Amandus Kahl

The company Amandus Kahl GmbH & Co. KG, a renowned manufacturer of individual machines and turn-key plants for feed processing, has commissioned a complete laboratory plant for compound feed in the Middle East.

Laboratory machines are machines with a capacity of 50 - 200 kg/h which are suited for compound feed processing. These devices have been long known and used as individual machines but not as a continuously operated complete plant, so far.

This plant design offers many possibilities:

• Development of formulae in cooperation with feeding test stations.
• Development and optimisation of processing parameters such as crushing degree, composition of mixture, thermal treatment, pressure treatment, shaping.
• Scale-up to large-scale plants.
• Optimisation of shaping/product design e.g. for pellets, coarse crumbles, fine crumbles, extruded pellets, expanded product.
• Development of new marketing strategies for existing and new markets.
• Production of special compound feed in small quantities such as pet food or feed for zoo animals, which would not be economic in a large-scale plant.
• Production of special feed for laboratory animals such as mice or rats which is required in universities or clinics.

The multifunctional laboratory plant described in the following is thus suitable for universities and research institutes, for small-scale producers of compound feed for special animals as well as for feed manufacturing groups with their own research and development department.

1. TASK

The user of the plant presented in this article made the following demands:

• Production of test feed with "new" formulae for poultry and fish feed.
• Determination of the optimum processing parameters and appropriate shaping of the feed.
• Optimisation of the processing parameters of existing formulae and scale-up to the existing large-scale plant.
• Inactivation of ANF in oilseeds and legumes.
• Installation of the plant in a new building.

For reasons of hygiene and in order to avoid contamination the laboratory plant and the feed mill have to be located in different buildings. To comply with veterinary regulations, laboratory animals must not be kept on the same premise.

Separate land for housing and breeding the different animals is available.

2. PLANT DESIGN

For the above mentioned reasons, a separate building was erected for the laboratory plant (Fig. 1).

Fig. 1: The laboratory plant is located in this building.

The design of the building allows for an extension of the existing plant or the installation of a second plant. The steel structure which the machines are mounted on consists of four levels. The first and the second level are provided with a glass on three sides. This provides for daylight in the plant and thus for pleasant working. The structure is provided with a spiral steel staircase for access to the levels and a separate elevator for transport of the raw materials. Furthermore, several office, laboratory and storage rooms are housed in the building.

The process diagrams of the weighing, grinding and mixing line (Fig. 2) and the expander, extruder and press line (Fig. 3) were developed and determined in accordance with the performance requirements.

With the new installation the following products can be produced:

• extruded fish feed
• expanded pelleted poultry feed
• pelleted cattle, sheep and horse feed
• hygienised, mealy layer feed
• hydrothermally treated individual components

Fig. 2: Weighing, grinding and mixing line

Fig. 3: Expander, extruder and press line

3. ProduCtion line WitH MachineS

3.1 WEIGHING, GRINDING And MiXING line

The first section of the plant is composed of the weighing, grinding and mixing line.

Four bins for bag filling are available for the storage of raw materials. The bagged product is transported to the corresponding level by means of the elevator. The weigher is fed by proportioning screws with two speed levels. Small quantities may also be manually fed into the weigher. The average batch size is 50 kg/batch depending on the variation of the bulk density. Four batches can be produced per hour which makes a capacity of 200 kg/h. The weigher is suspended to three load cells and can be filled rapidly due to the two different screw speeds. Subsequently, the material is conveyed to the prebin by means of a discontinuous suction conveying plant. Depending on the adjustment of the suction conveying plant, the suction time and the repeated starting time can be rapidly and easily adapted according to the bulk density or the conveying properties of the raw material.

In the following crushing process the product is ground to the desired particle size by means of an impact mill. According to the intended use, fish feed can be ground to an average particle size of 0.4 mm and poultry feed to 1.1 mm. The parameters for reaching the desired grinding fineness are among others speed, throughput, negative pressure, grinding surface, and grinding gap. More weighed-out coarse raw components can be added into the prebin.

Subsequently, the ground product is conveyed into a rapid mixer with a useful capacity of 100 l (Fig. 4). The mixing tools are arranged on the shaft and can be adjusted. Optionally, the shaft speed can be varied by means of a frequency converter. The product outlet is realised by an electropneumatically operated bottom flap over the entire width of the mixer.

Apart from micro-components, liquids can be added into the mixer. The mixing time can be determined according to the product.

Fig. 4: Rapid mixer

3.2 Expander/Extruder And PelletiNG line

The second section of the laboratory plant includes the thermal treatment and shaping units with conditioning, expander/extruder and pelleting line.

The throughput rate of this line is approximately 200 kg/h. Depending on the open perforated surface and the specific energy input etc., varying throughputs are possible.

The mixed product is conveyed by means of a suction conveying system and is fed into a prebin. From the prebin a proportioning system conveys it to the mixing conditioner.

Here, the product can be conditioned both with steam and water and with other liquids.

Subsequently, the heated and moistened product is fed into the long-term conditioner - for example to ensure an improved impact of the high amount of water added to fish feed. If no retention time is desired as a considerably smaller quantity of water is added, like for example in case of poultry feed, the products passes through the long-term conditioner without retention time.

Fig. 5: Extruder OEE 8 including upstream retention bin and proportioning unit

3.2.1 Expander/Extruder technologY

The expander/extruder OE 8 is one of the core machines of the plant. Depending on the chosen process, it can be used as an extruder (Fig. 5) or expander and consists of a thick-walled mixing tube with replaceable liners and cantilevered shaft which is fitted with proportioning, mixing and kneading elements.

The stop screws between the individual flanks of the paddles almost reach the surface of the shaft. Thus the product to be treated is uniformly kneaded and transported towards the outlet. The rapidly exchangeable outlet head forms the end of the outlet. It depends on the design of the outlet head whether the machine is used as an extruder or as an expander.

3.2.1.1 Expander

If the expander variant with the construction series name OER is required, the expander head is equipped with a hydraulically adjustable cone forming the patented annular gap together with the tube end (Fig. 6). By means of adjusting the cone, the pressure, the intensity of kneading, product heating, and energy consumption can be adjusted. The process can be controlled also automatically.

Fig. 6: Expander OER

At the outlet the pressure drops spontaneously, the material expands, and part of the water added into the mixing conditioner evaporates (flash evaporation). As considerably less water is added, less water evaporates. Thus only subsequent cooling and no additional upstream drying is required.

The size of the expanded product can be determined by means of a downstream crushing device. The expanded product can either be used for direct feeding or shaped to pellets for poultry feed. 

If desired, steam and various liquids can also be added directly into the expander.

3.2.1.2 Extruder

If the extruder variant with the construction series name OEE is required, the extruder head is equipped with a hydraulically adjustable die which can be moved in or out (Fig. 7 + 8). The knife head is provided with a separate drive and remains in its position during the die change. Due to the easy and rapid die change different products with different diameters and shapes can be produced. The machine is relieved in the event of overload by means of hydraulic opening of the outlet.

At the start of the production, the KAHL extruder OEE does not require an increased water addition and can be started with an "open" die.                 

Fig. 7: Extruder head OEE, closed variant                  

Fig. 8: Extruder head OEE, open variant

Depending on the selection of raw components, the composition, the grinding degree, conditioning, the extruder speed, the die geometry and the mechanical energy input, either sinking or floating fish feed with different sizes can be produced for different fish species. Due to the high amount of added water and steam, drying and subsequent cooling are necessary.

3.2.2 PelletING press

Another core machine of the laboratory plant is the flat die pelleting press of the construction series 14-175.

By means of pan grinder rollers the product - expanded poultry feed in this case - is pressed through a die. The knives below the die cut the pellets to the desired length (Fig. 9). According to the product and species, dies with different bore diameters are required.

Fig. 9: Functioning principle of a large size flat die pelleting press

The pelleting press can be operated with and without pre-treatment by means of the expander. Thus the plant is flexibly applicable and can be used also for those products that do not require pre-treatment using the expander such as sheep and horse feed.

3.2.3 HygienisATION

The expander/extruder ensures hygienisation of the product, i.e. the product is free from pathogenic germs such as mould, salmonellae and coliform bacteria. If mealy layer feed is to be hygienised, for example, this can be done by means of the long-term conditioner which provides hygienisation at 85 °C and a conditioning time of 6 min.

The long-term conditioner, expander or extruder provide an inactivation of antinutritive factors (ANF) such as:

• trypsin inhibitors (TIU)
• glucosinolates in rape seed
• gossypol in cotton seed
• TIU and lectins in legumes

According to the respective production process, the different products have to be dried and cooled or only cooled after shaping. This was realised in a vertical fluidized bed drier/cooler composed of two drying sections and one cooling section. The required hot air is generated by a steam/air heat exchanger.

Fish and poultry feed can be fat-coated by means of a downstream coating system.

The product to be discharged is transported into the finished product cell by means of a suction conveying system. Subsequently, it can be packed in different bag sizes by means of a bagging system.

SUMMARY

The described laboratory plant for compound feed meets all the requirements on processing small quantities of compound feed using different technologies.

Due to its dimension, the plant is easy to manage and operate.

The required product quantities are small and cost-saving.

A complete laboratory plant is the basis for research and development on a small scale - not only for feed producers but also for research institutes.