or saccharified for the beverage and confectionery industries. The demand for starch and its derivatives is expected to continue to increase in all industrial sectors.

If the starch or starch derivative is to be brought onto the market as a powder, then the major process engineering challenges are solid-liquid separation. In the first step, this is done mechanically in horizontally rotating peeler centrifuges or vertically rotating separators. The separation takes place due to the different densities of water and solid. Then the thermal drying step follows. Convection dryers such as flow dryers, ring dryers or grinding dryers are mostly used here. The water is discharged by hot air, whereby the moist starch is pneumatically swirled and conveyed. Thermal drying is a particularly cost-intensive process step.

At this point, the amixon® vacuum mix-dryer should be mentioned briefly when it comes to the gentle drying of high-quality derivatives, such as glucose. All surfaces of the apparatus are heated. If the vacuum is adjusted to 200 mbar absolute pressure, the water already evaporates at 60 °C. The thermal stress is therefore extremely low. The vertical design has many advantages, such as particularly good complete discharge and particularly gentle flow of the goods at low rotational speeds.


https://youtu.be/gVzx8jOgFF0  and https://youtu.be/FavGACava3M


© by amixon GmbH

© by amixon GmbH

The mixers shown above offer many user advantages: they mix quickly - regardless of the filling level, they empty largely without residue, they are particularly convenient to clean/inspect, they have large inspection doors. The spiral mixing tools are driven and mounted only at the top. 

The HM, KS, AM and VM mixing systems are precision mixers with very short mixing times. They are mostly manufactured with batch volumes from 1000 liters to 7000 liters. These mixers can be used for almost all types of dry, wet and suspended solids.

The HM type is a twin-shaft mixer with the highest efficiency, whose mixing time is extremely short: about 0.5 to 5 minutes, depending on the task. The AM and VM mixing systems are single-shaft mixers. Their mixing times are approx. 4 to 7 minutes, depending on the task. The achievable mixing qualities of the mixers always correspond to ideal homogeneity, which cannot be improved in practice.

The GM mixing system is a large-volume homogenizing mixer. However, if you want to distribute a very small component in the total batch, this mixing system is not the first choice. This process would take a very long time.

Do the HM and KS mixing systems have the same properties?

The characteristics are pretty much the same in terms of smooth, gentle operation. Both systems ensure maximum efficiency. The KS design is used when the mixing time is extremely short and when complete discharge has to take place in a few seconds. The KS system realizes cycle times of 1 to 4 minutes (cycle time is the sum of the times for filling, mixing, emptying and closing the valve). The mixer can also empty in a dosing or portioning manner.

The GM mixing system is a new development for classic homogenizing tasks, for example, when a large-volume mixing compound has to be homogenized. 

What are typical processing tasks when large quantities of raw material are delivered?

Bulk commodities such as tea, herbs, spices, tobacco or chemical raw materials are often delivered from overseas in 40-foot ocean containers. It must be assumed that the goods in the container have a wide variety of qualities, particle sizes, bulk densities, moisture levels, color and flavor characteristics, etc. A quality determination can only take place if a statistically secured sample is taken and analyzed.

 However, sampling only makes sense if the total mass has been homogenized. The KS mixing system can homogenize large quantities gently. Its motor power is low. The mixing unit rotates slowly. The mixing tool is moved without dead space along the cylinder wall with a defined distance to the cylinder wall. Its mixing time can be adjusted according to motor power and rotational frequency.

This large-capacity mixer is particularly compact and meets the highest hygiene requirements.

Can the KS mixing system be tested?

Yes, this mixing system is also available for trials in the test center. We recommend carrying out the tests on a 2 m³ scale. A scale-up to other sizes such as 20 m³ or 70 m³ is certainly ensured.

The food industry is a major driver for the application and further development of starch derivatives

  • as additives for instant foods 
  • as a for tablet filler for food supplements
  • as a viscosity adjuster and turbidity additive for instant beverages
  • for increasing the creaminess in dessert production
  • for the conditioning of sauces for frozen instant meals
  • as a base compound for oleoresins in flavour and spice refinement
  • to increase the water binding capacity in sausage and meat processing
  • as a binding agent in commercial kitchens and canteens
  • as a filler for flavour enhancers
  • as an additive to sugar for coating the particles with fat
  • as an additive for flour treatment agents and ready-to-bake flours
  • as a conditioning agent for breadcrumb coatings

As multifaceted as is the use of starch and its derivatives in the food industry, it is also used in the pharmaceutical industry.

  • as a lubricating powder for medical gloves
  • as a filler to make tablets a practical size
  • as coating and disintegrant for tablets
  • as a base compound for medical powders and deodorants
  • as a carrier to adhere medical active ingredients
  • to dilute cosmetic rouge
  • as a release agent and lubricant to make tablet presses work trouble-free
  • as a powdering compound to permanently separate sticky particles from each other
  • as viscosity adjuster for creams, emulsions, ointments and even aerosols

A wide variety of starch derivatives is also used in the process and heavy industries.

For example

  • for the production of flocculants and foam suppressors for water treatment
  • in the production of cooling lubricants for tunnel and earth drilling
  • to adjust the fluidity of concrete for concrete pumps
  • for the conditioning of mould sands in the foundry industry
  • for smoothing cotton threads to allow wear-free weaving in textile production
  • as an adhesive for postage stamps and corrugated cardboard
  • for the production of wood glues

In the vast majority of cases, starches and starch derivatives in powdery form are irreplaceable additives for the production of powder mixtures for the above products. The mixer determines the process. It must produce an ideal mixing quality in a short time - without heating the mixture - which cannot be improved in practice. This process is made more difficult when liquid additives are involved in the recipes, which is usually the case. Starches and their derivatives are usually very finely dispersed, dusty, swelling and poorly flowing. As products of organic origin, they are also moderately to particularly prone to dust explosions. Often, they have the tendency to adhere to the mixing tools and to the walls of the mixing chamber.

If starch and starch derivatives are used as carriers for liquid aromas, oleoresins, food dyes, baking extracts, oils and fats, it requires great experience to quickly and homogeneously bring about liquid residue-free wetting, because the most important goal must be that the energy input is as low as possible. The colder the overall mixture leaves the mixing plant, the better the later filling, storage, quality preservation and freshness consistency will work. The preparation of aroma and flavour, instant food, soups, dips and sauces is often a multi-step operation. Specific coating effects are intended to enclose and protect the liquid active ingredients. There is a major conflict of objectives to obtain the highest possible liquid material loading on the one hand and the best possible flowability of the finished mixtures on the other.

It is undisputed that the technology of mixing is a trendsetter for new process engineering and hygienic standards. In this respect, the mixing results of almost all other types of mixers can be reproduced and usually also improved. New process sequences often have to be established within the scope of product developments. We have ideally designed precision mixers available for piloting purposes.

These have vertically mounted helical mixing tools and can be used with a wide range of filling degrees. After a few revolutions, the mixing helix produces ideal homogeneity for almost all types of dry, wet and moist solids and pastes. Vertical - mixers are established worldwide and are known for their particularly hygienic design with a discharge rate of up to 99.98%. Large inspection doors are manufactured using the Clever-Cut® and OmgaSeal® processes. They seal permanently, are absolutely gas-tight and free of dead spaces, and permit both manual dry cleaning and automatic wet cleaning; fast and thorough drying is particularly important. More than 30 different vertical spiral mixers and sizes ranging from 10 liters to 2000 liters batch size are available in the pilot plant. A test day in the pilot plant provides the person carrying out the tests with a high level of knowledge and first-class test results that can be transferred to a wide range of sizes.

© by amixon GmbH

© by amixon GmbH

What prompted you to develop such a conical powder mixer, type KS?

This mixer type was developed for the mixing of particularly sensitive components. These include the goods resulting from freeze-drying or produced in the spray tower and agglomerator. These are primarily instant nutrients or agglomerated medicinal ingredients with excellent instant properties. Ideally, these goods would be packaged directly from the plant; in sachets, in bags, in foil pouches, folding cartons or in cans.

Are we talking about mixed products whose ingredients must not be heated?

Yes, that's exactly what it's about. Often there are components that must not be exposed to the thermal treatment of a spray tower or an agglomerator, such as vitamin B2, probiotics, prebiotics, omega-3 fatty acid or omega-6 fatty acid, then a final mixing process after the spraying process is unavoidable. During mixing, these substances must be agitated only very gently – nearly unnoticeable.

In these cases, however, the very highest mixing quality is essential. Is this not a conflict of aims - on the one hand to mix homogeneously, on the other hand to maintain the particles in their existing granulometry? The process of discharge from the mixer can also stress the mixed materials. Especially if the mixed materials are to be discharged from the mixer quickly and without residue?

It may seem illogical, but it is actually possible to homogenize such mixing goods adequately and discharge them without residue.

This is done by three-dimensional rearrangement. A specifically shaped mixing spiral rotates at low rotational frequency and conveys the goods upwards in the periphery of the mixing chamber. The goods flow downward in the center. In the process, they are returned to the outside by the inner cone. The ideal mixing quality is achieved after only a few revolutions. The homogeneity corresponds to the best possible distribution and can no longer be improved in practice. 

Is it true that a high mixing quality is only achieved when the mixing tool rotates at high speed?

This may be true for other mixing systems. For the mixer type presented here, the opposite is true. The entire content of the mixing chamber is completely conveyed and rearranged once after about 4-5 revolutions. This happens independently of the rotation frequency. As a rule, the ideal mixing quality is achieved after 8 to 20 revolutions. Then the conical closing element lowers and the goods flow out within a few seconds.

Is it then not irrelevant whether the mixing tool performs the mixing process with a lower or higher rotational frequency?

The consideration is indeed obvious. However, it must be borne in mind that the phenomena of wear and abrasion do not develop linearly with the relative speed. Often they even develop quadratically. This is the case when the mixing tool agitates the particles and when the particles flow relative to each other and rub against each other and "round off". Fine particles can then be produced. In this respect, the slow rotational movement of the mixing tool helix is of great importance.

Is there any other reason for using a vertical mixer of this type?

Yes, there undoubtedly are. It is the mundane things that can dominate everyday operations, for example when it comes to discharging residual material. The better a mixer discharges, the more effectively the mixing operation works. For the mixer described here, this means practically:

  • virtually no product carry-over due to residual mix
  • optional metering or emptying of the mixed goods within seconds
  • virtually no mix residues that have to be disposed of when a recipe change has to be carried out
  • All raw materials used are converted into high-quality selling goods.

Sustainability is becoming increasingly important with regard to our resources and consumer acceptance!

There are practically no sources of contamination. The mixing tool is driven and supported only at the top. The high-quality PTFE lip seal only seals against dust and is subject to virtually no wear. A classic lip seal air purge can be provided, but need not be. In this respect, hardly any dust is generated in the mixing chamber.

We would also like to mention at this point that it is much more motivating for the plant operator to operate a plant with excellent ergonomic visibility. As a rule, he will enjoy using and maintaining it. This makes sense in view of the long service life of these mixers. They often operate for more than 30 years.

KoneSlid mixers can be installed directly above filling lines. They operate either continuously or in batches, accurately and extremely fast. They can be installed as end-of-the-line mixers at the end of a process chain above the filling machine.

Trials with your original products eliminate doubts and uncertainty. Come to our technical center in Paderborn and bring your mixing goods with you. Cone mixers in various sizes are available here for your use. If you wish, you can also borrow our test machines. We recommend this procedure whenever a freshly produced powder changes in the course of the storage time.

© by amixon GmbH

© by amixon GmbH

Large-volume mixers that require only low electrical connected loads are always of interest when efficient and gentle homogenization is required. If no short mixing time is required here, but rather a cost-effective homogenizer that ensures a high mixing quality - regardless of the nature of the mixed materials, then the use of the Gyraton mixer shown here is recommended.

The mixer spiral rotates and conveys the mixed materials upwards. In addition to rotation, the mixer shaft performs a circular path above the floor of the mixing chamber. The pivot point of the shaft is in the plane of the head plate. The entire cylinder surface is tangent to the mixer spiral. Mixing takes place without dead space. 

The mixer shaft is only supported and driven at the top. The shaft feedthrough is permanently gas-tight and hygienically designed. The unit shown here can homogenize 70m³ of mixing material. This mixer design requires minimal installation space. The mixer can optionally have one or more discharge nozzles. 

All components of the equipment originate from the in-house fabrication in Paderborn, where production is carried out with a high degree of automation according to a regime of effective make-to-order production. Learn more here!

Author:
Ludger Hilleke, Member of the Management Board of amixon GmbH